Middle–Late Permian tetrapods from the Rio do Rasto Formation,Southern Brazil: a biostratigraphic reassessment

Dias‐da‐Silva, S. 2011: Middle–Late Permian tetrapods from the Rio do Rasto Formation, Southern Brazil: a biostratigraphic reassessment. Lethaia, Vol. 45, pp. 109–120. The Rio do Rasto Formation (Permian of Southern Brazil) was previously regarded as Guadalupian–early Lopingian age. Three tetrapod‐based localities are known: the Serra do Cadeado area, Aceguá and Posto Queimado. The latest tetrapod‐based biostratigraphic contribution considers that the Posto Queimado and Aceguá faunas are coeval and Wordian (middle Guadalupian) in age, correlated to the Isheevo faunas from Eastern Europe and to the Tapinocephalus Assemblage Zone of South Africa; whereas the Serra do Cadeado fauna is Capitanian (late Guadalupian), correlated to the Kotelnich fauna of Eastern Europe and, from bottom to top, to upper Pristerognathus, Tropidostoma and lower Cistecephalus assemblage zones of South Africa. A re‐evaluation of the tetrapods from the Rio do Rasto Formation and new fossil discoveries in the localities of Posto Queimado and Serra do Cadeado area (melosaurine and platyoposaurine temnospondyls, a basal anomodont, a dinocephalian and a basal dicynodont) supports a new tetrapod‐based biostratigraphic scheme for the Rio do Rasto Formation. Accordingly, the age of the fauna at Aceguá is late Roadian‐early Wordian, whereas the locality of Posto Queimado is late Wordian‐Capitanian. The Serra do Cadeado Area is correlated with both southernmost ones (Guadalupian) but also Wuchiapinghian (early Lopingian). □Paraná Basin, Passa Dois Group, tetrapod biostratigraphy, Western Gondwana.     

When and how did the terrestrial mid-Permian mass extinction occur? Evidence from the tetrapod record of the Karoo Basin,South Africa

A mid-Permian (Guadalupian epoch) extinction event at approximately 260 Ma has been mooted for two decades. This is based primarily on invertebrate biostratigraphy of Guadalupian–Lopingian marine carbonate platforms in southern China, which are temporally constrained by correlation to the associated Emeishan Large Igneous Province (LIP). Despite attempts to identify a similar biodiversity crisis in the terrestrial realm, the low resolution of mid-Permian tetrapod biostratigraphy and a lack of robust geochronological constraints have until now hampered both the correlation and quantification of terrestrial extinctions. Here we present an extensive compilation of tetrapod-stratigraphic data analysed by the constrained optimization (CONOP) algorithm that reveals a significant extinction event among tetrapods within the lower Beaufort Group of the Karoo Basin, South Africa, in the latest Capitanian. Our fossil dataset reveals a 74–80% loss of generic richness between the upper Tapinocephalus Assemblage Zone (AZ) and the mid-Pristerognathus AZ that is temporally constrained by a U–Pb zircon date (CA-TIMS method) of 260.259 ± 0.081 Ma from a tuff near the top of the Tapinocephalus AZ. This strengthens the biochronology of the Permian Beaufort Group and supports the existence of a mid-Permian mass extinction event on land near the end of the Guadalupian. Our results permit a temporal association between the extinction of dinocephalian therapsids and the LIP volcanism at Emeishan, as well as the marine end-Guadalupian extinctions.     

