Post by creature386 on Aug 11, 2013 0:22:12 GMT 5
Heterodontosaurus tucki
Temporal range: Lower Jurassic, Hettangian-Sinemurian[1]
Location: South Africa, Cape Province, Upper Elliot Formation and Clarens Formation[1]
Sciencifitic classification:
Dinosauria
Ornithischia
Heterodontosauridae
Heterodontosaurinae
Heterodontosaurus
H. tucki[2]
Size:
Silhouette skeletal showing the preserved bones of specimen SAM-PK-K1332.[3]
Heterodontosaurus was a small, heterodontosaurid dinosaur. It was over 1 m long,[4] weighing 1,8 kg,[5] making it one of the largest heterodontosaurids.[6] The specimen SAM-PK-K1332 (which is roughly 1 m long) has a skull length of 95 mm, making it larger than the holotype (skull length of 88 mm). SAM-PK-K1332 shows that Heterodontosaurus likely had a skull:body ratio of 1:10.[7]
Specimen and early finds:
Heterodontosaurus is known from the holotype SAM-PK-K337 (skull and partial skeleton) and seven referred specimen, of which SAM-PK-K1332 is the best preserved. Most specimen are known from Voisana.[8]
Early heterodontosaurid discoveries. C is the skull of AMNH.[9]
AMNH 24000 was the first discovered specimen, but it isn't the holotype, as it wasn't identified as a specimen of H. tucki, until recently. In 1913, the specimen was sold to the American Museum of Natural History by Broom, as part of the Broom Collection. The specimen shows many diagnostic characters and it is a subadult (it's skull is roughly half as long as the one of SAM-PK-K1332)
SAM-PK-K337 was the first specimen described as H. tucki. The specimen got described by Crompton and Charig in 1962[11] It was found in the Clarens Formation during a joint expedition between the South African and Brithish Museum in 1961-62.[12] The specimen is known from parts of the skeleton and an almost complete (although damaged during preparation) skull.[13] The skull shows many characteristic features of Heterodontosaurus, like the heterodont dentition and the canines.[11]
Description:
The vertebral column of Heterodontosaurus is virtually complete. Only very small parts (like the anterior part of the centrum of the C9) and tail vertebrae are missing. The cervical vertebrae can be divided into two groups.[14] The first group consists of the ones with long centra, long neurocentral junctions and widely separated pre/post zygapophyses (C2-5). The second group consists of the ones with short centra, narrow neurocentral junctions and closely juxtaposed pre/post zygapophyses (C6-9).[15] However, the height of the centra of the position of the parapophysis doesn't show a variation.[16]
The first three dorsals are in some way an intermediate stage between posterior cervicals and other dorsal vertebrae. For example they have a small ventral keel, while other dorsal vertebrae lack something like that.[17] The vertebrae D4-10 can be considered as more typical vertebrae, for example they lack the vertical ridges, which can be seen in the posterior cervicals.[18]
The humerus of Heterodontosaurus has a well developed proximal head, lying in the middle of the superior surface. The head is wider than the shaft it is connected with. The shaft is subcircular in cross section, at some part.[19] The humerus is also more robust than the one of Fabrosaurus (another small ornithopod), probably because Heterodontosaurus had different forelimb capabilities. In one feature the humerus differs from all other ornithishians, it lacks a depression between the radial and ulnar condyles, what limits the elbow extension. Therefore, Heterodontosaurus may had a semi-sprawling posture while walking quadrupedal.[20] The manus of Heterodontosaurus is very large, it's longer than the radius or the ulna[21] and could have been used for grasping.[22]
Heterodontosaurus manus.[21]
