Heterodontosaurus

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Heterodontosaurus
Living reconstruction and skull (from Sereno, 2012)

Living reconstruction and skull (from Sereno, 2012)

Temporal occurrence
Lower Jurassic ( Hettangian to Sinemurian )
201.3 to 190.8 million years
Locations
Systematics
Dinosaur (dinosauria)
Pelvic dinosaur (Ornithischia)
Heterodontosauridae
Heterodontosaurinae
Heterodontosaurus
Scientific name
Heterodontosaurus
Crompton & Charig , 1962
Art
  • Heterodontosaurus tucki
Skeleton reconstruction based on sample SAM-PK-K1332 (from Sereno, 2012)
Skull reconstruction (from Sereno, 2012)
A: Reconstruction of the forearm and hand, B: Reconstruction of the foot skeleton, C: Detailed view of the carpal bones

Heterodontosaurus ("lizard with different types of teeth") is a genus of the bird pelvic dinosaur (Ornithischia) and the eponymous representative of the Heterodontosauridae family . The genus lived during the Lower Jurassic ( Hettangian to Sinemurian , about 200 to 190 million years ago) in what is now South Africa . Fossil finds come from the Upper Elliot Formation and the Clarens Formation , whose deposits point to a desert-like climate during the lifetime of Heterodontosaurus . Heterodontosaurus wasscientifically described for the first timein 1962 by Alfred W. Crompton and Alan Charig with the only species H. tucki .

It was a small, two-legged herbivore or omnivore with an estimated length of 1 to 1.75 meters. It is named after the characteristic heterodontic dentition, which includes different types of teeth, including a pair of tusk-like "canine teeth" and chisel-shaped molars. Different types of teeth, while typical of mammals, are uncommon among reptiles. The lack of a continuous change of teeth, another very unusual feature for reptiles, led early studies to believe that the animals had a summer dormancy in which all teeth were changed at once. Further studies dealt with the question of whether the characteristic tusks of the teeth were present in both sexes or only in males ( sexual dimorphism ), whether the animals walked two-legged or four-legged, and whether they were herbivores or omnivores that did not spurn meat either .

features

Heterodontosaurus was a graceful, two-legged pelvic dinosaur from the group of the Heterodontosauridae . This group included some of the smallest bird pelvic dinosaurs known; for example, Fruitadens is estimated to be only 65 to 75 cm long. Heterodontosaurus is one of the largest heterodontosaurids: the body length is estimated at 1 to 1.75 meters, the weight was probably between 1.8 and 10 kilograms. Only Lycorhinus could have been bigger.

Skull and teeth

The skull is robustly built and appears triangular in side view. The snout ended in a toothless "beak" made of horn during his lifetime . The upper part of the "beak" sat on the premaxilla usually upstream bone, one of the main bone of the upper jaw (maxilla), while the lower beak the predentary sat up, the foremost lower jaw bone specifically the bird dinosaurs. The eye sockets are relatively large and roughly round, while the external nostrils are small. A large palpebral , a spur-like bone typical of pelvic dinosaurs, protrudes from the front into the eye socket. Below the eye socket, the zygomatic bone forms a horn-like extension directed to the side. Between the eye socket and the external nostril there is an extensive antorbital window , which, however, appears more like a hollow in the side wall of the skull and is therefore also called the antorbital fossa. This hollow houses two smaller openings, which, depending on the author, are called foramina or fenestrae. The lower edge of the antorbital pit is formed by a distinctive bone ridge, which is also the upper boundary of the lower part of the maxillary ( cheek recess ) that recedes inward (mediad) and carries the "molars" . The retreat of the tooth-bearing part of the maxillary is typical of bird's pelvis dinosaurs and is an indication that these animals, analogous to mammals, had cheek pouches and consequently relatively small mouth openings. Behind the eye opening lies the relatively large, almost egg-shaped, inclined lower temporal window. The elliptically shaped upper temporal window cannot be seen in side view. The upper temporal windows of both halves of the skull are separated from one another by a pronounced crest , which provided attachment surfaces for the jaw muscles.

