Piechowski, P., Tałanda, M., and J. Dzik. 2014. Skeletal variation and ontogeny of the Late Triassic Dinosauriform Silesaurus opolensis. Journal of Vertebrate Paleontology 34:1383-1393 DOI:10.1080/02724634.2014.873045
Abstract - A principal component analysis (PCA) performed for a set of 24 measurements on 33 femora and 15 measurements on 20 ilia of Silesaurus opolensis from the early Late Triassic of Krasiejów, southern Poland, shows that this sample is highly variable but probably monospecific. Most of the morphological variation is concentrated in the muscle attachments and proportions of bones, which significantly change in both size and position during ontogeny. Despite the small sample size, femora of smaller individuals have less flattened shafts and a more sinusoidal appearance. In many large specimens, proximal parts of muscle tendons are ossified at their attachment site on femora and remain attached to the bone in the largest specimens. The specimens with attached ossifications are interpreted as mature females that were statistically larger than proposed males. It is suggested that ossifications developed in females under calcitonin control. The intrapopulation variability of ilia is high, but less dependant on ontogeny. The population represented by a few specimens from the lower level at Krasiejów may represent a different stage in the evolution of the species than that from the upper horizon.
Showing posts with label dinosauriformes. Show all posts
Showing posts with label dinosauriformes. Show all posts
Dental Microwear of the Late Triassic Dinosauriform Silesaurus opolensis
Kubo, T., and M. O. Kubo. 2013. Dental microwear of a Late Triassic dinosauriform, Silesaurus opolensis. Acta Palaeontologica Polonica (in press).
doi: http://dx.doi.org/10.4202/app.
Abstract - Silesaurus opolensis belongs to Silesauridae, the closest sister group
to dinosaurs. The present study analyzed the dental microwear patterns of Silesaurus opolensis. Low pit-to-scratch ratios imply they did not feed on hard objects. Unimodal distributions of both wear-facet and non-facet scratch orientations indicate simple orthal jaw movement. Scratch orientation and density differ between microscopic regions in Silesaurus, and unlike hadrosaurid dinosaurs, the microwear patterns of small areas are not identical to those of whole teeth.
doi: http://dx.doi.org/10.4202/app.
Abstract - Silesaurus opolensis belongs to Silesauridae, the closest sister group
to dinosaurs. The present study analyzed the dental microwear patterns of Silesaurus opolensis. Low pit-to-scratch ratios imply they did not feed on hard objects. Unimodal distributions of both wear-facet and non-facet scratch orientations indicate simple orthal jaw movement. Scratch orientation and density differ between microscopic regions in Silesaurus, and unlike hadrosaurid dinosaurs, the microwear patterns of small areas are not identical to those of whole teeth.
New Basal Dinosauromorph Synthesis Paper
A solid review of our current knowledge of non-dinosaurian dinosauromorphs such as lagerpetids and silesaurids.
Langer, M. C., Nesbitt, S. J., Bittencourt, J. S., and R. B. Irmis. 2013. Non-Dinosaurian Dinosauromorpha. In Nesbitt, S. J., Desojo, J. B. and R. B. Irmis, (eds) Anatomy, Phylogeny and Palaeobiology of Early Archosaurs and their Kin. Geological Society, London, Special Publications, 379, http://dx.doi.org/10.1144/SP379.9
Abstract - Ichnological evidence suggests that dinosauromorphs originated by the Early Triassic, and skeletal remains of non-dinosaur representatives of the clade occur from the Anisian to the end of the Triassic. These taxa are small- to medium-sized, vary in feeding and locomotor features, and occurred over most of western Pangaea. They include the small lagerpetids from the Mid–Late Triassic of Argentina and the United States, and the larger, quadrupedal Silesauridae, with records in the Middle Triassic of Africa and Argentina, and in the Late Triassic of Europe, the Americas and northern Africa. The former group represents the earliest diverging dinosauromorphs, whereas silesaurids are more closely related to Dinosauria. Other dinosauromorphs include the archetypal early dinosauriform Marasuchus lilloensis (Middle Triassic of Argentina) and poorly known/controversial taxa such as Lewisuchus admixtus and Saltopus elginensis. The earliest diverging dinosauromorphs may have preyed on small animals (including insects), but cranio-dental remains are rare; by contrast, most silesaurids probably included plant material in their diet, as indicated by their modified jaw apparatus and teeth. Our knowledge of the anatomy and thus relationships of non-dinosaurian Dinosauromorpha is still deficient, and we suspect that future discoveries will continue to reveal novel patterns and hypotheses of palaeobiology and biogeography.
