Vertebrate Assemblages Research Articles

Climate and land-use change will lead to a faunal "savannization" on tropical rainforests.

Humans have fragmented, reduced or altered the biodiversity in tropical forests around the world. Climate and land-use change act synergistically, increasing drought and fire frequencies, converting several tropical rainforests into derived savannas, a phenomenon known as "savannization." Yet, we lack a full understanding of the faunal changes in response to the transformation of plant communities. We argue that the composition of vertebrate assemblages in ecotone regions of forest-savanna transitions from South America will be increasingly replaced by open savanna species, a phenomenon we name "faunal savannization." We combined projections from ecological niche models, habitat filter masks and dispersal simulations to forecast the distribution of 349 species of forest- and savanna-dwelling mammal species across South America. We found that the distribution of savanna species is likely to increase by 11%-30% and spread over lowland Amazon and Atlantic forests. Conversely, forest-specialists are expected to lose nearly 50% of their suitable ranges and to move toward core forest zones, which may thus receive an influx of more than 60 species on the move. Our findings indicate that South American ecotonal faunas might experience high rates of occupancy turnover, in a process parallel to that already experienced by plants. Climate-driven migrations of fauna in human-dominated landscapes will likely interact with fire-induced changes in plant communities to reshape the biodiversity in tropical rainforests worldwide.

Diverse vertebrate assemblage of the Kilmaluag Formation (Bathonian, Middle Jurassic) of Skye, Scotland

ABSTRACTThe Kilmaluag Formation on the Isle of Skye, Scotland, provides one of the richest Mesozoic vertebrate fossil assemblages in the UK, and is among the richest globally for Middle Jurassic tetrapods. Since its discovery in 1971, this assemblage has predominantly yielded small-bodied tetrapods, including salamanders, choristoderes, lepidosaurs, turtles, crocodylomorphs, pterosaurs, dinosaurs, non-mammalian cynodonts and mammals, alongside abundant fish and invertebrates. It is protected as a Site of Special Scientific Interest and by Nature Conservancy Order. Unlike contemporaneous localities from England, this assemblage yields associated partial skeletons, providing unprecedented new data. We present a comprehensive updated overview of the Kilmaluag Formation, including its geology and the fossil collections made to date, with evidence of several species occurrences presented here for the first time. We place the vertebrate faunal assemblage in an international context through comparisons with relevant contemporaneous localities from the UK, Europe, Africa, Asia and the US. This wealth of material reveals the Kilmaluag Formation as a vertebrate fossil assemblage of global significance, both in terms of understanding Middle Jurassic faunal composition and the completeness of specimens, with implications for the early evolutionary histories of mammals, squamates and amphibians.

The Age and Vertebrate Paleontology of Labor-of-Love Cave, White Pine County, Nevada

We report the first radiocarbon ages on vertebrate fossils from Labor-of-Love Cave, White Pine County, Nevada, based on purified collagen in teeth and bone, as well as a description of the cave's vertebrate paleontology. This cave was discovered in 1982 with the recovery of an associated partial skeleton of the extinct giant short-faced bear (Arctodus simus). Subsequent excavations in 1985 recovered additional fossil material of birds and mammals from stream deposits in the cave. These fossils, along with fossils collected from the surface during surveys in 2018, are reported here. Radiocarbon ages indicate that most fossil material was deposited in the cave before and during the Last Glacial Maximum (LGM; 21,441–27,774 cal yr BP) and eroded from stream deposits inside the cave following the LGM, presumably from increased precipitation and stream flow. The vertebrate assemblage includes 4 other extinct taxa including 1 carnivore (Panthera atrox) and 3 ungulates (Equus sp., Oreamnos harringtoni, Euceratherium collinum) and the first record of Canada lynx (Lynx canadensis) from the Great Basin. If contemporaneous, the assemblage as a whole indicates an open grassland/sagebrush/tundra environment in Spring Valley during the late Pleistocene, with coniferous forest on mountain slopes facing this valley and where the cave is situated. Although the entrance to the cave is now blocked by slumped talus and breakdown, in the Pleistocene it was likely a large accessible opening at the base of a limestone cliff, with stream flow emerging and flowing into the valley below during the late Pleistocene, when bears and other species possibly used the cave as a shelter or den.

