Middle Anisian Research Articles

Bimineralic Middle Triassic ooids from Hydra Island: Diagenetic pathways and implications for ancient seawater geochemistry

AbstractThis study reports on the occurrence of formerly bimineralic, ancient, calcitic coated grains, including half‐moon ooids and micritic to microsparitic ooids in the Middle Anisian (Middle Triassic) grain flow from Hydra Island (Greece), and discusses their importance for palaeoseawater geochemical interpretations. The bi‐partite fabric in half‐moon ooids resulted from early pre‐compaction rapid dissolution of both aragonitic cortices and the more‐soluble components of the high‐Mg calcite core in the primary ooid, as well as the collapse of less‐dissolved remnants to the bottom of the oomouldic cavity which was later filled with calcite cement. Zonal, micritic to microsparitic ooids formed through intracortical dissolution of primary aragonite lamellae which were later replaced by (micro)sparry calcite. At the same time, recrystallization of original high‐Mg calcite layers to micrite occurred. The stratigraphic occurrence of the investigated bimineralic ooids conforms to the global distribution of carbonate ooids through the Middle Triassic period. The cementation history of the grain flow hosting coated grains is well documented by the paragenetic sequence established in half‐moon ooids which predicts that calcite precipitated under burial (shallow to deep) conditions. The main control on precipitation of bimineralic ooids was the Mg/Ca ratio of seawater, with lesser influences from seawater temperature, salinity and ρCO2 which promoted the degree of carbonate saturation, leading to higher precipitation rates for both aragonite and high‐Mg calcite. The studied bimineralic ooids represent a change in the global carbonate factory during the Middle Triassic in response to secular variations in the chemistry of palaeoseawater.

Permian–Triassic magmatism in response to Palaeotethys subduction and pre-Late Triassic arrival of northeast Gondwana-derived continental fragments at the southern Eurasian margin: Detrital zircon evidence from Triassic sandstones of Central Iran

The closure of Palaeotethys that led to the collision of the Cimmerian blocks with the southern Eurasian margin causing the Eo-Cimmerian orogeny during the Early Mesozoic is still controversially discussed. The Triassic Nakhlak Group in Central Iran is a key sedimentary succession for better understanding the closure of Palaeotethys and the Eo-Cimmerian orogeny in the Middle East. The Nakhlak Group is composed of the Alam (Olenekian to Middle Anisian), Baqoroq (?Upper Anisian to Middle Ladinian) and Ashin (Upper Ladinian to ?Carnian) formations, which consist mainly of volcaniclastic sandstones, mixed siliciclastic conglomerates, and marine carbonates. Here we present for the first time detrital zircon UPb ages from the Nakhlak Group to unravel its provenance and constrain its palaeotectonic position within the Palaeotethyan realm. Most detrital zircons from the Nakhlak Group are euhedral and subhedral with Permian–Triassic ages (ca. 280–240 Ma) suggesting sediment supply from Permian–Triassic magmatic rocks of the Silk Road Arc. Minor zircon populations show pre-Permian Palaeozoic ages, with age peaks at ca. 320 Ma and 480 Ma, which are probably derived from the basement on which the magmatic arc developed. Neoproterozoic–latest Mesoproterozoic (ca. 550–1100 Ma) and Palaeoproterozoic (ca. 1800–2200 Ma) zircon grains are anhedral (rounded). The latter are prominent in the upper Baqoroq Formation (Middle Ladinian) suggesting recycling of older sedimentary rocks. Sandstone petrography points toward an additional metamorphic provenance for this formation. This short-lived provenance change can be explained by tectonic uplift in the source area that led to erosion of metamorphosed rocks with a northeast Gondwanan affinity. It clearly indicates that northeast Gondwana-derived continental fragments likely belonging to the Cimmerian blocks already arrived at the southern Eurasian margin in pre-Late Triassic time. Current palaeotectonic models of the closure of Palaeotethys and the Eo-Cimmerian orogeny in the Middle East during the Triassic may need to be revised.

