Crocodylus depressifrons, BLAINVILLE, 1855

Delfino, Massimo & Smith, Thierry, 2009, A reassessment of the morphology and taxonomic status of ‘ Crocodylus’ depressifrons Blainville, 1855 (Crocodylia, Crocodyloidea) based on the Early Eocene remains from Belgium, Zoological Journal of the Linnean Society 156 (1), pp. 140-167 : 141

CROCODYLUS DEPRESSIFRONS BLAINVILLE, 1855

The ‘Atlas du genre Crocodilus ’ published by Blainville does not only contain illustrations and information about extant Crocodylus . In the volume dedicated to the ‘explications de planches’ [1855; for the proper publication date of this section see Swinton (1938), and quoted reference] new fossil taxa were also introduced in the literature: among others, Crocodilus depressifrons , C. temporalis , and C. macrorhynchus .

The name C. depressifrons appears in the work by Blainville only as the caption ‘ C. depressifrons , du Soissonnais’ of some figures in table 6, figures portraying an incomplete skull and a lower jaw from the Early Eocene, ‘Sparnacian’, of France ( Fig. 1 ). Despite the fact that no description is associated to such a name, for a period of about a century, various remains from the Eocene of north-west Europe were referred, either in publications or simply in museum labels, to C. depressifrons Blainville, 1855 . The reasons for such identifications were usually based on the number of teeth/alveoli involved in the dentary symphysis (which in the figure by Blainville are clearly six in number), or based on the flattened frontal area, a character that although not obvious in the figure, is clearly implicit in the specific epithet. No attempts to provide a complete diagnosis have ever been made and the material formerly described by Blainville is nowadays so strongly pyritized ( Fig. 2 ; MNHN G 160; whose label reports the locality as ‘lignites de Muirancourt’ – Oise) that the original morphology is no longer visible. The casts of the skull and lower jaw (MNHN G 156), apparently produced before the pyritization started to alter them, are of little help in understanding the finer morphology of the taxon.

As for the validity of C. depressifrons , its possible status as a junior synonym was noted by Gervais (1859), who listed the name C. coelorhinus Pomel, 1847 , in the section dedicated to the former species, and added Laonnais to Soissonnais as if they were the ‘typical’ localities for it. If C. coelorhinus was a valid name it should have priority over C. depressifrons Blainville, 1855 , but as already discussed by Swinton (1938) and Vasse (1993), Pomel (1847) neither described nor figured C. coelorhinus , and therefore this name is considered a nomen nudum.

In conclusion, the validity of the species C. depressifrons is firmly granted by the figures published by Blainville, by the name and the locality associated to them, and therefore by the information they provide.

Berg (1966), in his comprehensive work concerning the crocodylians of Messel, the renowned German Eocene locality particularly rich in well-preserved crocodylian remains belonging to seven different taxa ( Morlo et al., 2004), marginally discussed the taxon erected by Blainville and suggested that it should be included in the genus Asiatosuchus (see also Berg, 1969).

Figures

Figure 1. ‘Crocodylus’ depressifrons Blainville, 1855, type specimens from ‘Soissonnais’, original drawings by Blainville (1855: plate 6), A, B, skull in dorsal and ventral view; C, D, right lower jaw in lateral view and enlarged detail of the symphysis in dorsal view, the arrows in (D) indicate the small and nearly confluent eight and ninth alveoli; E, F, skull in occipital and right lateral view; note that the reconstructed squamosal ‘horns’ are moderately developed in (E) but nearly flat in (F). The scale was not reported in the original drawing by Blainville but, on the basis of the remains still preserved in Paris (MNHN G 156, MNHN G 160), the total skull length can be estimated to be about 500 mm.

Figure 2. ‘Crocodylus’ depressifrons Blainville, 1855, type specimen (MNHN G 160) in dorsal view showing the current state of preservation; the original label reports ‘Lignites de Muirancourt (Oise)’.