Age constraints on the dispersal of dinosaurs in the Late Triassic from magnetochronology of the Los Colorados Formation (Argentina)

Abstract: Significance Uncertainties in reported 40Ar/39Ar dates from the Ischigualasto Formation of Argentina allow its dinosaur-bearing fauna to be Norian in age and possibly contemporaneous with some of the older U-Pb dated dinosaur-bearing units in the Chinle Formation of the American Southwest. Our magnetochronology of the previously undated Los Colorados Formation, which also contains a diverse dinosaur assemblage, constrains its age to the interval from 227 to 213 Ma (Norian) and thereby largely restricts the underlying Ischigualasto Formation to the Carnian. Rise of early dinosaurs was thus diachronous across the Americas with their dispersal from the austral temperate belt blocked until later in the Norian. The breakout may have resulted from critically lowered climatic barriers associated with decreasing atmospheric pCO2 levels. A measured magnetozone sequence defined by 24 sampling sites with normal polarity and 28 sites with reverse polarity characteristic magnetizations was established for the heretofore poorly age-constrained Los Colorados Formation and its dinosaur-bearing vertebrate fauna in the Ischigualasto–Villa Union continental rift basin of Argentina. The polarity pattern in this ∼600-m-thick red-bed section can be correlated to Chrons E7r to E15n of the Newark astrochronological polarity time scale. This represents a time interval from 227 to 213 Ma, indicating that the Los Colorados Formation is predominantly Norian in age, ending more than 11 My before the onset of the Jurassic. The magnetochronology confirms that the underlying Ischigualasto Formation and its vertebrate assemblages including some of the earliest known dinosaurs are of Carnian age. The oldest dated occurrences of vertebrate assemblages with dinosaurs in North America (Chinle Formation) are younger (Norian), and thus the rise of dinosaurs was diachronous across the Americas. Paleogeography of the Ischigualasto and Los Colorados Formations indicates prolonged residence in the austral temperate humid belt where a provincial vertebrate fauna with early dinosaurs may have incubated. Faunal dispersal across the Pangean supercontinent in the development of more cosmopolitan vertebrate assemblages later in the Norian may have been in response to reduced contrasts between climate zones and lowered barriers resulting from decreasing atmospheric pCO2 levels.

late triassic
magnetochronology
los colorados formation


Louse infestation of the Chiribaya culture, southern Peru: variation in prevalence by age and sex.

Abstract: In order to improve the interpretive potential of archaeoparasitology, it is important to demonstrate that the epidemiology of ancient parasites is comparable to that of modern parasites. Once this is demonstrated, then we can be secure that the evidence of ancient parasitism truly reflects the pathoecology of parasitic disease. Presented here is an analysis of the paleoepidemiology of Pediculus humanus infestation from 146 mummies from the Chiribaya culture 1000-1250 AD of Southern Peru. The study demonstrates the modern parasitological axiom that 10% of the population harbors 70% of the parasites holds true for ancient louse infestation. This is the first demonstration of the paleoepidemiology of prehistoric lice infestation.

chiribaya culture
southern peru
louse infestation


The Horseshoe Crab of the Genus Limulus: Living Fossil or Stabilomorph?

Abstract: A new horseshoe crab species, Limulus darwini, is described from the uppermost Jurassic (ca. 148 Ma) near-shore sediments of the Kcynia Formation, central Poland. The only extant species Limulus polyphemus (Linnaeus) inhabits brackish-marine, shallow water environments of the east coast of the United States. Here it is shown that there are no important morphological differences between the Kcynia Formation specimens and extant juvenile representatives of the genus Limulus. The palaeoecological setting inhabited by the new species and the trophic relationships of extant horseshoe crabs are discussed in an attempt to determine the potential range of food items ingested by these Mesozoic xiphosurans. In this paper we propose the adoption of a new term stabilomorphism, this being: an effect of a specific formula of adaptative strategy among organisms whose taxonomic status does not exceed genus-level. A high effectiveness of adaptation significantly reduces the need for differentiated phenotypic variants in response to environmental changes and provides for long-term evolutionary success.

horseshoe crab
living fossil
stabilomorph


Delayed recovery of non-marine tetrapods after the end-Permian mass extinction tracks global carbon cycle

Abstract: During the end-Permian mass extinction, marine ecosystems suffered a major drop in diversity, which was maintained throughout the Early Triassic until delayed recovery during the Middle Triassic. This depressed diversity in the Early Triassic correlates with multiple major perturbations to the global carbon cycle, interpreted as either intrinsic ecosystem or external palaeoenvironmental effects. In contrast, the terrestrial record of extinction and recovery is less clear; the effects and magnitude of the end-Permian extinction on non-marine vertebrates are particularly controversial. We use specimen-level data from southern Africa and Russia to investigate the palaeodiversity dynamics of non-marine tetrapods across the Permo-Triassic boundary by analysing sample-standardized generic richness, evenness and relative abundance. In addition, we investigate the potential effects of sampling, geological and taxonomic biases on these data. Our analyses demonstrate that non-marine tetrapods were severely affected by the end-Permian mass extinction, and that these assemblages did not begin to recover until the Middle Triassic. These data are congruent with those from land plants and marine invertebrates. Furthermore, they are consistent with the idea that unstable low-diversity post-extinction ecosystems were subject to boom–bust cycles, reflected in multiple Early Triassic perturbations of the carbon cycle.

recovery
non-marine tetrapod
end-permian mass extinction
ecosystem
middle triassic


Chemical characterization of pterosaur melanin challenges color inferences in extinct animals

Abstract: Melanosomes (melanin-bearing organelles) are common in the fossil record occurring as dense packs of globular microbodies. The organic component comprising the melanosome, melanin, is often preserved in fossils, allowing identification of the chemical nature of the constituent pigment. In present-day vertebrates, melanosome morphology correlates with their pigment content in selected melanin-containing structures, and this interdependency is employed in the color reconstruction of extinct animals. The lack of analyses integrating the morphology of fossil melanosomes with the chemical identification of pigments, however, makes these inferences tentative. Here, we chemically characterize the melanin content of the soft tissue headcrest of the pterosaur Tupandactylus imperator by alkaline hydrogen peroxide oxidation followed by high-performance liquid chromatography. Our results demonstrate the unequivocal presence of eumelanin in T. imperator headcrest. Scanning electron microscopy followed by statistical analyses, however, reveal that preserved melanosomes containing eumelanin are undistinguishable to pheomelanin-bearing organelles of extant vertebrates. Based on these new findings, straightforward color inferences based on melanosome morphology may not be valid for all fossil vertebrates, and color reconstructions based on ultrastructure alone should be regarded with caution.

