Megalosaurus bucklandii

Benson, Roger B. J., 2010, A description of Megalosaurus bucklandii (Dinosauria: Theropoda) from the Bathonian of the UK and the relationships of Middle Jurassic theropods, Zoological Journal of the Linnean Society 158 (4), pp. 882-935 : 913-930

M. BUCKLANDII

Remains of M. bucklandii are very common in lower and middle Bathonian deposits from England; diagnostic remains are known from the Taynton Limestone Formation (middle Bathonian) of Stonesfield, the Chipping Norton Limestone Formation (lowest Bathonian) of New Park Quarry, Oakham Quarry, and an unknown locality in Gloucestershire, the Sharp’s Hill Formation (lower–middle Bathonian) of Workhouse Quarry, Chipping Norton, Oxfordshire, and the Great Oolite Group (Bathonian) of Sarsgrove, near Chipping Norton, Oxfordshire. These remains constitute a high proportion of the diagnostic theropod remains from the Bathonian of England. This suggests that M. bucklandii was the most abundant large predator in the faunas in which it occurred, and probably the apex predator in British Bathonian ecosystems.

Although multiple theropod specimens are known from the Bathonian of France, none of these specimens can be referred to M. bucklandii . The French material includes the holotypes of Poekilopleuron bucklandii ( Eudes-Deslongchamps, 1838; Allain & Chure, 2002) and Dubreuillosaurus valesdunensis (Allain, 2002, 2005a) from the Calcaire de Caen Formation (lower Bathonian). The Calcaire de Caen Formation and the theropod-bearing Bathonian strata of Britain are all limestones derived from calcareous, shallow marine deposits, and so the absence of M. bucklandii in France is unlikely to be a consequence of differential environmental sampling. It is therefore notable that M. bucklandii is not represented by theropod material from the Bathonian of France, as it is so abundant in penecontemporaneous British strata. This may reflect genuine absence or be a consequence of the small number of French specimens. The sauropod Cetiosaurus is also known from multiple British specimens but not represented by French material ( Upchurch & Martin, 2002, 2003). However, very few Bajocian or Bathonian localities in France have yielded sauropod remains ( Weishampel et al., 2004). If Cetiosaurus and Megalosaurus were genuinely absent in the Bathonian of France, this implies the presence of a physical or environmental barrier preventing mixing between the Bathonian dinosaur faunas of Britain and France. During the Bathonian, much of Britain and Europe were covered with shallow epicontinental seas, with areas of high ground forming substantial insular landmasses (for example, Ager, 1956; Martin, 1962; Palmer & Jenkyns, 1975; Callomon, 1979; Evans & Milner, 1994). It is possible that dispersal between these landmasses was limited, leading to high levels of endemism that may explain the apparently restricted distributions of Cetiosaurus and Megalosaurus .

PHYLOGENETIC ANALYSIS

Taxon sample

Forty-one operational taxonomic units (OTUs) were selected for inclusion in a phylogenetic analysis constructed to resolve basal tetanuran relationships. This is the first cladistic analysis focusing on basal tetanuran relationships, as previous analyses including a good sample of basal tetanurans have been attempts to elucidate global theropod phylogeny. These have recovered widely differing topologies in this part of the tree, and branch support values for basal tetanuran clades have been low where reported ( Holtz, 2000; Rauhut, 2003; Holtz et al., 2004; Smith et al., 2007). Specimens from 35 (85%) of the OTUs were inspected first-hand and scores for the remaining taxa were entered on the basis of published descriptions (Appendix S1, see Supporting Information; Eocarcharia , Fukuiraptor , Guanlong , Irritator , Spinosaurus , Tyrannotitan ). The OTUs were selected to maximize the sample of basal tetanurans, and several have never been included in a phylogenetic analysis ( Chuandongocoelurus , Duriavenator , Lourinhanosaurus , Marshosaurus , Metriacanthosaurus , Piveteausaurus ). Almost all basal tetanurans were included in the analysis. However, descriptive work on a number of Chinese taxa is limited and, as these specimens were not examined first-hand, they were not included in the analysis ( Gasosaurus, Dong & Tang, 1985 ; Kaijiangosaurus, He, 1984 ; partial skeletons referred to Szechuanosaurus campi ; ‘ Szechuanosaurus ’ zigongensis, Gao, 1993; Yangchuanosaurus magnus, Dong, Zhou & Zhang, 1983 ; Yangchuanosaurus shangyouensis, Dong et al., 1979 ). Erectopus , from the lower Albian of France, was excluded from the analysis by Safe Taxonomic Reduction ( Wilkinson, 1992), as the fragmentary holotype does not possess any character states that are not present in Sinraptor , but has a high proportion of missing data (MNHN 2001-4). Although Allain (2005b) stated that the maxillary interdental plates were fused in Erectopus , it is not possible to determine this condition as only the broken first and fourth plates are preserved (MNHN 2001-4).

Four of the OTUs have been considered to lie outside of Tetanurae by almost every recent author ( Abelisauridae , Ceratosaurus , Dilophosaurus , ‘ Syntarsus ’ kayentakatae). Of these, ‘ Syntarsus ’ kayentakatae is generally considered to be the most basal (for example, Carrano & Sampson, 2008) and was formally designated as the outgroup. Another three OTUs ( Compsognathus , Guanlong , Tanycolagreus ) were selected to represent Coelurosauria. These taxa were chosen because of their relative completeness and Late Jurassic age. Coelurosaurs are most diverse and abundant in the Cretaceous and more complete coelurosaur specimens are known from this time. However, Cretaceous coelurosaurs are probably less useful in establishing the primitive anatomy of the clade. Chilantaisaurus , from the ‘middle’ Cretaceous (Aptian–Albian or <92 Mya) of China, was also included in the present analysis as previous phylogenetic analyses have recovered it as an allosauroid ( Harris, 1998) or megalosauroid (spinosauroid; Rauhut, 2003). However, Benson & Xu (2008) suggested that Chilantaisaurus was a coelurosaur.

Character list

A total of 213 characters was scored for taxa included in the present analysis. Characters from a range of previous studies were assembled. All those that had been scored as phylogenetically informative over the present taxon sample were considered for inclusion in the present study. The following analyses were particularly influential during this process as they include a high proportion of basal tetanuran taxa: Pérez-Moreno et al. (1993), Holtz (1994, 2000), Sereno et al. (1994, 1996, 1998), Harris (1998), Allain (2002), Carrano et al. (2002), Coria & Currie (2002), Rauhut (2003), Holtz et al. (2004), Sereno, Wilson & Conrad (2004), Smith et al. (2007) and Brusatte & Sereno (2008). Characters and data based on the datasets of Rauhut (2003) (for example, Yates, 2006; Xu et al., 2006) and Harris (1998) (for example, Currie & Carpenter, 2000; Coria & Currie, 2006) were also examined. Many of the characters employed herein have been used by previous authors. Most of these have been figured and clearly explained in the literature, and this will not be repeated here. Good sources for character explanations include Coria & Currie (2002; braincase), Rauhut (2003) and the references cited alongside each character (Appendix S2, see Supporting Information). Twenty-nine new characters were formulated based on personal observations of specimens and the literature.

16. Maxilla, pneumatic region on medial side of maxilla posteroventral to maxillary fenestra: absent (0); present (1). Bonaparte (1986: fig. 6) figured a depressed region containing two smaller recesses ventral to the antorbital fenestra on the medial surface of the maxilla of Piatnitzkysaurus . The smaller recesses penetrate the body of the bone and this region is interpreted as pneumatic because of its irregular structure and association with the antorbital fenestra, which was shown to be pneumatic by Witmer (1997). Similar structures are present in this region in most basal tetanurans, including Megalosaurus ( Fig. 2C ) and Duriavenator (BMNH R332; Benson, 2008a), but are absent in Dubreuillosaurus (MNHN 1998-13; Allain, 2002: fig. 4) and Torvosaurus (BYU 9122; Britt, 1991: fig. 4B). In theropods that possess a true maxillary fenestra, the medial pneumatic region is invariably present and is continuous with the maxillary antrum via the posterior fenestra of the maxillary antrum ( Albertosaurus , Allosaurus ; Witmer, 1997: figs 29B, 30D). In these taxa, accessory recesses are not always present.

18. Maxilla, position of anteromedial process: ventral, immediately dorsal to interdental plates (0); dorsal, immediately ventral to dorsal surface of maxillary anterior ramus (1). In most theropods, the anteromedial process of the maxilla is located dorsally on the medial surface of the maxillary anterior ramus, so that there is a gap between the anteromedial process and the interdental plates (for example, Fig. 2C, D, K, L, O ). However, in Marshosaurus ( Witmer, 1997: fig. 29D) and Sinraptor ( Currie & Zhao, 1994: fig. 4), the anteromedial process is located ventrally in a position immediately dorsal to the interdental plates, so that there is no gap between the structures.

24. Maxillary interdental plates: extend ventrally as far as lateral wall of maxilla (0); fall short of ventral level of lateral wall of maxilla (1). In most theropods, the maxillary interdental plates extend as far ventrally as the lateral wall of the maxilla. However, in Megalosaurus ( Fig. 2D, K, L ), Neovenator (MIWG 6348; Brusatte et al., 2008) and Torvosaurus (BYU 9122; Britt, 1991: fig. 4B), the ventral extent of the interdental plates falls well short of the lateral lamina of the maxilla, so that the medial surface of the lateral wall is broadly visible in medial view.

31. Nasal antorbital fossa: visible in lateral view (0); occluded in lateral view by a ventrolaterally overhanging lamina (1). Coria & Currie (2006: fig. 3C) figured a nasal extension of the antorbital fenestra that is only visible in ventral view in Mapusaurus . The nasal antorbital fossae of Carcharodontosaurus ( Sereno et al., 1996: fig. 2A) and Giganotosaurus (MUCPv-Ch 1) have a similar appearance. In all three cases, this is the consequence of a ventrolaterally oriented lamina that overhangs the fossa and occludes it in lateral view (MUCPv-Ch 1; SGM- Din 1). The situation in Acrocanthosaurus is unclear from the figures of Currie & Carpenter (2000: figs 2–3); indeed, the nasal antorbital fossa is simply absent (NCSM 14345).

