Athena Review Image Archive ™
Frog skeleton (Rana)
Skeleton of a green frog (Rana)
Extant amphibians including frogs, newts or salamanders, and caecilians are descended from Lissamphibia. These include Triadobatrachus, a salamander-like animal discovered in Madagascar who first appeared in the Early Triassic period at about 250 mya. Triadobatrachus, who lived around fresh water, was 10 cm long and had 26 vertebra, of which ten formed a long tail.
Frogs belong to the order Anura. The earliest known frog is Prosalirus ("to
leap forward"), from the Early Jurassic period (190 mya), found in the
Kayenta Formation of Arizona in 1981 by Farish Jenkins. The Prosaliris
skeleton has lost the salamander-like tail of early
Lissamphibians, and has only ten vertebra. It has long hip
bones, leg bones, and ankle bones similar to those of modern
frogs, and is designed to absorb the force of jumping with its
hind legs.
The first known modern frog, Liaobatrachus, was
found in China and dates from the Early Cretaceous period at 125
mya. It had ten vertebra (9 presacral and one sacral), and was 6
to 9 cm long, in many ways resembling present-day frogs.
The green frog (Rana clamitans or Lithobates clamitans)
is native to eastern North America. There are two subspecies, the
bronze frog and the northern green frog. The adults possess nine vertebra, and are 5 to 10 cm
long, with males larger than females.
References:
Benton, M.J. 2005. Vertebrate Paleontology. Blackwell.
Ji, S. and Ji, Q. 1998. The first Mesozoic frog from China (Amphibia: Anura), Liaobatrachus grabaui gen. et sp. nov. Chinese Geology, March 1998: 39-49.
Romer, A.S. 1966. Vertebrate Paleontology. University of Chicago Press
Shubin, N.H. and and F.A. Jenkins 1995. An Early Jurassic jumping frog. Nature. 377 (6544): 49–52.
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