Triassic: Thalattosauria evolution + Protuberum (bizarre traversodontid cynodont) from Brazil + Metoposaurus krasiejowensis mandible + more
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Ben Creisler
Sep 26, 2024, 2:47:52 PMSep 26
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Ben Creisler
Dylan Bastiaans (2024)
Thalattosauria in time and space: a review of thalattosaur spatiotemporal occurrences, presumed evolutionary relationships and current ecological hypotheses
Swiss Journal of Palaeontology 143: 36
https://doi.org/10.1186/s13358-024-00333-6
https://link.springer.com/article/10.1186/s13358-024-00333-6
In the wake of the greatest mass extinction in Earth’s history, the End-Permian Mass Extinction, the Triassic was a time of recovery and innovation. Aided by warm climatic conditions and favorable ecological circumstances, many reptilian clades originated and rapidly diversified during this time. This set the stage for numerous independent invasions of the marine realm by several reptilian clades, such as Ichthyosauriformes and Sauropterygia, shaping the oceanic ecosystems for the entire Mesozoic. Although comparatively less speciose, and temporally and latitudinally more restricted, another marine reptile clade, the Thalattosauriformes, stands out because of their unusual and highly disparate cranial, dental and skeletal morphology. Research on Thalattosauriformes has been hampered by a historic dearth of material, with the exception of rare material from Lagerstätten and highly fossiliferous localities, such as that from the UNESCO world heritage site of Monte San Giorgio. Consequently, their evolutionary origins and paleobiology remain poorly understood. The recent influx of new material from southwestern China and North America has renewed interest in this enigmatic group prompting the need for a detailed review of historic work and current views. The earliest representatives of the group may have been present from the late Early Triassic onwards in British Columbia. By the Ladinian the group had achieved a wide distribution across the northern hemisphere, spanning the eastern Panthalassic as well as the eastern and western Tethyan provinces. Distinct morphological and likely ecological differences exist between the two major clades of Thalattosauriformes, the Askeptosauroidea and the Thalattosauroidea, with the latter showing a higher degree of cranial and skeletal morphological disparity. In-group relationships remain poorly resolved beyond this bipartition. Overall, thalattosaurs may be closely related to other marine reptile groups such as ichthyopterygians and sauropterygians. However, their exact position within Diapsida remains elusive. Future focal points should utilize modern digital paleontological approaches to explore the many fragmentary specimens of otherwise poorly sampled localities.
Luca F. Quarto & Mateusz Antczak (2024)
Morphometrics of the mandible of Metoposaurus krasiejowensis Sulej, 2002 and its ecological implications
Acta Geologica Polonica 74(3): e18
doi: https://doi.org/10.24425/agp.2024.150010
https://journals.pan.pl/dlibra/publication/150010/edition/132678/content
Amphibians, due to their ecological plasticity, are some of the best environmental indicators among vertebrates nowadays and in the fossil record. One such example is the extinct family Metoposauridae Watson, 1919. Metoposaurids were abundant amphibians in Late Triassic Pangea. The remains of the genus Metoposaurus Lydekker, 1890 have been found in Germany, Poland and Portugal with three species, respectively Metoposaurus diagnosticus (Meyer, 1842), Metoposaurus krasiejowensis Sulej, 2002 and Metoposaurus algarvensis Brusatte, Butler, Mateus and Steyer, 2015. Since the majority of studies concern the skull and the pectoral girdle, in this work M. krasiejowensis has been analysed through a morphometric study of the mandible. This was made possible by the high abundance of fossils found in Krasiejów (SW Poland) in the last 20 years. The characteristics considered are the morphology of the mandible corpus and its most relevant bones, the adaptation to stress during biting and the dermal ornamentation. The results reveal that not only do these characters have great intraspecific variability, but that at least two groups of a single population of M. krasiejowensis probably had different lifestyles, one more aquatic and the other more terrestrial
