What is Elpistostegalia?
{{Automatic taxobox | fossil_range = <br>[[Late Devonian]] - [[Holocene|Present]], {{Fossil range|385|0}} | image = Panderichthys_BW.jpg | image_upright = 1.15 | image_caption = ''[[Panderichthys]]'' | taxon = Elpistostegalia | authority = Camp & Allison, 1961 | type_genus = ''[[Elpistostege]]'' | type_genus_authority = Westoll, 1938 | subdivision_ranks = Subgroups<ref name=SB12/> | subdivision = *{{extinct}}[[Panderichthyidae]] *[[Stegocephalia]] | synonyms = *Panderichthyida <small>Vorobyeva, 1989</small> }} '''Elpistostegalia''', also known as '''Panderichthyida''', is a type of [[prehistoric]] [[fish]] which lived about 385 to 374 million years ago.<ref>[http://taxonomicon.taxonomy.nl/TaxonName.aspx?id=987575&tree=0.1 Elpistostegidae on the Taxonomicon]</ref> == Why they evolved == A rise in the world's [[oxygen]] content caused [[predator]]y fish to [[evolve]],<ref name=Dahl>{{cite journal |vauthors=Dahl TW, Hammarlund EU, Anbar AD |title=Devonian rise in atmospheric oxygen correlated to the radiations of terrestrial plants and large predatory fish |journal=Proc. Natl. Acad. Sci. U.S.A. |volume=107 |issue=42 |pages=17911–5 |date=October 2010 |pmid=20884852 |pmc=2964239 |doi=10.1073/pnas.1011287107 |bibcode = 2010PNAS..10717911D |display-authors=etal|doi-access=free }}</ref> and this fish was the most successful.<ref>{{cite journal|last=Lewis Jr. |first=William M. |title=Morphological Adaptations of Cyprinodontoids for Inhabiting Oxygen Deficient Waters |journal=Copeia |date=1 June 1970 |volume=2 |issue=2 |pages=319–326 |url=http://ciresweb.colorado.edu/limnology/pubs/pdfs/Pub001.pdf |jstor=1441653 |doi=10.2307/1441653 |url-status=dead |archive-url=https://web.archive.org/web/20110813153431/http://ciresweb.colorado.edu/limnology/pubs/pdfs/Pub001.pdf |archive-date=2011-08-13 }}</ref> == What they evolved from == Below is a description of their evolutionary family tree.<ref name=SB12>{{cite journal | last = Swartz | first = B. | year = 2012 | title = A marine stem-tetrapod from the Devonian of Western Nor