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Systematics of the Anteosauria (Therapsida: Dinocephalia) Christian F. Kammerer∗ Department of Vertebrate Paleontology, American Museum of Natural History, New York 10024-5192, USA (Received 17 December 2009; accepted 26 April 2010; printed 31 May 2011)

Anteosaurs (Therapsida: Dinocephalia: Anteosauria) were the dominant terrestrial predators during the late Middle Permian period and are known from southern Africa, the former USSR, China and Brazil. This paper presents a critical taxonomic review of all known anteosaur taxa and a reevaluation of anteosaurian interrelationships. The following anteosaur species are considered to be valid: Anteosaurus magnificus, Archaeosyodon praeventor, Australosyodon nyaphuli, Microsyodon orlovi, Notosyodon gusevi, Sinophoneus yumenensis, Syodon biarmicum, Titanophoneus adamanteus and T. potens. Syodon efremovi is considered a junior synonym of S. biarmicum, Stenocybus acidentatus to represent juvenile material of Sinophoneus yumenensis, Doliosauriscus yanshinovi a junior synonym of Titanophoneus potens,andParanteosaurus primus a junior synonym of Anteosaurus magnificus. Admetophoneus kargalensis, Archaeosuchus cairncrossi, Brithopus bashkyricus, B. ponderus, B. priscus, Eccasaurus priscus, Lamiasaurus newtoni and Orthopus primaevus are regarded as nomina dubia. ‘Titanophoneus’ rugosus is tentatively considered the first representative of the genus Anteosaurus in Russia. Phyloge- netic analysis of anteosaurs recovers a monophyletic Anteosauridae containing two major clades, Syodontinae (containing Australosyodon, Notosyodon and Syodon) and Anteosaurinae (containing Anteosaurus, Sinophoneus and Titanophoneus). The Russian taxa Archaeosyodon and Microsyodon represent the most basal anteosaurs. Anteosaurian skulls share many features in common with those of large-bodied predatory taxa such as tyrannosaurid dinosaurs, and anteosaurines in particular exhibit characters associated with handling large prey items and possibly bone-crushing. Keywords: Therapsida; Dinocephalia; Anteosauria; Anteosauridae; Permian

Introduction Brithopus (a wastebasket taxon for Ural copper measures dinocephalian postcranial material) and better-known Anteosaurs are one of the two major groups of Russian taxa such as Syodon and Titanophoneus. Brithopo- dinocephalians, a diverse but short-lived therapsid clade didae was extensively used by subsequent workers (Romer that represented one of the most widespread and success- 1956, 1966; Watson & Romer 1956; Olson 1962; Boonstra ful amniote radiations in the Middle Permian. Anteosaurs 1963; Kemp 1982; Tchudinov 1983; Sues 1986; King 1988; were the largest terrestrial predators in the Middle Permian Battail & Surkov 2000) to refer to all non-Anteosaurus (∼270–260 Ma; Eodicynodon–Tapinocephalus Assem- anteosaurs (although not all of these authors considered blage Zones of South Africa, Zones I–II of Russia), with ‘anteosaurs’ to represent a natural group), and was later skulls exceeding 80 cm in length. They were also the emended to such nomenclaturally incorrect forms as Downloaded by [University of Guelph] at 12:37 30 April 2012 ﬁrst non-mammalian therapsids to be discovered, although Brithopidae and Brithopia (Boonstra 1972; Kemp 1982; they were not initially recognized as such (Kutorga 1838). King 1988). Indeed, despite their distinctive cranial anatomy (Fig. Hopson & Barghusen (1986) argued that use of the 1), anteosaurs were not recognized as a separate group term ‘Brithopodidae’ should be discontinued and that the of dinocephalians until work by Boonstra (1954a), who Russian taxa Syodon, Titanophoneus and Doliosauriscus separated Anteosauridae from Titanosuchidae, a group should be placed with Anteosaurus in Anteosauridae. of herbivorous therapsids currently placed in the other They recognized three additional taxa: Anteosauria, a major dinocephalian group, Tapinocephalia (Hopson & monofamilial higher taxon for Anteosauridae to com- Barghusen 1986). plement Tapinocephalia; Anteosaurinae, containing Even following Boonstra’s (1954a) recognition that Titanophoneus, Doliosauriscus and Anteosaurus; and Anteosaurus belonged to a distinct radiation of carnivorous Anteosaurini, containing only the giant anteosaurs dinocephalians, the various taxa currently considered Doliosauriscus and Anteosaurus. King (1988) retained anteosaurs had a tenuous history of association. Efremov Brithopidae [sic] (containing the subfamilies Brithopinae (1954) named a new family, Brithopodidae, to refer to [sic] and Anteosaurinae) and placed both ‘Brithopidae’

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ISSN 1477-2019 print / 1478-0941 online Copyright C 2011 The Natural History Museum DOI: 10.1080/14772019.2010.492645 http://www.informaworld.com 262 C. F. Kammerer

Titanosuchus and Jonkeria. Ivakhnenko (1994, p. 102) also argued that the taxon Brithopodidae is invalid, and that the ‘Titanophoneus-Deuterosaurus group’ probably belongs in Anteosauridae, in which case the proper name for this group would be Deuterosauridae Seeley, 1894. Ivakhnenko (1995, 2003) considered both families to be valid, and united Anteosauridae (including Anteosaurus and Titanophoneus) and Deuterosauridae (Deuterosaurus only) in the superfamily Deuterosauroidea, while placing Syodontidae in Titanosuchoidea. As indicated by the conﬂicting taxonomic schemes presented above, despite over 170 years of research, anteosaurian systematics remains in a state of great confu- sion. The purpose of this paper is to critically review anteosaur alpha taxonomy and to establish a phylogenetic framework for anteosaur classiﬁcation. Each nominal taxon currently considered distinct is treated separately. Nomi- nal taxa previously synonymized with other anteosaurian species are dealt with in the section concerning the oldest valid name.

Materials

Type material of each nominal anteosaurian taxon was personally examined by the author, with the exception of LGU 140/1, the holotypic canine of Syodon biarmicum, and the type material of Titanognathus lotzi, which was apparently destroyed during WWII (King 1988).

Institutional abbreviations Figure 1. The skull of a representative anteosaurid (Syodon AMG: Albany Museum, Grahamstown, South Africa; biarmicum)inA, right lateral; B, dorsal; and C, palatal views. AMNH: American Museum of Natural History, New Reconstruction based predominantly on PIN 157/2, the holotype of Cliorhizodon efremovi. Key anteosaurian characters visible in Yo r k C i t y, N e w Yo r k , U S A ; BMNH: Natural History A include the strongly recurved (‘hook-like’) canine, upward Museum, London, UK; BP: Bernard Price Institute, Univer- canted alveolar margin of the premaxilla, bulbous postcanines, sity of the Witwatersrand, Johannesburg, South Africa; and temporal fenestra undercutting the orbit. Note in B the contri- BSPG: Bayerische Staatssammlung fur¨ Palaontologie¨ und bution of the frontal to the anterior edge of the pineal boss and the

Downloaded by [University of Guelph] at 12:37 30 April 2012 historische Geologie, Munich, Germany; CGP: Council anterolateral curvature of the edge of the pineal boss where temporal musculature attached, characteristic of Syodon, Australosyodon for Geosciences, Pretoria, South Africa; FMNH:Field and Notosyodon. Key anteosaurian characters visible in C include Museum of Natural History, Chicago, Illinois, USA; the ‘scroll-like’ vomers and quadrate rami of the pterygoid bifur- GMV: Geological Museum of China, Beijing, China; cating the basisphenoid. IGCAGS: Institute of Geology, Chinese Academy of Geological Sciences, Beijing, China; IVPP: Institute for and Titanosuchidae (containing Titanosuchinae and Vertebrate Paleontology and Paleoanthropology, Beijing, Tapinocephalinae) in the superfamily Anteosauroidea. China; LGU: Saint Petersburg State University, St Peters- Ivakhnenko (1994) established a new family, Syodontidae burg, Russia; NMQR: National Museum, Bloemfontein, (including Syodon, Notosyodon and Archaeosyodon), South Africa; PEM: former collections of the Port Eliz- characterized by expansion of the temporal fenestra to abeth Museum, currently housed in the Albany Museum, incorporate the pineal boss (which is actually not present Grahamstown, South Africa; PIN: Paleontological Insti- in Archaeosyodon), a rounded, sharply recurved canine tute of the Russian Academy of Sciences, Moscow, Russia; without serrations, and distinctive sculpturing of the upper SAM: Iziko, South African Museum, Cape Town, South jaw bones. In a subsequent paper, Ivakhnenko (1995) Africa; TM: Transvaal Museum, Pretoria, South Africa; restricted Syodontidae to Syodon (including Notosyodon UCMP: University of California Museum of Paleontology, as a junior synonym), placing Archaeosyodon and the Berkeley, California, USA; UFRGS: Universidade Federal newly described Microsyodon in Titanosuchidae with do Rio Grande do Sul, Porto Alegre, Brazil. Systematics of the Anteosauria 263

Figure 2. Syodon biarmicum. A, LGU 140/1, the holotype of Syodon biarmicum (from Ivakhnenko et al. 1997, p. 187), an isolated left canine showing the characteristic curvature of the taxon; B, BMNH R4077, the holotype of Cliorhizodon orenburgensis,preservingthe left maxilla, premaxilla and associated dentition. Scale bars equal 1 cm.

Anatomical abbreviations Taxonomic review bs, basisphenoid; C, upper canine; cap, capitellum; dpc, deltopectoral crest; ec, ectopterygoid; ect, ectepicondyle; Valid anteosaurian taxa ect f, ectepicondylar foramen; ent, entepicondyle; ent f, entepicondylar foramen; f, frontal; j, jugal; la, lacrimal; Syodon biarmicum Kutorga, 1838 mx, maxilla; na, nasal; op, opisthotic; pa, parietal; pal, (Figs 1, 2) palatine; PC, upper postcanine; pf, pineal foramen; pmx, 1880 Cliorhizodon orenburgensis Twelvetrees: 543. premaxilla; po, postorbital; pof, postfrontal; ppt; palatal

Downloaded by [University of Guelph] at 12:37 30 April 2012 ramus of the pterygoid; prf, prefrontal; pt, pterygoid; q, Holotype. LGU 140/1, an isolated left canine (Fig. 2A). quadrate; qj, quadratojugal; qpt, quadrate ramus of the pterygoid; smx, septomaxilla; sq, squamosal; st, stapes; Age. Middle Permian (Sheshmian Horizon, Uﬁmian sup, supinator process; ta, tabular; tpt, transverse process Stage). of the pterygoid; tr, trochlea; v, vomer. Locus typicus. Cupriferous mines of the Perm Region (exact locality unknown), Russia (Ivakhnenko 2003).

Note on orthography Referred material. BMNH R4077, the holotype of Variations in transliterating Russian names from the Cyril- Cliorhizodon orenburgensis Twelvetrees, 1880, a partial lic into the Latin alphabet have resulted in a plethora left premaxilla and maxilla with intact dentition (Fig. 2B), of alternate spellings for Russian therapsid workers supposedly from the Rozhdestvenskii Rudnik locality. PIN (e.g. Amalitzky/Amalitskii; Tchudinov/Chudinov; Ivach- 273/4, a left femur from the Novo-Myasnikovskii Rudnik nenko/Ivakhnenko). The recommendations of ISO 9 (1995) locality, referred to Syodon biarmicum by Efremov (1954). are used for references cited throughout this paper. An exception is made for taxon authorships, which follow the Diagnosis. Syodon biarmicum can be distinguished from orthography used in the original publications. all anteosaurs except Archaeosyodon praeventor and 264 C. F. Kammerer

Microsyodon orlovi by its strongly recurved, ‘hook’-like tively longer and narrower than that of Archaeosyodon and canine. S. biarmicum can be distinguished from all other Microsyodon, especially at the base, which is massively anteosaurs except Notosyodon gusevi and Australosyodon expanded in Archaeosyodon. Syodon efremovi, known from nyaphuli by the adductor mandibulae musculature attach- a complete skull and mandibles (PIN 157/2), is here consid- ment site extending onto the pineal boss, frontal contribu- ered a junior synonym of S. biarmicum (see separate entry tion to the adductor musculature attachment site margin, on S. efremovi for rationale). The referral of PIN 157/2 to and frontal contribution to the pineal boss. Syodon can S. biarmicum allows for a more complete cranial diagnosis be distinguished from Notosyodon based on zygomatic of this taxon, and permits more thorough comparisons with morphology (thinner and more curved in Syodon,more Notosyodon and Australosyodon (see Diagnosis above). pachyostosed in Notosyodon) and by more extensive contact Anteosaurus magnificus Watson, 1921 between the frontal and the adductor musculature attach- (Figs 3, 4, 5C, D) ment site. Syodon can be distinguished from Australosyo- don by the absence of an interorbital boss and the presence 1929 Anteosaurus minor Broom: 35. of massive, low-crowned posterior postcanines. 1935 Titanognathus lotzi Broili & Schroder:¨ 112. 1936a Dinosuchus vorsteri Broom: 351. Remarks. Syodon biarmicum (Fig. 2A) was the first non- 1942 Broomosuchus vorsteri (Broom); Camp et al.: 478. mammalian synapsid to be described (along with Britho- 1952 Anteosaurus abeli Boonstra: 150. pus and Orthopus), predating Owen’s (1845) description of 1953 Anteosaurus vorsteri (Broom); Boonstra: 27. Dicynodon lacerticeps by six years. Its original descriptor, 1953 Titanosuchus lotzi (Broili & Schroder);¨ Boonstra: 28. S. S. Kutorga, considered it to be the tusk of a ‘pachy- 1954a Anteosaurus acutirostris Boonstra: 131. dermal’ mammal, and it was not officially recognized as 1954a Anteosaurus crassifrons Boonstra: 133. belonging to a non-mammalian synapsid until nearly 40 1954a Anteosaurus cruentus Boonstra: 139. years later (Owen 1876a), although a similarity to the teeth 1954a Anteosaurus laticeps Boonstra: 138. of Rhopalodon murchisonii had been noted by Eichwald 1954a Anteosaurus levops Boonstra: 141. (1848). 1954a Anteosaurus lotzi (Broili and Schroder);¨ Boonstra: Twelvetrees (1880) described a new taxon of ‘theri- 127. odont reptile’, Cliorhizodon orenburgensis (Fig. 2B), on 1954a Anteosaurus major Boonstra: 136. the basis of a left maxilla and premaxilla (BMNH R4077) 1954a Anteosaurus minusculus Boonstra: 142. from cupriferous marl in the Perm Region. The type local- 1954a Pseudanteosaurus minor (Broom); Boonstra: 125. ity of C. orenburgensis was given by Twelvetrees (1880, 1954b Micranteosaurus parvus Boonstra: 156. p. 540) as “the copper-mine of Roshdestvensk”, although Ivakhnenko (2003) doubted this attribution as other speci- Holotype. BMNH R3595, a partial skull (Fig. 3). mens from the Rozhdestvenskii ( = Roshdestvensk) Rudnik locality are enclosed in a slightly different matrix. Twelve- Age. Middle Permian (Tapinocephalus Assemblage Zone, trees (1880, p. 542) recognized that Cliorhizodon was very Abrahamskraal Formation, Beaufort Group). similar to the tapinocephalian dinocephalians Titanosuchus and Rhopalodon, but differentiated it from the latter genus on the basis of “the excessive obliquity of the root of Downloaded by [University of Guelph] at 12:37 30 April 2012 the canine” and the possession of bulbous, rather than phylliform, postcanines. These features have subsequently been recognized as two of the key diagnostic characters of Anteosauria (Hopson & Barghusen 1986). Efremov (1954), in his monographic treatment of therapsids from the copper sandstones of the western Fore-Urals, synonymized Cliorhizodon with Syodon and referred an isolated femur (PIN 273/4) to S. biarmicum. This femur closely resembles that of Titanophoneus (Orlov 1958) and should be considered Anteosauridae indet. The canine morphology of Syodon (Fig. 2A) is highly Figure 3. The holotype of Anteosaurus magnificus (BMNH distinctive and allows this taxon to be readily diagnosed R3595), shown in three-quarters profile view to illustrate the despite the incompleteness of the holotype. Syodon can be massive postfrontal bosses. Specimen is a dorsal skull roof preserving part of the snout, the supraorbital region, and the top distinguished from all anteosaurids other than Archaeosy- ◦ of the temporal arcade; anterior is towards the right. Part of the odon and Microsyodon by the strongly recurved (70 angle pachyostosed, transversely expanded postorbital bar typical of this between canine tip and canine base), ‘hook’-like morphol- taxon is visible underneath the right postfrontal boss. Scale bar ogy of the canine. The canine of S. biarmicum is rela- equals 20 cm. Systematics of the Anteosauria 265 Downloaded by [University of Guelph] at 12:37 30 April 2012

Figure 4. Cranial variation in Anteosaurus magnificus. A, Anteosaurus abeli (SAM-PK-11296); B, Anteosaurus crassifrons (SAM-PK- 11302); C, Anteosaurus vorsteri (SAM-PK-11577); D, Anteosaurus magnificus (SAM-PK-K360); E, Anteosaurus cruentus (SAM-PK- 11694); F, Anteosaurus magnificus (BP/1/1369). All specimens shown in left lateral view except for B, which is right lateral view flipped for illustrative purposes. Scale bars equal 20 cm.

Locus typicus. Tamboerfontein, Beaufort West, Western a partial snout from Antjiesfontein, Prince Albert. Cape Province, South Africa (Kitching 1977). BP/1/1369, a complete skull with lower jaws from De Bad, Beaufort West (Fig. 4F). BSPG unnumbered, the holotype Referred material. AMG 5993 (formerly PEM of Titanognathus lotzi, destroyed in WWII. CGP CBT118, 1518/56B), a weathered snout fragment, locality unknown. a fragmentary skull with lower jaws from De Vreede, AMNH 2224, a laterally compressed partial skull from Sutherland. FMNH PR 1142, three fragments of a skull (the Vanderbylskraal, Beaufort West referred to Anteosaurus front tip of the snout and lower jaw, the frontal boss, and minor by Boonstra (1936), later made the holotype of A. the temporal region) from Hottentotsrivier, Beaufort West. minusculus. BMNH R5742, the holotype of A. minor,a SAM-PK-2752, a partial skull missing the snout, partial partial skull from Merweville, Beaufort West. BP/1/280, humerus, and a coracoid from Viviers Siding, Beaufort 266 C. F. Kammerer

Figure 5. Comparison of skull shape in subadult and adult anteosaurids, showing the straight, downward-sloping snout profile of subadults against the concave profile of adults. A, Subadult Titanophoneus potens (PIN 157/1, the lectotype of T. potens); B, adult Titanophoneus potens (PIN 157/3, the holotype of Doliosauriscus yanshinovi); C, subadult Anteosaurus magnificus (SAM-PK-K284); D, adult Anteosaurus magnificus (SAM-PK-K1683). Specimens depicted in A, B and D are in left lateral view; specimen depicted in C is in right lateral view, flipped for illustrative purposes. Scale bars equal 10 cm.

