The Foot of Poposaurus gracilis, Further Convergence with Theropod Dinosaurs

....and the answer to the question we've all been wondering...what type of footprint would Poposaurus have left? It appears that Poposaurus  probably could have left a Grallator-like track.

Farlow, J. O., Schachner, E. R., Sarrazin, J. C., Klein, H., and P. J. Currie. 2014. Pedal Proportions of Poposaurus gracilis: Convergence and Divergence in the Feet of Archosaurs. The Anatomical Record, Early View. DOI: 10.1002/ar.22863.

Abstract - The crocodile-line basal suchian Poposaurus gracilis had body proportions suggesting that it was an erect, bipedal form like many dinosaurs, prompting questions of whether its pedal proportions, and the shape of its footprint, would likewise “mimic” those of bipedal dinosaurs. We addressed these questions through a comparison of phalangeal, digital, and metatarsal proportions of Poposaurus with those of extinct and extant crocodile-line archosaurs, obligate or facultatively bipedal non-avian dinosaurs, and ground birds of several clades, as well as a comparison of the footprint reconstructed from the foot skeleton of Poposaurus with known early Mesozoic archosaurian ichnotaxa. Bivariate and multivariate analyses of phalangeal and digital dimensions showed numerous instances of convergence in pedal morphology among disparate archosaurian clades. Overall, the foot of Poposaurus is indeed more like that of bipedal dinosaurs than other archosaur groups, but is not exactly like the foot of any particular bipedal dinosaur clade. Poposaurus likely had a digitigrade stance, and its footprint shape could have resembled grallatorid ichnotaxa, unless digit I of the foot of Poposaurus commonly left an impression.

Analysis of Triassic Archosauriform Trackways

Kubo, T. and M. O. Kubo. 2013. Analysis of Triassic archosauriform trackways: difference in stride/foot ratio between dinosauromorphs and other archosauriforms. Palaios 28: 259-265 doi:10.2110/palo.2012.p12-099r
Abstract - Fossilized trackways have rarely been analyzed quantitatively to examine major trends and patterns in evolution despite their potential utility, especially in understanding locomotory evolution. In the present study, trackways of Triassic archosauriforms were analyzed. The analyses showed foot and stride lengths of archosauriforms increased from the Early to Middle Triassic, especially those of dinosauromorphs, which tripled. Dinosauromorphs were much smaller in foot length and stride length compared to other archosauriforms during
the Early Triassic. They reached similar stride length compared with other archosauriforms during the Middle Triassic and similar foot length in the Late Triassic. Stride/foot ratio is significantly higher in dinosauromorphs compared to other archosauriforms throughout the Triassic. This relatively long stride length of dinosauromorphs is attributed to either faster speed or higher relative hip height that was probably caused by their digitigrade foot posture. Analyses of trackway data sets, especially in combination with precise trackmaker assignment and age determination, would bring us more thorough knowledge about locomotory evolution of tetrapods that complements body fossil evidence.

Chirotherium Trackways from the Middle Triassic of China

Xing, L., Klein, H., Lockley, M. G., Li, J., Zhang, J., Matsukawa, M., and J. Xiao. 2013. Chirotherium trackways from the Middle Triassic of Guizhou, China. Ichnos 20: 99-107. DOI:10.1080/10420940.2013.788505

Abstract - Triassic tetrapod footprints from China are less well known than those from the Jurassic and Cretaceous. Archosaurian trackways of the ichnogenus Chirotherium were found in the Middle Triassic Guanling Formation in Zhenfeng County (Guizhou Province) at the southwestern edge of the Yangtze plate in the early 1960s but were not correctly identified and adequately described until 40 years later. Here we give a detailed re-description and review of the trackways, which are known from two localities near the villages of Niuchang and Longchang. They occur on the bedding surface of a mud-cracked argillaceous dolostone deposited in a near-shore, shallow-water environment. Their morphology and general trackway pattern indicate that they pertain to the ichnospecies Chirotherium barthii, well known from Middle Triassic
track surfaces of Europe, North and South America, and northern Africa. A peculiarity of the trackways from China are the low pace angulation and stride length, reflecting slow-moving trackmakers, which were basal crown-group archosaurs, possibly early
representatives of the dinosaur-bird line or, alternatively, stem-group crocodylians. These tracks constitute the only chirotheriid record known from Asia thus far and indicate a Pangea-wide distribution for this ichnotaxon. Biostratigraphically, assemblages with C. barthii are characteristic of the early Anisian, an age assignment already supported for the Guanling Formation based on conodont and bivalve biostratigraphy. In contrast, however, radiometric data from an interlayered ash bed indicate a Ladinian age.

Six New Papers from the Forthcoming Volume 'Anatomy, Phylogeny, and Palaeobiology of Early Archosaurs and their Kin.

You can access the abstracts electronically here.

