Xenocretosuchus jaw articulation + Permian tetrapods from Africa: Amenoyengi, new captorhinid + Madumabisa, Lystrosauravus, Mdomowabata, new dicynodonts + more
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Ben Creisler
Aug 7, 2025, 2:28:54 PM8/7/25
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Ben Creisler
Roger M. H. Smith, Christian A. Sidor, Kenneth D. Angielczyk, Sterling J. Nesbitt, J-Sébastien Steyer & Neil J. Tabor (2025)
Origin of conglomerate-hosted bonebeds at the base of the upper Permian Usili Formation, Ruhuhu Basin, Tanzania
Journal of Vertebrate Paleontology 45(sup1): Memoir 23: Vertebrate Evolution in the Permian Rift Basins of Tanzania and Zambia: e2466442
doi: https://doi.org/10.1080/02724634.2025.2466442
https://www.tandfonline.com/doi/full/10.1080/02724634.2025.2466442
A diverse conglomerate-hosted fossil tetrapod assemblage occurs in a ∼4 m-thick interval at the base of the upper Permian Usili Formation in the Ruhuhu Basin, Tanzania. The interval comprises three 0.5–1.5 m-thick erosively based fining-upward sequences. Each begins with a lenticular body of clast to matrix-supported conglomerate capped by a thin bed of massively bedded granule conglomerate and sharply overlain by fine-grained sandstone. Conglomerate intraclasts include abundant spheroidal carbonate nodules with septarian shrinkage cracks, rounded mudstone pebbles, scattered carbonate mud discs and fragments of stromatolitic limestone, all locally-to-regionally sourced from erosion of the underlying Ruhuhu Formation lacustrine and lake-plain deposits. Isolated cranial and postcranial elements of burnetiamorphs, dicynodonts, gorgonopsians, pareiasaurs, and temnospondyls occur scattered within the conglomerate and overlying gritstone beds, becoming abundant in the capping fine-grained sandstone along with silicified tree trunks. Significantly, most bones are preferentially encrusted with hematite, which suggests generally wet soil conditions with seasonal drying, and tree rings show the normal seasonal growth patterns of a humid temperate climate. The basal Usili conglomerates are attributed to a period of tectonic reorientation of the Ruhuhu rift bounding faults resulting in a basin-wide transition from deep lacustrine (upper Ruhuhu Formation) to alluvial plain with an episode of axial river incision and lateral alluvial fan progradation (basal Usili Formation) before subsidence increased to allow floodplain aggradation (lower-to-upper Usili Formation). Taphonomic signatures of most of the bones suggests they were sourced from carcasses lying exposed on terrace surfaces and in alluvial fan channels rather than from reworking of previously fossilized bones.
====
Rhineceps karibaensis, sp. nov.
J.-Sébastien Steyer & Christian A. Sidor (2025)
The first Paleozoic temnospondyl from Zambia: a new species of Rhineceps from the Permian Madumabisa Mudstone Formation, Mid-Zambezi Basin
Journal of Vertebrate Paleontology 45(sup1): Memoir 23: Vertebrate Evolution in the Permian Rift Basins of Tanzania and Zambia: 2451312
doi: https://doi.org/10.1080/02724634.2025.2451312
https://www.tandfonline.com/doi/full/10.1080/02724634.2025.2451312
The Permian temnospondyl fossil record of South Africa’s Karoo Basin is well known but preserves a relatively low abundance and low diversity assemblage composed exclusively of rhinesuchids (viz., Lacosaurus, Rhinesuchoides, Rhinesuchus, and Uranocentrodon). Elsewhere in southern Pangea, temnospondyl taxonomic diversity is even lower, with coeval deposits yielding endemic forms such as Rhineceps nyasaensis from the Chiweta Beds of Malawi and Peltobatrachus pustulatus from the Usili Formation of Tanzania. Permian rocks are present in both the Mid-Zambezi and Luangwa basins of Zambia, but neither has yielded diagnostic temnospondyl fossils so far. Here we describe two nearly complete temnospondyl skulls from the lower portion of the upper Madumabisa Mudstone Formation of southern Zambia’s Mid-Zambezi Basin. These medium-sized skulls both show a subtriangular general outline with a well-developed snout, relatively large orbits, very posterolaterally extended tabulars, a small internarial opening on the dorsal surface of the snout, and a large, heart-shaped anteropalatal depression. We refer these specimens to a new species of rhinesuchid, Rhineceps karibaensis, sp. nov., which enlarges the geographic and stratigraphic range of the genus. The results of an updated cladistic analysis suggest that Rhineceps karibaensis, sp. nov. is the sister taxon of Rhineceps nyasaensis from Malawi. Our recognition of a rhinesuchid in southern Zambia increases the diversity of the amphibian fauna in southern Pangea prior to the end-Permian mass extinction and confirms the broad distribution of rhinesuchids across the region.
====
Amenoyengi mpunduensis gen. et sp. nov.
Xavier A. Jenkins, Claire Browning, Jonah Choiniere & Brandon R. Peecook (2025)
A new moradisaurine captorhinid from the Upper Permian (Lopingian) upper Madumabisa Mudstone Formation (Luangwa Basin) of Zambia
Journal of Vertebrate Paleontology 45(sup1): Memoir 23: Vertebrate Evolution in the Permian Rift Basins of Tanzania and Zambia: e2427529
doi: https://doi.org/10.1080/02724634.2024.2427529
https://www.tandfonline.com/doi/full/10.1080/02724634.2024.2427529
Captorhinidae are a diverse group of early or stem amniotes that were dominant components of early Permian terrestrial ecosystems, and one of the first reptiliomorphs to experiment with high-fiber herbivory. Moradisaurinae is a clade of large-bodied captorhinids that evolved by the middle Kungurian (∼280 Ma) and that possess multiple tooth rows on the maxilla and dentary. Here, we describe Amenoyengi mpunduensis gen. et sp. nov., a diminutive moradisaurine captorhinid from the Lopingian upper Madumabisa Mudstone Formation of the Luangwa Basin, Zambia and therefore one of the geologically youngest captorhinids. Amenoyengi bears a mosaic of cranial features including few maxillary tooth rows, a maxillary diastema, and caniniform teeth in the maxilla and dentary. An updated phylogenetic analysis places Amenoyengi mpunduensis as the sister taxon of Gansurhinus, a relationship supported by five unambiguous characters including a low number of maxillary tooth positions and tooth rows and the presence of a maxillary diastema. Our results indicate that moradisaurine interrelationships are influenced by ontogenetically variable characters, in agreement with recent studies. We review other late occurrences of Captorhinidae, and find that several, unnamed post-Cisuralian and small-bodied captorhinids can be referred to Moradisaurinae, and note that captorhinid specimens are unknown from later than the Wuchiapingian stage of the late Permian, and therefore the clade is not necessarily a victim of the end-Permian Mass Extinction.
