| Dissorophidae Temporal range: Late Carboniferous–Middle Permian, | |
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| Skeleton of Cacops in the Field Museum | |
Scientific classification  | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Order: | † Temnospondyli |
| Clade: | † Olsoniformes |
| Family: | † Dissorophidae Boulenger, 1902 |
| Subgroups | |
| Synonyms | |
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Dissorophidae is an extinct family of medium-sized temnospondyls that flourished during the late Carboniferous and early Permian periods. The clade is known almost exclusively from North America.
Dissorophidae is a diverse clade that was named in 1902 by George A. Boulenger. Junior synonyms include Otocoelidae, Stegopidae, and Aspidosauridae. [1] Early in the study of dissorophoids when the relationships of different taxa were not well-resolved and most taxa had not been described, Dissorophidae sometimes came to include taxa that are now not regarded as dissorophids and may have excluded earlier described taxa that are now regarded as dissorophids. Amphibamiforms were widely regarded as small-bodied dissorophids, [2] and at one point, Dissorophidae was also suggested to also include Trematopidae. [3]
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 Palévol: 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]
Dissorophids are most readily recognized for their distinctive osteoderms, although these are not unique to either dissorophids among temnospondyls or to temnospondyls among early tetrapods. It is also debated whether Platyhystrix has true osteoderms or simply ornamented neural spines with similar morphology to the ornamentation of osteoderms in other taxa. There is also great variability in the osteoderms, both in the number of series and in the overall proportions and anatomy. Dissorophines like Dissorophus typically possess wide osteoderms in contrast to eucacopines like Cacops. [32] Both groups have two series of osteoderms that are relatively flat, in contrast to aspidosaurines, which purportedly a single series that is dorsally keeled to form an inverted-V morphology; it has been suggested, based on CT data, that at least some aspidosaurines may actually have two series of osteoderms but that one is largely obscured. [47] Although osteoderm morphology has been shown to not exert a discernible influence on dissorophid phylogeny, [39] osteoderms remain a major hallmark used to differentiate major clades within Dissorophidae and remain useful for establishing the monophyly of the group within Dissorophoidea. Schoch & Milner (2014) list several features that diagnose dissorophids, but most of these are only useful for differentiating the clade from the closely related trematopids, and some are outdated in light of newer research: (1) maxillary tooth row terminating at or anterior to the posterior orbital margin; (2) basipterygoid region firmly sutured; (3) no prefrontal-postfrontal contact; (4) absence of denticles on the basal plate of the parasphenoid; (5) no pterygoid-vomer contact; (6) short postorbital; (7) long and parallel-sided choana; and (8) absence of a supinator process. [1]
Aspidosaurines and platyhystricines are represented largely by postcranial material, and thus features such as osteoderms are some of the only differentiators for these taxa, but dissorophines and eucacopiens also have many cranial differences, such as the relative proportions of the skull. Most dissorophids are medium-sized, being intermediate between the small amphibamiforms and the larger trematopids, but Dissorophidae includes the largest known dissorophoids, all from the middle Permian of Eurasia, with skull lengths exceeding 30 cm.
Below is a timeline of the known fossil ranges of dissorophids. [48]
Four subfamilies comprise the various dissorophids. Eucacopine (sensu Schoch & Sues, 2013) was traditionally referred to as Cacopinae and includes Cacops and the middle Permian Eurasian taxa (Anakamacops, Iratusaurus, Kamacops, Zygosaurus). [41] [43] Dissorophinae [4] includes Dissorophus and all four species of Broiliellus. These are the two most widely utilized distinctions within Dissorophidae, although Aspidosaurinae [8] (which includes only Aspidosaurus and indeterminate Aspidosaurus-like material) was recently revived along with the erection of the new Platyhystricinae (Platyhystrix and Astreptorhachis). [1] The placement of some more poorly known (Brevidorsum) or anatomically distinct (Scapanops) taxa is less resolved.
Below is a cladogram from Schoch (2012): [49]
| Dissorophoidea |
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Cacops, is a genus of dissorophid temnospondyls from the Kungurian stage of the early Permian of the United States. Cacops is one of the few olsoniforms whose ontogeny is known. Cacops fossils were almost exclusively known from the Cacops Bone Bed of the Lower Permian Arroyo Formation of Texas for much of the 20th century. New material collected from the Dolese Brothers Quarry, near Richards Spur, Oklahoma in the past few decades has been recovered, painting a clearer picture of what the animal looked and acted like.
