My very good friend and colleague Sterling Nesbitt has a new website detailing his work (mainly on Triassic archosauromorphs). Please go check it out and then totally harass him for PDFs of all of his papers.
Much of the renniassance in Triassic archosauromorph taxonomy and phylogeny is in a large part due to Sterling's work over the last decade. His forthcoming, in press, absolutely monstrous (over 500 manuscript pages) monograph on archosauromorph phylogeny (from his doctoral dissertation) promises to be the most comprehensive work ever done on this group (over 50 taxa and 400 characters, almost all scored through first hand observation of the actual specimens) and will be a foundation study for years to come.
The Future Direction of Late Triassic Terrestrial Ecosystem Research
Here is an excellent synthesis by Randall Irmis and Jessica Whiteside of ongoing and future research in the Late Triassic, particularly in North America. These are topics of great interest to me and Jeff Martz right now and we have a paper in press that will delve into our side of this research. We are also working closely with colleagues such as Randy and Jessica on some aspects of this work and I am proud that Petrified Forest National Park is one of the settings for this exciting research.
It is a Spotlight article so there is no abstract. You can e-mail Randall Irmis for a PDF.
This excerpt makes a key point that I have been a strong proponent for:
"The key for understanding Late Triassic terrestrial ecosystems is that all of these new studies focus on stratigraphic sections where multiple different research approaches can be applied to maximize the data recovered from the same area."
Instead of various researchers working haphazardly, conducting different studies on different outcrops, coordinating this research instead with everyone working in the same areas under the same detailed stratigraphic foundation allows for a final amalgamation of data leading to stronger supported interpretations for all parties involved. This is exactly what has been going on at the Petrified Forest over the last few years and the story coming out of the rocks and fossils is just amazing.
Irmis, R. B., and J. H. Whiteside. 2010. Newly integrated approaches to studying Late Triassic terrestrial ecosystems. Palaios 25:689-691. DOI: 10.2110/palo.2010.S06
It is a Spotlight article so there is no abstract. You can e-mail Randall Irmis for a PDF.
This excerpt makes a key point that I have been a strong proponent for:
"The key for understanding Late Triassic terrestrial ecosystems is that all of these new studies focus on stratigraphic sections where multiple different research approaches can be applied to maximize the data recovered from the same area."
Instead of various researchers working haphazardly, conducting different studies on different outcrops, coordinating this research instead with everyone working in the same areas under the same detailed stratigraphic foundation allows for a final amalgamation of data leading to stronger supported interpretations for all parties involved. This is exactly what has been going on at the Petrified Forest over the last few years and the story coming out of the rocks and fossils is just amazing.
Irmis, R. B., and J. H. Whiteside. 2010. Newly integrated approaches to studying Late Triassic terrestrial ecosystems. Palaios 25:689-691. DOI: 10.2110/palo.2010.S06
Sanjuansaurus gordilloi a new Herrerasaurid from Argentina
Here is a new herrerasaurid from the the Ischigualasto Formation of Argentina. Looks much more similar to Herrerasaurus than to Staurikosaurus or Chindesaurus, although the latter taxon was not included in the phylogenetic analysis. This analysis finds Herrerasauridae to be the sister taxon to Eoraptor + (Guaibasaurus + Neotheropoda), so we are back to the position of herrerasaurids still being dinosaurs but as basal saurischians rather than theropods. Comparison is provided in the text to Tawa hallae, but it is not included in the phylogenetic analysis. Too bad. However, I'm pretty certain that based on the current material coding Sanjuansaurus into the analysis of Nesbitt et al. (2009) would not change the position of herrerasaurids as basal theropods as recovered in that analysis. So whether or not herrerasaurids are theropods or not appears to be entirely dependent on the base matrix one uses. Thus, unfortunately, the analysis in this paper does not appear to offer anything particularly game-changing or significant in that regards. Also unfortunate is that there is no discussion of these differing hypotheses in the paper.
The further recognition of the increased diversity of basal saurischian dinosaurs in the latest Carnian is interesting and provides more circumstantial support for the earlier diversification of Archosauria in the Early Triassic as hypothesized by Nesbitt (2009) based on body fossils and more recently by Brusatte et al. (2010) based on footprint evidence.
