Dissorophidae

In 1895, American paleontologist Edward Drinker Cope named Dissorophus from the early Permian of Texas. This was the first dissorophid to be described as such, although Parioxys, named by Cope in 1878, and Zygosaurus, named by the Russian paleontologist Karl von Eichwald in 1848, have also been regarded as dissorophids. A second species of Dissorophus as well as both species of the genus Otocoelus that were all named in 1896 by Cope in two papers are now regarded as junior synonyms of the type species of Dissorophus, D. multicinctus.

The early 20th century saw a large expansion in the study of dissorophids. In 1904, German paleontologist Ferdinand Broili named the first species of Aspidosaurus, A. chiton, from the early Permian of Texas. Additional species of Aspidosaurus were named shortly thereafter, including Aspidosaurus glascocki from the early Permian of Texas and Aspidosaurus novomexicanus from the late Carboniferous of New Mexico. A third species, "Aspidosaurus crucifer" described by American paleontologist E.C. Case is now regarded as an indeterminate aspidosaurine. In 1910, two of the best-known dissorophid genera were named: Cacops aspidephorus[4] and Platyhystrix (as a species of Ctenosaurus;[5] proper name erected in 1911). Case also provided new information on Dissorophus in 1910.[6] In 1911, Case named Alegeinosaurus aphthitos from the early Permian of Texas.[7] In 1914, Samuel W. Williston described the first species of Broiliellus, B. texensis.[8] Additional information on Parioxys ferricolus was provided in two studies by Egyptian paleontologist Y.S. Moustafa in 1955.[9][10]

The 1960s were a particular productive time for dissorophid research. In two separate papers published in 1964, Canadian paleontologist Robert L. Carroll named four new taxa: Brevidorsum profundum, Broiliellus brevis, and Parioxys bolli from the early Permian of Texas and Conjunctio multidens from the early Permian of New Mexico.[11][12] Conjunctio was named from a specimen originally referred to Aspidosaurus novomexicanus by Case et al. (1913)[13] that was also placed in Broiliellus by American paleontologist Wann Langston in 1953[14] before being divided again by Carroll. In 1965, American paleontologist E.C. Olson described the first and only middle Permian dissorophid from North America, Fayella chickashaensis, on the basis of an isolated braincase and isolated fragments. A large postcranial skeleton from a different locality was referred to this taxon by Olson in 1972. In 1966, American paleontologist Robert E. DeMar named a new taxon, "Longiscitula houghae" from the early Permian of Texas;[15] this is now regarded as a junior synonym of Dissorophus multicinctus by British paleontologist Andrew Milner.[16] DeMar also provided the first synthesis of the morphological diversity and possible function of dissorophid osteoderms in 1966[17] and named two new species of Broiliellus in 1967, B. arroyoensis and B. olsoni,[18] and completed a detailed revision of D. multicinctus in 1968.[19]

In 1971, American paleontologist Peter Vaughn described one of the few dissorophids outside of New Mexico, Texas, and Oklahoma, Astreptorhachis ohioensis from the late Carboniferous of Ohio, represented by a series of fused neural spines and osteoderms.[20] American paleontologist John Bolt published a survey of dissorophid osteoderms in 1974 with an emphasis on taxonomic utility and differentiation and reports of material from the early Permian Richards Spur locality in Oklahoma;[21] in 1977, Bolt reported Cacops from the locality.[22] In 1980, Russian paleontologist Yuri Gubin described two new middle Permian dissorophids from Russia: Iratusaurus vorax and Kamacops acervalis.[23] The most complete cranial material of Platyhystrix rugosus was described in 1981 by a team led by American paleontologist David Berman.[24] Additional postcranial material of Platyhystrix, primarily the characteristic hyperelongate spines, was also periodically reported.[25][26][27] The revision of Ecolsonia cutlerensis in 1985 by Berman and colleagues placed the taxon as a dissorophid, but this taxon is more often recovered as a trematopid.[28] In 1999, Chinese paleontologists Li Jinling and Cheng Zhengwu described the first and only dissorophid from eastern Asia, the middle Permian Anakamacops petrolicus from China.[29]

In 2003, American paleontologists Berman and Spencer G. Lucas named a new species of Aspidosaurus from Texas, A. binasser.[30] Two papers on the osteoderm biomechanics of Cacops aspidephorus and Dissorophus multicinctus, led by Canadian paleontologist David Dilkes, were published in 2007 and 2009.[31][32] In 2009, a team led by Canadian paleontologist Robert Reisz described a new species of Cacops, C. morrisi, from the Richards Spur locality;[33] additional material of this taxon was described in 2018 by American paleontologist Bryan M. Gee and Reisz.[34] A second species from the locality was described in 2012 by German paleontologist Nadia B. Fröbisch and Reisz, C. woehri;[35] additional material of Cacops woehri was described in 2015 by a team led by Fröbisch.[36] A team led by German paleontologist Florian Witzmann published a comparative histology study that sampled a number of dissorophids in 2010.[37] May et al. (2011) described material of Aspidosaurus from the late Carboniferous of the mid-continent of North America.[38] The first phylogenetic review of the Dissorophidae was published in 2012 by Schoch.[39] In 2013, three new dissorophids were named in a festschrift dedicated to Reisz in Comptes Rendus Paleovol: Broiliellus reiszi from the early Permian of New Mexico in a study led by Canadian paleontologist Robert Holmes;[40] Scapanops neglecta from the early Permian of Texas in a study by German paleontologists Schoch and Hans-Dieter Sues, re-evaluating a specimen historically referred to as the Admiral Taxon;[41] and Reiszerpeton renascentis from the early Permian of Texas in a review of material referred to the amphibamiform Tersomius texensis by a team led by Canadian paleontologist Hillary C. Maddin.[42] In 2018, Chinese paleontologist Liu Jun provided an updated osteology of Anakamacops based on substantially more complete material and erected the tribe Kamacopini to group the middle Permian dissorophids from Eurasia.[43] Two separate studies led by Gee were also published that year, one reappraising the early Permian Alegeinosaurus aphthitos from Texas, which he suggested to be a junior synonym of Aspidosaurus,[44] and another reappraising the middle Permian Fayella chickashaensis from Oklahoma, in which the authors determined that the holotype was a nomen dubium but that the referred specimen was sufficiently distinct to warrant erecting a new taxon, Nooxobeia gracilis.[45] Also in 2018, Gee and Reisz reported postcrania of a large indeterminate dissorophid from Richards Spur,[46] which was followed by another study the following year by a team led by Gee that reported extensive new material from several dissorophids from Richards Spur, including the first documentation of Aspidosaurus and Dissorophus from the locality.[47]