======
Euptychognathus kingae, sp. nov.
Madumabisa opainion, gen. et sp. nov.
Lystrosauravus bothae, gen. et sp. nov.
Christian F. Kammerer, Kenneth D. Angielczyk & Jörg Fröbisch (2025)
Permian origins of the Lystrosauridae (Therapsida: Dicynodontia)
Journal of Vertebrate Paleontology 45(sup1): Memoir 23: Vertebrate Evolution in the Permian Rift Basins of Tanzania and Zambia: e2451813
doi: https://doi.org/10.1080/02724634.2025.2451813
https://www.tandfonline.com/doi/full/10.1080/02724634.2025.2451813
New material referable to the dicynodont family Lystrosauridae from the Permian of southern Africa is described. Three lystrosaurid species are recognized in the upper Madumabisa Mudstone Formation of the Luangwa Basin, Zambia, of which two are new (Euptychognathus kingae, sp. nov. and Madumabisa opainion, gen. et sp. nov.). Another new taxon, Lystrosauravus bothae, gen. et sp. nov., is described from the Cistecephalus Assemblage Zone of the South African Beaufort Group. The range of Euptychognathus bathyrhynchus is expanded, with new records from Zambia and possibly Zimbabwe. The holotype of the supposed basally branching lystrosaurid Kwazulusaurus shakai is reinterpreted as a juvenile specimen of Lystrosaurus. Inclusion of the new lystrosaurid taxa in a phylogenetic analysis of anomodonts recovers Madumabisa as the sister-taxon to Euptychognathus and Lystrosauravus as the sister-taxon to Lystrosaurus. Madumabisa is a relatively abundant taxon in the uppermost levels of the Madumabisa Mudstone Formation, indicating that lystrosaurids were not uniformly rare prior to habitat disruption surrounding the Permo–Triassic mass extinction, when Lystrosaurus became a hyper-abundant component of terrestrial faunas. The general morphological similarity of the Permian lystrosaurids to Lystrosaurus itself indicates that the unusual cranial morphology of this group did not evolve in response to pressures associated with the mass extinction, but may have been preadaptations aiding its survival.
====
Aulacephalodon kapoliwacela, sp. nov.
Henry N. Thomas, Kenneth D. Angielczyk & Brandon R. Peecook (2025)
The first geikiid dicynodont, Aulacephalodon kapoliwacela, sp. nov. (Therapsida, Anomodontia), from the upper Madumabisa Mudstone Formation, Zambia
Journal of Vertebrate Paleontology 45(sup1): Memoir 23: Vertebrate Evolution in the Permian Rift Basins of Tanzania and Zambia: e2446603
doi: https://doi.org/10.1080/02724634.2024.2446603
https://www.tandfonline.com/doi/full/10.1080/02724634.2024.2446603
Mdomowabata trilobops, gen. et sp. nov.
Kenneth D. Angielczyk & Benjamin K. A. Otoo (2025)
A new cryptodont dicynodont (Therapsida, Anomodontia) from the Lopingian Usili Formation, Ruhuhu Basin, Tanzania
Journal of Vertebrate Paleontology 45(sup1): Memoir 23: Vertebrate Evolution in the Permian Rift Basins of Tanzania and Zambia: 2441898
https://doi.org/10.1080/02724634.2024.2441898
https://www.tandfonline.com/doi/full/10.1080/02724634.2024.2441898
Cryptodontia is a diverse and widespread group of Permian dicynodonts, although its exact membership has been a subject of uncertainty in recent phylogenetic analyses. Cryptodont fossils were first reported from the Lopingian Usili Formation (Ruhuhu Basin, Tanzania) in 1932, with the current composition of the Usili cryptodont assemblage emerging from taxonomic revisions in the mid-2000s. Here we describe a new cryptodont, Mdomowabata trilobops, gen. et sp. nov., from the Usili Formation. Diagnostic characters of M. trilobops include: transversely expanded caniniform process of the maxilla that has a bluntly rounded ventral tip; paired nasal bosses; hatchet-shaped exposure of the postfrontal on the dorsal surface of the skull; parietals that are widely exposed dorsally; intertemporal portion of the postorbital that is oriented vertically with a concave lateral surface; triangular exposure of the postparietal on the skull roof; low, close-set anterior median palatal ridges; large palatine pad with a rugose posterior section and a smoother anterior section that is flush with the premaxillary secondary palate; transversely broad and anteroposteriorly short symphyseal region of the mandible; and prominent, round muscle scar anterior to the external mandibular fenestra. The plow-shaped snout and evidence of increased facial sensitivity suggest that Mdomowabata used its snout to interact with the substrate. A phylogenetic analysis recovers M. trilobops within a monophyletic Cryptodontia, on the stem leading to a clade comprising Oudenodontidae and Rhachiocephalidae. However, persistent problems in recovering stable relationships suggest that a critical reassessment of the character data underlying current dicynodont phylogenies is needed.
Some new non-dino papers:
Alexander O. Averianov, Alexey V. Lopatin, Dmitry A. Slobodin, Pavel P. Skutschas & Olga N. Vladimirova (2025)
Dentary–squamosal jaw articulation in a late surviving tritylodontid synapsid from the Early Cretaceous of Western Siberia, Russia
Journal of Mammalian Evolution 32: 32
https://doi.org/10.1007/s10914-025-09775-2
https://link.springer.com/article/10.1007/s10914-025-09775-2
The late Early Cretaceous (Aptian) tritylodontid synapsid Xenocretosuchus sibiricus from Western Siberia, Russia, exhibits a dentary–squamosal contact formed by a distinct condyloid process. This is a new case of independent development of the dentary–squamosal jaw articulation in synapsids, after that observed in derived ictidosaurs and mammaliaforms. The articular process of the dentary is remarkable for its length and is separated by a deep cleft from the condyloid process in Xenocretosuchus. It is hypothesised that the former covered the quadrate and the postdentary bones dorsally. The main function of the quadrate and the postdentary bones was sound transmission, suggesting that the dentary–squamosal articulation played the main role in load bearing in Xenocretosuchus. This is supported by the extreme development of the mandibular middle ear in Xenocretosuchus which may be related to the fossorial adaptations seen in the late surviving tritylodontids.
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Dentary–squamosal jaw articulation in a late surviving tritylodontid synapsid from the Early Cretaceous of Western Siberia, Russia
Journal of Mammalian Evolution 32: 32
https://doi.org/10.1007/s10914-025-09775-2
https://link.springer.com/article/10.1007/s10914-025-09775-2
The late Early Cretaceous (Aptian) tritylodontid synapsid Xenocretosuchus sibiricus from Western Siberia, Russia, exhibits a dentary–squamosal contact formed by a distinct condyloid process. This is a new case of independent development of the dentary–squamosal jaw articulation in synapsids, after that observed in derived ictidosaurs and mammaliaforms. The articular process of the dentary is remarkable for its length and is separated by a deep cleft from the condyloid process in Xenocretosuchus. It is hypothesised that the former covered the quadrate and the postdentary bones dorsally. The main function of the quadrate and the postdentary bones was sound transmission, suggesting that the dentary–squamosal articulation played the main role in load bearing in Xenocretosuchus. This is supported by the extreme development of the mandibular middle ear in Xenocretosuchus which may be related to the fossorial adaptations seen in the late surviving tritylodontids.