It also has at least seven slips of attachment, not a reduced number as seen in extant reptiles. A hyperextension of the proximal phalanges can be seen in metacarpal heads of the first three digits. Heterodontosaurus probably needed that extension for supporting it's weight when standing quadrupedal, what would support the idea of Heterodontosaurus being capable of quadruped locomotion.[23] However, due to it's elegant hind limbs adapted to bipedal locomotion, it was likely both, bipedal and quadrupedal.[24] The digits 4 and 5 are reduced and therefore likely functionless.[25] Overall, the forelimb of Heterodontosaurus is most similar to that of Iguanodon.[20]
Like most bones, the femora of Heterodontosaurus are complete, but they are damaged. The femur of Heterodontosaurus differs from that of ornithopods, because the trochanter is not separated from the femoral shaft by a cleft. Instead, there's a joint.[26] Because of that, the femur of Heterodontosaurus is not very similar to the one of ornithopods, it is actually more similar to that of theropods, although it shares some fetters with the femora of some ankylosaurs, some stegosaurs and Triceratops. The ischium too has little similarities with ornithopods.[27] Due to the pelvic structure, it is believed that Heterodontosaurus the femur could create a stance similar to that of birds.[24]
Skull of Heterodontosaurus.[28]
The dentition was quite unusual when compared to other dinosaurs, for example it had well developed canine teeth.[11]
The skull (especially the lower jaw) of Heterodontosaurus was relatively robust and compact. The skull was also surprisingly specialized, in comparison to that of other Lower Jurassic dinosaurs. Sutural structures form a symphysis near the Lower Jaw canine tooth.[29] There are no teeth anteriorly to that symphysis.[30] However, in the anterior part of the Upper Jaw, there are three canine tooth shaped teeth, which have a broad crown.[11] Apart from the mentioned tooth types, there are cheek teeth, showing heavy wear facets.[31]
Jaws of Heterodontosaurus. Pink tone=wear facets.[31]
The palate is narrow and deeply domed. There are connected structures at the sidewall of the braincase and the cranium is hollow, as seen in saurischians and basal archosaurs. In 2011, the Cranium musculature was reconstructed and it was reconstructed similarly to that of diapsids.[28]
Paleoecology
It was discussed wether lost teeth could be replaced[11], but this is unlikely, as replacement teeth are absent.[32] Instead heterodontosaurid dinosaurs may have had rest periods, where the whole dentition could regenerate. Although juveniles may have been capable of replacing their teeth.[33]
Regarding ontogenic changes, the almost complete skull SAM-PK-K10487 reveals evidence on the antigenic changes during maturity of this species. The reconstructed skull is 45 mm long. Using the proportions of SAM-PK-K1332, the TL of the specimen can be estimated at 45 cm, but this may be an overestimate, as juveniles tend to have proportionally larger heads.[7] The skull shows that juveniles have proportionally larger orbita and shorter preorbita. Also, there are unfused nasal and premaxilla bones. Because there are no differences in the dentition (except for the fact that adults have more teeth), it is suggested that the diet doesn't change while growing.[33]
Regarding the diet, Sereno views Heterodontosaurus as a herbivorous or at least mainly herbivorous species.[34] The wear facets show estimated edges in the food.[31]
It was discussed wether there is sexual dimorphism in heterodontosaurids. It was believed that tusks are a feature of males, because some adult, heterodontosaurid specimen lack tusks, like the Abrictosaurus holotype (BMNH RUB54). However, the vast majority of heterodontosaurid specimen has tusks, even juveniles. There is no even ratio between tusk less specimen and tusked specimen, as we would suspect it in sexual dimorphism. The Abrictosaurus holotype also can be seen in many ways as an exception.[33][35]
