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The origin and early radiation of the therapsid mammal‐like reptiles: a palaeobiological hypothesis
Author(s) -
KEMP T. S.
Publication year - 2006
Publication title -
journal of evolutionary biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.289
H-Index - 128
eISSN - 1420-9101
pISSN - 1010-061X
DOI - 10.1111/j.1420-9101.2005.01076.x
Subject(s) - biome , biology , extinction event , mammal , ecology , permian , permian–triassic extinction event , evolution of mammals , tetrapod (structure) , extinction (optical mineralogy) , taxon , macroevolution , paleontology , temperate climate , lineage (genetic) , fossil record , arid , ecosystem , phylogenetics , biological dispersal , population , biochemistry , demography , structural basin , sociology , gene
The replacement of the basal synapsid pelycosaurs by the more ‘mammal‐like’ therapsids in the Permian was an important event in the history of tetrapods because it initiated the eventual transition to the mammals. It is also an example of taxon replacement in the fossil record that is unusually amenable to explanation, based on a combination of analysis of the biological significance of the inferred character changes, with the stratigraphic, palaeogeographic and palaeoecological circumstances of the time. An hypothesis is presented in which the origin of the therapsids resulted from a correlated progression of character evolution leading to higher levels of metabolic activity and homeostatic regulation of the body. It was a response to the availability of a seasonally arid, savanna‐like biome. The subsequent explosive radiation of therapsids was associated with habitat expansion made possible by the Mid‐Permian development of geographical continuity between that biome and the temperate biomes. The final extinction of the pelycosaurs was a case of incumbent replacement by the new therapsid lineages.