Turtles of the World
Authors: C.H. Ernst, R.G.M. Altenburg & R.W. Barbour
Search
Scientific name:

Graptemys

Vernacular name:

Map turtles


Use the links below to jump to previous and next taxa in a text browser:
genus Deirochelys - Chicken turtles
genus Malaclemys - Diamondback terrapins

Agassiz, 1857
Map turtles

Recognition
The 12 species of Graptemys are North American riverine turtles highly adapted to a molluscivorous diet. Their oval carapaces bear a medial keel of varying development from a low, raised mound to well-developed, spiny or blunt protuberances; the posterior rim is strongly serrated. Neurals are usually hexagonal and anteriorly short sided, but the second is sometimes octagonal. The carapace usually bears a pattern of narrow, light, meandering lines or ocelli on the pleurals, vertebrals, and, sometimes, marginals which resembles contour lines on a map; thus, their common name of "map" turtles. The plastron lacks a hinge; axillary and inguinal buttresses are not well-developed. The entoplastron lies anterior to the humero-pectoral seam. The skull is usually narrow to moderately broad in males, but broader in females. It has a complete temporal arch, and the orbito-nasal foramen is enlarged into a fenestra. The flattened triturating surfaces of the jaws are broad and ridgeless. The anterior border of the inferior process of the parietal is thickened, and the pterygoid touches the exoccipital. The toes are webbed.

Remark
McDowell (1964) revived Boulenger's inclusion (1889) of Graptemys in the genus Malaclemys. Graptemys was not recognized even as a subgenus, because the differences between M. terrapin and G. pseudogeographica kohnii are no greater than those between G. p. kohnii and G. geographica. This arrangement was not widely accepted (see, for example, Ernst and Barbour, 1972; and Dobie and Jackson, 1979). Wood (1977) felt that McDowell had not made a convincing case for the all-inclusive Malaclemys and presented other evidence suggesting the origin of many, if not all, Graptemys from Malaclemys. However, Dobie (1981) showed Malaclemys to differ substantially from Graptemys in osteology. This point was settled most decisively by Lamb and Osentoski (1997) who generated a data set composed of DNA sequences for the mitochondrial control region and cytochrome b gene. They generated 32 different parsimonious trees from the sequence data that, all of which showed Graptemys and Malaclemys as distinct, monophyletic clades, refuting Wood's (1977) hypothesis.

Species identification
Jump to the key: Page 367: Genus Graptemys

genus Graptemys (Map turtles)
Description provides information about characters, distribution and habitat of the selected species or higher group. You can search using vernacular or scientific name.
General introduction, overview of the species treated and functionality of the site
A tree, picture gallery and alphabetical lists provide access to the species and higher groups
Descriptions of species
Descriptions of higher groups
Identification keys
Atlas
Glossary
Literature references
Test your knowledge of the species treated
Concise explanation of the BIS program
Authors of and contributors to this project
Return to the main index of the World Biodiversity Database