Pendraig milnerae , a new small-sized coelophysoid theropod from the Late Triassic of Wales

We describe a new small-bodied coelophysoid theropod dinosaur, Pendraig milnerae gen. et sp. nov, from the Late Triassic fissure fill deposits of Pant-y-ffynnon in southern Wales. The species is represented by the holotype, consisting of an articulated pelvic girdle, sacrum and posterior dorsal vertebrae, and an associated left femur, and by two referred specimens, comprising an isolated dorsal vertebra and a partial left ischium. Our phylogenetic analysis recovers P. milnerae as a non-coelophysid coelophysoid theropod, representing the first-named unambiguous theropod from the Triassic of the UK. Recently, it has been suggested that Pant-y-ffynnon and other nearby Late Triassic to Early Jurassic fissure fill faunas might have been subjected to insular dwarfism. To test this hypothesis for P. milnerae , we performed an ancestral state reconstruction analysis of body size in early neotheropods. Although our results indicate that a reduced body size is autapomorphic for P. milnerae , some other coelophysoid taxa show a similar size reduction, and there is, therefore, ambiguous evidence to indicate that this species was subjected to dwarfism. Our analyses further indicate that, in contrast with averostran-line neotheropods, which increased in body size during the Triassic, coelophysoids underwent a small body size decrease early in their evolution.

Nature and significance of rift-related, near-surface fissure-fill networks in fractured carbonates below regional unconformities

Fissure-fill networks are a widely recognized, but relatively little described, near-surface phenomenon (<1–2 km) hosted in carbonate and crystalline basement rocks below regional unconformities. Faults and fractures in otherwise tight Devonian carbonate basement rocks of the Tor Bay region, Devon, SW England are associated with the development of millimetre- to decametre-wide fissures containing red-coloured early Permian sedimentary material, vuggy calcite mineralization and wall rock collapse breccia. These features preserve evidence about the style and history of fault deformation and reactivation in near-surface settings and on fluid-related processes, such as elutriation and/or mineralization. Field observations, palaeostress analysis and fracture topology analyses show that the rift-related faults and fractures created a network of long-lived open cavities during the development of the Portland–Wight Basin in the early Permian. Once formed, they were subjected to episodic, probably seismically induced, fluid fluxing events and local karstification. The large, well-connected networks of naturally propped fractures were (and possibly still are) important fluid migration pathways within otherwise low-permeability host rocks. These structures are probably equivalent to those observed in many other rift-related, near-surface tectonic settings and suggest that the Tor Bay outcrops can be used as a global analogue for sub-unconformity open fissure systems hosted in low-permeability basement rocks.Supplementary material: Appendix A is available at https://doi.org/10.6084/m9.figshare.c.5023103

Bone histology of varanopids (Synapsida) from Richards Spur, Oklahoma, sheds light on growth patterns and lifestyle in early terrestrial colonizers

Varanopids were a group of small to medium-sized synapsids whose fossil record spans the Carboniferous through middle Permian. Although their phylogenetic relationships have received some interest in recent years, little is known about other aspects of their palaeobiology, including their skeletal growth, allometry and habitat preference. Here, we describe varanopid long bone histology based on a sample of well-preserved femora from the lower Permian Richards Spur fissure fill locality, Comanche County, Oklahoma, USA. The sample includes five femora from at least two varanopid taxa— Mycterosaurus and the large varanodontine Varanops brevirostris —and four additional mycterosaurine femora not diagnosed to genus. Prior work on femoral bone compactness provided a baseline to make lifestyle inferences and evaluate whether varanopids were ancestrally terrestrial. Moreover, the large availability of specimens spanning different sizes made possible an assessment of size-related ontogenetic histovariability. All specimens revealed moderately dense cortical bone tissues composed of sparsely vascularized parallel-fibred and lamellar bone with radially arranged rows of longitudinal canals (mostly simple), and many preserved regularly spaced growth marks (annuli and lines of arrested growth) as in modern varanids. We show that bone histology has the potential to explain how ballast was shed and the skeleton lightened for terrestrial mobility in ancestral synapsids and their basal amniote kin, as well as how adjustments in postnatal growth influenced the evolution of larger body sizes in the terrestrial frontier. This article is part of the theme issue ‘Vertebrate palaeophysiology'.