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Journal of Vertebrate Paleontology Memoir 23: Vertebrate Evolution in the Permian Rift Basins of Tanzania and Zambia
*******
Articles:
Articles:
Roger M. H. Smith, Christian A. Sidor, Kenneth D. Angielczyk, Sterling J. Nesbitt, J-Sébastien Steyer & Neil J. Tabor (2025)
Origin of conglomerate-hosted bonebeds at the base of the upper Permian Usili Formation, Ruhuhu Basin, Tanzania
Journal of Vertebrate Paleontology 45(sup1): Memoir 23: Vertebrate Evolution in the Permian Rift Basins of Tanzania and Zambia: e2466442
doi: https://doi.org/10.1080/02724634.2025.2466442
https://www.tandfonline.com/doi/full/10.1080/02724634.2025.2466442
A diverse conglomerate-hosted fossil tetrapod assemblage occurs in a ∼4 m-thick interval at the base of the upper Permian Usili Formation in the Ruhuhu Basin, Tanzania. The interval comprises three 0.5–1.5 m-thick erosively based fining-upward sequences. Each begins with a lenticular body of clast to matrix-supported conglomerate capped by a thin bed of massively bedded granule conglomerate and sharply overlain by fine-grained sandstone. Conglomerate intraclasts include abundant spheroidal carbonate nodules with septarian shrinkage cracks, rounded mudstone pebbles, scattered carbonate mud discs and fragments of stromatolitic limestone, all locally-to-regionally sourced from erosion of the underlying Ruhuhu Formation lacustrine and lake-plain deposits. Isolated cranial and postcranial elements of burnetiamorphs, dicynodonts, gorgonopsians, pareiasaurs, and temnospondyls occur scattered within the conglomerate and overlying gritstone beds, becoming abundant in the capping fine-grained sandstone along with silicified tree trunks. Significantly, most bones are preferentially encrusted with hematite, which suggests generally wet soil conditions with seasonal drying, and tree rings show the normal seasonal growth patterns of a humid temperate climate. The basal Usili conglomerates are attributed to a period of tectonic reorientation of the Ruhuhu rift bounding faults resulting in a basin-wide transition from deep lacustrine (upper Ruhuhu Formation) to alluvial plain with an episode of axial river incision and lateral alluvial fan progradation (basal Usili Formation) before subsidence increased to allow floodplain aggradation (lower-to-upper Usili Formation). Taphonomic signatures of most of the bones suggests they were sourced from carcasses lying exposed on terrace surfaces and in alluvial fan channels rather than from reworking of previously fossilized bones.
====
Rhineceps karibaensis, sp. nov.
J.-Sébastien Steyer & Christian A. Sidor (2025)
The first Paleozoic temnospondyl from Zambia: a new species of Rhineceps from the Permian Madumabisa Mudstone Formation, Mid-Zambezi Basin
Journal of Vertebrate Paleontology 45(sup1): Memoir 23: Vertebrate Evolution in the Permian Rift Basins of Tanzania and Zambia: 2451312
doi: https://doi.org/10.1080/02724634.2025.2451312
https://www.tandfonline.com/doi/full/10.1080/02724634.2025.2451312
The Permian temnospondyl fossil record of South Africa’s Karoo Basin is well known but preserves a relatively low abundance and low diversity assemblage composed exclusively of rhinesuchids (viz., Lacosaurus, Rhinesuchoides, Rhinesuchus, and Uranocentrodon). Elsewhere in southern Pangea, temnospondyl taxonomic diversity is even lower, with coeval deposits yielding endemic forms such as Rhineceps nyasaensis from the Chiweta Beds of Malawi and Peltobatrachus pustulatus from the Usili Formation of Tanzania. Permian rocks are present in both the Mid-Zambezi and Luangwa basins of Zambia, but neither has yielded diagnostic temnospondyl fossils so far. Here we describe two nearly complete temnospondyl skulls from the lower portion of the upper Madumabisa Mudstone Formation of southern Zambia’s Mid-Zambezi Basin. These medium-sized skulls both show a subtriangular general outline with a well-developed snout, relatively large orbits, very posterolaterally extended tabulars, a small internarial opening on the dorsal surface of the snout, and a large, heart-shaped anteropalatal depression. We refer these specimens to a new species of rhinesuchid, Rhineceps karibaensis, sp. nov., which enlarges the geographic and stratigraphic range of the genus. The results of an updated cladistic analysis suggest that Rhineceps karibaensis, sp. nov. is the sister taxon of Rhineceps nyasaensis from Malawi. Our recognition of a rhinesuchid in southern Zambia increases the diversity of the amphibian fauna in southern Pangea prior to the end-Permian mass extinction and confirms the broad distribution of rhinesuchids across the region.
====
Amenoyengi mpunduensis gen. et sp. nov.
Xavier A. Jenkins, Claire Browning, Jonah Choiniere & Brandon R. Peecook (2025)
A new moradisaurine captorhinid from the Upper Permian (Lopingian) upper Madumabisa Mudstone Formation (Luangwa Basin) of Zambia
Journal of Vertebrate Paleontology 45(sup1): Memoir 23: Vertebrate Evolution in the Permian Rift Basins of Tanzania and Zambia: e2427529
doi: https://doi.org/10.1080/02724634.2024.2427529
https://www.tandfonline.com/doi/full/10.1080/02724634.2024.2427529
Captorhinidae are a diverse group of early or stem amniotes that were dominant components of early Permian terrestrial ecosystems, and one of the first reptiliomorphs to experiment with high-fiber herbivory. Moradisaurinae is a clade of large-bodied captorhinids that evolved by the middle Kungurian (∼280 Ma) and that possess multiple tooth rows on the maxilla and dentary. Here, we describe Amenoyengi mpunduensis gen. et sp. nov., a diminutive moradisaurine captorhinid from the Lopingian upper Madumabisa Mudstone Formation of the Luangwa Basin, Zambia and therefore one of the geologically youngest captorhinids. Amenoyengi bears a mosaic of cranial features including few maxillary tooth rows, a maxillary diastema, and caniniform teeth in the maxilla and dentary. An updated phylogenetic analysis places Amenoyengi mpunduensis as the sister taxon of Gansurhinus, a relationship supported by five unambiguous characters including a low number of maxillary tooth positions and tooth rows and the presence of a maxillary diastema. Our results indicate that moradisaurine interrelationships are influenced by ontogenetically variable characters, in agreement with recent studies. We review other late occurrences of Captorhinidae, and find that several, unnamed post-Cisuralian and small-bodied captorhinids can be referred to Moradisaurinae, and note that captorhinid specimens are unknown from later than the Wuchiapingian stage of the late Permian, and therefore the clade is not necessarily a victim of the end-Permian Mass Extinction.
