The Different Paleoenvironments of the Vellberg's Middle Triassic Lagerstätten

A Middle Triassic palaeontological gold mine: The vertebrate deposits of Vellberg (Germany)

Authors:

Schoch et al

Abstract:

The lacustrine deposits of Vellberg, southern Germany, rank among the richest vertebrate fossil-lagerstätten of the Triassic worldwide. Continued excavation over one decade produced two chondrichthyans, 14 taxa of bony fishes, seven temnospondyls, one chroniosuchian, the stem-turtle Pappochelys, two procolophonians, four lepidosauromorphs, a choristodere, four archosauriforms, three pseudosuchian archosaurs, and around ten further reptile taxa only known by teeth. Sedimentary facies, fossil assemblage composition, and taphonomy suggest this deposit comprises a succession of rather different water bodies, situated on a floodplain dominated by dolomitic muds: (1) a coal swamp with occasional reptiles and temnospondyls, (2) a large but shallow, brackish lagoon inhabited by Bakevellia, Acrodus, Nothosaurus, and the temnospondyl Plagiosternum, (3) a small and shallow, well-protected, oligohaline freshwater lake dominated by various temnospondyls, and (4) a larger (6 km) and deeper freshwater lake, again with a rich fauna of fishes, temnospondyls, and small aquatic reptiles that was eventually filled by dolomitic coastal muds. Reworking and desiccation cracks indicate repeated phases of regression and drought, during which bonebeds formed and skeletons of terrestrial tetrapods were deposited.

The Diversity of German Middle Triassic Parareptiles

Owenettids and procolophonids from the lower Keuper shed new light on the diversity of parareptiles in the German Middle Triassic

Authors:

Martinelli et al

Abstract:

We report three isolated humeri of small-sized parareptiles, which represent two different taxa, from the lower Keuper (Erfurt Formation) of Germany. They constitute the first definitive evidence of parareptiles in the lower Keuper. The specimens represent the first records of an owenettid procolophonian (aff. Barasaurus) from Europe and of a putative gracile-built procolophonid. This indicates the coexistence in the Middle Triassic of Germany of two procolophonian lineages that first appeared in the fossil record in the late Permian and survived the Permian–Triassic extinction. Although based on isolated limb bones, they highlight the taxonomic diversity of the still poorly known tetrapod assemblage of the lower Keuper in southwestern Germany.

Dawazisaurus brevis: a new Middle Triassic Eosauropterygian From China

Dawazisaurus Brevis, A New Eosauropterygian From the Middle Triassic of Yunnan, China

Authors:

Chen et al

Abstract:


Dawazisaurus brevis (gen. et sp. nov.) is a newly discovered Triassic marine reptile, represented by a complete skeleton from Member II of the Guanling Formation of Luoping, Yunnan Province, China. This paper aims to (1) present a thorough description of the species, (2) make a detailed comparison to demonstrate if the species can be referred to any known sauropterygian taxa, and (3) conduct phylogenetic analyses to establish the internal relationships of the species with other sauropterygians. In addition, the discovery of Dawazisaurus provides a chance not only to test the phylogenetic patterns of the Sauropterygia obtained by previous studies but also to evaluate the previous hypotheses on the origin of the sauropterygian groups at different levels. D. brevis is an eosauropterygian, characterized by a unique combination of derived features such as a pair of large nasals joining in the formation of the internarial septum, a short trunk with 16 dorsal vertebrae; the zygapophyses of the trunk vertebrae very small or weakly developed; the posterior margin of the skull roof deeply V-shaped, and an ossified distal carpal 5. Phylogenetic analysis indicates that D. brevis appears to be more closely related to the Nothosauroidea than the Pistosauroidea within the Eosauropterygia.

