Vertebrate Assemblages Research Articles

Recursive anisotropy: a spatial taphonomic study of the Early Pleistocene vertebrate assemblage of Tsiotra Vryssi, Mygdonia Basin, Greece

By applying advanced spatial statistical methods, spatial taphonomy complements the traditional taphonomic approach and enhances our understanding of biostratinomic and diagenetic processes. In this study, we elaborate on a specific aspect – spatial anisotropy – of taphonomic processes. We aim to unravel the taphonomic history of the Early Pleistocene vertebrate assemblage of Tsiotra Vryssi (Mygdonia Basin, Greece). Circular statistics are used for the fabric analysis of elongated elements; geostatistics (directional variograms), wavelet and point pattern analyses are applied for detecting anisotropy at the assemblage level. The anisotropy of magnetic susceptibility (AMS) of sedimentary magnetic minerals is also investigated. The results, integrated with preliminary remarks about the differential preservation of skeletal elements, sedimentological and micromorphological observations, suggest multiple dispersion events and recurrent spatial re‐arrangement of a lag, (peri)autochthonous assemblage, consistent with the cyclical lateral switching of a braided fluvial system. Furthermore, this study offers a contribution to the building of a spatial taphonomic referential framework for the interpretation of other fossil vertebrate assemblages, including archaeo‐palaeontological ones.

Direct ESR dating of the Pleistocene vertebrate assemblage from Khok Sung locality, Nakhon Ratchasima Province, Northeast Thailand

We report here the first direct dating study of the faunal assemblage from Khok Sung locality, Thailand. This palaeontological site is of great biochronological, palaeoenvironmental and biogeographical significance. Firstly, it has yielded a rich and diversified Pleistocene vertebrate fauna with up to 15 mammalian species from 13 genera, 10 reptile species, as well as fish and bird remains. Interestingly, while most of the mainland Southeast Asian Pleistocene mammal fossils originate from cave deposits, the Khok Sung fossil layer is located within an 8 m thick fluvial terrace. Secondly, it is geographically located in an area of major importance for reconstructing the migration pathway of large mammals between South China and Java. Combined US-ESR dating of five teeth provides two possible ages of 130 ± 29 ka and 217 ± 36 ka for the fossils. The reason for the occurrence of these two age groups lies in the fact that it was not possible to obtain sediments that were directly associated with the measured samples, nor was it possible to carry out in situ gamma dose rate measurements due to the high water level. Sediment samples recovered from museum specimens show significantly variable concentrations of radioelements. Both options are equally plausible, as independent methods did not provide firm evidence favouring one or the other age range. The results illustrate the intrinsic limitations of the ESR dating method when fossil teeth are not collected in situ during the excavation. Regardless whether the age of the Khok Sung fauna corresponds to MIS 7 or early MIS5, it is nevertheless one of the oldest assemblages directly dated in the region. Further efforts are required for more accurate fossil identification and attribution and for additional numerical dating in this region to improve the biochronological framework of the Pleistocene mammalian faunas in Southeast Asia, which presently remains quite imprecise.

A new vertebrate continental assemblage from the Tortonian of Venezuela

A wide variety of aquatic vertebrates from fluvio-lacustrine facies of northern South America (Colombia and Venezuela) have been used as unequivocal evidence to support hydrographic connections between western Amazonia and the Proto-Caribbean Sea during the Miocene. By the end of the Miocene, changes in the major hydrographic systems of the region produced losses of habitats and a regional faunal turnover, as has been documented in the geological record of the Urumaco region. Here, we report a new Tortonian aquatic and terrestrial vertebrate assemblage from two localities of the Caujarao Formation (El Muaco Member) in western Venezuela. The vertebrate assemblage includes a gharial (cf. †Gryposuchus pachakamue), alligatorid crocodylians (†Purussaurus and Alligatoridae indet.), a freshwater turtle (Chelus sp.), snakes (cf. Eunectes sp.), serrasalmids and pimelodids and thorny catfishes, a rodent (†Potamarchus sp.), pampatheres (†Scirrotherium sp.), sloths, as well as plant remains (coal and amber). Although the Caujarao Formation has been referred to as a fully marine environment, the new assemblage reported here suggests a freshwater input to the coastal area. Taxonomic and biogeographic affinities between the Muaco Member community and that reported from the Miocene proto-Amazonian systems are indicative of the persistence of ecological and hydrographic continuity at minimum until the end of the Miocene in at least an area of northwestern South America.

