| Kentrosaurus | ||||||||||||
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Skelettrekonstruktion im Berliner Museum für Naturkunde | ||||||||||||
| Zeitliches Auftreten | ||||||||||||
| Oberer Jura | ||||||||||||
| 161,3 bis 145,5 Mio. Jahre | ||||||||||||
| Fundorte | ||||||||||||
| Systematik | ||||||||||||
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| Wissenschaftlicher Name | ||||||||||||
| Kentrosaurus | ||||||||||||
| Hennig, 1915 | ||||||||||||
| Art | ||||||||||||
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Kentrosaurus ist eine Gattung stegosaurider Dinosaurier aus dem Oberen Jura von Tansania. Funde sind nur aus den Tendaguru-Schichten in Tansania bekannt, die ins Kimmeridge (155.7 ± 4 bis 150.8 ± 4 Ma) datiert werden. Alle Funde gehöhrten wohl zu einer einzigen Art, Kentrosaurus aethiopicus Hennig, 1915.
Die Gattung wurde vom detuschen Paläontologen Edwin Hennig 1915 erstmals beschrieben.
Kentrosaurus was described by German palaeontologist Edwin Hennig in 1915. Often thought to be a primitive member of the Stegosauria, several recent cladistic analyses find it to be derived, and a close relative to Stegosaurus from the North American Morrison Formation.
Kentrosaurus generally measured around Vorlage:Convert in length as an adult, probably had a double row of small plates and spikes running down its back, and could use its tail as a "thagomizer" for defense. The femora (thigh bones) are strongly dimorphic, suggesting that one gender (likely the females) was larger and more stout than the other.
Beschreibung Bearbeiten
Kentrosaurus war ein kleiner Stegosaurier mit dem für Dinosaurier typischen Bauplan: ein langer Hald trug einen kleinen Kopf, die Vorderbeine waren deutlich kürzer als die Hinterbeine, und der Schwanz war lang und kräftig. Ebenfalls typisch für Stegosaurier sind die zahlreichen Osteoderme (Hautverknöcherungen), die bei Kentrosaurus aus kleinen Platten auf dem Hals und vorderen Rücken und langen, verschieden ausgeformten Stacheln and übrigen Körper bestanden.
Größe und Körperhaltung Bearbeiten
Kentrosaurus aethiopicus war kleiner als andere Stegosaurier, wie Stegosaurus mjosi und S. armatus, Dacentrurus armatus sowie Tuojiangosaurus multispinus, und etwa so groß wie Huayangosaurus taibaii. Die Gesamtlänge des im Museum für Naturkunde in Berlin aufgebauten Skeletts, das aus mehreren individuen zusammengestzt ist, beträgt von Schnauzenspitze zu Schwanzspitze etwa 4,5 m, wovon etwas mehr als die Hälfte auf den Schwanz entfällt.[1] Es wurden allerdings größere Einzelknochen gefunden,[2] so dass die Maxmialgröße eines erwachsenen Tieres vermutlich bis zu 5,5 m betrug.
Aufgrund des langen Schwanzes lag der Schwerpunkt von Kentrosauriern knapp vor der Hüfte, und somit für ein quadrupedes Tier ungewöhnlich weit hinten. Diese Lage ist eher für bipede Tiere typisch. Die geraden Femurschäfte deuten jedoch auf eine säulenartige Stellung der Hinterbeine hin. Somit konnten die Hinterfüße allein das Tier nicht stabil unterstützen, und um 10 bis 15% des Körpergewichts wurden von den Vorderfüßen getragen. Der weit hinten gelegene Schwerpuntk war für die Fortbewegung wohl nicht günstig, führte aber dazu, dass das Tier sich mittels seitlicher Bewegungen der Vorderbeine schnell umdrehen und so den Schwanz immer auf potentielle Gefahrenquellen ausrichten konnte.
Autapomorphies Bearbeiten
Kentrosaurus can be distinguished from other members of the Stegosauria by a number of osteological characters. Most notably, the neural spines in the tail are not sub-parallel, as in most dinosaurs. In the anterior third of the tail, they point backwards, the usual direction. In the middle tail, however, they are almost vertical, and further back they are hook-shaped and point forward. Also typical are, among other features, that the dorsal vertebrae have a neural arch more than twice as high as the centrum, and completely occupied by the extremely spacious neural canal. The preacetabular process of the ilium widens laterally, and does not taper.
