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Fossil Snake Fed On Hatchling Dinosaurs

March 2, 2010

The remains of an extraordinary fossil unearthed in 67 million-year old sediments from Gujarat, western India, provide a rare glimpse at an unusual feeding behavior in ancient snakes. An international paleontological team led by the University of Michigan’s Jeff Wilson, and the Geological Survey of India’s Dhananjay Mohabey, publish their discovery this week in the open-access journal PLoS Biology.

The remains of a nearly complete snake were found preserved in the nest of a sauropod dinosaur, the adults of which are the largest animals known to have walked the earth. The snake was coiled around a recently-hatched egg adjacent to a hatchling sauropod. Remains of other snake individuals associated with egg clutches at the same site suggest that the newly described snake made its living feeding on young dinosaurs.

“It was such a thrill to discover such a portentous moment frozen in time,” said Mohabey, who made the initial discovery in the early 1980s.

Working with the sediment-covered and inscrutable specimen in 1987, Mohabey recognized dinosaur eggshell and limb bones but was unable to fully interpret the specimen. In 2001, Wilson visited Mohabey at his office at the Geological Survey of India and was astonished when he examined the specimen.

“I saw the characteristic vertebral locking mechanism of snakes alongside dinosaur eggshell and larger bones, and I knew it was an extraordinary specimen ““ but I also knew we needed to develop it further,” Wilson said.

From that point began a decade-long odyssey that led to a formal agreement with the Government of India Ministry of Mines in 2004 that allowed preparation and study of the fossil at the University of Michigan Museum of Paleontology, weeks of museum study in India, and field reconnaissance at the original locality in Gujarat by a team that included Wilson, Mohabey, snake expert Jason Head of the University of Toronto, Mississaugua, and geologist Shanan Peters of the University of Wisconsin. The field research was funded by the National Geographic Society.

Preparation of the fossil at the University of Michigan revealed the snake was coiled around a crushed dinosaur egg next to a freshly hatched sauropod dinosaur. “We think that the hatchling had just exited its egg, and that activity attracted the snake,” explained Mohabey. “The eggs were lain in the loose sands near a small drainage and covered by a thin layer of sediment.” The arrangement of the bones and delicate structures, such as eggshells and the snake’s skull, point to quick entombment.

“Sanajeh was capable of ingesting the half meter-long sauropod hatchling because it was quite large itself, almost 3.5 meters long,” noted Jason Head.

In an accompanying article in PLoS Biology on how palaeontologists can infer behavior and function of fossil animals, Professor Mike Benton, from the University of Bristol, agrees that “it seems most likely, as the authors argue, that this 3.5-meter long snake was waiting and snatching juveniles as they hatched.” He concludes that “ingenious interpretations, and spectacular discoveries, such as the snake on the dinosaur nest can sometimes give us remarkable insights into the long-lost life of the past.”

The new snake, which was named Sanajeh indicus or “ancient-gaped one from India” because of its lizard-like gape, adds critical information that helps resolve the early diversification of snakes. Modern large-mouthed snakes are able to eat large prey because they have mobile skulls and wide gapes. Sanajeh bears only some of the traits of modern large-mouthed snakes and provides insight into how they evolved.

This discovery of Sanajeh adds to a growing body of evidence suggesting that India retained ties to southern landmasses for longer than once hypothesized. Sanajeh’s closest relatives are from Australia and speak to its strong ties to southern continents, collectively known as Gondwana.

A life-size flesh reconstruction of the scene immediately before burial was designed and executed by University of Chicago paleoartist Tyler Keillor. The team will donate the first cast to the Geological Survey of India at a formal function to be held in Mumbai, India on March 12, 2010.

Funding: Field research was supported by National Geographic Society Committee for Research and Exploration grant 8127-06 (JAW); collections work was supported by an Natural Sciences and Engineering Research Council discovery grant (JJH). JAW’s research was supported by a Woodrow Wilson National Fellowship Foundation Career Enhancement Fellowship for Junior Faculty. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

Competing interests statement: The authors declare that no competing interests exist.

Citation: Wilson JA, Mohabey DM, Peters SE, Head JJ (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

Image Caption: Snake-dinosaur fossil. Life-sized reconstruction of the moment just before preservation. The scales and patterning of Sanajeh’s skin is based on modern relatives of the fossil snake. The hatchling dinosaur is reconstructed from known skeletal materials, but its color is conjectural. The eggs are based directly on the fossils.  Sculpture by Tyler Keillor and original photography by Ximena Erickson; image modified by Bonnie Miljour [ More Images ]

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