Field of Science

Pelvic and Hindlimb Myology of the Basal Archosaur Poposaurus gracilis

Schachner, E. R., Manning, P. L., and P. Dodson. 2011. Pelvic and hindlimb myology of the basal archosaur Poposaurus gracilis (Archosauria: Poposauroidea). Journal of Morphology. doi: 10.1002/jmor.10997. [Epub ahead of print]

Abstract -
The discovery of a largely complete and well preserved specimen of Poposaurus gracilis has provided the opportunity to generate the first phylogenetically based reconstruction of pelvic and hindlimb musculature of an extinct nondinosaurian archosaur. As in dinosaurs, multiple lineages of basal archosaurs convergently evolved parasagittally erect limbs. However, in contrast to the laterally projecting acetabulum, or "buttress erect" hip morphology of ornithodirans, basal archosaurs evolved a very different, ventrally projecting acetabulum, or "pillar erect" hip. Reconstruction of the pelvic and hindlimb musculotendinous system in a bipedal suchian archosaur clarifies how the anatomical transformations associated with the evolution of bipedalism in basal archosaurs differed from that of bipedal dinosaurs and birds. This reconstruction is based on the direct examination of the osteology and myology of phylogenetically relevant extant taxa in conjunction with osteological correlates from the skeleton of P. gracilis. This data set includes a series of inferences (presence/absence of a structure, number of components, and origin/insertion sites) regarding 26 individual muscles or muscle groups, three pelvic ligaments, and two connective tissue structures in the pelvis, hindlimb, and pes of P. gracilis. These data provide a foundation for subsequent examination of variation in myological orientation and function based on pelvic and hindlimb morphology, across the basal archosaur lineage leading to extant crocodilians.

Biomechanical modeling of Coelophysis bauri

Jasinski, S. E. 2011. Biomechanical modeling of Coelophysis bauri: Possible feeding methods and behavior of a Late Triassic theropod. New Mexico Museum of Natural History and Science, Bulletin 53:195-201.

ABSTRACT—Coelophysis bauri is a small theropod dinosaur from the Late Triassic of the southwestern United States. The Whitaker (= Ghost Ranch)quarry, which preserves hundreds to perhaps thousands of individuals, has led to many hypotheses about its behavior and feeding strategies. The beam theory allows for a quantitative approach to reconstruction of the feeding mechanism of Coelophysis. The Coelophysis mandible behaves as a simple lever, similar to that of Varanus komodoensis, and thus is more inclined to produce slashing bites. The middentary region of the Coelophysis mandible has the greatest labiolingual strength, suggesting that this would have been the region most important to live prey capture. Comparisons of the juvenile and adult specimens of Coelophysis bauri show remarkable similarities in the relative mandibular strengths, suggesting juveniles would have been apt predators. Further study of the biomechanics of theropod dinosaurs such as Coelophysis bauri may lead to a better understanding of how they lived and behaved.

Chinleana is Moving to the Field of Science Blog Network

Regular readers have probably noticed some changes. Starting today the blog will be part of the Field of Science science blog network. The switch has started and will continue over the next day or two. As a result some aspects may not be accessible and I apologize for any inconvenience and hope to continue to access the site for all of your Triassic Period news and information..

Thank you.

Bill Parker

TR-J Carbon Isotope Excursions Caused by Global Disturbance and not by Vegetation Change

Bacon, K. L., Belcher, C. M., Hesselbo, S. P., and J. C. McElwain. 2011. The Triassic–Jurassic boundary carbon-isotope excursions expressed in taxonomically identified leaf cuticles. Palaios 26:461-469.

Abstract - A negative stable carbon-isotope excursion (CIE) has been identified at sites across the globe in strata that span the Triassic–Jurassic boundary. Different studies have suggested that this negative CIE could be the result of either a change in vegetation or a massive perturbation in the global carbon cycle at this time. To determine which, 84 hand-picked leaf cuticle fragments from plant macrofossils previously identified to genus level were analyzed for stable carbon-isotope values. The samples were taken from known heights in nine plant beds spanning the Rhaetian–Hettangian (Upper Triassic–Lower Jurassic) at Astartekløft, East Greenland. We have constructed taxon-specific stable carbon-isotope curves for Ginkgoales and Bennettitales and compared these to an existing δ13C curve based on fossil wood from the same section. This study reveals that taxon-specific carbon-isotope curves based on the leaf data from these two seed-plant groups both record the same negative CIE as the fossil wood, despite having different ecological roles and different relative abundances in the section. Correspondence analysis of the macrofossil abundance data, where the plants are considered in their ecological groups, shows that the δ13C values bear no relationship to changes in vegetation. This result further suggests that vegetation change had little role in determining the δ13C values at this time. Considered together, the bulk cuticle and taxon-specific δ13C record indicate that the negative CIE at the Triassic–Jurassic boundary is likely to have been caused by a massive perturbation of the global carbon cycle and not by vegetation change.

