New Triassic Papers

Thanks to Ben Creisler for originally compiling these...

Chen, Z. Q-., and M. J. Benton. 2012. The timing and pattern of biotic recovery following the end-Permian mass extinction. Nature Geoscience 5: 375–383doi:10.1038/ngeo1475
Abstract - The aftermath of the great end-Permian period mass extinction 252 Myr ago shows how life can recover from the loss of >90% species globally. The crisis was triggered by a number of physical environmental shocks (global warming, acid rain, ocean acidification and ocean anoxia), and some of these were repeated over the next 5–6 Myr. Ammonoids and some other groups diversified rapidly, within 1–3 Myr, but extinctions continued through the Early Triassic period. Triassic ecosystems were rebuilt stepwise from low to high trophic levels through the Early to Middle Triassic, and a stable, complex ecosystem did not re-emerge until the beginning of the Middle Triassic, 8–9 Myr after the crisis. A positive aspect of the recovery was the emergence of entirely new groups, such as marine reptiles and decapod crustaceans, as well as new tetrapods on land, including — eventually — dinosaurs. The stepwise recovery of life in the Triassic could have been delayed either by biotic drivers (complex multispecies interactions) or physical perturbations, or a combination of both. This is an example of the wider debate about the relative roles of intrinsic and extrinsic drivers of large-scale evolution.


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Lindström, S., van de Schootbrugge, B., Dybkjær, K., Pedersen, G. K.,  Fiebig, J., Nielsen, L. H.,  and S. Richoz. 2012.  No causal link between terrestrial ecosystem change and methane release during the end-Triassic mass extinction.
Geology 40(6): 531-534 doi: 10.1130/G32928.1

Abstract - Profound changes in both marine and terrestrial biota during the end-Triassic mass extinction event and associated successive carbon cycle perturbations across the Triassic-Jurassic boundary (T-J, 201.3 Ma) have primarily been attributed to volcanic emissions from the Central Atlantic Magmatic Province and/or injection of methane. Here we present a new extended organic carbon isotope record from a cored T-J boundary succession in the Danish Basin, dated by high-resolution palynostratigraphy and supplemented by a marine faunal record. Correlated with reference C-isotope and biotic records from the UK, it provides new evidence that the major biotic changes, both on land and in the oceans, commenced prior to the most prominent negative C-isotope excursion. If massive methane release was involved, it did not trigger the end-Triassic mass extinction. Instead, this negative C-isotope excursion is contemporaneous with the onset of floral recovery on land, whereas marine ecosystems remained perturbed. The decoupling between ecosystem recovery on land and in the sea is more likely explained by long-term flood basalt volcanism releasing both SO2 and CO2 with short- and long-term effects, respectively.

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Hamad, A. M. B. A. Jasper, A., and D. Uhl. 2012. The record of Triassic charcoal and other evidence for palaeo-wildfires: Signal for atmospheric oxygen levels, taphonomic biases or lack of fuel? International Journal of Coal Geology  96–97: 60–71 http://dx.doi.org/10.1016/j.coal.2012.03.006
Abstract - As wildfires are today important sources of disturbance in many terrestrial ecosystems, it is of great interest to understand how different environmental parameters and fire-activity interacted during past periods of the Earth history. Fossil charcoal, inertinites, and pyrogenic polycyclic aromatic hydrocarbons (PAHs) represent the only direct evidence for the occurrence of such palaeo-wildfires. In the present study, a review of published data, together with new data on the occurrence of fossil charcoal for the Permian and the Triassic is presented. For a long time, it has been speculated, that an assumed lack of evidence for palaeo-wildfires during the Triassic should be explained by a large drop in atmospheric oxygen concentration following or during the end-Permian mass extinction event, preventing the occurrence of wildfires. However, evidence for palaeo-wildfires is relatively common in many middle and late Triassic strata, whereas such evidence is almost totally lacking from early Triassic sediments. The interpretation of this “charcoal gap” or depression is difficult, as many factors (e.g. atmospheric oxygen concentration, taphonomical biases, lack of sediments suitable for the preservation of macroscopic charcoal, lack of fuel, and “ignorance” of scientists) may have influenced not only the production, but also the preservation and recovery of evidence for palaeo-wildfires during this period. Thus, it is not clear whether this Early Triassic “charcoal gap” can also be seen as evidence for an assumed “wildfire gap” or not. Without any doubt further investigations on the early Triassic record of charcoal and other evidence for palaeo-wildfires will be necessary before this problem can be solved. In fact, it can be expected that the number of published records of (early) Triassic evidence for palaeo-wildfires will increase in the future as more and more scientist working on
sediments of this age may become aware of the interest in fires from this time. This will certainly make it possible to give a much better picture of the temporal and regional distribution of wildfires during this period in the future.


