A Review of Kuehneotherium & its Mammaliaforme Relatives From Upper Triassic France

The Kuehneotheriidae (Mammaliaformes) from Saint-Nicolas-de-Port (Upper Triassic, France): a Systematic Review

Author:

Debuysschere

Abstract:

The origin and first diversification of mammals in the Upper Triassic remain poorly understood, in part because many fossil discoveries are not fully studied, and in part because the material remains poor. The Saint-Nicolas-de-Port quarry (Rhaetian, France) is the second most important locality that yielded remains of Kuehneotherium, after the fissure-fillings of the Glamorganshire (Lower Jurassic, Wales). This study identifies one new species of Kuehneotherium, K. stanislavi, sp. nov., and a new genus of Kuehneotheriidae, Fluctuodon necmergor, gen. et sp. nov. For these two new species, lower and upper molars are described and the first reconstructions of the postcanine row are proposed. Comparisons with material of Kuehneotherium from other Upper Triassic sites (Syren in Luxembourg, Emborough in England, and Jameson Land in Greenland) suggest two distinct Upper Triassic specific kuehneotheriid assemblages, respectively, west and east of the London Brabant Massif. They also suggest that the extinction event during the Triassic/Jurassic transition did not have a great impact on Kuehneotherium.

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).

"Giant" Pterosaur Found at Rhaetian (?) Triassic Oasis "Sandpit"

Scientists have found an unprecedented cache of fossils of weird animals that thrived at a desert oasis some 200 million years ago, providing a snapshot of a place and time that have long been a mystery.

The fossils include the bones of a fanged flying predator and creatures that looked, one scientist says, like tiny crocodiles with a Chihuahua's legs. Small reptiles whose "hands" resemble a mole's lived alongside dinosaurs that scampered on their hind legs.

Researchers suspect that many of the fossils represent entirely new species.

"Probably almost everything we're finding (at the site) is previously unknown to science," says Dan Chure of Dinosaur National Monument, one of the site's co-discoverers. "It's just an amazing paleontological candy shop."

The fossils are "a spectacular find," agrees University of Utah paleontologist Randall Irmis, who isn't involved in the project. "We so rarely get sites that preserve such a variety of different animals from the beginning of the age of dinosaurs."

The animals at the site should help illuminate the period just before the mass extinction that allowed the dinosaurs to take over the Earth, Irmis says. The fossils also illuminate exactly what was living in the vast sand box that filled what is now the western United States, where fossils from the Late Triassic fossils are scarce.

link.

Archosauriforms From a Flood Plain in Late Triassic Argentina

Archosauriform remains from the Late Triassic of San Luis province, Argentina, Quebrada del Barro Formation, Marayes–El Carrizal Basin

Authors:

Gianechini et al

Abstract:

Here we present archosauriform remains from ‘Abra de los Colorados’, a fossiliferous locality at Sierra de Guayaguas, NW San Luis Province. Two fossiliferous levels were identified in outcrops of the Quebrada del Barro Formation (Norian), which represent the southernmost outcrops of the Marayes–El Carrizal Basin. These levels are composed by massive muddy lithofacies, interpreted as floodplain deposits. The specimens consist of one incomplete maxilla (MIC-V718), one caudal vertebra (MIC-V719), one metatarsal (MIC-V720) and one indeterminate appendicular bone (MIC-V721). The materials can be assigned to Archosauriformes but the fragmentary nature and lack of unambiguous synapomorphies preclude a more precise taxomic assignment. The maxilla is remarkably large and robust and represents the posterior process. It preserved one partially erupted tooth with ziphodont morphology. This bone shows some anatomical traits and size match with ‘rauisuchians’ and theropods. MIC-V719 corresponds to a proximal caudal vertebra. It has a high centrum, a ventral longitudinal furrow, expanded articular processes for the chevrons, a posteriorly displaced diapophysis located below the level of the prezygapophyses, and short prezygapophyses. This vertebra would be from an indeterminate archosauriform. MIC-V720 presents a cylindrical diaphysis, with a well-developed distal trochlea, which present resemblances with metatarsals of theropods, pseudosuchians, and silesaurids, although the size matches better with theropods. MIC-V721 has a slender diaphysis and a convex triangular articular surface, and corresponds to an indeterminate archosauriform. Despite being fragmentary, these materials indicate the presence of a diverse archosauriforms association from Late Triassic beds of San Luis. Thus, they add to the faunal assemblage recently reported from this basin at San Juan Province, which is much rich and diverse than the coeval paleofauna well known from Los Colorados Formation in the Ischigualasto–Villa Union Basin.