Rare Occurrence of the Winged Seed Fraxinopsis from the Dockum Group of Texas

New paper from my friend Sid Ash.

Ash, S. R. 2011. Anomalous occurrence of the Gondwanan winged seed Fraxinopsis in a new Late Triassic (Norian) flora from west Texas, USA. 106. doi:10.1016/j.revpalbo.2011.05.007 Abstract - The small Late Triassic flora described here from a new locality in Palo Duro Canyon, west Texas, USA is noteworthy because it includes specimens of a new species of the Gondwanan winged seed Fraxinopsis, F. patharrisiae sp. nov. This is only the second time that Fraxinopsis has been found in Laurasia and thus adds support to the theory that at least limited floral migrations did take place between Gondwana and Laurasia during the Late Triassic. In addition to Fraxinopsis the locality has yielded a new species of the platyspermic seed Samaropsis, S. texensis sp. nov., the remains of the cycadophyte leaf Zamites powellii, and the leafy shoots and pollen and seed cones of Palodurophyton quanahensis gen. et sp. nov., a conifer of unknown relationships that has cheirolepidian-like epidermal features. This flora occurs in the Tecovas Formation in the lower part of the Dockum Group of Late Triassic (Norian) age. The description of the flora contributes to our understanding of the Dockum flora and its distribution in the American southwest and adds to our knowledge of the Late Triassic flora of western Laurentia as well.
Review of Palaeobotany and Palynology 166:94

Passing of Dr. Donald Baird

Dr. Donald Baird was a leading researcher of Triassic rocks of the eastern United States, publishing many papers on fossil trackways and other aspects of Triassic paleontology and geology, including an important paper describing specimens of the aetosaur Stegomus arcuatus.

From the Society of Vertebrate Paleontology Website:

Dr. Donald Baird recently passed away. He was a member of the SVP since 1949, and received the Society's Honorary Membership Award in 1991.

The following is from Zhe-Xi Luo and Mary R. Dawson of the Section of Vertebrate Paleontology at Carnegie Museum of Natural History.

We wish to share the sad news that long-time Research Associate Dr. Donald Baird of CMNH Vertebrate Paleontology Section passed away recently.

Donald was a Pittsburgh native, and began his interest in vertebrate paleontology at Carnegie Museum. After serving in the military during WW II, he received a BS degree at the University of Pittsburgh in 1948 and MS at the University of Colorado in 1949. He received his introduction to Paleozoic plants and animals of Western Pennsylvania and Ohio following his first trip to the famous Linton, Ohio, fossil locality in 1950. Then he moved to Harvard University as a PhD student under Professor Alfred S. Romer, for whom he had provided fossil footprints from the Pittsburgh region. He received his PhD degree in 1955. Don's paleontological heart remained with the Paleozoic fossils of the Ohio Valley, although he also moved on to research on Triassic and Cretaceous vertebrates of the northeast.

Beginning in 1957, Don entered the curatorial ranks in the paleontological collections at Princeton University, working with the late Professor Glenn Jepsen. He became the Director of Princeton's Museum of Natural History in 1973, a position he held until his retirement in 1988. Don returned to his roots in Pittsburgh following retirement. He was a Research Associate at Carnegie starting in 1984, an honorary position he also held at the American Museum of Natural History (New York) and the Academy of Natural Sciences of Philadelphia. He frequently visited our section up to 2000-2001, and supported numerous projects by our VP section.

Don was very active in paleontological research, both on the Carboniferous and on the Mesozoic of the eastern US. One of his many interests was in fossil footprints. Always one to see a little humor in his studies, Don even published a paper on the footprints of the infamous giant “Sasquatch!” He always delighted in studies on difficult vertebrate fossils from the Carboniferous of the Ohio Valley area, working for many years on these animals with Carnegie Curator David Berman.

