Amananulam sanogoi, Mccartney & Roberts & Tapanila & O’Leary, 2018
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publication ID |
https://doi.org/ 10.4202/app.00442.2017 |
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persistent identifier |
https://treatment.plazi.org/id/03878781-FF9B-0F4F-A425-C995FD078FC5 |
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treatment provided by |
Felipe |
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scientific name |
Amananulam sanogoi |
| status |
sp. nov. |
Amananulam sanogoi sp. nov.
Fig. 6 View Fig .
Etymology: Named in honor of Mamadou Sanogo, for his outstanding collaboration on the CNRST-SBU expeditions work in Mali.
Holotype: CNRST-SUNY 462 , a mid-trunk vertebra.
Type locality: Locality Mali-19, in Northeastern Mali.
Type horizon: Paleocene.
Material.—Known only from the holotype.
Diagnosis.—Nigerophiid snake with the autapomorphic restriction of the hemal keel to the posterior quarter of the centrum. Additionally differentiated from other nigerophiid snakes by the combination of a dorsoventrally tall zygosphene, a dorsally concave neural arch, and a neural spine that is restricted to the posterior one-third of the neural arch.
Description.— Amananulam sanogoi gen.et sp.nov. is known from only a single, mid-trunk vertebra. The vertebra is small at only 10 mm in preserved length, although damage to the condyle shortens it somewhat. It preserves much of the centrum, a partial zygosphene, and portions of the neural arch. No zygapophyses or synapophyses are completely preserved.
The neural spine is incompletely preserved, but it is clearly restricted to the posterior quarter of the neural arch. It has a laterally broad base that tapers superiorly; the anterior surface sweeps steeply posterodorsally. Anterior to the neural spine the neural arch is concave dorsally, bounded anteriorly by a dorsally-projecting zygosphene. The zygosphene is tall, with superiorly projecting facets giving it a gently w-shaped dorsal edge. The facets also project anteriorly, producing a concave anterior surface. The superior portion of the left zygosphenal facet is damaged, but enough is preserved to indicate that the zygosphene is narrower than the cotyle. The zygantrum is tall to accommodate the height of the zygosphene, but it is otherwise poorly preserved.
The neural canal is subtriangular in shape. The walls of the arch are thick, and taper anteriorly to a blunt ridge. The zygapophyses are entirely absent except for a small portion of the right prezygapophysis. Along the inferolateral border of this portion is the remnant of the synapophysis, which appears to face ventrally. The interzygapophyseal ridge is so weakly projecting that it is nearly absent.
The cotyle is large and slightly wider than tall. The condyle is incompletely preserved, but it lacks a precondylar constriction. Subcentral ridges are absent, giving the ventral surface a smooth appearance, interrupted only by a pair of subcentral foramina set slightly posterior to the midpoint of the vertebra. The hypapophysis or hemal keel is broken, but is restricted to the very posteriormost portion of the centrum, projecting as a small nubbin. There is no ridge or crest extending anteriorly from the hypapophysis toward the cotyle. The ventral surface of the vertebra is concave in lateral view.
Remarks.— Amananulam sanogoi gen. et sp. nov. is referable to Nigerophiidae on the basis of several features, including the restricted anteroposterior length of the neural spine, and the weakness of the interzygapophyseal and subcentral ridges. Nigerophiids also have ventrally facing synapophyses, as in Amananulam sanogoi gen. et sp. nov., although that feature is thought to be an adaptation to an aquatic lifestyle found in other aquatic snakes (e.g., Lucas 1898; Rage and Werner 1999). Amananulam sanogoi gen. et sp. nov. is unique among nigerophiids in lacking a hemal keel that extends anteriorly to the cotyle, having instead a low knob-like process only. It also differs from almost all nigerophiids in having a dorsoventrally deep zygosphene and zygantrum, a feature that is only present in the presumed nigerophiid Woutersophis novus from Belgium ( Rage 1980). The great height of the zygosphene gives the neural arch a swaybacked appearance with a deep concavity separating the zygosphene and neural spine; this morphology is shared with other species ( Indophis sahnii , “ Nessovophis ” zhylga , and Kelyophis hechti ; Rage and Prasad 1992; Averianov 1997; LaDuke et al. 2010), but in none is the depth of the concavity as great as in Amananulam sanogoi gen. et sp. nov. The near absence of the interzygapophyseal ridge and absence of subcentral ridges are features shared with Nigerophis and Nubianophis to the exclusion of other species referred to Nigerophiidae ( Rage and Werner 1999) .
Stratigraphic and geographic range.—Known only from the Paleocene locality Mali-19, eastern Mali.
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