Kentrosaurus
| Kentrosaurus Temporal range: Late Jurassic,
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| Mounted skeleton, Berliner Naturkundemuseum | |
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| Genus: | Kentrosaurus Hennig, 1915
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Kentrosaurus (meaning "pointed lizard"; Template:Pron-en KEN-tro-SAWR-əs, from the Greek kentron/κεντρον, meaning "point" or "prickle", and sauros/σαυρος meaning 'lizard',[1] is a genus of stegosaurid dinosaur from the Late Jurassic of Tanzania, related to the better-known Stegosaurus of North America. Its fossils have been found in the Tendaguru Formation, dated to the Kimmeridgian stage, between about 155.7 ± 4 Ma and 150.8 ± 4 Ma (million years ago).
This 4 meter long stegosaurian was described by Edwin Hennig in 1915. Like Stegosaurus, Kentrosaurus had a double row of plates running down its spine. The two differed in size, in the shape of their armour plating, and in their bodily flexibility, however. The bony plates gave way to spikes about mid-way along the spine. It also had spikes on its flanks.
The ceratopsid dinosaur Centrosaurus from the late Cretaceous period derives its name from the same Ancient Greek words, but the initial letter has changed to a 'C' and is pronounced as a soft C to avoid confusion.
Discovery and species
The 1909–1912 German expedition to East Africa resulted in the discovery of several new dinosaur genera, of which Kentrosaurus was one of the most important, for the reason outlined above — it implied a former proximity of Tanzania to the Morrison Formation, in the eastern part of the Rocky Mountains. Of the three paleontologists on this expedition, it was Edwin Hennig who first described Kentrosaurus, in 1915. Although no complete individuals were found, some material was found in association, including a nearly complete tail, hip, several dorsal vertebrae and some limb elements of one individual. These form the core of a mount in the Humboldt Museum, of the University of Berlin by Janensch.[2] The mount was dismantled during the museum renovation in 2006/2007, and re-mounted in an improved pose by Research Casting International. Some other material, including a braincase and spine, was thought to have been misplaced or destroyed during World War II.[3]. However, all the supposedly lost cranial material was later found in a drawer of a basement cupboard.[4]
The type species of Kentrosaurus is K. aethiopicus. This is currently the only known species. However, fragmentary fossil material from Wyoming, named Stegosaurus longispinus by Charles Gilmore in 1914,[5] may be a North American species of Kentrosaurus.
Naming controversy
Kentrosaurus was described by Edwin Hennig in 1915, but soon after its description, a controversy arose over its name, which is very similar to the ceratopsian dinosaur Centrosaurus. Under the rules of biological nomenclature, two animals may not be given the same name. Hennig renamed it Kentrurosaurus.[6], and Hungarian paleontologist Franz Nopcsa renamed the genus Doryphorosaurus. If a renaming was necessary, Hennig's has priority[7] However, because the spellings are different (Centrosaurus is spelled with a C), both Doryphorosaurus and Kentrurosaurus are unneeded replacement names; Kentrosaurus remains the valid name for the genus.
Paleobiology
Kentrosaurus was smaller than Stegosaurus. Kentrosaurus was just 4 metres (16 ft) long and weighed approximately 320 kg.[8] It was certainly small for a stegosaurian.
Diet
Kentrosaurus and other stegosaurids were herbivorous. Unlike other ornithischian dinosaurs, the stegosaurids had small teeth with horizontal wear facets indicating tooth-food contact[9] and a jaw probably capable of only orthal (up and down) movements. Kentrosaurus had distinctive, spade-shaped cheek teeth, with asymmetrical crowns and only seven denticles. These teeth were less complex than those of other stegosaurians.[10] Kentrosaurus would not have been able to browse on grass, as grasses did not evolve until late into the Cretaceous Period, long after Kentrosaurus had become extinct. One theory on stegosaurid diet holds that they were low-level browsers, eating foliage and low-growing fruit from various non-flowering plants.[11] It may also have been possible for Kentrosaurus to rear up on its hind legs to reach vegetation higher in trees.
Armor
Kentrosaurus armor is also rather different from that of Stegosaurus. Kentrosaurus had small dorsal plates along its neck and shoulders. Along the rest of the back and down the tail were several — typically six — spectacular pairs of imposing caudal spikes, each up to a foot in length (see also: Thagomizer). Like other stegosaurs, such as the European Lexovisaurus, it had another pair of spikes jutting backwards from the shoulders (often represented as jutting from the hips in older restorations). Unlike Stegosaurus, which may have used its large plates for thermoregulation, the spines of Kentrosaurus were not well suited to such a function. They could have been used as display features, or armour for self-defence.