Alcober O.A., and R. N. Martinez. 2010. A new herrerasaurid (Dinosauria, Saurischia) from the Upper Triassic Ischigualasto Formation of northwestern Argentina. ZooKeys 63 : 55 – 81 . doi: 10.3897/zookeys.63.550
Abstract - Herrerasauridae comprises a basal clade of dinosaurs best known from the Upper Triassic of Argentina and Brazil, which have yielded remains of Herrerasaurus ischigualastensis and Staurikosaurus pricei, respectively. Systematic opinion regarding the position of Herrerasauridae at the base of Dinosauria has varied. Here we describe a new herrerasaurid, Sanjuansaurus gordilloi gen. n., sp. n., based on a partial skeleton from Carnian-age strata of the the Upper Triassic Ischigualasto Formation of northwestern Argentina. The new taxon is diagnosed by numerous features, including long, band-shaped and posterolaterally oriented transverse process on the posterior cervical vertebrae; neural spines of the sixth to eighth dorsal vertebrae, at least, bearing acute anterior and posterior processes; scapula and coracoid with everted lateral margins of the glenoid; and short pubis (63% of the femoral length). Phylogenetic analysis placed Sanjuansaurus within a monophyletic Herrerasauridae, at the base of Theropoda and including Herrerasaurus and Staurikosaurus. The presence of Sanjuansaurus at the base of the Ischigualasto Formation, along with other dinosaurs such as Herrerasaurus, Eoraptor, Panphagia, and Chromogisaurus suggests that saurischian dinosaurs in southwestern Pangea were already widely diversified by the late Carnian rather than increasing in diversity across the Carnian-Norian boundary.
REFERENCES
Brusatte, S. L., Niedźwiedzki, G., and R. J. Butler. 2010. Footprints pull origin and diversification of dinosaur stem lineage deep into Early Triassic. Proceedings of the Royal Society B. doi: 10.1098/rspb.2010.1746
Nesbitt, S. J. 2009. The antiquity of Archosauria and the origin of Late Triassic archosaur assemblages. Journal of Vertebrate Paleontology 29:155A.
Nesbitt, S. J., Smith, N. D., Irmis, R. B.,Turner, A. H., Downs, A., and M. A. Norell. 2009. A Complete skeleton of a Late Triassic saurischian and the early evolution of dinosaurs. Science 326: 1530–1533.
The further recognition of the increased diversity of basal saurischian dinosaurs in the latest Carnian is interesting and provides more circumstantial support for the earlier diversification of Archosauria in the Early Triassic as hypothesized by Nesbitt (2009) based on body fossils and more recently by Brusatte et al. (2010) based on footprint evidence.
Alcober O.A., and R. N. Martinez. 2010. A new herrerasaurid (Dinosauria, Saurischia) from the Upper Triassic Ischigualasto Formation of northwestern Argentina. ZooKeys 63 : 55 – 81 . doi: 10.3897/zookeys.63.550
Abstract - Herrerasauridae comprises a basal clade of dinosaurs best known from the Upper Triassic of Argentina and Brazil, which have yielded remains of Herrerasaurus ischigualastensis and Staurikosaurus pricei, respectively. Systematic opinion regarding the position of Herrerasauridae at the base of Dinosauria has varied. Here we describe a new herrerasaurid, Sanjuansaurus gordilloi gen. n., sp. n., based on a partial skeleton from Carnian-age strata of the the Upper Triassic Ischigualasto Formation of northwestern Argentina. The new taxon is diagnosed by numerous features, including long, band-shaped and posterolaterally oriented transverse process on the posterior cervical vertebrae; neural spines of the sixth to eighth dorsal vertebrae, at least, bearing acute anterior and posterior processes; scapula and coracoid with everted lateral margins of the glenoid; and short pubis (63% of the femoral length). Phylogenetic analysis placed Sanjuansaurus within a monophyletic Herrerasauridae, at the base of Theropoda and including Herrerasaurus and Staurikosaurus. The presence of Sanjuansaurus at the base of the Ischigualasto Formation, along with other dinosaurs such as Herrerasaurus, Eoraptor, Panphagia, and Chromogisaurus suggests that saurischian dinosaurs in southwestern Pangea were already widely diversified by the late Carnian rather than increasing in diversity across the Carnian-Norian boundary.
 |
| Holotype specimen of Sanjuansaurus gordilloi (PVSJ 605) |
Brusatte, S. L., Niedźwiedzki, G., and R. J. Butler. 2010. Footprints pull origin and diversification of dinosaur stem lineage deep into Early Triassic. Proceedings of the Royal Society B. doi: 10.1098/rspb.2010.1746
Nesbitt, S. J. 2009. The antiquity of Archosauria and the origin of Late Triassic archosaur assemblages. Journal of Vertebrate Paleontology 29:155A.