Endothiodont dicynodonts from the Late Permian Kundaram Formation,India

The Kundaram Formation, a Lower Gondwana unit of the Pranhita-Godavari valley, contains the only known Permian dicynodonts in India. This dicynodont assemblage is dominated by Endothiodon. Two species (Endothiodon mahalanobisi sp. nov and Endothiodon uniseries Owen 1879) are described here. This is the first detailed study of Endothiodon from outside Africa. The study shows that Endothiodon jaw articulation permitted propalinal action when the opposing serrations in the upper and the lower jaw teeth occluded with the horn covered areas and helped in shearing and mastication. The presence of oblique wear facets on the upper and lower jaw teeth and a masseter-like muscle suggest a slightly lateral movement of the lower jaw which enhanced slicing of plant matter. A robust stapes with posterolateral notch constitutes the middle ear region though Endothiodon depended mainly on ground vibrations for hearing. Other features included a reduced olfactory sense and large eyes for vigilance and ease of detecting predators. Based on its vertebrate fauna, this fossiliferous Gondwana horizon of the Pranhita-Godavari valley is broadly correlated with the Tropidostoma and/or Cistecephalus Assemblage Zones of the Beaufort Group, Karoo Supergroup, South Africa. It indicates a probable Tatarian age for the Kundaram Formation.     

Osteomyelitis in a 265-million-year-old titanosuchid (Dinocephalia,Therapsida)

Abstract

Analytical palaeohistology techniques have allowed a better understanding of the microstructure of fossil bone, as well as of bone pathologies of extinct animals. Osteomyelitis is one of the oldest identified bone pathologies, occurring in Synapsida dating back as far as the Lower Permian. Here we show the presence of this pathology in the femur of Jonkeria parva, an omnivorous titanosuchid from the Tapinocephalus Assemblage Zone of the Karoo Basin of South Africa. The pathology is characterised by bony radial spicules growing perpendicular to the normal orientation of the unaffected fibrolamellar bone tissue, and shows localised increase in vascular canal size. Puncture marks on the femur suggests that an attack by a predator may have resulted in a bacterial infection that caused contiguous and subjacent osteomyelitis.     

Changes in Permo-Triassic terrestrial tetrapod ecological representation in the Beaufort Group (Karoo Supergroup) of South Africa

Nicolas, M. & Rubidge, B.S. 2010: Changes in Permo-Triassic terrestrial tetrapod ecological representation in the Beaufort Group (Karoo Supergroup) of South Africa. Lethaia, Vol. 43, pp. 45–59.
For more than a century, large collections of fossils from the Beaufort Group have been built up at various museums in South Africa and have been handled as separate databases in the individual museums. Because of the unique time-extensive record of continental vertebrate biodiversity represented by the fossils of the Beaufort Group, a single standardized database has been compiled for the fossils collected from the Beaufort Group housed in South African museums. This unique data set has enabled the determination of terrestrial tetrapod ecological representation from the Middle Permian to Middle Triassic Beaufort Group of South Africa. □ Beaufort Group , biodiversity , ecology , Permo-Triassic .     

Sharks, Rays and A Chimaeroid from the Kimmeridgian (Late Jurassic) of Ringstead, Southern England

Sampling of a lenticular concentration of vertebrate debris and associated sediments from the lower Kimmeridgian of southern England has allowed the study of a diverse and abundant assemblage of chondrichthyan remains. A number of previously undescribed species are recorded, of which three new species are named; Squatina? frequens, Synechodus plicatus and Protospinax planus. Additional diagnosis of the genus Paracestracion Koken is given to allow its identification from dental remains. Several nominal batoid species are synonymised with Spathobatis bugesiacus Thiolliere. This assemblage is considered to be typical of Middle–Late Jurassic neritic environments, and is compared to other contemporaneous selachian faunas.     

Predator–prey interactions amongst Permo‐Triassic terrestrial vertebrates as a deterministic factor influencing faunal collapse and turnover

