Weinbaum, J. C. 2013. Postcranial skeleton of Postosuchus kirkpatricki (Archosauria: Paracrocodylomorpha), from the upper Triassic of the United States. 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/SP379.7
Abstract - Postosuchus kirkpatricki is a Late Triassic (Norian) ‘rauisuchid’ archosaur from North America. The initial description of the Postosuchus type material included elements from two poposaurids. This confusion has prevented adequate description of the material. Recent examination of the type material and other specimens of Postosuchus, and of related taxa, has helped clarify the osteology of Postosuchus. The type specimens represent c. 75% of the skeleton. Together with other referred material, Postosuchus remains one of the most completely known rauisuchids. The paratype skeleton, which is relatively complete, would have been c. 3.5–4 m in length, and the holotype would have been closer to 5–6 m.
Analysis of the postcranial skeleton of Postosuchus suggests that it may have been an obligate biped (based in part on limb proportions, which are similar to some theropod dinosaurs, the size of the manus (30% of the size of the pes) and the highly reduced nature of the digits and vertebral measurements). Possible postcranial autapomorphies of Postosuchus include a large, rugose triangular supra-acetabular buttress confluent with the dorsal margin of the iliac blade, and a symmetrical pes with digits two and three being roughly equal in length.
De Franca, M. A. G., Langer, M. C., and J. Ferigolo. 2013. The skull anatomy of Decuriasuchus quartacolonia (Pseudosuchia: Suchia: Loricata) from the middle Triassic of Brazil. 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, doi:10.1144/SP379.8
Abstract - Unlike most rauisuchians, which are known based on partially preserved specimens, fossils attributed to Decuriasuchus quartacolonia include a monotaxonomic assemblage composed of nine associated individuals (MCN-PV10.105a–i), three with almost complete skulls (MCN-PV10.105a,c,d), and a partial disarticulated skull (MCN-PV10.004) collected in the Middle Triassic (Ladinian, Dinodontosaurus Biozone) beds of the Santa Maria Formation, in south Brazil. Because of its completeness and possible phylogenetic position, as one of the most basal loricatans, D. quartacolonia is a key taxon for anatomic, evolutionary and biomechanical studies of rauisuchians. The comparative description of its osteology reveals that the skull and mandible of D.quartacolonia are very similar to those of cf. Prestosuchus chiniquensis and Saurosuchus galilei, sharing a drop-shaped subnarial fenestra, a subtriangular antorbital fenestra with an elongated and narrow anterior point, a ‘roman nosed’ nasal, and a posteroventrally oriented ridge on the lateral surface of the ventral ramus of the squamosal. Among the differences are the autapomorphies of D.quartacolonia: numerous maxillary teeth (17), lateral expansion of the nasal/lacrimal covering the antorbital fenestra dorsally, and squamosal and quadratojugal forming a subtriangular projection that invades the lower temporal fenestra.
Showing posts with label rauisuchia. Show all posts
Showing posts with label rauisuchia. Show all posts
Paleohistology of Rauisuchid Osteoderms
Yes, I am still in Argentina. I'd planned on posting a little more, especially since I visited Ischigualasto National Park and spent some hours prospecting in the Ischigualasto Formation (it did not disappoint) but I've been up to my eyeballs in aetosaur specimens and trying to keep myself fed (meals take a long time here), so forgive me. Meanwhile here is a paper I've been waiting on for awhile now regarding osteoderm histology of rauisuchids with comparisons to some other archosaur groups as well.