Regarding metabolism, there was a paper studying metabolism in Heterodontosaurus and eleven other dinosaurs. They all were suspected to be endotherm:
A phylogenic tree, showing endotherm and ectotherm genera in Archosauria[36]
This bases on an estimated aerobic capacity, which exceeds the one of ectotherm animal. It is believed that dinosaurs like Heterodontosaurus were active, but only reached moderate running speeds.[36] It could have been cursorial though, due to the elongated tibia and metatarsus.[22]
Phylogenetic position:
Phylogenetic tree.[38]
Heterodontosaurus is the type species of heterodontosauridae, which appeared in the Lower Jurassic and went extinct in the Lower Cretaceous. The fact that they were abundant in the Lower Jurassic supports the idea of a dinosaurian radiation during that time.[34]
Paul C. Sereno described a new subfamily within that family called "heterodontosaurinae". Diagnostic characters include cheek teeth, with a crown taller than wide and a low manidabular jaw joint.[39] His cladogram shows Heterodontosaurus as a sister taxon of Abrictosaurus.[38]
Literature:
Paul C. Sereno: Taxonomy, morphology, masticatory function and phylogeny of heterodontosaurid dinosaurs. In: ZooKeys. 226, 2012, p. 1–225, doi:10.3897/zookeys.226.2840
Santa Luca, A. P. 1980. The postcranial skeleton of Heterodontosaurus tucki (Reptilia, Ornithischia) from the Stormberg of South Africa. In: Annals of the South African Museum 79: p. 159–211. PDF
Frank Seebacher: A new method to calculate allometric length-mass relationships of dinosaurs. In: Journal of Vertebrate Paleontology. 21, Nr. 1, 2001, p. 51–60, doi:10.1671/0272-4634(2001)021[0051:ANMTCA]2.0.CO;2
Richard J. Butler, Laura B. Porro and David B. Norman: A Juvenile Skull of the Primitive Ornithischian Dinosaur Heterodontosaurus tucki from the 'Stormberg' of Southern Africa. In: Journal of Vertebrate Paleontology. 28, Nr. 2, the Society of Vertebrate Paleontology, 2008, p. 702-711. PDF
Richard J Butler, Jin Liyong, Chen Jun, Pascal Godefroit: The Lower Jurassic ornithischian dinosaur Heterodontosaurus tucki Crompton & Charig, 1962: cranial anatomy, functional morphology, taxonomy, and relationships. In: Palaeontology. 54, Nr. 1, 20. Mai 2011, p. 182-276 doi:10.1111/j.1096-3642.2011.00697.x
Pontzer H, Allen V, Hutchinson JR: Biomechanics of Running Indicates Endothermy in Bipedal Dinosaurs. In: PLoS ONE. 4, Nr. 11, e7783, 2009, S. 1-9, doi:10.1371/journal.pone.0007783
Footnotes:
[1] Sereno 2012 p. 85
[2] Sereno 2012 p. 201
[3] Sereno 2012 p. 126
[4] Santa Luca 1980 p. 159
[5] Seebacher 2001 p. 53
[6] Sereno 2012 p. 161
[7] Bulter et al. 2010 p. 704
[8] Sereno 2012 p. 6
[9] Sereno 2012 p. 8
[10] Sereno 2012 p. 10
[11] Bulter et al. 2010 p. 702
[12] Sereno 2012 p. 14
[13] Sereno 2012 p. 15
[14] Santa Luca 1980 p. 163
[15] Santa Luca 1980 p. 164
[16] Santa Luca 1980 p. 165
[17] Santa Luca 1980 p. 166
[18] Santa Luca 1980 p. 167
[19] Santa Luca 1980 p. 174
[20] Santa Luca 1980 p. 183
[21] Santa Luca 1980 p. 176
[22] Santa Luca 1980 p. 204
[23] Santa Luca 1980 p. 180
[24] Santa Luca 1980 p. 203
[25] Santa Luca 1980 p. 181
[26] Santa Luca 1980 p. 189
[27] Santa Luca 1980 p. 196
[28] Sereno 2012 p. 181
[29] Bulter et al. 2010 p. 182
[30] Sereno 2012 p. 105
[31] Sereno 2012 p. 114
[32] Bulter et al. 2010 p. 708
[33] Bulter et al. 2010 p. 709
[34] Sereno 2012 p. 1
[35] Bulter et al. 2010 p. 710
[36] Pontzer et al. 2009, S. 5
[37] Pontzer et al. 2009, S. 2
[38] Sereno 2012 p. 201
[39] Sereno 2012 p. 68
All images in this post are under a CC license!
