A Reassessment of Kelmayisaurus petrolicus, a Large Theropod Dinosaur from the Early Cretaceous of China

The Early Cretaceous fossil record of large-bodied theropods from Asia is poor, hindering comparison of Asian predatory dinosaur faunas with those from other continents. One of the few large Asian theropod specimens from this interval is a partial skull (maxilla and dentary) from the Lianmugin Formation (?Valanginian—Albian), the holotype of Kelmayisaurus petrolicus. Most authors have either considered this specimen as an indeterminate basal tetanuran or a nomen dubium. We redescribe K. petrolicus and note that it possesses a single autapomorphy (a deep accessory groove on the lateral surface of the anterior dentary), as well as a unique combination of characters that differentiates it from other theropods, affirming its validity. A phylogenetic analysis recovers K. petrolicus as a basal carcharodontosaurid, which is supported by various features: very deep interdental plates (a carcharodontosaurid synapomorphy), fused interdental plates (present in carchardontosaurids and a limited number of other theropods), and the absence of diagnostic features of other clades of large-bodied theropods such as abelisaurids, megalosauroids, and coelurosaurs. As such, Kelmayisaurus is the second known carcharodontosaurid from Asia, and further evidence that this clade represented a global radiation of large-bodied predators during the Early—mid Cretaceous.


Introduction
The fossil record of large−bodied theropod dinosaurs from the Early Cretaceous of Africa, Europe, North America, and South America has improved dramatically over the past two decades.Entirely new groups of distinctive theropods, includ− ing carcharodontosaurians, abelisaurids, and spinosaurids, have been discovered and now represent some of the best− known megapredators in the dinosaur fossil record (e.g., Bonaparte 1985;Charig and Milner 1997;Sereno et al. 1996;Benson et al. 2010).However, comparatively little is known about the large−bodied theropods that inhabited Asia during the Early-middle Cretaceous.Recent discoveries indicate that carcharodontosaurians (including both neovenatorids and car− charodontosaurids) and spinosaurids were present in the Early Cretaceous of Asia (Milner et al. 2007;Buffetaut et al. 2008;Brusatte et al. 2009aBrusatte et al. , 2010;;Benson et al. 2010).Nevertheless, the large−bodied theropod record of Asia is poor, so single specimens can contribute to and potentially alter hypotheses of theropod biogeography and faunal change.
One of the few large−bodied theropod specimens from the Early Cretaceous of Asia is a partial skull, comprising a frag− mentary maxilla and complete dentary, which was referred to a new genus and species, Kelmayisaurus petrolicus, by Dong (1973).Although fragmentary, this specimen was consid− ered valid by Molnar et al. (1990) and Holtz et al. (2004), with the latter authors describing it as a basal tetanuran of un− certain affinities.However, in a review of small−bodied theropods from the Early Cretaceous of Asia, Rauhut and Xu (2005: 107) considered Kelmayisaurus to be a nomen dubium because of the "fragmentary nature of the type mate− rial and the lack of clearly diagnostic characters".Subse− quently, this critical specimen from a poorly sampled inter− val has been ignored in discussions of Asian theropod anat− omy, phylogeny, and evolution.
We redescribe the type specimen of Kelmayisaurus, pro− viding for the first time a detailed anatomical description and comparison to other large theropod taxa.We present evi− dence that Kelmayisaurus is a valid taxon, diagnosable by a single autapomorphy as well as a unique combination of other characters.Furthermore, a phylogenetic analysis and comparisons with other theropods indicate that Kelmayi− saurus is a member of Carcharodontosauridae, a clade of theropods that includes some of the largest predators to ever live and which was recently discovered in Asia for the first time (Shaochilong maortuensis: Brusatte et al. 2009a).Thus, Kelmayisaurus provides evidence that carcharodontosaurids were a long−lived component of Asian terrestrial ecosystems, and were a truly global radiation of hypercarnivorous (large−bodied, solely carnivorous) predators during the Early-mid Cretaceous.