Scheyer, T. M. and J. B. Desojo. 2011. Palaeohistology and external microanatomy of rauisuchian osteoderms (Archosauria: Pseudosuchia). Palaeontology (advance online publication) DOI: 10.1111/j.1475-4983.2011.01098.xhttp://onlinelibrary.wiley.com/doi/10.1111/j.1475-4983.2011.01098.x/abstract
Abstract - The presence of postcranial dermal armour is plesiomorphic for Archosauria. Here, we survey the external microanatomy and histology of postcranial osteoderms (i.e. dorsal paramedian and caudal osteoderms) of rauisuchians, a widely distributed assemblage of extinct predatory pseudosuchians from the Triassic. The osteoderms of eight rauisuchian taxa were found to be rather compact bones, which usually lack significant bone remodelling or large areas of cancellous bone. The presence of highly vascularized woven or fibrolamellar bone tissue deposited in the core areas indicates higher growth rates during earlier life stages, whereas a more compact parallel-fibred bone matrix indicates reduced growth rates in later development. This pattern of change corroborates earlier studies on long bone histology. With the exception of a bone tissue found in the sample of Batrachotomus kupferzellensis, which might be the result of metaplastic ossification, the general mode of skeletogenesis is comparable with intramembraneous ossification. The lack of cancellous bone tissue and remodelling processes associated with bone ornamentation, as well as the predominantly intramembraneous mode of ossification, indicates that rauisuchian osteoderm formation differs profoundly from that of the osteoderms of the only extant pseudosuchian lineage, the crocodylians.
Scheyer, T. M. and J. B. Desojo. 2011. Palaeohistology and external microanatomy of rauisuchian osteoderms (Archosauria: Pseudosuchia). Palaeontology (advance online publication) DOI: 10.1111/j.1475-4983.2011.01098.xhttp://onlinelibrary.wiley.com/doi/10.1111/j.1475-4983.2011.01098.x/abstract
Abstract - The presence of postcranial dermal armour is plesiomorphic for Archosauria. Here, we survey the external microanatomy and histology of postcranial osteoderms (i.e. dorsal paramedian and caudal osteoderms) of rauisuchians, a widely distributed assemblage of extinct predatory pseudosuchians from the Triassic. The osteoderms of eight rauisuchian taxa were found to be rather compact bones, which usually lack significant bone remodelling or large areas of cancellous bone. The presence of highly vascularized woven or fibrolamellar bone tissue deposited in the core areas indicates higher growth rates during earlier life stages, whereas a more compact parallel-fibred bone matrix indicates reduced growth rates in later development. This pattern of change corroborates earlier studies on long bone histology. With the exception of a bone tissue found in the sample of Batrachotomus kupferzellensis, which might be the result of metaplastic ossification, the general mode of skeletogenesis is comparable with intramembraneous ossification. The lack of cancellous bone tissue and remodelling processes associated with bone ornamentation, as well as the predominantly intramembraneous mode of ossification, indicates that rauisuchian osteoderm formation differs profoundly from that of the osteoderms of the only extant pseudosuchian lineage, the crocodylians.
New Postcranial Material of the Rauisuchian Saurosuchus galilei from the Late Triassic of Argentina
Trotteyn, M. J., Desojo, J. B., y O. A. Alcober. 2011. Nuevo material postcraneo de Saurosuchus galilei Reig (Archosauria: Crurotarsi) del Triasico Superior del centrooeste de Argentina. Ameghiniana 48:605 - 620.
Resumen - Saurosuchus galilei Reig es un “rauisúquido” proveniente de la Formación Ischigualasto (Triásico Superior, Carniano), del centrooeste Argentino. En esta contribución se presenta la primera descripción detallada del complejo proatlas-atlas-axis; columna vertebral completa y articulada; y ambas escápulas de este taxón. La morfología general del complejo proatlas-atlas-axis es similar a la de otros “rauisúquidos”. Las vértebras cervicales son comprimidas axialmente y elongadas dorsoventralmente. El complejo atlas-axis y las cervicales, presentan los rasgos típicos de un animal con cuello corto y robusto. En las cervicales y en las dorsales puede observarse una serie de láminas, depresiones interlaminares y depresiones en el cuerpo vertebral que también se han descrito en otros “rauisúquidos”. En las vértebras presacras se observa una quilla ventral y una marcada expansión del extremo dorsal de la espina neural. La serie caudal presenta centros comprimidos axialmente, con un surco ventral orientado anteroposteriormente. La escápula es robusta, la hoja escapular es moderadamente expandida y levemente curvada. La notable diversidad que presentan los “rauisúquidos” en general, hace que sea necesario un análisis profundo para abordar problemáticas morfofuncionales y filogenéticas, con las cuales se espera que contribuya este nuevo material.