The most distinctive feature is the strong differentiation of the dentition and the clearly different tooth types ( heterodontics ). While the front portion of the premaxilla is toothless and wore a horny beak, of the bone located in the rear portion of the three pin-shaped teeth, the third of which as greatly enlarged "Hauer" (English tusk is formed). The tusk is separated from the very narrow, chisel-shaped "molars" of the maxillary by a wide gap between the teeth ( diastema ). The pair of tusks of the lower jaw is significantly larger than the upper pair of tusks and, when the jaw was closed, reached into a recess in the area of ​​the tooth gap of the maxillary.

Postcranial skeleton

The neck was composed of nine cervical vertebrae and was curved in an S-shape, as indicated by the shape of the vertebral bodies in side view: the anterior vertebral bodies were shaped like a parallelogram , while those of the middle cervical vertebrae were rectangular and those of the rear cervical vertebrae trapezoidal . The trunk was relatively short and consisted of 12 vertebrae, to which 6 fused sacral vertebrae connected in the pelvic area. The proportionally long tail has not survived in full, but it probably consisted of 34 to 37 caudal vertebrae. The back spine was stiffened from the fourth vertebra by ossified tendons. This feature is found in many pelvic dinosaurs and presumably counteracted the bending forces that stressed the spine during the two-legged locomotion. In contrast to other bird pelvic dinosaurs, the tail of Heterodontosaurus showed no ossified tendons and was therefore presumably flexible.

The forelimbs were well built and relatively long, over 70% of the length of the hind limbs. The radius of the forearm measured 70% of the length of the humerus , while the relatively large hand was almost as long as the humerus. The hand ended in five easy-to-grasp fingers. The second finger was the longest of the hand, followed by the third and first finger (thumb). The fourth and fifth fingers, on the other hand, were severely receded and possibly functionless. The first three fingers ended in large and powerful claws. The phalangeal formula , which indicates the number of finger bones on each finger, was 2-3-4-3-2.

The hind limbs were long and graceful and ended in four toes, but only the second, third and fourth of which touched the ground. A feature unique to avian dinosaurs was the fusion of different leg and foot bones: the tibia and fibula were fused with the upper tarsal bones ( ankle and heel bone ) to form a tibiotarsus , while the lower tarsus was fused with the metatarsal bones to form a tarsometatarsus . This constellation is also found in today's birds and has developed independently of one another in these and Heterodontosaurus . The tibiotarsus was 30% longer than the femur.

Systematics

Cladogram of the Heterodontosauridae by Paul Sereno (2012). Representatives of the group are marked in red.

Heterodontosaurus is the eponymous and best known genus of the Heterodontosauridae , a group of very small, two-legged bird pelvic dinosaurs (Ornithischia). Most of the finds come from the Lower Jurassic South Africa; however, more recent finds show a much broader geographical and temporal distribution. Heterodontosaurids have now been identified from North America, South America, Europe and Asia; the group presumably existed from the Upper Triassic to the Lower Cretaceous for a period of approximately 100 million years. The systematic position of the group within the bird pelvic dinosaur remains controversial. Most studies suggest a relationship with the Ornithopoda ( Hadrosauridae and relatives) or the Marginocephalia ( horned and thick-headed dinosaurs ). Thus the Heterodontosauridae would be more derived than the Thyreophora ( stegosaurs and armored dinosaurs ). Some recent studies, however, place the group at the base of the bird dinosaur, so it would be more original than the Thyreophora.

Little is known about the relationship between Heterodontosaurus and other Heterodontosaurids, as most of the known representatives are only very fragmentary. For example, Feng-Lu Han and colleagues cannot resolve the internal systematics of the group in their phylogenetic analysis ; some other studies only achieve a resolution by removing some of the only fragmentary examples. Some analyzes consider Heterodontosaurus to be closely related to Lycorhinus, which also comes from South Africa . In addition, various analyzes come to the conclusion that Fruitadens and Tianyulong were more closely related to each other than to other genera. Paul Sereno (2012) summarizes the South African representatives ( Heterodontosaurus , Lycorhinus , Pegomastax , Abrictosaurus ) and the South American Manidens as Heterodontosaurinae , while he classifies the heterodontosaurids Echinodon , Fruitadens and Tianyulong from the northern land masses ( Laurasia ), outside of this group cannot resolve whether these genera themselves form a clade .