Temnospondyli or temnospondyls is a diverse ancient order of small to giant tetrapods—often considered primitive amphibians—that flourished worldwide during the Carboniferous, Permian and Triassic periods, with fossils being found on every continent. A few species continued into the Jurassic and Early Cretaceous periods, but all had gone extinct by the Late Cretaceous. During about 210 million years of evolutionary history, they adapted to a wide range of habitats, including freshwater, terrestrial, and even coastal marine environments. Their life history is well understood, with fossils known from the larval stage, metamorphosis and maturity. Most temnospondyls were semiaquatic, although some were almost fully terrestrial, returning to the water only to breed. These temnospondyls were some of the first vertebrates fully adapted to life on land. Although temnospondyls are amphibians, many had characteristics such as scales and armour-like bony plates that distinguish them from the modern soft-bodied lissamphibians.
Platyhystrix is an extinct temnospondyl amphibian with a distinctive sail along its back, similar to the unrelated synapsids, Dimetrodon and Edaphosaurus. It lived during the boundary between the latest Carboniferous and earliest Permian periods throughout what is now known as the Four Corners, Texas, and Kansas about 300 million years ago.
Zatrachys is an extinct genus of large and flat-headed zatracheidid temnospondyl from the early Permian of North America.
Trematopidae is a family of dissorophoid temnospondyls spanning the late Carboniferous to the early Permian. Together with Dissorophidae, the family forms Olsoniformes, a clade comprising the medium-large terrestrial dissorophoids. Trematopids are known from numerous localities in North America, primarily in New Mexico, Oklahoma, and Texas, and from the Bromacker quarry in Germany.
Aspidosaurus is an extinct genus of dissorophoid temnospondyl within the family Dissorophidae.
Anconastes is an extinct genus of dissorophoid temnospondyl within the family Trematopidae. It is known from two specimens from the Late Carboniferous Cutler Formation of north-central New Mexico in the southwestern United States. The genus name derives from two Greek roots, ankos and nastes ("inhabitant"), which refers to the type locality of El Cobre Canyon where the specimens were found. The specific name is derived from the Latin word vesperus ("western"). The more complete specimen, the holotype, is a partial skull with articulated mandibles and a substantial amount of the postcranial skeleton. The less complete specimen, the paratype, consists only of the right margin of the skull with an articulated mandible.
Broiliellus is an extinct genus of dissorophoid temnospondyl within the family Dissorophidae. Broiliellus is most closely related to the genus Dissorophus, and both have been placed in the subfamily Dissorophinae. Broiliellus is known from five species from the Early Permian: the type species is Broiliellus texensis, and the other species are Broiliellus brevis,Broiliellus olsoni, Broiliellus arroyoensis, and Broiliellus reiszi. An additional species, Broiliellus novomexicanus, which was originally named Aspidosaurus novomexicanus, is now thought to fall outside the genus as a member of the subfamily Eucacopinae.
Conjunctio is an extinct genus of dissorophid temnospondyl amphibian from the early Permian of New Mexico. The type species, Conjunctio multidens, was named by paleontologist Robert L. Carroll in 1964.
Ecolsonia is an extinct genus of trematopid temnospondyl. Its phylogenetic position within Olsoniformes has been historically debated, but it is presently considered to be a trematopid.
Dissorophus (DI-soh-ROH-fus) is an extinct genus of temnospondyl amphibian that lived during the Early Permian Period about 273 million years ago. Its fossils have been found in Texas and in Oklahoma in North America. Its heavy armor and robust build indicate Dissorophus was active on land, similar to other members of the clade Dissorophidae that are known from the Late Carboniferous to the Early Permian periods. Dissorphus is distinguished by its small body size, disproportionately large head and short trunk.
Tersomius is an extinct genus of dissorophoid temnospondyl within the family Micropholidae. It is known from the early Permian of North America.
