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bulletin de l'institut royal des sciences naturelles de belgique sciences de la terre, 74: 147-174, 2004 bulletin van het koninklijk belgisch instituut voor natuurwetenschappen aardwetenschappen, 74: 147-174, 2004 Systematic revision of the Miocene long-snouted dolphin Eurhinodelphis longirostris du Bus, 1872 (Cetacea, Odontoceti, Eurhinodelphinidae) by Olivier LAMBERT Lambert, O., 2004, - Systematic revision of the Miocene long-snouted dolphin Eurhinodelphis longirostris du Bus, 1872 (Cetacea, Odonto¬ ceti, Eurhinodelphinidae). Bulletin de l'Institut royal des Sciences naturelles de Belgique, Sciences de la Terre, 74: 147-174, 5 pis, 12 figs, 2 tables; Bruxelles-Brussel, March 31, 2004. - ISSN 0374-6291. Abstract On the basis of the redescription of Miocene Belgian specimens, the systematic status of the long-snouted dolphin genus Schizodelphis (Cetacea, Odontoceti, Eurhinodelphinidae) is revised. The only Bel¬ gian species previously recognized, S. longirostris, from the late early to middle Miocene of Antwerp (north of Belgium, southern margin of the North Sea basin), is divided here in two taxa. Some specimens are kept in that species, but re-establishing the combination Eurhinodel¬ phis longirostris. The content of the genus Eurhinodelphis is then investigated from several Miocene localities, essentially the Calvert Formation (Virginia and Maryland, east coast of USA) and the Belluno Sandstones from north-eastern Italy. The only recognized species are E. cocheteuxi and E. longirostris, both of them only found in the Belgian Miocene. Other previously described species are placed in an unnamed new genus, in Mycteriacetus n. gen., and in Ziphiodelphis. The other Belgian specimens are maintained in Schizodelphis, with the prioritary species name morckhoviensis. The species S. morckho- viensis is also identified in the Calvert Formation, while a restricted 5. barnesi is tentatively diagnosed from American specimens. Kev words: Eurhinodelphinidae, taxonomy, Miocene, Belgium, Schi¬ zodelphis, Eurhinodelphis. Résumé Sur base de la redescription de spécimens du Miocène de Belgique, le statut systématique du dauphin longirostre Schizodelphis (Cetacea, Odontoceti, Eurhinodelphinidae) est révisé. La seule espèce belge préalablement décrite, S. longirostris, de la fin du Miocène inférieur- Miocène moyen d'Anvers (nord de la Belgique, bord sud du bassin de la Mer du Nord), est divisée en deux taxa. Une partie des spécimens est maintenue dans cette espèce, mais en rétablissant la combinaison Eurhinodelphis longirostris. Le contenu du genre Eurhinodelphis est ensuite investigué dans plusieurs localités du Miocène, particulière¬ ment la Formation Calvert (Virginie et Maryland, côte est des Etats- Unis) et les Sables de Belluno (nord-est de l'Italie). Les seules espèces reconnues sont E. cocheteuxi et E. longirostris, et cela uniquement dans le Miocène belge. Les autres espèces précédemment décrites sont placées dans un nouveau genre non nommé, dans Mycteriacetus n. gen., et dans Ziphiodelphis. Une seconde partie des spécimens belges est maintenue dans le genre Schizodelphis, avec le nom d'espèce prioritaire morckhoviensis. Cette espèce S. morckhoviensis est également identifiée dans la For¬ mation Calvert, de même que l'espèce S. barnesi brièvement redéfinie. Mots-clefs: Eurhinodelphinidae, taxinomie, Miocène. Belgique, Schi¬ zodelphis, Eurhinodelphis. Introduction du Bus (1872) shortly described several species of long- snouted dolphins from the Miocene of Antwerp (North of Belgium), which he included in the genera Eurhinodel¬ phis du Bus, 1868 and Priscodelphinus (Leidy, 1851). Abel (1902) included in the same species E. longirostris individuals of the species Eurhinodelphis longirostris, E. am- biguus, Priscodelphinus morckhoviensis, P. elegans, and P. pulvinatus sensu du Bus, 1972. In his unpublished revi¬ sion of the eurhinodelphinids from the Calvert Formation, east coast of the USA, Myrick (1979) noticed the presence of the species E. longirostris in this area, which he referred to the genus Rhabdosteus by comparison with the holotype of the type-species of the genus ( R. latiradix (Cope, 1868)}, a partial rostrum also from the Calvert Formation. Flowever, this specimen was estimated by Muizon (1988a) as too fragmentary, and regarded as an incertae sedis. Muizon referred the species E. longirostris to the genus Schizodelphis Gervais, 1861, as well as all the Rhabdosteus species recognized by Myrick (1979) in the Calvert Formation (excluding R. latiradix). Muizon's conclusions were based on the study of the holotype of Schizodelphis sulcatus Gervais, 1853 (Miocene of France), the type-species of the genus. Muizon did not recognize S. longirostris in the Calvert Formation, where he only identified one species, S. barnesi, including the individuals from the species Rhabdosteus longirostris, R. barnesi and R. hruschkai sensu Myrick, 1979. A detailed observation of the Belgian specimens of Schizodelphis longirostris sensu Muizon, 1988a allows the récognition of two genera, Eurhinodelphis and Schi¬ zodelphis, for which an emended diagnosis and a rede- scription are presented here. Specimens from the Calvert Formation (Myrick, 1979), from the Belluno Sandstones (early Miocene of north-eastern Italy, Pilleri, 1985), and from several other localities, previously reported to the genus Eurhinodel¬ phis, are also briefly discussed.

Transcript of Museum of Natural Sciencesbiblio.naturalsciences.be/rbins-publications/bulletin-of-the-royal... ·...

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bulletin de l'institut royal des sciences naturelles de belgique sciences de la terre, 74: 147-174, 2004bulletin van het koninklijk belgisch instituut voor natuurwetenschappen aardwetenschappen, 74: 147-174, 2004

Systematic revision of the Miocene long-snouted dolphinEurhinodelphis longirostris du Bus, 1872 (Cetacea, Odontoceti,Eurhinodelphinidae)

by Olivier LAMBERT

Lambert, O., 2004, - Systematic revision of the Miocene long-snouteddolphin Eurhinodelphis longirostris du Bus, 1872 (Cetacea, Odonto¬ceti, Eurhinodelphinidae). Bulletin de l'Institut royal des Sciencesnaturelles de Belgique, Sciences de la Terre, 74: 147-174, 5 pis, 12 figs,2 tables; Bruxelles-Brussel, March 31, 2004. - ISSN 0374-6291.

Abstract

On the basis of the redescription of Miocene Belgian specimens, thesystematic status of the long-snouted dolphin genus Schizodelphis(Cetacea, Odontoceti, Eurhinodelphinidae) is revised. The only Bel¬gian species previously recognized, S. longirostris, from the late earlyto middle Miocene of Antwerp (north of Belgium, southern margin ofthe North Sea basin), is divided here in two taxa. Some specimens arekept in that species, but re-establishing the combination Eurhinodel¬phis longirostris. The content of the genus Eurhinodelphis is theninvestigated from several Miocene localities, essentially the CalvertFormation (Virginia and Maryland, east coast of USA) and the BellunoSandstones from north-eastern Italy. The only recognized species areE. cocheteuxi and E. longirostris, both of them only found in theBelgian Miocene. Other previously described species are placed inan unnamed new genus, in Mycteriacetus n. gen., and in Ziphiodelphis.

The other Belgian specimens are maintained in Schizodelphis, withthe prioritary species name morckhoviensis. The species S. morckho-viensis is also identified in the Calvert Formation, while a restricted5. barnesi is tentatively diagnosed from American specimens.

Kev words: Eurhinodelphinidae, taxonomy, Miocene, Belgium, Schi¬zodelphis, Eurhinodelphis.

Résumé

Sur base de la redescription de spécimens du Miocène de Belgique, lestatut systématique du dauphin longirostre Schizodelphis (Cetacea,Odontoceti, Eurhinodelphinidae) est révisé. La seule espèce belgepréalablement décrite, S. longirostris, de la fin du Miocène inférieur-Miocène moyen d'Anvers (nord de la Belgique, bord sud du bassin dela Mer du Nord), est divisée en deux taxa. Une partie des spécimens estmaintenue dans cette espèce, mais en rétablissant la combinaisonEurhinodelphis longirostris. Le contenu du genre Eurhinodelphis estensuite investigué dans plusieurs localités du Miocène, particulière¬ment la Formation Calvert (Virginie et Maryland, côte est des Etats-Unis) et les Sables de Belluno (nord-est de l'Italie). Les seules espècesreconnues sont E. cocheteuxi et E. longirostris, et cela uniquementdans le Miocène belge. Les autres espèces précédemment décrites sontplacées dans un nouveau genre non nommé, dans Mycteriacetus n. gen.,et dans Ziphiodelphis.

Une seconde partie des spécimens belges est maintenue dans legenre Schizodelphis, avec le nom d'espèce prioritaire morckhoviensis.Cette espèce S. morckhoviensis est également identifiée dans la For¬mation Calvert, de même que l'espèce S. barnesi brièvement redéfinie.

Mots-clefs: Eurhinodelphinidae, taxinomie, Miocène. Belgique, Schi¬zodelphis, Eurhinodelphis.

Introduction

du Bus (1872) shortly described several species of long-snouted dolphins from the Miocene of Antwerp (North ofBelgium), which he included in the genera Eurhinodel¬phis du Bus, 1868 and Priscodelphinus (Leidy, 1851).Abel (1902) included in the same species E. longirostrisindividuals ofthe species Eurhinodelphis longirostris, E. am-biguus, Priscodelphinus morckhoviensis, P. elegans, andP. pulvinatus sensu du Bus, 1972. In his unpublished revi¬sion of the eurhinodelphinids from the Calvert Formation,east coast of the USA, Myrick (1979) noticed the presenceof the species E. longirostris in this area, which he referredto the genus Rhabdosteus by comparison with the holotypeof the type-species of the genus ( R. latiradix (Cope, 1868)},a partial rostrum also from the Calvert Formation.

Flowever, this specimen was estimated by Muizon(1988a) as too fragmentary, and regarded as an incertaesedis. Muizon referred the species E. longirostris to thegenus Schizodelphis Gervais, 1861, as well as all theRhabdosteus species recognized by Myrick (1979) in theCalvert Formation (excluding R. latiradix). Muizon'sconclusions were based on the study of the holotype ofSchizodelphis sulcatus Gervais, 1853 (Miocene ofFrance), the type-species of the genus. Muizon did notrecognize S. longirostris in the Calvert Formation, wherehe only identified one species, S. barnesi, including theindividuals from the species Rhabdosteus longirostris,R. barnesi and R. hruschkai sensu Myrick, 1979.

A detailed observation of the Belgian specimens ofSchizodelphis longirostris sensu Muizon, 1988a allowsthe récognition of two genera, Eurhinodelphis and Schi¬zodelphis, for which an emended diagnosis and a rede-scription are presented here.

Specimens from the Calvert Formation (Myrick,1979), from the Belluno Sandstones (early Miocene ofnorth-eastern Italy, Pilleri, 1985), and from several otherlocalities, previously reported to the genus Eurhinodel¬phis, are also briefly discussed.

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148 Olivier LAMBERT

Material and methods

Most of the specimens used in this study are housed in theIRSNB. The main specimens are two well preserved skulls,IRSNB 3249-M.342 and IRSNB 3235-M.343, already describedby Abel (1902). Additional specimens from the IRSNB, USNM,CMM, and MGPD are more briefly discussed.

Though Myrick's Ph. D. thesis (1979) was not published, Iuse it as a starting point for the systematic revision of theCalvert eurhinodelphinids.

The species Eurhinodelphis cristatus sensu du Bus, 1872 andE. bossi sensu Kellogg, 1925 are referred to a new eurhino-delphinid genus that will be diagnosed in a paper in préparation;those two species are cited here as 'E.' cristatus and'£7 bossi.The Italian species E. bellunensis sensu Pilleri, 1985, includedby its author in the genus Eurhinodelphis, is referred to a newgenus, Mycteriacetus n. gen., diagnosed below.

Terminology. The terminology for cranial and ear bones anat-omy is mainly taken from: Fordyce (1983 and 1994); Kasuya(1973); Muizon (1984, 1987 and 1988a). The orientations ofthe tympanic bulla and periotic are simplified in the followingdescriptions, relatively to the anatomical position on the basi-cranium. The long axis of the tympanic is considered as antero-posterior, with ventral surfaces of inner and outer posteriorprominences indicating the horizontal plane. The anterior di¬rection of the periotic is given by the longitudinal axis of theanterior process, and the horizontal ventral plane by the surfacecontacting the most ventral points of pars cochlearis and ante¬rior process.