Niche Partitioning in Theropod Dinosaurs: Diet and Habitat Preference in Predators from the Uppermost Cedar Mountain Formation (Utah, U.S.A.)

We explore hypothetical ecologies to explain diversity among predatory dinosaurs in North America’s medial Cretaceous, based on occurrence, tooth morphology, and stable isotope analysis. The Mussentuchit local fauna, Utah, USA, is among the best-known terrestrial vertebrate assemblages from the Cretaceous. Study samples include teeth from six microvertebrate sites, ranging in depositional setting from distal floodplain to channel lags. We recognize four theropod morphotypes: a comparatively large theropod (morph 1), a medium-sized dromaeosaurid (morph 2), a small dromaeosaurid (morph 3), and a tooth-morph similar to the genus Richardoestesia (morph 4). These four morphotypes vary significantly in mean size, from 15.1 mm in the largest theropod to 3.7 mm in Richardoestesia. Further, tooth representation from two of the best-sampled microsites (representing a channel/splay and floodplain deposit) show differing patterns of abundances with morphs 1 and 3 having roughly the same abundance in both sites, while morph 2 was more abundant in the floodplain setting and morph 4 was more abundant in the channel/splay. Stable isotope analysis (δ13C; δ18O) of tooth carbonate from the theropod morphotypes, goniopholidid crocodilians, and matrix (to test for diagenesis) from these sites were also analyzed. The theropods show modest differences in δ13C values between each other, with carbonate from the teeth of morphs 1, 3, and 4 being enriched in 13C for the channel/splay relative to the floodplain environments, possibly indicative of dietary plasticity in these species. We hypothesize that these data indicate that the Mussentuchit theropods had different niches within the predator guild, suggesting plausible means by which ecospace was divided among the predatory dinosaurs of the Mussentuchit local fauna.

Reef fish functional traits evolve fastest at trophic extremes.

Trophic ecology is thought to exert a profound influence on biodiversity, but the specifics of the process are rarely examined at large spatial and evolutionary scales. We investigate how trophic position and diet breadth influence functional trait evolution in one of the most species-rich and complex vertebrate assemblages, coral reef fishes, within a large-scale phylogenetic framework. We show that, in contrast with established theory, functional traits evolve fastest in trophic specialists with narrow diet breadths at both very low and high trophic positions. Top trophic level specialists exhibit the most functional diversity, while omnivorous taxa with intermediate trophic positions and wide diet breadth have the least functional diversity. Our results reveal the importance of trophic position in shaping evolutionary dynamics while simultaneously highlighting the incredible trophic and functional diversity present in coral reef fish assemblages.

Identifying wildlife corridors for the restoration of regional habitat connectivity: A multispecies approach and comparison of resistance surfaces

Many large-scale connectivity initiatives have been proposed around the world with the aim of maintaining or restoring connectivity to offset the impacts on biodiversity of habitat loss and fragmentation. Frequently, these are based on the requirements of a single focal species of concern, but there is growing attention to identifying connectivity requirements for multi-species assemblages. A number of methods for modelling connectivity have been developed; likewise, different approaches have been used to construct resistance surfaces, the basic input data for connectivity analyses. In this study we modelled connectivity for a multi-species group of vertebrates representative of heavily fragmented forests in north-central Victoria, Australia. For each species, we used least-cost modelling and compared two alternate resistance surfaces, based on species distribution models and on expert opinion, respectively. We integrated the connectivity results across individual species to obtain a multi-species connectivity map for the region. A resistance surface based on expert assessment of the relative use of land-cover classes by the target species was more informative than one based on species distribution models. The former resulted in pathways more strongly aligned with existing patches and strips of native vegetation. In this region, pathways aligned with streams and their associated riparian vegetation have relatively high ecological potential and feasibility to contribute to regional connectivity for the assemblage of forest vertebrates.