Mastrantonio, B. M., Schultz, C. L., Desojo, J. B., and J.  Bittencourt Garcia. 2013. The braincase of Prestosuchus chiniquensis (Archosauria: Suchia)From: Nesbitt, S. J., Desojo, J. B. & Irmis, R. B. (eds) 2013. Anatomy, Phylogeny and Palaeobiology of Early Archosaurs and their Kin. Geological Society, London, Special Publications, 379, doi:10.1144/SP379.10

Abstract - The osteology of an almost complete braincase of the rauisuchian archosaurs Prestosuchus chiniquensis from the Middle Triassic of Brazil is described for first time, based on two specimens (UFRGS-PV-0629-T and UFRGS-PV-0156-T). A comparative description with other taxa of rauisuchians is presented that forms the basis of a phylogenetic analysis. To perform the phylogenetic analysis, we describe and discuss each character codification for a modified version of the recent matrices of Gower (2002), Gower & Nesbitt (2006) and Brusatte et al.(2010). The analysis resulted in two most parsimonious trees that differ from the topologies recovered by Gower (2002) in a few aspects within Rauisuchia, and Prestosuchus chiniquensis was unequivocally depicted as deeply nested within Pseudosuchia, as the sister taxon of Batrachotomus kuperferzellensis in both topologies, supported by a single synapomorphy: the reduced to small fissure of the post-temporal fenestra between parietal, supraoccipital and exoccipital-opisthotic.


Sues, H.-D., Desojo, J. B., and M. D. Ezcurra. 2013. Doswelliidae: a clade of unusual armoured archosauriforms from the Middle and Late Triassic. From: Nesbitt, S. J., Desojo, J. B. & Irmis, R. B. (eds) 2013. Anatomy, Phylogeny and Palaeobiology of Early Archosaurs and their Kin. Geological Society, London, Special Publications, 379, first published on April 23, 2013, doi:10.1144/SP379.13

Abstract - Doswelliidae is a clade of armoured non-archosaurian archosauriform reptiles more closely related to Archosauria than are Proterosuchidae, Erythrosuchidae and possibly Euparkeria capensis. It is currently known from the late Middle Triassic (Ladinian) of Germany, the late Middle to early Late Triassic (Ladinian–Carnian) of Argentina and Brazil, and the Late Triassic (Carnian–Norian) of the USA. To date, two unambiguous synapomorphies diagnose Doswelliidae: (i) osteoderm ornamentation coarse, incised, and composed of central regular pits of subequal size and shape, and (ii) osteoderms with anterior articular lamina. Five taxa are currently recognized: Archeopelta arborensis, Doswellia kaltenbachi, Doswellia sixmilensis, Tarjadia ruthae and a new taxon from Germany. Based on skeletal features and occurrence, doswelliid archosauriforms may have had a semi-aquatic mode of life.


Langer, M. C., and J. Ferigolo. 2013. The Late Triassic dinosauromorph Sacisaurus agudoensis (Caturrita Formation; Rio Grande do Sul, Brazil): anatomy and affinities. From: Nesbitt, S. J., Desojo, J. B. & Irmis, R. B. (eds) 2013. Anatomy, Phylogeny and Palaeobiology of Early Archosaurs and their Kin.  Geological Society, London, Special Publications, 379, first published on April 23, 2013, doi:10.1144/SP379.16

Abstract - Silesauridae is an exclusively Triassic group of dinosauromorphs, knowledge on the diversity of which has increased dramatically in the last few years. Silesaurid relationships are still contentious, as a result in part of different homology statements, particularly regarding the typical edentulous mandible tip of these animals. One of the most complete silesaurids yet discovered is Sacisaurus agudoensis from the Caturrita Formation (Late Triassic: Norian) of Rio Grande do Sul, Brazil, represented by numerous isolated bones recovered from a single site. The anatomy of S. agudoensis is fully described for the first time here, and comparisons are provided to other basal dinosauromorphs. S. agudoensis is a small-bodied animal (less than 1 m in length) that possesses a dentition consisting of leaf-shaped crowns with large denticles in the carinae, a plesiomorphic propubic pelvis with an almost fully closed acetabulum, elongate distal hindlimbs suggesting well-developed cursorial ability, and a laterally projected outer malleolus in the tibia. All previous numerical phylogenies supported a non-dinosaur dinosauromorph affinity for Silesauridae, but the reanalysis of one of those studies suggests that a position within Dinosauria is not unlikely, with silesaurids forming the basal branch of the ornithischian lineage.


Turner, A. H., and S. J. Nesbitt. 2013. Body size evolution during the Triassic archosauriform radiation. From: Nesbitt, S. J., Desojo, J. B. & Irmis, R. B. (eds) 2013. Anatomy, Phylogeny and Palaeobiology of Early Archosaurs and their Kin.  Geological Society, London, Special Publications, 379, first published on April 23, 2013, doi:10.1144/SP379.15

Abstract - The first large (>1 m) diapsids appeared near the Permian–Triassic extinction and a subset of diapsids, the archosauriforms, expanded their body size range soon after in the Early–Middle Triassic. Here, we examine body size at key evolutionary events within Archosauriformes during the Triassic and through the end-Triassic extinction. Using femoral length as a body size proxy and a temporally calibrated phylogeny of Archosauriformes, we estimate ancestral body sizes using a maximum likelihood approach and test for the presence of an adapative radiation by comparing the fit of competing evolutionary models. Archosauriform body size is characterized by punctuated change with more change occurring early in the Triassic. Archosaurs crossing the Triassic–Jurassic boundary show a wide range in ancestral size, and dinosaurs (sauropodomorphs and theropods) are considerably larger in the Jurassic. Crocodylomorph origins are characterized by a drop in body size; however, both the relative amount of change and the rate of change are matched among other archosaur clades. Archosauriforms increase in absolute body size through the Triassic and evidence suggests that a directional trend in size increase occurred in the early Mesozoic. The morphological signature of adaptive radiation is rare in comparative data from extant animals but is present at the origination of Archosauriformes.