Yuanansuchus maopingchangensis: a new Capitosauroid Temnospondyl From Middle Triassic China

Yuanansuchus maopingchangensis sp. nov., the second capitosauroid temnospondyl from the Middle Triassic Badong Formation of Yuanan, Hubei, China

Author:

Liu

Abstract:

A second species of Yuanansuchus, Y. maopingchangensis, is erected for new temnospondyl material from the Maopingchang site, Yuanan County, Hubei Province, China. These specimens are from the same horizon that produced Y. laticeps, the type species. Y. maopingchangensis shares the following features with Y. laticeps: postorbital portion of skull occupied more than 1/3 of skull length; tabular horn directed laterally; lateral line sulci continuous, well impressed; supraorbital sensory canal enters lacrimal; preorbital projection of jugal less than half length of snout; and vomerine plate short. However, Y. maopingchangensis differs from Y. laticeps in having an elongated skull, frontal extending posteriorly to the level of the posterior orbital margin, closed otic fenestra, cultriform process of parasphenoid extending to the level of the anterior margin of the interpterygoid vacuities, and absence of fodina vomeralis. Analysis of a new capitosaur phylogenetic data matrix, containing 56 characters and 29 species, confirms that the two species from Yuanan are sister taxa and that Capitosauroidea can be divided into two major clades: one including Parotosuchus, Eryosuchus, Calmasuchus and Cherninia, and another including Mastodonsaurus, Yuanansuchus, Stanocephalosaurus, Procyclotosaurus, Paracyclotosaurus, Antarctosuchus, Eocyclotosaurus, Quasicyclotosaurus, Tatrasuchus and Cyclotosaurus.

Climates Changes During the Early to Middle Triassic

Climate changes during the Early–Middle Triassic transition in the E. Iberian plate and their palaeogeographic significance in the western Tethys continental domain

Authors:

Borruel-Abadía et al

Abstract:

Until recently the climate of the Early–Middle Triassic at low latitudes was broadly considered as generally temperate-warm with no major climate oscillations. This work examines the climate of this period through a detailed study of the sedimentary, plant, soil and mineral records of continental rocks (Buntsandstein facies) in eastern Iberian basins. Our findings indicate temporal climate variations for these near equator (10°–14°N) regions and unveil the significance of such variations in the southern Laurasian domain.

The climate of Iberia's Early Triassic was mainly dominated by alternating brief (< 0.4 ma) arid and semi-arid climate periods, with two main arid periods documented at the end of the Smithian and middle Spathian. However, an initial short subhumid to semi-arid period was also observed in the late Spathian. Remarkably, this latter period appears just after an unconformity related to the tectonically induced Hardegsen Event in western Europe. It is also of interest that this short subhumid climate period is concurrent with the beginning of faunal and floral recovery in the basins examined. The Early Triassic ended again with a short very arid period. Although the beginning of the Anisian (Aegean) was represented by alternating arid and semi-arid to subhumid intervals, during the Bithynian and Pelsonian clearly wetter climates are recorded by the succession consisting of alternating semi–arid to semi-humid intervals. This general tendency was interrupted by three short but marked intervals, two humid intervals in the late Bithynian, and one arid period near the Bithynian/Pelsonian boundary. Iberia was crossed by prominent irregular highs separating marked corridors or isolated areas. This palaeogeography, prevailing since Variscan tectonics, clearly conditioned dominant climates and their geographical distribution. No clear climate belts developed in these conditions. However, isolated internal climate zones separated by elevated areas are identified. This palaeogeographic configuration and the low latitudinal position of Iberia determined central Iberia highs in the southernmost border of Laurasia, beyond which more humid conditions clearly extended towards the equator reaching the present-day Moroccan Meseta and Argana Basin.

More Insights Into the Anisian Triassic Luoping Biota

New Progress in the Study of Marine Reptiles from the Luoping Biota of Middle Triassic Anisian Period

Authors:

Wen et al

Abstract:

The Luoping Biota was discovered in 2007 by the Chengdu Center of China Geological Survey during 1:50000 regional mapping works at Dawazi Village, Luoxiong Town, 15 km southeast of Luoping City, Yunnan Province. The interval containing the Luoping biota is the middle to upper part of Member II of the Guanling Formation. The fossil assemblage of the Luoping biota is a mixture of marine animals, terrestrial plants and a few terrestrial animals. To date, more than ten fossil groups have been recovered, which include marine reptiles, fishes, arthropods, echinoderms, ammonites, bivalves, gastropods, lingulid brachiopods, foraminifers, and plants. The Luoping Biota is one of the most diverse Triassic marine fossil Lagerst?tten records in the world. The age of the Luoping biota is assigned to the Pelsonian Substage of the Middle Triassic Anisian Stage based on the index conodont Nicoraella Kockeli. Well-preserved, diverse marine reptiles are one of the highlights of the Luoping biota, including ichthyosaurs, sauropterygians, protorosaurs and archosauromorphs. Mesozoic is remarkable for marine reptiles, whose swimming modes, however, remain a topic of much controversy because of the absence of their tracks. Hundreds of seabed tracks found in Luoping Biota, which were assigned to Dikoposichnus luopingensis, provide new materials for the study of their locomotive mode. Besides, the macropredator Nothosaurus zhangi reported from Luoping Biota also supports the existence of the makers of Dikoposichnus luopingensis. The skull of Nothosaurus zhangi is the largest sauropterygian ever reported in Triassic. The occurrence of a different assemblage of marine reptiles as top predators in the food web indicates a well developed marine ecosystem, showing full rebuilding of the marine ecosystem after the mass extinction that happened about 250 million years ago.

