Studying how snakes got legless. 8 February 2011Last updated at 12:19 By Jonathan Amos Science correspondent, BBC News The snake would have slithered along the ground during the Late Cretaceous A 95-million-year-old fossil is helping scientists understand how snakes lost their legs through evolutionary time. Found in Lebanon, the specimen is one of only three examples of an ancient snake with preserved leg bones. One rear leg is clearly visible but researchers had to use a novel X-ray technique to examine another leg hidden inside the fossil rock. Writing in the Journal of Vertebrate Paleontology, the team says the snake records an early stage in limb loss. The scientists' high-resolution 3D images suggest the legs in this particular species, Eupodophis descouensi, grew more slowly, or for a shorter period of time. It is a conclusion made possible only after seeing all the bones obscured inside the limestone, and determining that although the creature possessed ankle bones, it actually had neither foot nor toe bones.
Human evolution: The old man of the mountain returns. The Tuatara, a Still-Evolving Original. There is the kiwi, of course, with its dense, furlike feathers, its catlike whiskers and its long, slender, curving bill tipped by a pair of ultrasensitive nostrils; and the kakapo, a heavy, flightless, nocturnal parrot with the flat-cheeked face of an owl; and the giant weta, a cricket the size of a human hand that displays by waving its formidably serrated rear legs high in the air as if brandishing a pair of saws. Yet the animal that may well be New Zealand’s most bizarrely instructive species at first glance looks surprisingly humdrum: the tuatara.
A reptile about 16 inches long with bumpy, khaki-colored skin and a lizardly profile, the tuatara could easily be mistaken for an iguana. Appearances in this case are wildly deceptive. The tuatara — whose name comes from the Maori language and means “peaks on the back” — is not an iguana, is not a lizard, is not like any other reptile alive today.
Adventures in Very Recent Evolution. Evolution in Action: Lizard Moving From Eggs to Live Birth. Evolution has been caught in the act, according to scientists who are decoding how a species of Australian lizard is abandoning egg-laying in favor of live birth. Along the warm coastal lowlands of New South Wales (map), the yellow-bellied three-toed skink lays eggs to reproduce. But individuals of the same species living in the state's higher, colder mountains are almost all giving birth to live young. Only two other modern reptiles—another skink species and a European lizard—use both types of reproduction. (Related: "Virgin Birth Expected at Christmas—By Komodo Dragon. ") Evolutionary records shows that nearly a hundred reptile lineages have independently made the transition from egg-laying to live birth in the past, and today about 20 percent of all living snakes and lizards give birth to live young only.
Eggs-to-Baby Switch Creates Nutrient Problem One of the mysteries of how reptiles switch from eggs to live babies is how the young get their nourishment before birth.