Turtles from the middle Miocene (MN5) of Somosaguas (Pozuelo de Alarcón, Madrid, Spain)

The systematic study of the vertebrate taxa found in the Middle Aragonian fossil sites of Somosaguas (Madrid, Spain) has provided important information on one of the most diverse vertebrate assemblages recognized in the Middle Miocene of the Madrid Basin. Although the mammals are the most abundant and diverse taxa recognized in Somosaguas, other vertebrate groups are also represented there. Several elements assigned to turtles, hitherto unpublished, are recognized. Their analyses allow to identify them as belonging to two terrestrial taxa, both assigned to Testudinidae. One of them is attributed cf. Cheirogaster, taxon very common in the Spanish Aragonian sites, and specifically in the Madrid Basin. The other taxon is identified as cf. Paleotestudo, a genus not previously cited in this basin

Nonmarine turtles from the Aguja Formation (Late Cretaceous, Campanian) of Chihuahua, Mexico

Fragments of turtle shell are known from several Upper Cretaceous formations in Mexico, including Corral de Enmedio and Packard Shale, Sonora; Aguja and Cerro del Pueblo, Coahuila; San Carlos, Chihuahua; El Gallo, Baja California; and Ocozocoautla, Chiapas. Turtles are important members of Upper Cretaceous vertebrate assemblages throughout North America and are considered a useful tool to define biogeographic patterns. The Upper Cretaceous sedimentary rocks exposed in the Aguja Formation record the final transgressive/regressive sequence of the Western Interior Cretaceous Seaway and the subsequent transition from a marine to terrestrial environment. The total area of outcrops is small compared to correlative exposures of these strata elsewhere in North America, in spite of this, numerous invertebrate and vertebrate fossils have been collected. The Aguja Formation in Texas preserves one of the southernmost well-studied Upper Cretaceous (Campanian) terrestrial vertebrate faunas in North America; contrary to what happens with the outcrops in northern Chihuahua, where the record of terrestrial vertebrates is scarce and especially those related to Testudines. Non-marine strata of the Aguja Formation do not appear to be present farther south in Mexico, and this is the reason why the Aguja fauna is relevant to documenting latitudinal variation in Campanian continental faunal associations. In this paper, the richness of Upper Cretaceous turtles collected from three localities within the Aguja Formation in Chihuahua is reviewed. Six taxa are recognized based on shell fragments with distinctive sculpture patterns: stem cryptodires, including cf. Baenidae, c.f. Denazinemys nodosa and cf. Compsemys victa, and crown group cryptodires including trionychians (trionchids and Basilemys sp.) and a kinosternoid (cf. Yelmochelys rosarioae). With the recognition of these taxa, new records are reported for the Aguja Formation (e.g. cf. Yelmochelys rosarioae) and Mexico (e.g. c.f. Denazinemys nodosa). The knowledge of Cretaceous turtle richness of the Aguja Formation and Mexico is increased and confirms the proposal of the variability richness along the North American localities. This latitudinal variability suggests that at any time turtles would have had a climatically controlled northern limit of distribution, and the richness of turtles would have decreased as this limit was reached.

Biostratigraphy of theDaptocephalusAssemblage Zone (Beaufort Group, Karoo Supergroup), South Africa

AbstractThe name Daptocephalus Assemblage Zone (DaAZ) is re-instated for vertebrate assemblages of the uppermost Permian strata (Balfour, upper Teekloof, and Normandien formations) of South Africa’s main Karoo Basin (MKB). This involved taxonomic revision of the dicynodontoid “Dicynodon” sensu lato, reviving Daptocephalus leoniceps, and revising the stratigraphic ranges of co-occurring index taxa (Theriognathus microps, Procynosuchus delaharpeae) of the Dicynodon Assemblage Zone (DiAZ) as it was known. This work has demonstrated the appearance of index taxa below the stratigraphically defined DiAZ. Moreover, the first appearance of Lystrosaurus maccaigi and Moschorhinus kitchingi in the upper reaches of the biozone calls for the establishment of a two-fold subdivision of the current DaAZ into lower (Dicynodon-Theriognathus) and upper (Lystrosaurus maccaigi-Moschorhinus) subzones. The biostratigraphic utility of Daptocephalus and other South African dicynodontoids outside of the MKB is limited due to basinal endemism at the species level and varying temporal ranges of dicynodontoids globally. Accordingly, their use is recommended only for correlation within the Karoo Basin at this stage.

