REVIEW OF EARLY TRIASSIC THYLACOCEPHALA

Thylacocephala (Euarthropoda: Eucrustacea?) is a group of enigmatic fossil euarthropods, known from at least the Silurian to the Cretaceous. The Triassic is considered to be the period during which thylacocephalans were the most diversified with 17 species reported from 19 localities in nine countries. However, Thylacocephala were assumed to be rare during the Early Triassic until recent discoveries in Japan, Nevada and Idaho, U.S.A.       Our study focuses on thylacocephalans from the Early Triassic, especially from Madagascar and Idaho. The revision of previously known taxa from Madagascar provides new important information. A new kind of ornamentation is reported for Paraostenia ambatolokobensis nov. comb., previously assigned to Ostenocaris ambatolokobensis. In addition, Ankitokazocaris acutirostris and Paraostenia ambatolokobensis are only the third and fourth thylacocephalan taxa for which possible cephalic appendages are described.  New occurrences of Thylacocephala in Nevada and Idaho, U.S.A., lead to the description of one new taxon and to the reassignement of Parisicaris triassica to Ankitokazocaris triassica nov. comb. Those occurrences provide a significant contribution to the knowledge of Thylacocephala taxonomic diversity and geographic distribution during the Early Triassic. An important revision of Early Triassic thylacocephalan taxa from Japan and China is also performed, including Ankitokazocaris chaohuensis, Ankitokazocaris parva nov. comb., Ankitokazocaris utatsuensis nov. comb. and Paraostenia sp. Overall, the taxonomic diversity of Triassic thylacocephalans has likely been slightly over-estimated (17 species before, 15 now). However, the Triassic represents the richest period in terms of thylacocephalan-bearing outcrops (19 localities from nine countries)

Biological Soil Crusts as Modern Analogues for the Archean Continental Biosphere: Insights from Carbon and Nitrogen Isotopes

Stable isotope signatures of elements related to life such as carbon and nitrogen can be powerful biomarkers that provide key information on the biological origin of organic remains and their paleoenvironments. Marked advances have been achieved in the last decade in our understanding of the coupled evolution of biological carbon and nitrogen cycling and the chemical evolution of the early Earth thanks, in part, to isotopic signatures preserved in fossilized microbial mats and organic matter of marine origin. However, the geologic record of the early continental biosphere, as well as its evolution and biosignatures, is still poorly constrained. Following a recent report of direct fossil evidence of life on land at 3.22 Ga, we compare here the carbon and nitrogen isotopic signals of this continental Archean biosphere with biosignatures of cyanobacteria biological soil crusts (cyanoBSCs) colonizing modern arid environments. We report the first extended δ13C and δ15N data set from modern cyanoBSCs and show that these modern communities harbor specific isotopic biosignatures that compare well with continental Archean organic remains. We therefore suggest that cyanoBSCs are likely relevant analogues for the earliest continental ecosystems. As such, they can provide key information on the timing, extent, and possibly mechanism of colonization of the early Earth's emergent landmasses

New thylacocephalans from the Early Triassic Paris Biota (Bear Lake County, Idaho, USA).

International audienceTwo new genera and species of thylacocephalans (Arthropoda, Thylacocephala), Parisicaris triassica Charbonnier and Ligulacaris parisiana Charbonnier, are described from the early Spathian Paris Biota. These new occurrences are the first reports of thylacocephalans from Triassic rocks in North America. They considerably enlarge the spatiotemporal distribution of these enigmatic arthropods and highlight their relatively high generic richness during the Early Triassic. It also confirms that the Triassic was the taxonomically richest period for Thylacocephala

Functional diversity of marine ecosystems after the Late Permian mass extinction event

Article can be accessed from http://www.nature.com/ngeo/journal/v7/n3/full/ngeo2079.htmlThe Late Permian mass extinction event was the most severe such crisis of the past 500 million years and occurred during an episode of global warming. It is assumed to have had significant ecological impact, but its effects on marine ecosystem functioning are unknown and the patterns of marine recovery are debated. We analysed the fossil occurrences of all known Permian-Triassic benthic marine genera and assigned each to a functional group based on their inferred life habit. We show that despite the selective extinction of 62-74% of marine genera there was no significant loss of functional diversity at the global scale, and only one novel mode of life originated in the extinction aftermath. Early Triassic marine ecosystems were not as ecologically depauperate as widely assumed, which explains the absence of a Cambrian-style Triassic radiation in higher taxa. Functional diversity was, however, significantly reduced in particular regions and habitats, such as tropical reefs, and at these scales recovery varied spatially and temporally, probably driven by migration of surviving groups. Marine ecosystems did not return to their pre-extinction state, however, and radiation of previously subordinate groups such as motile, epifaunal grazers led to greater functional evenness by the Middle Triassic