Nesbitt, S. J., Smith, N. D., Irmis, R. B.,Turner, A. H., Downs, A., and M. A. Norell. 2009. A Complete skeleton of a Late Triassic saurischian and the early evolution of dinosaurs. Science 326: 1530–1533.
The Role of the Calcaneal 'Heel' in Basal Archosaurs
Sullivan, C. 2010. The role of the calcaneal 'heel' as a propulsive lever in basal archosaurs and extant monitor lizards. Journal of Vertebrate Paleontology 30:1422-1432.
Abstract - The structurally complex ankles of Triassic archosaurs (Reptilia: Diapsida) have been repeatedly described, and tarsal characters have played an important role in analyses of archosaur phylogeny. Morphological variations in the ankle joint undoubtedly had a major impact on locomotion, but the functional implications of many ankle features remain poorly understood. This paper investigates the function of one such structure, the prominent and highly distinctive lateral to posterolateral calcaneal process that occurs throughout basal archosaurs and is homologous to the heel-like calcaneal tuber of pseudosuchians. A morphologically analogous lateral process occurs in extant varanid lizards, and X-ray rotoscopic analysis of the limb movements of savannah monitors (Varanus exanthematicus) indicates that the lateral process rotates into a vertical orientation as the limb retracts. As the varanid lateral process approaches the vertical, it becomes increasingly effective in adding to the propulsive moment arm of m. peroneus longus. A computer model of the ankle was compared to modified versions in which the lateral process and the associated proximal expansion of the fifth metatarsal were eliminated, and this virtual experiment demonstrated that the combination of the two structures increases the peak propulsive moment arm of the varanid m. peroneus longus by over 26%. The lateral calcaneal process of basal archosaurs probably acted similarly, enhancing the ability of the peroneus musculature to contribute to propulsion during walking. Like the calcaneal tuber of pseudosuchian archosaurs, the primitive lateral process was a lever that contributed to locomotion by allowing ankle plantarflexion to generate a greater propulsive moment.
Abstract - The structurally complex ankles of Triassic archosaurs (Reptilia: Diapsida) have been repeatedly described, and tarsal characters have played an important role in analyses of archosaur phylogeny. Morphological variations in the ankle joint undoubtedly had a major impact on locomotion, but the functional implications of many ankle features remain poorly understood. This paper investigates the function of one such structure, the prominent and highly distinctive lateral to posterolateral calcaneal process that occurs throughout basal archosaurs and is homologous to the heel-like calcaneal tuber of pseudosuchians. A morphologically analogous lateral process occurs in extant varanid lizards, and X-ray rotoscopic analysis of the limb movements of savannah monitors (Varanus exanthematicus) indicates that the lateral process rotates into a vertical orientation as the limb retracts. As the varanid lateral process approaches the vertical, it becomes increasingly effective in adding to the propulsive moment arm of m. peroneus longus. A computer model of the ankle was compared to modified versions in which the lateral process and the associated proximal expansion of the fifth metatarsal were eliminated, and this virtual experiment demonstrated that the combination of the two structures increases the peak propulsive moment arm of the varanid m. peroneus longus by over 26%. The lateral calcaneal process of basal archosaurs probably acted similarly, enhancing the ability of the peroneus musculature to contribute to propulsion during walking. Like the calcaneal tuber of pseudosuchian archosaurs, the primitive lateral process was a lever that contributed to locomotion by allowing ankle plantarflexion to generate a greater propulsive moment.
This is the Kind of Study I'd Like to See Get Done More Often
I remain convinced that figuring out larger problems starts with the detailed collection of data at a smaller scale. This is exactly the type of study I'd like to consider for the Chinle Formation.....
