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1. A new short-faced archosauriform from the Upper Triassic Placerias/Downs’ quarry complex, Arizona, USA, expands the morphological diversity of the Triassic archosauriform radiation

   https://doi.org/10.1007/s00114-021-01733-1  

   Heckert, Andrew B. ; Nesbitt, Sterling J. ; Stocker, Michelle R. ; Schneider, Vince P. ; Hoffman, Devin K. ; Zimmer, Brian W. ( August 2021 , The Science of Nature)

   Abstract The Placerias /Downs’ Quarry complex in eastern Arizona, USA, is the most diverse Upper Triassic vertebrate locality known. We report a new short-faced archosauriform, Syntomiprosopus sucherorum gen. et sp. nov., represented by four incomplete mandibles, that expands that diversity with a morphology unique among Late Triassic archosauriforms. The most distinctive feature of Syntomiprosopus gen. nov. is its anteroposteriorly short, robust mandible with 3–4 anterior, a larger caniniform, and 1–3 “postcanine” alveoli. The size and shape of the alveoli and the preserved tips of replacement teeth preclude assignment to any taxon known only from teeth. Additional autapomorphies of S. sucherorum gen. et sp. nov. include a large fossa associated with the mandibular fenestra, an interdigitating suture of the surangular with the dentary, fine texture ornamenting the medial surface of the splenial, and a surangular ridge that completes a 90° arc. The external surfaces of the mandibles bear shallow, densely packed, irregular, fine pits and narrow, arcuate grooves. This combination of character states allows an archosauriform assignment; however, an associated and similarly sized braincase indicates that Syntomiprosopus n. gen. may represent previously unsampled disparity in early-diverging crocodylomorphs. The Placerias Quarry is Adamanian (Norian, maximum depositional age ~219 Ma), and this specimen appears to be an early example of shortening of the skull, which occurs later in diverse archosaur lineages, including the Late Cretaceous crocodyliform Simosuchus . This is another case where Triassic archosauriforms occupied morphospace converged upon by other archosaurs later in the Mesozoic and further demonstrates that even well-sampled localities can yield new taxa. 

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2. Magnetostratigraphy of the Triassic Moenkopi Formation From the Continuous Cores Recovered in Colorado Plateau Coring Project Phase 1 (CPCP‐1), Petrified Forest National Park, Arizona, USA: Correlation of the Early to Middle Triassic Strata and Biota in Colorado Plateau and Its Environs

   https://doi.org/10.1029/2021JB021899  

   Haque, Ziaul ; Geissman, John W. ; Irmis, Randall B. ; Olsen, Paul E. ; Lepre, Christopher ; Buhedma, Hesham ; Mundil, Roland ; Parker, William G. ; Rasmussen, Cornelia ; Gehrels, George E. ( September 2021 , Journal of Geophysical Research: Solid Earth)

   The Colorado Plateau Coring Project Phase 1 (CPCP‐1) acquired three continuous drill cores from Petrified Forest National Park (PFNP), Arizona, U.S.A., two of which (CPCP‐PFNP13‐1A and CPCP‐PFNP13‐2B) intersected the Upper Triassic Chinle Formation, Lower(?)‐Middle Triassic Moenkopi Formation (MF) and Permian Coconino Sandstone. We examined both cores to construct a high‐resolution magnetostratigraphy of MF strata, and progressive demagnetization data yield well‐defined, interpretable paleomagnetic results. Each lithostratigraphic member of the MF (Wupatki, Moqui, and Holbrook members) contains authigenic and detrital hematite as the dominant magnetic carrier with distinguishing rock magnetic characteristics. Magnetostratigraphy of MF strata in both CPCP‐1 cores consists of six normal and six reverse polarity magnetozones, from the youngest to the oldest, MF1n to MF6r. Recent single‐crystal chemical abrasion–thermal ionization mass spectrometry (CA‐TIMS) U‐Pb data from a sample in magnetozone MF1n yield a latest Anisian/earliest Ladinian (241.38 ± 0.43 Ma) age. Correlation of the CA‐TIMS‐calibrated magnetostratigraphy with the astronomically tuned polarity timescale for the Middle Triassic deep‐marine Guandao (GD) section of South China ties the magnetozone MF1n with GD8 and MF6r with GD2r, and implies that the MF spans, at most, the earliest Anisian (Aegean) to latest Anisian (Illyrian)/earliest Ladinian stages (ca. 246.8 to 241.5 Ma). This age estimate for the MF suggests that the timespan of the regional, pre‐Norian disconformity is about 17 Ma, which demonstrates that MF vertebrate fossil assemblages in east‐central Arizona are millions of years (minimally 3–4 Ma) younger than previously suggested and are all Anisian in age, with no indications of substantial hiatuses in the MF section.

