Hyracoideahyraxes
Hyraxes, also known as dassies or conies, are jack-rabbit sized animals with short tails and peculiar, 3-toed hind feet with almost hoof-like nails on two of the toes (the inner toe has a claw). The forefeet have 5 toes. The soles of their fore- and hindfeet, which are moistened by special sweat glands, are remarkably soft and elastic, which works to increase their friction against the substrate. They have specialized muscles in the soles of the feet that help them to work almost like a suction cup. The feet of hyraxes are mesaxonic, meaning that the plane of symmetry of the foot goes through the third digit. In this they resemble perissodactyls.
The skulls of hyraxes have a short rostrum, prominent postorbital processes that form a postorbital bar, small bullae, a large jugal that contributes to the glenoid fossa, and a broad plate-like angular region of the mandible. Hyraxes have a single incisor on each side of the upper jaw (two on the lower), followed by a diastema -- an arrangement that looks very rodent-like. Like those of rodents, the incisors of hyraxes grow continuously and have enamel only on the anterior surface, creating a self-sharpening, chisel-like cutting edge. The molars have strongly developed lophs, as is common in species with herbivorous diets. The dental formula is 1/2, 0/0, 4/4, 3/3 = 34.
Hyracoids are usually grouped with elephants and sirenians as "subungulates," and they all may have all descended from a common stock
The diet of hyraxes consists mostly of leaves, bark and grasses, but they also eat some insects. Some species are arboreal, while others live on rock outcrops. All are quick and agile climbers. They are active during daylight hours. Rock-dwelling species live in colonies; arboreal species tend to be solitary. All make a variety of whistles, chatters, and other sounds.
There is a single family of hyraxes, Procaviidae, and seven living species. Hyraxes are found in sub-Saharan Africa and Middle East.
Literature and references cited
Feldhamer, G. A., L. C. Drickamer, S. H. Vessey, and J. F. Merritt. 1999. Mammalogy. Adaptation, Diversity, and Ecology. WCB McGraw-Hill, Boston. xii+563pp.
Jones, C. 1984. Tubulidentates, proboscideans, and hyracoideans. Pp. 523-535 in Anderson, S. and J. K. Jones, Jr. (eds). Orders and Families of Recent Mammals of the World. John Wiley and Sons, N.Y. xii+686 pp.
Vaughan, T. A. 1986. Mammalogy. Third Edition. Saunders College Publishing, Fort Worth. vii+576 pp.
Vaughan, T. A., J. M. Ryan, N. J. Czaplewski. 2000. Mammalogy. Fourth Edition. Saunders College Publishing, Philadelphia. vii+565pp.
Contributors
Phil Myers (author), Museum of Zoology, University of Michigan-Ann Arbor.
Glossary
- bilateral symmetry
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having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.
- chemical
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uses smells or other chemicals to communicate
- endothermic
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animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.
- motile
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having the capacity to move from one place to another.
- sexual
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reproduction that includes combining the genetic contribution of two individuals, a male and a female
- tactile
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uses touch to communicate