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Therocephalia are an important clade of non-mammalian therapsids that evolved a diverse array of morphotypes and body sizes throughout their evolutionary history. The postcranial anatomy of therocephalians has largely been overlooked, but remains important towards understanding aspects of their palaeobiology and phylogenetic relationships. Here, we provide the first postcranial description of the large akidnognathid eutherocephalian Moschorhinus kitchingi by examining multiple specimens from fossil collections in South Africa. We also compare the postcranial anatomy with previously described therocephalian postcranial material and provide an updated literature review to ensure a reliable foundation of comparison for future descriptive work. Moschorhinus shares all the postcranial features of eutherocephalians that differentiate them from early-diverging therocephalians, but is differentiated from other eutherocephalian taxa by aspects concerning the scapula, interclavicle, sternum, manus, and femur. The novel anatomical data from this contribution shows that Moschorhinus possessed a stocky bauplan with a particularly robust scapula, humerus, and femur. These attributes, coupled with the short and robust skull bearing enlarged conical canines imply that Moschorhinus was well equipped to grapple with and subdue prey items. Additionally, the combination of these attributes differ from those of similarly sized coeval gorgonopsians, which would have occupied a similar niche in late Permian ecosystems. Moreover, Moschorhinus was the only large carnivore known to have survived the Permo-Triassic mass extinction. Thus, the subtle but important postcranial differences may suggest a type of niche partitioning in the predator guild during the Permo-Triassic mass extinction interval.

The links between the Siberian Traps and the end-Permian mass extinction, and between the North Atlantic igneous province (NAIP) and the Paleocene–Eocene thermal maximum (PETM), demonstrate a critical role for large igneous provinces (LIPs) in the disruption of the Earth-surface carbon cycle (ESCC). High-precision ages for both volcanic provinces and the associated environmental crises show that, in both cases, the crisis was contemporaneous with the volcanism. The NAIP comprises two phases: the earlier Phase 1 (c. 61 Ma) and the much more voluminous Phase 2 (c. 56 Ma), linked to the opening of the NE Atlantic. The latter triggered the PETM, the largest Cenozoic hyperthermal. The Siberian Traps are significantly more voluminous than the NAIP, and triggered the end-Permian mass extinction. The masses of volcanic CO2 emitted from these provinces may have been much greater than previously suggested as substantial gas may come from intrusive bodies deep within the crust. Precursory warming due to the accumulation of volcanic CO2 in the atmosphere likely triggered the release of low-δ13C methane hydrate, although the masses of methane hydrate alone may have been insufficient to account for the observed temperature rises. The organic C was likely strongly supplemented by magmatically derived carbon and thermogenic carbon released during emplacement of sills and dykes into C-rich sedimentary units. More data are required on the volcanic flux rates in order to refine the cause–effect relationships between LIPs and the ESCC.

The disappearance of nonavian dinosaurs is probably the most notorious extinction event of all time, yet it is only a small part of a greater class of extinctions known as “mass extinctions.” Mass extinctions are global events characterized by unusually high rates of extinction. The magnitude of these rates is usually unspecified but it is generally significantly higher than the rate of so-called “background extinctions”; that is, extinctions that occur constantly through geologic time (Raup and Sepkoski 1982). Mass extinctions are also characterized by geologically short timescales and by a significant diminution in the number of surviving taxa, as well