Emended diagnosis.-Carcharodontosauridwith a single autapomorphy: the presence of a deeply inset and dorsally concave groove located anteriorly on the lateral surface of the dentary (Fig. 1B 1 ).Additionally, Kelmayisaurus shows a unique combination of characters not currently known in any other allosauroid: maxillary interdental plates more than twice as tall dorsoventrally as they are broad anteroposteriorly, prominent maxillary anterior process (the combination of these two characters results in a narrowing of the gap between the plates and the anteromedial process), and absence of an anteroventral "chin−like" process of the dentary.

Description
Maxilla.-Only a small fragment of the left maxilla is pres− ent, comprising the region anterior to the base of the ascend− ing process.A distinct anterior ramus is present, which is separated from the base of the ascending process by a con− cave step in lateral view.The shape of the ramus may have been slightly modified by breakage of the dorsal surface.However, neither cancellous bone texture nor alveolar crypts are exposed, suggesting that such breakage is minimal and the presence and general shape of the process are real.The anterior ramus is present in many basal theropods and its shape is often used as a phylogenetic character (e.g., Holtz et al. 2004).In Kelmayisaurus the process is slightly shorter anteroposteriorly (70 mm) than it is high dorsoventrally (100 mm), similar to the condition in Allosaurus (Madsen 1976), Neovenator (Brusatte et al. 2008), and Monolophosaurus (Brusatte et al. 2010;Zhao and Currie 1993).In contrast, carcharodontosaurids such as Carcharodontosaurus and Mapusaurus have an anterior process that is much taller than long anteroposteriorly, and thus is nearly indistinct as a dis− crete process (Sereno et al. 1996;Coria and Currie 2006).
The maxilla is heavily abraded but several regions of original bone surface are preserved.On the lateral surface, the best preserved patch of original surface texture is smooth, and lacks the rugose surface texture of abelisaurids (Samp− son and Witmer 2007;Sereno and Brusatte 2008) and de− rived carcharodontosaurids such as Carcharodontosaurus (Sereno et al. 1996;Brusatte and Sereno 2007).Additionally, there is a row of primary neurovascular foramina approxi− mately 15 mm above the ventral margin on the lateral sur− face.Where well preserved, the foramina are 4-5 mm in di− ameter and open ventrally into deep grooves that terminate at the alveolar margin.These grooves, along with other grooves on more abraded regions of the lateral surface, are marked by tightly packed and elongate internal bone grains.There are several larger foramina located dorsal to the primary row, but these do not appear to form a pattern.
The medial surface of the maxilla is poorly preserved, sug− gesting that it was exposed to subaerial weathering.However, important details of the interdental plates are apparent.Al− though the plates are damaged in many regions, it is clear that they were fused into a single lamina.Additionally, the first plate is preserved in its entirety; it extends dorsally to nearly the level of the anteromedial process and the two are only sep− arated by a slight concave margin.This is also the case in Sinraptor (Currie and Zhao 1993).However, in Sinraptor this results from the more ventral position of the anteromedial pro− cess, whereas in Kelmayisaurus the process is located close to the dorsal margin of the maxilla as in most theropods.Thus, the close position of the first interdental plate and the antero− medial process in Kelmayisaurus is due to the increased depth of the plate itself.It is approximately twice as deep dorso− ventrally as broad anteroposteriorly, as in derived carcharo− dontosaurids such as Acrocanthosaurus (NCSM 14345), Car− charodontosaurus (Brusatte and Sereno 2007), Giganoto− saurus (MUCPv−Ch 1), and Mapusaurus (Coria and Currie 2006), as well as the megalosaurids Megalosaurus (Benson 2010) and Torvosaurus (Britt 1991) and specimens of un− named related taxa such as DCM G10603 (Powell 1987;Benson and Barrett 2009).In contrast, other theropods, in− cluding the basal carcharodontosaurian Neovenator (Brusatte et al. 2008), more basal allosauroids (Allosaurus: Madsen 1976; Sinraptor: Currie and Zhao 1993), and ceratosaurids (Madsen and Welles 2000;Rauhut 2004) possess shallower plates.Because derived carcharodontosaurids lack a distinct maxillary anterior process, the anteromedial process in these taxa is located further dorsally relative to the interdental plates than in Kelmayisaurus.Therefore the combination of tall interdental plates and an anteromedial process that is close to the dorsal margin of the plates is known only in Kelmayi− saurus.