Temporal range: Lower Jurassic, Hettangian-Sinemurian[1]
Location: South Africa, Cape Province, Upper Elliot Formation and Clarens Formation[1]
Sciencifitic classification:
Dinosauria
Ornithischia
Heterodontosauridae
Heterodontosaurinae
Heterodontosaurus
H. tucki[2]
Size:
Silhouette skeletal showing the preserved bones of specimen SAM-PK-K1332.[3]
Heterodontosaurus was a small, heterodontosaurid dinosaur. It was over 1 m long,[4] weighing 1,8 kg,[5] making it one of the largest heterodontosaurids.[6] The specimen SAM-PK-K1332 (which is roughly 1 m long) has a skull length of 95 mm, making it larger than the holotype (skull length of 88 mm). SAM-PK-K1332 shows that Heterodontosaurus likely had a skull:body ratio of 1:10.[7]
Specimen and early finds:
Heterodontosaurus is known from the holotype SAM-PK-K337 (skull and partial skeleton) and seven referred specimen, of which SAM-PK-K1332 is the best preserved. Most specimen are known from Voisana.[8]
Early heterodontosaurid discoveries. C is the skull of AMNH.[9]
AMNH 24000 was the first discovered specimen, but it isn't the holotype, as it wasn't identified as a specimen of H. tucki, until recently. In 1913, the specimen was sold to the American Museum of Natural History by Broom, as part of the Broom Collection. The specimen shows many diagnostic characters and it is a subadult (it's skull is roughly half as long as the one of SAM-PK-K1332)
SAM-PK-K337 was the first specimen described as H. tucki. The specimen got described by Crompton and Charig in 1962[11] It was found in the Clarens Formation during a joint expedition between the South African and Brithish Museum in 1961-62.[12] The specimen is known from parts of the skeleton and an almost complete (although damaged during preparation) skull.[13] The skull shows many characteristic features of Heterodontosaurus, like the heterodont dentition and the canines.[11]
Description:
The vertebral column of Heterodontosaurus is virtually complete. Only very small parts (like the anterior part of the centrum of the C9) and tail vertebrae are missing. The cervical vertebrae can be divided into two groups.[14] The first group consists of the ones with long centra, long neurocentral junctions and widely separated pre/post zygapophyses (C2-5). The second group consists of the ones with short centra, narrow neurocentral junctions and closely juxtaposed pre/post zygapophyses (C6-9).[15] However, the height of the centra of the position of the parapophysis doesn't show a variation.[16]
The first three dorsals are in some way an intermediate stage between posterior cervicals and other dorsal vertebrae. For example they have a small ventral keel, while other dorsal vertebrae lack something like that.[17] The vertebrae D4-10 can be considered as more typical vertebrae, for example they lack the vertical ridges, which can be seen in the posterior cervicals.[18]
The humerus of Heterodontosaurus has a well developed proximal head, lying in the middle of the superior surface. The head is wider than the shaft it is connected with. The shaft is subcircular in cross section, at some part.[19] The humerus is also more robust than the one of Fabrosaurus (another small ornithopod), probably because Heterodontosaurus had different forelimb capabilities. In one feature the humerus differs from all other ornithishians, it lacks a depression between the radial and ulnar condyles, what limits the elbow extension. Therefore, Heterodontosaurus may had a semi-sprawling posture while walking quadrupedal.[20] The manus of Heterodontosaurus is very large, it's longer than the radius or the ulna[21] and could have been used for grasping.[22]
Heterodontosaurus manus.[21]