A novel archosauromorph from Antarctica and an updated review of a high-latitude vertebrate assemblage in the wake of the end-Permian mass extinction

Triassic-aged fossil vertebrates have been sporadically collected from the Fremouw Formation, central Transantarctic Mountains, since their initial discovery in the late 1960s, giving paleontologists insight into high-latitude faunas in the wake of the end-Permian mass extinction event. On a recent expedition (2010–2011), a small reptile skeleton was collected from Graphite Peak, which we present here alongside novel geological data and interpretations taken on site. Antarctanax shackletoni, gen. et sp. nov., is known from a partial postcranial skeleton including cervical and dorsal vertebrae, a humerus, and both pedes. Important morphological information includes well-defined laminae and deep fossae on cervicodorsal vertebrae. The new taxon can be differentiated from previously known Fremouw Formation reptiles (e.g., Prolacerta, Procolophon), as well as those from the Karoo Basin, South Africa (e.g., Mesosuchus, Proterosuchus, Euparkeria). Our inclusion of A. shackletoni in phylogenetic analyses of early amniotes finds it as an archosauriform archosauromorph, increasing known archosauriform diversity in the Early Triassic. The fauna of the lower Fremouw Formation traditionally has been considered to represent a subset of the Lystrosaurus Assemblage Zone of the Karoo Basin, with differences largely a result of pronounced differences in sampling intensity. However, a review of recent changes to the fauna, as well as a reassessment of occurrences based on older literature, indicates that significant discrepancies, including the co-occurrences of taxa known from both earlier and later in time and the presence of endemic forms in Antarctica, exist between the faunas of the Lystrosaurus Assemblage Zone and lower Fremouw Formation.http://zoobank.org/urn:lsid:zoobank.org:pub:B1DAD1A4-7054-454D-89B2-17CAF2865AD4SUPPLEMENTAL DATA—Supplemental materials are available for this article for free at www.tandfonline.com/UJVPCitation for this article: Peecook, B. R., R. M. H. Smith, and Christian A. Sidor. 2019. A novel archosauromorph from Antarctica and an updated review of a high-latitude vertebrate assemblage in the wake of the end-Permian mass extinction. Journal of Vertebrate Paleontology. DOI: 10.1080/02724634.2018.1536664.

Refining the environmental and climatic background of the Middle Pleistocene human cranium from Gruta da Aroeira (Torres Novas, Portugal)

The recent publication of a human cranium, dating to ca. 436–390 ka, from Gruta da Aroeira provides an important input to the debate about human evolution during the Middle Pleistocene in Europe and the origin of the Neanderthals. This cranium, chronologically located to Marine Isotope Stage 11c (MIS 11c), appears in association with Acheulean lithic tools and several faunal remains, among which cervids and equids are predominant. The small vertebrate assemblage associated with the Aroeira-3 cranium suggests an environment and a climate related to an open-woodland landscape and relatively mild and humid conditions, probably in connection with the end of MIS 11c. Moreover, comparison with other Middle Pleistocene Iberian sites with human remains suggests that these hominins lived in open forest areas during mild climatic substages.

Turtles from the Late Cretaceous (Campanian) of El Gallo Formation, Baja California, Mexico

Turtles are typically important members of Late Cretaceous vertebrate assemblages throughout North America, and are considered a useful tool to define biogeographic patterns. In Mexico, Cretaceous turtles have been recorded in the states of Baja California, Chiapas, Chihuahua, Coahuila, Nuevo León, Puebla, and Sonora; specifically the state of Coahuila shows so far, the highest diversity of turtles. In this paper, the diversity of Late Cretaceous turtles from the El Gallo Formation (Baja California) is reviewed. Previously, only Naomichelys speciosa was recognized in this Formation. Based on fragments with distinctive sculpture patterns four additional taxa are recognized, Compsemys victa, Basilemys sp., Trionychidae indet., and cf. Chelydridae. With the recognition of these new taxa, the knowledge of Cretaceous turtles diversity of the El Gallo Formation is increased. This assemblage is unusual compared to other North American turtle assemblages because it suggests the presence of previously unrecognized biogeographic patterns. Here we report the first record of Basilemys sp. from the Late Cretaceous of Mexico and the presence of cf. Chelydridae on the western side of Laramidia.