Microfacies and multi-isotope records of Anisian sequences from the Upper Yangtze Block: possible responses to tectonics and climate-driven relative sea-level change

The Middle Triassic epoch is the key to understanding the environment changes after the Permian–Triassic mass extinction. The Anisian Badong Formation is a carbonate and siliciclastic succession deposited on the Yangtze Platform, Upper Yangtze Block. In this paper, we use facies analysis combined with sequence stratigraphy of the Badong Formation in the Nashuixi section, Yangtze Block, to discuss the Anisian relative sea-level changes. Microfacies analyses were used to define ten microfacies in four depositional facies zones (tidal flat, restricted platform, restricted to open platform, and open platform) indicating an epeiric platform depositional environment. The lowstand, transgressive, and highstand systems tracts and two sequences were identified. Sequence stratigraphy interpretations indicate that relative sea-level at Nashuixi experienced two rises in the Middle Anisian, which is correlated with those in the Yangtze Block, confirming that sea-level changes during the Anisian were of eustatic origin. However, a distinct regression at Nashuixi occurred in the late Bithynian to IIIyrian while the global sea-level rose, which is likely to be caused by interference from regional tectonics during IIIyrian. The carbon and oxygen isotopic shifts in the Nashuixi section exhibit two negative-values stage in the time near end of Aegean and early Pelsonian, which is well correlated with the global typical sections, indicating two middle Anisian warming events. Our study indicated that the relative sea-level at Nashuixi was controlled by global sea-level change and regional tectonics (Indosinian Orogeny), and the C and O isotopes records respond to global climate change.

Sea lilies of the genera Holocrinus, Tollmannicrinus, and Eckicrinus (order Holocrinida) from the Anisian (Middle Triassic) of Qingyan, south-western China

Disarticulated stem remains of the crinoid genera Holocrinus, Tollmannicrinus, and Eckicrinus of the order Holocrinida from Anisian (early Middle Triassic) strata of the eastern and north-eastern outskirts of Qingyan, Guizhou Province, south-western China, are described. Holocrinus qingyanensis sp. nov. (family Holocrinidae) occurs in early early to middle middle Anisian deposits. Tollmannicrinus leidapoensis sp. nov. is described from latest middle Anisian strata, and the genus Tollmannicrinus is placed in the new family Tollmannicrinidae of the order Holocrinida. Eckicrinus cf. radiatus (Schauroth) is documented from early late Anisian deposits; the family level assignment of Eckicrinus is unclear. Holocrinus qingyanensis and Eckicrinus cf. radiatus resemble contemporaneous congeneric species from Europe. Tollmannicrinus leidapoensis is related to the younger species Tollmannicrinus saklibelensis from late Ladinian to early Carnian deposits of Turkey.

A highly diverse bivalve fauna from a Bithynian (Anisian, Middle Triassic) Tubiphytes‐microbial buildup in North Dobrogea (Romania)

AbstractThis paper describes a rich bivalve fauna from the Tubiphytes‐Limestone Member (Bithynian, early middle Anisian) of the Caerace Formation in North Dobrogea (Romania). We report 51 bivalve species, including 7 new species and 2 new genera: Atrina multicostata sp. nov., Pinna simionescui sp. nov., Chlamys (Praechlamys) prima sp. nov., Entolium reticulatum sp. nov., Scythentolium anisicum sp. nov., Romaniamya mahmudiaensis gen. et sp. nov. and Praedicerocardium vetulus gen. et sp. nov. The latter taxon represents the oldest Triassic megalodontoid. We provide detailed descriptions of the bivalve fauna, discuss the ecology and compare species richness in the Early and Middle Triassic, showing that the bivalve assemblage of North Dobrogea is much more diverse than all previously described Early Triassic bivalve faunas, but not as rich as several faunas from the late Anisian and Ladinian. The relative richness of the Dobrogea fauna with respect to geologically older and younger faunas suggests that it represents an early stage of the main rediversification of bivalves after the end‐Permian mass extinction.

Litho-, bio-, and chemostratigraphy of the Middle Triassic carbonate succession in the North-Central Coast Region of Vietnam

