Sungeodon kimkraemerae n. gen. n. sp., the oldest ...

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N. Jb. Geol. Paläont. Abh. 272/1 (2014), 1–12 Stuttgart, April 2014

Article

Sungeodon kimkraemerae n. gen. n. sp., the oldest kannemeyeriiform (Therapsida, Dicynodontia) and its implications for the early diversification of large herbivores after the P/T boundary Michael W. Maisch and Andreas T. Matzke With 3 figures

Abstract: The dicynodont Sungeodon kimkraemerae n. gen. n. sp. is described on the basis of a skull from the Lower Triassic Jiucaiyuan Formation of Dalongkou (Junggar Basin, Xinjiang Uygur Autonomous Region, People’s Republic of China). It is the first representative of Kannemeyeriiformes from the earliest Triassic. Kannemeyeriiforms were the predominant clade of Triassic dicynodonts, which constituted a major component of terrestrial Triassic ecosystems. The new taxon helps closing one of the most significant gaps in the fossil record of dicynodonts, since stem-kannemeyeriiforms are known from the Late Permian, whereas the first true kannemeyeriiforms previously known are late Early Triassic in age. After a phylogenetic analysis Sungeodon belongs to the family Stahleckeriidae. Therefore, the Stahleckeriidae may not have had its origin in Africa as previously assumed, but in Central Asia. More importantly, Sungeodon also suggests that the major radiation of kannemeyeriiform dicynodonts, including the emergence of all relevant subgroups of this clade, occurred not later than in the Early Triassic, soon after the end-Permian extinction. To date, only few dicynodont taxa are known from the earliest Triassic, none of which are kannemeyeriiforms. The addition of Sungeodon confirms previous predictions that our knowledge of Early Triassic dicynodont diversity and evolution is far from being complete, and that new discoveries from historically low-sampled geographic regions may fill this gap. A rapid post-extinction diversification of kannemeyeriiforms also fits with the emerging picture from other clades, such as archosaurs, of a rapid recovery from the end-Permian event in the terrestrial realm. Key words: Anomodontia, Kannemeyeriiformes, fossil record, end-Permian extinction, phylogeny, adaptive radiation.

boundary. Only a few genera and species are known to have survived into the earliest Triassic, including the famous, species-rich genus Lystrosaurus (i.e. in particular the species Lystrosaurus curvatus, Botha & Smith 2007) with an almost global distribution, and the small, perhaps burrowing Myosaurus. Lystrosaurus and its sister-taxon Kwazulusaurus (King 1997; Maisch 2002; Botha & Smith 2007) are already known from the Late Permian of South Africa. Lystrosaurids have not been found in sediments younger than the Early Triassic. Instead, they are replaced by a

1. Introduction Dicynodonts are among the most important terrestrial herbivores in the Permian and Triassic. They are highly diverse and have a significant fossil record in many areas of the world, most notably southern and south-eastern Africa, European Russia, Argentina, Brazil, India and China, although they have been recorded from all continents, including Antarctica (Fröbisch 2009). It is generally accepted that dicynodonts suffered a significant decrease in diversity across the P/T©2014 E. Schweizerbart’sche Verlagsbuchhandlung, Stuttgart, Germany

DOI: 10.1127/0077-7749/2014/0394

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M.W. Maisch and A.T. Matzke

Fig. 1. Holotype of Sungeodon kimkraemerae n. gen. n. sp., SGP 2002-Tr001, Jiucaiyuan Formation, Lower Triassic, of Dalongkou, Junggar Basin, Xinjiang, China. A, B – Right lateral, C – left lateral, and D, E – dorsal views. Abbreviations: ang, angular; d, dentary; f, frontal; j, jugal; l, lacrimal; mx, maxilla; n, nasal; pal, palatine; pmx, premaxilla; prf, prefrontal; pt, pterygoid; sg, surangular; smx, septomaxilla; sph, sphenethmoid. Scale bar equals 50 mm.

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Sungeodon kimkraemerae n. gen. n. sp., the oldest kannemeyeriiform (Therapsida, Dicynodontia)

diverse group of medium-sized to large-growing dicynodonts in the latest Early, Middle and Late Triassic, the Kannemeyeriiformes, generally accepted to form a monophyletic assemblage (see Kammerer et al. 2011 for the most recent analysis). Typical representatives of this taxon are the latest Early to Middle Triassic Kannemeyeria from South Africa, Stahleckeria from the Middle Triassic of Brazil and Placerias from the Late Triassic of the United States. Recent discoveries from the Germanic Basin indicate that kannemeyeriiforms survived up to the end of the Triassic (Dzik et al. 2008). A possible Early Cretaceous record from Australia remains controversial (Thulborn & Turner 2003). The origins of the kannemeyeriiformes are not perfectly clear, but it has been assumed that the rare, large-growing Dinanomodon from the Late Permian of South Africa represents a stem-kannemeyeriiform (Maisch 2001; Damiani et al. 2007), whereas other analyses indicate that taxa such as the Late Permian Turfanodon, may be even more closely related (Kammerer et al. 2011). Accepting this hypothesis, there is a significant gap in the fossil record of this group, spanning almost the entire Early Triassic. In the Middle Triassic, all subclades of the kannemeyeriiforms (shansiodontids, kannemeyeriids, stahleckeriids, sinokannemeyeriids) are already present and highly diversified. This points to an earlier, presumably earliest Triassic, radiation of the group. So far, there was no fossil record of earliest Triassic kannemeyeriiforms to substantiate these hypotheses. Here we describe an incomplete skull of a new kannemeyeriiform dicynodont from the Early Triassic of north-western China. It was discovered in summer 2002 by one of us, associated with several skulls and skeletons of Lystrosaurus and remains of Proterosuchus, so that its stratigraphic placement in the Early Triassic appears well-founded. It is thus the stratigraphically earliest record of a true kannemeyerii form dicynodont. Surprisingly, as will be shown, it is not a very basal member of the group, as would be expected, but more probably a plesiomorphic representative of the Stahleckeriidae, the most highly derived subclade within kannemeyeriiforms. This implies a much faster and more “explosive” adaptive radiation of kannemeyeriiforms very early in the Triassic, maybe even an initial radiation in the Upper Permian, and has significant impacts on our perception of the effects of the P/T-boundary-event on the dicynodont therapsids, one of the vertebrate groups apparently most affected by the event.