It also has at least seven slips of attachment, not a reduced number as seen in extant reptiles. A hyperextension of the proximal phalanges can be seen in metacarpal heads of the first three digits. Heterodontosaurus probably needed that extension for supporting it's weight when standing quadrupedal, what would support the idea of Heterodontosaurus being capable of quadruped locomotion.[23] However, due to it's elegant hind limbs adapted to bipedal locomotion, it was likely both, bipedal and quadrupedal.[24] The digits 4 and 5 are reduced and therefore likely functionless.[25] Overall, the forelimb of Heterodontosaurus is most similar to that of Iguanodon.[20]
Like most bones, the femora of Heterodontosaurus are complete, but they are damaged. The femur of Heterodontosaurus differs from that of ornithopods, because the trochanter is not separated from the femoral shaft by a cleft. Instead, there's a joint.[26] Because of that, the femur of Heterodontosaurus is not very similar to the one of ornithopods, it is actually more similar to that of theropods, although it shares some fetters with the femora of some ankylosaurs, some stegosaurs and Triceratops. The ischium too has little similarities with ornithopods.[27] Due to the pelvic structure, it is believed that Heterodontosaurus the femur could create a stance similar to that of birds.[24]
Skull of Heterodontosaurus.[28]
The dentition was quite unusual when compared to other dinosaurs, for example it had well developed canine teeth.[11]
The skull (especially the lower jaw) of Heterodontosaurus was relatively robust and compact. The skull was also surprisingly specialized, in comparison to that of other Lower Jurassic dinosaurs. Sutural structures form a symphysis near the Lower Jaw canine tooth.[29] There are no teeth anteriorly to that symphysis.[30] However, in the anterior part of the Upper Jaw, there are three canine tooth shaped teeth, which have a broad crown.[11] Apart from the mentioned tooth types, there are cheek teeth, showing heavy wear facets.[31]
Jaws of Heterodontosaurus. Pink tone=wear facets.[31]
The palate is narrow and deeply domed. There are connected structures at the sidewall of the braincase and the cranium is hollow, as seen in saurischians and basal archosaurs. In 2011, the Cranium musculature was reconstructed and it was reconstructed similarly to that of diapsids.[28]
Paleoecology
It was discussed wether lost teeth could be replaced[11], but this is unlikely, as replacement teeth are absent.[32] Instead heterodontosaurid dinosaurs may have had rest periods, where the whole dentition could regenerate. Although juveniles may have been capable of replacing their teeth.[33]
Regarding ontogenic changes, the almost complete skull SAM-PK-K10487 reveals evidence on the antigenic changes during maturity of this species. The reconstructed skull is 45 mm long. Using the proportions of SAM-PK-K1332, the TL of the specimen can be estimated at 45 cm, but this may be an overestimate, as juveniles tend to have proportionally larger heads.[7] The skull shows that juveniles have proportionally larger orbita and shorter preorbita. Also, there are unfused nasal and premaxilla bones. Because there are no differences in the dentition (except for the fact that adults have more teeth), it is suggested that the diet doesn't change while growing.[33]
Regarding the diet, Sereno views Heterodontosaurus as a herbivorous or at least mainly herbivorous species.[34] The wear facets show estimated edges in the food.[31]
It was discussed wether there is sexual dimorphism in heterodontosaurids. It was believed that tusks are a feature of males, because some adult, heterodontosaurid specimen lack tusks, like the Abrictosaurus holotype (BMNH RUB54). However, the vast majority of heterodontosaurid specimen has tusks, even juveniles. There is no even ratio between tusk less specimen and tusked specimen, as we would suspect it in sexual dimorphism. The Abrictosaurus holotype also can be seen in many ways as an exception.[33][35]
