By Phil Myers
Notice the range in size.
Molossids are known as free-tailed bats, because their 
bony tail extends to the end of a well-developed tail membrane (uropatagium) and considerably beyond. They often crawl backwards when on the ground, using their tail as a sort of "feeler." Molossids are small to moderately large bats, with forearms ranging from around 27 mm to approximately 86 mm in length. Their muzzles are usually short and broad, and they often have wide, fleshy lips that may have folds or creases. Many have a distinctive pad over their noses; this pad is often endowed with odd bristles with spatulate tips. Most free-tailed bats have relatively short but broad ears. The tragus is tiny, but opposite it, an antitragus is unusually well developed. All species have long, narrow wings, apparently adapted for fast but relatively unmanueverable flight in open places. Their wing and tail membranes are unusually tough and leathery. Molossids also have short, strong legs and broad feet. Like their nose pads, molossids' feet are well endowed with sensory bristles (also with spatulate tips). They are excellent climbers, perhaps because they launch themselves for flight from a considerable height above the ground. Because of their long, narrow wings, they must attain considerable speed before they can develop enough lift to fly. They accomplish this by falling some distance from their roost or take-off point.
Molossids generally have short, even velvety fur. Most are black or brown, and many species have distinctive reddish and brownish or blackish color phases.
Molossids are found in the New World from the central United States south to southern Argentina. In the Old World, they occur in southern Europe and Africa, eastward through tropical and subtropical Asia to Australia. All members of the family are insectivorous, catching their prey on the wing. Their roosting habits range from solitary to living in immense colonies of millions of bats, usually in caves. In the neighborhood of these large colonies, molossids may consume enormous numbers of insects. Approximately 85 species of molossids are placed in around 12 genera.
Technically, molossids can be recognized by a combination of the following characters:
- long tail, tip of tail free of uropatagium
- tragus tiny, antitragus conspicuous
- no noseleaf
- 3rd phalanx of the 3rd finger is cartilaginous for most of its length
- no postorbital processes
- premaxillae with or without palatal branches
- dilambdodont teeth
- dental formula 1/1-3, 1/1, 1-2/2, 2-3/3
The fossil record of the Molossidae extends to the late Eocene.
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.
Hill, J. E., and J. D. Smith. 1984. Bats, a Natural History. University of Texas Press, Austin. 243 pp.
Koopman, K.F. 1984. Bats. Pp. 145-186 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.
Nowak, Ronald M., 1994. Walker's Bats of the World . Johns Hopkins University Press, Baltimore.
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.
