Megophryidae
Megophryids are the most diverse family-level group of non-neobatrachian frogs. There are seven genera currently recognized, containing between 70 and 100 species. Distribution is limited to southern continental Asia, from Pakistan to western China, and to the Indonesian archipelago, west of Wallace's line and in the Philippines.
Megophryids range in size from 20 - 125 mm snout-vent length. Some of the larger species are cryptic, forest-floor dwellers with skin modified into dorsolateral folds that resembles dead leaves. Megophrys montana has points of skin on its eyelids that further enhances this crypsis. Likely synapomorphies of the family include the complete or almost complete absence of ceratohyals in adults, intervertebral cartilages with highly ossified centers, and paddle-shaped tongues. Additional characters include the lack of ribs, eight stegochordal presacral vertebrae with imbricate neural arches, broadly expanded sacral diapophyses, two tarsalia, astragalus and calcaneum fused only at the ends, dentate premaxillae and maxillae, inguinal amplexus, and indirect development with type IV tadpoles bearing beaks and denticles. Diploid number is 24 or 26.
Megophryids are tropical Asian frogs which were previously placed in two distinct subfamilies within the Pelobatidae. Frogs of the genus Scutiger typically occur at elevations above 1000 meters. When breeding, some Scutiger males exude nuptial excrescences on their venters. Females of Scutiger mammatus have rugose skin on the dorsum and flanks, which distinguishes them from males. Leptobrachella mjobergi are small frogs with digital disks, adaptations for stream life. Some megophryids have pond-type tadpoles; others have stream-dwelling tadpoles, with large buccal areas that allow them to cling to rocks. Megophrys tadpoles are surface-feeders with funnel-shaped mouths. Several species have large pectoral glands similar in structure to the dorsal parotid glands, but the significance of these glands is unknown. Megophrys montana exhibits a startling anti-predator behavior, in which it inflates its lung, elevates the body, opens the mouth, emits loud vocalizations, and jumps at potential predators.
Megophryids have traditionally been considered archaeobatrachians, members of the paraphyletic group of primitive frogs out of which the neobatrachians evolved. Traditionally, the superfamily Pelobatoidea, to which megophryids belong, has been considered sister to the neobatrachians. Some authors propose the use of the term Mesobatrachia to refer to the clade containing Pelobatoidea and Pipoidea, suggesting a sister relationship not between pelobatoids and neobatrachians, but between pelobatoids and pipoids. Together, the mesobatrachians and neobatrachians form a large clade referred to as Pipanura. The superfamily Pelobatoidea is widely recognized as a monophyletic group containing Megophryidae, Pelobatidae, and Pelodytidae. Synapomorphies of the Pelobatoidea include the presence of a palatine process of the maxilla, and the ossification of the sternum into a bony style. Many authors have included megophryids within Pelobatidae, as a distinct subfamily. Regardless of its subfamily or family status, the monophyly of Megophryidae is not in doubt.
No fossil megophryids are known.
Cannatella, D. 1996. Pelobatidae: Tree of Life. (Website.) http://tolweb.org/tree?group=Pelobatidae&contgroup=Salientia
Cannatella, D., L. Ford, and L. Bockstanz. 1996. Salientia: Tree of Life. (Website.) http://tolweb.org/tree?group=Salientia&contgroup=Living_Amphibians
Duellman, W. E., and L. Trueb. 1986. Biology of Amphibians. Johns Hopkins University Press, Baltimore, MD.
Ford, L. S., and D. Cannatella. 1993. The major clades of frogs. Herpetological Monographs 7:94-117.
Pough, F. H., R. M. Andrews, J. E. Cadle, M. L. Crump, A. H. Savitzky, and K. D. Wells. 1998. Herpetology. Prentice-Hall, Inc., Upper Saddle River, NJ.
Zug, G. R. 1993. Herpetology: an introductory biology of amphibians and reptiles. Academic Press, San Diego.
Contributors
Heather Heying (author).
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.
- ectothermic
-
animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature
- metamorphosis
-
A large change in the shape or structure of an animal that happens as the animal grows. In insects, "incomplete metamorphosis" is when young animals are similar to adults and change gradually into the adult form, and "complete metamorphosis" is when there is a profound change between larval and adult forms. Butterflies have complete metamorphosis, grasshoppers have incomplete metamorphosis.
- motile
-
having the capacity to move from one place to another.