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For instance, descendants of the first reptiles include modern reptiles, mammals and birds; the agnathans have given rise to the jawed vertebrates; the bony fishes have given rise to the land vertebrates; a group of amphibians, the labyrinthodonts, have given rise to the reptiles (traditionally including the mammal-like synapsids), which in ...
Unlike amphibians, reptiles do not have an aquatic larval stage. Most reptiles are oviparous, although several species of squamates are viviparous, as were some extinct aquatic clades [6] – the fetus develops within the mother, using a (non-mammalian) placenta rather than contained in an eggshell. As amniotes, reptile eggs are surrounded by ...
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 ...
Reptiles (Late Latin for creeping or crawling) do not have an aquatic larval stage, and in this way are unlike amphibians. Most reptiles are oviparous, although several species of squamates are viviparous , as were some extinct aquatic clades [ 25 ] — the fetus develops within the mother, contained in a placenta rather than an eggshell .
Comparative anatomy studies similarities and differences in organisms. The image shows homologous bones in the upper limb of various vertebrates.. Comparative anatomy is the study of similarities and differences in the anatomy of different species.
Amniotes have the ability to procreate without water bodies. Because the amnion and the fluid it secretes shields the embryo from environmental fluctuations, amniotes can reproduce on dry land by either laying shelled eggs (reptiles, birds and monotremes) or nurturing fertilized eggs within the mother (marsupial and placental mammals).
The hemipenis is the intromittent organ of Squamata, [4] which is the second largest order of vertebrates with over 9,000 species distributed around the world. They differ from the intromittent organs of most other amniotes such as mammals, archosaurs and turtles that have a single genital tubercle, as squamates have the paired genitalia remaining separate. [5]
The evolution of tetrapods began about 400 million years ago in the Devonian Period with the earliest tetrapods evolved from lobe-finned fishes. [1] Tetrapods (under the apomorphy-based definition used on this page) are categorized as animals in the biological superclass Tetrapoda, which includes all living and extinct amphibians, reptiles, birds, and mammals.