Early Triassic Ichnoassemblages of Wyoming

This new paper suggests the presence of dinosauromorph (cf. Rotodactylus) and turtle-like (cf. Chelonipus) trackmakers from the Lower Triassic of Wyoming.

Lovelace, D. M., and S. D. Lovelace. 2012. Paleoenvironments and paleoecology of a Lower Triassic invertebrate and vertebrate ichnoassemblage from the Red Peak Formation (Chugwater Group), central Wyoming. Palaios 27:636-657. doi: 10.2110/​palo.2012.p12-011r

Abstract - The Lower Triassic Red Peak Formation of the Chugwater Group has long been considered to have an extremely poor paleontological record, although the cause for the apparent dearth of fossils has yet to be been determined. During the course of fieldwork in central Wyoming numerous vertebrate and invertebrate ichnogenera (n ≥ 11) were observed. Vertebrate tracks and trackways representative of dinosauromorph, archosaur, lepidosaur, and testudinate trackmakers were found (cf. Rotodactylus, Chirotherium barthii, Rhynchosauroides, and cf. Chelonipus respectively). An invertebrate ichnoassemblage composed of at least 6 ichnogenera consistent with the Scoyenia ichnofacies were also found (e.g., Diplichnites, Lockeia, Fuersichnus communis, Palaeophycus striatus, cf. Scoyenia, and cf. Scolicia). The majority of these tracks and traces were found in the upper platy facies (upper 10–20 m of the Red Peak Formation), which is thought to be no younger than upper Spathian in age. Sedimentary structures, architectural elements, and lateral stratigraphic relationships support the interpretation of floodplain, fluvial, and lacustrine deposition for the upper platy facies in central Wyoming. The Red Peak Formation vertebrate and invertebrate ichnoassemblages, along with their associated depositional environments, are consistent with a fluviolacustrine (continental) setting comparable to those described from Lower to Middle Triassic strata with a Pangean distribution, including the Moenkopi Formation in the southwestern United States. This ichnoassemblage provides the first opportunity to observe paleoecological diversity and associated paleoenvironments within the Lower Triassic of the Chugwater Group.

New Triassic Trackway from Switzerland

Cavin, L., Avanzini, M., Bernardi, M., Piuz, A., Proz, P.-A., Meister, C., Boissonnas, J., and C. A. Meyer. 2012. New vertebrate trackway from the autochthonous cover of the Aiguilles Rouges Massif and reevaluation of the dinosaur record in the Valais, SW Switzerland. Swiss Journal of Palaeontology [online first] DOI: 10.1007/s13358-012-0040-0

Abstract - A new tracksite located in the Mesozoic autochthonous series covering the Aiguilles Rouges Massif, circa 7 km to the NNE of the tracksite of the Vieux Emosson, is briefly described. The trampled bed is most likely coeval with the outcrop in the Vieux Emosson area. Two poorly preserved quadrupedal trackways, almost parallel, measure 9.8 and 8 m in length, respectively. They are referred to the Chirotheriidae ABEL, 1835 form-family. A short and well-preserved quadrupedal trackway, composed of two manus-pes couples, is assigned to Chirotherium cf. barthii KAUP, 1835. A reinterpretation of the Vieux Emosson ichnotaxa reveals that most tracks, if not all, belong to indeterminate chirotheriid and that no clear evidence of dinosaur footprints is observed. The trampled bed of the cover of the Aiguilles Rouges Massif probably forms a megatracksite, which is Early or Middle Triassic in age.  

Reassessment of the Triassic "Bee Nest" from Petrified Forest National Park

Tapanila, L., and E. M. Roberts. 2012. The earliest evidence of holometabolan insect pupation in conifer wood. PLoS ONE 7(2): e31668. doi:10.1371/journal.pone.0031668.

Background

The pre-Jurassic record of terrestrial wood borings is poorly resolved, despite body fossil evidence of insect diversification among xylophilic clades starting in the late Paleozoic. Detailed analysis of borings in petrified wood provides direct evidence of wood utilization by invertebrate animals, which typically comprises feeding behaviors.

