Wang, W., Li, C., Scheyer, T. M., and Zhao, L. 2019. A new species of Cyamodus (Placodontia, Sauropterygia) from the early Late Triassic of south-west China. Journal of Systematic Palaeontology. Link.
Abstract - The Triassic eastern Tethyan faunas have continued to yield numerous specimens of marine reptile taxa in recent years. Nevertheless, compared with other sauropterygian clades, the diversity of placodonts in these faunas is low, and remains of this group are relatively rare in the fossil assemblages. Here, we report a new cyamodontoid specimen (ZMNH M8820) from the early Late Triassic of Guizhou, south-west China. This specimen is a nearly complete skeleton lacking only the forelimbs. It is distinct from other known Chinese placodonts as it features a large skull with remarkably enlarged supratemporal fenestrae and a small and less regularly arranged carapace. Interestingly, this new specimen resembles the European Cyamodus more than any Chinese cyamodontoid genera, particularly when considering the dentition and other cranial morphology. However, it differs from known Cyamodus species in some cranial features (e.g. epipterygoid fully ossified, posttemporal fenestra large, dentition derived) and the absence of a separate pelvic shield. Furthermore, based on an updated data matrix of placodonts, our phylogenetic results support the affinity of this new Chinese specimen with European Cyamodus species, and a new species, Cyamodus orientalis sp. nov., is erected here. This new material represents the first reported Cyamodus specimen in the world that preserves a three-dimensional skull with an associated postcranial skeleton and it extends the distribution of this genus into the early Carnian of the eastern Tethys. The existence of Cyamodus, a nearshore taxon, in south-west China at this time reveals greater similarity and more rapid intercommunication than previously known between western and eastern Tethyan vertebrate faunas, although the palaeobiogeographical origin and migration history of Cyamodontidae – and of other clades of placodont reptiles – are still obscure due to the scarcity of material from the northern and southern margins of the Palaeotethys.
Showing posts with label Late Triassic. Show all posts
Showing posts with label Late Triassic. Show all posts
New Osteological and Phylogenetic Review of the Triassic Loricatan Prestosuchus chiniquensis from Brazil
Roberto-Da-Silva, L., Müller , R. T., Gallo de França, M. A., Cabreira, S. F., and Dias-Da-Silva, S. 2018. An impressive skeleton of the giant top predator Prestosuchus chiniquensis (Pseudosuchia: Loricata) from the Triassic of Southern Brazil, with phylogenetic remarks. Historical Biology (Early Online).
Abstract - In the present contribution, we aim to present the osteology of ‘ULBRA-PVT-281’, which comprises the best-preserved skeleton of Prestosuchus chiniquensis ever found. ULBRA-PVT-281 combines the morphology of two classic specimens referred to P. chiniquensis, UFRGS-PV-0156-T and UFRGSPV- 0152-T, reunited in a single operational taxonomic unit (OTU) in previous phylogenetic studies. Therefore, the new specimen reinforces the combination of both specimens. We performed a phylogenetic analysis, combining the information of these three specimens plus braincase data from a fourth specimen, UFRGS-PV-0629-T, into a new P. chiniquensis terminal taxon. Moreover, our analysis also included some new taxa potentially related to P. chiniquensis. As a result, we found a topology slightly distinct from previous studies, where Ticinosuchus ferox is the basalmost member of Loricata, which also includes the new combined P. chiniquensis. Our results place P. chiniquensis, Luperosuchus fractus, and Saurosuchus galilei distributed in a pectinate paraphyletic pattern towards Crocodylomorpha. On the other hand, a constrained analysis forcing the monophyly of these taxa demands just a single extra step. Therefore, both scenarios are plausible and agree with the placement of P. chiniquensis within Loricata, whereas T. ferox nests in Loricata only in the unconstrained analysis.
Ichnofossil Assemblages and Paleosols of the Upper Triassic Chinle Formation, South-Eastern Utah
Adding to our understanding of the understudied Chinle Formation fossils of Utah.
Fischer, S. J. and S. T. Hasiotis 2018. Ichnofossil assemblages and palaeosols of the Upper Triassic Chinle Formation, south-eastern Utah (USA): Implications for depositional controls and palaeoclimate.
Annales Societatis Geologorum Poloniae 88(2): 127–162.
Abstract - The Upper Triassic Chinle Formation in the Stevens Canyon area in south-eastern Utah represents fluvial, palustrine, and lacustrine strata deposited in a continental back-arc basin on the western edge of Pangea. Previous investigations interpreted a megamonsoonal climate with increasing aridity for the Colorado Plateau towards the end of the Triassic. In this study, we systematically integrate ichnological and pedological features of the Chinle Formation into ichnopedofacies to interpret palaeoenvironmental and palaeoclimatic variations in the north-eastern part of the Chinle Basin. Seventeen ichnofossil morphotypes and six palaeosol orders are combined into twelve ichnopedofacies, whose development was controlled by autocyclic and allocyclic processes and hydrology. Ichnopedofacies are used to estimate palaeoprecipitation in conjunction with appropriate modern analogue latitudinal and geographic settings. In the north-east Chinle Basin, annual precipitation was ~1100–1300 mm in the Petrified Forest Member. Precipitation levels were >1300 mm/yr at the base of the lower Owl Rock Member, decreased to ~700–1100 mm/yr, and then to ~400–700 mm/yr. Two drying upward cycles from ~1100 mm/yr to ~700 mm/yr occurred in the middle and upper part of the Owl Rock Member. In the overlying Church Rock Member, precipitation decreased from ~400 mm/yr at the base of the unit to ~25–325 mm/yr at the end of Chinle Formation deposition. Ichnopedofacies indicate monsoonal conditions persisted until the end of the Triassic with decreasing precipitation that resulted from the northward migration of Pangea. Ichnopedofacies in the northeast Chinle Basin indicate both long-term drying of climate and short-term, wet-dry fluctuations.
Expanding the Late Triassic Record of the Dinosaur Precursor Dromomeron romeri: A New Record from the Chinle Formation of Arizona.
A new open access paper from my co-worker, friend, and colleague Adam Marsh documenting a new record of the dinosaur precursor Dromomeron romeri from the Chinle Formation Arizona. This further demonstrates the importance of museum collections and apomorphy based identification work to identify stratigraphic, chronologic, and bibliographical extensions, improving our understanding of early dinosaur distributions.
Abstract - The relatively recent discovery and contextualization of silesaurid and lagerpetid dinosauromorphs has led to a revolution in understanding the early evolutionary history of the dinosaurian lineage. Lagerpetids are known from North America and South America in Middle and Upper Triassic rocks, especially the Chinle Formation of New Mexico and the Dockum Group of Texas. Until now, only a single specimen of Dromomeron gregorii was known from the Upper Triassic Chinle Formation of Arizona. However, a new lagerpetid astragalus specimen (MNA V7237) from the Owl Rock Member of the Chinle Formation found on Ward Terrace in the Navajo Nation of Arizona is referred to Dromomeron romeri. MNA V7237 represents the youngest radioisotopically-dated record of Lagerpetidae, indicating that D. romeri persisted throughout the entire Norian (Otischalkian into the Apachean) in North America.