Parts of six alveoli are preserved; the anterior four are es− sentially complete and the posterior two are heavily weath− ered.Complete alveoli have oval outlines, which are wider mesiodistally than labiolingually.A replacement tooth is present in the crypt for alveolus 4.This tooth is 70 mm long apicobasally, its mesial margin is strongly curved, and its distal margin is nearly straight ventrally, similar to the re− placement teeth of many theropods.Unfortunately, surface details, such as the presence of enamel wrinkles (Brusatte et al. 2007), are difficult to discern due to erosion.The labial parapet of the alveoli, comprised of the lateral surface of the maxilla, extends much further ventrally than the lingual para− pet, formed from the interdental plates.However, this may be an artefact of poor preservation.
Dentary.-The left dentary is well preserved, and only the anterior tip and the fragile, sheet−like portion immediately posterior to the tooth row are missing.The dentary is 523 mm in length and keeps a relatively constant dorsoventral depth along most of the tooth row, but expands in depth posterior to alveolus 13.The anterior end is expanded only slightly rela− tive to the remainder of the tooth row, unlike the condition in derived carcharodontosaurids in which the anterior dentary is expanded and squared−off, primarily by the presence of a distinct "chin−like" anteroventral process (Fig. 2C; e.g., No− vas et al. 2005;Coria and Currie 2006;Brusatte and Sereno 2007).An unexpanded anterior dentary is also seen in the basal neovenatorid carcharodontosaurian Neovenator (Fig. 2A; Brusatte et al. 2008).The dorsal margin of the tooth row is concave when seen in lateral view, whereas the ventral margin is convex anteriorly and concave posteriorly.The http://dx.doi.org/10.4202/app.2010.0125dorsal section of the posterior margin of the dentary, which would have been overlapped by the surangular, is nearly ver− tical for a short distance before sloping posteroventrally.This is also the case in other allosauroids (e.g., Madsen 1976), whereas abelisaurids (e.g., Sampson and Witmer 2007) and many coelurosaurs (e.g., Currie 1995) have poste− rior margins that are essentially straight dorsoventrally.Al− though the posterior part of the dentary is well preserved, there is no obvious concave margin for the external mandibu− lar fenestra.Thus, if the dentary did border the fenestra, this contribution must have been small.
In dorsal view, the dentary is straight across its entire length, as in the carcharodontosaurians Acrocanthosaurus (NCSM 14345) and Neovenator (Fig. 2A  Original bone surface is present across most of the dentary, and the smooth lateral surface is especially well preserved.The primary neurovascular row is distinct.Anteriorly, the row is comprised of deep, circular foramina.There is approxi− mately one foramen per alveolus, and these are located only 15 mm ventral to the alveolar margin.Posterior to the fourth alveolus the row curves ventrally, such that it is 25 mm ventral to the alveolar margin at the level of alveolus 6.Additionally, posterior to alveolus 8 the individual foramina are replaced by a dorsoventrally deep and strongly inset groove.The groove curves dorsally as it extends posteriorly, giving it a concave dorsal margin when seen in lateral view.However, as this cur− vature occurs in concert with the posterior expansion of the dentary, the groove is still located 25 mm ventral to the tooth row where it terminates.The primary groove is especially deep and well defined in Kelmayisaurus, similar to the condi− tion in some megalosauroids (e.g., Rauhut 2003) and some carcharodontosaurids (Fig. 2C) but contrasting with the weaker grooves of most other theropods (Rauhut 2003).In Allosaurus and Neovenator a discrete groove is absent, and fo− ramina are simply arrayed in a series (Fig. 2A 1 , B).
