Ischyrochampsa, Vasse, 1995
|
publication ID |
https://doi.org/ 10.1111/zoj.12331 |
|
persistent identifier |
https://treatment.plazi.org/id/860A821E-FFDB-C273-BD2A-0D05FCB6DDCD |
|
treatment provided by |
Marcus |
|
scientific name |
Ischyrochampsa |
| status |
|
AND ISCHYROCHAMPSA
Description of the VBN specimens allows us for the first time to confidently assign a dentary bone (MMS/ VBN-12-10B found in association with the skull MMS/ VBN-12-10A) to the genus Allodaposuchus . Whether Allodaposuchus precedens and Musturzabalsuchus buffetauti ( Buscalioni et al., 1997, 1999) represent the same taxon has already been questioned (Martin, 2010). The specimen MMS/VBN-12-10B ( Fig. 10 View Figure 10 ) and M. buffetauti share the following features of the dentary: an enlarged fourth dentary alveolus located at the level of the posterior end of the symphysis; a diastema between the seventh and eighth alveoli; an occlusion mark lateral to this diastema; the ventral surface of the dentary being broad and flat in the symphysial area; the dorsal edge of the dentary being festooned in lateral view; at the level of the surangular suture, the ornamentation of the dentary is weaker or absent and the dentary becomes thin; the extension of the splenial that stops at the posterior end of the dentary symphysis; the fifth dentary alveolus extremely reduced relative to the fourth; and the likely absence of an external mandibular fenestra. In addition, both taxa may share 16 dentary alveoli. Although the posterior region of the dentary MMS/VBN-12-10B is broken off, the observed number of 16 alveoli could be close to the complete count because of the presence of the surangular suture that indicates the end of the tooth row. Finally, the dentition of M. buffetauti described with sharp carinae, and the crown surface profusely ridged with the margin crenulated ( Buscalioni et al., 1999: 219) is reminiscent of the morphology in Allodaposuchus ( Buscalioni et al., 2001; Delfino et al., 2008a; Martin, 2010; Blanco et al., 2014; see also Fig. 11 View Figure 11 ). Although we have not seen M. buffetauti first-hand, these similarities are striking and invite the evaluation of the synonymy of M. buffetauti with Allodaposuchus when more complete mandibular specimens become available.
The trematochampsid Ischyrochampsa meridionalis was erected on the basis of the extremity of a rostrum and relatively complete, albeit poorly preserved mandibular rami from the Late Cretaceous of Saint- Estève Janson, Bouches-du-Rhône, France ( Vasse, 1995). In his diagnosis of I. meridionalis, Vasse (1995) noted the following characters that now show striking resemblances with Musturzabalsuchus ( Buscalioni et al., 1997, 1999): short mandibular symphysis extending back to the level of the fourth alveolus; splenial that reaches but does not participate in the symphysis; the first, fourth and eleventh alveoli are the largest; and robust teeth with ‘mousse’ apex, smooth carinae and crown surface with ridges. As in A. precedens , the teeth of I. meridionalis ( Fig. 11G, H View Figure 11 ) are conical, recurved and possess sharp mesiodistal carinae, which are shifted on the lingual side of the crown. Ridges ornament the crown surface on both the lingual and the labial sides. Vasse (1995) reported a total of 11 dentary alveoli. However, the condition of preservation of the specimen referred to I. meridionalis obscures the last alveoli and it is probable that this specimen hosts at least 15 alveoli ( Fig. 14 View Figure 14 ). Vasse (1995) also identified an external mandibular fenestra, but direct examination of the specimen reveals that it corresponds to a break, indicating that an external fenestra is probably absent, as in the mandible of M. buffetauti . Recent reexamination of I. meridionalis reveals that no diagnostic characters could be validated for this taxon. The mandible of I. meridionalis has experienced considerable crushing as evidenced from several fractures, as already noted by Vasse (1995). In lateral view, the posterior mandibular ramus is collapsed and possibly some anatomical features have been slightly displaced. As such, a large mark of occlusion is present on the lateral side of the dentary of I. meridionalis at the level of the eighth or maybe the ninth alveolus ( Fig. 14 View Figure 14 ). In MMS/VBN-12-10B and in M. buffetauti , this occlusion mark is placed between the seventh and the eighth alveoli. Other features cannot be checked on MMS/ VBN-12-10B, but are readily comparable in the mandibles of M. buffetauti and in I. meridionalis . In these, the surangular has a mediolaterally developed dorsal surface; the tooth row is slightly shorter than the posterior region of the edentulous mandibular ramus.
Comparison of the mandible MMS/VBN-12-10B with two other taxa from the Late Cretaceous of Europe, Musturzabalsuchus and Ischyrochampsa , leads to the conclusion that the latter two taxa could reasonably represent junior synonyms of Allodaposuchus . Alternatively, because of the absence of clearly diagnostic characters, Ischyrochampsa meridionalis should be considered a nomen vanum (sensu Sanchíz, 1998). Of note is that I. meridionalis was originally considered as a non-eusuchian taxon with Gondwanian affinities ( Vasse, 1995), but this hypothesis is no longer supported and the diversity of non-eusuchians in the Late Cretaceous of Europe is restricted to the genera Theriosuchus and Doratodon ( Martin & Delfino, 2010; Martin, Rabi & Csiki, 2010; Martin et al., 2014a; Rabi & Sebök, 2014).
No known copyright restrictions apply. See Agosti, D., Egloff, W., 2009. Taxonomic information exchange and copyright: the Plazi approach. BMC Research Notes 2009, 2:53 for further explanation.