Langer, M. C., Nesbitt, S. J., Bittencourt, J. S., and R. B. Irmis. 2013. Non-Dinosaurian Dinosauromorpha. In Nesbitt, S. J., Desojo, J. B. and R. B. Irmis, (eds) Anatomy, Phylogeny and Palaeobiology of Early Archosaurs and their Kin. Geological Society, London, Special Publications, 379, http://dx.doi.org/10.1144/SP379.9
Abstract - Ichnological evidence suggests that dinosauromorphs originated by the Early Triassic, and skeletal remains of non-dinosaur representatives of the clade occur from the Anisian to the end of the Triassic. These taxa are small- to medium-sized, vary in feeding and locomotor features, and occurred over most of western Pangaea. They include the small lagerpetids from the Mid–Late Triassic of Argentina and the United States, and the larger, quadrupedal Silesauridae, with records in the Middle Triassic of Africa and Argentina, and in the Late Triassic of Europe, the Americas and northern Africa. The former group represents the earliest diverging dinosauromorphs, whereas silesaurids are more closely related to Dinosauria. Other dinosauromorphs include the archetypal early dinosauriform Marasuchus lilloensis (Middle Triassic of Argentina) and poorly known/controversial taxa such as Lewisuchus admixtus and Saltopus elginensis. The earliest diverging dinosauromorphs may have preyed on small animals (including insects), but cranio-dental remains are rare; by contrast, most silesaurids probably included plant material in their diet, as indicated by their modified jaw apparatus and teeth. Our knowledge of the anatomy and thus relationships of non-dinosaurian Dinosauromorpha is still deficient, and we suspect that future discoveries will continue to reveal novel patterns and hypotheses of palaeobiology and biogeography.
Evolution of Bipedality and Herbivory Among Triassic Dinosauromorphs
Note that this paper is in Japanese with an English version of the abstract.
Kubo, T. 2011. Evolution of bipedality and herbivory among
Triassic dinosauromorphs. Memoir of the Fukui Prefectural Dinosaur Museum 10:55－62．
Abstract - Discoveries of Triassic non-dinosaur dinosauromorphs since
2000 revealed that they were more widely spread chronologically and
geographically than previously thought. A member of silesaurids, the sister clade
of dinosaurs, Silesaurus was a
quadrupedal and herbivorous animal that differs considerably from the condition
previously assumed for the ancestor of dinosaurs that are bipedal and
carnivorous. Currently, stance and diet of the common ancestor of dinosaurs are
not clear. To redeem this situation, Ancestral State Reconstruction methods
were conducted to infer how quadrupedality and herbivory were evolved among
dinosauromorphs. The results of analyses indicate that quadrupedal stance
evolved only among silesaurids. Herbivorous diet was readily evolved from
carnivorous diet among Dinosauromorpha and the ancestral state reconstruction
using likelihood methods indicated that the possibility of the common ancestor
of dinosaurs being herbivore is more than 60%.
Diodorus scytobrachion, A New Silesaurid from the Late Triassic of Morocco
I've had this paper in the queue for a bit as I still don't like the idea of online publishing of new taxon names at the "accepted manuscript" stage, but the knowledge of this proposed new taxon is increasingly widespead so I'll post the abstract and link here now. Silesaurids are amazingly cosmopolitan in their distribution and must have been significant members of various Triassic ecosystems, most likely filling the role later occupied by ornithischians.
I'm a big fan of the creative taxonomic name as well.
Kammerer, C. F., Nesbitt, S. J., and N. H. Shubin. In press. The first basal dinosauriform (Silesauridae) from the Late Triassic of Morocco. Acta Palaeontologica Polonica. doi: 10.4202/app.2011.0015
Abstract - Disarticulated material from the Late Triassic Timezgadiouine Formation in the Argana Basin of Morocco represents a new taxon of silesaurid dinosauromorph,
Diodorus scytobrachion gen. et sp. nov. D. scytobrachion can be distinguished from other silesaurids by the presence of anteriorly-canted teeth that decrease in size towards the anterior end of the dentary and a distinct lateral ridge running parallel to the dentary alveolar margin. In a phylogenetic analysis, D. scytobrachion is recovered as the sister taxon to the Brazilian Sacisaurus agudoensis, nested deep within Silesauridae. This new taxon provides further evidence of a near-cosmopolitan range for basal dinosauriforms in the Late Triassic and further demonstrates the disparity of dental morphologies within Silesauridae.
