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Tetrapodophis, new four-legged snake from Early Cretaceous of Brazil (Gondwana)

From: Ben Creisler

In the new issue of Science:

David M. Martill, Helmut Tischlinger, and Nicholas R. Longrich (2015)
A four-legged snake from the Early Cretaceous of Gondwana.
Science 349 (6246): 416-419.
DOI: 10.1126/science.aaa9208
Supplement is free:

Snakes are a remarkably diverse and successful group today, but their
evolutionary origins are obscure. The discovery of snakes with two
legs has shed light on the transition from lizards to snakes, but no
snake has been described with four limbs, and the ecology of early
snakes is poorly known. We describe a four-limbed snake from the Early
Cretaceous (Aptian) Crato Formation of Brazil. The snake has a
serpentiform body plan with an elongate trunk, short tail, and large
ventral scales suggesting characteristic serpentine locomotion, yet
retains small prehensile limbs. Skull and body proportions as well as
reduced neural spines indicate fossorial adaptation, suggesting that
snakes evolved from burrowing rather than marine ancestors. Hooked
teeth, an intramandibular joint, a flexible spine capable of
constricting prey, and the presence of vertebrate remains in the guts
indicate that this species preyed on vertebrates and that snakes made
the transition to carnivory early in their history. The structure of
the limbs suggests that they were adapted for grasping, either to
seize prey or as claspers during mating. Together with a diverse fauna
of basal snakes from the Cretaceous of South America, Africa, and
India, this snake suggests that crown Serpentes originated in



Susan Evans (2015)
Four legs too many?
Science  349 (6246): 374-375
DOI: 10.1126/science.aac5672

A classic Gary Larson cartoon shows a robed and bearded figure rolling
out clay strips, with the caption: “God makes the snake.” Body
elongation was certainly fundamental in the evolution of snakes from
lizards, as was the shrinking and ultimately the loss of limb pairs
(limb reduction). However, informative early fossils are rare, and
many details of the transition remain unresolved. A remarkable fossil
described on page 416 of this issue by Martill et al. brings fresh
perspective to the debate. The aptly named Tetrapodophis combines a
snakelike body with fore- and hindlimbs bearing five well-developed
digits (see the illustration).