41. Lacrimal, morphology of lateral lamina of ventral process: anteriormost point situated around midheight of ventral process (0); anteriormost point situated dorsal to midheight of ventral process and a distinct rugose patch is present on the lateral surface (1). Smith et al. (2007: fig. 4) figured an unusual morphology of the lateral lamina of the lacrimal of Cryolophosaurus , in which the apex of that structure was located dorsally relative to the situation in other basal theropods (for example, Madsen, 1976a). This morphology is also present in Dilophosaurus (UCMP 37302) and ‘ Syntarsus ’ kayentakatae (MNA 2623).

52. Squamosal, anterodorsal lamina: emarginated by supratemporal fenestra (0); unemarginated (1). In many basal theropods, such as Allosaurus ( Madsen, 1976a; UMNH VP specimens) and Sinraptor ( Currie & Zhao, 1994) , the anterodorsal lamina of the squamosal is a broad sheet of bone located posterolateral to the supratemporal fenestra. Contrastingly, in Afrovenator (UC OBA 1), Dubreuillosaurus (MNHN 1998-13; Allain, 2002: fig. 9B), Eustreptospondylus (OUMNH J.13558; Sadleir et al., 2008: fig. 1), Guanlong ( Xu et al., 2006) and Marshosaurus (CMNH 021704), the anterodorsal lamina is embayed by the supratemporal fenestra so that it does not form a sheet.

54. Pneumatization of the quadrate: absent (0); present (1). Although pneumatization of the quadrate has been recognized as present in some coelurosaurs by the authors of many previous analyses (for example, Currie, Hurum & Sabath, 2003: character 55; Rauhut, 2003: character 48), it was observed only recently in the non-coelurosaurian tetanuran, Mapusaurus ( Coria & Currie, 2006: fig. 7). Acrocanthosaurus (NCSM 14345) and Giganotosaurus (MUCPv-Ch 1) also possess pneumatic quadrates.

57. Quadrate, depression and foramen on medial surface in the vicinity of the mandibular condyle: absent (0); fossa adjacent to mandibular condyle, foramen more dorsally at base of pterygoid process (1). Britt (1991) described a triangular fossa and small foramen on the medial surface of the quadrate adjacent to the mandibular condyles of Torvosaurus . The presence of these structures was confirmed during the present study ( Fig. 19A ; BYU 5110). The same arrangement is also present in Afrovenator (UC OBA 1), but is absent in all other taxa considered. A small, circular depression is present adjacent to the mandibular condyle in Marshosaurus (CMNH 021704). This may represent incipient development of the derived condition, but is considered here as absence.

67. Basioccipital apron, fossa ventral to occipital condyle: narrow and groove-like (0); broad depression approximately two-thirds the width of the occipital condyle (1). In most theropods, the posterior surface of the basioccipital ventral to the occipital condyle bears a narrow horizontal groove separating paired depressions that extend onto the posterior surfaces of the basal tubera ( Acrocanthosaurus ; NCSM 14345; Allosaurus ; Madsen, 1976a: fig. 13; Ceratosaurus ; Madsen & Welles, 2000: pl. 4C). However, in megalosaurids, such as Dubreuillosaurus (Allain, 2002: fig. 14A) and Eustreptospondylus (OUMNH J.13558; Sadleir et al., 2008: fig. 11A), and in spinosaurids ( Charig & Milner, 1997: fig. 9A; Sues et al., 2002: fig. 3), this groove is modified to form a broad depression at least two-thirds the width of the occipital condyle.

73. Basipterygoid processes: located anterior or anteroventral to basal tubera (0); located ventral to basal tubera (1). In most theropods, the basipterygoid processes are located anterior or anteroventral to the basal tubera, so that the ventral surface of the basisphenoid, including the basisphenoid recess, is visible in ventral view. Contrastingly, in Baryonyx (BMNH R9951; Charig & Milner, 1997: fig. 9), Dilophosaurus (UCMP 37302; Welles, 1984: fig. 6) and Irritator ( Sues et al., 2002: fig. 3), the basipterygoid processes are long, ventrally directed structures located almost ventral to the basal tubera, so that the basisphenoid recess is also visible in posterior view.

80. Dentary, longitudinal groove housing dorsally situated row of neurovascular foramina on lateral surface: absent or weak (0); present and well defined (1). Rauhut (2003) considered the presence of a well-defined groove on the lateral surface of the dentary as an autapomorphy of Magnosaurus ( Eustreptospondylus and Magnosaurus ). However, this groove is also present in a range of other theropods, including Dubreuillosaurus (MNHN 1998-13; Allain, 2002: fig. 15) and carcharodontosaurids, such as Acrocanthosaurus (NCSM 14345), Giganotosaurus (MUCPv-Ch 1) and Mapusaurus (MCF-PVPH- 108.125; Coria & Currie, 2006: fig. 9), and Sinraptor (IVPP 10600; Currie & Zhao, 1994).

81. Dentary, paradental groove wide anteriorly: no, narrow anteriorly (0); yes (1). Benson et al. (2008) observed that the paradental grooves of Dubreuillosaurus and Megalosaurus were wide anteriorly, defining a gap between the medial wall of the dentary and the interdental plates. This is also the case in other megalosaurids, such as Duriavenator ( Benson, 2008a: fig. 1S), Eustreptospondylus (OUMNH J.13558; Sadleir et al., 2008: fig. 8C) and spinosaurids, such as Baryonyx (BMNH R9951). In other theropods, the groove is narrow anteriorly.

82. Dentary, number of Meckelian foramina: one (0); two (1). Whereas, in the majority of basal tetanurans, two Meckelian foramina are present in the dentary (for example, Madsen, 1976a), in some allosauroids, such as Giganotosaurus (MUCPv-Ch 1), Mapusaurus ( Coria & Currie, 2006: fig. 8D) and Neovenator (Brusatte et al., 2008: fig. 8B), only a single foramen is present. A single Meckelian foramen is also present in abelisaurids ( Sampson & Witmer, 2007: fig. 26) and some coelurosaurs ( Brochu, 2002: fig. 40).

89. Lateral teeth, mesial carina: extends to base of crown (0); terminates around midheight of crown or more dorsally (1). In carcharodontosaurids with specialized teeth, such as Mapusaurus (MCF-PVPH-108.8; Coria & Currie, 2006), spinosaurids, such as Baryonyx (BMNH R9951; Charig & Milner, 1997), and non-tetanuran theropods, such as abelisaurids (Smith, 2007) and Dilophosaurus (UCMP 37302), the mesial carina extends to the base of the crown. In other theropods, the mesial carina extends only halfway towards the tooth base.

90. Lateral teeth, interdenticular sulci: absent (0); present (1). Currie, Rigby & Sloan (1990) described ‘blood grooves’ in tyrannosaurid teeth from the Judith River Formation (late Campanian) of Alberta. These take the form of fine grooves that continue a short distance onto the labial and lingual surfaces of the tooth from between the denticles. They were subsequently noted in other theropods, such as Fukuiraptor ( Azuma & Currie, 2000) , Majungasaurus (Smith, 2007) and Megalosaurus ( Benson, 2009) . Smith (2007) renamed these structures ‘interdenticular sulci’. This name is preferred here as it explicitly refers to the morphology without invoking possible function.

100. Surangular, number of posterior surangular foramina: one (0); two (1). In all basal theropods, at least one foramen is present posteriorly on the lateral surface of the surangular ventral to the mandibular condyle. Usually, only a single foramen is present ( Fig. 5A–C, F ), but, in Allosaurus (UMNH VP 9191; contra Madsen, 1976a) and Sinraptor (IVPP 10600; Currie & Zhao, 1994), two are present.

112. Middle cervical vertebrae, pleurocoel penetrates centrum through parapophysis: no (0); yes (1). In most theropods, the pleurocoels of the middle cervical vertebrae are located posterior or posterodorsal to the parapophyses ( Holtz et al., 2004). However, in Condorraptor ( Rauhut, 2005: fig. 4) and Marshosaurus (CMNH 021704), the pleurocoel (= pneumatic foramen) of some middle cervical vertebrae penetrates through the posterodorsal part of the parapophysis. The condition of this character is unknown in Piatnitzkysaurus .

117. Dorsal vertebrae, hyposphene: laminae diverge ventrolaterally to form a triangular shape in posterior view (0); laminae vertical forming a sheet-like hyposphene (1). The hyposphene of theropods is composed of paired laminae that extend ventrally or ventrolaterally from the ventromedial contact between the postzygapophyses. In most basal theropods, these laminae diverge ventrolaterally so that the hyposphene has a triangular outline in posterior view ( Fig. 6Q, R ; Madsen, 1976a). However, in abelisaurids, such as Carnotaurus (MACN-CH 894) and Majungasaurus ( O’Connor, 2007) , and in carcharodontosaurids, such as Giganotosaurus (MUCPv-Ch 1), Mapusaurus (MPEF-PVPH- 108.84; Coria & Currie, 2006: fig. 15C) and Neovenator (BMNH R10001; Brusatte et al., 2008), the laminae extend ventrally parallel to each other, giving the hyposphene a sheet-like morphology.

119. Dorsal vertebrae, neural spines: transversely compressed sheets (0); transversely broadened anteriorly and posteriorly, and central regions of lateral surfaces embayed by deep, vertically oriented troughs (1). Most theropods have thin, sheet-like or slightly transversely thickened dorsal neural spines (for example, Madsen, 1976a; Britt, 1991; Holtz et al., 2004). However, in some carcharodontosaurids, including Acrocanthosaurus (OMNH 10146), Giganotosaurus (MUCPv-Ch 1) and Mapusaurus ( Coria & Currie, 2006: fig. 15), the dorsal neural spines have the structure of an I-beam. They are transversely expanded anteriorly and posteriorly and broad longitudinal troughs on the lateral surfaces that cause the central part to be much narrower.

127. Sacrum, fenestrae between sacral neural spines: absent (0); present (1). In Lourinhanosaurus (ML 370) and Megalosaurus ( Fig. 7 ), fenestrae are present between the sacral neural spines. In some other basal tetanurans, these are absent and the anterior and posterior margins of adjacent sacral neural spines are in contact along their length (for example, Madsen, 1976a; Currie & Zhao, 1994). Unfortunately, few basal theropod sacra are well preserved and this character could not be scored in many taxa.

