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Turtle skulls vary in shape, from the long and narrow skulls of softshells to the broad and flattened skull of the mata mata. [25] Some turtle species have developed large and thick heads, allowing for greater muscle mass and stronger bites. [26] Turtles that are carnivorous or durophagous (eating hard-shelled animals) have the most powerful bites.
A = Anapsid, B = Synapsid, C = Diapsid. It was traditionally assumed that first reptiles were anapsids, having a solid skull with holes only for the nose, eyes, spinal cord, etc.; [10] the discoveries of synapsid-like openings in the skull roof of the skulls of several members of Parareptilia, including lanthanosuchoids, millerettids, bolosaurids, some nycteroleterids, some procolophonoids and ...
Evidence that the plastron evolved before the carapace, as indicated by the lack of carapace in Odontochelys semitestacea, is often viewed as an indication of the aquatic origin of turtles. [1] The fossil was found in marine deposits, further supporting that the primitive turtle frequented shallow marine water.
In biology, evolution is any change across successive generations in the heritable characteristics of biological populations. Evolutionary processes give rise to diversity at every level of biological organization , from kingdoms to species , and individual organisms and molecules , such as DNA and proteins .
The first fully terrestrial vertebrates were reptilian amniotes — their eggs had internal membranes that allowed the developing embryo to breathe but kept water in. This allowed amniotes to lay eggs on dry land, while amphibians generally need to lay their eggs in water (a few amphibians, such as the common Suriname toad, have evolved other ways of getting around this limitation).
Turtles have been traditionally believed to be surviving parareptiles, on the basis of their anapsid skull structure, which was assumed to be primitive trait. [50] The rationale for this classification has been disputed, with some arguing that turtles are diapsids that evolved anapsid skulls, improving their armor. [21]
Although some diapsids have lost either one hole (lizards), or both holes (snakes and turtles), or have a heavily restructured skull (modern birds), they are still classified as diapsids based on their ancestry. At least 17,084 species of diapsid animals are extant: 9,159 birds, [3] and 7,925 snakes, lizards, tuatara, turtles, and crocodiles. [4]
General American usage agrees; turtle is often a general term; tortoise is used only in reference to terrestrial turtles or, more narrowly, only those members of Testudinidae, the family of modern land tortoises; and terrapin may refer to turtles that are small and live in fresh and brackish water, in particular the diamondback terrapin ...