Megalosaurus, BUCKLAND, 1824

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 : 883-886

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

Figures

Figure 1. Silhouette of Megalosaurus bucklandii containing skeletal reconstruction. Known material is illustrated in white; grey tone indicates reconstructed areas. Scale bar, 1 m.

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 4. Left dentaries of Megalosaurus bucklandii from the Chipping Norton Limestone Formation of an unknown locality in Gloucestershire (probably New Park Quarry) in medial (A, D), lateral (B, E) and dorsal (C) views. A–C, BMNH 8305; D, E, BMNH R8304. idp, interdental plate; meg, Meckelian groove; 2nd, tooth in second alveolus. 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 8. Proximal caudal vertebrae of Megalosaurus bucklandii from the Chipping Norton Limestone Formation of New Park Quarry, Gloucestershire (A–I) and the Taynton Limestone Formation of Stonesfield, Oxfordshire (J–L) in left lateral (A, B, J), anterior (C, K), right lateral (D, H, I), posterior (E), ventral (F) and dorsal (G, L) views. A–G, BMNH R9672; H, I, BMNH R9677; J–L, OUMNH J.13579. In line drawings (B, I), dark grey tone indicates broken bone surface and cross-hatching indicates matrix. for, foramen; ns, neural spine; poz, postzygapophysis; trp, transverse process. Scale bar, 100 mm.

Figure 9. Middle caudal vertebrae of Megalosaurus bucklandii from the Chipping Norton Limestone Formation of New Park Quarry, Gloucestershire (A, B, F–J) and the Taynton Limestone Formation of Stonesfield, Oxfordshire (C–E) in anterior (A, D, G), dorsal (B, H), right lateral (C, F), ventral (E, I) and posterior (J) views. A, B, proximal middle caudal vertebra, BMNH R9675; C–E, middle caudal vertebra, BMNH 31812; F–J, middle caudal vertebra, SDM 1944.5. for, foramen; poz, postzygapophysis; prez, prezygapophysis; trp, transverse process. Scale bar, 100 mm.

Figure 10. Ribs of Megalosaurus bucklandii from the Taynton Limestone Formation of Stonesfield, Oxfordshire in anterior (A, B, D, F), posterior (C) and lateral (E) views. A, left cervical rib, OUMNH J.13585; B, left anterior–middle dorsal rib, OUMNH J.13582; C, left middle dorsal rib, OUMNH J.13583; D, left posterior dorsal rib, OUMNH J.13580; E, F, left middle dorsal rib, BMNH 37303. pfl, posterior flange. Scale bars, 100 mm.

Figure 11. Pectoral girdle elements of Megalosaurus bucklandii from the Taynton Limestone Formation of Stonesfield (A–E, G, H) and Sharp’s Hill Formation of Workhouse Quarry, Chipping Norton (F), both in Oxfordshire, in lateral (A, B, F–H), ventral (C, D) and medial (E) views. A–E, right scapulocoracoid, OUMNH J.13574; F, right scapula, OUMNH J.29800; G, H, left scapulocoracoid, BMNH R1099. In line drawings (B, D, H), light grey tone indicates restored bone surface and dark grey tone indicates broken bone surface. acr, acromion process; cf, coracoid foramen; dfl, dorsal flange; gl, glenoid. Scale bars, 300 mm.

Figure 12. Humeri of Megalosaurus bucklandii from the Taynton Limestone Formation of Stonesfield, Oxfordshire (A–L, N, O) and the Chipping Norton Limestone Formation of New Park Quarry, Gloucestershire (M) in anterior (A, B, K–O), lateral (C, D), posterior (E, F), medial (G, H), proximal (I) and distal (J) views. A–J, left humerus, OUMNH J.13575; K, L, right humerus, OUMNH J.29869 (only questionably from Stonesfield); M, left humerus, SDM 1944.18; N, O, left humerus, OUMNH J.29761. In line drawings (B, D, F, H, L, O), light grey tone indicates reconstructed bone surface and dark grey tone indicates broken bone surface. dpc, deltopectoral crest; ext, external tuberosity; for, foramen; int, internal tuberosity; rac, radial condyle. Scale bar, 200 mm.

Figure 13. Left ulna (BMNH 36585) from the Taynton Limestone Formation of Stonesfield, Oxfordshire in lateral (A, B), anterior (C), medial (D, E), posterior (F), proximal (G) and distal (H) views. In line drawings (B, E), light grey tone indicates reconstructed bone surface and dark grey tone indicates broken bone surface. frac, fracture line; ole, olecranon process; path, pathological swelling. Scale bar, 100 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 15. Pelvic bones of Megalosaurus bucklandii from the Taynton Limestone Formation of Stonesfield, Oxfordshire (A–N) and the Chipping Norton Limestone Formation of Oakham Quarry, Gloucestershire (O, P) in lateral (A, B, G, H, O, P), posterior (C, I), medial (D, E, J, K), anterior (F, L), distal (M) and proximal (N) views. A–F, left pubis, OUMNH J.13567; G–N, left ischium, OUMNH J.13565 (M, N, magnified ¥2); O, P, left ischium, SDM 1944.20. In line drawings (B, E, H, K, P), light grey tone indicates restored surface, dark grey tone indicates broken bone surface and crossed hatching indicates matrix. dit, distal ischial tubercle; isa, ischial apron; isb, ischial boot; ist, ischial tubercle; obf, obturator foramen; obn, obturator notch; pua, pubic apron. Scale bar, 300 mm.

Figure 16. Right femur (BMNH 31806) of Megalosaurus bucklandii from the Taynton Limestone Formation of Stonesfield, Oxfordshire in anterior (A, B), medial (C, D), lateral (E, F), posterior (G, H) and distal (I, J) views. I, J, magnified (¥2). In line drawings (B, D, F, H, J), light grey tone indicates reconstructed bone surface and dark grey tone indicates broken bone surface. act, accessory trochanter; ctf, crista tibiofibularis; exg, extensor groove; ft, fourth trochanter; gt, greater trochanter; lco, lateral condyle; lt, lesser trochanter; mco, medial condyle; mdc, medial distal crest; pof, posterior flange of caput. 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 18. Metatarsals of Megalosaurus bucklandii from the Taynton Limestone Formation of Stonesfield, Oxfordshire (A–K, R–U) and the Chipping Norton Limestone Formation of Oakham Quarry (L–Q) in medial (A, L, R), dorsal (B, E, F, K, M, S), lateral (C, J, N, T), ventral (D, O, U), proximal (G, P) and distal (H, I, Q) views. A–D, G, H, left metatarsal II, GSM 57809; E, I, left metatarsal II, OUMNH J.13573; F, left metatarsal II, OUMNH J.13572; J, K, right metatarsal III, OUMNH J.13569; L–Q, left metatarsal III, BMNH R9665; R–U, left metatarsal IV, BMNH 40128a. In line drawings (right image in A–D, L, M, R, U), light grey tone indicates restored bone surface and dark grey tone indicates broken bone surface. clp, collateral ligament pit; II, articular surface for second metatarsal; III, articular surface for third metatarsal. Scale bar, 100 mm; G–I, P, Q magnified (¥1.5).