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Bodzioch, A., and M. Kowal-Linka. 2012. Unraveling the origin of the Late Triassic multitaxic bone accumulation at Krasiejów (S Poland) by diagenetic analysis. Palaeogeography, Palaeoclimatology, Palaeoecology (advance online publication) http://dx.doi.org/10.1016/j.palaeo.2012.05.015

Abstract - A study of aquatic and terrestrial vertebrate remains from a bonebed in the Late Triassic continental succession near Krasiejów (S Poland) shows it was deposited by a single catastrophic event, perhaps a flood. Hardparts of Metoposaurus, Paleorhinus, and Stagonolepis show sedimentary infill and geochemical evidence for early diagenesis at different times and in different microenvironments. The infills in the aquatic animal bones (sediment, pyrite, calcite) show deposition in a freshwater environment, while those in the terrestrial Stagonolepis remains (mainly barite) point to an arid terrestial environment. The trace element content of the remains, together with the absence of a distinct pattern of element distribution, supports the conclusion that individual hardparts underwent diagenesis in various microenvironments and at different times. The accumulation of multitaxic vertebrate remains in a single bed clearly indicates event deposition. The hardparts must originally have been deposited at various locations during different times, but were later transported and deposited together in a pond by a short-lived, high-energy event, probably a flood after catastrophic rainfall.

Taphonomy of an Upper Triassic Rhynchosaur Bonebed From India

Mukherje, D. and  & S. Ray. 2012. Taphonomy of an Upper Triassic vertebrate bonebed: A new rhynchosaur (Reptilia; Archosauromorpha) accumulation from India. Palaeogeography, Palaeoclimatology, Palaeoecology (advance online publication) http://dx.doi.org/10.1016/j.palaeo.2012.03.010


Abstract - The Upper Triassic Tiki Formation of India is a rich storehouse of varied vertebrate fossil assemblages. So far, there is no information on taphonomic signatures of the Tiki vertebrate assemblages in comparison to that of other fossiliferous horizons of India. We report a new, low diversity, mono-dominant, multitaxic vertebrate accumulation where rhynchosaurs constitute the dominant component. The formation of the rhynchosaur bonebed is attributed to biological aggregation with a hydraulic overprint resulting in a mixed-origin concentration. Other taxa include rauisuchid, phytosaur, small indeterminate archosaur and cynodonts. Taphonomic study based on 617 skeletal specimens of rhynchosaurs collected from nine sites within an area of about 250x217 sq m shows that most of the specimens are disarticulated and disassociated but in close spatial proximity to one another; some are associated specimens and few are articulated. About 13 to 20 individuals of rhynchosaur at different ontogenetic stages are estimated from the specimens collected, suggesting gregarious behaviour, possibly herding. These specimens show varying degree of weathering, breakage, encrustation, abrasion and deformation. The bonebed is preserved within the Tiki red mudstone unit and is found in association with paleosol profiles, suggesting prolonged subaerial exposure. Spatial distribution and relative bone frequencies show differential susceptibility of the skeletal specimens to fluvial transport. 55.4% of the collected skeletal specimens belonged to Voorhies Group I, whereas 12.4% and 24% constituted Voorhies Group II and III respectively, and 8.2% of the collected specimens belonged to the intermediate group I and II. It appears that the animals concentrated in the vicinity of the water sources during prolonged period of aridity and died possibly during high seasonal rainfall that resulted in a major flood event. Subsequently, the soft tissues decomposed, and the skeletons suffered prolonged subaerial exposure when the water receded leading to disarticulation and fragmentation followed by minor dispersion by low velocity water currents. This resulted in segregation of skeletal specimens, which were gradually covered by mud deposited during later flooding events. Based on the known flora and fauna, the Tiki Upper Triassic ecosystem is reconstructed for the first time. In the aquatic ecosystem, the metoposaurid labyrinthodonts occupied the top of the food pyramid together with the semi-aquatic parasuchids, which occupied an ecological niche similar to that of the present day crocodilians. The abundance of herbivorous rhynchosaurs at the base with few large and carnivorous rauisuchids and parasuchids at the top suggest a trophic structure similar to that of a modern day terrestrial ecosystem.