West referred to Anteosaurus sp. by Boonstra (1954a). to A. cruentus by Boonstra (1954a). SAM-PK-9329, the SAM-PK-2753a, a skull fragment and the proximal and holotype of A. acutirostris, a complete skull and lower distal ends of a femur from Viviers Siding, Beaufort jaw from Kruisvlei, Beaufort West. SAM-PK-11293, the West referred to Anteosaurus sp. by Boonstra (1955). holotype of A. major, a dorsoventrally compressed skull Downloaded by [University of Guelph] at 12:37 30 April 2012 SAM-PK-4323, the holotype of Micranteosaurus parvus, missing the snout from Boesmansrivier, Beaufort West. a snout and partial postcranium from Merweville, Beaufort SAM-PK-11296, the holotype of A. abeli, a complete West. SAM-PK-4340, a complete skull and partial lower skull and lower jaw (Fig. 4A) from Kruisrivier, Suther- jaw from Leeurivier, Beaufort West referred to A. abeli by land. SAM-PK-11302, a weathered skull (Fig. 4B) from Boonstra (1952). SAM-PK-5614, two dentaries, a partial Buffelsvlei, Beaufort West, referred to A. crassifrons scapula, partial ilium and the proximal end of a femur from by Boonstra (1954a). SAM-PK-11492, the holotype Abrahamskraal, Prince Albert, referred to Anteosaurus sp. of A. levops, a weathered skull from Mynhardtskraal, by Boonstra (1955). SAM-PK-5621, two fragments of the Beaufort West. SAM-PK-11576, a snout tip preserving dorsal region of a skull from Leeurivier, Beaufort West, the premaxillae and symphyseal region of the dentaries referred to A. abeli by Boonstra (1954a). SAM-PK-7396, from Kleinkoedoeskop, Beaufort West, referred to A. abeli a coracoid from Abrahamskraal, Prince Albert, referred by Boonstra (1954a). SAM-PK-11577, a nearly complete to Anteosaurus sp. by Boonstra (1955). SAM-PK-9123, a skull (Fig. 4C) from Bulwater, Beaufort West, referred partial skull from Voelfontein,¨ Prince Albert, referred to to A. vorsteri by Boonstra (1954a). SAM-PK-11592, the A. abeli by Boonstra (1954a). SAM-PK-9139, a weathered holotype of A. laticeps, a partial skull from Dikbome, skull fragment assigned to Anteosaurus but not referred Laingsburg. SAM-PK-11694, the holotype of A. cruentus, to species by Boonstra (1954a). SAM-PK-9140, a frag- a nearly complete skull (Fig. 4E) missing part of the mentary skull from Voelfontein,¨ Prince Albert, referred right temporal region from Koringplaas, Laingsburg. Systematics of the Anteosauria 267

SAM-PK-11887, a coracoid from Vindraersfontein, 3) was initially described by Broom (1910) and Watson Beaufort West, referred to Anteosaurus sp. by Boonstra (1914) as a new specimen of Titanosuchus ferox.Watson (1955). SAM-PK-11929, a partial, weathered skull from (1921) described further elements of this specimen, includ- an unknown locality (probably near Abrahamskraal, ing a premaxilla, which Watson believed to have only Prince Albert according to Boonstra 1954a), referred to three incisors. Based on this interpretation, Watson (1921) A. crassifrons by Boonstra (1954a). SAM-PK-11946, the assigned BMNH R3595 to a new taxon, Anteosaurus holotype of A. crassifrons, a complete, but distorted, skull magnificus. Broom (1929) described a second species of from Buffelsvlei, Beaufort West. SAM-PK-11949, two Anteosaurus, A. minor, on the basis of the rear portion of a skull fragments, a snout and part of the temporal region, skull (BMNH R5742) he collected near Merweville, Beau- referred to Anteosaurus abeli by Boonstra (1954a). SAM- fort West. Setting the precedent for anteosaur splitting to PK-11972a, an interclavicle from Kruisvlei, Beaufort West. come, he wrote that he “would be inclined to think that SAM-PK-11977a, two femora associated with the holotype this skull might be that of a young and perhaps female of A. acutirostris (SAM-PK-9329) from Kruisvlei, Beau- Anteosaurus magnificus were it not that the shape of the fort West, referred to A. acutirostris by Boonstra (1955). temporal fossa differs sufficiently greatly in the two forms SAM-PK-11996, an interclavicle from Koedoeskop, as to render it practically certain that this new skull repre- Beaufort West, assigned to Anteosauridae incertae sedis sents a distinct species” (Broom 1929, p. 35). by Boonstra (1955). SAM-PK-12082, a sectioned skull Broom (1936a) gave a preliminary description of a from Boesmanskop, Beaufort West. SAM-PK-12083, new dinocephalian, Dinosuchus vorsteri, based on a nearly skull fragments from Boesmanskop, Beaufort West. SAM- complete skull associated with the posterior half of a right PK-12088, the proximal end of a femur and associated lower jaw (TM 265). He distinguished Dinosuchus from limb bone fragments from Sewefontein, Prince Albert. other dinocephalians on the basis of the extreme width of SAM-PK-12120, skull fragments from De Puts, Prince the occiput, and, in a subsequent, more thorough descrip- Albert. SAM-PK-12241, the anterior region of a lower tion of the taxon (Broom 1936b), on the “very low position jaw from Knoffelfontein, Beaufort West. SAM-PK-K275, of the temporal arch” (p. 734). Broom (1936a, b) argued a fragmentary skull from Perdefontein, Beaufort West. that Dinosuchus and Anteosaurus were closely related and SAM-PK-K284, a complete skull (Fig. 5C) from Leeuw- established that Anteosaurus possessed five upper incisors, fontein, Beaufort West. SAM-PK-K288, a fragmentary rather than three as described by Watson (1921). Camp skull and limb bone fragments from Morewag, Beaufort et al. (1942) proposed a new name (Broomosuchus)for West. SAM-PK-K291, a vertebra and the proximal end of a Dinosuchus Broom, 1936a, which proved to be preoccu- femur from Die Krans, Beaufort West. SAM-PK-K300, an pied by a fossil crocodylian (Dinosuchus Gervais, 1876). ilium and limb bone fragments from Kranskraal, Beaufort Boonstra (1952) briefly described a new species of West. SAM-PK-K316, a femoral fragment from Kran- Anteosaurus, A. abeli, based on a distorted but complete skraal, Beaufort West. SAM-PK-K360, a complete skull and well-preserved skull, SAM-PK-11296 (Fig. 4A). Addi- (Fig. 4D) from Nuwelande, Fraserburg. SAM-PK-K1683, tionally, Boonstra (1952) listed a number of specimens a skull with lower jaw (Fig. 5D) and postcranial fragments (SAM-PK-4340, 5621, 9123, 9329, 11302, 11393, 11485, from Welgevonden, Sutherland. TM 265, the holotype of 11592 and 11929) as ‘cotypes’ of A. abeli, many of which Dinosuchus vorsteri, a nearly complete skull and partial would later (Boonstra 1954a) be made holotypes of separate lower jaw from Stinkfontein, Prince Albert. UCMP 42411, species. Boonstra (1953) revised ‘titanosuchian’ taxonomy Downloaded by [University of Guelph] at 12:37 30 April 2012 a nearly complete but badly distorted and fragmented skull and synonymized Dinosuchus with Anteosaurus, creating from Wilgerfontein, Prince Albert. the new combination Anteosaurus vorsteri (Broom, 1936a). He also referred new specimens to A. minor (SAM-PK- Diagnosis. Anteosaurus magnificus can be distinguished 11492 and 11694). These specimens would later be made from all anteosaurs other than the two species of the holotypes of A. levops Boonstra, 1954a, and A. cruentus Titanophoneus on the basis of an angular boss, heavily Boonstra, 1954a, respectively. pachyostosed skull roof including a massive frontal boss, Boonstra (1954a) described six new species of concave alveolar margin of the precanine region, concave Anteosaurus (A. acutirostris, A. crassifrons, A. cruentus, dorsal snout profile, posterolateral cant of the poste- A. laticeps, A. levops and A. major) on the basis of riormost upper postcanines, and anteroventrally-rotated skulls in the collections of the South African Museum. suspensorium. Anteosaurus can be distinguished from Additionally, he established a new genus (Pseudan- Titanophoneus on the basis of an oval angular boss and the teosaurus)forAnteosaurus minor, because the type spec- presence of ‘brow horns’ formed by the massively pachyos- imen does not exhibit the postfrontal bosses (‘horns’) tosed postfrontals. that Boonstra (1954a) considered to be the only diagnostic feature of Anteosaurus. The referred specimen of Remarks. The material that would eventually become the Anteosaurus minor (AMNH 2224), however, he consid- holotype of Anteosaurus magnificus (BMNH R3595) (Fig. ered to represent Anteosaurus, albeit as a new species, 268 C. F. Kammerer

A. minusculus. Finally, he established that Titanognathus appear to lack pachyostosis altogether. That said, size or represents a junior synonym of Anteosaurus, rather than a age-based change cannot explain all of the cranial vari- synonym of Titanosuchus as argued by Boonstra (1953), ation in Anteosaurus. For example, SAM-PK-11577, one but retained the species as valid in the new combina- of the larger Anteosaurus skulls (see Fig. 4C), has a very tion Anteosaurus lotzi (Broili & Schroder,¨ 1935). Boonstra weak frontal boss. SAM-PK-K360 and BP/1/1369, which (1954b) named a new genus and species, Micranteosaurus appear to lack a frontal boss altogether, are also very large parvus, on the basis of SAM-PK-4323, the anterior section skulls (Fig. 4D, F). It is possible that frontal boss devel- of a skull and lower jaws with associated postcranial mate- opment is a sexually dimorphic feature in Anteosaurus. rial (manus, tarsus, femur, radius, fibula, humeral head, Frontal bosses in dinocephalians have been implicated in coracoid and caudal vertebrae). Boonstra (1954b) empha- agonistic behavior (Barghusen 1975). It is difficult to test sized the similarity of this material to Anteosaurus, and this hypothesis in Anteosaurus, however, because although distinguished Micranteosaurus from Anteosaurus solely on this taxon is known from more reasonably complete skulls the basis of smaller size. than any other anteosaur (over 30 known, making it the In his comprehensive review of Tapinocephalus Assem- most common South African dinocephalian in collections), blage Zone tetrapods, Boonstra (1969) synonymized the most specimens come from different localities and (proba- majority of South African anteosaurids with Anteosaurus bly) horizons. As such they do not form a fossil ‘population’ magnificus. Boonstra (1969) argued that the types of A. that can be used for demographic analysis, as has been done cruentus, A. levops, A. minor, A. minusculus and Micran- in several anomodont therapsid taxa shown to be sexually teosaurus parvus represent immature individuals, and that dimorphic, such as Diictodon (Sullivan et al. 2003) and the characters used to distinguish these species from A. Lystrosaurus (Ray 2005). magnificus are best interpreted as ontogenetic variations. Boonstra (1969) interpreted the differences between the Titanophoneus potens Efremov, 1938 types of A. abeli, A. acutirostris, A. crassifrons, A. lati- (Figs 5A, B, 6, 7) ceps, A. major, A. vorsteri and A. magnificus as repre- 1956 Doliosaurus yanshinovi Orlov: 59. senting either taphonomic distortion or minor differences 1958 Doliosaurus yanshinovi Orlov: 105. in pachyostosis that could be attributed to ontogenetic, 1961 Doliosauriscus yanshinovi (Orlov); Kuhn: 79. sexual or individual variation. Boonstra considered A. lotzi 1964 Doliosuchus yanshinovi (Orlov); Orlov: 218. and Eccasaurus priscus to be “specifically indeterminable” (Boonstra 1969, p. 34), and with such a designation they Lectotype. PIN 157/1, a well-preserved skull (Fig. 6) and should technically be considered nomina dubia rather than complete skeleton, designated by Orlov (1958). junior synonyms of A. magnificus. However, the angular morphology illustrated by Broili & Schroder¨ (1935) in their description of the Titanognathus lotzi holotype allows it to Age. Middle Permian (Urzhumian Horizon, Lower Tatar- be positively identified as A. magnificus. The status of Ecca- ian Substage). saurus priscus is dealt with in a separate entry. The known specimens of Anteosaurus exhibit a remark- Locus typicus. Kamenny Ovrag (‘Stone Ravine’), near the able range of variation in cranial proportions and extent village of Isheevo, Apastovskii District, Tatarstan, Russia of pachyostosis (Fig. 4). The level of development of (Orlov 1958). Downloaded by [University of Guelph] at 12:37 30 April 2012 the postfrontal horns and the frontal boss is particularly variable between specimens. In some individuals, both Referred material. PIN 157/3, the holotype of the horns and the boss are massively pachyostosed (e.g. Doliosaurus yanshinovi Orlov, 1956, and former syntype BMNH R3595, SAM-PK-11296, UCMP 42411), whereas of T. potens, a complete skull (Fig. 7) and partial skeleton others have well-developed horns but a weak or nonexis- from the type locality (all subsequent PIN 157/# speci- tent boss (SAM-PK-K360), and yet others have negligibly mens also from the type locality). PIN 157/180, a frontal. developed horns and boss (BP/1/1369). Morphology of the PIN 157/181, a frontal. PIN 157/182, a postorbital. PIN postfrontal horns is also variable, even between specimens 157/186, transverse process of a pterygoid. PIN 157/187, a that fall into the ‘very heavily pachyostosed’ category: in prefrontal. PIN 157/188, a postorbital. PIN 157/190, trans- SAM-PK-11296, the horns are relatively small compared verse process of a pterygoid. PIN 157/192, a postorbital. to the boss (Fig. 4A), whereas in BMNH R3595 the horns PIN 157/193, a pterygoid. PIN 157/194, a pterygoid. PIN are especially massive (Fig. 3). Some of the variation in 157/195, transverse process of a pterygoid. PIN 157/208, cranial pachyostosis in Anteosaurus can be attributed to a partial squamosal. PIN 157/209, an isolated angular boss ontogenetic changes: smaller skulls (e.g. SAM-PK-11492, (Fig. 8C). PIN 157/272, an angular. PIN 157/275, a ptery- the holotype of A. levops, and SAM-PK-K284) tend to goid. PIN 157/648, a palatine. PIN 157/972, a pterygoid. exhibit smaller horns and bosses (Fig. 5C), and very small PIN 2793/4, a postorbital from the Novo-Nikol’skoe local- skulls (e.g. AMNH 2224, the holotype of A. minusculus) ity, Aleksandrovskii District, Orenburg Region. Systematics of the Anteosauria 269

Figure 6. Titanophoneus potens. The lectotype (PIN 157/1) skull in A, right lateral; B, dorsal and C, palatal views. Scale bars equal 10 cm.

Diagnosis. Titanophoneus potens can be distinguished from all anteosaurs except T. adamanteus and Anteosaurus magnificus by the presence of an angular boss, concave dorsal snout profile, concave alveolar margin of the Figure 7. Titanophoneus potens. The holotype of Doliosauriscus Downloaded by [University of Guelph] at 12:37 30 April 2012 precanine region, and massive pachyostosis of the dorsal yanshinovi (PIN 157/3) in A, right lateral; B, dorsal; and C, palatal surface of the skull. T. potens can be distinguished from views. Scale bars equal 10 cm. Anteosaurus by the lack of postfrontal horns and the lenticu- PIN 157/1), making it the most completely known of all lar shape of the angular boss. T. potens can be distinguished anteosaurs. Additionally, Orlov (1956, 1958) removed the from T. adamanteus by its relatively smaller palatine bosses extremely large skull PIN 157/3 from the syntype series and broader angular bosses. of T. potens and made it the holotype of a new genus and species, Doliosaurus yanshinovi. Unfortunately, the Remarks. Efremov (1938) briefly described name Doliosaurus proved to be preoccupied by a phryno- Titanophoneus potens on the basis of two skulls somatid lizard, Doliosaurus Girard, 1858 (a subgenus of with associated postcrania (the syntypes PIN 157/1 and Phrynosoma Wiegmann, 1828), and Kuhn (1961) replaced PIN 157/3) from the Isheevo locality (Russian ‘Zone II’). it with Doliosauriscus. Unaware of Kuhn’s replacement, in Although these two skulls (Figs 6, 7) differ in a number a 1964 letter to the editor of Vertebrata PalAsiatica,Orlov of characters, Efremov (1938) considered them simply to mentioned that in a future Russian publication, he planned represent small and large individuals of a single species, to propose Doliosuchus as a replacement name for the a position he reiterated in later papers (Efremov 1940, preoccupied Doliosaurus. Further usage of Doliosuchus 1941). Orlov (1958) thoroughly described and figured never materialized, presumably because Orlov learned of the skull and postcranium of Titanophoneus (based on Kuhn’s earlier replacement name Doliosauriscus. 270 C. F. Kammerer

Figure 8. Angular boss morphology in Russian anteosaurids. A, Titanophoneus rugosus (PIN 1955/1, the holotype); B, Titanophoneus potens (PIN 157/3, the holotype of Doliosauriscus yanshinovi); C, Titanophoneus potens (PIN 157/209); D, Titanophoneus adamanteus (PIN 520/2, the holotype); E, Titanophoneus adamanteus (PIN 520/25). All specimens in left lateral view. Scale bars equal 5 cm.

Ivakhnenko (2003) considered D. yanshinovi to represent a junior synonym of T. potens. Titanophoneus potens has traditionally been distinguished from Doliosauriscus yanshinovi on the basis of the relatively small, narrow skull, pachyostosis limited to the orbital rim, weakly developed angular boss, and straight snout profile (Tchudinov 1983; Hopson & Barghusen 1986; King 1988; Rubidge 1994). However, Ivakhnenko (1995, 2003) called this distinction into question, noting that skull width and extent of pachyostosis are age-related characters in dinocephalians. Further- more, Ivakhnenko (2003) argued that the apparent difference in snout profiles is artefactual, as this region was broken in PIN 157/1 and displaced upon repair. The results of personal examination of all known material of Titanophoneus potens and Doliosauriscus yanshinovi are in agreement with Ivakhnenko’s (2003) conclusions. As he noted, there exist several specimens in the PIN collec- Downloaded by [University of Guelph] at 12:37 30 April 2012 tions (e.g. PIN 157/180, 157/182, 157/272) that occupy an intermediate size (and extent of cranial pachyostosis) range between PIN 157/1 and PIN 157/3. As regards snout profile, however, it actually appears that the lectotype skull suffered minimal, if any, vertical displacement following its repair, and the snout profile observed in this specimen is probably close to the original condition. Although this shape differs from that of PIN 157/3, the differences in snout profile between these two skulls are also observed between small and large individuals of Anteosaurus (Fig. 5), so this distinction can be attributed to ontogeny.

Titanophoneus adamanteus (Orlov, 1958) (Figs 9, 10) Figure 9. Titanophoneus adamanteus. The holotype (PIN 520/1) 1958 Doliosaurus adamanteus Orlov: 105. in A, right lateral; B, dorsal; and C, palatal views. Scale bars equal 1961 Doliosauriscus adamanteus (Orlov); Kuhn: 79. 10 cm. Systematics of the Anteosauria 271

Figure 10. Titanophoneus adamanteus. The lower jaws (PIN 520/2) of the holotype (PIN 520/1) in left lateral view. Scale bar equals 10 cm.

1997 Titanophoneus adamanteus (Orlov); Ivakhnenko tine bosses and distinctive angular boss morphology, with et al.: 31. an elongate anterior process and smooth texture.

