Erythrolamprus juliae cf. copeae ( Parker, 1936 )

Bochaton, Corentin, Boistel, Renaud, Grouard, Sandrine, Ineich, Ivan, Tresset, Anne & Bailon, Salvador, 2019, Fossil dipsadid snakes from the Guadeloupe Islands (French West-Indies) and their interactions with past human populations, Geodiversitas 41 (12), pp. 501-523 : 512-514

Erythrolamprus juliae cf. copeae ( Parker, 1936)

EXAMINED MATERIAL. — Six elements, all trunk vertebrae, collected from Basse-Terre and Grande-Terre islands (see Table 1 ), are attributed to the species Erythrolamprus juliae cf. copeae.

DESCRIPTION

Trunk vertebrae (6 elements; Fig. 6B)

These six vertebrae have centra lengths between 2.7 and 3.2 mm. In dorsal view,they are more elongate than the previously described fossil vertebrae and clearly longer than wide (ratio CL/WIC = 1.18-1.35). The prezygapophyseal processes are thick, conical, with blunted apex, and are more anteriorly oriented than in Alsophis fossil morphotypes. Prezygapophyseal facets are ovoid in dorsal outline. The medial constriction is less pronounced than in the previously described vertebrae. The zygosphene is wide, with a slightly lobate anterior margin. The postero-medial notch of the neural arch is less flared than in other fossil vertebrae described here and forms an angle of 45°.There is no epizygapophyseal spine. In lateral view, the neural spine is long and low, approximately 3.5 times longer than high. This structure has a concave anterior margin with a slightly overhanging anterior projection and a vertical posterior margins without any overhang. The interzygapophyseal crest is straight.In the synapophysis, the diapophysis and parapo-

F.

physis are slightly more separated than in Alsophis morphotypes, but their relative positions are similar. The diapophysis is clearly larger than the parapophysis. Ventrally, a long and shallow hemal keel with a straight ventral edge and a slight posterior projection is visible. In anterior view, the cotyle is circular and it is bordered laterally by paracotylar foramina and deep paracotylar depressions. In posterior view, the condyle is circular and the neural arch is dorsally flattened. The centrum is cylindrical in transverse section. In ventral view, the centrum has weakly marked subcentral ridges and lacks the precondylar constriction occurring in Alsophis fossil vertebrae. The hemal keel is shaped like a gladius shape and its width is constant along its whole length. Two subcentral depressions of shallow depth and limited extent are visible on the anterior part of the centrum below the synapophysis.Sub-cotylar tubercles occur ventral to the cotyle on some specimens.

REMARKS

These vertebrae present two characters occurring in Erythrolamprus and not in Alsophis : the vertebra is clearly longer than wide and the neural spine is anteroposteriorly elongate and low. These same fossils also exhibit several differences with our two comparative extant specimens of Erythrolamprus perfuscus: lack of a strongly trilobed anterior margin of the zygosphene in dorsal view; cylindrical shape of the centrum with weakly defined lateral margins; lack of precondylar constriction separating the centrum from the condyle; and narrowness of the postero-medial notch in the neural arch forming an angle clearly less than 90° in dorsal view. All these characters that do not occur in E. perfuscus occur on our unique individual of E. juliae copeae (MNHN-RA-1998.485). Still, some differences exist between this last individual and the fossil vertebrae. Most notably, in our modern individual, the prezygapophyseal processes are wider and shorter and the zygosphene is narrower than in some fossils. In addition, the hemal keel in the modern individual is shorter and its posterior end is enlarged in ventral view, and the cotyle is ovoid in anterior view. Considering the strong morphological affinities between the fossil vertebrae and our modern specimen of E. j. copeae and the fact that this sub-species currently occurs on the Guadeloupe Islands, the fossils may belong to that sub-species. However, because comparative specimens of Erythrolamprus juliae are scarce (n = 5) we are unable to determine if the observed morphological differences between fossils and our modern specimens are reliably diagnostic at the sub-species level. We thus conservatively identify these six fossil vertebrae as Erythrolamprus juliae cf. copeae. A gross comparison of the centrum length of fossil vertebrae with modern specimens indicates fossils snakes were about 44-54 cm in total length, a size similar to the modern individuals of E. j. copeae (see Breuil 2002).

Superfamily COLUBROIDEA Oppel, 1811

EXAMINED MATERIAL. — 128 bone elements all representing colubridae (sensu lato) fragmented pre-cloacal and post-cloacal vertebrae could not be identified to the genus level.