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New Triassic papers:
Free pdf:
Dylan Bastiaans (2024)
Thalattosauria in time and space: a review of thalattosaur spatiotemporal occurrences, presumed evolutionary relationships and current ecological hypotheses
Swiss Journal of Palaeontology 143: 36
https://doi.org/10.1186/s13358-024-00333-6
https://link.springer.com/article/10.1186/s13358-024-00333-6
In the wake of the greatest mass extinction in Earth’s history, the End-Permian Mass Extinction, the Triassic was a time of recovery and innovation. Aided by warm climatic conditions and favorable ecological circumstances, many reptilian clades originated and rapidly diversified during this time. This set the stage for numerous independent invasions of the marine realm by several reptilian clades, such as Ichthyosauriformes and Sauropterygia, shaping the oceanic ecosystems for the entire Mesozoic. Although comparatively less speciose, and temporally and latitudinally more restricted, another marine reptile clade, the Thalattosauriformes, stands out because of their unusual and highly disparate cranial, dental and skeletal morphology. Research on Thalattosauriformes has been hampered by a historic dearth of material, with the exception of rare material from Lagerstätten and highly fossiliferous localities, such as that from the UNESCO world heritage site of Monte San Giorgio. Consequently, their evolutionary origins and paleobiology remain poorly understood. The recent influx of new material from southwestern China and North America has renewed interest in this enigmatic group prompting the need for a detailed review of historic work and current views. The earliest representatives of the group may have been present from the late Early Triassic onwards in British Columbia. By the Ladinian the group had achieved a wide distribution across the northern hemisphere, spanning the eastern Panthalassic as well as the eastern and western Tethyan provinces. Distinct morphological and likely ecological differences exist between the two major clades of Thalattosauriformes, the Askeptosauroidea and the Thalattosauroidea, with the latter showing a higher degree of cranial and skeletal morphological disparity. In-group relationships remain poorly resolved beyond this bipartition. Overall, thalattosaurs may be closely related to other marine reptile groups such as ichthyopterygians and sauropterygians. However, their exact position within Diapsida remains elusive. Future focal points should utilize modern digital paleontological approaches to explore the many fragmentary specimens of otherwise poorly sampled localities.
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Rodrigo Temp Müller, Agustín G. Martinelli, Fabiula Prestes de Bem, Maurício Rodrigo Schmitt & Leonardo Kerber (2024)
Biostratigraphic significance of a new record of Protuberum cabralense, a bizarre traversodontid cynodont from the Middle‑Late Triassic of Southern Brazil
Historical Biology (advance online publication)
doi: https://doi.org/10.1080/08912963.2024.2403603
https://www.tandfonline.com/doi/full/10.1080/08912963.2024.2403603
Traversodontid cynodonts are one of the most abundant and diverse groups of tetrapods in the Triassic assemblages of Brazil. These cynodonts are distributed across four Brazilian Assemblage Zones (AZ), ranging from the late Ladinian to the early Norian. The most taxonomically diverse record comes from the Dinodontosaurus AZ, which has so far yielded at least six traversodontid genera. Among these taxa, Protuberum cabralense represents one of the most bizarre forms. This cynodont is characterised by the presence of enlarged and rounded protuberances along the dorsal surface of the ribs, the vertebral neural spines and dorsal portion of the iliac blades. These structures have been suggested to serve as a defensive mechanism or related to burrowing/digging habits. We report the first occurrence of P. cabralense at the Linha Várzea 1 site, located in the municipality of Paraíso do Sul, Brazil. This site is considered late Ladinian to early Carnian in age. The new material consists of five rib fragments, which possess the characteristic protuberances on their dorsal surface. A biostratigraphic investigation demonstrates the absence of P. cabralense in fossiliferous sites that yielded the cynodonts Luangwa. This observation contributes to the discussion regarding a potential subdivision within the Dinodontosaurus AZ.
