Pollen and volcanic ash date a new alligator ancestor to 350,000 years after the impact

The 350,000-year date comes from fossil pollen and from radiometrically dated volcanic ash in the beds that hold the skulls, not from the bones ^[11]. Set against the 66 million years since the asteroid struck, 350,000 years is about half of one percent of the elapsed time ^[1].

That date only carries weight if the animal really belongs on the alligator branch. The team scored 330 anatomical features, among them tooth counts, skull proportions and the shapes and positions of individual bones, then compared each against the same features in nearly 150 living and extinct crocodilians ^[10]. Multiply those out and the comparison spans roughly 49,000 feature-by-taxon cells ^[2]. Micro-CT scans of selected fossils showed a short, broad, alligator-like snout, with pointed front teeth giving way to bulbous back "button" teeth ^[9]. The New Scientist account does not say how many of the 330 features could be scored in the new species.

Fifteen individuals is the count behind the claim of abundance, and all of the material comes from Corral Bluffs, one fossil site in central Colorado, where the Denver Museum of Nature & Science team has recovered hundreds of bones, teeth and bony skin plates since it began finding the fossils about a decade ago ^[8][2]. The genus name joins the Greek mandra, an enclosed space or corral, for Corral Bluffs, to Suchus, the Greek name for the crocodile-headed Egyptian god Sobek; the species name honours Ian Miller, who used to work at the museum and who found many of the specimens ^[13].

"We have a bunch of these specimens, so they were quite abundant," said Sadie Sherman, one of the team ^[4]. "And so to have a large-bodied apex predator not just living, but actually thriving, so soon after such an apocalyptic event is really telling," she said ^[5]. The animal was about 2 metres long and looked like a smaller version of a modern alligator ^[1][3].

Adam Cossette at the New York Institute of Technology in Long Island said that "Mandrasuchus milleri provides a rare insight into how alligatorids diversified almost immediately after the end-Cretaceous extinction" ^[14]. "The fossils are compelling," he said ^[15]. Pedro Godoy at the University of Sao Paulo said the fossils "are beautifully preserved, and that's always exciting" ^[16].

Its front teeth were pointed, for seizing prey, and its back teeth rounded and molar-like, able to crush shellfish and other hard-bodied prey ^[3]. "It was probably just eating anything it could get its mouth on," Sherman said ^[19]. Teeth of that shape establish the range of foods an animal can process; what it ate most often is a separate question. Sherman also said freshwater habitats may have offered semiaquatic crocodilians a safer refuge, and that a broad diet let them cope when particular prey disappeared: "If you're not picky, you have a much better chance of surviving an extinction event, right?" ^[18][17]