Holotype. PIN 520/1, a laterally crushed skull (Fig. 9) with Remarks. In addition to the type species Doliosauriscus lower jaws (Fig. 10) (numbered separately as PIN 520/2) yanshinovi (here considered a junior synonym of and several vertebrae. Titanophoneus potens, see above), Orlov (1958) described a second species of the genus, D. adamanteus, based on Age. Middle Permian (Lower Tatarian Substage, Urzhu- a partial skull and lower jaws (Figs 9, 10) from the banks mian Horizon). of the river Malyi Uran. Orlov distinguished this species from D. yanshinovi on the basis of its shorter facial region, Locus typicus. Malyi Uran locality, Krasnogvardeiskii absence of pits for the reception of the lower postcanines, = District, Orenburg Region, Russia (Ivakhnenko 2003). and possession of fewer lower ‘precanines’ ( incisors) and postcanines. The apparent lack of pits in the palate of PIN 520/1 can be attributed to the strong lateral compression Referred material. PIN 520/20, PIN 520/25 (Fig. 8E), of this specimen, and does not represent a valid distinction. PIN 520/28, isolated angulars. PIN 520/29, a left dentary Additionally, although the mandible of D. adamanteus only fragment. PIN 520/54, 56, 57 and 74, cranial frag- exhibits three visible incisors on the right side (as opposed ments. The following postcranial elements were referred to the usual anteosaurid four), the root of a fourth incisor to Doliosaurus adamanteus by Olson (1962): PIN 520/13, is present on the left side. PIN 520/1 (D. adamanteus) does a series of four caudal vertebrae; PIN 520/14, a series of have a relatively shorter facial region than PIN 157/3 (D. Downloaded by [University of Guelph] at 12:37 30 April 2012 nine caudal vertebrae; PIN 520/15, an axis articulated with yanshinovi), but the extent of this proportional difference is four cervical vertebrae; PIN 520/31 and PIN 520/32, clav- rendered uncertain by the opposite modes of deformation icles; PIN 520/34 and PIN 520/35, humeri; PIN 520/36, in these two specimens—lateral compression in the former, the distal end of a radius; PIN 520/38, PIN 520/39, PIN and dorsoventral compression in the latter. 520/40, PIN 520/41, and PIN 520/42, fragmentary femora; Despite the problems with Orlov’s (1958) diagnosis, D. PIN 520/35 and PIN 520/46, tibiae. All referred specimens adamanteus does appear to represent a distinct anteosaurid are from the type locality. species that differs from D. yanshinovi (= Titanophoneus potens) on the basis of its relatively larger palatine bosses Diagnosis. Titanophoneus adamanteus can be distin- and autapomorphic angular boss morphology. In both D. guished from all anteosaurs except T. potens and adamanteus and D. yanshinovi this boss is lozenge-shaped, Anteosaurus magniﬁcus by the presence of an angular boss, but whereas the boss of D. yanshinovi is extremely bulbous concave dorsal snout proﬁle, concave alveolar margin of the at its centre, with rugose texture and a very short anterior precanine region, and massive pachyostosis of the dorsal projection, the boss of D. adamanteus is narrow, with rela- surface of the skull. T. adamanteus can be distinguished tively smooth texture and a long, tapering anterior projec- from Anteosaurus by the lack of postfrontal horns and the tion greater in length than the rest of the boss. As noted lenticular shape of the angular boss. T. adamanteus can be by Ivakhnenko (2003), boss morphology in these two taxa distinguished from T. potens by its relatively larger pala- appears to be highly conservative. All isolated angular 272 C. F. Kammerer

Figure 11. Archaeosyodon praeventor. A, PIN 1758/293 in left lateral and C, dorsal views; B, The holotype (PIN 1758/3) in right lateral and D, palatal views. Scale bars equal 10 cm.

bosses (e.g. PIN 157/209) from the Isheevo locality are of Archaeosyodon praeventor Tchudinov, 1960 the D. yanshinovi morphotype, whereas all isolated angular (Figs 11–13) bosses (e.g. PIN 520/20, 25 and 28) from the Malyi Uran locality are of the D. adamanteus morphotype (Fig. 8B–E). Following the synonymy of Doliosauriscus yanshinovi Holotype. PIN 1758/3, a partial skull preserving the snout with Titanophoneus potens, Ivakhnenko (2003) included region (Fig. 11B, D). D. yanshinovi within Titanophoneus,asT. adamanteus. Whether this species should be included within the genus Age. Middle Permian (Lower Tatarian Substage, Urzhu- Titanophoneus is considered in the Discussion. mian Horizon). Downloaded by [University of Guelph] at 12:37 30 April 2012

Figure 12. Archaeosyodon praeventor. PIN 1758/297, a dentary of Archaeosyodon, in left lateral view. Scale bar equals 10 cm. Systematics of the Anteosauria 273

1758/328, a partial right dentary. All referred specimens are from the type locality.

Diagnosis. Archaeosyodon praeventor can be distinguished from all anteosaurs except Sinophoneus yumenensis by its bulbous snout. Archaeosyodon can be distinguished from all other anteosaurs by its extremely broad, short, strongly recurved canine and ‘scalloped’ postcanines with prominent lingual cingula and longitudinal striations.

Remarks. Tchudinov (1960) described Archaeosyodon praeventor as a new ‘brithopodid’ dinocephalian on the basis of a partial skull (Fig. 11B, D) from the Ezhovo locality, the Russian ‘Zone I’ site that also produced the type material of Biarmosuchus, the tapinocephalian Estemmeno- suchus, and the early anomodont Otsheria. Archaeosyo- don was distinguished from other ‘brithopodids’ on the basis of its heavily dentigerous (∼15 teeth on each boss) palatal bosses and transverse processes of the pterygoid and its short, deep choanae occupying an anterior position, which Tchudinov (1960) and Olson (1962) argued represent primitive character states. Tchudinov (1983) provided a more detailed description of Archaeosyodon based on numerous new specimens (see Referred material above), including lower jaws (Fig. 12). Ivakhnenko (1994) included Archaeosyodon in his new family Syodontidae, along with Syodon and Australosyodon, but later (1995, 2003) placed Archaeosyodon in Titanosuchidae on the basis of its rounded, strongly curved canine (Fig. 13A) and sharply angled adductor musculature attachment site on the skull Figure 13. Archaeosyodon praeventor. A, PIN 1758/95 in right roof. Despite being known from plentiful material, the rela- lateral; B, dorsal; and C, palatal views. Scale bars equal 10 cm. tionships of Archaeosyodon remain poorly understood, and it has not been included in any previous phylogenetic analyses of dinocephalians. Locus typicus. Ezhovo (Ocher) locality, Ocherskii Archaeosyodon can be recognized as an anteosaur rather District, Perm Region, Russia (Ivakhnenko 2003). than a titanosuchid based on the convex alveolar margin of the maxilla, upturned alveolar margin of the premax-

Downloaded by [University of Guelph] at 12:37 30 April 2012 illa, and the lack of such titanosuchid characteristics Referred material. Tchudinov (1983) referred the follow- as phylliform postcanine dentition, postcanine tooth row ing specimens to A. praeventor: PIN 1758/93, a fragmen- extending medial to canine, vomers expanded anteriorly, tary skull; PIN 1758/94, a fragmentary skull; PIN 1758/95, and occiput rotated anteroventrally. Archaeosyodon can be a largely complete skull missing the occipital region (Fig. distinguished from all other anteosaurs by the retention 13); PIN 1758/293, a laterally crushed but nearly complete of numerous features believed to be primitive for therap- skull missing part of the temporal arches (Fig. 11A, C); sids (Hopson & Barghusen 1986), including a tall, triangu- PIN 1758/294, the symphyseal region of a left dentary; lar maxilla and extensive palatal dentition. Archaeosyodon PIN 1758/295, a partial left dentary; PIN 1758/296, a right differs from all other anteosaurs except Sinophoneus in maxilla; PIN 1758/297, a nearly complete left dentary (Fig. its bulbous snout. Finally, Archaeosyodon exhibits several 12); PIN 1758/309, a series of palatal fragments including dental autapomorphies, such as the unusually broad, short, a well preserved pterygoid boss; PIN 1758/310, a fragmen- strongly recurved canine and ‘scalloped’ postcanines with tary skull; PIN 1758/311, an isolated parietal region of a prominent lingual cingula and longitudinal striations. skull roof; PIN 1758/312, a right maxilla; PIN 1758/313, a left maxilla; PIN 1758/314, a nearly complete right dentary; Notosyodon gusevi Tchudinov, 1968 PIN 1758/315, a left canine; PIN 1758/316, a fragmentary (Fig. 14) left maxilla with canine; PIN 1758/317, a fragmentary left maxilla with canine; PIN 1758/318, a left maxilla; and PIN 1997 Syodon gusevi (Tchudinov); Ivakhnenko et al.: 30. 274 C. F. Kammerer

to the pineal boss and a contact between the frontal and the attachment site of the jaw adductor musculature. Noto- syodon can be distinguished from Syodon on the basis of its shallow, nearly horizontal zygomatic arch and rugose, thickened posterior edges to the orbit and temporal fenestra. Notosyodon can be distinguished from both Syodon and Australosyodon by the lesser extent of contact between the frontal and jaw adductor attachment site.

Remarks. Tchudinov (1968) described Notosyodon gusevi on the basis of a partial skull (Fig. 14) from a sandstone lens in the Aktyubinsk Region of the USSR (present-day Kazakhstan). The Notosyodon type material was found in the Lower Aktyubinsk regional subsuite, which has been correlated with the Russian Isheevo fauna based on bivalve fossils (Tchudinov 1968). Tchudinov (1968) considered Notosyodon to represent a ‘brithopodid’ similar to the Isheevo forms Syodon and Titanophoneus, but distinguished from these taxa by its thickened orbital rim, wide interorbital region, relatively large parietal boss and occipital condyle, narrow and strongly slanted occipital region, and well ossified basisphenoid. Tchudinov (1968) also considered Notosyodon to differ from all other ‘brithopodids’ in having fewer marginal teeth, based on the referred partial dentary PIN 2608/1. Ivakhnenko (2003) considered this taxon to represent a species of Syodon (S. gusevi). Noting that comparison between S. biarmicum and N. gusevi was rendered difficult by the lack of overlapping material, he nevertheless suggested that N. gusevi might represent a junior synonym of S. biarmicum based on similar postcanine morphology Figure 14. The holotype of Notosyodon gusevi (PIN 2505/1), an (Ivakhnenko 1995, 2003). Ivakhnenko (2003) also argued orbito-temporal fragment in A, left lateral (anterior is left) and B, that the mandibular element referred to Notosyodon (PIN dorsal (anterior is right) views. Scale bars equal 5 cm. 2608/1) should instead be considered Titanophoneus sp. based on the massive, vertical symphysis, a conclusion that Holotype. PIN 2505/1, a partial skull preserving the is agreed with here. orbital, occipital, and basicranial regions (Fig. 14). Notosyodon gusevi can be distinguished from Syodon biarmicum (represented for comparative purposes by PIN Downloaded by [University of Guelph] at 12:37 30 April 2012 Age. Middle Permian (Urzhumian Horizon, Lower Tatar- 157/2, the holotype of S. efremovi, as this is the only spec- ian Substage). imen of Syodon preserving the temporal region) on the basis of its shallow, nearly horizontal zygomatic arch (the Locus typicus. Bank of the Zhaksy-Karagala River, zygomatic arch is relatively deep and noticeably curved Aktyubinsk Region, Kazakhstan (Ivakhnenko 2003). ventrally in Syodon) and rugose, thickened posterior edges to the orbit and temporal fenestra (only the dorsal edge Referred material. Tchudinov (1968) referred the follow- of the orbit is ornamented in Syodon). Notosyodon can ing specimens to N. gusevi: PIN 2505/2, a right lower be distinguished from both Syodon and Australosyodon by incisor, and PIN 2505/3, a left upper postcanine, both from the extent of contact between the frontal and jaw adductor the type locality and found associated with the holotype; attachment site. In Syodon and Australosyodon, the frontal PIN 2608/1, the anterior half of a left dentary from the forms the majority of the anterior border of the adductor right bank of the Donguz River, near Dolmatovskii Farm, area, excepting only the orbital rim, whereas in Notosyo- Sol-Iletsk District, Orenburg Region, Russia. don, the frontal forms only the medial anterior border with the adductor area. As such, Notosyodon gusevi is herein Diagnosis. Notosyodon gusevi can be distinguished from considered a valid taxon of anteosaurid. Whether it should all anteosaurs except Syodon biarmicum and Australosyo- be classified as a species of Syodon, as per Ivakhnenko don nyaphuli on the basis of having a frontal contribution (2003), is considered in the Discussion. Systematics of the Anteosauria 275

Australosyodon nyaphuli Rubidge, 1994 pineal boss and a contact between the frontal and the attach- (Figs 15, 16) ment site of the jaw adductor musculature. Australosyodon can be distinguished from Notosyodon by a greater extent Holotype. NMQR 3152, a crushed but almost entirely of contact between the frontal and jaw adductor attachment complete skull (Fig. 15) with lower jaws (Fig. 16). site and narrower zygomatic arch. Australosyodon can be distinguished from Syodon by its straight canine, enlarged Age. Middle Permian (Eodicynodon Assemblage Zone, posterolateral teeth on the palatine boss, and conical post- Abrahamskraal Formation, Beaufort Group). canines of varying size and orientation.

Locus typicus. Tuinkraal, Prince Albert Road, Prince Remarks. Rubidge (1994) described Australosyodon Albert District, Western Cape Province, South Africa nyaphuli on the basis of a crushed skull with lower jaws (Rubidge 1994). (Figs 15, 16) from the Eodicynodon Assemblage Zone, the lowest biozone in the South African Beaufort Group. Diagnosis. Australosyodon nyaphuli can be distinguished Australosyodon represents the second dinocephalian to from all anteosaurs except Syodon biarmicum and Noto- be described from the Eodicynodon Assemblage Zone syodon gusevi on the basis of a frontal contribution to the (the ﬁrst being the basal tapinocephalid Tapinocaninus Downloaded by [University of Guelph] at 12:37 30 April 2012

Figure 15. Australosyodon nyaphuli. The holotype (NMQR 3152) in A, left lateral; B, dorsal; and C, palatal views. Scale bars equal 10 cm. 276 C. F. Kammerer

Figure 16. Australosyodon nyaphuli. The mandible of the holotype (NMQR 3152) in left lateral view. Scale bar equals 10 cm.

pamelae Rubidge, 1991) and the first new anteosaurian Age. Middle Permian (Lower Kazanian Substage, Belebei taxon from South Africa described in 40 years. Rubidge Formation). (1994) considered Australosyodon to be closely related to Syodon based on skull roofing characters, but separated Locus typicus. Golyusherma locality, Kama River, it from the Russian form on the basis of less ventrally- Udmurtia, Russia (Ivakhnenko 2003). protruding palatine bosses, presence of at least seven teeth on the palatal ramus of the pterygoid, canine not rounded Referred material. PIN 4310/2, an isolated left maxilla in cross section, less robust maxillary teeth, frontal midline (Fig. 17B, C) from the Berezovyye Polyanki locality, ridge with lateral expansions to form an interorbital boss, Vyatka River, Vyatka-Polyanskiy district, Kirov region, and slightly greater contact of the frontal with the dorsal Russia. Referred to Microsyodon cf. M. orlovi by border of the orbits in Australosyodon. Ivakhnenko (2003) Ivakhnenko (1995). considered Australosyodon to belong to Syodontidae along with Syodon. Diagnosis. Microsyodon orlovi can be distinguished from Australosyodon differs from Notosyodon but is similar all anteosaurs except Archaeosyodon and Syodon by its to Syodon in that the frontal forms the majority of the strongly recurved, ‘hooked’ canine. Microsyodon can be anterior border of the area of attachment of the adduc- distinguished from all other anteosaurs by the presence of tor mandibulae. In addition to the characters given by a maxillary precanine. Rubidge (1994), Australosyodon can be distinguished from Syodon by its enlarged posterolateral teeth on the palatine boss, slightly recurved (rather than ‘hooked’) canines, Remarks. Ivakhnenko (1995) described Microsyodon narrower zygoma, greater curvature of the tooth row on orlovi on the basis of a very small (59 mm long) the palatal boss of the pterygoid, and autapomorphic post- right maxilla from the Golyusherma locality (Fig. 17A). Ivakhnenko (1995, 2003) considered Microsyodon to Downloaded by [University of Guelph] at 12:37 30 April 2012 canine morphology. Although the postcanines all follow the basic bulbous anteosaur pattern, they differ greatly represent a titanosuchid, and distinguished it from other in size, relative width, and orientation. The anteriormost titanosuchids (Titanosuchus, Jonkeria, and, in his classifi- upper postcanines of Australosyodon immediately follow cation, Archaeosyodon) on the basis of small size, a canine the canine and are also directed anteroventrally, followed with a narrow base, and the presence of a precanine. It by posteroventrally directed postcanines of varying size. In was further distinguished from Titanosuchus and Jonkeria the dentary, most of the postcanines are tall, conical teeth, by having fewer postcanines and from Archaeosyodon by but the posteriormost postcanines are short and anteropos- postcanine morphology. teriorly elongate. The posteriormost lower postcanines of Microsyodon is one of a number of problematic Syodon are also anteroposteriorly longer than more ante- early Russian therapsid taxa based on fragmentary, rior teeth in the series, but are much more robust than in probably juvenile material, others of which include Australosyodon. the ‘nikkasaurids’, Niaftasuchus, Biarmosuchoides, and Microurania (Ivakhnenko 1990, 1996, 2000; Tverdokhle- Microsyodon orlovi Ivachnenko, 1995 bova & Ivachnenko 1994). The current higher-level taxo- (Fig. 17) nomic assignments of these therapsids are extremely dubious. Indeed, ‘Microurania’ appears to include material Holotype. PIN 4276/13, an isolated right maxilla (Fig. from two different major therapsid groups, with the type 17A). species M. minima Ivachnenko, 1995, representing a Systematics of the Anteosauria 277

juvenile dinocephalian and the referred species M. mikia Ivachnenko, 2003, representing a juvenile venyukovioid anomodont (Kammerer pers. obs.) As for Microsyodon, it can be recognized as an anteosaur rather than a titanosuchid on the basis of the convex ventral margin of the maxilla. Microsyodon differs from all anteosaurs other than Archaeosyodon, Australosyodon and Syodon in the high number of postcanines (10–11), and from all anteosaurs other than Stenocybus in the recurved, laterally compressed postcanine morphology (though see below). Uniquely among anteosaurs, Microsyodon possesses a precanine tooth immediately anterior to the canine. The shape and angulation of this tooth suggest that it does not represent a replacement canine. The precanine of Microsyo- don is relatively small and, based on the referred specimen, directed anteroventrally at an angle of roughly 25◦ from the anterior edge of the canine. Ivakhnenko (1995) considered the second specimen (PIN 4310/2) (Fig. 17B, C) to be referable only to Microsy- odon cf. M. orlovi, as “the absence of crowns on the post-tusk teeth imposes limitations on the precision of its identiﬁcation” (Ivakhnenko 1995, p. 126), and later (Ivakhnenko 2003) referred to this specimen as Microsyo- don sp. However, as this specimen displays the same canine morphology and tooth count as the holotype in addition to the diagnostic precanine, it is herein considered to represent an individual of M. orlovi. It is possible that Microsyodon represents the juvenile morphology of another Russian anteosaur, such as Archaeosyodon. Microsyodon’s relatively short, ‘hooked’ canine and high postcanine count are strongly reminis- cent of the condition in Archaeosyodon. Although Microsy- odon’s recurved, laterally compressed postcanines are dissimilar to the bulbous postcanines with lingual cingula found in Archaeosyodon, and Microsyodon’s canine is not massively expanded at the base as in Archaeosyo- don, these differences are probably ontogenetic. Laterally compressed canines and postcanines are observed in other Downloaded by [University of Guelph] at 12:37 30 April 2012 juvenile anteosaurs, such as the holotypes of Stenocybus and Micranteosaurus. That said, given the discrete precanine character and the fact that the Microsyodon material comes from a stratigraphically earlier subassemblage than Archaeosyodon (Ivakhnenko 1995), Microsyodon orlovi is tentatively considered to represent a valid anteosaurian taxon. Sinophoneus yumenensis Cheng & Ji, 1996 Figure 17. Microsyodon orlovi. A, The holotype, PIN 4276/13, (Fig. 18) an isolated right maxilla in right lateral view (from Ivakhnenko et al. 1997, p. 185); B, PIN 4310/2, a referred left maxilla in left Holotype. GMV 1601, a nearly complete skull missing the lateral and C, right medial view. The precanine in the holotype temporal arches. is not complete, and the reconstruction of a posteroventral angle for this tooth rather than the anteroventral angle preserved in the referred specimen is speculative. Scale bars equal 1 cm. Age. Middle Permian (Xidagou Formation). 278 C. F. Kammerer

an oval-shaped orbit. Personal examination of GMV 1601 suggests that the oval shape of the orbit is deformational in Sinophoneus. Sinophoneus yumenensis is herein considered to represent a valid taxon diagnosed primarily on the basis of a unique mixture of characters observed in other anteosaurids. The bulbous snout is similar to that of Archaeosyodon, whereas the massive, palmate transverse processes of the pterygoid and palatal bosses bearing single tooth rows are similar to those in Titanophoneus and Anteosaurus. Autapomorphic for Sinophoneus is the well- developed median ridge on the skull. A narrow median interorbital ridge is developed to some extent in Syodon, Australosyodon, and Titanophoneus, but is largely restricted to the frontals. In Sinophoneus the interorbital portion of this ridge is similarly weakly developed, but atop the snout is robust and prominent.