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2. Systematic palaeontology Dicynodontia Owen, 1859 Kannemeyeriiformes von Huene, 1948 Stahleckeriidae Lehman, 1961 Genus Sungeodon n. gen. Etymology: In honour of Prof. Dr. Sun Ge, of Jilin University, for his great support during our scientific work in Xinjiang, and from Greek odous (tooth), referring to the big tusks of the specimen. Type species: Sungeodon kimkraemerae n. sp., monotypic. Diagnosis: See diagnosis of the type species.

Sungeodon kimkraemerae n. sp. Figs. 1-2 Etymology: In honour of Kim Krämer, former technician at the Staatliches Museum für Naturkunde Stuttgart, who skilfully did the difficult preparation of the holotype. Holotype: SGP-2002-Tr-001 – the specimen is currently housed for study at the Eberhard Karls University in Tübingen, Germany. The entire collection of the SGP-project remains property of the People’s Republic of China and will be returned after scientific investigation has finished. The final repository is to be announced in a widely circulated international journal. Type locality: Dalongkou near Jimusar, southern Junggar Basin, Xinjiang Uygur Autonomous Region, People’s Republic of China. Type horizon: Middle part of the Jiucaiyuan Formation, Lower Triassic (Griesbachian). Diagnosis: Medium-sized dicynodont, skull very short and high, maxilla with long ascending process and pronounced median ridge, maxilla with large tusks, no postcaniniform crest, no embayment anterior to caninform process, nasals with very short median suture, frontals with extensive anterior and narrow lateral process, no nasal or prefrontal bosses, labial fossa present, bordered by maxilla and palatine, lower jaw with short and high symphysis, lateral dentary shelf very weakly developed, prearticular very high.

3. Description The specimen (Figs. 1-2) preserves the skull up to the level of the orbits, as well as most of the lower jaw, which is preserved for a length of 18 cm. The postorbital bars and entire postorbital skull segment are missing. The right lower jaw ramus is largely complete up

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Fig. 2. Holotype of Sungeodon kimkraemerae n. gen. n. sp., SGP 2002-Tr001, Jiucaiyuan Formation, Lower Triassic, Dalongkou, Junggar Basin, Xinjiang, China. A – Anterior view, B – close-up of the left naris with the septomaxilla, and C, D – area of the fossa labialis in the right part of the skull. Abbreviations see Fig. 1.

partially exposed by weathering. The right side is therefore generally better preserved. It has been prepared purely mechanically. The premaxillaries are complete and fully fused. Their entire lateral and dorsal surface is markedly ru-

to the lamina reflecta angularis, only the glenoidal portion and retroarticular process are absent. The left lower jaw ramus preserves the symphyseal region only. The skull has suffered much from lateral compression and was collected lying on its side with the left side

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surrounding skull roof elements posteriorly. A large septomaxillary foramen is present between the septomaxilla and the lacrimal. The anterodorsal margin of the septomaxilla bears a deep notch. Due to compression, the lacrimal is not well preserved on both sides of the skull, but on the left side its borders can be clearly seen. It forms the anteroventral orbital margin, being pierced by a single foramen lacrimale. Anteriorly the lacrimal intervenes between the nasal and the maxilla, reaching the posterior margin of the septomaxilla. The prefrontal, as the lacrimal, is better preserved on the left side. Ventrally, it forms a serrated anteroposteriorly running suture with the lacrimal. Anteriorly a serrated contact with the nasal is established, whereas medially a more straight suture with the frontal is formed. The prefrontal is elongate anteroposteriorly in dorsal view. It bears no prefrontal boss and its anterodorsal border is not markedly thickened. Both frontals are almost complete. They form a straight median suture. Anteriorly, they extend between the nasals via a pair of markedly developed anterior frontal processes, but fail to meet the premaxilla. A lateral process, preserved only on the right side, extends laterally posterior to the prefrontal, forming a rather narrow part of the dorsal orbital margin. It remains unclear whether a postfrontal was present. The right frontal only shows a posterior sutural facet which may have received either postfrontal, postorbital or both. The anterior end of the jugal is preserved on the right side. It is laterally largely covered by the suborbital process of the maxilla. On the medioventral surface of the suborbital arch it extends towards the labial fossa, but fails to meet it. Instead, the maxilla underlaps a tongue-shaped process of the jugal and extends further medially below it to establish contact with the dorsal exposure of the palatine (Fig. 2C, D). The jugal takes part in the formation of the ventral orbital margin where it meets the lacrimal at about half orbital length, excluding the maxilla from the orbit. Much of the sphenethmoid is preserved. It is a thin, vertical plate of bone somewhat expanding dorsally. Anterodorsally there is a marked sulcus, bordered by a ridge ventrally, that probably indicates the course of the nervus olfactorius. There is no evidence for more than one ossification in the sphenethmoid complex. Posteroventrally the sphenethmoid rested on the presphenoid, but the exact nature of the contact and detailed morphology of the presphenoid are unintelligible due to compression.