Evidence of Avian-like Behavior in a Basal Saurischian Dinosaur

There has been a rash of Triassic vertebrate papers in the last two weeks.  Here is one that looks at the taphonomy of a specimen of the basal saurischian Guaibasaurus and suggests that it had a avian style of resting.

Agnolin, F., and Martinelli, A.G. 2012. Guaibasaurus candelariensis (Dinosauria, Saurischia) and the early origin of avian-like resting posture. Alcheringa (1–5) [advance online] DOI:10.1080/03115518.2012.634203

Abstract - A specimen of the basal saurischian Guaibasaurus candelariensis Bonaparte, Ferigolo and Ribeiro (UFRGS-PV-0725-T) from the Faxinal do Soturno locality, Rio Grande do Sul State, Brazil (Caturrita Formation; Late Triassic) lacks any sign of post-mortem transport and burial deformation, and exhibits features (flexed forelimbs, folded hindlimbs under the body and curved neck) that indicate a typical avian-like resting position. The presence in Guaibasaurus of an avian-like resting posture and related physiological implications would extend this unique trait, previously considered restricted to derived maniraptoran theropods, to the base of the Theropoda (or even
Saurischia) clade.

Taphonomic Effects on the Stratigraphic Ranges of Rare Taxa in the Chinle Formation of Arizona

Loughney, K. M., Fastovsky, D. E., and W. G. Parker. 2011. Vertebrate fossil preservation in blue paleosols from the Petrified Forest National Park, Arizona, with implications for vertebrate biostratigraphy in the Chinle Formation. Palaios 26:700-719.

Abstract - Exposures of the Chinle Formation in Petrified Forest National Park (PEFO), Arizona, preserve one of the most important Upper Triassic terrestrial faunal assemblages in the world: in it are found key elements in the global and regional correlation of continental deposits of Upper Triassic age. Rare components of the Chinle Formation faunal assemblage, including dinosaurs and small-bodied amniotes, appear to be mostly restricted to distinctive blue-colored horizons observed at only a few sites in PEFO. The blue sites represent paleosols formed in fine-grained, abandoned channel fills and contrast markedly with red-colored floodplain deposits and paleosols that characterize most fossil localities in the Chinle Formation. The distinctive blue color is interpreted as a weathered feature of hydromorphically reduced iron. The coincidence of rare taxa and sites bearing the blue-colored paleosols suggests that the stratigraphic positions of the sites and the rare taxa they contain appear to relate to fluvial sequence tracts in PEFO and may not reflect the true stratigraphic ranges of these taxa.

Lamy Amphibian Quarry Taphonomy Redux and "Forensic Taphonomy"

The Lamy amphibian quarry is a famous quarry in the Garita Creek (=Tecovas) Formation of the Dockum Group in New Mexico. The quarry is well known for its large assemblage of metoposaurs, all presumably belonging to the taxon Koskinonodon perfectum (previously known as Buettneria perfecta). Anyone who has visited the Triassic portion of the Smithsonian Museum of Natural History in Washington, D.C. has probably seen the block of metoposaur skulls from this quarry on exhibit. It was originally interpreted to represent a group of metoposaurs dying in a small body of water dessicated by drought, but this new study proposes little evidence of this. Furthermore, the quarry was reopened and new blocks collected providing new information.