Niedźwiedzki, G., Brusatte, S. L., and R. J. Butler. 2013. Prorotodactylus and Rotodactylus tracks: an ichnological record of dinosauromorphs from the Early–Middle Triassic of Poland. From: Nesbitt, S. J., Desojo, J. B. & Irmis, R. B. (eds) 2013. Anatomy, Phylogeny and Palaeobiology of Early Archosaurs and their Kin. Geological Society, London, Special Publications, 379, first published on April 23, 2013, doi:10.1144/SP379.12

Abstract - We present the first comprehensive description of Prorotodactylus and Rotodactylus  dinosauromorph tracks from the Early and Middle Triassic of the Holy Cross Mountains, Poland. We describe and comprehensively figure tracks that have been mentioned briefly in previous accounts as well as new, recently discovered material, and analyse the variation and stratigraphic distribution of these specimens. Tracks have been recorded from four sites – Koszary, Stryczowice, Wióry and Baranów – which span the early Olenekian – early Anisian (c.250–246 Ma). These tracks therefore represent an ichnological record of the evolutionary succession of early dinosauromorphs during the earliest part of their evolutionary history. Recognized track types include cf. Prorotodactylus isp., Prorotodactylus isp., Prorotodactylus mirus, Rotodactylus cursorius, Rotodactylus isp. and cf. Rotodactylus isp. At least three distinct Early and early Middle Triassic early dinosauromorph ichnofaunas can be recognized. The oldest, which is early Olenekian in age, is characterized by the presence of Prorotodactylus isp., cf.Prorotodactylus isp. and non-archosaurian archosauromorph or archosaur tracks (e.g. Synaptichnium isp., Protochirotherium isp.), recorded at the Stryczowice and Koszary sites. The following assemblage, recorded at the late Olenekian Wióry site, displays the highest ichnodiversity of dinosauromorphs, with four track types present (Prorotodactylus isp., Prorotodactylus mirus, Rotodactylus cursorius and cf. Rotodactylus isp.). The youngest site, Baranów, includes Rotodactylus isp., as well as other larger dinosauromorph tracks. The first body fossil evidence of dinosauromorphs is a few million years younger than the youngest Polish tracks, so Prorotodactylus and Rotodactylus tracks currently provide the oldest record of dinosauromorph morphology, biology and evolution.


Ezcurra, M. D., Butler, R. J., and D. J. Gower. 2013. ‘Proterosuchia’: the origin and early history of Archosauriformes.. From: Nesbitt, S. J., Desojo, J. B. & Irmis, R. B. (eds) 2013. Anatomy, Phylogeny and Palaeobiology of Early Archosaurs and their Kin. Geological Society, London, Special Publications, 379, first published on April 23, 2013, doi:10.1144/SP379.11

Abstract - The earliest history of Archosauriformes is mainly represented by members of Proterosuchidae and Erythrosuchidae, which are known worldwide from latest Permian to Middle Triassic beds. These two groups were historically combined within ‘Proterosuchia’, with approximately 30 nominal species. Two morphotypes have been recognized among proterosuchians: proterosuchids with a generally more sprawling gait and elongated and low skulls with an overhanging premaxilla, and the more heavily built erythrosuchids, with a probably less sprawling gait and large, presumably hypercarnivorous, skulls. The systematics of ‘Proterosuchia’ was relatively chaotic throughout most of the twentieth century, but currently there exists consensus regarding the non-monophyly of proterosuchians and their phylogenetic position outside all other archosauriforms. In contrast, the delimitation and taxonomic content of Proterosuchidae and Erythrosuchidae remain unstable. Few studies of proterosuchian palaeobiology have been carried out. Current lines of evidence favour a predominantly terrestrial lifestyle for proterosuchians. Limb bone histology indicates rapid continuous growth rates in Proterosuchus and Erythrosuchus before reaching sexual maturity. A better knowledge of proterosuchian anatomy, systematics, evolution and ecology is important for advancing understanding of the origin and early radiation of Archosauriformes and the patterns of biotic recovery following the Permo-Triassic mass extinction event. There remains much research to be carried out in proterosuchian palaeobiology.

Diverse Tetrapod Track Assemblages from the Late Triassic of Morocco

Lagnaoui, A. Klein, H., Voigt, S., Hminna, A., Saber, H., Schneider, J. W., and R. Werneburg. 2012. Late Triassic Tetrapod-Dominated Ichnoassemblages from the Argana Basin (Western High Atlas, Morocco). Ichnos 19:238-253. 