Lyson, T. R., and N. R. Longrich. 2010. Spatial niche partitioning in dinosaurs from the latest cretaceous (Maastrichtian) of North America. Proceedings of the Royal Society B. Published online before print October 13, 2010, doi: 10.1098/rspb.2010.1444
Abstract - We examine patterns of occurrence of associated dinosaur specimens (n = 343) from the North American Upper Cretaceous Hell Creek Formation and equivalent beds, by comparing their relative abundance in sandstone and mudstone. Ceratopsians preferentially occur in mudstone, whereas hadrosaurs and the small ornithopod Thescelosaurus show a strong association with sandstone. By contrast, the giant carnivore Tyrannosaurus rex shows no preferred association with either lithology. These lithologies are used as an indicator of environment of deposition, with sandstone generally representing river environments, and finer grained sediments typically representing floodplain environments. Given these patterns of occurrence, we argue that spatial niche partitioning helped reduce competition for resources between the herbivorous dinosaurs. Within coastal lowlands ceratopsians preferred habitats farther away from rivers, whereas hadrosaurs and Thescelosaurus preferred habitats in close proximity to rivers, and T. rex, the ecosystem's sole large carnivore, inhabited both palaeoenvironments. Spatial partitioning of the environment helps explain how several species of large herbivorous dinosaurs coexisted. This study emphasizes that different lithologies can preserve dramatically dissimilar vertebrate assemblages, even when deposited in close proximity and within a narrow window of time. The lithology in which fossils are preserved should be recorded as these data can provide unique insights into the palaeoecology of the animals they preserve.
Lyson, T. R., and N. R. Longrich. 2010. Spatial niche partitioning in dinosaurs from the latest cretaceous (Maastrichtian) of North America. Proceedings of the Royal Society B. Published online before print October 13, 2010, doi: 10.1098/rspb.2010.1444
Abstract - We examine patterns of occurrence of associated dinosaur specimens (n = 343) from the North American Upper Cretaceous Hell Creek Formation and equivalent beds, by comparing their relative abundance in sandstone and mudstone. Ceratopsians preferentially occur in mudstone, whereas hadrosaurs and the small ornithopod Thescelosaurus show a strong association with sandstone. By contrast, the giant carnivore Tyrannosaurus rex shows no preferred association with either lithology. These lithologies are used as an indicator of environment of deposition, with sandstone generally representing river environments, and finer grained sediments typically representing floodplain environments. Given these patterns of occurrence, we argue that spatial niche partitioning helped reduce competition for resources between the herbivorous dinosaurs. Within coastal lowlands ceratopsians preferred habitats farther away from rivers, whereas hadrosaurs and Thescelosaurus preferred habitats in close proximity to rivers, and T. rex, the ecosystem's sole large carnivore, inhabited both palaeoenvironments. Spatial partitioning of the environment helps explain how several species of large herbivorous dinosaurs coexisted. This study emphasizes that different lithologies can preserve dramatically dissimilar vertebrate assemblages, even when deposited in close proximity and within a narrow window of time. The lithology in which fossils are preserved should be recorded as these data can provide unique insights into the palaeoecology of the animals they preserve.
Ouch! Spondarthritis in a Triassic Archosaur
Cisneros, J. C. , Gomes Cabral, U., de Beer, F., Damiani, R., and Costa Fortier, D. (2010) Spondarthritis in the Triassic. PLoS ONE 5(10): e13425. doi:10.1371/journal.pone.0013425
Abstract
Background: The evidence of several forms of arthritis has been well documented in the fossil record. However, for pre-Cenozoic vertebrates, especially regarding reptiles, this record is rather scarce. In this work we present a case report of spondarthritis found in a vertebral series that belonged to a carnivorous archosaurian reptile from the Lower Triassic (~245 million years old) of the South African Karoo.
Methodology/Principal Findings: Neutron tomography confirmed macroscopic data, revealing the ossification of the entire intervertebral disc space (both annulus fibrosus and nucleus pulposus), which supports the diagnosis of spondarthritis.
Conclusions/Significance: The presence of spondarthritis in the new specimen represents by far the earliest evidence of any form of arthritis in the fossil record. The present find is nearly 100 million years older than the previous oldest report of this pathology, based on a Late Jurassic dinosaur. Spondarthritis may have indirectly contributed to the death of the animal under study.
Abstract
Background: The evidence of several forms of arthritis has been well documented in the fossil record. However, for pre-Cenozoic vertebrates, especially regarding reptiles, this record is rather scarce. In this work we present a case report of spondarthritis found in a vertebral series that belonged to a carnivorous archosaurian reptile from the Lower Triassic (~245 million years old) of the South African Karoo.