gose, indicative of horny covering in vivo. The preservation of the bone surface is not good enough to assess the presence of nutritive foramina, which would also be indicators of horny covering. A low median premaxillary ridge extends from the anterior alveolar border to the posterior end of the ascending premaxillary process, where it terminates. The anterior margin of the premaxillaries is blunt and rounded. A sagittal notch is present at the alveolar border. The premaxillamaxilla suture extends straight ventrally from the external naris. It is slightly serrated and aligned with the premaxillary-nasal suture. The maxilla is largely preserved but its posterolateral zygomatic process is missing. It bears a large and conspicuous processus caniniformis with a rugose surface similar to that on the premaxilla. Dorsal to the process, the surface of the bone is smooth, indicating that no horny covering was present there. There is no notch or embayment anterior to the processus caniniformis and a postcaniniform crest is lacking. The process bears a long, slender, slightly curved tusk. The tusk is incomplete apically on both sides, but still extends almost to the ventral border of the mandible. On the left side the maxilla is weathered so that most of the root of the tusk, which reaches the level of the ventral orbital margin, is exposed. It is about 15 cm in total preserved length. Posteriorly the maxilla and palatine form the borders of a large and well-developed fossa labialis. The maxilla broadly contacts the pterygoid posteromedially. There is no evidence for a separate ectopterygoid. Dorsally, the maxilla contacts the septomaxilla and lacrimal. No contact with the nasal is present. A sharp crest is formed by the maxilla at the anteroventral margin of the suborbital arch. The nasals are separated for most of their length by the ascending process of the premaxilla and the anterior processes of the frontals. Their midline suture is therefore short (about 2 cm), measuring less than one third the length of the bone. The entire nasal surface is pitted and rugose, indicating horny covering. Although the nasals are convex dorsally, they do not bear distinct nasal bosses. Their general morphology is very reminiscent of Kannemeyeria and numerous other kannemeyeriiforms. The septomaxilla (Fig. 2B) is large. It forms the entire posterior and ventral border of the external naris, which is bordered by the premaxilla anteriorly and the nasal dorsally. The septomaxilla contacts the lacrimal along its posterodorsal and the nasal along its anterodorsal margin. The septomaxilla has a significant facial exposure, its surface merging smoothly with the

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Fig. 3. Strict consensus tree of the two most parsimonious trees showing the phylogenetic position of Sungeodon kimkraemerae n. gen. n. sp. within kannemeyeriiforms. Dicynodon and Dinanomodon are outgroups. Coding for Dinanomodon is based on the type specimen of Dinanomodon rubidgei only. Tree length 149 steps, CI 0.44; RI 0.57.

dentary are so tightly fused that no clear suture is visible, indicating that the specimen represents a fully mature individual. The anterior symphyseal surface bears a marked sagittal ridge and is very rugose and corrugated. The lateral dentary surface, in contrast, is smooth, indicating the absence of a horny covering there. On the left side, a short shallow dorsal dentary sulcus is present, bordered by a high medial but much lower lateral ridge. A lateral dentary shelf is present, extending from the level of the processus caniniformis backwards, but it is very weak. The entire dentary is

Parts of the anterior palatal rami of both pterygoids are preserved. The pterygoid contacts the maxilla extensively on the lateral surface of the palatal bar. Dorsally, the pterygoid contacts the palatine, which forms the posterior border of the fossa labialis, and the presphenoid complex. A small portion of the vomer is visible anteroventral to the sphenethmoid complex, apparently forming part of its support. The dentary is completely preserved on the right side. It forms a very high, posteroventrally sloping symphysis together with the splenial. The splenial and