Further Investigating the Biogeographic Origins of Dinosauria
New paper out in Palaeontology.
Marsola, J. C., Ferreira, G. S., Langer, M. C., Button, D. J., and R. J. Butler. 2018. Increases in sampling support the southern Gondwanan hypothesis for the origins of dinosaurs. Palaeontology. Early Online. https://doi.org/10.1111/pala.12411
Abstract - Dinosaurs were ubiquitous in terrestrial ecosystems through most of the Mesozoic and are still diversely represented in the modern fauna in the form of birds. Recent efforts to better understand the origins of the group have resulted in the discovery of many new species of early dinosaur and their closest relatives (dinosauromorphs). In addition, recent re‐examinations of early dinosaur phylogeny have highlighted uncertainties regarding the interrelationships of the main dinosaur lineages (Sauropodomorpha, Theropoda and Ornithischia), and questioned the traditional hypothesis that the group originated in South Gondwana and gradually dispersed over Pangaea. Here, we use an historical approach to examine the impact of new fossil discoveries and changing phylogenetic hypotheses on biogeographical scenarios for dinosaur origins over 20 years of research time, and analyse the results in the light of different fossil record sampling regimes. Our results consistently optimize South Gondwana as the ancestral area for Dinosauria, as well as for more inclusive clades including Dinosauromorpha, and show that this hypothesis is robust to increased taxonomic and geographic sampling and divergent phylogenetic results. Our results do not find any support for the recently proposed Laurasian origin of dinosaurs and suggest that a southern Gondwanan origin is by far the most plausible given our current knowledge of the diversity of early dinosaurs and non‐dinosaurian dinosauromorphs.
Baron, M. G., Norman, D. B. and Barrett, P. M. 2017a. A new hypothesis of dinosaur relationships and early dinosaur evolution. Nature, 543, 501–506.
Baron, M. G., Norman, D. B. and Barrett, P. M. 2017b. Baron et al. reply. Nature, 551, E4–E5.
Marsola, J. C., Ferreira, G. S., Langer, M. C., Button, D. J., and R. J. Butler. 2018. Increases in sampling support the southern Gondwanan hypothesis for the origins of dinosaurs. Palaeontology. Early Online. https://doi.org/10.1111/pala.12411
Abstract - Dinosaurs were ubiquitous in terrestrial ecosystems through most of the Mesozoic and are still diversely represented in the modern fauna in the form of birds. Recent efforts to better understand the origins of the group have resulted in the discovery of many new species of early dinosaur and their closest relatives (dinosauromorphs). In addition, recent re‐examinations of early dinosaur phylogeny have highlighted uncertainties regarding the interrelationships of the main dinosaur lineages (Sauropodomorpha, Theropoda and Ornithischia), and questioned the traditional hypothesis that the group originated in South Gondwana and gradually dispersed over Pangaea. Here, we use an historical approach to examine the impact of new fossil discoveries and changing phylogenetic hypotheses on biogeographical scenarios for dinosaur origins over 20 years of research time, and analyse the results in the light of different fossil record sampling regimes. Our results consistently optimize South Gondwana as the ancestral area for Dinosauria, as well as for more inclusive clades including Dinosauromorpha, and show that this hypothesis is robust to increased taxonomic and geographic sampling and divergent phylogenetic results. Our results do not find any support for the recently proposed Laurasian origin of dinosaurs and suggest that a southern Gondwanan origin is by far the most plausible given our current knowledge of the diversity of early dinosaurs and non‐dinosaurian dinosauromorphs.
An interesting new study out today that uses phylogeny based biogeographical analyses to test the hypothesis of Baron et al. (2017a,b) that stem-dinosaurs originated in Laurasia. Their results reject that hypothesis in favor of the long standing hypothesis of a Gondwanan origin. I couldn't access the supplemental data in Dryad because the article isn't officially out. I'm not suggesting that the conclusions are wrong, but do have a few questions/comments about the data and how specimen sampling issues from Western North America could affect a rerun of the analysis.
1) Some of the separation of taxa into biogeographical bins is confusing. For example most of the Chinle Formation taxa Chindesaurus, Tawa, and Eucoelophysis are shown in green depicting the 'Equatorial Belt' as the ancestral zone, yet taxa from the same formation and localities therein such as Dromomeron gregorii and D. romeri are shown in yellow from the 'Euroamerica' zone. Why are they separated?
2) I am not aware of any Rhaetian occurrences of Eucoelophysis baldwini. This taxon occurs in a couple of quarries from around Ghost Ranch, New Mexico and one of them, the Hayden Quarry, is solidly dated in the middle-late Norian at about 212 Ma (Irmis et al., 2011). There is a purported occurrence (Rinehart et al., 2009) of Eucoelophysis from the Coelophysis Quarry at Ghost Ranch that is most likely Rhaetian in age; however, this occurrence is based on the rejected hypothesis that Eucoelophysis remains a neotheropod dinosaur with the holotype representing a highly weathered individual (Rinehart et al., 2009). This referred specimen is simply another specimen of Coelophysis. Thus all presently known occurrences of Eucoelophysis are Norian in age.
3) Recent fieldwork in the Chinle Formation, especially at Petrified Forest National Park, has recovered a significant amount of early dinosaur material. This includes the earliest known dated neotheropod specimen and early occurrences of dinosauriforms. This material is presently under study. Combined with already published accounts of silesaurids and coelophysids (e.g., Padian, 1986; Parker et al., 2006), these show a robust record of dinosauromorphs in the early-middle Norian of Arizona. Thus a specimen based study using autapomorphy-based identifications would pull Equatorial Laurasian silesaurids and neotheropods down into the early-middle Norian. Also important is a recently mentioned occurrence of Dromomeron gregorii from the Otischalkian Boren Quarry in the Dockum Group of Texas which is older than any of the Chinle Formation occurrences and pulls these occurrences down even further (Lessner et al., 2018).
4) Many of the specimens mentioned above are of interest because they originate from some of the lowest fossil bearing beds in the Chinle Formation, the Blue Mesa Member. To date no diagnostic vertebrate fossils from the Chinle Formation are known from below the middle of the Blue Mesa Member, thus the vertebrate faunas of the lower Chinle (lower Blue Mesa, Mesa Redondo, Shinarump) are unknown. This is significant because these units represent the earliest Norian based on the 'long-Norian' hypothesis (227-208 Ma). Coupled with the Moenkopi/Chinle unconformity much of the well-sampled Triassic of the western U.S. is apparently lacking the Carnian and earliest Norian. This is a bias that should not be ignored. Possible Carnian rocks elsewhere such as the base of the Dockum Group in Texas and units in Wyoming need to be better sampled.