Armor Bearbeiten
The spikes and plates of Kentrosaurus were likely covered by horn. Aside from a few exceptions they were not found in close association with other skeletal remains. Thus, the exact position of most osteoderms is uncertain. A pair of closely spaced spikes was found articulated with a tail tip, and a number of spikes were found apparently regularly spaced in pairs along the path of an articulated tail.[2] Hennig[2] and Janensch[1], while grouping the dermal armour elements into four distinct types, recognized an apparently continuous change of shape among them, suggesting an uninterrupted distribution along the entire body. Because each type of osteoderm was found in two handed versions, it seems probably that all types of osteoderms were distributed in two rows along the back of the animal, a marked contrast to the better-known North American Stegosaurus, which had one row of plates on the neck, trunk and tail, and two rows of spikes on the tail tip. There is one type of spike that differs from all others in being strongly, and not only slightly, asymmetrical. Because of bone morphology classic reconstructions placed it on the hips, while many recent reconstructions place it on the should, because a similarly shaped spike is known to have existed on the should in the Chinese stegosaur Gigantspinosaurus.
Discovery and species Bearbeiten
The first fossils of Kentrosaurus were discovered by the German Tendaguru Expedition in 1909, recognized as belonging to a stegosaur by expedition leader Werner Janensch on 24 July 1910, and described by German palaeontologist Edwin Hennig in 1915.[3] During four field seasons, the German Expedition found over 1200 bones of Kentrosaurus,[2] many of which were destroyed during the Second World War.[4] Today, almost all remaining material is housed in the Museum für Naturkunde Berlin (roughly 350 remaining specimens), while the museum of the Institute for Geosciences of the Eberhard-Karls-University Tübingen houses a composite mount, roughly 50% of it being original bones.[5] 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 Museum für Naturkunde by Janensch.[1] 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.[6] However, all the supposedly lost cranial material was later found in a drawer of a basement cupboard.[7] The British Tendaguru Expedition also found material, but it is unclear how much, in what state of preservation, and where it is today. The type and sole species of Kentrosaurus is K. aethiopicus. Fragmentary fossil material from Wyoming, named Stegosaurus longispinus by Charles Gilmore in 1914,[8] has been suggested to belong to a North American species of Kentrosaurus. However, this notion has not found any support in the professional community.
Etymology Bearbeiten
When Hennig named his new stegosaur, he chose to highlight the extensive dermal armour in the generic name. From the Greek kentron/κεντρον, meaning "point" or "prickle", and sauros/σαυρος meaning "lizard",[9] Hennig created Kentrosaurus (Vorlage:Pron-en Vorlage:Respell), adding the species name aethiopicus to denote the provenance.
Naming controversy Bearbeiten
Kentrosaurus was described by Edwin Hennig in 1915,[3] 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 his stegosaur Kentrurosaurus,[10] while Hungarian paleontologist Franz Nopcsa renamed the genus Doryphorosaurus.[11] If a renaming had been necessary, Hennig's would have had priority.[12] However, because both the spellings are different (Centrosaurus is pronounced with a soft C), both Doryphorosaurus and Kentrurosaurus are unneeded replacement names; Kentrosaurus remains the valid name for the genus.
Type specimens and type locality Bearbeiten
In the original description, Hennig did not define a holotype specimen. However, in a detailed monography on the osteology, systematic position and palaeobiology of Kentrosaurus in 1925, Hennig picked the most complete partial skeleton as a lectotype (see syntype).[2] This material includes a nearly complete series of tail vertebrae, several vertebrae of the back, a sacrum with five sacral vertebrae and both ilia, both femora and an ulna, and is included in the mounted skeleton at the Museum für Naturkunde in Berlin, Germany. The type locality is Kindope, Tanzania, near the Tendaguru hill. Unaware that Hennig had already defined a lectotype, Peter Galton[13] selected two dorsal vertebrae from the material figured in Hennig's 1915 description as 'holotypes'. This definition of a holotype is not valid, because Hennig's selection has priority.[5]
Paleobiology Bearbeiten
Dentition and diet Bearbeiten