Abstract - New postcranial material of Saurosuchus galilei Reig (Archosauria : Crurotarsi) from the Late Triassic of Central-Western Argentina . Saurosuchus galilei Reig is a “rauisuchid” from the Ischigualasto Formation (late Carnian, Late Triassic) located in central-western Argentina. This paper is the first detailed description of the proatlas-atlas-axis complex of this taxon, of a complete and articulated vertebral column, and of both scapulae. Overall morphology of the proatlas-atlas-axis complex is similar to that of other “rauisuchids”. This complex and the post-axial cervical vertebrae show the typical traits of an animal with a short and strong neck. The cervical vertebrae are anteroposteriorly compressed and dorsoventrally elongated. Vertebral laminae, interlaminar depressions, and lateral depressions on the centra are present in the cervical and dorsal vertebrae, as in other “rauisuchids”. The presacral series bears ventrally keeled centra and large transversal expansions of the distal ends of the neural spines. The caudal series shows axially compressed centra with a longitudinal ventral groove. The scapulae are very robust and have a brief expansion and a slightly curved scapular blade. The remarkable diversity of “rauisuchids” in general, makes a detailed analysis necessary in order to approach morphofunctional and phylogenetic problems; this new material is expected to contribute towards the solution of these problems.
Resumen - Saurosuchus galilei Reig es un “rauisúquido” proveniente de la Formación Ischigualasto (Triásico Superior, Carniano), del centrooeste Argentino. En esta contribución se presenta la primera descripción detallada del complejo proatlas-atlas-axis; columna vertebral completa y articulada; y ambas escápulas de este taxón. La morfología general del complejo proatlas-atlas-axis es similar a la de otros “rauisúquidos”. Las vértebras cervicales son comprimidas axialmente y elongadas dorsoventralmente. El complejo atlas-axis y las cervicales, presentan los rasgos típicos de un animal con cuello corto y robusto. En las cervicales y en las dorsales puede observarse una serie de láminas, depresiones interlaminares y depresiones en el cuerpo vertebral que también se han descrito en otros “rauisúquidos”. En las vértebras presacras se observa una quilla ventral y una marcada expansión del extremo dorsal de la espina neural. La serie caudal presenta centros comprimidos axialmente, con un surco ventral orientado anteroposteriormente. La escápula es robusta, la hoja escapular es moderadamente expandida y levemente curvada. La notable diversidad que presentan los “rauisúquidos” en general, hace que sea necesario un análisis profundo para abordar problemáticas morfofuncionales y filogenéticas, con las cuales se espera que contribuya este nuevo material.
Abstract - New postcranial material of Saurosuchus galilei Reig (Archosauria : Crurotarsi) from the Late Triassic of Central-Western Argentina . Saurosuchus galilei Reig is a “rauisuchid” from the Ischigualasto Formation (late Carnian, Late Triassic) located in central-western Argentina. This paper is the first detailed description of the proatlas-atlas-axis complex of this taxon, of a complete and articulated vertebral column, and of both scapulae. Overall morphology of the proatlas-atlas-axis complex is similar to that of other “rauisuchids”. This complex and the post-axial cervical vertebrae show the typical traits of an animal with a short and strong neck. The cervical vertebrae are anteroposteriorly compressed and dorsoventrally elongated. Vertebral laminae, interlaminar depressions, and lateral depressions on the centra are present in the cervical and dorsal vertebrae, as in other “rauisuchids”. The presacral series bears ventrally keeled centra and large transversal expansions of the distal ends of the neural spines. The caudal series shows axially compressed centra with a longitudinal ventral groove. The scapulae are very robust and have a brief expansion and a slightly curved scapular blade. The remarkable diversity of “rauisuchids” in general, makes a detailed analysis necessary in order to approach morphofunctional and phylogenetic problems; this new material is expected to contribute towards the solution of these problems.