DOI:

10.1080/10420940.2012.718014

Abstract - Diverse tetrapod track assemblages with Scoyenia invertebrate traces were discovered in the Triassic Timezgadiouine and Bigoudine formations of the Argana Basin (Western High Atlas, Morocco). The ichnofossils occur in alluvial plain sandstones and mudstones of the Irohalène Member (T5) and Tadart Ouadou Member (T6) considered Carnian-Norian in age by vertebrate remains and palynomorphs. Tetrapod footprints are assigned to Apatopus, Atreipus-Grallator,Eubrontes isp., Parachirotherium, cf. Parachirotherium postchirotherioides, Rhynchosauroides ispp., and Synaptichnium isp. They can be referred to lepidosauromorph/ archosauromorph, basal archosaur, and dinosauromorph trackmakers. Apatopus represented by 11 tracks of a more than 4 m long trackway, is recorded for the first time outside of North America and Europe. The assemblage concurs with the proposed Late Triassic age of the track-bearing beds by the occurrence of Apatopus, Atreipus-Grallator, and Eubrontes. If this is accepted, the stratigraphic range of Synaptichnium and Parachirotherium, hitherto known only from Early or Middle Triassic deposits, has to be extended to the Carnian-Norian. The occurrence of Eubrontes in the Irohalene Member (T5) provides further evidence for large theropods in pre-Jurassic strata. All assemblages are referred to the Scoyenia ichnofacies indicating continental environments with alternating wet and dry conditions.

Footprints of Large Theropod Dinosaurs from the Late Triassic of Brazil

The Caturrita Formation may be younger than previously thought and there is a currently undiscovered large theropod in the latest Triassic of Brazil.

da Silva, R. C., Barboni, R., Dutra, T., Godoy, M. M., and R. B. Binotto. 2012. Footprints of large theropod dinosaurs and implications on the age of Triassic biotas from southern Brazil. Journal of South American Earth Sciences 39:16-23. http://dx.doi.org/10.1016/j.jsames.2012.06.017

Abstract - Dinosaur footprints found in an outcrop of the Caturrita Formation (Rio Grande do Sul State, Southern Brazil), associated with a diverse and well preserved record of fauna and flora, reopen the debate about its exclusive Triassic age. The studied footprints were identified as Eubrontes isp. and are interpreted as having been produced by large theropod dinosaurs. The morphological characteristics and dimensions of the footprints are more derived than those commonly found in the Carnian–Norian, and are more consistent with those found during the Rhaetian–Jurassic. The trackmaker does not correspond to any type of dinosaur yet known from Triassic rocks of Brazil. Recent studies with the paleofloristic content of this unit also support a more advanced Rhaetian or even Jurassic age for this unit.

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.  

Hitchcock's Birds

Brian Switek has a wonderful post on the dinosaur trackways of New England over at the Dinosaur Tracking Blog.  I grew up in Connecticut and as a boy enjoyed going to Dinosaur State Park to see the trackways.  My first foray into the Triassic.

Aetosaurs Made Brachychirotherium Footprints

Lucas, S. G., and A. B. Heckert. 2011. Late Triassic aetosaurs as the trackmaker of the tetrapod footprint ichnotaxon Brachychirotherium. Ichnos 8: 197-208 DOI:10.1080/10420940.2011.632456

Abstract - Brachychirotherium is the common ichnogenus of Late Triassic chirothere footprints well known from western Europe, North America, Argentina and South Africa. Although it has long been agreed by most workers that the trackmaker of Brachychirotherium was a derived crurotarsan archosaur, the trackmaker has been identified as either a rauisuchian or an aetosaur, and some workers attribute it to a primitive crocodylomorph (sphenosuchian). New knowledge of the osteology of the manus and pes of a large aetosaur, Typothorax coccinarum, indicates a close correspondence between the manus and pes structure of aetosaurs and the morphology of Brachychirotherium. Furthermore, functional analysis of complete skeletons indicates aetosaurs plausibly placed their feet in the narrow gauge, nearly the overstepped walk characteristic of Brachychirotherium. Brachychirotherium and aetosaurs have matched distributions, that is, they were Pangea-wide during the Late Triassic. The manus and pes morphology of rauisuchians and early crocodylomorphs (sphenosuchians) deviate from Brachychirotherium footprint morphology in key features, thus excluding their identification as trackmakers. Aetosaurs made Brachychirotherium footprints.

Footprint Evidence of Late Triassic Ornithischians from Central Europe?

This footprint assemblage from the Upper Triassic of Central Europe purportedly contains evidence for Triassic ornithischian dinosaurs (cf. Anomoepus isp.). As stated by the author this would be remarkable and offer new information regarding the early evolution of this group. However, the evidence is not conclusive as the taxonomic ID of the tracks is not certain, but I'd love to hear from someone who is more familiar with archosaur tracks what they think of this ID and discovery.

Niedźwiedzki, G. 2011. A Late Triassic dinosaur−dominated ichnofauna from the Tomanová Formation of the Tatra Mountains, Central Europe. Acta Palaeontologica Polonica 56: 291–300. doi:10.4202/app.2010.0027
Abstract - Osteological fossils of dinosaurs are relatively rare in the Late Triassic and Early Jurassic. Thus, ichnofossils are a critical source of information on Late Triassic terrestrial vertebrate communities. The outcrops of the Tomanová Formation (?late Norian–Rhaetian) in the Tatra Mountains of Poland and Slovakia have yielded a diverse ichnofauna. Seven more or less distinct morphotypes of dinosaur tracks have been recognized and are discussed. Most tracks are partly eroded or deformed, but are preserved well enough to be assigned to a range of trackmakers, including early ornithischians, small and large theropods (coelophysoids and/or possibly early tetanurans), and probably basal sauropodomorphs (“prosauropods”) or first true sauropods.