Evolution of the Dinosauriform Respiratory Apparatus: New Evidence from the Postcranial Axial Skeleton
Schachner, E. R., Farmer, C. G., McDonald, A. T., and P. Dodson. 2011. Evolution of the dinosauriform respiratory apparatus: new evidence from the postcranial axial skeleton. The Anatomical Record Early View. DOI: 10.1002/ar.21439
Abstract - Examination of the thoracic rib and vertebral anatomy of extant archosaurs indicates a relationship between the postcranial axial skeleton and pulmonary anatomy. Lung ventilation in extant crocodilians is primarily achieved with a hepatic piston pump and costal rotation. The tubercula and capitula of the ribs lie on the horizontal plane, forming a smooth thoracic ‘‘ceiling’’ facilitating movement of the viscera. Although the parietal pleura is anchored to the dorsal thoracic wall, the dorsal visceral pleura exhibits a greater freedom of movement. The air sac system and lungs of birds are associated with bicapitate ribs with a ventrally positioned capitular articulation, generating a rigid and furrowed rib cage that minimizes dorsoventral changes in volume in the dorsal thorax. The thin walled bronchi are kept from collapsing by fusion of the lung to the thorax on all sides. Data from this study suggest a progression from a dorsally rigid, heterogeneously partitioned, multichambered lung in basal dinosauriform archosaurs towards the small entirely rigid avian-style lung that was likely present in saurischian dinosaurs, consistent with a constant volume cavum pulmonale, thin walled parabronchi, and distinct air sacs. There is no vertebral evidence for a crocodilian hepatic piston pump in any of the taxa reviewed. The evidence for both a rigid lung and unidirectional airflow in dinosauriformes raises the possibility that these animals had a highly efficient lung relative to other Mesozoic vertebrates, which may have contributed to their successful radiation during this time period.
Abstract - Examination of the thoracic rib and vertebral anatomy of extant archosaurs indicates a relationship between the postcranial axial skeleton and pulmonary anatomy. Lung ventilation in extant crocodilians is primarily achieved with a hepatic piston pump and costal rotation. The tubercula and capitula of the ribs lie on the horizontal plane, forming a smooth thoracic ‘‘ceiling’’ facilitating movement of the viscera. Although the parietal pleura is anchored to the dorsal thoracic wall, the dorsal visceral pleura exhibits a greater freedom of movement. The air sac system and lungs of birds are associated with bicapitate ribs with a ventrally positioned capitular articulation, generating a rigid and furrowed rib cage that minimizes dorsoventral changes in volume in the dorsal thorax. The thin walled bronchi are kept from collapsing by fusion of the lung to the thorax on all sides. Data from this study suggest a progression from a dorsally rigid, heterogeneously partitioned, multichambered lung in basal dinosauriform archosaurs towards the small entirely rigid avian-style lung that was likely present in saurischian dinosaurs, consistent with a constant volume cavum pulmonale, thin walled parabronchi, and distinct air sacs. There is no vertebral evidence for a crocodilian hepatic piston pump in any of the taxa reviewed. The evidence for both a rigid lung and unidirectional airflow in dinosauriformes raises the possibility that these animals had a highly efficient lung relative to other Mesozoic vertebrates, which may have contributed to their successful radiation during this time period.
Silesaurus opolensis Reconstruction by Jeff Martz
This is my favorite in Jeff's dinosauromorph series. The silesaurid dinosauriform Silesaurus from the Upper Triassic of Poland.
New Information on the Triassic Dinosauriform Silesaurus opolensis
Piechowski, R., and J. Dzik. 2010. The axial skeleton of Silesaurus opolensis. Journal of Vertebrate Paleontology 30:1127 – 1141. DOI: 10.1080/02724634.2010.483547
Abstract - A recent find of an articulated skeleton of Silesaurus opolensis at its early Late Triassic type locality Krasiejów (Poland), with skull, neck, pectoral girdle, and thorax, supplemented by additional preparation of previously collected articulated specimens, enables complete restoration of the vertebral column and associated skeletal parts. Cervical ribs of Silesaurus, well preserved in their original disposition, are parallel to the neck and extend backward for a few vertebral lengths. There is a sudden change in their morphology behind the seventh vertebra, although otherwise the transition from the cervical to the dorsal vertebrae is very gradual. Parapophyses slowly migrate upward along the anterior margin of the centrum and leave the centrum at the sixth or seventh dorsal vertebra. Narrowing of the dorsal extremities of the neural spines of the fourth and neighboring vertebrae suggests the ability of this region of the vertebral column to bent upward. There is thus a disparity between the structural and functional neck-thorax transition. The presence of three sacrals firmly connected by their ribs with the ilia and the long tail of Silesaurus, providing a counterbalance to the weight of the body in front of the pelvis, suggests the ability for fast bipedal running. However, unusually long but gracile forelimbs of Silesaurus suggest that it represents a transition towards secondarily quadrupedal locomotion, characterizing most of the later herbivorous dinosaurs.