Middle Triassic carbonates extend from the North-Central Coast region of Vietnam to northern Laos. We conducted sedimentological, paleontological, and geochemical analyses on the carbonates of the Hoang Mai Formation in Nghe An province, Vietnam. The carbonates consist of the following six lithostratigraphic units (from bottom to top): sandy limestone (unit 1), peloidal packstone with a microbialite interlayer (unit 2), peloidal packstone and oncoidal floatstone (unit 3), peloidal–bioclastic packstone (unit 4), peloidal packstone with variable quantities of bioclasts and microbialite (unit 5), and peloidal packstone with variable quantities of bioclasts (unit 6). The sandy nature of unit 1 and of three of the interlayers in unit 2 indicates a supply of terrigenous material during the early stages of formation of the Hoang Mai carbonate platform. The dominance of carbonates with a fine-grained matrix throughout the overlying succession implies a low-energy depositional environment. Common occurrences of dasycladalean algae in units 4–6 indicate a back-reef lagoon environment. A total of 24 foraminiferal taxa, including Citaella dinarica and C. deformata, were identified. These two age-diagnostic species occur in units 3–6, suggesting that this interval is correlated with the Pelsonian and that the lower units (units 1–2) are potentially correlated with the Bithynian. Thus, the entire core section can be assigned to the middle Anisian (lower Middle Triassic). An assessment of the diagenetic alteration using geochemical parameters indicates that the carbonates of the studied succession have not retained their initial strontium (87Sr/86Sr) and oxygen (δ18O) isotope compositions. In contrast, the carbonates in the lower (units 1–2) and middle (units 2–5) intervals have retained their initial carbon isotope compositions (δ13C), making them suitable for C isotopic analyses. In the lower interval, we observe a slight δ13C-enrichment, followed by a gradual δ13C-depletion upwards into the middle interval. The observed trend in δ13C values from the Hoang Mai Formation can be correlated with similar trends reported from South China and Romania. Samples within the upper interval (units 5–6) of the Vietnamese δ13C profile are relatively δ13C-depleted, which is likely the result of diagenetic overprinting.

Foraminiferal Biochronology of the Triassic Hoang Mai Formation, Central Vietnam

AbstractForaminiferal biostratigraphy was investigated for the first time in the Triassic Hoang Mai Formation distributed in the southeastern part of the Sam Nua Basin which was developed along the northeastern margin of the Indochina Block during the Permian–Triassic. The formation consists entirely of carbonates and is embedded within the underlying volcano-sedimentary Dong Trau Formation and overlying fine-siliciclastic Quy Lang Formation. We examined an approximately 300 m-long core section drilled in the northeastern part of Nghe An province of north Central Vietnam. Based upon the stratigraphic distributions of 24 foraminiferal taxa, including Citaella dinarica, Citaella? deformata, Endotriada tyrrhenica, Endotriadella wirzi, Endotriadella pentacamerata, Pilamminella grandis, Pilammina cf. densa, and Triadodiscus cf. praecursor, we assigned a Pelsonian age for the main part of the Hoang Mai Formation, with its lower/basal part of the core section probably extending down into the Bithynian. Thus, the Hoang Mai Formation is referred to the middle Anisian (early Middle Triassic). We also attempted taxonomic reexamination of foraminifera reported previously from the formation and confirmed the probable occurrence of Aulotortus eotriasicus. This and other taxonomic revision executed on formerly reported foraminifera resulted in further strengthening a middle Anisian appraisal for this formation. In ascending order, the three Middle Triassic lithostratigraphic units distributed in the Sam Nua Basin are the Dong Trau, Hoang Mai, and Quy Lang formations; they have been considered to overlie each other with simple superposition. Elsewhere in the Sam Nua Basin in north Central Vietnam, however, the Balatonites ammonoid fauna, which is considered to be coeval with the present foraminiferal fauna from the Hoang Mai Formation, is known in the uppermost part of the “underlying” Dong Trau Formation and the lowermost part of the “overlying” Quy Lang Formation. This strongly implies heteropic facies development of these three formations in the Sam Nua Basin during Middle Triassic time.

Apparatus architecture of the conodont Nicoraella kockeli (Gondolelloidea, Prioniodinina) constrains functional interpretations

AbstractWe reconstruct the apparatus architecture of the gondollelid conodont Nicoraella kockeli based on fused clusters from the early Middle Triassic (middle Anisian, Pelsonian) of Luoping County, east Yunnan Province, south‐west China. This material was characterized non‐invasively using synchrotron x‐ray tomographic microscopy and the ensuing data analysed using computed tomography, allowing us to infer the composition, homologies and architectural arrangement of elements within the apparatus. Much of the original three‐dimensional architecture of the apparatus is preserved and our apparatus reconstruction is the best characterized of any taxon within the superfamily Gondolelloidea. This allows us to test architectural models for gondolelloids and prioniodinins, more generally, as well as the functional interpretations based upon them. In particular, we reject a recent functional interpretation of the conodont feeding apparatus which was based on a biomechanically‐optimized inference of apparatus architecture in a close gondolelloid relative of Nicoraella. Nevertheless, our architectural model provides a foundation for future functional interpretations of gondolleloids and prioniodinins, more generally.

