A wonderful reconstruction of the prehistoric nimravid - mammalian predators better known as "false saber-toothed cats" - Eusmilus, by the talented artist Mario Lanzas. Anyone who is already familiar with nimravids knows that Eusmilus looks like one of the famously called saber-toothed cats, but for those who don't know; nimravids like Eusmilus evolved down a separate genetic line, they found themselves living in a world where there was a predatory niche open for cat-like predators. Growing large, they developed enlarged upper canine teeth that were almost as long as their skulls, fossil evidence suggests that nimravids went along derived evolutionary pathways; resulting in conical teeth, dirk teeth, and scimitar teeth, with that their evolutionary paths then split in two, leading to saber-toothed and conical-toothed forms that convergently evolved with those of true felids tens of millions of years later. Meaning, despite Eusmilus having long saber teeth and looking like a saber-toothed cat, nimravids were actually a so-called "false saber-tooth" that only bore this resemblance due to convergent evolution. There are only three valid species of Eusmilus known; the type species E. bidentatus (Filhol, 1873), along with E. villebramarensis (Peigne and Brunet, 2003), and lastly, E. adelos (Barrett, 2021) the largest species in the genus. Ironically, Eusmilus' name means "true saber" - despite having the nickname 'false saber-tooth' - or "early knife," depending on the translation. Eusmilus is classified as Eukaryota, Animalia, Chordata, Mammalia, Carnivora, Feliformia, Nimravidae, and Hoplophoninae.
Fossils of Eusmilus have been unearthed throughout Europe and North America. It lived during the Paleogene Period, Late Eocene to Early Oligocene Epochs, Priabonian to Rupelian Ages 37.2 - 28.4 million years ago. Most Eusmilus species had a long body, and compared to modern leopards their legs were short, but despite that were about as tall as leopards, reaching a shoulder height of 60 - 70 centimeters (24 - 28 inches). Some specimens reached 2.5 meters (8 feet) long, E. adelos was comparable to African lion proportions, reaching a weight of 111 kilograms (244.7 lbs), and thus was the largest of the holplophonine nimravids. Eusmilus would have been a hunter of medium to large sized animals; much like rhinoceratids, tapirids, anthracotheriids, or upon the diversity of ‘oreodont', equid, and camelid taxa. Their enlarged canines were the primary killing tools employed by Eusmilus, and analysis of the skeleton supports this. The muscle attachment points on the skull show that Eusmilus actually had weak jaw closing muscles, but this was to allow for a wide jaw opening angle. To properly use their saber teeth, Eusmilus could open their jaw to an impressive ninety degrees wide, thirty degrees more than a modern African lion (Panthera leo).
Curiously, Eusmilus possessed fewer teeth than other mammalian carnivores, only 26 instead of the usual 44 teeth. To help compensate for the weak bite force, the neck and shoulders evolved to allow for powerful downward thrusts that drove the saber-teeth through its victim without the need for using the jaw muscles. Once punctured into a critical area such as the neck, death would come in a matter of minutes at most for the prey. Unfortunately, nimravids most likely went extinct due to general faunal turnover that saw a major reduction in diversity of numerous prey taxa, such as equids, camelids, antilocaprids and dromomerycids, from about 7.5 to 6.8 million years ago. The second image shows the partial skeleton of Eusmilus adelos specimen USNM 12820, with shaded known elements. Cranial abbreviations: fr frontal, na nasal, mp mastoid process, (A) cn carnassial notch, mc main cusp of P3, pa paracone, pcc posterior cingular cusp of P3, ps parastyle; (B - D) bis brachialis insertion site, lg lateral groove of ulna, rn radial notch, sln semilunar notch, (E - G) ce capitular eminence of radius, rt radial tuberosity, (H - J) dpc delto-pectoral crest, of olecranon fossa, sc supinator crest (brachial flange), remnants of bridge enclosing epicondylar foramen. Eusmilus adelos skeletal reconstruction by Dhruv Franklin. Photo credit: Paul Zachary Barrett, 2021.
Trouvé ici.