Junior synonyms Syodon efremovi (Orlov, 1940) (Figs 19, 20) 1940 Cliorhizodon efremovi Orlov: 226. 1958 Syodon efremovi (Orlov); Orlov: 103.

Holotype. PIN 157/2, a complete, largely undistorted skull (Fig. 19) with lower jaws (Fig. 20).

Age. Middle Permian (Urzhumian Horizon, Lower Tatar- ian Substage).

Figure 18. Sinophoneus yumenensis. Cast of the holotype (GMV Locus typicus. Kamenny Ovrag (‘Stone Ravine’), near the 1601) in A, right lateral; B, dorsal; and C, palatal views. Scale village of Isheevo, Apastovskii District, Tatarstan, Russia bars equal 10 cm. (Orlov 1958).

Locus typicus. Dashankou, Yumen, Gansu Province, Referred material. PIN 157/184, a partial basicranium. China (Li 2001). PIN 157/251, an incisor. PIN 157/252, an incisor. PIN Downloaded by [University of Guelph] at 12:37 30 April 2012 157/253, an incisor. PIN 157/254, an incisor. PIN 157/256, Diagnosis. Sinophoneus yumenensis can be distinguished an incisor. PIN 157/540, a palatine. PIN 157/604, a post- from all anteosaurs except for Archaeosyodon praeven- frontal. PIN 157/637, a palatine. PIN 157/638, a pala- tor by its bulbous snout. Sinophoneus can be distin- tine. PIN 157/639, a palatine.PIN 157/641, a palatine. PIN guished from all other anteosaurs by the presence of a 157/642, a palatine. PIN 157/643, a palatine. PIN 157/644, well-developed midline ridge extending from the snout to a palatine. PIN 157/645, a palatine. PIN 157/646, a pala- between the orbits. tine. PIN 157/647, a palatine. PIN 157/649, a palatine. PIN 157/650, a palatine. PIN 157/651, a lacrimal. PIN 157/654, Remarks. Cheng & Ji (1996) described Sinophoneus a lacrimal. PIN 157/655, a postorbital. PIN 157/656, a yumenensis as the ﬁrst Chinese anteosaurid on the basis of a palatine. PIN 157/657, a partial vomer. PIN 157/659, a somewhat crushed but largely complete cranium (Fig. 18). frontal. PIN 157/660, a lacrimal. PIN 157/661, a frontal. Cheng & Ji (1996) considered Sinophoneus to be most simi- PIN 157/662, a frontal. PIN 157/663, a postfrontal. PIN lar to Titanophoneus, but distinguished it from the Russian 157/665, a postfrontal. PIN 157/673, a dentary fragment. taxon on the basis of its relatively smaller naris, presence PIN 157/674, a partial maxilla. PIN 157/675, a maxilla. of a median ridge on the snout, and more greatly expanded PIN 157/676, a mandibular symphysis. PIN 157/677, a set distal portion of the transverse ﬂange of the pterygoid. of lower jaws broken off anterior to the articular region. Additionally, Sinophoneus was stated to share with Syodon PIN 157/683, a partial pterygoid. PIN 157/684, a pterygoid. Systematics of the Anteosauria 279

characters to be invalid. The postcanine tooth row of S. efremovi is not separated from the canine by a diastema, features small, sharp postcanines similar to those of S. biarmicum anteriorly, and has a similar postcanine count to S. biarmicum. However, Orlov (1958) retained both species as valid, arguing that the incisors of S. efremovi have well-developed heels while those of S. biarmicum do not. Ivakhnenko (2003, p. S380) established that, contrary to Orlov’s (1958) interpretation, the incisors of S. efremovi “virtually lack heels”, and the single known incisor of S. biarmicum (in BMNH R4077, the holotype of Cliorhizodon orenburgensis) is essentially identical (Ivakhnenko 1995). Yet Ivakhnenko too considered S. biarmicum and S. efremovi to represent separate taxa, claiming that S. biarmicum has strongly hooked canines and narrow postcanines with short necks, whereas S. efremovi has weakly curved canines and broad postcanines with no necks. Personal examination of PIN 157/2 reveals that all characters previously used to separate Syodon biarmicum and S. efremovi are problematic. Orlov’s (1958) refutatations of Efremov’s (1954) characters and Ivakhnenko’s (2003) refutation of Orlov’s (1958) character are all correct. Addi- tionally, contrary to Ivakhnenko (2003), the canines of S. efremovi are very strongly hooked and are identical in morphology to those of S. biarmicum (Figs 2, 19A) and the supposed ‘necks’ of S. biarmicum postcanines are a preservational artefact in BMNH R4077 (Fig. 2B). As the type skull of S. efremovi exhibits no features that can distinguish it from S. biarmicum and shares the diagnostic canine morphology of that species, S. efremovi is herein considered a junior synonym of S. biarmicum, in agreement with the conclusions of Tchudinov (1983).

Figure 19. Syodon efremovi. The holotype (PIN 157/2) in A, right Paranteosaurus primus Boonstra, 1954c lateral; B, dorsal; and C, palatal views. Scale bars equal 5 cm. (Figs 21, 22)

PIN 157/1062, a partial vomer. All referred specimens are Holotype. SAM-PK-11485, a weathered snout (Fig. 21), from the type locality. dorsal skull roof fragment (Fig. 22), proximal end of a left Downloaded by [University of Guelph] at 12:37 30 April 2012 femur, and a vertebra. Remarks. Efremov (1940) gave a preliminary description of PIN 157/2 (Figs 19, 20), which he referred to Cliorhi- Age. Middle Permian (Tapinocephalus Assemblage Zone, zodon sp., but also noted that the specimen could represent Abrahamskraal Formation, Beaufort Group). a juvenile Titanophoneus potens. Shortly thereafter, Orlov (1940) brieﬂy described this specimen as a new species of Cliorhizodon, C. efremovi. Efremov (1954) argued that the Locus typicus. Mynhardtskraal, Beaufort West, Western Isheevo Syodon skull (PIN 157/2) could be distinguished Cape Province, South Africa (Kitching 1977). from S. biarmicum (represented by the Cliorhizodon orenburgensis holotype) by three characters: a diastema sepa- Remarks. Boonstra (1954c) described Paranteosaurus rating the canine and postcanines (supposedly absent in S. primus on the basis of a fragmentary skull in two pieces biarmicum and present in S. efremovi), postcanine morphol- and two postcranial elements. The snout (Fig. 21) he recog- ogy (smaller, sharper postcanines in S. biarmicum than S. nized as being identical to that of Anteosaurus, and he efremovi), and postcanine number (greater in S. biarmicum erected the new genus solely based on the lack of postfrontal than in S. efremovi). Orlov (1958), in his thorough descrip- bosses on the skull roof fragment (Fig. 22). Boonstra (1955) tion of the skull of Syodon efremovi, noted that further remarked that the femoral fragment of SAM-PK-11485 is preparation of the skull showed these supposed differential indistinguishable from that of Anteosaurus. 280 C. F. Kammerer Downloaded by [University of Guelph] at 12:37 30 April 2012

Figure 20. Syodon efremovi. The mandible of the holotype (PIN 157/2) in A, right lateral; B, medial; and C, dorsal views. Scale bars equal 5 cm.

Paranteosaurus primus was the sole species of South cus (see, however, remarks on Pseudanteosaurus minor in African anteosaurid not synonymized with Anteosaurus the entry on Anteosaurus). As such, the difference in this magniﬁcus by Boonstra (1969), on the grounds that it character between Anteosaurus and Paranteosaurus cannot lacks postorbital bosses. Boonstra (1954c, 1969) argued be attributed to ontogenetic changes. SAM-PK-11694 (the that these bosses can be observed in even the smallest spec- holotype of A. cruentus), which is nearly identical in size to imens of Anteosaurus (e.g. the holotype of A. minuscu- the holotype of P. primus, has notably better-developed lus), which he (1969) regarded as juveniles of A. magniﬁ- postorbital bosses. However, as discussed in the entry Systematics of the Anteosauria 281

Figure 21. Paranteosaurus primus. The holotypic (SAM-PK- 11485) snout region in A, left lateral; B, dorsal; and C, palatal views. Scale bars equal 5 cm. Figure 22. Paranteosaurus primus. The holotypic (SAM-PK- 11485) skull roof fragment in dorsal view, anterior at right. Sutures on Anteosaurus, extensive variation in boss development highlighted on the left side of the skull; note the weathered texture exists among specimens, even those of comparable size, of the postfrontals. Scale bar equals 5 cm. considered to be A. magniﬁcus by Boonstra (1969) and Downloaded by [University of Guelph] at 12:37 30 April 2012 all subsequent authors. The specimen BP/1/1369 (Fig. 4F) Age. Middle Permian (Xidagou Formation). exhibits a similar level of boss development as P. primus. Additionally, as the skull roof fragment of SAM-PK-11485 Locus typicus. Dashankou, Yumen, Gansu Province, is badly weathered, the weak development of the postfrontal China (Li 2001). bosses may be, at least in part, artefactual. Regardless of whether sexual dimorphism or regular individual variation Referred material. The paratype, IVPP V12008, a frag- underlies the differences in boss development observed mentary right maxilla, premaxilla, and dentary with intact in Anteosaurus skulls, simple degree of pachyostosis of dentition from the type locality. a single bone known to exhibit extreme variability in that very feature is an inadequate basis on which to recognize a Remarks. Cheng & Li (1997) described Stenocybus distinct anteosaurian taxon. Paranteosaurus primus should acidentatus on the basis of a laterally compressed complete be added to the synonymy of Anteosaurus magniﬁcus. skull (the holotype, IGCAGS V 361) (Fig. 23) and a frag- Stenocybus acidentatus Cheng & Li, 1997 ment of the right gnathic region of another skull preserving (Fig. 23) part of the maxilla, premaxilla, and dentary (the paratype, IVPP V12008). Stenocybus was described as the sole Holotype. IGCAGS V 361, a complete skull with lower member of a new family, Stenocybusidae Cheng and Li, jaws (Fig. 23). 1997 (correctly emended to Stenocybidae by Ivakhnenko 282 C. F. Kammerer

of crushing. The intranarial position of the septomaxilla is at least partially attributable to displacement as a result of lateral compression of the skull. On the right side of the skull in particular, the premaxilla is displaced anteriorly so that it no longer contacts the maxilla ventrally, and the septomaxilla is displaced along with it. There is a long posterior extension of the septomaxilla between the nasal and maxilla, typical for therapsids but contrary to Cheng & Li’s(1997) reconstruction. Cheng & Li’s(1997) reconstruction of the Stenocybus skull in left lateral view also depicts the postorbital bar of this taxon as an essentially straight structure. However, the left postorbital bar is broken—on the right side of the skull, the postorbital bar is undam- aged and exhibits a ‘scoop’-like morphology, with strong anteroventral curvature. Finally, Cheng & Li (1997) recon- struct Stenocybus with elongate, ‘pelycosaur’-like anterior processes of the prefrontal and lacrimal. The preorbital region of IGCAGS V 361 bears numerous cracks, and the supposed ‘anterior processes’ of the preorbital bones represent breaks in the maxilla rather than the actual sutural boundaries of the prefrontal and lacrimal. The convex ventral margin of the maxilla, upturned alveolar margin of the premaxilla, and ‘scoop’-shaped postorbital bar all indicate anteosaurian affinities for Stenocybus. Cheng & Li (1997, p. 43) listed five characters supporting a position basal to all other anteosaurs for Stenocybus. Two of these characters (“small and light-structured skull” and “large-sized orbit and small triangular-shaped temporal fenestra”) are commonly observed in juvenile therapsids (Ivakhnenko 1999; Sidor & Rubidge 2006) and can be attributed to the immature Figure 23. Stenocybus acidentatus. The holotype (IGCAGS V state of the Stenocybus material. Another character, 361) in A, right lateral; B, dorsal; and C, palatal views. Scale bars equal 5 cm. “triangular-shaped maxilla with its top above the canine and anteriorly extended lacrimal”, is partially attributable to immaturity (greatest dorsoventral depth of maxilla (1999), as this taxon was named before 1999 and thus is above canine, rather than posterior to it) and partially not subject to Article 29.4 of the Fourth Edition of the to breakage (the supposed anterior extension of the ICZN) (International Commission on Zoological Nomen- lacrimal). A fourth character, “lower jaw articulation in Downloaded by [University of Guelph] at 12:37 30 April 2012 clature 1999). Cheng & Li (1997) distinguished Steno- Stenocybus has not been anteriorly moved as in other cybidae from Anteosauridae on the basis of the lightly anteosaurids”, is also problematic. Among anteosaurs, structured skull, large orbits, and small temporal fenes- only in the giant forms Titanophoneus and Anteosaurus is trae in the former. Additionally, they argued that the the suspensorium markedly rotated anteroventrally, similar triangular maxilla, restriction of the septomaxilla within to the condition in tapinocephalians (Hopson & Barghusen the naris, and anteriorly stretched lacrimal of Stenocybus 1986). As such, the posterior location of the suspensorium are unique in therapsids and more closely resemble the in Stenocybus is only evidence that it falls outside a condition in ‘pelycosaur’-grade synapsids. In their clado- Titanophoneus + Anteosaurus grouping, not anteosaurs as gram, Cheng & Li (1997) show Stenocybidae to repre- a whole. The final character, “depression receiving lower sent the most basal dinocephalian group (i.e. outside of the jaw adductor appears on dorsal surface of postfrontal Anteosauria–Tapinocephalia split), but this position is not in Stenocybus, rather than on frontal as in Australosyo- discussed in the text, where it is only argued that Steno- don”, presupposes a basal position for Australosyodon cybus is basal to other anteosaurs. Presumably, the figured within anteosaurids. Although Rubidge (1994) depicted position for Stenocybus was based on the ‘pelycosaur’-like Australosyodon and Syodon as the most basal anteosaurids features of the skull. in his description of the former taxon, his cladogram does Examination of the type skull reveals that some of the not include several important taxa, such as Archaeosy- features used to diagnose Stenocybus are artefactual results odon and Notosyodon. Also, given that the condition in Systematics of the Anteosauria 283

Stenocybus is observed both in more basal therapsids Sinophoneus. This information strongly supports the iden- (e.g. Biarmosuchus) and ‘advanced’ anteosaurids tification of ‘Stenocybus’ as a juvenile Sinophoneus, and (Titanophoneus and Anteosaurus), a jaw adductor attach- Stenocybus acidentatus is here considered a junior synonym ment site extending onto the frontal is most parsimoniously of Sinophoneus yumenensis. interpreted as a derived feature of Australosyodon and Syodon rather than the ancestral condition in anteosaurids Indeterminate Anteosauria (see also Phylogenetic analysis in this paper). In summary, Titanophoneus rugosus (Trautschold, 1884) none of the characters listed by Cheng & Li (1997) strongly (Fig. 8A) support a basal position for Stenocybus, either within dinocephalians as a whole or anteosaurs in particular. Addi- 1884 Oudenodon rugosus Trautschold: 35. tionally, the palatal dentition of Stenocybus is in conflict 1997 Titanophoneus rugosus (Trautschold); Ivakhnenko with a basal position for this taxon. Basal therapsids et al.: 31. (e.g. Biarmosuchus), like their sphenacodontian ancestors, possess numerous palatal teeth in broad patches extending Holotype. PIN 1955/1, an isolated angular boss (Fig. 8A) across the palatine and pterygoid bones. Although more and other jaw fragments. restricted in their extent than in Biarmosuchus, the palatal teeth of Archaeosyodon (and basal tapinocephalians such Age. Middle Permian (Urzhumian Horizon, Lower Tatar- as Estemmenosuchus) are nevertheless numerous and ian Substage). present in multiple rows on the palatines and pterygoids. However, in Stenocybus, the palatal teeth are extremely Locus typicus. Butlerovka locality, Alekseevskii District, restricted in location and contained in single tooth rows, as Tatarstan, Russia (Ivakhnenko 2003). in anteosaurids such as Anteosaurus and Titanophoneus. The dentary morphology of Stenocybus is also more similar Remarks. Trautschold (1884), in his study of Permian to Anteosaurus and Titanophoneus than either basal therap- tetrapods in the collections of the University of Kazan, sids or early anteosaurs such as Archaeosyodon. The incisor described a therapsid skull fragment (Fig. 8A) that he alveolar margin of the dentary in Stenocybus is canted interpreted as the isolated snout boss of a dicynodont. downwards and bears a distinct mentum as in Anteosaurus Trautschold considered this specimen (currently numbered and Titanophoneus, but unlike earlier taxa in which the PIN 1955/1) to represent a new species of the South African lower incisor alveolar margin is subhorizontal and the genus Oudenodon, O. rugosus. Trautschold considered O. anterior ventral margin of the dentary is gently sloping. rugosus to be most similar to O. prognathus (currently Ivakhnenko (2003) suggested that Stenocybus could considered a junior synonym of the type species O. bainii; represent the juvenile of Sinophoneus. This idea bears see Keyser 1975; Botha & Angielczyk 2007), but could be further consideration. Stenocybus differs from Sinophoneus distinguished from previous species of Oudenodon by its in its smaller size, relatively larger orbits, relatively smaller furrowed surface and orientation. He argued that, unlike in temporal fenestrae, relatively taller, narrower skull, later- O. bainii and O. prognathus in which the nasal boss extends ally compressed canines and postcanines, relatively longer diagonally down to the premaxilla in lateral view, the boss of precanine region of the snout, and narrower transverse O. rugosus would have been horizontal and extended back processes of the pterygoid. All of these characters are towards the orbit. In addition to the type boss, he consid- Downloaded by [University of Guelph] at 12:37 30 April 2012 general features of juvenile therapsids that are known to ered the symphyseal region of a left dentary and another change over the course of ontogeny (Ivakhnenko 1999; jaw fragment to be referable to O. rugosus. Sidor & Rubidge 2006). As such, there are no charac- Seeley (1894) was the first to propose a non-dicynodont ters in Stenocybus that immediately rule out identity as identification for Oudenodon rugosus, suggesting that it a juvenile Sinophoneus. Furthermore, the type skull of might represent part of the skull of Deuterosaurus.Efre- Stenocybus exhibits a combination of characters other- mov (1954) recognized that PIN 1955/1 represents the wise known only in Sinophoneus. The bulbous rostrum of angular boss of an anteosaurid (‘brithopodid’, in Efre- Stenocybus is otherwise observed only in Sinophoneus and mov’s terminology), and assigned it to Titanophoneus sp. Archaeosyodon among anteosaurs (Syodon and Australosy- Ivakhnenko et al. (1997) resurrected the species in the odon have relatively straight dorsal snout profiles, whereas combination Titanophoneus rugosus without comment, but Titanophoneus and Anteosaurus have concave snouts). later, Ivakhnenko (2003) argued that, as the morphology Stenocybus differs from Archaeosyodon in having fewer of the angular boss appears to be highly conservative postcanines (eight, the same number as Sinophoneus,as within anteosaurid species (see remarks on Titanophoneus opposed to the 10–11 of Archaeosyodon) and lacking an adamanteus above) and as PIN 1955/1 does not correspond extensive palatal dentition. Additionally, despite its lack of to either of the known Russian anteosaurid angular morpho- pachyostosis, the type skull of Stenocybus already exhibits types, O. rugosus should be recognized as a valid species the dorsal median ridge on the snout that is diagnostic for of Titanophoneus. 284 C. F. Kammerer