Abstract - A recent find of an articulated skeleton of Silesaurus opolensis at its early Late Triassic type locality Krasiejów (Poland), with skull, neck, pectoral girdle, and thorax, supplemented by additional preparation of previously collected articulated specimens, enables complete restoration of the vertebral column and associated skeletal parts. Cervical ribs of Silesaurus, well preserved in their original disposition, are parallel to the neck and extend backward for a few vertebral lengths. There is a sudden change in their morphology behind the seventh vertebra, although otherwise the transition from the cervical to the dorsal vertebrae is very gradual. Parapophyses slowly migrate upward along the anterior margin of the centrum and leave the centrum at the sixth or seventh dorsal vertebra. Narrowing of the dorsal extremities of the neural spines of the fourth and neighboring vertebrae suggests the ability of this region of the vertebral column to bent upward. There is thus a disparity between the structural and functional neck-thorax transition. The presence of three sacrals firmly connected by their ribs with the ilia and the long tail of Silesaurus, providing a counterbalance to the weight of the body in front of the pelvis, suggests the ability for fast bipedal running. However, unusually long but gracile forelimbs of Silesaurus suggest that it represents a transition towards secondarily quadrupedal locomotion, characterizing most of the later herbivorous dinosaurs.
Asilisaurus kongwe, the Oldest Avian-line Archosaur and the Early Diversification of Ornithodira
Nesbitt, S.J., Sidor, C.A., Irmis, R.B., Angielczyk, K.D., Smith, R.M.H., and L. A. Tsuji. 2010. Ecologically distinct dinosaurian sister group shows early diversification of Ornithodira. Nature. doi:10.1038/nature08718
Abstract - The early evolutionary history of Ornithodira (avian-line archosaurs) has hitherto been documented by incomplete (Lagerpeton) or unusually specialized forms (pterosaurs and Silesaurus). Recently, a variety of Silesaurus-like taxa have been reported from the Triassic Period of both Gondwana and Laurasia, but their relationships to each other and to dinosaurs remain a subject of debate. Here we report on a new avian-line archosaur from the early Middle Triassic (Anisian) of Tanzania. Phylogenetic analysis places Asilisaurus kongwe gen. et sp. nov. as an avian-line archosaur and a member of the Silesauridae, which is here considered the sister taxon to Dinosauria. Silesaurids were diverse and had a wide distribution by the Late Triassic, with a novel ornithodiran bauplan including leaf-shaped teeth, a beak-like lower jaw, long, gracile limbs, and a quadrupedal stance. Our analysis suggests that the dentition and diet of silesaurids, ornithischians and sauropodomorphs evolved independently from a plesiomorphic carnivorous form. As the oldest avian-line archosaur, Asilisaurus demonstrates the antiquity of both Ornithodira and the dinosaurian lineage. The initial diversification of Archosauria, previously documented by crocodilian-line archosaurs in the Anisian, can now be shown to include a contemporaneous avian-line radiation. The unparalleled taxonomic diversity of the Manda archosaur assemblage indicates that archosaur diversification was well underway by the Middle Triassic or earlier.
Life restoration of Asilisaurus with sail-backed poposauroid in the background. Image by M.H. Donnelly (Field Museum).
Prior to 2003 the non-dinosaurian dinosauriforms known as silesaurids were unrecognized in the fossil record. Specimens existed in collections, collected as early as the 1930s, while others were given tentative identifications (e.g., the ornithosuchid of Long and Murry, 1995 and the ornithischian Technosaurus). Dzik (2003) described the first, Silesaurus opolensis from the Carnian of Poland, with its very distinctive femoral and morphologies. Suddenly similar forms were recognized from all over the globe (e.g., Eucoelophysis, Sacisaurus; Ezcurra 2006; Nesbitt et al. 2007; Irmis et al. 2007a), whereas new specimens were being discovered from the Chinle Formation of New Mexico and Arizona (Parker et al. 2006; Irmis et al. 2007b).
Still, because the earliest pseudosuchian archosaurs were known from the Anisian (e.g., the Moenkopi Formation of Arizona), whereas the earliest ornithodirans were from the Ladinian of Argentina, there was a proposed ghost lineage for Ornithodira existing back into the Anisian.