Rodrigo Temp Müller, Agustín G. Martinelli, Fabiula Prestes de Bem, Maurício Rodrigo Schmitt & Leonardo Kerber (2024)
Biostratigraphic significance of a new record of Protuberum cabralense, a bizarre traversodontid cynodont from the Middle‑Late Triassic of Southern Brazil
Historical Biology (advance online publication)
doi: https://doi.org/10.1080/08912963.2024.2403603
https://www.tandfonline.com/doi/full/10.1080/08912963.2024.2403603
Traversodontid cynodonts are one of the most abundant and diverse groups of tetrapods in the Triassic assemblages of Brazil. These cynodonts are distributed across four Brazilian Assemblage Zones (AZ), ranging from the late Ladinian to the early Norian. The most taxonomically diverse record comes from the Dinodontosaurus AZ, which has so far yielded at least six traversodontid genera. Among these taxa, Protuberum cabralense represents one of the most bizarre forms. This cynodont is characterised by the presence of enlarged and rounded protuberances along the dorsal surface of the ribs, the vertebral neural spines and dorsal portion of the iliac blades. These structures have been suggested to serve as a defensive mechanism or related to burrowing/digging habits. We report the first occurrence of P. cabralense at the Linha Várzea 1 site, located in the municipality of Paraíso do Sul, Brazil. This site is considered late Ladinian to early Carnian in age. The new material consists of five rib fragments, which possess the characteristic protuberances on their dorsal surface. A biostratigraphic investigation demonstrates the absence of P. cabralense in fossiliferous sites that yielded the cynodonts Luangwa. This observation contributes to the discussion regarding a potential subdivision within the Dinodontosaurus AZ.
====
Free pdf:
Luca F. Quarto & Mateusz Antczak (2024)
Morphometrics of the mandible of Metoposaurus krasiejowensis Sulej, 2002 and its ecological implications
Acta Geologica Polonica 74(3): e18
doi: https://doi.org/10.24425/agp.2024.150010
https://journals.pan.pl/dlibra/publication/150010/edition/132678/content
Amphibians, due to their ecological plasticity, are some of the best environmental indicators among vertebrates nowadays and in the fossil record. One such example is the extinct family Metoposauridae Watson, 1919. Metoposaurids were abundant amphibians in Late Triassic Pangea. The remains of the genus Metoposaurus Lydekker, 1890 have been found in Germany, Poland and Portugal with three species, respectively Metoposaurus diagnosticus (Meyer, 1842), Metoposaurus krasiejowensis Sulej, 2002 and Metoposaurus algarvensis Brusatte, Butler, Mateus and Steyer, 2015. Since the majority of studies concern the skull and the pectoral girdle, in this work M. krasiejowensis has been analysed through a morphometric study of the mandible. This was made possible by the high abundance of fossils found in Krasiejów (SW Poland) in the last 20 years. The characteristics considered are the morphology of the mandible corpus and its most relevant bones, the adaptation to stress during biting and the dermal ornamentation. The results reveal that not only do these characters have great intraspecific variability, but that at least two groups of a single population of M. krasiejowensis probably had different lifestyles, one more aquatic and the other more terrestrial
=====
=======
=======
Free pdf:
Jerry Z.X. Lei, Jon M. Husson, Martyn L. Golding, Connor S. van Wieren, Michael J. Orchard, Andrew H. Caruthers & Elizabeth S. Carter (2024)
Late Triassic carbon isotope anomalies in the Canadian Cordillera: Paleoenvironmental disturbances associated with the Norian/Rhaetian boundary and end-Triassic mass extinction event
Global and Planetary Change 242: 104563
doi: https://doi.org/10.1016/j.gloplacha.2024.104563
https://www.sciencedirect.com/science/article/pii/S0921818124002108
Highlights
Panthalassan record of Late Triassic δ13C values compiled from eight sections.
Three distinct negative excursions are observed: NRB, within Rhaetian, and TJB.
Large magnitude of some excursions suggest local amplification mechanism.
Persistent carbon cycling instability after the NRB supports protracted ETME.
Exact cause and positioning of these ETME leadup excursions remain elusive.