While in Princeton, Don was an inspirational mentor to several youngsters who later moved on to careers in geosciences and paleontology, including Paul Olsen. He also actively supported several junior colleagues earlier in their careers, such as Jack Horner, Kevin Padian, Neil Shubin and Hans Dieter-Sues.

Don was a dedicated member of the Society of Vertebrate Paleontology, financially supporting publication of the Society’s Bibliographies during their period of transition to an electronic format. He was elected Honorary Member of SVP for his long-time contribution to the science of vertebrate paleontology.

We extend our most sincere sympathies to his family, through whom his legacy lives on, as well as through a body of significant research and the outstanding fossils he collected for our museum.

Atmospheric Carbon Injection Linked to End-Triassic Mass Extinction

Ruhl, M., Bonis, M. R., Reichart, G-.R., Sinninghe Damste, J. S., and W. M. Kürschner. 2011. Atmospheric Carbon Injection Linked to End-Triassic Mass Extinction. Science 333:430-434. DOI:10.1126/science.1204255.

Abstract - The end-Triassic mass extinction (~201.4 million years ago), marked by terrestrial ecosystem turnover and up to ~50% loss in marine biodiversity, has been attributed to intensified volcanic activity during the break-up of Pangaea. Here, we present compound-specific carbon-isotope data of long-chain n-alkanes derived from waxes of land plants, showing a ~8.5 per mil negative excursion, coincident with the extinction interval. These data indicate strong carbon-13 depletion of the end-Triassic atmosphere, within only 10,000 to 20,000 years. The magnitude and rate of this carbon-cycle disruption can be explained by the injection of at least ~12 × 103 gigatons of isotopically depleted carbon as methane into the atmosphere. Concurrent vegetation changes reflect strong warming and an enhanced hydrological cycle. Hence, end-Triassic events are robustly linked to methane-derived massive carbon release and associated climate change.

MicroRNAs Show that Turtles are Lepidosauromorph Diapsids

Last spring when I was in Austin, Kevin Peterson came and gave a talk on the promise of microRNA's in determining phylogenetic relationships of organisms. In a follow-up question Sterling Nesbitt and I asked him if this could be used to solve the debate regarding the relationships of turtles. Peterson replied that they were already working on the problem and that preliminary data suggested that turtles were close to lepidosaurs. You can read more details from the final study below. Fascinating stuff.

Update: Here is the abstract

Lyson, T. R., Sperling, E. A., Heimberg, A. M., Gauthier, J. A., King, B. L., and K. J. Peterson. 2011. MicroRNAs support a turtle + lizard clade. Biology Letters. doi: 10.1098/rsbl.2011.0477

Abstract - Despite much interest in amniote systematics, the origin of turtles remains elusive. Traditional morphological phylogenetic analyses place turtles outside Diapsida—amniotes whose ancestor had two fenestrae in the temporal region of the skull (among the living forms the tuatara, lizards, birds and crocodilians)—and allied with some unfenestrate-skulled (anapsid) taxa. Nonetheless, some morphological analyses place turtles within Diapsida, allied with Lepidosauria (tuatara and lizards). Most molecular studies agree that turtles are diapsids, but rather than allying them with lepidosaurs, instead place turtles near or within Archosauria (crocodilians and birds). Thus, three basic phylogenetic positions for turtles with respect to extant Diapsida are currently debated: (i) sister to Diapsida, (ii) sister to Lepidosauria, or (iii) sister to, or within, Archosauria. Interestingly, although these three alternatives are consistent with a single unrooted four-taxon tree for extant reptiles, they differ with respect to the position of the root. Here, we apply a novel molecular dataset, the presence versus absence of specific microRNAs, to the problem of the phylogenetic position of turtles and the root of the reptilian tree, and find that this dataset unambiguously supports a turtle + lepidosaur group. We find that turtles and lizards share four unique miRNA gene families that are not found in any other organisms' genome or small RNA library, and no miRNAs are found in all diapsids but not turtles, or in turtles and archosaurs but not in lizards. The concordance between our result and some morphological analyses suggests that there have been numerous morphological convergences and reversals in reptile phylogeny, including the loss of temporal fenestrae.