Two additional neurovascular features are present on the lateral surface.A ventral row of foramina, which are more ovoid than the primary foramina, is located along the ventral margin of the anterior dentary.These are present below the first four alveoli, and there is one foramen per alveolus.Addi− tionally, there is a pronounced groove anteriorly, anterior to alveolus 5.This groove is 74 mm in length and curves dorsally as it continues posteriorly, eventually becoming confluent with the primary groove at the level of alveolus 6.Within this groove are four deep foramina, which decrease in size posteri− orly.This groove is not present in other basal tetanurans (Fig. 2; e.g., Madsen 1976;Currie and Zhao 1993;Allain 2002), and is thus considered an autapomorphy of Kelmayisaurus.
The medial surface of the dentary is well preserved.The symphysis is nearly flat and poorly−defined, not bulbous and rugose as in derived carcharodontosaurids (Brusatte and Se− reno 2007).However, an anterodorsally−inclined longitudi− nal ridge traverses the symphysis immediately ventral to midheight.This feature has been noted in megalosauroids  (Benson 2008) and may be widespread among theropods.Ventral to the third alveolus are two Meckelian foramina; both are ovoid, equal in size, and one is located anterodorsal to the other.The Meckelian groove is shallowly inset where it meets the foramina, but becomes more deeply inset and taller dorsoventrally as it continues posteriorly.Ventral to alveolus 13 the groove is marked by a distinct step where it meets the adductor fossa; ventral to this step is a rectangular notch for the splenial articulation.The groove extends anteroventrally and its dorsal margin is better defined than its ventral margin.It is bordered dorsally by the lingual bar, which is deepest anteriorly above the Meckelian foramina.The bar tapers in depth posteriorly until the level of alveolus 9, from which point it maintains a constant depth.It also be− comes more robust posteriorly, in concert with the progres− sively more inset Meckelian groove.The bar is bordered dor− sally by the paradental groove, above which the interdental plates are fused into a single lamina across the first 11 alve− oli.The posterior−most three alveoli are small, triangular, and unfused.No tooth replacement foramina are clearly visi− ble.
Fifteen alveoli are clearly visible, and there was likely a 16 th alveolus that is missing at the broken anterodorsal corner of the dentary.All alveoli are suboval in dorsal view and much longer mesiodistally than labiolingually.Even the sec− ond and third alveoli are suboval, unlike the situation in many megalosauroids (e.g., Charig and Milner 1997;Allain 2002;Sadleir et al. 2008) and Acrocanthosaurus (NCSM 14345), in which the anterior three alveoli are subcircular and the third is relatively enlarged compared to the other al− veoli.The third dentary alveolus of Neovenator is also rela− tively enlarged (Fig. 2A 3 ).In Neovenator the alveoli are subrectangular, similar to the condition in abelisaurids (e.g., Sereno et al. 2004) but unlike all other basal tetanurans.No erupted or replacement teeth are clearly preserved in Kelmayisaurus, but the labiolingually thin alveoli may sug− gest that the teeth were transversely compressed, as in some derived carcharodontosaurids (Sereno et al. 1996).

