Tragulidaechevrotains and mouse deer
This small family of artiodactyls (3 genera and 4 species) is found in southeastern Asia and Africa. Usually solitary and nocturnal, tragulids live in dense vegetation on the forest floor. They are primarily herbivorous, feeding on grasses, leaves, and some fruit, but they also eat invertebrates, small mammals, and even sometimes feed on carrion.
Mouse deer earn their common name because they are small; the largest individuals weigh around 4.5 kg. Their coats are some shade of brown above and white below. White spots and stripes can be seen on the body. Their muzzles are hairless. Their bodies appear short and compact, while the legs seem thin (relatively sturdier in the African species). They lack the facial and foot glands common to many members of their order.
Tragulids have a curious combination of primitive and derived traits. Their limbs, for example, are long and slender and end in hoofs. The carpals are cuboidal and highly specialized. Yet the lateral digits are present in tragulids (although not strongly developed), and tragulids are sometimes digitigrade. Even stranger, while the hindfeet have a cannon bone, the third and fourth metacarpals of the forefeet are either unfused (African species) or only partially fused (Asian species). Tragulids also have a unique ossified plate to which the sacral vertebrae attach.
Tragulids have neither antlers nor horns. A postorbital bar is present. There is no sagittal crest, and the mandibular condyle is long. Like bovids and cervids, they have a full set of lower incisors, but the uppers are replaced by a horny pad. Canines are present. These are sexually dimorphic: large and curved in males, smaller in females. The canines of males actually extend below the lower lips. The cheek teeth are selenodont, and the dental formula is 0/3, 1/1, 3/3, 3/3 = 34.
The stomach of mouse deer is three chambered (lacking a well-developed omasum), and these animals are ruminants.
The fossil record of tragulids extends to the early Miocene.
References and literature 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.
Nowak, R.M. and J.L. Paradiso. 1983. Walker's Mammals of the World, 4th edition . John Hopkins University Press, Baltimore, MD.
Savage, R. J. G. and M. R. Long. 1986. Mammal Evolution: An Illustrated Guide. Facts on File Publications, UK. 251 pp.
Simpson, C. D. 1984. Artiodactyls. Pp. 563-587 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, N.Y. vii+576 pp.
Vaughan, T. A., J. M. Ryan, N. J. Czaplewski. 2000. Mammalogy. Fourth Edition. Saunders College Publishing, Philadelphia. vii+565pp.
Wilson, D. E., and D. M. Reeder. 1993. Mammal Species of the World, A Taxonomic and Geographic Reference. 2nd edition. Smithsonian Institution Press, Washington. xviii+1206 pp.
Contributors
Phil Myers (author), Museum of Zoology, University of Michigan-Ann Arbor.
Glossary
- bilateral symmetry
-
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
-
uses smells or other chemicals to communicate
- endothermic
-
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
-
having the capacity to move from one place to another.
- sexual
-
reproduction that includes combining the genetic contribution of two individuals, a male and a female
- tactile
-
uses touch to communicate