Billings Gap Strikes Again! Another New Phytosaur Skull from this Historically Fossiliferous Area of the Petrified Forest

Billings Gap is a small valley on the east side of Petrified National Park between Blue Mesa and an unnamed mesa to the east. Triassic vertebrate paleontologists familiar with the area know that historically Billings Gap contains very fossiliferous beds of the Blue Mesa and lower Sonsela Members. Starting in the 1920s groups from the University of California Museum of Paleontology, the Smithsonian, and the American Museum of Natural History have worked this area and come away with phytosaur skulls for their museum collections. When the National Park Service acquired a portion of Billings Gap in 2007 we explored the area the day the land ownership changed and were rewarded immediately with a partial skull, and a year later with a complete skull.

Hoping to have similar luck this year we headed into the Gap and were rewarded when Susan Drymala recovered the almost completely preserved skull shown below. The specimen is palate-side down and oriented obliquely in this photo with the snout directed to the lower right of the photo. The skull roof is still covered in matrix, but you can see the right side of the skull in this picture. This specimen, from the Camp Butte Beds of the Sonsela Member (sensu Martz and Parker, 2010), probably belongs to the genus Smilosuchus (sensu Stocker, 2010); however, we need to complete the excavation and get this thing prepared to test its taxonomic affinities.

While Susan was finding and uncovering this beauty, I was about a half mile away prospecting lower levels of the Upper Blue Mesa Member. I found a lot of bone, but was especially excited about the recovery of ornamented skull fragments and several vertebrate of what looks suspiciously like Doswellia. If so this would be a first occurrence of this taxon in the Petrified Forest area. Unfortunately I have no photos of the material to post at this time.

Reassessment of the Early Neotheropod Camposaurus arizonensis and some Comments on the Stratigraphic Position of the Placerias Quarry

Ezcurra, M. D., and S. L. Brusatte. 2011. Taxonomic and phylogenetic reassessment of the early neotheropod dinosaur Camposaurus arizonensis from the Late Triassic of North America. Palaeontology 54:763-772. DOI: 10.1111/j.1475-4983.2011.01069.x

Abstract - Camposaurus arizonensis, a small theropod dinosaur from the early–middle Norian of Arizona (USA), is widely considered the oldest known neotheropod. However, despite its importance, Camposaurus is the subject of taxonomic and phylogenetic uncertainty and is often considered a nomen dubium, largely because of a fragmentary holotype. We here reassess the holotype of Camposaurus and identify two autapomorphies: the posterior edge of the tibial articular surface for the fibula offset as a sharp and prominent ridge and the absence of an anteriorly expanded medial condyle of the astragalus. We therefore consider Camposaurus to be a valid and diagnostic taxon of basal theropod dinosaur. For the first time, we include Camposaurus in a phylogenetic analysis, which confirms its neotheropod placement and recovers it as a close relative of Coelophysis rhodesiensis within Coelophysoidea sensu stricto. The position of Camposaurus as the oldest neotheropod provides an important calibration point, but necessitates long ghost lineages, indicating that our knowledge of the early evolutionary history of theropod dinosaurs is still patchy. Furthermore, our phylogenetic analysis recovers a polytomy at the base of Neotheropoda, as most parsimonious trees disagree in recovering a monophyletic or paraphyletic ‘traditional’ Coelophysoidea. This suggests that basal theropod phylogeny remains in a state of flux, and the monophyly of ‘traditional’ Coelophysoidea remains an open question.

This paper provides a redescription of the neotheropod Camposaurus arizonensis Hunt et al. 1998 from the Upper Triassic Placerias Quarry (Chinle Formation) of Arizona. Furthermore it argues that the taxon is valid and diagnosable based on two autapomorphies and provides a phylogenetic analysis that recovers Camposaurus within the clade Coelophysis as the sister taxon to C. rhodesiensis. However, the authors refrain from assigning this taxon to Coelophysis until better material is found (the holotype consists of only the right and left distal ends of the fibulae and tibiae fused to their corresponding astragalocalcanea.