Unlike modern mammalian communities, terrestrial Paleozoic and Mesozoic vertebrate systems were characterized by carnivore faunas that were as diverse as their herbivore faunas. The comparatively narrow food base available to carnivores in these paleosystems raises the possibility that predator–prey interactions contributed to unstable ecosystems by driving populations to extinction. Here, we develop a model of predator–prey interactions based on diversity, abundance and body size patterns observed in the Permo‐Triassic vertebrate fossil record of the Karoo Basin, South Africa. Our simulations reflect empirical evidence that despite relatively high carnivore: herbivore species ratios, herbivore abundances were sufficient for carnivores to maintain required intake levels through most of the Karoo sequence. However, high mortality rates amongst herbivore populations, even accounting for birth rates of different‐sized species, are predicted for assemblages immediately preceding the end‐Guadalupian and end‐Permian mass extinctions, as well as in the Middle Triassic when archosaurs replaced therapsids as the dominant terrestrial fauna. These results suggest that high rates of herbivore mortality could have played an important role in biodiversity declines leading up to each of these turnover events. Such declines would have made the systems especially vulnerable to subsequent stochastic events and environmental perturbations, culminating in large‐scale extinctions.     

Micromorphological,geochemical, and diagenetic characterization of sirenian ribs preserved in the Late Miocene paleontological site of Cessaniti (southern Calabria,Italy)

The site of Cessaniti (Vibo Valentia, Italy) has been well known since the 19th century for the richness and good preservation of its Miocene fauna and flora. The sedimentary succession of the site represents a paralic system that evolved toward an open-marine environment recording the Tortonian transgression. The fossil assemblage contains rich invertebrate (corals, bivalves, gastropods, brachiopods, echinoids, benthic and planktonic foraminifers) and vertebrate faunas (proboscideans, rhinoceroses, giraffids, bovids, sirenids, marine turtles, and fish remains). The fossils recovered at the Cessaniti site have a relevant role in phylogenetic studies and paleogeographic reconstructions of Late Miocene environments of the southern Italy. This research is focused on the microstructure and preservation state of the fossil bones. Samples of Metaxytherium sp. bones have been analyzed to understand the diagenetic profile of the bone assemblages that characterizes the taphonomic history of the Cessaniti site. The analyses provided a comprehensive account of how bone mineral (bioapatite) has been altered and demonstrated that the post-burial processes did not significantly affect the micromorphological and biogeochemical features of the bones. The excellent preservation state of the bones strengthens the importance of the Cessaniti site for studies of the Mediterranean Miocene vertebrate fauna.     

Fossil vertebrate faunas of the British Rhaetian (latest Triassic)

Rhaetian fossil vertebrate faunas of Britain represent rich but biased samples of taxonomic diversity during uppermost Triassic time. Review of the Westbury Formation, Penarth Group, in particular, reveals a combination of marine, littoral, and terrestrial elements. Minimally, six species of shark are preserved along with a myriacanthid holocephalan, at least four actinopterygian taxa, a characteristic lungfish, ichthyosaurs, plesiosaurs, dinosaurs, and potentially the earliest representative of the Choristodera. Rare mammalian occurrences in the Westbury beds are also possible. Severnichthys gen. nov. is a large osteichthyan, probably a palaeonisciform chondrostean, which historically has been mistaken for a labyrinthodont amphibian. At least two additional actinopterygian species and a holocephalan are known from die Lilstock Formation, and a mammal or mammallike reptile is recorded from the uppermost Blue Anchor Formation. Analysis of element abundance in the disarticulated Westbury Formation assemblage indicates that many parts of some taxa are never preserved while other elements of the same form are common. Such preservational bias suggests that many species may be missing entirely from this long-studied but poorly understood taphocoenosis. Possibly contemporaneous cave faunas from nearby upland areas give a similarly biased picture of the terrestrial fauna during this time of widespread marine transgression.     

