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{{italictitle}}{{speciesbox |
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| name = ''Timimus'' |
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| fossil_range = [[Early Cretaceous]] |
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| image = Timimus.tif |
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| image_width = 250px |
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| image_caption = [[Holotypic]] left femur of ''T. hermani'', NMV P186303 |
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| genus = Timimus |
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| parent_authority = Rich & Vickers-Rich, 1993 |
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| species = hermani |
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| authority = Rich & Vickers-Rich, 1993 |
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}} |
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'''''Timimus''''' is a [[genus]] of small [[coelurosauria]]n [[Theropoda|theropod]] [[dinosaur]], which was originally identified as an [[ornithomimosaur]], from the [[Early Cretaceous]] of [[Australia]]. |
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==Discovery and species== |
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In 1991, two [[femur|femora]] (thighbones), one from an adult and one from a juvenile, were found within a metre of each other at the [[Dinosaur Cove|Dinosaur Cove East]] site, in the small "Lake Copco" quarry, at the southern tip of [[Australia]]. |
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The [[type species]], ''Timimus hermani'', was formally named and shortly described by Dr [[Thomas Rich]] and his wife [[Patricia Vickers-Rich]] in 1993/1994. The generic name means "Tim's Mimic" and combines the name of both the discoverers' son Timothy Rich and palaeontologist [[Tim Flannery]] with a [[Latin]] ''mimus'', "mimic", a reference to the presumed affinity of the species with the [[Ornithomimosauria]]. The [[specific name (zoology)|specific name]] honours volunteer John Herman who many years assisted the Dinosaur Cove project.<ref>T.H. Rich and P. Vickers-Rich, 1994, "Neoceratopsians and ornithomimosaurs: dinosaurs of Gondwana origin?", ''National Geographic Research and Exploration'' '''10'''(1): 129-131</ref> |
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The [[holotype]] specimen, '''NMV P186303''', was found in a layer of the [[Eumeralla Formation]], dating to the [[Albian]] [[faunal stage]] in the early [[Cretaceous]], some 106 million years ago. It consists of a left femur of an adult individual. |
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In 1994 Dr Rich commented that while it would have been more ideal to have had the most complete specimen possible as a [[holotype]], it was highly unlikely that future material of ''Timimus'' would be found, due to the limited nature of sites to be explored in the area. Also, the holotype would have had characteristics which both identified it as an ornithomimosaur and a new genus within that group. Thus the name would serve as a reference point for the material within paleontological literature. Rich stated: "By themselves, the names of dinosaurs are like telephone numbers - they are labels that go with specimens and the ideas that flow from the analysis of the material. Confusing labels, like an inaccurate telephone book, lead to an unworkable system, so one must be careful in putting names or labels on things. But the act of doing so is not creating those specimens or the ideas associated with them; it is merely creating a convenient "handle" for purposes of communication".<ref>{{cite journal|author=Rich T.H.|year=1994|title=Naming a new Genus & Species of Dinosaur on the basis of a Single Bone.|journal=Dinosaur Report|pages=10–11}}</ref> |
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The second femur, that of a juvenile, was assigned as the [[paratype]], specimen NMV P186323. Some [[vertebra]]e from the site have been referred to the [[species]], as well as some other South Australian material. |
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==Description== |
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The holotype thighbone is 44 centimetres long. From this a total length of the animal of 2.5 metres has been extrapolated.<ref name="long1998">Long, J.A. (1998). ''Dinosaurs of Australia and New Zealand and Other Animals of the Mesozoic Era'', Harvard University Press, p. 108</ref> The slenderness of the bone suggest a lithe animal. The paratype femur is 19.5 centimetres long. The femora show several features that were considered diagnostic. There is no extensor groove between the condyles of the lower joint, which would have been a basal trait for a ornithomimosaur.<ref name="long1998"/> The femoral head is anteroposteriorally flattened. The anterior trochanter is in a high position and reaches the level of the major trochanter. |
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==Phylogeny== |