The First Vertebrate Assemblage Dominated by Fishes and Turtles of the Jehol Biota in Jilin Province, NE China

The First Vertebrate Assemblage Dominated by Fishes and Turtles of the Jehol Biota in Jilin Province, NE China

Compendium of data, source code and text associated with the publication: D. Giusti et al., "Recursive anisotropy: A spatial taphonomic study of the Early Pleistocene vertebrate assemblage of Tsiotra Vryssi, Mygdonia Basin, Greece"

Compendium of data, source code and text associated with the publication: D. Giusti et al., "Recursive anisotropy: A spatial taphonomic study of the Early Pleistocene vertebrate assemblage of Tsiotra Vryssi, Mygdonia Basin, Greece"

Faunal remains and environments from the Bronze age of Kalehkoob, Lut Desert, eastern Iran

The study of faunal remains from Kalehkoob, an archeological site in southern Khorasan, Sarayan, represents the first investigation of prehistoric vertebrates in the northern part of the Lut desert, in the east Iranian plateau. A vertebrate assemblage containing >200 specimens was found at various depths (155 cm to 595 cm) of an excavation trench. A combination of morphological and morphometric methods led to the identification of Artiodactyla, namely Bovidae (Ovis, Gazella, and Bos) and Perissodactyla, namely Equidae (Equus asinus and Equus caballus). Combined zooarcheological and sedimentological analyses points to three phases and two sub phases of depositional. Transition between the second phase and the first and third phases suggests that changes in faunal composition were potentially a response to different environmental conditions during each phase, such as a reduction of river water volume and humidity. Radiocarbon dating of bones from two depths, 155 cm (scapula) and 462 cm (horse tooth) from phases 1 and 2, respectively, provides ages of 3227–3060 cal BP and 5914–5749 cal BP for the deposit. Given the high chemical quality of both samples of scapula and tooth, δ13C and δ15N analyses were also conducted, suggesting the presence of arid environmental conditions.

Taphonomy and palaeoecology of the lower Miocene marine vertebrate assemblage of Ullujaya (Chilcatay Formation, East Pisco Basin, southern Peru)

The taphonomy and palaeoecology of the early Miocene (Burdigalian) vertebrate assemblage of Ullujaya (East Pisco Basin, Peru) is here described. Vertebrate remains are concentrated in marine facies (Ct1a association) of the exposed Chilcatay Formation (dated 19–18 Ma) deposited within a 30–40 m deep, semi-enclosed, offshore environment. Coupled with ichnological observations, the size distribution of pyrite framboid relics reveals fluctuation of euxinic and oxic-dysoxic conditions at the seafloor. The assemblage is dominated by toothed cetaceans (kentriodontids, squalodelphinids, physeteroids, and the eurhinodelphinid-like Chilcacetus), together with a large dermochelyid turtle, some bony fish, and diverse elasmobranchs, mostly juveniles of Carcharhinus brachyurus and Cosmopolitodus hastalis. The vertebrate assemblage comprises a coastal community, dominated by mesopredators, representative of a warm-temperate, sheltered embayment connected with riverine and open-ocean environments. Vertebrate skeletons are typically disarticulated and incomplete, and some bone elements display shark bite marks. Microborings are observed at the bone surface. Bones exhibit a good degree of apatite mineralisation and bone cavities are locally filled by Ca-Mg carbonates. Our taphonomic observations suggest prolonged flotation of carcasses during which they were subject to biogenic and physical processes of partial destruction (including scavenging by sharks), before final deposition on a soft compact substrate. Preservation was favoured by the oxygen-deficient bottom conditions that inhibited the action of benthic macro-scavengers.