Discovery story

Locations with heterodontosaurid finds in southern Africa. Heterodontosaurus itself is known from the localities Tushielaw, Tyinindini and Voyizane.

The first Heterodontosaurus fossil was discovered by Robert Broom at the beginning of the 20th century , but only recently recognized as such. Broom sold the fossil along with numerous other South African fossils to the American Museum of Natural History in New York in 1913 , where it has since been archived together with the synapsid fossils in the Broom collection (copy number AMNH 24000). It wasn't until almost a century later that Paul Sereno became aware of the fossil while looking through the collection, most of which was still trapped in a boulder. The subsequent preparation revealed the skull fragment of a not yet adult Heterodontosaurus . Parts of several cervical vertebrae were also found behind the skull, which suggests that parts of the rest of the skeleton may have been preserved, but remained in the rock at the site. As Sereno indicates, the fossil likely came from the Clarens Formation . The find was first published in 2012.

In the early 1960s, a partial skeleton with an almost complete skull finally appeared in the Transkei immediately south of Lesotho . The find ( holotype , SAM-PK-K337) comes from the Clarens Formation and was made between 1961 and 1962 by Alfred W. Crompton during a joint paleontological expedition of the Iziko South African Museum and the British Museum ; the site is known today as the Tyinindini locality. The preparation of the skull carried out by Arthur E. Rixon turned out to be difficult because a thin but very hard coating of hematite required the use of a diamond saw; the skull was slightly damaged when sawing. As early as 1962, Crompton and Alan Charig published a preliminary description of the skull in the journal Nature , and named Heterodontosaurus tucki as a new species and genus. The name Heterodontosaurus ( Greek hetero - "different"; odous - "tooth"; sauros - "lizard") points to the heterodontic dentition, which is unusual for a pelvic dinosaur , while the name tucki honors GC Tuck, the manager of the South African branch of Austin Motor Company , which supported the expedition. In 2011, David Norman and colleagues published a more extensive description of the skull; however, the remaining skeleton was never described and seems to be lost today. The skull is now kept in the Iziko South African Museum in Cape Town.

Skeleton cast in the Iziko South African Museum

The same find area was examined by another joint expedition in the summer of 1966–1967; this time, alongside the Iziko South African Museum and the British Museum, Yale University and University College London were also involved. Five Heterodontosaurus specimens came to light from a single site in the Upper Elliot Formation, known as Voyizane , including the most complete find to date, an almost complete skeleton with a skull (SAM-PK-K1332). This skeleton was also discovered by Crompton and found embedded in red sandstones. The skull prepared by Ione Rudner at the Iziko South African Museum is better preserved than the holotype skull and was not covered with hematite like the latter. Numerous small cracks were repaired with glue, however, and the surfaces of bones and teeth were stabilized with a layer of glue, which sometimes obscures finer anatomical details. The remaining finds from Voyizane include the anterior section of the skull of a young animal (SAM-PK-K10487); two maxillary fragments (SAM-PK-K1326 and SAM-PK-K1334); as well as a fragmentary, skullless skeleton including parts of the spine, the pelvic girdle and the fore and hind extremities (SAM-PK-K1328).

A relatively large snout fragment (NM QR 1788) was discovered in 1975 on the Tushielaw farm, about 60 km east of Voyizane. This fossil was long ascribed to the prosauropod Massospondylus , until Porro and colleagues showed in 2011 that the specimen kept in the National Museum of South Africa was actually another Heterodontosaurus fossil.