Methodology/Principal Findings: Neutron tomography confirmed macroscopic data, revealing the ossification of the entire intervertebral disc space (both annulus fibrosus and nucleus pulposus), which supports the diagnosis of spondarthritis.
Conclusions/Significance: The presence of spondarthritis in the new specimen represents by far the earliest evidence of any form of arthritis in the fossil record. The present find is nearly 100 million years older than the previous oldest report of this pathology, based on a Late Jurassic dinosaur. Spondarthritis may have indirectly contributed to the death of the animal under study.
Did you Celebrate the 1st Annual National Fossil Day?
I spent the day guiding visitors at Petrified Forest National Park through our fossil preparation lab and conducted a tour out to a well known fossil locality known as the Dying Grounds.
You can read more about this at the following link. Check out the Official National Fossil Day song and video. Some of the people in the video look somewhat familiar.....
http://www.nature.nps.gov/geology/nationalfossilday/index.cfm
Preview of New Early Jurassic "Coelophysoid" Fossil from China
This is a link to an article discussing new finds of "coelophysoid" material from Lufeng.
http://english.peopledaily.com.cn/90001/90782/7161153.html
Photos of the new material can be seen here. Pretty impressive!
http://www.cnr.cn/newscenter/xwtz/201010/t20101008_507139251.html#javascript_intro
Added 9 pm 10/9/2010: Looking at this a bit closer now that I have some time... I'm not convinced it is coelophysoid. The snout is too short and the face isn't "pointed" enough. There is a short-snouted form of "Coelophysis" out of the Coelophysis quarry that was mentioned by David Smith in a 2006 paper (I don't have the ref right now), but this also appears to be different than that. Rather this appears to be some kind of basal theropod, which would be very interesting out of an Early Jurassic deposit.
http://english.peopledaily.com.cn/90001/90782/7161153.html
Photos of the new material can be seen here. Pretty impressive!
http://www.cnr.cn/newscenter/xwtz/201010/t20101008_507139251.html#javascript_intro
Added 9 pm 10/9/2010: Looking at this a bit closer now that I have some time... I'm not convinced it is coelophysoid. The snout is too short and the face isn't "pointed" enough. There is a short-snouted form of "Coelophysis" out of the Coelophysis quarry that was mentioned by David Smith in a 2006 paper (I don't have the ref right now), but this also appears to be different than that. Rather this appears to be some kind of basal theropod, which would be very interesting out of an Early Jurassic deposit.
Dispersal as a Key Factor in Early Dinosaur Diversification of North America and the Myth of a 'Cosmopolitan' Dinosaur Fauna in the Early Mesozoic
New and available free from the Royal Society website. Popular news story here.
Rowe, T. B., Sues, H.-D., and R. Reisz. 2010. Dispersal and diversity in the earliest North American sauropodomorph dinosaurs, with a description of a new taxon. Proceedings of the Royal Society B, First Cite. doi:10.1098/rspb.2010.1867
Abstract - Sauropodomorph dinosaurs originated in the Southern Hemisphere in the Middle or Late Triassic and are commonly portrayed as spreading rapidly to all corners of Pangaea as part of a uniform Late Triassic to Early Jurassic cosmopolitan dinosaur fauna. Under this model, dispersal allegedly inhibited dinosaurian diversification, while vicariance and local extinction enhanced it. However, apomorphy-based analyses of the known fossil record indicate that sauropodomorphs were absent in North America until the Early Jurassic, reframing the temporal context of their arrival. We describe a new taxon from the Kayenta Formation of Arizona that comprises the third diagnosable sauropodomorph from the Early Jurassic of North America. We analysed its relationships to test whether sauropodomorphs reached North America in a single sweepstakes event or in separate dispersals. Our finding of separate arrivals by all three taxa suggests dispersal as a chief factor in dinosaurian diversification during at least the early Mesozoic. It questions whether a ‘cosmopolitan’ dinosaur fauna ever existed, and corroborates that vicariance, extinction and dispersal did not operate uniformly in time or under uniform conditions during the Mesozoic. Their relative importance is best measured in narrow time slices and circumscribed geographical regions.
