Megalosaurus BUCKLAND 1824
Creators: name: Benson, Roger B. J.
Publisher: name: Zenodo
Year: 2010
Subjects: Biodiversity
Taxonomy
Animalia
Chordata
Reptilia
Saurischia
Megalosauridae
Megalosaurus

description: MEGALOSAURUS BUCKLAND, 1824   
 Type and only species: Megalosaurus bucklandii Mantell, 1827.   
 Diagnosis: As for the type and only species, given below.   
884 R. B. J. BENSON  
 MEGALOSAURUS BUCKLANDII MANTELL, 1827   
(FIGS 1–18)  
 1826 Megalosaurus conybeari von Ritgen (1826: 354) (nomen nudum).   
 1827 Megalosaurus bucklandii Mantell (1827: 67, pl. 18, fig. 2; pl. 19, figs 1, 8, 12, 14–16).   
 1832 Megalosaurus bucklandi von Meyer (1832: 110).   
 Lectotype: OUMNH J.13505, a right dentary.   
 Paralectotype series: The series of theropod remains described by Buckland (1824), including: a tooth (whereabouts unknown); a posterior dorsal vertebra (OUMNH J.13577); a sacrum (OUMNH J.13576); a proximal caudal vertebra (OUMNH J.13579); an anterior dorsal rib (OUMNH J.13585); a midposterior dorsal rib (OUMNH J.13580); a right ilium (OUMNH J.29881); a right pubis (originally described as a fibula; OUMNH J.13563); a left ischium (originally described as a clavicle; OUMNH J.13565); a right femur (OUMNH J.13561); and the distal portion of a left metatarsal II (OUMNH J.13572). Buckland (1824) referred some additional bone fragments that may not refer to theropods to Megalosaurus as the ischium and scapula. These bones cannot be referred to Megalosaurus and are excluded from the hypodigm. Their present whereabouts are unknown.   
 Type locality and horizon: One or more discrete horizons (‘Stonesfield Slate’; Boneham & Wyatt, 1993) within the Taynton Limestone Formation (middle Bathonian Procerites progracilis ammonite zone) of Stonesfield, Oxfordshire, UK.   
 Additional occurrences: Hook Norton Limestone Member of the Chipping Norton Limestone Formation (lowest Bathonian, Zigzag ammonite zone) of New Park Quarry, Chipping Norton Limestone Formation of Oakham Quarry, and of unknown provenance that probably corresponds to New Park Quarry, Gloucestershire; Sharp’s Hill Formation (lower–middle Bathonian) of Workhouse Quarry, Chipping Norton, Oxfordshire; and Great Oolite Group (Bathonian) of Sarsgrove near Chipping Norton, Oxfordshire.   
 Hypodigm: The lectotype dentary (OUMNH J.13505), specimens from the paralectotype series indicated above and additional material listed below.   
 As the large-bodied theropod fossil assemblage of Stonesfield is interpreted as representing a single species (Benson, 2009), the following additional material from that locality is referred to M. bucklandii: two left maxillae (OUMNH J.13506, J.13559); a right jugal (BMNH 31828); the posterior fragment of a right mandible (OUMNH J.29813); isolated teeth (BMNH R234 [2 specimens], 2331, 40127 [3 specimens], 41305, 42024, 47963 [2 specimens]; GSM 113081; OUMNH J.29762, J.29777, J.29809, J.29810, J.29863, J.29864, J.48171); a posterior dorsal vertebra (BMNH 31813); two sacra (BMNH R700, 28957 / R1098 [in two parts, catalogued separately]) and two sacral fragments (OUMNH J.29766, J.29767); two proximal caudal vertebrae (OUMNH J.13578, J.29768); three middle caudal vertebrae (BMNH 25581, 33229, 31812); dorsal ribs (BMNH 31824, 31825, 37303, 44097, 44097 a; OUMNH J.13582, J.13583, J.13584, J.29792, J.29893); a left scapulocoracoid (BMNH R1099) and four right scapulocoracoids (CAMSM Woodwardian Collection D.11.35.c; OUMNH J.13574, J.29891, J.29888); a right coracoid (BMNH 31810) and a?coracoid fragment (BMNH 40131); a left humerus (OUMNH J.13575) and a fragmentary right humerus (BMNH 2016); a left ulna (BMNH 36585); an ungual phalanx (OUMNH J.29779); five right ilia (BMNH R283, R1101, 31811; OUMNH J.13560, J.29882) and one left ilium (BMNH R1100); a right pubis (OUMNH J.13567); a fragmentary left ischium (OUMNH J.29872); three right femora (BMNH 31806; OUMNH J.29753, J.29803) and three left femora (BMNH 31804, 31808; MNHN 9630); three right tibiae (BMNH R1102; OUMNH J.13562, J.29875) and three left tibiae (BMNH 31809, R1103; OUMNH 13568); two left metatarsal II (GSM 57809; OUMNH J.13573); a right metatarsal III (OUMNH J.13569); and a left metatarsal IV (BMNH 40128 a).   