melanin
color inference
extinct animal
microbodie
electron microscopy


Evidence for an extraterrestrial impact 12,900 years ago that contributed to the megafaunal extinctions and the Younger Dryas cooling

Abstract: A carbon-rich black layer, dating to ≈12.9 ka, has been previously identified at ≈50 Clovis-age sites across North America and appears contemporaneous with the abrupt onset of Younger Dryas (YD) cooling. The in situ bones of extinct Pleistocene megafauna, along with Clovis tool assemblages, occur below this black layer but not within or above it. Causes for the extinctions, YD cooling, and termination of Clovis culture have long been controversial. In this paper, we provide evidence for an extraterrestrial (ET) impact event at ≅12.9 ka, which we hypothesize caused abrupt environmental changes that contributed to YD cooling, major ecological reorganization, broad-scale extinctions, and rapid human behavioral shifts at the end of the Clovis Period. Clovis-age sites in North American are overlain by a thin, discrete layer with varying peak abundances of (i) magnetic grains with iridium, (ii) magnetic microspherules, (iii) charcoal, (iv) soot, (v) carbon spherules, (vi) glass-like carbon containing nanodiamonds, and (vii) fullerenes with ET helium, all of which are evidence for an ET impact and associated biomass burning at ≈12.9 ka. This layer also extends throughout at least 15 Carolina Bays, which are unique, elliptical depressions, oriented to the northwest across the Atlantic Coastal Plain. We propose that one or more large, low-density ET objects exploded over northern North America, partially destabilizing the Laurentide Ice Sheet and triggering YD cooling. The shock wave, thermal pulse, and event-related environmental effects (e.g., extensive biomass burning and food limitations) contributed to end-Pleistocene megafaunal extinctions and adaptive shifts among PaleoAmericans in North America.

extraterrestrial impact
megafaunal extinction
younger dryas


A New Madtsoiid Snake from the Paleogene of South America (Northwestern Argentina), Based on an Articulated Postcranial Skeleton

Abstract: ABSTRACT The Madtsoiidae are an extinct lineage of snakes known from the Late Cretaceous to the Late Pleistocene, with a rich fossil record distributed mainly across Gondwanan landmasses. However, only a few taxa are represented by cranial or articulated remains, and most madtsoiids are known only by isolated vertebrae. The unambiguous record of Madtsoiidae from the Cenozoic in South America had been restricted to the genus Madtsoia from Eocene and Oligocene deposits of Patagonia and Brazil. Here, we describe a new madtsoiid taxon, Powellophis andina gen. et sp. nov., based on an articulated postcranial skeleton from the Mealla Formation (middle–late Paleocene) in northwestern Argentina. The new taxon is estimated to be around 3 meters long, with a vertebral morphology sharing similar features with other mid-to-large forms. Its inclusion in a recent analysis of madtsoiid relationships recovers Powellophis as an early member of a clade formed by mostly large bodied and gigantic taxa. Its presence in the Paleocene of northwestern Argentina fills the gap between the diverse Late Cretaceous and Eocene–Oligocene records of madtsoiids in South America, confirms their presence in northern Gondwana by the early Paleogene, and expands the diversity of the group.

new madtsoiid snake
paleogene
northwestern argentina
postcranial skeleton


Environmental preferences of brachiopods and bivalves across major climatic changes during the Late Palaeozoic ice age (Pennsylvanian, western Argentina)

Abstract: During the late Palaeozoic ice age (LPIA), ice‐proximal marine regional communities record contrasting responses to climate change compared to ice‐distal communities. However, there is still much to be understood in distal regions in order to fully understand the palaeobiological consequences of the LPIA. Here, were analyse brachiopod and bivalve environmental preferences along the bathymetric gradient during a major glacial event and the subsequent non‐glacial interval in western Argentina. Median environmental breadths did not change with the reassembly of communities during the non‐glacial interval. Moreover, bivalves and brachiopod immigrants show similar environmental breadths although they tend to have immigrated from different palaeogeographical regions. These patterns reinforce the idea that the worldwide marine fauna was probably culled of stenotopic taxa during the LPIA. On the other hand, analysis of the preferred depths of survivors and immigrants sheds light on the substantial modification of the bathymetric diversity gradient. Among different possible explanations, the immigration of taxa with affinities for deep environments is the only one supported. In addition, results underscore the observation that the higher turnover in the offshore environment was probably driven by immigration rather than extinction. Finally, stability in environmental preferences at a regional scale is not mirrored by stability in survivors’ individual preferences, because survivors’ preferred depth is not correlated during the glacial and non‐glacial intervals. Moreover, the amount of change in survivors preferred depth is not related to their environmental breadth, nor to their occupancy. These patterns suggest: (1) instability in realized niches; and (2) individual responses of survivor genera.

bivalve
climate change
western argentina
environmental preference


Fossil-Lagerstätte Enspel–a short review of current knowledge, the fossil association, and a bibliography

Abstract: Almost two decades ago, the Generaldirektion Kulturelles Erbe Rheinland-Pfalz initiated annual field campaigns in order to investigate geological and palaeobiological aspects of the Fossil-Lagerstätte Enspel, an upper Oligocene crater lake. Since then, the fossil-bearing 'oilshale' became more and more exposed due to the removal of the overlying basalt, which is still being commercially exploited. This contribution briefly summarizes the current knowledge that accumulated mainly within the last 20 years, gives a taxonomic listing of the fossil association, and includes a bibliography.

current knowledge
fossil association
bibliography
oligocene
excavation


Tidal mixing and the Meridional Overturning Circulation from the Last Glacial Maximum

Abstract: Using a global tidal model it is shown that the supply of tidal energy to the deep ocean was larger during the Last Glacial Maximum (LGM; 18,000–22,000 years BP). The results were used to modify the rate of vertical mixing in a coupled ocean‐atmosphere model set up for the present and LGM oceans. The increased levels of mechanical energy during the LGM were countered by a fresher upper North Atlantic, which led to a reduced circulation and deep water formation in spite of a trebling of the implicit mixing energy. This identifies the significance of accurately representing vertical mixing in climate models to estimate the recovery time‐scales and timings of rapid catastrophic paleoceanographic events. From the estimated levels of implicit energy in the vertical mixing scheme an amendment to diffusivity based mixing schemes is suggested.