Reassessment of the Middle Triassic Rauisuchian Archosaurs Ticinosuchus ferox and Stagonosuchus nyassicus
Note: One error I did find in this paper after a quick glance is that hyposphene-hypantrum vertebral articulations are not restricted to only rauisuchians within pseudosuchians, they are also found in the aetosaur Desmatosuchus spurensis (Parker 2003, 2008). In fact they are very well-developed in that taxon.
Lautenschlager, S. and J. B. Desojo. 2011. Reassessment of the Middle Triassic rauisuchian archosaurs Ticinosuchus ferox and Stagonosuchus nyassicus. Paläontologische Zeitschrift Online First DOI: 10.1007/s12542-011-0105-1
Abstract- The Middle Triassic (Anisian) rauisuchian archosaurs Ticinosuchus ferox and Stagonosuchus nyassicus are two of the earliest representatives of this group and therefore of special importance for our understanding of the evolution and early diversification of Rauisuchia. Both taxa are well preserved and, in the case of the holotype of Ticinosuchus ferox, nearly complete and articulated. However, the original descriptions and recent revisions of the material do not sufficiently cover all aspects of their osteology. We identify new skull elements previously unknown for Ticinosuchus ferox and present new reconstructions of the pectoral and pelvic girdle elements. Vertebral laminae and fossae are described for the first time in both Ticinosuchus ferox and Stagonosuchus nyassicus. Newly recognised character states of Stagonosuchus nyassicus include the presence of additional infraprezygapophyseal and infrapostzygapophyseal laminae in the cervical vertebrae, a hyposphene-hypantrum articulation in the dorsal vertebrae and a fibula with a posteromedial depression. Furthermore, we provide a revised and emended diagnosis for both taxa, including several autapomorphies for Stagonosuchus nyassicus (e.g. a boss-like protuberance on the postacetabular process of the iliac blade and a marked short dorsolateral crest on the proximal ischium). We review the taxonomic status of a further specimen of Ticinosuchus ferox, as well as material related to Stagonosuchus nyassicus from the Manda Beds of Tanzania. Additionally, we discuss the distribution and possible function of rauisuchian characters, such as accessory neural spines in the caudal vertebrae, in these and other rauisuchian taxa.
Lautenschlager, S. and J. B. Desojo. 2011. Reassessment of the Middle Triassic rauisuchian archosaurs Ticinosuchus ferox and Stagonosuchus nyassicus. Paläontologische Zeitschrift Online First DOI: 10.1007/s12542-011-0105-1
Abstract- The Middle Triassic (Anisian) rauisuchian archosaurs Ticinosuchus ferox and Stagonosuchus nyassicus are two of the earliest representatives of this group and therefore of special importance for our understanding of the evolution and early diversification of Rauisuchia. Both taxa are well preserved and, in the case of the holotype of Ticinosuchus ferox, nearly complete and articulated. However, the original descriptions and recent revisions of the material do not sufficiently cover all aspects of their osteology. We identify new skull elements previously unknown for Ticinosuchus ferox and present new reconstructions of the pectoral and pelvic girdle elements. Vertebral laminae and fossae are described for the first time in both Ticinosuchus ferox and Stagonosuchus nyassicus. Newly recognised character states of Stagonosuchus nyassicus include the presence of additional infraprezygapophyseal and infrapostzygapophyseal laminae in the cervical vertebrae, a hyposphene-hypantrum articulation in the dorsal vertebrae and a fibula with a posteromedial depression. Furthermore, we provide a revised and emended diagnosis for both taxa, including several autapomorphies for Stagonosuchus nyassicus (e.g. a boss-like protuberance on the postacetabular process of the iliac blade and a marked short dorsolateral crest on the proximal ischium). We review the taxonomic status of a further specimen of Ticinosuchus ferox, as well as material related to Stagonosuchus nyassicus from the Manda Beds of Tanzania. Additionally, we discuss the distribution and possible function of rauisuchian characters, such as accessory neural spines in the caudal vertebrae, in these and other rauisuchian taxa.