Abbreviations. CMM: Calvert Marine Museum, Solomons,Maryland, USA; IRSNB: Institut Royal des Sciences Naturellesde Belgique, Brussels; M: Fossil mammals collection of typesand figured specimens from the IRSNB; MGPD: Museum ofGeology and Palaeontology of Padova, Italy; MNHN: MuséumNational d'Histoire Naturelle, Paris, France; USNM: UnitedStates National Museum, Smithsonian Institution, WashingtonD.C., USA.

Exploitations of the measurements. Fig. 1.

Systematic palaeontology

Order Cetacea Brisson, 1762

Suborder Odontoceti Flower, 1867

Superfamily Eurhinodelphinoidea Muizon, 1988a

Family Eurhinodelphinidae Abel, 1901

Type-genus. Eurhinodelphis du Bus, 1867Included genera. Eurhinodelphis, Schizodelphis Ger-

vais, 1861, Ziphiodelphis Dal Piaz, 1908, ArgyrocetusLydekker, 1894, Macrodelphinus Wilson, 1935, andMycteriacetus n. gen.

Emended diagnosis. Family of long-snouted odonto-cetes differing from all the other families by an edentu-lous premaxillary anterior part of the rostrum, longer thanthe mandible.

Additionally, the family differs fforn the probably closelyrelated family Eoplatanisidae by: a more inclined dorso-medial portion of the supraoccipital shield, a generallylower temporal fossa, the presence of a marked médiangroove on the tympanic, a longer anterior process of theperiotic; and from the Squalodontidae, Waipatiidae andother more primitive odontocetes by: an homodont dentitionwith single-rooted teeth, premaxillae widened at the level ofthe posterior margin of the bony nares, a higher vertex.

Eurhinodelphis du Bus, 1867

Type species. E. cocheteuxi du Bus, 1867Included species. E. cocheteuxi and E. longirostris du

Bus, 1872. The species E. cocheteuxi was redescribed in aprevious paper (Lambert, in press).

Diagnosis. The genus Eurhinodelphis differs from thegenera Schizodelphis and Ziphiodelphis in: maxillary partof the rostrum relatively shorter (ratio between bizygo-matic width of the skull and length of the maxillary part ofthe rostrum > 0.5); vertical medial plate of the maxillaalong the vertex antero-dorsally developed; flat to convexsupraoccipital shield (shield concave in the two othergenera); more elevated and narrower paroccipital processof the exoccipital with occipital condyles more highlypositioned (ventral margin of the condyles nearly reachingthe level of the floor of the temporal fossa); less excavatedpremaxillary sac fossae, which are roughly flat; zygomaticprocess of the squamosal relatively higher in latéral viewand narrower in ventral view; absence of fossa for thepostorbital lobe of the pterygoid sinus on the ventral sur¬face of the supraorbital process (that fossa is sometimesvery short but nearly always present in Schizodelphis andZiphiodelphis). The last character is probably in a primitivestate, but it clearly separates the genera.

It differs from Macrodelphinus by: more longitudinallytelescoped and more elevated vertex with frontals shorterthan the nasals; flat to convex supraoccipital shield.

It differs from Argyrocetus (provisionally only includingthe species A. patagonicus) in: a more elevated vertex andflat to convex more vertical supraoccipital shield.

It differs from Mycteriacetus n. gen. in: a relativelywider and shorter face (ratio between bizygomatic widthand length of the face from the antorbital notch to theoccipital condyle > 0.95); a more elevated vertex withshorter frontals and wider nasals; flat to convex and morevertical supraoccipital shield.

Eurhinodelphis longirostris du Bus, 1872

* 1872 Eurhinodelphis longirostris du Bus, p. 491.v. 1880 Eurhinodelphis longirostris Van Beneden & Ger-

vais, p. 493, pl. 58, fig. 2.v. 1902 Eurhinodelphis longirostris Abel, pl. 11, 12 and 13,

pl. 17, fig. 1.v. 1988a Schizodelphis longirostris Muizon, p. 40.

Emended diagnosis. This species differs from Eurhino¬delphis cocheteuxi by: the distinctly smaller size of the

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Systematic revision of Eurhinodelphis longirostris 149

Fig. 1 - Description of the measurements on the skull of eurhinodelphinids, outlines of the holotype of Eurhinodelphis cocheteuxiIRSNB 3252-M.294. A. left latéral view. B. dorsal view. C. posterior view. Explanation of the measurements on Tables 1-2.

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150 Olivier LAMBERT

cranial skull (the général dimensions of the cranial skullof the holotype of E. longirostris vary between 70 and80 % of the dimensions of the holotype of E. cocheteuxi);relatively longer and more slender rostrum (ratio betweenpostorbital width of the skull and length of the rostrum< 0.25), especially the premaxillary apical part of therostrum; narrower base of the rostrum; relatively nar-rower vertex with a strong compression of the frontalsbetween the supraoccipital and the nasals (a contactbetween nasals and supraoccipital is present on two speci¬mens of E. longirostris).

Holotype. IRSNB 3249-M.342, a well preserved skull,only lacking teeth and ear bones, fragments of the basi-cranium and of the rostrum (found in January 1862,individual 1 of the species Eurhinodelphis longirostrisin Abel, 1902, figured in pl. 11, 12 and 13).

Referred specimens. IRSNB 3250-M. 1858, a partialskull including a part of the rostrum, the two supraorbitalprocesses, a portion of the vertex and the basicranium(individual 3 of the species Eurhinodelphis longirostris inAbel, 1902); IRSNB 3251, a part of the rostrum with theposterior part of the left maxilla (individual 7 of thespecies E. longirostris in Abel, 1902). No skull fromthe Calvert Formation could be referred to this species.

Comments on the other specimens referred to E. longi¬rostris by Abel (1902)

The fragmentary rostrum IRSNB 3245, individual 17of the species Eurhinodelphis longirostris sensu Abel,1902, shows very flattened and wide premaxillae at thebase of the rostrum, and should then be reported to 'E.'cristatus (paper in prep.).

The left side of a face IRSNB 3495 (Eurhinodelphisambiguus sensu du Bus, 1872 and individual 15 of thespecies E. longirostris sensu Abel, 1902) is probably a partof a juvénile specimen of 'E.' bossi (Lambert, in press).

The partial skull IRSNB 3238-M.344 (individual 2 ofE. longirostris sensu Abel, 1902, pl. 18, fig. 1, figuredhere in Pl. 1, Fig. 2, including the base of the rostrum, thesupraorbital processes, a portion of the vertex with thenasals, a fragment of the supraoccipital, the two squamo-sals and the paroccipital process of the left exoccipital)shows some features that place it in the genus Eurhino¬delphis: slightly excavated premaxillary sac fossa, flatposterior portion of the maxilla laterally to the vertex,elevated and narrow paroccipital process of the exocci¬pital, and absence of fossa for the postorbital lobe of thepterygoid sinus. A striking characteristic of this specimenis the strong development of the transverse premaxillarycrests that are wide and thick. The measurements of theskull (see Table 1) are similar to the measured specimensof E. longirostris. However, it differs from these speci¬mens in the smaller nasals less posteriorly displaced, andthe more dorso-ventrally flattened zygomatic process ofthe squamosal. Because of those différences, and becauseit is fragmentary, this specimen IRSNB 3238-M.344 isreferred to Eurhinodelphis cf. longirostris.

The partial rostrum IRSNB 3225 (individual 8 of thespecies Eurhinodelphis longirostris sensu Abel, 1902)has size and proportions similarities with E. longirostris

but no diagnostic character is observable and this frag¬ment is referred to Eurhinodelphinidae incertae sedis.

The isolated fragments of mandible IRSNB 3258-M.347 (figured by Abel, 1902, plate 17, fig. 4) probablybelong to an eurhinodelphinid, with proportions roughlysimilar to 'Eurhinodelphis ' bossi USNM 167629. None ofthe individuals of E. longirostris is associated with amandible, and the lack of diagnostic features on thismandible precludes its attribution to any eurhinodelphi¬nid species. It is placed in Odontoceti aff. Eurhinodelphi¬nidae.

The périodes associated with the specimen IRSNB3447-M.351 (Eurhinodelphis ambiguus sensu du Bus,1872, figured in Abel, 1902, p. 122, fig. 19 and plate17, figs. 11-12) were already clearly recognized as be-longing to a physeterid (Kellogg, 1927). The erro-neously associated symphyseal portion of mandible(figured by Abel, 1902, plate 17, fig. 6) is regarded asan Odontoceti aff. Eurhinodelphinidae.

The specimen IRSNB 3244-M.346 (holotype of Pris-codelphinus elegans sensu du Bus, 1872) is a hypothe-tical association of a partial small basicranium and avertex (figured by Abel, 1902, pl. 17, fig. 2), but withoutbony contact between them. The squamosal shows simi¬larities with that of Eurhinodelphis longirostris, with azygomatic process high in latéral view and narrow inventral view. However, the vertex is close to that ofseveral specimens of Rhabdosteus hruschkai sensu

Myrick (1979), e.g. USNM 187211, with an antero-lateral projection of the prominent nasal along the exter-nal nare. As most of the specimens of R. hruschkai sensuMyrick (1979) are probably referrable to the genus Schi-zodelphis, the association basicranium-vertex of IRSNB3244-M.346 is regarded as doubtful and those fragmentsare considered as Eurhinodelphinidae incertae sedis.

Locus typicus. The holotype of Eurhinodelphis longi¬rostris was found in Antwerp, in January 1862, and thelocality cited by Abel (1902) is '4e Section'. This localitycorresponds to the south-eastern portion of the city wallaround Antwerp, built during fortification works in the1860's (see Van den Broeck, 1878), in Berchem. Thissection matches the south-eastern part of the presentmotorway RI, around the city.

Stratum typicum. No précisé stratigraphie data areavailable for the holotype and referred specimens.However, the préservation and colour of those specimensare very similar to that of the skulls of Eurhinodelphiscocheteuxi, known from the Antwerp Sands. This stronglysuggests an origin in the same member, dated from lateearly to middle Miocene (see Louwye et al. 2000).

Redescription of the species Eurhinodelphis longirostris(Pl. 1, Fig. 1 ; Pl. 2, Fig. 1; Figs. 2-4)

General morphology. Eurhinodelphis longirostris hasa relatively small braincase and a very long rostrum (seemeasurements, Table 1), which is nearly completely pre¬served on the holotype. The rostrum constitutes morethan 80 % of the total length of the skull, with more than50 % of its length made by the premaxillae.

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Systematic revision of Eurhinodelphis longirostris 151

Table 1 - Measurements on the skulls of Eurhinodelphis longirostris. Measurements are in millimétrés, (e) indicates estimate, '+'nearly complete, and no data.

Measurements on the skulls of E. longirostris

HolotypeIRSNB3249-M.342

IRSNB3250-

M.1858

IRSNB3238-M.344E. aff.

longirostris

1. total length skull +1018 _ _

2. length base rostrum-anterior maxilla 390 — —

3. length anterior orbit-posterior skull 214 190 —

4. length anterior supraoccipital-anterior orbit 114 117 e 125

5. length orbit 86 82 66

6. length temporal fossa e75 - -

7. width rostrum anterior maxillae 29 - -

8. width base rostrum 103 e96 el05

9. width premaxillae base rostrum 67 - e64

10. width skull postorbital processes 199 - e 198

11. width skull zygomatic processes 210 197 -

12. width bony nares 44 - 32

13. width nasals 68 - 34

14. maximal posterior premaxillary width 97 - e98

15. minimal posterior distance between maxillae 65 - -

16. width medio-ventral margins exoccipitals 98 85 -

17. width latéral margins occipital condyles + 80 76 -

18. width inner margins occipital condyles 34 34 -

19. height cranium 146 --

20. height rostrum at anterior maxillae 30 - -

21. height base rostrum 57 e49 69

22. height temporal fossa e58 - -

23. height ventral margin occipital condyles 48 44 -

24. height occipital condyles 43 43 —

Dorsal view. The dorsal surface of the premaxilla isconvex and prominent until the base of the rostrum, witha slight narrowing and lowering just anterior to that level.The triangular elongated surface antero-medial to thepremaxillary foramen is nearly smooth and partiallylower than the thick and rounded latéral part of thepremaxilla at that level. The premaxillary sac fossa isthick, roughly flat and progressively raising towards thevertex, lacking the deeper concavity and the more abruptposterior élévation of Schizodelphis morckhoviensis(see below). The posterior extremity of the premaxillacontacts the antero-lateral angle of the nasal and islongitudinally incised by the erected médian edge of themaxilla. The contact between premaxilla and frontal isprobably absent on the holotype but it is present onIRSNB 3250-M.1858, depending upon the shape andposition of the nasals on the vertex.