146. Humerus, anterior surface of bone immediately proximal to ulnar condyle: smooth or gently depressed (0); bears well-defined fossa (1). The anterior surface of the humerus adjacent to the ulnar condyle is smooth in many basal theropods (for example, Sadleir et al., 2008). However, in abelisaurids ( Carrano, 2007), allosauroids, such as Allosaurus ( Madsen, 1976a) , and in Piatnitzkysaurus and Xuanhanosaurus ( Dong, 1984; Bonaparte, 1986), a well-defined fossa bound medially and laterally by low, proximodistally elongate ridges is present.

147. Humerus, prominent ulnar epicondyle: absent (0); present (1). A weak, mound-like structure on the lateral surface of the distal humerus adjacent to the ulnar condyle represents the ulnar epicondyle of theropods. In Acrocanthosaurus , Allosaurus and Chilantaisaurus , this structure is hypertrophied and prominent ( Benson & Xu, 2008).

149. Ulna, proximal end with hypertrophied medial and lateral processes: no (0); yes (1). Charig & Milner (1997: fig. 34) described the distinctive ulna of Baryonyx . It possesses a prominent olecranon process that extends further medially than in most other theropods, and a prominent but broken lateral process (= lateral tuberosity) that is not present in other theropods (BMNH R9951). They described the most unusual feature of the ulna as the broad distal end. Sereno et al. (1998: ch 33) formulated a character describing a hypertrophied ulnar internal tuberosity (and radial external tuberosity) at the distal end of the bone that was scored as present in Baryonyx and Suchomimus . This structure is also present in Acrocanthosaurus (NCSM 14345; Currie & Carpenter, 2000: fig. 9), whereas the medial and lateral processes of the proximal end of the bone that are the subject of the present character are only present in Baryonyx and Suchomimus (MNN GDF 500). Smith et al. (2008: character 349) formulated a character to describe the ‘robust’ lateral tuberosity of the proximal end of the ulna of Megaraptor , Torvosaurus and spinosaurids such as Baryonyx and Suchomimus . However, although, in Megaraptor and Torvosaurus , this tuberosity is a small, ridge-like structure, not unlike the rounded condition in most theropods, in spinosaurids the structure is enlarged and comparable in width to the humeral articular surface of the ulna ( Suchomimus ; MNN GDF 500), and an even more prominent medial process, that is absent in the other taxa, is present ( Baryonyx ; Charig & Milner, 1997: fig. 34). Therefore, the homology statement implied by Smith et al. (2008: ch 349), wherein the lateral tuberosity of Megaraptor and Torvosaurus is likened to the condition in spinosaurids, is not adopted here.

152. Radius, tuber around midlength on posteromedial surface: absent (0); present (1). Allain & Chure (2002: fig. 3D–E) stated that the radius of Poekilopleuron was unique in the presence of a mound-like ulnar process located around midlength. However, Currie & Carpenter (2000: fig. 9G, I) described a similar structure in Acrocanthosaurus , and its presence was confirmed during the present study (NCSM 14345).

167. Ilium, acetabular margin of pubic peduncle: mediolaterally convex or flat (0); mediolaterally concave (1). In most theropods, the posterior surface of the pubic peduncle that bounds the acetabulum is mediolaterally flat or convex. In the megalosaurids Afrovenator (UC OBA 1), Eustreptospondylus (OUMNH J.29775), Megalosaurus ( Fig. 14A–B ) and Torvosaurus (BYU 4977), this margin is concave.

188. Femur, groove on proximal surface of head oriented oblique to the long axis of the head: absent (0); present (1). Carrano et al. (2002: fig. 14E) described an ‘articular groove’ on the proximal surface of the femoral head of Masiakasaurus . This is also present in Megalosaurus and a range of other non-neotetanuran theropods. In neotetanurans, such as Allosaurus (UMNH VP specimens; femoral head directed anteromedially at around 20°; Benson, 2009) and Tyrannosaurus ( Brochu, 2002: fig. 95I; femoral head directed medially), the groove is absent. This is even true in Neovenator (Brusatte et al., 2008: pl 40, fig. 7), which has a femoral head that is directed anteromedially at approximately 45°. This suggests that the presence of the groove is not correlated with the increasingly medial orientation of the femoral head in neotetanurans.

198. Femur, long axis of medial condyle in distal view: oriented anteroposteriorly (0); inclined posterolaterally (1). Whereas, in the majority of theropods, the medial condyle of the femur is oriented anteroposteriorly (for example, Madsen, 1976a; Holtz et al., 2004), in some taxa, including the spinosaurids Baryonyx ( Charig & Milner, 1997: fig. 41E) and Suchomimus (MNN GDF 500), the long axis of the condyle diverges posteromedially.

203. Tibia, fibular flange shape: transversely narrow flange (0); oval mound (1). The fibular flange of the tibia usually forms a transversely narrow flange (for example, Madsen, 1976a; Britt, 1991). However, in Megalosaurus ( Fig. 17C–D ), Piatnitzkysaurus (PVL 4073) and Sinraptor ( Currie & Zhao, 1994: fig. 22L), the fibular flange is transversely expanded and takes the form of a mound-like rugose tuber.

207. Fibula, lateral surface of proximal end: shallow longitudinal trough situated posteriorly (0); trough absent or weak groove present (1). In most theropods, the lateral surface of the fibula is anteroposteriorly convex (for example, Dubreuillosaurus, Allain, 2005a ) or bears only a weak longitudinal groove posteriorly. However, in Afrovenator (UC OBA 1), Chuandongocoelurus (CCG 20010), Suchomimus (MNN GDF 500) and ‘ Syntarsus ’ kayentakatae (MNA 2623; TMM 43688), a shallow longitudinal trough is located posteriorly.

Analysis

The complete dataset used herein is given in Appendix S3 (see Supporting Information) and is also available on request from the author. The Parsimony Ratchet is a method for rapid searching of large phylogenetic datasets ( Nixon, 1999). Nixon (1999) regarded this search strategy as one that maximized computing time spent on improving the current tree and breaking out of ‘islands’ of short (but not necessarily shortest) trees in ‘tree space’. This method is most impressive when applied to very large datasets of several hundred taxa ( Nixon, 1999). However, its effectiveness in sampling numerous tree ‘islands’ is an important property that is exploited here to maximize exploration of ‘tree space’. In the analyses performed herein, a preliminary search was conducted using the Parsimony Ratchet as implemented by PAUPRat ( Sikes & Lewis, 2001). The trees saved from this preliminary search were filtered so that only the most parsimonious trees (MPTs) were retained, and condensed so that only unique topologies were stored. Trees in the resulting set of unique MPTs were used as the starting point for tree bisection–reconnection (TBR) branch swapping to fully explore the ‘tree islands’ that they represented. This resulted in the generation of a larger set of MPTs. Although this search strategy is ‘heuristic’, two repeats of this process failed to find any additional unique MPTs for any analysis. This suggests that the complete set of MPTs was recovered in all cases.

The preliminary Parsimony Ratchet search recovered 106 unique MPTs, each 596 steps long. TBR branch swapping generated additional trees of this length, resulting in a total of 189 456 MPTs. In the strict consensus of these cladograms, only four clades were resolved within Tetanurae: Condorraptor + Piatnitzkysaurus ; Chuandongocoelurus + Monolophosaurus ; Coelurosauria ( Chilantaisaurus , Compsognathus , Guanlong and Tanycolagreus ); and Spinosauridae ( Baryonyx , Suchomimus , Irritator and Spinosaurus ). Poor resolution of the strict consensus resulted from the unstable phylogenetic positions of six ‘wildcard’ taxa, Eocarcharia , Magnosaurus , Megaraptor , Piveteausaurus , Poekilopleuron and Streptospondylus , which have high proportions of missing data ( Table 5). These were deleted from the MPTs following the strict reduced consensus method of Wilkinson (1994). This resulted in a reduction to 24 unique topologies. The strict (reduced) consensus of these cladograms is identical to the Adams consensus, indicating that further pruning will not result in an increase in resolution. To confirm the result recovered by strict reduced consensus, a reduced version of the original dataset was created by a priori deletion of the ‘wildcard’ taxa from the data matrix. Eight unique MPTs, each 586 steps long, were recovered using PAUPRat. TBR branch swapping based on these trees resulted in an increase to 16 MPTs. The strict consensus of these trees ( Fig. 20 ) only differs from the strict reduced consensus of the original dataset in one respect: a clade comprising Metriacanthosaurus and Sinraptor is resolved as the sister taxon of Lourinhanosaurus within Sinraptoridae . Details of the optimization of characters over this topology are given in Table 6 and Appendix S2. Aspects of character optimization among megalosauroid clades are discussed below.

Systematic position of ‘wildcard’ taxa

It is not possible to fully resolve the phylogenetic position of taxa deleted as part of the strict reduced consensus method. However, by examining the position of each taxon in the Adams consensus of MPTs generated by analysis of the original dataset, and the effect on resolution caused by pruning of each taxon, it is possible to say which clade they belong to based on the current dataset.

Eocarcharia and Poekilopleuron form a polytomy with Allosaurus , Carcharodontosauridae and Sinraptoridae at the base of Allosauroidea in the Adams consensus of MPTs. This indicates that Eocarcharia and Poekilopleuron are allosauroids. Deletion of either taxon individually from the MPTs had no effect on resolution. Deletion of both Eocarcharia and Poekilopleuron concurrently with Megaraptor and Streptospondylus improved resolution among allosauroids other than carcharodontosaurines. This indicates the existence of MPTs in which either taxon is a sinraptorid or non-carcharodontosaurine carcharodontosaurid.

A lack of diagnostic features in Poekilopleuron caused Allain & Chure (2002) to tentatively assign the taxon to Spinosauroidea incertae sedis pending a detailed phylogenetic analysis of the European Megalosauridae . Allain & Chure (2002) noted the absence of putative allosauroid characters in Poekilopleuron : a sigmoidal humerus; a medial process on the posterior margin of the articular surface of the astragalus; and L-shaped middle caudal chevrons. However, these observations are problematic for the reasons outlined below.

The humerus of Poekilopleuron is incomplete, but was interpreted as sigmoidal in the present study based on the preserved portion (MNHN 1897-2; contra Allain & Chure, 2002). However, a sigmoidal humerus is not an allosauroid synapomorphy. Although it is present in Allosaurus ( Madsen, 1976a) , it is also known in a range of other theropods, including Dilophosaurus ( Welles, 1984) and Piatnitzkysaurus ( Bonaparte, 1986) . Furthermore, the humerus of carcharodontosaurids, such as Acrocanthosaurus ( Currie & Carpenter, 2000) and Mapusaurus ( Coria & Currie, 2006) , is straight.

