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Milleretta (Permian reptile) cranial anatomy + Triassic terrestrial tetrapod faunas of the Central European Basin + Hupehsuchus skull
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Ben Creisler
Mar 4, 2025, 2:32:55 PMMar 4
to DinosaurMa...@googlegroups.com
Ben Creisler
ZHAO Bi, ZOU Yarui, LI Jiangli, CHEN Gang, WAN Shan, YUAN Jinling & WU Kui (2025)
A new cranium material of the Early Triassic Hupehsuchus nanchangensis (Diapsida: Hupehsuchia) with a further study
Acta Geologica Sinica 99(2): 337-351 (in Chinese)
DOI: 10.19762/j.cnki.dizhixuebao.2023332
https://www.geojournals.cn/dzxbe/dzxbe/article/abstract/2023102
Free pdf:
https://www.geojournals.cn/dzxbe/dzxbe/article/pdf/2023102
Hupehsuchus nanchangensis is the most representative species of the Nanzhang-Yuanan Fauna and one of the oldest known marine reptiles. However, information regarding the key cranial features of this species remains scarce. To address this gap, a recently collected fossil specimen was carefully repaired and studied using comparative anatomical methods. This study revises the following cranial diagnoses of this species: 1. a narrow bony space develops along the midline of the skull develops along the two branches of the upper jaws; 2. the premaxillae contact each other at their anterior ends, while the nasals only contact at their posterior ends; 3. a groove is present on the premaxilla, aligned with a similar groove on the maxilla; 4. the skull roof is flat and lacks a sagittal crest; 5. the parietal bone is larger than the frontal, and the pineal foramen is located in the anteromedial part of the parietal; 6. the upper temporal fenestra is formed by parietal, postfrontal, postorbital, and squamosal bones, excluding supratemporal; 7. the jugal is a triradiate bone with a thin, elongated anterior process and a short ventral process; 8. the supraoccipital is large and nearly circular; and 9. the exoccipital has clearly visible nerve openings. Comparative analysis reveals that Hupehsuchus nanchangensis, Nanchangosaurus, and Eretmorhipis all possess bony spaces formed between the upper jaws, which may represent a homologous character of Hupehsuchia. In Hupehsuchus nanchangensis, the supratemporal does not participate in the formation of the upper temporal fenestra. In addition, this species retains morphological vestiges of the jugal' s ventral process, and its inferior temporal fenestra is not fully reduced, resembling the condition in the oldest diapsid reptiles but different from the advanced ichthyosauromorphs. It is speculated that during the evolution of ichthyosauromorphs, the supratemporal gradually shifted anteriorly and became incorporated into the upper temporal fenestra, while the inferior temporal fenestra gradually closed. The new material also shows that the external naris of Hupehsuchus nanchangensis faces dorsally, and its bite force was relatively weak. These features suggest that this species had a unique feeding mechanism distinct from other ichthyosauromorphs.
Recent papers:
Xavier A Jenkins, Roger B J Benson, Maya Elliott, Gabriel Jeppson, Kathleen Dollman, Vincent Fernandez, Claire Browning, David P Ford, Jonah Choiniere & Brandon R Peecook (2025)
New information on the anatomically derived millerettid Milleretta rubidgei from the latest Permian based on µCT data
Zoological Journal of the Linnean Society 203(3): zlaf004
doi: https://doi.org/10.1093/zoolinnean/zlaf004
https://academic.oup.com/zoolinnean/article-abstract/203/3/zlaf004/8045081
The fossil reptile Milleretta holds a prominent role in phylogenetic analyses of early reptile relationships. It has often been used as the sole marker for the anatomically diverse middle to late Permian Millerettidae, a clade that has been hypothesized as the earliest diverging parareptiles and therefore only distantly related to the reptile crown group. However, the anatomy of Milleretta remains incompletely documented, presenting an obstacle to phylogenetic studies of early reptile evolution. We re-examine the cranial anatomy of Milleretta rubidgei using synchrotron micro-computed tomography of two specimens, representing a juvenile and a subadult. These immature individuals have clearly visible sutures, differing from osteologically mature individuals, in which cranial osteoderms obscure the cranial anatomy, particularly in the antorbital region. We demonstrate that Milleretta and other millerettids share many derived similarities with Neodiapsida (a derived clade that includes the reptile crown group), particularly of the neurocranium and palatoquadrate. Comparison with other millerettids reveals that some features seen in adult specimens of Milleretta are, in fact, derived features, resulting from secondary modification in osteologically mature individuals. These observations suggest that Milleretta is an anatomically derived millerettid and urge caution in using this taxon as the semaphorant of this disparate group of stem reptiles.
