The cheetah, Acinonyx jubatus, formerly ranged throughout much of the arid wood, bush, and grasslands of Africa and southwest Asia. At present, documented populations occur in Algeria, sub-Saharan Africa, Iran, and isolated oases in the Qattara Depression in Egypt. A near-extinction event about 10,000 years ago and subsequent population "bottlenecks" have resulted in low genetic diversity in Acinonyx. This is of utmost concern to conservation biologists because it is a threat to the survival of the species in addition to growing conflicts with humans over livestock, loss of habitat, and interspecific competition with other large carnivorans in protected areas. Acinonyx jubatus is listed on CITES Appendix I and is declared as endangered by the U.S. and IUCN (A. j. venaticus, the Asiatic cheetah only other subspecies listed as threatened). In Iran, there are currently only 60 cheetahs remaining in the wild.
Acinonyx pardinensis, an extinct cheetah about the size of an extant lion (Panthera leo), appeared in Eurasia about 3 million years ago, roughly synchronous with the appearance of Acinonyx jubatus in Africa. Cheetah-like cats (species of the extinct genus Miracinonyx) appeared in North America at about this time, suggesting speciation events occurring as members of the lineage migrated from North America to Eurasia to Africa.
Analyses of morphological and molecular data obtained from extant felids recognize Acinonyx jubatus as the sister taxon to Puma concolor (puma) and Herpailurus yagouaroundi (jaguarundi). Fossils of their most recent common ancestor have yet to be identified, but mtDNA gene divergence data suggest that this ancestor was present in North America 8.25 million years ago.
The skull of Acinonyx jubatus presents some characteristic morphology. It is vaulted in profile, the frontals being the highest point. The frontal is very broad and encloses an extremely enlarged frontal sinus. The diameter of the infraorbital foramen is reduced, which may be related to the reduction of vibrissae, receptors of which are innervated by branches of the trigeminal nerve. When the jaws are closed there is no space behind the upper canines. This external feature is created by the alignment of the lower canine and post-canine teeth (the anterior portion of the dentary is not elevated as in other felids), and the positions of both the upper and lower premolars. The upper canines are relatively small, and their roots border an enlarged nasal opening. It has been suggested that, because cheetahs employ rapid acceleration to capture prey, the cranial modifications for more air intake came at the expense of large canines.
The effect of the genetic homogeneity of Acinonyx jubatus can be observed in its cranial morphology. Developmental instability, a consequence of inbreeding, has been implicated in the occurrence of fluctuating asymmetry in the cranial morphology of an east African population of Acinonyx jubatus.
About the Species
This specimen, a female of the subspecies raineyi, was collected in the Shinyanga Region of Tanzania by Dumah R in 1928. It was made available to The University of Texas High-Resolution X-ray CT Facility for scanning courtesy of Drs. Blaire Van Valkenburgh and Jessica Theodor, Department of Organismic Biology, Ecology, and Evolution, University of California, Los Angeles. Funding for scanning was provided by Dr. Van Valkenburgh and by a National Science Foundation Digital Libraries Initiative grant to Dr. Timothy Rowe of The University of Texas at Austin. The cheetah is one of several felid carnivorans included in ongoing research of respiratory turbinates by Drs. Van Valkenburgh and Theodor.
About this Specimen
The specimen was scanned by Matthew Colbert on 11 March 2001 along the coronal axis for a total of 363 slices, each slice 0.5 mm thick, with an interslice spacing of 0.46 mm. The dataset displayed was reduced for optimal Web delivery from the original, much higher-resolution CT data.
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