Paleohabitat

Heterodontosaurus fossils come from the Upper Elliot Formation and the Clarens Formation above . This layer interval is also known as the Massospondylus range zone , named after the prosauropod dinosaur Massospondylus , which is the most common fossil in these layers. The Upper Elliot Formation, which contained the majority of the fossils, is made up of reddish, fluviatil (by rivers) to aeolian (by wind) deposited sandstones . The somewhat younger Clarens formation contained, among other things, the holotype specimen of Heterodontosaurus . The formation, built up by cream-colored sediments, was partly Aeolian and partly within a Lake Playa . The Clarens Formation is less fossil-rich than the Upper Elliot Formation; In addition, it prefers to form cliffs, which makes it difficult to access.

Heterodontosaurus presumably lived in a dry, desert-like climate. Three other heterodontosaurids are known from the Upper Elliot Formation - Abrictosaurus , Lycorhinus and Pegomastax - so this formation represents the largest known variety of this group worldwide. In the Clarens formation, Heterodontosaurus occurs together with the Heterodontosauriden Geranosaurus . In addition to heterodontosaurids, other dinosaurs (including Lesothosaurus , Megapnosaurus and Massospondylus ), temnospondyle amphibians, turtles, sphenodont animals , rauisuchians , crocodile relatives , and various cynodont animals (mammalian precursors) were found.

Paleobiology

ontogenesis

A: Stereoscopic photo of a juvenile skull (SAM-PK-K10487), B: Sketch

Little is known about the individual development history ( ontogenesis ) of Heterodontosaurus . The skull of a young animal described in 2006 (SAM-PK-K10487) allows for the first time insights into anatomical changes that took place in the development from young animal to adult: For example, the eye sockets become proportionally smaller with increasing age , while the section of the skull in front of the eye sockets becomes more elongated becomes. In addition, parts of the nasal bone and the intermaxillary bone fuse together . Since there are no changes in the dentition apart from the increase in the number of teeth in the upper jaw, it is believed that the diet of the animal did not change as it grew. The total length of the skull is reconstructed to 45 mm. If the young animal had shown the same body proportions as an adult animal, the body length would have been 45 cm - in fact, the animal was probably smaller, since skulls in young animals are generally proportionally larger than in adult animals ( child scheme ).

Sexual dimorphism

Reconstruction of Heterodontosaurus tucki in time lapse.

Richard Thulborn assumed in 1974 that the enlarged tusks of the heterodontosaurids were a secondary sexual characteristic ( sexual dimorphism ). Thus only male specimens would have had tusks, while tuseless specimens, such as the type specimen of Abrictosaurus , would have been females. Richard Butler and colleagues (2006) recently questioned the hypothesis: The skull they described, originating from a young animal, shows that tusks were already pronounced at an early stage of development - gender-specific differences were not to be expected at such an early stage. In addition, tusks are present in almost all known skulls; in the case of a real sexual dimorphism, however, a 50:50 ratio between tusk-bearing and tuskless specimens can be expected. The only exception is the type specimen of Abrictosaurus - the lack of tusks, however, presumably represents a specialization of this genus.

Summer rest and change of teeth

A: Reconstruction of the upper jaw (maxillary and premaxillary) viewed from below (ventral), B: Reconstruction of the lower jaw (dental and predentals) viewed from above (dorsal)
Posterior dentition of a juvenile skull (AMNH 24000). A: stereoscopic photo , B: sketch. Wearing areas resulting from tooth-to-tooth contact are shown in pink.

Thulborn (1974, 1978) coined the hypothesis that heterodontosaurids spent the dry and nutrient-poor season in a summer dormancy . The hypothesis was based on observations of the dentition of Heterodontosaurus : There is no evidence of a continuous change of teeth, as is typical for dinosaurs and other diapside reptiles . The molars were worn uniformly with no freshly erupted teeth. According to Thulborn, however, the presumably resilient plant food would have caused the teeth to wear out quickly, which makes it essential to change the teeth regularly. A change in the entire dentition could only have taken place in the phases of summer rest, when the animals did not eat. As a further argument for the summer rest hypothesis, Thulborn lists the wear facets of the teeth, which were caused by contact between the upper and lower teeth. In the contemporary Ornithischia Fabrosaurus , each tooth has an anterior and posterior wear facet, which is caused by the meshing of the upper and lower teeth. The jaw movement in Fabrosaurus was thus exclusively vertical. In the case of heterodontosaurids, however, the wear facets merged and form a path over the entire row of teeth. This indicates that the animals did not chop their food with vertical movements, but with forward-backward movements of the jaws. These back and forth movements are only possible if the teeth are uniform in terms of their degree of wear and their size; this requirement is not given with a continuous tooth change. This is an indication that the entire teeth were changed periodically as a unit during the summer rest.