New Triassic Terror: Rauisuchian Packs, New Evidence from the Middle Triassic of Brazil
I'm glad everyone enjoyed my April Fools joke; however, the Triassic is here to stay and especially Triassic vertebrate paleontology because the month of April is going to see the publication of numerous new papers on the subject. In fact, April 2011 has the possibility of being the best month ever for Triassic VP, especially archosaurs. We'll revisit this at the end of the month and see if this is true.
The first paper of April 2011 describes the recovery of nine articulated and associated rauisuchian skeletons from the Middle Triassic of Brazil. They have been assigned to a new Prestosuchus-like taxon named Decuriasuchus quartacolonia ("legion of ten crocodile from Quarta Colonia"). The material looks amazing and finds like this are extremely rare in the Triassic so I hope that a full description of the material will be forthcoming.
The phylogenetic analysis utilizes the dataset of Brusatte et al. (2010) and recovers a paraphyletic "rauisuchidae" with Decuriasuchus nesting with Prestosuchus and Batrachotomus; however, the paper and supplemental materials do discuss problems with the existing dataset and therefore these results should be considered very tentative.
One interesting point of the paper is the potential social implications of finding nine rauisuchians clustered together in a single spot. Franca et al., argue that the taphomomy of the site precludes that this is not a time averaged assemblage and instead it appears that these animals (all adults) congregated for some reason before dying. Whether the group was assembled and killed by a sudden catastrophy (e.g, flash flood) or accumulated and died because of another type of event (e.g., drought) is undeterminable with the current evidence, but in either case this would call for a certain degree of interaction between these predators. Modern crocodilians congregate in large number for various reasons, but mainly for feeding and in some cases have been reported to work together to herd fish. Thus, the circumstantial evidence from this new find may suggest that rauisuchians may also have worked together in some cases for hunting strategies. As stated by Franca et al in their concluding sentence, this would represent "the earliest evidence of possible group behavior among archosaurs". I personally would think that a hunting pack of large rauisuchians would be quite formidable, but then again this Brazilian group appears to have lacked invulnerability. Furthermore this would be extremely difficult to support with the evidence.
Note: The Revueltosaurus bonebed in Petrified Forest National Park is a monotypic assemblage of at least a dozen individuals (all of the same size and situated on a levee adjacent to the river channel).
Franca, M. A. G., Ferigolo, J., and M. C. Langer. 2011. Associated skeletons of a new middle Triassic “Rauisuchia” from Brazil. Naturwissenschaften (online first) DOI: 10.1007/s00114-011-0782-3
Abstract - For more than 30 million years, in early Mesozoic Pangea, “rauisuchian” archosaurs were the apex predators in most terrestrial ecosystems, but their biology and evolutionary history remain poorly understood. We describe a new “rauisuchian” based on ten individuals found in a single locality from the Middle Triassic (Ladinian) Santa Maria Formation of southern Brazil. Nine articulated and associated skeletons were discovered, three of which have nearly complete skulls. Along with sedimentological and taphonomic data, this suggests that those highly successful predators exhibited some kind of intraspecific interaction. Other monotaxic assemblages of Triassic archosaurs are Late Triassic (Norian-Rhaetian) in age, approximately 10 million years younger than the material described here. Indeed, the studied assemblage may represent the earliest evidence of gregariousness among archosaurs, adding to our knowledge on the origin of a behavior pattern typical of extant taxa.
The first paper of April 2011 describes the recovery of nine articulated and associated rauisuchian skeletons from the Middle Triassic of Brazil. They have been assigned to a new Prestosuchus-like taxon named Decuriasuchus quartacolonia ("legion of ten crocodile from Quarta Colonia"). The material looks amazing and finds like this are extremely rare in the Triassic so I hope that a full description of the material will be forthcoming.
The phylogenetic analysis utilizes the dataset of Brusatte et al. (2010) and recovers a paraphyletic "rauisuchidae" with Decuriasuchus nesting with Prestosuchus and Batrachotomus; however, the paper and supplemental materials do discuss problems with the existing dataset and therefore these results should be considered very tentative.