It's difficult to say how these details would affect these early dinosaur biogeographical studies, but there are data out there that should be included in future analyses.
REFERENCES
Baron, M. G., Norman, D. B. and Barrett, P. M. 2017b. Baron et al. reply. Nature, 551, E4–E5.
Irmis, R. B., Mundil, R., Martz, J. W., and W. G. Parker. 2011. High resolution U-Pb ages from the Upper Triassic Chinle Formation (New Mexico, U.S.A.) support a diachronous rise of dinosaurs. Earth and Planetary Science Letters 309:258-267.
Lessner, E. J., Parker, W. G., Marsh, A. D., Nesbitt, S. J., Irmis, R. B. and B. Mueller. 2018. New insights into Late Triassic dinosauromorph-bearing assemblages from Texas using apomorphy-based identifications. PaleoBios, 35.ucmp_paleobios_39960.
Padian, K.. 1986. On the type material of Coelophysis Cope (Saurischia: Theropoda), and a new specimen from the Petrified Forest of Arizona (Late Triassic: Chinle Formation), p. 45-60. In K. Padian (ed.), The beginning of the Age of Dinosaurs: Faunal change across the Triassic-Jurassic boundary. Cambridge University Press, Cambridge.
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.
Rinehart, L. F., Lucas, S. G., Heckert, A. B., Spielmann, J. A., and M. D. Celeskey. 2009. The paleobiology of Coelophysis bauri (Cope) from the Upper Triassic (Apachean) Whitaker Quarry, New Mexico, with detailed analysis of a single quarry block. New Mexico Museum of Natural History and Science Bulletin 45.
New Triassic Vertebrate Papers and the Cold Case of the Phytosaurs
After an almost three year hiatus I am looking to start posting again. Is anyone still out there? Did anyone miss me?
Here are a few new Triassic papers officially out today, all open access. A couple were out as early access, but the new phytosaur phylogeny paper is new today in PeerJ. This represents the bulk of the senior authors dissertation, is an exhaustive analysis of the phytosaurs, and a great exercise in database exploration for a group that has been particularly troublesome to deal with taxonomically and phylogenetically.
Phytosaurs are an incredible group of archosauriforms, common in Late Triassic rocks. Although problematic they serve as a great group for students to learn basic cranial and skeletal anatomy and we use them for this purpose at the Petrified Forest. Numerous and diverse they go extinct at the end of the Triassic and that is a mystery that colleagues such as Randall Irmis from the University of Utah are trying to solve. This research was featured last week on Science Friday.
Jones, A. S., and R. J. Butler. 2018. A new phylogenetic analysis of Phytosauria (Archosauria: Pseudosuchia) with the application of continuous and geometric morphometric character coding. PeerJ 6:e5901 DOI 10.7717/peerj.5901
Marsola, J. C. A., Bittencourt, J. S., Da Rosa, Á. A. S., Martinelli, A. G., Ribeiro, A. M., Ferigolo, J., and M. C. Langer. 2018. New sauropodomorph and cynodont remains from the Late Triassic Sacisaurus site in southern Brazil and its stratigraphic position in the Norian Caturrita Formation. Acta Palaeontologica Polonica 63 (4): 653–669.
Here are a few new Triassic papers officially out today, all open access. A couple were out as early access, but the new phytosaur phylogeny paper is new today in PeerJ. This represents the bulk of the senior authors dissertation, is an exhaustive analysis of the phytosaurs, and a great exercise in database exploration for a group that has been particularly troublesome to deal with taxonomically and phylogenetically.
Phytosaurs are an incredible group of archosauriforms, common in Late Triassic rocks. Although problematic they serve as a great group for students to learn basic cranial and skeletal anatomy and we use them for this purpose at the Petrified Forest. Numerous and diverse they go extinct at the end of the Triassic and that is a mystery that colleagues such as Randall Irmis from the University of Utah are trying to solve. This research was featured last week on Science Friday.
Jones, A. S., and R. J. Butler. 2018. A new phylogenetic analysis of Phytosauria (Archosauria: Pseudosuchia) with the application of continuous and geometric morphometric character coding. PeerJ 6:e5901 DOI 10.7717/peerj.5901
Marsola, J. C. A., Bittencourt, J. S., Da Rosa, Á. A. S., Martinelli, A. G., Ribeiro, A. M., Ferigolo, J., and M. C. Langer. 2018. New sauropodomorph and cynodont remains from the Late Triassic Sacisaurus site in southern Brazil and its stratigraphic position in the Norian Caturrita Formation. Acta Palaeontologica Polonica 63 (4): 653–669.
Niedźwiedzki, G. and E. Budziszewska-Karwowska. 2018. A new occurrence of the Late Triassic archosaur Smok in
southern Poland. Acta Palaeontologica Polonica 68 (4): 703–712.
De Oliveira, T. M., Oliveira, D., Schultz, C. L., Kerber, L., and F. L. Pinheiro. 2018. Tanystropheid archosauromorphs in
the Lower Triassic of Gondwana. Acta Palaeontologica Polonica 63 (4): 713–723.
Reanalysis of the Diapsid Reptile Elachistosuchus huenei from the Late Triassic of Germany
Sobral, G., Sues, H.-D., and J. Müller. 2015. Anatomy of the enigmatic reptile Elachistosuchus
huenei Janensch, 1949 (Reptilia: Diapsida) from the
Upper Triassic of Germany and its relevance for the
origin of Sauria. PLoS ONE 10(9): e0135114.
doi:10.1371/journal.pone.0135114
Abstract - The holotype and only known specimen of the enigmatic small reptile Elachistosuchus huenei Janensch, 1949 from the Upper Triassic (Norian) Arnstadt Formation of Saxony-Anhalt (Germany) is redescribed using μCT scans of the material. This re-examination revealed new information on the morphology of this taxon, including previously unknown parts of the skeleton such as the palate, braincase, and shoulder girdle. Elachistosuchus is diagnosed especially by the presence of the posterolateral process of the frontal, the extension of the maxillary tooth row to the posterior margin of the orbit, the free posterior process of the jugal, and the notched anterior margin of the interclavicle. Phylogenetic analyses using two recently published character-taxon matrices recovered conflicting results for the phylogenetic position of Elachistosuchus–either as an archosauromorph, as a lepidosauromorph or as a more basal, non-saurian diapsid. These different placements highlight the need of a thorough revision of critical taxa and new character sets used for inferring neodiapsid relationships.