The latéral margin of the maxilla exhibits a very weakswelling about 100 mm anterior to the antorbital notch.Several dorsal infraorbital foramina pierce the maxillaalong its suture with the premaxilla, at the level and

anterior to the shallow and antero-laterally open antorbi¬tal notch. The preorbital process is narrow in dorsal viewand its latéral margin diverges posteriorly. A distinctélévation of the maxilla is present above the orbit. It isseparated from the premaxillary sac fossa by a narrowlongitudinal dépression. The posterior portion of themaxilla is roughly flat and slopes antero-laterally. It isonly slightly concave at the level of its overhangingmédian edge along the vertex. The posterior margin ofthe maxilla extends posteriorly 20 mm beyond the antero-median margin of the supraoccipital.

The shape of the nasals strongly varies between the twoskulls on which it is preserved. On the holotype, thosebones are somewhat eroded. They are wider than long andexhibit a wide contact with the supraoccipital. The fron-tals are reduced on the vertex to three small trianglesbetween the nasals and the supraoccipital. This specialmorphology was correctly recognized by Abel (1902),but Kellogg (1932) erroneously identified the two wideand short bones as the frontals. On IRSNB 3250-M.1858,with only the right part of the vertex preserved, the nasal

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152 Olivier LAMBERT

supraoccipital

antorbital note]

latéral groove

mesethmoid

premaxilla

vomer

maxilla

frontal

dorsal infraorbital foramina

premaxillary sac fossabony naré . . .

worn mesethmoid nasal squamosal

occipitalcondyle

frontalfloor of temporal

fossa

erected médian edgeof maxilla

postero-lateral sulcuspremaxillary foramen

antero-median sulcus

temporal fossamédian longitudinal

dépression

Fig. 2 - Schematic drawing of the dorsal view of the skull of Eurhinodelphis longirostris IRSNB 3249-M.342 (holotype), fromAntwerp, ? Antwerp Sands, late early to middle Miocene.

also contacts the supraoccipital on most of its width.However, the nasal is narrower than on the holotype,and a wide part of the frontal is dorsally exposed, latéralto the nasal (see Fig. 3a). The trend to a posterior shift ofthe nasals towards the supraocipital is present on bothspecimens, but variably modelling the bones of the ver-tex. The sagittal section of the vertex of the skull IRSNB3250-M.l 858 allows the observation of the posterior partof the mesethmoid. This bone deeply penetrates the fron¬tal posteriorly below the nasal, nearly reaching the suturewith the supraoccipital (see Fig. 3b).

The supraoccipital shield is convex, only hollowed bya médian longitudinal dépression ending 15 mm before itsanterior margin. This rounded shield is regularly slopingposteriorly, with a mean slope of ca. 35°.

Posterior view. The paroccipital process of the exoc¬cipital is high and narrow. As a conséquence, the occipitalcondyles are elevated, with a ventral margin nearly reach¬ing the level of the floor of the temporal fossa. Thebasioccipital crests are sharp and ventrally shorter thanthe exoccipitals.

Latéral view. The latéral groove of the rostrum starts180 mm anteriorly to the antorbital notch. It is deep andwidens over 100 mm forwardly. Then it progressively

shallows and disappears more than 100 mm posteriorly tothe apex of the rostrum. The maxilla-premaxilla sutureleaves the floor of the groove 250 mm anteriorly to theantorbital notch, 140 mm posteriorly to the apex of themaxilla.

The roof of the orbit is long and lower than the top ofthe temporal fossa. The frontal is roughly as thick as themaxilla. The lacrymal-jugal complex is visible in latéralview for a short length antero-ventral to the preorbitalprocess of the frontal. The elevated zygomatic process ofthe squamosal is stronger than the rounded postglenoidprocess.

Ventral view. The premaxillary part of the rostrumdoes not bear alveoli; the alveolar groove of the maxillaextends in the premaxilla as a thin groove with rectilinearedges precluding the presence of teeth inserted in thebone. The maxillary alveoli are eroded on the holotype,but are preserved on the proximal part of the rostrum ofIRSNB 3250-M.l858. The first alveolus is 30 mm ante¬rior to the antorbital notch. Forty-two deep alveoli arepresent on the first 243 mm of the right side of the rostrumand 40 on the left side. The average diameter is 4-5 mmand the septa are less than 3 mm thick. Considering thelength of the maxilla on the rostrum of the holotype, the

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Systematic revision of Eurhinodelphis longirostris 153

total number ofalveoli on each side should be around 60.On the right alveolar row of IRSNB 3250, the 14thalveolus is distinctly shifted laterally and the 15th,medially, as if the posterior part of the row was pushedagainst the anterior part (see Pl. 2, Fig. 1 c). This mightindicate a trend towards an increase in the number of

maxillary teeth, or more simply a pathology.The palatines are short; their apex extends until 10 mm

beyond the level of the antorbital notches. The thin latéralplate of the palatine contacts the large infraorbital fora-men. This part of the palatine was erroneously identifïedas part of the pterygoid by Abel (1902). The condition ofEurhinodelphis longirostris is similar to that observed inE. cocheteuxi (see Lambert, in press). As in this species,the palatine plate is crossed by a longitudinal crest, whichdisappears anteriorly before reaching the palatine-maxillasuture. Only small fragments of the pterygoid arepreserved anteriorly. The anterior pterygoid fossa clearlyexcavates the palatine anterior to the choana, on a shortdistance (10 to 25 mm).

The jugal-lacrymal complex is only preserved as asmall eroded knob in the bottom of the antorbital notch.The ventral face of the roof of the orbit is hollowed by ashallow sulcus which runs from the large infraorbitalforamen towards the antorbital notch. There is no fossafor the postorbital lobe of the pterygoid sinus, as inEurhinodelphis cocheteuxi, and contrary to Schizodelphismorckhoviensis (see below).

The zygomatic process of the squamosal is anteriorlypointed, with a ventral apical projection for the contactwith the missing jugal. The ventral apex of the postgle-noid process is transversely flattened. The tympanosqua-mosal recess is deep, laterally extending for a short dis¬tance dorsal to the glenoid surface. The recess does nothave a clear anterior limit, extending on the medial sideof the zygomatic process. The falciform process of thesquamosal is not completely preserved. On the holotype,it takes an anterior direction, and is interrupted by atransverse canal, very likely the path for the mandibularnerve V3, exiting in the temporal fossa through the fora¬men 'pseudo-ovale' (see Fordyce, 1994). As the falci¬form process is incomplete, the presence or absence of alatéral lamina of the pterygoid can not be asserted. On theskull IRSNB 3250-M.1858, the anterior part of the falci¬form process is more clearly antero-laterally deflected,along a well developed pterygoid sinus fossa on the ali-sphenoid. This condition, observed on every skull ofEurhinodelphis cocheteuxi, is probably related to the lossor the important réduction of the latéral lamina of thepterygoid (Lambert, in press). The foramina of the basi-cranium are poorly preserved. On the holotype, only thecarotid foramen and the anterior margin of the foramenovale can be observed. On the skull IRSNB 3250-M.1858, the posterior lacerate foramen has an elongatedshape, with a maximal length of 18 mm and a smallmédian constriction. There is no posterior sinus fossa,

maxillafrontal.

mesethmoid

olfactoryforamen

frontalpremaxilla

supraoccipital suture

■•premaxilla-maxillasuture mark

Fig. 3 - Schematic drawings of the right portion of the face of Eurhinodelphis longirostris IRSNB 3250-M.1858, from Antwerp,? Antwerp Sands, late early to middle Miocene, showing the posterior shift of the nasal and mesethmoid, respectivelyabove and through the frontal. A. dorsal view. B. detail of the sagittal section in medial view.

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154 Olivier LAMBERT

external auditory meatuspath mandibular nerve 1 spiny process

zygomatic process^ / foramen ovale

fragment of pterygoidinfraorbital foramen

worn alveolar groove

shallow sulcus'

longitudinal crest'pterygoid sinus fossa'

choanâforamen 'pseudo-ovale'

falciform process"glenoid surface'

tympanosquamosal recess postglenoid process

asioccipital crest >paroccipital process

of exoccipital

Fig. 4 - Schematic drawing of the ventral view of the skull of Eurhinodelphis longirostris 1RSNB 3249-M.342 (holotype), fromAntwerp, ? Antwerp Sands, late early to middle Miocene.

and the surface dorso-medial to the spiny process issmooth and unexcavated.

Comments on specimens from the Calvert Formationreferred to Eurhinodelphis by Myrick (1979, unpublishedthesis)

The only previously published eurhinodelphinid fromthe Calvert Formation (early to middle Miocene of Mary-land and Virginia) is the species 'Eurhinodelphis' bossiKellogg, 1925. In his unpublished thesis, Myrick (1979)also recognized the species 'E.' cristatus in the CalvertFormation, and described four additional new species:'E.' vaughni, 'E.' ashbyi, 'E.' whitmorei and 'E.' morrisi.It is outside the scope of the present study to carry out acomplete systematic revision of the high number ofeurhinodelphinid specimens from the Calvert Formation,but the different species of Eurhinodelphis erected byMyrick (1979) are briefly discussed here.

After 'E.' cristatus, Eurhinodelphis vaughni sensuMyrick, 1979 is the most common species of the genus,with seven skulls identified from the Calvert Formation.In the diagnosis of the species, Myrick (1979, p. 222)gave few characters differentiating it from 'E.' cristatus,

'E.' whitmorei and 'E.' ashbyi: lack of fold on the pos-terior margin of the maxilla along the transverse crest,premaxillae not mesially sloping at the level of the an-torbital notches and supraorbital processes slightly ele-vated. Those characters roughly consist in the main fea¬tures of 'E.' bossi as defined relatively to 'E.' cristatus.And Myrick (1979) could not give différences with 'E.'bossi, probably because of 'the great disparity in mor¬phologie features and morphometrics among the fourspecimens (of 'E.' bossi)'. Actually, the measurementson the skulls of 'E.' vaughni are globally close to 'E.'bossi, and no clear séparation could be found for anymeasurement. The large width of the rostrum at its basesuggested by Myrick (1979) is only measured in onespecimen that slighly exceeds in this respect the largest'E.' bossi. Furthermore, the morphology of the face isvery similar in both groups. I suggest therefore to includethe specimens identified by Myrick (1979) as Eurhino¬delphis vaughni in 'E.' bossi.

It should be noticed that the four specimens identifiedas 'E.' bossi by Kellogg (1925) were found in threedifferent stratigraphie levels of the Calvert Formation,the beds 3, 5 and 10 of Shattuck (1904), and that the

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Systematic revision of Eurhinodelphis longirostris 155

seven specimens of 'E.' vaugni sensu Myrick 1979 cornefrom the beds 12 (six of them) and 13. Supposing a highlyspéculative uniform rate of déposition along the twomillion years duration of the Calvert Formation, Myrick(1979) suggested an average time of 120.000 years forthe déposition of each of the 15 beds of the formation.The morphological variability among 'E.' bossi as de-fined here might then be partially explained by, on oneside, the différence of âge between the beds containingthe different specimens of 'E.' bossi sensu Kellogg,1925, and on the other side the younger age of the bedsproviding the specimens of 'E.' vaughni sensu Myrick,1979.

The species 'Eurhinodelphis' ashbyi sensu Myrick,1979 is based on two partial skulls USNM 244401 andUSNM 244411. It is diagnosed by Myrick (1979, p. 249)as somewhat similar to 'E.' cristatus, with the followingdifférences: probably smaller maximum adult size; pen-tagonal frontals with apex pointed forward between na-sals; larger nasals; more pronounced overhanging of themaxillary plate by the supraoccipital crest; supraorbitalprocesses thick but not protubérant or abruptly elevated.Flowever, the morphology of the vertex is only observa¬ble in one of the specimens and it could easily be ex¬plained by individual variation. Actually, the shape of thefrontals and nasals is close to the Belgian 'E.' cristatusIRSNB 3237 for instance. The longitudinal telescoping ofthe face is also variable, giving a more or less pronouncedélévation of the transverse supraoccipital crest. The élé¬vation of the supraorbital protubérance was shown to bevariable in 'E.' cristatus (e.g. Abel, 1905, p. 118).Furthermore, the size of the face, even if smaller thanthe average for 'E.' cristatus fits the smaller specimens ofthe species, including the Belgian ones. As most of thediagnostic characters of 'E.' cristatus are observed in thetwo specimens of 'E.' ashbyi sensu Myrick, 1979, Ipropose to synonymize this species with 'E.' cristatus.

Eurhinodelphis ' whitmorei sensu Myrick, 1979, basedon the skull USNM 25666, was diagnosed in Myrick(1979, p. 254) by: a smaller maximum size relativelyto E.' cristatus, thicker nasals, premaxillae not mesiallysloping at the level of the antorbital notches and antero-lateral curve of the dorsal margin of the maxilla not asmarked. The skull USNM 25666 presents all the featuresdifferentiating 'E.' cristatus from 'E.' bossi, except its facewhich is longer relatively to its width than on specimensof 'E.' cristatus. That peculiarity, also present on somespecimens of 'E. ' bossi does not seem sufficiënt to create anew species. Because the characters given by Myrick(1979) are variable within 'E.' cristatus, USNM 25666is referred here to that species.

