Vertebrate Paleontology Research Articles

Cerinichthys koelblae, gen. et sp. nov., from the Upper Jurassic of Cerin, France, and its phylogenetic setting, leading to a reassessment of the phylogenetic relationships of Halecomorphi (Actinopterygii)

ABSTRACTUnknown, well-preserved fish specimens from the Upper Jurassic Plattenkalk of Cerin, France, found in the historical collection in Muséum d'Histoire Naturelle de Lyon, France, and from the excavation site of the Collections de Géologie, Université Claude Bernard Lyon 1, France, permit description of Cerinichthys koelblae, gen. et sp. nov. This new genus differs from all other Halecomorphi in the following combination of features: 27 caudal principal rays; 51 vertical scale rows; presence of broadened basal fin segments in the posterior rays of the pectoral, pelvic, anal, and dorsal fins and the median rays of the caudal fin; complete absence of vertebral centra in adult-sized individuals and multiple small scales in the median and ventral parts of the caudal peduncle. Investigations concerning the phylogenetic setting of the new genus Cerinichthys led to a proposal for a revision of the Halecomorphi, with Cerinichthys as a basal member of the new order Ophiopsiformes. The new family Ophiopsiellidae, as replacement for Ophiopsidae, within the Ophiopsiformes, are ganoin-scaled Halecomorphi with one horizontally elongated dorsal fin or two dorsal fins. The Ionoscopidae are proposed to belong in the Amiiformes, and the order Ionoscopiformes needs to be reconsidered. The more basal Halecomorphi with massive ganoin scales remain poorly known, compared with the more advanced halecomorph group of the Amiidae. Closer investigation of their morphology and taxonomic relationships is therefore important for understanding broader patterns of halecomorph evolution.http://zoobank.org/urn:lsid:zoobank.org:pub:0D13F672-DBC1-4484-AE30-7D360DCD3123SUPPLEMENTAL DATA—Supplemental materials are available for this article for free at www.tandfonline.com/UJVPCitation for this article: Ebert, M. 2018. Cerinichthys koelblae, gen. et sp. nov., from the Upper Jurassic of Cerin, France, and its phylogenetic setting, leading to a reassessment of the phylogenetic relationships of Halecomorphi (Actinopterygii). Journal of Vertebrate Paleontology. DOI: 10.1080/02724634.2017.1420071.

The air-abrasive technique: A re-evaluation of its use in fossil preparation

Copyright: August 2018 Society of Vertebrate Paleontology. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Institute of Vertebrate Paleontology and Paleoanthropology

Institute of Vertebrate Paleontology and Paleoanthropology

Why fossil scientists are suing Trump over monuments move.

Downsizing of Utah preserves puts unique deposits at risk of damage from development, researchers argue.

Updated geology and vertebrate paleontology of the Triassic Ntawere Formation of northeastern Zambia, with special emphasis on the archosauromorphs

ABSTRACTThe two vertebrate fossil assemblages from the ?Middle Triassic Ntawere Formation have been known since the 1960s, but little new work has been done since the description of novel taxa in the 1960s and 1970s. Three recent field seasons have increased vertebrate diversity in the upper Ntawere assemblage and expanded biostratigraphic connections between the lower and upper Ntawere assemblages and assemblages in fossiliferous basins across southern Pangea. The upper Ntawere contains hybodontoid sharks, ptychoceratodontid lungfish, large- and small-bodied stereospondyl amphibians (Cherninia, ‘Stanocephalosaurus,’ Batrachosuchus, a new taxon), stahleckeriid dicynodonts (Sangusaurus, Zambiasaurus), traversodontid and trirachodontid cynodonts (Luangwa, a new species, Cricodon), and at least four archosauromorphs, including a large loricatan pseudosuchian, a shuvosaurid poposauroid, and silesaurid dinosauriforms (Lutungutali), whereas the lower Ntawere contains the cynodonts Cynognathus and Diademodon and species of the dicynodont Kannemeyeria. The lower and upper Ntawere assemblages have been correlated with the middle and upper subzones of the Cynognathus Assemblage Zone of the Karoo Basin, South Africa, into a network of connections between assemblages in modern day Tanzania, Argentina, Brazil, Namibia, Antarctica, and India. Although lower Ntawere correlations are reinforced by the occurrence of Cynognathus, new observations from the upper Ntawere, in combination with field work in Tanzania, Namibia, and Brazil, have shifted the geographic focus of biostratigraphic connection away from the Karoo later in the Triassic. A recent radiometric date from Argentina from below the horizon correlated with both the Karoo and the lower Ntawere places these, and all higher assemblages, into the Carnian Stage of the Late Triassic.Citation for this article: Peecook, B. R., J. S. Steyer, N. J. Tabor, and R. M. H. Smith. 2018. Updated geology and vertebrate paleontology of the Triassic Ntawere Formation of northeastern Zambia, with special emphasis on the archosauromorphs; pp. 8–38 in C. A. Sidor and S. J. Nesbitt (eds.), Vertebrate and Climatic Evolution in the Triassic Rift Basins of Tanzania and Zambia. Society of Vertebrate Paleontology Memoir 17. Journal of Vertebrate Paleontology 37(6, Supplement).