Geological Setting and Age of Australopithecus sediba from Southern Africa

Abstract: From Australopithecus to Homo Our genus Homo is thought to have evolved a little more than 2 million years ago from the earlier hominid Australopithecus. But there are few fossils that provide detailed information on this transition. Berger et al. (p. 195; see the cover) now describe two partial skeletons, including most of the skull, pelvis, and ankle, of a new species of Australopithecus that are informative. The skeletons were found in a cave in South Africa encased in sediments dated by Dirks et al. (p. 205) to about 1.8 to 1.9 million years ago. The fossils share many derived features with the earliest Homo species, including in its pelvis and smaller teeth, and imply that the transition to Homo was in stages. A new species of Australopithecus, about 1.9 million years old, shows many derived features with Homo, helping to reveal its evolution. We describe the geological, geochronological, geomorphological, and faunal context of the Malapa site and the fossils of Australopithecus sediba. The hominins occur with a macrofauna assemblage that existed in Africa between 2.36 and 1.50 million years ago (Ma). The fossils are encased in water-laid, clastic sediments that were deposited along the lower parts of what is now a deeply eroded cave system, immediately above a flowstone layer with a U-Pb date of 2.026 ± 0.021 Ma. The flowstone has a reversed paleomagnetic signature and the overlying hominin-bearing sediments are of normal polarity, indicating deposition during the 1.95- to 1.78-Ma Olduvai Subchron. The two hominin specimens were buried together in a single debris flow that lithified soon after deposition in a phreatic environment inaccessible to scavengers.

australopithecus sediba
south africa
hominin specimen


Attenuation of millennial-scale events by bioturbation in marine sediments

Abstract: The discovery of large, millennial-scale oscillations (1- 10 kyr period) in climate records from ice cores and marine sediments in the North Atlantic has motivated the search to understand their cause and evaluate the geographic extent of this variability. One uncertainty in comparing marine geologic records of millennial-scale variability is the extent to which mixing of sediment by organisms at the seafloor (bioturbation) may attenuate millennial-scale events in the stratigraphic record. Evidence of attenuation of millennial variability can be found in cores with sedimentation rates in the range of 5 -15 cm/kyr. Modeling the attenuation of a hypothetical input time series similar to GISP2 using a moderate level of mixing provides estimates of attenuation as a function of sedimentation rate. The amplitude of a 4 kyr duration event is reduced by 50% for sedimentation rates10 cm/kyr and reduced by 20% for sedimentation rates of 20 cm/kyr. Minimal attenuation (<5%) is achieved only when the sedimentation rate exceeds 50 cm/kyr for a 4 kyr duration event and 70 cm/kyr for a 2 kyr duration event. The intensity of mixing plays a role in determining how much attenuation occurs. The amplitude of a 4 kyr duration event in a 10 cm/kyr core is reduced by 75% under strong mixing or reduced by 25% under weak mixing. This study indicates that the original amplitude of Dansgaard-Oeschger (DO) millennial-scale events observed during the last glacial may be twice the observed amplitude for cores with sedimentation rates 10 - 20 cm/kyr that have experienced moderate bioturbation. Regional comparisons of the amplitude of millennial-scale variability will require cores with weak mixing or sedimentation rates exceeding 50 cm/kyr in order to avoid biased estimates of the amplitude of millennial-scale (4 kyr duration) variability.

millennial-scale event
bioturbation
marine sediment
amplitude


Amphibia of Enspel (Late Oligocene, Germany)

Abstract:
Amphibia from the Late Oligocene (MP 28) locality Enspel, Germany are represented by two caudates: a hyperossified salamandrid Chelotriton paradoxus and an indeterminate salamandrid different from Chelotriton in proportions of vertebral column. Anurans are represented by two forms of the genus Palaeobatrachus, one of which is nearly as large as P. gigas (now synonymized with P. grandipes). Pelobates cf. decheni, represented in this locality by three nearly complete adult skeletons and a large number of tadpoles, is the earliest record for the genus. Compared with later representatives of the genus, it does not yet possess specializations for burrowing. Ranidae are represented by two rather fragmentary and incomplete skeletons referred to as Rana sp. A comparatively large series of tadpoles was assigned to the Pelobatidae on the basis of tripartite frontoparietal complex. Most of them are premetamorphic larvae, and a few older ones are postmetamorphic, but they do not exceed Gossner stage 42.
One specimen is a large premetamorphic tadpole (no rudimentary limbs) with a total body length of 147 mm. Anatomically, it can be equally assigned to Pelobates or to Eopelobates; the second possibility was excluded only on the basis of absence of adult Eopelobates in this locality.


Ecomorphological diversification in squamates from conserved pattern of cranial integration

Abstract: Significance With >10,000 living species, squamate reptiles (lizards, snakes) exhibit enormous phenotypic variation reflecting their incredible range in ecology and developmental strategies. What drove this exceptional diversity? We analyze high-density surface morphometric data for skulls representing ∼200 modern and extinct species to provide a comprehensive, clade-wide investigation of how ecological and developmental factors contributed to cranial evolution across geologic time, skull regions, and taxa. Although diet and habitat have had an overarching impact on skull evolution (e.g., herbivory, along with aquatic and fossorial habitats, are associated with rapid evolution), lizards and snakes surprisingly share a common pattern of trait correlations (integration). The remarkable ecological and morphological diversity in squamates thus arose from selection acting on a conserved architecture of phenotypic integration. Factors intrinsic and extrinsic to organisms dictate the course of morphological evolution but are seldom considered together in comparative analyses. Among vertebrates, squamates (lizards and snakes) exhibit remarkable morphological and developmental variations that parallel their incredible ecological spectrum. However, this exceptional diversity also makes systematic quantification and analysis of their morphological evolution challenging. We present a squamate-wide, high-density morphometric analysis of the skull across 181 modern and extinct species to identify the primary drivers of their cranial evolution within a unified, quantitative framework. Diet and habitat preferences, but not reproductive mode, are major influences on skull-shape evolution across squamates, with fossorial and aquatic taxa exhibiting convergent and rapid changes in skull shape. In lizards, diet is associated with the shape of the rostrum, reflecting its use in grasping prey, whereas snakes show a correlation between diet and the shape of posterior skull bones important for gape widening. Similarly, we observe the highest rates of evolution and greatest disparity in regions associated with jaw musculature in lizards, whereas those forming the jaw articulation evolve faster in snakes. In addition, high-resolution ancestral cranial reconstructions from these data support a terrestrial, nonfossorial origin for snakes. Despite their disparate evolutionary trends, lizards and snakes unexpectedly share a common pattern of trait integration, with the highest correlations in the occiput, jaw articulation, and palate. We thus demonstrate that highly diverse phenotypes, exemplified by lizards and snakes, can and do arise from differential selection acting on conserved patterns of phenotypic integration.


