How croc got its smile
2004-08-24 13:04
Paris - Crocodiles developed their characteristic wide skull and "smiley" jaws millions of years before they ventured from the land and into water, according to a study of a crocodilian ancestor found in China.
The fossil, which dates back to the Middle Jurassic period of between 144 and 205 million years ago, is of a creature called a sphenosuchian, measuring about 1.5 metres at most, and is believed to be the most directly-related forerunner of today's crocodiles and ancestors.
The specimen has the thick, broad skull familiar of the croc, pointing to the powerful jaw muscles that are used to crush its victims to death.
But it also has slender, erect limbs and graceful hands that are aligned with the rest of the forelimb - rather than splayed out as in living crocodilians - and this shows sphenosuchians were designed for walking on the ground.
"The consolidation of the crocodilian skull thus began well before crocodilians entered the water," says the study, lead-authored by George Washington University palaeontologist James Clark.
The research appears on Thursday in Nature, the British weekly science journal.
Living crocodilians comprise three families in 23 species, divided into three families - crocodiles; alligators and caimans; and a third family called gavialidae.
These creatures have remained essentially unchanged for 65 million years, making them among the most successful animals in the world today.
The fossil studied by Clark's team was found in Wucaiwang, Xinjiang province, in northeastern China.