A possible new specimen of Ruhuhuaria reiszi from the Manda Beds (?Middle Triassic) of southern Tanzania and its implications for small sauropsids in the Triassic

ABSTRACTDuring the recovery from the end-Permian extinctions in the Middle Triassic, small reptiles (<50 cm) are exceptionally rare, and this gap in the fossil record inhibits our understanding of small reptile ecology and evolution during such a critical transition in Earth history. Here, we fully describe two fragments of left and right hemimandibles of a small sauropsid (UMZC T1162) that likely belonged to the same individual. The specimen bears anteriorly enlarged dentary teeth and labiolingually expanded crown bases, two character states unique to Ruhuhuaria reiszi (Procolophonoidea: Owenettidae), a taxon recently described from the same locality. From this, we tentatively assign UMZC T1162 to Ruhuhuaria reiszi. Micro-computed tomography (CT) and scanning electron microscopy (SEM) were employed to fully examine the morphology of the new specimen and illuminate details of the teeth not available in the holotype. The dentition of UMZC T1162 is better preserved than that of the holotype and shows that the more posterior teeth of this animal were chisel-shaped rather than pointed, that at least some of the teeth were transversely expanded at the base, and that tooth implantation is acrodont in the posterior portion and pleurodont in the anterior portion of the dentary. This potential second specimen of Ruhuhuaria reiszi complicates the previously hypothesized relationships of the taxon and further illustrates the difficulties in assigning small sauropsids to various clades in the Triassic Period. If UMZC T1162 does represent another specimen of Ruhuhuaria reiszi, it would show that small Triassic sauropsids had more variation in their tooth implantation and tooth disparity than previously appreciated.Citation for this article: Bradley, A. B., and S. J. Nesbitt. 2017. A possible new specimen of Ruhuhuaria reiszi from the Manda Beds (?Middle Triassic) of southern Tanzania and its implications for small sauropsids in the Triassic; pp. 88–95 in C. A. Sidor and S. J. Nesbitt (eds.), Vertebrate and Climatic Evolution in the Triassic Rift Basins of Tanzania and Zambia. Society of Vertebrate Paleontology Memoir 17. Journal of Vertebrate Paleontology 37(6, Supplement).

Mandasuchus tanyauchen, gen. et sp. nov., a pseudosuchian archosaur from the Manda Beds (?Middle Triassic) of Tanzania

ABSTRACTThe diverse assemblage of extinct archosaur species known from the Manda Beds of Tanzania has provided key insights into the timing and tempo of the early part of the archosaur radiation during the Middle Triassic. Several archosaur specimens were collected from the Manda Beds in 1933 by F. R. Parrington, and three of these were subsequently described and made the basis of a new genus, ‘Mandasuchus,’ in a 1956 doctoral dissertation. However, this important fossil material was never formally published, and >60 years later ‘Mandasuchus’ and ‘Mandasuchus tanyauchen’ remain nomina nuda, despite frequent references to them in the literature. Here, we provide a detailed description of this material, provide the first formal diagnosis of Mandasuchus tanyauchen, gen. et sp. nov., and assess its phylogenetic position. The holotype of M. tanyauchen includes a well-preserved partial postcranial skeleton and fragmentary cranial remains. Four referred specimens include two partial skeletons, consisting primary of postcranial remains, a partial maxilla that was previously assigned to the dinosaur clade Saurischia, and a well-preserved astragalus and calcaneum that may belong to the holotype individual. Mandasuchus tanyauchen is diagnosed by a unique combination of character states, as well as by two possible autapomorphies (ascending process of maxilla thin and compressed from anterolateral to posteromedial; femur with distinct pit lateral to the distal-most expression of the posteromedial tuber). Our phylogenetic analysis recovered M. tanyauchen within Paracrocodylomorpha, as the sister taxon to all other sampled members of Loricata.http://zoobank.org/urn:lsid:zoobank.org:pub:7DA9AF92-9365-4200-AE19-C7D6AE4C4966SUPPLEMENTAL DATA—Supplemental materials are available for this article for free at www.tandfonline.com/UJVPCitation for this article: Butler, R. J., S. J. Nesbitt, A. J. Charig, D. J. Gower, and P. M. Barrett. 2018. Mandasuchus tanyauchen, gen. et sp. nov., a pseudosuchian archosaur from the Manda Beds (?Middle Triassic) of Tanzania; pp. 96–121 in C. A. Sidor and S. J. Nesbitt (eds.), Vertebrate and Climatic Evolution in the Triassic Rift Basins of Tanzania and Zambia. Society of Vertebrate Paleontology Memoir 17. Journal of Vertebrate Paleontology 37(6, Supplement).