Academic Bun Fight! Upper Triassic Cotham Marble is NOT Evidence of a Mass Extinction

That was NOT a sign!

COMMENT TO IBARRA ET AL. MICROFACIES OF THE COTHAM MARBLE: A TUBESTONE MICROBIALITE FROM THE UPPER TRIASSIC, SOUTHWESTERN U.K

Authors:

Mayall et al

Abstract:

Ibarra et al. (2014) have presented an interesting paper on the Cotham Marble, an enigmatic microbialite from the Rhaetian Penarth Group of SW England, and an iconic piece of British stratigraphy. They have re-interpreted some aspects of our earlier work (Wright and Mayall 1981) in which we tried to be amongst the first researchers to apply an ethological approach to decipher an ancient microbial texture. That paper (Wright and Mayall 1981) was restricted editorially with respect to its content requiring a second one to illustrate the microbial microtextures we felt were critical to understanding the morphogenesis of the limestone (Mayall and Wright 1981). In addition to challenging previously published work, Ibarra et al. (2014) use the Cotham Marble to identify evidence for the late Triassic mass extinction event, thus substantially broadening the importance of this unit for the wider readership. However we would like to take this opportunity to question a number of their conclusions, in particular using the Cotham Marble as an indicator of a mass extinction event and the role of Microtubus communis in forming the Cotham Marble.

Yes, it is!

MICROFACIES OF THE COTHAM MARBLE: A TUBESTONE CARBONATE MICROBIALITE FROM THE UPPER TRIASSIC SOUTHWESTERN U.K.: A REPLY

Authors:

Ibarra et al

Abstract:

Mayall and Wright question interpretations in our microfacies analysis of the Cotham Marble microbialites (Ibarra et al. 2014) in which we primarily highlight previously overlooked aspects of Cotham Marble microbialite formation. They are specifically unconvinced about the Cotham Marble’s potential relevance to the end-Triassic mass extinction and our interpretation that Microtubus is not integral to the formation of the dendrolitic microbialite phases. Here we address Mayall and Wright’s comments under the same headings in which they present them.

Norian/Rhaetian Triassic Sichuan Basin, China had two Warm, Humid and two Cooler, Drier PaleoClimate Events

Late Triassic palynofloras in the Sichuan Basin, South China: Synthesis and perspective

Authors:

Li et al

Abstract:

Mesozoic strata are well developed and exposed continuously across the Sichuan Basin, South China. In particular, the Upper Triassic strata yield diverse and abundant spore-pollen fossils, providing a significant reference for the study of palaeoenvironmental variations across the Triassic–Jurassic transition where mass extinctions were occurring. In this paper, we summarize the major progress on Late Triassic palynological studies in this basin. To date, 151 genera (454 species) of sporomorph fossils have been reported from the Late Triassic strata in the Sichuan Basin. Three palynological assemblages are distinguished for the Late Triassic in the Sichuan Basin. Late Triassic vegetation in the Sichuan Basin shows a remarkable predominance of ferns, followed by conifers and cycads/ginkgophytes, and conifers show a distinct increase in abundance in the latest Triassic. In general, the Late Triassic palaeoclimate in the Sichuan Basin was tropical-subtropical, humid and warm. A synthesis of the data shows that the Late Triassic did not have a constant paleoclimate in the Sichuan Basin, several climatic events are recognized: two warm and humid climate events in Norian-Rhaetian time, coupled with a cooler and drier condition in the latest Late Triassic. Further investigations in higher resolution at more continuous sections in the Sichuan Basin are needed to better understand the Late Triassic vegetation response, climate changes, as well as palaeoecosystem variations across the Triassic–Jurassic boundary.

