Sarcosaurus

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Not to be confused with Sarcolestes or Sarcosuchus.

Sarcosaurus
Temporal range:
Ma
Skeletons of the known specimens of Sarcosaurus woodi (restored as a ceratosaur)
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Clade: Dinosauria
Clade: Saurischia
Clade: Theropoda
Clade: Neotheropoda
Genus: †Sarcosaurus
Andrews, 1921
Type species
†Sarcosaurus woodi
Andrews, 1921
Synonyms

Sarcosaurus (

neotheropod dinosaur, roughly 3.5 metres (11 ft) long. It lived in what is now England and maybe Ireland and Scotland during the Hettangian-Sinemurian stages of the Early Jurassic, about 199-196 million years ago. Sarcosaurus is one of the earliest known Jurassic theropods, and one of only a handful of theropod genera from this time period. Along with Dracoraptor hanigani it is one of the two described neotheropods from the lowermost Jurassic of the United Kingdom.[1]

Description

Size comparison of the two known partial skeletons of Sarcosaurus woodi (restored as a basal neotheropod)

The holotype is NHMUK PV R4840 a partial skeleton that includes a posterior

caudal vertebra, dorsal rib fragments, left ilium, right and left pubes, femora and tibiae, proximal end of left fibula, probable distal half of fibula, distal portions of metatarsals IV, II or III proximal half of left pedal phalanx II-1, and three indeterminate bone fragments.[1][2] Sarcosaurus shares certain morphological conditions with other neotheropods, including Liliensternus liliensterni (collateral fossae of the metatarsal II with similar development and shape on both sides, larger ratio on the centrum) and Dilophosaurus wetherilli (lateral collateral fossa is bigger than the medial one in the metatarsal, middle caudal series proportionately lower and narrower than the middle−posterior dorsal vertebra). Sarcosaurus was a bipedal predator, probably able to run fast and catch small prey. The holotype belonged to a 3.5-metre-long animal whose weight was no greater than 50–60 kg. NHMUK PV R3542 belonged to a larger animal, estimated to have had a maximum length of 5 m and a weight of 140 kg.[3]

History of discovery

Pelvis and parts of femur and dorsal vertebra

The

Warwick Museum to S. woodi but the identity was unproven; in 1995 it was given the informal name "Liassaurus"[10] but this has remained a nomen nudum. The specimen is likely one individual, located in the same stratiagraphic position as the holotypic specimen. Unfortunately, there are few available overlapping elements from the specimen and the holotype. Both specimens preserve a relatively complete femur: however, the features of both (an anteromedially directed head, a relatively long fourth trochanter and a trochanteric shelf) are plesiomorphic and thus do not indicate conspecifity or clade membership. It is noted, however, that there are no features which are present in one specimen but not the other. In 2020 WARMS G667–690 was given a comprehensive redescription, which proposed that all three specimens belonged to the same species, Sarcosaurus woodi.[1]

Between the years 1980 and 2000, three fossils were discovered on a beach near

neotheropod, probably related to Sarcosaurus or from an indeterminate megalosauroid. The scelidosaur femur and theropod tibia are the only known remains of dinosaurs from Ireland, which has a poor Mesozoic fossil record entirely consisting of marine localities, and the scelidosaur specimen was the first ever reported from the island.[11]

In 2023, a partial Theropod Specimen recovered from the lower Sinemurian Broadford Beds Formation of the Isle of Skye, previously referred to a Coelophysoid-grade theropod, was reclassified as Cf.Sarcosaurus, clading with Tachiraptor as a branch leading to Averostra. This specimen, NMS G.1994.10.1, consists on an isolated left tibia lacking its proximal region.[12]