Novel hind limb morphology in a kannemeyeriiform dicynodont from the Manda Beds (Songea Group, Ruhuhu Basin) of Tanzania

ABSTRACTA partial hind limb (femur and tibia) from the Triassic Lifua Member of the Manda Beds (Tanzania) is recognized as a new morphotype of kannemeyeriiform dicynodont. The femur of this specimen is the largest known dicynodont postcranial element from the Manda Beds and indicates an animal nearing the size of the Late Triassic Stahleckeria potens from Brazil and Namibia. This specimen also resembles both Stahleckeria and the related Argentine stahleckeriid Ischigualastia in having an unusually elongate, straight femoral shaft and a massive and bulbous femoral head, but it differs in its compact distal end of the femur and the relative gracility of both its femur and tibia. The recognition of this specimen as a novel form of Manda dicynodont indicates that as many as six distinct kannemeyeriiforms are present in the mid-to-upper Lifua Member fauna, equaling or exceeding the species richness of previously known Laurasian faunas and substantially exceeding the richness of coeval Gondwanan faunas.Citation for this article: Kammerer, C. F., K. D. Angielczyk, and S. J. Nesbitt. 2018. Novel hind limb morphology in a kannemeyeriiform dicynodont from the Manda Beds (Songea Group, Ruhuhu Basin) of Tanzania; pp. 178–188 in C. A. Sidor and S. J. Nesbitt (eds.), Vertebrate and Climatic Evolution in the Triassic Rift Basins of Tanzania and Zambia. Society of Vertebrate Paleontology Memoir 17. Journal of Vertebrate Paleontology 37(6, Supplement).

Taphonomy and paleoenvironments of Middle Triassic bone accumulations in the Lifua Member of the Manda Beds, Songea Group (Ruhuhu Basin), Tanzania

ABSTRACTWe report new data on the climate, paleoenvironments, and burial history of tetrapod fossils in the Middle Triassic Lifua Member of the Manda Beds (Songea Group) of southern Tanzania. Two bone-bearing intervals have been identified, both hosted by rubified floodplain mudrocks deposited alongside rivers that flowed from the Ruhuhu rift scarps into a series of subsiding basins under a warm, seasonally wet climate. The lower occurrence is a bonebed containing fossils of a large dicynodont (Dolichuranus), large cynodonts (Cynognathus), temnospondyls, small reptiles, and at least two archosauromorph reptiles. A chaotic melange of semiarticulated, disarticulated, and reworked bones associated with pedogenically mottled sandy siltstone is interpreted as having accumulated in a distal crevasse splay complex. The middle to upper Lifua bone accumulations are associated with floodplain pond and sheetwash deposits. Outcropping as isolated patches of strongly calcified rubified mudstones with lenses of reworked glaebule conglomerate, these accumulations contain partially articulated archosaur (Asilisaurus, Nundasuchus) and cynodont (Scalenodon) skeletons along with vertebrate coprolites and nonmarine bivalves (‘Unio’). Changes in floodplain facies, faunal assemblage, and taphonomic style between lower and middle to upper Lifua strata are similar to those recorded between the middle and upper Burgersdorp Formation (subzones B to C of the Cynognathus Assemblage Zone) of the main Karoo Basin of South Africa. We propose that an increase in mean annual temperature and rainfall in southwestern Gondwana during Early to Middle Triassic times resulted in vegetated, semipermanent water bodies in the floodplain depressions that supported a relatively diverse assemblage of herbivorous dicynodont, cynodont, and early archosaur populations.Citation for this article: Smith, R. M. H., C. A. Sidor, K. D. Angielczyk, S. J. Nesbitt, and N. J. Tabor. 2018. Taphonomy and paleoenvironments of Middle Triassic bone accumulations in the Lifua Member of the Manda Beds, Songea Group (Ruhuhu Basin), Tanzania; pp. 65–79 in C. A. Sidor and S. J. Nesbitt (eds.), Vertebrate and Climatic Evolution in the Triassic Rift Basins of Tanzania and Zambia. Society of Vertebrate Paleontology Memoir 17. Journal of Vertebrate Paleontology 37(6,Supplement).