Methodology/Principal Findings

We describe a U-shaped boring in petrified wood from the Late Triassic Chinle Formation of southern Utah that demonstrates a strong linkage between insect ontogeny and conifer wood resources. Xylokrypta durossi new ichnogenus and ichnospecies is a large excavation in wood that is backfilled with partially digested xylem, creating a secluded chamber. The tracemaker exited the chamber by way of a small vertical shaft. This sequence of behaviors is most consistent with the entrance of a larva followed by pupal quiescence and adult emergence — hallmarks of holometabolous insect ontogeny. Among the known body fossil record of Triassic insects, cupedid beetles (Coleoptera: Archostemata) are deemed the most plausible tracemakers of Xylokrypta, based on their body size and modern xylobiotic lifestyle.

Conclusions/Significance

This oldest record of pupation in fossil wood provides an alternative interpretation to borings once regarded as evidence for Triassic bees. Instead Xylokrypta suggests that early archostematan beetles were leaders in exploiting wood substrates well before modern clades of xylophages arose in the late Mesozoic.

Complex Tetrapod Burrows from the Middle Triassic of Morocco

Too bad there are not any body fossils associated with this find....

Voigt, S., Schneider, J. W., Saber, H.,  Hminna, A.,  Lagnaoui, A.,  Klein, H.,  Brosig, A., and J. Fischer. 2011. Complex tetrapod burrows from Middle Triassic red beds of The Argana Basin (Western High Atlas, Morocco). Palaios 26:555-556.

Abstract - Although burrowing ability has been widespread in tetrapods for more than 300 million years, subsurface dwelling structures that indicate communal behavior are poorly evidenced from pre-Cenozoic strata. Here we present recently discovered tetrapod burrows from Middle Triassic red beds of the Argana Basin in central Morocco, whose complexity suggests an origin by gregarious animals. The well-preserved burrows occur in interbedded mudstones and sandstones interpreted as channel and overbank deposits of ephemeral, braided streams. All burrows originate from the top of thick-bedded sandstones and descend as moderately inclined (10°–30°), partially spiral tunnels to laterally extended, branched chambers in underlying mudstones. Tunnel segments are biconvex to planoconvex in cross section, up to 20 cm wide and 12 cm in maximum height and exhibit transverse scratch marks along the ceilings and sidewalls. Distinctive burrow characteristics include a laterally sinuous geometry (wavelength λ  =  38–45 cm; amplitude A  =  5–10 cm) of the tubelike passages and the presence of grouped alcoves in terminal chambers. We attribute the burrows to procolophonids or therapsids based on closely associated tetrapod tracks and the limited diameter of the excavations. Our findings represent the second oldest record of communal fossorial behavior by tetrapods and the oldest example from low-latitude areas. Beyond providing refuge from predators, these elaborate underground structures probably functioned as a buffer against diurnal or seasonal variations of air temperature and humidity in a semiarid habitat that was situated just north of the paleoequator.

Possible Evidence for Archosaur Predation on Horseshoe Crabs

Diedrich, C. G. 2011. Middle Triassic horseshoe crab reproduction areas on intertidal flats of Europe with evidence of predation by archosaurs. Biological Journal of the Linnean Society103: 76–105. doi: 10.1111/j.1095-8312.2011.01635.x

Abstract - A systematically excavated track site in a 243.5 Myr old Middle Triassic (Karlstadt Formation, Pelsonian, middle Anisian) intertidal carbonate mud-flat palaeoenvironment at Bernburg (Saxony-Anhalt, central Germany) has revealed extensive horseshoe crab trackways attributable to the Kouphichnium Nopsca, 1923 ichnogenus. The exposed track bed of a Germanic Basin-wide spanned intertidal megatrack site is a mud-cracked biolaminate surface on which detailed tracks have been preserved because of rapid drying and cementation as a result of high temperatures, followed by rapid covering with a protective layer of arenitic storm or tsunami sediments. The different trackway types and their orientations have allowed a tidal sequence to be reconstructed, with the initial appearance of swimming horseshoe crabs followed by half-swimming/half-hopping limulids under the shallowest water conditions. The Bernburg trackways, which have mapped lengths of up to 40 m, were all produced by adult animals and exhibit a variety of shapes and patterns that reflect a range of subaquatic locomotion behaviour more typical of mating than of feeding activities. The closest match to the proportions and dimensions of the horseshoe crab tracks at Bernburg is provided by the largest known Middle Triassic limulid Tachypleus gadeai, which is known from the north-western Tethys in Spain. The horseshoe crab body fossils recognized in the German Mesozoic intertidal zones, instead, are from juveniles. The uniformly adult size indicated by the trackways therefore suggests that they may record the oldest intertidal reproductive zones of horseshoe crabs known from anywhere in the world, with the track-makers having possibly migrated thousands of kilometres from shallow marine areas of the north-western Tethys to reproduce in the intertidal palaeoenvironments of the Germanic Basin. Chirotherium trackways of large thecodont archosaurs also appeared on these flats where they appear to have fed on the limulids. With the tidal ebb, smaller reptiles such as Macrocnemus (Rhynchosauroides trackways) appeared on the dry intertidal flats, probably feeding on marine organisms and possibly also on horseshoe crab eggs.