Massetognathus ochagaviae: a new Middle Triassic Traversodontid Cynodont From Brazil

New information on the postcranial skeleton of Massetognathus ochagaviae Barberena, 1981 (Eucynodontia, Traversodontidae), from the Middle Triassic of Southern Brazil

Authors:

Branco Pavanatto et al

Abstract:

New postcranial remains of Massetognathus ochagaviae are described based on a new specimen collected at the Dinodontosaurus Assemblage Zone from the Middle Triassic of Southern Brazil. Several isolated teeth collected together with the postcranial skeleton allowed a taxonomic assignation of the specimen to M. ochagaviae. Its postcranial morphology is quite similar to Massetognathus pascuali, especially regarding the morphology of the transverse process of presacral vertebrae (i.e. laminar in the anterior most and rounded in the posterior most presacral vertebrae); humerus (i.e. the head is dorsally deflected with a ‘fan-shaped’ distal end a deltopectoral crest abruptly ending at the middle of shaft); and femur (with a bulbous and dorsomedially inclined femoral head, lesser trochanter which abruptly begins near the intertrochanteric fossa and extending up to the middle of the femoral shaft and the medial condyle more pronounced and ventrally projected than the lateral one). On the other hand, the clavicle of M. ochagaviae is less lateromedially elongated than in M. pascuali.

‘Chasmatosaurus ultimus,’ is NOT an Anisian Triassic Proterosuchid Archosauriform

‘Chasmatosaurus ultimus,’ a putative proterosuchid archosauriform from the Middle Triassic, is an indeterminate crown archosaur

Authors:

Liu et al

Abstract:

Proterosuchids represent the earliest known radiation of the highly diverse and important clade Archosauriformes (Gauthier et al., 1988; Nesbitt, 2011; Ezcurra et al., 2013). Huene (1908) erected Proterosuchidae as a monotypic Linnean family containing only Proterosuchus fergusi from the lowermost Triassic of South Africa, and several other species have been referred to this group in the subsequent century. However, phylogenetic analyses have provided only partial support for the existence of a diverse proterosuchid clade, and it is possible that some or even most putative proterosuchids form a series of outgroups to more derived archosauriforms rather than a monophyletic group (Ezcurra et al., 2010, 2013). Proterosuchids were historically classified alongside erythrosuchids in the Proterosuchia (e.g., Charig and Reig, 1970), but cladistic analyses (e.g., Benton, 1985; Gauthier et al., 1988; Gower and Sennikov, 1997; Ezcurra et al., 2010; Nesbitt, 2011) have uniformly found erythrosuchids to be phylogenetically closer to Archosauria (using a crown-group definition for the clade) than are any putative proterosuchids. Many of the species that have been assigned to Proterosuchidae require anatomical and taxonomic reevaluation (e.g., Ezcurra et al., 2010, 2013, 2014; Ezcurra, 2014), a research effort that is essential in order to clarify the phylogenetic relationships of the earliest archosauriforms and patterns of character evolution in taxa of this grade.

