Extinct American Cheetahs (Miracinonyx spp.) Fact Sheet: Physical Characteristics

Careful study of fossil bone or tooth anatomy yields much exact information about placement and strength of muscles, tendons, ligaments, nerves, and blood vessels. In rare cases, skin and hair impressions or actual skin or hair is preserved. Body weight is more difficult to gauge because fat leaves no impression on the skeleton.

General

• 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)

Teeth

• 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.

Shaw & Cox (2006)
Turner & Anton (1997)
Van Valkenburgh et al (1990)