Consistent patterns in diatom assemblages and diversity measures across water‐depth gradients from eight Boreal lakes from north‐western Ontario (Canada)

1. Until recently, the distribution of diatom species assemblages and their attributes (e.g. species richness and evenness) in relation to water depth have been identified but not quantified, especially across several lakes in a region. Here, we examined diatom assemblages in the surface sediment across a water‐depth gradient in eight small, boreal lakes in north‐western Ontario, minimally disturbed by human activities. 2. Surface‐sediment diatom assemblages were collected within each lake along a gentle slope from near‐shore to the centre deep basin of the lake, at a resolution of ～1 m water depth. Analysis of sedimentary samples provided an integrated view of assemblages that were living in the lake over several years and enabled a high‐resolution analysis of many lakes. The study lakes ranged in water chemistry, morphology and size and are located along an east–west transect approximately 250 km long in north‐western Ontario (Canada). 3. The majority of diatom species were distributed along a continuum of depth, with those taxa having similar habitat requirements forming distinct, though overlapping, assemblages. Three major zones of diatom assemblages in each lake were consistently identified: (i) a near‐shore assemblage of Achnanthes (sensu lato), Nitzschia, Cymbella (sensu lato) and other benthic species; (ii) a mid‐depth assemblage of small Fragilaria (sensu lato)/small Aulacoseira and various Navicula taxa; and (iii) a deep‐water assemblage of planktonic origin (mainly Discotella spp.). 4. The depth of the transition between assemblage zones varied between the eight lakes. The boundary between the deep‐water planktonic zone and the mid‐depth benthic zone varied according to water chemistry and was probably related to light attenuation. The boundary was deeper in lakes with the lower dissolved organic carbon and total phosphorus (TP) (i.e. less light attenuation) and vice versa. 5. Generally, species richness, species evenness and turnover rate of species as a function of depth were significantly lower in the planktonic assemblage zone in comparison with the two zones nearer the shore. Reproducibility of species and assemblage distributions across the depth gradient of the lakes illustrated that, despite potential for sediment transport, detailed ecological characterisation of diatom species can be gleaned from sedimentary data. Such data are often lacking, particularly for near‐shore benthic species.     

Late Jurassic decapod crustaceans from northeast Japan

Abstract: Astacidean and thalassinidean macrurans (Glyphea sp., ?Eryma sp. and Protaxius sp.) and a new longodromitid crab, Planoprosopon kashimaensis, are recorded from the Upper Jurassic (upper Kimmeridgian to lower Tithonian) of Fukushima Prefecture, northeast Japan. Material was collected from the Tatenosawa Sandstone Member of the Nakanosawa Formation, Somanakamura Group, from which abundant Tethyan‐type marine invertebrates are known. Planoprosopon kashimaensis sp. nov. closely resembles P. heydeni (von Meyer), a common form in the Upper Jurassic of the Tethyan realm in Europe, and represents the oldest record of a brachyuran from the circum‐Pacific region. Similarities to contemporaneous decapod assemblages in southern Germany indicate that closely comparable, parallel decapod faunas in the Tethyan realm, inclusive of brachyurans, had already been established in the western circum‐Pacific region by the Late Jurassic.     

Edaphic and climatic history has driven current dung beetle species pool and assemblage structure across a transition zone in central South Africa

We investigate biogeographical, regional and sub‐regional‐scale responses of scarabaeine dung beetles to late Cenozoic changes in edaphic and climatic character that created a Savanna/Karoo transition zone in the Northern Cape, South Africa. Across a 50 200 km² study area, the Northern Cape species pool comprised six biogeographical groups defined from distribution across southern Africa. These species groups contributed in different proportions to five regional assemblages defined from structural differences across the transition zone. Towards transition zone peripheries, regional assemblage structure was more strongly correlated to sandiness dating from Miocene to Pliocene deposition (Kalahari), aridity dating from Pliocene to Pleistocene climatic change (Bushmanland Karoo), or cooler temperatures dating from Miocene to Pliocene uplift (Upper Karoo). Correlates of sub‐regional assemblages trended to intensification of dominant drivers towards regional peripheries. Drivers of central transition zone, regional assemblages (‘Gariep Karoo’, ‘Gariep Stony Karoo’) showed no dominance. Biogeographically, endemism dominates the Northern Cape transition zone: south‐west arid groups in Nama Karoo regions; Kalahari plus north‐east savanna groups in the Kalahari. Regionally, transition drives assemblage structure: unique variance, 60% in the Kalahari, 21–30% in four Nama Karoo regions; shared variance (overlap), 25–65% between Kalahari and warmer Karoo regions, 11–71% between mainly cooler Karoo regions.     