PIN 1955/1 differs markedly in shape from the lentic- Locus typicus. Sandvlakte, Prince Albert, Western Cape ular bosses (Fig. 8B–E) of Titanophoneus potens and T. Province, South Africa (Kitching 1977). adamanteus, but is very similar to that of Anteosaurus magnificus.InTitanophoneus, the angular boss has a Remarks. Broom (1905) described Archaeosuchus cairn- prominent central swelling that tapers anteroventrally and crossi on the basis of an isolated maxilla (Fig. 24) discov- posterodorsally, whereas in PIN 1955/1 and Anteosaurus ered by J. L. Cairncross in a clay pellet conglomerate the boss is roughly the same thickness throughout its length, near Prince Albert. Archaeosuchus was the first terres- with blunt anterior and posterior edges. As such, PIN 1955/1 trial tetrapod taxon described from purported Ecca Group is tentatively considered the first representative of the genus deposits, which underlie the better-known Beaufort Group Anteosaurus from Russia. It is possible that this material (SACS 1980). Broom noted the similarity of the canine of does represent a distinct species, in which case it would Archaeosuchus to that of Titanosuchus, but separated the warrant the new combination Anteosaurus rugosus.The two genera on the basis of their very dissimilar ‘molars’ (= dermal sculpturing of the boss, with prominent furrows, postcanines), and ultimately referred Archaeosuchus to the is different from that observed in the few specimens of A. Therocephalia. Williston (1925) assigned Archaeosuchus to magnificus with a well-preserved lower jaw, such as SAM- Tapinocephalidae without comment. Broom (1932, p. 19) PK-11296 and BP/1/1369. However, as the bone surface of placed Archaeosuchus in the “carnivorous Dinocephalia” most Anteosaurus angular bosses is very poorly preserved, (‘Titanosuchia’) and commented on its similarity to the it is currently impossible to gauge the variation in dermal Russian genus Rhopalodon. Boonstra (1953) synonymized sculpturing between A. magnificus individuals. Given this Archaeosuchus with Titanosuchus and listed T. cairncrossi uncertainty, Titanophoneus rugosus should provisionally be as a questionable species. Later, Boonstra (1969) retained considered a nomen dubium (Anteosaurus sp.) The discov- Archaeosuchus in Titanosuchidae, but argued that, as the ery of more complete Russian material with the ‘rugosus’ holotype exhibits no diagnostic features, the taxon should boss morphology is necessary to allow clarification of this be considered a nomen dubium. taxon’s relationship to A. magnificus. SAM-PK-916 preserves the right canine and five postca- Archaeosuchus cairncrossi Broom, 1905 nines. The canine is broken at the tip and slightly laterally (Fig. 24) compressed with an unserrated posterior sectorial edge. The anterior three postcanines are weathered and frag- 1953 Titanosuchus cairncrossi (Broom); Boonstra: 28. mentary, but the posterior two are well preserved with the enamel intact. The bulbous, smoothly textured, relatively widely spaced postcanines of Archaeosuchus indicate Holotype. SAM-PK-916, a partial right maxilla (Fig. 24). that it represents an anteosaurid rather than a titanosuchid. Titanosuchid postcanines are labiolingually compressed Age. Middle Permian (Tapinocephalus Assemblage Zone, rather than bulbous, have denticulated edges and a grooved Abrahamskraal Formation, Beaufort Group). surface, and are closely packed in the maxilla. The Downloaded by [University of Guelph] at 12:37 30 April 2012

Figure 24. The holotype of Archaeosuchus cairncrossi (SAM-PK-916), a partial right maxilla. In this image, the surrounding matrix has been lightened to highlight the fossil. Numbering of the posterior three postcanines is tentative, based on the condition in Anteosaurus and Titanophoneus. Note that PC7? ﬂares outwards, as in Anteosaurus and Titanophoneus. Anterior is left. Scale bar equals 5 cm. Systematics of the Anteosauria 285

Holotype. SAM-PK-915, a left humerus (Fig. 25), two partial femora, distal end of a tibia, ﬁbula, nine vertebrae, rib fragments, a possible radius, an incisor, and skull fragments.

Age. Middle Permian (Tapinocephalus Assemblage Zone, Abrahamskraal Formation, Beaufort Group).

Locus typicus. Sandvlakte, Prince Albert, Western Cape Province, South Africa (Kitching 1977).

Referred material. AMNH 5625, an isolated tooth from near Prince Albert referred by Broom (1912). SAM-PK- 11597, a partial right shoulder girdle (the distal tip of the scapula, coracoid, and procoracoid), humerus, and ulna from Dikbome, Laingsburg referred by Boonstra (1955).

Remarks. Broom (1909) described Eccasaurus priscus on the basis of a large (344 mm long) humerus (Fig. 25) found near Prince Albert. As the generic name indicates, Broom believed Eccasaurus to be from the Ecca Group rather than the Beaufort Group, like the previously described Archaeosuchus. Broom argued that Eccasaurus was not a therapsid but an animal similar to the parareptile Procolophon, and represented “a primative Diaptosaurian [sic] which probably belongs to a distinct and new sub- order” (Broom 1909, p. 277). Broom distinguished the Eccasaurus humerus from that of Procolophon based on the relative sizes of their epicondyles, and also noted that the Eccasaurus humerus features an unusually short deltopectoral crest. Broom (1912) referred an isolated, Tapinocephalus-like tooth (AMNH 5625), unassociated with the type material of Eccasaurus,toE. priscus. Based partially on this tooth, Watson (1914) considered E. priscus to represent a ‘tapinocephaloid’ dinocephalian, and Nopcsa (1928) included Eccasaurus within Tapinocephalidae. In Figure 25. The holotype of Eccasaurus priscus (SAM-PK-915), his monographic treatment of Karoo synapsids, Broom (1932, p. 45) stated that the Eccasaurus type humerus

Downloaded by [University of Guelph] at 12:37 30 April 2012 a fragmentary left humerus, in posterior view. Note the short deltopectoral crest and very weak supinator process, typical of is “undoubtedly of a Tapinocephaloid” without support- anteosaurids (Boonstra 1955). The articular surfaces of the capitel- ing comments other than that it “resembles somewhat that lum and trochlea are broken off in this specimen, and the condylar of Moschops” or mention of its previous ‘Diaptosaurian’ foramina are not exposed. Scale bar equals 10 cm. identiﬁcation. Broom (1932) also suggested that the short deltopectoral crest of Eccasaurus might be a preservational posteriormost postcanines in SAM-PK-916 are canted artefact. outwards, as in Anteosaurus and Titanophoneus. Based Boonstra (1955) established that Eccasaurus represents on the size and stratigraphic and geographic location of an anteosaurid rather than a tapinocephalian. Boonstra SAM-PK-916, it almost certainly represents an individual noted that although Broom described only the humerus of Anteosaurus magniﬁcus. However, as this specimen is of Eccasaurus, SAM-PK-915 actually includes a number so poor that none of the diagnostic features used to sepa- of associated skeletal fragments, such as femora, verte- rate Anteosaurus from Titanophoneus or Sinophoneus are brae, and cranial elements including a probable incisor. preserved, Archaeosuchus cairncrossi must be considered, Additionally, he referred a second specimen (SAM-PK- as Boonstra (1969) stated, a nomen dubium. 11597), made up of a scapulocoracoid, partial humerus, and ulna, to Eccasaurus priscus. Boonstra argued that Eccasaurus priscus Broom, 1909 the short deltopectoral crest, slender femur with strongly (Fig. 25) proximally situated trochanter, and scapula with a distinct 286 C. F. Kammerer

tricipital tubercle allow this material to be identified as ably size related. Given the inadequate state of knowledge anteosaurian. Furthermore, Boonstra stated that although regarding postcranial variation in anteosaurids, Eccasaurus the Tapinocephalus-like tooth (AMNH 5625) referred to priscus must be considered a nomen dubium. Should future E. priscus (Broom 1912) represents a tapinocephalid, discoveries of large Titanophoneus (‘Doliosauriscus’) and the incisor actually associated with the type humerus is Anteosaurus postcrania demonstrate that the Eccasaurus recognizably anteosaurid. Boonstra (1955) retained Ecca- humerus is specifically diagnosable as A. magnificus, E. saurus as a valid taxon separate from Anteosaurus without priscus would have priority over A. magnificus as the valid comment, but later (1969), he argued that the genus repre- name for this taxon, and it would be necessary to petition sents a nomen dubium identifiable only to family. Contra- the ICZN to preserve Anteosaurus. dictorily, however, in the section on Anteosaurus in the same paper, Boonstra (1969, p. 34) listed E. priscus as a junior Admetophoneus kargalensis Efremov, 1954 synonym of A. magnificus. (Fig. 26) Recent stratigraphic work on the Karoo Basin has demonstrated that Eccasaurus and the other therapsids from Lectotype. PIN 1954/5, a fragmentary maxilla (Fig. 26B), purported Ecca deposits (Archaeosuchus, Karroowalte- designated by Tchudinov (1983). ria) actually come from the Beaufort Group, specifically the Tapinocephalus Assemblage Zone (Kitching 1977; Age. Middle Permian (Lower Tatarian Substage, Urzhu- Rubidge 1995), confirming von Huene’s (1931) assign- mian Horizon). ment of Eccasaurus to this zone. As for Archaeosuchus, the size and geographic position of SAM-PK-915 suggest Locus typicus. Kargalinskii Rudnik (Kargalinsk mines) that it represents an individual of Anteosaurus magnificus. (exact locality unknown), Orenburg Region, Russia However, as very few anteosaurian postcrania are known, (Ivakhnenko 2003). it is difficult to identify any apomorphies in the Ecca- saurus type material that allow it to be diagnosed as a Referred material. Paralectotype: PIN 1954/6, a set of particular anteosaurid species. The Eccasaurus humerus is interlocked incisors (Fig. 26A) from the type locality. broader and more massive than that of the Titanophoneus Paratypes: PIN 1954/4, a fragmentary pterygoid preserv- lectotype (PIN 157/1) (Orlov 1958), but compares well ing the right palatal boss and transverse process from the with the partial humerus of PIN 157/3 (the holotype of type locality; and PIN 273/1, an isolated right humerus from Doliosauriscus yanshinovi), so these differences are prob- the Novo-Myasnikovskii Rudnik locality. Downloaded by [University of Guelph] at 12:37 30 April 2012

Figure 26. Admetophoneus kargalensis. A, The paralectotype (PIN 1954/6), an interlocked set of incisors; and B, lectotype (PIN 1954/5), a partial left maxilla with associated dentition, in left lateral view. The anteriormost tooth in B is a replacement canine, the root of the old canine is visible immediately behind it. Scale bars equal 5 cm. Systematics of the Anteosauria 287

Remarks. Efremov (1954) described Admetophoneus kargalensis on the basis of a fragmentary maxilla (PIN 1954/5) (Fig. 26B), a set of interlocked incisors (PIN 1954/6) (Fig. 26A) and a partial pterygoid (PIN 1954/4) from the Kargalinsk copper mines, and a right humerus (PIN 273/1) from the Novo-Myasnikovskii mine. He diagnosed A. kargalensis on the basis of its exceptionally long lower incisors and a straight, rather than recurved, lower canine. However, the lower incisors of A. kargalensis are not proportionally longer than those of Titanophoneus or Anteosaurus (Kammerer pers. obs.) and the supposed ‘straight’ lower canine is actually an old upper canine in the process of replacement (Ivakhnenko 2003). Orlov (1958) distinguished Admetophoneus from Doliosaurus on the basis of the strong transverse ridges on the upper canine of PIN 1954/5, producing a ‘ribbed’ texture. The tooth in question is largely unerupted, and the distinctive texture can probably be attributed to this fact, as the old canine being replaced lacks this texture. Tchudinov (1983) retained Admetophoneus as a valid taxon, but questioned its assignment to Brithopodidae, suggesting that it might instead represent an ‘eotheriodont’. Ivakhnenko (2003) referred the lectotype of Adme- tophoneus kargalensis (PIN 1954/5) to Titanophoneus sp., but argued that the incisors (PIN 1954/6) resemble those of Estemmenosuchus and cannot be identiﬁed as an anteosaurid. However, the incisors of PIN 1954/6 have distinct sectorial edges on their lateral margins, a feature that is typical of anteosaurids but absent in Estemmeno- suchus. The incisors of PIN 1954/6 are identical to those of the holotype of Titanophoneus potens (PIN 157/1) and there is no reason to suspect that they belong to a different taxon than PIN 1954/5. Based on size and general morphology, the gnathic material (including the lectotype) of Admetophoneus could easily represent Titanophoneus, but lacks any diagnostic features at the generic level that would allow precise referral to that taxon. As such, Admeto- phoneus kargalensis must be considered a nomen dubium. Downloaded by [University of Guelph] at 12:37 30 April 2012 The referred humerus, PIN 273/1, closely resembles that Figure 27. The Brazilian anteosaurid dentary fragment UFRGS 0249T in A, dorsal (anterior at right) and B, left lateral views. of T. potens, and shows the sharply angled head, short Scale bars equal 1 cm. deltopectoral crest, and weak supinator process typical of anteosaurids. The proximal end of the humerus in PIN 273/1 is relatively broader than in the holotype of T. potens,but Referred material. UFRGS PV 0249T, a left dentary frag- is similar to the condition in PIN 157/3 (the holotype of ment (Fig. 27). UFRGS PV 0314T, a partial incisor. Doliosauriscus yanshinovi). Remarks. Langer (2000) described the only known South Anteosauridae indet. American dinocephalians on the basis of several isolated (Fig. 27) tooth and jaw fragments from the Rio do Rasto Forma- tion of Brazil. Of these specimens, Langer (2000) assigned a tooth-bearing dentary fragment (UFRGS PV 0249T) to Age. Middle Permian (Morro Pelado Member, Rio do ‘Anteosauridae, Brithopodinae’ and an isolated, fragmen- Rasto Formation). tary incisor (UFRGS PV 0314T) to ‘Anteosauroidea’ (sensu King 1988, i.e. either Anteosauridae or Titanosuchidae). Locality. Posto Queimado locality, Rio Grande do Sul UFRGS PV 0314T has a very small lingual ‘heel’, which is State, Brazil (Langer 2000). at odds with a titanosuchid identiﬁcation, and it is more 288 C. F. Kammerer

likely that this specimen represents a worn anteosaurid 1838 Orthopus primaevus Kutorga: 273. incisor. 1866 Eurosaurus verus von Meyer [partim]: 112. UFRGS PV 0249T (Fig. 27) preserves four teeth: one with a well-preserved crown, two with the crowns broken Plastotype. PIN 296/4, cast of the distal end of a left off, and a fragment of the root. The preserved crown exhibits humerus (original specimen lost). an extremely bulbous base, conical tip, and anterolingual and posterolabial serrated keels. The postcanine morphol- Age. Middle Permian (Uﬁmian Stage, Sheshmian Hori- ogy of UFRGS PV 0249T is generally very similar to that zon). of Anteosaurus and Titanophoneus. Indeed, it is entirely possible that this specimen represents a South American Locus typicus. Cupriferous mines of the Perm Region individual of Anteosaurus, as a number of taxa other- (exact locality unknown), Russia (Ivakhnenko 2003). wise known primarily from the Karoo Basin are now known to occur in the Rio do Rasto Formation (e.g. the Referred material. The following specimens were dicynodont Endothiodon and rhinesuchid temnospondyls) referred to Brithopus priscus by Efremov (1954): PIN (Langer 2000; Cisneros et al. 2005). In the absence of more 1954/53, proximal end of a left humerus (Fig. 28A), complete material, however, UFRGS PV 0249T can only holotype of Orthopus primaevus Kutorga, 1838; PIN be regarded as Anteosauridae indet. 296/1, fragmentary gnathic region of a skull, the holotype of Rhopalodon murchisonii Fischer de Waldheim, Taxa incorrectly assigned to Anteosauria 1845 (specimen lost, but a cast is preserved in the PIN collections); PIN 1954/17, a right scapulocoracoid; PIN Brithopus priscus Kutorga, 1838 1954/18, distal region of a left scapula and procoracoid; (Fig. 28) PIN 1954/19, distal region of right scapula and procoracoid; PIN 1954/23, a coracoid fragment; PIN 1954/24, a partial left scapula; PIN 1954/26, a proximal scapular fragment; PIN 1954/39, a fragmentary humerus. PIN 1954/41, the proximal end of a right humerus; PIN 1954/45, a humeral fragment; PIN 1954/53, a humeral fragment; PIN 1954/54, a partial pelvis with articulated femoral head; PIN 1954/55, a partial right pelvis; PIN 1954/58, a partial right pubis; PIN 1954/62, a partial left pelvis and femur; PIN 1954/67, a partial left pelvis and femur; PIN 1954/87, a damaged ﬁbula; PIN 1954/96, an isolated postcanine tooth row.