Abstract - The holotype and only known specimen of the enigmatic small reptile Elachistosuchus huenei Janensch, 1949 from the Upper Triassic (Norian) Arnstadt Formation of Saxony-Anhalt (Germany) is redescribed using μCT scans of the material. This re-examination revealed new information on the morphology of this taxon, including previously unknown parts of the skeleton such as the palate, braincase, and shoulder girdle. Elachistosuchus is diagnosed especially by the presence of the posterolateral process of the frontal, the extension of the maxillary tooth row to the posterior margin of the orbit, the free posterior process of the jugal, and the notched anterior margin of the interclavicle. Phylogenetic analyses using two recently published character-taxon matrices recovered conflicting results for the phylogenetic position of Elachistosuchus–either as an archosauromorph, as a lepidosauromorph or as a more basal, non-saurian diapsid. These different placements highlight the need of a thorough revision of critical taxa and new character sets used for inferring neodiapsid relationships.
Description of the Ornithosuchid Archosaurian Venaticosuchus rusconii from the Late Triassic of Argentina and the Phylogeny of the Ornithosuchidae
Von Baczko, M. B., Desojo, J. B., and D. Pol. 2014. Anatomy and phylogenetic position of Venaticosuchus rusconii Bonaparte, 1970 (Archosauria, Pseudosuchia), from the Ischigualasto Formation (Late Triassic), La Rioja, Argentina. Journal of Vertebrate Paleontology 34:1342-1356 DOI:10.1080/02724634.2014.860150
Abstract - Ornithosuchidae is a group of Late Triassic pseudosuchian archosaurs of controversial phylogenetic affinities. This clade currently comprises three taxa: Venaticosuchus rusconii and Riojasuchus tenuisceps, both from Argentina, and Ornithosuchus longidens, from Scotland. V. rusconii was erected on the basis of an incomplete skull with articulated lower jaws and some elements of the postcranium that are currently lost. Venaticosuchus rusconii is redescribed here and included for the first time in a phylogenetic analysis to test its affinities with ornithosuchids. The bizarre morphology of V. rusconii has a unique combination of traits that distinguishes it from the other ornithosuchids, such as basipterygoid processes directed ventrally, dentary with the dorsal margin of the anterior end dorsally expanded, articular without a foramen on its medial side, and the absence of a surangular foramen, corroborating the validity of this taxon. V. rusconii is recovered as an ornithosuchid more closely related to R. tenuisceps than to O. longidens, based on the presence of a nearly pointed anterior margin of the antorbital fenestra, and a vertical bony strut of the jugal that separates the antorbital fenestra from the infratemporal fenestra.
Abstract - Ornithosuchidae is a group of Late Triassic pseudosuchian archosaurs of controversial phylogenetic affinities. This clade currently comprises three taxa: Venaticosuchus rusconii and Riojasuchus tenuisceps, both from Argentina, and Ornithosuchus longidens, from Scotland. V. rusconii was erected on the basis of an incomplete skull with articulated lower jaws and some elements of the postcranium that are currently lost. Venaticosuchus rusconii is redescribed here and included for the first time in a phylogenetic analysis to test its affinities with ornithosuchids. The bizarre morphology of V. rusconii has a unique combination of traits that distinguishes it from the other ornithosuchids, such as basipterygoid processes directed ventrally, dentary with the dorsal margin of the anterior end dorsally expanded, articular without a foramen on its medial side, and the absence of a surangular foramen, corroborating the validity of this taxon. V. rusconii is recovered as an ornithosuchid more closely related to R. tenuisceps than to O. longidens, based on the presence of a nearly pointed anterior margin of the antorbital fenestra, and a vertical bony strut of the jugal that separates the antorbital fenestra from the infratemporal fenestra.
Principal Features of the Mammalian Nasal Cavity were Present in Triassic Eucynodonts
Ruf, I., Maier, W., Rodrigues, P. G., and C. L. Schultz. 2014. Nasal Anatomy of the Non-mammaliaform Cynodont Brasilitherium riograndensis (Eucynodontia, Therapsida) Reveals New Insight into Mammalian Evolution. The Anatomical Record 297: 2018–2030. DOI: 10.1002/ar.23022
Abstract - The mammalian nasal cavity is characterized by a unique anatomy with complex internal features. The evolution of turbinals was correlated with endothermic and macrosmatic adaptations in therapsids and in early mammals, which is still apparent in their twofold function (warming and moistening of air, olfaction). Fossil evidence for the transformation from the nonmammalian to the mammalian nasal cavity pattern has been poor and inadequate. Ossification of the cartilaginous nasal capsule and turbinals seems to be a feature that occurred only very late in synapsid evolution but delicate ethmoidal bones are rarely preserved. Here we provide the first µCT investigation of the nasal cavity of the advanced non-mammaliaform cynodont Brasilitherium riograndensis from the Late Triassic of Southern Brazil, a member of the sister-group of mammaliaforms, in order to elucidate a critical anatomical transition in early mammalian evolution. Brasilitherium riograndensis already had at least partially ossified turbinals as remnants of the nasoturbinal and the first ethmoturbinal are preserved. The posterior nasal septum is partly ossified and contributes to a mesethmoid. The nasal cavity is posteriorly expanded and forms a distinctive pars posterior (ethmoidal recess) that is ventrally separated from the nasopharyngeal duct by a distinct lamina terminalis. Thus, our observations clearly demonstrate that principal features of the mammalian nasal cavity were already present in the sister-group of mammaliaforms.
Abstract - The mammalian nasal cavity is characterized by a unique anatomy with complex internal features. The evolution of turbinals was correlated with endothermic and macrosmatic adaptations in therapsids and in early mammals, which is still apparent in their twofold function (warming and moistening of air, olfaction). Fossil evidence for the transformation from the nonmammalian to the mammalian nasal cavity pattern has been poor and inadequate. Ossification of the cartilaginous nasal capsule and turbinals seems to be a feature that occurred only very late in synapsid evolution but delicate ethmoidal bones are rarely preserved. Here we provide the first µCT investigation of the nasal cavity of the advanced non-mammaliaform cynodont Brasilitherium riograndensis from the Late Triassic of Southern Brazil, a member of the sister-group of mammaliaforms, in order to elucidate a critical anatomical transition in early mammalian evolution. Brasilitherium riograndensis already had at least partially ossified turbinals as remnants of the nasoturbinal and the first ethmoturbinal are preserved. The posterior nasal septum is partly ossified and contributes to a mesethmoid. The nasal cavity is posteriorly expanded and forms a distinctive pars posterior (ethmoidal recess) that is ventrally separated from the nasopharyngeal duct by a distinct lamina terminalis. Thus, our observations clearly demonstrate that principal features of the mammalian nasal cavity were already present in the sister-group of mammaliaforms.
Triassic Period: Reptiles Rule. Video from the Discovery Channel.