The first occurrence of Cynognathus crateronotus (Cynodontia: Cynognathia) in Tanzania and Zambia, with implications for the age and biostratigraphic correlation of Triassic strata in southern Pangea

ABSTRACTCynognathus crateronotus is a species of large carnivorous cynodont, first named and best known from the Triassic Burgersdorp Formation (Beaufort Group, Karoo Basin) of South Africa. Fossils of the genus have also been reported from the upper Fremouw Formation of Antarctica, the Upper Omingonde Formation of Namibia, and the Río Seco de la Quebrada Formation of Argentina. Without associated cranial material, however, distinguishing the postcrania of Cynognathus from that of the closely related cynognathian, Diademodon tetragonus, has proven difficult. Here we provide a more comprehensive diagnosis for Cynognathus crateronotus and describe two novel occurrences. First, parts of a medium-sized individual were recovered from a scrambled mass of dental and semiarticulated postcranial material from the lower Ntawere Formation of Zambia, a horizon that previously produced fossils of Diademodon and Kannemeyeria. Second, a large individual was collected from a recently discovered locality within the lower part of the Lifua Member of the Manda Beds of Tanzania. A large proportion of the postcranial skeleton, along with some craniodental remains, was found ex situ in a sandy streambed just downstream from a quarry that has produced the dicynodont Dolichuranus, an azendohsaurid archosauromorph, and the avemetatarsalian Teleocrater rhadinus. The widespread occurrence of Cynognathus across southern Pangea demonstrates its utility as a biostratigraphic marker, but recently published radiometric age estimates from Argentina suggest that either the genus persisted for over 10 million years or African strata traditionally interpreted as Middle Triassic are better understood as Late Triassic in age.Citation for this article: Wynd, B. M., B. R. Peecook, M. R. Whitney, and C. A. Sidor. 2018. The first occurrence of Cynognathus crateronotus (Cynodontia: Cynognathia) in Tanzania and Zambia, with implications for the age and biostratigraphic correlation of Triassic strata in southern Pangea; pp. 228–239 in C. A. Sidor and S. J. Nesbitt (eds.), Vertebrate and Climatic Evolution in the Triassic Rift Basins of Tanzania and Zambia. Society of Vertebrate Paleontology Memoir 17. Journal of Vertebrate Paleontology 37(6, Supplement).

The anatomy of Teleocrater Rhadinus, an early avemetatarsalian from the lower portion of the Lifua Member of the Manda Beds (Middle Triassic)

ABSTRACTBird-line archosaurs (= Avemetatarsalia, the clade containing birds, dinosaurs, pterosaurs, and their kin) originated in the Triassic Period. However, the earliest evolution of this group is poorly documented because fossils are extremely rare and consist mostly of postcrania. Here, we document the osteology of Teleocrater rhadinus, an early avemetatarsalian from the lower portion of the Middle Triassic Lifua Member of the Manda Beds of the Ruhuhu Basin, southwestern Tanzania. Material of Teleocrater rhadinus includes the holotype partial skeleton comprising a single individual, including cervical, trunk, and caudal vertebrae, pectoral, pelvic, forelimb, and hind limb material, and referred specimens representing parts (skull elements, vertebrae, pectoral, pelvic, and limb elements) of at least three other individuals collected from a bonebed. Character states of the skull elements, vertebrae, girdles, and limbs indicate that Teleocrater rhadinus represents the first documented non-ornithodiran avemetatarsalian known from well-preserved, associated material. Furthermore, Teleocrater rhadinus forms part of a newly recognized clade, Aphanosauria, which also contains formerly enigmatic archosaur taxa from across Pangea, including Dongusuchus efremovi from the Middle Triassic of Russia, Yarasuchus deccanensis from the Middle Triassic of India, and Spondylosoma absconditum from the ?Middle Triassic of Brazil. This new clade and other new discoveries from the Middle to Late Triassic elucidate the sequence of character acquisitions at the base of Avemetatarsalia and fill a crucial gap in the understanding of the anatomical transformations that enabled dinosaurs to flourish later in the Mesozoic.SUPPLEMENTAL DATA—Supplemental materials are available for this article for free at www.tandfonline.com/UJVPCitation for this article: Nesbitt, S. J., R. J. Butler, M. D. Ezcurra, A. J. Charig, and P. M. Barrett. 2018. The anatomy of Teleocrater rhadinus, an early avemetatarsalian from the lower portion of the Lifua Member of the Manda Beds (Middle Triassic); pp. 142–177 in C. A. Sidor and S. J. Nesbitt (eds.), Vertebrate and Climatic Evolution in the Triassic Rift Basins of Tanzania and Zambia. Society of Vertebrate Paleontology Memoir 17. Journal of Vertebrate Paleontology 37(6, Supplement).