First Occurrence of a Middle Triassic Tetrapod Ichnofauna from Morocco

Klein, H., Voigt, S., Saber, H., Schneider, J. W., Hminna, A., Fischer, J., Lagnaoui, A., and A. Brosig. 2011. First occurrence of a Middle Triassic tetrapod ichnofauna from the Argana Basin (Western High Atlas, Morocco). Palaeogeography, Palaeoclimatology, Palaeoecology (advance online publication) doi:10.1016/j.palaeo.2011.05.021

Abstract - Footprints of Early Mesozoic terrestrial tetrapods are inadequately known from NW Africa despite pervasive and well-exposed continental strata of corresponding age in that region. Here, we report on the first occurrence of a tetrapod ichnofauna from the middle part of the Triassic Timezgadiouine Formation in the Argana Basin, Central Morocco that is outstanding in terms of abundance, preservation, and diversity. Footprints of this assemblage are assigned to the ichnotaxa Chirotherium barthii, Isochirotherium coureli, Synaptichnium isp., Atreipus–Grallator, Rotodactylus isp., Rhynchosauroides isp., and Procolophonichnium isp., suggesting early archosaurian, dinosauromorph, lepidosauromorph and possible therapsid or procolophonoid trackmakers. Based on comparison with the abundant record of Early Mesozoic vertebrate ichnofossils from Europe and North America, the ichnofauna presented here indicates a Middle Triassic (Anisian–Ladinian) age for the track-bearing horizon in the Argana Basin. Its clearly Euramerican affinity sheds light on the migration and dispersal of early archosaur-dominated tetrapod faunas considering that several ichnotaxa of the assemblage are documented from Africa for the first time.

As pointed out by Ben Creisler on the Dinosaur Mailing List, this paper is closely related to one published last year by many of the same authors.

Evidence for an Early Triassic Origin for the Dinosaur Stem Lineage

Brusatte, S. L., Niedźwiedzki, G., and R. J. Butler. 2010. Footprints pull origin and diversification of dinosaur stem lineage deep into Early Triassic. Proceedings of the Royal Society B. doi: 10.1098/rspb.2010.1746

Abstract - The ascent of dinosaurs in the Triassic is an exemplary evolutionary radiation, but the earliest phase of dinosaur history remains poorly understood. Body fossils of close dinosaur relatives are rare, but indicate that the dinosaur stem lineage (Dinosauromorpha) originated by the latest Anisian (ca 242–244 Ma). Here, we report footprints from the Early–Middle Triassic of Poland, stratigraphically well constrained and identified using a conservative synapomorphy-based approach, which shifts the origin of the dinosaur stem lineage back to the Early Olenekian (ca 249–251 Ma), approximately 5–9 Myr earlier than indicated by body fossils, earlier than demonstrated by previous footprint records, and just a few million years after the Permian/Triassic mass extinction (252.3 Ma). Dinosauromorph tracks are rare in all Polish assemblages, suggesting that these animals were minor faunal components. The oldest tracks are quadrupedal, a morphology uncommon among the earliest dinosauromorph body fossils, but bipedality and moderately large body size had arisen by the Early Anisian (ca 246 Ma). Integrating trace fossils and body fossils demonstrates that the rise of dinosaurs was a drawn-out affair, perhaps initiated during recovery from the Permo-Triassic extinction.

Popular news story here with a horrible title as they are not true dinosaur footprints.

Early Triassic Archosaur-dominated Footprint Assemblage from Morocco

Klein, H., Voigt, S., Hminna, A., Saber, H., Schneider, J., and D. Hmich. 2010. Early Triassic Archosaur-Dominated Footprint Assemblage from the Argana Basin (Western High Atlas, Morocco). Ichnos 17:1–13. DOI: 10.1080/10420940.2010.510030 


Abstract - An assemblage of abundant and well-preserved tetrapod footprints has been discovered in the Tanamert Member (T3) of the Triassic Timezgadiouine Formation (Argana basin, western High Atlas, Morocco). It is the first fossil record from T3. Surfaces from different localities show a uniform tetrapod ichnofauna that consists of chirotherian and small lacertoid forms. The chirotherians are assigned to the plexus Protochirotherium—Synaptichnium, their trackmakers interpreted as basal archosaurs. The lacertoid imprints show close affinities with Rhynchosauroides and may reflect archosauromorphs or lepidosauromorphs. Protochirotherium—Synaptichnium assemblages are characteristic of the Early Triassic and were known previously only from units of this age in central Europe. Biostratigraphically, the European record implies a wide-spread pre-Anisian Protochirotherium—Synaptichnium dominated assemblage preceding the first appearance of Chirotherium barthii near the Olenekian-
Anisian boundary. The stratigraphic position of T3 between Late Permian (uppermost T2) and Middle Triassic (T4) and the European correlatives suggest an Early Triassic age of this unit. It is the first record of Early Triassic continental deposits in Morocco. The surfaces from T3 open up perspectives for further contributions to ecology, biogeography and locomotion of early archosaurs. Furthermore, excellent outcrops and quality of footprint preservation in the Argana basin offer a potential for clarification of ichnotaxonomic and biostratigraphic issues.