Trophic innovations fuel reef fish diversification

Reef fishes are an exceptionally speciose vertebrate assemblage, yet the main drivers of their diversification remain unclear. It has been suggested that Miocene reef rearrangements promoted opportunities for lineage diversification, however, the specific mechanisms are not well understood. Here, we assemble near-complete reef fish phylogenies to assess the importance of ecological and geographical factors in explaining lineage origination patterns. We reveal that reef fish diversification is strongly associated with species’ trophic identity and body size. Large-bodied herbivorous fishes outpace all other trophic groups in recent diversification rates, a pattern that is consistent through time. Additionally, we show that omnivory acts as an intermediate evolutionary step between higher and lower trophic levels, while planktivory represents a common transition destination. Overall, these results suggest that Miocene changes in reef configurations were likely driven by, and subsequently promoted, trophic innovations. This highlights trophic evolution as a key element in enhancing reef fish diversification.

Oldest co-occurrence of Varanus and Python from Africa-first record of squamates from the early Miocene of Moghra Formation, Western Desert, Egypt.

Lizard and snake remains from the early Miocene (Burdigalian) of the Moghra Formation, Egypt, are described herein. This material comprises the first fossil remains of squamates recovered from the otherwise rich and well known vertebrate assemblage of Moghra. The material pertains to two different genera, the varanid lizard Varanus and the pythonid snake Python and adds to the so far rather poorly known squamate fossil record from Africa. On the basis of the new remains, Moghra marks the oldest so far described co-occurrence of Varanus and Python in the African continent. The close sympatry of these two genera in the African fossil record is thoroughly analyzed and discussed, a co-existence, which is still widespread in the extant herpetofauna of the continent. Situated rather close to the so called “Levantine Corridor” and dated at the Burdigalian, practically when Afro-Arabia collided with Eurasia, the Moghra squamate assemblage offers the potential of important insights in the biogeography and dispersal events of vertebrate groups during the early Miocene.

New insights on the quaternary fossil record of Isla de la Juventud, Cuba

The fossil record of Isla de la Juventud, the second largest island in the Cuban archipelago, is very limited in the number of taxa and localities so far studied but can be key to further understand the biogeographical history and extinction of the fauna in the region. Here, we report the faunal assemblages of two recently discovered Quaternary deposits containing numerous vertebrates and land snails in northern Isla de la Juventud. The first locality, a marble breccia on the coast of Punta Bibijagua, contained remains of an extinct rodent and a sloth. The second locality, a dissolution fissure filled with fossil-bearing sediment in a marble quarry in Sierra de Casas, contained a rich assemblage of land snails and vertebrates. Nineteen species, 14 genera and nine families of gastropods were identified, of which 11 species and two genera are endemic. The snail fossil assemblage is similar to the community of living gastropods in the locality. Moreover, 12 taxa, four of them extinct, 11 genera from ten families of terrestrial vertebrates were recognized; including the first report of fossils frogs, toads, lizards, snakes, and tortoises from Isla de la Juventud. Because remains at Sierra de Casas were collected ex-situ, any possible stratigraphic relationship among them was lost, but we were able to determine the presence of at least two taphonomic modes that suggest different depositional histories. Furthermore, we found no evidence of extinction or extirpation among land snails in the region, but of the vertebrates’ assemblage two rodents, two sloths and a tortoise went extinct. These five taxa also disappeared in the mainland, suggesting that the extinction was in some cases taxonomic specific across the Cuban Archipelago.

The Youngest Triassic Land Vertebrate Assemblage of Russia: Composition and Dating

The youngest Triassic faunistic assemblage of land vertebrates in Russia originates from the upper beds of the Bukobay Formation (Middle Triassic) of the South Cis-Urals in the Lysov locality (Orenburg Region). Bivalve mollusks, a diverse macro-flora, and a rich palynological assemblage were identified at this locality, in addition to tetrapods and fish. The study of the palynological assemblage enabled reliable confirmation of the Ladinian age of the bone-bearing rocks. The Bukobay time represents a separate (Ladinian) stage in the evolution of the fauna and flora of the South Cis-Urals.