Phylogeny

Sarcosaurus restored as a basal neotheropod

Andrews originally assigned Sarcosaurus to the Megalosauridae. The first to suggest a more basal position was Samuel Paul Welles who placed it in the Coelophysidae.[13] Later analyses resulted in either a position in the Ceratosauria,[14] or in the Coelophysoidea.[15] Ezcurra (2012) found Sarcosaurus to be the most basal ceratosaur in a large unpublished analysis.[16] In 2018, Andrea Cau in the large analysis of Saltriovenator found Sarcosaurus to be a dilophosaurid with good amount of support in the data.[17] In 2020, Ezcurra et al. recovered Sarcosaurus as a close relative of Averostra due to the presence of shared characters including an anteroventrally oriented ventral margin of the preacetabular process in lateral view on the ilium and a femur with a poorly posteriorly developed fourth trochanter. Their cladogram is shown below:[1] A latter work reinforced that clade made of Sarcosaurus woodi + (Tachiraptor admirabilis + Averostra).[12]

Theropoda 

Palaeoenvironment

Holotype specimen was collected from strata (bucklandi zone, Sinemurian) that were deposited in epicontinental, shallow, marine settings affected by sea-level fluctuations and a warm, predominantly humid climate.

Blue Lias Formation. with typical lithofacies of alternating mudrocks and generally fine-grained and frequently highly fossiliferous limestones.[19]
the Rugby Limestone Member was deposited at a palaeolatitude of approximately 35° N in a storm-influenced offshore setting.
London Platform at 60–80 km to the south-east was probably the principal source of terrestrial biodebris.[22]

See also

References

  1. ^
    hdl:11336/160038
    .
  2. ISSN 0028-3630
    .
  3. S2CID 243596687
    , retrieved 2023-10-19
  4. ISSN 0374-5481
    .
  5. ^ Von Huene, F. (1932). "Die fossile Reptil-Ordnung Saurischia, ihre Entwicklung und Geschichte". Monographien zur Geologie und Paläontologie. 1 (4): 361. Retrieved 19 October 2023.
  6. ISSN 0374-5481
    .
  7. JSTOR 1440541
    .
  8. ^ Waldman, M. (1974). "Megalosaurids from the Bajocian (Middle Jurassic) of Dorset". Paleontology. 17 (2): 325–339. Retrieved 19 October 2023.
  9. S2CID 129624992
    .
  10. ^ Pickering, S. (1995). Jurassic Park: Unauthorized Jewish Fractals in Philopatry. A Fractal Scaling in Dinosaurology Project (2 ed.). Capitola. p. 478.{{cite book}}: CS1 maint: location missing publisher (link)
  11. S2CID 228811170
    .
  12. ^
    S2CID 264343748
    .
  13. ^ Welles, S.P. (1984). "Dilophosaurus wetherilli (Dinosauria, Theropoda): osteology and comparisons". Palaeontographica Abteilung A. 185: 85–180. Retrieved 19 October 2023.
  14. ^ Gauthier, J. A. (1986). "Saurischian monophyly and the origin of birds". Memoirs of the California Academy of Sciences. 8 (1): 1–55. Retrieved 19 October 2023.
  15. S2CID 30039789
    .
  16. ^ Ezcurra, M. (2012). "Phylogenetic analysis of Late Triassic – Early Jurassic neotheropod dinosaurs: Implications for the early theropod radiation". Journal of Vertebrate Paleontology. Program and Abstracts. 32: 1–91.
  17. PMID 30588396
    .
  18. ISSN 0016-7878
    .
  19. ISSN 0016-7878
    .
  20. S2CID 133014351
    .
  21. ^ Radley, J.D. (2003). "Warwickshire's Jurassic geology, past,present and future" (PDF). Mercian Geologist. 15 (1): 209–218. Retrieved 19 October 2023.
  22. ^ Cox, BM; Sumbler, MG; Ivimey-Cook, HC (1999). "A formational framework for the Lower Jurassic of England and Wales (onshore area)". British Geological Survey Research Report. 99 (1): 1–28. Retrieved 19 October 2023.

External links

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