Phylogeny of the hillstream loach genus Mesonoemacheilus reveals widespread diversification through ancient drainage connections in the Western Ghats Biodiversity Hotspot

Rivers draining the Western Ghats (WG) mountain ranges in peninsular India harbor an exceptionally diverse, unique and evolutionarily distinct assemblage of lower vertebrates with high levels of endemism, attributed to their evolution and potentially long history of isolation during the Late Cretaceous or Early Tertiary. A molecular phylogeny of hillstream loaches of the genus Mesonoemacheilus endemic to the WG revealed the presence of four clades which we designate as ‘species groups’. A consensus of various species delimitation methods indicates the likelihood of ‘at least’ seven more undescribed species within Mesonoemacheilus. Molecular clock analysis dates the basal clade around 38 mya in the Paleogene, and subsequent diversification in the Neogene and Quaternary periods resulting in the current genetic diversity. Biogeographic analysis suggests that vicariance events which separated the rivers on either side of the two geological barriers/gaps, the Palghat and Shencottah, in the Neogene, as well as range contractions and cladogenetic events contributed to the current patterns of diversity and distribution of this genus. Our results also provide preliminary indications on the interconnections and faunal exchange between historical river drainages in the WG region.

Depositional setting, taphonomy and geochronology of new fossil sites in the Catskill Formation (Upper Devonian) of north-central Pennsylvania, USA, including a new early tetrapod fossil

Late Devonian terrestrial floodplain environments were important sites of plant and animal diversification and evolution. Recently discovered fossil sites in the Catskill Formation in north-central Pennsylvania yield important insights into Late Devonian terrestrial environments and ecologies. The fossil sites yield the progymnosperm plant Archaeopteris ssp., Archanodon bivalves, as well as abundant placoderms, acanthodians, and sarcopterygians including a new specimen of an early tetrapod. Most vertebrate fossils occur as abraded and disarticulated teeth, scales, and dermal bone fragments within basal lags of fluvial channel-bar complexes and articulated skull material, well-preserved scales, bones, and teeth in shallow temporary channels that meandered across vegetated floodplains. Fossil sites in these nearly flat-lying fluvial strata occur in multiple stratigraphic horizons spanning hundreds of meters of stratigraphy that represent the Sherman Creek Member and overlying Duncannon Member. The strata coarsen upsection and record progressively larger channel-bar complexes and better-developed paleosols. Applied detrital muscovite 40Ar/39Ar geochronology supplies the first quantitative age data from the sampled strata and provides information on erosion rate parameters and channel network morphology. Detrital ages indicate rapid uplift, erosion, and deposition of sediments in the Catskill fluvial system during Late Devonian time. Detrital ages also indicate temporal variation and lack of depositional linkages among Late Devonian fossil sites. Variations in the fossil assemblages between sites reflect paleoecological variations among paleo-subenvironments (channel-bars vs. floodplains) and/or taphonomic processes. Vertebrate assemblages and fluvial lithofacies documented at the recently discovered sites are broadly comparable with those in slightly younger strata at Red Hill, a well-studied site ~50 km to the west that yields a diverse vertebrate assemblage, including several taxa of early tetrapods. These heterogeneous, shallow, non-marine aquatic habitats were a crucible for experimentation in limb mobility and other specializations among sarcopterygians during Late Devonian time. Integration of paleontological, sedimentological, and geochronological data offers new insights into Late Devonian fluvial ecosystem evolution.