Phytosaurs as the Likely Trackmaker for Apatopus from the Late Triassic of North America

Padian, K., Li, C., and J. Pchelnikova. 2009. The trackmaker of Apatopus (Late Triassic: North America): implications for the evolution of archosaur stance and gait. Palaeontology (early view). doi: 10.1111/j.1475-4983.2009.00924.x

Abstract - For some decades, a major focus of research has been on how locomotor modes changed in some archosaurian reptiles from a more or less ‘sprawling’ to an ‘erect’ posture, whether there were discrete intermediate stages, and how many times ‘erect’ posture evolved. The classic paradigm for the evolution of stance and gait in archosaurs, a three-stage transition from sprawling to ‘semi-erect’ to erect posture, has been replaced by a subtler understanding of a continuum of changing limb joint angles. We suggest a further separation of terminology related to stance vs. gait so as not to entail different processes: ‘sprawling’ and ‘erect’ should refer to continua of stance; ‘rotatory’ and ‘parasagittal’ are more appropriate ends of a continuum that describes the motions of gait. We show that the Triassic trackway Apatopus best fits the anatomy and proportions of phytosaurs, based on a new reconstruction of their foot skeleton; it is less likely to have been made by another pseudosuchian or nonarchosaurian archosauromorph. Moreover, the trackmaker was performing the high walk. A phytosaurian trackmaker would imply that the common ancestor of pseudosuchians, and therefore archosaurs could approximate the high walk (depending on phylogeny), and if so, erect stance and parasagittal gait did not evolve independently in pseudosuchians and ornithosuchians, although the kinematic mechanisms differed in the two groups. It remains to be seen how far outside Archosauria, if at all, more or less erect posture and parasagittal gait may have evolved.

Just In Case You Missed This One

This came out about three weeks ago in PLoS ONE. Pretty cool study showing how different types of dinosaurs would negotiate a particularily difficult terrain.

Wilson, J. A., Marsicano, C. A., and R. M. H. Smith. 2009. Dynamic Locomotor Capabilities Revealed by Early Dinosaur Trackmakers from Southern Africa. PLoS ONE 4(10): e7331. doi:10.1371/journal.pone.0007331.

ABSTRACT

Background

A new investigation of the sedimentology and ichnology of the Early Jurassic Moyeni tracksite in Lesotho, southern Africa has yielded new insights into the behavior and locomotor dynamics of early dinosaurs.

Methodology/Principal Findings

The tracksite is an ancient point bar preserving a heterogeneous substrate of varied consistency and inclination that includes a ripple-marked riverbed, a bar slope, and a stable algal-matted bar top surface. Several basal ornithischian dinosaurs and a single theropod dinosaur crossed its surface within days or perhaps weeks of one another, but responded to substrate heterogeneity differently. Whereas the theropod trackmaker accommodated sloping and slippery surfaces by gripping the substrate with its pedal claws, the basal ornithischian trackmakers adjusted to the terrain by changing between quadrupedal and bipedal stance, wide and narrow gauge limb support (abduction range = 31°), and plantigrade and digitigrade foot posture.

Conclusions/Significance

The locomotor adjustments coincide with changes in substrate consistency along the trackway and appear to reflect ‘real time’ responses to a complex terrain. It is proposed that these responses foreshadow important locomotor transformations characterizing the later evolution of the two main dinosaur lineages. Ornithischians, which shifted from bipedal to quadrupedal posture at least three times in their evolutionary history, are shown to have been capable of adopting both postures early in their evolutionary history. The substrate-gripping behavior demonstrated by the early theropod, in turn, is consistent with the hypothesized function of pedal claws in bird ancestors.

Did Tetrapods Undergo a Postural Shift after the End-Permian Extinction?

Kubo, T. and M. J. Benton. 2009. Tetrapod postural shift estimated from Permian and Triassic trackways. Palaeontology 52:1029-1037. doi: 10.1111/j.1475-4983.2009.00897.x

Abstract- The end-Permian mass extinction, 252 million years (myr) ago, marks a major shift in the posture of tetrapods. Before the mass extinction, terrestrial tetrapods were sprawlers, walking with their limbs extended to the sides; after the event, most large tetrapods had adopted an erect posture with their limbs tucked under the body. This shift had been suspected from the study of skeletal fossils, but had been documented as a long process that occupied some 15–20 myr of the Triassic. This study reads posture directly from fossil tracks, using a clear criterion for sprawling vs erect posture. The track record is richer than the skeletal record, especially for the Early and Middle Triassic intervals, the critical 20 myr during which period the postural shift occurred. The shift to erect posture was completed within the 6 myr of the Early Triassic and affected both lineages of medium to large tetrapods of the time, the diapsids and synapsids.

Latest Literature: Triassic redbeds, footprints, and Eshanosaurus

Thanks to Jerry Harris for pointing these out...

Zaghloul, M.N., Critelli, S., Perri, F., Mongelli, G., Perrone, V., Sonnino, M., Tucker, M., Aiello, M., and Ventimiglia, C. 2009. Depositional systems, composition and geochemistry of Triassic rifted-continental margin redbeds of the Internal Rif Chain, Morocco. Sedimentology. doi: 10.1111/j.1365-3091.2009.01080.x.

