Classification and relationships of the Ordovician encrinurines Frencrinoides Lespérance and Desbiens and Walencrinoides Lespérance and Desbiens are poorly understood, with little evidence for monophyly of either genus. We revise the type species of both genera, F. capitonis (Frederickson) and W. rarus (Walcott), using new and archival material. We explore their species composition and phylogenetic relationships with a parsimony analysis that includes 17 well-documented ingroup species that can be coded readily, and which is rooted with Encrinuroides regularis Parnaste, the oldest known encrinurine. The results support monophyly of Frencrinuroides and Walencrinuroides, albeit with more limited species membership than proposed by Lespérance and Desbiens. Previous suggestions that both E. uncatus Evitt and Tripp and E. neuter Evitt and Tripp should be assigned to Erratencrinurus Kruger are also supported by our analysis, as is monophyly of Physemataspis Evitt and Tripp. New species are W. rolfi and W. tremblayi.

A new dataset of the highest quality specimens of fully articulated, juvenile and mature exoskeletons of the Czech middle Silurian trilobite Aulacopleura koninckii offers improved resolution of original morphology by all measures considered. The degree of variation in both size and shape among later meraspid instars was constant, and suggesting targeted growth in both attributes. Size-related changes in the shape of the dorsal exoskeleton and of the segment-invariant cephalon were detected in the meraspid stage, but in the holaspid phase marked allometry was detected only in the trunk region, with the pygidium showing notable expansion in relative size. Meraspid cranidial allometry was subtle, with significant changes in instar form detectable only after several molts. This trilobite developed gradually throughout meraspid and holaspid ontogeny, with the synchronous cessation of trunk segment appearance and release at the onset of the holaspid phase. Precise development of shape and size occurs in the context of marked variability in the number of trunk segments at maturity, illustrating complex patterns of character variation within a species. A new systematic description establishes the synonymy of several subspecies with A. koninckii.

The Middle Permian tetrapod fauna of the South African Beaufort Group is taxonomically diverse and includes representatives of all major therapsid groups, including the earliest records of Eutheriodontia. In the Middle Permian, eutheriodonts are represented mainly by large therocephalians, which made up a large proportion of the vertebrate predators in these faunas. Here we describe the skull and partial skeleton of a large therocephalian from the uppermost Tapinocephalus Assemblage Zone (AZ) of South Africa. A combination of features, including the short snout, presence of three to four upper postcanines and presence of teeth on the pterygoid processes, indicates that the new specimen belongs to the earliest-diverging therocephalian family, Lycosuchidae. The presence of a well-developed midline ridge on the ventral surface of the vomer indicates that the new specimen can be referred to Simorhinella baini, a species previously represented only by a tiny juvenile skull. The new specimen forms the basis for a taxonomic re-evaluation of the Lycosuchidae as well as of the geographic and stratigraphic range of the family. We recognize two valid species within the Lycosuchidae: the type species Lycosuchus vanderrieti represented by five specimens and Simorhinella baini represented by two specimens, with an additional 22 specimens currently identifiable as Lycosuchidae incertae sedis. Lycosuchid specimens range throughout the Tapinocephalus and Pristerognathus AZs; specimens of Simorhinella are restricted to the Tapinocephalus AZ, whereas Lycosuchus specimens are documented in both the Tapinocephalus and Pristerognathus AZs.

The Mississippian Fort Payne Formation of Kentucky, Tennessee, and Alabama is well known for its abundant crinoids and a diverse array of autochthonous and allochthonous carbonate and siliciclastic facies. Using Principal Coordinate Analysis and Non-Metric Multidimensional Scaling, it is demonstrated that distinct, contemporaneous, and geographically adjacent autochthonous facies in south-central Kentucky supported distinct crinoid assemblages. The two carbonate buildup facies had different assemblages dominated by camerate crinoids, carbonate channel-fill deposits were dominated by advanced cladid crinoids and the camerate Elegantocrinus hemisphaericus, and green shale facies supported a fauna dominated by disparids and primitive cladid crinoids. Allochthonous facies contain neither distinctive nor exotic taxa. Thus, these transported assemblages are considered a mixture of elements from the recognized, autochthonous facies. Faunal assemblages from Dale Hollow Reservoir are allochthonous; and faunas in north-central Alabama and south-central Tennessee are different from others, which may reflect slight biogeographic distinctions.

Phragmactis grayae Spencer and Swataria derstleri new genus new species are early (Ordovician) asterozoans (Echinodermata) that comprise the Phragmactinidae. Asterozoans are complexly varied, but as is true for other echinoderms, ambulacral construction is critical to interpretation. Phragmactinids share plesiomorphic aspects of ambulacral form and articulation with basal somasteroids and stenuroids whereas the apomorphic ambulacral expressions of asteroids and ophiuroids are lacking. Phragmactinids, like asteroids and ophiuroids, have only one virgal-series ossicle associated with each ambulacral, unlike the multiple ossicles of somasteroids and stenuroids. Virgal morphology of phragmactinids is reminiscent of expressions in somasteroids and stenuroids. Aspects of phragmactinid mouth frame construction are apomorphic. Morphologies of other ossicular series are similarly varied, and as a result, the family cannot be easily fitted into a recently proposed class-level taxonomy of early asterozoans; it is left in open nomenclature. Phragmactinid morphology does not indicate behavior significantly different from that of other early asterozaons. Asterozoan diversity suggests an early period of rapid evolutionary radiation.