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found to be the sister-group of the kannemeyeriiforms. The position of Xiyukannemeyeria as a sister-taxon of Sinokannemeyeria and Parakannemeyeria advocated by Liu & Li (2003) was corroborated. In addition, a monophyletic Shansiodontidae, comprising Shansiodon and Tetragonias, but not Vinceria, was found. Instead Vinceria appears as the sister taxon of the remaining kannemeyeriiforms. Probably this is a result of the recent synonymization of Vinceria andina and Kannemeyeria argentinensis by Renaut & Hancox (2001); two taxa may be distinct (see also Domnanovich & Marsicano 2012). The remaining kannemeyeriiforms are distributed among three monophyletic groups. One of these, the Kannemeyeriidae, comprises Kannemeyeria and Wadiasaurus (as proposed by Maisch 2001). The second, the sinokannemeyeriids, comprise Sinokannemeyeria, Parakannemeyeria and Xiyukannemeyeria, with Dolichuranus as sister taxon. The third group, including the majority of Triassic dicynodonts, is the Stahleckeriidae. That Dolichuranus is not the sister taxon of the Stahleckeriidae, as proposed by Damiani et al. 2007, but rather of the Sinokannemeyeriidae certainly results from the different taxon sampling and different set of characters of both analyses. Damiani et al.’s (2007) analysis includes many Permian, but few Triassic dicynodonts, the sinokannemeyeriids are, e.g., completely omitted. This is also the reason, why the phylogenetic analyses of Maisch (2001) and Vega-Dias et al. (2004), who included larger samples of Triassic taxa, were preferred in the present paper. Most surprisingly, Sungeodon is found as a member of the Stahleckeriidae, being even more derived than Dinodontosaurus and forming a polytomy with Placerias and the remaining stahleckeriids (Stahleckeria, Angonisaurus, Ischigualastia and Jachaleria). This placement is also reproduced in a 50% majority rule consensus tree, with a bootstrap value of 54 for all stahleckeriids above Dinodontosaurus. The genus Sungeodon is accordingly classified here as a member of the family Stahleckeriidae. Apart of Dinodontosaurus and Placerias (and, probably Moghreberia), it is the only tusked stahleckeriid known, as well as the by far oldest member of the group.

unusually high and short, as is the complete lower jaw and skull. The angular is very short, as well, forming the entire ventral border of the large, elongated, oval fenestra mandibularis. A well-developed lamina reflecta angularis extends posteroventrally. It is remarkably thin (about 1-2 mm only). As the glenoidal region is missing, it is not known how much it approached the articular. On the medial surface of the mandible, the extensive and unusually high prearticular is remarkable, which closes off the medial opening of the fenestra mandibularis almost entirely. The ventral margin of the prearticular is reinforced by a pronounced ridge.

4. Phylogenetic analysis In order to assess the phylogenetic position of Sungeodon, a phylogenetic analysis of Triassic and some Permian dicynodonts was conducted, building on the data matrices of Maisch (2001) and Vega-Dias et al. (2004). We refrained from employing the more recent analysis by Kammerer et al. (2011) for two reasons, because of its more stringent focus on the non-kannemeyeriiform taxa, and because of its rather extensive employment of continuous morphometric characters. The Permian forms Dicynodon lacerticeps and Dinanomodon gilli were used as outgroups. The lystrosaurids Lystrosaurus and Kwazulusaurus were both included in the analysis, to test the possibility if Sungeodon was an aberrant lystrosaurid instead of a kannemeyeriiform. In addition to the kannemeyeriiform taxa analysed by Vega-Dias et al. (2004) the recently re-described genera Vinceria (including Kannemeyeria argentinensis, see Renaut & Hancox 2001, but see also Donanovich & Marsicano 2012) and Dolichuranus (Damiani et al. 2007) were included, as well as Xiyukannemeyeria (formerly Parakannemeyeria brevirostris, Liu & Li 2003), which is from the Middle Triassic Karamay Formation of the Junggar Basin and therefore suspect to have some closer relationship to Sungeodon, particularly as it also exhibits an unusually short skull. The parsimony analysis thus including 2 outgroups and 18 ingroup taxa and based on 54 characters, was carried out with PAUP 4.0b10 for Windows. A heuristic search was conducted with usual defaults in effect; all characters were treated as unordered. Only 2 most parsimonious trees with a length of 149 steps, a CI of 0.44 and a RI of 0.57 were found, the phylogenetic resolution thus being much better than in the cladogram of Vega-Dias et al. (2004). Contra Maisch (2002) but in accordance with other studies, the lystrosaurids were

5. Discussion The phylogenetic placement of Sungeodon as a basal member of the Stahleckeriidae (Fig. 3) has certain implications. First of all, previous studies (e.g., Maisch 2001; Vega-Dias et al. 2004; Damiani et al. 2007) sup-

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dicynodont, Lystrosaurus, was known from the lowermost Triassic, and it was generally agreed that this taxon was a classical example of a disaster taxon (Fröbisch 2009). With the discovery of Sungeodon, this picture has changed. One is left to ask, why kannemeyeriiforms, if they were indeed present, are not found more often in strata of earliest Triassic age. The reason may be that they differed significantly in ecology from the probably semiaquatic Lystrosaurus (see Kümmell 2009 for the most recent and most in-depth discussion on locomotion in Lystrosaurus, which again provides some evidence of a more aquatic lifestyle in this genus, contra King 1991). Perhaps the early kannemeyeriiforms had been restricted to more dry environments of higher altitudes, were the chance of preservation was very low. Fröbisch (2008) noted the biased rock record particularly across the P/T-boundary and its possible effects on our perception of dicynodont diversity. It may also have provided an ecological filter against certain groups, such as the kannemeyeriiforms. After the extinction of the lystrosaurids, the kannemeyeriiforms may have invaded the ecological niches previously occupied by these ubiquitous and common animals. This, together with the better Middle Triassic terrestrial rock record (Fröbisch 2008) may have improved their fossil record significantly. The discovery and analysis of the postcranial skeleton of Sungeodon could significantly help to test these hypotheses. It is remarkable that Dinanomodon, not too far related to kannemeyeriiforms, although an exceptionally large animal, is also a rare component of the South African Karoo, with only few well-preserved specimens being referable to that taxon with certainty (see Kammerer et al. 2011). This could be seen as further evidence for a lifestyle of early kannemeyeriiforms that made them particularly unlikely animals to be adequately represented in the fossil record. Unfortunately, the postcranial skeleton of Dinanomodon, which might reveal a lot about its locomotion adaptations and probable lifestyle, is unknown either. Another possibility is that the early evolution of kannemeyeriiforms took actually place in historically low-studied areas like northwestern China compared to e.g. the well-studied South African Karoo. In summary, the discovery of Sungeodon kimkraemerae is surprising. It significantly changes our ideas not only about the early evolution of the Stahleckeriidae and Kannemeyeriiformes, but even calls into question our current understanding of the effects of the P/T-event and its aftermath on large terrestrial herbivores in general. If further findings should sup-