Skeletal reconstruction of Asilisaurus, with missing bones in gray. Image by S. Nesbitt.
Abstract - The early evolutionary history of Ornithodira (avian-line archosaurs) has hitherto been documented by incomplete (Lagerpeton) or unusually specialized forms (pterosaurs and Silesaurus). Recently, a variety of Silesaurus-like taxa have been reported from the Triassic Period of both Gondwana and Laurasia, but their relationships to each other and to dinosaurs remain a subject of debate. Here we report on a new avian-line archosaur from the early Middle Triassic (Anisian) of Tanzania. Phylogenetic analysis places Asilisaurus kongwe gen. et sp. nov. as an avian-line archosaur and a member of the Silesauridae, which is here considered the sister taxon to Dinosauria. Silesaurids were diverse and had a wide distribution by the Late Triassic, with a novel ornithodiran bauplan including leaf-shaped teeth, a beak-like lower jaw, long, gracile limbs, and a quadrupedal stance. Our analysis suggests that the dentition and diet of silesaurids, ornithischians and sauropodomorphs evolved independently from a plesiomorphic carnivorous form. As the oldest avian-line archosaur, Asilisaurus demonstrates the antiquity of both Ornithodira and the dinosaurian lineage. The initial diversification of Archosauria, previously documented by crocodilian-line archosaurs in the Anisian, can now be shown to include a contemporaneous avian-line radiation. The unparalleled taxonomic diversity of the Manda archosaur assemblage indicates that archosaur diversification was well underway by the Middle Triassic or earlier.
Life restoration of Asilisaurus with sail-backed poposauroid in the background. Image by M.H. Donnelly (Field Museum).Prior to 2003 the non-dinosaurian dinosauriforms known as silesaurids were unrecognized in the fossil record. Specimens existed in collections, collected as early as the 1930s, while others were given tentative identifications (e.g., the ornithosuchid of Long and Murry, 1995 and the ornithischian Technosaurus). Dzik (2003) described the first, Silesaurus opolensis from the Carnian of Poland, with its very distinctive femoral and morphologies. Suddenly similar forms were recognized from all over the globe (e.g., Eucoelophysis, Sacisaurus; Ezcurra 2006; Nesbitt et al. 2007; Irmis et al. 2007a), whereas new specimens were being discovered from the Chinle Formation of New Mexico and Arizona (Parker et al. 2006; Irmis et al. 2007b).
Still, because the earliest pseudosuchian archosaurs were known from the Anisian (e.g., the Moenkopi Formation of Arizona), whereas the earliest ornithodirans were from the Ladinian of Argentina, there was a proposed ghost lineage for Ornithodira existing back into the Anisian.
Sterling Nesbitt looks over the Ruhuhu Valley in 2007. Photo by L. Tsuji.
One of the strengths of phylogentic analysis is the ability to make predictions as to where in time and space certain groups should and could be found. Sterling Nesbitt clearly recognized the strong possibility that the earliest representatives of ornithodira could be found in the Manda beds of Tanzania as this fauna was known for its pseudosuchian constituents. A few years back this prediction paid off, as a team lead by Christian Sidor in 2007 to explore the Permian and Triassic rocks of Tanzanian, uncovered an amazing deposit of early archosaurs including numerous specimens of a silesaurid. Named Asilisaurus kongwe (Ancient ancestor lizard) these specimens represent the earliest known member of the lineage leading to dinosaurs and strongly supports the diversification of the Archosauria by the early Middle Triassic (~243 million years ago).
The tibia of Asilisaurus, following excavation in 2007. Photo by R. Smith.
This find also strongly suggests that adaptations for an omnivorous or herbivorous diet evolved independently in silesaurids, ornithischians, and sauropodomorphs, from carnivorous ancestors. The paper also phylogenetically defines the Silesauridae and proposes that the South American archosaurs Lewisuchus and Pseudlagosuchus are members of this clade and probably also synonymous. Another early appearance of a non-dinosaurian dinosauriform in
Gondwana also provides further support for a southern origin for this group.
Skeletal reconstruction of Asilisaurus, with missing bones in gray. Image by S. Nesbitt.One final point, silesaurs have been proposed to be basal ornithischians (e.g., Ferigolo & Langer, 2007) and represent the Late Triassic radiation of that clade. However, if this is the case, despite the lack of support in phylogentic analyses (e.g., Irmis et al., 2007b), the discovery of early Middle Triassic ornithichians would pull the split with saurischians back as early as the Early Triassic and create a sizeable ghost lineage for the base of Saurischia.