A New, Early Puercan (Earliest Paleocene) Species of Purgatorius (Plesiadapiformes, Primates) from Saskatchewan, Canada

Abstract: Abstract The early Paleocene Purgatorius Van Valen and Sloan is the most primitive plesiadapiform primate yet discovered, mostly known from middle to late Puercan strata in Montana, deposited during the interval C29N of the geomagnetic polarity time scale. Here we describe Purgatorius coracis n. sp. from the Ravenscrag Formation, at the Rav W-1 horizon, Medicine Hat Brick and Tile Quarry, southwestern Saskatchewan. This horizon occurs within C29R, making P. coracis the earliest known primate, while strengthening the evidence that plesiadapiforms, and hence primates, originated and underwent their initial evolutionary diversification in North America. Most North American mammalian local faunas correlating with C29R have been assigned to the Pu1 (earliest Puercan) interval zone, but the taxonomic composition of the mammals accompanying P. coracis at Rav W-1 more resembles local faunas of Pu2 age. The occurrence at Rav W-1 of Pu2 aspect mammals within C29R agrees with similar occurrences at the Hiatt and PITA Flats localities in Montana and North Dakota, also possibly correlated with C29R. The evidence from these three sites, all in the Williston Basin, suggests that in some areas of the Western Interior Pu2 aspect local faunas were coeval with those of latest Pu1 age, having evolved earlier than has commonly been assumed.


A wide-gauge, large-mammal trackway from the upper Paleocene of Alberta, Canada

Abstract: A very rare 11.2 m long wide-gauge trackway, made by an as yet undetermined large mammal, is described from the Lacombe Member (Late Paleocene) of the Paskapoo Formation (Paleocene). The exposure of the trackway was connected with the record-setting floods of 2013 in the province of Alberta as the tracks were exposed close to the base of the Brazeau Dam in west-central Alberta. The tracks are preserved on the top surface of a siltstone, but extensive erosion of the tracks resulted in the removal of details such as claw and digit traces, as well as any heel or palm impressions. The tracks are all circular to subcircular in outline, and it is not possible to determine the direction of travel of the trackmaker. Sequences of distinct pairings of adjacent tracks on both the left and right set of traces are present, and these are interpreted to represent manus-pes couples. The tracks do not show any overprinting. The mean pace angulations of the two best preserved sections range from 113° to 125°, while their mean stride lengths range from 95 to 96 cm. The lack of any distinctive anatomical details being preserved in the tracks prevents a precise identification of the trackmaker, but the sizes, shapes, and age of the tracks suggest that they could have been made by a large pantodont.


A new species of early Cambrian arthropod reconstructed from exceptionally preserved mandibles and associated small carbonaceous fossils (SCFs)

Abstract: Mandibulate arthropods (myriapods, hexapods and crustaceans) account for a major component of extant animal diversity but their origins remain unclear. Here, we re‐examine the record of exceptionally preserved arthropodan microfossils, including mandibles, from the lower Cambrian (Stage 4) Mount Clark Formation, Northwest Territories, Canada. The assemblage comes from a single drillcore horizon and occurs as thousands of small carbonaceous fossils (SCFs) representing disarticulated body parts. The mandibles occur as isolated molar surfaces with an elongate outline, a heavy setal fringe, and a subtle right–left asymmetry. These are sufficiently distinctive to diagnose a new genus and species of arthropod, Masticaris fimbriata. Co‐occurring SCFs include diverse appendage lobes and ventral body fragments, along with spines and setae assignable to 53 morphological categories and occurring either singly or in arrays, including filter plates. Most are plausibly interpreted as belonging to the feeding apparatus of M. fimbriata. The mandibles and filter plates correspond to those in extant pancrustaceans, particularly branchiopods, although the mouthparts of some more basal Cambrian arthropods raise the possibility of convergent feeding adaptations. Overall, anatomical and taphonomic continuity with younger SCFs suggests that M. fimbriata belongs to an early pancrustacean radiation that is still largely cryptic in the fossil record. More generally, the assemblage provides an inventory of fine‐scale cuticular specializations in early Cambrian arthropods that prefigure the trophic versatility and ecological dominance of crustaceans in the modern marine fauna.

early cambrian arthropod
mandible
carbonaceous fossil


Porotic hyperostosis: a new perspective.

Abstract: Porotic hyperostosis is a paleopathologic condition that has intrigued researchers for over a century and a half. It is now generally accepted that anemia, most probably an iron deficiency anemia, is the etiologic factor responsible for lesion production. Although there can be a number of factors involved in the development of iron deficiency anemia, a dietary explanation has often been invoked to explain the occurrence of porotic hyperostosis in past human skeletal populations. In fact, porotic hyperostosis has been referred to as a "nutritional" stress indicator. Traditionally those groups with a higher incidence of porotic hyperostosis have been considered to be less successful in adapting to their environment or more nutritionally disadvantaged than other groups. A new perspective is emerging that is challenging previous views of the role of iron in health and disease, thus having profound implications for the understanding of porotic hyperostosis. There is a new appreciation of the adaptability and flexibility of iron metabolism; as a result it has become apparent that diet plays a very minor role in the development of iron deficiency anemia. It is now understood that, rather than being detrimental, hypoferremia (deficiency of iron in the blood) is actually an adaptation to disease and microorganism invasion. When faced with chronic and/or heavy pathogen loads individuals become hypoferremic as part of their defense against these pathogens, thus increasing their susceptibility to iron deficiency anemia. Within the context of this new perspective porotic hyperostosis is seen not as a nutritional stress indicator, but as a indication that a population is attempting to adapt to the pathogen load in its environment.

new perspective
disease
porotic hyperostosis


Total-Evidence Dating under the Fossilized Birth–Death Process

Abstract: Bayesian total-evidence dating involves the simultaneous analysis of morphological data from the fossil record and morphological and sequence data from recent organisms, and it accommodates the uncertainty in the placement of fossils while dating the phylogenetic tree. Due to the flexibility of the Bayesian approach, total-evidence dating can also incorporate additional sources of information. Here, we take advantage of this and expand the analysis to include information about fossilization and sampling processes. Our work is based on the recently described fossilized birth–death (FBD) process, which has been used to model speciation, extinction, and fossilization rates that can vary over time in a piecewise manner. So far, sampling of extant and fossil taxa has been assumed to be either complete or uniformly at random, an assumption which is only valid for a minority of data sets. We therefore extend the FBD process to accommodate diversified sampling of extant taxa, which is standard practice in studies of higher-level taxa. We verify the implementation using simulations and apply it to the early radiation of Hymenoptera (wasps, ants, and bees). Previous total-evidence dating analyses of this data set were based on a simple uniform tree prior and dated the initial radiation of extant Hymenoptera to the late Carboniferous (309 Ma). The analyses using the FBD prior under diversified sampling, however, date the radiation to the Triassic and Permian (252 Ma), slightly older than the age of the oldest hymenopteran fossils. By exploring a variety of FBD model assumptions, we show that it is mainly the accommodation of diversified sampling that causes the push toward more recent divergence times. Accounting for diversified sampling thus has the potential to close the long-discussed gap between rocks and clocks. We conclude that the explicit modeling of fossilization and sampling processes can improve divergence time estimates, but only if all important model aspects, including sampling biases, are adequately addressed.

