Ozimek volans: a Carnian Triassic Gliding Protorosaur

An early Late Triassic long-necked reptile with a bony pectoral shield and gracile appendages

Authors:

Dzik et al

Abstract:

Several partially articulated specimens and numerous isolated bones of Ozimek volans gen. et sp. nov., from the late Carnian lacustrine deposits exposed at Krasiejów in southern Poland, enable a reconstruction of most of the skeleton. The unique character of the animal is its enlarged plate-like coracoids presumably fused with sterna. Other aspects of the skeleton seem to be comparable to those of the only known specimen of Sharovipteryx mirabilis from the latest Middle Triassic of Kyrgyzstan, which supports interpretation of both forms as protorosaurians. One may expect that the pectoral girdle of S. mirabilis, probably covered by the rock matrix in its only specimen, was similar to that of O. volans gen. et sp. nov. The Krasiejów material shows sharp teeth, low crescent scapula, three sacrals in a generalized pelvis (two of the sacrals being in contact with the ilium) and curved robust metatarsal of the fifth digit in the pes, which are unknown in Sharovipteryx. Other traits are plesiomorphic and, except for the pelvic girdle and extreme elongation of appendages, do not allow to identify any close connection of the sharovipterygids within the Triassic protorosaurians.

A Dinosaur Footprint Found From Carnian Triassic Spain?

Spain says a footprint of a dinosaur that roamed the area 230 million years ago has been found in northeastern Catalonia, and says it's the best preserved dinosaur print seen so far in the Iberian Peninsula.

The print of a reptile-like creature called an Isochirotherium — an ancestor of dinosaurs and crocodiles — was discovered in early April by a person out walking in Olesa de Montserrat, 40 kilometers (25 miles) north of Barcelona.

link.

Ethiopia's Paleoclimate Became Humid, Wetter and Possibly Monsoonal During the Carnian/Norian Triassic

Paleoclimatic records of Late Triassic paleosols from Central Ethiopia

Author:

Dawit

Abstract:

The present study documents the major paleosols types within the Lower Adigrat Sandstone in the Blue Nile Basin of central Ethiopia, with the aim of unraveling the paleoclimatic signatures embedded in them. The paleosols developed within an 80-m-thick siliciclastic succession deposited in a mixed tide- and wave-dominated incised valley estuary during the Late Triassic.

Based on down-profile variations in pedogenic features, three major paleosol types (i.e., types I, II and III) were identified. Type I paleosols dominate the lower part of the section and are interpreted as moderately well-drained argillic Vertisols. The dominant pedogenic process was shrinking and swelling of expandable clays (i.e., smectite) through repeated wetting and drying cycles. The morphologies and the mineralogy of the paleosols provide persuasive evidence for pedogenesis under semi-arid subtropical climatic conditions with pronounced wet-dry seasonality, highly fluctuating soil moisture regime, and deep groundwater table. The presence of a calcic Bk horizon deep in the profiles is consistent with elevated soil moisture deficits and low to moderate mean annual precipitation (MAP). Type II paleosols, interpreted to represent vertic Gleysols, are more common in the middle part of the section. The pervasive gleying reflects poor soil drainage and a shallow groundwater table where the soil is waterlogged most of the year. These paleosols suggest a humid tropical climate characterized by alternating wet-dry seasonality but with more wet months per year. The top of the unit is dominated by type III paleosols that represent gleyed Oxisols, reflecting a more humid equatorial climate marked by wet seasons, elevated annual soil moisture content, and a high water table. The presence of plinthite/laterite is in agreement with a wet equatorial climate characterized by extensive chemical weathering and long periods of landscape stability.