A taphonomic analysis of a multitaxic bonebed from the St. Mary River Formation (uppermost Campanian to lowermost Maastrichtian) of Alberta, dominated by cf. Edmontosaurus regalis (Ornithischia: Hadrosauridae), with significant remains of Pachyrhinosaurus canadensis (Ornithischia: Ceratopsidae)

Scabby Butte is an isolated exposure of Upper Cretaceous (uppermost Campanian to lowermost Maastrichtian) strata of the St. Mary River Formation. These rocks have produced a diverse assemblage of both terrestrial and aquatic vertebrates, although hadrosaurid and ceratopsid dinosaurs represent the largest component by volume. Almost all of these dinosaur remains were collected from a single bonebed (Site 2) at Scabby Butte and have been referred to the hadrosaurid Edmontosaurus regalis Lambe, 1917 and the ceratopsid Pachyrhinosaurus canadensis Sternberg, 1950. This study presents a quantitative taphonomic reanalysis of the originally published data, providing new information previously overlooked and important information about the age-class structure of the dinosaur fauna preserved at the site. Site 2 is a lag deposit with a minimum number of 11 individuals (two ceratopsid, nine hadrosaurid), with three-quarters of the material being adult-sized based on size-class analysis. Most elements have undergone moderate to severe breakage and abrasion, and are completely disarticulated, suggesting that they were transported from where they died; post-mortem scavenging is also a possibility, as evidenced by the presence of tooth marks and trample marks on several elements. Burial took place soon after scavenging, as there is little evidence of subaerial weathering.

Microstructure and geochemical features of hard dental tissues of Deltavjatia vjatkensis and Suminia getmanovi Permian tetrapods (Kotelnich site, Kirov region, Russia)

The Kotelnich pareiasaur site, one of the richest of the Permian period, is characterized by the unique integrity of fossil vertebrate assemblages and the preservation of bones’ internal structure (including fossil cellular structures) due to their burial features. Pareiasaur and suminia are two most widespread and most frequently encountered representatives of fossil fauna at the Kotelnich site, belonging to the herbivorous form of trophic affiliation. In the present work, a high degree of the structural preservation of the hard dental tissues of pareiasaur and suminia is demonstrated using scanning electron microscopy and energy dispersive X-ray spectroscopy. Fluorapatite composition of tooth tissues is indicated with trace rare earth elements and uranium incorporated from the host rock as a result of diagenetic alteration during fossilization. No secondary mineralization has been found in the pulp chamber uncovered by a cleavage. The features of its primary internal structure are observed such as pseudomorphs of iron-containing minerals over the fibrils of collagen fibers connecting odontoblastic processes with the walls of dentin tubules, as well as spherical pseudomorphs over blood-like cells.

Geology and paleontology of the Upper Cretaceous Kem Kem Group of eastern Morocco.

The geological and paleoenvironmental setting and the vertebrate taxonomy of the fossiliferous, Cenomanian-age deltaic sediments in eastern Morocco, generally referred to as the “Kem Kem beds”, are reviewed. These strata are recognized here as the Kem Kem Group, which is composed of the lower Gara Sbaa and upper Douira formations. Both formations have yielded a similar fossil vertebrate assemblage of predominantly isolated elements pertaining to cartilaginous and bony fishes, turtles, crocodyliforms, pterosaurs, and dinosaurs, as well as invertebrate, plant, and trace fossils. These fossils, now in collections around the world, are reviewed and tabulated. The Kem Kem vertebrate fauna is biased toward large-bodied carnivores including at least four large-bodied non-avian theropods (an abelisaurid, Spinosaurus, Carcharodontosaurus, and Deltadromeus), several large-bodied pterosaurs, and several large crocodyliforms. No comparable modern terrestrial ecosystem exists with similar bias toward large-bodied carnivores. The Kem Kem vertebrate assemblage, currently the best documented association just prior to the onset of the Cenomanian-Turonian marine transgression, captures the taxonomic diversity of a widespread northern African fauna better than any other contemporary assemblage from elsewhere in Africa.