This paper also coins a new term "forensic taphonomy", which is the study of the taphonomy of a site solely utilizing field notes and previous publications without actually visiting the study area first hand. This type of work had been done previously for this site and while these authors defend this type of study in general, I'm left with the overall feeling that it is bad practice to discuss something as dependent on the proper interpretation of sedimentary structures and specimen orientations as taphomony without first hand observation of the site. Therefore, I'm glad they have revised their previous work by actually getting access to and reopening the quarry.

Finally, the authors briefly discuss an important caveat when studying specimens collected from bone-beds decades ago. To highlight what was thought to be key elements of the quarry, in this case the metoposaur skulls, the exhibitors had staff cover over many of the smaller bones around the skulls such as limb bones.  Thus "forensic taphonomy" interpretations based on this display block were skewed by the preparation and exhibit technique used.  This type of technique was also used to highlight two Coelophysis skeletons from the Late Triassic Coelophysis quarry, which are on exhibit at the American Museum of Natural History. "Undesirable" bones were removed or covered over, and tails were added to these specimens to make them complete.  Recent preparation techniques discourage the use of materials to mimic bone to make specimens appear complete, and also the past practice of amalgamating different specimens in bone panel mounts such as these.  Indeed, it can be extremely difficult to study older specimens prepared in this manner, as features of the specimens may not be real.  In fact some older, well known specimen descriptions actually describe the reconstruction, not the real bones. Be careful out there.

Lucas, S. G., Rinehart, L. F., Krainer, K., Spielmann, J. A., and A. B. Heckert. 2010. Taphonomy of the Lamy amphibian quarry: A Late Triassic bonebed in New Mexico, U.S.A. Palaeogeography, Palaeoclimatology, Palaeoecology 298:388–398. doi:10.1016/j.palaeo.2010.10.025

Abstract - Located in Santa Fe County, New Mexico, USA, the Lamy amphibian quarry is a Late Triassic (Adamanian) bonebed stratigraphically low in the Garita Creek Formation of the Chinle Group. Well known for its mass accumulation of metoposaurid amphibians, it was initially interpreted as a drought-induced death assemblage. Based on microstratigraphic and sedimentological studies, additional and extensive collecting at the quarry and a revised understanding of the bonebed, we provide a detailed taphonomic analysis of the Lamy amphibian quarry that identifies it as a low diversity multitaxic and monodominant bonebed in pedogenically modified floodplain mudstone. The Lamy bonebed shows no evidence of drought and is characterized by a high density of completely dissociated bones that show clear alignment by current and sorting (enrichment of Voorhies Group II and III elements). The bones show no significant abrasion or weathering (stage 0), preserve virtually no evidence of scavenging and show no evidence of trampling. Based on skull lengths, the metoposaurid assemblage has a type I survivorship curve and lacks juveniles. We thus posit that the following sequence of events formed the Lamy amphibian bonebed: (1) aggregation (cause unknown) of a large number of metoposaurid amphibians at a site different from the location of the bonebed, though not distant; (2) catastrophic mass mortality; (3) complete disarticulation and disassociation of the skeletons; and (4) rapid transport of the disarticulated bones onto a floodplain surface that was undergoing pedogenesis. The Lamy amphibian bonebed is representative of the Late Triassic metoposaurid bonebeds from Morocco and the western USA, which are monodominant and nearly monotaxic. They indicate that aggregation (probably of breeding populations) and mass death of metoposaurids were relatively common across the riverine floodplains of Late Triassic Pangea.

This is the Kind of Study I'd Like to See Get Done More Often

I remain convinced that figuring out larger problems starts with the detailed collection of data at a smaller scale.  This is exactly the type of study I'd like to consider for the Chinle Formation.....