Kentrosaurus would have been preyed upon by theropods similar to Allosaurus and Ceratosaurus. It could have used its tail to ward off attacks by lashing the tail from side to side. The spines along Kentrosaurus' flanks would also have helped protect the animal from attacks.
Posture
Kentrosaurus also differed from Stegosaurus in one other key feature — it lacked the pronounced spines on the backbone, near the hip and tail region, that characterize the vertebrae of a Stegosaurus. The length of the thigh bone compared with the rest of the leg indicates that Kentrosaurus was a slow and inactive dinosaur. It may have reared up on its hind legs to reach twigs and leaves, but would normally have been fully quadrupedal.
Paleoecology
Fossils of Kentrosaurus have been found in the Tendaguru Formation, a rich fossil bed in Tanzania. The fossils consist of two composite skeletons and additional isolated fossilized bones from both adult and juvenile specimens.[10] These fossils have been dated to the Kimmeridgian stage, between about 155.7 ± 4 Ma and 150.8 ± 4 Ma (million years ago).
The similarities and differences between kentrosaurs and stegosaurs illustrate well the geological principle of continental drift. The similarity between the kentrosaur fossils found in Tendaguru, Tanzania and the stegosaur fossils found in North America are evidence that these two points of the globe, now widely separated, were once very close together and indeed part of a supercontinent, known by geologists as Pangaea and, later, the northern half, known as Laurasia. These two points must also have had very similar climatic conditions, in order to have produced such similar specimens. Meanwhile, the differences between the animals illustrate the changes that their different ancestors underwent divergent evolution as the two groups of animals parted company, because of the subsequent separation of the tectonic plates.
References
- ^ Liddell, Henry George and Robert Scott (1980). A Greek-English Lexicon (Abridged Edition). United Kingdom: Oxford University Press. ISBN 0-19-910207-4.
- ^ Janensch, W. (1925). "Ein aufgestelltes Skelett von Kentrurosaurus aethiopicus E. Hennig aus den Tendaguru-Schichten Deutsch-Ostafrikas". Palaeontographica. Suppl. 7 I: 255–276.
- ^ Glut, Donald F. (1997). "Kentrosaurus". Dinosaurs: The Encyclopedia. Jefferson, North Carolina: McFarland & Co. pp. 516–519. ISBN 0-89950-917-7.
- ^ Galton, Peter M. (1988). "Skull bones and endocranial casts of stegosaurian dinosaur Kentrosaurus Hennig, 1915 from Upper Jurassic of Tanzania, East Africa". Geologica et Palaeontologica. 22: 123–143.
- ^ Gilmore, C.W. (1914). "Osteology of the armored Dinosauria in the United States National Museum, with special reference to the genus Stegosaurus". United States National Museum Bulletin 89: 1–136
- ^ Hennig, E. (1916). "Zweite Mitteilung über den Stegosauriden vom Tendaguru" [Second report on the stegosaurids of Tendaguru]. Sitzungsberichte der Gesellschaft Naturforschender Freunde zu Berlin 1916(6):175–182
- ^ Hennig, E. (1916). "Kentrurosaurus, non Dorypphorosaurus.
- ^ Seebacher, Frank (2001). "A new method to calculate allometric length-mass relationship of dinosaurs". Journal of Vertebrate Paleontology. 21 (1): 51–60. doi:10.1671/0272-4634(2001)021[0051:ANMTCA]2.0.CO;2.
{{cite journal}}: Cite has empty unknown parameter:|coauthors=(help) - ^ Barrett PM (2001). "Tooth wear and possible jaw action of Scelidosaurus harrisoni and a review of feeding mechanisms in other thyreophoran dinosaurs.". In Carpenter, Kenneth(ed) (ed.). The Armored Dinosaurs. Indiana University Press. pp. 25–52. ISBN 0-253-33964-2.
{{cite book}}:|editor=has generic name (help) - ^ a b Galton P.M., Upchurch P. (2004). "Stegosauria". In Weishampel D.B., Dodson P., Osmólska H. (ed.). The Dinosauria (2nd Edition). University of California Press. p. 361. ISBN 0-520-24209-2.
{{cite book}}: CS1 maint: multiple names: editors list (link) - ^ Weishampel DB (1984). "Interactions between Mesozoic Plants and Vertebrates: Fructifications and seed predation". N. Jb. Geol. Paläontol. Abhandl. 167: 224–250.
External links
- Kentrosaurus in The Dinosaur Encyclopaedia at Dino Russ's Lair
- Stegosauria from Thescelosaurus.com (Includes details on Kentrosaurus, its junior synonyms, and other material)
- Kentrosaurus from DinoData.org