Rowe, T. B., Sues, H.-D., and R. Reisz. 2010. Dispersal and diversity in the earliest North American sauropodomorph dinosaurs, with a description of a new taxon. Proceedings of the Royal Society B, First Cite. doi:10.1098/rspb.2010.1867
Abstract - Sauropodomorph dinosaurs originated in the Southern Hemisphere in the Middle or Late Triassic and are commonly portrayed as spreading rapidly to all corners of Pangaea as part of a uniform Late Triassic to Early Jurassic cosmopolitan dinosaur fauna. Under this model, dispersal allegedly inhibited dinosaurian diversification, while vicariance and local extinction enhanced it. However, apomorphy-based analyses of the known fossil record indicate that sauropodomorphs were absent in North America until the Early Jurassic, reframing the temporal context of their arrival. We describe a new taxon from the Kayenta Formation of Arizona that comprises the third diagnosable sauropodomorph from the Early Jurassic of North America. We analysed its relationships to test whether sauropodomorphs reached North America in a single sweepstakes event or in separate dispersals. Our finding of separate arrivals by all three taxa suggests dispersal as a chief factor in dinosaurian diversification during at least the early Mesozoic. It questions whether a ‘cosmopolitan’ dinosaur fauna ever existed, and corroborates that vicariance, extinction and dispersal did not operate uniformly in time or under uniform conditions during the Mesozoic. Their relative importance is best measured in narrow time slices and circumscribed geographical regions.
Evidence for an Early Triassic Origin for the Dinosaur Stem Lineage
Brusatte, S. L., Niedźwiedzki, G., and R. J. Butler. 2010. Footprints pull origin and diversification of dinosaur stem lineage deep into Early Triassic. Proceedings of the Royal Society B. doi: 10.1098/rspb.2010.1746
Abstract - The ascent of dinosaurs in the Triassic is an exemplary evolutionary radiation, but the earliest phase of dinosaur history remains poorly understood. Body fossils of close dinosaur relatives are rare, but indicate that the dinosaur stem lineage (Dinosauromorpha) originated by the latest Anisian (ca 242–244 Ma). Here, we report footprints from the Early–Middle Triassic of Poland, stratigraphically well constrained and identified using a conservative synapomorphy-based approach, which shifts the origin of the dinosaur stem lineage back to the Early Olenekian (ca 249–251 Ma), approximately 5–9 Myr earlier than indicated by body fossils, earlier than demonstrated by previous footprint records, and just a few million years after the Permian/Triassic mass extinction (252.3 Ma). Dinosauromorph tracks are rare in all Polish assemblages, suggesting that these animals were minor faunal components. The oldest tracks are quadrupedal, a morphology uncommon among the earliest dinosauromorph body fossils, but bipedality and moderately large body size had arisen by the Early Anisian (ca 246 Ma). Integrating trace fossils and body fossils demonstrates that the rise of dinosaurs was a drawn-out affair, perhaps initiated during recovery from the Permo-Triassic extinction.
Popular news story here with a horrible title as they are not true dinosaur footprints.
Abstract - The ascent of dinosaurs in the Triassic is an exemplary evolutionary radiation, but the earliest phase of dinosaur history remains poorly understood. Body fossils of close dinosaur relatives are rare, but indicate that the dinosaur stem lineage (Dinosauromorpha) originated by the latest Anisian (ca 242–244 Ma). Here, we report footprints from the Early–Middle Triassic of Poland, stratigraphically well constrained and identified using a conservative synapomorphy-based approach, which shifts the origin of the dinosaur stem lineage back to the Early Olenekian (ca 249–251 Ma), approximately 5–9 Myr earlier than indicated by body fossils, earlier than demonstrated by previous footprint records, and just a few million years after the Permian/Triassic mass extinction (252.3 Ma). Dinosauromorph tracks are rare in all Polish assemblages, suggesting that these animals were minor faunal components. The oldest tracks are quadrupedal, a morphology uncommon among the earliest dinosauromorph body fossils, but bipedality and moderately large body size had arisen by the Early Anisian (ca 246 Ma). Integrating trace fossils and body fossils demonstrates that the rise of dinosaurs was a drawn-out affair, perhaps initiated during recovery from the Permo-Triassic extinction.
Popular news story here with a horrible title as they are not true dinosaur footprints.