Like all ornithischians, Kentrosaurus was a herbivore. Only a single complete tooth was known when Hennig published his monography in 1925.[2] Later, a part of a dentary was found, which bears a just emerging tooth,[14] and some tooth fragments were recovered from matrix sticking to other bones. The dentary is almost identical in shape to that of Stegosaurus, albeit much smaller. Similarly, the tooth is a typical stegosaurian tooth, with a widened base and vertical grooves creating five ridges. It indicates a herbivorous diet. The fodder was barely chewed and swallowed in large chunks. One theory on stegosaurid diet holds that they were low-level browsers, eating foliage and low-growing fruit from various non-flowering plants.[15] It may also have been possible for Kentrosaurus to rear up on its hind legs to reach vegetation higher in trees.[16]
Defense Bearbeiten
Because the tail had at least 40 caudal vertebrae,[2] it was highly mobile.[16] Probably, it could flex as much as the tails of modern crocodiles, which are almost able to touch the tips of their tails to the body side. This made the tail a dangerous weapon, able to cover a large arc when swinging quickly. A biomechanical study by German palaeontologist Heinrich Mallison found that whiphlash swing speeds of the tail tip may have been as high as 140 km/h, causing lethal strikes against e.g. theropod skulls, and significant harm when other body parts were hit.[17]
References Bearbeiten
<references> [13] [7] [8] [6] [3] [10] [12] [2] [14] [1] [9] [4] [17] [5] [16] [11] [15] }}
- ↑ a b c d Janensch, W. (1925). "Ein aufgestelltes Skelett des Stegosauriers Kentrurosaurus aethiopicus HENNIG 1915 aus den Tendaguru-Schichten Deutsch-Ostafrikas." ("A mounted skeleton of the Stegosaur Kentrurosaurus aethiopicus HENNIG 1915 from the Tendaguru layers of German East Africa.") Palaeontographica Supplement 7:257-276.[German]
- ↑ a b c d e f g h Hennig, E. (1925). "Kentrurosaurus aethiopicus. Die Stegosaurier-Funde vom Tendaguru, Deutsch-Ostafrika." ("Kentrurosaurus aethiopicus. The Stegosaur finds from Tendaguru, German East-Africa") Palaeontographica Supplement 7:101-254German
- ↑ a b c Hennig, E. (1915). "Kentrosaurus aethiopicus, der Stegosauride des Tendaguru." ("Kentrosaurus aethiopicus, the stegosaur of Tendaguru") Sitzungsberichte der Gesellschaft naturforschender Freunde zu Berlin 1915:219-247 German
- ↑ a b Maier, G. African Dinosaurs Unearthed. The Tendaguru Expeditions. Indiana University Press, Bloomington, Indiana.
- ↑ a b c Mallison, H. (2011). "The real lectotype of Kentrosaurus aethiopicus HENNIG 1915". Neues Jahrbuch für Geologie und Paläontologie 259(2):197-206
- ↑ a b Donald F. Glut: Dinosaurs: The Encyclopedia. McFarland & Co, Jefferson, North Carolina 1997, ISBN 0-89950-917-7, Kentrosaurus, S. 516–519.
- ↑ a b Galton, P.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.
- ↑ a b 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
- ↑ a b Liddell, Henry George and Robert Scott: [[A Greek-English Lexicon]] (Abridged Edition). Oxford University Press, United Kingdom 1980, ISBN 0-19-910207-4.
- ↑ a b Hennig, E. (1916). "Zweite Mitteilung über den Stegosauriden vom Tendaguru" ("Second report on the stegosaurid of Tendaguru"). Sitzungsberichte der Gesellschaft Naturforschender Freunde zu Berlin 1916(6):175–182 German
- ↑ a b Nopcsa, F. (1915). "Die Dinosaurier der Siebenbürgischen Landesteile Ungarns." ("The dinosaurs of the Siebenbürgen part of the Hungarian Empire"). Mitteilungen aus dem Jahrbuche der Königlich Ungarischen Geologischen Reichsanstalt 23:1–26 German
- ↑ a b Hennig, E. (1916). "Kentrurosaurus, non Dorypphorosaurus. Centralblatt für Mineralogie, Geologie und Paläontologie, Stuttgart 1916:578. German
- ↑ a b Galton, P.M. (1982). "The postcranial anatomy of stegosaurian dinosaur Kentrosaurus from the Upper Jurassic of Tanzania, East Africa". Geologica et Palaeontologica 15:139-165
- ↑ a b Hennig, E. (1936). "Ein Dentale von Kentrurosaurus aethiopicus HENNIG" ("A dentary of Kentrurosaurus aethiopcius HENNIG"). Palaeontographica Supplement 7 Part II':311-312 German
- ↑ a b Weishampel DB: Interactions between Mesozoic Plants and Vertebrates: Fructifications and seed predation. In: Neues Jahrbuch für Geologie und Paläontologie, Abhandlungen. 167. Jahrgang, 1984, S. 224–250.
- ↑ a b c Mallison, H. (2010). "CAD assessment of the posture and range of motion of Kentrosaurus aethiopicus HENNIG 1915" Swiss Journal of Geosciences online first: [1]
- ↑ a b Mallison, H. (2011). "Defense capabilities of Kentrosaurus aethiopicus HENNIG 1915". Palaeontologia Electronica 14.2.10A(open access)
