Science & Technology

An Eye for a Tooth: Bizarre Saber-Tooth Predator From South America Was No Saber-Tooth Cat

Skulls and life reconstructions of the marsupial saber-tooth Thylacosmilus atrox (left) and the saber-tooth cat Smilodon fatalis (proper). Credit score: Stephan Lautenschlager

A brand new research led by researchers from the College of Bristol has proven that not all saber-tooths had been fearsome predators.

Saber-tooth cats, such because the North American species Smilodon fatalis, are among the many most iconic fossil animals with a popularity for being fierce predators. Nevertheless, saber-tooths got here in all styles and sizes and practically a hundred totally different saber-tooths are recognized to science to this point.

Thylacosmilus atrox (which implies ‘horrible pouched knife’) is a well-known animal that lived round 5 million years in the past in Argentina.

A jaguar-sized marsupial, it’s popularly often known as the ‘marsupial saber-tooth’, in contrast with the sabertoothed cats elsewhere on this planet, and it’s typically offered as a traditional case of convergent evolution — the place animals seem comparable in kind regardless of having very totally different evolutionary relationships (equivalent to marsupial flying possums and placental flying squirrels — each after all being gliders quite than true fliers).

Thylacosmilus had large, ever-growing canines, main folks to take a position that it was an much more vicious predator than the placental carnivores it superficially resembled equivalent to Smilodon.

However was it actually a fierce predator just like the extinct placental saber-toothed cats, which appear to have been very similar to fashionable cats however with a totally different mode of killing their prey?

An worldwide staff of researchers, led by Professor Christine Janis from Bristol’s Faculty of Earth Sciences, have carried out a collection of research on the cranium and tooth of this animal and have come to a totally different conclusion. Their findings are printed within the journal PeerJ.

Professor Janis stated: “The title of this paper, ‘An Eye for a Tooth’, sums up how we predict this animal has been perceived.

“It has spectacular canines, for positive: however in case you take a look at the entire image of its anatomy, a lot of issues merely don’t add up. For instance, it nearly lacks incisors, which huge cats immediately use to get meat off the bone, and its decrease jaws weren’t fused collectively.

“As well as, the canines of Thylacosmilus had been totally different from the tooth of different saber-toothed mammals, being triangular in form like a claw quite than flat like a blade.”

A statistical research, evaluating features of the cranium and tooth of Thylacosmilus with each present-day huge cats and a range of extinct saber-toothed cats, confirmed suspicions in regards to the variations from its placental supposed counterparts.

Co-author Borja Figueirido of the College of Málaga (Spain) added: “The cranium superficially seems to be quite like that of a saber-toothed placental.

“However in case you truly quantify issues, it turns into clear that Thylacosmilus’ cranium was totally different in lots of particulars from any recognized carnivorous mammal, previous or current.”

Detailed biomechanical research evaluating the skulls of Thylacosmilus and Smilodon, simulating efficiency below totally different circumstances, had been additionally revealing.

Stephan Lautenschlager from the College of Birmingham, the contributing creator on the paper who carried out these analyses, stated: “Earlier research by different researchers have proven Thylacosmilus to have had a weaker chunk than Smilodon.

“However what we are able to present is there was most likely a distinction in habits between the 2 species: Thylacosmilus’ cranium and canines are weaker in a stabbing motion than these of Smilodon, however are stronger in a ‘pull-back’ sort of motion. This means that Thylacosmilus was not utilizing its canines to kill with, however maybe as an alternative to open carcasses.”

Lastly, the opposite tooth of Thylacosmilus additionally pose issues for the interpretation of this animal as a cat-like predator, whether or not saber-toothed or not. In addition to the puzzling lack of incisors, the molars are small, and didn’t put on down alongside the perimeters as seen in an animal feeding on meat.

Larisa DeSantis from Vanderbilt College (USA), who carried out a detailed dental research, added: “The molars are inclined to put on flat from the highest, quite such as you see in a bone crusher.

“However in case you look at the detailed microwear on tooth surfaces, it’s clear that it was consuming gentle meals. Its put on is most just like that of cheetahs which eat from contemporary carcasses and suggests a good softer weight-reduction plan than fed to captive lions.

“Thylacosmilus was not a bone-crusher and will have as an alternative specialised on inside organs.”

Professor Janis stated: “It’s a little bit of a thriller as to what this animal was truly doing but it surely’s clear that it wasn’t simply a marsupial model of a saber-toothed cat-like Smilodon.

“Along with the variations within the cranium and the tooth, it was additionally short-legged and stiff-backed, and lacked retractile claws, so it will have had difficulties in pursuing its prey, pouncing on it and holding on to it. I think it was some type of specialised scavenger.

“It could have employed these canines to open carcasses and maybe additionally used a huge tongue to assist extract the innards: different mammals which have misplaced the incisors, like walruses and anteaters, even have huge tongues that they use in feeding.”

When Thylacosmilus lived on the plains of Argentina 5 million years in the past, it will have inhabited a very totally different sort of ecosystem to any fashionable one. Then the massive predators had been large flightless birds, the “terror birds” or phorusrachiformes, now all extinct. Life prior to now might have been very totally different to the current day.

Borja Figueirido added: “In Africa immediately it’s the mammals who’re the killers and the massive birds, like vultures, are the scavengers. However maybe 5 million years in the past in Argentina it was the opposite means round, and it was the mammals who had been the scavengers.”

Reference: “An eye for a tooth: Thylacosmilus was not a marsupial saber-tooth predator” by Christine M. Janis, Borja Figueirido, Larisa DeSantis and Stephan Lautenschlager, 26 June 2020, PeerJ.
DOI: 10.7717/peerj.9346
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