Remarks. Kutorga (1838) described Brithopus priscus on the basis of the distal end of a left humerus (Fig. 28C, D) recovered from the copper measures near Perm. He considered Brithopus to represent an enormous Permian Downloaded by [University of Guelph] at 12:37 30 April 2012 xenarthran, intermediate between Bradypus and Dasy- pus. Based on another isolated humeral fragment (PIN 1954/53) (Fig. 28A) recovered from near Perm, Kutorga (1838) described an additional taxon of purported Permian mammal, Orthopus primaevus. Kutorga considered the O. primaevus holotype (PIN 1954/53) to represent the distal end of a humerus, and diagnosed the new taxon based on Figure 28. Brithopus priscus. A, PIN 1954/53, the holotype of this element’s unusual shape and position of the condylar Orthopus primaevus (the proximal end of a left humerus) in anterior view; B, a partial maxilla (PIN 1954/7) referred to Brithopus foramina. sp. by Efremov (1954), here considered to represent a specimen Although he listed Brithopus and Orthopus among of Syodon biarmicum; C, the Natural History Museum (London) the Mammalia in his Nomenclator Zoologicus,Agas- cast, BMNH 35398, of the lost holotype of Brithopus priscus (the siz (1842) doubted this attribution and instead proposed distal end of a humerus) that Owen (1876a) used to determine the possible reptilian affinities for these taxa, a suggestion therapsid affinities of this taxon, in anterior and D, posterior views. Note the large entepicondylar foramen and well-developed supina- later confirmed by Eichwald (1860), von Meyer (1866) tor process with distinct separation from the ectepicondyle, unlike and Owen (1876a). Owen (1876a) recognized the simi- the condition in anteosaurids (compare with the distal humerus of larity between the humerus of Brithopus priscus (based Eccasaurus priscus in Fig. 25). Scale bars equal 5 cm. on BMNH 39358, a cast of the holotype) and his Systematics of the Anteosauria 289

own Cynodraco (currently considered an indeterminate PIN 1954/3 makes it difficult to tell if this feature is real or gorgonopsian; see Sigogneau 1970), and argued that Britho- artefactual in Orthopus. It is probable that the type mate- pus represented a ‘theriodontal’ reptile ( = therapsid). Addi- rial of both Orthopus and Brithopus represent humeral tionally, Owen corrected Kutorga’s (1838) identification of fragments of an estemmenosuchid-like tapinocephalian. the holotype of Orthopus primaevus, noting that it repre- However, the poor preservation of PIN 1954/3 and incom- sents the proximal, not distal, end of the humerus, thereby pleteness of PIN 296/4 make these elements impossi- explaining the unusual shape and foraminal position given ble to identify at generic level. As PIN 296/4 and PIN in its initial description. Arguing that the Orthopus and 1954/3 display no unambiguous autapomorphic features Brithopus humeral fragments probably belong to the same that allow identification beyond Tapinocephalia indet., species (and going so far as to suggest that they may repre- Brithopus priscus and Orthopus primaevus must be consid- sent two ends of the same humerus), Owen stated that, ered nomina dubia, and the taxon Brithopodidae Efremov, among therapsids, the ‘complete’ Brithopus humerus was 1954 should be treated as invalid. Of the material referred most similar to that of the cynodont Galesaurus and the to B. priscus by Efremov (1954), PIN 1954/55 and 96 dicynodont Dicynodon. can be identified as anteosaurian. PIN 1954/55 is a pelvic Efremov (1954) listed a number of differences between girdle that appears to be anteosaurian on the basis of the the humeri of Titanophoneus and Brithopus, and retained anteriorly directed pubis—in tapinocephalians, the pubis both genera as valid in his new family Brithopodidae. points downwards (Boonstra 1955). A sharply anteriorly In addition to the holotypes of Orthopus primaevus and directed pubis is primitive for synapsids, but PIN 1954/55 Dinosaurus (formerly Rhopalodon) murchisonii, Efremov can be identified as a dinocephalian by its broad, ventrally (1954) referred numerous new isolated skeletal fragments directed ischium. PIN 1954/96 is a partial tooth row exhibit- to B. priscus (see Referred material). Most subsequent ing the bulbous postcanine morphology of Anteosauri- authors (Romer 1956, 1966; Watson & Romer 1956; Olson dae. PIN 294/7, a scapulocoracoid, lacks the characteris- 1962; Boonstra 1963; Kemp 1982; Tchudinov 1983; Sues tic tricipital tubercle of anteosaurids (Boonstra 1955), and 1986; King 1988; Battail & Surkov 2000) have followed instead represents an indeterminate tapinocephalian. Addi- Efremov (1954) in considering Brithopus priscus to repre- tional scapular elements referred to B. priscus (e.g. PIN sent a valid taxon of anteosaurian dinocephalian and using 1954/17, 18, 19, 24, 26) also lack any clear anteosaurid Brithopodidae to refer to all non-Anteosaurus anteosauri- characteristics and can only be identified as Dinocephalia ans. Ivakhnenko (2003), however, restricted Brithopodidae indet. Other supposed B. priscus material described by to Brithopus priscus, which he declared to be a nomen Efremov (1954) (e.g. PIN 1954/23, 45, 87) is so frag- dubium without further comment. mentary that it can only be identified as Dinocephalia Restudy of the type specimens of Brithopus priscus and or even Therapsida indet. PIN 1954/7, a maxillary frag- Orthopus primaevus reveals that they are probably non- ment (Fig. 28B) referred to Brithopus sp. by Efremov anteosaurid. The proximal humeral fragment of Orthopus (1954), can be positively identified as belonging to Syodon has a greatly expanded neck, weakly angled head, and rela- biarmicum on the basis of canine morphology. PIN 296/1, tively long deltopectoral crest, whereas anteosaurid humeri the type of Dinosaurus murchisonii, was referred to Britho- are characterized by relatively narrow necks, steeply angled pus priscus by Efremov (1954), but is not recognizably heads, and short deltopectoral crests (Boonstra 1955; Orlov dinocephalian. Ivakhnenko (2003) considered Dinosaurus 1958). The distal humeral fragment of Brithopus has a to represent the senior synonym of the problematic basal Downloaded by [University of Guelph] at 12:37 30 April 2012 relatively large entepicondylar foramen and well-developed therapsid Phthinosuchus Efremov, 1954. This proposal is supinator process, whereas in anteosaurs the entepicondy- difficult to confirm considering the poor quality of the D. lar foramen and supinator process are relatively small murchisonii type material (a plaster cast of a partial maxilla (Boonstra 1955; Orlov 1958). The morphology of the and dentary). Brithopus and Orthopus type material is consistent with a tapinocephalian identification. The Orthopus fragment in Deuterosaurus biarmicus Eichwald, 1848 particular is similar to the proximal humerus of the estemmenosuchid tapinocephalian Estemmenosuchus uralensis (personal observation of PIN 1758/23, 89, 100, 268). The Holotype. PIN 1954/10, an axial column. deltopectoral crest of Orthopus is developed to a similar extent as that of Estemmenosuchus and tapinocephalids: Age. Middle Permian (Urzhumian Horizon, Lower Tatar- proportionally longer than that of anteosaurs, but not as long ian Substage). as titanosuchids, in which it extends down to the midpoint of the humerus (Boonstra 1955). Furthermore, Orthopus and Estemmenosuchus appear to have a sharper angle between Locus typicus. Klyuchevskii Rudnik-2 locality, Ster- the head of the humerus and the latissimus dorsi process libashevskii District, Bashkortostan, Russia (Ivakhnenko than do titanosuchids, although the fragmentary nature of 2003). 290 C. F. Kammerer

Remarks. Watson (1914) described Lamiasaurus newtoni on the basis of various cranial fragments (several occipital fragments and a left snout fragment, collectively catalogued as BMNH 49385) collected by Thomas Bain in 1878. Watson believed these fragments pertained to a single individual, although he noted that the occipital and snout fragments were “only connected ...by documentary evidence” (Watson 1914, p. 751). In the original description, Watson considered Lamiasaurus to be a ‘tapinocephaloid’, and later placed this genus in Tapinocephalidae in his ‘sketch classification’ of pre-Jurassic tetrapods (Watson 1917). Nopcsa (1928) believed Lamiasaurus represented a titanosuchian and established the new family Lamiasauridae for Lami- asaurus Watson, 1914, Anteosaurus Watson, 1921, Dinar- tamus Broom, 1923, Dinophoneus Broom, 1923, Enobius Broom, 1923, Glaridodon Seeley, 1888 and Scapanodon Broom, 1904. Of the additional ‘lamiasaurid’ taxa listed by Nopcsa (1928), only Anteosaurus is currently considered valid; the others represent invalid titanosuchid genera (Boonstra 1969). The material originally assigned to Lamiasaurus by Watson (1914) was recognized as chimaerical by Williston (1925), who considered the occipital portion of the skull to represent a tapinocephalid and the snout portion to represent a titanosuchid. In the classification of therapsids given in Williston’s Osteology of the Reptiles, he listed Lamiasaurus [cranium] under Tapinocephalidae and ‘Lamiasaurus’ [snout] under Titanosuchidae, thereby establishing the occiput as the name-bearing portion. Broom (1929, 1932) also recognized that the fragments described by Watson constituted a mixture of different dinocephalian taxa, but Figure 29. Stereopair images of the titanosuchid snout frag- argued that the holotype should be restricted to the snout, ment making up part of the chimaerical holotype of Lamiasaurus and this act was followed by most subsequent workers. newtoni (BMNH 49385), in palatal view. Anterior is left, the Indeed, Watson himself later (Watson & Romer 1956) listed left side of the snout is preserved. Note the robust anterior end Lamiasaurus in Jonkeriidae (= Titanosuchidae) follow- of the vomer where it contacts the premaxilla, characteristic of titanosuchids. Scale bar equals 5 cm. ing Broom’s restriction of the type to the snout portion. Boonstra (1953) considered Lamiasaurus to be a junior synonym of Titanosuchus, and created the new combination Downloaded by [University of Guelph] at 12:37 30 April 2012 Remarks. This taxon has variously been considered a tapinocephalian (Nopcsa 1928), an anteosaur (King 1988; Titanosuchus newtoni (Watson, 1914), although he ques- Ivakhnenko 2003), or a chimaera composed of both (Boon- tioned its specific validity. Boonstra (1953, p. 25) claimed stra 1965). Recent study (Kammerer pers. obs.) confirms that the “premaxillary border is not dorsally directed” in the the tapinocephalian nature of this taxon, and as such it is snout of Lamiasaurus, and as such cannot represent an not treated further here. anteosaurid. However, Boonstra later (1969, p. 36) argued that this “jaw fragment cannot be identified even as to Lamiasaurus newtoni Watson, 1914 family—it may be either titanosuchid or anteosaurid”. (Fig. 29) The snout portion (the left premaxilla, part of the 1953 Titanosuchus newtoni (Watson); Boonstra: 28. maxilla, and vomer) of BMNH 49385 (Fig. 29) is poorly preserved and incompletely prepared. It preserves the Holotype. BMNH 49385, fragments of the rear portion of roots of the canine and three postcanines and five incisor a skull. alveoli. As noted by Boonstra (1953), there does not Age. Middle Permian (Tapinocephalus Assemblage Zone, appear to be an inclined ventral border of the premax- Abrahamskraal Formation, Beaufort Group). illa, which would suggest that this represents a titanosuchid rather than an anteosaurid. This character alone cannot be Locus typicus. Warmbad, Beaufort West, Western Cape considered definitive, as the snout fragment is so crushed Province, South Africa (Kitching 1977). and worn that the apparent lack of incline could be Systematics of the Anteosauria 291

deformational. However, this snout can be confidently Eosyodon hudsoni Olson, 1962 assigned to Titanosuchidae on the basis of its vomerine morphology. In titanosuchids, the vomer is forked anteri- Holotype. FMNH UR 575, a crushed right femur. orly, and each vomerine ramus is greatly expanded near its contact with the premaxilla. In anteosaurids, the vomers Age. Early Permian (San Angelo Formation, Late Leonar- remain appressed at the contact with the premaxilla and are dian). proportionally shallow and narrow anteriorly rather than expanded. The snout fragment of BMNH 49385 displays the Locus typicus. Kahn Quarry, Driver Ranch, Knox County, characteristic expanded anterior portion of the left vomer Texas, USA (Olson 1962). of a titanosuchid. Titanosuchid genera cannot currently be distinguished on the basis of cranial material, and the ‘Lami- Referred material. Specimens referred to E. hudsoni by asaurus’ snout fragment can only be considered an indeter- Olson (1962): FMNH UR 496, a partial occiput; FMNH UR minate titanosuchid. 499, a dentary; FMNH UR 500, a tooth-bearing palatine Despite the predominant association of the name Lami- fragment; FMNH UR 711, a partial postcranium including asaurus with the snout portion of BMNH 49385, Williston a femur, possible fibula, vertebral fragments, partial scapula (1925) has priority over Broom (1929) as first reviser of the and interclavicle, and 15 rib fragments; FMNH UR 712, an taxon, and as such Williston’s restriction of the holotype isolated metapodial; FMNH UR 826, a dentary. All referred to the occipital fragments rather than the snout fragment is specimens are from the type locality. valid. The occiput does indeed represent a tapinocephalid, as argued by Williston (1925) and Broom (1932), but it Remarks. Olson (1962) described Eosyodon hudsoni on is indeterminate to genus, and thus Lamiasaurus must be the basis of a crushed right femur (FMNH UR 575) and considered a nomen dubium. Lamiasauridae Nopcsa, 1928 various cranial and postcranial fragments from the upper is a junior synonym of Tapinocephalidae Lydekker, 1889. part of the Texan San Angelo Formation. Olson stated that these specimens were “distinctly therapsid in cast” (p. 61) Brithopus ponderus Efremov, 1954 and “unmistakably similar to [those] of brithopodids”, and Brithopus bashkyricus Efremov, 1954 considered Eosyodon to be closely related to the Russian Archaeosyodon. Olson’s Eosyodon specimens, supposedly Types. PIN 1954/41, the proximal end of a right humerus, from the Middle or Late Permian, are actually from the Early the holotype of Brithopus ponderus. PIN 294/10, cast of a Permian (DiMichele et al. 2001). Sidor and Hopson (1995) partial scapula, the plastotype of B. bashkyricus. argue that this material pertains to a sphenacodontid ‘pelycosaur’ rather than a dinocephalian. Personal examination of the type of Eosyodon is in concordance with a non- Age. Middle Permian (Urzhumian Horizon, Lower Tatar- anteosaurid identification. The referred gnathic material of ian Substage). E. hudsoni is completely unlike that of any anteosaurid, lacking bulbous postcanines or a distinct, reniform pala- Locus typicus. Klyuchevskii Rudnik-2 locality, Ster- tine boss, but is very similar to sphenacodontids such as libashevskii District, Bashkortostan, Russia (Ivakhnenko Dimetrodon. E. hudsoni should be considered a nomen 2003). dubium (Sphenacodontidae indet.). Downloaded by [University of Guelph] at 12:37 30 April 2012

Remarks. Efremov (1954) described two additional Phylogenetic analysis species of Brithopus, B. ponderus and B. bashkyricus,on Few previous phylogenetic analyses have addressed the basis of appendicular fragments. Efremov (1954) distin- anteosaurian interrelationships—most phylogenetic anal- guished B. ponderus from the type species B. priscus on yses including anteosaurids have included only one or two the basis of its larger size and greater robusticity. Efremov anteosaurian OTUs (Rubidge & van den Heever 1997; diagnosed B. bashkyricus, based on the cast of a specimen Sidor & Hopson 1998; Angielczyk 2004; Sidor & Rubidge initially described by von Meyer (1866), by its greater width 2006; Liu et al. 2010). The only numerical cladistic analy- across the scapular spine than that of specimens (e.g. PIN ses that have addressed anteosaurian interrelationships are 1954/17) he considered to represent B. priscus. Based on those of Sidor (2000; including Syodon, Titanophoneus their size and stratigraphic position, Brithopus ponderus and Anteosaurus) and Liu et al. (2009; including Stenocy- and B. bashkyricus probably represent dinocephalians, and bus, Syodon and Titanophoneus), whose results supported the weakly angled humeral head of B. ponderus suggests prior hand-drawn phylogenies of the group (Hopson and that it is non-anteosaurid. Beyond this, however, the mate- Barghusen 1986; Rubidge 1994; Cheng & Li 1997). Most rial is undiagnosable, and B. ponderus and B. bashkyri- anteosaurid taxa have never been included in a phylo- cus should be considered nomina dubia, as proposed by genetic analysis. To address this problem, the relation- Ivakhnenko (2003). ships of the nine anteosaurian species herein considered 292 C. F. Kammerer Downloaded by [University of Guelph] at 12:37 30 April 2012

Figure 30. The skulls of all valid anteosaurid species (excluding Microsyodon orlovi) reconstructed in left lateral view. A, Archaeosyodon praeventor; B, Notosyodon gusevi; C, Australosyodon nyaphuli; D, Syodon biarmicum; E, Sinophoneus yumenensis; F, Titanophoneus potens; G, Titanophoneus adamanteus; H, Anteosaurus magniﬁcus.

to be valid (Fig. 30) were assessed in a new phylogenetic nus pamelae Rubidge, 1991 (NMQR 2985, 2986, 2987). analysis using a data matrix of 35 characters (see Appendix Estemmenosuchus is currently thought to be a basal 1). The biarmosuchian Biarmosuchus tener Tchudinov, tapinocephalian (Hopson & Barghusen 1986; Rubidge & 1960 was used as the outgroup (based on the phylogenies of van den Heever 1997; Sidor 2000), and Tapinocaninus Hopson & Barghusen 1986; Rubidge & Sidor 2001), coded represents the most basal known tapinocephalid (Rubidge on the basis of the holotype PIN 1758/2. Tapinocephalian 1991). The data matrix was analysed using branch-and- dinocephalians were represented by Estemmenosuchus bound searching in the parsimony program PAUP∗ (Swof- mirabilis Tchudinov, 1968b (PIN 1758/6) and Tapinocani- ford 2003). Systematics of the Anteosauria 293

In cases where multiple anteosaur specimens of different size of a given taxon were present and character codings for this taxon differed consistently based on size class, codings were based on the largest known (‘adult’) specimens. Three additional runs were performed in which the influence of specimens herein considered to be juveniles or subadults was examined. In the first additional run, Sinophoneus was coded solely on the basis of the holotype (GMV 1601), without supplementary information derived from the ‘Stenocy- bus’ specimens (IGCAGS V 361 and IVPP V12008). In the second additional run, an ‘immature OTUs’ analysis was performed in which ‘Stenocybus acidentatus’(IGCAGSV 361) and Titanophoneus potens (PIN 157/1) were coded separately from Sinophoneus yumenensis (GMV 1601) and ‘Doliosauriscus yanshinovi’ (PIN 157/3) to examine the effects of ontogenetic character change on tree topology. In the final additional run, taxa known from adult and juvenile specimens (Sinophoneus, Titanophoneus potens and Anteosaurus) were coded as polymorphic for those characters in which the adults and juveniles differ.

Characters Characters used in previous phylogenetic analyses of dinocephalians (Hopson & Barghusen 1986; Rubidge & van den Heever 1997; and Sidor 2000, which includes characters also used in Sidor & Hopson 1998 and Sidor & Rubidge 2006) are noted. Characters 26 and 30 contain intermediate character states between extremes, so they were treated as ordered. See Appendix 1.