Conodont-based age calibration of the Middle Triassic Anisian radiolarian biozones in pelagic deep-sea bedded chert

The age of pelagic Panthalassic deep-sea bedded chert has been assigned based on radiolarian biostratigraphy. However, Triassic radiolarian biostratigraphy is in many cases not precisely correlated to the conodont zones and the standard geological timescale. In this study, we investigated the conodont biostratigraphy of two radiolarian-controlled bedded chert sections of Anisian age: the Ajiro Island section in Oita Prefecture and the Kurusu section in Aichi Prefecture. We recognised six conodont biozones in the studied sections: the upper Olenekian Novispathodus brevissimus-Icriospathodus collinsoni and Triassospathodus homeri Zones, the lower Anisian Chiosella timorensis Zone, the middle Anisian Paragondolella bulgarica Zone, the upper Anisian Paragondolella excelsa Zone and the uppermost Anisian to lowermost Ladinian Paragondolella trammeri Zone. These conodont zones were successfully correlated to the standard Triassic radiolarian zonation proposed by Sugiyama (1997, Bull. Mizunami Foss. Mus., vol. 24, p. 79–193). Sugiyama’s radiolarian TR 1 Zone, previously considered to be of Olenekian age, extends to the middle Anisian. The TR 2A Zone, the TR 2B Zone and the lower part of the TR 2C Zone are correlated to the middle Anisian, while the upper part of the TR 2C Zone and the lower part of the TR 3A Zone are correlated to the upper Anisian. The upper part of the TR 3A Zone and the lower part of the TR 3B Zone are probably correlative to the uppermost Anisian, but the possibility that they are correlative to the lowermost Ladinian cannot be ruled out.

Paleoenvironmental reconstruction for termination stage of Superanoxia in Middle Triassic (Anisian) sedimentary sequence of the Mino belt, central Japan

AbstractSuperanoxia across the Permian/Triassic boundary, which is a long period of oceanic anoxia from the late Middle Permian to the early Middle Triassic, has been recognized and debated well in the context of the end Permian mass extinction. However, few studies have focused on the Middle Triassic anoxia because of limited application of geochemical proxies. To reconstruct paleoenvironmental changes during the termination stage of Superanoxia, various geochemical proxies were applied to chemical compositions of the Middle Triassic (Anisian) bedded chert sequence in the Mino belt, Japan, which accumulated in a deep seafloor environment in a low‐ to mid‐latitude zone of the Panthalassa Ocean. Three anoxic events were identified by statistically robust geochemical proxies during the middle Anisian. Degrees of calibrated‐chemical weathering intensity show higher values during these anoxic events, suggesting that the intensified continental weathering was a trigger mechanism for the oceanic anoxic events in the middle Anisian. Furthermore, our data indicate that the termination of Superanoxia in the Panthalassa Ocean was associated with a gradual decrease in continental weathering rates during the middle to late Anisian.

A new Anisian (Middle Triassic) eosauropterygian (Reptilia, Sauropterygia) from Panzhou, Guizhou Province, China

ABSTRACT—Eosauropterygians rapidly diversified in the Anisian (Middle Triassic), a period by which the invertebrates had already completely recovered from the end-Permian mass extinction. The Pelsonian (Anisian) deposits of the small Panxian and Luoping intraplatform basins in southwestern China alone yielded seven or more eosauropterygian taxa. A new Middle Triassic sauropterygian, Panzhousaurus rotundirostris, gen. et sp. nov., is here described based on an almost complete skeleton from the middle Anisian (Middle Triassic) of Panzhou (Guizhou Province, southwestern China). The upper temporal fenestra smaller than the orbit, the broad and flat parietal table, the cervical ribs with two proximal articular heads, the pachyostotic proximal ends of the dorsal ribs, and the unexpanded sacral ribs indicate that the specimen is a pachypleurosaur-like eosauropterygian. The new species also shows some differences from all other eosauropterygians, such as a rounded and shortened snout, 24 cervical and 20 dorsal vertebrae, a straight ulna with a concave posterior margin, and four distal carpals. Phylogenetic analysis also reveals that Panzhousaurus is an eosauropterygian, closely related to pachypleurosaur-like forms. The discovery of Panzhousaurus enriches our knowledge of the diversity of the Panxian fauna and provides new information to test phylogenetic relationships among known eosauropterygians.http://zoobank.org/urn:lsid:zoobank.org:pub:682A4FDD-C048-469F-867A-9F1D5847BD5ASupplemental Data—Supplemental materials are available for this article for free at www.tandfonline.com/UJVPCitation for this article: Jiang, D.-Y., W.-B. Lin, O. Rieppel, R. Motani, and Z.-Y. Sun. 2019. A new Anisian (Middle Triassic) eosauropterygian (Reptilia, Sauropterygia) from Panzhou, Guizhou Province, China. Journal of Vertebrate Paleontology. DOI:10.1080/02724634.2018.1480113.