More photos and information on Ruhuhu Basin Research can be found here:
http://protist.biology.washington.edu/sidor/Ruhuhu/asilisaurus.html
REFERENCES
Dzik, J. 2003. A beaked herbivorous archosaur with dinosaur affinities from the early Late Triassic of Poland. Journal of Vertebrate Paleontology 23:556-574.
Ezcurra, M.D. 2006. A review of the systematic position of the dinosauriform archosaur Eucoelophysis baldwini from the Upper Triassic of New Mexico, U.S.A. Geodiversitas 28:649-684.
Ferigolo, J. and M. Langer. 2007. A late Triassic dinosauriform from south Brazil and the origin of the ornithischian predentary bone. Historical Biology 19:23-33.
Irmis, R.B., Parker, W.G., Nesbitt, S.J., and J. Liu. 2007a. Early ornithischian dinosaurs: the Triassic record. Historical Biology 19:3-22.
Irmis, R. B., Nesbitt, S. J., Padian, K., Smith, N. D., Turner, A. H., Woody, D., and A. Downs. 2007a. A Late Triassic dinosauromorph assemblage from New Mexico and the rise of dinosaurs. Science 317:358-361.
Nesbitt, S.J., Irmis, R.B., and W.G. Parker. 2007. A critical re-evaluation of the Late Triassic dinosaur taxa of North America. Journal of Systematic Palaeontology 5:209-243.
Parker, W.G., Irmis, R.B., and S.J. Nesbitt. 2006. Review of the Late Triassic dinosaur record from Petrified Forest National Park, Arizona. Museum of Northern Arizona Bulletin 62:160-161.
http://protist.biology.washington.edu/sidor/Ruhuhu/asilisaurus.html
REFERENCES
Dzik, J. 2003. A beaked herbivorous archosaur with dinosaur affinities from the early Late Triassic of Poland. Journal of Vertebrate Paleontology 23:556-574.
Ezcurra, M.D. 2006. A review of the systematic position of the dinosauriform archosaur Eucoelophysis baldwini from the Upper Triassic of New Mexico, U.S.A. Geodiversitas 28:649-684.
Ferigolo, J. and M. Langer. 2007. A late Triassic dinosauriform from south Brazil and the origin of the ornithischian predentary bone. Historical Biology 19:23-33.
Irmis, R.B., Parker, W.G., Nesbitt, S.J., and J. Liu. 2007a. Early ornithischian dinosaurs: the Triassic record. Historical Biology 19:3-22.
Irmis, R. B., Nesbitt, S. J., Padian, K., Smith, N. D., Turner, A. H., Woody, D., and A. Downs. 2007a. A Late Triassic dinosauromorph assemblage from New Mexico and the rise of dinosaurs. Science 317:358-361.
Nesbitt, S.J., Irmis, R.B., and W.G. Parker. 2007. A critical re-evaluation of the Late Triassic dinosaur taxa of North America. Journal of Systematic Palaeontology 5:209-243.
Parker, W.G., Irmis, R.B., and S.J. Nesbitt. 2006. Review of the Late Triassic dinosaur record from Petrified Forest National Park, Arizona. Museum of Northern Arizona Bulletin 62:160-161.
Bone Histology of the Late Triassic Dinosauriform Silesaurus opolensis
Fostowicz-Frelik, L., and T. Sulej. 2009. Bone histology of Silesaurus opolensis Dzik, 2003 from the Late Triassic of Poland. Lethaia. 10.1111/j.1502-3931.2009.00179.x
Abstract- The phylogenetic relationships of Silesaurus opolensis have been the subject of intense debate since its discovery. Silesaurus possesses some features characteristic of ornithischian dinosaurs, such as the presence of a beak at the front of the lower jaw, yet it lacks a number of important femoral and dental synapomorphies of Dinosauria. The microstructure of the long bones (femur, tibia and metatarsal) and ribs of this species reveals a relatively intensive rate of growth, comparable with that seen in small dinosaurs and the gracile crocodylomorph Terrestrisuchus. Cortical bone formed mainly by periosteal tissue with fibro-lamellar matrix (in older specimens parallel fibred) shows very little secondary remodelling and only in one specimen (large tibia ZPAL Ab III ⁄ 1885) few lines of arrested growth are present in the outermost cortex. The vascularization is relatively dense, mainly longitudinal and ceases towards the periphery, forming almost avascular parallel fibred bone at the bone surface. This indicates maturation and significant decrease in the growth ratio in mature specimens of S. opolensis. The delicate trabeculae exhibit cores formed by the primary cancellous tissue lined with lamellar endosteal bone. The rather intense growth of S. opolensis implies a relatively high metabolic rate. Moreover, evidence from the fibro-lamellar tissue, predominant in the cortex, suggests that this kind of rapid bone deposition could be more typical of Archosauria than previously assumed, a prerequisite for the evolution of the very fast growth rates observed in large ornithischians, sauropods and large theropods.