The last species of Eurhinodelphis described byMyrick (1979), E. morrisi, is also based on a singlespecimen, USNM 167622. The diagnosis given byMyrick (1979, p. 270) mainly differentiates it from 'E.'cristatus. This seems correct as the derived charactersof 'E.' cristatus are absent on the skull. But here again,there is no comparison with 'E. ' bossi. The dimensions ofthe skull are globally at the lower limit of the interval

for E. ' bossi (including 'E. ' vaughni sensu Myrick, 1979),and are very close to the skull USNM 171103 (= E.'vaughni sensu Myrick, 1979). Several différences with'E.' bossi appear: lower and flatter supraorbital process;more concave and erected medial plate of the maxillaalong the vertex; absence of medio-anterior point of thefrontals on the vertex. It seems, however, difficult to builda new species on so few characteristics, observed in onlyone specimen. Therefore, the holotype of 'E.' morrisisensu Myrick, 1979 is provisionally referred to 'E.' bossi.

To summarize, the list of species from the genusEurhinodelphis' proposed by Myrick (1979) is re-stricted to two species: 'E.' bossi (including 'E.' vaughniand 'E.' morrisi sensu Myrick, 1979) and 'E.' cristatus(including 'E.' ashbyi and 'E.' whitmorei sensu Myrick,1979). Because those two species are referred here to anew genus described in work in progress, no species ofthe genus Eurhinodelphis - restricted to the species E.cocheteuxi and E. longirostris - is recognized in theCalvert Formation.

Comments about specimens from the Belluno Sandstones(north eastern Italv) referred to Eurhinodelphis bv Pil¬leri (1985)

In 1985, Pilleri described Eurhinodelphis sigmoideuson the basis of a well preserved skull MGPD 26396 fromthe Belluno Sandstones (lower Miocene of northeasternItaly), lacking the apex of the rostrum, the mandible andteeth, but with one tympanic in situ and associated withfive cervical vertebrae and two thoracics. Pilleri gavethe following short justification for the attribution of thespecies to Eurhinodelphis'. ' Taxonomically speaking, thisis a new species, which in view of the essential morpho¬logical features of the skull and the spinal column be-longs to the genus Eurhinodelphis... .' First, it should benoticed here that the schematic drawing of the dorsalview of the skull of Eurhinodelphis sigmoideus sensuPilleri, 1985 presented by Pilleri (1985, fig. 21) bearssome important mistakes: the posterior apex of the pre¬maxillae is much too long and wide, the nasals are toonodulous, narrower than in reality, and the nasals are tooshort on the vertex (see corrected drawing, Fig. 5).

When considering the genus Eurhinodelphis only in¬cluding the species E. cocheteuxi and E. longirostris,E. sigmoideus sensu Pilleri, 1985 is closer to membersof the genus Schizodelphis than to members of the genusEurhinodelphis, with a stronger longitudinal compressionof the vertex correlated to a more erected supraoccipitalshield. But the most striking similarities are in fact ob¬served when comparing E. sigmoideus sensu Pilleri,1985 with Ziphiodelphis abeli, as suggested by Bianucci& Landini (2002). Those two species share the followingcharacters, absent in Eurhinodelphis and Schizodelphis:- Wide and flattened surface of the premaxilla at the

level of the antorbital notches with a médian portionregularly laterally sloping. In Eurhinodelphis and Schi¬zodelphis, this area medial to the antero-medial sulcusis narrower, thicker and less medially elevated, with amore regular triangular shape.

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156 Olivier LAMBERT

Fig. 5 - Corrected schematic drawing of the dorsal view of the skull of Ziphiodelphis sigmoideus (Pilleri, 1985), from Belluno,north-eastern Italy, Belluno Sandstones, early Miocene.

- Thickened antero-dorsal portion of the nasals consti-tuting the highest surface of the vertex.

- Medial plate of the maxilla against the vertex keepingan elevated dorsal margin in a postero-lateral direction,giving the postero-dorsal corner of the skull a more

angular aspect in latéral view.- The ventral view of the right tympanic preserved in situ

on the basicranium of the type of E. sigmoideus sensuPilleri, 1985 (see Pilleri, 1985, Plate 45) has propor¬tions and size close to the tympanic of the holotypeof Ziphiodelphis abeli MGPD 26194 (see Dal Piaz,1977, Plate 3, Fig. 9), anteriorly wider than the morepointed tympanic of Eurhinodelphis cocheteuxiIRSNB M. 1856 (see Lambert, in press), 'E.' bossiUSNM 16581 and Schizodelphis barnesi USNM24413 (both figured in Muizon, 1988a, Fig. 6).The holotype of Eurhinodelphis sigmoideus sensu Pil¬

leri, 1985 is clearly smaller than the holotype of Ziphio¬delphis abeli, with a général size of the facial skull closeto the smallest individuals of 'Eurhinodelphis ' cristatus.lts face is relatively longer than that of Z abeli. Thevertex is slightly more elevated. A small fossa for thepostorbital lobe of the pterygoid sinus nearly reaches theventral face of the roof of the orbit in E. sigmoideus sensuPilleri, 1985, while it is dorsally shorter in the holotypeof Ziphiodelphis abeli. The most striking différence is thedorsal élévation of the premaxillae, forming an elongatedbulge with a maximal height of 28 mm at a level 80-90 mm anteriorly to the antorbital notches. This médianprominence gives the base of the rostrum a sigmoidprofile (inspiring the species name sigmoideus to Pilleri,1985). Those différences seem sufficiënt to excludeEurhinodelphis sigmoideus sensu Pilleri, 1985 fromthe species Ziphiodelphis abeli, and I suggest to place itin the same genus, as Ziphiodelphis sigmoideus.

An additional observation can be made on that skull:the descent of the suture between premaxilla and maxilla

on the latéral surface of the rostrum far before the apex,characteristic of at least the genera Eurhinodelphis, Schi¬zodelphis, and the species 'E.' cristatus, 'E.' bossi, andZiphiodelphis abeli, is visible on the type of Z. sigmoi¬deus. The maximal length of the maxilla on the rostrum isestimated to 510 mm. The ratio between the width of theskull at the level of the zygomatic processes and thatlength is close to the ratio calculated for an undescribedBelgian skull of 'E.' cristatus, and smaller than the ratiofor E. cocheteuxi and E. longirostris. The maxillary partof the rostrum is then relatively longer in Eurhinodelphiswhen compared to E. ' cristatus and Ziphiodelphis.

The second 'Eurhinodelphis ' species from the BellunoSandstones, E. bellunensis sensu Pilleri, 1985, is basedon the skull MGPD 26404, only lacking the very apicalportion of the rostrum, with the two tympanics in situ,several teeth, and associated with its roughly completemandible. Fiere again, the attribution by Pilleri (1985) tothe genus Eurhinodelphis is not supported by characters.

The most striking différences between E. bellunensissensu Pilleri, 1985 and the species of the revisited genusEurhinodelphis are given here. First, the face of E. bellu¬nensis sensu Pilleri, 1985 is relatively longer than that ofE. longirostris and clearly longer than that of E. coche¬teuxi, with a ratio between bizygomatic width of the skulland length of the face from the antorbital notch to theoccipital condyle < 0.9. The maximal width of the pre¬maxillae on the face is smaller, but with closer médianmargins just anteriorly to the external nares. The postero-lateral surface of the maxilla is much less laterally in-clined, with a posterior portion narrower. The nasals arenarrower (relatively to their length) and the frontals are

longer. The occipital shield is strongly concave, while itis roughly flat in E. cocheteuxi and slightly convex in E.longirostris. The ventral margin of the occipital condylesis relatively lower, because of the lower paroccipitalprocess of the exoccipital.

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Systematic revision of Eurhinodelphis longirostris 157

Taken separately, some of the différences here aboveare found in Ziphiodelphis: e.g. the shape of the pre-maxillae anteriorly to the external nares, the concavityof the supraoccipital shield, or the low paroccipitalprocess of the exoccipital. But the face of Eurhinodelphisbellunensis sensu Pilleri, 1985 is proportionally longerthan that of Ziphiodelphis abeli and Z. sigmoideus, andthe proportions of the nasals and frontals are verydifferent on its lower vertex.

In his discussion of the genus Dalpiazina, Muizon(1988a, p. 73) briefly suggested that the holotype ofEurhinodelphis bellunensis sensu Pilleri, 1985 probablybelongs to the genus Argyrocetus. It is also probably tothat specimen that Cozzuol (1996) referred when he iden-tified a species of the genus Argyrocetus from northernItaly. When restricting the genus Argyrocetus to its frag-mentary known Argentinian type-species A. patagonicus,some similarities appear between this species and theholotype of Eurhinodelphis bellunensis sensu Pilleri,1985: a low vertex, with the nasals higher than thefrontals; a weakly erected concave supraoccipital shield;a général latéral view of the mandible roughly similar;most of the measurements relatively close. However, apart of those features are linked to the low rate oflongitudinal telescoping of the skull. And this is clearlya primitive character, placing E. bellunensis sensuPilleri, 1985 and Argyrocetus patagonicus in a basaiposition in the phylogenetic tree of the eurhinodelphinids.Actually, the only portion of the skull of A. patagonicuswhich can be more precisely compared with Eurhinodel¬phis bellunensis sensu Pilleri, 1985 is the vertex. On thisarea, the nasals are more dorso-anteriorly elevated andrelatively wider in Argyrocetus patagonicus, and thefrontals shorter. The anterior portion of the face seemsalso relatively shorter in A. patagonicus. Actually, thistype-species of the genus Argyrocetus seems too frag-mentarily known to allow the inclusion of other species.

Because the holotype skull of Eurhinodelphis bellunen¬sis sensu Pilleri, 1985 is nearly complete, I suggest itsinclusion in a new genus, Mycteriacetus n. gen. This nameis chosen in reference to Mycteria ibis, the African yellow-billed stork, characterized by a long and robust beak similarin latéral view to the rostrum of the eurhinodelphinids.

Mycteriacetus n. gen. is diagnosed by: longer andnarrower supraorbital process of the maxilla, lower vertexand less erected supraoccipital shield relatively toEurhinodelphis, Schizodelphis, and Ziphiodelphis', longeranterior part of the face, vertex more elevated, narrowernodular nasals not antero-dorsally projecting, and longerfrontals on that vertex relatively to Argyrocetus', smallersize, more excavated premaxillary sac fossae, longernasals and shorter frontals on the vertex relatively toMacrodelphinus.

Comments about other specimens referred to Eurhinodel¬phis

The brief review of Fordyce (1983) is discussed here,in addition to comments about more recently describedspecimens.

The fragment of rostrum constituting the holotype ofthe Miocene Sardinian species Eurhinodelphis sassarien-sis sensu Capellini, 1887 is undiagnostic as suggested byAbel (1931), Myrick (1979), and Bianucci et al. (1994).The palate seems flatter than in eurhinodelphinids, with arostrum relatively wider at its base and a faster anteriornarrowing.

The holotype of E. pacificus sensu Matsumoto, 1926,Middle Miocene of Japan, is an anterior fragment ofrostrum with the corresponding mandible in situ. Theauthor justified the attribution to the genus Eurhinodel¬phis by the fact that the premaxillae are longer than themaxillae and do not bear teeth. The anterior lowering ofthe maxilla in latéral view is much stronger than inEurhinodelphis and other eurhinodelphinids for whichthis area is known. This feature gives the ventral marginof the maxilla on the rostrum a very convex shape, andallows to suggest that the premaxilla was not much longerthan the maxilla. Actually, the mandible fragment mighthave been anteriorly shifted relatively to the rostrum,giving the impression of premaxillae much longer ante¬riorly. This undiagnostic fragment shows more similari¬ties with delphinoids than with eurhinodelphinids, ac-cording to the opinion of Abel (1931) who excluded itfrom the genus Eurhinodelphis.

The holotype of E. salentinus Zei, 1950, from the Mio¬cene of Pietra leccese (Apulia, Italy), is a skull too frag-mentary at the level of the face to give a generic attribu¬tion. Zei (1950) described the maxillae as occupying 3/5 ofthe length of the rostrum. This character is sufficiënt toplace the specimen in the family Eurhinodelphinidae. Itwas placed by Bianucci & Landini (2002) in cf. Argy¬rocetus salentinus but no common diagnostic feature couldbe noticed from the figures of Zei (1950) with the type¬species of the genus Argyrocetus, A. patagonicus.

Another partial skull from the Pietra leccese was iden-tified by Bianucci et al. (1994) as Eurhinodelphis cris-tatus sensu Abel, 1902. This skull lacks the thickening ofthe maxilla on the roof of the orbit and the forwardsindentation of the supraoccipital and frontal on theposterior edge of the maxilla laterally to the vertex, bothcharacters defining the species 'E.' cristatus. This skullshows actually more similarities with 'E.' bossi and itsmeasurements fit well with the variability observedamong the individuals of that species. However, E.' bossiis quite difficult to diagnose relatively to E.' cristatus, asno clearly derived characters are isolated for the firstspecies. Furthermore the skull from Pietra leccese is notwell preserved and no information is available on thedetails of the basicranium. The strong flattening of theface might also hide characteristics of E.' cristatus.Therefore, the Pietra leccese specimen is referred to E.'aff. bossi.