Systematic and palaeoecological significance of the first record of Pygocephalomorpha females bearing oöstegites (Malacostraca,Peracarida) from the lower Permian of southern Brazil

Malacostracan crustaceans of the fossil order Pygocephalomorpha are conspicuous elements in brackish to freshwater faunas in the upper Carboniferous of Laurentia and lower Permian of Gondwana. A pronounced sexual dimorphism is recognizable within its members, with Pygocephalomorpha females bearing oöstegites: modified epipodites that hold a brood pouch where the eggs develop until juvenile stage, with no planktonic dispersal of larvae. The preservation of oöstegites is quite rare and is described here for the first time from the American continents. The specimens, ventrally preserved Liocaris huenei females bearing oöstegites, come from the Irati Formation, a lower Permian sequence of the Paraná Basin, from an outcrop in southern Brazil. The oöstegites are similar to those previously described for Pygocephalomorpha, displaying seven pairs of overlapping epipodites that cover the whole cephalothorax. The scarcity of these structures in the fossil record may be explained by taphonomic bias (it requires ventrally preserved crustaceans) but more likely by palaeobiological aspects, such as preservation of an ovigerous moult. The record from the Irati Formation suggests that pygocephalomorphs had seasonal reproduction, with females maturing at the same time and acquiring oöstegites that would be lost after the release of juveniles. This record confirms the relationship of the Brazilian Liocaris Beurlen to the English Pygocephalus Huxley and South African Notocaris Broom pygocephalomorphs and provides an insight into its palaeoecological significance.     

Taphonomy and taxonomy of a vertebrate microsite in the mid-Cretaceous (Albian–Cenomanian) Blackleaf Formation,southwest Montana

The vertebrate fauna of the Cretaceous Blackleaf Formation of southwest Montana remains largely undocumented. A microsite (BL1) discovered in the Flood Member in the Lima Peaks area, Montana, consists of a green siltstone and yields taxa previously unreported from the formation, including several dinosaurs: a hypsilophodont, dromaeosaurid, tyrannosauroid, hadrosaurid and an ankylosaurian. Non-dinosaurian taxa include goniopholidid and Bernissartia crocodilians; Glyptops, cf. chelydrid and other turtles and at least two neopterygiian fish. This diversity corresponds well with the fluvial–deltaic–estuarine environment interpreted for the uppermost unit of the Flood Member. Taphonomic data and sedimentologic relationships suggest that this assemblage represents a floodplain depression accumulation. Comparisons with contemporaneous faunas from around the Western Interior of the USA suggest a remarkably consistent faunal makeup, at least at the family level, existed across western North America in the mid-Cretaceous.     

Early Cretaceous stratigraphy and SHRIMP U‐Pb age constrain the Valanginian–Hauterivian boundary in southern Tibet