Cynodont Burrows from the Upper Triassic of Poland

Tałanda, M., Dzieçioł, S., Sulej, T., and G. Niedźwiedzki. 2011. Vertebrate burrow system from the Upper Triassic of Poland. Palaios 26:99-105. DOI: 10.2110/palo.2010.p10-024r

 Abstract - In this paper we report on a rare fossil vertebrate burrow system in Upper Triassic (Norian) fluvial deposits of the Holy Cross Mountains in central Poland. The burrows are preserved mainly by prominent green infillings in red mudstone and claystone exposed in the wall of a clay pit. The mode of occurrence, morphology, and size of the burrows suggests that cynodont therapsids most likely constructed them.

Bite Traces on Dicynodont Bones and the Early Evolution of Large Terrestrial Predators

Niedźwiedzki, G., Gorzelak, P. & Sulej, T. 2010: Bite traces on dicynodont bones and the early evolution of large terrestrial predators. Lethaia, DOI: 10.1111/j.1502-3931.2010.00227.x.


Abstract - Dicynodont (Synapsida: Anomodontia) bones from the Late Triassic (late Norian ⁄ early Rhaetian) of Poland yield characteristic tooth marks that can be attributed to three ichnotaxa (Linichnus serratus, Knethichnus parallelum and Nihilichnus nihilicus). The general shape and dimension of these traces perfectly match the dental morphology of a co-occurring carnivorous dinosaur. It is therefore concluded that early carnivorous dinosaurs were feeding on dicynodonts. This discovery constitutes one of the oldest evidence of dinosaur predator–prey interaction. It is suggested that an evolutionary increase in the size of dicynodonts across the Late Triassic may have been driven by selection pressure to reach a size refuge from early dinosaur predators.

My Thoughts on the Peer Review Process (Part 3) - Wait Until the Peer-reviewed Paper (a case study from the ongoing debate surrounding reports of Triassic nests from Arizona).

When I was working on my MS thesis at Northern Arizona University on aetosaurs, I was struck by the announced discovery of fossil "reptile nests" (Hasiotis and Martin, 1999) and the earliest records of many social insect nests including bees (e.g., Hasiotis et al., 1998).  It seemed possible that aetosaurs could have been the nest maker, and evidence from the site had also suggested some degree of parental care from whomever the nest maker was.  Likewise, I had been tossing around the idea of possible alternative food sources for aetosaurs and insects might just fit the bill, especially if there was evidence for social insect nests during the Late Triassic.  This early bee record also suggested that bees evolved before and separately from angiosperms.

Photograph of purported reptile nests from Petrified Forest National Park.  From Hasiotis and Martin, 1999.

 When I started working at the park one of the first sites my supervisor took me to was the site of these "reptile nests" as she was curious what another geologist/paleontologist would think of them.  Needless to say I was extremely disappointed.  Every geologist I have showed them to since agrees with my assessment, they are simply erosional potholes in a sandstone.  Visiting the site provides the detailed evidence for this determination.  Unfortunately this discovery resulted in much popular press and these "nests" even make into more recent research papers; however, no detailed rebuttal has yet been published.  Other nests attributed to aetosaurs have been described from the Triassic of Italy (Avanzini et al., 2007), but I have not been able to see these first hand to evaluate them.

[Note: I had forgotten about the rebuttal on the Petrified Forest 'nests' by Lucas and Hunt (2006)].

Purported "Bee's Nests" from Petrified Forest National Park.  NPS photo.

The bee's nest record, from a log in the Petrified Forest, was immediately criticized by entomologists (e.g., Grimaldi, 1999; Engel, 2001), arguing that these traces provide no signature evidence of bee activity.  Unlike the "reptile nests"; however, these must have been made by some type of organism, and beetles have been the most cited tracemaker.  Also unlike the 'reptile nests' there is a detailed rebuttal paper that provides good evidence that these traces are not bee's nests, but rather represent a new form of beetle trace (Lucas et al., 2010 - see abstract below).  Like the 'reptile nests' every person with an entomological background that I have shown these to agrees with this assessment and like the 'reptile nests' these story too received much popular press before a paper was published. 