Middle Triassic (Anisian, Bithynian) gastropods from North Dobrogea (Romania) and their significance for gastropod recovery from the end‐Permian mass extinction event

AbstractA new early middle Anisian (Bithynian) gastropod fauna is described from the Mahmudia quarry in North Dobrogea, Romania. At least 22 species are reported, nearly all of them from Tubiphytes‐limestones which represent a microbial buildup. Twenty species from Tubiphytes‐buildup limestones are characterized, ten of which in open nomenclature due to insufficient preservation. One genus (Murchisonietta gen. nov) and ten species are described as new. The new species are Euryalox applanatus, Rasatomaria multistriata, Sisenna inaequistriata, Worthenia (Worthenia) dobrogeana, Worthenia (Humiliworthenia) microstriata, Worthenia (Humiliworthenia) anisica, Marmolatella iordanae, Ladinaticella simionescui, Murchisonietta acuta and Coelostylina micropunctata. The present fauna is one of the most diverse Anisian gastropod faunas known to date and sheds light on the pattern of ongoing recovery from the end‐Permian mass extinction event. It is dominated by Neritimorpha, Caenogastropoda and Pleurotomariida both in abundance and number of species. Diversity of Pleurotomariida strongly exceeds that of any known Early Triassic gastropod fauna and suggest a pronounced rebound of this group. High‐spired smooth caenogastropods (Omphaloptycha and Polygyrina) are relatively abundant but for the most part not enough well preserved for species identification. The present gastropod fauna is part of a diverse invertebrate fauna probably comprising more than 50 species with gastropods being the most diverse followed by bivalves and brachiopods. They were microbial‐buildup dwellers while metazoan frame‐builders, especially corals, were still absent as consequence of the end‐Permian mass extinction event. The Mahmudia fauna suggests that metazoan reefs recovered more slowly than benthic faunas.

Growth patterns, sexual dimorphism, and maturation modeled in Pachypleurosauria from Middle Triassic of central Europe (Diapsida: Sauropterygia)

Abstract. Bone tissue, microanatomy, and growth are studied in humeri of the pachypleurosaurs Dactylosaurus from the early Anisian of Poland and of aff. Neusticosaurus pusillus from the Lettenkeuper (early Ladinian) of southern Germany. Histology and modeled growth curves are compared to already published data of other pachypleurosaurs. Therefore, we herein established growth curves for Anarosaurus from the middle Anisian of Winterswijk (the Netherlands) and for pachypleurosaurs from the Anisian/Ladinian of the Alpine Triassic (i.e., Neusticosaurus spp. and Serpianosaurus). Humeri of Dactylosaurus, Anarosaurus, and aff. N. pusillus, all from the Germanic Basin, usually display an inner ring of (pre-)hatchling bone tissue. In some samples this tissue is surrounded by a layer of perpendicularly oriented fine fibers, which could indicate the start of active locomotion for foraging or might be related to viviparity. However, pachypleurosaurs from the Alpine Triassic do not show this tissue. This in turn could be related to overall differences in the environments inhabited (Germanic Basin vs. Alpine Triassic). Histological comparison revealed distinct taxon-specific differences in microanatomy and bone tissue type between Anarosaurus on the one hand and Dactylosaurus and the Neusticosaurus–Serpianosaurus clade on the other hand. Microanatomical differences imply a different degree in secondary adaptation to an aquatic environment. Life-history traits derived histologically and obtained from modeling growth were in general rather similar for all studied pachypleurosaurs. Onset of sexual maturation was within the first third of life. Asymptotic ages (maximum life span) considerably exceeded documented and modeled ages at death in all pachypleurosaur taxa. All traits modeled (more or less) matched values seen in similar-sized extant reptiles. Growth curves revealed differences in growth and maturation strategies within taxa that could indicate sexual dimorphism expressed in different adult sizes and a different onset of sexual maturation. Differences in gender size and morphology is well documented for the Chinese pachypleurosaur Keichousaurus and for Neusticosaurus spp. from the Alpine Triassic. Birth-to-adult size ratios of herein studied pachypleurosaurs were consistent with those seen in other viviparous Sauropterygia, other viviparous extinct taxa as well as extant viviparous reptiles. Anarosaurus had the highest maximum growth rates of all pachypleurosaurs studied, which best conformed to those seen in today's similar-sized reptiles and is expected from its bone tissue type. The other pachypleurosaur taxa had lower rates than the average seen in similar-sized extant reptiles. We hypothesize from our data that the considerably higher asymptotic ages compared to ages at death, early onset of maturation compared to asymptotic age, and viviparity reflect that pachypleurosaurs lived in predator-dominated environments.