I assume this is supposed to be the southwest U.S. during the Late Triassic, but there is a hodge-podge of animals from different ages. Still pretty cool though; however, I wish the aetosaur and photosaur were on the scene a little longer, and where is the ubiquitous Postosuchus?
http://www.discovery.com/video-topics/other/dinosaur-videos/triassic-period-reptiles-rule.htm
http://www.discovery.com/video-topics/other/dinosaur-videos/triassic-period-reptiles-rule.htm
Large Body Size in Non-dinosaurian Dinosauromorphs - Evidence from a Large Silesaurid from Late Triassic of Tanzania
Barrett, P. M., Nesbitt, S. J., and B. R. Peecook. 2014. A large-bodied silesaurid from the Lifua Member of the Manda beds (Middle Triassic) of Tanzania and its implications for body-size evolution in Dinosauromorpha. Gondwana Research (accepted manuscript). http://dx.doi.org/10.1016/j.gr.2013.12.015
Abstract - Many dinosaur lineages were characterised by wide ranges of body-size, ranging from taxa that were <1 m in length to the largest of all terrestrial vertebrates. On the other hand, the closest relatives of dinosaurs, the non-dinosaurian dinosauromorphs, such as Marasuchus and lagerpetids, were small-bodied animals with little variation in body-size. Here, we describe a partial femur of an unexpectedly large-bodied silesaurid (non-dinosaurian dinosauriform) from the Lifua Member of the Manda beds (?late Anisian) from southwestern Tanzania. This specimen (NHMUK R16303) is estimated to have had a femoral length of approximately 345 mm, which exceeds that of many Triassic and Lower Jurassic dinosaurs, and is either a large individual of the contemporary Asilisaurus kongwe or represents a new and otherwise unknown silesaurid taxon. In either case, it shows that body-size increases were more prevalent among early dinosauromorphs than realised previously. Moreover, silesaurid size increase occurred in parallel with that in early dinosaurs, alongside the convergent acquisition of other features related to locomotion and herbivory. However, Late Triassic faunas including large-bodied sauropodomorph and theropod dinosaurs lack similarly-sized non-dinosaurian dinosauromorphs, whereas the Lifua Member fauna includes both a large silesaurid and the early ?dinosaur Nyasasaurus, which overlapped in size.
Abstract - Many dinosaur lineages were characterised by wide ranges of body-size, ranging from taxa that were <1 m in length to the largest of all terrestrial vertebrates. On the other hand, the closest relatives of dinosaurs, the non-dinosaurian dinosauromorphs, such as Marasuchus and lagerpetids, were small-bodied animals with little variation in body-size. Here, we describe a partial femur of an unexpectedly large-bodied silesaurid (non-dinosaurian dinosauriform) from the Lifua Member of the Manda beds (?late Anisian) from southwestern Tanzania. This specimen (NHMUK R16303) is estimated to have had a femoral length of approximately 345 mm, which exceeds that of many Triassic and Lower Jurassic dinosaurs, and is either a large individual of the contemporary Asilisaurus kongwe or represents a new and otherwise unknown silesaurid taxon. In either case, it shows that body-size increases were more prevalent among early dinosauromorphs than realised previously. Moreover, silesaurid size increase occurred in parallel with that in early dinosaurs, alongside the convergent acquisition of other features related to locomotion and herbivory. However, Late Triassic faunas including large-bodied sauropodomorph and theropod dinosaurs lack similarly-sized non-dinosaurian dinosauromorphs, whereas the Lifua Member fauna includes both a large silesaurid and the early ?dinosaur Nyasasaurus, which overlapped in size.
Redescription of "Paleorhinus" (Phytosauria) Specimens from Germany
Butler, R. J., Rauhut, O. W. M., Stocker, M. R., and R. Bronowicz. 2013. Redescription of the phytosaurs Paleorhinus (‘Francosuchus’) angustifrons and Ebrachosuchus neukami from Germany, with implications for Late Triassic biochronology. Zoological Journal of the Linnean Society Early View. DOI: 10.1111/zoj.12094
Abstract - Phytosaurs are a diverse and morphologically distinctive clade of superficially crocodile-like archosauriforms that had a near global distribution during the Late Triassic. Because their remains are among the most abundant vertebrate remains recovered in many Upper Triassic terrestrial formations, phytosaurs are used extensively in long-range biochronological and biostratigraphic correlations. The biochronologically oldest and earliest branching known phytosaurs include an array of nominal species from the early Late Triassic of the United States, Germany, Poland, Morocco, and India that have been synonymized within the genus Paleorhinus, and subsequently used to define a global ‘Paleorhinus biochron’. However, recent phylogenetic work suggested that the North American species previously referred to Paleorhinus are paraphyletic. Here, we reassess the systematics and anatomy of putative specimens of Paleorhinus from southern Germany. Two well-preserved basal phytosaur skulls from the Blasensandstein (Carnian) of Bavaria form the holotypes of Francosuchus angustifrons and Ebrachosuchus neukami, both of which were synonymized with Paleorhinus by previous workers. We demonstrate that Francosuchus angustifrons shares unique synapomorphies with specimens referred to Paleorhinus bransoni from the Late Triassic of Texas, and thus refer the species to Paleorhinus. By contrast, the longirostrine Ebrachosuchus is highly distinctive in morphology, and our new cladistic analysis of Phytosauria demonstrates that it represents a valid taxon that is more closely related to Phytosauridae than to Paleorhinus. We provide the first autapomorphy-based support for a monophyletic but restricted Paleorhinus (supported by a nodal row on the jugal, and low paired ridges on the squamosal) and confirm that previous broader conceptions of Paleorhinus are likely to be paraphyletic.
Abstract - Phytosaurs are a diverse and morphologically distinctive clade of superficially crocodile-like archosauriforms that had a near global distribution during the Late Triassic. Because their remains are among the most abundant vertebrate remains recovered in many Upper Triassic terrestrial formations, phytosaurs are used extensively in long-range biochronological and biostratigraphic correlations. The biochronologically oldest and earliest branching known phytosaurs include an array of nominal species from the early Late Triassic of the United States, Germany, Poland, Morocco, and India that have been synonymized within the genus Paleorhinus, and subsequently used to define a global ‘Paleorhinus biochron’. However, recent phylogenetic work suggested that the North American species previously referred to Paleorhinus are paraphyletic. Here, we reassess the systematics and anatomy of putative specimens of Paleorhinus from southern Germany. Two well-preserved basal phytosaur skulls from the Blasensandstein (Carnian) of Bavaria form the holotypes of Francosuchus angustifrons and Ebrachosuchus neukami, both of which were synonymized with Paleorhinus by previous workers. We demonstrate that Francosuchus angustifrons shares unique synapomorphies with specimens referred to Paleorhinus bransoni from the Late Triassic of Texas, and thus refer the species to Paleorhinus. By contrast, the longirostrine Ebrachosuchus is highly distinctive in morphology, and our new cladistic analysis of Phytosauria demonstrates that it represents a valid taxon that is more closely related to Phytosauridae than to Paleorhinus. We provide the first autapomorphy-based support for a monophyletic but restricted Paleorhinus (supported by a nodal row on the jugal, and low paired ridges on the squamosal) and confirm that previous broader conceptions of Paleorhinus are likely to be paraphyletic.
