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Anatomy of an amniotic egg. Zoologists characterize amniotes in part by embryonic development that includes the formation of several extensive membranes, the amnion , chorion , and allantois . Amniotes develop directly into a (typically) terrestrial form with limbs and a thick stratified epithelium (rather than first entering a feeding larval ...
The three modern orders are Anura (the frogs), Caudata (or Urodela, the salamanders), and Gymnophiona (or Apoda, the caecilians). [15] It has been suggested that salamanders arose separately from a temnospondyl-like ancestor, and even that caecilians are the sister group of the advanced reptiliomorph amphibians, and thus of amniotes. [16]
Amphipoda (/ æ m ˈ f ɪ p ə d ə /) is an order of malacostracan crustaceans with no carapace and generally with laterally compressed bodies. Amphipods (/ ˈ æ m f ɪ p ɒ d z /) range in size from 1 to 340 millimetres (0.039 to 13 in) and are mostly detritivores or scavengers.
The Lissamphibia (from Greek λισσός (lissós, "smooth") + ἀμφίβια (amphíbia), meaning "smooth amphibians") is a group of tetrapods that includes all modern amphibians. Lissamphibians consist of three living groups: the Salientia (frogs and their extinct relatives), the Caudata (salamanders and their extinct relatives), and the ...
Crayfish can move backward much faster than they can move forward. Gait analysis is the study of gait in humans and other animals. This may involve videoing subjects with markers on particular anatomical landmarks and measuring the forces of their footfall using floor transducers ( strain gauges ).
After metamorphosis the anatomy becomes more symmetrical, but some asymmetrical traits are still present also as adults, such as the nervous system and the location of the gonads which are found on the right side in Asymmetron and Epigonichthys (in Branchiostoma gonads develop on both sides of body).
Tetrapoda includes three living classes: amphibians, reptiles, and mammals. Overall, the biodiversity of lissamphibians, [23] as well as of tetrapods generally, [24] has grown exponentially over time; the more than 30,000 species living today are descended from a single amphibian group in the Early to Middle Devonian.
This change from a body plan for breathing and navigating in gravity-neutral water to a body plan with mechanisms enabling the animal to breath in air without dehydrating and move on land is one of the most profound evolutionary changes known. [18] [19] Tetrapods can be divided into four classes: amphibians, reptiles, birds and mammals.