The Molossidae, or free-tailed bats, are a family of bats within the order Chiroptera.[1]
The Molossidae is the fourth-largest family of bats, containing about 110 species as of 2012.[2] They are generally quite robust, and consist of many strong-flying forms with relatively long and narrow wings with wrinkled lips shared through their genus.[3] Their strong flying form allows them to fly 60 miles per hour using tail winds and at altitudes over 10,000 feet.[3] This makes them unique among bats, as they are the only bat family that withstands the elevation. They are widespread, being found on every continent except Antarctica. They are typically found in caves, abandoned mines, or tunnels.[3]
The family's scientific name comes from the type genusMolossus, which in turn is from the Molossus breed of dogs.[4]
The family's common name is derived from a length of "free" tail, projecting beyond the end of the uropatagium—the membrane that connects the base of the tail to the hind legs.
Another common name for some members of this group, and indeed a few species from other families, is mastiff bat. The western mastiff bat (Eumops perotis), a large species from the southwestern United States and Mexico with wings over 0.5 m (1.6 ft) across, is perhaps one of the best known with this name. They are widespread, being found on every continent except Antarctica.
The tail is usually best seen when resting. A special ring of cartilage slides up or down the tail vertebrae by muscular action to stretch or retract the tail membrane. This gives many species a degree of fine tuning in their flight maneuvers to rival their day-flying ecological equivalents, such as swifts, swallows, and martins. As a result, these animals include the fastest-flying of all bat species among their number.[5] The dental formula of free-tailed bats varies between species: 1.1.1-2.2-31-3.1.2.3
Free-tailed bats are usually grey, brown, or black in color, with some exceptions. They range from 4 to 12 cm (1.6 to 4.7 in) in length, excluding the tail, and can weigh from 8 to 220 g (0.28 to 7.76 oz), depending on species. They are insectivorous, and catch their food on the wing. While some species roost in small groups in hollow trees or rocky crevices, some cave-dwelling species form vast colonies of up to 50 million individuals.[5]
Molecular sequence data support the monophyly of the Molossidae as a whole, but not that of many of its genera, such as Chaerephon, Mops, Mormopterus, and Tadarida. The grouping of Chaerephon minus C. jobimena plus Mops was found to be monophyletic, as was Otomops.[6]
A 2012 study attempted to show the relationships of genera within the subfamily Molossinae (the other subfamily of Molossidae, Tomopeatinae, only contains the blunt-eared bat).[2]
This study used genetic data to create a phylogeny, which contrasted from previous phylogenies constructed using morphological data.
Traits that were previously used to group species, such as having a flat skull, were shown to have no relation to evolutionary relationship, meaning that flat-headedness evolved multiple times within the family.
Of the 16 genera of Molossinae, 15 were used to create the phylogeny (left), with researchers unable to include Peters's flat-headed bat, the only member of Platymops.
The results of this study showed that Chaerephonisparaphyletic, forming a clade with Mops.
There was strong support for Old World and New World clades.
While the genus Tadarida has one New World species, the Mexican free-tailed bat, the genus itself has its origins in the Old World.
The most recent common ancestor of Tadarida with New World genera was 29 million years ago.
Several tribes have been proposed within the Molossinae.
Ammerman et al. proposed Molossini (containing Molossus, Eumops, Molossops, Cynomops, Neoplatymops, Nyctinomops, and Promops); Tadarini (containing Tadarida, Chaerephon, Mops, Platymops, Sauromys, Myopterus, and Otomops); Cheiromelini (containing Cheiromeles); and Mormopterini (containing Mormopterus)[2]
^Skinner, J. D.; Chimimba, C. T. (2006). The Mammals of the Southern African Subregion. New York: Cambridge University Press. p. 277. ISBN978-0521844185. The name of the [free-tailed bats] family is derived from the Greek molossus, a kind of dog used by Greek shepherds in ancient times
^Lamb, J. M.; Ralph, T. M. C.; Naidoo, T.; Taylor, P. J.; Ratrimomanarivo, F.; Stanley, W. T.; Goodman, S. M. (June 2011). "Toward a Molecular Phylogeny for the Molossidae (Chiroptera) of the Afro-Malagasy Region". Acta Chiropterologica. 13 (1): 1–16. doi:10.3161/150811011X578589. S2CID85394657.
^Czaplewski, N. J. (1997). "Chiroptera". In Kay, R. F.; Madden, R. H.; Cifelli, R. L.; Flynn, J. J. (eds.). Vertebrate Paleontology in the Neotropics: The Miocene Fauna of La Venta, Colombia. Washington, D.C.: Smithsonian Institution Press. pp. 410–431. ISBN978-1560984184.
Corbet, G. B.; Hill, J. E. (1992). The Mammals of the Indomalayan Region: A Systematic Review. Oxford: Oxford University Press. ISBN978-0198546931.
Mohd-Azlan, J.; Maryanto, I.; Kartono, A. P.; Abdullah, M. T. (2003). "Diversity, relative abundance and conservation of chiropterans in Kayan Menterang National Park, East Kalimantan, Indonesia". Sarawak Museum Journal. 53 (79): 251–265.