Evidence of a 3.3 to 7.8 km Carbonaceous Chondrite Asteroid Impact From the Upper Triassic

Sedimentary PGE signatures in the Late Triassic ejecta deposits from Japan: implications for the identification of impactor

Authors:

Sato et al

Abstract:

Positive platinum group element (PGE) concentration and negative Os isotope anomalies reported from a claystone layer in the Upper Triassic bedded chert succession of the Sakahogi section, Mino Belt, central Japan, are thought to have been derived from an impact event. Stratigraphic variations and concentrations of PGE were examined in the Sakahogi section to determine the type of the impactor. Upper Triassic claystone layers, where PGE anomalies have been newly discovered in bedded chert successions in southwest Japan, were also examined. These include (i) the Unuma section in the Inuyama area, Mino Belt; (ii) the Hisuikyo section in the Kamiaso area, Mino Belt; and (iii) the Enoura section in the Tsukumi area, Chichibu Belt. Radiolarian and conodont biostratigraphic data indicates that these claystone layers are of upper middle Norian age. Reconstruction of bedded chert in these sections suggests that they originate from open-ocean pelagic deep-sea sediments deposited in the Panthalassa Ocean.

The relatively flat CI-chondrite normalized patterns of the least mobile PGEs (Ir, Ru, and Rh) and the Ru/Ir ratio determined by linear regression analysis suggest that a chondritic impactor is the source of the PGE anomalies preserved in claystone samples from the study sections. Although Ru/Ir ratios cannot conclusively distinguish chondrites from iron meteorites, the Cr/Ir ratios of the claystone layers range from 104 to 105, clearly indicating contribution from chondritic materials. The chondritic impactor of the suggested size (3.3–7.8 km in diameter) implies that a large amount of debris and/or climatically active gasses (e.g., sulfur oxides) would have been released from the impactor, which would have had a marked effect on the environment.

Haramiyidans Were NOT Mammals or Closely Related to Multituberculates According to Evidence From Rhaetian Triassic Greenland

Mandibular and dental characteristics of Late Triassic mammaliaform Haramiyavia and their ramifications for basal mammal evolution

Authors:

Luo et al

Abstract:

As one of the earliest-known mammaliaforms, Haramiyavia clemmenseni from the Rhaetic (Late Triassic) of East Greenland has held an important place in understanding the timing of the earliest radiation of the group. Reanalysis of the type specimen using high-resolution computed tomography (CT) has revealed new details, such as the presence of the dentary condyle of the mammalian jaw hinge and the postdentary trough for mandibular attachment of the middle ear—a transitional condition of the predecessors to crown Mammalia. Our tests of competing phylogenetic hypotheses with these new data show that Late Triassic haramiyids are a separate clade from multituberculate mammals and are excluded from the Mammalia. Consequently, hypotheses of a Late Triassic diversification of the Mammalia that depend on multituberculate affinities of haramiyidans are rejected. Scanning electron microscopy study of tooth-wear facets and kinematic functional simulation of occlusion with virtual 3D models from CT scans confirm that Haramiyavia had a major orthal occlusion with the tallest lingual cusp of the lower molars occluding into the lingual embrasure of the upper molars, followed by a short palinal movement along the cusp rows alternating between upper and lower molars. This movement differs from the minimal orthal but extensive palinal occlusal movement of multituberculate mammals, which previously were regarded as relatives of haramiyidans. The disparity of tooth morphology and the diversity of dental functions of haramiyids and their contemporary mammaliaforms suggest that dietary diversification is a major factor in the earliest mammaliaform evolution.

