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Stegocephalia
Stegocephalia is a group of four-limbed stem-tetrapods, as well as their modern-day four limbed tetrapod descendants. The term was coined in 1868 by American palaentologist Edward Drinker Cope and comes from Greek ''στεγοκεφαλια'' - "roofed head", and refer to the copious amounts of dermal armour some of the larger primitive forms evidently had.〔Cope E. D. 1868. Synopsis of the extinct Batrachia of North America. ''Proceedings of The Academy of Natural Sciences of Philadelphia'': pp 208-221〕 Canadian paleontologist Michel Laurin gave the group its first formal phylogenetic definition, roughly including all vertebrates with toes rather than fins.
==History of classification==
Originally, the term was used as a systematic unit at the rank of order. The term rose to prominence in American and British science in the 19th century, though the largely equivalent term Labyrinthodontia had been coined 18 years earlier by Hermann Burmeister in reference to the tooth structure.〔Burmeister, H. (1850): Die Labyrinthodonten aus dem Saarbrücker Steinkohlengebirge, Dritte Abtheilung: der Geschichte der Deutschen Labyrinthodonten Archegosaurus. Berlin: G. Reimer, 74 pp.〕 The terms were used interchangeably during the early 20th century, usually divided into three orders.〔Romer, A. S., (1947, revised ed. 1966) Vertebrate Paleontology, University of Chicago Press, Chicago〕 However, the Stegocephalia (and the Labyrinthodontia) being paraphyletic, the name is now used in an informal way to denote the early non-piscine vertebrates, excluding amniotes (the first reptiles and their descendants) and modern lissamphibians).
Paleontologist Michel Laurin took up the older term and defined stegocephalians cladistically as all vertebrates more closely related to temnospondyli than to ''Panderichthys'' (the closest relative of tetrapods known to have retained paired fins, see below) 〔Laurin M. (1998): The importance of global parsimony and historical bias in understanding tetrapod evolution. Part I-systematics, middle ear evolution, and jaw suspension. ''Annales des Sciences Naturelles'', Zoologie, Paris, 13e Series 19: pp 1-42.〕 Therefore, Stegocephalia includes all vertebrate groups that have toes rather than fins, and a few (''Elginerpeton'', ''Metaxygnathus'', ''Ventastega'' and possibly ''Hynerpeton'') that may have retained paired fins. Contrary to the old usage of this term, the Stegocephali refers to a clade in this scheme. This concept of the clade Stegocephalia was chosen to substitute for the name Tetrapoda by those who sought to restrict Tetrapoda to the crown group.〔Laurin & al. (Terrestrial Vertebrates. Stegocephalians: Tetrapods and other digit-bearing vertebrates ). Tree of life〕 As such, it encompasses all presently living land vertebrates as well as their early amphibious ancestors.
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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