The observed vertical progression in the major paleosol types from Vertsols to Gleysols and Oxisols implies a systematic change in the number of wet months, most probably in response to regional tectonics and long-term climate change. Because the number of wet months is, in part, related to latitude and monsoonal climates, the upward stratigraphic trend in paleosol orders is interpreted to signal the northward or equatorward migration of the Blue Nile Basin and central Ethiopia within Pangea from dry subtropical low-latitudes in the early Late Triassic (Carnian‐Norian) toward the humid, wet equatorial, possibly monsoonal, paleoclimatic zone in the Late Triassic (Norian‐Rhaetian).

Carnian/Norian Boundary Environmental Changes Were NOT Caused by Methane Hydrates or Volcanic Eruptions

Paleoenvironmental changes across the Carnian/Norian boundary in the Black Bear Ridge section, British Columbia, Canada

Authors:

Onoue et al

Abstract:

The Black Bear Ridge section in northeastern British Columbia, Canada, consists of a continuously exposed sequence of Upper Carnian through Lower Norian (Upper Triassic) continental margin strata. The section has been proposed as a candidate Global Stratotype Section and Point (GSSP) for the Carnian/Norian boundary (CNB). In order to assess Late Carnian to Early Norian environmental changes recorded in the section, we examined stratigraphic variations in 87Sr/86Sr, δ13C, and δ18O values, and also values of redox sensitive elements (V, Ni and Cr), in the CNB interval. The study section is located along the north shore of Williston Lake, northeastern British Columbia. The Black Bear Ridge section was deposited in a distal ramp environment on the passive western margin of the North American craton.

The strata across the CNB display a positive shift in δ13C values and a corresponding increase in the redox indices V/(V + Ni) and V/Cr. The synchronous increase in δ13C values and redox indices suggests that burial rates of marine organic carbon increased in response to the development of anoxic conditions in the water column. An increase in δ13C values in carbonate rocks across the CNB has also been reported from Upper Triassic sections in the western Tethys (e.g., in the Pizzo Mondello section, Sicily), which suggests that the development of anoxic conditions within the CNB interval was widespread, affecting both the Panthalassan Ocean and Tethyan Sea. The geochemical data from this study, as well as from research into conodont biostratigraphy in the Black Bear Ridge section, show that the onset of oceanic anoxic conditions may have been responsible for the faunal turnover event at the CNB. The cause of this anoxic event is unknown, but the 87Sr/86Sr and δ13C isotope data largely exclude the possibility that the event was triggered by dissociation of methane hydrates and degassing related to large-scale volcanic activity.

Dinosaurs Arose From Relatives Quickly in the Carnian Triassic

A new study by a team of scientists from Argentina, Brazil, California and the Natural History Museum of Utah at the University of Utah has determined that the time elapsed between the emergence of early dinosaur relatives and the origin of the first dinosaurs is much shorter than previously believed. The discovery not only places a new timeline on the connection between early dinosaur relatives and the first dinosaurs in this particular geologic formation, but also in other formations across the world.

The team, which included Randall Irmis, associate professor and curator of paleontology at the Natural History Museum, employed radioactive isotope measurements to date zircon crystals found in the sediments of the Chañares Formation, which is famous for its fossils of early dinosaur relatives.

The team found that the formation, and therefore the fossils found in it, is 234 to 236 million years old, from the Late Triassic Period; this is 5-10 million years younger than previous estimate of a Middle Triassic age.

"To discover that these early dinosaur relatives were geologically much younger than previously thought was totally unexpected," said Irmis.

link.

paper link.

Climate Variability during the Carnian Pluvial Phase (Carnian Triassic Wet Phase)

Climate variability during the Carnian Pluvial Phase — A quantitative palynological study of the Carnian sedimentary succession at Lunz am See, Northern Calcareous Alps, Austria

Authors:

Mueller et al

Abstract:

The Middle and Upper Triassic prevailing dry climate was interrupted by a global phase of increased humidity during the Early Carnian, the Carnian Pluvial Phase (CPP). It started at the Julian 1–2 boundary and lasted approximately until the latest Julian or early Tuvalian. In the Tethys this is reflected by a change from limestone deposits to, first, organic rich mudstones and then to siliciclastics. The CPP occurred along the northern rim of the Tethys and is reported from many locations within and surrounding Europe. In this study samples from Lunz am See in Austria were analyzed for palynology and for bulk carbon isotope values covering a 450 m thick succession. A known − 3‰ bulk organic carbon isotope excursion, possibly as a result of the eruption of large amounts of volcanogenic material, in the Göstling Member and the basal Reingraben Formation has been confirmed. A total of five distinctive palynology assemblages were recognized and correlated regionally. While the under- and overlying formations yield terrestrial and subordinate also marine palynomorphs, the palynoflora of the Lunz Formation is near wholly terrestrial in origin. Climate trends were inferred from multivariate statistical analysis (PCA) of the palynofloral record. Palynomorphs show a general trend from a dry climate during the Julian 1 to wetter conditions during the Julian 2. The wetter conditions were periodically interrupted by shorter periods of dryer climate. In terms of temperature trends the climate was warmer during the early Julian 2 which corresponds with the deposition of the Reingraben Formation, temperature decreased again and remained fairly stable during most of later part of the Julian 2, which corresponds to the deposition of the Lunz Formation. This study correlates with similar observations from other locations from the western Tethys region that support the theory of a wide-ranging to global Carnian Pluvial Phase.

The Unstable Paleoenvironmental Reasons why Dionsaurs Didn't Dominate the Late Triassic Tropics

Extreme ecosystem instability suppressed tropical dinosaur dominance for 30 million years

Authors:

Whiteside et al

Abstract:

A major unresolved aspect of the rise of dinosaurs is why early dinosaurs and their relatives were rare and species-poor at low paleolatitudes throughout the Late Triassic Period, a pattern persisting 30 million years after their origin and 10–15 million years after they became abundant and speciose at higher latitudes. New palynological, wildfire, organic carbon isotope, and atmospheric pCO2 data from early dinosaur-bearing strata of low paleolatitudes in western North America show that large, high-frequency, tightly correlated variations in δ13Corg and palynomorph ecotypes occurred within a context of elevated and increasing pCO2 and pervasive wildfires. Whereas pseudosuchian archosaur-dominated communities were able to persist in these same regions under rapidly fluctuating extreme climatic conditions until the end-Triassic, large-bodied, fast-growing tachymetabolic dinosaurian herbivores requiring greater resources were unable to adapt to unstable high CO2 environmental conditions of the Late Triassic.

tsk, tsk.  Multiple instances of wild fire during the Triassic.  Can't have had too bad of an oxygen crash.  All we need to finish that theory are examples from the jurassic.

Ruberodon roychowdhurii: a new Carnian Triassic Traversodontid Cynodont From India

A new Late Triassic traversodontid cynodont (Therapsida, Eucynodontia) from India

Author:

Ray

Abstract:

A large traversodontid cynodont Ruberodon roychowdhurii, gen et. sp. nov., is described from the Late Triassic Tiki Formation of the Rewa Gondwana Basin, India, based on an ontogenetic series of five partial lower jaws. Ruberodon is characterized by a robust and deep dentary symphysis, lower dental formula of i3-c1-pc9, procumbent and hypertrophied first lower incisor, a large canine, long diastema between the lower canine and first postcanine, and a high coronoid process at 60° to the horizontal tooth row. With growth, the symphyseal region became relatively more slender with lengthening of the diastema. Phylogenetic analysis based on 19 taxa and 35 craniodental characters places Ruberodon within the clade containing Gomphodontosuchus, Menadon, Protuberum, Scalenodontoides, and the multispecific Exaeretodon. The new genus forms a sister taxon to E. statisticae and is more advanced than E. riograndensis and E. argentinus based on the presence of a strong coronoid ridge anterior to the masseteric fossa. Based on its tetrapod assemblage, the Tiki Formation may be globally correlated with other formations such as the lower part of the Maleri Formation of India, the Isalo II Beds of Madagascar, and the upper part of the Santa Maria Formation of Brazil. An early Carnian age is proposed for the Tiki Formation.