The medial process on the posterior margin of the astragalar articular surface is present as a low mound in allosauroids, such as Acrocanthosaurus (NCSM 14345) and Allosaurus ( Madsen, 1976a) . However, the region of the astragalus in which a posteromedial process would be present is damaged in Poekilopleuron and the condition is indeterminate ( Eudes-Deslongchamps, 1838: pl. 6; reproduced in Allain & Chure, 2002: fig. 4).

In theropods with L-shaped middle caudal chevrons (character 135.1), this condition is only fully manifest in the more distal middle caudal chevrons. In Poekilopleuron , these chevrons are not preserved, but the middle caudal chevrons that are preserved show incipient development of the L-shaped condition ( Allain & Chure, 2002: fig. 1A). Consequently, Poekilopleuron is scored as possessing ‘L-shaped’ middle caudal chevrons in the present study.

Allain & Chure (2002) identified a putative megalosauroid (spinosauroid) synapomorphy in Poekilopleuron : a humeral deltopectoral crest more than 45% of the humeral length. However, the humerus of Poekilopleuron is heavily restored and this character was scored as indeterminate for Poekilopleuron in the present study. Galton & Jensen (1979) noted similarity between the robust forelimb elements of Poekilopleuron and the megalosauroids Megalosaurus and Torvosaurus . A character describing this potential synapomorphy was included in the present analysis (character 148), but does not support a megalosauroid affiliation of Poekilopleuron , as a robust forelimb is also present in the allosauroid Acrocanthosaurus (NCSM 14345; Currie & Carpenter, 2000). Poekilopleuron also shares the presence of a tuber around midlength on the lateral surface of the radius with Acrocanthosaurus (NCSM 14345), a condition not found in any other theropod (character 152.1).

Sereno & Brusatte (2008) recovered Eocarcharia as the sister taxon of Acrocanthosaurus within Carcharodontosauridae . They also noted that it lacked features of derived carcharodontosaurids, such as rugose craniofacial bones and transversely compressed teeth with marginal enamel wrinkles. However, it also lacks the features of more basal carcharodontosaurids, such as Acrocanthosaurus (NCSM 14345): a prominent suborbital flange of the postorbital and a ‘palpebral’ ossification fused to the postorbital (cf. Coria & Currie, 2006). Sereno & Brusatte (2008) cited the presence of a robust postorbital ‘brow’ (character 45.1). However, this feature is also present in Sinraptor (IVPP 10600; Currie & Zhao, 1994: fig. 3A). They also note the presence of a small articular surface for the lacrimal on the postorbital, which is only otherwise present in carcharodontosaurids among allosauroids. Taxon Optimization

Ceratosauria + Tetanurae Unambiguous: 1 (2 → 0); 7 (1 → 0); 10 (1 → 0); 11 (1 → 0); 28 (2 → 0); 41

(1 → 0); 64 (2 → 1); 72 (0 → 1); 77 (1 → 0); 102 (0 → 1); 137 (0 → 1); 163 (0 → 1); 173 (0 → 2); 195 (0 → 1); 204 (0 → 1)

ACCTRAN: 15 (0 → 1); 18 (0 → 1); 25 (0 → 1); 26 (0 → 1); 51 (1 → 0); 90

(0 → 1); 98 (1 → 0); 107 (0 → 1); 110 (0 → 1); 132 (0 → 1); 160 (1 → 0)

Ceratosauria Marsh, 1884 Unambiguous: 13 (1 → 2); 21 (0 → 1); 55 (0 → 1); 74 (0 → 1); 104 (1 → 0); 105 (1 → 0); 121 (0 → 1); 125 (0 → 1); 136 (0 → 1); 186 (0 → 1); 197

(0 → 1); 199 (0 → 1); 201 (0 → 1)

ACCTRAN: 17 (0 → 1); 109 (1 → 2); 148 (1 → 0); 205 (0 → 1)

DELTRAN: 51 (1 → 0); 90 (0 → 1); 109 (0 → 2)

Tetanurae Gauthier, 1986 Unambiguous: 16 (0 → 1); 71 (0 → 1); 89 (0 → 1); 92 (1 → 2); 99 (0 → 1); 106 (0 → 1); 111 (0 → 1); 113 (0 → 1); 140 (0 → 1); 153 (0 → 1); 156 (0 → 1); 165 (0 → 1); 170 (0 → 1); 187 (0 → 1); 193 (0 → 1); 208 (3 → 1);

209 (2 → 1); 210 (0 → 1); 212 (0 → 1)

ACCTRAN: 52 (1 → 0); 76 (0 → 1); 95 (0 → 1); 127 (0 → 1); 130 (0 → 1); 131 (2 → 0); 139 (1 → 0); 141 (1 → 2); 155 (1 → 0); 162 (0 → 1); 181 (0 → 1); 190 (0 → 1)

DELTRAN: 18 (0 → 1); 107 (0 → 1); 109 (0 → 1); 110 (0 → 1); 132 (0 → 1); 160 (1 → 0); 190 (0 → 1)

Megalosauroidea ( Huxley, 1869) Unambiguous: 48 (0 → 1); 64 (1 → 0); 116 (0 → 1); 118 (0 → 1); 120 (0 → 1); 134 (0 → 1); 166 (0 → 1); 194 (1 → 0)

ACCTRAN: 38 (0 → 1); 69 (0 → 1); 86 (1 → 0); 87 (0 → 1); 90 (1 → 0);

97 (0 → 1); 161 (1 → 0); 177 (1 → 0)

DELTRAN: 15 (0 → 1); 52 (1 → 0); 162 (0 → 1)

New clade A1 Unambiguous: 146 (0 → 1)

( Xuanhanosaurus + A2) ACCTRAN: 13 (1 → 0); 78 (0 → 1); 102 (1 → 0); 112 (0 → 1); 128 (0 → 1); 131 (0 → 2)

DELTRAN: 141 (1 → 2)

New clade A2 ( Marshosaurus + Unambiguous: 143 (1 → 0)

Condorraptor + Piatnitzkysaurus ) ACCTRAN: 124 (0 → 1)

DELTRAN: 13 (1 → 0); 102 (1 → 0); 112 (0 → 1)

Condorraptor + Piatnitzkysaurus Unambiguous : 113 (1 → 0)

ACCTRAN: 23 (0 → 1); 86 (0 → 1)

DELTRAN: 95 (0 → 1); 128 (0 → 1)

New clade B Unambiguous: 9 (0 → 1); 77 (0 → 1); 200 (1 → 0)

ACCTRAN: 12 (1 → 0); 56 (0 → 1); 81 (0 → 1); 103 (0 → 1); 141 (2 → 0); 148 (1 → 0); 159 (0 → 1); 181 (1 → 0); 206 (0 → 1); 207 (0 → 1);

208 (1 → 0).

DELTRAN: 25 (0 → 1); 26 (0 → 1); 86 (1 → 0); 161 (1 → 0)

Chuandongocoeulurus + Unambiguous: 169 (0 → 1); 170 (1 → 0)

Monolophosaurus ACCTRAN : 5 (0 → 1); 29 (0 → 1); 30 (0 → 1); 32 (0 → 1); 34 (0 → 1);

50 (0 → 1); 51 (0 → 1); 59 (0 → 1); 171 (0 → 1); 187 (1 → 0); 193 (1 → 0); 208 (0 → 2); 209 (1 → 2)

Megalosauridae + Spinosauridae Unambiguous : 1 (0 → 2); 13 (1 → 2); 67 (0 → 1); 79 (0 → 1); 166 (1 → 2); 195 (1 → 0)

ACCTRAN: 10 (0 → 1); 27 (0 → 1); 33 (2 → 1); 39 (0 → 1); 47 (0 → 1);

56 (1 → 2); 95 (1 → 0); 167 (0 → 1)

DELTRAN: 81 (0 → 1); 131 (2 → 0); 141 (1 → 0); 148 (1 → 0); 208 (1 → 0)

Megalosauridae Huxley, 1869 Unambiguous : 55 (0 → 1); 71 (1 → 0); 80 (0 → 1); 144 (1 → 2); 178 (0 → 1); 180 (0 → 1); 184 (0 → 1); 209 (1 → 0)

ACCTRAN: 37 (1 → 0); 87 (1 → 0); 140 (1 → 0); 206 (1 → 0); 207 (1 → 0)

DELTRAN: 38 (0 → 1); 39 (0 → 1); 47 (0 → 1); 51 (1 → 0); 69 (0 → 1);

167 (0 → 1)

Clade C Unambiguous: 1 (2 → 1); 57 (0 → 1); 107 (1 → 0); 189 (1 → 0)

Taxon Optimization

Megalosaurids other than ACCTRAN: 10 (1 → 0); 12 (0 → 1); 70 (0 → 1); 77 (1 → 0); 90 (0 → 1);

Eustreptospondylus 137 (1 → 0); 168 (1 → 0)

Afrovenator + Dubreuillosaurus Unambiguous : 11 (0 → 1)

ACCTRAN: 37 (0 → 1); 38 (1 → 2); 77 (0 → 1); 102 (1 → 0); 103 (1 → 0);

159 (1 → 0); 177 (0 → 1); 205 (0 → 1)

DELTRAN: 90 (0 → 1)

Megalosaurus + Torvosaurus Unambiguous : 24 (0 → 1); 80 (1 → 0); 95 (0 → 1)

ACCTRAN: 42 (0 → 1); 104 (1 → 0); 105 (1 → 0); 155 (0 → 1); 210 (1 → 2)

DELTRAN: 77 (1 → 0); 90 (0 → 1); 130 (0 → 1); 137 (1 → 0); 140 (1 → 0);

168 (1 → 0); 177 (1 → 0)

Spinosauridae Stromer, 1915 Unambiguous : 2 (0 → 1); 7 (0 → 1); 8 (0 → 1); 9 (1 → 2); 15 (1 → 0); 19 (0 → 1); 20 (0 → 1); 22 (0 → 1); 35 (1 → 0); 38 (1 → 3); 42 (0 → 1); 73 (0 → 1); 83 (1 → 3); 85 (0 → 1); 91 (0 → 1); 93 (0 → 1); 94 (0 → 1); 120 (1 → 2)