Following Proterosuchus, the next proterosuchid genera to be erected were Chasmatosaurus, established by Haughton (1924) for the new species C. vanhoepeni, and Elaphrosuchus, established by Broom (1946) for the new species E. rubidgei. A second species of Chasmatosaurus, C. alexanderi, was subsequently added (Hoffman, 1965). Chasmatosaurus vanhoepeni, C. alexanderi, and E. rubidgei were all based, like P. fergusi, on specimens from the Lower Triassic of South Africa, and more recently all of them have been suggested to represent subjective junior synonyms of P. fergusi (Welman, 1998). Occurrences of Chasmatosaurus have also been reported outside South Africa, including C. yuani (Young, 1936, 1963, 1978) from the Lower Triassic of China, Chasmatosaurus sp. from the Lower Triassic of India (Satsangi, 1964), and C. ultimus from the Middle Triassic of China (Young, 1958, 1964). The last of these species has the distinction of being one of only two putative proterosuchids from above the Lower–Middle Triassic boundary, the other being Sarmatosuchus otschevi from the Anisian of Russia (Gower and Sennikov, 1997, 2000; Ezcurra et al., 2013). However, the proterosuchid affinities of S. otschevi are questionable (Ezcurra et al., 2010, 2013), with S. otschevi having been recovered closer to erythrosuchids and archosaurs than to proterosuchids by Ezcurra et al. (2010). Thus, C. ultimus is the only generally accepted proterosuchid record younger than Early Triassic.

The holotype of C. ultimus is a partial skull including parts of the preorbital region preserved together with the anterior ends of the lower jaws, collected from the upper member of the Ermaying Formation of Shanxi Province in northern China, which is Anisian in age (Liu et al., 2013). This fragmentary specimen was originally assigned by Young (1958) to C. yuani, but later used by Young (1964) to erect C. ultimus based on differences in size and tooth curvature from the former species. Here we redescribe the specimen and show that ‘C. ultimus’ is not a proterosuchid but rather an indeterminate crown archosaur. An important implication of this revision is the absence of any confirmed record of proterosuchid archosauriforms from rocks of Middle Triassic age or younger.

New Kannemeyeriiforme Dicynodonts From Middle Triassic China

New discoveries from the Sinokannemeyeria-Shansisuchus Assemblage Zone: 1. Kannemeyeriiformes from Shanxi, China

Author:

Jun

Abstract:

Recently, some new tetrapod fossils were collected along the Yellow River in Shanxi Province. From the Member I of the Tongchuan Formation at Baidaoyu in Linxian County, at least one species of Parakannemeyeria, and one new species of Sinokannemeyeria, S. baidaoyuensis, are identified. The new species is characterized by prefrontal anterior extension level to posterior margin of postnarial excavation. From the Ermaying Formation in Liulin County, a third kannemeyeriid genus is identified for the Sinokannemeyeria-Shansisuchus Assemblage. The new findings increase the content and time extension of the Sinokannemeyeria-Shansisuchus Assemblage.

Vertebrate Fauna of the Anisian Triassic Otter Sandstone River

The ‘Otter Sandstone River’ of the mid-Triassic and its vertebrate fauna

Author:

Hart

Abstract:

The Triassic succession of the East Devon coastline is a key component of the Jurassic Coast World Heritage Site. Within these strata are the sediments deposited by two major river systems: the Budleigh Salterton Pebble Beds and the Otter Sandstone Formation. The latter are significant as both a reservoir for the Dorset oilfields near Wareham and as a source of significant numbers of vertebrate fossils. The Otter Sandstone Formation, of Anisian (Middle Triassic) age, has a lower part formed of aeolian sands but these pass upwards into a series of river channel deposits. These river channels, which are best seen between the mouth of the River Otter and Ladram Bay, contain a series of classic features such as erosive channel bases, channel lag deposits, de-watering structures, calcified root systems (rhizoliths), reworked calcretes and (rare) overbank mudstones. The rivers that formed the various braided channel deposits flowed northwards or north-eastwards and there are at least 4 or 5 separate channel units within the Ladram Bay area. The Otter Sandstone Formation has yielded a great many rhynchosaur fragments and at least one partial skeleton. This juvenile individual appears to have fallen into one of the channels, resulting in the loss of its head (skull), as this was not recovered when the specimen was found by the author in 1990. This important specimen of Fodonyx spenceri (Benton, 1990) is housed in the Royal Albert Memorial Museum in Exeter.