Regarding metabolism, there was a paper studying metabolism in Heterodontosaurus and eleven other dinosaurs. They all were suspected to be endotherm:
A phylogenic tree, showing endotherm and ectotherm genera in Archosauria[36]
This bases on an estimated aerobic capacity, which exceeds the one of ectotherm animal. It is believed that dinosaurs like Heterodontosaurus were active, but only reached moderate running speeds.[36] It could have been cursorial though, due to the elongated tibia and metatarsus.[22]
Phylogenetic position:
Phylogenetic tree.[38]
Heterodontosaurus is the type species of heterodontosauridae, which appeared in the Lower Jurassic and went extinct in the Lower Cretaceous. The fact that they were abundant in the Lower Jurassic supports the idea of a dinosaurian radiation during that time.[34]
Paul C. Sereno described a new subfamily within that family called "heterodontosaurinae". Diagnostic characters include cheek teeth, with a crown taller than wide and a low manidabular jaw joint.[39] His cladogram shows Heterodontosaurus as a sister taxon of Abrictosaurus.[38]
Literature:
Paul C. Sereno: Taxonomy, morphology, masticatory function and phylogeny of heterodontosaurid dinosaurs. In: ZooKeys. 226, 2012, p. 1–225, doi:10.3897/zookeys.226.2840
Santa Luca, A. P. 1980. The postcranial skeleton of Heterodontosaurus tucki (Reptilia, Ornithischia) from the Stormberg of South Africa. In: Annals of the South African Museum 79: p. 159–211. PDF
Frank Seebacher: A new method to calculate allometric length-mass relationships of dinosaurs. In: Journal of Vertebrate Paleontology. 21, Nr. 1, 2001, p. 51–60, doi:10.1671/0272-4634(2001)021[0051:ANMTCA]2.0.CO;2
Richard J. Butler, Laura B. Porro and David B. Norman: A Juvenile Skull of the Primitive Ornithischian Dinosaur Heterodontosaurus tucki from the 'Stormberg' of Southern Africa. In: Journal of Vertebrate Paleontology. 28, Nr. 2, the Society of Vertebrate Paleontology, 2008, p. 702-711. PDF
Richard J Butler, Jin Liyong, Chen Jun, Pascal Godefroit: The Lower Jurassic ornithischian dinosaur Heterodontosaurus tucki Crompton & Charig, 1962: cranial anatomy, functional morphology, taxonomy, and relationships. In: Palaeontology. 54, Nr. 1, 20. Mai 2011, p. 182-276 doi:10.1111/j.1096-3642.2011.00697.x
Pontzer H, Allen V, Hutchinson JR: Biomechanics of Running Indicates Endothermy in Bipedal Dinosaurs. In: PLoS ONE. 4, Nr. 11, e7783, 2009, S. 1-9, doi:10.1371/journal.pone.0007783
Footnotes:
[1] Sereno 2012 p. 85
[2] Sereno 2012 p. 201
[3] Sereno 2012 p. 126
[4] Santa Luca 1980 p. 159
[5] Seebacher 2001 p. 53
[6] Sereno 2012 p. 161
[7] Bulter et al. 2010 p. 704
[8] Sereno 2012 p. 6
[9] Sereno 2012 p. 8
[10] Sereno 2012 p. 10
[11] Bulter et al. 2010 p. 702
[12] Sereno 2012 p. 14
[13] Sereno 2012 p. 15
[14] Santa Luca 1980 p. 163
[15] Santa Luca 1980 p. 164
[16] Santa Luca 1980 p. 165
[17] Santa Luca 1980 p. 166
[18] Santa Luca 1980 p. 167
[19] Santa Luca 1980 p. 174
[20] Santa Luca 1980 p. 183
[21] Santa Luca 1980 p. 176
[22] Santa Luca 1980 p. 204
[23] Santa Luca 1980 p. 180
[24] Santa Luca 1980 p. 203
[25] Santa Luca 1980 p. 181
[26] Santa Luca 1980 p. 189
[27] Santa Luca 1980 p. 196
[28] Sereno 2012 p. 181
[29] Bulter et al. 2010 p. 182
[30] Sereno 2012 p. 105
[31] Sereno 2012 p. 114
[32] Bulter et al. 2010 p. 708
[33] Bulter et al. 2010 p. 709
[34] Sereno 2012 p. 1
[35] Bulter et al. 2010 p. 710
[36] Pontzer et al. 2009, S. 5
[37] Pontzer et al. 2009, S. 2
[38] Sereno 2012 p. 201
[39] Sereno 2012 p. 68
All images in this post are under a CC license!