The Earliest Post-Paleozoic Freshwater Bivalves Preserved in Coprolites from the Karoo Basin, South Africa

Background: Several clades of bivalve molluscs have invaded freshwaters at various times throughout Phanerozoic history. The most successful freshwater clade in the modern world is the Unionoida. Unionoids arose in the Triassic Period, sometime after the major extinction event at the End-Permian boundary and are now widely distributed across all continents except Antarctica. Until now, no freshwater bivalves of any kind were known to exist in the Early Triassic. Principal Findings: Here we report on a faunule of two small freshwater bivalve species preserved in vertebrate coprolites from the Olenekian (Lower Triassic) of the Burgersdorp Formation of the Karoo Basin, South Africa. Positive identification of these bivalves is not possible due to the limited material. Nevertheless they do show similarities with Unionoida although they fall below the size range of extant unionoids. Phylogenetic analysis is not possible with such limited material and consequently the assignment remains somewhat speculative. Conclusions: Bivalve molluscs re-invaded freshwaters soon after the End-Permian extinction event, during the earliest part of the recovery phase during the Olenekian Stage of the Early Triassic. If the specimens do represent unionoids then these Early Triassic examples may be an example of the Lilliput effect. Since the oldest incontrovertible freshwater unionoids are also from sub-Saharan Africa, it is possible that this subcontinent hosted the initial freshwater radiation of the Unionoida. This find also demonstrates the importance of coprolites as microenvironments of exceptional preservation that contai

Short-Snouted Toothless Ichthyosaur from China Suggests Late Triassic Diversification of Suction Feeding Ichthyosaurs

Ichthyosaurs were an important group of Mesozoic marine reptiles and existed from the Early Triassic to the early Late Cretaceous. Despite a great diversity in body shapes and feeding adaptations, all share greatly enlarged eyes, an elongated rostrum with numerous conical teeth, and a streamlined body.. may be linked to the Late Triassic minimum in atmospheric oxygen

Environmental Predictors of Diversity in Recent Planktonic Foraminifera as Recorded in Marine Sediments

© 2016 Fenton et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. [4.0 license]. The attached file is the published version of the article

Smithian (Early Triassic) ammonoid faunas from northwestern Guangxi (South China): taxonomy and biochronology

The highly fossiliferous succession of Smithian (Early Triassic) ammonoids from northwestern Guangxi (South China) provides a key equatorial record, at the boundary between Tethys and Panthalassa. After the end-Permian extinction, ammonoids reached their first major diversity peak during Smithian times, coupled with a marked contrast in their latitudinal distribution. This monograph contains a part of the fundamental taxonomic and biostratigraphic data of a more comprehensive research project addressing patterns of recovery in time and space of Early Triassic ammonoids and other marine clades, in conjunction with global paleoceanographic and paleoclimatic changes

Gastropod evidence against the Early Triassic Lilliput effect: reply

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Smithian and spathian (early triassic) ammonoid assemblages from terranes: paleoceanographic and paleogeographic implications

Early Triassic paleobiogeography is characterised by the stable supercontinental assembly of Pangea. However, at that time, several terranes such as the South Kitakami Massif (SK), South Primorye (SP) and Chulitna (respectively, and presently located in Japan, eastern Russia and Alaska) straddled the vast oceans surrounding Pangea. By means of quantitative biogeographical methods including Cluster Analysis, Non-metric Multidimensional Scaling and Bootstrapped Spanning Network applied to Smithian and Spathian (Early Triassic) ammonoid assemblages; we analyze similarity relationships between faunas and suggest paleopositions for the above-cited terranes. Taxonomic similarities between faunas indicate that primary drivers of the ammonoid distribution were Sea Surface Temperature and currents. Possible connections due to current-controlled faunal exchanges between both sides of the Panthalassa are shown and terranes such as SK, SP and Chulitna played an important role as stepping stones in the dispersal of ammonoids. SK and SP terranes show strong sub-equatorial affinities during the Smithian, thus suggesting a location close to South China. At the same time, the Chulitna terrane shows strong affinities with equatorial faunas of the eastern Panthalassa. This paleoceanographic pattern was markedly altered during the Spathian, possibly indicating significant modifications of oceanic circulation at that time, as illustrated by the development of a marked intertropical faunal belt across Tethys and Panthalassa