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

ABSTRACT

We 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.

ACKNOWLEDGMENTS

We thank all Mahajanga Basin Project expedition members for their Herculean efforts in the field; H. Andriamialison and A. Rasoamiaramanana (University of Antananarivo), B. Andriamihaja and P. Wright (Institute for the Conservation of Tropical Ecosystems), and the villagers in the Berivotra and Lac Kinkony study areas for logistical support; J. Groenke and V. Heisey for fossil preparation; J. Neville for photography; J. Maisano (The University of Texas at Austin) for CT scanning and processing; I. Wallace for CT scanning at the Center for Biotechnology at Stony Brook University; L. Betti-Nash for assistance with figures; N. Ratsimbaholison for pronunciation of Malagasy names; and the National Science Foundation and the National Geographic Society for funding. In addition, we thank J.-C. Rage and an anonymous reviewer for comments and criticisms that greatly improved the quality of this paper.

Handling editor: Jack Conrad.