Miracinonyx

Above: Mauricio Anton's reconstruction of Miracinonyx trumani

For my own amusement and in the hope of improving my abysmal writing skills, im going to try and do a few posts about my favourite extinct cats.  First off, is one of the less well known felines of the Pleistocene.

The American cheetah (genus Miracinonyx) is one of the most interesting cats that people have never heard of.  Only really identified in the 1970s, before then, remains of this genus had been classified as Puma concolor (puma, cougar, mountain lion) and it was only with the recovery of nearly complete specimens from Natural Trap Cave in Wyoming that palaeontologists realised this cat was something  really different. The late Pleistocene species (Miracinonyx trumani) had the proportions of a running cat- like the African cheetah (Acinonyx jubatus), very long legs, flexible back, enlarged nasal openings for efficient airflow.  Since the discovery, many have argued as to whether M.trumani was actually more closely related to the cheetah or the puma (which, despite not looking very similar are quite closely related). Should the American cheetah be Acinonyx trumani or Puma trumani? Or could it retain its unique generic status?

Not just a question of taxonomic squabbling, the answer informs our understanding of species movement between the old world and the new world, and about the way in which evolution, when presented with similar situations, produces similar outcomes.

As part of my PhD I was involved with a project looking at the genetics of extinct American felines. We managed to extract some from the Natural Trap Cave material.

Ancient DNA from Miracinonyx clearly showed that it was a sister species to the puma.  An authentic American species that had developed a bodyplan paralleling the cheetah in response to the pressures of living in an open grassland.  The American cheetah lived on the wide open prairie plains of the new world, a pleistocene biome that would have looked very similar to the African  Serengeti of today, where cheetah thrive.

The pronghorn antelope (Antilocapra americana) may actually be an evolutionary ghost, shaped by an arms race with Miracinonyx. Pronghorn are incredibly fast- >50mph over reasonable distances- much faster than the wolves, coyotes, puma, or bear that hunt alongside them.  Its possible that this speed evolved in response to Miracinonyx and now that the American cheetah is gone, the pronghorn lives on, hopelessly outclassing the predators that survive today.

The etymology of the cheetahs provides a nice link with the blog name. Megalonyx comes from the greek for "great"(mega) and "claw" (onyx). The African cheetah, Acinonyx, means "without"(a-), "moving"(kino), and "claw"(onyx) in reference to the apparent non-retractile claws in the cheetah (which are alleged to help provide traction when running). Miracinonyx therefore means "unexpected cheetah" from "unexpected"(mira-) and Acinonyx.

Refs:

Barnett, R., Yamaguchi, N., Barnes, I. & Cooper, A. 2006. The origin, current diversity and future conservation of the modern lion Panthera leo. Proceedings of the Royal Society B 273, 2119-2125.

Adams, D. B. 1979. The cheetah: native American. Science 205, 1155-1158

Martin, L. D., Gilbert, B. M., Adams, D. B. 1977. A cheetah like cat in the North American Pleistocene. Science 195, 981-982

Why Megalonyx?

I like giant sloths. Who wouldn't? Although almost all my work has been on Pleistocene and recent felids, the Pleistocene megafauna is so amazingly diverse that there are bound to be genera and species that capture the imagination.  The giant Xenarthra are so unlike anything that's around today that I cant help but wonder how they fitted into the ecology of ancient America, what they looked like in the flesh, and what the people who had the privilege of seeing them 10,000 years ago thought about them.  

A lot of the history of Quaternary study is closely tied to giant sloths. Megalonyx ("great claw"), as well as having a cool name, was the first superstar of American palaeontology. At a time when European palaeontology was starting out and people were impressed by remains of cave bears (Ursus spelaeus), cave lions (Panthera leo spelaea) cave hyaenas (Crocuta crocuta spelaea), Irish Elk (Megaloceros giganteus), and Mammoths (Mammuthus primigenius), these animals were used to argue that the Americas were somehow inferior and lacking in any comparable fauna.  

Megalonyx was named by Thomas Jefferson (American president and polymath) who was given some bones from western Virginia and correctly surmised they belonged to an animal about three times as large as a lion. He was also able to suggest it had some affinity to another recently discovered animal- the Megatherium, which had been dug up from the La Plata river in Paraguay and sent to the King of Spain. 

Megatherium and Megalonyx are both still regarded as valid genera of giant sloth. Jefferson, writing over 200 years ago, was smart enough to work out that his bones came from a giant animal, probably related to the "bradypus, dasypus, and pangolin" (i.e. sloths and pangolins) and very rare (at a time when most of western America was unexplored this seemed a safe bet). Given the state of palaeontology in the 18th century, Jefferson was certainly extremely prescient.  One of the most common Pleistocene Megalonychid sloths is named in his honour- Megalonyx jeffersonii.

See the original fossils that Jefferson described here.

More information on Megalonyx

Great reconstructions here.

Ref:

Jefferson, T. (1799)"A memoir on the discovery of certain bones of a quadruped of the clawed kind in the western parts of Virginia" Trans.Amer.Phil.Soc V4, P246-260