posed a probable African origin of stahleckeriids, as the most basal members of the group, as well as the stratigraphically oldest records, were found in Africa (Angonisaurus and Dolichuranus, both from the Lower Middle Triassic, as pointed out above Dolichuranus is not regarded as a stahleckeriid by us). As Sungeodon is one of the most basal and the hitherto stratigraphically oldest stahleckeriid, it may instead be a viable hypothesis that the stahleckeriids originated in Central Asia. Other stahleckeriids, such as Dinodontosaurus and Placerias that turn out as basal members of the family in our analysis, are from South and North America respectively, so that a new world origin of the group cannot be excluded either. Obviously our knowledge of these dicynodonts, their stratigraphic and geographic distribution and thus their evolution is far from being perfect and any ideas on their palaeobiogeographic origin and distribution patterns must be considered preliminary. What is much more significant than the importance of Sungeodon for stahleckeriid evolution is the fact, that such a highly derived kannemeyeriiform should have been present so early in the Triassic. As pointed out above, the specimen was found in the same locality and bed as several articulated specimens of Lystrosaurus, a genus otherwise exclusively known from latest Permain and earliest Triassic (Induan) strata. A specimen of the basal archosaur Proterosuchus yuani was also found nearby. The Jiucaiyuan Formation of the Junggar Basin is widely regarded and recognized to be earliest Triassic in age (Induan, see Metcalfe et al. 2009 for recent and comprehensive data), containing a typical Lystrosaurus-fauna as it is similarly found in the South African Karoo, European Russia, India and Antarctica. It is therefore considered most likely that Sungeodon is of earliest Triassic (Griesbachian) age. If it is indeed a stahleckeriid, and if the phylogeny proposed here, which generally agrees with previous studies on the subject, differing only in details, is considered as even moderately reliable, this implies, that the adaptive radiation of kannemeyeriiform dicynodonts took place very early in the Triassic, more or less immediately after the P/T-event, and that all subclades of kannemeyeriiform dicynodonts were already present in the earliest Triassic. It is even conceivable, although it remains unproven, that part of this radiation already took part in the latest Permian, which would considerably affect our understanding of dicynodont diversity across the P/T-boundary, and the effect of the P/Tevent on large terrestrial herbivores. Until now, only a single genus of moderately large

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port the idea suggested here, namely that the kannemeyeriiforms underwent a very early, significant radiation that possibly spans the P/T-boundary, or at least took place as a flash-recovery, similar to that recently documented in ammonoids by Brayard et al. (2009), the current understanding of the effects of this largest of all mass-extinctions “when life nearly died” (Benton 2005) on the dicynodonts (see e.g., Fröbisch 2008) would be seriously called into question. Data from the South African Karoo (Botha & Smith 2006) already suggested that the recovery of terrestrial vertebrates after the P/T-boundary was surprisingly fast. It may have been significantly faster than even these authors conceived. Evidence accumulates that some regions such as Antarctica may have provided shelter for many taxa across the P/T-boundary (Fröbisch et al. 2009) that became extinct elsewhere, and it is conceivable that not only survival, but even diversification took place there. Dicynodonts hitherto serve as an arch-example of vertebrate palaeontology to illustrate how disastrous the P/T-mass extinction was, and that it only left few survivors. Lystrosaurus still serves as an arch-example of a classic disaster taxon (Fröbisch 2009), turning into a failed survivor, but this may be only half of the story.