Discussion
Body size of the holotype.-Estimatingthe body size of the Kelmayisaurus holotype is difficult, as all of the appendi− cular bones commonly used as size or mass proxies are miss− ing.However, Currie (2003a) reported that skull length and femur length are approximately isometric in another clade of large theropods, the tyrannosaurids.Thus, a reasonable body length estimate may be obtained by comparing the length of the dentary to that of other theropods.The dentary of Kel− mayisaurus is 523 mm long, slightly larger (approximately 5%) than typical adult individuals of Allosaurus (e.g., Mad− sen 1976).Thus, to a first approximation, Kelmayisaurus can be considered as approximately the same body length and mass as Allosaurus, which is estimated to have reached masses of 1620 kg and body lengths of 10-12 m (Christian− sen and Farina 2004).This is much larger than the estimated body size of the younger Asian carcharodontosaurid Shao− chilong, which has a maxilla that is only 75% the length of that of Allosaurus (Brusatte et al. 2009a).When analyzed with the same search strategy described by Benson et al. (2010), the new analysis recovered 1728 most parsimonious trees (MPTs) with a length of 639 steps, a con− sistency index (CI) of 0.44, and a retention index (RI) of 0.64 (strict consensus presented in Fig. 3).As in the initial analy− sis of Benson et al. (2010), Megalosauridae and Megaraptora were poorly resolved in the strict consensus due to a small number of wildcard taxa.Most important, however, Kel− mayisaurus was recovered as a basal carcharodontosaurid in all MPTs, and in the strict consensus it falls into a polytomy with Eocarcharia and a clade comprising Acrocanthosaurus and all more derived carcharodontosaurids. Therefore, we refer Kelmayisaurus to Carcharodontosauridae, and regard it as a basal member of the clade.We note that, after deletion of the wildcard taxon Poekilopleuron, one additional step al− lows Kelmayisaurus to be recovered (i) within Allosauroidea as the sister taxon of Neovenatoridae + Carcharodonto− sauridae; (ii) within Megalosauridae as the sister taxon of Megalosaurus bucklandii + Torvosaurus tanneri; or (iii) within Coelurosauria as the sister taxon of Guanlong, Tany− colagreus, or Tanycolagreus + Guanlong.Thus, the frag− mentary nature of the Kelmayisaurus holotype, coupled with homoplasy in the phylogenetic analysis, renders weak sup− port for a carcharodontosaurid affinity.

Systematic affinities of
With this being said, a carcharodontosaurid referral is also supported by a careful review of characters and compar− http://dx.doi.org/10.4202/app.2010.0125isons to other theropods.Kelmayisaurus possesses maxillary interdental plates that are more than twice as tall dorso− ventrally as they are wide anteroposteriorly, a feature only found in carcharodontosaurids such as Acrocanthosaurus (NCSM 14345) and Carcharodontosaurus (Brusatte and Sereno 2007) and the megalosaurids Megalosaurus (Benson 2010) and Torvosaurus (Britt 1991).In contrast, plesio− morphically short plates are present in the closest carcharo− dontosaurid outgroups (e.g., Neovenator: Brusatte et al. 2008).Tall interdental plates were recovered as a synapo− morphy of a clade of derived carcharodontosaurids (equiva− lent to Carcharodontosauridae sensu Benson et al. 2010) by Brusatte and Sereno (2008) and Brusatte et al. (2009a) The presence of fused interdental plates is also consistent with derived allosauroid affinities, as this feature is seen in Allosaurus (Madsen 1976) and carcharodontosaurians (e.g., Fig. 2A 2 ; Sereno et al. 1996).This was also derived inde− pendently in ceratosaurs (Madsen and Welles 2000;Carrano and Sampson 2008) and the megalosaurid Torvosaurus (Britt 1991).Nevertheless, Kelmayisaurus is unlikely to pertain to a derived megalosauroid (Megalosauridae or Spinosauridae) because it lacks a unique synapomorphy of the clade com− prising these two families: a paradental groove that is wide anteriorly, defining a distinct gap between the interdental plates and the medial wall of the maxilla (Benson 2008(Benson , 2010;;Benson et al. 2008).Additionally, many megalosauro− ids, including Torvosaurus (Britt 1991), possess an expan− ded, subcircular third dentary alveolus, which is not present in Kelmayisaurus.
