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Megalosaurus = Torvosaurus in Europe
In my book-in-progress Mutanda Dinosaurologica, Megalosauridae in Europe is restricted to three valid species of Megalosaurus, Metriacanthosaurus is revised and expanded into three species, Eustreptospondylus is retained in this clade, as is Poecilopleuron/Poekilopleuron (the former name has priority, but the nomenclature has yet to be clarified). Streptospondylus is close to (if not synonymous with) Allosaurus, and it is not a Megalosauridae taxon, but, again, we are dealing with hypodigms of often just one individual, whereas Allosaurus, to be sure, is known from growth series. Also in this clade is Metriacanthosaurus shangyouensis (Dong et al. 1978). Sam Welles and I both believed that Gregory Paul's synonymization of Megalosaurus/Torvosaurus to be valid, and I retain th!
e synonymization in my manuscript. These conclusions are the results of Sam's examination and photographing of all of the Jurassic UK theropod hypodigms known in the 1970s, which I have in my files. The irony, indeed, is that since Buckland's original illustrative description (with the exception of Ronan Allain's fine adaptation of Sam's original manuscript pages re: Streptospondylus), none of these specimens have been illustrated with detailed photographs and osteological comparisons, and the name Megalosaurus used for isolated bones and teeth from a wide range of temporal indices. The nonsensical posturing in the literature since von Huene's predilection for obfuscating taxonomy with haphazard naming (akin to numerologists -- some call them paleo-ornithologists -- refusing to accept the decimal system), means that the Megalosauridae clade has never been clearly defined...until Sam Welles began the arduous task of examining, photographing, meas!
uring, comparing all of the hypodigms. What emerged from Sam's investigations, as he and I began revising his unpublished mss., is that they were a basal group of theropods, perhaps related to the ceratosaurs, perhaps related to the allosaurs...the ambiguity derives from plesiomorphies all of the taxa share.
The picture of Megalosauridae, hence, may be summarized: complex maxillary sinus, laterodorsomedially perforate; orbit ventrally constricted by intrusion of ventral part of lacrimal vs. constriction caused by invasion of postorbital into orbit; no squamosal-quadratojugal flange intruding deeply into infratemporal fenestra, squamosal-quadratojugal border behind lower temporal nearly vertical in late ontogeny; presence of both M. adductor mandibulae externus superficialis and M. adductor mandibulae externus medialis; incipient surangular foramen (larger than neurovascular foramen); when present, dentary symphysis a medially flattened surface; dentary alveoli often continuous to rostral margin; Meckelian groove uniformly narrow; rugosae fused or variably separate, replacement teeth visible at base between rugosae or through notches between them; dentary tooth row interval:tooth row indices 9.3-10.3; splenial aperture reduced;!
some cervicals opisthocoelous; midcaudal transverse processes medially positioned on centrum table vs. distally; scapular glenoid expansion at an angle of ca. 50-60 degrees to axis of blade; humerus with pronounced entotuberosity; radius distal end inclined ca. 45 degrees to axis of shaft; ilium length = ca. 7 central (caudal dorsals, sacrum, most proximal caudals); cranial distal pubic expansion ca. 50% of length of caudal region; ischial obturator process trapezoid in lateral view; anterior femoral trochanter a blunt cone on craniolateral edge of shaft; astragalus with moderately high dorsal process set into cranial tibial face, but with free, medial horizontal component (convergent in Coelurus fragilis...et al.?); ascending process restricted to lateral part of bone; medial condyle larger than lateral, rounded median end, deep upper horizontal groove developing at cranial base of dorsal process and deep lower horizontal groove across face of condyles; calcaneum free!
Compared with Ceratosauria, this revised Megalosauridae has a combination of apomorphies related to increased size, a complex including an enlarged, narrowed, elongate skull; shortening of the neck; reduction in size of the forearm and manal digits; and a more stoutly constructed skeleton. Moreover: Pm 4-5+ / M 15-18 / D 11-16+; premaxillary teeth non-incisiform; 10-11 cervicals, 3 pectorals, 5 sacrals (Gauthier 1984), up to 51 caudals. Axis differs from Ceratosauria in lack of ventral keel, deep notches between spine and postzygapophysis, strong diapophysis. Cervicals differ from Ceratosauria in lacking nearly flat anterior end, double pleurocoels, and in differently structured chonoses and spines. Megalosauridae cervicals-pectorals-dorsals, when in articulation, cavernous, opisthocoelous, remaining dorsals when known in articulation platycoelous, penultimate dorsals variably amphiplatyan. From caudal 2 to near distal region, centra wi!
th chevron arches. Where known, rib cages with short cranial and long caudal ribs. Forelimb nearly 50% of hindlimb length; scapula with cranial projection variably opposite (Eustreptospondylus) or level (Megalosaurus bucklandii) with glenoid crest. Manus functionally tridactyl, 2-3-4-0-0; in larger adult taxa manus 70% of pes. Ilium with reduced, higher anterior blade than Ceratosauria, caudal notch incipient or fully developed (?sexual dimorphism). Ischium elongate, rod-like, distally expanded. Pubis with open obturator notch, large distal expansion in most taxa. 4th trochanter above middle of shaft in all known Megalosauridae, anterior trochanter projecting proximally and somewhat cranially, ento- and ectocondyle separated by shallow (cranial) and distal grooves, and a deep caudal groove ("intercondylar fossa" of some authors) leading dorsally onto shaft, ectocondyle with a tuberous process, the caudal projection, narrower than body of condyle.
This Megalosauridae (in roughly chronological order: Megalosaurus nethercombensis, M. bucklandii, Metriacanthosaurus reynoldsi, M. brevis, Eustreptospondylus oxoniensis, Metriacanthosaurus parkeri, Megalosaurus phillipsi, Poecilopleuron bucklandii, Megalosaurus tanneri, Metriacanthosaurus shangyouensis) has apomorphies retained plesiomorphically in Alectrosaurus and Tyrannosauridae (?other taxa): relationships between parietal and supraoccipital; surangular foramen; weakly developed axial spine; persistence of elongate caudal prezygapophyses; elaboration of distal chevrons; posteroventral angle of coracoid; reduced ischial peduncle; pubic foot; angular obturator process of ischium; pronounced attachment areas of M. femora-tibialis; small tibial process parallel to fibula head.