First report of ostracods (Crustacea) associated with Bithynian (Anisian, Middle Triassic) Tubiphytes‐microbial reef in the North Dobrogean Orogen (Romania)

AbstractThe Mahmudia Quarry is located in the North Dobrogean Orogen (Romania), representing the western tip of the Palaeotethys‐issued Cimmeride Orogenic System. One sample from the Tubiphytes‐microbial reef exposed in the quarry yielded an abundant well‐preserved ostracod assemblage of Bithynian, early Middle Anisian, Middle Triassic age. We report the occurrence of 56 ostracod species distributed among 23 genera. Ten species are newly described: Acratia caeracella sp. nov., Bairdia mandruella sp. nov., B. liviae sp. nov., Hungarella mahmudiaensis sp. nov., Kempfina tineriella sp. nov., Liuzhinia antalyaformis sp. nov., L. bithynica sp. nov., L. edvardgriegi sp. nov., Microcheilinella? contrariella sp. nov., Paracypris oanaella sp. nov. One species is renamed, Bairdia monostorii nom. nov. and the diagnosis of the genus Palaeocypridina is emended to include the central muscle scars pattern. The Tubiphytes ecosystem is complex with a multi‐layer food chain, as shown by the presence of diversified carnivorous nekto‐benthic ostracods, being both prey and predators of other organisms. The palaeoenvironmental requirements of the main ostracod taxa indicate a deposition in an open marine environment, on the outer platform‐upper slope zone, in accordance with information provided by other proxies. We discuss the relationship between ostracods and microbial mats during the Triassic and conclude that the composition of assemblages is related both to the characteristics of this chemosynthetically‐driven habitat and to bathymetry. However, some taxa, such as the genus Liuzhinia, are typical of Triassic microbial ecosystems. We perform the first analysis of ostracod provincialism during the Anisian and identify a distinct peri‐Palaeo‐Tethyan province.

First report on swimming trace fossils of fish from the Upper Permian and Lower Triassic of the Dolomites (Italy)

In the Upper Permian continental to marginal-marine succession of the Southern Alps (Dolomites, north Italy), the ichnological record consists of diverse vertebrate footprints and non-diverse invertebrate trace fossils, mainly occurring in the “Bletterbach ichnoassociation” of the Val Gardena Sandstone Formation. After the Permian-Triassic Boundary event, vertebrate ichnoassociations are scarce until the Middle Triassic (Anisian), whereas the uppermost Permian–Lower Triassic Werfen Formation preserves a rich invertebrate trace-fossil record. To date, fish body and trace fossils ( Undichna ) are very rare in the pre- and post-extinction deposits of the Dolomites; only Undichna gosiutensis Gibert, 2001 was identified in the “Voltago Conglomerate” (Middle Anisian), whereas some unidentified fossil fish casts were found in the Permian Val Gardena Sandstone and some fish remains in the overlying Werfen Formation. Recently, for the first time, fish trails have been discovered in the Val Gardena Sandstone (Lopingian) and in the Werfen Formation (Campil member, Early Triassic, Smithian). Val Gardena Sandstone yielded Undichna cf. quina Trewin, 2000 and U. bina Anderson, 1976 and these represent the oldest fish trails found in the Southern Alps so far. Conversely, the specimens found in the Werfen Formation can be assigned to Undichna cf. britannica Higgs, 1988. They represent the oldest Mesozoic record of fish trace fossils in northern Italy and one of the few records of Undichna from marine environments. These trace fossils are consistent with the fossil association found in the two formations and reflect fish swimming activity in different environments: in very shallow, calm, brackish distal-floodplain to marginal-marine environments in the Late Permian, in association with abundant and diverse tetrapod tracks, and non-diverse invertebrate trace fossils, and in inter- to subtidal calm, shallow, marine environments in the Early Triassic, together with abundant, but not diverse invertebrate trace fossils.