Abstract- The phylogenetic relationships of Silesaurus opolensis have been the subject of intense debate since its discovery. Silesaurus possesses some features characteristic of ornithischian dinosaurs, such as the presence of a beak at the front of the lower jaw, yet it lacks a number of important femoral and dental synapomorphies of Dinosauria. The microstructure of the long bones (femur, tibia and metatarsal) and ribs of this species reveals a relatively intensive rate of growth, comparable with that seen in small dinosaurs and the gracile crocodylomorph Terrestrisuchus. Cortical bone formed mainly by periosteal tissue with fibro-lamellar matrix (in older specimens parallel fibred) shows very little secondary remodelling and only in one specimen (large tibia ZPAL Ab III ⁄ 1885) few lines of arrested growth are present in the outermost cortex. The vascularization is relatively dense, mainly longitudinal and ceases towards the periphery, forming almost avascular parallel fibred bone at the bone surface. This indicates maturation and significant decrease in the growth ratio in mature specimens of S. opolensis. The delicate trabeculae exhibit cores formed by the primary cancellous tissue lined with lamellar endosteal bone. The rather intense growth of S. opolensis implies a relatively high metabolic rate. Moreover, evidence from the fibro-lamellar tissue, predominant in the cortex, suggests that this kind of rapid bone deposition could be more typical of Archosauria than previously assumed, a prerequisite for the evolution of the very fast growth rates observed in large ornithischians, sauropods and large theropods.
New Paper on Triassic Dinosauriform Footprints from Brazil
This was just announced as now being out in Ameghiniana, although I was not able to find a link to this article on-line (the Ameghiniana website is often behind). One quick note: Sacisaurus is a "silesaurid" dinosauriform and not a dinosaurian.
Da Silva, R.C., Carvalho, I., and A.C.S. Fernandes. 2009. Dinosaur footprints from the Triassic (Santa Maria Formation) of Brazil. Ameghiniana 45: 783-790.
Abstract. Dinosaur footprints in Jurassic and Cretaceous rocks are common in Brazil , but there are only a few records from Triassic. In Rio Grande do Sul State , tridactyl medium size footprints were found in Carnian rocks. The material proceeds from Predebon outcrop, São João do Polêsine County, Rio Grande do Sul State, that corresponds to the higher portion of the Alemoa Member, Santa Maria Formation. The footprints occur in sandstone lenses. The ichnofossils were identified as dinosaur footprints indet. and as Grallator ? sp. The footprints should correspond to undertracks, since many superficial characteristics are absent, so that the differences between the footprints could correspond to preservational factors. On the basis of morphologic and stratigraphic criteria, the footprints can be attributed to basal dinosaurs. Some dinosaurs known for the Brazilian Triassic, such as Staurikosaurus , Saturnalia, and Sacisaurus, could be the producers of these footprints. The occurrences of dinosaur footprints of the Predebon outcrop correspond to the oldest ones of Brazil , and moreover, they are compatible with the known paleofauna of Alemoa-Caturrita sequence.
Da Silva, R.C., Carvalho, I., and A.C.S. Fernandes. 2009. Dinosaur footprints from the Triassic (Santa Maria Formation) of Brazil. Ameghiniana 45: 783-790.
Abstract. Dinosaur footprints in Jurassic and Cretaceous rocks are common in Brazil , but there are only a few records from Triassic. In Rio Grande do Sul State , tridactyl medium size footprints were found in Carnian rocks. The material proceeds from Predebon outcrop, São João do Polêsine County, Rio Grande do Sul State, that corresponds to the higher portion of the Alemoa Member, Santa Maria Formation. The footprints occur in sandstone lenses. The ichnofossils were identified as dinosaur footprints indet. and as Grallator ? sp. The footprints should correspond to undertracks, since many superficial characteristics are absent, so that the differences between the footprints could correspond to preservational factors. On the basis of morphologic and stratigraphic criteria, the footprints can be attributed to basal dinosaurs. Some dinosaurs known for the Brazilian Triassic, such as Staurikosaurus , Saturnalia, and Sacisaurus, could be the producers of these footprints. The occurrences of dinosaur footprints of the Predebon outcrop correspond to the oldest ones of Brazil , and moreover, they are compatible with the known paleofauna of Alemoa-Caturrita sequence.
