Eosuchus lerichei Dollo, 1907

Delfino, Massimo, Piras, Paolo & Smith, Thierry, 2005, Anatomy and phylogeny of the gavialoid crocodylian Eosuchus lerichei from the Paleocene of Europe, Acta Palaeontologica Polonica 50 (3), pp. 565-580 : 567-568

Eosuchus lerichei Dollo, 1907

Holotype: Specimen IRSNB R 49 is represented by a nearly complete skull ( Figs. 2–4 ), an incomplete lower jaws ( Fig. 5 ), the axis ( Fig. 6A ), three cervical vertebrae, an isolated neural arch, three ribs, a fragmentary ulna and radius, a carpal element and fourteen osteoderms (or their fragments; Fig. 6B ). All the remains seem to belong to one single individual.

Type locality: Jeumont (Maubeuge, Nord Department), France. The locality, few meters far from the Franco−Belgian border, is part of the well known fossiliferous area of Erquelinnes, Belgium.

Horizon and age: Grandglise Member, Hannut Formation, Thanetian, upper Paleocene.

Emended diagnosis.— Eosuchus lerichei can be distinguished from E. minor by the axis neural arch devoid of any lateral process, a relatively slender postorbital bar, the presence of the triple junction between frontal, parietal and postorbital on the skull table, ectopterygoids separated from the toothrow by maxilla and palatine anterior process showing a irregular morphology that can be assimilated to a U−shaped condition. Nasals are relatively narrower and frontal process slightly longer than in E. minor .

Moreover, the holotype —and only known specimen— shows 5 premaxillary (see description), 16/17 maxillary and at least 22 dentary teeth; the symphysis reaches posteriorly the sixteenth tooth position; teeth have a peculiar shape since they do not show any evident labio−lingual compression or mesio−distal keels but several ridges of similar development occurring on the entire crown surface.

Figures

Fig. 2. Holotype of Eosuchus lerichei Dollo, 1907. IRSNB R 48, Jeumont, France, late Paleocene, skull in dorsal view (A) and explanatory drawing of the same (B).

Fig. 3. Holotype of Eosuchus lerichei Dollo, 1907. IRSNB R 48, Jeumont, France, late Paleocene, skull in ventral view (A) and explanatory drawing of the same (B).

Fig. 4. Holotype of Eosuchus lerichei Dollo, 1907. IRSNB R 48, Jeumont, France, late Paleocene, skull in occipital view (A) and explanatory drawing of the same (B).

Fig. 5. Holotype of Eosuchus lerichei Dollo, 1907. IRSNB R 48, Jeumont, France, late Paleocene, lower jaw in dorsal view (A) and explanatory drawing of the same (B).

Fig. 6. Holotype of Eosuchus lerichei Dollo, 1907. IRSNB R 48, Jeumont, France, late Paleocene. A. Axis in left lateral view. B. Nuchal osteoderms in dorsal view. C. Detail of the orbital region of the skull showing the L−shaped deflected postorbital bars and the “step−like” structures characteriszing the antero−medial margin of the orbits. D. Detail of right quadrate showing the extremely enlarged foramen aereum. E. Detail of lower jaw showing the couplets of teeth and the asymmetrical alveolar arrangement.