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The most popular definition states that Sauropsida is the sibling taxon to Synapsida, the other clade of amniotes which includes mammals as its only modern representatives. Although early synapsids have historically been referred to as "mammal-like reptiles", all synapsids are more closely related to mammals than to any modern reptile.
Whales share this characteristic with extinct marine reptiles, but not present-day marine mammals. [ 61 ] A very derived form of hyperphalangy, with six or more phalanges per digit, evolved convergently in rorqual whales and oceanic dolphins , and was likely associated with another wave of signaling within the interdigital tissues.
An evolutionary tree (of Amniota, for example, the last common ancestor of mammals and reptiles, and all its descendants) illustrates the initial conditions causing evolutionary patterns of similarity (e.g., all Amniotes produce an egg that possesses the amnios) and the patterns of divergence amongst lineages (e.g., mammals and reptiles ...
While reptiles and amphibians can be quite similar externally, the French zoologist Pierre André Latreille recognized the large physiological differences at the beginning of the 19th century and split the herptiles into two classes, giving the four familiar classes of tetrapods: amphibians, reptiles, birds and mammals.
The French zoologist Etienne Geoffroy Saint-Hilaire showed in 1818 in his theorie d'analogue ("theory of homologues") that structures were shared between fishes, reptiles, birds, and mammals. [5] When Geoffroy went further and sought homologies between Georges Cuvier 's embranchements , such as vertebrates and molluscs, his claims triggered the ...
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. It is closely related to evolutionary biology and phylogeny [1] (the evolution of species).
The term polyphyly, or polyphyletic, derives from the two Ancient Greek words πολύς (polús) 'many, a lot of', and φῦλον (phûlon) 'genus, species', [8] [9] and refers to the fact that a polyphyletic group includes organisms (e.g., genera, species) arising from multiple ancestral sources.
Mammals and birds filled the empty niches left behind by the reptilian megafauna and, while reptile diversification slowed, bird and mammal diversification took an exponential turn. [44] However, reptiles were still important components of the megafauna, particularly in the form of large and giant tortoises .