Megalancosaurus: A Nightmare Chameleon-like Late Triassic Drepanosaur That Grabbed Prey With is Vice-Clawed Hands

The role of the forelimb in prey capture in the Late Triassic reptile Megalancosaurus (Diapsida, Drepanosauromorpha)

Authors:

Castiello et al

Abstract:

The pectoral girdle and forelimb of the Late Triassic drepanosauromorph reptile Megalancosaurus are redescribed and their function reinterpreted. The whole skeleton of this diapsid is highly specialised for arboreal life, and also the peculiarities of the shoulder girdle and forelimb were interpreted as adaptations for a limb-based locomotion using gap-bridging to move from one support to another, as in chameleons. Re-examination of the pectoral girdle and forelimb revealed the presence of clavicles fused into a furcula-like structure, a saddle-shaped glenoid and a tight connection between the radius and ulna that strengthened the forearm but hindered pronation and supination movements at that joint. The new information plus a reconstruction of the pectoral and forelimb musculature suggests that the forelimb was also specialised for grasping and raking in addition to climbing and thus prey capture may have been an important function for the forelimb. The new functional interpretation fits well with the overall body architecture of Megalancosaurus’ skeleton, suggesting that this reptile was an ambush predator that may have assumed a stable tripodal position, secured by the hooked tail and hind limbs, freeing its forelimbs to catch prey by sudden extension of the arm and firm grasping with the pincer-like digits.

Evidence Late Triassic Traversodontid Exaeretodons Were Scavenged

Biogenic control on the origin of a vertebrate monotypic accumulation from the Late Triassic of southern Brazil

Authors:

Müller et al

Abstract:

This study is a taphonomic investigation of a new Late Triassic monotypic association from the Hyperodapedon Assemblage Zone (Santa Maria Formation, southern Brazil). All skeletal elements belong to the traversodontid cynodont Exaeretodon, representing a minimum of four individuals from different ontogenetic stages. Biogenic traces are identifiable on some elements, such as invertebrate scavenging traces, vertebrate bite marks, and evidence of trampling which was probably responsible for accelerating the disarticulation of upper postcanine teeth and for fracturing a skull and a lower jaw. We classify this accumulation as generated by extrinsic biogenic action (predation/necrophagy and possibly trampling) due to the following reasons: (i) random spatial orientation of the elements enclosed into the matrix; (ii) absence of hydraulic equivalence among the specimens and presence of mudstone lenses in close association with the fossils; (iii) presence of nearly all Voorhies’ groups; (iv) association of a large number of cranial elements presenting different stages of disarticulation; and (v) presence of biogenic traces. Both disarticulation patterns and invertebrate scavenging traces indicate that the bones remained exposed for some time before burial. During this time of exposure, carnivore vertebrates also scavenged on some nutritive and transportable postcranial elements. We suggest an ecteniniid cynodont as a potential modifier agent (predation/necrophagy) of this particular monotypic accumulation of synapsids.

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.

A new Norian/Rhaetian Triassic Vertebrate Assemblage from Argentina

A NEW LATE TRIASSIC VERTEBRATE ASSEMBLAGE FROM NORTHWESTERN ARGENTINA

Authors:

Martínez et al

Abstract:

The Quebrada del Barro Formation (QBF) is part of the continental Marayes-El Carrizal Basin, in NW Argentina. Here we report a diverse faunal assemblage recently discovered at the Quebrada del Barro Formation, along with a preliminary discussion of the taxonomic status and affinities of numerous vertebrate specimens found at two localities of this unit. The new vertebrate association includes remains of at least 12 different new species related to six major vertebrate groups: Cynodontia, Testudinata, Sphenodontia, Pseudosuchia, Pterosauria, and Dinosauromorpha. The most abundant specimens in this faunal assemblage are opisthodontian sphenodonts, tritheledontid cynodonts and basal sauropodomorph dinosaurs, but the assemblage also includes diagnostic remains of lagerpetid dinosauromorphs, theropods, pterosaurs, basal crocodylomorphs, and stem testudinatans. Several of these groups have also been reported for the Los Colorados Formation (LCF), although the two units differ in their taxonomic content at the species level and in the relative abundance of different taxonomic groups. A comparison of these two faunal assemblage suggest the fauna of QBF is younger than that of LCF and we tentatively assess a late Norian–Rhaetian age for the QBF. Some of the specimens reported here are known from well-preserved specimens and contain important new information for understanding the evolution of these groups, which underscores the relevance of the QBF fauna for assessing the dynamics of the major groups of vertebrates that dominated the terrestrial ecosystems during the early Mesozoic in Pangea.

Metoposaurus algarvensis: A new, Giant Metoposaur Temnospondyl From Norian Triassic Portugal

A new species of Metoposaurus from the Late Triassic of Portugal and comments on the systematics and biogeography of metoposaurid temnospondyls

Authors:

Brusatte et al

Abstract:

Metoposaurids are a group of temnospondyl amphibians that filled crocodile-like predatory niches in fluvial and lacustrine environments during the Late Triassic. Metoposaurids are common in the Upper Triassic sediments of North Africa, Europe, India, and North America, but many questions about their systematics and phylogeny remain unresolved. We here erect Metoposaurus algarvensis, sp. nov., the first Metoposaurus species from the Iberian Peninsula, based on several new specimens from a Late Triassic bonebed in Algarve, southern Portugal. We describe the cranial and pectoral anatomy of M. algarvensis and compare it with other metoposaurids (particularly other specimens of Metoposaurus from Germany and Poland). We provide a revised diagnosis and species-level taxonomy for the genus Metoposaurus, which is currently represented with certainty by three European species (M. diagnosticus, M. krasiejowensis, M. algarvensis). We also identify cranial characters that differentiate these three species, and may have phylogenetic significance. These include features of the braincase and mandible, which indicate that metoposaurid skulls are more variable than previously thought. The new Portuguese bonebed provides further evidence that metoposaurids congregated in fluvial and lacustrine settings across their geographic range and often succumbed to mass death events. We provide an updated paleogeographic map depicting all known metoposaurid occurrences, which shows that these temnospondyls were globally distributed in low latitudes during the Late Triassic and had a similar, but not identical, paleogeographic range as phytosaurs.

New Dinosaur Fossils Found From Late Triassic Brazil

New dinosaur remains from the Late Triassic of southern Brazil (Candelária Sequence, Hyperodapedon Assemblage Zone)

Authors:

Pretto et al

Abstract:

The oldest unequivocal dinosaurian records come from Upper Triassic strata, mostly from Argentina and Brazil. Recent fieldwork in the Brazilian deposits of Ischigualastian age (late Carnian–earliest Norian) have resulted in the collection of a new specimen (UFRGS-PV-1240-T) identified as dinosaurian by the presence of a concave emargination on the ventral surface of the femoral head and a well-developed deltopectoral crest on the humerus, which extends for ca 40% of its estimated proximodistal length. Although fragmentary, the material increases the dinosaurian record from the Late Triassic of Brazil, which is still modest when compared with coeval Argentine strata. Additionally, UFRGS-PV-1240-T augments the dinosaurian diversity at the ‘Sítio Janner’ site, which was until now restricted to the sauropodomorph Pampadromaeus barberenai. The new specimen is larger than most early dinosaurians (except for herrerasaurids), implying that members of the group were already occupying niches otherwise explored by other larger-bodied taxa in the ‘Sítio Janner’ palaeofauna, and Late Triassic palaeoenvironments in general.