=====
Eudald Mujal, Hans-Dieter Sues, Raphael Moreno, Joep Schaeffer, Gabriela Sobral, Sanjukta Chakravorti, Stephan N.F. Spiekman & Rainer R. Schoch (2025)
Triassic terrestrial tetrapod faunas of the Central European Basin, their stratigraphical distribution, and their palaeoenvironments
Earth-Science Reviews 105085
doi: https://doi.org/10.1016/j.earscirev.2025.105085
https://www.sciencedirect.com/science/article/abs/pii/S0012825225000467
Highlights
Review of Triassic terrestrial tetrapod communities from the Central European Basin.
Osteological and ichnological records provide complementary pictures of ecosystems.
Tetrapod (ichno)faunas correlated to palaeoenvironments show evolution of ecosystems.
More gradual changes from Middle to Late Triassic assemblages than previously thought.
The Central European Basin is a model for Triassic terrestrial tetrapod ecosystems.
Abstract
Since the early nineteenth century, the Central European Basin (CEB) has been a historically important region for the study of terrestrial tetrapods from the Triassic Period, and continues to yield a wealth of new finds. A review of the fossil evidence permits the recognition of new patterns of diversity for various clades during the recovery period following the end-Permian mass extinction. Unfortunately, the fossil record for tetrapods in the CEB across the Permian–Triassic boundary is virtually non-existent. The lowermost Triassic strata are almost entirely devoid of tetrapod fossils in the CEB, which is in marked contrast with coeval terrestrial deposits in higher-palaeolatitude regions such as South Africa. Temnospondyls were present in many Olenekian horizons and diversified at the beginning of the Anisian, attaining their greatest diversity in the late Ladinian, probably as a response to an increase in available freshwater environments and tolerance of fluctuating salinity in at least some forms. Among amniotes, only procolophonoids have been found in both Olenekian and Anisian strata in Germany, in each instance with two taxa, and they persisted into the late Ladinian. The ichnofaunas tell a rather different (partly complementary) story. Especially in the Olenekian, the poor body fossil record for tetrapods contrasts sharply with the abundance and high diversity of tetrapod ichnofossils, particularly those produced by archosauromorph reptiles. Large tetrapod tracks (Protochirotherium) suggest that large-bodied archosauriforms were present, but no skeletal remains of such forms have been recovered from known coeval horizons in the CEB to date. Strata of the lower Anisian have recently yielded procolophonids, rhynchosaurs, tanysaurians, a eucrocopodan archosauriform, a ‘sail-backed’ poposauroid pseudosuchian, and a drepanosauromorph. For this time interval, the body fossil record (with three temnospondyl and seven amniote taxa) approaches the diversity of the rich tetrapod track record. The differences between Middle and Late Triassic faunas are not as profound as had traditionally been assumed. Whereas there was an almost complete replacement of temnospondyl taxa except for the long-ranging Gerrothorax pulcherrimus, the composition of terrestrial amniote assemblages appears to have changed more gradually from the Anisian to the Norian. The Ladinian of southern Germany has yielded a wide range of taxa not otherwise represented in the CEB nor elsewhere. This includes several taxa of lepidosauromorphs including a rhynchocephalian, a colognathid, a trilophosaurid, a shell-less stem-turtle, an owenettid and a procolophonid, and four different archosauriform taxa. A recently discovered late Carnian assemblage from the Stuttgart Formation, which is currently under study, includes small diapsids resembling those from the Ladinian. Diverse Early and Late Triassic microvertebrate assemblages have been described from Poland in recent years, and identification of comparable depositional environments elsewhere in the CEB would undoubtedly lead to the discovery of many additional small-sized tetrapod taxa. In summary, the CEB provides an excellent record for studying the evolution of Triassic terrestrial tetrapod faunas along with environmental changes over much of that period.