Results Two most parsimonious trees (MPTs) of length 53 were recovered, with a consistency index (CI) of 0.704, retention index (RI) of 0.805, and rescaled consistency index (RC) of 0.566 (Fig. 31A). The two trees differed only in the relative position of Microsyodon to Archaeosyodon:in the ﬁrst tree, Microsyodon falls outside of a clade containing Archaeosyodon and all other anteosaurs, whereas in Downloaded by [University of Guelph] at 12:37 30 April 2012 the second tree Microsyodon and Archaeosyodon are sister taxa. Archaeosyodon or an Archaeosyodon + Microsyodon clade represents the sister-group to a large clade containing all other anteosaurs. This ‘higher anteosaur’ clade is composed of two subclades, one containing Notosyodon, Syodon, and Australosyodon, and the other containing Sino- phoneus, both species of Titanophoneus, and Anteosaurus. Notosyodon was found to be the sister-group of a Syodon + Australosyodon clade, and Sinophoneus was found to Figure 31. Results of the phylogenetic analysis. A, Strict consen- be the sister-group to the unresolved trichotomy of T. sus tree of anteosaurian relationships. Numbers above branches potens, T. adamanteus and Anteosaurus. In a bootstrap represent bootstrap values; B, topology resulting from analysis analysis (branch and bound) using 10,000 replicates, all in which immature specimens (‘Stenocybus acidentatus’ based of the consensus clades were well supported (Fig. 31A). on the holotype, IGCAGS V 361, and paratype, IVPP V12008; Titanophoneus potens based solely on the lectotype, PIN 157/2) Anteosauria and Tapinocephalia themselves are the most were coded as OTUs; C, topology resulting from analysis in which weakly supported clades on the tree as a result of homo- taxa differing in character states across ontogeny (Sinophoneus plasy between tapinocephalids (Tapinocaninus) and the yumenensis, Titanophoneus potens and Anteosaurus magniﬁcus) giant anteosaurs (Titanophoneus and Anteosaurus). Within were coded as polymorphic. 294 C. F. Kammerer

Anteosauria, each of the consensus clades has strong boot- represent a dinocephalian synapomorphy (contra King strap support. 1988). Several characters appear to be homoplastic between Coding Sinophoneus based solely on the holotypic skull anteosaurs and tapinocephalians, with the highest degree did not alter its position on the tree. Coding subadults of convergence occurring between the giant anteosaurs separately from adults (i.e. treating ‘Stenocybus aciden- Titanophoneus and Anteosaurus and the tapinocephalids. tatus’ and ‘Doliosauriscus yanshinovi’ as OTUs) resulted Homoplastic character states present in these taxa include in three most parsimonious trees of length 58. In this reduced palatal dentition, fronto-nasal suture near the ante- analysis, Microsyodon and Archaeosyodon consistently rior edge of the orbits, transversely expanded postorbital form a clade, ‘Stenocybus’ is the sister-group of ‘higher bar, heavy pachyostosis over the entire dorsal surface of anteosaurs’, and Sinophoneus and Titanophoneus potens the skull, tall dentary of roughly even height, and jaw (PIN 157/1) fall into an unresolved trichotomy with the articulation rotated forward. Because of its completeness clade containing ‘Doliosauriscus yanshinovi’, T. adaman- and Orlov’s (1958) monographic treatment, Titanophoneus teus and Anteosaurus (Fig. 31B). Coding taxa as poly- potens has usually been used as the anteosaurian exemplar morphic for characters thought to change over ontogeny in analyses of therapsid relationships (e.g. Angielczyk resulted in 12 most parsimonious trees of length 54, identi- 2004). However, the results of the present analysis demon- cal to that of the ‘normal’ analysis with the exception that strate that T. potens is nested deeply within anteosaurs Sinophoneus falls into a trichotomy with the clades (Noto- and is a poor choice to represent the basal anteosaurian syodon + (Australosyodon + Syodon)) and (T. potens + T. condition. Indeed, use of Titanophoneus has already been adamanteus + Anteosaurus) (Fig. 31C). positively misleading in some analyses in which a derived character state within anteosaurs present in Titanophoneus (e.g. Character 9 of Angielczyk 2004, length of maxillary Discussion alveolar region) is used to polarize that state as ‘primitive’ for another group. It is suggested that any future therapsid Anteosaurs represent a monophyletic group of cranial analyses with a single anteosaurian exemplar utilize dinocephalians supported by the following unam- Archaeosyodon rather than Titanophoneus. biguous synapomorphies: upwardly canted premaxilla (7), In the analysis of immature anteosaurs as separate OTUs, vomers with raised, elongated edges (10), tightly appressed the immature specimens occupy more basal positions on the quadrate rami of the pterygoids (17), convex ventral tree than the adults. Subadult Titanophoneus potens (PIN maxillary border (18), jugal-lacrimal ridge (22), and 157/1) falls outside of the clade containing adult T. potens strongly anteroventrally curved postorbital bar (28). The (‘Doliosauriscus yanshinovi’, PIN 157/3), T. adaman- placement of Microsyodon as the most basal anteosaurid in teus and Anteosaurus. Juvenile Sinophoneus (‘Stenocybus the first of the two MPTs is based on a character believed acidentatus’) falls outside of ‘higher anteosaurs’ entirely. to change over the course of ontogeny in anteosaurids: However, it must be noted that even when coded as a postcanine morphology. The placement of Microsyodon separate taxon, Stenocybus is not recovered as the most as the sister-group of Archaeosyodon in the second MPT basal anteosaur (Microsyodon + Archaeosyodon occupy is based on the shared possession of ‘hook’-like canines. that position), contra Cheng & Li (1997). As this morphology is also present in Syodon, it is likely that this ‘hooked’ morphology is the ancestral state in Higher level taxonomy of Anteosauria Downloaded by [University of Guelph] at 12:37 30 April 2012 anteosaurs, as is reconstructed in the first MPT. However, The results of the phylogenetic analysis presented above until more complete material of Microsyodon is discov- allow for a reconsideration of generic and higher- ered, its position relative to Archaeosyodon will remain level anteosaur taxonomy. The generic name Notosyo- questionable. ‘Higher anteosaurs’ (all anteosaurs other don is retained for the species gusevi, as including this than Microsyodon and Archaeosyodon)areaverywell- species within the genus Syodon (sensu Ivakhnenko 1995, supported group (bootstrap value of 91%) supported by 2003) would render Syodon paraphyletic with regards to the following unambiguous synapomorphies: non-terminal Australosyodon. Titanophoneus potens,‘Doliosauriscus’ naris (6), broad, triangular premaxillary plate palatally adamanteus and Anteosaurus magnificus form an unre- (9), single palatine tooth row (12), reduced dentition on solved trichotomy in this analysis. For taxonomic purposes, the palatal ramus of the pterygoid (13), reduced dentition it is proposed that the species potens and adamanteus both on the transverse process of the pterygoid (14), dorsal be included in the genus Titanophoneus (sensu Ivakhnenko border of the maxilla with a posterior process overhanging 2003), but with the caveat that, at present, this assignment the lacrimal (19), interorbital crest on the frontal midline is based solely on phenetic grounds. The possession of a (24), and dentary with a post-canine ‘step’ (32). The most lenticular (rather than oval, as in Anteosaurus) angular boss basal anteosaurs (Archaeosyodon) and tapinocephalians is probably a synapomorphy of Titanophoneus, but as it is (Estemmenosuchus) possess terminal nares, suggesting currently impossible to polarize this character (given the that non-terminal nares were evolved independently in absence of angular bosses outside of the three species in anteosaurids and derived tapinocephalians and do not question), this is speculative. Systematics of the Anteosauria 295

Anteosauria, as circumscribed here (see also Sidor Ivakhnenko 2003; Smith et al. 2006). Although some 2000), consist of all taxa more closely related endemic early therapsid clades are currently recognized to Anteosaurus magnificus Watson, 1921, than to (e.g. estemmenosuchid dinocephalians and venyukovioid Tapinocephalus atherstonei Owen, 1876b (Tapinocephalia anomodonts in Russia), the main anteosaurid subclades represents the converse, i.e. all taxa more closely (Syodontinae and Anteosaurinae) are found in both Laura- related to Tapinocephalus than to Anteosaurus). Although sia and Gondwana. The most basal anteosaurs (Archaeosyo- Anteosauria and Anteosauridae are compositionally equiv- don and Microsyodon) are restricted to Russia, but it seems alent at present, it is intended that Anteosauridae proper premature to suggest that the group originated there. The refer to the restricted subset of Anteosauria diagnosed by the earliest therapsids are known from only three areas world- combined presence of an anterodorsally canted premaxilla, wide (the Eodicynodon Assemblage Zone in South Africa, convex ventral maxillary margin, ‘scroll’ vomers, quadrate ‘Zone I’ in Russia, and the Dashankou fauna in China), rami of the pterygoid that bifurcate the anterior margin of with many taxa known from a single specimen. Given the the basisphenoid, a ridge on the jugal-lacrimal suture, and paucity of material and localities, it is currently impossi- a ‘scoop’-shaped (strongly anteroventrally curved) postor- ble to draw any robust conclusions about biogeography and bital bar. Ivakhnenko’s (1994) Syodontidae, here reduced therapsid origins. Any claims in support of either Gond- to subfamilial status, is used to refer to the clade of Syodon, wana or Laurasia as a ‘centre of origin’ for various therap- Australosyodon and Notosyodon. This clade is diagnosed sid clades or the group as a whole are currently not tenable by a frontal contribution to the pineal boss, frontal contri- considering the state of the early therapsid fossil record. bution to the edge of the adductor musculature attachment The weak support for such hypotheses is indicated by the site in the temporal rim, and adductor musculature attach- frequency with which they are overturned by single discov- ment on the pineal boss. As circumscribed here, Syodon- eries, e.g. the anomodont ‘centre of origin’, once consid- tinae consists of all taxa more closely related to Syodon ered Laurasian based on the Russian ‘Zone I’ venyukovioid biarmicum Kutorga, 1838 than to Anteosaurus magnifi- Otsheria (Olson 1962), then Gondwanan based on Anomo- cus Watson, 1921. Anteosaurinae (first given subfamilial cephalus from the Tapinocephalus Assemblage Zone of status in Hopson & Barghusen 1986) is used to refer to South Africa (Modesto et al. 1999), and currently once the clade of Anteosaurus, Titanophoneus and Sinophoneus. again Laurasian based on a new skull of Biseridens show- This clade is diagnosed by massive expansion of the distal ing it to be the basalmost anomodont (Liu et al. 2010). end of the transverse processes of the pterygoid, transverse expansion of the postorbital bar, enlarged postfrontals, and Anteosaurid palaeobiology possession of a dentary with a nearly vertical anterior edge. Anteosaurs have often been associated with an amphibi- As circumscribed here, Anteosaurinae consists of all taxa ous lifestyle (Olson 1962; King 1988), and recently, more closely related to Anteosaurus magnificus Watson, Ivakhnenko (2001, 2003, 2008) argued that all anteosaurs 1921 than to Syodon biarmicum Kutorga, 1838. were obligatory “ichthyophagous hydrobionts of otterlike The following taxonomic scheme is proposed for biomorph type” (Ivakhnenko 2008, p. 983). There are anteosaurs: several problems with the hypothesis that anteosaurs repre- Anteosauria Boonstra, 1962 sented amphibious, obligate fish-eaters. A suite of char- Family Anteosauridae Boonstra, 1954a acters are typical of piscivorous tetrapod lineages: the Archaeosyodon praeventor Tchudinov, 1960 teeth of piscivores tend to be elongate, numerous, strongly Downloaded by [University of Guelph] at 12:37 30 April 2012 Microsyodon orlovi Ivachnenko, 1995 recurved, and very sharp to hold and kill slippery prey Subfamily Syodontinae Ivachnenko, 1994 (Savitzky 1983; Massare 1987), and the jaws of pisci- Syodon biarmicum Kutorga, 1838 vores tend to be long and narrow to maximize speed of Notosyodon gusevi Tchudinov, 1968a jaw closing and minimize water resistance during shake- Australosyodon nyaphuli Rubidge, 1994 feeding (Taylor 1987; Westneat 2004). These adaptations Subfamily Anteosaurinae Boonstra, 1954a are observed in piscivorous amniote taxa from the Permian Anteosaurus magnificus Watson, 1921 (e.g. mesosaurids) to the present day, and thus are not exclu- Titanophoneus potens Efremov, 1938 sive to predators of the current teleost-dominated ichthy- Titanophoneus adamanteus (Orlov, 1958) ofauna (Massare 1987; Taylor 1992; Modesto 2006). The Sinophoneus yumenensis Cheng and Ji, 1996 teeth of anteosaurs, on the other hand, are profoundly poorly adapted to piscivory: the postcanines are bulbous and blunt, Anteosaurid palaeobiogeography and the only recurved tooth, the canine, is massive. Aquatic Anteosaurs are known from Laurasia (Russia and China) and semiaquatic piscivores generally have a relatively small and Gondwana (Africa and South America) in the Middle cranium (excluding the jaws), as a heavy skull would Permian, similar to other early therapsids (e.g. biarmosuchi- reduce acceleration during pursuit of evasive prey (Taylor ans, tapinocephalians and basal anomodonts) that appear 1992); in anteosaurs, the non-jaw region of the skull is to have had a cosmopolitan distribution (Rubidge 1995; massive, extremely so in the giant taxa Titanophoneus and 296 C. F. Kammerer

Anteosaurus. The postcranial anatomy of anteosaurids is anteosaurines may also have been utilized in intraspe- also not suggestive of amphibious habits. Contra to recon- cific agonistic behaviour, as has been proposed for structions depicting anteosaurid limbs as short, flipper-like tapinocephalids (Barghusen 1975). structures (Ivakhnenko 2001, 2008), anteosaurids have rela- Although the earliest known anteosaurids were relatively elongate limbs for dinocephalians (Boonstra 1955). tively small dinocephalians (skull length ∼30 cm in Although anteosaur fossils are usually found in deltaic Archaeosyodon) coexisting with larger-bodied predatory facies (Olson 1962; Rubidge 1995), taphonomic evidence eotitanosuchids (Ivakhnenko 2003), by the time of the suggests that, at least for the South African taxa, these South African Tapinocephalus Assemblage Zone and remains were washed in from upland habitats (Boonstra Russian ‘Zone II’, anteosaurids included the largest 1969; Kitching 1977). It is probable that anteosaurines terrestrial predators the world had yet known. Increas- such as Anteosaurus preyed on the other dinocephalians ing body size in anteosaurine anteosaurids (culminating in upland environments, notably the gigantic (∼5m) in Anteosaurus magnificus) coincides with the appear- titanosuchids and tapinocephalids. Boonstra (1955, p. ance of the first terrestrial vertebrate megaherbivores 325) suggested that anteosaurs would have been “slink- (tapinocephalids and pareiasaurian parareptiles), suggesting carrion-eaters”, scavenging kills made by the common ing coevolution between predator and prey. The extinction lycosuchid and scylacosaurid therocephalians in the of dinocephalians towards the end of the Middle Permian Tapinocephalus Assemblage Zone. The sheer size of the left a major size gap in therapsid faunas, although this herbivorous dinocephalians would have made predation was eventually filled by the appearance of giant cryptodont by most gorgonopsians and therocephalians difficult, but and dicynodontoid dicynodonts (e.g. Rhachiocephalus) they would have been vulnerable to attack by the equally in the Late Permian (Maisch 2002). Following the re- enormous Anteosaurus. This is not to say that the large evolution of extremely large-bodied herbivorous therap- size of anteosaurines would not have made them profi- sids, the anteosaurine morphotype also reappeared, in the cient in stealing carcasses from other predatory therap- form of the gigantic rubidgeine gorgonopsians of south- sids, merely that, as in other groups of large-bodied terres- ern Africa, a group characterized by heavily pachyostosed trial predators (e.g. tyrannosaurid dinosaurs), an obligatory skulls, massive canines, and expanded supraorbital regions scavenging lifestyle is not likely (Holtz 2008). Anteosaurid (Sigogneau 1970). Another group of giant gorgonop- postcanines, with their massively thickened bases, faceted sians, the inostranceviids, evolved in Russia at the same surfaces, and obliquely angled serrations, are similar to the time in association with giant pareiasaurs (Scutosaurus) incrassate teeth of tyrannosaurids, which have been impli- (Ivakhnenko 2008). Although the Permo-Triassic mass cated in bone-crunching (Hurum & Currie 2000; Schu- extinction extinguished the anteosaurine body form in bert & Ungar 2005; Holtz 2008). Based on this dental the Therapsida, this morphotype later appeared in various similarity, bone-crunching may also have been an impor- large-bodied, predatory archosauriforms (erythrosuchids in tant component of anteosaurian feeding, although further the Early Triassic and ‘rauisuchians’ in the Middle and research on the functional morphology of the anteosaurid Late Triassic) coexisting with the giant kannemeyeriiform skull and dentition and taphonomy of anteosaurid-bearing dicynodonts (Sun 1980; Ivakhnenko et al. 1997; Langer et assemblages is necessary to test this hypothesis. al. 2007). Though anteosaurs themselves were one of the Ivakhnenko (2003, p. S382) proposed that the extreme shortest-lived therapsid clades, the anteosaurine morpho- pachyostosis of the supraorbital region in Titanophoneus type remained dominant in terrestrial top predators through- Downloaded by [University of Guelph] at 12:37 30 April 2012 and Anteosaurus served a protective function, for navigat- out the Permo-Triassic. ing “through dense nearshore helophyte thickets”. Given the dubious aquatic habits of anteosaurs, this proposal seems unlikely. Using finite element analysis, Young et Acknowledgements al. (2010) demonstrated that expansion of the supraorbital bones over the orbits acted as a stress sink in the hyper- For access to collections, kind thanks are given to Billy carnivorous thalattosuchian Dakosaurus. They suggested DeKlerk (AMG), Carl Mehling (AMNH), Paul Barrett that this morphology would have alleviated the high levels and Sandra Chapman (BMNH), Bruce Rubidge, Michael of cranial stress associated with feeding on large prey Raath, and Fernando Abdala (BPI), Johann Neveling (and potentially bone-crunching), and noted that simi- (CGP), Bill Simpson (FMNH), Li Jinling and Li Zhifeng larly thickened supraorbital regions are found in taxa with (IVPP), Jennifer Botha-Brink and Elize Butler (NMQR), potentially similar feeding strategies, such as mosasaurs, Andrey Kurkin and Mikhail Ivakhnenko (PIN), Sheena sebecosuchians, large theropods, and ‘rauisuchians’. Kaal (SAM), Stephany Potze (TM), Pat Holroyd (UCMP), Syodontines, which remained at relatively small body and Cesar Schultz and Juan Cisneros (UFRGS). I thank size throughout their history, lacked these cranial rein- Jun Liu for permission to publish my photographs of the forcements and would have been limited to small-bodied Chinese anteosaurs. I am grateful to Chris Sidor and James prey. The heavily pachyostosed frontoparietal region in Hopson for many engaging discussions of dinocephalian Systematics of the Anteosauria 297

phylogeny and for encouraging my interest in this topic odon bainii and Tropidostoma microtrema (Therapsida: throughout my scientific career. This research was under- Anomodontia). Palaeontology, 50, 1175–1209. taken as a graduate student in the Committee on Evolution- Broili, F. & Schroder¨ , J. 1935. Beobachtungen an Wirbeltieren der Karrooformation. VIII. Ein Dinocephalen- ary Biology at the University of Chicago, and was funded Rest aus den unteren Beaufort-Schichten. Sitzungsberichte in part by NSF DEB-0608415 to Neil Shubin and Christian der mathematisch-naturwissenschaftlichen Abteilung der Kammerer, the University of Chicago Hinds Fund, and a Bayerischen Akademie der Wissenschaften zu Munchen¨ , 1935, grant from Sigma Xi. The manuscript was greatly improved 93–114. by comments from Neil Shubin, James Hopson, Callum Broom, R. 1904. Notice of a new fossil reptile (Scapanodon duplessisi) from the Lower Karroo beds of Prince Albert, Ross, Peter Wagner and two anonymous reviewers. 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In tetrapod vertebrates. Proceedings of the Zoological Society of London, 1917, 167–186. anteosaurs, the serrated edges of the postcanines Watson,D.M.S.1921. The bases of classification of the Theri- are distinctly angled, with anterolingual and postero- odontia. Proceedings of the Zoological Society of London, labial branches. The postcanines of Archaeosyodon 1921, 35–98. lack serrations, and instead bear a ‘scalloped’ lingual Watson,D.M.S.& Romer, A. S. 1956. A classification of cingulum. Archaeosyodon is coded as ‘?’ for this therapsid reptiles. Bulletin of the Museum of Comparative Zoology, 114, 35–89. character. Westneat, M. W. 2004. Evolution of levers and linkages in the 3. Posteriormost upper postcanines canted postero- feeding mechanisms of fishes. Integrative and Comparative laterally: 0 [no]; 1 [yes]. In Titanophoneus and Biology, 44, 378–389. Anteosaurus, the last three to four postcanine teeth Wiegmann, A. F. 1828. Beytrage¨ zur Amphibienkunde. Isis are out-of-plane with the rest of the tooth row, (Oken), 21, 364–383. Williston, S. W. 1925. The Osteology of the Reptiles. Harvard being directed strongly backwards and somewhat University Press, Cambridge, MA, xiii + 300 pp. outwards. Sinophoneus is coded as ‘0’ for this char- Young, M. T., Brusatte, S. L., Ruta, M. & Andrade, M. acter based on the condition in the ‘Stenocybus’ spec- B. 2010. The evolution of Metriorhynchoidea (Mesoeu- imens. crocodylia, Thalattosuchia): an integrated approach using 4. Canine curvature: 0 [straight or slightly recurved; geometric morphometrics, analysis of disparity, and biome- curvature of canine measured as the angle between chanics. Zoological Journal of the Linnean Society, 158, ◦ 801–859. canine tip and canine base less than 40 ]; 1 [strongly recurved; curvature of canine measured as the angle between canine tip and canine base greater than 70◦]. Appendix 1: morphological characters Some degree of canine curvature is common to all Downloaded by [University of Guelph] at 12:37 30 April 2012 anteosaurs, but in Microsyodon, Archaeosyodon, and 1. Postcanine morphology: 0 [‘bladelike’, laterally Syodon, the canine is extremely recurved, with a compressed and pointed]; 1 [robust, bulbous at ‘hook’-like morphology. base of crown]; 2 [phylliform, laterally compressed 5. Incisors with lingual heels: 0 [no]; 1 [yes]. (Char- and leaf-shaped with roughly denticulated edges]. acter 5.3 of Hopson & Barghusen 1986; Character (Modified version of Character 12.2 of Hopson 1 of Rubidge & van den Heever 1997). The pres- & Barghusen 1986; Character 2 of Rubidge & ence of lingual heels on the incisor teeth has long van den Heever 1997). Basal therapsids, such as been considered one of the key diagnostic features Biarmosuchus, generally have laterally compressed, of dinocephalians (Watson 1914). All anteosaurs and triangular postcanines with finely serrated anterior tapinocephalids for which the relevant dentition is and posterior edges. Tapinocephalian dinocephalians preserved bear lingual heels on the incisors, but have leaf-shaped postcanines with large denticles, incisor heels are absent in Estemmenosuchus. rather than fine serrations, running along the cutting 6. Location of external naris: 0 [terminal]; 1 [nonter- edges of the teeth. Anteosaurs have characteristically minal]. (Character 8 of Sidor 2000). The presence of bulbous postcanines with thickened bases, usually a nonterminal external naris has been considered a conical crowns, and serrations that, when present, are dinocephalian synapomorphy (Hopson 1991; Grine fine. Anteosaur postcanines also usually feature wear 1997; Sidor 2000). However, one of the features Systematics of the Anteosauria 301