======
Euptychognathus kingae, sp. nov.
Madumabisa opainion, gen. et sp. nov.
Lystrosauravus bothae, gen. et sp. nov.
Christian F. Kammerer, Kenneth D. Angielczyk & Jörg Fröbisch (2025)
Permian origins of the Lystrosauridae (Therapsida: Dicynodontia)
Journal of Vertebrate Paleontology 45(sup1): Memoir 23: Vertebrate Evolution in the Permian Rift Basins of Tanzania and Zambia: e2451813
doi: https://doi.org/10.1080/02724634.2025.2451813
https://www.tandfonline.com/doi/full/10.1080/02724634.2025.2451813
New material referable to the dicynodont family Lystrosauridae from the Permian of southern Africa is described. Three lystrosaurid species are recognized in the upper Madumabisa Mudstone Formation of the Luangwa Basin, Zambia, of which two are new (Euptychognathus kingae, sp. nov. and Madumabisa opainion, gen. et sp. nov.). Another new taxon, Lystrosauravus bothae, gen. et sp. nov., is described from the Cistecephalus Assemblage Zone of the South African Beaufort Group. The range of Euptychognathus bathyrhynchus is expanded, with new records from Zambia and possibly Zimbabwe. The holotype of the supposed basally branching lystrosaurid Kwazulusaurus shakai is reinterpreted as a juvenile specimen of Lystrosaurus. Inclusion of the new lystrosaurid taxa in a phylogenetic analysis of anomodonts recovers Madumabisa as the sister-taxon to Euptychognathus and Lystrosauravus as the sister-taxon to Lystrosaurus. Madumabisa is a relatively abundant taxon in the uppermost levels of the Madumabisa Mudstone Formation, indicating that lystrosaurids were not uniformly rare prior to habitat disruption surrounding the Permo–Triassic mass extinction, when Lystrosaurus became a hyper-abundant component of terrestrial faunas. The general morphological similarity of the Permian lystrosaurids to Lystrosaurus itself indicates that the unusual cranial morphology of this group did not evolve in response to pressures associated with the mass extinction, but may have been preadaptations aiding its survival.
====
Aulacephalodon kapoliwacela, sp. nov.
Henry N. Thomas, Kenneth D. Angielczyk & Brandon R. Peecook (2025)
The first geikiid dicynodont, Aulacephalodon kapoliwacela, sp. nov. (Therapsida, Anomodontia), from the upper Madumabisa Mudstone Formation, Zambia
Journal of Vertebrate Paleontology 45(sup1): Memoir 23: Vertebrate Evolution in the Permian Rift Basins of Tanzania and Zambia: e2446603
doi: https://doi.org/10.1080/02724634.2024.2446603
https://www.tandfonline.com/doi/full/10.1080/02724634.2024.2446603
The upper Madumabisa Mudstone Formation is a richly fossiliferous rock formation exposed in the Luangwa Basin in Zambia, with well-documented upper Permian vertebrate assemblages comparable to those of coeval basins in Tanzania and South Africa. The tetrapod communities of the upper Madumabisa Mudstone include 20 species of dicynodonts. Although most Permian dicynodont clades are represented in the upper Madumabisa Mudstone assemblages, the ornamented clade Geikiidae, which occurs in both the Karoo and Ruhuhu basins, has yet to be reliably reported in the Luangwa Basin; historical reports likely represent other cryptodont taxa. We report a new species of geikiid, Aulacephalodon kapoliwacela, sp. nov., known from both the lower and upper assemblages of the upper Madumabisa Mudstone Formation. This species closely resembles the abundant South African taxon Aulacephalodon bainii, including bearing robust tusks, bosses on the squamosals, and a tall ascending process of the jugal, but differs in the absence of a pineal boss and differing ontogenetic trajectories of the postfrontal and postcaniniform crests. We also provisionally rediagnose A. bainii using only characters visible in the holotype, and for the first time provide a diagnosis for the genus. Phylogenetic analysis supports a close relationship between Zambian and South African geikiids. Multiple juvenile individuals of A. kapoliwacela help clarify ontogenetic trends within Geikiidae, including differences in development and fusion of the postfrontal between geikiid species. Large wear facets on the tusks of some individuals indicate substrate-focused foraging behavior in Aulacephalodon.
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Mdomowabata trilobops, gen. et sp. nov.
Kenneth D. Angielczyk & Benjamin K. A. Otoo (2025)
A new cryptodont dicynodont (Therapsida, Anomodontia) from the Lopingian Usili Formation, Ruhuhu Basin, Tanzania
Journal of Vertebrate Paleontology 45(sup1): Memoir 23: Vertebrate Evolution in the Permian Rift Basins of Tanzania and Zambia: 2441898
https://doi.org/10.1080/02724634.2024.2441898
https://www.tandfonline.com/doi/full/10.1080/02724634.2024.2441898
Cryptodontia is a diverse and widespread group of Permian dicynodonts, although its exact membership has been a subject of uncertainty in recent phylogenetic analyses. Cryptodont fossils were first reported from the Lopingian Usili Formation (Ruhuhu Basin, Tanzania) in 1932, with the current composition of the Usili cryptodont assemblage emerging from taxonomic revisions in the mid-2000s. Here we describe a new cryptodont, Mdomowabata trilobops, gen. et sp. nov., from the Usili Formation. Diagnostic characters of M. trilobops include: transversely expanded caniniform process of the maxilla that has a bluntly rounded ventral tip; paired nasal bosses; hatchet-shaped exposure of the postfrontal on the dorsal surface of the skull; parietals that are widely exposed dorsally; intertemporal portion of the postorbital that is oriented vertically with a concave lateral surface; triangular exposure of the postparietal on the skull roof; low, close-set anterior median palatal ridges; large palatine pad with a rugose posterior section and a smoother anterior section that is flush with the premaxillary secondary palate; transversely broad and anteroposteriorly short symphyseal region of the mandible; and prominent, round muscle scar anterior to the external mandibular fenestra. The plow-shaped snout and evidence of increased facial sensitivity suggest that Mdomowabata used its snout to interact with the substrate. A phylogenetic analysis recovers M. trilobops within a monophyletic Cryptodontia, on the stem leading to a clade comprising Oudenodontidae and Rhachiocephalidae. However, persistent problems in recovering stable relationships suggest that a critical reassessment of the character data underlying current dicynodont phylogenies is needed.
======
Dicynodontoides kubwa, sp. nov.