Sedimentology of Dinosauriform-bearing Triassic Rocks in Poland
I have been away dealing with a personal issue (the sudden passing of my mother), but am taking a much needed break to check messages and such and found this paper in my mailbox (thanks Randy)so I decided to do some therapeutic blogging. It is from last year but provides an important sedimentological and depositional system study of Triassic rocks in Poland which contain the Krasiejow fauna, which is famous for the presence of the dinosauriform Silesaurus opolensis. One of the key aspects of this paper is the support of a Norian age for this fauna rather than a Carnian age as previously supposed. This study removes another "Carnian" record from the record of dinosauriforms demonstrating a global survival of non-dinosaurian dinosauriforms into the Norian (at least in Laurasia)where they were contemporaneous with dinosaurs. This paper also provides evidence that the Krasiejow environment was subtropical and wet, but punctuated with dry periods, thus the climate was monsoonal as has been proposed for the Chinle Formation.
Note: Someone e-mailed me asking about the recent Chinese Jurassic theropod paper. I accidentally deleted your message so please resend.
Gruszka, B. and T. Zielinski. 2008. Evidence for a very low-energy fluvial system: a case study from the dinosaur-bearing Upper Triassic rocks of Southern Poland. Geological Quarterly 52:239-252.
The Upper Triassic succession in S Poland in which dinosaur bones have been found consists predominantly of siltstones and claystones. Three units are distinguished. The lowermost and the upper most units reflect an alluvial environment, whereas the middle one represents lacustrine facies. The lower alluvial unit is interpreted as a record of ephemeral, sinuous, suspended-load channels with rapid vertical accretion. Channel barforms are lacking. The environment is interpreted as a low-energy anastomosing fluvial system. The clayey middle unit is interpreted as having formed in a wide long-lived lake. The top of the lacustrine deposits shows signs of vertisol-type pedogenesis, most probably under subtropical conditions, with seasonally-in duced wet and dry intervals. The upper unit reflects a low-energy meandering river system. Silty point bars were abundant and the channels migrated freely. The energy level of this fluvial system was slightly higher than that of the earlier one, which is interpreted as an effect of base-level lowering in combination with an increasingly humid climate. The almost exclusively silty/clayey alluvial deposits represent an exceptionally rare facies. The drainage basin must have been an extremely flat lowland. The presence of vertebrate bones within the anastomosing and meandering river deposits indicates that low-energy alluvial plains were apparently favourable habitats for both reptiles and amphibians during the Late Triassic: under the subtropical, seasonally dry conditions, the animals must have preferred moist low areas, i.e. the flood basins and abandoned channels on the flat valley floors.
Note: Someone e-mailed me asking about the recent Chinese Jurassic theropod paper. I accidentally deleted your message so please resend.
Gruszka, B. and T. Zielinski. 2008. Evidence for a very low-energy fluvial system: a case study from the dinosaur-bearing Upper Triassic rocks of Southern Poland. Geological Quarterly 52:239-252.
The Upper Triassic succession in S Poland in which dinosaur bones have been found consists predominantly of siltstones and claystones. Three units are distinguished. The lowermost and the upper most units reflect an alluvial environment, whereas the middle one represents lacustrine facies. The lower alluvial unit is interpreted as a record of ephemeral, sinuous, suspended-load channels with rapid vertical accretion. Channel barforms are lacking. The environment is interpreted as a low-energy anastomosing fluvial system. The clayey middle unit is interpreted as having formed in a wide long-lived lake. The top of the lacustrine deposits shows signs of vertisol-type pedogenesis, most probably under subtropical conditions, with seasonally-in duced wet and dry intervals. The upper unit reflects a low-energy meandering river system. Silty point bars were abundant and the channels migrated freely. The energy level of this fluvial system was slightly higher than that of the earlier one, which is interpreted as an effect of base-level lowering in combination with an increasingly humid climate. The almost exclusively silty/clayey alluvial deposits represent an exceptionally rare facies. The drainage basin must have been an extremely flat lowland. The presence of vertebrate bones within the anastomosing and meandering river deposits indicates that low-energy alluvial plains were apparently favourable habitats for both reptiles and amphibians during the Late Triassic: under the subtropical, seasonally dry conditions, the animals must have preferred moist low areas, i.e. the flood basins and abandoned channels on the flat valley floors.
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