New insights into Late Triassic dinosauromorph-bearing assemblages from Texas using apomorphy-based identifications

The Upper Triassic Dockum Group of Garza County, Texas (lower, middle, and upper Cooper Canyon Formation) captures the radiation of Triassic non-marine tetrapods by preserving a variety of Late Triassic taxa from the southwestern United States. Our understanding of the vertebrate assemblage from these strata largely comes from a single site, the Post Quarry (lower Cooper Canyon Formation), with previous research documenting a variety of temnospondyls, sphenodontians, non-archosauriform archosauromorphs, and archosauriforms including a phytosaur, three species of aetosaurs, a poposauroid, a rauisuchid, a crocodylomorph, and several dinosauromorphs. To more completely reconstruct the vertebrate assemblage of the Dockum Group of Garza County we use an apomorphy-based approach to identify morphologically similar disarticulated and fragmentary elements from a variety of localities that span the entire Cooper Canyon Formation (Norian-Rhaetian), allowing assignments from the large clade level to the species level. Many skeletal elements are incomplete yet diagnostic and are assigned to the least inclusive clade if discrete character states do not allow for an unambiguous species-level identification. We identify new specimens referable to numerous clades including Tanystropheidae, Allokotosauria + Prolacerta + Archosauriformes, Vancleavea + Litorosuchus, Phytosauria, Paracrocodylomorpha, Dinosauriformes, and Saurischia, in addition to additional species identifications of the aetosaur Scutarx deltatlyus, and the dinosauromorph Dromomeron gregorii. Our study of this material demonstrates the utility of an apomorphy-based approach in making testable and repeatable observations for identifying small, isolated fragmentary fossil tetrapod material to reconstruct a more accurate faunal hypothesis for a portion of the Late Triassic of Texas. Previous claims of the earliest dinosaurs from near the base of the Dockum Group do not pass the apomorphy-based identification test, and the question of whether the oldest known North American dinosaurs are present in the Chinle Formation or Dockum Group can be resolved by utilizing vertebrate biostratigraphic correlation. Our revision of these fossil assemblages supports the hypothesis that early diapsids, early archosauromorphs, and non-dinosaurian dinosauromorphs were more common, diverse, and widespread in low latitudes during this time than previously thought.

FOSSO DELLA FITTAIA: THE OLDEST TUSCO-SARDINIAN LATE MIOCENE ENDEMIC VERTEBRATE ASSEMBLAGES (BACCINELLO-CINIGIANO BASIN, TUSCANY, ITALY)

The late Miocene continental successions of the Baccinello-Cinigiano basin (Grosseto), one of the longest and most continuous vertebrate-bearing continental successions in the Neogene Italian record, yielded at least four superimposed vertebrate assemblages bracketed in the time span 8.3 - 6.4 Ma. The Baccinello-Cinigiano basin is famous for recording endemic vertebrate assemblages that include the youngest European Miocene hominoid, Oreopithecus bambolii . The late Miocene endemic vertebrate fauna known as the Baccinello V0 assemblage is the oldest vertebrate fauna within the Baccinello-Cinigiano basin succession, being correlated to the European mammal Neogene unit MN11. Recent field surveys along the Trasubbie river allowed studying in detail the basal Baccinello-Cinigiano sedimentary succession, and sampling fossiliferous level bearing microvertebrates along the small creek Fosso della Fittaia. The sample “Fosso della Fittaia 2013” yielded about 170 fossil remains improving our documentation of the oldest vertebrate assemblages from the Baccinello-Cinigian basin. As far as rodents are concerned, in addition to the already recognized murid Huerzelerimys and glirid Anthracoglis , a few dental remains are assigned to a new genus and species of giant dormouse. It is further worth noting the occurrence in the sample of shrew remains (the first described from the Baccinello-Cinigiano basin) identified as cf. Lartetium . The latter attests the presence of a crocidosoricine in the Fosso della Fittaia 2013 assemblage, postdating the youngest known occurrences of the subfamily by at least 1 my. The vertebrate assemblage is completed by a diverse herpetofauna and the first fish remains reported from the basin.