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In 1994 the describers assigned ''Timimus'' to the "Ornithomimosauridae" with which the [[Ornithomimidae]] were meant. Ornithomimosaur remains from [[Gondwana]] are rare and dubious; ''Timimus'' was thus presented as proof that the group was indeed present in the [[Southern Hemisphere]] and would even have originated there. Immediately however, a position within the Ornithomimosauria was doubted by [[Thomas Holtz]].<ref>Holtz, T. R., Jr. 1994. "The phylogenetic position of the Tyrannosauridae: Implications for theropod systematics". ''Journal of Paleontology'' '''68''': 1100-1117</ref> Today it is recognised that ''Timimus'' shares no derived traits, [[synapomorphies]], with the Ornithomimosauria and that thus any proof it would belong to this group is lacking. It perhaps belongs to some coelurosaurian group; some workers consider it a ''[[nomen dubium]]''.<ref>S.A. Hocknull, M.A. White, T.R. Tischler, A.G. Cook, N.D. Calleja, T. Sloan, and D.A. Elliot. 2009. "New mid-Cretaceous (latest Albian) dinosaurs from Winton, Queensland, Australia". ''PLoS ONE'' '''4'''(7):e6190: 1-51</ref> A 2012 study found it to be a valid [[tyrannosauroid]].<ref>{{Cite doi|10.1371/journal.pone.0037122}}</ref> |
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==Paleobiology== |
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The [[habitat]] of ''Timimus'' consisted of polar forests with mild summers but cold and dark winters due to the closer proximity of the area to the [[South Pole]] during the Early Cretaceous. In 1996, [[Anusuya Chinsamy]], an expert on the microstructure of fossil bones, examined bone material from ''Timimus'' and ''[[Leaellynasaura]]'' and discovered they exhibited different bone histology. The [[ornithischia]]n showed a continuous rate of bone deposition, while the coelurosaur had a cyclical pattern of bone formation, which suggested ''Timimus'' may have hibernated in colder months.<ref>Chinsamy, A., Rich, T., and Rich-Vickers, P. (1996). "Bone histology of dinosaurs from Dinosaur Cove, Australia", ''Journal of Vertebrate Paleontology'' '''16'''(Supplement to No.3), 28A</ref> A possible ''Timimus hermani'' or related form from the [[Strzelecki Group]] near [[Inverloch, Victoria]] left a fossil of the first phalanx of its third toe with a depressed fracture on the [[plantar]] surface.<ref name="molnar-paleopathology">Molnar, R. E., 2001, Theropod paleopathology: a literature survey: In: Mesozoic Vertebrate Life, edited by Tanke, D. H., and Carpenter, K., Indiana University Press, p. 337-363.</ref> |
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==Notes== |
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{{reflist}} |
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==References== |
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* {{cite book|author=Rich TH, Vickers-Rich P|year=2000|title=Dinosaurs of Darkness|publisher=Allen & Unwin|isbn=1-86508-496-4}} |
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* {{cite journal|doi=10.1080/02724634.1998.10011066|author=Chinsamy A, Rich TH, Vickers-Rich P|year=1998|title=Polar dinosaur bone histology.|journal=Journal of Vertebrate Paleontology|volume = 18|issue = 2|pages=385–390}} |
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*[http://www.vertpaleo.org/jvp/18-385-390.html Online abstract of preceding article] |
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==External links== |
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*[http://www.alphalink.com.au/~dannj/timimus.htm Dann's Dinosaur Info: Timimus] |
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{{Portal|Dinosaurs}} |
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[[Category:Cretaceous dinosaurs]] |
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[[Category:Coelurosaurs]] |
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[[Category:Dinosaurs of Australia]] |
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[[zh:似提姆龙]] |
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Version du 1 août 2012 à 00:29
Modèle:ItalictitleModèle:Speciesbox
Timimus is a genus of small coelurosaurian theropod dinosaur, which was originally identified as an ornithomimosaur, from the Early Cretaceous of Australia.
Discovery and species
In 1991, two femora (thighbones), one from an adult and one from a juvenile, were found within a metre of each other at the Dinosaur Cove East site, in the small "Lake Copco" quarry, at the southern tip of Australia. The type species, Timimus hermani, was formally named and shortly described by Dr Thomas Rich and his wife Patricia Vickers-Rich in 1993/1994. The generic name means "Tim's Mimic" and combines the name of both the discoverers' son Timothy Rich and palaeontologist Tim Flannery with a Latin mimus, "mimic", a reference to the presumed affinity of the species with the Ornithomimosauria. The specific name honours volunteer John Herman who many years assisted the Dinosaur Cove project.[1]
The holotype specimen, NMV P186303, was found in a layer of the Eumeralla Formation, dating to the Albian faunal stage in the early Cretaceous, some 106 million years ago. It consists of a left femur of an adult individual.
