Tuesday, October 26, 2010

Indian Fossil Snakes and Old Tropical Rainforests


Snakes from the Eocene of India were diverse. Jean-Claude Rage (2002) reported on the early Eocene serpent fauna of India using fossils from the Panandhro Mine in northwestern India. This locality produced a rich snake fauna that was dominated by the highly aquatic palaeophiids. Rage found three families represented in the fossil beds: the aquatic Palaeophiidae; fossils that may be ?Madtsoiidae or Boidae; and a representative  of the Colubroidea. The Palaeophiidae include remains of two species: Pterosphenus kutchensis and Pt. biswasi .They are the earliest known representatives of the genus. Madtsoiidae (or Boidae) were represented by two specimens that do not permit distinction between these two families. If the fossils belong to the Boidae, they would be the earliest representatives of that family in Asia. And the colubroid snake from this site ranks among the earliest Cenozoic representatives of the clade. The possibility that it belongs to the Colubridae could not be eliminated – it had a very light build. If true it would be the earliest known snake in the family Colubridae. Nearly all fossil specimens at the mine belonged to Pterosphenus, a highly aquatic genus. It lived in shallow water, probably in marine environment close to the coasts or in freshwater. In a second paper, Rage and colleagues (2008) reported on a second India early Eocene fossil site, the Vastan Lignite Mine in Gujarat, western India. The fossils included at least 10 species that belong to the Madtsoiidae; Palaeophiidae (Palaeophis and Pterosphenus); Boidae; and several Caenophidia.  The Colubroidea were represented by Russellophis crassus. (Russellophiidae) and by Procerophis sahnii. As well as Thaumastophis missiaeni a caenophidian of uncertain family status. The authors write, “The number of taxa that represent the Colubroidea or at least the Caenophidia, i.e., advanced snakes, is astonishing for the Eocene. This is consistent with the view that Asia played an important part in the early history of these taxa.”  The Vastan Mine fossils come from marine and continental levels and includes highly aquatic, amphibious, and terrestrial snakes. The composition of the fauna from Vastan seems similar to that of the more poorly known early Eocene of Europe.

Also consider the recent discover of Sanajeh indicus by Wilson et al. 2010. Sanajeh was  from the very late Cretaceous and found near Dholi Dungri village in Gujarat, Western India. Sanajeh indicus was preserved in a sauropod dinosaur nesting ground associated with eggs and a hatchling sauropod. The new fossils provided the first evidence of snake predation on hatchling dinosaurs.

Thus the time span between late Cretaceous and the early Eocene of India appears to have been rich is snake species. Today there is evidence to suggest that India had the oldest tropical forests known during this time. Rust et al. (2010), describe the Cambay amber of Gujarat, in western India and fossilized wood as the oldest evidence for tropical forests in Asia. The amber has been chemically linked to dipterocarps (Dipterocarpaceae), a family of hardwood trees that today make up 80 percent of the forest canopy in Southeast Asia. The fossilized wood from this family makes this deposit the earliest record of these plants in India and demonstrates that the family is nearly twice as old as was commonly believed. The forest was like to have been present when portions of the southern supercontinent Gondwana were still connected. The paper also describes 100 species of arthropod representing 55 families and 14 orders. Some of these species are early relatives of highly social, or eusocial, insects like honey bees and stingless bees, rhinotermitid termites, and ants, suggesting that these groups radiated during or just prior to the early Eocene. Many of the Cambay fossils have relatives on other continents—although not where it would be expected. Rather than finding evolutionary ties to Africa and Madagascar, landmasses that India had most recently been linked to as part of Gondwana, the researchers found relatives in Northern Europe, Asia, Australia, and the Americas.

References
Rage J.-C., Bajpai S., Thewissen J. G. M. & Tiwari B. N. 2003. — Early Eocene snakes from
Kutch, Western India, with a review of the Palaeophiidae. Geodiversitas 25 (4):695-716.

Rage, J.-C., A. Folie, R. S. Rana, H. Singh, K. D. Rose, T. Smith. 2008. A Diverse Snake Fauna from the Early Eocene of Vastan Lignite Mine, Gujarat, India. Acta Palaeontologica Polonica, 53 (3):391-403.

Rust, J., H. Singh, R. S. Rana, T. McCann, L. Singh, K. Anderson, N. Sarkar, P. C. Nascimbene, F. Stebner, J C. Thomas, M. S. Kraemer, C. J. Williams, M. S. Engel, A. Sahni, and D. Grimaldi 2010. Biogeographic and evolutionary implications of a diverse paleobiota in amber from the Early Eocene of India. PNAS published ahead of print October 25, 2010, doi:10.1073/pnas.1007407107

Wilson J. A., Mohabey D,M., Peters S.E., Head J.J.  2010. Predation upon Hatchling Dinosaurs by a New Snake from the Late Cretaceous of India. PLoS Biol 8(3): e1000322. doi:10.1371/journal.pbio.1000322

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