    

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3. Widespread azendohsaurids (Archosauromorpha, Allokotosauria) from the Late Triassic of western USA and India

   https://doi.org/10.1002/spp2.1413  

   Nesbitt, Sterling J. ; Stocker, Michelle R. ; Ezcurra, Martín D. ; Fraser, Nicholas C. ; Heckert, Andrew B. ; Parker, William G. ; Mueller, Bill ; Sengupta, Saradee ; Bandyopadhyay, Saswati ; Pritchard, Adam C. ; et al ( December 2021 , Papers in Palaeontology)

   Archosauromorph reptiles underwent rapid lineage diversification, increases in morphological and body size disparity, and expansion into new adaptive landscapes. Several of the primary early archosauromorph clades (e.g. rhynchosaurs) are easy to differentiate from others because of their characteristic body types, whereas the more lizard‐like and carnivorous forms with long necks (e.g. tanystropheids) were historically all relegated to the groups Protorosauria or Prolacertiformes. However, it is now clear that these groups are polyphyletic and that a lizard‐like, carnivorous form is plesiomorphic for Archosauromorpha, and multiple subclades started with that body plan. Among these early forms isMalerisaurusfrom the Upper Triassic of India (M. robinsonae) and the Upper Triassic of south‐western USA (M. langstoni). In this paper, we critically re‐evaluate the genus. We find both species ofMalerisaurusas valid, and identifyMalerisaurusas an early diverging, but late‐surviving, carnivorous member of Azendohsauridae within Allokotosauria. Our histological analysis and assessment of ontogenetic changes of limb bones of small and large individuals demonstrate that the skeletons of the small forms grew slowly and became more robust through ontogeny, and that the larger recovered bones are at or near the maximum size of the taxon.MalerisaurusandMalerisaurus‐like taxa were common members of the Otischalkian–Adamanian (late Carnian to mid‐Norian) faunal assemblages from Upper Triassic strata of the south western USA, but they are absent from the younger Revueltian holochronozone. Specimens from western North America show that Allokotosauria had a near‐Pangaean distribution for much of the Middle Triassic to Late Triassic.

    

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4. Paleoclimate-induced stress on polar forested ecosystems prior to the Permian–Triassic mass extinction

   https://doi.org/10.1038/s41598-022-12842-w  

   Gulbranson, Erik L. ; Mellum, Morgan M. ; Corti, Valentina ; Dahlseid, Aidan ; Atkinson, Brian A. ; Ryberg, Patricia E. ; Cornamusini, Gianluca ( May 2022 , Scientific Reports)

   The end-Permian extinction (EPE) has been considered to be contemporaneous on land and in the oceans. However, re-examined floristic records and new radiometric ages from Gondwana indicate a nuanced terrestrial ecosystem response to EPE global change. Paleosol geochemistry and climate simulations indicate paleoclimate change likely caused the demise of the widespread glossopterid ecosystems in Gondwana. Here, we evaluate the climate response of plants to the EPE via dendrochronology snapshots to produce annual-resolution records of tree-ring growth for a succession of late Permian and early Middle Triassic fossil forests from Antarctica. Paleosol geochemistry indicates a shift in paleoclimate towards more humid conditions in the Early and early Middle Triassic relative to the late Permian. Paleosol morphology, however, supports inferences of a lack of forested ecosystems in the Early Triassic. The plant responses to this paleoclimate change were accompanied by enhanced stress during the latest Permian as determined by high-resolution paleoclimate analysis of wood growth intervals. These results suggest that paleoclimate change during the late Permian exerted significant stress on high-latitude forests, consistent with the hypothesis that climate change was likely the primary driver of the extinction of the glossopterid ecosystems.

    

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5. Garzapelta muelleri gen. et sp. nov., a new aetosaur ( Archosauria: Pseudosuchia ) from the Late Triassic (middle Norian ) middle Cooper Canyon Formation, Dockum Group, Texas, USA , and its implications on our understanding of the morphological disparity of the aetosaurian dorsal carapace

   https://doi.org/10.1002/ar.25379  

   Reyes, William A. ; Martz, Jeffrey W. ; Small, Bryan J. ( January 2024 , The Anatomical Record)

   The Late Triassic Dockum Group in northwestern Texas preserves a rich diversity of pseudosuchian taxa, particularly of aetosaurs. In this contribution, we presentGarzapelta muellerigen. et sp. nov., a new aetosaur from the Late Triassic middle Cooper Canyon Formation (latest Adamanian–earliest Revueltian teilzones) in Garza County, Texas, based on an associated specimen that preserves a significant portion of its dorsal carapace. The carapace ofG.muelleriexhibits a striking degree of similarity between that of the paratypothoracinRioarribasuchus chamaensisand desmatosuchins. We quantitatively assessed the relationships ofG.muelleriusing several iterations of the matrix. Scoring the paramedian and lateral osteoderms ofG.muelleriindependently results in conflicting topologies. Thus, it is evident that our current matrix is limited in its ability to discern the convergence within this new taxon and that our current character lists are not fully accounting for the morphological disparity of the aetosaurian carapace. Qualitative comparisons suggest thatG.muelleriis aRioarribasuchus‐like paratypothoracin with lateral osteoderms that are convergent with those of desmatosuchins. Although the shape of the dorsal eminence, and the presence of a dorsal flange that is rectangular and proportionately longer than the lateral flange are desmatosuchin‐like features ofG.muelleri, the taxon does not exhibit the articulation style between the paramedian and lateral osteoderms which diagnose the Desmatosuchini (i.e., a rigid interlocking contact, and an anteromedial edge of the lateral osteoderm that overlaps the adjacent paramedian osteoderm).

    

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