Lyson, T. R., and N. R. Longrich. 2010. Spatial niche partitioning in dinosaurs from the latest cretaceous (Maastrichtian) of North America. Proceedings of the Royal Society B. Published online before print October 13, 2010, doi: 10.1098/rspb.2010.1444

Abstract - We examine patterns of occurrence of associated dinosaur specimens (n = 343) from the North American Upper Cretaceous Hell Creek Formation and equivalent beds, by comparing their relative abundance in sandstone and mudstone. Ceratopsians preferentially occur in mudstone, whereas hadrosaurs and the small ornithopod Thescelosaurus show a strong association with sandstone. By contrast, the giant carnivore Tyrannosaurus rex shows no preferred association with either lithology. These lithologies are used as an indicator of environment of deposition, with sandstone generally representing river environments, and finer grained sediments typically representing floodplain environments. Given these patterns of occurrence, we argue that spatial niche partitioning helped reduce competition for resources between the herbivorous dinosaurs. Within coastal lowlands ceratopsians preferred habitats farther away from rivers, whereas hadrosaurs and Thescelosaurus preferred habitats in close proximity to rivers, and T. rex, the ecosystem's sole large carnivore, inhabited both palaeoenvironments. Spatial partitioning of the environment helps explain how several species of large herbivorous dinosaurs coexisted. This study emphasizes that different lithologies can preserve dramatically dissimilar vertebrate assemblages, even when deposited in close proximity and within a narrow window of time. The lithology in which fossils are preserved should be recorded as these data can provide unique insights into the palaeoecology of the animals they preserve.

Using Forensic Science to Determine the Taphonomic History of a Sauropod Dinosaur Quarry

Congratulations to Kenneth Bader. Kenneth has worked in the fossil preparation lab at Petrified Forest National Park since last summer. Prior to this he completed his Master of Science Degree at Kansas University. Kenneth's first paper from his thesis was just published in the journal Palaios. It is an interesting paper which looks at the taphonomy of sauropod skeletons from a quarry in the Jurassic Morrison Formation of Wyoming.

Kenneth closely examined the skeletons and documented hundreds of trace fossils of varying morphologies. Some were interpreted as tooth marks from predators and/or scavengers, but more interestingly many of the trace fossils can be attributed to various arthropods. Comparisons were made with arthropod traces and modern bones and from this a taphonomic hypothesis using forensic entomology can be proposed.

Bader et al. hypothesize that based on this evidence these sauropods died during the dry season, were scavenged, and then went through several detailed stages of decomposition, including a "dry stage" where tracemakers tunneled through dried flesh and created pupation chambers adjacent to bones. Larvae hatched and then contributed to the final removal of soft tissue from the bones. Total time from death until complete burial was estimate to be about 1-3 years.

Congrats again to Kenneth on a very interesting study.

BADER, K., HASIOTIS, S., & MARTIN, L. (2009). APPLICATION OF FORENSIC SCIENCE TECHNIQUES TO TRACE FOSSILS ON DINOSAUR BONES FROM A QUARRY IN THE UPPER JURASSIC MORRISON FORMATION, NORTHEASTERN WYOMING PALAIOS, 24 (3), 140-158 DOI: 10.2110/palo.2008.p08-058r

Abstract- Trace fossils on sauropod skeletons from a quarry in fluvial deposits of the Morrison Formation, Wyoming, are used to reconstruct the taphonomic history of the dinosaur bone accumulation. Shallow pits; rosettes; hemispherical pits; thin, curvilinear, branching grooves; and U- to V-shaped linear grooves make up trace fossils found on sauropod skeletons. The traces were interpreted by comparisons to traces on modern bone. Rosettes are circular rings of modified bone and are likely an early stage in the production of shallow pits. They are interpreted as pupation chambers constructed in dried flesh in contact with sauropod bone. Hemispherical pits are circular with a U-shaped cross section and interpreted as dermestid pupation chambers completed in sauropod bone. Thin, curvilinear, branching grooves are semicircular in cross section, form irregular dendritic or looping patterns, and are interpreted as root etchings. U- to V-shaped linear grooves are interpreted as theropod or crocodilian bite marks. Skeletal articulation and condition and distribution of bone modification traces suggest the skeletons accumulated at this site over no more than 3.5 years, with the bulk of the skeletons contributed during the dry season in the final 3–6 months. Carcasses went through all stages of decomposition—including the dry stage, represented by shallow pits, rosettes, and hemispherical pits. Vertebrate scavengers and necrophagous arthropods fed on the carcasses during all decomposition stages prior to burial of the assemblage.