Late Triassic Rhynchosaur Hyperodapedon Bone Growth Suggests Archosauromorphs Basally Grew Fast

New insights from bone microanatomy of the Late Triassic Hyperodapedon (Archosauromorpha, Rhynchosauria): implications for archosauromorph growth strategy

Author:

Mukherjee

Abstract:

Bone microanatomy of multiple postcranial skeletal elements of several individuals of Hyperodapedon collected from India is reported. This reveals that fibrolamellar bone tissue is predominant in the mid- and inner cortices, whereas the peripheral region of the cortex is composed of either parallel-fibred and/or lamellar bone. The pattern of primary osteons mostly ranges between laminar and subplexiform. Such predominance of fibrolamellar bone tissue in the cortex suggests an overall fast growth, which slowed down considerably later in ontogeny. Four distinct ontogenetic stages are identified based on the bone microstructure. During the juvenile stage, growth was fast and continuous, but it became punctuated during the early and late sub-adult stages. In adult individuals, growth was slow and showed periodic interruption but did not stop completely, suggesting that Hyperodapedon had an indeterminate growth strategy. Interelemental histovariations affecting cortical thickness, organization of the vascular network, incidence of growth rings and extent of secondary reconstruction are noted. Throughout ontogeny, the femora show higher cortical thickness than humeri and tibiae, suggesting differential appositional growth rate between the skeletal elements. Differences in cortical thickness are noted in the ribs, which suggest differential functional constraints based on anatomical site-specific occurrences. Although fibrolamellar bone tissue became progressively more dominant towards the archosaurs, there are considerable variations in the growth patterns of the archosauromorphs. This is exemplified by the bone microstructure of Hyperodapedon, which deviates from the generalized slow-growth pattern proposed for all basal archosauromorphs, suggesting that rapid growth was already present in the archosauromorphs. The cortical thickness of various long bones of Hyperodapedon bears similarity with that of several extant terrestrial quadrupeds, suggesting that Hyperodapedon was essentially a terrestrial quadruped.

Late Triassic Vertebrates of East Greenland Were Rather Diverse

New perspectives on the Late Triassic vertebrates of East Greenland: preliminary results of a Polish−Danish palaeontological expedition

Authors:

Sulej et al

Abstract:

The Fleming Fjord Formation (Jameson Land, East Greenland) documents a diverse assemblage of terrestrial vertebrates of Late Triassic age. Expeditions from the turn of the 21st century have discovered many important fossils that form the basis of our current knowledge of Late Triassic Greenlandic faunas. However, due to the scarcity and incompleteness of the fossils and their insufficient study, our understanding of the taxonomic diversity of the Fleming Fjord Formation is hindered. Here, we report the preliminary findings of a Polish-Danish expedition to the Fleming Fjord Formation that took place in 2014. Three areas were visited – the fairly well known MacKnight Bjerg and Wood Bjerg and the virtually unexplored Liasryggen. MacKnigth Bjerg and Liasryggen yielded fossils which promise to significantly broaden our knowledge of vertebrate evolution in the Late Triassic. Stem-mammal remains were discovered at Liasryggen. Other fossils found at both sites include remains of actinopterygians, sarcopterygians, temnospondyl amphibians and various archosaurs (including early dinosaurs). Numerous vertebrate trace fossils, including coprolites, pseudosuchian footprints, theropod and sauropodomorph dinosaur tracks, were also discovered. Newly discovered skeletal remains as well as abundant trace fossils indicate higher tetrapod diversity in the Late Triassic of Greenland than previously thought. Trace fossils also allow inferences of early theropod and sauropodomorph dinosaur behaviour.

