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Torvosaurus is a genus of large, carnivorous theropod dinosaurs that inhabited western North America and Portugal during the late Jurassic period, 153 to 148 million years ago. In 1979 the type species Torvosaurus tanneri was named: it was a large, heavily built, bipedal carnivore, that could grow to a length of about 10 meters. T. tanneri was among the largest carnivores of its time, together with Epanterias and Saurophaganax (which could be both synonyms of Allosaurus). Specimens referred to Torvosaurus gurneyi were initially claimed to be up to eleven metres long, but later shown to be smaller.[1] Based on bone morphology Torvosaurus is thought to have had short but very powerful arms.

Description

Torvosaurus was a very large predator, with an estimated maximum body length of 10 meters and mass of 3.6-4.5 tons for both T. tanneri and T. gurneyi,[1][2][3] making Torvosaurus among the largest carnivores of the Jurassic. Claims have been made indicating even larger sizes. The synonymous Edmarka rex was named thus because it was assumed to rival Tyrannosaurus rex in length. Likewise "Brontoraptor" was supposed to be a torvosaur of gigantic size.[4] The T. gurneyi specimens from Portugal initially prompted larger size estimates to be made. In 2006 a lower end of a thighbone, specimen ML 632, was referred to Torvosaurus sp. and later to T. gurneyi. This specimen was initially stated to indicate a length of 11 meters. Applying the extrapolation method of J.F. Anderson, correlating mammal weights to their femur circumference, resulted in a weight of 1930 kilogrammes. However, revised estimates performed in 2014 suggested a slightly smaller total body size for this specimen, of about 10 meters.[1] Among the differentiating features between T. gurneyi and T. tanneri are the number of teeth and size and shape of mouth. While the upper jaw of T. tanneri has more than 11 teeth, that of T. gurneyi has less.[1][5]

Torvosaurus had an elongated, narrow snout, with a kink in its profile just above the large nostrils. The frontmost snout bone, the praemaxilla, bore three rather flat teeth oriented somewhat outwards with the front edge of the teeth crown overlapping the outer side of the rear edge of the preceding crown. The maxilla was tall and bore at least eleven rather long teeth. The antorbital fenestra was relatively short. The lacrimal bone had a distinctive lacrimal horn on top; its lower end was broad in side view. The eye socket was tall with a pointed lower end. The jugal was long and transversely thin. The lower front side of the quadrate bone was hollowed out by a tear-shaped depression, the contact surface with the quadratojugal. Both the neck vertebrae and the front dorsal vertebrae had relatively flexible ball-in-socket joints. The balls, on the front side of the vertebral centra, had a wide rim, a condition by Britt likened to a Derby hat. The tail base was stiffened in the vertical plane by high and in side view wide neural spines. The upper arm was robust; the lower arm robust but short. Whether the thumb claw was especially enlarged, is uncertain. In the pelvis, the ilium resembled that of Megalosaurus and had a tall, short, front blade and a longer pointed rear blade. The pelvis as a whole was massively built, with the bone skirts between the pubic bones and the ischia contacting each other and forming a vaulted closed underside.[6]

Systematics and classification

When first described in 1979 by Galton and Jensen,[2] Torvosaurus was classified as a megalosaurid, which is the current consensus.[7] It was later assigned to Carnosauria by Ralph Molnar et al. in 1990,[8] and to a basal position in Spinosauroidea by Oliver Walter Mischa Rauhut in 2003[9] and to a very basal position in the Tetanurae by Thomas Holtz in 1994;[10] all these assignments are not supported by present phylogenetic analysis.[7] In 1985, Jensen assigned Torvosaurus a family of its own, the Torvosauridae.[11] Despite support for this concept by Paul Sereno[12] and Mateus,[13] it seems redundant as Torvosaurus is closely related to, and perhaps the sister species of, the earlier Megalosaurus within a Megalosaurinae.[7] However, Torvosauridae may be used as an alternative name for Megalosauridae if Megalosaurus is considered an indeterminable nomen dubium.[14] Though a close relative of Megalosaurus, Torvosaurus is seemingly more advanced or apomorphic. Torvosaurus's larger clade, the Megalosauridae, is most commonly held as a basal branch of the Tetanurae, and considered less derived than carnosaurs or coelurosaurs, and likely related to the spinosaurids.[7]

Distinguishing anatomical features

A diagnosis is a statement of the anatomical features of an organism (or group) that collectively distinguish it from all other organisms. Some, but not all, of the features in a diagnosis are also autapomorphies. An autapomorphy is a distinctive anatomical feature that is unique to a given organism or group.

According to Carrano et al. (2012), Torvosaurus can be distinguished based on the following characteristics:[15]

  • the presence of a very shallow maxillary fossa (it lacks a fenestra maxillaris piercing the bone wall)
  • the presence of fused interdental plates
  • the pneumatic fossae in the posterior dorsal and the anterior caudal vertebrae centra are expanded, forming enlarged, deep openings
  • the puboischiadic plate is highly ossified (the paired bony plates, of both sides, connect and close off the entire underside of the pelvis, a very basal trait that Galton & Jensen saw as an indication that Theropoda was polyphyletic, the Carnosauria having independently evolved from carnivorous Prosauropoda)[2]
  • a distal expansion of the ischium shaft with a prominent lateral midline crest and an oval outline when examined in lateral view
  • the cervical vertebrae are opisthocoelous with a pronounced flat rim around the, anterior, ball (according to Rauhut, 2000)
  • a (transverse) fenestra is situated in the neural arch of the dorsal vertebrae in front of the hyposphene (according to Rauhut, 2000)[16]

