Sarcosaurus woodi Andrews, 1921

Ezcurra, Martín D, Butler, Richard J, Maidment, Susannah C R, Sansom, Ivan J, Meade, Luke E & Radley, Jonathan D, 2021, A revision of the early neotheropod genus Sarcosaurus from the Early Jurassic (Hettangian-Sinemurian) of central England, Zoological Journal of the Linnean Society 191 (1), pp. 113-149 : 117-118

Sarcosaurus woodi Andrews, 1921 .

Megalosaurus sp. : Huene, 1908 (NHMUK PV R3542). Sarcosaurus sp. : Andrews, 1921 (NHMUK PV R3542). Megalosaurus (subgenus a) sp.: von Huene, 1926 (NHMUK PV R3542).

Sarcosaurus andrewsi: von Huene, 1932: 51 (NHMUK PV R3542).

Magnosaurus woodwardi: von Huene, 1932: 19 (NHMUK PV R3542).

Megalosaurus andrewsi: Waldman, 1974 (NHMUK PV R3542).

cf. Sarcosaurus woodi: Carrano & Sampson, 2004 (WARMS G667–690).

Holotype: NHMUK PV R4840 , a posterior dorsal vertebra, partial left and right ilia each fused to the proximal portion of their respective pubis, and left femur missing most of the femoral head and with a severely damaged distal end.

Ontogenetic stage of holotype: This specimen shows some indicators of skeletal maturity and is not an early juvenile, but its ontogenetic stage cannot be constrained further based on the available evidence (see Discussion).

Type locality and horizon: Barrow upon Soar, Leicestershire, England, UK. Bucklandi zone of the Scunthorpe Mudstone Formation, Lias Group, Early Jurassic (lowermost Sinemurian) ( Fig. 1 ).

Referred specimens: NHMUK PV R3542 , a complete right tibia (holotype of ‘ Sarcosaurus andrewsi ’). WARMS G667–690, partial skeleton of a single individual ( Fig. 2 ), including a partial middle– posterior dorsal vertebra (G678), a partial anterior– middle caudal vertebra (G679), dorsal rib fragments (G670, G675, G676, G685, G686), fragment of the pubic peduncle of the left ilium (G690), partial right and left pubes (G683/684, G688), femora (G681, G682) and tibiae (G668, G680), proximal end of left fibula (G669), probable distal half of fibula (G674), distal portions of left metatarsal II (G672), metatarsal III (G673) and metatarsal IV (G677), proximal end of a metatarsal II or III (G671), proximal half of left pedal phalanx II-1 (G687), and three indeterminate bone fragments (G680, G681, G689) (collected by J. W. Kirshaw) .

Ontogenetic stage of referred specimens: NHMUK PV R 3542 is considerably larger than the other referred specimen but its ontogenetic stage is unknown. WARMS G667–690 was not a juvenile, but had not reached skeletal maturity at the time of its death (see Discussion).

Locality and horizons of referred specimens: Wilmcote , Warwickshire, England, UK. NHMUK PV R3542 is from the angulata zone of the Blue Lias Formation, Lias Group, Early Jurassic (upper Hettangian); and WARMS G667–690 comes from the bucklandi Zone of the upper part of the Rugby Limestone Member of the Blue Lias Formation, Early Jurassic (lowermost Sinemurian) ( Fig. 1 ) .

Diagnosis: Sarcosaurus woodi is a medium-sized (estimated femoral length c. 48 cm in NHMUK PV R 3542), non-averostran neotheropod that differs from other dinosaurs in the following unique combination of character states present in the holotype (autapomorphies indicated with an asterisk): ilium with main axis of the preacetabular process strongly anteroventrally oriented in lateral view (also present in the ceratosaurian Eoabelisaurus mefi ); ilium with an only slightly posteriorly projecting ischiadic peduncle*; ilium without a laterally exposed ventromedial margin of the brevis fossa (only a short portion of its base is exposed, also present in Cryolophosaurus ellioti Hammer & Hickerson, 1994 ); ilium with a poorly transversely expanded brevis fossa (also present in non-coelophysid neotheropods); femur with a dorsolateral trochanter on the proximal end (also present in WARMS G667–690 and non-averostran neotheropods) and femoral fourth trochanter poorly posteriorly expanded (also present in WARMS G667– 690, coelophysids and early ceratosaurians).

The diagnosis of the species can be expanded with the following unique combination of character states present in the referred specimens, but unknown in the holotype (autapomorphies indicated with an asterisk): femur without an anterior extensor groove on the distal end (only known in WARMS G667–690); tibia with a fibular crest that reaches the posterior lateral hemicondyle of the proximal end; tibia with an anteroposterior depth versus mediolateral width ratio ≥ 0.6; tibia with an anteroposteriorly narrow facet for the reception of the ascending process of the astragalus (indicating a non-blocky, but rather laminar ascending process of the astragalus); tibia with an angle between the main axis of the lateral half of the facet for reception of the ascending process of the astragalus and the longitudinal axis of the bone ≥ 25° in anterior view; tibia with a well proximally extended posteromedial notch on the distal end; tibia with a poorly projected medial malleolus; and fibula with a poorly projected and tab-like posterior margin of the proximal end in lateral view* (only known in WARMS G667–690).

See Discussion for a differential diagnosis of the species among early neotheropods.

DESCRIPTION OF WARMS G667–690

The holotypes of Sarcosaurus woodi and ‘ Sarcosaurus andrewsi ’ have been recently redescribed in detail by Carrano & Sampson (2004). Thus, we do not provide new redescriptions here, although comments on their anatomy are provided in the discussion of the taxonomy of the genus Sarcosaurus and we do refigure both specimens. By contrast, WARMS G667–690 was described and figured with line drawings by von Huene (1932), but no detailed redescription has been provided to date.

Figures

Figure 1. Map showing the geographic occurrences of the holotype of Sarcosaurus woodi (Barrow upon Soar) and referred specimens (Wilmcote) indicated with stars. The outcrop of the Lias Group is shown in grey.

Figure 2. Silhouette showing the preserved bones of referred specimen of Sarcosaurus woodi, WARMS G667–690. Skeletal reconstruction from Mark Witton.