Produced
by the Population Genetics and Evolution class, Furman University |
The
Carboniferous: Protorothyrids |
The protorothyrids
(family Protorothyrididae) were small, lizardlike animals believed to
be the earliest true reptiles (Encyclopedia Britannica 2010). Key morphological
traits that establish them as the first true reptiles include specializations
of the adductor chamber, cheek, and occiput leading to greater size and
enhanced efficiency of the jaw musculature. Protorothyrids are also characterized
by a small increase in body size, a relative increase in both the size
of the skull and length of the limbs, and a fusion of the axis intercentrum
to the atlas pleurocentrum (Carroll 1982). The most famous member of the
protorothyrids is Hylonomus lyelli, which was first discovered
in 1852 near Joggins, Nova Scotia by Sir William Dawson, who named it
in honor of his teacher, the eminent geologist Sir Charles Lyell. (CMN
2009). The earliest known animal fully adapted to life on land, this 315
million-year-old primitive lizard measured about 20 cm long and featured
a small skull, relatively short limbs, a short neck, a long tail, and
around 40 marginal pointed teeth (Carroll 1982). Researchers believe that
Hylonomus was most likely an insectivore that lived predominantly
in forested areas where millipedes, insects, and land snails were plentiful,
and moist, sheltered areas were available for the females to lay their
eggs (CMN 2009). Page by Robert Mazgaj |
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Hylonomus lyelli Photo credit: Palaeos.com |
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Canadian Museum of Nature. 2009. Hylonumus: The Earliest Reptile. Accessed 3 Mar. 2010. Carroll, Robert L. 1982. Early Evolution of Reptiles. Ann. Rev. Ecol. Syst. 13: 87-109. Encyclopedia
Britannica. 2010. Reptile fossil distribution. Accessed 3 Mar. 2010.
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