ACCTRAN: 53 (1 → 0); 69 (1 → 0); 86 (0 → 2); 89 (1 → 0); 97 (1 → 0); 98

(0 → 1); 105 (1 → 0); 133 (1 → 0); 145 (0 → 1); 149 (0 → 1); 150 (0 → 1); 191 (0 → 1); 198 (0 → 1); 202 (0 → 1)

DELTRAN: 10 (0 → 1)

Baryonychinae (Charig & Milner, Unambiguous: 3 (1 → 0); 122 (0 → 1); 123 (0 → 1)

1986) ACCTRAN: 12 (0 → 1)

DELTRAN: 86 (0 → 2); 87 (0 → 1); 89 (1 → 0); 105 (1 → 0); 133 (1 → 0); 145 (0 → 1); 149 (0 → 1); 150 (0 → 1); 159 (0 → 1); 198 (0 → 1)

Spinosaurinae ( Stromer, 1915) Unambiguous : 88 (0 → 1); 96 (0 → 1)

ACCTRAN: 4 (1 → 0); 5 (0 → 1); 13 (2 → 0); 39 (1 → 0)

Neotetanurae Sereno et al., 1994 Unambiguous: 188 (1 → 0)

ACCTRAN: 4 (1 → 0); 15 (1 → 2); 25 (1 → 0); 26 (1 → 0); 34 (0 → 1); 36 (1 → 0); 40 (0 → 1); 49 (1 → 0); 51 (0 → 1); 66 (0 → 1); 70 (0 → 1); 84 (0 → 1); 101 (0 → 1); 138 (0 → 1); 147 (0 → 1); 158 (0 → 1); 164 (0 → 1); 172 (0 → 1); 174 (0 → 1); 184 (0 → 1); 191 (0 → 1); 213 (0 → 1)

DELTRAN: 90 (0 → 1)

Allosauroidea + Coelurosauria Unambiguous: 166 (0 → 3); 202 (0 → 1)

ACCTRAN: 144 (1 → 0)

DELTRAN: 4 (1 → 0); 15 (0 → 2); 36 (1 → 0); 49 (1 → 0); 84 (0 → 1); 131

(2 → 0); 147 (0 → 1); 158 (0 → 1); 174 (0 → 1); 191 (0 → 1); 213 (0 → 1)

Allosauroidea ( Marsh, 1878) Unambiguous: 30 (0 → 1); 32 (0 → 1); 38 (0 → 2); 39 (0 → 1); 43 (0 → 1); 45 (0 → 1); 124 (0 → 1); 135 (0 → 1); 142 (0 → 1); 146 (0 → 1); 175 (0 → 1)

ACCTRAN: 21 (0 → 1); 52 (0 → 1); 56 (0 → 1); 98 (0 → 1); 100 (0 → 1); 104 (1 → 0); 105 (1 → 0); 157 (0 → 1)

DELTRAN: 40 (0 → 1); 76 (0 → 1); 95 (0 → 1); 130 (0 → 1); 138 (0 → 1); 139 (1 → 0); 141 (1 → 2); 144 (1 → 0); 155 (1 → 0); 162 (0 → 1); 164 (0 → 1); 181 (0 → 1)

Carcharodontosauridae Stromer, Unambiguous : 25 (0 → 1); 82 (1 → 0); 109 (1 → 2); 111 (1 → 2); 115 (1 → 2);

1931 117 (0 → 1); 179 (0 → 1); 187 (1 → 2); 205 (0 → 2)

ACCTRAN: 1 (0 → 1); 29 (0 → 1); 36 (0 → 1); 44 (0 → 1); 46 (0 → 1); 47 (0 → 2); 50 (0 → 2); 54 (0 → 1); 56 (1 → 0); 64 (1 → 0); 66 (1 → 0); 68 (0 → 1); 70 (1 → 0); 77 (0 → 1); 84 (1 → 0); 100 (1 → 0); 128 (0 → 2); 148 (1 → 0); 150 (0 → 1); 151 (0 → 1); 152 (0 → 1); 154 (0 → 1); 157 (1 → 0)

DELTRAN: 21 (0 → 1); 101 (0 → 1); 104 (1 → 0); 105 (1 → 0); 172 (0 → 1); 184 (0 → 1)

Clade D ( Acrocanthosaurus + Unambiguous: 14 (0 → 1); 80 (0 → 1); 107 (1 → 0); 119 (0 → 1); 120 (0 → 2);

Tyrannotitan + 137 (1 → 2); 208 (1 → 2); 210 (1 → 2)

Carcharodontosaurinae ) ACCTRAN: 5 (0 → 1); 29 (1 → 2); 31 (0 → 1); 77 (1 → 2); 95 (1 → 2);

126 (0 → 1)

DELTRAN: 34 (0 → 1); 44 (0 → 1); 46 (0 → 1); 47 (0 → 2); 50 (0 → 2);

54 (0 → 1); 64 (1 → 0); 68 (0 → 1); 77 (0 → 2); 154 (0 → 1)

0); 0 Lacrimal–postorbital contact was scored as present in Eocarcharia (character 44.1), but does not unequivocally support a carcharodontosaurid affiliation. Although it is likely that Eocarcharia is a carcharodontosaurid on the basis of geographical and temporal provenance, the preserved materials are not sufficient to confirm this hypothesis.

Magnosaurus forms a polytomy at the base of Megalosauridae with Eustreptospondylus and a clade comprising all other megalosaurids in the Adams consensus of MPTs. This indicates that it is a megalosaurid. Deletion of Magnosaurus from the MPTs resulted in the resolution of Eustreptospondylus as sister taxon to a clade comprising all other megalosaurids. This indicates the existence of MPTs in which Magnosaurus is the sister taxon of Eustreptospondylus or a member of the clade of all other megalosaurids. Rauhut (2003) noted features shared with Eustreptospondylus , on which basis he suggested that the taxa were congeneric. However, these features are also found in Dubreuillosaurus (Allain, 2002; Sadleir et al., 2008), and as such they do not support a sister taxon relationship between Eustreptospondylus and Magnosaurus .

Megaraptor forms a polytomy with Allosauroidea, Coelurosauria and Fukuiraptor at the base of Neotetanurae in the Adams consensus of MPTs constructed by analysis of the unreduced dataset. This indicates that Megaraptor is a neotetanuran. Deletion of Megaraptor from the MPTs resulted in the resolution of Carcharodontosaurinae . Although Coelurosauria was fully resolved in the unreduced strict consensus, the resolution of Allosauroidea could not be further improved by deletion of any other taxon, without the concurrent deletion of Megaraptor and Streptospondylus . This indicates the presence of MPTs in which Megaraptor is a basal neotetanuran, and MPTs in which it is a member of every allosauroid clade. The unstable phylogenetic position of Megaraptor is consistent with the high proportion of missing data in this taxon, and the absence of synapomorphies of any major clade within Neotetanurae in the fragmentary material currently referred to the taxon ( Novas, 1998; Calvo et al., 2004).

Smith et al. (2007) recovered Megaraptor in a polytomy with Carcharodontosaurus and Giganotosaurus on the basis of the number and orientation of the cervical pleurocoels, the presence of a marked prezygapophyseal–epipophyseal lamina, the presence of a hyposphene/hypantrum-like articulation in the cervical vertebrae and the presence of pleurocoels in the caudal vertebrae. However, none of these conditions supports a carcharodontosaurid affinity of Megaraptor in the present study, as discussed below.

In carcharodontosaurids, the cervical pleurocoels comprise two openings, the second located posterodorsal to the first, or small, single openings similar to those of other tetanurans (variable within a single individual: MIWG 6348; OMNH 10146; Harris, 1998; Brusatte et al., 2008). Calvo et al. (2004) clearly described the autapomorphic cervical pleurocoels of Megaraptor , which are unlike those of carcharodontosaurids (contra Smith et al., 2007). They are anteroposteriorly elongate and large compared with those of other theropods (MUCPv 341). Although Calvo et al. (2004: fig. 4A, B) seem to figure the presence of two pleurocoels in the carcharodontosaurid style, the posterodorsal ‘pleurocoel’ is an imperforate depression (MUCPv 341; Fig. 19C, D ), identical to the imperforate, and possibly non-pneumatic depression (= pleurocentral depression) in this location in other theropods, such as Allosaurus ( Madsen, 1976a) .

The character of a prominent prezygapophyseal– epipophyseal lamina was not included in the present analysis, as it was deemed to form a continuous spectrum of prominence, both between taxa and within the cervical series of included taxa. Only in abelisaurids was a notably prominent prezygapophyseal– epipophyseal lamina present. As Abelisauridae was incorporated as a single OTU, this condition is not phylogenetically informative over the present taxon sample. The hyposphene/hypantrum-like articulation in the cervical vertebrae, mentioned by Smith et al. (2007), could not be confirmed during the course of the present study; the condition appears to be similar to that of most basal tetanurans (MUCPv 341; Calvo et al., 2004: fig. 4).

On the basis of these observations, the only character that may unite Megaraptor with carcharodontosaurids is the presence of caudal pleurocoels. These are present in Carcharodontosaurus , but absent in Acrocanthosaurus (OMNH 10146; SMU 74646, contra Harris, 1998), Giganotosaurus (MUCPv-Ch 1) and Neovenator (MIWG 6348; Brusatte et al., 2008). Although this character was included in the present analysis (character 129), it does not unequivocally support a carcharodontosaurid affiliation of Megaraptor . Although Megaraptor may be a carcharodontosaurid, referred material is not sufficiently diagnostic to support this hypothesis at present. Alternatively, the discovery of new carcharodontosaurid synapomorphies may support the inclusion of Megaraptor in this clade.

The inclusion of Piveteausaurus has an effect on resolution only within Megalosauridae : no clade can be resolved within Megalosauridae without the deletion of this taxon. This indicates the existence of MPTs in which Piveteausaurus is the sister taxon of every megalosaurid, and that Piveteausaurus belongs within Megalosauridae . Piveteausaurus possesses several characters that support this relationship: a broad fossa ventral to the basioccipital condyle (character 67.1), which is a unique, unambiguous synapomorphy of Megalosauridae + Spinosauridae ; three cranial nerve foramina exit ventrolateral to the condyle, indicating that cranial nerves X and XI exited posteriorly as in megalosaurids and several unrelated taxa (character 69.1), but not in spinosaurids; laterally directed paraoccipital processes (character 71.0), which are an unambiguous synapomorphy of Megalosauridae that represents a reversal to the non-tetanuran condition.