Brenlee K. Shipps, Christian A. Sidor & Kenneth D. Angielczyk (2025)
Dicynodontoides kubwa, sp. nov. (Synapsida: Anomodontia), a new large emydopoid from the base of the Usili Formation (Ruhuhu Basin, Tanzania)
Journal of Vertebrate Paleontology 45(sup1): Memoir 23: Vertebrate Evolution in the Permian Rift Basins of Tanzania and Zambia: 2440112
doi: https://doi.org/10.1080/02724634.2024.2440112
https://www.tandfonline.com/doi/full/10.1080/02724634.2024.2440112
Approximately 40% of the vertebrate species recorded from the upper Permian Usili Formation of Tanzania are dicynodonts. Among these are several members of Emydopoidea, a clade of small- to medium-sized dicynodonts notable for their high morphological disparity. Here, we describe Dicynodontoides kubwa, sp. nov. as a new species of emydopoid from the basal conglomerate of the Usili Formation. This horizon contains endemic taxa and taxa very rare in Africa, including the enigmatic temnospondyl Peltobatrachus, the burnetiamorph Pembecephalus, and the giant gorgonopsian Inostrancevia. Like other emydopoids, the anterior dentary of Dicynodontoides kubwa is shovel-shaped and the humerus bears an ectepicondylar foramen. Within Emydopoidea, we refer this material to Dicynodontoides due to its wide lateral dentary shelf with a deep dorsal depression, lack of both dentary table and posterior dentary sulcus, and a plate-like outgrowth on the distal shaft of the fibula. Dicynodontoides kubwa is distinguished from its congeners primarily by size: all elements are at least twice as large as those of D. nowacki, making it the largest emydopoid to date. Other clear distinctions between D. kubwa and both D. nowacki and D. recurvidens include perpendicular grooves on the lateral edges of the anterior dentary and a more laterally curved ilium that has a thicker, more rounded anterior end. The recognition of a new species of Dicynodontoides adds to the complexity of the basal conglomerate tetrapod assemblage, especially how its dicynodont component relates to dicynodont diversity higher in the Usili section.
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Caroline P. Abbott, Selena A. Martinez, Jacqueline K. Lungmus, Isaac Magallanes & Kenneth D. Angielczyk (2025)
The postcranial anatomy of Kembawacela kitchingi (Therapsida, Anomodontia) and the functional diversity of cistecephalid forelimbs
Journal of Vertebrate Paleontology 45(sup1): Memoir 23: Vertebrate Evolution in the Permian Rift Basins of Tanzania and Zambia: e2486068
doi: https://doi.org/10.1080/02724634.2025.2486068
https://www.tandfonline.com/doi/full/10.1080/02724634.2025.2486068
Cistecephalid dicynodonts were one of the first amniote clades to evolve a highly specialized ecomorphology. They share a suite of postcranial characteristics indicative of fossorial lifestyle, reminiscent of modern subterranean mammals. These characters include a tall scapulocoracoid with well-defined glenoid; a robust humerus with expanded processes, significant long-axis, diaphyseal torsion, and well-developed humeral head; an elongate olecranon process of the ulna; broad manus with spatulate unguals; and interlocking vertical zygapophyses in the vertebral column. Yet within this broad morphotype, cistecephalids exhibit distinct variation. Here we describe the postcranial morphology of a specimen of Kembawacela kitchingi from the Luangwa Basin, Zambia, which highlights this variation compared with other cistecephalids. Kembawacela possesses a less specialized version of the cistecephalid body plan, with a dorsoventrally shorter scapulocoracoid; a humerus with less long-axis torsion, a less defined humeral head, and a shorter deltopectoral crest; and a shorter olecranon process of the ulna. However, Kembawacela also exhibits features not shared by other cistecephalids, including a distinctive pinna-like process on the posterior border of the humeral shaft and a prominent facet on the trochlea of the ulna for the capitulum of the humerus. A morphometric analysis of forelimb proportions in 26 extant fossorial amniotes and seven anomodonts underscores the similarity of cistecephalids to extant fossors, but also the considerable variation among cistecephalids. Our results are consistent with a hypothesis of mosaic adaptation to a substrate-moving, fossorial lifestyle in cistecephalids, making the clade a particularly interesting case study of the evolution of extreme ecomorphotypes in early amniotes.
=====
Zoe T. Kulik (2025)
Bone histology of a gorgonopsian skeleton from the upper Madumabisa Mudstone Formation, Zambia
Journal of Vertebrate Paleontology 45(sup1): Memoir 23: Vertebrate Evolution in the Permian Rift Basins of Tanzania and Zambia: 2490799
doi: https://doi.org/10.1080/02724634.2025.2490799
https://www.tandfonline.com/doi/full/10.1080/02724634.2025.2490799
Dicynodontoides kubwa, sp. nov.
Brenlee K. Shipps, Christian A. Sidor & Kenneth D. Angielczyk (2025)
Dicynodontoides kubwa, sp. nov. (Synapsida: Anomodontia), a new large emydopoid from the base of the Usili Formation (Ruhuhu Basin, Tanzania)
Journal of Vertebrate Paleontology 45(sup1): Memoir 23: Vertebrate Evolution in the Permian Rift Basins of Tanzania and Zambia: 2440112
doi: https://doi.org/10.1080/02724634.2024.2440112
https://www.tandfonline.com/doi/full/10.1080/02724634.2024.2440112
Approximately 40% of the vertebrate species recorded from the upper Permian Usili Formation of Tanzania are dicynodonts. Among these are several members of Emydopoidea, a clade of small- to medium-sized dicynodonts notable for their high morphological disparity. Here, we describe Dicynodontoides kubwa, sp. nov. as a new species of emydopoid from the basal conglomerate of the Usili Formation. This horizon contains endemic taxa and taxa very rare in Africa, including the enigmatic temnospondyl Peltobatrachus, the burnetiamorph Pembecephalus, and the giant gorgonopsian Inostrancevia. Like other emydopoids, the anterior dentary of Dicynodontoides kubwa is shovel-shaped and the humerus bears an ectepicondylar foramen. Within Emydopoidea, we refer this material to Dicynodontoides due to its wide lateral dentary shelf with a deep dorsal depression, lack of both dentary table and posterior dentary sulcus, and a plate-like outgrowth on the distal shaft of the fibula. Dicynodontoides kubwa is distinguished from its congeners primarily by size: all elements are at least twice as large as those of D. nowacki, making it the largest emydopoid to date. Other clear distinctions between D. kubwa and both D. nowacki and D. recurvidens include perpendicular grooves on the lateral edges of the anterior dentary and a more laterally curved ilium that has a thicker, more rounded anterior end. The recognition of a new species of Dicynodontoides adds to the complexity of the basal conglomerate tetrapod assemblage, especially how its dicynodont component relates to dicynodont diversity higher in the Usili section.