Cricodon metabolus (Cynodontia: Gomphodontia) from the Triassic Ntawere Formation of northeastern Zambia: patterns of tooth replacement and a systematic review of the Trirachodontidae

ABSTRACTThe partial skull and postcranial skeleton of a subadult Cricodon metabolus is described as the first record of a trirachodontid cynodont from the upper Ntawere Formation of northeastern Zambia. On the basis of features in the type and referred specimen, Cricodon metabolus can be diagnosed by the presence of a posterior cingulum in the lower postcanines that opens labially in a ‘V’-shaped notch between a large basal cuspule and the steeply descending posterior ridge of the principal labial cusp, and by a pair of large foramina on the maxillary shelf. The subadult specimen shows evidence for four series of postcanine teeth, including a wave of small gomphodont teeth being replaced by a younger wave of larger gomphodont teeth. Cladistic analysis of 75 characters in 27 cynodonts recovers Trirachodontidae as a clade that is the sister taxon of Traversodontidae. Trirachodontidae includes four species, with Langbergia modisei as the earliest diverging taxon. Our analysis also recovers ‘Trirachodon’ kannemeyeri as the sister taxon of Cricodon metabolus, leading us to transfer the former species to the genus Cricodon. Trirachodon berryi is determined to be a valid taxon that is sister to Cricodon. Two reputed trirachodontids from China, Sinognathus gracilis and Beishanodon youngi, do not appear as trirachodontids in our analysis but rather resolve as sister taxa within Traversodontidae. Although this hypothesis of relationships is not supported by the current analysis, we suggest that the two Chinese species might be probainognathians that convergently evolved expanded postcanine teeth rather than gomphodontians.Citation for this article: Sidor, C. A., and J. A. Hopson. 2018. Cricodon metabolus (Cynodontia: Gomphodontia) from the Triassic Ntawere Formation of northeastern Zambia: patterns of tooth replacement and a systematic review of the Trirachodontidae; pp. 39–64 in C. A. Sidor and S. J. Nesbitt (eds.), Vertebrate and Climatic Evolution in the Triassic Rift Basins of Tanzania and Zambia. Society of Vertebrate Paleontology Memoir 17. Journal of Vertebrate Paleontology 37(6,Supplement).

Introduction to vertebrate and climatic evolution in the Triassic Rift Basins of Tanzania and Zambia

Citation for this article: Sidor, C. A., and S. J. Nesbitt. 2018. Introduction to vertebrate and climatic evolution in the Triassic rift basins of Tanzania and Zambia; pp. 1–7 in C. A. Sidor and S. J. Nesbitt (eds.), Vertebrate and Climatic Evolution in the Triassic Rift Basins of Tanzania and Zambia. Society of Vertebrate Paleontology Memoir 17. Journal of Vertebrate Paleontology 37 (6, Supplement).

Mandaphon nadra, gen. et sp. nov., a new procolophonid from the Manda Beds of Tanzania