Taquet & Welles (1977: 192, in French) assigned Piveteausaurus to Megalosauridae ‘as a matter of convenience’, because they did not wish to erect a new family on the basis of an isolated braincase. Holtz et al. (2004) considered the genus as Tetanurae incertae sedis. Piveteausaurus has never been included in a phylogenetic analysis and the present work represents the first attempt to elucidate its affinities within the context of a phylogenetic analysis.

Streptospondylus forms a polytomy with Neotetanurae and Megalosauroidea in the Adams consensus. This indicates that it must be a tetanuran, as suggested by the possession of tetanuran characters, such as the presence of single pleurocoels in pneumatic vertebrae (character 111.1). Deletion of Streptospondylus from the MPTs resulted in a great improvement in resolution of Spinosauroidea in the strict consensus, indicating the presence of MPTs in which Streptospondylus is a member of every megalosauroid clade, except for those resolved in the unreduced strict consensus. Without first deleting Streptospondylus , it is not possible to improve resolution within Allosauroidea by deletion of any taxon other than Megaraptor (resolves Carcharodontosaurinae ). This indicates the presence of MPTs in which Streptospondylus is a member of every allosauroid clade other than Carcharodontosaurinae .

Streptospondylus lacks synapomorphies of any major clade within Tetanurae (MNHN 8605–8609, 8707, 8789–8794, 8907, 9645). Although Allain (2001) claimed that Streptospondylus possesses a distinctive hypapophysis morphology of one of the ‘pectoral’ (sensu Welles, 1984) vertebrae, he did not figure this structure, which is figured herein ( Fig. 19B ). Allain (2001) stated that this morphology was also present in Eustreptospondylus , and Smith et al. (2007) found this structure as a synapomorphy of a clade comprising these two taxa. However, the structure is absent in Eustreptospondylus (OUMNH J.13558) and should be considered an autapomorphy of Streptospondylus . Although Sadleir et al. (2008: pl. 5, fig. 11; pl. 6, fig. 11) figured a depression bounded laterally by low ridges on the ventral surface of the tenth cervical and second dorsal vertebrae of Eustreptospondylus , this depression is more likely to be homologous with the hypapophysis of other theropods than with the specific morphology of a bifurcated hypapophysis seen in Streptospondylus ( Fig. 19B ). However, objective comparison of these structures is difficult because of the subadult juvenile status of Eustreptospondylus (OUMNH J.13558), which may have developed a more prominent hypapophysis later in ontogeny.

Megalosauroidea

Megalosauroidea herein is equivalent to Spinosauroidea of several previous authors (for example, Sereno et al., 1996; Rauhut, 2003; Holtz et al., 2004). Megalosauridae was first employed as a family group taxon by Fitzinger (1843) (Megalosauri; Buffetaut, Cuny & Le Loeuff, 1991). The superfamily Spinosauroidea ( Stromer, 1915) is therefore a junior synonym of Megalosauroidea as long as it contains the genus Megalosaurus . Numerous taxa not previously included in Megalosauroidea were recovered as megalosauroids ( M. bucklandii and all taxa sharing a more recent common ancestor with it than with Allosaurus fragilis or Passer domesticus ) ( Fig. 20 ). Previous authors have recovered Megalosauroidea or Spinosauroidea as a clade comprising taxa recovered as megalosaurids or spinosaurids in the present analysis ( Sereno et al., 1994, 1998; Smith et al., 2007), although Holtz et al. (2004) found Piatnitzkysaurus within Megalosauroidea ( Spinosauroidea ) as a megalosaurid, and Rauhut (2003) found Chilantaisaurus as the sister taxon to Spinosauridae within Megalosauroidea ( Spinosauroidea ). Two additional clades of basal megalosauroids were recovered by the present analysis. The most basal clade within Megalosauroidea is that comprising Condorraptor , Marshosaurus , Piatnitzkysaurus and Xuanhanosaurus (new clade A1). The next most basal is the clade comprising Chuandongocoelurus and Monolophosaurus . The affiliation of these clades with Megalosauroidea is poorly supported by tree support metrics ( Fig. 20 ), and it is possible that they will be recovered outside of Megalosauroidea by future analyses.

Megalosauroidea, as currently conceived, is supported by three unique, unambiguous synapomorphies: ventral process of the postorbital U-shaped (character 48.1); proximal articular surface of chevrons without distinct anterior and posterior facets, low mounds may be present laterally on either side (character 134.1); length to width ratio of pubic peduncle of the ilium 1.3–1.4 (character 166.1; transformed to 2 in Megalosauridae + Spinosauridae ). There are also a number of unambiguous synapomorphies of Megalosauroidea that are present in other clades: supraoccipital contribution to the dorsal margin of the foramen magnum large (character 64.0; also in Carcharodontosauridae ); anterior dorsal vertebrae with prominent ventral keels, around onethird the height of and inset from the lateral surfaces of the centrum (character 116.1; reversed in Eustreptospondylus and Marshosaurus ; also present in Carcharodontosaurus and Sinraptor ); dorsal vertebrae with distinct step-like ridge within infrapostzygapophyseal fossa (character 118.1; also in Sinraptor ); dorsal neural spine height 1.4–1.7 times the height of the centrum (character 120.1; also in Dilophosaurus ; transformed to 2 in Megalosaurus and Spinosauridae ); muscle scar situated medially on the anterior surface of the distal femur present as a rugose patch not extending to the distal end of the femur (character 194.0; also in Dilophosaurus and Lourinhanosaurus ).

The following character is a synapomorphy of Megalosauroidea under ACCTRAN: cranial nerves X and XI exit posteriorly through a foramen lateral to the exit of cranial nerve XII and the occipital condyle (character 69.1; reversed in Spinosauridae ; also present in Acrocanthosaurus and Dilophosaurus ). This is acquired separately in Condorraptor – Xuanhanosaurus and Megalosauridae under DELTRAN.

The presence of a maxillary ‘fenestra’ with the form of a subcircular fossa (character 15.1; transformed to 2 in Irritator ) is a synapomorphy of Megalosauroidea under DELTRAN. This is also scored as present in Ceratosaurus and is a synapomorphy of Ceratosauria + Tetanurae under ACCTRAN that is lost in Abelisauridae , transformed to a true fenestra (character 15.2) in Neotetanurae. However, in Ceratosaurus , a set of three fossae is present in the anteroventral corner of the antorbital fossa, and this is different to the single fossa present in megalosauroids. As such, the presence of a maxillary ‘fenestra’ with the form of a single subcircular fossa should be considered a unique synapomorphy of Megalosauroidea.

A squamosal anterodorsal lamina that is emarginated by the supratemporal fenestra (character 52.0) is also a megalosauroid synapomorphy under DELTRAN. This feature is also present in the coelurosaur Guanlong and so is recovered as a tetanuran synapomorphy that is reversed in Allosauroidea under ACCTRAN. The feature is also present in some coelurosaurs that were not included in the present analysis, such as Tyrannosaurus rex ( Brochu, 2002) , and a full understanding of its systematic distribution has not yet been attained.

New clade A1 receives low support values ( Fig. 20 ). It is supported by only one unambiguous synapomorphy: the anterior surface of the distal humerus bears a well-defined fossa (character 146.1; also in Abelisauridae and Allosauroidea). Several characters are synapomorphies of the clade comprising all four taxa under ACCTRAN, but Condorraptor + Marshosaurus + Piatnitzkysaurus under DELTRAN because of the high proportion of missing data in Xuanhanosaurus ( Table 5): characters 13.0, 102.0 and 112.1. It is therefore possible that further material of Xuanhanosaurus will reveal that it is not related to the other three taxa. A sigmoidal humerus (character 143.0; also in Allosaurus , Dilophosaurus , Guanlong and Fukuiraptor ) is an unambiguous synapomorphy of Condorraptor + Marshosaurus + Piatnitzkysaurus (new clade A2).

A flat anterior surface of the anterior presacral centra is an unambiguous synapomorphy uniting Condorraptor and Piatnitzkysaurus (character 113.0; also in non-tetanurans). Smith et al. (2007) also recovered a clade comprising Condorraptor and Piatnitzkysaurus based on two unambiguous synapomorphies: the presence of a step-like ridge lateral to the hyposphene in the infrapostzygapophyseal fossa of dorsal vertebrae; and the presence of a low, robust ridge running across the base of the transverse process of the first sacral vertebra, connecting the pre- and postzygapophysis. During the present study, the step-like ridge of the infrapostzygapophyseal fossa of the dorsal vertebrae was identified in a range of other taxa, including Baryonyx (BMNH R9951), Eustreptospondylus (OUMNH J.13558), Megalosaurus ( Fig. 6L ) and Sinraptor ( Currie & Zhao, 1994: fig. 15C), and was found as an unambiguous synapomorphy of Megalosauroidea (character 118.1).

Smith et al. (2007) cited Rauhut (2005) in reference to the character of a low ridge connecting the first sacral zygapophyses. Rauhut (2005: fig. 8A, B) described and figured a high ridge with a dorsolaterally inclined apex on the dorsolateral surface of the ‘transverse process’. It appears that this ridge is the broken base of the true transverse process, located dorsal to the sacral rib articulation (MPEF-PV 1701; not a transverse process, contra Rauhut, 2005). Very few basal tetanuran sacra are well preserved, and Rauhut (2005) probably believed that the transverse process and parapophyses were combined in the first sacral vertebra to form a single rib articulation that he termed the ‘transverse process’. However, comparison with the well-preserved sacrum of Lourinhanosaurus shows that this is not the case (ML 370). In Lourinhanosaurus , all sacral transverse processes form dorsolaterally oriented sheets of bone that connect the part of the neural arch dorsal to the sacral rib attachment to the medial surface of the ilium. In Megalosaurus , the base of the first sacral transverse process is also preserved in a similar fashion to that in Condorraptor ( Fig. 7 ). As the presence of sacral transverse processes seems to be invariant across the present taxon sample, it was not employed as a character in the present analysis.