Paleobiology

Eggs and ovipary

The careful study of fossil dinosaur embryos provides researchers with information about the transformation of the embryo over time, the different developmental pathways present in dinosaur lineages, dinosaur reproductive behavior, and dinosaur parental care.[17][18][19]

In 2013, Araújo et al. announced the discovery of specimen ML1188, a clutch of crushed dinosaur eggs and embryonic material attributed to Torvosaurus. This discovery further supports the hypothesis that large theropod dinosaurs were oviparous, meaning that they laid eggs and hence that embryonic development occurred outside the body of female dinosaurs. This discovery was made in 2005 by the Dutch amateur fossil-hunter Aart Walen at the Lourinhã Formation in Western Portugal, in fluvial overbank sediments that are considered to be from the Tithonian stage of the [[Jurassic Period, approximately 152 to 145 million years ago. This discovery is significant paleontologically for a number of reasons: (a) these are the most primitive dinosaur embryos known; (b) these are the only basal theropod embryos known; (c) fossilized eggs and embryos are rarely found together; (d) it represents the first evidence of a one-layered eggshell for theropod dinosaurs; and (e) it allows researchers to link a new eggshell morphology to the osteology of a particular group of theropod dinosaurs.[20] The specimen is housed at the Museu da Lourinhã, in Portugal. As the eggs were abandoned due to unknown circumstances, it is not known if Torvosaurus provided parental care to its eggs and young or abandoned them shortly after laying.[21]

Torvosaurus in The Land Before Time

A family of theropods, possibly Torvosaurus, appear in The Lonely Journey, an episode of The Land Before Time television series.

Gallery

References

  1. Cite error: Invalid <ref> tag; no text was provided for refs named gurneyi
  2. 2.0 2.1 2.2 P. M. Galton and J. A. Jensen. 1979. A new large theropod dinosaur from the Upper Jurassic of Colorado. Brigham Young University Geology Studies 26(1):1-12
  3. Paul, Gregory S. (1988). Predatory Dinosaurs of the World. Simon & Schuster. p. 282. ISBN 0-671-61946-2. 
  4. Siegwarth, J., Linbeck, R., Bakker, R. and Southwell, B., 1996, "Giant carnivorous dinosaurs of the family Megalosauridae", Hunteria 3: 1-77
  5. "Torvosaurus gurneyi: New Giant Dinosaur Discovered in Portugal". Sci-News.com. 6 March 2014. http://www.sci-news.com/paleontology/science-torvosaurus-gurneyi-giant-dinosaur-portugal-01794.html. Retrieved on 8 March 2014. 
  6. Cite error: Invalid <ref> tag; no text was provided for refs named Britt1991
  7. Cite error: Invalid <ref> tag; no text was provided for refs named Carrano2012
  8. R. E. Molnar, S. M. Kurzanov, and Z. Dong. 1990. "Carnosauria". In: D. B. Weishampel, H. Osmólska, and P. Dodson (eds.), The Dinosauria. University of California Press, Berkeley
  9. O. W. M. Rauhut. 2003. The interrelationships and evolution of basal theropod dinosaurs. Special Papers in Palaeontology 69:1-213
  10. T.R. Holtz, 1994, "The phylogenetic position of the Tyrannosauridae: implications for theropod systematics", Journal of Paleontology 68(5): 1100-1117
  11. Cite error: Invalid <ref> tag; no text was provided for refs named Jensen1985
  12. P.C. Sereno, J.A. Wilson, H.C.E. Larsson, D.B. Dutheil, and H.-D. Sues, 1994, "Early Cretaceous dinosaurs from the Sahara", Science 266(5183): 267-271
  13. Cite error: Invalid <ref> tag; no text was provided for refs named mateusetal06
  14. P.C. Sereno, 1998, "A rationale for phylogenetic definitions, with application to the higher-level taxonomy of Dinosauria", Neues Jahrbuch für Geologie und Paläontologie, Abhandlungen 210(1): 41-83
  15. Carrano, Benson and Sampson, 2012. The phylogeny of Tetanurae (Dinosauria: Theropoda). Journal of Systematic Palaeontology. 10(2), 211-300
  16. Rauhut, 2000. The interrelationships and evolution of basal theropods (Dinosauria, Saurischia). Ph.D. dissertation, Univ. Bristol [U.K.], 1-440.
  17. Long, J. A. & McNamara, K. J. Heterochrony: The key to dinosaur evolution. in The Dinofest International (Wolberg, D.L., Stump, E. & Rosenberg, G. D., eds.) 113–123 ( Acad. Nat. Sci. Phil. , 1997).
  18. Balanoff, A. M., Norell, M. A., Grellet-Tinner, G. & Lewin, M. R. Digital preparation of a probable neoceratopsian preserved within an egg, with comments on microstructural anatomy of ornithischian eggshells. Naturwissenschaften 95 , 493–500 (2008).
  19. Varricchio, D. J. et al . Avian paternal care had dinosaur origin. Science 322 , 1826– 1828 (2008).
  20. Ricardo Araújo, Rui Castanhinha, Rui M. S. Martins, Octávio Mateus, Christophe Hendrickx, F. Beckmann, N. Schell & L. C. Alves (2013) Filling the gaps of dinosaur eggshell phylogeny: Late Jurassic Theropod clutch with embryos from Portugal. Scientific Reports 3 : Article number: 1924 doi:10.1038/srep01924
  21. http://www.nbcnews.com/science/rare-find-abandoned-dinosaur-nests-eggshells-6C10843146

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