Mammal-like Tooth from the Upper Triassic of Poland
Świło, M., Niedźwiedzki, G., and T. Sulej. 2013. Mammal-like tooth from the Upper Triassic of Poland. Acta Palaeontologica Polonica Accepted Manuscript doi:http://dx.doi.org/10.4202/
Abstract - Triassic discoveries have extended the record of near-mammals (Mammaliaformes) back to the Norian, about 215 Ma, and reveal a significant diversity of Late Triassic (Norian-Rhaetian) forms. We now add to this Late Triassic diversity a nearly complete double-rooted right lower molariform tooth (ZPAL V.33/734) from the Polish Upper Triassic that is significant because it comes from uppermost Norian–lower Rhaetian rocks and is the first discovery of a mammal-like tooth in the Mesozoic of Poland. The described tooth shows transitional dental morphology between advanced cynodonts and mammaliaforms and it appears to represent a basal mammaliaform (Hallautherium genus), probably belonging to Morganucodonta.
Abstract - Triassic discoveries have extended the record of near-mammals (Mammaliaformes) back to the Norian, about 215 Ma, and reveal a significant diversity of Late Triassic (Norian-Rhaetian) forms. We now add to this Late Triassic diversity a nearly complete double-rooted right lower molariform tooth (ZPAL V.33/734) from the Polish Upper Triassic that is significant because it comes from uppermost Norian–lower Rhaetian rocks and is the first discovery of a mammal-like tooth in the Mesozoic of Poland. The described tooth shows transitional dental morphology between advanced cynodonts and mammaliaforms and it appears to represent a basal mammaliaform (Hallautherium genus), probably belonging to Morganucodonta.
Ignotosaurus fragilis, a New Silesaurid Dinosauriform from the Late Triassic of Argentina and the Vertebrate Succession of the Ischigualasto Formation
Martínez, R. N., Apaldetti, C., Alcober, O. A., Colombi, C. E., Sereno, P. C., Fernandez, E., Santi Malnis, P., Correa, G. A., and D. Abelin. 2013. Vertebrate succession in the Ischigualasto
Formation, Journal of Vertebrate Paleontology, 32:sup1, 10-30, DOI: 10.1080/02724634.2013.818546
Abstract - The Upper Triassic (Carnian–Norian) Ischigualasto Formation has yielded a diverse vertebrate fauna that records the initial phase of dinosaur evolution. Radioisotopic dates from ash layers within the formation provide a chronostratigraphic framework, and stratigraphic and sedimetological studies have subdivided the formation into four members and three abundance-based biozones. We describe two new basal dinosauromorphs, an unnamed lagerpetid and a new silesaurid, Ignotosaurus fragilis, gen. et sp. nov., which increase to 29 the number of vertebrates in the Ischigualasto fauna. We provide a census of 848 fossil specimens representing 26 vertebrate taxa logged to stratigraphic intervals of 50 m. This temporally calibrated census shows that abundance and taxonomic diversity within the Ischigualasto Formation does not change suddenly but rather appears to gradually decline in response to climatic deterioration. The only abrupt shift in faunal composition occurs at the end of the second of three biozones, when the abundant cynodont Exaeretodon is replaced by the rare dicynodont Jachaleria.
Formation, Journal of Vertebrate Paleontology, 32:sup1, 10-30, DOI: 10.1080/02724634.2013.818546
Abstract - The Upper Triassic (Carnian–Norian) Ischigualasto Formation has yielded a diverse vertebrate fauna that records the initial phase of dinosaur evolution. Radioisotopic dates from ash layers within the formation provide a chronostratigraphic framework, and stratigraphic and sedimetological studies have subdivided the formation into four members and three abundance-based biozones. We describe two new basal dinosauromorphs, an unnamed lagerpetid and a new silesaurid, Ignotosaurus fragilis, gen. et sp. nov., which increase to 29 the number of vertebrates in the Ischigualasto fauna. We provide a census of 848 fossil specimens representing 26 vertebrate taxa logged to stratigraphic intervals of 50 m. This temporally calibrated census shows that abundance and taxonomic diversity within the Ischigualasto Formation does not change suddenly but rather appears to gradually decline in response to climatic deterioration. The only abrupt shift in faunal composition occurs at the end of the second of three biozones, when the abundant cynodont Exaeretodon is replaced by the rare dicynodont Jachaleria.
New Information on the Temnospondyl Calamops paludosus from the Upper Triassic of Pennsylvania
Sues, H.-D., and R. R. Schoch. 2013. Anatomy and phylogenetic relationships of Calamops paludosus (Temnospondyli, Stereospondyli) from the Triassic of the Newark Basin, Pennsylvania. Journal of Vertebrate Paleontology 33:1061-1070. DOI:10.1080/02724634.2013.759120
Abstract - The holotype of the large temnospondyl Calamops paludosus is the oldest known tetrapod fossil from the Triassic of the Newark basin in Pennsylvania. Although it is usually placed in Metoposauridae, its affinities have remained unknown since its original description because the unique specimen had never been prepared. Preparation and casting of the specimen, which comprises three pieces of a left mandibular ramus, now permits detailed anatomical description of the jaw and assessment of its affinities. Calamops paludosus is a valid taxon of trematosauroid temnospondyls that can be diagnosed by several autapomorphies. It represents one of the geologically youngest known records of long-snouted trematosaurs and the first record of these temnospondyls from the Late Triassic of North America.
Postcranial Anatomy and Phylogenetic Relationships of the Sauropodomorph Mussaurus patagonicus
Otero, A. and D. Pol. 2013. Postcranial anatomy and phylogenetic relationships of Mussaurus patagonicus (Dinosauria: Sauropodomorpha). Journal of Vertebrate Paleontology 33:1138-1168.
Abstract - The transition from basal sauropodomorphs to sauropods is one of the most dramatic evolutionary transformations in the history of dinosaurs. Constituent taxa of this transition were recorded mainly in South Africa and South America, and to a lesser extent in North America. We describe here the postcranial anatomy of four specimens of basal sauropodomorphs from the Late Triassic of Patagonia, Argentina, and identify them as adult individuals of Mussaurus patagonicus. The material is composed of one subadult and three adult specimens and was originally identified as Plateosaurus. The completeness of the material provides more complete knowledge of this taxon and allows us to introduce aspects of basal sauropodomorph anatomy that were poorly understood until now, such as the configuration and arrangement of the distal carpal elements. The phylogenetic relationships of Mussaurus patagonicus are tested through a cladistic analysis of basal sauropodomorphs based on the anatomy of these specimens rather than on the post-hatchling and juvenile specimens previously known for this taxon. Mussaurus is recovered as a non-sauropod anchisaurian, being the sister group of Aardonyx plus more derived sauropodomorphs and is depicted outside the ‘quadrupedal clade,’ given the presence of plesiomorphic features such as a humerus/femur ratio <0.8, a curved femoral shaft in lateral view, and a nearly circular femoral midshaft cross-section. Mussaurus patagonicus adds new and valuable information that helps to clarify the core of the basal sauropodomorph-sauropod transition.
