A skull of the immigrant Eurasian beardog Cynelos (Carnivora, Amphicyonidae) from the early Miocene of southern California
Authors:
Hunt et al
Abstract:
At ∼23 Ma, large amphicyonid carnivorans participated in the initial Neogene mammal migration passing though the Bering filter en route to North America. Among the migrants were the amphicyonines Cynelos and Ysengrinia, first appearing in early Miocene sediments of the upper Arikaree Group in Nebraska and Wyoming, having entered the New World with chalicotheres, small cervoids, and the cursorial rhinoceros Menoceras. Early representatives of these immigrant carnivores had not, until recently, been recovered from localities along the Pacific coastal corridor of western North America. Here we report the discovery of a unique skull that establishes the presence of an early Neogene species of Cynelos (C. malasi, sp. nov.) in coastal southern California. The skull shares craniodental features with early Miocene species of the genus in Europe. Dentition (P4-M1-M2) and cranial morphology of Cynelos malasi compare with C. helbingi (southern Germany) and C. lemanensis (France, Germany) but uniquely combine size and occlusal detail to preclude assignment to these species. Cynelos malasi is assigned a latest Arikareean (Ar4) age in the North American Land Mammal Age (NALMA) chronology. By the early Miocene, species of Cynelos had dispersed from western Europe to northern Africa and into western North America. Whether the taxon arrived in North America by following a coastal southern Asian route or by Palaearctic dispersal is unconfirmed. Given the similarity between North American and European species of Cynelos, we suspect that the genus spanned Asia during the early Miocene.
(Miocene carnivores of Florida, similar, but not the same as below. img credit)
The fossilized fangs of saber-toothed cats hold clues to how the extinct mammals shared space and food with other large predators 9 million years ago.
Led by the University of Michigan and the Museo Nacional de Ciencias Naturales in Madrid, a team of paleontologists has analyzed the tooth enamel of two species of saber-toothed cats and a bear dog unearthed in geological pits near Madrid. Bear dogs, also extinct, had dog-like teeth and a bear-like body and gait.
The researchers found that the cat species—a leopard-sized Promegantereon ogygia and a much larger, lion-sized Machairodus aphanistus—lived together in a woodland area. They likely hunted the same prey—horses and wild boar. In this habitat, the small saber-toothed cats could have used tree cover to avoid encountering the larger ones. The bear dog hunted antelope in a more open area that overlapped the cats' territory, but was slightly separated.
"These three animals were sympatric—they inhabited the same geographic area at the same time. What they did to coexist was to avoid each other and partition the resources," said Soledad Domingo, a postdoctoral fellow at the U-M Museum of Paleontology and the first author of a paper on the findings published in the Nov. 7 edition of Proceedings of the Royal Society B.
Millions of years before the first humans, the predators lived during the late Miocene Period in a forested area that had patches of grassland. Large carnivores such as these are rare in the fossil record, primarily because plant-eating animals lower on the food chain have outnumbered meat-eaters throughout history.
Cerro de los Batallones, where Domingo has been excavating for the past eight years, is special. Of its nine sites, two are ancient pits with an abundance of meat-eating mammal bones. Agile predators, the researchers say, likely leapt into the natural traps in search of trapped prey.
"These sites offer a unique window to understand life in the past," Domingo said.
To arrive at their findings, the researchers conducted what's called a stable carbon isotope analysis on the animals' teeth. Using a dentist's drill with a diamond bit, they sampled teeth from 69 specimens, including 27 saber-toothed cats and bear dogs. The rest were plant-eaters. They isolated the carbon from the tooth enamel. Using a mass spectrometer, which you could think of as a type of scale, they measured the ratio of the more massive carbon 13 molecules to the less-massive carbon 12. An isotope is a version of an element that contains a different number of neutrons in its nucleus.
[..]
Because the researchers can tell what the herbivores ate, they can surmise what their habitat was like. They believe the animals in this study lived in a wooded area that contained patches of grassland.
The cats showed no significant difference in their stable carbon isotope ratios. That means they likely fed on the same prey and lived in the same habitat, but the posits that the species each fed on different-sized prey.
[...]
"The three largest mammalian predators captured prey in different portions of the habitat, as do coexisting large predators today. So even though none of the species in this 9-million year old ecosystem are still alive today (some of their descendants are), we found evidence for similar ecological interactions as in modern ecosystems," said Catherine Badgley, co-author of the new study and assistant professor of ecology and evolutionary biology.