ABSTRACT: The Middle to Upper Triassic redbeds at the base of the Ghomaride and Internal 'Dorsale Calcaire' Nappes in the Rifian sector of the Maghrebian Chain have been studied for their sedimentological, petrographic, mineralogical and chemical features. Redbeds lie unconformably on a Variscan low-grade metamorphic basement in a 300 m thick, upward fining and thinning megasequence. Successions are composed of predominantly fluvial red sandstones, with many intercalations of quartzose conglomerates in the lower part that pass upwards into fine-grained micaceous siltstones and massive mudstones, with some carbonate and evaporite beds. This suite of sediments suggests that palaeoenvironments evolved from mostly arenaceous alluvial systems (Middle Triassic) to muddy flood and coastal plain deposits. The successions are characterized by local carbonate and evaporite episodes in the Late Triassic. The growth of carbonate platforms is related to the increasing subsidence (Norian-Rhaetian) during the break-up of Pangea and the earliest stages of the Western Tethys opening. Carbonate platforms became widespread in the Sinemurian. Sandstones are quartzose to quartzolithic in composition, testifying a recycled orogenic provenance from low-grade Palaeozoic metasedimentary rocks. Palaeoweathering indices (Chemical Index of Alteration, Chemical Index of Weathering and Plagioclase Index of Alteration) suggest both a K-enrichment during the burial history and a source area that experienced intense weathering and recycling processes. These processes were favoured by seasonal climatic alternations, characterized by hot, episodically humid conditions with a prolonged dry season. These climatic alternations produced illitization of silicate minerals, iron oxidation and quartz-rich red sediments in alluvial systems. The estimated burial temperature for the continental redbeds is in the range of 100 to 160 °C with lithostatic/tectonic loading of ca 4 to 6 km. These redbeds can be considered as regional petrofacies that mark!the onseern Pangea (Middle Triassic) before the opening of the western part of Tethys in the Middle Jurassic. The studied redbeds and the coeval redbeds of many Alpine successions (Betic, Tellian and Apenninic orogens) show a quite similar history; they identify a Mesomediterranean continental block originating from the break-up of Pangea, which then played an important role in the post-Triassic evolution of the Western Mediterranean region.

Gierlinski, G.D. 2009. A preliminary report on new dinosaur tracks from the Triassic, Jurassic and Cretaceous of Poland; pp. 75-90 in Salas, C.A.-P. (ed.), Actas de las IV Jornadas Internacionales sobre Paleontologia de Dinosaurios y su Entorno. Colectivo Arqueológico-Paleontológico de Salas de los Infantes, Burgos.

ABSTRACT: Dinosaur tracks in Poland are mainly recognized in the Lower Jurassic (Hettangian) of the Holy CrossMountains. There are only few finds, so far reported, from the Upper Triassic of the Tatra Mountains and Silesia. Dinosaur footprints in the Upper Jurassic of the Holy Cross Mountains are also little recognized. Field investigations, in 2006 and 2007, revealed new finds of dinosaur footprints in the Upper Triassic (Norian), Lower Jurassic (Pliensbachian) and Upper Jurassic (Oxfordian) of the Holy Cross Mountains (central Poland), and the Upper Cretaceous (Maastrichtian) of the Roztocze region (southeastern Poland). Norian material comprises prosauropod tracks, which came from the coarse-clastic sequences exposed in the Skarszyny outcrops. New Jurassic finds, in the Holy Cross Mountains, are the Pliensbachian sauropod and small theropod footprints from the Smilow sandstone quarry, and the Oxfordian theropod, and small ornithopod tracks from Baltow limestones. Dinosaur footprints, in the Roztocze carbonates, are discovered in the lowermost part of Szopowe quarry on the Mlynarka Mount. The material from Mlynarka Mount resembles Asiatic ichnotaxa, a small didactyl maniraptoran track of Velociraptorichnus, bird-like ichnite similar to Saurexallopus and a large tetradactyl footprint of Macropodosaurus, a form recently supposed of the therizonosauroid origin.

Barrett, P.M. 2009. The affinities of the enigmatic dinosaur Eshanosaurus deguchiianus from the Early Jurassic of Yunnan Province, People's Republic of China. Palaeontology. doi: 10.1111/j.1475-4983.2009.00887.x.

ABSTRACT: Eshanosaurus deguchiianus is based on a single left dentary from the Lower Lufeng Formation (Lower Jurassic) of Yunnan Province, China. It was originally identified as the earliest known member of Therizinosauroidea (Theropoda: Coelurosauria), a conclusion that results in a significant downward range extension for this clade (>65 million years) and for many other major lineages within Coelurosauria. However, this interpretation has been questioned and several authors have proposed that the anatomical features used to refer Eshanosaurus to Therizinosauroidea are more consistent with attribution to a basal sauropodomorph dinosaur. Detailed consideration of the holotype specimen suggests that several features of the dentary and dentition exclude Eshanosaurus from Sauropodomorpha and support its inclusion within Therizinosauroidea. If accepted as an Early Jurassic coelurosaur, Eshanosaurus has important implications for understanding the timing and tempo of early theropod diversification. Moreover, its provenance also suggests that substantial portions of the coelurosaur fossil record may be missing or unsampled. However, the Early Jurassic age of Eshanosaurus requires confirmation if this taxon is to be fully incorporated into broader evolutionary studies.