The partial odontocete skull from the late Miocene ofPortugal reported by Da Mata (1963) as Eurhinodelphiscf. cristatus sensu Abel, 1902 lacks all the diagnosticcharacteristics of the species, contradicting Myrick(1979, p. 13). Even its attribution to the family Eurhino¬delphinidae is denied here. The morphology of the vertex,

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158 Olivier LAMBERT

with a strong transversal pinching of the frontals behindwider nasals and the loss of contact between the posteriorapex of the premaxillae and the ffontals might indicateaffinities with some kentriodontids, e.g. Liolithax pappus(see Kellogg, 1955; Barnes, 1978).

As suggested by Fordyce (1983), the periotic from theMiocene 'faluns' of Touraine and Anjou (France) identi-fied by Ginsburg & Janvier (1971) as Eurhinodelphissp. lacks several features present in the family Eurhino-delphinidae, for example the well excavated anteriorbullar facet. It was actually compared by Ginsburg &Janvier (1971) to the physeterid periotic from Antwerperroneously reported by Abel (1902, pl. 17, figs. 11-12)to Eurhinodelphis longirostris. The periotic of the 'fa-luns' shows similarities with kentriodontids such as Lio¬lithax pappus (Kellogg, 1955) (see Barnes, 1978,figs- lj-2j).

The holotype of Eurhinodelphis minoensis sensu Oka-zakj, 1976 from the early to middle Miocene of Japan is apartial mandible associated to vertebrae, ribs and de-tached teeth. Those fragments are not diagnostic at ageneric level and no character allows a strict attribu¬tion to the family Eurhinodelphinidae. Eurhinodelphisminoensis sensu Okazaki, 1976 should therefore beconsidered as Odontoceti incertae sedis.

From the same fonnation, Okazaki (1976) described apartial skull with a periotic and placed it as Eurhinodel¬phis sp. [erroneously discussed by Fordyce (1983) as aspecimen of Eurhinodelphis minoensis]. The periotic wascompared by Fordyce (1983) to kentriodontids. Theskull is very incomplete and the reconstruction of thevertex by Okazaki (1976, fig. 4) is doubtful. Fromplate 2, figure 3, there are no contradictions to the ken-triodontid affmities of the periotic, excluding the speci¬men from the family Eurhinodelphinidae. An additionalisolated periotic identified as Eurhinodelphis sp. by Oka¬zaki (1976, pl. 2, fig. 1) might also belong to a kentrio-dontid. It is referred here, as the fïrst one, to the super-family Delphinoidea sensu Muizon (1988b).

The cervical vertebra from the early Miocene ofCatalonia, Spain, identified by Pilleri (1988) as Eurhi¬nodelphis sp. (cf. E. sigmoideus) is probably not diag¬nostic at the generic level, as already suggested by Bia-nucci & Landini (2002) who considered it as Eurhino¬delphinidae indet. From the systematic revision of thegenus Eurhinodelphis, 1 only recognize the speciesE. cocheteuxi and E. longirostris, for which no associatedcervical vertebra are known.

Systematic discussionMuizon (1988a, p. 40-41) differentiated the Belgian

specimens front the American specimens of Schizodel-phis longirostris, contradicting Myrick (1979), by a listof cranial characters: shape and position of the nasals,height of the mesethmoid, excavation of the premaxillarysac fossae and their élévation towards the vertex, mor-phology of the base of the rostrum. From the observationof the Belgian specimens, most of those différences are

present in the holotype of Eurhinodelphis longirostris

IRSNB 3249-M.342 (see description above), but theyare absent in the second most complete specimen ofE. longirostris sensu Abel, 1902, IRSNB 3235-M.343:- While the nasals of the holotype of E. longirostris are

in contact with the supraoccipital, 15 mm separatethose bones from the supraoccipital on IRSNB 3235-M.343.

- The mesethmoid of IRSNB 3235-M.343 reaches theantero-dorsal margin of the nasals, but this character isalso observed in some American specimens.

- The élévation of the premaxillae towards the vertex ofIRSNB 3235-M.343 begins more posteriorly and ismore abrupt than in the holotype of E. longirostris,as is the case in the American specimens.

- The premaxillary sac fossae of IRSNB 3235-M.343are distinctly more concave than in the holotype ofE. longirostris, as is the case in the American speci¬mens.

- The left side of the rostrum of IRSNB 3235-M.343 isinterrupted 140 mm anteriorly to its base, and itsslightly medially compressed right side shows a slighttransverse swelling, probably homologous to the swel-ling described by Muizon (1988a) for the Americanspecimens.In fact, it seems that, in his comparison of the Belgian

and American specimens, Myrick (1979) referred moreto the skull IRSNB 3235-M.343, well figured in dorsaland ventral view by Abel (1902, pl. 14, figs. 1-2), than tothe holotype of E. longirostris IRSNB 3249-M.342.

IRSNB 3235-M.343 should be excluded from E. lon¬girostris, and referred to the same genus as the Americanspecimens, Schizodelphis. This skull IRSNB 3235-M.343was first described by du Bus (1872) as the only speci¬men of the species Priscodelphinus morckhoviensis (andthus the holotype). It was not figured by du Bus (1872),but the fact that it is identifiable from his description, andthat it is well preserved and associated with a periotic anda fragment of tympanic bulla, leads to recognize IRSNB3235-M.343 as the holotype of Schizodelphis morckho¬viensis (see below).

Schizodelphis Gervais, 1861

Type species. Schizodelphis sulcatus (Gervais, 1853)lncluded species. S. sulcatus, ? S. barnesi Muizon,

1988a, and S. morckhoviensis (du Bus, 1872)Diagnosis. This genus differs from:

- Eurhinodelphis in: maxillary part of the rostrum rela-tively shorter; vertical medial plate of the maxi 11aalong the vertex less antero-dorsally developed; con¬cave supraoccipital shield; less elevated and widerparoccipital process of the exoccipital, with loweroccipital condyles (ventral margin of the condylesmuch lower than the level of the floor of the temporalfossa); more excavated premaxillary sac fossa; zygo-matic process of the squamosal lower in latéral viewand wider in ventral view; presence of a small fossa forthe postorbital lobe of the pterygoid sinus on the ven¬tral surface of the supraorbital process.

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Systematic revision of Eurhinodelphis longirostris 159

- Ziphiodelphis in: narrower and thicker triangular sur¬face of the premaxilla medially to the premaxillaryforamen lacking the more regular flatness and latéralslope seen in Ziphiodelphis; vertical medial plate of themaxilla along the vertex less postero-dorsally ex-tended, giving the postero-dorsal outline of the skulla more rounded aspect in latéral view; narrower vertexwith narrower nasals lacking the antero-dorsal projec¬tion characterizing Ziphiodelphis.

- Argyrocetus and Macrodelphinus in: more elevatedand more transversely compressed vertex with nar¬rower nasals; more erected supraoccipital shield closeto the vertical.

- Mycteriacetus n. gen. by: relatively wider and shorterface; more elevated vertex with frontals shorter thanthe nasals; more vertical supraoccipital shield.

Schizodelphis morckhoviensis (du Bus, 1872)

* 1872 Priscodelphinus morckhoviensis du Bus, p. 495.v. 1872 Priscodelphinus pulvinatus du Bus, p. 496.v. 1880 Priscodelphinus morckhoviensis Van Beneden &

Gervais, p. 495.v. 1902 Eurhinodelphis longirostris Abel, pl. 14, figs. 1-2,

pl. 17, fig. 5, pl. 18, fig. 2.v. 1979 Rhabdosteus longirostris Myrick, pl. 19, figs. b-d,

pl. 20, figs. a, c and d, pl. 21, fig. b, pl. 22, fig. b andfig. 10 (unpublished).

v. 1988a Schizodelphis longirostris Muizon, p. 45, figs. 7a and8a.

Diagnosis. Schizodelphis morckhoviensis differs from thetype-species S. sulcatus in its rostrum being higher at thelevel of its base. Apart from that feature, no clear diag¬nostic character could be isolated, mainly because of theincompleteness of the holotype of 5. sulcatus (see com-parison below).

S. morckhoviensis differs from the possibly valid spe¬cies S. barnesi in: a less transversely compressed vertexwith relatively wider frontals; nasals wider than long; themédian margin of the maxilla along the vertex distinctlymore latéral than the latéral margin of the bony nare(those two margins are roughly at the same level inS. barnesi).

Holotype. IRSNB 3235-M.343, a well preserved skull,associated with the left periotic (figured by Muizon,1988a, p. 45, figs 7-8) and a fragment of left tympanic,lacking the anterior part of the rostrum, the teeth andfragments of the basicranium (found June the 4th 1861,holotype of Priscodelphinus morckhoviensis sensu duBus, 1872, individual 4 of Eurhinodelphis longirostrisin Abel, 1902, figured in pl. 14, figs 1-2 and 17, fig. 1).

Referred specimens. IRSNB 3239-M.345, a partialskull (holotype of Priscodelphinus pulvinatus sensu duBus, 1872 and individual 6 of Eurhinodelphis longiros¬tris sensu Abel, 1902); IRSNB M.1859, a left tympanicbulla associated with a malleus {found by R. Marquet inJune 1996, in Antwerp, on the excavations for a car parknear the Keyzerlei (under the Rex cinema)}; and at leastthe individuals USNM 21291, USNM 187306, USNM

167676, from the east coast of the USA, identified byMyrick (1979) as Rhabdosteus longirostris.

Discussion. The partial skull IRSNB 8343Z-M.1860(PI. 5, Figs a-b, found in Kessel, 18 km south-east ofAntwerp, January the 30st 1913, lacking the apical portionof the rostrum and the squamosals) shares characters withmembers of the genus Schizodelphis: very low occipitalcondyles and probably concave dorso-median surface ofthe supraoccipital. However, it seems to lack a fossa forthe postorbital lobe of the pterygoid sinus, and the pos-tero-median plate of the maxilla might be less concavethan in that genus. Nevertheless, the préservation state -numerous small plates of bone separated by intervalsfïlled with sediment, very different from the previouslydescribed specimens from Antwerp, precludes good esti¬mations of the three dimensional morphology. It seemstherefore more conservative to place IRSNB 8343Z-M.1860 in Eurhinodelphinidae aff. Schizodelphis.

Locus typicus. The holotype was found on June 4,h1861, in Antwerp, and the locality cited by Abel (1902) is'Je Section'. This section is situated north-east to the4e section where the holotype of Eurhinodelphis longi¬rostris was found, also along the present motorwayaround the city.

Stratum typicum. No data are avalaible for the holo¬type. The tympanic bulla IRSNB M.1859 was found inthe Antwerp Sands, late early to middle Miocene(Louwye et al. 2000). The specimens USNM 21291,USNM 187306 and USNM 167676 all come from theCalvert Formation, and more precisely from the beds 3,11 and 12 respectively, as defmed by Shattuck (1904)(see Myrick, 1979). Those beds are late early to middleMiocene of age (Verteuil & Norris, 1996, fig. 4).

Redescription of the holotype of S. morckhoviensisIRSNB 3235-M.343

Skull (PI. 2, Figs 2a-b ; PI. 3; Figs. 6-9)The following parts of the skull are missing: apical part

of the rostrum, right preorbital process, fragments of themaxillae on the face, fragments of the supraoccipital andof the parietals, the right zygomatic process, and a majorpart of the pterygoids. The teeth are lost, as on most of theeurhinodelphinids from Antwerp. The right periotic andthe fragmentary right tympanic were detached from theskull after the description of Abel (1902). The mainmeasurements are given hereafter (Table 2). This skullis slightly smaller than the holotype of Eurhinodelphislongirostris.

Dorsal view. The rostrum is preserved for only200 mm. The flattening of the premaxilla towards thebase of the rostrum is located on the latéral part of thatbone, which has a dorsal level roughly the same as thebordering maxilla at the level of the antorbital notch.Medially, the elongated and raised rugous triangular plateof the premaxilla, limited by the antero-median sulcus,reaches the dorsal level of the preorbital surfaces of themaxillae. The premaxillary foramen, slightly more pos-terior than the antorbital notch, is followed by a markedpostero-lateral sulcus and a shallow postero-median sul-

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160 Olivier LAMBERT

Table 2 - Measurements on skulls ofSchizodelphis morckhoviensis and ? S. barnesi. Measurements are in millimétrés, (e) indicatesestimate, '+' nearly complete, and no data. The four first specimens are placed in Schizodelphis morckhoviensis, andthe three last (USNM 244403, 187312 and 187317) in the possibly valid 5". barnesi.

