100-million-year-old croc could chew
The mammal-like crocodile unearthed in Tanzania knew how to chew, something its modern gash-and-gulp cousins cannot do.
Wed, Aug 04, 2010 at 01:57 PM
CROCS: The discovery adds to a growing body of evidence suggesting that crocodiles were once far more diverse that they are today in body type, habitat and appetites. (Photo: ZUMA Press)
Scientists on Wednesday announced the discovery of an ancient, mammal-like crocodile that knew how to chew, something its modern gash-and-gulp cousins cannot do.
The 100-million-year-old reptile, unearthed in Tanzania, was about the size of a domesticated cat and more at home on land than in water.
It had an unusually lean profile, a flexible backbone and relatively little scaly armour around its midriff, the better to leap in the air to grab giant dragonflies and other airborne prey.
But the most bitingly distinctive feature of Pakasuchus kapilimai, the researchers said, was its choppers.
It shared the overhanging, fang-like canines that today's alligators and crocodiles use to rip into their victims' flesh before swallowing them more-or-less whole.
But it also had specialized teeth that looked suspiciously like the molars — adpated for grinding food rather than slashing it — once thought to be unique to our distant warm-blooded ancestors.
"At first glance, this croc is trying very hard to be a mammal," quipped Patrick O'Connor, a professor at Ohio University in Athens and lead author of the study, published in Nature.
"A number of characteristics of this new species are very similar to features that were critical during the course of mammalian evolution from the Mesozoic into the Cenozoic," which began 65 million years ago, he said in a statement.
The discovery adds to a growing body of evidence suggesting that crocodiles were once far more diverse that they are today in body type, habitat and appetites.
The diminutive croc would have co-existed with carnivorous theropods such as Tyrannosaurus rex and Velociraptor, as well as the huge, plant-eating Sauropods.
O'Connor and colleagues found a complete skeleton of Pakasuchus in Tanzania's Rukwa Rift Basin in 2008, and have also recovered portions of seven different individuals.
They conjecture that the land-loving animal was abundant between 110 and 80 million years ago on what was then the super-continent of Gondwana, the land mass that eventually broke up into Africa, the Arabian peninsula, Australia, Madagascar, India, Antarctica and South America.
Only scant traces of mammals from the same period have been found on these continents, and the ones that have turned up do not appear to be related to modern mammalia.
"We suspect that notosuchians" — the extinct crocodile group to which Pakasuchus belonged — "were very successful in the southern hemisphere because they were exploiting a certain ecological niche," said O'Connor.
"This is an environment that was quite different from what we typically think of for crocodiles."
Little is known about the vegetation during that period, but clues from the sediment suggest the landscape was dominated by a large, long-lived river system and floodplains rich in vertebrate animal life.
The new crocodile's name comes from "paka", the Swahili word for cat, and "souchos," Greek for crocodile.
"Kapilimai" is a nod to Tanzania's pioneering palaeontologist Saidi Kapilima.
When found, the fossil skull was encased in hard, red sandstone, and the jaws were tightly closed, so scientists used medical scanning technology to reveal details about its teeth.
"The research was conducted with such a degree of accuracy that the complexity and mechanics of food processing could be modeled," O'Connor said.
Copyright 2010 AFP Global Edition