Abstract
The Late Triassic was a particularly turbulent interval of the geologic past, marked by repeated paleoenvironmental instability culminating in the end-Triassic mass extinction (ETME). These episodes of disturbance are associated with enhanced volcanism, harbinger of the eventual break-up of Pangea. As evidenced by geochemical signals in the marine carbon isotope record, these events were often significant enough to disrupt the global carbon cycle. However, the duration and extent of ETME-associated disturbances leading up to the Triassic/Jurassic boundary (TJB) remain contentious. The present study investigates eight stratigraphic sections from across British Columbia to create a comprehensive Panthalassan carbon isotope record spanning the Norian to early Hettangian. Three distinct negative excursions are observed: an excursion proximal to the Norian/Rhaetian boundary (NRB), another excursion within the Rhaetian, and a final excursion coinciding with the TJB. This is generally consistent with prior studies, but suggests there may be no clear distinction between the negative excursion associated with the NRB, and the oldest Rhaetian “precursor” excursion proposed to be associated with the TJB. Several of the excursions observed in the present study are too large in magnitude to plausibly reflect global ocean water chemistry (∼10 ‰ compared to the expected ∼3 ‰), indicating some local mechanism was amplifying these carbon isotope excursions. A potential explanation is increased organic carbon respiration in restricted marine environments, triggered during episodes of paleoenvironmental disturbance. Regardless, this evidence for repeated carbon isotope excursions supports paleontological data suggesting that the ETME is not a singular and geologically instantaneous event at the TJB, but is instead the amalgamation of several turnovers beginning as early as the NRB.
Jerry Z.X. Lei, Jon M. Husson, Martyn L. Golding, Connor S. van Wieren, Michael J. Orchard, Andrew H. Caruthers & Elizabeth S. Carter (2024)
Late Triassic carbon isotope anomalies in the Canadian Cordillera: Paleoenvironmental disturbances associated with the Norian/Rhaetian boundary and end-Triassic mass extinction event
Global and Planetary Change 242: 104563
doi: https://doi.org/10.1016/j.gloplacha.2024.104563
https://www.sciencedirect.com/science/article/pii/S0921818124002108
Highlights
Panthalassan record of Late Triassic δ13C values compiled from eight sections.
Three distinct negative excursions are observed: NRB, within Rhaetian, and TJB.
Large magnitude of some excursions suggest local amplification mechanism.
Persistent carbon cycling instability after the NRB supports protracted ETME.
Exact cause and positioning of these ETME leadup excursions remain elusive.
Abstract
The Late Triassic was a particularly turbulent interval of the geologic past, marked by repeated paleoenvironmental instability culminating in the end-Triassic mass extinction (ETME). These episodes of disturbance are associated with enhanced volcanism, harbinger of the eventual break-up of Pangea. As evidenced by geochemical signals in the marine carbon isotope record, these events were often significant enough to disrupt the global carbon cycle. However, the duration and extent of ETME-associated disturbances leading up to the Triassic/Jurassic boundary (TJB) remain contentious. The present study investigates eight stratigraphic sections from across British Columbia to create a comprehensive Panthalassan carbon isotope record spanning the Norian to early Hettangian. Three distinct negative excursions are observed: an excursion proximal to the Norian/Rhaetian boundary (NRB), another excursion within the Rhaetian, and a final excursion coinciding with the TJB. This is generally consistent with prior studies, but suggests there may be no clear distinction between the negative excursion associated with the NRB, and the oldest Rhaetian “precursor” excursion proposed to be associated with the TJB. Several of the excursions observed in the present study are too large in magnitude to plausibly reflect global ocean water chemistry (∼10 ‰ compared to the expected ∼3 ‰), indicating some local mechanism was amplifying these carbon isotope excursions. A potential explanation is increased organic carbon respiration in restricted marine environments, triggered during episodes of paleoenvironmental disturbance. Regardless, this evidence for repeated carbon isotope excursions supports paleontological data suggesting that the ETME is not a singular and geologically instantaneous event at the TJB, but is instead the amalgamation of several turnovers beginning as early as the NRB.
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