birth–death
tree
fossil taxa
fbd model
total-evidence


No deep diving: evidence of predation on epipelagic fish for a stem beaked whale from the Late Miocene of Peru

Abstract: Although modern beaked whales (Ziphiidae) are known to be highly specialized toothed whales that predominantly feed at great depths upon benthic and benthopelagic prey, only limited palaeontological data document this major ecological shift. We report on a ziphiid–fish assemblage from the Late Miocene of Peru that we interpret as the first direct evidence of a predator–prey relationship between a ziphiid and epipelagic fish. Preserved in a dolomite concretion, a skeleton of the stem ziphiid Messapicetus gregarius was discovered together with numerous skeletons of a clupeiform fish closely related to the epipelagic extant Pacific sardine (Sardinops sagax). Based on the position of fish individuals along the head and chest regions of the ziphiid, the lack of digestion marks on fish remains and the homogeneous size of individuals, we propose that this assemblage results from the death of the whale (possibly via toxin poisoning) shortly after the capture of prey from a single school. Together with morphological data and the frequent discovery of fossil crown ziphiids in deep-sea deposits, this exceptional record supports the hypothesis that only more derived ziphiids were regular deep divers and that the extinction of epipelagic forms may coincide with the radiation of true dolphins.

epipelagic fish
whale
late miocene
ziphiidae


History matters: ecometrics and integrative climate change biology

Abstract: Climate change research is increasingly focusing on the dynamics among species, ecosystems and climates. Better data about the historical behaviours of these dynamics are urgently needed. Such data are already available from ecology, archaeology, palaeontology and geology, but their integration into climate change research is hampered by differences in their temporal and geographical scales. One productive way to unite data across scales is the study of functional morphological traits, which can form a common denominator for studying interactions between species and climate across taxa, across ecosystems, across space and through time—an approach we call ‘ecometrics’. The sampling methods that have become established in palaeontology to standardize over different scales can be synthesized with tools from community ecology and climate change biology to improve our understanding of the dynamics among species, ecosystems, climates and earth systems over time. Developing these approaches into an integrative climate change biology will help enrich our understanding of the changes our modern world is undergoing.

ecometric
climate change biology
dynamic


The Fin to Limb Transition: New Data, Interpretations, and Hypotheses from Paleontology and Developmental Biology

Abstract: After a brief historical review of the fin to limb transition and consideration of a theoretical “prototetrapod,” this article considers new ideas generated from recent fossil finds and from developmental biology that bear on the question of how limbs, digits, limb joints, and pentadactyly evolved. Among the first changes to take place were those to the humerus, in concert with those to the breathing apparatus, and these adaptations were acquired while the animals were still basically aquatic with the evolution of digits occurring during this phase. Studies from developmental biology of modern taxa can be integrated with information from fossils to produce a fuller picture. The acquisition of pentadactyly was among the last changes to occur in the modification of a fin into a limb. This vision differs radically from older theoretical ideas which perceived land locomotion as the prime evolutionary force driving the transition.

fin
limb transition
developmental biology


Insect mimicry of plants dates back to the Permian

Abstract: In response to predation pressure, some insects have developed spectacular plant mimicry strategies (homomorphy), involving important changes in their morphology. The fossil record of plant mimicry provides clues to the importance of predation pressure in the deep past. Surprisingly, to date, the oldest confirmed records of insect leaf mimicry are Mesozoic. Here we document a crucial step in the story of adaptive responses to predation by describing a leaf-mimicking katydid from the Middle Permian. Our morphometric analysis demonstrates that leaf-mimicking wings of katydids can be morphologically characterized in a non-arbitrary manner and shows that the new genus and species Permotettigonia gallica developed a mimicking pattern of forewings very similar to those of the modern leaf-like katydids. Our finding suggests that predation pressure was already high enough during the Permian to favour investment in leaf mimicry.


A symbiotic association of a boring polychaete and an echinoid from the Late Cretaceous of Germany

Abstract: From the Early Maastrichtian white chalk of Rügen Island (N Germany), a specimen of the echinoid Echinocorys ovata featuring 27 boring traces of the ichnogenus Caulostrepsis is described. Individual traces are shallow to moderately deep U-shaped depressions and show distinct regeneration textures evidencing a syn-vivo infestation. All traces are located on the plastron between the peristome and periproct of the host echinoid, indicating an adaptation of the trace maker by choosing the most advantageous position of the specific host. The traces are attributed to the work of boring spionid polychaetes (Polydora complex), grounded on the close morphological resemblance with initial borings of Recent polydorids. This is the first evidence for a possible association of a boring polychaete not only with an echinoid but with an echinoderm in general. The symbiotic relationship was commensalistic in nature with the spionid probably taking advantage of organic matter resuspended by the echinoids locomotion and feeding activity and benefiting from effective shelter. For the host echinoid, the association was moderately harmful. The soft bottom environment of the chalk sea provided very limited hard substrate ecospace for settlers and bioeroders, available only in form of biogenic structures. Echinocorys was a dominant component of this benthic community and can be considered as a suitable host for symbiotic interactions because of its size and assumed longevity.


Prolonged co-existence of ‘archaic’ and ‘modern’ Palaeozoic ophiuroids – evidence from the early Permian, Southern Carnarvon Basin, Western Australia

Abstract: The discovery of a very large ophiuroid (disk diameter of 80 mm) in the early Permian (Kungurian) Cundlego Formation in the Southern Carnarvon Basin of Western Australia extends the stratigraphical range of ‘archaic’ ophiuroids unequivocally into the Permian, unlocking a lost fossil record of this group. Hitherto such ophiuroids have been discovered preserved articulated from strata no younger than the late Carboniferous. Herein we describe the new ophiuroid as Teleosaster creasyi gen. et sp. nov. Although existing temporally with Permian ophiuroids with a ‘modern’ morphological architecture, Teleosaster was biogeographically separated. This ‘archaic’ ophiuroid persisted in high latitude seas, suggesting such ‘archaic’ forms were displaced from the shallow-water, low latitude niches by the ‘modern’ ophiuroids. In modern oceans, ophiuroid gigantism similar to that in Teleosaster creasyi is typically only expressed in cold, high latitude oceans. It has been argued that the frequent occurrence of gigantism in such environments is due to the much lower levels of predation pressure. Unlike other echinoderm classes, the morphological and ecological transformation that resulted in the evolution of ‘modern’ ophiuroids had already taken place well before the events of the Permo–Triassic mass extinction. With the increase in diversity of durophagous predators in low latitude shallow-water communities during the mid-Palaeozoic Marine Revolution, we argue that ‘archaic’ ophiuroids were more susceptible to these higher levels of predation than the ‘modern’ forms and were displaced into regimes of lower predation pressure in high latitude oceans. http://zoobank.org/urn:lsid:zoobank.org:pub:E4FD9264-127D-4995-AD12-C9721F212FCD

