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Phylum: Craniata (Chordata)
Class: Reptilia
In
the late Devonian (360-370 million years ago), a fish ancestor gave
rise to animals with 4 legs, the tetrapods,
all of which were at first fully aquatic, using their feet to move around
the bottom of shallow rivers and lakes. One group within the tetrapod
lineage remained aquatic or semi-aquatic and is recogognizable as modern
day amphibians. Another ancient amphibian lineage, the anthracosaurs,
invaded the terrestial environment.
Early in anthracosaur evolution, some species developed the necessary adaptations allowing the colonization of land. These included stronger legs, jaws and vertebrae to support the weight of the body on land, as well as a cornified skin to limit water loss, and claws to facilitate crawling and digging. Probably the most important adaptation is the shelled amniotic egg, which eliminated the need for a moist habitat for egg laying, and the hazardous free-living larval stage present in many amphibians. Life on land also required a mored advanced respiratory and circulatory system. The reptiles split into 2 major groups based on how the primitive amphibian double aortic heart was modified. The first group which gave rise to the modern reptiles, dinosaurs, and birds, developed an aorta on the right side of the body. The other group, the synapsid reptiles developed an aorta on the left. This is the group that eventually produced the mammals (Carroll, 1988).
Reptile Diversity
Herpetologists (scientists who study reptiles and amphibians) have described 6000 species of reptiles, within four major orders (Zug 1993). Order Crocodylia includes the alligators, crocodiles, and the gharials. These are all moderate to large aquatic reptiles, and represent the closest exant reptilian group to dinosaurs and birds. Order Testudinea includes the turtles and tortises. Turtles are easily distinguished by the presence of a shell which encloses the animal in a bony case. Turtles inhabit a variety of terrestrial and aquatic environments, from the open ocean to the arid deserts. Order Squamata includes the snakes (Suborder serpentes) and the lizards (Suborder Lacertilia). This is the largest reptilian order inhabiting diverse habitats. Many lizards are diurnal, brightly colored and display interesting social behavior. Snakes are legless, and rely heavily on scent rather than vision. Legglessness has evolved repeatedly among the squamates, as all snakes, and many lizards lack legs (Pough et al 1998). The Tuatara (Order Rhynchocephalia) lives only in offshore islands of New Zealand. These are long-lived (up to 60 years) reptiles with low reproductive rates (Pough et al 1998). They are closely related to the squamates. Reptiles are most abundent in tropical regions, although many have adapted to temperate zones like Wisconsin.
Northeastern Wisconsin Reptiles
Two reptilian orders, Testudine (turtles) and Squamata (snakes and lizards) are found in northeast Wisconsin. There are seven turtles, one lizard, and ten species of snake for a total of 18 species. Many reptiles can commonly be seen while fishing, hiking, and enjoying the outdoors. Common species include the painted turtles, which are frequently seen basking on logs in ponds and lakes, and the eastern garter snake which occupy many city parks and recreational areas. However, many species remain hidden and are rarely seen. Other species are strongly associated with a particular vegetation, soil type, or specific aquatic environment. Therefore, some reptiles can act as environmental indicators for a healthy environment.
Examples of unique habitat specialists include the eastern spiny softshell turtle (Apalone spinifera spinefera) whose primary habitat is rivers with muddy or sandy bottoms (Vogt 1981). This large aquatic turtle with a pancake-like shell is not found in areas with low oxygen concentrations. Therefore, it can be a moniter of low oxygen concentrations and other related pollution (Vogt 1981). The northern ribbon snake is another northeastern Wisconsin representative tied to particular environment. This slender semiaquatic snake inhabits spagnum bogs and surronded areas. It is very rare, and possibly could be extirpated from northeast Wisconsin. Many other reptiles like the eastern hognose snake, Blanding's turtle, and five-lined skinks are tied to a particular environment. Preserving natural habitat is essential for the continued existence of the regional herpetofauna.
Reptilian Importance
Although
many people may fear the sight of a snake crossing their path, in reality
the snake displays the signs of a healthy and properly functioning environment.
With the exception of some turtles, the reptiles of northeast Wisconsin
are primarily carnivores. The five-lined skink, northeast Wisconsin's
only lizard representitive, is a strict carnivore feeding on insects,
spiders, and occassionaly small vertebrates. Larger snakes, such as the
fox snake and the milk snake, feed on rodents and other endothermic prey.
Smaller snakes, like the garter snake and the water snake, prefer a diet
consisting of ectothermic vertebrates.Many area reptiles are also specialist
feeders exploiting one food source. The eastern hognose snake consumes
primarily toads, whereas map turtles prefer a diet based largely upon
molluscs. Reptiles are efficient predators, however in many occasions
the predator becomes the prey. Mammals, like skunks and raccoons, cherish
the seasonal delicacy of turtle eggs (Harding 1997 ). Young turtles are
readily consumed by birds, fish, and mammals. Many raptoral birds predate
highly upon snakes and lizards. Young snakes and lizards are commonly
consumed by foraging mammals. Human consumption of the common snapping
turtle and the spiny softshell have reduced their populations. Reptiles
undoubtably play an important role in the proper functioning of the regional
ecosystem.
Biodiversity Topics: Introduction . Plants . Animals . Mammals . Birds . Reptiles & Amphibians . Arthropods . Spiders . Insects
© 2001-2004 The Cofrin Center
for Biodiversity and the University of Wisconsin Green Bay,
All Rights Reserved
Last
updated on
July 6, 2006