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Yates, A. (2007): Dolichuranus primaevus (Therapsida: Anomodontia) from the Middle Triassic of Namibia and its phylogenetic relationships. – Palaeontology, 50: 1531-1546. Domnanovich, N.S. & Marsicano, C.A. (2012): The Triassic dicynodont Vinceria (Therapsida: Anomodontia) from Argentina and a discussion of basal Kannemeyeriiformes. – Geobios, 45: 173-186. Dzik, J., Sulej, T. & Niedźwiedzki, G. (2008): A dicynodont-theropod association in the latest Triassic of Poland. – Acta Palaeontologica Polonica, 53: 733-738. Fröbisch, J. (2008): Global Taxonomic Diversity of Anomodonts (Tetrapoda, Therapsida) and the Terrestrial Roch record Across the Permo-Triassic boundary. – PlosOne, 3 (11): e37733. Fröbisch, J. (2009): Composition and similarity of global anomodont-bearing tetrapod faunas. – Earth Science Reviews, 95: 119-157. Fröbisch, J., Angielczyk, K. & Sidor, C.A. (2009): The Triassic dicynodont Kombuisia (Synapsida: Anomodontia) from Antarctica, a refuge from the terrestrial PermianTriassic mass extinction. – Naturwissenschaften, 97: 187-196. Kammerer, C.F., Angielczyk, K.D. & Fröbisch, J. (2011): A comprehensive taxonomic revision of Dicynodon (Therapsida, Anomodontia) and its implications for dicynodont phylogeny, biogeography, and biostratigraphy. – Journal of Vertebrate Paleontology, 31 (Suppl. 1): 1-158. King, G.M. (1991): The aquatic Lystrosaurus: a palaeontological myth. – Historical Biology, 4: 285-321. King, G.M. (1997): The dicynodont Lystrosaurus from the Upper Permian of Zambia: evolutionary and stratigraphical implications. – Palaeontology, 40: 149-156. Kümmell, S. (2009): Die Digiti der Synapsida: Anatomie, Evolution und Konstruktionsmorphologie. – 426 pp.; Aachen (Shaker). Liu, J. & Li, J.-L. (2003): A new material of kannemeyerid from Xinjiang and the restudy of Parakannemeyeria brevirostris. – Vertebrata PalAsiatica, 41: 147-156. Maisch, M.W. (2001): Observations on Karoo and Gondwana vertebrates. Part 2: A new skull-reconstruction of Stahleckeria potens von Huene, 1935 (Dicynodontia, Middle Triassic) and a reconsideration of kannemeyeriiform phylogeny. – Neues Jahrbuch für Geologie und Paläontologie, Abhandlungen, 220: 127-152. Maisch, M.W. (2002): A new basal lystrosaurid dicynodont from the Upper Permian of South Africa. – Palaeontology, 45: 343-359. Metcalfe, I., Foster, C.B., Afonin, S.A., Nicoll, R.S., Mundil, R., Wang X.F. & Lucas, S.G. (2009): Stratigraphy, biostratigraphy and C-isotopes of the Permian-Triassic non-marine sequence at Dalongkou and Lucaogou, Xinjiang Province, China. – Journal of Asian Earth Sciences, 36: 503-520. Renaut, A.J. & Hancox, P.J. (2001): Cranial description and taxonomic re-evaluation of Kannemeyeria argentinensis (Therapsida: Dicynodontia). – Palaeontologica Africana, 37: 81-91. Thulborn, T. & Turner, S. (2003): The last dicynodont: an Australian Cretaceous relict. – Proceedings of the Royal Society of London, (B), 270: 985-993.

Acknowledgements We express our thanks to Prof. Dr. Sun Ge of Jilin University, and the Geological Survey No. 1 of Xinjiang and its staff for their long-standing support of our fieldwork and scientific studies in north-western China. Kim Krämer (formerly SMNS) is cordially thanked for the preparation of the specimen. Dr. Kenneth Angielczyk (Chicago) and an anonymous reviewer are heartily thanked for their helpful suggestions.

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Vega-Dias, C., Maisch, M.W. & Schultz, C.L. (2004): A new phylogenetic analysis of Triassic dicynodonts (Therapsida) and the systematic position of Jachaleria candelariensis from the Upper Triassic of Brazil. – Neues Jahrbuch für Geologie und Paläontologie, Abhandlungen, 231: 145-166.

Addresses of the authors:

Michael W. Maisch, Hartmeyerstr. 6, 72076 Tübingen, Germany; e-mail: [email protected] Andreas T. Matzke, Am Stadtgraben 3, 72070 Tübingen, Germany; e-mail: [email protected]

Manuscript received: December 14th, 2012. Revised version accepted by the Stuttgart editor: February 5th, 2014.