A detailed analysis by James Hopson (1980) challenged Thulborn's ideas. Hopson showed that the pattern of the wear facets actually speaks for a vertical and lateral jaw movement, but not a fore-and-aft jaw movement. In addition, the degree of wear of the individual teeth would vary, which indicates a continuous change of teeth. However, x-rays showed that no teeth were actually newly formed in the jaws of the most complete Heterodontosaurus skeleton. Hopson concluded that young animals exhibited a continuous change of teeth, which however came to a standstill in adult animals. Hopson sums up that there is no evidence for Thulborn's summer rest hypothesis.

Butler and colleagues (2008) eventually performed computed tomography scans on a juvenile skull that, to the surprise of these researchers, did not show any teeth being formed. The researchers explain that there must have been a change of teeth in the animals' individual development: the teeth of the young animal's skull show the same morphology as those of adult animals - these features would not have been preserved if the tooth had simply grown continuously. The change of teeth in Heterodontosaurus was more sporadic than in related genera. Replacement teeth that had not yet erupted could only be detected in an upper jaw (SAM-PK-K1334) described by Norman and colleagues (2011) and in a juvenile skull (AMNH 24000) described by Paul Sereno (2012). As these findings show, the change of teeth was episodic and not continuous as in other heterodontosaurids. The replacement teeth showed the triangular crowns typical of the original ornithischia when viewed from the side. The broken molars got their characteristic chisel-like shape only through mutual wear of the upper and lower teeth.

Locomotion and metabolism

Although most studies depict heterodontosaurus as a two-legged ( bipedal ) runner, some authors have suggested partial or complete four-legged ( quadruped ) locomotion. Santa Luca (1980) described various features of the arm skeleton, which are also found in quadruped animals and indicate strong arm muscles: The olecranon of the ulna was relatively large, which increases the lever arm of the forearm. The large medial epicondyle of the humerus provided an attachment point for strong flexor muscles of the forearm, while appendages on the claws show that the hand was capable of strong forward thrust when walking. Heterodontosaurus would have moved four-legged when walking slowly, but would have switched to two-legged locomotion to run. Teresa Maryańska and Halszka Osmólska (1985) also suspected quadruple locomotion; as a further argument they listed the strongly downwardly curved spinal column in the most complete known specimen. Gregory Paul (1987), on the other hand, assumed that these animals basically moved quadruped - higher speeds were achieved by galloping. However, Paul does not give any anatomical features to support this hypothesis. David Weishampel and Lawrence Witmer (1990) as well as Norman and colleagues (2004) argued in favor of exclusively bipedal locomotion based on the shape of the claws and the anatomy of the shoulder girdle. The characteristics described by Santa Luca are adaptations for foraging - the powerful arms could have been used to dig up roots or to break up insect nests.

Most recent studies consider dinosaurs to be endothermic (warm-blooded) animals with a metabolism comparable to that of modern mammals and birds. Pontzer and colleagues (2009) calculated the aerobic endurance required for locomotion in various dinosaurs and were able to conclude from this that endothermia was found in most of the species examined. Even at moderate running speeds, Heterodontosaurus would have exceeded the maximum aerobic endurance that would be available to an ectothermic animal of the same size .

Nutrition and function of the tusks

Heterodontosaurus skull reconstruction . A: jaw closed, B: jaw moderately open

Much of the published studies consider Heterodontosaurus a herbivore . As Molnar (1977) noted, the tusks had no function in the feeding of the animals, but may have been used as a sex-specific characteristic in intra-species fights and for display. A similar function would be found in the elongated canines of today's muntjaks .