A postura locomotora de Protolipterna ellipsodontoides Cifelli, 1983 (Mammalia: Litopterna: Protolipternidae) da Bacia de São José de Itaboraí, Rio de Janeiro (Paleoceno superior)

The Litopterna is a group of endemic South America ungulates that lived from Late Paleocene (Itaboraiense) to Late Pleistocene (Lujanense). The order is divided in two large groups based on dental features: the Bunolipterna, in which the Protolipternidae is placed, is composed by taxa with primitive bunodont teeth; and the Lopholipterna, grouping taxa with derived lophodont teeth. In both the postcranial morphology is derived and uniform since the early forms. The Itaborai Basin, located at São José district, Itaboraí city, Rio de Janeiro state, is filled with different kinds of limestones, cut vertically by fissure fill deposits, where most of the fossils were collected. Protolipterna ellipsodontoides was described in 1983 based on dental features, but later postcranial bones were associated to this species. The main goal of this article is to infer the foot posture of P. ellipsodontoides. The material studied consists of femora, astragali, calcanea and metatarsals III, comprising 165 bones. All fossils were deposited in the fossil mammal collection of Departamento Nacional da Produção Mineral, in Rio de Janeiro state, Brasil. The methodology employed consisted of 15 linear and curvilinear measurements, which were submitted to a multivariate analysis (Principal Component Analysis -PCA and Discriminant Function Analysis -DFA). The results suggested a digitigrade posture to P. ellipsodontoides. Other morphological features of the skeleton, associated with a digitigrades posture, are suggestive of a cursorial locomotion, but with probable saltatory habits.

A new microsaur (Tetrapoda: Lepospondyli) from the Lower Permian of Richards Spur (Fort Sill), Oklahoma

Bolterpeton carrolli n.gen. n.sp. is described from the Lower Permian fissure-fill deposits of Richards Spur, Oklahoma. Bolterpeton is united with the gymnarthrid microsaur Cardiocephalus by having teeth compressed labiolingually, a narrow anterior process of the prearticular penetrating the splenial, and the arrangement of the contacts among the splenial, prearticular, and coronoids. It is united with both Cardiocephalus and Euryodus by the size and distribution of the coronoid teeth and the presence of longitudinal striations of enamel on the lingual tooth surface. Unlike those two genera Bolterpeton has peg-like teeth, but it remains unknown whether this represents the primitive condition or a reversal of the massive conical teeth typical of gymnarthrids. Bolterpeton possesses a flat lamina that runs along the lingual surface of the tooth margin. Where two laminae meet at the point of the tooth a labiolingual ridge is formed, which is most pronounced at smaller sizes. Reexamination of Cardiocephalus shows it to have the same morphology on its "incisors." Previous authors have defined teeth bearing this ridge as "weakly bicuspid." If this ridge were homologous with the "strongly bicuspid" condition of lissamphibians, Bolterpeton would provide the first example of this tooth morphology in lepospondyls and would strengthen recent hypotheses suggesting lepospondyls gave rise to some, if not all, modern amphibians.

Paleoanthropological Implications of the Nonarcheological Bone Assemblage from Swartklip I, South-Western Cape Province, South Africa

The relative frequencies of different skeletal elements within the bone assemblage recovered from a late Pleistocene fissure fill at Swartklip (South-Western Cape Province, South Africa) are shown to resemble those in the assemblage from the Transvaal australopithecine site of Makapansgat. Since there is evidence that carnivores, probably hyenas, accumulated the bones at Swartklip, it follows that carnivores, rather than hominids, may have accumulated the bones at Makapansgat.