The clade of megalosauroids other than new clade A1 (termed new clade B) is supported by three unambiguous synapomorphies: a prominent maxillary anterior ramus (character 9.1; also in Allosaurus and Neovenator ; transformed to 2 in Spinosauridae ); the anterior end of the dentary expanded dorsoventrally (character 77.1; also in Neovenator ); lateral condyle of the tibia confluent with cnemial crest in proximal view (character 200.0; reversed in Megalosaurus ). A convex anterior margin of the ilium (character 161.0) is a synapomorphy of this clade under DELTRAN, but is a synapomorphy of Megalosauroidea under ACCTRAN, as the preacetabular blade of the ilium is not known in new clade A1.

Chuandongocoelurus and Monolophosaurus were recovered as sister taxa in the present analysis, although this relationship received low support ( Fig. 20 ). Both taxa have a relatively high proportion of missing data ( Table 5), but share an unusual combination of primitive and derived characters of the ilium (CCG 20010; IVPP 84019). The pubic peduncle is large relative to the ischial peduncle (character 165.1) in both taxa, as in other tetanurans. However, the articular surface of the pubic peduncle is composed of two facets (character 169.1), and the supracetabular crest is hood-like and hypertrophied (character 170.0). Both of these characters are unambiguous synapomorphies of the clade comprising Chuandongocoelurus and Monolophosaurus . The hood-like supracetabular crest is a reversal from the derived condition of a crest formed as a ventrolaterally oriented shelf found in all other tetanurans (character 170.1); the double facet of the pubic peduncle is only otherwise found in Dilophosaurus among the taxa included in the present study, but has also been reported in other non-tetanuran theropods in which the pubis is not fused to the ilium ( Sereno, 1999).

Because Monolophosaurus preserves cranial, axial and pelvic material, whereas Chuandongocoelurus preserves pelvic and hindlimb material (CCG 20010), a number of potential synapomorphies of the clade comprising these two taxa are only recovered under ACCTRAN optimization. These characters are considered to be autapomorphies under DELTRAN. Chuandongocoelurus possesses a ventromedially inclined femoral head (character 187.0), the absence of a femoral extensor groove (character 193.0), a fossa on the medial surface of the proximal fibula that is more than two-thirds the anteroposterior width of the fibula (character 208.2) and a fibular anterolateral process developed as an anterolaterally curving flange (character 209.2). These states of characters 187, 193 and 209 are only otherwise found in non-tetanurans.

Monolophosaurus possesses a subnarial foramen on the suture between the premaxilla and the maxilla (character 5.1), rugose nasal bones (character 29.1), overlap of the antorbital fossa onto the lateral surface of the nasal (character 30.1), pneumatic foramina in the nasals (character 32.1), pneumatization of the jugal (character 34.1), a small suborbital process on the postorbital (character 50.1), squamosal constriction of the infratemporal fenestra (character 51.1), the anterior end of the quadratojugal anterior to the lateral temporal fenestra (character 59.1), and pubic shafts that curve posteroventrally (character 171.1). Some of these character states are found only in non-tetanuran theropods (characters 59.1 and 171.1). However, the pneumatic features of the skull (characters 30.1, 32.1, 34.1, 51.1) are synapomorphies of Allosauroidea or Neotetanurae, although a nasal antorbital fossa (character 30.1) is also found in Cryolophosaurus and Dilophosaurus ( Smith et al., 2007) , and a pneumatic jugal (character 34.1) is also found in Megalosaurus ( Fig. 3 ). These pneumatic characters have been found by previous authors to support an allosauroid affinity of Monolophosaurus (for example, Rauhut, 2003; Holtz et al., 2004), although Smith et al. (2007) proposed that Monolophosaurus was a basal neotetanuran. However, pneumatic features are notoriously homoplastic ( Witmer, 1997) and their presence in Monolophosaurus may be a parallel development as recovered by the present analysis. If Chuandongocoelurus and Monolophosaurus are sister taxa, then Monolophosaurus probably has a number of primitive characters of the hindlimbs and may be more primitive than has previously been appreciated.

Afrovenator , Duriavenator , Dubreuillosaurus , Eustreptospondylus , Magnosaurus , Megalosaurus and Torvosaurus are recovered in a monophyletic Megalosauridae that is the sister taxon to Spinosauridae in the present analysis. This grouping receives a Bremer support value of two. Sereno et al. (1998) and Holtz et al. (2004) found a similar arrangement of taxa, whereas Sereno et al. (1994), Rauhut (2003) and Smith et al. (2007) recovered several of the component taxa of Megalosauridae as a paraphyletic grouping leading to Spinosauridae . Earlier authors, such as Holtz (1994, 2000), recovered Spinosauridae and component taxa of Megalosauridae as a paraphyletic series of outgroups to Neotetanurae. A similar arrangement was also found recently by Yates (2006), in which a clade comprising Afrovenator , Eustreptospondylus and Magnosaurus was the sister taxon to a group comprising Neotetanurae and a clade comprising Chilantaisaurus , Spinosauridae and Torvosaurus .

The clade comprising Megalosauridae + Spinosauridae is supported by six unambiguous synapomorphies: external naris located posterior to premaxillary tooth row (character 1.2); lateral lamina of the maxilla obscuring the anteroventral corner of the antorbital fossa present as a large shelf (character 13.2; also in Carcharodontosaurinae and Ceratosauria; reversed to 0 in Megalosauridae ); basioccipital apron bears a broad midline depression approximately two-thirds the width of the occipital condyle (character 67.1); third dentary alveolus subcircular and enlarged (character 79.1; reversed in Megalosaurus ; also in Acrocanthosaurus , Dilophosaurus and Neovenator ); length to width ratio of pubic peduncle 1.55–1.75 (character 166.2; reversed in Torvosaurus ; transformed to 0 in Eustreptospondylus ; also present in Sinraptoridae ); femoral medial distal crest present as a stout bar (character 195.0; also in Piatnitzkysaurus and theropods outside of Ceratosauria + Tetanurae). The absence of a proximal concavity on the medial surface of the fibula (character 208.0) is only present in megalosaurids and spinosaurids. As the fibula of Monolophosaurus is not known and a locally autapomorphic state (character 208.2) is present in Chuandongocoelurus , this condition is only recovered as a synapomorphy of Megalosauridae + Spinosauridae under DELTRAN, but should be considered a synapomorphy of the clade.

A paradental groove of the dentary that is wide anteriorly but narrow posteriorly is recovered as a synapomorphy of the clade comprising Megalosauridae and Spinosauridae under DELTRAN (character 81.1). This character is scored as uncertain in Monolophosaurus and the dentary is not known in Chuandongocoelurus . The absence of a coracoid tubercle (character 141.0, also in Abelisauridae ) and ulna with a length to minimum circumference ratio greater than 2.6 (character 140.1) have similar distributions.

The anterior end of the maxillary alveolar border is upturned relative to the premaxilla (character 10.1; also in theropods outside of the clade comprising Ceratosauria and Tetanurae; reversed in megalosaurids other than Eustreptospondylus ). This character state is a synapomorphy of Megalosauridae and Spinosauridae that is subsequently reversed in megalosaurids other than Eustreptospondylus under ACCTRAN. However, under DELTRAN, it is independently derived in Eustreptospondylus and Spinosauridae . The absence of enamel wrinkles is also a synapomorphy of Megalosauridae + Spinosauridae under ACCTRAN (character 95.0). These are subsequently regained in the clade comprising Megalosaurus and Torvosaurus .

Because of the partial preservation of most specimens of taxa referred to this clade ( Table 5), a number of potential synapomorphies are only known from Megalosauridae or Spinosauridae , but not both. The presence of a median horn on the nasals is known in Baryonyx , but no other megalosaurid or spinosaurid nasals are known (character 27.1; also in Ceratosaurus ). In several megalosaurids, the supratemporal fossa extends onto the dorsal surface of only the anterior ramus of the postorbital (character 47.1), but the postorbital is not well preserved in any spinosaurid. The acetabular margin of the pubic peduncle is transversely concave in megalosaurids (character 167.1), but the condition of this character is indeterminate in spinosaurids. These characters are synapomorphies of the clade comprising Megalosauridae and Spinosauridae under ACCTRAN, but only of Megalosauridae or Spinosauridae under DELTRAN.

Megalosauridae was used by Holtz et al. (2004) to refer to the clade comprising Megalosaurus and all taxa sharing a more recent common ancestry with it than with Eustreptospondylus , which was included in Eustreptospondylidae. Torvosauridae was used by Sereno et al. (1994) to refer to a composite OTU comprising Eustreptospondylus and Torvosaurus . As Megalosaurus is the sister taxon of Torvosaurus , Megalosauridae and Torvosauridae should be synonymous or each constitute monotypic families. Assuming that Megalosaurus is the sister taxon of Torvosaurus , then Eustreptospondylidae is also monotypic when Holtz et al. ’s (2004) definition is applied to the topologies of several recent authors ( Rauhut, 2003; Smith et al., 2007). In the present work, I use a definition of Megalosauridae as M. bucklandii and all taxa sharing a more recent common ancestry with it than with Spinosaurus aegyptiacus , Allosaurus fragilis , Carcharodontosaurus saharicus or Sinraptor dongi . This allows for a stable definition with respect to other well-recognized families within Allosauroidea and Megalosauroidea.

Megalosauridae receives a Bremer support value of two and is supported by two unique, unambiguous synapomorphies: a humeral deltopectoral crest that terminates at least 0.52 of the way along the humeral shaft (character 144.2); and the absence of a fibular anterolateral tubercle (character 209.0). Six unambiguous synapomorphies of Megalosauridae are also found in other groups: the absence of a quadrate foramen (character 55.1; also in Ceratosauria); paroccipital processes directed dorsolaterally or laterally (character 71.0; also in non-tetanurans); well-defined longitudinal groove housing neurovascular foramina on the lateral surface of the dentary (character 80.1; reversed in Megalosaurus + Torvosaurus ); ischial shaft curves anteroventrally (character 178.1; also in Compsognathus and ‘ Syntarsus ’ kayentakatae); ischial antitrochanter absent (character 180.1; also in Allosaurus and Coelurosauria); ischial symphysis expanded as an apron (character 184.1; also in most neotetanurans).