 A left maxilla (SDM 1944.1) from New Park Quarry is referred to M. bucklandii on the basis of a unique character combination shared with the maxillae from Stonesfield (Benson, 2009: 13–14 teeth; third dentary alveolus unexpanded; dentary straight in dorsal view with unexpanded symphysial area; lateral row of neurovascular foramina housed in a shallow longitudinal groove; interdental plates tall and unfused; two Meckelian foramina; Meckelian groove shallow), and a partial sacrum (SDM 1944.4) is referred to M. bucklandii on the basis of an autapomorphy: a longitudinal ridge on the ventral surface of the second sacral centrum. The large theropod assemblage from New Park Quarry was interpreted as representing a single species by Benson (2009). However, because of the smaller number of fossils from this locality, this interpretation is only tentative, as the apparently ‘monospecific’ assemblage could result from the small sample size. Consequently, additional material from New Park Quarry that is almost identical to that referred to M. bucklandii from Stonesfield, but does not share autapomorphies with that material, is tentatively referred to M. bucklandii: a tooth (SDM 1944.3); a cervical vertebra (BMNH R9674); an anterior dorsal vertebra (BMNH R9678); a dorsal centrum (SDM 1944.6); four proximal caudal vertebrae (BMNH R9672, R9673, R9677; SDM 1944.7); three middle caudal vertebrae (BMNH R9675, R9676; SDM 1944.5); two dorsal ribs (BMNH R9669; SDM 1944.13); two right coracoids (SDM 1944.14, 1944.15; although one of these specimens may be the coracoid from Oakham Quarry listed by Gardiner, 1937); a left humerus (SDM 1944.18); a right ischium (BMNH R9668); the distal end of a left ischium (SDM 1944.21); two right femora (SDM 1944.23, 1944.24); and two metatarsal IV (BMNH R9666, SDM 1944.25).   
 The following material from Oakham Quarry is referred to M. bucklandii on the basis of autapomorphies shared with the material from Stonesfield: a left ischium (SDM 1944.20); and a left metatarsal III (BMNH R9665). As other large theropod specimens from Oakham Quarry can be referred to a second, unnamed taxon (R. B. J. Benson, unpubl. data), undiagnostic material from this locality cannot be referred to M. bucklandii.   
 A left maxilla (BMNH R8303) and two left dentaries (BMNH R8304, R8305) from the Chipping Norton Limestone Formation (lower Bathonian) of an unknown locality in Gloucestershire can be referred to M. bucklandii on the basis of a unique character combination (maxilla: see above for SDM 1944.1; dentary: see Diagnosis, below). Other material with the same provenance (BMNH specimens; ribs and bone fragments) is undiagnostic and cannot be referred to M. bucklandii. All such material is in the Reynold’s Collection. This collection was obtained from the Chipping Norton Limestone Formation (lowest Bathonian) of New Park Quarry and Oakham Quarry, both in Gloucestershire (Gardiner, 1937, 1938; Reynolds, 1938, 1939). As the majority of Reynold’s material was collected from New Park Quarry, it is likely that BMNH R8303, R8304 and R8305 were recovered from New Park Quarry.   
 A right metatarsal III (BMNH R413) from the Great Oolite Group (Bathonian) of Sarsgrove, near Chipping Norton, Oxfordshire is referred to M. bucklandii on the basis of an autapomorphic ridge on the surface that articulated with metatarsal II.   
 A right scapula (OUMNH J.29800) from the Sharp’s Hill Formation (lower–middle Bathonian; Torrens, 1980) of Workhouse Quarry, Chipping Norton, Oxfordshire is referred to M. bucklandii on the basis of an autapomorphy: a dorsally directed flange around midheight of the blade.   
 The following large theropod specimens of unknown provenance are likely to have come from Stonesfield (unpublished curation records at BMNH and OUMNH) and can possibly be referred to M. bucklandii, although they lack autapomorphies: ribs (OUMNH J.29892, J.29895, J.29751, J.29752); a right scapulocoracoid (OUMNH J.29889); two right scapulae (OUMNH J.29874, J.29879) and a left scapula (OUMNH J.29890); a right humerus (OUMNH J.29869) and a left humerus (OUMNH J.29761); three iliac fragments (OUMNH J.29883, J.29884, J.29885); a right pubic fragment (OUMNH J.29808); a proximal fragment of a right ischium (OUMNH J.29873); a right femur (OUMNH J.29802) and two femoral fragments (OUMNH J.29754, J.29880); three right tibiae (BMNH R12557, 31805; OUMNH J.29758); and a long bone shaft (OUMNH J.29764).   
 Revised diagnosis: Megalosauroid theropod with the following unique combination of dentary characters: 13–14 teeth; third alveolus unexpanded; dentary straight in dorsal view with unexpanded symphysial area; lateral row of neurovascular foramina housed in a shallow longitudinal groove; interdental plates tall and unfused; two Meckelian foramina; Meckelian groove shallow.   
 Megalosaurus bucklandii also possesses the following autapomorphies identified using referred material: ventral surfaces of first and third to fifth sacral centra evenly rounded, ventral surface of second sacral centrum bearing longitudinal, angular ridge; dorsally directed flange around midheight on the scapular blade (Walker, 1964); an array of posterodorsally inclined grooves on the lateral surface of the median iliac ridge; anteroposteriorly thick ischial apron with an almost flat medial surface; a prominent, rugose distal ischial tubercle; and complementary groove and ridge structures on the articular surfaces between metatarsals II and III.   
 Megalosaurus bucklandii possesses the following characters that are absent in all other megalosaurids: a pneumatic jugal; an unexpanded third dentary alveolus; dorsal neural spines more than 1.9 times the height of the centrum; deltopectoral crest inclined anterolaterally; and characters that are absent in other megalosauroids: maxillary anterior process higher dorsoventrally than long anteroposteriorly.   
DESCRIPTION
description: Published as part of 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, pp. 882-935 in Zoological Journal of the Linnean Society 158 (4) on pages 883-886, DOI: 10.1111/j.1096-3642.2009.00569.x, http://zenodo.org/record/5438464