One interesting point of the paper is the potential social implications of finding nine rauisuchians clustered together in a single spot. Franca et al., argue that the taphomomy of the site precludes that this is not a time averaged assemblage and instead it appears that these animals (all adults) congregated for some reason before dying. Whether the group was assembled and killed by a sudden catastrophy (e.g, flash flood) or accumulated and died because of another type of event (e.g., drought) is undeterminable with the current evidence, but in either case this would call for a certain degree of interaction between these predators. Modern crocodilians congregate in large number for various reasons, but mainly for feeding and in some cases have been reported to work together to herd fish. Thus, the circumstantial evidence from this new find may suggest that rauisuchians may also have worked together in some cases for hunting strategies. As stated by Franca et al in their concluding sentence, this would represent "the earliest evidence of possible group behavior among archosaurs". I personally would think that a hunting pack of large rauisuchians would be quite formidable, but then again this Brazilian group appears to have lacked invulnerability. Furthermore this would be extremely difficult to support with the evidence.
Note: The Revueltosaurus bonebed in Petrified Forest National Park is a monotypic assemblage of at least a dozen individuals (all of the same size and situated on a levee adjacent to the river channel).
Franca, M. A. G., Ferigolo, J., and M. C. Langer. 2011. Associated skeletons of a new middle Triassic “Rauisuchia” from Brazil. Naturwissenschaften (online first) DOI: 10.1007/s00114-011-0782-3
Abstract - For more than 30 million years, in early Mesozoic Pangea, “rauisuchian” archosaurs were the apex predators in most terrestrial ecosystems, but their biology and evolutionary history remain poorly understood. We describe a new “rauisuchian” based on ten individuals found in a single locality from the Middle Triassic (Ladinian) Santa Maria Formation of southern Brazil. Nine articulated and associated skeletons were discovered, three of which have nearly complete skulls. Along with sedimentological and taphonomic data, this suggests that those highly successful predators exhibited some kind of intraspecific interaction. Other monotaxic assemblages of Triassic archosaurs are Late Triassic (Norian-Rhaetian) in age, approximately 10 million years younger than the material described here. Indeed, the studied assemblage may represent the earliest evidence of gregariousness among archosaurs, adding to our knowledge on the origin of a behavior pattern typical of extant taxa.
Redescription of the Holotype Skull of the Late Triassic Rauisuchian Postosuchus kirkpatricki
I'm glad to see this out, the long awaited skull description of the rauisuchian Postosuchus kirkpatricki, which was previously only available in M.S. and PhD theses by Johnathan Weinbaum. The holotype skull was originally described by Chatterjee in 1985; however, repreparation of the material, including the removal of much matrix and plaster, has resulted in the determination of many new features. It is an absolutely fantastic skull.
One thing I have always wondered is if P. kirkpatricki was named for the Kirkpatrick family, how come no one ever amended the species name to P. kirkpatrickorum? Although such changes are no longer required by the ICZN, does this still apply to taxa named before the rule change occurred?
Weinbaum, J.C.2011. The skull of Postosuchus kirkpatricki (Archosauria: Paracrocodyliformes) from the Upper Triassic of the United States. PaleoBios 30: (February 18, 2011)
Abstract - The skull of Postosuchus kirkpatricki Chatterjee 1985 is known from the holotype and paratype specimens along with disassociated skull elements from several Triassic localities in the southwestern and eastern United States. Recent preparation of the holotype skull allows for more careful examination of the cranial elements and comparison with related taxa. This description indicates that Postosuchus shares several previously unrecognized synapomorphies with crocodylomorphs, including fossae and foramina in the dermatocranium that are not present in other basal pseudosuchians. The sutural arrangements of the skull of Postosuchus presented in this paper differ considerably from previous descriptions, due in part to the reassignment of what was previously considered the prefrontal to the palpebral bone. Also, further preparation of skull elements revealed morphologies that differ from previous descriptions. This new description also indicates a close relationship with Polonosuchus silesiacus Sulej 2005. The only autapomorphic characters of the skull are a distinct, rounded lateral ridge on the maxilla and a foramen present in a large fossa on the anteromedial surface of the maxilla.
