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Anguilla Bank skink
Photo Credit: Karl Questel, courtesy of Penn State University |
Lizards are part of a group of squamate reptiles. Squamate reptiles are distinguished by their skins, which bear horny scales or shields.
Lizards, part of the Lacertilia suborder, is defined as all extant members of the Lepidosauria (reptiles with overlapping scales), which are neither sphenodonts (i.e., tuatara) nor snakes. Because of this, the lizard group form an evolutionary grade.
Sphenodonts are the sister group to the Squamates, the larger monophyletic group, which includes both the lizards and the snakes. An evolutionary grade is defined as a group of species united by traits that are either morphological or physiological, that has given rise to another group that differs markedly from the ancestral condition, and is not considered part of that ancestral group.
These reptiles typically have feet and external ears. Snakes do not have these features. Since lizards are excluded from the snake family, the group does not have any unique distinguishing characteristic as a group. Lizards and snakes share a movable quadrate bone, distinguishing them from the sphenodonts, which have a more primitive and solid diapsid skull.
Most lizards can detach their tails to escape from predators, an act called autotomy. Vision, including color vision, is particularly well developed in most lizards, and most communicate with body language or bright colors on their bodies as well as with pheromones.
24 new species of lizards discovered on Caribbean islands are close to extinction
In a single new scientific publication, 24 new species of lizards known as skinks, all from islands in the Caribbean, have been discovered and scientifically named. According to Blair Hedges, a professor of biology at Penn State University and the leader of the research team, half of the newly added skink species already may be extinct or close to extinction, and all of the others on the Caribbean islands are threatened with extinction. The researchers found that the loss of many skink species can be attributed primarily to predation by the mongoose -- an invasive predatory mammal that was introduced by farmers to control rats in sugarcane fields during the late nineteenth century. The research team reports on the newly discovered skinks in a 245-page article to be published on 30 April 2012 in the journal Zootaxa.
About 130 species of reptiles from all over the world are added to the global species count each year in dozens of scientific articles. However, not since the 1800s have more than 20 reptile species been added at one time. Primarily through examination of museum specimens, the team identified a total of 39 species of skinks from the Caribbean islands, including 6 species currently recognized, and another 9 named long ago but considered invalid until now. Hedges and his team also used DNA sequences, but most of the taxonomic information, such as counts and shapes of scales, came from examination of the animals themselves. "Now, one of the smallest groups of lizards in this region of the world has become one of the largest groups," Hedges said. "We were completely surprised to find what amounts to a new fauna, with co-occurring species and different ecological types." He added that some of the new species are 6 times larger in body size than other species in the new fauna.
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