Appendix List of characters used in the phylogenetic analysis

Character 1 (Maisch 2001, character 14; Vega-Dias et al. 2004, character 1). Caniniform process of maxilla not considering tusks rounded, not far extending ventrally (0); rounded with anterior and posterior constriction (1); pointed shaped, ventrally directed (2). Character 2 (Maisch 2001, character 9; Vega-Dias et al. 2004, character 2). Tusks present (0); absent (1). Character 3 (Vega-Dias et al. 2004, character 3). Position of the anterior edge of the orbit in relation to the caniniform process of the maxilla: caniniform process in front of the orbit (0); orbit and caniniform process aligned (1). Character 4 (Vega-Dias et al. 2004, character 4). Nasal with extensive median suture, at least half the length of the nasals (0); with short median suture, clearly less than half the length of the nasals (1); separated by frontals (2). Character 5 (Vega-Dias et al. 2004, character 5). Relation between premaxilla-maxilla/premaxilla/nasal sutures: suture line premaxilla-maxilla behind the premaxilla-nasal suture (0); sutures vertically aligned (1); suture line premaxilla-maxilla in front of the premaxilla-nasal suture (2). Character 6 (Maisch 2001, character 7; Vega-Dias et al. 2004, character 6). Mid-nasal ridge little developed, only on premaxilla (0); strongly developed, extending on skull-roof, closely approaching the parietal foramen (1); absent (2). Character 7 (Maisch 2001, character 13; Vega-Dias et al. 2004, character 7). Naso-frontal suture in dorsal view more or less transverse (0); frontals intruding deeply between nasals (1). Character 8 (Maisch 2001, character 25; Vega-Dias et al. 2004, character 8). Deep postnarial excavation in lateral view of the snout absent (0); present (1). Character 9 (Maisch 2001, character 22; Vega-Dias et al. 2004, character 9). Lacrimal separated from septomaxilla by nasal and maxilla (0); lacrimal contacts septomaxilla (1). Character 10 (Vega-Dias et al. 2004, character 10). Prefrontal in dorsal view expanded more antero-posteriorly than latero-medially (0); expanded more latero-medially than antero-posteriorly (1); equivalent measure (2). Character 11 (Vega-Dias et al. 2004, character 11). Maxilla-squamosal contact straight (0); pointed shaped or serrated (1). Character 12 (Vega-Dias et al. 2004, character 12). Squamosal projected posterior beyond mandibular articulation with posterior margin inclined for at least 10° (0); in line with mandibular articulation and with vertical posterior margin (1). Character 13 (Maisch 2001, character 1; Vega-Dias et al. 2004, character 13). Posterior process of postorbital in dorsal view reaches squamosal (0); does not reach squamosal (1). Character 14 (Maisch 2001, character 5; Vega-Dias et al. 2004, character 14). Preparietal present (0); absent (1). Character 15 (Maisch 2001, character 1; Vega-Dias et al. 2004, character 15). Interparietal in dorsal view restricted to occipital surface (0); narrowly exposed on skull roof (1); forms much of the intertemporal skull roof (2). Character 16 (Maisch 2001, character 4; Vega-Dias et al. 2004, character 16). Sagittal crest measured from the dorsal margin of the orbit less than one orbital diameter in height (0); less than two orbital diameters in height (1); more than two orbital diameters in height (2). Character 17 (Maisch 2001, character 11; Vega-Dias et al. 2004, character 17). Temporal fenestrae more than 1/3 of skull length (0); less than 1/3 of skull length (1).

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Character 18 (Maisch 2001, character 23, Vega-Dias et al. 2004, character 18). Squamosal width: squamosals form less than half the width of the occiput (0); more than half of the width of the occiput (1): Character 19 (Maisch 2001, character 24, Vega-Dias et al. 2004, character 19). Orbits well visible in dorsal view (0); interorbital skull roof obscures orbits in dorsal view (1). Character 20 (Vega-Dias et al. 2004, character 20). Proportion between preorbital region (including the orbit) and the postorbital region in dorsal view: preorbital region is shorter than postorbital region (0); preorbital region is longer than the postorbital region (1). Character 21 (Maisch 2001, character 15; Vega-Dias et al. 2004, character 21). Occipital width less than the skull length (0); larger than the skull length (1). Character 22 (Maisch 2001, character 17; Vega-Dias et al. 2004, character 22). Skull length exceeds 30 cm in the adult (0); less than 30 cm in the adult (1). Character 23 (Maisch 2001, character 21; Vega-Dias et al. 2004, character 23). Height of suspensorium less than 3/5 total skull length (0); exceeds 3/5 total skull length (1). Character 24 (Maisch 2001, character 27; Vega-Dias et al. 2004, character 24). Width of pterygoid girder less than half the distance between quadrate condyles (0); more than half the distance between quadrate condyles (1). Character 25 (Maisch 2001, character 28; Vega-Dias et al. 2004, character 25). Reflected lamina of angular separated from articular by an extensive gap (0); separated only by a narrow slit or contacting angular (1). Character 26 (Vega-Dias et al. 2004, character 26). Projection of the attachment of the triceps muscle on scapula present (0); absent (1). Character 27 (Vega-Dias et al. 2004, character 27). Development of the acromion process: well defined acromion process present (0); acromion process reduced to a small knob (1). Character 28 (Vega-Dias et al. 2004, character 28). Acromion process in anterior view does not emerge like a spine (0); emerges from a spine in the lateral anterior part of the scapula (1). Character 29 (Vega-Dias et al. 2004, character 29). Coracoid foramen position: inside precoracoid (0); inbetween scapula/precoracoid (1). Character 30 (Vega-Dias et al. 2004, character 30). Proportion between the maximum width of the scapular blade and the width measured at the level of the acromion process (excluding acromion process): 1.5 or less (0); more than 1.5 (1). Character 31 (Vega-Dias et al. 2004, character 31). Constriction of the sternum absent (0); present in the posterior region of the sternal bosses (1). Character 32 (Vega-Dias et al. 2004, character 32). Bosses of the sternum: two bosses (0); four bosses (1). Character 33 (Vega-Dias et al. 2004, character 33). Twist disposition of the humerus between 40 and 45° (0); between 60 and 90° (1). Character 34 (Vega-Dias et al. 2004, character 34). Size of deltopectoral crest: crest extends almost half the length of the humerus (0); crest exceeds 50% of the length of the humerus (1); crest is clearly smaller than half of the length of the humerus (2). Character 35 (Vega-Dias et al. 2004, character 35). Comparison between the length of humerus and femus: femur bigger than the humerus (0); femur of the same size or smaller than the humerus (1). Character 36 (Maisch 2001, character 34; Vega-Dias et al. 2004, character 36). Proportions between the distal portion of the sigmoid notch (articulation with the radius) and the proximal portion (including the sigmoid notch and the olecranon process) of the ulna: distal portion is bigger than the proximal portion (0); distal portion: smaller than the proximal portion (1); both portions are almost of the same size (2). Character 37 (Maisch 2001, character 35, inverted polarity; Vega-Dias et al. 2004, character 37). Body of the radius slender (0); short and robust (1). Character 38 (Vega-Dias et al. 2004, character 38). Iliac blade: anteroventral margin does not reach to the level of dorsal acetabular margin (0); reaches to the level of dorsal acetabular margin (1). Character 39 (Vega-Dias et al. 2004, character 39). Supraacetabular notch present (0); absent (1). Character 40 (Vega-Dias et al. 2004, character 40). Ischium is not projected dorsal to the acetabular cavity (0); projected dorsal to the acetabular cavity (1). Character 41 (Vega-Dias et al. 2004, character 41). Pubic tubercle does not extend anterior to the acetabular cavity (0); extends anterior to the acetabular cavity (1). Character 42 (Vega-Dias et al. 2004, character 42). Orientation of the femoral head in lateral view: equally expanded antero-posteriorly (0); expanded more anteriorly (1).