palaeozoic ophiuroid
ophiuroid
southern carnarvon basin


Feeding habits in trilobites

Abstract: We briefly review the various types of feeding habits in marine arthropods, and suggest that the trilobites adopted a range of different feeding strategies. We show that much of the variety of trilobite exoskeletal development, particularly in the cephalon, can be explained as a response to the adoption of specific feeding modes. We regard the primitive mode as having been predatory/scavenging, both from morphological grounds and by out-group comparison, but this habit had a long subsequent history in the group. Predators/scavengers included those trilobites with rigidly braced and attached conterminant or impendent hypostomes, which often developed posterior forks or rasps used by the animals for manipulating prey after it had been grasped by the ‘gnathobases’. Advanced predators often acquired expanded anterior glabellar lobes which are associated with the ingestion of bulky food; concomitantly, the largest trilobites of all had predatory morphology. Associated trace fossils are of the Rusophycus type in which impressions of limb bases and rarely the hypostome can be seen. Detritivors were derived from predators by detachment of the hypostome from the doublure in natant mode; it is significant that the hypostome of such feeders exhibited little change thereafter. The typical detritivor morphology is of the ‘generalized’ ptychopariid type, common in outer shelf habitats, with rectangular or tapering glabellas and small to moderate overall size. It is suggested that in some species the hypostome may have functioned as a ‘scoop’ directly to aid ingestion of sediment. Trace fossils of Cruziana semiplicatatype have been associated with sediment ploughing in this feeding mode. Filter feeders evolved a vaulted cephalic chamber of trinucleimorph type, and elevated thoraces, often flanked by extended genal spines. Where it is known, the hypostome is curved up inside the cephalic chamber, within which sediment stirred into suspension by the limbs was sorted for edible particles. Filter feeding trilobites are typically small, and are uncommon outside muddy habitats. Bean-likeRusophycusare the associated trace fossils. In trinucleids ingress of the feeding current was alongside the thorax and out through the fringe pits. The combination of different feeding modes with adaptation for different prey and/or particle sizes goes some way to account for the variety of trilobites cohabiting in a single site (alpha diversity). We do not claim that the model accounts for all morphological variation displayed by the group. TR I L O B I T E S are remarkable for their great variety of exoskeletal shapes. Their morphological complexity increased from the Cambrian into the Ordovician (Fortey and Owens 1990; Foote 1991), and a considerable array of forms persisted even into the Carboniferous. Yet comparatively little is known about how this morphological variety related to life habits. It is common to find reference to certain phases of trilobite history as ‘radiations’, for example, at the beginning of the Cambrian (Briggs and Fortey 1992), through much of the Ordovician (Droser t al. 1996) and in the Malvinokaffric Province of the Devonian (Eldredge 1980), yet although the implication clearly is that radiations were into a variety of niches, it is unclear what these niches were, nor whether the morphological compass displayed can be related to their life habits. Broad habitat differentiation is better known. It is clear that the trilobites were able to occupy normal marine habitats (biofacies) ranging from near inshore, to deep water, even ‘slope’ environments, at several hundred metres of water depth, from early in the Cambrian until the later Carboniferous (review in Fortey and Owens 1997). This differentiation accounts for some of the richness in species of trilobites of any given geological age, but it does not account for the subdivision of each habitat by its constituent species (alpha diversity). Biofacies can vary in the number of species and genera they include, but it is not uncommon for a single biofacies to include 20 or more benthic taxa (e.g. Ludvigsen et al. 1989). Presumably, such co-occurring species found ways of exploiting their total environment which allowed them to compete adequately with their neighbours. The kinds of niche subdivisions of habitat which were possible for trilobites have been little investigated (Bergström 1973). For such an extinct arthropod group, particularly one of which the appendages of so few species are known, the interpretation of life habits is not an easy matter. However, this should not prevent attempts to interpret reasonably function from form. This paper presents a model for trilobite feeding [Palaeontology, Vol. 42, Part 3, 1999, pp. 429–465] q The Palaeontological Association habits, with an aim of answering one of the commonest questions advanced about the group: why many different kinds of trilobites co-exist in the same rock bed. Not all trilobites were benthic; a free swimming fauna also lived within the water column, at least during the Cambrian and Ordovician (Robison 1972; Fortey 1985; Fortey and Owens 1987). Robison (1975) explained the co-occurrence of differently sized planktic agnostids as resource partitioning, whereby adult trilobite size reflected optimal utilization of different food particle sizes, thus relating taxonomic variety and aspects of morphology to feeding specialization. However, there are often references to feeding mode in otherwise morphological and taxonomic accounts, and we have attempted to review the scattered literature of the past 50 years in this paper. Such a review should be of use to the non-specialist palaeontologist for teaching purposes. Our prime purpose is to identify a number of morphological designs connected with different feeding habits, discuss their geological history, and associate them broadly with their appropriate trace fossils. T H E R A N G E O F P O S S I B I L I T I E S F O R T R I L O B I T E F E E D I N G H A B I T S Marine arthropods occupy many different niches, and not all of these are capable of being deduced from fossil evidence. There is no necessary relationship between belonging to a particular high level taxon and having a specific life habit. Virtually all larger Arachnida, for example, are predatory in habit, while crustaceans may be filter feeders, sediment feeders, parasites, or predators (Schram 1986). Even within a single crustacean group (e.g. Cladocera, see Fryer 1968) there may be a variety of feeding habits. Hence the recognition of the feeding habits of one species is no guarantee that the rest of the group to which it belongs will have similar habits. For trilobites, we are perforce concerned only with the broadest categories of feeding strategies, and we cannot approach the refinements known for the living fauna. To give one example, Laval (1980) describes how hyperiid amphipods have evolved a close relationship with medusoids and ctenophores, using them as a nursery for young, or in some cases killing them to construct their own floating accommodation. Such habits will forever elude palaeontological evidence. In the sections that follow, the attitude and position of the trilobite hypostome will be of importance. Throughout the rest of this paper we accept the commonly held view that the trilobite’s mouth lay at the back of the hypostome, and that the oesophagus lay above it. The oesophagus opened into the stomach situated beneath the glabella, especially its anterior part. The oesophagus was elevated or contracted by muscles which attached between the hypostome and the oesophagal wall. This is an arrangement similar to that described for the living notostracan Lepidurus arcticusby Fryer (1988, fig. 63). The life habits available to arthropods (and conceivably to trilobites) can be summarized briefly as follows: 1. Predatory. Hunting habits are common among crustaceans (e.g. Stomatopoda) and dominant in Arachnida.Limulusis capable of breaking clams with its gnathobasic jaws. There is a gradation between hunting activity and scavenging, and many crustaceans which are capable of hunting, e.g. among the decapods, are also opportunistic scavengers if the possibility arises. The manipulation of comparatively bulky food unites these two activities, and, because of the relatively high nutritional value of such food, larger arthropods tend to have such habits. We cannnot distinguish scavenging from predatory habits here. 2. Particle feeding. Feeding on edible detritus is a common mode of life among crustaceans, including branchiopods, ostracodes and isopods, among animals ranging from a few millimetres to a few tens of millimetres long (Brusca and Brusca 1990). Included in this category is feeding using the ventral median line as a food groove, such as has been described in the diminutive and primitive cephalocarid Hutchinsoniella by Sanders (1963). Sorting of edible from inedible particles is achieved by the appendages. A variant on this life mode is scraping or collecting edible material, usually algal, directly from rocks or sedimentary surfaces. 3. Suspension feeding. Many arthropods, notostracans, conchostracans and phyllocarids among them, stir up sediment in order to extract edible organic particles, or they exploit algal ‘soup’ in similar fashion. The notostracanTriops, for example, stirs up clouds of sediment beneath its dorsal carapace, and passes the edible particles sorted from suspension towards the mouth along the ventral food groove (Fryer 1988). One might suspect that this mode of life ought to be present among trilobites, especially in view of the similarity of the vaulted headshield of many species to that of Triops. 430 P A L A E O N T O L O G Y , V O L U M E 4 2