Late Triassic Non-mammaliaform Cynodont Brasilitherium riograndensis had Mammal-like Nasal Cavity

Nasal Anatomy of the Non-mammaliaform Cynodont Brasilitherium riograndensis (Eucynodontia, Therapsida) Reveals New Insight into Mammalian Evolution

Authors:

Ruf et al

Abstract:

The mammalian nasal cavity is characterized by a unique anatomy with complex internal features. The evolution of turbinals was correlated with endothermic and macrosmatic adaptations in therapsids and in early mammals, which is still apparent in their twofold function (warming and moistening of air, olfaction). Fossil evidence for the transformation from the nonmammalian to the mammalian nasal cavity pattern has been poor and inadequate. Ossification of the cartilaginous nasal capsule and turbinals seems to be a feature that occurred only very late in synapsid evolution but delicate ethmoidal bones are rarely preserved. Here we provide the first µCT investigation of the nasal cavity of the advanced non-mammaliaform cynodont Brasilitherium riograndensis from the Late Triassic of Southern Brazil, a member of the sister-group of mammaliaforms, in order to elucidate a critical anatomical transition in early mammalian evolution. Brasilitherium riograndensis already had at least partially ossified turbinals as remnants of the nasoturbinal and the first ethmoturbinal are preserved. The posterior nasal septum is partly ossified and contributes to a mesethmoid. The nasal cavity is posteriorly expanded and forms a distinctive pars posterior (ethmoidal recess) that is ventrally separated from the nasopharyngeal duct by a distinct lamina terminalis. Thus, our observations clearly demonstrate that principal features of the mammalian nasal cavity were already present in the sister-group of mammaliaforms.

An Apex Predator Eat Apex Predator World in the Norian Triassic Chinle Formation

Direct evidence of trophic interactions among apex predators in the Late Triassic of western North America

Authors:

Drumheller et al

Abstract:

Hypotheses of feeding behaviors and community structure are testable with rare direct evidence of trophic interactions in the fossil record (e.g., bite marks). We present evidence of four predation, scavenging, and/or interspecific fighting events involving two large paracrocodylomorphs (=‘rauisuchians’) from the Upper Triassic Chinle Formation (∼220–210 Ma). The larger femur preserves a rare history of interactions with multiple actors prior to and after death of this ∼8–9-m individual. A large embedded tooth crown and punctures, all of which display reaction tissue formed through healing, record evidence of a failed attack on this individual. The second paracrocodylomorph femur exhibits four unhealed bite marks, indicating the animal either did not survive the attack or was scavenged soon after death. The combination of character states observed (e.g., morphology of the embedded tooth, ‘D’-shaped punctures, evidence of bicarination of the marking teeth, spacing of potentially serial marks) indicates that large phytosaurs were actors in both cases. Our analysis of these specimens demonstrates phytosaurs targeted large paracrocodylomorphs in these Late Triassic ecosystems. Previous distinctions between ‘aquatic’ and ‘terrestrial’ Late Triassic trophic structures were overly simplistic and built upon mistaken paleoecological assumptions; we show they were intimately connected at the highest trophic levels. Our data also support that size cannot be the sole factor in determining trophic status. Furthermore, these marks provide an opportunity to start exploring the seemingly unbalanced terrestrial ecosystems from the Late Triassic of North America, in which large carnivores far outnumber herbivores in terms of both abundance and diversity.

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.

British Triassic Pterosaur is Really a Drepanosaur

Re-examination of the purported pterosaur wing metacarpals from the Upper Triassic of England

Authors:

Dalla Vecchia et al

Abstract:

Two small bones from the Upper Triassic of Cromhall Quarry (Gloucestershire, England), which are referred in the literature to pterosaurian wing metacarpals, are compared with wing metacarpals of unequivocal pterosaur specimens from the Upper Triassic of Italy and Greenland as well as those of the Liassic Dimorphodon macronyx from England. The two are morphologically distinct from the unequivocal wing metacarpals. Comparison with the phalanges of drepanosauromorphs suggests that they are probably penultimate phalanges of those bizarre diapsids. Drepanosauromorphs are now known from Cromhall Quarry, but they were not in 1990 when the two presumed wing metacarpals were described. There is no definitive evidence of the presence of pterosaurs in the Triassic of the UK.