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Character 43 (Vega-Dias et al. 2004, character 43). Greater trochanter of femur aligned with the shaft (0); aligned and oblique to the shaft (1); s-shaped (2). Character 44 (Vega-Dias et al. 2004, character 44). Length of greater trochanter: lateral margin extends up to 1/3 femoral length (0); lateral margin extends more than 1/3 femoral length (1). Character 45 (Maisch 2001, character 8). Nasal bosses weak (0); strong (1). Character 46 (Maisch 2001, character 10). Snout blunt, ovoid or rectangular (0); very pointed, triangular (1). Character 47 (Maisch 2001, character 16). Strong kink between dorsal and intertemporal skull roof absent (0); present (1). Character 48 (Maisch 2001, character 18). Postfrontal present (0); absent (1). Character 49 (Maisch 2001, character 19). ‘Prefrontal not or moderately protruding along anterodorsal orbital margin (0); forming strong, thickened lateral projection (1). Character 50 (Maisch 2001, character 26). Interpterygoid vacuity moderately elongate (0); very short and reduced (1). Character 51 (modified from Maisch 2001, character 3). Spatium intertemporale widened in primitive (lystrosaurid etc.) fashion (0); narrow sagittal crest (1); moderately narrow (2); widened in stahleckeriid (derived) fashion (3) (see Maisch 2001 for a detailed explanation of these terms). Character 52 (Maisch 2002, character 19). Ectopterygoid present (0); absent (1). Character 53 (Maisch 2002, character 2). Premaxillary-palatine contact in the secondary palate extensive (0); reduced to a point-contact in ventral view (1); entirely lost by intervening spur of the maxilla (2). Character 54 (Maisch 2002, character 25). Snout region low, produced not far ventrally (0); short and deep, strongly extending ventrally (1).

Data matrix Outgroup: Dicynodon Dinanomodon

00000 00000 00000 00000 00000 00000 ??000 00000 00010 00000 1010 10002 10000 ?0000 00000 0100? ????? ????? ????? ????0 10000 1010

Ingroup: Lystrosaurus Kwazulusaurus Shansiodon Tetragonias Vinceria Kannemeyeria Wadiasaurus Dolichuranus Parakannemeyeria Sinokannemeyeria Xiyukannemeyeria Dinodontosaurus Sungeodon Placerias Angonisaurus Stahleckeria Ischigualastia Jachaleria

00101 00011 01000 00001 00000 00011 00020 00000 00000 00000 0121 00020 21000 00000 01001 0100? ????? ????? ????? ????0 00001 0101 001?? 1?00? ?01?0 00?00 01000 10000 ??100 000?? ?0001 00?0? 1110 00100 00012 ?0100 00000 01000 10100 00101 00000 10001 00101 1110 00011 10010 00001 00000 01000 ????? ????? ????? ????0 00101 1?10 000?1 10000 10001 20000 00000 10100 1?000 00101 10100 01101 1110 000?2 0?00? ?0?01 20000 00000 00110 ?110? 201?0 00110 01?0? 1110 10001 00000 0000100101 00000 ????? ????? ????? ????0 00101 2110 10000 01102 00010 11011 00000 10100 ??100 210?0 00010 00111 2110 10000 0?102 00010 11011 00010 10100 0010? 210?? ?1010 00111 2110 10000 00002 00001 10011 00010 10??? ??100 000?0 ????0 00101 2110 00001 00000 10101 01101 00001 10100 00001 01011 1?210 00101 2110 10011 01010 ????? ???0? ?0??? ????? ????? ????? ????0 0??0? ?1?0 2000? 01010 10102 10000 001?1 0010? 0012? 11??0 10110 11101 3110 011?? 0?0?? ?101? 00110 1011? 0010? ????? ???11 0???0 00101 3110 01010 01001 11012 00101 10101 00100 01121 11111 11110 00101 3110 01011 11000 10102 10010 00111 11011 ???1? 11??? ?1100 11101 3110 01110 21011 11102 10010 0011? 01011 11??? ?1001 1???0 00101 2110

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