Wan, X., Scott, R., Chen, W., Gao, L. & Zhang, Y. 2011: Early Cretaceous stratigraphy and SHRIMP U‐Pb age constrain the Valanginian–Hauterivian boundary in southern Tibet. Lethaia, Vol. 44, pp. 231–244. The Late Jurassic to the Early Cretaceous marine strata are extensively distributed in southern Tibet. In Gyangze, the strata are divided into the Weimei and Jiabula formations. In Nagarze, they are divided into the Weimei and Sangxiu formations. Previous work has reported diverse ammonite species of Haplophylloceras and Himalayites in the Weimei Formation, and a few species of Spiticeras in the lower Jiabula and Sangxiu formations. The present study has found the bivalve Inoceramus and nannofossil assemblages in the lower Jiabula and Sangxiu formations. The nannofossil assemblage of Nannoconus steimannii steinmannii, N. steinmannii minor and Watznaueria barnesae indicates Berriasian age, and the Calcicalathina oblongata–Speetonia colligata assemblage is Valanginian in age. Numerical ages for the Jiabula and Jiabula‐goukou sections in Gyangze have been interpolated by comparing the fossil ranges with ages calibrated in other sections. The correlation experiment plots fossil ranges in the two sections to the CRET1 Database. The estimated rate of sediment accumulation of the lower Sangxiu Formation is 22.6 m/myr. The Jurassic–Cretaceous (J/K) boundary is at the bottom of the Jiabula Formation in Gyangze, and the base of the Sangxiu Formation in Nagarze. The boundary is marked by the appearance of the ammonite Spiticeras and the nannofossil assemblage of Nannoconus st. steinmannii–N. st. minor–Watznaueria barnesae. The radiometric age in Tibet is the first to be integrated with upper Valanginian fossils. The volcanic rocks of the upper Sangxiu Formation are dated at 136 ± 3.0 Ma deduced from zircon SHRIMP age of rhyolite. By consideration of the rate of sediment accumulation of the underlying sedimentary deposits, the J/K boundary in the Gyangze–Nagarze area is approximately 145 Ma as suggested by the newly issued International Stratigraphic Chart, and the Valanginian/Hauterivian boundary lies between 134 Ma and 136 Ma. □ Biostratigraphy, graphic plot, Jurassic/Cretaceous boundary, nannofossil, SHRIMP U‐Pb age, Southern Tibet, Valanginian/Hauterivian boundary.     

Diversity and palaeoecology of a highly diverse Late Triassic marine biota from the Cassian Formation of north Italy

A sample of marine invertebrates from the Late Triassic Cassian Formation (north Italy) yielded one of the most diverse Early Mesozoic fossil assemblages ever reported (c. 170 species). The assemblage was found in basin clays, but was transported from nearby carbonate platforms as indicated by fragmentation, microbial encrustation and the presence of coated grains and ooids. Most of the specimens are small (< 1 cm) reflecting both, small adult sizes and size sorting during transport. Rarefaction analysis suggests that diversity of surface collection and bulk sampling is the same. However, rank abundance, species richness and taxonomic composition differ strongly according to sampling method. Low‐grade lithification of the sediments is the main reason that high diversity can be recognized, because it facilitates disaggregation and finding of small molluscs. Sample standardization shows that the studied assemblage is much more diverse than known Early Triassic assemblages. However, its diversity is similar to that of Anisian assemblages. This suggests that recovery from the end‐Permian mass‐extinction was quite advanced in the Middle Triassic and alpha‐diversity remained high until the Late Triassic. According to current models, Early Triassic and Anisian faunas match the niche overlap phase of recovery during which diversity is built up by increasing alpha‐diversity, whereas beta‐diversity rises slowly. Subsequently, habitat width of species contracts because of increasing competition, making beta‐diversity the principal drive of overall diversity increase. The diversity pattern of various Late Triassic Cassian associations meets the predictions for the transition from the niche overlap to the habitat contraction phase.: Triassic, Cassian Formation, palaeoecology, diversity, mollusc dominance.     

Frasnian vertebrate taphonomy and sedimentology of macrofossil concentrations from the Langsēde Cliff,Latvia