Allometric growth in the extant coelacanth lung during ontogenetic development

Abstract: Coelacanths are lobe-finned fishes known from the Devonian to Recent that were long considered extinct, until the discovery of two living species in deep marine waters of the Mozambique Channel and Sulawesi. Despite extensive studies, the pulmonary system of extant coelacanths has not been fully investigated. Here we confirm the presence of a lung and discuss its allometric growth in Latimeria chalumnae, based on a unique ontogenetic series. Our results demonstrate the presence of a potentially functional, well-developed lung in the earliest known coelacanth embryo, and its arrested growth at later ontogenetic stages, when the lung is clearly vestigial. The parallel development of a fatty organ for buoyancy control suggests a unique adaptation to deep-water environments. Furthermore, we provide the first evidence for the presence of small, hard, flexible plates around the lung in L. chalumnae, and consider them homologous to the plates of the ‘calcified lung' of fossil coelacanths.

coelacanth
lung
latimeria chalumnae
allometric growth


Jaws for a spiral-tooth whorl: CT images reveal novel adaptation and phylogeny in fossil Helicoprion

Abstract: New CT scans of the spiral-tooth fossil, Helicoprion, resolve a longstanding mystery concerning the form and phylogeny of this ancient cartilaginous fish. We present the first three-dimensional images that show the tooth whorl occupying the entire mandibular arch, and which is supported along the midline of the lower jaw. Several characters of the upper jaw show that it articulated with the neurocranium in two places and that the hyomandibula was not part of the jaw suspension. These features identify Helicoprion as a member of the stem holocephalan group Euchondrocephali. Our reconstruction illustrates novel adaptations, such as lateral cartilage to buttress the tooth whorl, which accommodated the unusual trait of continuous addition and retention of teeth in a predatory chondrichthyan. Helicoprion exemplifies the climax of stem holocephalan diversification and body size in Late Palaeozoic seas, a role dominated today by sharks and rays.


The genesis and environmental significance of red and black sedimentary interlayers in coral reef of well Nanyong 2

Abstract: The results of paleogeomagnetics and geochemistry of the coral reef in well Nanyong 2 of Nansha Islands showed that the bottom of the black sedimentary interlayer corresponds to the conversion boundary line between Brunhes Postive Polarity and Matuyama Reversed Polarity (B/M) and the cold/warm (19/20) climatic conversion bounds on δ18O curve, 0.78 Ma ago; and the red sedimentary interlayer corresponds to the Reunion I polarity excursion (reversion) of the geomagnetic field, 2.01–2.04 Ma ago. Comparing with the normal light-coloured coral reef rock, the magnetic susceptibility (χ), residual magnetization intensity (Mr) and the content of MnO and Fe2O3 of the black sedimentary layer appeared obviously positive abnormity. The magnetic susceptibility (χ), residual magnetization intensity (Mr) and the content of Fe2O3 of the red sedimentary layer also appeared positive abnormity. Combining with the analyzing results of paleontology, we hold that this pair of special and typical sedimentary interlayers was relative to the sudden change of paleoclimate, i.e. the global climatic change and its incidental polarity reversal of the geomagnetic field directly affected the living environment of the paleontological species as well as the dispersion and enrichment of some chemical elements, especially the elements sensitive to redox such as Fe and Mn. For example, the elements Fe and Mn concentrated in the glacial period would be largely oxidized and diluted when the climate warmed up suddenly, and the originally oxidized high valence Fe would be condensed again when the climate cooled suddenly. This is possibly one of the important reasons of appearing and disappearing of the red and black sedimentary events of coral reef in well Nanyong 2.

sedimentary interlayer
coral reef
nansha islands


Early Silurian (Llandovery) trilobites from the Cotton Formation, near Forbes, New South Wales, Australia

Abstract: A trilobite fauna from the upper part of the Cotton Formation (late Llandovery, Spirograptus turriculatus Zone) in central west New South Wales includes the new species Raphiophorus sandfordi, Odontopleura (Sinespinaspis) markhami and Aulacopleura pogsoni. Species of Odontopleura and Aulacopleura have not previously been documented in Australasia. The association of these genera is observed in offshore biofacies in the Llandovery/Wenlock on several palaeocontinents. Affinities of the species are with congeners from Bohemia and northwestern Canada (Odontopleura, Aulacopleura) and Tarim and South China (Aulacopleura, Raphiophorus).

llandovery
cotton formation
new south wales


Exceptional preservation of reproductive organs and giant sperm in Cretaceous ostracods

Abstract: The bivalved crustacean ostracods have the richest fossil record of any arthropod group and display complex reproductive strategies contributing to their evolutionary success. Sexual reproduction involving giant sperm, shared by three superfamilies of living ostracod crustaceans, is among the most fascinating behaviours. However, the origin and evolution of this reproductive mechanism has remained largely unexplored because fossil preservation of such features is extremely rare. Here, we report exceptionally preserved ostracods with soft parts (appendages and reproductive organs) in a single piece of mid-Cretaceous Kachin amber (approximately 100 Myr old). The ostracod assemblage is composed of 39 individuals. Thirty-one individuals belong to a new species and genus, Myanmarcypris hui gen. et sp. nov., exhibiting an ontogenetic sequence from juveniles to adults (male and female). Seven individuals are assigned to Thalassocypria sp. (Cypridoidea, Candonidae, Paracypridinae) and one to Sanyuania sp. (Cytheroidea, Loxoconchidae). Our micro-CT reconstruction provides direct evidence of the male clasper, sperm pumps (Zenker organs), hemipenes, eggs and female seminal receptacles with giant sperm. Our results reveal that the reproduction behavioural repertoire, which is associated with considerable morphological adaptations, has remained unchanged over at least 100 million years—a paramount example of evolutionary stasis. These results also double the age of the oldest unequivocal fossil animal sperm. This discovery highlights the capacity of amber to document invertebrate soft parts that are rarely recorded by other depositional environments.


