Integrated bio-chemostratigraphy of Lower and Middle Triassic marine successions at Spiti in the Indian Himalaya: Implications for the Early Triassic nutrient crisis

Delayed biotic recovery from the end-Permian mass extinction has long been interpreted to result from environmental inhibition. Recently, evidence of more rapid recovery has begun to emerge, suggesting the role of environmental inhibition was previously overestimated. However, there have been few high-resolution taxonomic and ecological studies spanning the full Early and Middle Triassic recovery interval, leaving the precise pattern of recovery and underlying mechanisms poorly constrained. In this study, we document Early and Middle Triassic trends in taxonomic diversity, assemblage evenness, and size distribution of benthic foraminifers on an exceptionally exposed carbonate platform in south China. We observe gradual increases in all metrics through Early Triassic and earliest Middle Triassic time, with stable values reached early in the Anisian. There is little support in our data set for a substantial Early Triassic lag interval during the recovery of foraminifers or for a stepwise recovery pattern. The recovery pattern of foraminifers on the GBG corresponds well with available global data for this taxon and appears to parallel that of many benthic invertebrate clades. Early Triassic diversity increase in foraminifers was more gradual than in ammonoids and conodonts. However, foraminifers continued to increase in diversity, size, and evenness into Middle Triassic time, whereas diversity of ammonoids and conodonts declined. These contrasts suggest decoupling of recovery between benthic and pelagic environments; it is unclear whether these discrepancies reflect inherent contrasts in their evolutionary dynamics or the differential impact of Early Triassic ocean anoxia or associated environmental parameters on benthic ecosystems.

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Helmolepis cyphognathus, sp. nov., a new platysiagid actinopterygian from the Lower Triassic Sulphur Mountain Formation (British Columbia, Canada)

Canadian Journal of Earth Sciences ◽

10.1139/e04-096 ◽

2005 ◽

Vol 42 (1) ◽

pp. 25-36 ◽

Cited By ~ 13

Author(s):

Andrew G Neuman ◽

Raoul J Mutter

Keyword(s):

British Columbia ◽

New Species ◽

Central Europe ◽

Middle Triassic ◽

Lower Triassic ◽

Western Canada ◽

Early Triassic ◽

East Greenland ◽

The Family ◽

A New Species

A new species of stem actinopterygian, Helmolepis cyphognatus sp. nov., is reported from the Lower Triassic Sulphur Mountain Formation of western Canada (probably Smithian). This taxon differs from the only other known Early Triassic platysiagid, H. gracilis from the Lower Triassic Wordie Creek Formation of East Greenland (Griesbachian), in counts of branchiostegal rays, shape of the maxilla, shape (and possibly counts) of extrascapulars, and the size ratio of major opercular bones. In spite of their overall unfavorable preservation, the numerous available specimens amend our knowledge of the little known genus Helmolepis considerably: it has become evident that the morphology of Helmolepis cyphognatus sp. nov. comes closest to Platysiagum minus (Middle Triassic Besano Formation of central Europe). This study suggests placement of the two genera in the family Platysiagidae. Investigation of this new species also shows certain features of the cheek and the caudal fin are more primitive than previously believed, whereas the snout region is probably derived but of yet uncertain affinities in Helmolepis.

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Flat latitudinal diversity gradient caused by the Permian–Triassic mass extinction

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1918953117 ◽

2020 ◽

Vol 117 (30) ◽

pp. 17578-17583 ◽

Cited By ~ 3

Author(s):

Haijun Song ◽

Shan Huang ◽

Enhao Jia ◽

Xu Dai ◽

Paul B. Wignall ◽

...

