Discovery_and_classification Sphenacodon

restoration of 2 specimens

the american paleontologist o.c. marsh named sphenacodon (from greek sphen wedge + ake point + odous (-odon) tooth ) in 1878, based on part of lower jaw (dentary) bone found in redbeds of northern new mexico fossil collector david baldwin. in short description of jaw, marsh cited teeth characteristic ( crowns compressed, , have sharp cutting edges without crenulations ) , assessed animal 6 feet in length, , carnivorous in habit, although rest of skeleton not known. did not provide illustration of specimen. marsh gave genus latin species name ferox fierce , erected new family sphenacodontidae, placed under primitive reptilian order “rhynchocephala” [= rhynchocephalia], including groups of reptiles in addition living tuatara.

other paleontologists overlooked marsh’s brief mention of sphenacodon 3 decades. in meantime, sail-backed dimetrodon, named in 1878 rival paleontologist edward drinker cope, became scientifically important genus,known numerous fossils. recognition of sphenacodon low-spined carnivorous “pelycosaur” distinct dimetrodon came in 20th century discovery of more fossils in new mexico. proposed taxa elcabrosaurus baldwini case, 1907 , scoliomus williston , case, 1913 considered junior synonyms of sphenacodon ferox.

in 1937, alfred sherwood romer described second species new mexico named sphenacodon ferocior ( fiercer ) larger , more robust, proportionately longer neural spines. romer , price (1940) provided detailed descriptions of both ferox , ferocior skeletal reconstructions.

a third species, sphenacodon britannicus, has been cited in literature. in 1908 german paleontologist f. von huene described oxyodon britannicus, based on part of maxilla found in england, (the generic name oxyodon preoccupied fish (oxyodon baur, 1906) , invalid.) specimen had been identified earlier possible triassic dinosaur, von huene recognized “pelycosaur.” paton transferred species sphenacodon in 1974, noting have been animal size of sphenacodon ferox. however, more recent studies have questioned whether such limited fossil material can used distinguish between dimetrodon , sphenacodon—or own genus. species “oxyodon” britannicus (or sphenacodon (?) britannicus) classified sphenacodontidae incertae sedis (of uncertain placement).