A new archosauromorph from South America provides insights on the early diversification of tanystropheids.

After the Permo-Triassic mass extinction, the archosauromorph fossil record is comparatively abundant and ecologically diverse. Among early archosauromorphs, tanystropheids gained considerable attention due to the presence of extreme skeletal adaptations in response to sometimes overspecialized lifestyles. The origin and early radiation of Tanystropheidae, however, remains elusive. Here, a new Early Triassic archosauromorph is described and phylogenetically recovered as the sister-taxon of Tanystropheidae. The new specimen, considered a new genus and species, comprises a complete posterior limb articulated with pelvic elements. It was recovered from the Sanga do Cabral Formation (Sanga do Cabral Supersequence, Lower Triassic of the Paraná Basin, Southern Brazil), which has already yielded a typical Early Triassic vertebrate assemblage of temnospondyls, procolophonoids, and scarce archosauromorph remains. This new taxon provides insights on the early diversification of tanystropheids and represents further evidence for a premature wide geographical distribution of this clade. The morphology of the new specimen is consistent with a terrestrial lifestyle, suggesting that this condition was plesiomorphic for Tanystropheidae.

Effects of illegal logging on Amazonian medium and large-sized terrestrial vertebrates

Selective logging is a major form of land use in tropical rainforests, with more than half of the world’s tropical forest already explored. In the Brazilian Amazon, most logging operations are illegal and highly damaging to forests. However, the effects of illegal logging on wildlife are poorly studied. Here we investigate the effects of illegal logging on the assemblage of medium- to large-bodied terrestrial vertebrates at the Gurupi Biological Reserve, a protected area in extreme eastern Amazonia that has been subjected to three decades of illegal logging. We used camera traps to survey the terrestrial vertebrate assemblage and visual interpretation of Landsat time series data (1984–2016) to assess the history of illegal logging (number of logging bouts and recovery time) for each camera trap site. Hierarchical Modelling of Species Communities (HMSC) indicates that logging had a minor effect on both the assemblage composition and individual species abundance. At the local level, the study demonstrates that the reserve effectively safeguards a significant portion of the regional biodiversity even though it suffered degradation by illegal logging. At a wider scale, the results suggest that illegally logged forests can retain much of their conservation value, if they are protected from further anthropogenic impacts such as hunting, fragmentation and fires. However, our study represents a best-case scenario, unlikely to be met in most other illegally logged areas in the tropics, where logging is usually followed by secondary effects that amplify its impacts.

The impact of major warming at 14.7 ka on environmental changes and activity of Final Palaeolithic hunters at a local scale (Orawa-Nowy Targ Basin, Western Carpathians, Poland

There is a widespread belief that the abrupt warming at 14.7 ka had a profound impact on the environment. However, the direct correlation between the global climatic event and changes in local environments is not obvious. We examined faunal succession in an intra-mountain basin of the Western Carpathians to assess the potential influence of the climatic change between Greenland Stadial-2a and Greenland Interstadial-1e on the local environment. We investigated three vertebrate assemblages (total number of identified specimens = 18,745; minimum number of individuals = 7515; 138 taxa) from Obłazowa Cave (western entrance) and a Rock overhang in Cisowa Rock, radiocarbon dated to the period before and after the global warming, between ca. 17.0 and 14.0 ka. Our data revealed that the major abrupt warming that occurred 14.7 ka had little impact on the local environment, which could suggest that ecosystems in Central Europe were resilient to the abrupt global climate changes. The increase in fauna population sizes and species diversities in local biotopes was gradual and began long before the temperature increase. This was supported by the analysis of ancient DNA of Microtus arvalis, which showed a gradual increase in effective population size after 19.0 ka. The results of palaeoclimatic reconstruction pointed out that the compared sites were characterized by similar climatic conditions. According to our calculations, the differences in the annual mean temperatures did not exceed 0.5 °C and mean annual thermal amplitude changed from 22.9 to 22.4 °C. The environmental changes before 14.7 ka had no impact on the activity of Final Palaeolithic hunters in the studied area.