One point I'd like to address the the stratigraphic position listed for the holotype and for the Placerias Quarry. This is actually very important because as stated by the authors Camposaurus represents the stratigraphically lowest occurrence of a neotheropod dinosaur in the Chinle Formation and in part the current confusion is a result of a decision I made back in 2005. Recent papers such as Ezcurra and Brusatte (2011) and others (e.g., Irmis, 2005; Nesbitt et al., 2007; Langer et al., 2010) list the Placerias Quarry as situated in the Mesa Redondo Member of the Chinle Formation. This is mainly because this is the unit I placed the quarry in in my 2005 review of major localities from the Chinle Formation (Parker, 2005). Prior to this the quarry had been placed in the lower Petrified Forest Member (e.g., Jacobs and Murry, 1980) or more recently in the Bluewater Creek Member (e.g., Lucas et al., 1997). Heckert and Lucas (2003) also argued for the latter placement, but in the same paper argued that the Mesa Redondo and Bluewater Creek Members were synonymous. Unlike those authors who prefered the usage of the name Bluewater Creek, I (Parker, 2005) argued that the name Mesa Redondo had priority as it was the older of the two names. This usage was followed by Irmis (2005), Nesbitt et al. (2007) and most subsequent authors including the new paper by Ezcurra and Brusatte.

Interestingly, my recent stratigraphical investigations of the Chinle Formation in conjunction with Jeff Martz have determined that these units are not synonymous and actually quite distinct (the Mesa Redondo Member underlies the Bluewater Creek Member) and even more interestingly the Placerias Quarry does not occur in either of them!  Instead it is above the Bluewater Creek Member in the Blue Mesa Member (Parker and Martz, 2011; Irmis et al., in press).  This makes for an extremely confusing situation with at least four straigraphic unit names listed in the recent literature for the quarry, but hopefully this will stabilize in the future. Furthermore, this revised positioning implies that Camposaurus is younger than previously believed (Hunt et al., 1998; Irmis et al., in press).


Heckert, A.B., Lucas, S.G., 2003. Stratigraphy and paleontology of the lower Chinle Group (Adamanian - latest Carnian) in the vicinity of St. Johns, Arizona. New Mexico Geological Society Guidebook 54, 281-288.

Hunt, A.P., Lucas, S.G., Heckert, A.B., Sullivan, R.M., Lockley, M.G., 1998. Late Triassic dinosaurs from the western United States. Geobios 31, 511-531.

Irmis, R.B., 2005. The vertebrate fauna of the Upper Triassic Chinle Formation in northern Arizona. Mesa Southwest Museum Bulletin 9, 63-88.

Irmis, R. B., Mundil, R., Martz, J. W., and W. G. Parker. in press.New high-resolution U/Pb ages from the Late Triassic Chinle Formation (New Mexico, USA) support a diachronous rise of dinosaurs. Earth and Planetary Science Letters
Jacobs, L. L., and P. A Murry. 1980. The vertebrate community of the Triassic Chinle Formation near St. Johns, Arizona, p. 99-123. In L. L. Jacobs (ed.), Aspects of Vertebrate History: Essays in honor of Edwin Colbert Harris. Museum of Northern Arizona, Flagstaff, AZ.

Langer, M.C., Ezcurra, M.D., Bittencourt, J.S., Novas, F.E., 2010. The origin and early evolution of dinosaurs. Biological Reviews 85, 55-110.

Lucas, S.G., Heckert, A.B., Hunt, A.P., 1997. Stratigraphy and biochronological significance of the Late Triassic Placerias Quarry, eastern Arizona (U.S.A.). Neues Jahrbuch für Geologie und Paläontologie, Abhandlungen 203, 23-46.

Nesbitt, S.J., Irmis, R.B., Parker, W.G., 2007. A critical re-evaluation of the Late Triassic dinosaur taxa of North America. Journal of Systematic Palaeontology 5, 209-243.

Parker, W.G., 2005. Faunal review of the Upper Triassic Chinle Formation of Arizona. Mesa Southwest Museum Bulletin 11, 34-54.

Parker, W.G., Martz, J.W., 2011. The Late Triassic (Norian) Adamanian-Revueltian tetrapod faunal transition in the Chinle Formation of Petrified Forest National Park, Arizona. Earth & Environmental Science Transactions of the Royal Society of Edinburgh 101, 231-260.

