A 2-metre-long reptile that flourished in North American waterways shortly after an asteroid wiped out most dinosaurs 66 million years ago has been identified as the oldest known representative of the alligator group. Scientists have uncovered bones from about 15 individuals of the previously unknown species, which probably ambush-hunted near freshwater channels and may have sheltered in burrows. The newly named Mandrasuchus milleri looked like a smaller version of a modern alligator, with pointed front teeth for seizing prey and rounded, molar-like back teeth that could crush shellfish and other hard-bodied prey.
Spectacular fossil preserves internal organs of ancient marine reptile Combined, these characteristics may help explain its success in a dying world. This success may then have paved the way for the widespread expansion of alligators, says Sadie Sherman at the Denver Museum of Nature & Science in Colorado. Crocodilians, however, fared considerably better: multiple lineages, including the “true crocodiles” and the gharials, survived.
The alligatorids survived, too. They are divided into two subfamilies. The “alligatorines” include the two living species of alligator – the Chinese and American.
The other subfamily is the “caimaninae”, which includes the six known species of caimans. Freshwater habitats may have offered some protection from the devastation, giving semiaquatic crocodilians a safer refuge, while their ability to eat a wide range of foods meant they could cope when particular prey disappeared, says Sherman. A team from the Denver Museum, including Sherman, may have uncovered an important piece of the puzzle.
Around a decade ago, they began finding well-preserved fossils of an unknown crocodilian at Corral Bluffs, a fossil site in central Colorado. The team has since recovered hundreds of bones, teeth and bony skin plates, or osteoderms, says team member Emily Lessner. Dinosaur found with a crocodile in its jaws named as new species Close examination and micro-CT scans of selected fossils suggested they belonged to a crocodilian with a short, broad, alligator-like snout and pointed front teeth that gave way to bulbous back “button” teeth.
After looking at 330 anatomical features – including tooth numbers, skull proportions and the shapes and positions of individual bones – and comparing them with the same features in nearly 150 living and extinct crocodilians, the researchers argue that M. milleri was an alligatorine. Analyses of fossil pollen and radiometrically dated volcanic ash revealed that the oldest skulls date to a mere 350,000 years after the asteroid strike, making M. milleri the oldest known member of its subfamily. Several M. milleri skeletons were found with bones still connected, including one inside what may have been a burrow.
Extract — continue reading at the source.