The lesson here is that we should avoid oversensationalizing 'amazing' discoveries like these until peer reviewed papers describing them in detail are published in the relevant literature.  Failing to do so can cause long term misunderstandings regarding our fossil resources. This also happened in the case of Chindesaurus bryansmalli ("Gertie") which was hailed as the world's "earliest" dinosaur, a claim which still makes it in to occasional brochures and webpages about Petrified Forest National Park. 

It can be very tempting to get excited about the finds and want to make a big media splash, but in the end they cannot be considered valid or relevant until they pass the critical test of peer review. As I argued in a previous post, having these papers reviewed by qualified entomologists and geological colleagues can help avoid having your work criticized and/or not accepted by future workers. 

Having seen the specimens I believe that the Lucas et al's. interpretation has much merit; as do several other entomologists; however, it would appear that the debate is not entirely closed.  I do especially have to agree with the last quote in this news story.  I'd like to see more evidence for such a sensational claim.

Lucas, S. G., Minter, N. J., and A. P. Hunt.  2010. Re-evaluation of alleged bees' nests from the Upper Triassic of Arizona. Palaeogeography, Palaeoclimatology, Palaeoecology 286:194–201.

Abstract - Published records of supposed Triassic bees' nests are based on trace fossils in silicified wood and in sandstone in Upper Triassic strata of the Chinle Group in Petrified Forest National Park, Arizona. A critical, firsthand restudy of these trace fossils indicates that they lack diagnostic features of bees' nests, such as cells with smooth linings and spiral closure caps. Indeed, many of the observations claimed to identify these traces as bees' nests cannot be replicated. Instead, the putative Triassic bees' nests can be classified as: 1. Clavate borings in petrified wood, somewhat similar to Teredolites; these borings preferentially penetrate
heart-rot fungus (Polyporites) and are mostly likely larval chambers of wood-boring beetles. 2. Cylindrical,
vertical burrows in sandstone assignable to Skolithos; these are almost certainly arthropod produced. The
recognition that the Chinle Group trace fossils are not bees' nests eliminates them as evidence that decouples
bee origins from the Cretaceous origin of angiosperms. The Triassic trace fossils in silicified wood are also a
new and unique record of likely beetle borings in Triassic wood.

REFERENCES

Avanzini, M., Dalla Vecchia, F.M., Mietto, P., Piubelli, D., Preto, N., Rigo, M., and G. Roghi. 2007. A vertebrate nesting site in northeastern Italy reveals unexpectedly complex behavior for Late Carnian reptiles. Palaios 22:465-475.

Engel, M.S. 2001. A monograph of the Baltic amber bees and the evolution of the Apoidea (Hymenoptera). Bulletin of the American Museum of Natural History 259:1–192.

Grimaldi, D. 1999. The co-radiations of pollinating insects and angiosperms in the Cretaceous. Annals of the Missouri Botanical Garden 86, 373–406.

Hasiotis, S.T., and Martin, A., 1999, Probable reptile nests from the Upper Triassic Chinle Formation, Petrified Forest National Park, Arizona, in Santucci, V., and McClelland, L., eds., National Park Service, Paleontological Research, v. 4, p. 85–90.

Hasiotis, S.T., Dubiel, R.F., Kay, P.T., Demko, T.M., Kowalska, K., and D. McDaniel. 1998. Research update on hymenopteran nests and cocoons, Upper Triassic Chinle Formation, Petrified Forest National Park, Arizona. In: Santucci, V.L., McClelland, L. (Eds.), National Park Service Paleontological Research. Technical Report NPS/NRGRD/GRDTR-98/01, pp. 116–121.

Lucas, S.G., and Hunt, A.P. 2006. Reappraisal of 'reptile nests' from the Upper Triassic Chinle Group, Petrified Forest National Park, Arizona. New Mexico Museum of Natural History and Science Bulletin 37:155-159.

Lucas, S. G., Minter, N. J., and A. P. Hunt. 2010. Re-evaluation of alleged bees' nests from the Upper Triassic of Arizona. Palaeogeography, Palaeoclimatology, Palaeoecology 286:194–201.

Two New Triassic Papers in Paleo3

The latest Triassic publication fest continues.