Mysterious Wet PaleoClimate Interlude During Mid Carnian Triassic

The mysterious Mid-Carnian “Wet Intermezzo” global event

Author:

Ogg

Abstract:

Approximately 230 million years ago in the middle of the Carnian stage of the Upper Triassic, the sedimentary records in different regional basins display dramatic changes. Tropical carbonate platforms abruptly ended, and engorged river systems left widespread sand-rich layers across inland basins and coastal regions. This pulse lasted less than a million years in some basins, but constituted a permanent shift in others. Following this event, the Late Carnian has the earliest record of significant dinosaurs on land and the emergence of the calcareous nannoplankton in the oceans that now govern Earth’s carbon cycle. This “most distinctive climate change within the Triassic” has been interpreted by some geoscientists as a global disruption of the Earth’s land-ocean-biological system. The eruption of the Wrangellia large igneous province may have been the trigger for a sudden carbon-dioxide-induced warming and associated increased rainfall in some of these regions. Indeed, some workers have proposed that this “wet intermezzo” warming event is a useful analog to aid in predicting the effects of our future greenhouse on land ecosystems and ocean chemistry. However, the understanding of the onset, duration, global impacts and relatively rapid termination of this postulated warming pulse has been hindered by lack of a global dataset with inter-calibrated terrestrial and marine biostratigraphy, precise radio-isotopic ages, stable isotope records of temperature and the carbon system, and cycle-calibrated rates of regional and global change.

Evidence of Climate Change During Carnian Triassic

Sequence stratigraphy after the demise of a high-relief carbonate platform (Carnian of the Dolomites): sea-level and climate disentangled

Authors:

Gattolin et al

Abstract:

Sedimentary facies analysis aided by quantitative 3D georeferenced field data are applied to constrain the sequence stratigraphy of a complex stratigraphic interval in the Late Triassic of the Dolomites. This multidisciplinary approach was the key to disentangle the timing of climatic change vs. sea-level fluctuation and their effects on shallow water carbonate depositional systems. The “Carnian Pluvial Event”, a global episode of climate change worldwide documented at low latitudes, involved increased rainfall and possibly global warming. This climatic event begins before a drop of sea-level and caused the demise of microbial-dominated high-relief carbonate platforms that dominated the Dolomites region, and was followed by a period of coexistence of small microbial carbonate mounds and arenaceous skeletal-oolitic grainstones. A subsequent sea-level fall brought to the definitive disappearance of microbialites and shallow water carbonates switched to ramps dominated by oolitic-bioclastic grainstones. The crisis of early Carnian shallow water carbonate systems of the Dolomites generated a geological surface similar to a drowning unconformity, although no transgression occurred. As the high-relief microbial carbonate systems characterized by steep slopes switched to gently inclined oolitic-skeletal-siliciclastic ramps, basins were rapidly filled. The change of carbonate depositional systems was associated with an increase in siliciclastic input, in turn triggered by the onset of a humid climatic event and only later to a sea-level drop. This evolution of carbonate systems cannot be interpreted in the light of sea-level changes only: climate change, and consequent ecological changes in the main carbonate producing biotas, induced significant modifications in depositional geometries. This case study may serve as a conceptual model for the sedimentary evolution of carbonate systems subject to ecological crisis that do not evolve in platform drowning because, despite a drop in shallow water carbonate production, a combination of low subsidence and/or sea level drop maintains the platform top at shallow depth.