ABSTRACTA collaborative field work program in the Triassic of Tanzania and Zambia has produced a plethora of new fossil material. Parareptiles, however, are rare, with only one procolophonoid specimen found to date. In 2012, a new procolophonid parareptile, Mandaphon nadra, gen. et sp. nov., was discovered. The single specimen, consisting of a skull and partial postcranium, displays the autapomorphy of two raised, lozenge-shaped bosses on the quadratojugal. Whereas the posterior maxillary teeth are small, labiolingually expanded, and vaguely bicuspid, the premaxillary teeth are much larger and conical, a trait more commonly found in leptopleuronine procolophonids. The large, lozenge-shaped bosses on the quadratojugal do not correspond to additional ossification in other areas in the skull. In a phylogenetic analysis of procolophonoid relationships consisting of 59 characters and 28 procolophonoid taxa, Mandaphon appears within a poorly supported but monophyletic Leptopleuroninae, the first of this clade found in Africa. The presence of Mandaphon along with the procolophonoid Ruhuhuaria in the Manda Beds is only the third known co-occurrence of members of these two groups, with most non-procolophonid procolophonoids restricted to the Permian and Early Triassic.http://zoobank.org/urn:lsid:zoobank.org:pub:002EE9DA-1D38-41C5-9B0F-2A4BA7A90686SUPPLEMENTAL DATA–Supplemental materials are available for this article for free at www.tandfonline.com/UJVP.Citation for this article: Tsuji, L. A. 2018. Mandaphon nadra, gen. et sp. nov., a new procolophonid from the Manda Beds of Tanzania; pp. 80–87 in C. A. Sidor and S. J. Nesbitt (eds.), Vertebrate and Climatic Evolution in the Triassic Rift Basins of Tanzania and Zambia. Society of Vertebrate Paleontology Memoir 17. Journal of Vertebrate Paleontology 37(6, Supplement).

Paleosols of the Permian-Triassic: proxies for rainfall, climate change and major changes in terrestrial tetrapod diversity

ABSTRACTStable carbon isotope analysis of coexisting soil calcite and organic matter sampled from modern, California soil profiles representing 18 different U.S. Department of Agriculture (USDA) official soil series yields 51 paired calcite–organic matter δ13C values (Δ13Ccc-om values). These paired values correspond to atmospheric pCO2 estimates ranging from less than ∼100 to 2200 ppmV using standard assumed soil pCO2 concentrations at temperatures spanning the typical range of modern soil calcite crystallization. Nevertheless, there is a strong negative correlation of Δ13Ccc-om values with mean annual precipitation (MAP) among these modern sites, offering a potential means to estimate paleo-MAP values from calcite and associated, occluded organic matter in paleosols. One hundred and twenty-five Δ13Ccc-om values from lower Permian–lower Middle Triassic paleosol profiles in the southwestern U.S.A., northwestern China, and Africa are presented as a proxy for paleorainfall over ∼85° of paleolatitude. The results indicate substantial spatiotemporal variation in MAP and appear to reflect the development and strengthening of global megamonsoonal atmospheric circulation associated with assembly of the supercontinent Pangea. The data also indicate extremely low rainfall values in regions with endemic tetrapod fossil assemblages, suggesting that climate change was a principal driver of biogeography, biodiversity, and evolution of tetrapod faunas across continental landscapes during Permo-Triassic time.Citation for this article: Tabor, N. J., C. A. Sidor, R. M. H. Smith, S. J. Nesbitt, and K. Angielczyk. 2018. Paleosols of the Permian-Triassic: proxies for rainfall, climate change, and major changes in terrestrial tetrapod diversity; pp. 240–253 in C. A. Sidor and S. J. Nesbitt (eds.), Vertebrate and Climatic Evolution in the Triassic Rift Basins of Tanzania and Zambia. Society of Vertebrate Paleontology Memoir 17. Journal of Vertebrate Paleontology 37(6, Supplement).

Comparative ecological dynamics of Permian-Triassic communities from the Karoo, Luangwa, and Ruhuhu Basins of southern Africa

ABSTRACTThe Permian-Triassic mass extinction (PTME) was one of the transformative events of the Phanerozoic, marked by extinction, post-Permian transformation of surviving ecosystems, and the formation of new communities. The South African Karoo Basin has served as the primary source of data on the terrestrial component of these events, but its global applicability remains poorly known. Here, we compare Permian-Triassic communities of the Karoo Basin with those from the Luangwa and Ruhuhu basins of Zambia and Tanzania, respectively, analyzing their functional structures and simulating dynamic responses to environmental perturbation. Results show that compositional similarities of late Permian communities among the basins underlie similarities in their dynamics and resistance to secondary extinction. The Karoo Basin ecosystem also displays evidence of a transformation to increased resistance during the late Permian. Although the Karoo Basin ecosystem was reduced significantly by the PTME, structural features of that resistance persisted into the Early Triassic, facilitated by a greater susceptibility to extinction of small-body-sized amniotes and large carnivorous amniotes. It was undone by the initial stages of postextinction restructuring. Continued evolution of the Triassic ecosystem led to a recovery of resistance, but in a community compositionally dissimilar from its Permian antecedents. Likewise, the upper part of the Lifua Member of the Manda Beds (Middle Triassic) of Tanzania was structurally distinct from the Karoo Basin communities but displayed similar dynamics. The recurrence and convergence of communities with different histories toward similar dynamics suggest that there are taxon-independent norms of community assembly and function operating on geological timescales.SUPPLEMENTAL DATA—Supplemental materials are available for this article for free at www.tandfonline.com/UJVPCitation for this article: Roopnarine, P. D., K. D. Angielczyk, S. Olroyd, S. J. Nesbitt, J. Botha-Brink, B. R. Peecook, M. O. Day, and R. M. H. Smith. 2018. Comparative ecological dynamics of Permian-Triassic communities from the Karoo, Luangwa, and Ruhuhu basins of southern Africa; pp. 254–272 in C. A. Sidor and S. J. Nesbitt (eds.), Vertebrate and Climatic Evolution in the Triassic Rift Basins of Tanzania and Zambia. Society of Vertebrate Paleontology Memoir 17. Journal of Vertebrate Paleontology 37(6, Supplement).

