An unidentified fossil collected greater than three a long time in the past was truly a mysterious species of saber-toothed carnivore that after stalked prey by means of the traditional rainforests of Southern California.
The fossil features a near-complete decrease jawbone and a set of well-preserved teeth, in keeping with a brand new examine, revealed Tuesday (March 15) within the journal PeerJ. Paleontologists on the San Diego Pure Historical past Museum (The Nat) initially collected the specimen in 1988 from a web site generally known as the Santiago Formation in Oceanside, a metropolis in San Diego County, California. The geological formation is estimated to be about 42 million years outdated, so fossils from the positioning date again to the Eocene epoch (55.8 million to 33.9 million years in the past), in keeping with the American Museum of Natural History.
When the fossilized jawbone was initially found, “it had been very correctly recognized as a meat-eating animal,” mentioned examine co-author Ashley Poust, a postdoctoral researcher in vertebrate paleontology on the Nat. The specimen bears “massive, slicing, scissoring enamel” which are ideally suited to shredding recent meat, reasonably than for crunching by means of nuts or gnawing on bones, as an example, Poust mentioned.
The museum paleontologists initially thought these formidable enamel would possibly belong to a nimravid, a kind of cat-like hypercarnivore, an animal whose weight loss program consisted largely of meat. The nimravids are sometimes known as “false saber-toothed cats,” as they resemble the well-known felines however do not belong to the Felidae household as true cats do, Live Science previously reported.
Nevertheless, examine co-author Hugh Wagner, a paleontologist on the Nat, later instructed that the jawbone would possibly belong to a extra mysterious group of hypercarnivores with scant illustration within the fossil file: the machaeroidines. Stays of those unusual beasts have been uncovered solely at choose websites in Asia and North America, and previous to the brand new examine, solely 14 specimens had ever been discovered, in keeping with the PeerJ report. The now-extinct group consists of the earliest recognized saber-toothed mammalian carnivores, which aren’t carefully associated to any residing carnivores.
Two of those specimens — a partial skeleton and a jawbone — have been found in Wyoming and Utah and described in prior papers by the examine’s co-first creator Shawn Zack, an assistant professor on the College of Arizona School of Medication and an professional in historic carnivores. For the brand new paper, Zack, Poust and Wagner teamed as much as reexamine the perplexing carnivore jawbone within the Nat’s assortment and decide, as soon as and for all, whether or not it belonged to a machaeroidine.
The workforce snapped pictures of the fossil from many angles in an effort to assemble a detailed 3D model of the bone and enamel, and after a radical examination, they confirmed that the specimen was not solely a machaeroidine, however a never-before-seen genus and species of machaeroidine.
They named the newfound creature Diegoaelurus vanvalkenburghae in honor of San Diego County, the place the specimen was discovered, and scientist Blaire Van Valkenburgh, a previous president of the Society of Vertebrate Paleontology whose work significantly influenced scientists’ understanding of carnivore evolution.
“Discovering this explicit group was fairly shocking,” as a result of no different machaeroidine specimens within the U.S. had been discovered west of the Rocky Mountains, Poust informed Reside Science. “We did not know that these occurred out right here in any respect.”
Primarily based on the dimensions of the jawbone, the researchers decided that D. vanvalkenburghae was in regards to the measurement of a bobcat, in keeping with the examine. The animal carried blade-like, slicing enamel at the back of its mouth and had “kind of decreased enamel within the entrance — it’s very misplaced the primary [tooth] behind its decrease canine,” Poust mentioned. Trendy cats even have this hole behind their decrease canines, to create space for his or her massive higher canines to chunk down, he famous. Along with this hole, D. vanvalkenburghae had a downturned, bony chin that additionally would have helped to accommodate its spectacular saber enamel.
About 42 million years in the past, D. vanvalkenburghae would have lived in a really totally different surroundings than may be present in San Diego County at present, Poust famous.
The Eocene kicked off with a interval of intensive warming, which fueled the expansion of scorching, humid rainforests world wide, in keeping with the American Museum of Pure Historical past. Fossils recovered from Santiago Formation counsel that the plush rainforests of historic Southern California have been as soon as house to lemur-like primates, marsupials, boar-size tapirs and tiny rhinos. In concept, D. vanvalkenburghae could have preyed on these animals, though the predator’s precise weight loss program is unknown, Poust mentioned.
The brand new species helps fill out the sparse machaeroidine fossil file, however it additionally raises new questions in regards to the cat-like predators, Poust mentioned.
For instance, did D. vanvalkenburghae ever coexist and compete for prey with nimravids? The oldest nimravid stays discovered within the U.S. are roughly 5 million years youthful than the newly recognized D. vanvalkenburghae fossil, so it will partially depend upon when the machaeroidine went extinct. The precise timing and motive for this extinction additionally stay mysterious, though it is clear that machaeroidines died out many tens of millions of years earlier than the emergence of true saber-toothed cats (Smilodon), Poust famous.
Initially revealed on Reside Science.