Xinpusaurus Revisited: A Carnian Triassic Thalattosaur From China

On the morphoplogy and taxonomic status of Xinpusaurus kohi JIANG et al., 2004 (Diapsida: Thalattosauria) from the Upper Triassic of China

Author:

Maisch

Abstract:

Additional preparation has revealed new information on the cranium and the vertebral column of the type and only specimen of Xinpusaurus kohi JIANG et al., 2004, a thalattosaur from the Upper Triassic Xiaowa Formation of Guanling County (Guizhou, south-western China). The new data allow to supplement existing descriptions and to decide on some controversial points raised in recent discussions. Although the skeleton is almost complete, there is some reconstruction, which makes the low presacral vertebral number and the narrow proximal end of the femur, originally regarded as diagnostic characters, doubtful. All other diagnostic characters of the species are valid. Comparison to another thalattosaur species from the Xiaowa Formation, Xinpusaurus bamaolinensis, shows great similarities, but is limited due to its insufficient description. Hence, it cannot be excluded that X. kohi is a junior subjective synonym of X. bamaolinensis. However, the recent claim that X. kohi and X. bamaolinensis are synonyms of X. suni, the type species of the genus, is not supported by the new data. The description of X. bamaolinensis leaves many points unclear. Pending a re-description of that specimen that may allow for a more meaningful comparison, X. kohi should be allowed to stand.

Revisting Carnian Triassic Rauisuchid Rauisuchus tiradentes

Osteology of Rauisuchus tiradentes from the Late Triassic (Carnian) Santa Maria Formation of Brazil, and its implications for rauisuchid anatomy and phylogeny

Authors:

Lautenschlager et al

Abstract:

As the eponymous type species for rauisuchians, Rauisuchus tiradentes von Huene, 1938 represents an important but inadequately known specimen. The revision of the type material from the Upper Triassic (Carnian) Santa Maria Formation of Brazil reveals new anatomical data and previously unrecognised characters, including three new possible autapomorphies: a knob-like thickening on the base of the posterior process of the premaxilla; short and ventrally keeled cervicals lacking postzygodiapophyseal laminae; and mid-caudal vertebrae with an accessory neural spine and a postspinal lamina. Several elements are re-identified, including a postorbital (originally identified as postfrontal) and a pterygoid (originally identified as a prefrontal), and additional material from a secondary fossil site, originally assigned to R. tiradentes, including a left ilium, is excluded. Based on the recovered information and new morphological data, the systematic position of R. tiradentes is tested in a comparison of two phylogenetic reanalyses. Both analyses differ in respect to the phylogenetic position of R. tiradentes, and recover ‘rauisuchians’ as a paraphyletic assemblage of non-crocodylomoprh archosaurs. © 2014 The Linnean Society of London

Pseudochampsa ischigualastensis: a new Genus for a Proterochampsid From Carnian (?) Triassic Brazil

Osteology of Pseudochampsa ischigualastensis gen. et comb. nov. (Archosauriformes: Proterochampsidae) from the Early Late Triassic Ischigualasto Formation of Northwestern Argentina

Authors:

Trotteyn et al

Abstract:

Proterochampsids are crocodile-like, probably semi-aquatic, quadrupedal archosauriforms characterized by an elongated and dorsoventrally low skull. The group is endemic from the Middle-Late Triassic of South America. The most recently erected proterochampsid species is “Chanaresuchus ischigualastensis”, based on a single, fairly complete skeleton from the early Late Triassic Ischigualasto Formation of northwestern Argentina. We describe here in detail the non-braincase cranial and postcranial anatomy of this species and revisit its taxonomy and phylogenetic relationships. The phylogenetic analysis recovered ‘Chanaresuchus ischigualastensis’ as part of a trichotomy together with Gualosuchus reigi and Chanaresuchus bonapartei. Accordingly, “Chanaresuchus ischigualastensis” can be potentially more closely related to Gualosuchus reigi, or even Rhadinosuchus gracilis, than to Chanaresuchus bonapartei. In addition, after discussing previously claimed synapomorphies of Chanaresuchus, we could not find unambiguous support for the monophyly of the genus. As a result, we propose here the erection of the new genus Pseudochampsa for ‘Chanaresuchus ischigualastensis’, which results in the new combination Pseudochampsa ischigualastensis. The information provided here about the anatomy and taxonomy of Pseudochampsa ischiguaslastensis will be useful for future quantitative analyses focused on the biogeography and macroevolutionary history of proterochampsids.

