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Coniophis, primitive Late Cretaceous snake redescribed



From: Ben Creisler
bcreisler@gmail.com

A new online article about Coniophis in Nature:

Nicholas R. Longrich, Bhart-Anjan S. Bhullar & Jacques A. Gauthier (2012)
A transitional snake from the Late Cretaceous period of North America.
Nature (advance online publication)
doi:10.1038/nature11227
http://www.nature.com/nature/journal/vaop/ncurrent/full/nature11227.html



Snakes are the most diverse group of lizards, but their origins and
early evolution remain poorly understood owing to a lack of
transitional forms. Several major issues remain outstanding, such as
whether snakes originated in a marine or terrestrial environment and
how their unique feeding mechanism evolved. The Cretaceous Coniophis
precedens was among the first Mesozoic snakes discovered, but until
now only an isolated vertebra has been described and it has therefore
been overlooked in discussions of snake evolution. Here we report on
previously undescribed material from this ancient snake, including the
maxilla, dentary and additional vertebrae. Coniophis is not an
anilioid as previously thought; a revised phylogenetic analysis of
Ophidia shows that it instead represents the most primitive known
snake. Accordingly, its morphology and ecology are critical to
understanding snake evolution. Coniophis occurs in a continental
floodplain environment, consistent with a terrestrial rather than a
marine origin; furthermore, its small size and reduced neural spines
indicate fossorial habits, suggesting that snakes evolved from
burrowing lizards. The skull is intermediate between that of lizards
and snakes. Hooked teeth and an intramandibular joint indicate that
Coniophis fed on relatively large, soft-bodied prey. However, the
maxilla is firmly united with the skull, indicating an akinetic
rostrum. Coniophis therefore represents a transitional snake,
combining a snake-like body and a lizard-like head. Subsequent to the
evolution of a serpentine body and carnivory, snakes evolved a highly
specialized, kinetic skull, which was followed by a major adaptive
radiation in the Early Cretaceous period. This pattern suggests that
the kinetic skull was a key innovation that permitted the
diversification of snakes.