Marsicano, C.A., Mancuso, A.C., Palma, R.M., and Krapovickas, V. 2010. Tetrapod tracks in a marginal lacustrine setting (Middle Triassic, Argentina): taphonomy and significance. Palaeogeography, Palaeoclimatology, Palaeoecology. doi: 10.1016/j.palaeo.2010.03.009.

ABSTRACT - Fossil tetrapod footprints not only provide valuable information about trackmaker paleobiology but also to give insight into details of the depositional conditions of the substrate at the time of imprinting. Therefore, in the present study the mode of formation and taphonomy of footprints in different substrates was used to investigate the gait and walking dynamics of the trackmakers as well as a source of additional information on the environmental conditions of the track-bearing beds during imprinting. The analyzed section corresponds to thick Middle Triassic lacustrine/deltaic deposits of the Ischichuca/Los Rastros Formation (Ischigualasto-Villa Unión Basin) that crops out at the Quebrada de Ischichuca in northwestern Argentina. Part of the track-bearing surfaces correspond to the top of sandy distributary channel mouth bars in a distal delta front setting that were exposed along the lake margin during a lake level fall. Cross-cutting relationships observed among ripple-marks, the footprints, and invertebrate traces of a softground suite of the Scoyenia ichnofacies suggest an omission surface. Measured trackway orientations in the sandstones are perpendicular to the paleo-shoreline, with the animals coming and going along the exposed top of the bars, probably for drinking. Laterally, the distal delta front deposits interfinger with track-bearing wackestone beds of palustrine origin deposited in a restricted local embayment lateral to the delta influenced environment. Trackway orientations in the wackestones are, in contrast, consistent with the animals moving nearly parallel to the lake border, probably along a preferred route. Evidences of a relative high groundwater table at the time of imprinting in the track-bearing surfaces are revealed by the well developed rims of extruded sediment and collapsed digits in the studied tracks and the nearly absence of associated desiccation cracks on the same surfaces. Nevertheless, temporary emergence cannot be ruled out when paleosoil formation was probably promoted as can be observed in the microstructure of both sandstones and wackestones. Moreover, footprint preservation in the wackestones might have been enhanced by partial hardening of the trampled surface during subaerial exposure. Combining ichnofossil content and taphonomy with facies analysis we identified in the lower part of the Ischichuca/Los Rastros succession a relatively rapid withdrawal of the water basinward that was probably due to a forced regression during early rifting of basin evolution. Footprints can also provide valuable information about locomotion dynamics and trackmaker behavior. Thus, the sideways deformation observed in the studied footprints, attributed to basal archosaurs and putative basal dinosaurs, can be related to an outward rotation of the foot during the step cycle, a condition that might allied to the development of the parasagittal posture in Archosauria. Besides, the densely trampled surface described herein constitutes the first documented evidence of putative social behavior among therapsid dicynodonts, the most important group of herviborous animals in the early Mesozoic terrestrial ecosystems throughout Gondwana.


Preto, N., Kustatscher, E., and Wignall, P.B. 2010. Triassic climates -- state of the art and perspectives. Palaeogeography, Palaeoclimatology, Palaeoecology. doi: 10.1016/j.palaeo.2010.03.015.

ABSTRACT - The climate of the Triassic period was characterized by a non-zonal pattern, dictated by a strong global monsoon system with effects that are most evident in the Tethys realm. This strong monsoonal regime is related to the aggregation of the Pangaean supercontinent, which by Triassic time was already completed. Climate oscillations existed within this framework. The harsh hothouse climatic conditions that characterized the Late Permian, and perhaps precipitated the end-Permian mass extinction, were probably maintained during the Early Triassic and may account for the impoverished, but distinctive, faunal and floral Lower Triassic associations. Although metazoan reef builders were probably the most
affected group, carbonate production remained high at least in the western Tethys realm. The Middle Triassic was characterised locally by humid episodes, although their geographical distribution has yet to be clarified. The Carnian Pluvial Event, marks an episode of increased rainfall documented worldwide, was the most distinctive climate change within the Triassic. Different hypotheses have been proposed for its causes: changes of atmospheric or ocean circulation driven by plate tectonics; a peak of the global monsoon due to maximum continent aggregation; or triggering by the eruption of a large igneous province. Subsequently, the late Carnian and Norian seem to have been climatically stable, although minor climatic changes have recently been described even from this time period. Finally, the end Triassic extinction event is also associated with climate change, specifically warming and increased rainfall, but this evidence comes mostly from the northern parts of the Central Atlantic Magmatic Province, and the global pattern of climate change at the Triassic / Jurassic boundary has still to be resolved. Many facets of Triassic climate are intriguing and deserve further research. However, paleoclimate studies on the Triassic have so far been carried out only locally with different proxies. Those proxies will require inter-calibration, in order to depict correctly the temporal and geographical patterns of Triassic climate.