Keyword(s):

Mass Extinction ◽

Middle Triassic ◽

Early Triassic ◽

Deep Time ◽

Latitudinal Diversity Gradient ◽

Diversity Gradient ◽

Environmental Extremes ◽

Low Latitudes ◽

Marine Fossils ◽

Selective Extinction

The latitudinal diversity gradient (LDG) is recognized as one of the most pervasive, global patterns of present-day biodiversity. However, the controlling mechanisms have proved difficult to identify because many potential drivers covary in space. The geological record presents a unique opportunity for understanding the mechanisms which drive the LDG by providing a direct window to deep-time biogeographic dynamics. Here we used a comprehensive database containing 52,318 occurrences of marine fossils to show that the shape of the LDG changed greatly during the Permian–Triassic mass extinction from showing a significant tropical peak to a flattened LDG. The flat LDG lasted for the entire Early Triassic (∼5 My) before reverting to a modern-like shape in the Middle Triassic. The environmental extremes that prevailed globally, especially the dramatic warming, likely induced selective extinction in low latitudes and accumulation of diversity in high latitudes through origination and poleward migration, which combined together account for the flat LDG of the Early Triassic.

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Cranial anatomy and taxonomy of the erythrosuchid archosauriform ‘Vjushkovia triplicostata’ Huene, 1960, from the Early Triassic of European Russia

Royal Society Open Science ◽

10.1098/rsos.191289 ◽

2019 ◽

Vol 6 (11) ◽

pp. 191289 ◽

Cited By ~ 4

Author(s):

Richard J. Butler ◽

Andrey G. Sennikov ◽

Emma M. Dunne ◽

Martin D. Ezcurra ◽

Brandon P. Hedrick ◽

...

Keyword(s):

Middle Triassic ◽

Terrestrial Ecosystems ◽

Extensive Study ◽

European Russia ◽

Early Triassic ◽

Apex Predators ◽

Comprehensive Description ◽

Additional Information ◽

First Time ◽

Globally Distributed

Erythrosuchidae are a globally distributed and important group of apex predators that occupied Early and Middle Triassic terrestrial ecosystems following the Permo-Triassic mass extinction. The stratigraphically oldest known genus of Erythrosuchidae is Garjainia Ochev, 1958, which is known from the late Early Triassic (late Olenekian) of European Russia and South Africa. Two species of Garjainia have been reported from Russia: the type species, Garjainia prima Ochev, 1958, and ‘ Vjushkovia triplicostata ’ von Huene, 1960, which has been referred to Garjainia as either congeneric ( Garjainia triplicostata ) or conspecific ( G. prima ). The holotype of G. prima has received relatively extensive study, but little work has been conducted on type or referred material attributed to ‘ V. triplicostata ’. However, this material includes well-preserved fossils representing all parts of the skeleton and comprises seven individuals. Here, we provide a comprehensive description and review of the cranial anatomy of material attributed to ‘ V. triplicostata ’, and draw comparisons with G. prima . We conclude that the two Russian taxa are indeed conspecific, and that minor differences between them result from a combination of preservation or intraspecific variation. Our reassessment therefore provides additional information on the cranial anatomy of G. prima . Moreover, we quantify relative head size in erythrosuchids and other early archosauromorphs in an explicit phylogenetic context for the first time. Our results show that erythrosuchids do indeed appear to have disproportionately large skulls, but that this is also true for other early archosauriforms (i.e. proterosuchids), and may reflect the invasion of hypercarnivorous niches by these groups following the Permo-Triassic extinction.

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Comparative size evolution of marine clades from the Late Permian through Middle Triassic

Paleobiology ◽

10.1017/pab.2015.36 ◽

2015 ◽

Vol 42 (1) ◽

pp. 127-142 ◽

Cited By ~ 21

Author(s):

Ellen K. Schaal ◽

Matthew E. Clapham ◽

Brianna L. Rego ◽

Steve C. Wang ◽

Jonathan L. Payne

Keyword(s):