Various recent studies, however, raised the possibility that the tusks of Heterodontosaurus might actually have been used for the occasional ripping of prey. Paul Barrett (2000) shows that the cutting edges of the tusks have a fine serration, similar to that found in theropods (carnivorous dinosaurs). With muntjaks, however, there is no toothing. Another indication of an optional omnivorous diet is the shape of the two teeth in front of the upper tusk. Richard Butler and colleagues (2008) argue that the tusks are not a gender-specific characteristic and that they emerged early in the animals' development - thus it appears more likely that the tusks were used in an omnivorous diet or for defense than in intra-species competitive behavior. Researchers working with David Norman (2011) emphasize that the arms and hands were relatively long and equipped with large, curved claws, which made it possible to pack small prey. In contrast, the hind legs were long and made it possible to run quickly. As an omnivore, Heterodontosaurus would have had a clear selection advantage during dry seasons with little vegetation .

Paul Sereno (2012), on the other hand, lists various features of the skull and teeth that, according to this researcher, speak in favor of a pure or predominantly herbivorous diet in heterodontosaurids. These animals have a beak that can be cut off, specialized molars with a cutting function, and cheeks that are used for the oral processing of the food. The sphincter muscles of the jaw were enlarged, while the temporomandibular joint was lowered relative to the row of teeth, which increased the effectiveness of the jaw muscles in processing plant material. After all, the differences in the size and position of the tusks in different heterodontosaurids are too great for them to have a specific function in nutrition. Sereno suspects that heterodontosaurids can best be compared to today's umbilical pigs , which have similar tusks and feed on a variety of different plant materials, including roots, tubers, fruits and vegetation close to the ground.

