Snake & lizard with intermediate legs

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Snake & lizard with intermediate legs

Postby Chris Sergeant » Tue Feb 15, 2011 5:27 pm

X-ray imaging technology is helping scientists better understand how in the course of evolution snakes have lost their legs. New, detailed 3-D images reveal that the internal architecture of an ancient snake leg bones strongly resembles that of modern terrestrial lizard legs. Eupodophis descouensi from 95 myr rocks in Lebanon. Around 50 cm length with a small leg, about 2 cm long, attached to the pelvis. Fossil represents an intermediate evolutionary stage when ancient snakes had not yet completely lost the legs they inherited from earlier lizards. The fine detail of the buried second small leg, suggest that this species lost its legs because they grew more slowly, or for a shorter period of time. ... 142619.htm

A 95 myr marine lizard with minuscule front legs may shed new light on the evolution of modern reptiles, particularly snakes, scientists have reported. Fossilized remains of the reptile represent the earliest known example of a lizard evolving toward a limbless state. The vestigial, or no longer functional, forelimbs barely protrude from its long, snakelike body. Rear legs of normal size.
Adriosaurus microbrachis (small-armed Adriosaurus) belongs to the lizard group most closely related to snakes. Noted that the new fossil dates to the same period as fossils of primitive snakes that also retained their hind legs.
The fossil suggests that in both kinds of ancient animals, the front limbs shrank before the hind legs. Shows that in Cretaceous lizards, and by analogy, snakes, the forelimb was lost in stages, before any obvious reductions of the rear limb assembly. ... kes_2.html
Chris Sergeant
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