In 2002, at the Chubut province of Punta Peligro (Argentina), paleontologist Guillermo Rougier found fossil remains of a frog preserved in an uncommon structure. The bones were not so much articulated or disarticulated, but strangely tangled (...)
Now, 18 years after the find, Paula Muzzopappa, researcher for Conicet at the Center for Natural, Environmental and Anthropological Sciences of the Maimónides University, along with other two scientists, provided further information.
Through a tomography it was possible to analyze the strange structure without taking it apart (...).
"I could not figure out why the frog was preserved in such a strange manner. Then along came Agustín Martinelli, researcher for Conicet at the Argentinian Museum of Natural Sciences, who understood that the fossil we were studying was actually a bird pellet.
This "vomit" is really a ball of remains of undigested food, regurgitated by a bird. Although it is frequent, for example, for owls to regurgitate the harder parts of prey such as bones, fur, wings or insect cuticles, it is uncommon for these pellets to fossilize and even more to be found preserved three-dimensionally as in this case. Pellets even older than this one, however, from the Mesozoic even, have been discovered.
Certain characteristics of the fossil such as shape and the wear pattern of the bones inside it have allowed us to determine that it was produced by a bird of prey. Although it was expected that raptors inhabited the region 60 million years ago, there haven´t been skeletal remains to confirm it, so this is indirect evidence of their presence.
The study of the bones concluded that this frog belonged to a species unknown until know, related to today's large Chilean frog Calyptocephalella gayi, which today exists only in lakes in central Chile. The new species has been named Calyptocephalella sabrosa ("sabrosa" meaning tasty seeing as it was the tasty meal for another animal).
Family Calyptocephalellidae has been present in the Patagonian region since the late Mesozoic, and after surviving the catastrophe that wiped out the (non-avian) dinosaurs, it became especially abundant in the Cenozoic faunas. But around 15 million years, this frog family became extinct in Argentina and survived only in Chile, represented by a few species in genus Telmatobufo and by Calyptocephalella gayi, the last of its genus.
All the elements of the skeleton we found are consistent with the hypothesis that this was one single individual and that the bird pellet contains remains of only one frog."
Muzzopappa estimates that the frog was around 15 cm long, around the size of the Chilean frog today, and that it had a highly ossified skull and robust body. As for the lifestyle, it must have been similar to C. gayi, "which lives in lakes and comes out only to hunt and eat. They are hyper voracious, they will eat anything they find."