Earth’s largest biotic crisis occurred during the Permo–Triassic Transition (PTT). On land, this event witnessed a turnover from synapsid- to archosauromorph-dominated assemblages and a restructuring of terrestrial ecosystems. However, understanding extinction patterns has been limited by a lack of high-precision fossil occurrence data to resolve events on submillion-year timescales. We analyzed a unique database of 588 fossil tetrapod specimens from South Africa’s Karoo Basin, spanning ∼4 My, and 13 stratigraphic bin intervals averaging 300,000 y each. Using samplestandardized methods, we characterized faunal assemblage dynamics during the PTT. High regional extinction rates occurred through a protracted interval of ∼1 Ma, initially co-occurring with low origination rates. This resulted in declining diversity up to the acme of extinction near the Daptocephalus–Lystrosaurus declivis Assemblage Zone boundary. Regional origination rates increased abruptly above this boundary, co-occurring with high extinction rates to drive rapid turnover and an assemblage of short-lived species symptomatic of ecosystem instability. The “disaster taxon” Lystrosaurus shows a long-term trend of increasing abundance initiated in the latest Permian. Lystrosaurus comprised 54% of all specimens by the onset of mass extinction and 70% in the extinction aftermath. This early Lystrosaurus abundance suggests its expansion was facilitated by environmental changes rather than by ecological opportunity following the extinctions of other species as commonly assumed for disaster taxa. Our findings conservatively place the Karoo extinction interval closer in time, but not coeval with, the more rapid marine event and reveal key differences between the PTT extinctions on land and in the oceans.

Actinopterygians (ray-finned fishes) successfully passed through four of the big five mass extinction events of the Phanerozoic, but the effects of these crises on the group are poorly understood. Many researchers have assumed that the Permo-Triassic mass extinction (PTME) and end-Triassic extinction (ETE) had little impact on actinopterygians, despite devastating many other groups. Here, two morphometric techniques, geometric (body shape) and functional (jaw morphology), are used to assess the effects of these two extinction events on the group. The PTME elicits no significant shifts in functional disparity while body shape disparity increases. An expansion of body shape and functional disparity coincides with the neopterygian radiation and evolution of novel feeding adaptations in the Middle-Late Triassic. Through the ETE, small decreases are seen in shape and functional disparity, but are unlikely to represent major changes brought about by the extinction event. In the Early Jurassic, further expansions into novel areas of ecospace indicative of durophagy occur, potentially linked to losses in the ETE. As no evidence is found for major perturbations in actinopterygian evolution through either extinction event, the group appears to have been immune to two major environmental crises that were disastrous to most other organisms.

A major macroevolutionary question concerns how long-term patterns of body-size evolution are underpinned by smaller scale processes along lineages. One outstanding long-term transition is the replacement of basal therapsids (stem-group mammals) by archosauromorphs, including dinosaurs, as the dominant large-bodied terrestrial fauna during the Triassic (approx. 252–201 million years ago). This landmark event preceded more than 150 million years of archosauromorph dominance. We analyse a new body-size dataset of more than 400 therapsid and archosauromorph species spanning the Late Permian–Middle Jurassic. Maximum-likelihood analyses indicate that Cope's rule (an active within-lineage trend of body-size increase) is extremely rare, despite conspicuous patterns of body-size turnover, and contrary to proposals that Cope's rule is central to vertebrate evolution. Instead, passive processes predominate in taxonomically and ecomorphologically more inclusive clades, with stasis common in less inclusive clades. Body-size limits are clade-dependent, suggesting intrinsic, biological factors are more important than the external environment. This clade-dependence is exemplified by maximum size of Middle–early Late Triassic archosauromorph predators exceeding that of contemporary herbivores, breaking a widely-accepted ‘rule’ that herbivore maximum size greatly exceeds carnivore maximum size. Archosauromorph and dinosaur dominance occurred via opportunistic replacement of therapsids following extinction, but were facilitated by higher archosauromorph growth rates.

The Brsnina Permian–Triassic nearshore marine sediments were deposited on the Adria carbonate platform in tropical latitudes at the western end of the Neotethys Ocean. Continuous channel samples across the boundary show no consistent change in element or element/Al ratios, except that most element/Al ratios increase in the top 0.5 m of the Permian strata. Though there are sporadic higher values of some element/element ratios, such as Ti/Zr, Th/Sc, Zr/Sc, Cr/Ni, Y/Ni, Co/Th, Cu/Zn, and Nb/Ta, La/Sc, the overall geochemistry indicates that the sediments were derived from dominantly silica-rich continental rather than silica-poor sources though with some more silica-poor inputs at times. Sporadic high Ti/Zr ratios indicate periods of increased aridity, but no overall increase across the boundary. Various geochemical redox proxies suggest mainly oxic depositional conditions, with episodes of anoxia, but with little systematic variation across the boundary. Geochemical proxies for productivity indicate little change up the section with values two orders of magnitude less than elsewhere. The lack of consistent element geochemical changes across the boundary accompanied by significant C, S, and other isotopic changes suggests that atmospheric and oceanic chemical variations drove the Permian–Triassic boundary environmental changes at least on the sabkha environments of the tropical Adria platform.