One thing I have always wondered is if P. kirkpatricki was named for the Kirkpatrick family, how come no one ever amended the species name to P. kirkpatrickorum? Although such changes are no longer required by the ICZN, does this still apply to taxa named before the rule change occurred?
Weinbaum, J.C.2011. The skull of Postosuchus kirkpatricki (Archosauria: Paracrocodyliformes) from the Upper Triassic of the United States. PaleoBios 30: (February 18, 2011)
Abstract - The skull of Postosuchus kirkpatricki Chatterjee 1985 is known from the holotype and paratype specimens along with disassociated skull elements from several Triassic localities in the southwestern and eastern United States. Recent preparation of the holotype skull allows for more careful examination of the cranial elements and comparison with related taxa. This description indicates that Postosuchus shares several previously unrecognized synapomorphies with crocodylomorphs, including fossae and foramina in the dermatocranium that are not present in other basal pseudosuchians. The sutural arrangements of the skull of Postosuchus presented in this paper differ considerably from previous descriptions, due in part to the reassignment of what was previously considered the prefrontal to the palpebral bone. Also, further preparation of skull elements revealed morphologies that differ from previous descriptions. This new description also indicates a close relationship with Polonosuchus silesiacus Sulej 2005. The only autapomorphic characters of the skull are a distinct, rounded lateral ridge on the maxilla and a foramen present in a large fossa on the anteromedial surface of the maxilla.
Polonosuchus silesiacus, a New Name for the 'Rauisuchian' Archosaur Teratosaurus silesiacus from the Upper Triassic of Poland
Brusatte, S.L., Butler, R.J., Sulej, T., and G. Niedźwiedzki. 2009. The taxonomy and anatomy of rauisuchian archosaurs from the Late Triassic of Germany and Poland. Acta Palaeontologica Polonica 54: 221–230.
http://app.pan.pl/acta54/app54−221.pdf
Abstract - The German Late Triassic archosaur Teratosaurus suevicus is a historically important taxon, being the first described rauisuchian. Unfortunately the holotype is a single element, a maxilla, which is poorly preserved and incomplete. We redescribe this maxilla and identify a single potential autapomorphy. The fragmentary type specimen complicates attempts to refer additional material to this taxon, and other unassociated archosaur and rauisuchian specimens from the Mittlerer Stubensandstein of Germany cannot be referred to T. suevicus with any degree of confidence. The stratigraphically older T. silesiacus, from the upper Carnian of Poland, is represented by a much more complete and better preserved specimen. Comparison of the maxillae of T. suevicus and T. silesiacus reveals that the two are distinct taxa, contra recent suggestions, but also that they do not share any synapomorphies or a unique combination of characters relative to Postosuchus kirkpatricki and other rauisuchians. Thus, the Polish material must be transferred to a new genus, Polonosuchus gen. nov. Both Polonosuchus and Teratosaurus are very similar to Postosuchus kirkpatricki, and the three taxa are likely closely related.
http://app.pan.pl/acta54/app54−221.pdf
Abstract - The German Late Triassic archosaur Teratosaurus suevicus is a historically important taxon, being the first described rauisuchian. Unfortunately the holotype is a single element, a maxilla, which is poorly preserved and incomplete. We redescribe this maxilla and identify a single potential autapomorphy. The fragmentary type specimen complicates attempts to refer additional material to this taxon, and other unassociated archosaur and rauisuchian specimens from the Mittlerer Stubensandstein of Germany cannot be referred to T. suevicus with any degree of confidence. The stratigraphically older T. silesiacus, from the upper Carnian of Poland, is represented by a much more complete and better preserved specimen. Comparison of the maxillae of T. suevicus and T. silesiacus reveals that the two are distinct taxa, contra recent suggestions, but also that they do not share any synapomorphies or a unique combination of characters relative to Postosuchus kirkpatricki and other rauisuchians. Thus, the Polish material must be transferred to a new genus, Polonosuchus gen. nov. Both Polonosuchus and Teratosaurus are very similar to Postosuchus kirkpatricki, and the three taxa are likely closely related.
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