New Thalattosaur Specimen from the Late Triassic of Alaska

New Record of Large Archosauromorphs from the Early Triassic of Antarctica

Smith, N. D., Crandall, J. R., Hellert, S. M., Hammer, W. R., and P. J. Makovicky. 2011. Anatomy and affinities of large archosauromorphs from the lower Fremouw Formation (Early Triassic) of Antarctica. Journal of Vertebrate Paleontology 31:784-797. DOI:10.1080/02724634.2011.586662

Abstract - The vertebrate assemblage of the lower Fremouw Formation has been studied for nearly 50 years, but many components remain poorly known. We describe a partial presacral vertebra and the distal end of a left humerus collected just above the Permian–Triassic boundary in the Shackleton Glacier region of the central Transantarctic Mountains. Our identification of these specimens as archosauromorphs that represent at least one taxon of large-bodied archosauriform increases the known reptile diversity of the Fremouw Formation considerably, and provides the first definitive evidence for the presence of Archosauriformes in the Early Triassic of Antarctica. These records increase faunal similarities between the lower Fremouw Formation and other Early Triassic assemblages. Although the lower Fremouw assemblage is typically considered a subset of the coeval Lystrosaurus Assemblage Zone (LAZ) of South Africa, the discrepancy in inferred body size between the Antarctic specimens and Proterosuchus fergusi, coupled with the fact that the LAZ of the Karoo Basin has been sampled much more thoroughly, suggests a real disparity in the maximum body size of apex carnivores between the lower Fremouw assemblage and the LAZ. The lower Fremouw specimens also demonstrate that one or more lineages of archosauriform had attained the large body size characteristic of later members of the clade very soon after the end-Permian mass extinction. This offers a point of contrast with the global pattern of post-extinction terrestrial communities, which are typified by a marked reduction in body size (the ‘Lilliput effect’).

The Petrified Forest on You Tube

Mark Nelson (Teacher-Ranger-Teacher) accompanied us in the field last summer and recorded us discussing some of the geological and paleontological features of the park. He has edited these into 10 - 15 minute clips for You Tube, which is the first time the park has been officially featured on this site.  You can check them out at the links below.  I think they are not bad for a first attempt, however, I'd like to do some shorter clips (~ 5 mins. max) on some of the behind the scenes stuff at the park as well as explaining other aspects of the paleontology and geology. Anyone have any requests or ideas for some short and interesting clips? I think next time we'll try to be a little more excited... ;).

Current Clips:

Evident Renewal (A visit to the badlands of the Painted Desert located in the Petrified Forest National Park with Bill Parker: paleontologist and Tammo Reichgelt; Utrecht University researcher as they discuss climate change and impacts on Earth's five mass extinctions. Filmed and edited on location by Mark Nelson TRT and Chicago artist 2010).

Triassic Waters (Follow Bill Parker: Paleontologist and Jeff Martz: Physical Scientist, into the badlands of the Painted Desert as they explore soil erosion and geological formations dating back to the Late triassic Epoch in the Petrified Forest National Park. Filmed and edited on location by Mark Nelson TRT and Chicago artist 2010).

Mud to Museum (Visit with fossil preparator Kenneth Bader in the Petrified Forest National Park preparation laboratory. Filmed and edited on location by Mark Nelson TRT and Chicago artist 2010).

Rats, Bats, and Artifacts (Matt Smith, museum curator and preparator takes us on a "behind the scenes" look at the assorted collection of paleo fossils, treasures, and relics in the vaults of the Petrified Forest National Park center. Filmed and edited on location by Mark Nelson TRT and Chicago artist 2010).

Review of the Lower Triassic Temnospondyl Fauna of Germany

Schoch, R. R. 2011. How diverse is the temnospondyl fauna in the Lower Triassic of southern Germany? Neues Jahrbuch für Geologie und Paläontologie - Abhandlungen 261:49-60. DOI: 10.1127/0077-7749/2011/0147

Abstract - Among the few fossiliferous Lower Triassic deposits in Europe, the Lower to Middle Buntsandstein of the German southwest has yielded a range of interesting finds. A review of the published and new material gives the following results: (1) The oldest identified remain is a mandible of a small stereospondyl from the Bernburg Formation (Induan); (2) A new palate from the early Olenekian (Badischer Bausandstein) stems from a basal capitosaur similar to Wetlugasaurus; (3) In the late Olenekian (Hardegsen Formation), two well-defined temnospondyl genera are present: the basal capitosauroids Meyerosuchus fuerstenbergianus and Odenwaldia heidelbergensis. Large remains formerly referred to Mastodonsaurus either pertain to a different family or are undiagnostic, pushing the first occurrence of mastodonsaurids into the Anisian. These finds highlight the presence of large aquatic predators by early Triassic time, revealing an increasing diversity of aquatic predators from the Induan to the Anisian. The documented faunal changes involved patterns of immigration and extinction/emigration rather than endemic evolution within the basin. In contrast to the northern parts of the basin, the genera Trematosaurus, Parotosuchus, and Sclerothorax are absent in the southern part, where Meyerosuchus and Odenwaldia existed.