In 1994 Dr Rich commented that while it would have been more ideal to have had the most complete specimen possible as a holotype, it was highly unlikely that future material of Timimus would be found, due to the limited nature of sites to be explored in the area. Also, the holotype would have had characteristics which both identified it as an ornithomimosaur and a new genus within that group. Thus the name would serve as a reference point for the material within paleontological literature. Rich stated: "By themselves, the names of dinosaurs are like telephone numbers - they are labels that go with specimens and the ideas that flow from the analysis of the material. Confusing labels, like an inaccurate telephone book, lead to an unworkable system, so one must be careful in putting names or labels on things. But the act of doing so is not creating those specimens or the ideas associated with them; it is merely creating a convenient "handle" for purposes of communication".[2]
The second femur, that of a juvenile, was assigned as the paratype, specimen NMV P186323. Some vertebrae from the site have been referred to the species, as well as some other South Australian material.
Description
The holotype thighbone is 44 centimetres long. From this a total length of the animal of 2.5 metres has been extrapolated.[3] The slenderness of the bone suggest a lithe animal. The paratype femur is 19.5 centimetres long. The femora show several features that were considered diagnostic. There is no extensor groove between the condyles of the lower joint, which would have been a basal trait for a ornithomimosaur.[3] The femoral head is anteroposteriorally flattened. The anterior trochanter is in a high position and reaches the level of the major trochanter.
Phylogeny
In 1994 the describers assigned Timimus to the "Ornithomimosauridae" with which the Ornithomimidae were meant. Ornithomimosaur remains from Gondwana are rare and dubious; Timimus was thus presented as proof that the group was indeed present in the Southern Hemisphere and would even have originated there. Immediately however, a position within the Ornithomimosauria was doubted by Thomas Holtz.[4] Today it is recognised that Timimus shares no derived traits, synapomorphies, with the Ornithomimosauria and that thus any proof it would belong to this group is lacking. It perhaps belongs to some coelurosaurian group; some workers consider it a nomen dubium.[5] A 2012 study found it to be a valid tyrannosauroid.[6]
Paleobiology
The habitat of Timimus consisted of polar forests with mild summers but cold and dark winters due to the closer proximity of the area to the South Pole during the Early Cretaceous. In 1996, Anusuya Chinsamy, an expert on the microstructure of fossil bones, examined bone material from Timimus and Leaellynasaura and discovered they exhibited different bone histology. The ornithischian showed a continuous rate of bone deposition, while the coelurosaur had a cyclical pattern of bone formation, which suggested Timimus may have hibernated in colder months.[7] A possible Timimus hermani or related form from the Strzelecki Group near Inverloch, Victoria left a fossil of the first phalanx of its third toe with a depressed fracture on the plantar surface.[8]
Notes
- T.H. Rich and P. Vickers-Rich, 1994, "Neoceratopsians and ornithomimosaurs: dinosaurs of Gondwana origin?", National Geographic Research and Exploration 10(1): 129-131
- Rich T.H., « Naming a new Genus & Species of Dinosaur on the basis of a Single Bone. », Dinosaur Report, , p. 10–11
- Long, J.A. (1998). Dinosaurs of Australia and New Zealand and Other Animals of the Mesozoic Era, Harvard University Press, p. 108
- Holtz, T. R., Jr. 1994. "The phylogenetic position of the Tyrannosauridae: Implications for theropod systematics". Journal of Paleontology 68: 1100-1117
- S.A. Hocknull, M.A. White, T.R. Tischler, A.G. Cook, N.D. Calleja, T. Sloan, and D.A. Elliot. 2009. "New mid-Cretaceous (latest Albian) dinosaurs from Winton, Queensland, Australia". PLoS ONE 4(7):e6190: 1-51
- DOI 10.1371/journal.pone.0037122
- Chinsamy, A., Rich, T., and Rich-Vickers, P. (1996). "Bone histology of dinosaurs from Dinosaur Cove, Australia", Journal of Vertebrate Paleontology 16(Supplement to No.3), 28A
- Molnar, R. E., 2001, Theropod paleopathology: a literature survey: In: Mesozoic Vertebrate Life, edited by Tanke, D. H., and Carpenter, K., Indiana University Press, p. 337-363.
References
- (en) Rich TH, Vickers-Rich P, Dinosaurs of Darkness, Allen & Unwin, (ISBN 1-86508-496-4)
- Chinsamy A, Rich TH, Vickers-Rich P, « Polar dinosaur bone histology. », Journal of Vertebrate Paleontology, vol. 18, no 2, , p. 385–390 (DOI 10.1080/02724634.1998.10011066)
- Online abstract of preceding article