Seismophis septentrionalis, Hsiou & Albino & Medeiros & Santos, 2014

Hsiou, Annie S., Albino, Adriana M., Medeiros, Manuel A. & Santos, Ronny A. B., 2014, The oldest Brazilian snakes from the Cenomanian (early Late Cretaceous), Acta Palaeontologica Polonica 59 (3), pp. 635-642 : 638-639

cf. Seismophis septentrionalis sp. nov.

Fig. 3 .

Referred material.— CPHNA-MA VT-1222 , incomplete midtrunk vertebra from the same locality of Seismophis septentrionalis sp. nov. exposed at the Falésia do Sismito (2 º 28’43.0”S; 44 º 8’10.3”W) of Cajual Island , Maranhão, northeastern Brazil; Cenomanian (early Late Cretaceous), Alcântara Formation , Itapecuru Group, São Luis-Grajaú Basin ( Góes and Rossetti 2001) .

Description.—The material is an incomplete isolated vertebra poorly preserved, lacking most of the prezygapophyses, part of the anterior edge of the zygosphene, the distal end of the neural spine, both paradiapophyses, much of the condyle, and much of the posterior portion of the neural arch. For this reason, measurements and ratios are not used in the description. In general, the vertebra is small, relatively robust, short, wide and moderately high, with the centrum probably shorter than the neural arch width (cl <naw). In anterior view, although very fragmented, the zygosphene is narrow and moderately thick, apparently narrower than the cotyle (zw <ctw) and probably bearing a flat roof that is not elevated in the middle. Although broken, the prezygapophyses are nearly horizontalized, and it is not possible to observe if they carried prezygapophyseal processes. The neural canal is triangular and small. The cotyle is slightly wider than high, and there are no paracotylar foramina, only a deep fossa on each side of the cotyle. The paradiapophyses are fragment- ed, hindering further detail; however, they were apparently well developed and lateroventrally oriented, with the dorsal portion (diapophysis) almost reaching the prezygapophyseal articular surface, and the parapophysis probably not surpassing the ventral rim of the cotyle.

In posterior view, the neural arch is vaulted, with the roof clearly arched. The zygantrum is deep, with small zygantral foramina. There is one parazygantral foramen lateral to the right zygantral facet of the zygantrum. The posterior face of the neural arch is broken on the left side making impossible to verify the presence of this foramen. The condyle is eroded, nearly circular (cow~coh). In lateral view, the centrum is shorter than the neural arch. In this view, the neural spine is obliquely oriented because the neural arch becomes higher posteriorly. Small lateral foramina are present on each lateral wall of the neural arch. From this view, the interzygapophyseal ridges look rather inclined anteroposteriorly.

In dorsal view, the neural arch is apparently wider than long (pr-pr> pr-po). The prezygapophyseal facets are oval and anterolaterally oriented. The neural spine was apparently thicker posteriorly than anteriorly, although its posterior part is broken. It is low, starting posterior to the zygosphene and extending all along the roof of the neural arch. The roof of the neural arch shows a strongly pronounced ridge joining the lateral edge of the zygosphene and the posteromedial margin of the postzygapophysis on each side of the neural spine. Although the interzygapophyseal constriction is quite deformed, it looks somewhat deep. In ventral view, the centrum is strongly triangular in outline and broader anteriorly than posteriorly with marked and straight subcentral ridges. The precondylar constriction is moderately marked. The haemal keel is well defined, thick, and slightly prominent from the ventral surface of the centrum.

Figures

Fig. 3. Midtrunk vertebra of the snake cf. Seismophis septentrionalis sp. nov. (CPHNA-MA VT 1222), from the Cenomanian (early Late Cretaceous) of Falésia do Sismito, Cajual Island, Maranhão, northeastern Brazil. Photographs (A1–E1) and explanatory drawings (A2–E2), in anterior (A), posterior (B), lateral (C), dorsal (D), and ventral (E) views.