=====
Caroline P. Abbott, Selena A. Martinez, Jacqueline K. Lungmus, Isaac Magallanes & Kenneth D. Angielczyk (2025)
The postcranial anatomy of Kembawacela kitchingi (Therapsida, Anomodontia) and the functional diversity of cistecephalid forelimbs
Journal of Vertebrate Paleontology 45(sup1): Memoir 23: Vertebrate Evolution in the Permian Rift Basins of Tanzania and Zambia: e2486068
doi: https://doi.org/10.1080/02724634.2025.2486068
https://www.tandfonline.com/doi/full/10.1080/02724634.2025.2486068
Cistecephalid dicynodonts were one of the first amniote clades to evolve a highly specialized ecomorphology. They share a suite of postcranial characteristics indicative of fossorial lifestyle, reminiscent of modern subterranean mammals. These characters include a tall scapulocoracoid with well-defined glenoid; a robust humerus with expanded processes, significant long-axis, diaphyseal torsion, and well-developed humeral head; an elongate olecranon process of the ulna; broad manus with spatulate unguals; and interlocking vertical zygapophyses in the vertebral column. Yet within this broad morphotype, cistecephalids exhibit distinct variation. Here we describe the postcranial morphology of a specimen of Kembawacela kitchingi from the Luangwa Basin, Zambia, which highlights this variation compared with other cistecephalids. Kembawacela possesses a less specialized version of the cistecephalid body plan, with a dorsoventrally shorter scapulocoracoid; a humerus with less long-axis torsion, a less defined humeral head, and a shorter deltopectoral crest; and a shorter olecranon process of the ulna. However, Kembawacela also exhibits features not shared by other cistecephalids, including a distinctive pinna-like process on the posterior border of the humeral shaft and a prominent facet on the trochlea of the ulna for the capitulum of the humerus. A morphometric analysis of forelimb proportions in 26 extant fossorial amniotes and seven anomodonts underscores the similarity of cistecephalids to extant fossors, but also the considerable variation among cistecephalids. Our results are consistent with a hypothesis of mosaic adaptation to a substrate-moving, fossorial lifestyle in cistecephalids, making the clade a particularly interesting case study of the evolution of extreme ecomorphotypes in early amniotes.
=====
Zoe T. Kulik (2025)
Bone histology of a gorgonopsian skeleton from the upper Madumabisa Mudstone Formation, Zambia
Journal of Vertebrate Paleontology 45(sup1): Memoir 23: Vertebrate Evolution in the Permian Rift Basins of Tanzania and Zambia: 2490799
doi: https://doi.org/10.1080/02724634.2025.2490799
https://www.tandfonline.com/doi/full/10.1080/02724634.2025.2490799
Gorgonopsians were an iconic group of non-mammalian therapsids that lived during the middle–late Permian, most known for their long, saber-like canine teeth. While not close relatives of mammals, gorgonopsians share a suite of mammalian skeletal traits, but their paleobiology and growth dynamics are poorly understood. Recent histological analyses of South African (Karoo Basin) gorgonopsians show that fast, cyclic growth is typical for the clade, with environmental influences playing a key role. To assess the life history of gorgonopsians outside of the main Karoo Basin, I sampled six skeletal elements from an indeterminate species from the Luangwa Basin of Zambia. My results show that despite excellent surface preservation, the bone tissue of this species has taphonomic overprinting in the form of filamentous and globular structures that may represent bioerosion. Intact bone tissue type varies across elements, leading to differences in growth rates and vascular orientation. Growth is generally composed of parallel-fibered bone with small, longitudinal primary osteons. One growth mark appears in the femur, and growth spurts are indicated by highly vascularized bone in the tibia and radius. The individual had not reached somatic maturity before death. Compared with Karoo Basin gorgonopsians, which exhibit fast, cyclical growth with abundant growth marks, this Zambian specimen grew more slowly with fewer growth marks. This suggests that small- to medium-sized gorgonopsians displayed a range of moderate to fast growth rates during early ontogeny.
======
Alex Acker, Brandon R. Peecook, Christian A. Sidor & Megan R. Whitney (2025)
The first occurrence of Cyonosaurus (Therapsida, Gorgonopsia) from the Luangwa Basin of Zambia
Journal of Vertebrate Paleontology 45(sup1): Memoir 23: Vertebrate Evolution in the Permian Rift Basins of Tanzania and Zambia: 2444407
doi: https://doi.org/10.1080/02724634.2024.2444407
https://www.tandfonline.com/doi/full/10.1080/02724634.2024.2444407
Gorgonopsian therapsids represent the apex predators of the late Permian ecosystems they inhabited and were a taxonomically rich group known from across Africa, as well as India, western Russia, and China. Gorgonopsians from the Karoo Basin of South Africa have been densely sampled and, as a result, their taxonomy and stratigraphic distribution are well-established and serve as a baseline to which other contemporaneous localities can be compared. Here, using micro-computed tomography imaging, we describe the skull of a small-bodied gorgonopsian collected from the upper Madumabisa Mudstone Formation in the Luangwa Basin of Zambia. Based on its dentition, palatal anatomy, and postfrontal anatomy, we identify this specimen as Cyonosaurus. This record expands the geographic distribution of this gorgonopsian genus outside of the Karoo Basin and into more northern localities. The presence of Cyonosaurus in the upper Madumabisa Mudstone Formation of Zambia supports the recognition of these beds as late Wuchiapingian in age. Finally, the co-occurrence of Cyonosaurus with several other gorgonopsian species provides a system to better understand the ways body size and feeding specializations may have allowed for cryptic niche partitioning of predators in these late Permian ecosystems.
=======
Arctops umulunshi, sp. nov.
Arjan Mann & Christian A. Sidor (2025)
Arctops umulunshi, sp. nov. (Therapsida: Gorgonopsia) from the upper Madumabisa Mudstone Formation of Zambia, with new information on gorgonopsian postcranial anatomy
Journal of Vertebrate Paleontology 45(sup1): Memoir 23: Vertebrate Evolution in the Permian Rift Basins of Tanzania and Zambia: 2444405
doi: https://doi.org/10.1080/02724634.2024.2444405
https://www.tandfonline.com/doi/full/10.1080/02724634.2024.2444405
The fossil record of Zambian gorgonopsians includes reports from the Madumabisa Mudstone Formation in both the Mid-Zambezi and Luangwa basins. Despite a longer history of collection, previous reports of gorgonopsians from the Luangwa Basin have been restricted to taxonomic lists, with little in the way of voucher specimens or diagnostic features referenced. Here we introduce Arctops umulunshi, sp. nov., the type of which comprises a nearly complete skull and lower jaws, as well as a large portion of the appendicular skeleton and several vertebrae. The skull is robust and broad-snouted, with three maxillary postcanine teeth, a median vomerine ridge that is displaced anteriorly relative to the lateral ridges, and three teeth on the pterygoid transverse flange surrounded by raised rim of bone. Limb proportions suggest a stocky, strongly built carnivore and potentially diagnostic postcranial features include: atlas intercentrum substantially wider than atlas pleurocentrum, at least one accessory ectepicondylar foramen, and ungual phalanx of pedal digit five very reduced. Our phylogenetic analysis finds Smilesaurus as most closely related to A. willistoni + A. umulunshi, with Lycaenops as the immediate outgroup. These three genera are the sister taxon to a large clade including rubidgeines + Arctognathus. Despite less intensive sampling, the upper Madumabisa Mudstone Formation hosts a gorgonopsian diversity approaching that of coeval South African strata, with most of the same genera represented. Continued detailed anatomical work will further refine the tetrapod biogeography of southern Pangea as well as shed light on ecomorphological differences permitting niche partitioning among coexisting gorgonopsian species.