On the basis of the lithostratigraphy and microscopic characters, the paper describes the facies interpretation of the upper Upper Permian (Changhsingian) and Lower Triassic (Griesbachian to Spathian) carbonates of southwest Japan, with a focus upon the lowermost Triassic (Griesbachian) microbial bindstone-cementstone. We emphasize the significant sediment-binding and stabilizing agencies of microbes chiefly of cyanobacteria along with the syndepositional cementation for the carbonate deposition on a Panthalassan buildup in a period of the Scythian reef gap. Cyanobacteria flourished as postmass extinction disaster forms in the beginning of the Triassic. The Griesbachian microbial bindstone-cementstone we describe comprises the oldest known Triassic microbial facies.Examined were the Changhsingian Mitai Formation and the Triassic Kamura Formation (Griesbachian to Norian) in southwest Japan. These units consist entirely of carbonates and are reconstructed as relict of a shallowmarine buildup upon a seamount in the Panthalassa.The Changhsingian Mitai carbonates (ca. 35 m thick) consist mainly of grainstone and packstone with a small amount of lime-mudstone. The topmost part is intensely dolomitized. The carbonate succession is characterized by an upward-decrease in number and taxonomic diversity of shallow-marine skeletal debris and an increase up-section in an amount of peloidal particles. The lower Mitai rocks are interpreted to have accumulated as skeletal sand in an oxygenated subtidal environment and the upper Mitai carbonates are considered to have been formed in a quiet intertidal environment where peloidal particles predominantly accumulated. The facies interpretation suggests the late Changhsingian regression, which led to an increase of an inhospitable condition for shallow-marine benthic communities and to an intensive dolomitization.The Kamura Formation (ca. 38 m thick) disconformably rests upon the Mitai Formation with a drastic lithologic change. The Lower Triassic rocks we focused reach 15.5 m thick and comprise the Griesbachian and Dienerian to Spathian sections.The lower part (ca. 5.5 m) of the Griesbachian section consists of dark gray carbonaceous limestone composed of thinly layered triplets of a gastropod-bearing peloidal grainstone layer, a spar-cemented frame of clotted peloids, and a thin-laminated and occasionally stromatolitic cover of cryptomicrobial micrite in ascending order. The upper two members of a triplet often form a bindstone-cementstone layer characterized by a low-relief domed structure, or a broad hump. The upper part (ca. 2 m thick) of the Griesbachian section is composed of oncolitic limestone that contains laminae packed with gastropods. The Dienerian to Spathian section (ca. 8 m thick) consists of coquinites comprising an explosive flourish and accumulation of pectinacean bivalves.We interpret the Griesbachian rocks to have accumulated in a stagnant, ecologically rigorous tidal flat, where microbes, of possible cyanobacteria, flourished. The flourish of gastropods reflects an intermittent inundation by spring tide into the peritidal environment. The deposition of gastropods was followed by a dominant cyanobacterial activity that formed a microbial bindstone-cementstone layer along with the syndepositional cementation in an intertidal zone. The cyanobacterial activity contributed to the formation of gently undulated, sediment-binding and stabilizing mats. The oncolitic limestone in the upper part of the Griesbachian section also suggests the cyanobacterial, or algal activity. The Griesbachian microbial-controlled sedimentation was followed by the mass accumulation of bivalves that most possibly reflects a rapid transgression in Dienerian time.All the results permit us to conclude that possible cyanobacteria were the significant rock-forming organisms as post-mass extinction disaster forms on a panthalassan buildup in the beginning of the Scythian reef gap. The Griesbachian carbonates here described are similar in having the important microbial control on the sedimentation to the Lower Triassic stromatolitic and thrombolitic carbonates previously known in the Tethyan platform.