Luk?evi?s, E., Ahlberg, P.E., Stinkulis, ?., Vasi?kova, J. & Zupi??, I. 2011: Frasnian vertebrate taphonomy and sedimentology of macrofossil concentrations from the Langsēde Cliff, Latvia. Lethaia, Vol. 45, pp. 356–370. The siliciclastic sequence of the Upper Devonian of Kurzeme, Western Latvia, is renowned for abundant vertebrate fossils, including the stem tetrapods Obruchevichthys gracilis and Ventastega curonica. During the first detailed taphonomic study of the vertebrate assemblage from the Ogre Formation cropping out at the Langsēde Cliff, Imula River, abundant vertebrate remains have been examined and identified as belonging to one psammosteid, two acanthodian and three sarcopterygian genera; the placoderm Bothriolepis maxima dominates the assemblage. Besides fully disarticulated placoderm and psammosteid plates, separate sarcopterygian scales and teeth, and acanthodian spines, partly articulated specimens including complete distal segments of Bothriolepis pectoral fins, Bothriolepis head shields and sarcopterygian lower jaws have been found. The size distribution of the placoderm bones demonstrates that the individuals within the assemblage are of approximately uniform age. Distinct zones have been traced within the horizontal distribution of the bones. These linear zones are almost perpendicular to the dominant dip azimuth of the cross‐beds and ripple‐laminae and most probably correspond to the depressions between subaqueous dunes. Concavity ratio varies significantly within the excavation area. The degree of fragmentation of the bones and disarticulation of the skeletons suggest that the carcasses were reworked and slightly transported before burial. Sedimentological data suggest deposition in a shallow marine environment under the influence of rapid currents. The fossiliferous bed consists of a basal bone conglomerate covered by a cross‐stratified sandstone with mud drapes, which is in turn overlain by ripple laminated sandstone, indicating the bones were buried by the gradual infilling of a tidal channel. All the Middle–Upper Devonian vertebrate bone‐beds from Latvia are associated with sandy to clayey deposits and have been formed in a sea‐coastal zone during rapid sedimentation episodes, but differ in fossil abundance and degree of preservation. □Agnathans, Devonian, facies analysis, fish, fossil assemblage, palaeoenvironment.     

Phu Din Daeng,a new Early Cretaceous vertebrate locality on the Khorat Plateau,NE Thailand

In this paper, we report on a new Early Cretaceous vertebrate locality, Phu Din Daeng, in Nakhon Phanom Province, NE Thailand. The Phu Din Daeng site has yielded a diverse vertebrate assemblage, including sharks (Heteroptychodus steinmanni), bony fishes (Pycnodontiformes; Sinamiidae cf. Siamamia and ?Vidalamiinae, and Ginglymodi), adocid turtles, indeterminate neosuchian crocodiles, pterosaurs and dinosaurs (spinosaurids and indeterminate theropods). A new adocid turtle, Protoshachemys rubra n. g. n. sp. is described on the basis of shell material. Field investigations on the geology and comparisons with other vertebrate faunas place Phu Din Daeng in the Sao Khua Formation (Barremian) of the Khorat Group.     

Tetrapod and invertebrate trace fossils from aeolian deposits of the lower Permian of central-western Argentina

Abundant tetrapod footprints are described from the Early Permian Yacimiento Los Reyunos Formation including both collected and in situ specimens. The slabs come from several quarries at the Sierra Pintada and Sierra de las Peñas area, south-west of Mendoza, Argentina. The trace fossil assemblage, which constitutes one of the oldest known from Gondwana, comprises excellent-preserved tetrapod tracks (Chelichnusduncani, Chelichnusgigas and ‘pear-like’ footprints) and invertebrate simple sub-horizontal (Palaeophycustubularis) and vertical (Skolithos isp.) burrows formed in a aeolian dune field. The analysis of the tetrapod track producers indicates the presence of at least three different taxa of sprawling to semi-erect therapsids, thus suggesting the presence of members of this clade, or closest relatives, in the Early Permian of southern Gondwana. Moreover, a series of measurements and simple indexes were developed to estimate body proportions and locomotion styles of the putative trackmakers. The new assemblage, analysed in the context of other known Permian assemblages from Pangea, is one the few known in Gondwana to be present in an aeolian environment. The evaluation of the assemblage, in the light of aeolian ichnofacies (Chelichnus, Octopodichnus and Entradichnus), shows that it has common elements with the Chelichnus and Entradichnus ichnofacies.