Taxonomic and Nomenclatural Justification For the Triassic Meandrospiral Foraminiferal Genus Citaella Premoli Silva, 1964

AbstractTaxonomy and nomenclature of Triassic meandrospiral foraminifers have been confused for a long time and they have been misinterpreted to relate to Cretaceous Meandrospira in most studies. We comprehensively reviewed their research history, considering morphology, phylogenetic relation, taxonomy, and nomenclature. This allowed us to confirm their original porcelaneous wall composition based on well-preserved specimens, and to legitimize the use of the generic name Citaella Premoli Silva, 1964 for Triassic meandrospiral foraminifers. Citaella is here redefined as a miliolate genus having a porcelaneous shell and typical meandrospiral arrangement in its tubular deuteroloculus. The genus is restricted in the late Early to early Middle Triassic (Olenekian–Anisian) of the Tethyan realm. It was likely derived from a cornuspiroidean ancestor in earliest Triassic time, although the ancestral taxon is still unclear. Citaella gave rise to two descendant genera, Meandrospiranella and Turriglomina, in the early–middle Anisian. These three taxa formed a single phylogenetic clade in the Triassic, to which the subfamily Turriglomininae Zaninetti 1987 is best applicable. Citaella is phylogenetically distinct from its homeomorphic miliolate genera Streblospira in the Early Permian and Meandrospira in the Early Cretaceous, although they have the same wall compositions and very similar arrangement patterns in deuteroloculi. After scrutinizing literature, we recognized four distinct species in the genus Citaella including one with questionable generic assignment. We also made taxonomic emendation of the subfamily Turriglomininae and the genus Citaella, and demonstrated nomenclatural precedency of Citaella pusilla over other synonymous species that were proposed simultaneously in the same article.

Slipped through the bottleneck: Lazarechinus mirabeti gen. et sp. nov., a Paleozoic-like echinoid from the Triassic Muschelkalk (late Anisian) of East France

The unique find of a stem group echinoid with a rotular, flexible corona composed of multiserial ambulacra and interambulacra from the Upper Muschelkalk Calcaire a Entroques (Middle Triassic, late Anisian, late Illyrian) of East France is described. The articulate specimen allows description of all characters besides the apical disc that was lost. The echinoid described as Lazarechinus mirabeti represents a new species and genus of the Carboniferous through Late Permian stem group echinoid family Proterocidaridae. Between the latest Permian proterocidarid Pronechinus and the new Lazarechinus is a gap of approx. 16 Ma covering the Early and early Middle Triassic. This makes the new genus a typical Lazarus taxon belonging to a lineage that disappeared during times of crisis and awoke in times of biotic recovery. Additional references of stem group echinoids are known from the middle Anisian of Southwest China and from the Carnian of Italy and Central China. The new finds provide evidence that the current concepts of echinoid evolution around the Permian–Triassic boundary require thorough reappraisal. The fortunate discovery of Lazarechinus in a Muschelkalk conservation Lagerstatte also encourages the systematic search of isolated sclerites assignable to stem group echinoids in Triassic sediments to provide more information on abundance, distribution, and habitats.