Postosuchus was Even Bigger Than we Thought
Holliday, C. M., Ridgely, R. C., Sedlmayr, J. C., and L. M. Witmer. 2010. Cartilaginous Epiphyses in Extant Archosaurs and Their Implications for Reconstructing Limb Function in Dinosaurs. PLoS ONE 5(9): e13120. doi:10.1371/journal.pone.0013120
Abstract - Extinct archosaurs, including many non-avian dinosaurs, exhibit relatively simply shaped condylar regions in their appendicular bones, suggesting potentially large amounts of unpreserved epiphyseal (articular) cartilage. This “lost anatomy” is often underappreciated such that the ends of bones are typically considered to be the joint surfaces, potentially having a major impact on functional interpretation. Extant alligators and birds were used to establish an objective basis for inferences about cartilaginous articular structures in such extinct archosaur clades as non-avian dinosaurs. Limb elements of alligators, ostriches, and other birds were dissected, disarticulated, and defleshed. Lengths and condylar shapes of elements with intact epiphyses were measured. Limbs were subsequently completely skeletonized and the measurements repeated. Removal of cartilaginous condylar regions resulted in statistically significant changes in element length and condylar breadth. Moreover, there was marked loss of those cartilaginous structures responsible for joint architecture and congruence. Compared to alligators, birds showed less dramatic, but still significant changes. Condylar morphologies of dinosaur limb bones suggest that most non-coelurosaurian clades possessed large cartilaginous epiphyses that relied on the maintenance of vascular channels that are otherwise eliminated early in ontogeny in smaller-bodied tetrapods. A sensitivity analysis using cartilage correction factors (CCFs) obtained from extant taxa indicates that whereas the presence of cartilaginous epiphyses only moderately increases estimates of dinosaur height and speed, it has important implications for our ability to infer joint morphology, posture, and the complicated functional movements in the limbs of many extinct archosaurs. Evidence suggests that the sizes of sauropod epiphyseal cartilages surpassed those of alligators, which account for at least 10% of hindlimb length. These data suggest that large cartilaginous epiphyses were widely distributed among non-avian archosaurs and must be considered when making inferences about locomotor functional morphology in fossil taxa.
Abstract - Extinct archosaurs, including many non-avian dinosaurs, exhibit relatively simply shaped condylar regions in their appendicular bones, suggesting potentially large amounts of unpreserved epiphyseal (articular) cartilage. This “lost anatomy” is often underappreciated such that the ends of bones are typically considered to be the joint surfaces, potentially having a major impact on functional interpretation. Extant alligators and birds were used to establish an objective basis for inferences about cartilaginous articular structures in such extinct archosaur clades as non-avian dinosaurs. Limb elements of alligators, ostriches, and other birds were dissected, disarticulated, and defleshed. Lengths and condylar shapes of elements with intact epiphyses were measured. Limbs were subsequently completely skeletonized and the measurements repeated. Removal of cartilaginous condylar regions resulted in statistically significant changes in element length and condylar breadth. Moreover, there was marked loss of those cartilaginous structures responsible for joint architecture and congruence. Compared to alligators, birds showed less dramatic, but still significant changes. Condylar morphologies of dinosaur limb bones suggest that most non-coelurosaurian clades possessed large cartilaginous epiphyses that relied on the maintenance of vascular channels that are otherwise eliminated early in ontogeny in smaller-bodied tetrapods. A sensitivity analysis using cartilage correction factors (CCFs) obtained from extant taxa indicates that whereas the presence of cartilaginous epiphyses only moderately increases estimates of dinosaur height and speed, it has important implications for our ability to infer joint morphology, posture, and the complicated functional movements in the limbs of many extinct archosaurs. Evidence suggests that the sizes of sauropod epiphyseal cartilages surpassed those of alligators, which account for at least 10% of hindlimb length. These data suggest that large cartilaginous epiphyses were widely distributed among non-avian archosaurs and must be considered when making inferences about locomotor functional morphology in fossil taxa.
Dentition and Tooth Replacement in an Upper Triassic Traversodont Cynodont from the Eastern United States
Liu, J., and H.-D. Sues. 2010. Dentition and tooth replacement of Boreogomphodon (Cynodontia: Traversodontidae) from the Upper Triassic of North Carolina, USA. Vertebrata PalAsiatica 48:169-184.