Measurements on the skulls of Schizodelphismorckhoviensis and 1S. barnesi

IRSNB3235-M.343

USNM21291

USNM187306

USNM167676

1S. barnesiUSNM244403

1S. barnesiUSNM187312

1S. barnesiUSNM187317

3. length anterior orbit-posterior skull 170 172 175 165 177 160 1524. length anterior supraoccipital-anterior orbit 120 120 107 102 125 117 1205. length orbit 67 61 - - 61 e56 e538. width base rostrum 93 88 91 - 106 87 899. width premaxillae base rostrum 56 61 59 - 53 46 44

10. width skull postorbital processes 185 e202 - el 86 214 178 17611. width skull zygomatic processes 187 - 185 el 77 201 184 17712. width bony nares 32 26 28 20 24 e23 2213. width nasals 52 43 36 34 26 26 2314. maximal posterior premaxillary width 73 80 76 68 72 72 6915. minimal posterior distance between maxillae 60 68 57 43 34 28 2416. width medio-ventral margins exoccipitals 102 - 98 89 95 91 8817. width latéral margins occipital condyles 80 74 80 83 73 78 7418. width inner margins occipital condyles 34 35 36 37 30 - 3319. height cranium 150 - -

- - - -

21. height base rostrum 60 53 e63 - 55 _ e5022. height temporal fossa 58 - 39 - - - _

23. height ventral margin occipital condyles 22 - 32 26 e20 _ 2224. height occipital condyles 42 - 38 39 36 - 37

bony nare

premaxillarysac fossa

postero-lateral sulcus

postero-median sulcuspremaxillary foramen

antero-median sulcusmesorostral groove

mesethmoidnasal

frontals

latéral grooveinfraorbital foramina

premaxillajugal

antorbital no'tch

preorbital processfrontal

supraoccipital

squamosal protubérance formaxilla max'"ary foramen m- semispinalis

Fig. 6 - Schematic drawing of the dorsal view of the skull of Schizodelphis morckhoviensis 1RSNB 3235-M.343 (holotype) fromAntwerp, ? Antwerp Sands, late early to middle Miocene.

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Systematic revision of Eurhinodelphis longirostris 161

eus. The premaxillary sac fossa is relatively short, con¬cave, with a laterally sloping médian portion partiallycovering the mesethmoid in front of the bony nares.The élévation of the premaxilla towards the vertex isaccentuated on the last centimetres. The posterior apexof the premaxilla extends at least farther than mid-lengthof the nasal, and exhibits a wide contact with the frontal.The shape of the suture between premaxilla and frontal isprobably less clearly defined than suggested by the figureof Abel (1902, pl. 14, fig. 1).

The antorbital notch is short and wide. The narrow con¬

cave medial plate of the maxilla along the latéral edge of thevertex is abrupt. The posterior margin of the bone is alsoelevated against the supraoccipital shield, forming a thickpostero-laterally directed crest. This crest extends posteriorlyfarther than the anterior margin of the supraoccipital.

The nasals are wider than long, higher than the frontals,with a smoother dorsal surface, slightly sloping ante-riorly. They are anteriorly margined by the posterior plateof the mesethmoid, only partially preserved. However,fragments applied on the anterior face of the nasals showthat the plate was reaching the level of the antero-dorsaledge of the nasals. Without those small and thin frag¬ments, not connected to the more ventral part of the plate,it would have been concluded that the mesethmoid islower than the nasals. On the postero-lateral corner ofthe bony nare, at the junction between mesethmoid andmaxilla under the level of the premaxilla, is a thin laminaof the maxilla medially limiting a small rounded fossa(PI. 2, Fig. 2a ; Fig. 7). This fossa is antero-ventrallyfollowed by a short sulcus along the mesethmoid. Thishollowed space of the maxilla inside the bony nare is toolatéral relatively to the terminal nerve foramina observedin for instance Tursiops (Rommel, 1990, fig. 2) to be

directly correlated to an olfactory function. lts positionseems to be homologous to that of a small foramenobserved in several odontocetes, ventrally exiting onthe orbit roof, in the posterior portion of the large infra-orbital foramen (observed in Mesoplodon), or justposterior to that foramen (in Tursiops or Delphinus). Itwould then correspond to the additional dorsal exit frontthe infraorbital complex described by Rommel (1990,p. 36) on the latéral aspect of the internai bony nares ofTursiops, and considered as an arterial foramen, probablyjoined to a branch of the infraorbital nerve. A smallforamen is indeed localised on the ventral surface of theorbit roofof IRSNB 3235-M.343, 5 mm posteriorly to thelarge infraorbital foramen.

The dorso-medial part of the supraoccipital shield isstrongly concave with a vertical wall against the frontalsfor more or less 10 mm. The ventral two thirds of the shieldare globally convex towards the occipital condyles, with asagittal groove. Well developed circular protubérances arepresent on the dorsolateral areas of the supraoccipitalshield for the insertion of the muscle semispinalis.

Latéral view. The suture between maxilla and pre¬maxilla on the rostrum is hollowed by a deep longitudinalgroove anteriorly following a dorsal infraorbital foramenpiercing the maxilla 50-60 mm anteriorly to the antorbitalnotches. The rostrum is too incompletely preserved toestimate the apical shape of the suture - and therefore therelative length of the maxillae and premaxillae. The frontalpart of the preorbital process is moderately thickened,while the maxilla is very thin in that région. The roof ofthe temporal fossa is slightly higher than the roof of theorbit.

The zygomatic process of the squamosal is thick inlatéral view, stronger than the narrow lobe of the post-

mesethmoid

mesethmoii

short sulcus

premaxillary sac fossa

.maxilla

bony'nare / lamina medially limitinga small fossa

partially broke'n dorsalopening of the fossa

Fig. 7 - Schematic drawing of the bony nares of Schizodelphis morekhoviensis IRSNB 3235-M.343 (holotype), from Antwerp,? Antwerp Sands, late early to middle Miocene, in right dorso-lateral view, with the detail of a small fossa on the left side.

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162 Olivier LAMBERT

palatinevomer

alveoli

fossa for postorbital lobe of pterygoid sinus? fossa for preorbital lobe

ventral exit for arterial foramen in bony nareantorbital notch

jugal

contact with jugaloptic canal \ P^rygoid

tympanosquamosal recessparoccipital process

of exoccipital

fossa for anterior sinus

-oo °maxilla

vomer

? area for muscle insertioninfraorbital foramen

fossa for pterygoid sinuschoanâ

path for mandibularnerve V3

foramen ovalebasioccipital crest

extërnal auditory meatusfalciform process posterior lacerate foramen

Fig. 8 - Schematic drawing of the ventral view of the skull of Schizodelphis morckhoviensis 1RSNB 3235-M.343 (holotype), fromAntwerp, ? Antwerp Sands, late early to middle Miocene.

glenoid process. The occipital condyles are strongly pro¬tubérant, with a long distinct condylar pedicle.

Posterior view. The dorsal margin of the supraoccipitalshield is regularly rounded. The paroccipital process ofthe exoccipital is relatively low and wide (when com-pared for example with Eurhinodelphis longirostris),slightly shorter ventrally than the thick basioccipitalcrests. The occipital condyles are very low, with a ventralmargin much lower (ca. 30 mm) than the floor of thetemporal fossa.

Ventral view. The first small alveolus appears at 75 mmof the antorbital notch. It has a diameter of 3 mm and is

separated from the next one by a septum of 3 mm. On theright side, 16 alveoli are present on a length of 118 mm.The last one has a diameter of 5 mm, and is separatedfrom the previous one by a septum of 4.5 mm. Thevomer is ventrally visible through a fenestra betweenthe maxillae, with a maximal width of 7 mm.

The palatines are long and narrow on the base of therostrum, with a pointed apex 55 mm anterior to theantorbital notches. The médian additional curve drawnon the palate of the specimen to limit a smooth andslightly excavated surface (see Abel, 1902, pl. 14,fig. 2) probably corresponds to an area of insertion ofmuscles (and not to the insertion of a sinus, as proposedby Abel, 1902, pl. 18, fig. 2). The finger-like latéral curvecorresponds to the limits of a fossa for the anterior sinus.This well defmed narrow fossa medially borders the baseof the jugal, with the apex 30 mm anterior to the antorbi¬tal notches. This fossa has a shape and position similar

to the anterior sinus of delphinids such as Tursiops orDelphinus (Fraser & Purves, 1960, fig. 25 and plates44-46), but with a more limited extension. It should benoticed that the anterior sinuses of Tursiops and Delphi¬nus are not always positioned in well defined and deepfossae as those described on the specimen IRSNB 3235-M.343. The fossa for the pterygoid sinus on the palatinereaches anteriorly the level of the antorbital notches. Thepterygoids are lost in that région of the skull.

The base of the jugal is antero-medial to the antorbitalnotch. The lacrymal is partially lacking and the lacrymal-maxilla suture is not visible.

The optic canal is posteriorly bordered for its mostmedial part by a deep fossa, at the junction between thelatéral wall of the cranial cavity and the roof of the orbit.This fossa, laterally limited by a crest, is homologous tothe fossa for the postorbital lobe of the pterygoid sinusobserved in 'Eurhinodelphis ' cristatus. lts shorter latéraldevelopment on the specimen IRSNB 3235-M.343 isconsidered as primitive relatively to 'E.' cristatus, butmore derived than in Eurhinodelphis (as defined here).A slightly concave and smooth surface, anterior to theoptic canal and at the same transverse level than thatfossa, might be a shallow fossa for the preorbital lobeof the pterygoid sinus.

The ventral surface of the zygomatic process is wideand flat, with the exception of a protubérance indicatingthe contact with the jugal. The glenoid surface is wide,pointed towards the apex of the postglenoid process. Thetympanosquamosal recess is well excavated and ante-

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Systematic revision of Eurhinodelphis longirostris 163

squamosal

basioccipital crestbasioccipital

shallow dépressionposterior lacerate

foramen

exoccipitalparietal

? area of contact

with ear bones

external auditory.meatus

postglenoid process

glenoid fossa

carotid foramen

pterygoidalisphenoid

pterygoid sinus fossa■foramen ovale

path for mandibularnerve V3

falciform process■foramen 'pseudo-ovale'

tympanosquamosalrecess

zygomatic process

Fig. 9 - Detail of the left side of basicranium of Schizodelphis morckhoviensis IRSNB 3235-M.343 (holotype), from Antwerp,? Antwerp Sands, late early to middle Miocene in ventro-lateral view.

riorly limited to the anterior margin of the roof of thetemporal fossa. The falciform process of the squamosal ishigh and antero-medially developed. By comparison withbetter preserved specimens of Schizodelphis from theCalvert Formation (e.g. USNM 187211), this morphologyclearly indicates a contact with a complete latéral laminaof the pterygoid.

On the alisphenoid, the small foramen ovale (diameterof 4-5 mm) is followed latero-anteriorly by a sulcus(path for mandibular nerve V3 sensu Fordyce, 1994)that pierces the dorsal surface of the alisphenoid after8-9 mm. It emerges in a small cavity dorso-median to thefalciform process of the squamosal, pierces the latéralwall of that cavity, and reaches the roof of the temporalfossa dorsally to the falciform process (= foramen 'pseu¬do-ovale'). The cavity is probably a dorso-posterior ex¬tension of the pterygoid sinus fossa in the alisphenoid,which is not preserved here. The carotid foramen, locatedon the latéral face of the basioccipital crest at thelongitudinal level of the foramen ovale, is surroundedby a slightly depressed and smooth area. The posteriorlacerate foramen might be more or less completelydivided in a smaller posterior and a larger anterior portionby a transverse septum.

Before removal by Muizon (pers. comm.), the leftperiotic and tympanic were firmly fixed to the basicra¬nium (see Abel, 1902, plate 14, fig. 2). Flowever, theposition of the ear bones at that time was already the factof a replacement, as a number written by Abel or an olderauthor appears on the dorsal face of the periotic. Never-

theless, the breaks on the basicranium and ear bonessuggest that the attachment was made by the posteriorprocesses of the periotic and tympanic at the level of theposterior meatal crest and post-tympanic process of thesquamosal. No dépression excavates the squamosal dor¬sally to the spiny process or the anterior surface of theparoccipital process of the exoccipital.