Kelmayisaurus is also not likely to be a ceratosaur: it lacks the external bone texturing of derived abelisaurids (e.g., Sampson and Witmer 2007); possesses a prominent an− terior process of the maxilla (absent in ceratosaurs, Rauhut 2003); has a more steeply posteroventrally inclined dorsal margin of the posterior dentary compared to the more dorso− ventrally straight profile of abelisaurids (Sampson and Witmer 2007), noasaurids (Carrano et al. 2002), and cerato− saurids (Madsen and Welles 2000); has a deeper and more pronounced primary neurovascular groove on the dentary than in noasaurids (Carrano et al. 2002) and abelisaurids (Sampson and Witmer 2007); has a primary neurovascular groove located closer to the tooth row than in ceratosaurids (Madsen and Welles 2000) and abelisaurids (Sampson and Witmer 2007); and does not have the characteristic expanded anterior dentary and heterodont dentition of the best−known noasaurid, Masiakasaurus (Carrano et al. 2002).
Finally, Kelmayisaurus is unlikely to be a large−bodied coelurosaur.The interdental plates are fused and the anterior dentary is rounded, unlike the condition in tyrannosaurids in which the plates are unfused and the anterior end of the den− tary is straight and slopes posteroventrally (e.g., Brochu 2003;Currie 2003b;Brusatte et al. 2009b).Dromaeosaurids possess dentaries with a more anterodorsally−straight poste− rior margin, a weaker and less defined primary neurovascular groove, and Meckelian foramina that are positioned far apart (not adjacent to each other), as well as maxillae with shal− lower interdental plates (e.g., Currie 1995;Norell et al. 2006).Other coelurosaur groups with known large−bodied members can easily be distinguished from Kelmayisaurus by their peculiar skulls, which are often edentulous and clearly modified for a diet that is not primarily based on procuring large prey (e.g., Xu et al. 2007).

Implications of the carcharodontosaurid affiliation of
Kelmayisaurus.-Kelmayisaurus represents the second known Asian carcharodontosaurid.Carcharodontosaurids were originally discovered in Africa (Stromer 1931) and later in South America (Coria and Salgado 1995), and were once considered to be an endemic Gondwanan clade (e.g., Currie and Carpenter 2000;Allain 2002;Novas et al. 2005).The rein− terpretation of Acrocanthosaurus as a carcharodontosaurid (Sereno et al. 1996;Harris 1998), along with the discovery of the British Neovenator (Hutt et al. 1996) and more recently the Spanish Concavenator (Ortega et al. 2010), suggests that carcharodontosaurids and their immediate relatives instead represent a global radiation.However, until the recent re− description of Shaochilong (Brusatte et al. 2009a) there was no strong evidence that these giant predators inhabited Asia.
The identification of Kelmayisaurus as a carcharodonto− saurid not only adds further evidence that this clade inhabited Asia, but also suggests that carcharodontosaurids were present in Asia for a lengthy period of time.Shaochilong is from ca. 92 Ma rocks (Turonian), making it the youngest unequivocal carcharodontosaurid (Brusatte et al. 2009a).The age of the Lianmugin Formation, the rocks entombing the holotype of Kelmayisaurus, is not known with certainty, but falls some− where within the Valanginian to the Albian (i.e., ca.140-99.6Ma).There is no evidence that Kelmayisaurus and Shao− chilong belong to the same subclade or lineage, but the pres− ence of two carcharodontosaurids separated by at least 8 Myr indicates that these large predators may have been a common and long−lived component of Early-mid Cretaceous terrestrial ecosystems in Asia.Indeed, the Asian carcharodontosaurid re− cord now eclipses that of North America and Europe, both of which have yielded only a single carcharodontosaurid taxon.Emerging evidence, therefore, strongly supports a global radi− ation of carcharodontosaurids within the large−predator niche during the Early-mid Cretaceous.
Kelmayisaurus.-To test the phylo− genetic position of Kelmayisaurus, we added it to the cla− distic data matrix of Benson et al. (2010) (Appendix 1).
Currie and Carpenter 2000).This character re− view, therefore, is congruent with the phylogenetic analysis in suggesting that Kelmayisaurus is a basal carcharodonto− saurid that falls on the line towards more derived members of the clade.This phylogenetic position is consistent with the Early Cretaceous age of Kelmayisaurus, as most derived carcharodontosaurids are younger than Albian in age, the youngest possible age for the Lianmugin Formation.