Ancient Snake Fossil Identifies Snake Ancestry
By on July 26th, 2012

Biologically, snakes are just glorified lizards. Glorified, they are, for a reason. There are around 3000 species of snakes in a variety of habitats. Together, they form one of the most successful groups in the animal kingdom.

Did Snakes Evolve on the Land or in the Sea?

Where did snakes evolve from? Did they arise from marine environments, as their bodies became more slender in an adaptation for swimming, or did they arise from terrestrial environments, in which case their bodies would have become adapted for burrowing? Also, snakes have remarkably flexible jaws which allow them to devour prey much larger than themselves. Chances are that you haven’t come across any pictures of lizards ingesting huge animals. This is because lizards have inflexible jaws. How, then, did snakes get these jaws when their cousins don’t have them?

We don’t know the answers to these questions because of the incomplete fossil records in the serpent lineage. There haven’t been any fossils that connect snakes and lizards. Now, a snake fossil forming the missing link between these two classes of reptiles has been found.

Jaws of lizards (a), Coniophis (b) and modern snakes (c). Coniophis has hooked teeth like modern snakes, but its skull is still fixed. [Image Credit: Nicholas Longrich: taken from the publication in Nature]

New Snake Fossil Provides Perfect Snapshot of Evolution

Coniophis precedens from the plains of North America represents one of the most primitive snakes. Based on species comparison (also called ‘phylogenetic analysis’) with other snakes, it has been found to be amongst the most ancient. In what is a perfect snapshot in the evolutionary process, it has a snake-like body and a lizard-like head with snake-like teeth. Its small size and reduced spines both point to it being fossorial—adapted for digging. This points us towards snakes having evolved from burrowing lizards, and not from marine environments. Its hooked teeth, like those of its contemporary kin, are suitable for chewing on relatively large, soft-bodied prey, but like lizards, its jaw remains relatively fixed. Its slender body enabled it to slither, and according to Professor Nicolas Longrich, who headed this study, it could have slithered “beneath the feet of the dinosaur Tyrannosaurus rex”.

The picture that emerges is that Coniophis was a small carnivorous land snake that preyed upon small vertebrates. Snakes that followed it evolved flexible jaws in a series of adaptations that enabled them to feed on a greater variety to prey. Coniophis thus represents a stage in the stepwise accumulation of adaptations.

The bones of this ancient and important connecting link in the evolution of snakes are in museum collections in the United States of America.You can read more about this research here.

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Author: Shweta Ramdas
Beginning life as a grad student studying human genetics.

Shweta Ramdas has written and can be contacted at shweta@techie-buzz.com.
 
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