Evidence of Prey Item Stashing in Burrows by Early Triassic Theriodontids?

Modesto, S. P., and J. Botha-Brink. 2010. A burrow cast with Lystrosaurus skeletal remains from the Lower Triassic of South Africa. Palaios 25:274-281. DOI: 10.2110/palo.2009.p09-077r

Abstract - We report on a large burrow cast with skeletal contents from Lower Triassic strata of the Palingkloof Member of the Balfour Formation, which forms the lowermost portion of the Lystrosaurus Assemblage Zone(LAZ) of South Africa. The burrow cast is similar to large burrow casts previously described from the LAZ that were identified as large-scale Scoyenia domichnia. It is the first large burrow cast from the LAZ found to contain diagnostic fossil bone. The burrow cast is a relatively straight, subhorizontal (inclined ,12u), dorsoventrally compressed tube consisting of an entry ramp and living chamber; the entrance to the burrow is not preserved and there is no evidence that the ramp formed a spiral section. The skeletal material comprises a single, partial, disarticulated skeleton a juvenile animal that can be assigned with confidence to the dicynodont genus Lystrosaurus. Whereas similar large-diameter burrow casts from strata slightly higher in the LAZ have been attributed to Lystrosaurus, we present an alternative hypothesis that a carnivorous tetrapod constructed the burrow. Our preferred hypothesis is supported by the observation that the interred Lystrosaurus skeleton is too small to be the maker of this particular burrow, by the general observation that carnivorous tetrapods construct relatively straight burrows, and by the partial, disarticulated state of the skeleton, which we interpret as the remains of larded prey. We suggest that akidnognathid theriodonts of the genera Moschorhinus or Olivierosuchus, the most conspicuous large predators of the LAZ, were the constructors of large-diameter, subhorizontal burrows.

Two New Triassic Trace Fossil Papers in Ichnos.

The second paper has the shortest abstract I've ever seen, so it must not be saying too much.

Voight, S., D. Hoppe. 2010. and Mass Occurrence of Penetrative Trace Fossils in Triassic Lake Deposits (Kyrgyzstan, Central Asia). Ichnos 17:1-11. http://dx.doi.org/10.1080/10420940903358081

Abstract - Bioturbation and the breakdown of organic detritus by burrowing macro-invertebrates are key factors for the energy flow in recent freshwater ecosystems due to the acceleration of nutrient cycling. According to the current state of knowledge, food webs similar to those of modern lakes were not operating until the Late Mesozoic, when a well-established freshwater infauna evolved. Here we describe laterally extended networks of irregularly branched burrows that constitute the most common ichnofossils in lacustrine deposits of the Middle to Late Triassic Madygen Formation, SW Kyrgyzstan. The shallow penetrative trace fossils give evidence that exploitation of lake-bottom sediments by benthic invertebrates was already in place in the Early Mesozoic. Architecture and size of the fossil burrows indicate deposit-feeding, worm-like trace makers of similar morphology and behavior to extant oligochaetes or aquatic insect larvae. Maximum intensity of bioturbation is recorded in mudstones of the transitional sublittoral to profundal lake zone, which usually represent the thermocline/chemocline level in modern stratified lakes. Taking into account the low-oxygen tolerance of many recent oligochaetes and insect larvae, we propose that ecospace utilization of deep-water lacustrine settings was originally impelled by two factors: the exploitation of additional food resources and the avoidance of predation by carnivorous animals from well-aerated lake zones. Spatial restriction of the described fossil traces could offer a basic approach to subdivide the Mermia ichnofacies.


Hubert, J. F., and J. A. Dutcher. 2010. Scoyenia Escape Burrows in Fluvial Pebbly Sand: Upper Triassic Sugarloaf Arkose, Deerfield Rift Basin, Massachusetts, USA. Ichnos 17-20-24. http://dx.doi.org/10.1080/10420940903358529

Abstract - Late Triassic larvae of an insect, probably a beetle, moved diagonally upwards though fluvial pebbly sand along a thin mud layer, constructing Scoyenia burrows in the Sugarloaf Arkose, Deerfield rift basin, Massachusetts. They may have been escaping a temporary rise of the water table in the monsoonal dry season.

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.