Evolution of Morphological Disparity in Pterosaurs

Prentice, K. C., Ruta, M. and M. J. Benton. 2011. Evolution of morphological disparity in pterosaurs. Journal of Systematic Palaeontology DOI:10.1080/14772019.2011.565081

Abstract - Pterosaurs were important flying vertebrates for most of the Mesozoic, from the Late Triassic to the end of the Cretaceous (225–65 Ma). They varied enormously through time in overall size (with wing spans from about 250 mm to about 12 m), and in features of their cranial and postcranial skeletons. Comparisons of disparity based on discrete cladistic characters show that the basal paraphyletic rhamphorhynchoids (Triassic–Early Cretaceous) occupied a distinct, and relatively small, region of morphospace compared to the derived pterodactyloids (Late Jurassic–Late Cretaceous). This separation is unexpected, especially in view of common constraints on anatomy caused by the requirements of flight. Pterodactyloid disparity shifted through time, with different, small portions of morphospace occupied in the Late Jurassic and Late Cretaceous, and a much larger portion in the Early Cretaceous. This explosion in disparity after 100 Ma of evolution is matched by the highest diversity of the clade: evidently, pterosaurs express a rather ‘top heavy’ clade shape, and this is reflected in delayed morphological evolution, again an unexpected finding. The expansion of disparity among pterodactyloids was comparable across subclades: pairwise comparisons among the four pterodactyloid superfamilies show that, for the most part, these clades display significant morphological separation, except in the case of Dsungaripteroidea and Azhdarchoidea. Finally, there is no evidence that rhamphorhynchoids as a whole were outcompeted by pterodactyloids, or that pterosaurs were driven to extinction by the rise of birds.

A Sectorial Toothed Cynodont (Therapsida) from the Triassic of Southern Brazil

Soares M. B., Abdala F. and C. Bertoni-Machado. 2011. A sectorial toothed cynodont (Therapsida) from the Triassic Santa Cruz do Sul fauna, Santa Maria Formation, Southern Brazil. Geodiversitas 33: 265-278.

ABSTRACT - A sectorial toothed cynodont from the Triassic Santa Cruz do Sul fauna, Santa Maria Formation, Parana Basin, southern Brazil, is described. The taxon is represented by a tiny portion of a right lower jaw which preserves partially the last postcanine. A comparative analysis of the postcanine morphology of the Santa Cruz do Sul specimen with South American Triassic cynodonts is made. The crown morphology of the Santa Cruz do Sul cynodont is closer to that of the juvenile single specimen of cf. Probainognathus from the Carnian Ischigualasto Formation and of juveniles of Probainognathus jenseni Romer, 1970 from the Ladinian Chañares Formation in Argentina. There are, however, some important differences between the tooth of the new specimen and those of P. jenseni juveniles, and therefore we provisionally assign the new Santa Cruz do Sul material to cf. Probainognathus. The fauna of Santa Cruz do Sul, dominated by traversodontid cynodonts, is now composed of a proterochampsid archosauriform, three traversodontids and two sectorial toothed cynodonts and we refer to it as Santacruzodon Assemblage Zone. We also propose the name of Riograndia Assemblage Zone for the faunas from the Upper Triassic Caturrita Formation, on the basis of the abundance yet restricted record of this taxon in these faunas. A brief summary of the Brazilian Middle and Upper Triassic biostratigraphy is presented within the framework of two different time scales.

The Aetosaurus Block

After a crazy spring things are pretty slow in the Triassic right now, with hardly any new papers coming out in recent weeks.  Even our fieldwork has pretty much ground to a halt given the recent extreme heat in the western U.S. Plus, I'm taking a week off from work, so things will be even slower; however, I'm expecting things to take off again pretty soon. 

In the meantime here is a shot showing the famous block of Aetosaurus ferratus specimens from the Lower Stubensanstein of Germany.

a close-up of one of the best preserved skulls

and an older reconstruction (from Wikipedia) showing several Aetosaurus perishing in a sandstorm.

These specimens (collected and first described in the 1800s) were the subject of an excellent detailed description by Rainer Schoch in 2007.


Schoch, R. R. 2007. Osteology of the small archosaur Aetosaurus from the Upper Triassic of Germany. N. Jb. Geol. Paläont. Abh. 246:1– 35