Xavier A Jenkins, Roger B J Benson, Maya Elliott, Gabriel Jeppson, Kathleen Dollman, Vincent Fernandez, Claire Browning, David P Ford, Jonah Choiniere & Brandon R Peecook (2025)
New information on the anatomically derived millerettid Milleretta rubidgei from the latest Permian based on µCT data
Zoological Journal of the Linnean Society 203(3): zlaf004
doi: https://doi.org/10.1093/zoolinnean/zlaf004
https://academic.oup.com/zoolinnean/article-abstract/203/3/zlaf004/8045081
The fossil reptile Milleretta holds a prominent role in phylogenetic analyses of early reptile relationships. It has often been used as the sole marker for the anatomically diverse middle to late Permian Millerettidae, a clade that has been hypothesized as the earliest diverging parareptiles and therefore only distantly related to the reptile crown group. However, the anatomy of Milleretta remains incompletely documented, presenting an obstacle to phylogenetic studies of early reptile evolution. We re-examine the cranial anatomy of Milleretta rubidgei using synchrotron micro-computed tomography of two specimens, representing a juvenile and a subadult. These immature individuals have clearly visible sutures, differing from osteologically mature individuals, in which cranial osteoderms obscure the cranial anatomy, particularly in the antorbital region. We demonstrate that Milleretta and other millerettids share many derived similarities with Neodiapsida (a derived clade that includes the reptile crown group), particularly of the neurocranium and palatoquadrate. Comparison with other millerettids reveals that some features seen in adult specimens of Milleretta are, in fact, derived features, resulting from secondary modification in osteologically mature individuals. These observations suggest that Milleretta is an anatomically derived millerettid and urge caution in using this taxon as the semaphorant of this disparate group of stem reptiles.
=====
Eudald Mujal, Hans-Dieter Sues, Raphael Moreno, Joep Schaeffer, Gabriela Sobral, Sanjukta Chakravorti, Stephan N.F. Spiekman & Rainer R. Schoch (2025)
Triassic terrestrial tetrapod faunas of the Central European Basin, their stratigraphical distribution, and their palaeoenvironments
Earth-Science Reviews 105085
doi: https://doi.org/10.1016/j.earscirev.2025.105085
https://www.sciencedirect.com/science/article/abs/pii/S0012825225000467
Highlights
Review of Triassic terrestrial tetrapod communities from the Central European Basin.
Osteological and ichnological records provide complementary pictures of ecosystems.
Tetrapod (ichno)faunas correlated to palaeoenvironments show evolution of ecosystems.
More gradual changes from Middle to Late Triassic assemblages than previously thought.
The Central European Basin is a model for Triassic terrestrial tetrapod ecosystems.
Abstract
Since the early nineteenth century, the Central European Basin (CEB) has been a historically important region for the study of terrestrial tetrapods from the Triassic Period, and continues to yield a wealth of new finds. A review of the fossil evidence permits the recognition of new patterns of diversity for various clades during the recovery period following the end-Permian mass extinction. Unfortunately, the fossil record for tetrapods in the CEB across the Permian–Triassic boundary is virtually non-existent. The lowermost Triassic strata are almost entirely devoid of tetrapod fossils in the CEB, which is in marked contrast with coeval terrestrial deposits in higher-palaeolatitude regions such as South Africa. Temnospondyls were present in many Olenekian horizons and diversified at the beginning of the Anisian, attaining their greatest diversity in the late Ladinian, probably as a response to an increase in available freshwater environments and tolerance of fluctuating salinity in at least some forms. Among amniotes, only procolophonoids have been found in both Olenekian and Anisian strata in Germany, in each instance with two taxa, and they persisted into the late Ladinian. The ichnofaunas tell a rather different (partly complementary) story. Especially in the Olenekian, the poor body fossil record for tetrapods contrasts sharply with the abundance and high diversity of tetrapod ichnofossils, particularly those produced by archosauromorph reptiles. Large tetrapod tracks (Protochirotherium) suggest that large-bodied archosauriforms were present, but no skeletal remains of such forms have been recovered from known coeval horizons