Olsoniformes is an extinct clade of dissorophoid temnospondyls, including the families Dissorophidae and Trematopidae. Most members of the clade were highly adapted to a terrestrial lifestyle. The clade was named in 2008 and is defined as the least inclusive clade containing Dissorophus multicinctus and Acheloma cumminsi but not Amphibamus grandiceps, Micromelerpeton credneri, or Apateon pedestris. Olsoniforms share various features such as a stout and low ilium and a thin cultriform process. The earliest-branching olsoniform is Palodromeus bairdi, from the Late Carboniferous of Ohio.
Dissorophinae is a subfamily of dissorophid temnospondyls that includes Dissorophus and Broiliellus.
Parioxys is an extinct genus of temnospondyl amphibian from the Early Permian of Texas.
Scapanops is an extinct genus of dissorophid temnospondyl amphibian known from the Early Permian Nocona Formation of north-central Texas, United States. It contains only the type species Scapanops neglecta, which was named by Rainer R. Schoch and Hans-Dieter Sues in 2013. Scapanops differs from other dissorophids in having a very small skull table, which means that its eye sockets are unusually close to the back of the skull. The eye sockets are also very large and spaced far apart. Scapanops was probably small-bodied with a proportionally large head and short trunk and tail. Like other dissorophids, it probably spent most of its life on land.
Eucacopinae is an extinct clade of dissorophid temnospondyls. Eucacopines differ from the other main group of dissorophids, the Dissorophinae, in having more lightly built skeletons and more knobby skulls. The subfamily was originally named Cacopinae, but since the name was already established for a group of living microhylid frogs in 1931, the name was changed to Eucacopinae in 2013. Eucacopinae is a stem-based taxon defined as the most inclusive clade containing the species Cacops apsidephorus but not Dissorophus multicinctus, which belongs to Dissorophinae. According to the most recent phylogenetic analyses of Dissorophidae, Eucacopinae includes the basal ("primitive") species Conjunctio multidens and Scapanops neglecta from the southwestern United States and a more derived ("advanced") group including several species of Cacops and the Russian genera Kamacops and Zygosaurus. Derived eucacopines have two rows of bony plates called osteoderms running down their backs, while the more basal eucacopines have only a single row. Dissorophines also have a double row of osteoderms but probably evolved them independently because the most recent common ancestor of the two groups had a single row of osteoderms.
Reiszerpeton is an extinct genus of dissorophid temnospondyl known from the Early Permian Archer City Formation of Texas. It is known solely from the holotype, MCZ 1911, a complete skull. This specimen was originally referred to the amphibamiform Tersomius texensis. A reappraisal of the holotype of T. texensis and a number of other referred specimens by Maddin et al. (2013) noted a number of differences from both T. texensis and amphibamiforms more broadly that suggested affinities with the Dissorophidae. This was confirmed by a phylogenetic analysis, which placed it as the sister taxon to the Eucacopinae. Reiszerpeton is known only from the type species, R. renascentis, which was named for Canadian paleontologist Robert Reisz. The species name refers to the recognition of Reisz as a "renaissance paleontologist." It is differentiated from other dissorophids by its small size, small and more numerous maxillary teeth, smooth cranial ornamentation, and greater distance between the orbit and the otic notch.
Amphibamiformes is an unranked clade with Dissorophoidea created by Schoch (2018). It encompasses all of the taxa traditionally considered to be "amphibamids", branchiosaurids, and hypothetically lissamphibians under the traditional temnospondyl hypothesis of lissamphibian origins. These taxa are typically small-bodied dissorophoids and form the sister group to Olsoniformes, which comprises dissorophids and trematopids.
Richards Spur is a Permian fossil locality located at the Dolese Brothers Limestone Quarry north of Lawton, Oklahoma. The locality preserves clay and mudstone fissure fills of a karst system eroded out of Ordovician limestone and dolomite, with the infilling dating to the Artinskian stage of the early Permian (Cisuralian), around 289 to 286 million years ago. Fossils of terrestrial animals are abundant and well-preserved, representing one of the most diverse Paleozoic tetrapod communities known. A common historical name for the site is Fort Sill, in reference to the nearby military base. Fossils were first reported at the quarry by workers in 1932, spurring a wave of collecting by local and international geologists. Early taxa of interest included the abundant reptile Captorhinus and microsaurs such as Cardiocephalus and Euryodus. Later notable discoveries include Doleserpeton, the most diverse assortment of parareptiles in the Early Permian, and the rare early diapsid Orovenator.
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