Botucaraitherium belarminoi: a new Prozostrodontian Cynodont from Carnian Triassic Brazil

A new prozostrodontian cynodont (Therapsida) from the Late Triassic Riograndia Assemblage Zone (Santa Maria Supersequence) of Southern Brazil.

Authors:

Soares et al

Abstract:

Here we report on a new prozostrodontian cynodont, Botucaraitherium belarminoi gen. et sp. nov., from the Riograndia Assemblage Zone (AZ) of the Candelária Sequence (Santa Maria Supersequence), collected in the Botucaraí Hill Site, Candelária Municipality, state of Rio Grande do Sul, Brazil. The new taxon is based on a single specimen (holotype MMACR-PV-003-T) which includes a left lower jaw, without postdentary bones, bearing the root of the last incisor, canine and four postcanines plus one partial crown inside the dentary, not erupted, and two maxillary fragments, one with a broken canine and another with one postcanine. The features of the lower jaw and lower/upper postcanines resemble those of the prozostrodontians Prozostrodon brasiliensis from the older Hyperodapedon AZ and Brasilodon quadrangularis and Brasilitherium riograndensis from the same Riograndia AZ. The inclusion of Botucaraitherium within a broad phylogenetic analysis, positioned it as a less inclusive taxon than tritylodontids, and as the sister-taxon of Brasilodon, Brasilitherium and Mammaliaformes. Although the new taxon is based on few cranial elements, it represents a additional faunal component of the Triassic Riograndia AZ of southern Brazil, in which small-sized derived non-mammaliaform cynodonts, intimately related to the origin of mammaliaforms, were ecologically well succeed and taxonomically diverse.

Venaticosuchus rusconii: a Carnian/Norian Triassic Pseudosuchian Archosaur Revisited

Anatomy and phylogenetic position of Venaticosuchus rusconii Bonaparte, 1970 (Archosauria, Pseudosuchia), from the Ischigualasto Formation (Late Triassic), La Rioja, Argentina

Authors:

Belén Von Baczko et al

Abstract:

Ornithosuchidae is a group of Late Triassic pseudosuchian archosaurs of controversial phylogenetic affinities. This clade currently comprises three taxa: Venaticosuchus rusconii and Riojasuchus tenuisceps, both from Argentina, and Ornithosuchus longidens, from Scotland. V. rusconii was erected on the basis of an incomplete skull with articulated lower jaws and some elements of the postcranium that are currently lost. Venaticosuchus rusconii is redescribed here and included for the first time in a phylogenetic analysis to test its affinities with ornithosuchids. The bizarre morphology of V. rusconii has a unique combination of traits that distinguishes it from the other ornithosuchids, such as basipterygoid processes directed ventrally, dentary with the dorsal margin of the anterior end dorsally expanded, articular without a foramen on its medial side, and the absence of a surangular foramen, corroborating the validity of this taxon. V. rusconii is recovered as an ornithosuchid more closely related to R. tenuisceps than to O. longidens, based on the presence of a nearly pointed anterior margin of the antorbital fenestra, and a vertical bony strut of the jugal that separates the antorbital fenestra from the infratemporal fenestra.

How Dinosauriform Silesaurus Grew

Skeletal variation and ontogeny of the Late Triassic Dinosauriform Silesaurus opolensis

Authors:

Piechowski et al

Abstract:

A principal component analysis (PCA) performed for a set of 24 measurements on 33 femora and 15 measurements on 20 ilia of Silesaurus opolensis from the early Late Triassic of Krasiejów, southern Poland, shows that this sample is highly variable but probably monospecific. Most of the morphological variation is concentrated in the muscle attachments and proportions of bones, which significantly change in both size and position during ontogeny. Despite the small sample size, femora of smaller individuals have less flattened shafts and a more sinusoidal appearance. In many large specimens, proximal parts of muscle tendons are ossified at their attachment site on femora and remain attached to the bone in the largest specimens. The specimens with attached ossifications are interpreted as mature females that were statistically larger than proposed males. It is suggested that ossifications developed in females under calcitonin control. The intrapopulation variability of ilia is high, but less dependant on ontogeny. The population represented by a few specimens from the lower level at Krasiejów may represent a different stage in the evolution of the species than that from the upper horizon.