Body Size ◽

Middle Triassic ◽

Size Reduction ◽

Late Triassic ◽

Early Triassic ◽

Large Species ◽

Late Permian ◽

Triassic Boundary ◽

Median Size ◽

Permian Extinction

AbstractThe small size of Early Triassic marine organisms has important implications for the ecological and environmental pressures operating during and after the end-Permian mass extinction. However, this “Lilliput Effect” has only been documented quantitatively in a few invertebrate clades. Moreover, the discovery of Early Triassic gastropod specimens larger than any previously known has called the extent and duration of the Early Triassic size reduction into question. Here, we document and compare Permian-Triassic body size trends globally in eight marine clades (gastropods, bivalves, calcitic and phosphatic brachiopods, ammonoids, ostracods, conodonts, and foraminiferans). Our database contains maximum size measurements for 11,224 specimens and 2,743 species spanning the Late Permian through the Middle to Late Triassic. The Permian/Triassic boundary (PTB) shows more size reduction among species than any other interval. For most higher taxa, maximum and median size among species decreased dramatically from the latest Permian (Changhsingian) to the earliest Triassic (Induan), and then increased during Olenekian (late Early Triassic) and Anisian (early Middle Triassic) time. During the Induan, the only higher taxon much larger than its long-term mean size was the ammonoids; they increased significantly in median size across the PTB, a response perhaps related to their comparatively rapid diversity recovery after the end-Permian extinction. The loss of large species in multiple clades across the PTB resulted from both selective extinction of larger species and evolution of surviving lineages toward smaller sizes. The within-lineage component of size decrease suggests that only part of the size decrease can be related to the end-Permian kill mechanism; in addition, Early Triassic environmental conditions or ecological pressures must have continued to favor small body size as well. After the end-Permian extinction, size decrease occurred across ecologically and physiologically disparate clades, but this size reduction was limited to the first part of the Early Triassic (Induan). Nektonic habitat or physiological buffering capacity may explain the contrast of Early Triassic size increase and diversification in ammonoids versus size reduction and slow recovery in benthic clades.

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The main stage of recovery after the end-Permian mass extinction: taxonomic rediversification and ecologic reorganization of marine level-bottom communities during the Middle Triassic

PeerJ ◽

10.7717/peerj.11654 ◽

2021 ◽

Vol 9 ◽

pp. e11654

Author(s):

Evelyn Friesenbichler ◽

Michael Hautmann ◽

Hugo Bucher

Keyword(s):

Mass Extinction ◽

Middle Triassic ◽

Biotic Interactions ◽

Trophic Relationships ◽

Lag Phase ◽

Early Triassic ◽

Bottom Communities ◽

Extinction Event ◽

Mass Extinction Event ◽

Permian Mass Extinction

The recovery of marine life from the end-Permian mass extinction event provides a test-case for biodiversification models in general, but few studies have addressed this episode in its full length and ecological context. This study analyses the recovery of marine level-bottom communities from the end-Permian mass extinction event over a period of 15 Ma, with a main focus on the previously neglected main phase during the Middle Triassic. Our analyses are based on faunas from 37 lithological units representing different environmental settings, ranging from lagoons to inner, mid- and outer ramps. Our dataset comprises 1562 species, which belong to 13 higher taxa and 12 ecological guilds. The diversification pattern of most taxa and guilds shows an initial Early Triassic lag phase that is followed by a hyperbolic diversity increase during the Bithynian (early middle Anisian) and became damped later in the Middle Triassic. The hyperbolic diversity increase is not predicted by models that suggest environmental causes for the initial lag phase. We therefore advocate a model in which diversification is primarily driven by the intensity of biotic interactions. Accordingly, the Early Triassic lag phase represents the time when the reduced species richness in the wake of the end-Permian mass extinction was insufficient for stimulating major diversifications, whereas the Anisian main diversification event started when self-accelerating processes became effective and stopped when niche-crowding prevented further diversification. Biotic interactions that might drive this pattern include interspecific competition but also habitat construction, ecosystem engineering and new options for trophic relationships. The latter factors are discussed in the context of the resurgence of large carbonate platforms, which occurred simultaneously with the diversification of benthic communities. These did not only provide new hardground habitats for a variety of epifaunal taxa, but also new options for grazing gastropods that supposedly fed from microalgae growing on dasycladaceans and other macroalgae. Whereas we do not claim that changing environmental conditions were generally unimportant for the recovery of marine level-bottom communities, we note that their actual role can only be assessed when tested against predictions of the biotic model.