New fossils of the giant pholidosaurid genus Sarcosuchus from the Early Cretaceous of Tunisia

The Lower Cretaceous vertebrate assemblages from southeastern Tunisia contain one of the most diverse, unique and significant vertebrate faunas of this period in North Africa. The fossil record of crocodyliforms from these assemblages is becoming better understood with the increasing number of palaeontological discoveries that have been made over the past few years. However, very little data is available on the North Gondwanan pholidosaurid crocodyliform Sarcosuchus due to the paucity of material likely because of selective taphonomic factors. Here, I describe and figure new fossils of the pholidosaurid genus Sarcosuchus from Aptian-Albian deposits of the Tataouine Basin in southeastern Tunisia. These fossils include well-preserved dorsal osteoderms, which were found in anatomical connection, several isolated teeth and fragmentary remains mostly pertaining to the appendicular and axial skeletons. Anatomical studies and comparisons with other specimens have been performed, supporting the attribution of the material to the genus Sarcosuchus. I show that no attempt at a specific level can be made on the basis of the present fossils. The large size of the osteoderms and the stout conical teeth indicate that many Sarcosuchus individuals reached enormous body sizes.Sarcosuchus would have prospered in a flood dominated river-delta system that characterized the Tethyan margin of Gondwana by the end of the Lower Cretaceous. The abundant remains of diverse fish taxa including actinopterygians, sarcopterygians and chondrichthyans are indicative of a productive ecosystem, and further suggest that the diet of the Tunisian taxon included large bodied fish. This discovery provides a substantial addition to the extremely poor record of the North African crocodylomorphs with new insights into their palaeobiogeographic distribution, palaeoecology and extinction.

Weak environmental controls on the composition and diversity of medium and large‐sized vertebrate assemblages in neotropical rain forests of the Guiana Shield

AbstractAimDespite their often high‐trophic position and their contribution to many ecosystem functions, little is known about the factors affecting assemblage structure of medium‐ and large‐sized neotropical vertebrates. We examined the relative roles played by the physical and biological environment, and by purely spatial processes, in shaping the composition and diversities of these vertebrate assemblages. Then, based on the theory that the Guianan forest cover shrank to isolated pockets during the late Pleistocene–Holocene, we tested if the past forest refugia may have shaped current vertebrate assemblages.LocationFrench Guiana, Guiana Shield, South America.MethodsAbundances of 19 medium‐ and large‐sized vertebrates were estimated at 21 locations in undisturbed Guianan rain forests. Using taxonomic, functional and phylogenetic metrics, we partitioned the effects of a range of physical and biological environmental conditions and purely spatial predictors in shaping both assemblage composition and (alpha and beta) diversities.ResultsWe identified a significant, but weak relationship between taxonomic, functional and phylogenetic assemblage composition and environmental conditions. Assemblage diversity patterns were mainly explained by spatial predictors irrespective of the metrics. Current assemblage diversities are correlated with Pleistocene–Holocene forest history, with the highest alpha diversities outside of putative forest refugia, and the highest beta diversities inside these areas.Main conclusionsCurrent vertebrate assemblage composition is not strongly marked by common environmental factors. Our main conclusion is that assemblage composition results from individual species responses to the environment. Our findings also suggest that dispersal‐related processes or more probably historical processes shape (alpha and beta) diversity patterns. In fact, forest fragmentation during Pleistocene–Holocene climate changes could have led to isolated vertebrate assemblages evolving into unique species assemblages creating the current high beta diversity inside refugia, whereas the lower habitat stability outside of refugia could have led to mixed assemblages in areas recolonized by forest vertebrates (current high alpha diversity outside of refugia).

Microvertebrates from the Silurian–Devonian boundary beds of the Eastport Formation, Maine, eastern USA

Agnathan and gnathostome remains, associated with lingulid brachiopod fragments and distinctive ostracods, have been extracted from a small calcareous mudstone sample collected from the type section of the Eastport Formation on the northern shore of Moose Island, Maine. The vertebrate assemblage includes osteostracan, anaspid, and thelodont scales, and acanthodian scales, spines and teeth, which support a late Pridoli, or possibly earliest Lochkovian, age for the stratum. The thelodont Paralogania denisoni n. sp. is described, associated with a single thelodont scale referred tentatively to Talivalia? sp. indet., and acanthodians Nostolepis striata, Gomphonchus sandelensis, andPoracanthodes punctatus in a fauna that shows similarities to late Pridoli assemblages in Britain, parts of Europe, Russia, Greenland, and arctic Canada.