Carnian/Norian Triassic Boundary Succession in Nevada at Berlin-Ichthyosaur State Park

The Carnian/Norian boundary succession at Berlin-Ichthyosaur State Park (Upper Triassic, central Nevada, USA)

Authors:

Balini et al

Abstract:

The Upper Carnian-Lower Norian (Upper Triassic) Luning Formation at Berlin-Ichthyosaur State Park (BISP) in central NV (USA) has been sampled using for the first time the bed-by-bed approach for ammonoids, pelagic bivalves, and conodonts, more than 60 years after its first description by Silberling (U.S. Geological Survey Professional Paper 322: 1–63, 1959). BISP is historically important for the definition of the uppermost Carnian of the North American Triassic chronostratigraphic scale and is known worldwide as one of the most important ichthyosaur Fossil-Lagerstätte because of its extraordinary record of 37 articulated, large-sized specimens of Shonisaurus popularis. Nearly 190 ammonoids were collected from two stratigraphic sections, documenting all the latest Carnian to Early Norian ammonoid faunas previously described by Silberling. Halobiids were collected from five levels, and the first report of conodonts from BISP includes faunas from 13 levels. The ~340-m thick Brick Pile section, the most complete in the study area, includes the uppermost Carnian Macrolobatus Zone, which provides conodont faunas of the lower primitia zone and Halobia septentrionalis. The 200-m thick lowermost Norian Kerri Zone, which begins 52 m above the Macrolobatus Zone, yields conodonts of the upper primitia zone in its lower part, together with H. cf. beyrichi and H. cf. selwyni. The ichthyosaur-bearing interval, whose stratigraphic position has been interpreted quite differently by previous authors, is documented in the uppermost Carnian Macrolobatus Zone and is characterized by rich Tropites-dominated ammonoid faunas and by the onset of Halobia. All models proposed by various workers to explain the unusual ichthyosaur record are discussed and an additional explanation for the main ichthyosaur-bearing bed is proposed. The new hypothesis is that a harmful algal bloom (HAB) may have been the trigger for the mass mortality recorded in this level. Although the C/N boundary in the Brick Pile section lies within a 52 m interval that presently lacks paleontologic data, this succession is included in a small group of sections that are expected to contribute to the definition of the GSSP of the Norian stage. Correlation of the Brick Pile section with the best Carnian/Norian sections in northeastern British Columbia is discussed. Compared to the British Columbia Juvavites Cove and the GSSP candidate Black Bear Ridge sections, the Brick Pile section exhibits an ammonoid and Halobia record that is slightly more similar to that of the Tethyan sections. Correlation of the Brick Pile section with the second GSSP candidate Pizzo Mondello (Sicily, Italy) well demonstrates the significant problems encountered in calibration of the Tethyan and North American scales.

Mark Whitton on Scleromochlus taylori: the Carnian Triassic Ornithodiran Archosaur Pretending to be a Gerbil

Go read and behold the awesomeness.