Ear bones (Pl. 4; Figs. 10-11)Periotic. The complete left periotic of IRSNB 3235-

M.343, figured by Muizon (1988a, figs. 7a-8a), has atotal length of 35 mm. The slender and long anteriorprocess is hollowed in ventral face by a very long anddeep anterior bullar facet. This groove is occupied onmore than the two thirds of its length by a fragment of theprocessus tubarius of the tympanic, indicating a firmcontact of the two bones at that level. The elongatedaccessory ossicle is also preserved, medially to the facet.In latéral view, the anterior process is pointed, with a baseslightly widened by a small tubercle that follows poster-iorly the low dorsal crest. The moderate sized latéraltuberosity has an angulated latéral margin, and is asseparated from the anterior process as for example inEurhinodelphis cocheteuxi. The mallear fossa is wellindividualized. The hiatus epitympanicus is wide andshallow, nearly continuous with the posterior bullar facetsurface. That ventral surface of the posterior process iswide, medio-ventrally and postero-latero-ventrallycurved, elongated in a ventrally to ventro-lateral direc¬tion. It is separated from the pars cochlearis by a widespace including the facial sulcus and the stapedial muscle

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164 Olivier LAMBERT

dorsal

articular rim postcnor processmed

aperture forcochlear aqueductA

fenestra rotunda

stapedial muscle fossa

facial sulcus.

dorsal keel.

posterior bullar facetfossa inc'udis

pars cochlearis

fenestra ovalis

ventral foramenof facial canal

accessory ossicleanterior bullar

facet

_ tractus spiralis foraminosusD internai auditory

meatus

thin septum

foramen singulare

facial canal

fragment of' mallear fossa\ processus tubarius

latéral tuberosity med

anterior process

aperture forendolymphatic duct

dorsal crest

small tubercule

hiatus epitympanicuslatéral tuberosity

Fig. 10 - Schematic drawings of the left periotic and tympanic of Schizodelphis morckhoviensis IRSNB 3235-M.343 (holotype),from Antwerp, ? Antwerp Sands, late early to middle Miocene. A-B. left periotic. A. ventral view. B. dorsal view. C. lefttympanic in médian view.

fossa. The small fossa incudis, located on the anteriorapex of the posterior bullar fossa, is antero-ventrallyoriented. The dorsal face of the posterior process bearsan acute keel, progressively lowering and widening to-wards the internai auditory meatus. The keel delimits,with the médian margin of the posterior bullar facet, awide and concave médian surface of the process. A lowridge on the ventro-lateral edge of the posterior process,just posterior to the hiatus epitympanicus, probably cor¬responds to the articular rim discussed by Muizon (1987)on platanistids and squalodelphinids, and by Fordyce(1994) on Waipatia.

The pars cochlearis is relatively small, regularlyrounded and medio-laterally flattened in ventral view.The fenestra rotunda is roughly circular, with a slightmedial elongation and a very shallow groove towards theaperture of the cochlear aqueduct. The latter is large,located on the medio-posterior area of the pars cochlearis,with an opening dorsally oriented. The aperture for theendolymphatic aqueduct is small and circular, medial tothe anterior extremity of the dorsal keel of the posteriorprocess, at the transverse level of the tractus spiralis

foraminosus. The latter is included in the antero-laterallyelongated internai auditory meatus. The meatus nearlyreaches the pars cochlearis-anterior process contact. Inthe meatus, the small foramen singulare and the moreanterior facial canal are clearly separated from the tractusspiralis foraminosus by a thin longitudinal septum.

Tympanic bulla. The only preserved parts of the lefttympanic bulla of IRSNB 3235-M.343 are the médianhalf of the bone and the posterior process. At least twolevels of break between the involucrum and the posteriorprocess were previously approximately repaired; the re¬lative orientations of those two parts could therefore notbe described. The total length of the bone (without theposterior process) is more than 33 mm, with a maximalheight of the involucrum of 14 mm. The inner posteriorprominence is narrow in ventral view, laterally marginedby a well marked groove, probably ending at 22 mm fromthe posterior limit of the bone. The dorsal margin of theinvolucrum is high and parallel to the ventral margin for13 mm. More anteriorly, the involucrum strongly narrowstransversely and the dorsal margin descends progres¬sively ventrally, without indentation. The posterior pro-

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Systematic revision of Eurhinodelphis longirostris 165

cess is rectangular and convex in postero-medial view.Irregular surfaces on the postero-lateral and anterolateralsurfaces and a relatively long process indicate a more orless strong attachment to the basicranium.

A second lefit tympanic IRSNB M. 1859 (Pl. 4,Figs. 2a-d), found in situ in the Antwerp Sands, isassociated with the corresponding malleus (Pl. 4,Figs. 2e-f; Fig. 11). The involucrum of this tympanic isroughly identical to that of the holotype of Schizodelphismorckhoviensis. The tympanic, only lacking the posteriorprocess, has a total length of 38 mm and a width of22.5 mm. The médian groove is deep and antero-laterallydeflected. The inner posterior prominence is distinctlyshorter and narrower than the outer one. There is no

anterior spine and antero-lateral concavity. The dorsalmargin of the involucrum is flat for 16 mm, then itdescends progressively anteriorly, without indentation,until a 4-5 mm long thin lamina. The sigmoid processis regularly transversely oriented, with a rounded postero-ventral margin. The latéral furrow is long, narrow anddeep. The similarities with S. morckhoviensis IRSNB3235-M.343 at the level of the involucrum and inner

posterior prominence are also present on the isolatedtympanic of S. cf. sulcatus figured by Muizon (1988a,fig. 6c-d). No tympanic or période is known for Eurhi¬nodelphis longirostris, precluding a comparison with thisroughly similarly sized species.

The associated malleus has a robust processus gracilis,with a long contact to the base of the sigmoid process ofthe tympanic. The malleus has a total length of 5.3 mm inpostero-medial view, including 3.7 mm for the articularfacets. The tuberculum is then relatively short, and morepointed than in Eurhinodelphis cocheteuxi, 'E.' cristatusand 'E.' bossi. The manubrium is slightly higher than theprocessus muscularis. This malleus is close to the onesreferred by Muizon (1988a, figs. 5a-b) to Schizodelphis

sulcatus (MNFfN RL 11 ) and S. cf. sulcatus (none of themis articulated to a skull).

Comparison with the holotype ofSchizodelphis sulcatusAs suggested by Muizon (1988a), the holotype of

Schizodelphis sulcatus MNFIN RL 12 has a relativelyflattened rostrum base, with a height of 46 mm at thelevel of the antorbital notches. This is less than the 60 mm

measured on the skull IRSNB 3235-M.343, with a similargénéral size. This character is very variable among theAmerican specimens of Schizodelphis. For example, inthe group F of the species Rhabdosteus (= Schizodelphis)hruschkai sensu Myrick (1979), one skull has a height ofthe rostrum at the level of the antorbital notches of47 mm,and the other one of 63 mm, for a général size of the skulldiffering very little.

The second différence between S. sulcatus and theAmerican and Belgian Schizodelphis sensu Muizon(1988a) is, according to Muizon (1988a), the more slen-der and less thick zygomatic process of the squamosal.This différence is clearly present between S. sulcatus andthe Belgian Eurhinodelphis longirostris as revised here.However, the squamosal ofSchizodelphis morckhoviensisIRSNB 3235-M.343 has a zygomatic process very similarto that of S. sulcatus, flattened in latéral view and wide inventral view.

Additional measurements taken on both the holotypeof S. sulcatus and IRSNB 3235-M.343 give very similarsize and proportions. Actually, the size différences for theface and basicranium between those two specimens al-most never exceed 6-7 mm, with the exception of theheight of the base of the rostrum. Among other dif¬férences, the fossa for the postorbital lobe of the pterygoidsinus is deeper in IRSNB 3235-M.343, and the dépressionfor the preorbital lobe is less individualized. The absenceof informations about the vertex and the dorsal part of the

A B

processus muscularis manubrium

tuberculum

articular facets

processus gracilis

broken contact with

tympanic bulla

Fig. 11 - Schematic drawings of the detached left malleus of Schizodelphis morckhoviensis IRSNB M.1859, from Antwerp,Antwerp Sands, late early to middle Miocene. A. postero-median view. B. postero-ventral view.

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166 Olivier LAMBERT

supraoccipital shield of S. sulcatus precludes deepercomparison. I assume those two specimens to be similarenough to be placed in the same species, but the frag-mentary state of the holotype of S. sulcatus and its lowerrostrum base lead us to retain IRSNB 3235-M.343 in a

distinct species of the same genus, S. morckhoviensis.

Comparison with the American SchizodelphisConsidering the transfer of some Belgian specimens to

the genus Eurhinodelphis, the restricted species Schizodel¬phis morckhoviensis is compared to the skulls from theCalvert Formation placed in Rhabdosteus (= Schizodelphissensu Muizon, 1988a) longirostris by Myrick (1979).

The holotype of Schizodelphis morckhoviensis IRSNB3235-M.343 has skull measurements very close to thoseof the American specimens USNM 21291, USNM187306 and USNM 167676, all of them identified asRhabdosteus (= Schizodelphis) longirostris by Myrick(1979) (Table 2). The général morphology of the skullis similar, with a concave and short premaxillary sacfossa, a thin maxilla on the preorbital process, a verticaland concave medial plate of the maxilla along the vertex,depressed frontals with an irregular surface on the vertex,a dorso-ventrally flattened zygomatic process of thesquamosal, a short fossa for the postorbital lobe of thepterygoid sinus on the ventral surface of the roof of theorbit, and a low and wide paroccipital process of theexoccipital with low occipital condyles. The only maindifférence is the size of the nasals; they are wider inIRSNB 3235-M.343 than in any of the three USNMspecimens. The very thin dorsal part of the posterior plateof the mesethmoid is not well enough preserved in thosespecimens to predict the height it reaches in front of thenasals. Nevertheless, skulls like CMM-V-886, from theCalvert Formation, clearly congeneric with the USNM speci¬mens, have a mesethmoid plate nearly as high as the nasals.

The similarities are convincing enough to place thespecimens USNM 21291, USNM 187306 and USNM167676 in the species Schizodelphis morckhoviensis.Those newly referred specimens add information aboutthe species at the level of the rostrum and the basicra-nium.

The rostrum of USNM 21291 is nearly completelypreserved, with a total length of at least 659 mm. Thislength is slightly smaller (relatively to the width of theface) than in 'Eurhinodelphis' bossi, 'E.' cristatus andE. longirostris, but close to E. cocheteuxi. However, thenumber of specimens of the same species with a roughlycomplete rostrum is low, and the relative length shouldonly be considered as indicative. The posterior part of thesuture between maxilla and premaxilla on the rostrum isvisible on USNM 21291. 400 mm anteriorly to the antor-bital notch, the maxilla still has a height of 8 mm. Themaxillary part of the rostrum is therefore relatively longerthan in Eurhinodelphis longirostris, for which the maxillaends at 390 mm of the antorbital notches.

The basicranium of the specimen USNM 167676 isfinely preserved, with a complete latéral lamina of thepterygoid in contact with the falciform process of thesquamosal. A high and antero-medially directed falci¬form process, as observed on Schizodelphis morckhovien¬sis IRSNB 3235-M.343, seems to be a good indicator ofthe presence of a latéral lamina of the pterygoid, a fragilestructure never preserved in Belgian specimens.

Besides the species Rhabdosteus latiradix Cope, 1868(Odontoceti incertae sedis following Muizon, 1988a) andR. longirostris, Myrick (1979) described two additionalspecies of the genus in the Calvert Formation : R. barnesiand R. hruschkai. The diagnoses given by Myrick (1979)provide only few différences between the species, mainlybased on the size of the skull, the shape of the nasals andthe proportions of the vertex. Inside the species R.hruschkai, he also isolated seven morphological groups(A, Al, B, C, D, E and F), mainly differentiated by theshape of the nasals (Myrick, 1979, p. 121).

When comparing the specimens two by two, strongdifférences quickly appear, that could easily be inter-preted as diagnostic at a spécifie level. Flowever, whengroups of more than three or four specimens must beisolated by a series of characters, strict limits are hardlyfound. For example, for the shape of the nasals, it ispossible to fmd a series of morphological intermediatesbetween completely different conditions. In that way, itseems difficult to give a clear définition of R. hruschkai

frontal

maxilla.nasal,

premaxilla.bony nare.

Fig. 12 - Schematic drawings of the vertex of Schizodelphis specimens in dorsal view, showing the différence in the degree oftransverse compression between the species S. morckhoviensis and S. barnesi. A. S. morckhoviensis USNM 21291. B.S. barnesi USNM 244403. Both of them corne from Maryland, USA, Calvert Fonnation, late early to middle Miocene.

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Systematic revision of Eurhinodelphis longirostris 167

sensu Myrick, 1979, with a combination of charactersfound in ail the specimens of the species.

For R. barnesi sensu Myrick 1979, with a lowernumber of specimens, the measurements on the skullsand the morphology are more homogeneous (three skullson Table 2). The four specimens USNM 244403, USNM187624, USNM 187312, and USNM 187317, all ofthemfound in the bed 12 of the Calvert Formation (sensuShattuck, 1904), are characterized by nasals longer thanwide on a vertex very transversely compressed. Thischaracter can be visual ized by the médian margin of themaxilla along the vertex being roughly at the same trans-verse level than the latéral margin of the bony nare (seeFig. 12). This seems sufficiënt to define an additionalspecies of Schizodelphis, but only because it representsone extremity of the range of morphologies for the vertexin the American Schizodelphis.