in the CEB to date. Strata of the lower Anisian have recently yielded procolophonids, rhynchosaurs, tanysaurians, a eucrocopodan archosauriform, a ‘sail-backed’ poposauroid pseudosuchian, and a drepanosauromorph. For this time interval, the body fossil record (with three temnospondyl and seven amniote taxa) approaches the diversity of the rich tetrapod track record. The differences between Middle and Late Triassic faunas are not as profound as had traditionally been assumed. Whereas there was an almost complete replacement of temnospondyl taxa except for the long-ranging Gerrothorax pulcherrimus, the composition of terrestrial amniote assemblages appears to have changed more gradually from the Anisian to the Norian. The Ladinian of southern Germany has yielded a wide range of taxa not otherwise represented in the CEB nor elsewhere. This includes several taxa of lepidosauromorphs including a rhynchocephalian, a colognathid, a trilophosaurid, a shell-less stem-turtle, an owenettid and a procolophonid, and four different archosauriform taxa. A recently discovered late Carnian assemblage from the Stuttgart Formation, which is currently under study, includes small diapsids resembling those from the Ladinian. Diverse Early and Late Triassic microvertebrate assemblages have been described from Poland in recent years, and identification of comparable depositional environments elsewhere in the CEB would undoubtedly lead to the discovery of many additional small-sized tetrapod taxa. In summary, the CEB provides an excellent record for studying the evolution of Triassic terrestrial tetrapod faunas along with environmental changes over much of that period.
====
====
Free pdf:
ZHAO Bi, ZOU Yarui, LI Jiangli, CHEN Gang, WAN Shan, YUAN Jinling & WU Kui (2025)
A new cranium material of the Early Triassic Hupehsuchus nanchangensis (Diapsida: Hupehsuchia) with a further study
Acta Geologica Sinica 99(2): 337-351 (in Chinese)
DOI: 10.19762/j.cnki.dizhixuebao.2023332
https://www.geojournals.cn/dzxbe/dzxbe/article/abstract/2023102
Free pdf:
https://www.geojournals.cn/dzxbe/dzxbe/article/pdf/2023102
Hupehsuchus nanchangensis is the most representative species of the Nanzhang-Yuanan Fauna and one of the oldest known marine reptiles. However, information regarding the key cranial features of this species remains scarce. To address this gap, a recently collected fossil specimen was carefully repaired and studied using comparative anatomical methods. This study revises the following cranial diagnoses of this species: 1. a narrow bony space develops along the midline of the skull develops along the two branches of the upper jaws; 2. the premaxillae contact each other at their anterior ends, while the nasals only contact at their posterior ends; 3. a groove is present on the premaxilla, aligned with a similar groove on the maxilla; 4. the skull roof is flat and lacks a sagittal crest; 5. the parietal bone is larger than the frontal, and the pineal foramen is located in the anteromedial part of the parietal; 6. the upper temporal fenestra is formed by parietal, postfrontal, postorbital, and squamosal bones, excluding supratemporal; 7. the jugal is a triradiate bone with a thin, elongated anterior process and a short ventral process; 8. the supraoccipital is large and nearly circular; and 9. the exoccipital has clearly visible nerve openings. Comparative analysis reveals that Hupehsuchus nanchangensis, Nanchangosaurus, and Eretmorhipis all possess bony spaces formed between the upper jaws, which may represent a homologous character of Hupehsuchia. In Hupehsuchus nanchangensis, the supratemporal does not participate in the formation of the upper temporal fenestra. In addition, this species retains morphological vestiges of the jugal' s ventral process, and its inferior temporal fenestra is not fully reduced, resembling the condition in the oldest diapsid reptiles but different from the advanced ichthyosauromorphs. It is speculated that during the evolution of ichthyosauromorphs, the supratemporal gradually shifted anteriorly and became incorporated into the upper temporal fenestra, while the inferior temporal fenestra gradually closed. The new material also shows that the external naris of Hupehsuchus nanchangensis faces dorsally, and its bite force was relatively weak. These features suggest that this species had a unique feeding mechanism distinct from other ichthyosauromorphs.
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