Stromatolites From Anisian Triassic Southwest China

Early Middle Triassic stromatolites from the Luoping area, Yunnan Province, Southwest China: Geobiologic features and environmental implications

Authors:

Luo et al

Abstract:

An early Middle Triassic stromatolite deposit is documented from the Guanling Formation of the Luoping area, Yunnan, SW China. The Luoping stromatolite shows five types of constructional microbial forms in various magnifications: 1) typical stratified columnar structures, up to 20 cm high, with crinkled laminae. Dark coloured laminae, 1 mm thick, are composed of upright filamentous tubes, averagely 29.4 μm in diameter, showing a vertical growth fabric. 2) Laminoid fenestrae, 0.5–1 mm wide, and 3) prostrate filaments, which are reflected by strong fluorescence in sharp contrast to dolomite cement in fluorescent images. 4) Rod-like aggregates, 4.6–18 μm in diameter, composed of minute dolomite rhombs, are very common in stromatolitic laminae; they resemble present-day cyanobacterial trichome, and thus may represent putative fossilized cyanobacteria. 5) Moreover, small pits, coccoid-like spheroids, calcified biofilms, and fibrous structures are also common in stromatolitic laminae. The last two may represent calcified extracellular polymeric substances (EPS) that contributed to the development and lithification of stromatolites. Authigenic quartz grains are common and may also have involved biological processes in stromatolite formation. Of these microbial functional-groups driving accretion and lithification processes of stromatolite documented in literature, both lithified cyanobacteria/oxygenic phototrophs and possible sulfate-reducing bacteria (SRB), which induced microbial formation of dolomite and contributed to the accretion of the Luoping stromatolite, are suggestive of biogenic origin. The Luoping stromatolite differs from the Permian–Triassic boundary microbialites (PTBMs) in having abundant filamentous structures and growing in an oxic marine environment. Both sedimentary facies analysis and abundant fossilized cyanobacteria may indicate proliferation of oxygenic phototrophs in a normal, oxic habitat during the middle Anisian (early Middle Triassic), a period when hospitable environments, coupled with biotic diversification, prevailed in South China and set an agenda for the full recovery of marine ecosystems in middle–late Anisian. However, the post-extinction stromatolites and other anachronistic facies are not necessarily indicative of anoxic or oxic conditions, and their environmental settings are much more complex than previously thought.

Tetrapods from Middle Triassic Antarctica

New Middle Triassic tetrapods from the upper Fremouw Formation of Antarctica and their depositional setting

Authors:

Sidor et al

Abstract:

Renewed field work in the Beardmore Glacier region of Antarctica has led to a new collection of tetrapod fossils from the upper member of the Fremouw Formation near Fremouw Peak. This locality records a sedimentary environment remarkably similar to that preserved at Gordon Valley, the only other locality known to preserve Cynognathus Assemblage Zone–equivalent taxa from Antarctica. Fossil bones are generally disarticulated and mixed with logs and reworked mudrock clasts, forming an intraformational channel-lag conglomerate. To date, very few bones of small-bodied taxa have been recovered from the upper Fremouw conglomerates, suggesting that they did not survive the reworking process. We use an apomorphy-based approach to record three previously unrecognized taxa from the upper Fremouw Formation: the dicynodont Angonisaurus, an indeterminate therocephalian therapsid, and an indeterminate crown-group archosaur. Combined with previous data, our work demonstrates that 10 distinct taxa can be recognized from the upper Fremouw, including two endemic temnospondyl species. Our recognition of Angonisaurus in the upper Fremouw Formation provides a new piece of evidence in favor of a correlation with the Cynognathus C subzone (uppermost Burgersdorp Formation) of South Africa and the Lifua Member of the Manda beds of Tanzania.

Stuffed Full of Shrimp the Middle Triassic Luoping Biota was

Penaeoid Decapoda (Dendrobranchiata) from the Luoping Biota (Middle Triassic) of China: systematics and taphonomic framework

Authors:

Schweitzer et al

Abstract:

Two new genera, Anisaeger and Distaeger, and three new species, Anisaeger brevirostrus, A. spiniferus, and Distaeger prodigiosus, extend the range of the Aegeridae (Dendrobranchiata, Penaeoidea) into the Middle Triassic (Anisian) of China. Seven decapod crustacean species are now known from the Luoping biota of southern China. Morphological features of shrimp that are present but rarely mentioned in the neontological literature are recognized as potentially useful in classifying fossil material, including a diaeresis on the exopod of the uropods and multiarticulate flagellae on pleopods. Unusual taphonomic features of the shrimp include fractured cuticle, preservation in lateral, dorsal, and ventral position, and twisted cephalothoraxes.