A redescription of the Triassic kannemeyeriiform dicynodont Sangusaurus (Therapsida, Anomodontia), with an analysis of its feeding system

ABSTRACTThe Triassic dicynodont Sangusaurus is poorly known because the holotype of the first species to be described (S. edentatus from Zambia) is fragmentary, and the description of the second species (S. parringtonii from Tanzania) is extremely brief. Nevertheless, the genus has played a role in Triassic biostratigraphy by linking the Ntawere Formation and the Manda Beds. Here, we redescribe Sangusaurus, including a new, nearly complete skull from Tanzania. The incomplete holotype of S. edentatus results in few characters diagnosing the genus. The skull of S. parringtonii, however, is highly autapomorphic. The snout is telescoped, with only a thin strip of frontals separating the nasals and the parietals. The external surfaces of the premaxilla, the maxillae, the nasals, and the prefrontals are extremely rugose; a sharp median crest extends from the premaxilla to the frontals, terminating in a thickened boss. The occiput is broader than the skull is long, and the adductor fossa on the squamosal is nearly vertical. Our phylogenetic analysis shows that Sangusaurus is not a kannemeyeriid but instead is a stahleckeriid. The feeding system of Sangusaurus emphasizes an orthal jaw motion. The articular surfaces of the jaw joint form a single posteroventrally sloping surface; translating the quadrate and the articular results in a primarily orthal movement of the jaw symphysis. The internal and external jaw adductors provide a strong, dorsally-directed component to the power stroke. Adductor mechanical advantage is similar to Stahleckeria, but Sangusaurus likely had a stronger transverse component of jaw movement because of the very lateral placement of M. adductor mandibulae externus lateralis.SUPPLEMENTAL DATA—Supplemental materials are available for this article for free at www.tandfonline.com/UJVPCitation for this article: Angielczyk, K. D., P. J. Hancox, and A. Nabavizadeh. 2018. A redescription of the Triassic kannemeyeriiform dicynodont Sangusaurus (Therapsida, Anomodontia), with an analysis of its feeding system; pp. 189–227 in C. A. Sidor and S. J. Nesbitt (eds.), Vertebrate and Climatic Evolution in the Triassic Rift Basins of Tanzania and Zambia. Society of Vertebrate Paleontology Memoir 17. Journal of Vertebrate Paleontology 37(6, Supplement).

The braincase and endocast of Parringtonia gracilis, a Middle Triassic suchian (Archosaur: Pseudosuchia)

ABSTRACTThe evolution of the braincase and brain of early pseudosuchians through to the earliest crocodylomorphs is poorly understood given the paucity of specimens, lack of well-preserved material, and lack of consensus on the phylogenetic relationships of the major clades of Pseudosuchia. Here, we describe three differently sized braincases diagnosable as belonging to the archosaur Parringtonia gracilis from the Middle Triassic Manda Beds of Tanzania. One of them, a nearly complete and exceptionally preserved braincase, possesses a complex set of character states typically present in early-diverging Pseudosuchia, but it also possesses nearly all of the character states previously hypothesized to represent synapomorphies exclusive to aetosaurs and crocodylomorphs. Details of the internal anatomy and a reconstructed endocast were obtained through high-resolution computed tomographic data and show a high degree of conservation of brain architecture across Pseudosuchia, in stark contrast to the extensive shifts observed within Theropoda to crown Aves. Integrating cranial and postcranial data into a phylogenetic analysis, we find Parringtonia gracilis to be closely related to a Revueltosaurus-Aetosauria clade at the base of Suchia and distantly related to crocodylomorphs. No matter which pseudosuchian clade is the most closely related to crocodylomorphs, we deduce that homoplasy in the braincase appears to be common across Pseudosuchia.SUPPLEMENTAL DATA—Supplemental materials are available for this article for free at www.tandfonline.com/UJVPCitation for this article: Nesbitt, S. J., M. R. Stocker, W. G. Parker, T. A. Wood, C. A. Sidor, and K. D. Angielczyk. 2018. The braincase and endocast of Parringtonia gracilis, a Middle Triassic suchian (Archosauria: Pseudosuchia); pp. 122–141 in C. A. Sidor and S. J. Nesbitt (eds.), Vertebrate and Climatic Evolution in the Triassic Rift Basins of Tanzania and Zambia. Society of Vertebrate Paleontology Memoir 17. Journal of Vertebrate Paleontology 37(6,Supplement).