Abstract - The transition from basal sauropodomorphs to sauropods is one of the most dramatic evolutionary transformations in the history of dinosaurs. Constituent taxa of this transition were recorded mainly in South Africa and South America, and to a lesser extent in North America. We describe here the postcranial anatomy of four specimens of basal sauropodomorphs from the Late Triassic of Patagonia, Argentina, and identify them as adult individuals of Mussaurus patagonicus. The material is composed of one subadult and three adult specimens and was originally identified as Plateosaurus. The completeness of the material provides more complete knowledge of this taxon and allows us to introduce aspects of basal sauropodomorph anatomy that were poorly understood until now, such as the configuration and arrangement of the distal carpal elements. The phylogenetic relationships of Mussaurus patagonicus are tested through a cladistic analysis of basal sauropodomorphs based on the anatomy of these specimens rather than on the post-hatchling and juvenile specimens previously known for this taxon. Mussaurus is recovered as a non-sauropod anchisaurian, being the sister group of Aardonyx plus more derived sauropodomorphs and is depicted outside the ‘quadrupedal clade,’ given the presence of plesiomorphic features such as a humerus/femur ratio <0.8, a curved femoral shaft in lateral view, and a nearly circular femoral midshaft cross-section. Mussaurus patagonicus adds new and valuable information that helps to clarify the core of the basal sauropodomorph-sauropod transition.
Paleoenvironmental Interpretation of a Fossil Locality from the Late Triassic of Germany
Havlik, P., Aiglstorfer, M., Atfy, Haytham, E. and D. Uhl, Dieter. 2013. A peculiar bonebed from the Norian Stubensandstein (Löwenstein Formation, Late Triassic) of southern Germany and its palaeoenvironmental interpretation. Neues Jahrbuch für Geologie und Paläontologie, Abhandlungen 269 : 321-337
DOI: http://dx.doi.org/10.1127/
Abstract - Despite the abundance of Triassic outcrops in S Germany knowledge about continental ecosystems from the Norian is rather scarce so far for this region. A new fossil-bearing site from the Lower Löwenstein Formation (Unterer Stubensandstein; Norian) of north-eastern Baden-Württemberg (SW Germany), discovered in 2011, yielded disarticulated vertebrate remains together with a moderately diverse palynoflora, ichnofossils and gymnospermous charcoal. These remains are accumulated in a bonebed layer. Palynomorphs support a Late Triassic age of the source sediment, showing a high diversity of conifers. The new site provides the second conclusive evidence for wildfires in the Norian of Europe and the first record of phytosaurs from Schwäbisch Gmünd. Based on sedimentological evidence and taphonomical interpretations of the charcoal remains, it seems possible that the bonebed can be regarded as the result of increased erosion following catastrophic wildfire.
DOI: http://dx.doi.org/10.1127/
Abstract - Despite the abundance of Triassic outcrops in S Germany knowledge about continental ecosystems from the Norian is rather scarce so far for this region. A new fossil-bearing site from the Lower Löwenstein Formation (Unterer Stubensandstein; Norian) of north-eastern Baden-Württemberg (SW Germany), discovered in 2011, yielded disarticulated vertebrate remains together with a moderately diverse palynoflora, ichnofossils and gymnospermous charcoal. These remains are accumulated in a bonebed layer. Palynomorphs support a Late Triassic age of the source sediment, showing a high diversity of conifers. The new site provides the second conclusive evidence for wildfires in the Norian of Europe and the first record of phytosaurs from Schwäbisch Gmünd. Based on sedimentological evidence and taphonomical interpretations of the charcoal remains, it seems possible that the bonebed can be regarded as the result of increased erosion following catastrophic wildfire.
Halticosaurus orbitoangulatus is a Pseudosuchian, Not a Dinosaur
Brian Switek has the details regarding this new study at his blog Laelaps.
Sues, H.-D., and R. R. Schoch. 2013. Reassessment of cf. Halticosaurus orbitoangulatus from the Upper Triassic (Norian) of Germany – a pseudosuchian, not a dinosaur. Zoological Journal of the Linnean Society 168(4): 859–872 DOI: 10.1111/zoj.12038
Abstract - The holotype of cf. Halticosaurus orbitoangulatus Huene, 1932, comprises an incomplete and macerated but associated skull of an archosaurian reptile from the middle (second) Stubensandstein (middle Löwenstein Formation; Upper Triassic: Norian) of Baden-Württemberg, Germany. It was originally interpreted as a theropod dinosaur but more recently it has been suggested that this taxon has crocodylomorph affinities. Detailed preparation of the holotype of cf. H. orbitoangulatus has revealed much new anatomical information and permitted reassessment of its affinities. The maxilla lacks both a distinct antorbital fossa and a medial bony lamina bordering the antorbital fenestra. The lateral surface of the dentary bears a pronounced horizontal ridge. The squamosal differs from that of basal crocodylomorphs in being L-shaped rather than arcuate in dorsal view, lacking a dorsolateral overhang, and lacking an interlocking contact with the paroccipital process as, for example, in the basal crocodylomorph Saltoposuchus connectens from the same horizon and locality. Phylogenetic analysis placed cf. H. orbitoangulatus amongst loricatan pseudosuchians (but not amongst Crocodylomorpha) rather than amongst theropod dinosaurs. The holotype of cf. H. orbitoangulatus represents a previously unrecognized taxon of loricatan pseudosuchian, which is here named Apatosuchus orbitoangulatus and set apart from other known Norian-age non-crocodylomorph loricatans by its apparently much smaller size.
Sues, H.-D., and R. R. Schoch. 2013. Reassessment of cf. Halticosaurus orbitoangulatus from the Upper Triassic (Norian) of Germany – a pseudosuchian, not a dinosaur. Zoological Journal of the Linnean Society 168(4): 859–872 DOI: 10.1111/zoj.12038
Abstract - The holotype of cf. Halticosaurus orbitoangulatus Huene, 1932, comprises an incomplete and macerated but associated skull of an archosaurian reptile from the middle (second) Stubensandstein (middle Löwenstein Formation; Upper Triassic: Norian) of Baden-Württemberg, Germany. It was originally interpreted as a theropod dinosaur but more recently it has been suggested that this taxon has crocodylomorph affinities. Detailed preparation of the holotype of cf. H. orbitoangulatus has revealed much new anatomical information and permitted reassessment of its affinities. The maxilla lacks both a distinct antorbital fossa and a medial bony lamina bordering the antorbital fenestra. The lateral surface of the dentary bears a pronounced horizontal ridge. The squamosal differs from that of basal crocodylomorphs in being L-shaped rather than arcuate in dorsal view, lacking a dorsolateral overhang, and lacking an interlocking contact with the paroccipital process as, for example, in the basal crocodylomorph Saltoposuchus connectens from the same horizon and locality. Phylogenetic analysis placed cf. H. orbitoangulatus amongst loricatan pseudosuchians (but not amongst Crocodylomorpha) rather than amongst theropod dinosaurs. The holotype of cf. H. orbitoangulatus represents a previously unrecognized taxon of loricatan pseudosuchian, which is here named Apatosuchus orbitoangulatus and set apart from other known Norian-age non-crocodylomorph loricatans by its apparently much smaller size.