======
Adam K. Huttenlocker, Claire Browning, Brandon R. Peecook, Roger M. H. Smith & Pia A. Viglietti (2025)
The stratigraphic record of the therocephalian Theriognathus (Synapsida) and its utility as a biostratigraphic index in Karoo-Aged basins
Journal of Vertebrate Paleontology 45(sup1): Memoir 23: Vertebrate Evolution in the Permian Rift Basins of Tanzania and Zambia: 2441899
doi: https://doi.org/10.1080/02724634.2024.2441899
https://www.tandfonline.com/doi/full/10.1080/02724634.2024.2441899
The stratigraphic record of the whaitsiid therocephalian Theriognathus in the Karoo basins of southern Africa is reviewed, with special emphasis on biostratigraphic correlations of the Ruhuhu (Tanzania) and Luangwa (Zambia) basins. Historically, tetrapod-bearing horizons in the Usili Formation of Tanzania and upper Madumabisa Mudstone of Zambia have been inconsistently correlated to the Cistecephalus Assemblage Zone (AZ), Daptocephalus AZ, or have not been conclusively subdivided to the level of the Karoo biozonation. Recent collecting in the main Karoo Basin reference section helps to resolve the first (FAD) and last (LAD) appearance datum of Theriognathus and may reconcile the differing opinions on these formation’s age assignments. The relative abundance of Theriognathus peaks in the middle third of its range in the Daggaboersnek Member of the Balfour Formation (lower Daptocephalus AZ), but a new specimen collected from the Oukloof Member in 2020 and a review of prior records confirms the FAD of Theriognathus in the middle Cistecephalus AZ. Refinements to the FAD partly help to reconcile inconsistent age assignments for Theriognathus in the literature, especially for its occurrences in the Ruhuhu and Luangwa basins which have been most recently interpreted as Cistecephalus AZ-equivalent. We suggest that the well-documented genus Theriognathus provides a reliable biostratigraphic index for the Usili Formation and upper Madumabisa Mudstone Formation, and, in conjunction with its associated dicynodont fauna, is most consistent with the upper Cistecephalus to lower Daptocephalus AZ which has been dated as late Wuchiapingian in age (ca. 256–253 Ma).
======
Brandon R. Peecook, Christian A. Sidor, Julia A. McIntosh, Pia A. Viglietti, Roger M. H. Smith, Neil J. Tabor, Christian F. Kammerer, Jacqueline K. Lungmus, Joseph Museba, Stephen Tolan, Megan R. Whitney & Kenneth D. Angielczyk (2025)
Successive assemblages of upper Permian vertebrates in the upper Madumabisa Mudstone Formation of the Luangwa Basin, Zambia
Journal of Vertebrate Paleontology 45(sup1): Memoir 23: Vertebrate Evolution in the Permian Rift Basins of Tanzania and Zambia: e2486065
doi: https://doi.org/10.1080/02724634.2025.2486065
https://www.tandfonline.com/doi/full/10.1080/02724634.2025.2486065
The mid-Luangwa Basin has a continuous area of Permo–Triassic fossiliferous exposure, in contrast to the faulted outcrops of the northern basin where most fossils of the 20th century were collected. The richest deposits are in the upper Permian upper Madumabisa Mudstone Formation, which preserve a diverse therapsid assemblage with accompanying pareiasaurian reptiles, temnospondyl amphibians, actinopterygians, and elasmobranchs. In recent analyses of biogeography and ecosystem structure, the upper Madumabisa Mudstone fauna has been treated as a single operational unit, biostratigraphically correlated to the therapsid-dominated Cistecephalus and/or Daptocephalus assemblage zones of the South African Karoo Basin. However, increased sampling, a revised stratigraphic framework, and substantial geological observations in 2018–19 now allow us to delineate at least two distinct vertebrate assemblages from the upper member of the Madumabisa Mudstone Formation. We also identify four lithofacies including fluvial, floodplain, lacustrine, and alluvial plain facies in the lower and upper Madumabisa Mudstone. The assemblages mirror turnover events seen in the Karoo Basin between the upper subzone of the Endothiodon Assemblage Zone and the overlying lower subzone of the Daptocephalus Assemblage Zone (AZ), which bracket a shorter and relatively less well defined Cistecephalus AZ. The lower assemblage is dominated by cryptodonts such as Oudenodon and contains records of Endothiodon and Odontocyclops, whereas the upper assemblage preserves the dicynodontoids Daptocephalus, two species of Dicynodon, two novel lystrosaurid species, and the cynodont Procynosuchus. Successive assemblages in the Luangwa Basin offer a geographically distinct study system for ecosystem changes leading up to the end-Permian mass extinction.
==========
======
Alex Acker, Brandon R. Peecook, Christian A. Sidor & Megan R. Whitney (2025)
The first occurrence of Cyonosaurus (Therapsida, Gorgonopsia) from the Luangwa Basin of Zambia
Journal of Vertebrate Paleontology 45(sup1): Memoir 23: Vertebrate Evolution in the Permian Rift Basins of Tanzania and Zambia: 2444407
doi: https://doi.org/10.1080/02724634.2024.2444407
https://www.tandfonline.com/doi/full/10.1080/02724634.2024.2444407
Gorgonopsian therapsids represent the apex predators of the late Permian ecosystems they inhabited and were a taxonomically rich group known from across Africa, as well as India, western Russia, and China. Gorgonopsians from the Karoo Basin of South Africa have been densely sampled and, as a result, their taxonomy and stratigraphic distribution are well-established and serve as a baseline to which other contemporaneous localities can be compared. Here, using micro-computed tomography imaging, we describe the skull of a small-bodied gorgonopsian collected from the upper Madumabisa Mudstone Formation in the Luangwa Basin of Zambia. Based on its dentition, palatal anatomy, and postfrontal anatomy, we identify this specimen as Cyonosaurus. This record expands the geographic distribution of this gorgonopsian genus outside of the Karoo Basin and into more northern localities. The presence of Cyonosaurus in the upper Madumabisa Mudstone Formation of Zambia supports the recognition of these beds as late Wuchiapingian in age. Finally, the co-occurrence of Cyonosaurus with several other gorgonopsian species provides a system to better understand the ways body size and feeding specializations may have allowed for cryptic niche partitioning of predators in these late Permian ecosystems.