The systematic position of the fossil species referred to Calliotropis is currently under debate due to the striking resemblance between these forms with their extant counterparts in general shell morphology and ornament pattern. We propose two temporal subgenera of Calliotropis: Calliotropis (Riselloidea) for Mesozoic species and Calliotropis (Calliotropis) for Cenozoic and Recent taxa. We also synonymize the families Eucyclidae and Calliotropidae, and redescribe the type genus of Eucylidae based on topotypic material of E. obeliscus from Normandy. We argue that the generic name Amberleya should be restricted to its type species Amberleya bathonica. For the species that were traditionally included in Amberleya, we propose the new genus Ambercyclus, with its type species Amberleya orbignyana. The present paper also provides descriptions of three Calliotropis species from the Early Jurassic marine deposits of Argentina. The occurrence of Calliotropis (Riselloidea) keideli n. sp., Calliotropis (Riselloidea) cf. C. (R.) keideli and Calliotropis (Riselloidea) sp. in the Jurassic of Chubut and Neuquén provinces represents a new record of the genus in Early Jurassic sediments of Argentina and South America. Moreover, two species of Ambercyclus n. gen., such as Ambercyclus espinosus and Ambercyclus? isabelensis n. sp., are described from the same deposits. Eucyclus, Amberleya, Ambercyclus, and Calliotropis are included into Eucyclidae, which we consider to be a family of Seguenzioidea.

The trace-fossil name Tubotomaculum has been extensively used to refer to spindle-shaped pellet-filled tubes present in Upper Cretaceous to Miocene deep-marine deposits of the western Mediterranean region. However, it has never been formally diagnosed, and accordingly it was regarded as a nomen nudum. In this paper, we formally introduce the ichnogenus Tubotomaculum, including the new ichnospecies Tubotomaculum mediterranensis. Bioglyphs, represented by scratch traces that may be present on the basal and lateral surfaces of the structure, suggesting production by crustaceans. The functional meaning of these structures challenges the simple model of a mining strategy. Instead, the storing of pellets to use them as a bacteria-enriched resource during times when organic detritus was scarce is suggested. The association with chemoautothrophic bacteria in modern analogs of Tubotomaculum provides a crucial piece of evidence to support the cache model. Integration of information from modern environments and the fossil record points to a connection between Tubotomaculum, mud volcanism, fluid venting, and hydrocarbon seeps. The presence of bioglyphs suggests firmgrounds that may have resulted from bottom current scouring of the sea sediment, leading to erosional exhumation of previously buried compacted sediment, which was therefore available for colonization by the infauna. However, an alternative scenario involves enriched fluids related to mud-volcanism resulting in reducing conditions that favored carbonate precipitation and nodule formation just a few centimeters below the sediment-water interface.

The Pantolestidae are an extinct family of mammals known principally from the early Paleocene to late Oligocene (from approximately 64 to 30 million years ago) of North America and Europe. Although never particularly abundant, pantolestids are relatively well represented in the Eocene and Oligocene, with several taxa known from exceptionally well-preserved skulls and postcranial material. The early evolutionary history of the group, however, similar to that of many contemporaneous mammals, remains comparatively poorly known. The current study reports on several previously undescribed pantolestids from the early late Paleocene (late middle Tiffanian, Ti4) Roche Percée local fauna, Ravenscrag Formation, of southeastern Saskatchewan, Canada. Aatotomus placochton n. gen. n. sp. resembles the enigmatic pantolestid Paleotomus in having sectorial premolars with well-developed crests and tall, sharp molar trigonids, but differs principally in possessing narrow molar talonids. Besseocetor krausei n. sp. shares numerous similarities with B. thomsoni and B. septentrionalis but differs in being considerably smaller and less robust. Palaeosinopa reclusum n. sp., the oldest species of Palaeosinopa yet discovered, reveals a unique combination of primitive and derived pantolestid features, and supports previous suggestions of a close evolutionary relationship between Palaeosinopa and Bessoecetor. The new taxa document an unusually high diversity of pantolestids in the Tiffanian of western Canada and provide important new knowledge to the evolutionary history of this group during the Paleocene.

A new species of Apiocrinites is described from the Matmor Formation (Middle Jurassic, upper Callovian) of Hamakhtesh Hagadol, southern Israel. Apiocrinites feldmani n. sp. is a small species associated with the larger A. negevensis in a calcareous sponge and coral patch reef community. During life the columns of A. feldmani were commonly and preferentially infested with a soft-bodied parasite that grew with the crinoid and became embedded in its skeleton. These parasites embedded at the articulation between columnals, forcing the columnals to grow around them and producing with time a conical pit surrounded by swollen stereom. If the parasite died while the crinoid was still growing, the conical pit was roofed over by continued growth of columnals, resulting in a swelling with no external opening. Because the crinoids invested energy in forming extra skeleton around these parasites and because the crinoid stems were consequently deformed and likely lost flexibility, we consider these parasites to have caused significant harm. Curiously, these parasites apparently did not infect the larger and more common contemporaneous A. negevensis that lived in the same community.