Abstract - The teeth of new specimens of the traversodontid cynodont Boreogomphodon from the Upper Triassic of North Carolina are described. Based on dental features, especially the postcanine morphology, the North Carolina specimens are tentatively referred to Boreogomphodon jeffersoni, although their lower gomphodont postcanines typically have two rather than three cusps on the anterior transverse ridge. Based on the tooth size, direct replacement on all available specimens, the gomphodont teeth were shed anteriorly and added posteriorly. Only one generation of gomphodont teeth, at least one and possibly two generations of sectorial postcanines were present.
Abstract - The teeth of new specimens of the traversodontid cynodont Boreogomphodon from the Upper Triassic of North Carolina are described. Based on dental features, especially the postcanine morphology, the North Carolina specimens are tentatively referred to Boreogomphodon jeffersoni, although their lower gomphodont postcanines typically have two rather than three cusps on the anterior transverse ridge. Based on the tooth size, direct replacement on all available specimens, the gomphodont teeth were shed anteriorly and added posteriorly. Only one generation of gomphodont teeth, at least one and possibly two generations of sectorial postcanines were present.
Tonganosaurus hei A New Sauropod from the Lower Jurassic of China
Li, K.Yang C.-Y., Liu, J., and Wang, Z.-X. 2010. A new sauropod from the Lower Jurassic of , Sichuan, China. Vertebrata PalAsiatica 48:185-202.
Huili
Abstract - A new sauropod, Tonganosaurus hei gen. et sp. nov. from the Yimen Formation (Lower Jurassic) of Sichuan, China, is described on the basis of a collection of bones. These fossils include about 20 vertebrae, a complete right pectoral girdle and right forelimb, the distal end of a left scapula, a pair of complete ischia, a somplete right hindlimb, the proximal and distal ends of a left femur, right metatarsals (mt. I, II, III, and V), a right pedal ungual, and ten neural spine and rib fragments. The third cervical and anterial caudals are most similar in shape to those of the mamenchisaurid Omeisaurus (from the Middle Jurassic, Sichuan Basin), and quite different from those of other sauropods. The material was therefore assigned to the Family Mamenchisauridae Young & Chao, 1972 and a new genus and species were established. This represents the first discovery of a sauropod in the Lower Jurassic of China since Gongxianosaurus was found in Sichuan Basin. The Tonganosaurus material is of great importance for understanding the phylogenetics of the early Sauropoda.
Huili
Abstract - A new sauropod, Tonganosaurus hei gen. et sp. nov. from the Yimen Formation (Lower Jurassic) of Sichuan, China, is described on the basis of a collection of bones. These fossils include about 20 vertebrae, a complete right pectoral girdle and right forelimb, the distal end of a left scapula, a pair of complete ischia, a somplete right hindlimb, the proximal and distal ends of a left femur, right metatarsals (mt. I, II, III, and V), a right pedal ungual, and ten neural spine and rib fragments. The third cervical and anterial caudals are most similar in shape to those of the mamenchisaurid Omeisaurus (from the Middle Jurassic, Sichuan Basin), and quite different from those of other sauropods. The material was therefore assigned to the Family Mamenchisauridae Young & Chao, 1972 and a new genus and species were established. This represents the first discovery of a sauropod in the Lower Jurassic of China since Gongxianosaurus was found in Sichuan Basin. The Tonganosaurus material is of great importance for understanding the phylogenetics of the early Sauropoda.
The Cranial Morphology of Trematosaurus galae From the Early Triassic of Russia
Novikov, I. V. 2010. New Data on Trematosauroid Labyrinthodonts of Eastern Europe: 2. Trematosaurus galae sp. nov.: Cranial Morphology. Paleontological Journal 44:94-104. DOI: 10.1134/S003103011004012X
Abstract - The cranial morphology of a new species of the genus of Trematosaurus, T. galae sp. nov., represented by fragmentary specimens from the Lower Triassic Donskaya Luka locality (Volgograd Region), is described in detail. The diagnosis of the genus Trematosaurus is amended.
Abstract - The cranial morphology of a new species of the genus of Trematosaurus, T. galae sp. nov., represented by fragmentary specimens from the Lower Triassic Donskaya Luka locality (Volgograd Region), is described in detail. The diagnosis of the genus Trematosaurus is amended.
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