A well-preserved new mid-paleocene penguin (Aves, Sphenisciformes) from the Waipara Greensand in New Zealand

ABSTRACTWe describe a partial skeleton of a new stem group representative of the Sphenisciformes from the mid-Paleocene Waipara Greensand in New Zealand, which represents the best-preserved and most complete Paleocene penguin found so far. Sequiwaimanu rosieae, n. gen. et sp., is the fourth penguin species from the Waipara Greensand, which previously yielded two species that were assigned to the taxon Waimanu, in addition to leg bones of an unnamed giant penguin. Among other features, the new species is characterized by an articular facet for the furcula on the apex carinae of the sternum, which is unknown from other sphenisciforms. We perform detailed comparisons with the species assigned to Waimanu and show that the type species Waimanu manneringi differs in tarsometatarsus morphology from its putative congener ‘W.’ tuatahi, which is here assigned to the new taxon Muriwaimanu. Sequiwaimanu rosieae exhibits a more derived morphology than Muriwaimanu tuatahi, but its exact affinities to W. manneringi are unresolved owing to the incompletely known osteology of the latter species. With S. rosieae being more closely related to the crown group than M. tuatahi, shared characteristics of the two taxa are likely to be plesiomorphic for sphenisciforms. Although the skeletal morphology of these sphenisciform stem species shows some similarities to plotopterids (i.e., wing-propelled diving seabirds from the North Pacific Basin) in some characters, the stem group sphenisciforms from the Waipara Greensand are clearly distinguished from plotopterids.http://zoobank.org/urn:lsid:zoobank.org:pub:86031231-EADB-45EF-930B-8E55833D32F6SUPPLEMENTAL DATA—Supplemental materials are available for this article for free at www.tandfonline.com/UJVPCitation for this article: Mayr, G., V. L. De Pietri, L. Love, A. A. Mannering, and R. P. Scofield. 2018. A well-preserved new mid-Paleocene penguin (Aves, Sphenisciformes) from the Waipara Greensand in New Zealand. Journal of Vertebrate Paleontology. DOI: 10.1080/02724634.2017.1398169.

A new chelydroid turtle, Lutemys warreni, gen. et sp. nov., from the Upper Cretaceous (Campanian) Kaiparowits Formation of southern utah

ABSTRACTA fragmentary skeleton from the Kaiparowits Formation (Upper Campanian) of southern Utah represents a new taxon of chelydroid turtle herein named Lutemys warreni. Lutemys warreni differs from other chelydroids in the presence of a smooth shell, lack of plastral or carapacial fontanelles, and development of a thin, gracile plastron. A maximum parsimony analysis of all Late Cretaceous and early Paleogene chelydroids from Laramidia suggests that L. warreni is the most basal known stem kinosternoid. Lutemys warreni therefore represents the fourth named pan-kinosternoid from the Late Cretaceous western island landmass of Laramidia and the first named pan-kinosternoid from the Kaiparowits Formation. The description of L. warreni increases the taxonomic diversity of the Kaiparowits Formation to 16 turtle taxa, making it one of the most diverse fossil turtle assemblages.http://zoobank.org/urn:lsid:zoobank.org:pub:C199E9AE-6F3C-442A-AA12-3960B28F4066SUPPLEMENTAL DATA—Supplemental materials are available for this article for free at www.tandfonline.com/UJVPCitation for this article: Lyson, T. R., W. G. Joyce, and J. J. W. Sertich. 2017. A new chelydroid turtle, Lutemys warreni, gen. et sp. nov., from the Upper Cretaceous (Campanian) Kaiparowits Formation of southern Utah. Journal of Vertebrate Paleontology. DOI: 10.1080/02724634.2017.1390672.