New snakes from the Upper Cretaceous (Maastrichtian) Maevarano Formation, Mahajanga Basin, Madagascar

Abstract

ABSTRACTWe describe three new fossil snakes on the basis of recently discovered vertebrae collected from the Upper Cretaceous (Maastrichtian) Maevarano Formation of Madagascar. One represents a new genus and species of madtsoiid, Adinophis fisaka, the third member of this family recognized from the Maevarano Formation. It exhibits dorsoventrally compressed centra and dorsally placed synapophyses. The second taxon is a new species of the nigerophiid genus Indophis, I. fanambinana, representing the second nigerophiid taxon known from the Maevarano Formation. It shares numerous features with the Indian nigerophiid I. sahnii, including small synapophyses positioned ventrolaterally on distinct synapophyseal processes and a unique cotylar shape in posterior trunk vertebrae. The discovery of I. fanambinana demonstrates a strong biogeographic link with penecontemporaneous snake faunas from India. A third new taxon is represented by a partial centrum that cannot be assessed thoroughly due to its incompleteness; this specimen is conservatively assigned to Serpentes incertae sedis, gen. et sp. indeterminate. It is distinct from other snakes known from the Late Cretaceous of Madagascar in possessing a strongly depressed condyle and relatively large lateral foramina. These new discoveries, together with previous descriptions of snakes from the Maevarano Formation, make the Maevarano snake fauna one of the most taxonomically diverse snake assemblages known from the Mesozoic and the most diverse in terms of body size range.