The gastropod fauna of the Lower Cretaceous of the Argentinian Neuquén Basin contains three aporrhaid species. Protohemichenopus neuquensis Camacho, 1953 is the most abundant, longest-lived, and most geographically widespread of the aporrhaids of this basin, and its protoconch and early teleoconch whorls were unknown until now. The new species Dimorphosoma weaveri features convex to subtly angular spire whorls with opisthocyrt collabral ribs that are more prominent towards the mid-whorl, a bicarinate last whorl with small rounded nodes on the adapical carina, a simple, falcate labral wing which is more or less rectangular proximally and tapering and curving towards its distal end, and a short, straight rostrum. Tylostoma jaworskii Weaver, 1931 is now placed in Harpagodes, and other previous, scattered, coeval records of this genus in the basin are now recognized as part of this single species. It is believed that whereas H. jaworskii preferred shallower-water carbonate settings of low to moderate energy, P. neuquensis and D. weaveri favored siliciclastic to mixed clastic-carbonate environments, in deeper waters. In spite of its endemic elements, this aporrhaid association depicts a predominantly Tethyan influence.

Arctotherium angustidens Gervais and Ameghino, 1880 (the South American giant short-faced bear) is known for being the earliest (Ensenadan Age, early to middle Pleistocene) and largest (body mass over 1 ton) of five described Arctotherium species endemic to South America. Here we assess the diet of this bear from multiple proxies: morphology, biomechanics, dental pathology, stable isotopes and a previous study using geometric morphometric methodology. Results favor the idea of animal matter consumption, probably from large vertebrates in addition to vegetable matter consumption. Most probably, active hunting was not the unique strategy of this bear for feeding, since its large size and great power may have allowed him to fight for the prey hunted by other Pleistocene carnivores. However, scavenging over mega mammal carcasses was probably another frequent way of feeding. South American short-faced bears adjusted their size and modified their diet through Pleistocene times, probably as a response to the diversification of the carnivore guild (from the few precursory taxa that crossed the Panamanian Isthmus during the Great American Biotic Interchange).

A single specimen of a shrimp-like crustacean, Devonostenopus pennsylvaniensis, new genus and species is described from the Huntley Mountain Formation, which is Devonian–Carboniferous (Mississippian) in age. The specimen was collected in north-central Pennsylvania. Devonostenopus pennsylvaniensis is attributed to Stenopodidae. Co-occurrence of the specimen with pinnules of Archaeopteris halliana Goeppert, 1852, suggests that it is Devonian in age. Occurrence of a stenopodidean in the Devonian of North America is significant, as only three definitive decapods have been previously described from the Paleozoic and only two have been described from the Devonian. The earliest stenopodideans described to date are Cretaceous (Cenomanian and Santonian) in age. As such, Devonostenopus pennsylvaniensis extends the geologic range of Stenopodidea from Cretaceous to Late Devonian. Occurrence of a stenopodidean in the Devonian of North America, as well as the occurrence of the only two other known Devonian decapods in North America, suggests that Laurentia might have been a major area of endemism for Devonian decapods.

The fossil record of solemydid turtles is primarily based on isolated fragments collected from Late Jurassic to Late Cretaceous sediments throughout North America and Europe and little is therefore known about the morphology and evolutionary history of the group. We here provide a detailed description of the only known near-complete solemydid skeleton, which was collected from the Lower Cretaceous (Aptian–Albian) Antlers Formation of Texas during the mid-twentieth century, but essentially remains undescribed to date. Though comparison is limited, the skeleton is referred to Naomichelys speciosa, which is based on an isolated entoplastron from the Lower Cretaceous (Aptian–Albian) Kootenai (Cloverly) Formation of Montana. The absence of temporal emarginations, contribution of the jugals to the orbits, and a clear subdivision of the middle and inner cavities, and the presence of elongate postorbitals, posteriorly expanded squamosals, a triangular fossa at the posterior margin of the squamosals, an additional pair of tubercula basioccipitale that is formed by the pterygoids, foramina pro ramo nervi vidiani (VII) that are visible in ventral view, shell sculpturing consisting of high tubercles, a large entoplastron with entoplastral scute, V-shaped anterior peripherals, and limb osteoderms with tubercular sculpture diagnose Naomichelys speciosa as a representative of Solemydidae. The full visibility of the parabasisphenoid complex in ventral view, the presence of an expanded symphyseal shelf, and the unusual ventromedial folding of the coronoid process are the primary characteristics that distinguish Naomichelys speciosa from the near-coeval European taxon Helochelydra nopcsai.