A dorsoventrally slender anterior process of the lacrimal (ch. 37.0) is recovered as a megalosaurid synapomorphy under ACCTRAN that is reversed in Afrovenator + Dubreuillosaurus . A lacrimal ‘horn’ present as a low rugose swelling (character 38.1) is recovered as a megalosaurid synapomorphy under DELTRAN, although it is modified to a robust, rugose ridge in Afrovenator (character 38.2). A weak posteroventral process of the coracoid (character 140.0; also in non-tetanurans) is recovered as a megalosaurid synapomorphy under ACCTRAN. The coracoid is only known in Megalosaurus and Torvosaurus , and this character state is a synapomorphy of Megalosaurus + Torvosaurus under DELTRAN.

Eustreptospondylus is the sister taxon to all other megalosaurids. Correspondingly, megalosaurids other than Eustreptospondylus possess two unique, unambiguous synapomorphies: the presence of depressions on the lateral surface of the quadrate in the vicinity of the mandibular condyle (character 57.1); a low posterior flange of the femoral caput (character 189.0); and two unambiguous synapomorphies that are found in other clades: an angle of less than 70° between the anterior surface of the premaxilla and the alveolar margin, with the naris overlapping the premaxillary tooth row (character 1.1; also in Acrocanthosaurus , Neovenator and Compsognathus ); a ventral keel on the axis and anterior cervical vertebrae (character 107.1; also in Abelisauridae and carcharodontosaurids other than Neovenator ).

Two clades are resolved among megalosaurids other than Eustreptospondylus : a clade comprising Afrovenator and Dubreuillosaurus , and a clade comprising Megalosaurus and Torvosaurus . Afrovenator and Dubreuillosaurus are united on the basis of a single unambiguous synapomorphy: the outline of the anterior margin of the antorbital fossa is squared off in lateral view (character 11.1; also outside of Ceratosauria + Tetanurae).

Spinosauridae is supported by 17 unambiguous synapomorphies. Sixteen of these are cranial, five of which are dental. This is understandable in the light of the highly specialized and autapomorphic skull morphology and tooth form of spinosaurids ( Charig & Milner, 1997; Sereno et al., 1998; Sues et al., 2002; Dal Sasso et al., 2005). Spinosauridae is also supported by a single postcranial synapomorphy: dorsal neural spine height 1.9 or more times centrum height (character 120.2; also in Ceratosaurus , Megalosaurus , Metriacanthosaurus + Sinraptor and carcharodontosaurids other than Neovenator ). The postcranium of spinosaurids is not well known and it is probable that further postcranial synapomorphies will come to light with future discoveries.

The systematic position of Megalosaurus

Although Benson et al. (2008) were unable to identify features of the lectotype dentary that supported megalosauroid affinities (as had been proposed by Holtz et al., 2004) for M. bucklandii , material referred to the taxon demonstrates the presence of several features that are synapomorphies of Megalosauroidea or less inclusive groups within Megalosauroidea. The only feature of the dentary is the morphology of the paradental groove. In M. bucklandii and other members of the clade comprising Megalosauridae + Spinosauridae , the groove is wide anteriorly, where the medial wall of the dentary does not contact the medial surfaces of the interdental plates. Around the level of the fifth interdental plate, the groove becomes narrow so that the medial wall of the dentary contacts the interdental plates. The dentary is otherwise unlike those of other members of this clade, as it does not possess an enlarged, subcircular third alveolus.

Megalosaurus bucklandii possesses an imperforate maxillary ‘fenestra’ ( Fig. 2A, B, F, G ), which is a megalosauroid synapomorphy. It also possesses postcranial synapomorphies of the clade comprising Megalosauridae + Spinosauridae : the absence of the coracoid tubercle; a ratio of ulnar length to minimum circumference of less than 2.6; and a concave acetabular margin of the pubic peduncle. As in other megalosaurids, M. bucklandii has an anteroventrally curving ischial shaft and a deltopectoral crest that extends more than 0.52 of the length of the humerus. As in megalosaurids other than Eustreptospondylus , the posterior flange of the femoral caput is low in M. bucklandii .

Among megalosaurids, M. bucklandii is most similar to Torvosaurus . It shares with Torvosaurus : relatively tall interdental plates that fall short of the ventralmost extent of the lateral wall of the maxilla; a weak, not prominent, longitudinal groove on the lateral surface of the dentary; and band-like enamel wrinkles on the labial and lingual tooth surfaces. The ratio of the scapular length to the minimum dorsoventral breadth is less than seven in Megalosaurus and Torvosaurus ( Table 1) and the brevis fossa of the ilium is narrow. These two characters may be synapomorphies of Megalosaurus and Torvosaurus or of a more inclusive clade, as they are not preserved in other megalosaurids barring Eustreptospondylus .

Figures

Figure 2. Left maxillae of Megalosaurus bucklandii from the Taynton Limestone Formation of Stonesfield, Oxfordshire (A–G) and the Chipping Norton Limestone Formation of New Park Quarry, Gloucestershire (H–M) in lateral (A, B, F–I), medial (C, D, J, K, M), anterior (E) and ventral (L) views. A–C, OUMNH J.13506; D–G, OUMNH J.13559; H–K, BMNH R8303 (only questionably from New Park Quarry) with magnification (¥2) showing foramina ventral to anteromedial process (J); L, M, SDM 1944.1 with magnification (¥2) showing foramina ventral to anteromedial process (M). In line drawings (G, I, K), light grey tone indicates tooth, mid-grey tone indicates restored bone surface, dark grey tone indicates broken bone surface, and crossed hatching indicates matrix. amp, anteromedial process; for, foramen; idp, interdental plate; jf, jugal facet; mxf, maxillary ‘fenestra’ (imperforate); pnu, pneumatic fossa. Scale bar, 100 mm.

Figure 3. Right jugal (BMNH 31828) from the Taynton Limestone Formation of Stonesfield, Oxfordshire in lateral view: A, photograph; B, line drawing. Dark grey tone indicates broken bone surface and cross-hatching indicates matrix in the line drawing. for, foramen; juf, jugal foramen. Scale bar, 100 mm.

Figure 5. Posterior fragment of a right mandible (OUMNH J.29813) from the Taynton Limestone Formation of Stonesfield, Oxfordshire in lateral (A, B), dorsal (C, F) and medial (D, E) views. Dark grey tone indicates broken bone surface in line drawings (B, E, F). ANG, angular; AR, articular; for, foramen; PRA, prearticular; SA, surangular. Scale bar, 100 mm.

Figure 6. Presacral vertebrae of Megalosaurus from the Chipping Norton Limestone Formation of New Park Quarry, Gloucestershire (A–J) and the Taynton Limestone Formation of Stonesfield, Oxfordshire (K–R) in right lateral (A, B, G, H, P), anterior (C, F, N, O), posterior (D, E, Q, R), ventral (I, J, M) and left lateral (K, L) views. A–E, anterior cervical vertebra, BMNH R9674; F–J, ‘pectoral’ vertebra (sensu Welles, 1984), BMNH R9678; K–R, posterior dorsal vertebra, OUMNH J.13577. In line drawings (B, E, H, J, L, O, R), light grey tone indicates restored bone surface, dark grey tone indicates broken bone surface and crossed hatching indicates matrix. cam, camera; epi, epipophysis; for, foramen; hys, hyposphene; nec, neural canal; ns, neural spine; pcdl, posterior centrodiapophyseal lamina; poz, postzygapophysis; prez, prezygapophysis; trp, transverse process; Scale bar, 100 mm.

Figure 7. Sacra of Megalosaurus bucklandii from the Taynton Limestone Formation of Stonesfield, Oxfordshire (A–N) and the Chipping Norton Limestone Formation of New Park Quarry (O–Q) in left lateral (A, B, K–M, O), posterior (C, D), right lateral (E, F, P), anterior (G, H) and ventral (I, J, N, Q) views. A–I, OUMNH J.13576; J–L, BMNH 28957/R1098; M, N, BMNH R700; O–Q, SDM 1944.4. In line drawings (B, D, F, H, L), light grey tone indicates restored surface and dark grey tone indicates broken bone surface. fen, fenestra between neural arches; for, foramen; ivf, intervertebral foramen; nc, neural canal; ns, neural spine; poz, postzygapophysis; prez, prezygapophysis; sr1–5, first to fifth sacral rib articulations; trp, transverse process; 1–5, first to fifth sacral centra. Scale bar, 200 mm.

Figure 14. Left ilium (BMNH R1100) from the Taynton Limestone Formation of Stonesfield, Oxfordshire in lateral (A, B) and ventral (C) views: A, with magnification (¥2) of the median ridge; D, magnification (¥2) of the pubic peduncle in articular view; E, magnification (¥2) of the ischial peduncle in articular view. Light grey tone indicates reconstructed bone surface in the line drawing (B). brf, brevis fossa; isp, ischial peduncle; meb, medial blade; pob, posterior blade; pop, posterior process; pup, pubic peduncle; sac, supracetabular crest. Scale bar, 300 mm.

Figure 17. Left tibia (BMNH 31809) of Megalosaurus bucklandii from the Taynton Limestone Formation of Stonesfield, Oxfordshire in anterior (A, B), lateral (C, D), posterior (E), medial (F), proximal (G) and distal (H) views. G, H, magnified (¥1.5). In line drawings (B, D), light grey tone indicates reconstructed bone surface and dark grey tone indicates broken bone surface. cnc, cnemial crest; ffl, fibular flange; for, foramen; ict, incisura tibialis; lco, lateral condyle; mco, medial condyle; sab, supracetabular buttress. Scale bar, 300 mm.

Figure 19. Theropod bones showing features discussed in the text. A, BYU 5110, right quadrate of Torvosaurus in medial view; B, MNHN 8787, ‘pectoral’ vertebrae (sensu Welles, 1984) of Streptospondylus in ventral view; C, D, MUCPv 341, cervical vertebra of Megaraptor in left lateral (C) and right lateral (D) views. dep, depression; for, foramen; hpp, hypapophysis; pcd, pleurocentral depression; plc, pleurocoel. Scale bars: 100 mm (A) and 50 mm (B–D).

Figure 20. Time-calibrated strict reduced consensus of 24 unique tree topologies remaining after deletion of Eocarcharia, Magnosaurus, Megaraptor, Piveteausaurus, Poekilopleuron and Streptospondylus from 189 456 MPTs resulting from analysis of the total dataset (Appendix S3) of 41 taxa and 213 characters. Ensemble consistency index, 0.438; ensemble retention index, 0.604; ensemble rescaled consistency index, 0.264. Bremer support (single digit values) and bootstrap (multi-digit values) are recorded at the nodes.