A New Snake Skull from the Paleocene of Bolivia Sheds Light on the Evolution of Macrostomatans

Abstract

Macrostomatan snakes, one of the most diverse extant clades of squamates, display an impressive arsenal of cranial features to consume a vast array of preys. In the absence of indisputable fossil representatives of this clade with well-preserved skulls, the mode and timing of these extraordinary morphological novelties remain obscure. Here, we report the discovery of Kataria anisodonta n. gen. n. sp., a macrostomatan snake recovered in the Early Palaeocene locality of Tiupampa, Bolivia. The holotype consists of a partial, minute skull that exhibits a combination of booid and caenophidian characters, being the presence of an anisodont dentition and diastema in the maxilla the most distinctive trait. Phylogenetic analysis places Kataria basal to the Caenophidia+Tropidophiidae, and represents along with bolyeriids a distinctive clade of derived macrostomatans. The discovery of Kataria highlights the morphological diversity in the maxilla among derived macrostomatans, demonstrating the relevance of maxillary transformations in the evolution of this clade. Kataria represents the oldest macrostomatan skull recovered, revealing that the diversification of macrostomatans was well under way in early Tertiary times. This record also reinforces the importance of Gondwanan territories in the history of snakes, not only in the origin of the entire group but also in the evolution of ingroup clades.

An Overview of the South American Fossil Squamates

“…The fossil mostly includes snout bones of an articulated skull. Its phylogenetic relationships show it would be a derived macrostomatan, basal to the Caenophidia+Tropidophiidae (Scanferla et al, ). This finding, together with other evidences, suggests that the origin and early diversification of derived macrostomatans may have taken place in southern continents during the early Cenozoic (Scanferla et al, ).…”

“…Rieppel (1979) regarded Dinilysia as the sister group of the Alethinophidia. More recently, Dinilysia has been included in several phylogenetic analyses (Caldwell, 1999;Rieppel and Zaher, 2000;Scanlon and Lee, 2000;Tchernov et al, 2000;Lee and Scanlon, 2002;Scanlon, 2006;Conrad, 2008;Zaher and Scanferla, 2011;Gauthier et al, 2012;Scanferla et al, 2013). All these recent hypotheses show Dinilysia as a relatively basal snake appearing as the sister group of the Alethinophidia or as the sister group to all extant snakes (Scolecophidia 1 Alethinophidia).…”

“…Paleocene faunas of Patagonia, such as the wellknown Peligran SALMA ( Fig. 1), have not provided, thus far, remains of squamates, although lizards and snakes are well represented in other South American regions with Paleocene deposits (de Muizon et al, 1983;Rage, 1991;Head et al, 2009;Scanferla et al, 2013).…”

Avances en El Conocimiento De Los Reptiles Escamosos Fósiles Continentales De América Del Sur

“…Con respecto al Cenozoico, las más antiguas serpientes del Paleógeno sudamericano proceden del Paleoceno de Bolivia, donde se identifica un "anilioideo" indeterminado, al menos dos géneros de boideos, un madtsoideo o boideo, un tropidófido y el macrostomado derivado Kataria anisodonta (de Muizon et al, 1983;Rage, 1991;Scanferla et al, 2013). Rage (1981) (Albino, 1990;Rage, 1998Rage, , 2001Rage, , 2008.…”

Reptiles Extintos - Volumen en Homenaje a Zulma Gasparini

“…Con respecto al Cenozoico, las más antiguas serpientes del Paleógeno sudamericano proceden del Paleoceno de Bolivia, donde se identifica un "anilioideo" indeterminado, al menos dos géneros de boideos, un madtsoideo o boideo, un tropidófido y el macrostomado derivado Kataria anisodonta (de Muizon et al, 1983;Rage, 1991;Scanferla et al, 2013). Rage (1981) (Albino, 1990;Rage, 1998Rage, , 2001Rage, , 2008.…”