To summarize, the possibility exists that, contradictingthe hypothesis of Muizon (1988a), more than one species

of the genus Schizodelphis (sensu Muizon, 1988a) ispresent on the Calvert Formation, but because of the highvariability observed for the shape of the vertex, thedéfinition of supplementary species does not providemuch additional systematic information. The only speciesof Schizodelphis from the Calvert Formation also presentin Antwerp is S. morckhoviensis.

Acknowledgements

P. Bultynck gave the author the opportunity to study the odontocetesfrom the IRSNB collections. D.J. Bohaska (Washington D.C.),S.J. Godfrey (Solomons, Maryland), C. de Muizon (Paris), Maria-gabriella Fornasiero and Letizia Del Favero (Padoua) kindly providedaccess to the fossils in their care. R. Marquet presented the ear bonesIRSNB M.1859 and indications about their stratigraphie position.

Discussions with C. de Muizon and G. Bianucci were veryconstructive.

W. Miseur did part of the photographie work and J. Cillis took theSEM pictures.

References

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Cozzuol, M. A., 1996. The record of Aquatic Mammals inSouthern South America. Miinchner Geowissenschaftliche Ab-handlungen, 30(A): 321-342.Dal Piaz, G., 1977. Gli Odontoceti del Miocene Bellunese.Parti Quinta-decima Cyrtodelphis, Acrodelphis, Protodelphi-nus, Ziphiodelphis, Scaldicetus. Memorie dell 'Istituto geologi-

co délia Université di Padova, publ. Dal Prof. G. Dal Piaz,Allegato al vol. IV (1916): 1-128.Da Mata, C. R., 1963. Nota preliminar sobre um delfinideo(Eurhinodelphis cf. cristatus) do Miocénio do Penedo, a Nortedo Cabo Espichel. Boletim do Museu e Laboratorio Mineralo-gico e Geologico da Faculdade de Ciências, Universidade deLisboa, 9 (2): 157-166.du Bus, B. A. L., 1867. Sur quelques Mammifères du Cragd'Anvers. Bulletin de l'Académie royale des Sciences de Bel¬gique, 24: 562-577.du Bus, B. A. L., 1872. Mammifères nouveaux du Crag d'An¬vers. Bulletin de l'Académie rovale des Sciences de Belgique,34: 491-509.

Fordyce, R. E., 1983. Rhabdosteid dolphins (Mammalia : Ce¬tacea) from the middle Miocene, Lake Frome area, SouthAustralia. Alcheringa, 7: 27-40.Fordyce, R. E., 1994. Waipatia maerewhenua, new genus andnew species (Waipatiidae, new family), an archaic late Oligo¬cène dolphin from New Zealand. In: A. Berta & T. A. DemérÉ(eds.). Contributions in marine mammal paleontology honoringFrank C. Whitmore, Jr. Proceedings ofthe San Diego Society ofNatural History, 29: 147-178.Fraser, F. C. & Purves, P. E., 1960. Hearing in cetaceans:Evolution of the accessory air sacs and the structure of the outerand middle ear in recent cetaceans. Bulletin of the BritishMuseum (Natural History), Zoology, 7: 1-140.Gervais, P., 1853. Description de quelques espèces de phoqueset de cétacés. Annales des Sciences naturelles (Zoologie), 20:281-292.

Gervais, P. 1861. Sur différentes espèces de vertébrés fossilesobservées pour la plupart dans le Midi de la France. Mémoiresde l'Académie des Sciences et des Lettres de Montpellier, 16:117-132.

Ginsburg, L. & Janvier, P., 1971. Les mammifères marins desfaluns miocènes de la Touraine et de l'Anjou. Bulletin duMuséum national d'Histoire naturelle, Paris, 22: 161-195.

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Kasuya, T. 1973. Systematic considération of recent toothedwhales based on the morphology of tympano-periotic bone.Scientific Reports of the Whales Research Institute, Tokyo,25: 1-103.

Kellogg, R., 1925. On the occurrence of remains of fossilporpoises of the genus Eurhinodelphis in North America. Pro-ceedings of the United States National Muséum, 66 (26): 1-40.Kellogg, R., 1932. A Miocene long-beaked porpoise fromCalifomia. Smithsonian Miscellaneous collections, 87 (2): 1-11.Kellogg, R., 1955. Three Miocene porpoises from the CalvertCliffs, Maryland. Proceedings of the United States NationalMuseum, 105: 101-154.Lambert, O., in press. Phylogenetic affmities of the long-snouted dolphin Eurhinodelphis (Cetacea, Odontoceti) fromthe Miocene of Antwerp. Palaeontology.Louwye, S., De Coninck, J. & Verniers, J., 2000. Shallowmarine Lower and Middle Miocene deposits at the southemmargin of the North Sea Basin (northern Belgium): dinoflagel-late cyst biostratigraphy and depositional history. GeologicalMagazine, 137 (4): 381-394.Leidy, J., 1851. Proceedings of the Academy of NaturalSciences ofPhiladelphia, 5: 326-327.Lydekker, R., 1893. Contribution to the knowledge of thefossil vertebrates of Argentina. Part II. Cetacean skulls fromPatagonia. Anales del Museo de La Plata, 1893: 1-14.Matsumoto, H., 1926. On some fossil Cetaceans of Japan. TheScience Reports of the Tôhoku impérial University, Sendai,Japan, (2) (Geology), 10 (1): 17-27.Muizon, C. de, 1984. Les Vertébrés de la Formation Pisco(Pérou). Deuxième partie: Les Odontocètes (Cetacea, Mamma-lia) du Pliocène inférieur du Sud-Sacaco. Travaux de l'Institutfrançais d'Etudes andines, 27 : 1-188. In: Recherches SurCivilisations, Mémoire 50, ADPF Paris.Muizon, C. de, 1987. The affinities of Notocetus vanbenedeni,an Early Miocene platanistoid (Cetacea Mammalia) from Pa¬tagonia, southern Argentina. American Museum Novitates,2904: 1-27.

Muizon, C. de, 1988a. Le polyphylétisme des Acrodelphidae,odontocètes longirostres du Miocène européen. Bulletin duMuséum national d'Histoire naturelle, Paris, (4), 10, C, (1):31-88.

Muizon, C. de, 1988b. Les relations phylogénétiques des Del-phinida. Annales de Paléontologie, 74 (4): 159-227.Myrick, A. C., 1979. Variation, taphonomy and adaptation ofthe Rhabdosteidae (= Eurhinodelphidae) (Odontoceti, Mam¬malia) from the Calvert Formation ofMaryland and Virginia.Ph. D. Dissertation, University of Califomia, Los Angeles,

1-347, University Microfilms International Ann Arbor, Michi-gan.

Okazaki, Y., 1976. Miocene long-snouted porpoises from theMizunami Group, Central Japan. Bulletin of the MizunamiFossil Museum, 3: 25-40.Pilleri, G., 1985. The Miocene Cetacea of the Belluno sand-stones (Eastem Southem Alps). Memorie di Scienze Geolo-giche, 36: 1-87.Pilleri, G., 1988. Record of Eurhinodelphis (Cetacea : Rhab¬dosteidae) from the Miocene of Catalonia, Spain. In: G. Pilleri(éd.), Contributions to the Paleontology of some Tethyan Ce¬tacea and Sirenia, Brain Anatomy Institute, Ostermunigen,pp. 19-40.Rommel, S., 1990. Osteology of the Bottlenose Dolphin. In:S. Leatherwood & R. R. Reeves (eds), The Bottlenose Dol¬phin. Academie Press, San Diego, pp. 29-49.Shattuck, G. B., 1904. Geological and paleontological rela¬tions, with a review of earlier investigations. In: W. B. Clark(éd.), Maryland Geological Survey, Miocene. Johns HopkinsPress, Baltimore. 543 p.Van Beneden, P. J. & Gervais, P., 1880. Ostéographie descétacés vivants etfossiles. Paris, Arthus Bertrand. 634 p + atlas64 pis.Vanden Broeck, E., 1878. Esquisse géologique et paléontolo-gique des dépôts plioc'enes des environs d'Anvers, 1ère partie,Les Sables Moyens et les Sables Supérieurs d'Anvers. G. Mayo-lez, Bruxelles. 296 p.

Verteuil, L. De & Norris, G., 1996. Miocene dinoflagellatestratigraphy and systematics of Maryland and Virginia. Micro-paleontology, suppl. 42 : 1-172.Wilson, L. E., 1935. Miocene marine mammals from theBakersfield région, Califomia. Bulletin ofthe Peabody Museumofnatural History, 4 : 1-143.Zei, M. M., 1950. Sopra una nuova specie di Eurhinodelphisdélia Pietra leccese. Rendiconto dell 'Accademia delle Scienze

fisiche e matematiche, Società nazionale di Scienze, Lettere edArti in Napoli, (4), 17: 190-200.

Olivier Lambert (boursier F.R.I.A.)Department of PalaeontologyInstitut Royal des Sciences Naturelles de BelgiqueRue Vautier 29, B-1000 BrusselsBelgiume-mail : [email protected]

Typescript submitted: October 1, 2003.Revised typescript received: January 8, 2004.

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Systematic revision of Eurhinodelphis longirostris 169

Explanation of plates

Plate 1

Fig. 1 — Skull of Eurhinodelphis longirostris IRSNB 3249-M.342 (holotype), from Antwerp, ? Antwerp Sands, late early tomiddle Miocene. A. left latéral view. Scale bar= 150 mm. B. dorsal view. C. posterior view. D. ventral view. Scale barfor B -D = 50 mm. Labels on the skull were written at the time of the work of Abel (see comments on the text for someof them wrongly identified). as: alisphenoid; bo: basioccipital; bs: basisphenoid; eo: exoccipital; me: mesethmoid;pl: palatine; pmx: premaxilla; pt: pterygoid; smx: maxilla; so: supraoccipital; v: vomer.

Fig. 2 — Skull of Eurhinodelphis cf. longirostris IRSNB 3238-M.344, from Antwerp, ? Antwerp Sands, late early to middleMiocene, in dorsal view. Scale bar = 100 mm.

Plate 2

Fig. 1 — Eurhinodelphis longirostris IRSNB 3250-M.1858, from Antwerp, ? Antwerp Sands, late early to middle Miocene. A.Dorsal view of the right part of the face. Scale bar = 30 mm. B. Sagittal section giving a medial view of the right half ofthe vertex. Scale bar = 20 mm. C. Ventral view of the palate showing the right alveolar row. Scale bar = 30 mm.

Fig. 2 — Skull of Schizodelphis morckhoviensis IRSNB 3235-M.343 (holotype), from Antwerp, ? Antwerp Sands, late early tomiddle Miocene. A. bony nares in right dorso-lateral view with the detail of a small fossa on the left side. Scale bar =20 mm. B. posterior view. Scale bar = 50 mm. Labels on that skull were written at the time of the work of Abel.eo: exoccipital; me: mesethmoid; n: nasal; pmx: premaxilla; so: supraoccipital.

Plate 3

Skull of Schizodelphis morckhoviensis IRSNB 3235-M.343 (holotype), from Antwerp, ? Antwerp Sands, late early to middleMiocene. A. dorsal view. B. lefi latéral view. C. ventral view. Scale bar for A-C = 50 mm. D. detail of the left side of basicraniumin ventro-lateral view. Scale bar = 20 mm. Labels on the skull were written at the time of the work of Abel. as: alisphenoid;bo: basioccipital; bs: basisphenoid; f: frontal; me: mesethmoid; n: nasal; pl: palatine; pmx: premaxilla; pt: pterygoid; smx: maxilla;so: supraoccipital; v: vomer.

Plate 4

Fig. 1 — Ear bones of Schizodelphis morckhoviensis IRSNB 3235-M.343 (holotype), from Antwerp, ? Antwerp Sands, late earlyto middle Miocene. A-D. left periotic. A. ventral view. B. medial view. C. dorsal view. D. latéral view. Scale bar forA-D = 10 mm . E. partial left tympanic in medial view. The contact between posterior process and rest of the bone isbroken at several levels, precluding checking of the correct relative position of the two parts. Scale bar = 10 mm.

Fig. 2 — Ear bones of Schizodelphis morckhoviensis IRSNB M. 1859, from Antwerp, Antwerp Sands, late early to middle Miocene.A-D. left tympanic. A. medial view. B. latéral view. C. ventral view. D. dorsal view. Same scale bar than IE. E-F. SEMpictures of left malleus. E. postero-median view. F. postero-ventral view

Plate 5

Eurhinodelphinidae aff Schizodelphis IRSNB 8343Z-M.1860, from Kessel, Antwerp Sands, late early to middle Miocene. A. dorsalview. B. posterior view. Scale bar = 100 mm.

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Plate 1

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Systematic revision of Eurhinodelphis longirostris 171

Plate 2

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Plate 3

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Systematic revision of Eurhinodelphis longirostris 173

Plate 4

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174 Olivier LAMBERT

Plate 5