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A Short-Snouted, Middle Triassic Phytosaur and its Implications for the Morphological Evolution and Biogeography of Phytosauria

Scientific Reports ◽

10.1038/srep46028 ◽

2017 ◽

Vol 7 (1) ◽

Cited By ~ 21

Author(s):

Michelle R. Stocker ◽

Li-Jun Zhao ◽

Sterling J. Nesbitt ◽

Xiao-Chun Wu ◽

Chun Li

Keyword(s):

Middle Triassic ◽

Prey Capture ◽

General Trend ◽

Morphological Evolution ◽

Phylogenetic Analyses ◽

Late Triassic ◽

Early Triassic ◽

Terrestrial Vertebrate ◽

Nearshore Environments ◽

Permian Extinction

Abstract Following the end-Permian extinction, terrestrial vertebrate diversity recovered by the Middle Triassic, and that diversity was now dominated by reptiles. However, those reptilian clades, including archosaurs and their closest relatives, are not commonly found until ~30 million years post-extinction in Late Triassic deposits despite time-calibrated phylogenetic analyses predicting an Early Triassic divergence for those clades. One of these groups from the Late Triassic, Phytosauria, is well known from a near-Pangean distribution, and this easily recognized clade bears an elongated rostrum with posteriorly retracted nares and numerous postcranial synapomorphies that are unique compared with all other contemporary reptiles. Here, we recognize the exquisitely preserved, nearly complete skeleton of Diandongosuchus fuyuanensis from the Middle Triassic of China as the oldest and basalmost phytosaur. The Middle Triassic age and lack of the characteristically-elongated rostrum fill a critical morphological and temporal gap in phytosaur evolution, indicating that the characteristic elongated rostrum of phytosaurs appeared subsequent to cranial and postcranial modifications associated with enhanced prey capture, predating that general trend of morphological evolution observed within Crocodyliformes. Additionally, Diandongosuchus supports that the clade was present across Pangea, suggesting early ecosystem exploration for Archosauriformes through nearshore environments and leading to ease of dispersal across the Tethys.

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A sail-backed suchian from the Heshanggou Formation (Early Triassic: Olenekian) of China

Earth and Environmental Science Transactions of the Royal Society of Edinburgh ◽

10.1017/s1755691011020044 ◽

2010 ◽

Vol 101 (3-4) ◽

pp. 271-284 ◽

Cited By ~ 36

Author(s):

Sterling J. Nesbitt ◽

Jun Liu ◽

Chun Li

Keyword(s):

Phylogenetic Analysis ◽

Middle Triassic ◽

Central China ◽

Phylogenetic Position ◽

Early Triassic ◽

Temporal Constraints ◽

Crown Group ◽

North Central ◽

Partial Skeleton ◽

Common Components

ABSTRACTThe two major lineages of extant archosaurs, crocodylians and avians, diverged in the Triassic, but the details and timing of this event are incompletely understood. Fragmentary and phylogenetically uninformative specimens, in addition to poor temporal constraints on rock units from the Early and Middle Triassic, typify obstacles in identifying early archosaurs. This paper re-describes the partial skeleton of the only known specimen of Xilousuchus sapingensis Wu, 1981 from the Early Triassic Heshanggou Formation in north-central China. Originally assigned to the non-archosaurian archosauriform clade Proterosuchidae, an extensive phylogenetic analysis posits X. sapingensis as a crown-group archosaur within Suchia, thus making this taxon the unequivocally oldest known member of Archosauria. The age and phylogenetic position of X. sapingensis indicate that many archosaurs, including all major clades of non-archosaurian archosauriforms, the avianline, ornithosuchids, aetosaurs and paracrocodylomorph lineages, must have diverged by the end of the Early Triassic. X. sapingensis is part of a possible clade of sail-backed poposauroids that were common components of archosaur assemblages during the Early to Middle Triassic.