Astrochronology of the Anisian stage (Middle Triassic) at the Guandao reference section, South China

A high-precision global timescale for the Early and Middle Triassic is the key to understanding the nature, pattern and rates of biotic recovery following the end-Permian mass extinction. The Guandao section of Guizhou Province of South China is an important reference section for the magnetic polarity pattern, conodont datums, geochemical anomalies and interpreted temperature history through the Anisian (Middle Triassic). We analyzed the high-resolution gamma-ray and magnetic susceptibility series from the complete Anisian stage. Intensity variations are indicative of fluctuating terrestrial clay influxes showing strong signals that match predicted astronomical solutions for eccentricity and precession. Astronomical tuning of these series to interpreted 405-kyr long-eccentricity cycles yields a 5.3 Myr duration for the Anisian at Guandao. When combined with the astrochronology of the Early Triassic, then the projected age of the Anisian–Ladinian boundary relative to the base-Triassic date of 251.9 Ma is 241.5±0.1 Ma. This provides a 10-Myr reference timescale for other key geological events, including conodont zones, geomagnetic polarity chrons, rates of marine carbon- and oxygen isotope excursions and global sea-level changes, that were associated with the repeated biotic crises and recovery episodes after the end-Permian mass extinction. The middle Anisian humid phase in ca. 244–244.5 Ma was probably a global event, which may have been linked to the middle Anisian warming event and sea-level change. Sea-level fluctuations at Guandao generally correlate with those in western Tethyan and Boreal regions in time, confirming sea-level changes during the Anisian were of eustatic origin.

High sediment input and possible oceanic anoxia in the pelagic Panthalassa during the latest Olenekian and early Anisian: Insights from a new deep-sea section in Ogama, Tochigi, Japan

Ecosystem recovery from the end-Permian mass extinction took around 5millionyears of the Early Triassic. In the pelagic deep-sea of the superocean Panthalassa, deposition of bedded chert ceased during this period, and instead, siliceous claystone lithofacies with minor chert beds was deposited. The reappearance of bedded chert around the Early-Middle Triassic (Olenekian-Anisian) boundary (OAB) was assumed to be related to recovery of radiolarian production in the pelagic realm. This study reports a new pelagic deep-sea section covering the transition from siliceous claystone lithofacies to bedded chert from Ogama in Tochigi Prefecture, Japan. Based on conodont and radiolarian biostratigraphy and carbon isotope stratigraphy, the Ogama section was dated as uppermost Olenekian to middle Anisian. The OAB was recognised by the occurrence of the conodont Chiosella timorensis, while the radiolarian-based OAB adopted by previous studies on bedded chert in Japan was revealed to be within the middle Anisian. In the Ogama section, the transition from siliceous claystone lithofacies to bedded chert is in the middle Anisian. The OAB is characterised by black organic-rich siliceous claystone, which implies oceanic oxygen depletion. Importantly, the linear sedimentation rate of the siliceous claystone lithofacies was found to be higher than that of Middle Triassic and Jurassic bedded chert. This shows that increased accumulation of clastic material was an important factor that caused the deposition of siliceous claystone in the pelagic Panthalassa at the OAB. Hence, the deposition of black siliceous claystone at the OAB may have occurred under different conditions from that at the end-Permian mass extinction, which is thought to be a result of diminished biogenic silica production.

Middle Triassic foraminifers from northern Laos and their paleobiogeographic significance

Triassic foraminifers are reported for the first time from limestones in the upper part of the Nam Sam Suite distributed in the Sam Neua area of northern Laos. The study area is located in the northern part of the Indochina Block, based on the basic geotectonic subdivision of mainland Southeast Asia. The fauna consists of 17 taxa and includes age-diagnostic Pilammina densa, Pilamminella grandis, Citaella dinarica, C.? deformata, Arenovidalina amylovoluta, and Diplotremina astrofimbriata. It is referable to the middle Anisian (Pelsonian) of the Middle Triassic. The microfacies of the studied samples are subdivided into three types, suggesting low wave-energy uppermost subtidal, moderately wave-agitated uppermost subtidal, and intertidal environments, respectively. Two species are specific to the intertidal microfacies. A notable paleontological feature is the dominance of P. densa, shown by the large number of individuals in the foraminiferal assemblage. This could be related to its opportunistic nature in the stressful conditions of the intertidal environment. We also consider that C.? deformata may be ecologically adapted to a hypersaline environment. The Sam Neua fauna shares several important species, such as C. dinarica, P. densa, P. grandis, and A. amylovoluta, with those found in the Sibumasu Block, Sukhothai Zone, and South China Block, suggesting that these major geotectonic domains in mainland Southeast Asia formed a single paleobiogeographic province during Anisian time. In view of paleogeography, the present results point toward a rather restricted (narrow) Paleo-Tethyan ocean basin allowing faunal interchanges among separated Eastern Tethyan continental blocks during the Middle Triassic.