supporting documents

literature

Individual evidence

  1. a b Sereno 2012 p. 85
  2. a b c Richard J. Butler, Peter M. Galton , Laura B. Porro, Luis M. Chiappe , Donald M. Henderson, Gregory M. Erickson: Lower limits of ornithischian dinosaur body size inferred from a new Upper Jurassic heterodontosaurid from North America. In: Proceedings of the Royal Society. Series B: Biological Sciences. Vol. 277, No. 1680, 2010, ISSN  0080-4649 , pp. 375-381, here pp. 375, 380, doi : 10.1098 / rspb.2009.1494 .
  3. a b c Weishampel and Witmer 1990, pp. 486-491
  4. a b Sereno 2012 p. 161
  5. ^ Frank Seebacher: A new method to calculate allometric length-mass relationships of dinosaurs. In: Journal of Vertebrate Paleontology. Vol. 21, No. 1, 2001, pp. 51-60, here p. 53, doi : 10.1671 / 0272-4634 (2001) 021 [0051: ANMTCA] 2.0.CO; 2 , digitized version (PDF; 141 kB) .
  6. a b Richard J. Butler, Laura B. Porro, Peter M. Galton, Luis M. Chiappe: Anatomy and Cranial Functional Morphology of the Small-Bodied Dinosaur Fruitadens haagarorum from the Upper Jurassic of the USA. In: PLoS ONE . Vol. 7, No. 4, 2012, p. E31556, doi : 10.1371 / journal.pone.0031556 .
  7. Christopher E. Gow: A tooth-bearing maxilla referable to Lycorhinus angustidens Haughton, 1924 (Dinosauria, Ornithischia). In: Annals of the South African Museum. Vol. 99, No. 10, 1990, pp. 367-380, here p. 379, digitized .
  8. a b c d e f Norman et al. 2011, pp. 194-195
  9. Norman et al. 2011, pp. 227-228
  10. a b c d e f g h i Weishampel and Witmer 1990, pp. 491–494
  11. Santa Luca 1980 pp. 163-166
  12. a b Santa Luca 1980 pp. 197-198
  13. a b c d e Sereno 2012 pp. 187–193
  14. Santa Luca 1980 p. 181
  15. Norman et al. 2004, p. 408
  16. Sereno 2012 p. 132
  17. Sereno 2012 p. 1
  18. a b c d e f Sereno 2012 pp. 193–204
  19. Feng-Lu Han, Paul M. Barrett , Richard J. Butler, Xing Xu : Postcranial anatomy of Jeholosaurus shangyuanensis (Dinosauria, Ornithischia) from the Lower Cretaceous Yixian Formation of China. In: Journal of Vertebrate Paleontology. Vol. 32, No. 6, 2012, pp. 1370-1395, here p. 1391, doi : 10.1080 / 02724634.2012.694385 .
  20. Richard J. Butler, David B. Norman, Alfred W. Crompton, Laura B. Porro, Alan J. Charig: The postcranial osteology and phylogenetic position of the small ornithischian dinosaur Changchunsaurus parvus from the Quantou Formation (Cretaceous: Aptian – Cenomanian) of Jilin Province, north ‐ eastern China. In: Palaeontology. Vol. 54, No. 3, 2011, pp. 667-683, doi : 10.1111 / j.1475-4983.2011.01046.x .
  21. Sereno 2012 p. 10
  22. a b c d Sereno 2012 pp. 14-17
  23. a b c Crompton and Charig 1962
  24. a b c d Norman et al. 2011, p. 189
  25. ^ Donald F. Glut : Dinosaurs. The Encyclopedia. McFarland & Company, Jefferson NC 1997, ISBN 0-89950-917-7 , pp. 467-469.
  26. a b Norman et al. 2011, p. 182
  27. ^ A b Fabien Knoll: The tetrapod fauna of the Upper Elliot and Clarens formations in the main Karoo Basin (South Africa and Lesotho). In: Bulletin de la Société Géologique de France. Vol. 176, No. 1, 2005, ISSN  0037-9409 , pp. 81-91, here pp. 81-85, doi : 10.2113 / 176.1.81 .
  28. Butler et al. 2008 p. 702
  29. a b Sereno 2012 pp. 10–11
  30. Michael R. Cooper: The prosauropod dinosaur Massospondylus carinatus Owen from Zimbabwe: its biology, mode of life and phylogenetic significance (= Occasional Papers of the National Museums and Monuments of Rhodesia. ) Series B: Natural Sciences. Vol. 6, No. 10, 1981, ZDB -ID 405377-1 , p. 812.
  31. a b c d e Butler et al. 2008 pp. 709-710
  32. Butler et al. 2008 p. 704
  33. a b Thulborn 1974
  34. ^ Thulborn 1978
  35. a b Hopson 1980
  36. a b Norman et al. 2011, pp. 220-221
  37. Sereno 2012 p. 163
  38. ^ Teresa Maryańska , Halszka Osmólska: On ornithischian phylogeny. In: Acta Palaeontologica Polonica. Vol. 30, No. 3/4, 1985, ISSN 0567-7920 , pp. 137-150, here p. 147, online .  
  39. ^ Gregory S. Paul : The Science and Art of Restoring the Life Appearance of Dinosaurs and Their Relatives; a Rigorous How-to Guide. In: Sylvia J. Czerkas, Everett C. Olson (Eds.): Dinosaurs, Past and Present. Volume 2. University of Washington Press et al., Seattle WA et al. 1987, ISBN 0-295-96570-3 , p. 33.
  40. a b Weishampel and Witmer 1990, p. 497
  41. Norman et al. 2004, p. 412
  42. Herman Pontzer, Vivian Allen, John R. Hutchinson: Biomechanics of Running Indicates Endothermy in Bipedal Dinosaurs. In: PLoS ONE. Vol. 4, No. 11, 2009, e7783, doi : 10.1371 / journal.pone.0007783 .
  43. a b Paul M. Barrett: Prosauropod dinosaurs and iguanas: speculations on the diets of extinct reptiles. In: Hans-Dieter Sues: Evolution of herbivory in terrestrial vertebrates. Perspectives from the fossil record. Cambridge University Press, Cambridge et al. 2000, ISBN 0-521-59449-9 , pp. 42-78, here p. 64, doi : 10.1017 / CBO9780511549717.004 .
  44. a b Norman et al. 2011, p. 231

Web links

Commons : Heterodontosaurus  - collection of images, videos and audio files
This article was added to the list of excellent articles on October 23, 2013 in this version .