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Chapter 18 Triassic history

Geological Society London Memoirs ◽

10.1144/gsl.mem.1997.017.01.18 ◽

1997 ◽

Vol 17 (1) ◽

pp. 340-362 ◽

Cited By ~ 2

Author(s):

W. Brian Harland ◽

Isobel Geddes

Keyword(s):

Middle Triassic ◽

Early Jurassic ◽

Late Triassic ◽

Early Triassic ◽

Marked Contrast ◽

Angular Unconformity ◽

Triassic Period ◽

Age Determinations

The Triassic Period of about 40 million years dutation spanned about a third of that of the Carboniferous and Permian interval. The Triassic rocks of Svalbard are easily distinguished from the underlying Permian strata because of a distinct desconformity between them and a marked contrast in facies from the resistant. pale coloured, cherls and siliciclastics of the Kapp Starostin Formation to the softer, darker areno-argillaceous Vardebukta and equivalent formations. Figure 18.1 shows the distribution of Triassic strata in Svalbard.The minor angular unconformity represents a hiatus mainly in the Permian rather than the Triassic record. The dominantly argillaceous facies constitute the Early Triassic to Late Middle Triassic Sassendalen Group. The rocks can be well dated from ammonoids, typically within calcareous concretions in the shales.The succeding Kapp Toscana Group is distinguished by a dominatly sandy deltaic facies in which age determinations are difficult. It spans both Late Triassic and Early Jurassic spoehs (roughly mid-Ladinian to mid-Bathonian). The Triassic-Jurassic boundary is not easy to estimate. Nevertheless towards the end of Triassic time (e.g. Rhaetian) the overall scene changed. Thus of the three formations of the Kapp Toscana Group the lower two (Tschermakfjellet and De Geerdalen) belong to the Triassic story. The overlying Wilhelmøya Formation may possibly range from Latest Triassic through Liassic time, and due to its complexity it is also discussed in the Jurassic-Crataceous chapter (19).The facies of the two groups reflect two distinct environmental configurations. The Sassendalen Group was deposited on a distal marine muddy shelf with a

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The early Triassic rhynchosaur Mesosuchus browni and the interrelationships of basal archosauromorph reptiles

Philosophical Transactions of the Royal Society B Biological Sciences ◽

10.1098/rstb.1998.0225 ◽

1998 ◽

Vol 353 (1368) ◽

pp. 501-541 ◽

Cited By ~ 131

Author(s):

David W. Dilkes

Keyword(s):

Middle Triassic ◽

Sister Group ◽

Recent Common Ancestor ◽

Early Triassic ◽

Late Permian ◽

Assemblage Zone ◽

Stratigraphic Ranges ◽

Permian Mass Extinction ◽

Fossil Records ◽

Early Middle Triassic

Restudy of the unique diapsid reptile Mesosuchus browni Watson, from the Cynognathus Assemblage Zone (late Early Triassic to early Middle Triassic) of the Burgersdorp Formation (Tarkastad Subgroup; Beaufort Group) of South Africa, confirms that it is the most plesiomorphic known member of the Rhynchosauria. A new phylogenetic analysis of basal taxa of Archosauromorpha indicates that Choristodera falls outside of the Sauria, Prolacertiformes is a paraphyletic taxon with Prolacerta sharing a more recent common ancestor with Archosauriformes than with any other clade, Megalancosaurus and Drepanosaurus are sister taxa in the clade Drepanosauridae within Archosauromorpha, and are the sister group to the clade Tanystropheidae composed of Tanystropheus , Macrocnemus , and Langobardisaurus . Combination of the phylogenetic relationships of basal archosauromorphs and their known stratigraphic ranges reveals significant gaps in the fossil records of Late Permian and Triassic diapsids. Extensions of the temporal ranges of several lineages of diapsids into the Late Permian suggests that more groups of terrestrial reptiles survived the end-Permian mass extinction than thought previously.

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