Revised Chronostratigraphy of Chinle Formation has Implications for Late Triassic Dinosaur Evolution

Revised chronostratigraphy of the Lower Chinle Formation strata in Arizona and New Mexico (USA): High-precision U-Pb geochronological constraints on the Late Triassic evolution of dinosaurs

Authors:

Ramezani et al

Abstract:

The early history of dinosaurs in North America is obscured by an incomplete fossil record, taxonomic uncertainties and speculative correlations of tetrapod-bearing rocks, as well as poor calibration of the Late Triassic time scale. High-precision U-Pb geochronology provides a reliable means of correlating terrestrial rock formations independent of equivocal lithostratigraphy or vertebrate biostratigraphy, and hence the possibility of properly evaluating models for the early radiation and diversification of Dinosauria. Here we present new, high-precision, U-Pb ID-TIMS zircon geochronology from the presumed lowermost strata of the Upper Triassic Chinle Formation of the Colorado Plateau in Southwest United States, including a mean 206Pb/238U date of 219.39 ± 0.16 Ma from the renowned Placerias Quarry Bone Bed in eastern Arizona. The new results prompt revisions to the chronostratigraphy of the lower Chinle and provide a new temporal context for its rich tetrapod fauna.

The oldest documented dinosaurs of North America coexisted with their non-dinosaurian near-relatives for a minimum of 12 m.y., from ca. 223 Ma to ca. 211 Ma, in the Norian. This early dinosauromorph record follows a ca. 6 m.y. period from which no tetrapod fossils have been documented and which was itself preceded by a ca. 10 m.y. depositional hiatus spanning nearly the entire Ladinian and Carnian stages of the terrestrial North America. The supposed late appearance of dinosauromorphs in North America compared to those in South America thus appears to be an artifact of incomplete preservation, as well as unsubstantiated age interpretations. This, together with the conspicuous biogeographic distinctions among the Triassic dinosauromorph assemblages, invalidates a simple diachronous model for the transcontinental radiation of early dinosaurs.

First Phytosaur Found in Carnian/Norian Triassic Portugal

The first phytosaur (Diapsida, Archosauriformes) from the Late Triassic of the Iberian Peninsula

Authors:

Mateus et al

Abstract:

The Triassic was first defined based on the characteristic threefold sequence of rocks that crops out across much of Europe, and many of the first records of Triassic dinosaurs, crocodile-line archosaurs, and other vertebrates were discovered in Great Britain, France, Switzerland, and Germany. These discoveries helped paint a general picture of the Triassic as a critical transitional interval in Earth’s history, during which Earth recovered from a devastating extinction and more modern terrestrial ecosystems composed of dinosaurs, crocodylomorphs, squamates, and mammals were first established (e.g., Sues and Fraser, 2010). Over the past 50 years, however, the focus of Triassic vertebrate research has shifted to the fossil-rich deposits of South America and western and northeastern North America. The European record has been overshadowed, but new discoveries are stimulating a major expansion of Triassic vertebrate work across Europe, especially in Germany and Poland (e.g., Gower, 1999; Dzik, 2001; Schoch, 2006; Dzik and Sulej, 2007).

Despite considerable exposures of Triassic terrestrial sedimentary rock, the Iberian Peninsula of southwestern Europe has to date contributed little to this renewed focus on the European Triassic vertebrate record. This situation is changing with recent descriptions of Triassic terrestrial vertebrates from Spain (e.g., Fortuny et al., 2011) and Portugal (Witzmann and Gassner, 2008; Steyer et al., 2011). Here, we describe the first Iberian record of a major clade of Triassic vertebrates, the long-snouted, semiaquatic phytosaurs that are part of the great post-Permian archosauromorph radiation (e.g., Stocker and Butler, 2013). This specimen, the posterior end of a mandible and associated teeth, was discovered in southern Portugal, 2.7 m above and about 5 m lateral to a bonebed of the temnospondyl Metoposaurus in a mudstone unit within the same stratigraphic section as Central Atlantic Magmatic Province (CAMP) basalts, in a classic northern Pangean rift sequence (Fig. 1). The discovery of this specimen helps to better constrain the age of the Portuguese site and provides further evidence that basal phytosaurs were widely distributed in areas with a monsoonal-type climate during the Triassic (e.g., Buffetaut, 1993; Brusatte et al., 2013).