Field Research: Indo-Pakistan

 
 

The Mesozoic Era is an ideal setting for investigation of the interplay between geographical changes and evolution of terrestrial biota because of the dramatic rearrangements of continental landmasses and the diversification of land animals that took place simultaneously. Early in the Mesozoic, dinosaurs and other large land vertebrates enjoyed genetic connectedness on Pangea that is readily apparent in the similarities in the skeletons of animals that lived quite far from one another. Late in the Mesozoic, in contrast, rising sea level and tectonic activity severed connections between landmasses, creating large island continents, each seeded with its own constituent flora and fauna. I am interested in how the faunal and floral composition of these emerging islands was shaped by processes of vicariant evolution, extinction, and dispersal.


Indo-Pakistan experienced dramatic geographical changes during the Mesozoic and early Cenozoic, transporting its evolving biota 6,000 km across the equator from a position in southern Pangaea to one near Asia. Paleogeographers disagree on exactly how fast Indo-Pakistan drifted and on the nature its connections, but under any scenario Indo-Pakistan can be expected to have experienced major changes in latitude and land connections that may have influenced the evolution of its biota. Although the biota of Indo-Pakistan is well known well before and well after these paleogeographic changes occurred, its transitional late Mesozoic faunas are relatively poorly known.  Fossils have long been recorded in uppermost Cretaceous sediments of India, but articulated or associated remains are rare. In contrast, late Mesozoic fossils were discovered only recently in Pakistan and provide a new source of information to complement the Indian record. A clearer picture of the pre-impact Indian Plate biota can be reconstructed by integrating and interpreting the fossil records of India and Pakistan through continued prospection and reexamination of previously described fossils.


Our museum research and field exploration have endeavored to recognize associated skeletons (i.e., bones that represent single individuals) and identify diagnostic features to build a reliable faunal list of the fossil reptiles of Indo-Pakistan. Our approach has been to exhaustively survey and interpret all fossils that have already been collected, which are housed in museums throughout the subcontinent, and to actively discover new associations in the field. Our museum efforts have led to the discovery of individual associations that had been lost, not recognized, or misidentified. Our ongoing reinterpretation of the fossil reptile fauna of India has led to description of the meat-eating theropod dinosaur Rajasaurus narmadensis (Wilson et al. 2003) and the plant-eating sauropods Isisaurus colberti (Wilson & Upchurch 2003; Wilson et al. 2005) and Jainosaurus septentrionalis (Carrano et al. in press; Wilson et al. 2009b, in review b).


In collaboration with my colleague Dhananjay Mohabey, we have just published the discovery of an extraordinary new snake fossil that we named Sanajeh indicus (Wilson et al. 2010). This 3.5 m long snake was was preserved inside a sauropod nest feeding on a 0.5 m long sauropod dinosaur hatchling. It represents the first articulated snake known from Indo-Pakistan before the Miocene (ca. 15 Ma) and rare evidence of feeding behavior in an ancient snake. Sanajeh preserves anatomical features that help to sort out early snake interrelationships, which have been controversial, and suggests that the narrow gape of basal-most snakes is a specialized condition. It also identifies a previously unknown predation pressure on hatchling sauropod dinosaurs. Other recent field discoveries include a second, larger snake, Madtsoia pisdurensis (holotypic vertebrae of which I am holding in the photo above), and articulated turtle and crocodile fossils that will represent new species. Our field research is supported by a grant from the National Geographic Society.


Our preliminary findings recognize strong connections between the latest Cretaceous dinosaurs of Indo-Pakistan and those of Madagascar, and to a lesser extent those on South America. The contemporaneous snake fauna of India suggests connection to Madagascar and South America and also to Australia. At this point we can say that until the end of the Mesozoic, Indo-Pakistan retained fairly strong biogeographic connections to other southern landmasses; no isolation and no northern connections have been identified in the Mesozoic.

Indo-Pakistan

Sanajeh indicus links:

  1. The paper can be found here:

  2. Photos of 2007 field work can be found here.

  3. A popular article I wrote summarizing the Sanajeh find, “Greater India Before the Himalayas and Dinosaur-Eating Snakes”, can be found on 3QuarksDaily.

  4. Podcast interview by Arthor Danchest at “Tiffin Talk” (http://www.tiffintalk.org/the-episodes/)

  5. University of Michigan press release, slideshow, & video (http://www.ns.umich.edu/htdocs/releases/story.php?id=7549)

  6. National Public Radio interview & story (http://www.npr.org/templates/story/story.php?storyId=124217483)

  7. Scientific American (http://www.scientificamerican.com/article.cfm?id=snake-eating-dinosaur)

  8. National Geographic (http://news.nationalgeographic.com/news/2010/03//100301-snake-eats-dinosaurs-fossils-sanejeh-indicus-scitech/)

  9. Wired (http://www.wired.com/wiredscience/2010/03/snake-eats-babydinosaurs/)

  10. LiveScience (http://www.livescience.com/animals/snakes-ate-baby-dinosaurs-100301.html)

  11. Nature (http://www.nature.com/news/2010/100302/full/news.2010.98.html)

JAW in Pisdura, central India holding the holotype vertebrae of the ca. 5 m long new fossil snake species Madtsoia pisdurensis (see article by Mohabey et al. 2011). [photo by Monica Wilson]