=======
Arctops umulunshi, sp. nov.
Arjan Mann & Christian A. Sidor (2025)
Arctops umulunshi, sp. nov. (Therapsida: Gorgonopsia) from the upper Madumabisa Mudstone Formation of Zambia, with new information on gorgonopsian postcranial anatomy
Journal of Vertebrate Paleontology 45(sup1): Memoir 23: Vertebrate Evolution in the Permian Rift Basins of Tanzania and Zambia: 2444405
doi: https://doi.org/10.1080/02724634.2024.2444405
https://www.tandfonline.com/doi/full/10.1080/02724634.2024.2444405
The fossil record of Zambian gorgonopsians includes reports from the Madumabisa Mudstone Formation in both the Mid-Zambezi and Luangwa basins. Despite a longer history of collection, previous reports of gorgonopsians from the Luangwa Basin have been restricted to taxonomic lists, with little in the way of voucher specimens or diagnostic features referenced. Here we introduce Arctops umulunshi, sp. nov., the type of which comprises a nearly complete skull and lower jaws, as well as a large portion of the appendicular skeleton and several vertebrae. The skull is robust and broad-snouted, with three maxillary postcanine teeth, a median vomerine ridge that is displaced anteriorly relative to the lateral ridges, and three teeth on the pterygoid transverse flange surrounded by raised rim of bone. Limb proportions suggest a stocky, strongly built carnivore and potentially diagnostic postcranial features include: atlas intercentrum substantially wider than atlas pleurocentrum, at least one accessory ectepicondylar foramen, and ungual phalanx of pedal digit five very reduced. Our phylogenetic analysis finds Smilesaurus as most closely related to A. willistoni + A. umulunshi, with Lycaenops as the immediate outgroup. These three genera are the sister taxon to a large clade including rubidgeines + Arctognathus. Despite less intensive sampling, the upper Madumabisa Mudstone Formation hosts a gorgonopsian diversity approaching that of coeval South African strata, with most of the same genera represented. Continued detailed anatomical work will further refine the tetrapod biogeography of southern Pangea as well as shed light on ecomorphological differences permitting niche partitioning among coexisting gorgonopsian species.
======
Adam K. Huttenlocker, Claire Browning, Brandon R. Peecook, Roger M. H. Smith & Pia A. Viglietti (2025)
The stratigraphic record of the therocephalian Theriognathus (Synapsida) and its utility as a biostratigraphic index in Karoo-Aged basins
Journal of Vertebrate Paleontology 45(sup1): Memoir 23: Vertebrate Evolution in the Permian Rift Basins of Tanzania and Zambia: 2441899
doi: https://doi.org/10.1080/02724634.2024.2441899
https://www.tandfonline.com/doi/full/10.1080/02724634.2024.2441899
The stratigraphic record of the whaitsiid therocephalian Theriognathus in the Karoo basins of southern Africa is reviewed, with special emphasis on biostratigraphic correlations of the Ruhuhu (Tanzania) and Luangwa (Zambia) basins. Historically, tetrapod-bearing horizons in the Usili Formation of Tanzania and upper Madumabisa Mudstone of Zambia have been inconsistently correlated to the Cistecephalus Assemblage Zone (AZ), Daptocephalus AZ, or have not been conclusively subdivided to the level of the Karoo biozonation. Recent collecting in the main Karoo Basin reference section helps to resolve the first (FAD) and last (LAD) appearance datum of Theriognathus and may reconcile the differing opinions on these formation’s age assignments. The relative abundance of Theriognathus peaks in the middle third of its range in the Daggaboersnek Member of the Balfour Formation (lower Daptocephalus AZ), but a new specimen collected from the Oukloof Member in 2020 and a review of prior records confirms the FAD of Theriognathus in the middle Cistecephalus AZ. Refinements to the FAD partly help to reconcile inconsistent age assignments for Theriognathus in the literature, especially for its occurrences in the Ruhuhu and Luangwa basins which have been most recently interpreted as Cistecephalus AZ-equivalent. We suggest that the well-documented genus Theriognathus provides a reliable biostratigraphic index for the Usili Formation and upper Madumabisa Mudstone Formation, and, in conjunction with its associated dicynodont fauna, is most consistent with the upper Cistecephalus to lower Daptocephalus AZ which has been dated as late Wuchiapingian in age (ca. 256–253 Ma).
======
Brandon R. Peecook, Christian A. Sidor, Julia A. McIntosh, Pia A. Viglietti, Roger M. H. Smith, Neil J. Tabor, Christian F. Kammerer, Jacqueline K. Lungmus, Joseph Museba, Stephen Tolan, Megan R. Whitney & Kenneth D. Angielczyk (2025)
Successive assemblages of upper Permian vertebrates in the upper Madumabisa Mudstone Formation of the Luangwa Basin, Zambia
Journal of Vertebrate Paleontology 45(sup1): Memoir 23: Vertebrate Evolution in the Permian Rift Basins of Tanzania and Zambia: e2486065
doi: https://doi.org/10.1080/02724634.2025.2486065
https://www.tandfonline.com/doi/full/10.1080/02724634.2025.2486065
The mid-Luangwa Basin has a continuous area of Permo–Triassic fossiliferous exposure, in contrast to the faulted outcrops of the northern basin where most fossils of the 20th century were collected. The richest deposits are in the upper Permian upper Madumabisa Mudstone Formation, which preserve a diverse therapsid assemblage with accompanying pareiasaurian reptiles, temnospondyl amphibians, actinopterygians, and elasmobranchs. In recent analyses of biogeography and ecosystem structure, the upper Madumabisa Mudstone fauna has been treated as a single operational unit, biostratigraphically correlated to the therapsid-dominated Cistecephalus and/or Daptocephalus assemblage zones of the South African Karoo Basin. However, increased sampling, a revised stratigraphic framework, and substantial geological observations in 2018–19 now allow us to delineate at least two distinct vertebrate assemblages from the upper member of the Madumabisa Mudstone Formation. We also identify four lithofacies including fluvial, floodplain, lacustrine, and alluvial plain facies in the lower and upper Madumabisa Mudstone. The assemblages mirror turnover events seen in the Karoo Basin between the upper subzone of the Endothiodon Assemblage Zone and the overlying lower subzone of the Daptocephalus Assemblage Zone (AZ), which bracket a shorter and relatively less well defined Cistecephalus AZ. The lower assemblage is dominated by cryptodonts such as Oudenodon and contains records of Endothiodon and Odontocyclops, whereas the upper assemblage preserves the dicynodontoids Daptocephalus, two species of Dicynodon, two novel lystrosaurid species, and the cynodont Procynosuchus. Successive assemblages in the Luangwa Basin offer a geographically distinct study system for ecosystem changes leading up to the end-Permian mass extinction.
==========
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