Extinct American Cheetah, Miracinonyx inexpectatus July 2010

Kingdom: Animalia
    Phylum: Chordata
        Class: Mammalia
             Order: Carnivora
                Suborder: Feliformia
                    Family: Felidae
                           Genus: Acinonyx Kurtén (EXTINCT) Newly discovered cheetah species
                                        (Christiansen & Mazak 2009)    
                           Genus: Miracinonyx (EXTINCT)
                                  Species: Miracinonyx inexpectatus (EXTINCT) American cheetah
                                  Species: Miracinonyx trumani (EXTINCT)

• Taxonomy of the American cheetah has been difficult
  • Previously assigned to the genera Felis, Puma and Acinonyx (Van Valkenburgh et al 1990)
  • Now thought distinct enough to be in its own genus, Miracinonyx. (Van Valkenburgh et al 1990)
  • American cheetahs and African cheetahs have only a small number of shared traits, thus should not be in the same genera. (Van Valkenburgh et al 1990)
  • A third native American cat, the jaguarundi, groups with Miracinonyx and the puma according to DNA studies. (Barnett et al 2005)
• Cheetahs and pumas share many traits and have a close relationship, according to modern DNA studies (Barnett et al 2005)
• Scientific name: Miracinonyx inexpectatus.
  • Mira from Latin for "wonderful"
  • acinonyx from Gk. akineo (no movement) + onyx (claw), referring to false belief that cheetahs have non-retractable claws
  • inexpectatus from Latin for "unexpected"
  • thus, "wonderful unexpected cheetah"
• Common name
  • M. inexpectatus: American cheetah

• Cats of the cheetah-puma group diverged between 7.2 million years ago (Miocene) from the cat family, Felidae. (Johnson et al 2006)
• Much discussion in literature about Old World vs New World origins for cheetahs and the relationship between modern cheetahs (Acinonyx) and the extinct American cheetah (Miracinonyx) (Christiansen & Mazak 2009)
  • An extensive molecular phylogeny of the cat family suggests the American cheetah originated in the North American puma lineage and later migrated to central Asia and Africa. (Johnson et al 2006)
  • Other studies of actual fossils suggest that American cheetah ancestors came from Europe/Asia and migrated to North America (Kurtén 1976) (Christiansen & Mazak 2009)
    • Not likely that American cheetah came from an endemic North American ancestor shared with pumas since oldest NA pumas date to only 400,000 years ago; older more primitive pumas lived in Europe and Asia
    • Puma-Miracinonyx-Acinonyx group may be of Eurasian-African origin, perhaps migrating more than once to North America. (Van Valkenburgh et al 1990)
• Miracinonxy and Acinonyx had separate evolutionary histories for about the last 4 million years (Van Valkenburgh et al 1990)
• Miracinonyx inexpectatus first appears between 3.2 and 2.5 million years ago (Pliocene) in Texas. (Van Valkenburgh et al 1990)
• In equally old sediments, fossils of a true cheetah found recently in China (Christiansen 2009)
  • Acinonyx kurten (2.55-2.16 million years ago (Pliocene)
  • Has both puma-like and cheetah-like features..
• M. trumani occurs in younger sediments (Pleistocene) and doesn't overlap in time with M. inexpectatus
  • Looks more like modern cheetahs in its skull and tooth morphology (Christiansen & Mazak 2009)
• Miracinonyx became extinct with other Pleistocene megafauna around 12,000 years ago.
• Modern cheetahs display a significant reduction (90-99%) in genetic variation compared to other felid species (Menotti-Raymond & O'Brien 1993)
  • Reduction seems to be the result of near-extinction 10,000 years ago (the end of the Pleistocene).
• Cheetahs, although present almost entirely in African grasslands and semi-deserts, until exterminated by humans existed also in Asia .

• Older records ( Late Pliocene) Texas and California (M. inexpectatus)
• Younger records (Pleistocene) Wyoming, Nebraska, Arkansas, Maryland, Pennsylvania, West Virginia, Florida (M. trumani)
• Arizona (M. trumani) - new Pleistocene record (Hodnett 2010)
• See The Paleobiology Database for map

• A variety of habitats:
  • Coastal savannah
  • Forest with open areas,
  • Appalachian mountain stream valleys (Van Valkenburgh et al 1990)
  • High mountain meadows/forested and rocky slopes (Martin et al 1979)
• A new discovery of Miracinonyx in Arizona indicates habitat along steep slopes within the Grand Canyon. (Hodnett 2010)

