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Salamanders, caecilians and some frogs have one or two rows of teeth in both jaws, but some frogs (Rana spp.) lack teeth in the lower jaw, and toads (Bufo spp.) have no teeth. In many amphibians there are also vomerine teeth attached to a facial bone in the roof of the mouth. [144] Edible frog (Pelophylax esculentus) exhibiting cannibalism
At first sight, frogs seem rather defenceless because of their small size, slow movement, thin skin, and lack of defensive structures, such as spines, claws or teeth. Many use camouflage to avoid detection, the skin often being spotted or streaked in neutral colours that allow a stationary frog to merge into its surroundings.
An early branch was the terrestrial reptile-like amphibians, variously called Anthracosauria or Reptiliomorpha. Tulerpeton has been suggested as the earliest member of the line, indicating the split may have happened before the Devonian-Carboniferous transition. [27] Their skulls were relatively deep and narrow compared to other labyrinthodonts.
The body is cylindrical and often darkly coloured, and the skull is bullet-shaped and strongly built. Caecilian heads have several unique adaptations, including fused cranial and jaw bones, a two-part system of jaw muscles, and a chemosensory tentacle in front of the eye. The skin is slimy and bears ringlike markings or grooves and may contain ...
Despite their success, vertebrates still only make up less than five percent of all described animal species. The first vertebrates appeared in the Cambrian explosion some 518 million years ago. Jawed vertebrates evolved in the Ordovician, followed by bony fishes in the Devonian. The first amphibians appeared on land in the Carboniferous.
Preserved in its eye sockets were palpebral bones - or eyelid bones - a feature absent in today's amphibians. Its skull is constructed of roof-like bones, in contrast to the thin and strut-like ...
Scientists found that members of the new species are smaller than their offshore common bottlenose counterparts, eat different fish and have spines adapted to navigating the tight spaces of rivers ...
Each is a member of one of three monophylitic clades. All tunicate larvae have the standard chordate features, including long, tadpole-like tails. Their larva also have rudimentary brains, light sensors and tilt sensors. [28] The smallest of the three groups of tunicates is the Appendicularia. They retain tadpole-like shapes and active swimming ...