Cheng & Ji (1996) used to diagnose Sinophoneus rior to the incisors that separates the vomers from was possession of a terminal external naris. This the tooth row. This represents an expansion of the apparent conflict seems to be the result of differing main body of the premaxilla, not elongation of the usages of the term ‘terminal naris’. In Sinophoneus, vomerine process as in anomodonts (Sidor 2000). the naris begins and ends anterior to the level of the 10. Vomers with ‘scroll-like’ raised edges: 0 [no]; 1 canine, whereas in most specimens of Anteosaurus, [yes]. A great diversity in vomerine morphology the naris begins over the canine and ends posterior to exists among non-mammalian therapsids, with both it. However, narial position with regards to the canine fused and unfused vomers represented, some with is not consistent even within a species, as demon- median ridges and others with median troughs strated by specimens of Anteosaurus (e.g. SAM-PK- (Sidor 2000). Anteosaurs exhibit a unique vomer- 9329a, 11577) in which the naris begins anterior to ine morphology in which the lateral edges of the the canine and ends over it. In this analysis, ‘terminal’ vomers are elongated, plate-like structures, extend- or ‘nonterminal’ refers to the distance between the ing well below a deep central vomerine trough. In external naris and the alveolar margin of the premax- anteosaur specimens where the vomer is exception- illa, i.e. height of the premaxilla. In basal therapsids ally well preserved (e.g. PIN 250/1, the holotype such as Biarmosuchus, the external naris is located of Titanophoneus adamanteus, and PIN 157/2, the close to the ventral margin of the upper jaw, such that holotype of Syodon efremovi), these raised edges the distance between the premaxillary margin and curl medially over the main body of the vomer, nearly the external naris is less than the height of the naris contacting each other. All anteosaurid taxa are coded itself. In most anteosaurs (but not Archaeosyodon), as ‘1’ for this character except for Microsyodon the premaxilla is dorsoventrally expanded, such that and Notosyodon, in which the vomer is unknown, the distance between the premaxillary margin and the and Sinophoneus, in which it is extremely poorly external naris is greater than the height of the naris. preserved. Although the vomers are poorly preserved Under this definition, Sinophoneus is considered to or absent in most specimens of Archaeosyodon,they possess a nonterminal naris. A nonterminal naris is are relatively complete in PIN 1758/93 and clearly also present in most tapinocephalians, but the prim- have raised edges. itive condition is present in Estemmenosuchus. 11. Morphology of the dentigerous region of the pala- 7. Alveolar margin of premaxilla: 0 [subhorizontal]; tine: 0 [elongate triangular region]; 1 [distinct reni- 1 [canted upwards]. (Character 12.1 of Hopson & form boss]. In Biarmosuchus and various other basal Barghusen 1986; Character 19 of Rubidge & van den therapsids, the numerous palatine teeth occur in an Heever 1997; Character 2 of Sidor 2000). In most elongate, vaguely triangular raised patch on each therapsids, the ventral margin of the premaxilla is palatine. In dinocephalians, the palatine teeth are horizontal or slightly angled upwards in lateral view. borne on a prominent reniform boss. This boss is One of the most striking features of the anteosaurian lost in some tapinocephalids, but is present in basal skull is the extreme upward cant of the premaxillary members of all major tapinocephalian groups (e.g. margin, generally at an angle of 30–35◦ relative to Estemmenosuchus, Tapinocaninus)aswellasall the ventral margin of the maxilla. anteosaurs. 8. Alveolar margin of the precanine region: 0 [straight]; 12. Dentition on palatine: 0 [multiple tooth rows]; Downloaded by [University of Guelph] at 12:37 30 April 2012 1 [concave]. In most anteosaurs, the premaxilla cants 1 [single tooth row]. Among the dinocephalians upwards in a roughly straight line, in line with the included in this analysis, Archaeosyodon and Estem- anterior edge of the maxilla. In Titanophoneus and menosuchus retain the primitive therapsid condi- Anteosaurus, the anterior tip of the premaxilla angles tion of multiple rows of teeth on each pala- ventrally, making the alveolar margin of the preca- tine. In Tapinocaninus and all non-Archaeosyodon nine region concave. anteosaurs in which the palatine is preserved, there 9. Premaxilla forms broad, triangular plate palatally is only a single row of teeth on the palatine, although that separates anterior edge of vomers from incisor some anteosaur specimens (e.g. Syodon, Australosy- tooth row: 0 [no]; 1 [yes]. In basal therapsids, odon) exhibit sets of smaller replacement teeth out- tapinocephalians and Archaeosyodon,thevomer of-plane with the main palatine tooth row. abuts the posterior edge of the premaxilla imme- 13. Dentition on palatal ramus of pterygoid: 0 [numerous diately behind the incisor alveoli. In these taxa, the teeth]; 1 [reduced, 1 or 0 teeth]. (Modified version anteroposterior extent of the premaxilla is of uniform of Character 51 of Sidor 2000). In Biarmosuchus, length along the posterior rim of the incisor tooth plentiful palatal teeth are present in a confluent row. In all anteosaurs other than Archaeosyodon in patch that extends across the palatines and ptery- which the premaxilla is known, the palatal surface of goids. As mentioned above, in dinocephalians the the premaxilla forms a broad, triangular plate poste- palatine teeth are restricted to a distinct reniform 302 C. F. Kammerer

boss. Additionally, the palatal ramus of the ptery- processes are massively expanded distally, producing goid in dinocephalians is developed into a ridge a ‘palmate’ morphology. running anterolaterally from the midpoint of the 17. Quadrate rami of pterygoids intimately appressed, transverse processes and eventually contacting the bifurcating the anterior margin of the basisphenoid: palatine boss. In Archaeosyodon, Australosyodon 0 [no]; 1 [yes]. (Character 54 of Sidor 2000). In and Estemmenosuchus, this ridge is covered with basal therapsids and tapinocephalians, an anterior numerous teeth, but other anteosaurs have only a ramus of the basisphenoid separates the two quadrate single tooth (e.g. Syodon, Titanophoneus adaman- rami of the pterygoids. In anteosaurs, however, the teus) or no teeth (e.g. Anteosaurus, Titanophoneus quadrate rami remain closely appressed, bifurcating potens) on the palatal ramus of the pterygoid. the anterior margin of the basisphenoid. 14. Dentition on transverse process of pterygoid: 0 18. Ventral margin of maxilla: 0 [subhorizontal]; 1 [extensive, present along the majority of the palatal [highly convex]. (Character 10 of Sidor 2000). The surface]; 1 [absent or reduced to a few teeth at the ventral maxillary margin of anteosaurs features a medial edges of the processes]. (Modified version greater convexity than most other therapsids (includ- of Character 16 of Rubidge & van den Heever ing other dinocephalians), such that the canine alveo- 1997; Character 52 of Sidor 2000). Primitively in lus is directed anteroventrally (at an angle of 20–30◦ therapsids, numerous teeth are present on the ventral relative to the long axis of the skull) rather than surface of the transverse processes of the pterygoids. ventrally. These teeth have been lost to varying degrees in 19. Dorsal margin of maxilla: 0 [gently rounded, several therapsid groups, including anteosaurs. The with no overhang on lacrimal]; 1 [with dorso- primitive condition is present in Archaeosyodon,but posterior process partly overhanging upper margin other anteosaurs have only a few teeth on the trans- of lacrimal]. In Biarmosuchus, Microsyodon and verse processes or none at all. In those taxa where Archaeosyodon, the dorsal sutural border of the a few teeth are present, they are generally restricted maxilla is essentially rounded. In other anteosaurs, to the medial edge of the transverse process, rather the posterior dorsal border of the maxilla features than extending along the entirety of the process as a prominent process contacting the prefrontal and in the primitive condition (an exception is PIN 157/1, overhanging the anterior edge of the lacrimal. the lectotype of Titanophoneus potens, in which 20. Dorsal margin of snout: 0 [gradually sloping towards a single tooth is present on the distally expanded tip]; 1 [markedly concave, sloping upwards acutely portion of the process). There is some evidence that post-naris]. Titanophoneus and Anteosaurus exhibit the presence of these teeth is an age-related feature, a concave dorsal snout margin, with a ‘dip’ between as smaller specimens (e.g. PIN 157/1 and IGCAGS the frons and snout tip creating a roughly ‘shoe- V 361, the holotype of Stenocybus acidentatus) shaped’ skull. This distinctive feature of the giant feature teeth on the transverse processes that are anteosaurs has largely been overlooked in treat- absent in larger individuals of the same taxa (e.g. ments of the Russian forms. Orlov (1958) correctly PIN 157/3, the holotype of Doliosauriscus yanshi- depicted this feature in his figure (Orlov 1958, fig. 5) novi, and GMV 1601, the holotype of Sinophoneus of the holotype of Doliosauriscus yanshinovi (PIN yumenensis). Sidor & Welman (2003) came to the 157/3), but, noting that this skull had been subject to Downloaded by [University of Guelph] at 12:37 30 April 2012 same conclusion concerning the development of dorsoventral compression, also featured an ‘unde- these teeth in the burnetiamorph Lemurosaurus. formed’ reconstruction of the skull (Orlov 1958, 15. Transverse process of pterygoid with posterior shelf: figs 6, 15) that erroneously completely straightened 0 [no]; 1 [yes]. (Character 15.5 of Hopson & out the snout. Unfortunately, this reconstruction has Barghusen 1986; Character 7 of Rubidge & van den been the basis for most subsequent consideration Heever 1997; Character 50 of Sidor 2000). A distinct of the specimen (e.g. Boonstra 1963; Ivakhnenko shelf making up the posterior part of the transverse 2003), causing the similarity in snout curvature with process of the pterygoid is a characteristic feature of Anteosaurus to be ignored. tapinocephalians. This shelf is absent in basal thera- 21. Snout proportions: 0 [relatively short and broad, psids and anteosaurs. snout width posterior to canine greater than 35% 16. Transverse process of pterygoid: 0 [not expanded of total dorsal skull length]; 1 [long and narrow, distally in palatal view]; 1 [palmate, massively snout width posterior to canine less than 25% of expanded distally]. In basal therapsids and most total dorsal skull length]. Most dinocephalians have anteosaurs, the anteroposterior width of the trans- a relatively broad skull, with a snout width equiv- verse processes of the pterygoid is not appreciably alent to over a third of the skull length. In Syodon different at the proximal and distal ends. However, in and Australosyodon, the snout is relatively long and Sinophoneus, Titanophoneus and Anteosaurus, these narrow, with a snout width equivalent to less than Systematics of the Anteosauria 303

a quarter of the skull length (although the propor- tor area, excepting only the orbital rim, made of the tions of NMQR 3152, the holotype of Australosy- postorbital]. Although the attachment site for the jaw odon nyaphuli, have been somewhat distorted by adductor musculature in all anteosaurs is expanded lateral crushing, the preserved skull can still be compared to basal therapsids such as Biarmosuchus, recognized as signiﬁcantly narrower than similarly most anteosaurian taxa retain the primitive condition distorted anteosaurid skulls, such as PIN 520/1, the of excluding the frontals from the adductor area. In holotype of Titanophoneus adamanteus). A long, Notosyodon, the frontal contributes to the adductor narrow snout is also present in Biarmosuchus and area, but only medially. In Syodon and Australosyo- most basal therapsids. don, the frontal is the major element making up the 22. Ridge extending along external surface of jugal- attachment area’s anterior border. lacrimal suture: 0 [absent]; 1 [present]. An exter- 27. Jaw adductor musculature attachment on pineal boss: nal ridge on the lateral surface of the maxilla asso- 0 [absent]; 1 [present]. The attachment site for the ciated with the root of the canine is typical for jaw adductor musculature extends to the sides of the therapsids, but unique to anteosaurs is a promi- pineal boss in Syodon, Notosyodon and Australosy- nent ridge along the jugal-lacrimal suture, extend- odon. ing to the orbital rim. This ridge is visible even 28. Shape of postorbital bar: 0 [gently curved]; 1 [strong in poorly preserved anteosaurian skulls such as anteroventral curvature, temporal fenestra undercuts the holotype of Australosyodon nyaphuli (NMQR orbit]. (Character 19 of Sidor 2000). In most thera- 3152). psids, the temporal fenestra and the orbit are sepa- 23. Location of fronto-nasal suture: 0 [far anterior to rated by an essentially straight postorbital bar, such orbits]; 1 [at anterior edge of orbits]. The frontals that the anterior margin of the temporal fenestra of Biarmosuchus and Archaeosyodon extend to a is located entirely posterior to the orbit in lateral level far beyond the orbital region (in Biarmosuchus, view. In anteosaurs, however, the postorbital bar 2.5 cm anterior to the orbit on a 20.9 cm long skull, curves anteroventrally, such that the temporal fenes- and in Archaeosyodon, 5.3 cm anterior to the orbit on tra undercuts the orbit in lateral view. 30.3 cm long skull). In contrast, the anterior edge of 29. Postorbital bar: 0 [transversely narrow] 1 [trans- the frontals of tapinocephalians and later anteosaurs versely expanded]. The postorbital bar is thin in basal is located at roughly the same level as the anterior therapsids, but is markedly expanded transversely in edges of the orbits. certain taxa, such as tapinocephalid dinocephalians. 24. Interorbital crest on midline of frontals: 0 Transverse expansion of the postorbital bar is present [absent]; 1 [present]. Whereas Archaeosyodon and in Sinophoneus, Titanophoneus and Anteosaurus tapinocephalians have ﬂat frontal sutures, several among anteosaurs. anteosaurs have low interorbital crests on the frontal 30. Pachyostosis of skull: 0 [absent]; 1 [pachyostosis midline. In Australosyodon, the interorbital crest present but restricted to orbital and temporal rims]; extends laterally, forming a small boss. In Sino- 2 [entire dorsal surface of skull heavily pachyos- phoneus, the crest becomes extremely well devel- tosed]. Cranial pachyostosis is present in several oped on the nasals, but the interorbital portion groups of therapsids (e.g. burnetiamorphs, rubidgeid is low and weak, as in other anteosaurids. The gorgonopsians), but is most common and strongly Downloaded by [University of Guelph] at 12:37 30 April 2012 midfrontal suture is obliterated by pachyostosis in developed in the Dinocephalia. Extremely pachyos- Titanophoneus adamanteus and Anteosaurus,so tosed skulls are present in tapinocephalians and the these taxa are coded as ‘?’. In large specimens of giant anteosaurs Titanophoneus and Anteosaurus. Titanophoneus potens (e.g. PIN 157/3), the frontal In these taxa, the snout as well as the orbital region is too heavily pachyostosed to tell, but smaller and temporal regions is heavily pachyostosed. In specimens (e.g. PIN 157/1) demonstrate that a weak other anteosaurs, however, the skull is only weakly interorbital crest was present. pachyostosed around the orbit and temporal rim (e.g. 25. Frontal contribution to anterior border of pineal Syodon, Notosyodon, Sinophoneus) or not pachyos- boss: 0 [absent]; 1 [present]. In most anteosaurs, tosed at all (Archaeosyodon). An unpachyostosed the pineal boss is made up entirely of the parietals, skull is present in Biarmosuchus. but in Syodon, Notosyodon, and Australosyodon,the 31. Shape of symphysial region of mandible: 0 [ante- frontals have posterior processes that contribute to rior edge gradually sloping upwards]; 1 [anterior the anterior border of the boss. edge massive, nearly vertical]. Titanophoneus and 26. Frontal forms anterior margin of area of jaw adduc- Anteosaurus differ from basal therapsids and most tor musculature attachment: 0 [no]; 1 [frontal forms other anteosaurs in that their dentaries have a only medial anterior border of adductor area]; 2 massive, almost vertical anterior border as opposed [frontal forms majority of anterior border of adduc- to a gently sloping one. Although the lower jaw 304 C. F. Kammerer

is not preserved in the holotype of Sinophoneus essentially uniform height between the canine and (GMV 1601), this taxon appears to have had a coronoid process. Titanophoneus-style dentary based on the condition 34. Angular boss: 0 [absent]; 1 [present]. (Character 13.1 in ‘Stenocybus.’ of Hopson & Barghusen 1986; Character 66 of Sidor 32. Dentary with marked ‘step’ down after canine: 2000). A prominent, pachyostosed, ovoid boss on 0 [no]; 1 [yes, canine on an elevated plat- the lateral surface of the angular is present in the form relative to all postcanines]. (Character 58 of giant anteosaurids Titanophoneus and Anteosaurus. Sidor 2000). In Biarmosuchus, Archaeosyodon and The condition in Sinophoneus is unknown, as the tapinocephalians, the lower postcanines are immedi- holotype (GMV 1601) lacks a lower jaw. Both spec- ately posterior to the lower canine and are at least imens of Stenocybus lack an angular boss, but this is in part on a level with the canine. In Estemmeno- considered inconclusive, as development of the boss suchus, the postcanines are actually located higher appears to be a size-related feature (in PIN 157/1, on the dentary than the canine, and continue medi- the lectotype of Titanophoneus potens, the boss is ally to it. In most anteosaurs, on the other hand, the present but small and poorly developed, and the same lower postcanine row is separated from the canine is true of smaller Anteosaurus jaws). As such, Sino- by a distinct ‘step’, with the postcanines located at a phoneus is coded as ‘?’ in this analysis. level ventral to the base of the canine. 35. Position of jaw articulation: 0 [at back of skull]; 33. Dentary proportions in the region posterior to the 1 [rotated forward]. (Character 15.1 of Hopson & canine and anterior to the coronoid process: 0 Barghusen 1986; Character 5 of Rubidge & van [dorsoventrally narrow, constricted at region of post- den Heever 1997; Character 55 of Sidor 2000). canine tooth row]; 1 [tall, of constant height]. In Biar- A terminal posterior position for the suspenso- mosuchus, Syodon and Australosyodon, the dentary rium is primitive for therapsids in general, includ- is relatively thin and of uneven height posterior to the ing dinocephalians. In two types of dinocephalians, canine, narrowing most markedly at the anterior half the suspensorium has been rotated forward: of the postcanine tooth row. In Archaeosyodon, Sino- tapinocephalians (extremely so in tapinocephalids) phoneus (based on ‘Stenocybus’), Titanophoneus and the giant anteosaurs Titanophoneus and and Anteosaurus, the dentary is massive and of Anteosaurus. Downloaded by [University of Guelph] at 12:37 30 April 2012 本文献由“学霸图书馆-文献云下载”收集自网络，仅供学习交流使用。

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