• Slightly larger than a modern cheetah, with long limbs, a long tail, and a small, domed skull. 
• M. inexpectatus had lower limbs slightly less elongated than living cheetah and was better equipped for climbing (Turner & Anton 1997)
• M. inexpectatus was intermediate in body form between a modern mountain lion and a modern cheetah. (Van Valkenburgh et al 1990)

• Diagnostic feature distinguishing Miracinonyx from the living cheetah, Acinonyx
  • Shape of the upper slicing carnassial tooth (P4)
  • All cheetah share upper pre-molar teeth more slender and blade-like than in other large cats
• As in all cats, no molar teeth for chewing
• The cheetah’s relatively small canine teeth keep the roots of the upper canines from growing into the nasal passage
  • Allows space for large nasal passages for increased air intake
  • Air intake helps a cheetah’s recovery following a sprint
• Teeth may be used to roughly gauge age as shown in a study of fossils from Rancho La Brea (Meachen-Samuels & Binder 2009)
  • Dentin fills in pulp cavity as animal ages
  • Young middle and old age assessments possible
  • If approximate age plus jaw length are known, males can be distinquished from females (otherwise large old females and males, for example, can be confused - size alone can't be used)

Pelage

•  Unknown.

•  Not enough fossils to be well studied.

• A long and flexible back. (Turner & Anton 1997)
• Claws were fully retractile in both M. inexpectatus and M. trumani (Van Valkenburgh et al 1990)
  • Claws in living African cheetahs may look as if they are not retracted because they aren't covered with as much of a sheath as in other cats but the claws are fully retractable. (Turner & Anton 1997)
• Throat bones (hyoid and epihyal) typical of modern non-roaring pumas and cheetahs were found with very complete American cheetah skeleton from Hamilton Cave, West Virginia. (Van Valkenburgh et al 1990)
• M. trumani appears highly modified for running, as is the modern cheetah (Martin et al 1977)
• M. trumani is slightly smaller than M. inexpectatus.

• Unknown.
• Modern cheetahs have unique social structure among cats: females are solitary and raise young, males form groups.
• New reports of M. trumani fossils in the Grand Canyon may indicate different life style from cheetahs.

• Most interpretations of this animal's gait compare it to the modern African cheetah. (Turner & Anton 1997)
  • Very fast running in an open grassland habitat
• A new discovery of this extinct cheetah (M. trumani) in a cave within Arizona's Grand Canyon
  • May have been adapted for rapid bounding up rocky slopes like the modern snow leopard (rather than high speed running) (Hodnett et al 2010)
  • Most common possible prey items in Grand Canyon: extinct mountain goat Oreamos harringtoni.

• Found in western U.S. habitats with now-extinct mountain goats (Oreamos harringtoni) and mountain sheep
  • American cheetah may have filled an ecological role quite unlike that of modern cheetahs and may have instead pursued prey in steep rocky terrains as do Asian snow leopards. (Hodnett et al 2010)
• Often found associated with jaguars and sabertooth cats (Smilodon) (Van Valkenburgh et al 1990)
  • Perhaps occupied ecological niches like modern leopards, cheetahs, and lions in Africa.

• Pronghorn often suggested as possible diet options for the extinct American cheetah.
• Associated fossils with Miracinonyx at Natural Trap Cave in Wyoming (Martin et al 1979)
• Extinct mountain sheep
• Extinct horses
• A model for the feeding ecology of the Grand Canyon population of M. trumani proposed by Hodnett (2010)
  • Most common associated fossils in 3 Grand Canyon caves: extinct mountain goats
• Perhaps filled ecological role similar to modern snow leopard (Uncia uncia) on rocky slopes.

•  Pathologists examining fossils of Miracinonyx from Natural Trap Cave, Wyoming found evidence of osteoarthritis in their upper leg bones. (Rothschild & Martin 2003)

• Natural History Museum of Los Angeles County's George C. Page Museum has a web site introducing many of the region's Late Pleistocene animals. The Page Museum at Rancho la Brea displays most of the iconic large mammal fossils and a large number of rarely seen bird fossils from Late Pleistocene times. Visitors can view technicians working in a large fossil preparation lab.
• The Paleobiology Database: This site is a scientific organization run by paleontological researchers from around the world. It features taxonomic and distribution information for the entire fossil record; has maps
• University of Kansas Natural History Museum: Skeletons of Late Pleistocene American cheetah and extinct mountain sheep on display

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