By Richard M. Lehtenin
The three species that make up the Leiopelmatidae are the only anurans native to New Zealand and are only found on North Island.
As with Ascaphidae, to which the leiopelmatids are closely related, these frogs have a suite of primitive characteristics. For example, Leiopelma lacks tympana and other ear structures, has nine presacral vertebrae (all other frogs, except Ascaphus, have eight or fewer) with amphicoelous centra, amplexus is inguinal (in two species, unknown in the third) and the pectoral girdle is arciferal. Leiopelma (along with Ascaphus) also has vestigial tail-wagging muscles, likely an evolutionary relict of its tailed ancestors (see Triadobatrachus). In addition, Leiopelma is unique among extant frogs in possessing bony inscriptional ribs which are embedded into the ventral body musculature and an exceedingly odd system of up to 15 supernumerary heteromorphic sex chromosomes.
Interestingly, Leiopelma has direct development, rather than a free-living larval stage (like Ascaphus). This means that the 20 to 70 large, unpigmented eggs laid by females develop directly into miniature froglets without passing through a larval stage. This type of development is relatively common among more advanced frogs, but rare among primitive ones. The developing embryos possess neither jaw sheaths nor denticles.
Males in two species are known to guard egg clutches and carry hatchlings on their backs. They are smallish frogs (up to 50 mm in length) that are primarily active at night. Two of the three leiopelmatid species are terrestrial and one inhabits streams.
Fossils, which are sometimes attributed to the closely related Ascaphidae, are known from the Jurassic of Patagonian Argentina.
Little is known about the conservation status of leiopelmatids, but amphibians in general are thought to be sensitive to changes in their environment (see AmphibiaWeb's 
declining amphibians page).
Duellman, W.M. and L. Trueb. 1984. Biology of the Amphibians.
Pough, F.H., R.M Andrews, J.E. Cadle, M.L. Crump, A.H. Savitzsky, K.D. Wells. 1998. Herpetology. Prentice-Hall, Upper Saddle River, NJ.
Frost, Darrel R. 2002. Amphibian Species of the World: an online reference.
V2.21 (15 July 2002). Electronic database available at http://research.amnh.org/herpetology/amphibia/index.html.
Contributors
Richard M. Lehtenin (author).