Late Jurassic theropod dinosaur bones from the Langenberg Quarry (Lower Saxony, Germany) provide evidence for several theropod lineages in the central European archipelago.

Marine limestones and marls in the Langenberg Quarry provide unique insights into a Late Jurassic island ecosystem in central Europe. The beds yield a varied assemblage of terrestrial vertebrates including extremely rare bones of theropod from theropod dinosaurs, which we describe here for the first time. All of the theropod bones belong to relatively small individuals but represent a wide taxonomic range. The material comprises an allosauroid small pedal ungual and pedal phalanx, a ceratosaurian anterior chevron, a left fibula of a megalosauroid, and a distal caudal vertebra of a tetanuran. Additionally, a small pedal phalanx III-1 and the proximal part of a small right fibula can be assigned to indeterminate theropods. The ontogenetic stages of the material are currently unknown, although the assignment of some of the bones to juvenile individuals is plausible. The finds confirm the presence of several taxa of theropod dinosaurs in the archipelago and add to our growing understanding of theropod diversity and evolution during the Late Jurassic of Europe.

Dispersion fields reveal the compositional structure of South American vertebrate assemblages

The causes of continental patterns in species richness continue to spur heated discussion. Hypotheses based on ambient energy have dominated the debate, but are increasingly being challenged by hypotheses that model richness as the overlap of species ranges, ultimately controlled by continental range dynamics of individual species. At the heart of this controversy lies the question of whether species richness of individual grid cells is controlled by local factors, or reflects larger-scale spatial patterns in the turnover of species’ ranges. Here, we develop a new approach based on assemblage dispersion fields, formed by overlaying the geographic ranges of all species co-occurring in a grid cell. We created dispersion fields for all tetrapods of South America, and characterized the orientation and shape of dispersion fields as a vector field. The resulting maps demonstrate the existence of macro-structures in the turnover of biotic similarity at continental scale that are congruent among vertebrate classes. These structures underline the importance of continental-scale processes for species richness in individual assemblages.

Modeling the dynamics of a Late Triassic vertebrate extinction: The Adamanian/Revueltian faunal turnover, Petrified Forest National Park, Arizona, USA

Abstract The coincidence of a diverse vertebrate assemblage with a high-precision geochronology and lithostratigraphy in Petrified Forest National Park (Arizona, USA) allows Bayesian quantification of the dynamics of a Late Triassic vertebrate extinction and replacement, the Adamanian/Revueltian (A/R) faunal turnover. This approach uniquely identifies probabilities for the tempo of the replacement of the Adamanian assemblage by that of the Revueltian, precisely tracking the turnover. While the method does not designate the moment of extinction, there is a negligible probability that all Adamanian extinctions, as well as all Revueltian originations, are synchronous. A protracted A/R turnover is incompatible with the geologically instantaneous Manicouagan impact (215.4 ± 0.20 Ma; Québec, Canada) as a dominant causal mechanism. This analytical framework constitutes a flexible means of reconstructing biotic turnover in a variety of deep time contexts.

Geochemical study of the vertebrate assemblage zones of the Santa Maria Supersequence (Middle to Late Triassic), Paraná Basin, Brazil

The Middle-Upper Triassic section of the Paraná Basin is included in the Santa Maria Supersequence. This stratigraphic unit is classified as a second-order Supersequence, being subdivided into three third-order sequences in which four Assemblage Zones (AZ) based on tetrapods are recognized. In this work, chemical analyses of fossils and hosting rocks of each AZ were performed in order to verify whether the geochemical patterns of the rocks could serve to distinguish them even in the absence of fossils. For this purpose, nine samples of fossils and their sedimentary matrices were analyzed, by ICP-MS. The results show that there were changes in the chemical parameters in force at the depositional time of each sequence (and corresponding AZ). In general, the lower portion of the package was deposited under more basic and dry environmental conditions, indicated by the Ca and Ba concentrations found in the rocks and bones that contains them. By its turn, the top of the section is characterized by more acid and humid conditions, evidenced by Al, Si, and Sr increase. Such a geochemical shift from dry to humid conditions occurred just at the beginning of the Late Triassic and is probably related to the Carnian Pluvial Episode.