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The Osteolepiformes and Elpistostegalia are two crown groups of rhipidistians with respect to the tetrapods. [2] The development of skull roof and cheekbone patterns in these organisms match those found in the first tetrapods. Palatal and nasal skeletal features like choanae are present in these groups and are also observed in modern amphibians.
Comparative anatomy is the study of similarities and differences in the anatomy of different species. It is closely related to evolutionary biology and phylogeny [ 1 ] (the evolution of species). The science began in the classical era , continuing in the early modern period with work by Pierre Belon who noted the similarities of the skeletons ...
Class Amphibia (amphibians, some ancestral to the amniotes)—now a paraphyletic group; Class Synapsida (mammals and their extinct relatives) Class Sauropsida (reptiles and birds) While this traditional taxonomy is orderly, most of the groups are paraphyletic, meaning that the structure does not accurately reflect the natural evolved grouping. [47]
Catlike sabre-toothed predators evolved in three distinct lineages of mammals – carnivorans like the sabre-toothed cats, and nimravids ("false" sabre-tooths), the sparassodont family Thylacosmilidae ("marsupial" sabre-tooths), the gorgonopsids and the creodonts also developed long canine teeth, but with no other particular physical ...
The adult tetrapods had an estimated length of 2.5 m (8 feet), and lived in a lagoon with an average depth of 1–2 m, although it is not known at what depth the underwater tracks were made. The lagoon was inhabited by a variety of marine organisms and was apparently salt water. The average water temperature was 30 degrees C (86 F).
A common bottlenose dolphin (Tursiops truncatus). A dolphin is an aquatic mammal in the clade Odontoceti (toothed whale).Dolphins belong to the families Delphinidae (the oceanic dolphins), Platanistidae (the Indian river dolphins), Iniidae (the New World river dolphins), Pontoporiidae (the brackish dolphins), and possibly extinct Lipotidae (baiji or Chinese river dolphin).
The latter subclass is divided into two infraclasses: pouched mammals (metatherians or marsupials), and placental mammals (eutherians, for which see List of placental mammals). Classification updated from Wilson and Reeder's "Mammal Species of the World: A Taxonomic and Geographic Reference" using the "Planet Mammifères" website. [1]
Between the inner layer and the outer layer lies the dermis, which contains all the pigments and cells that make up the snake's distinguishing pattern and color. The epidermis, or outer layer, is formed of a substance called keratin, which in mammals is the same basic material that forms nails, claws, and hair. The snake's epidermis of keratin ...