"Francosuchus" trauthi is Not a Phytosaur - Implications for Late Triassic Global Vertebrate Biostratigraphy
This eliminates the marine tie for the Otischalkian Land Vertebrate Faunachron, although the identification of this specimen as 'Paleorhinus' was already pretty weak as argued by Irmis et al. (2010).
Butler, R. J., 2013. ‘Francosuchus’ trauthi is not Paleorhinus: implications for Late Triassic
vertebrate biostratigraphy, Journal of Vertebrate Paleontology, 33:858-864.
Abstract - A rostrum fragment from the marginal marine upper Lunz Formation of Austria (early Late Triassic: late Carnian) was previously identified as a new species of phytosaurian archosauriform, ‘Francosuchus’ trauthi. ‘Francosuchus’ trauthi was subsequently synonymized with the non-phytosaurid phytosaur Paleorhinus, and this synonymy was used as evidence to correlate the ‘Paleorhinus biochron’ and the Otischalkian land-vertebrate faunachron to the marine timescale. Here, I provide a redescription of ‘Francosuchus’ trauthi and document anatomical features that differ substantially from all known species of non-phytosaurid phytosaur. There is no evidence to support synonymy of ‘Francosuchus’ trauthi with Paleorhinus, and no unambiguous features to support a phytosaurian identification. However, ‘Francosuchus’ trauthi possesses a unique combination of characters that distinguish it from all other Triassic tetrapods, and necessitates referral of the species to a new genus, Dolerosaurus, gen. nov. Rejection of the proposed synonymy between ‘Francosuchus’ trauthi and Paleorhinus means that the ‘Paleorhinus biochron’ cannot be tied to the marine late Carnian as previously suggested, and provides further evidence of the problems inherent in attempting to correlate the terrestrial Triassic to the marine timescale.
Butler, R. J., 2013. ‘Francosuchus’ trauthi is not Paleorhinus: implications for Late Triassic
vertebrate biostratigraphy, Journal of Vertebrate Paleontology, 33:858-864.
Abstract - A rostrum fragment from the marginal marine upper Lunz Formation of Austria (early Late Triassic: late Carnian) was previously identified as a new species of phytosaurian archosauriform, ‘Francosuchus’ trauthi. ‘Francosuchus’ trauthi was subsequently synonymized with the non-phytosaurid phytosaur Paleorhinus, and this synonymy was used as evidence to correlate the ‘Paleorhinus biochron’ and the Otischalkian land-vertebrate faunachron to the marine timescale. Here, I provide a redescription of ‘Francosuchus’ trauthi and document anatomical features that differ substantially from all known species of non-phytosaurid phytosaur. There is no evidence to support synonymy of ‘Francosuchus’ trauthi with Paleorhinus, and no unambiguous features to support a phytosaurian identification. However, ‘Francosuchus’ trauthi possesses a unique combination of characters that distinguish it from all other Triassic tetrapods, and necessitates referral of the species to a new genus, Dolerosaurus, gen. nov. Rejection of the proposed synonymy between ‘Francosuchus’ trauthi and Paleorhinus means that the ‘Paleorhinus biochron’ cannot be tied to the marine late Carnian as previously suggested, and provides further evidence of the problems inherent in attempting to correlate the terrestrial Triassic to the marine timescale.
Overview of the Aetosaurs
Desojo, J. B., Heckert, A. B., Martz, J. W., Parker, W. G., Schoch, R. R., Small, B. J., and T. Sulej. 2013. Aetosauria: a clade of armoured pseudosuchians from the Upper Triassic continental beds; From Nesbitt, S. J., Desojo, J. B., and R. B. Irmis (eds.) Anatomy, Phylogeny and Palaeobiology of Early Archosaurs and their Kin, Geological Society Special Publication 379: doi:10.1144/SP379.17
Abstract - Aetosauria is a clade of obligately quadrupedal, heavily armoured pseudosuchians known from Upper Triassic (late Carnian–Rhaetian) strata on every modern continent except Australia and Antarctica. As many as 22 genera and 26 species ranging from 1 to 6 m in length, and with a body mass ranging from less than 10 to more than 500 kg, are known. Aetosauroides scagliai was recently recovered as the most basal aetosaur, placed outside of Stagonolepididae (the last common ancestor of Desmatosuchus and Aetosaurus). Interrelationships among the basal aetosaurs are not well understood but two clades with relatively apomorphic armour – the spinose Desmatosuchinae and the generally wide-bodied Typothoracisinae – are consistently recognized. Paramedian and lateral osteoderms are often distinctive at the generic level but variation within the carapace is not well understood in many taxa, warranting caution in assigning isolated osteoderms to specific taxa. The aetosaur skull and dentition varies across taxa, and there is increasing evidence that at least some aetosaurs relied on invertebrates and/or small vertebrates as a food source. Histological evidence indicates that, after an initial period of rapid growth, lines of arrested growth (LAGs) are common and later growth was relatively slow. The common and widespread Late Triassic ichnogenus Brachychirotherium probably represents the track of an aetosaur.
Abstract - Aetosauria is a clade of obligately quadrupedal, heavily armoured pseudosuchians known from Upper Triassic (late Carnian–Rhaetian) strata on every modern continent except Australia and Antarctica. As many as 22 genera and 26 species ranging from 1 to 6 m in length, and with a body mass ranging from less than 10 to more than 500 kg, are known. Aetosauroides scagliai was recently recovered as the most basal aetosaur, placed outside of Stagonolepididae (the last common ancestor of Desmatosuchus and Aetosaurus). Interrelationships among the basal aetosaurs are not well understood but two clades with relatively apomorphic armour – the spinose Desmatosuchinae and the generally wide-bodied Typothoracisinae – are consistently recognized. Paramedian and lateral osteoderms are often distinctive at the generic level but variation within the carapace is not well understood in many taxa, warranting caution in assigning isolated osteoderms to specific taxa. The aetosaur skull and dentition varies across taxa, and there is increasing evidence that at least some aetosaurs relied on invertebrates and/or small vertebrates as a food source. Histological evidence indicates that, after an initial period of rapid growth, lines of arrested growth (LAGs) are common and later growth was relatively slow. The common and widespread Late Triassic ichnogenus Brachychirotherium probably represents the track of an aetosaur.
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