New Paper on Triassic Dinosauriform Footprints from Brazil

This was just announced as now being out in Ameghiniana, although I was not able to find a link to this article on-line (the Ameghiniana website is often behind). One quick note: Sacisaurus is a "silesaurid" dinosauriform and not a dinosaurian.

Da Silva, R.C., Carvalho, I., and A.C.S. Fernandes. 2009. Dinosaur footprints from the Triassic (Santa Maria Formation) of Brazil. Ameghiniana 45: 783-790.

Abstract. Dinosaur footprints in Jurassic and Cretaceous rocks are common in Brazil , but there are only a few records from Triassic. In Rio Grande do Sul State , tridactyl medium size footprints were found in Carnian rocks. The material proceeds from Predebon outcrop, São João do Polêsine County, Rio Grande do Sul State, that corresponds to the higher portion of the Alemoa Member, Santa Maria Formation. The footprints occur in sandstone lenses. The ichnofossils were identified as dinosaur footprints indet. and as Grallator ? sp. The footprints should correspond to undertracks, since many superficial characteristics are absent, so that the differences between the footprints could correspond to preservational factors. On the basis of morphologic and stratigraphic criteria, the footprints can be attributed to basal dinosaurs. Some dinosaurs known for the Brazilian Triassic, such as Staurikosaurus , Saturnalia, and Sacisaurus, could be the producers of these footprints. The occurrences of dinosaur footprints of the Predebon outcrop correspond to the oldest ones of Brazil , and moreover, they are compatible with the known paleofauna of Alemoa-Caturrita sequence.

Conodonts Squished by Thoughtless Dinosaurs

The 52nd annual meeting of the Palaeontological Association was held in December 2008 in the University of Glasgow. Although I was unable to attend (someday I will) the following poster presentation caught my eye. Probably not too many people are experts on World War I tunnels, stromatolites, conodonts, dinosaurs, and archosaur trackways but here is where all of these fields finally collide....

Belvedere, M., Mietto, P., Avanzini, M., and M. Rigo. 2008. Dinosaurs stepping on the conodont animals; p. 44 in Programme and Abstracts for the 52nd meeting of the Palaeontological Association. The Palaeontological Association Newsletter 69.

On the roof of a First World War tunnel in the Monte Pasubio (North Eastern Italy), on a supratidal stromatolitic bed of the Dolomia Principale Formation, 11 tracks have been found. Among them occur some clear dinosaurian tridactyl footprints, from small grallatorid-like to medium-large eubrontid, as well as some tetradactyl footprints. This formation contains the principal dinosaur footprints for the Triassic of the southern alps. All previous findings were on fallen blocks which, given the poor paleontological content of the formation, and the lack of precise stratigraphical position, made their biostratigraphical constraints very difficult to determine. In this case, for the first time, the trampled surface crops out in situ, about 500m from the bottom of the formation. Conodont sampling was carried out on the subtidal level just below the trampled surface. Unexpectedly, two conodonts were found: an advanced Epigondolella praeslovakensis and a true Mockina slovakensis, an association exclusive for the Middle Norian (latest Alaunian). Thus being so precisely contrained, the ichnoassociation could be used to date the other isolated blocks of the Dolomites. Moreover this co-occurrence of tetrpod footprints and conodonts can be used to confirm the Middle Norian age of the Eubrontes-Grallator biochron.

Dinosaur skeletons covered with ammonites have been found in marine strata , but as the authors state this is a first for conodonts and footprints. It's too bad that this does not happen more often to tie together marine and non-marine biostratigraphies. By the way, the small tridactyl tracks probably are ornithodiran as no self respecting pseudosuchian would stomp on conodonts ;).

New Triassic themed blog and another earliest dinosaur claim

I just recently became aware of this relatively new blog "The Life of Madygen" which has featured several posts on Triassic paleontology. Check it out. One recent post discusses purported sauropodomorph dinosaur footprints from Middle Triassic rocks near Bernberg Germany (also see this related article and my earlier post). If indeed attributable to dinosaurs, this find would represent the earliest occurrence of dinosaurs in the world; a claim which would need some accompanying body fossils to it back up, given the wide variety of Triassic critters that could hypothetically create a "dinosaur" track. One of the more outspoken critics of the claim seems to be Dr. Hartmut Haubold, an archosaur track specialist, who stated "It's ridiculous, it's as if someone found a 10-million-year-old stone and claimed it was a hand axe made by humans." "Dinosaurs didn't come into existence until a good 15 million years later" than these tracks. Haubold believes the trackmaker is Cheirotherium, which has been attributed to crocodile-line archosaurs such as "rauisuchians" (who do have body fossils preserved in Middle Triassic deposits).

Whereas I consider tracks to provide important information regarding the fossil record, especially information about the "living animal" that bones alone cannot preserve, I feel that claims such as these should only be made in concert with other lines of evidence, especially body fossils. I am reminded of a talk I saw a few years ago where it was stated that based on track evidence, the most common animal in the Late Triassic fauna of North America were sauropods. I found this claim quite perplexing given that not even a single bone of a sauropodomorph has ever been found in rocks of this age.