Sampling diverse characters improves phylogenies: Craniodental and postcranial characters of vertebrates often imply different trees

Abstract: Morphological cladograms of vertebrates are often inferred from greater numbers of characters describing the skull and teeth than from postcranial characters. This is either because the skull is believed to yield characters with a stronger phylogenetic signal (i.e., contain less homoplasy), because morphological variation therein is more readily atomized, or because craniodental material is more widely available (particularly in the palaeontological case). An analysis of 85 vertebrate datasets published between 2000 and 2013 confirms that craniodental characters are significantly more numerous than postcranial characters, but finds no evidence that levels of homoplasy differ in the two partitions. However, a new partition test, based on tree‐to‐tree distances (as measured by the Robinson Foulds metric) rather than tree length, reveals that relationships inferred from the partitions are significantly different about one time in three, much more often than expected. Such differences may reflect divergent selective pressures in different body regions, resulting in different localized patterns of homoplasy. Most systematists attempt to sample characters broadly across body regions, but this is not always possible. We conclude that trees inferred largely from either craniodental or postcranial characters in isolation may differ significantly from those that would result from a more holistic approach. We urge the latter.

postcranial character
vertebrate
homoplasy


Burrows without a trace—How meioturbation affects rock fabrics and leaves a record of meiobenthos activity in shales and mudstones

Abstract: Understanding fine-grained sediment accumulation is critical for developing robust geologic models and inferring environmental conditions. Here we report on processes that produce compositional layering at the mm and sub-mm scale, with gradational rather than sharp layer boundaries. Sometimes described as fuzzy laminae, this feature occurs in modern muds that accumulate under oxygen-stressed conditions, caused by meiofauna (tiny organisms; benthic foraminifera, polychaetes, nematodes, etc.) that disrupts the original fabric. In the rock record, fuzzy laminae are common in shales that accumulated under presumed oxygen-stressed conditions. Like their presumed modern analogs, ancient examples contain remains of benthic foraminifera and other small benthic organisms that were the likely agents of fabric disruption. As preserved lamination is considered indicative of bottom water anoxia in ancient shales, we need to better understand the cause of fuzzy lamination, because such insights have the potential to allow much refined assessments of the depositional history of laminated organic-rich shales. In experiments, nematode activity blurred the originally sharp contacts between successive sediment layers with contrasting composition. Although nematode activity produces tiny temporary traces aside of blurring of primary fabric, the former have minimal preservation potential due to compaction of the water-rich substrate. Experimental fabrics compare well to those observed in a wide range of ancient black shales, suggesting common meiofaunal activity in the latter. Our findings imply that the details of lamination (fuzzy vs. sharp) in ancient shales are not necessarily controlled by bottom water oxygenation, but instead result from the interplay between sedimentation rates and bottom current activity.


Abstract: Kear, B.P. 2016. Cretaceous marine amniotes of Australia: perspectives on a decade of new research. Memoirs of Museum Victoria 74: 17–28. Cretaceous marine amniote fossils have been documented from Australia for more than 150 years, however, their global significance has only come to the fore in the last decade. This recognition is a product of accelerated research coupled with spectacular new discoveries from the Aptian–Albian epeiric sequences of the Eromanga Basin – especially the opal-bearing deposits of South Australia and vast lagerstätten exposures of central-northern Queensland. Novel fragmentary records have also surfaced in Cenomanian and Maastrichtian strata from Western Australia. The most notable advances include a proliferation of plesiosaurian taxa, as well as detailed characterization of the ‘last surviving’ ichthyosaurian Platypterygius, and some of the stratigraphically oldest protostegid sea turtles based on exceptionally preserved remains. Compositionally, the Australian assemblages provide a unique window into the otherwise poorly known Early Cretaceous marine amniote faunas of Gondwana. Their association with freezing high latitude palaeoenvironments is also extremely unusual, and evinces a climate change coincident diversity turnover incorporating the nascent radiation of lineages that went on to dominate later Mesozoic seas.

australia
new research
cretaceous marine amniote


Abstract: Abstract 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-89B2-17CAF2865AD4 SUPPLEMENTAL DATA—Supplemental materials are available for this article for free at www.tandfonline.com/UJVP Citation 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.

review
high-latitude vertebrate assemblage
end-permian mass extinction


The Mazon Creek Lagerstätte: a diverse late Paleozoic ecosystem entombed within siderite concretions

Abstract: One of the best records of late Paleozoic ecosystems, the Mazon Creek Lagerstätte is world famous for its striking flora and fauna preserved within siderite concretions. Distinct from other late Carboniferous concretionary Lagerstätten because of the remarkable fidelity of soft tissues and pigments that are frequently preserved, the Mazon Creek has seen a revival in investigations during the last 10 years using modern palaeontological techniques. However, many of these modern investigations build upon a literature that incorrectly interprets the palaeoenvironment of the Mazon Creek and the separate biotas: there is a lack of evidence to support a distinct freshwater fauna. Here, we present a detailed overview of the Mazon Creek Lagerstätte, including the palaeoenvironmental conditions, organisms present and the complex taphonomic processes involved in fossil formation. Investigation into the formation of siderite concretions and the complex taphonomic processes controlling soft-bodied preservation are still continuing but are reviewed in detail.

mazon creek lagerstätte
paleozoic ecosystem
concretion


The Earliest Elcanidae (Insecta, Orthoptera) from the Upper Triassic of North America

Abstract: Abstract. A new genus and species of the Elcanidae (Orthoptera, Elcanoidea), Cascadelcana virginiana n. gen. n. sp., is described based on a forewing specimen from the Upper Triassic (Norian) Cow Branch Formation in the Solite Quarry Lagerstätte near the North Carolina-Virginia boundary, USA. It is distinguished from other elcanid species by its RP +MA1 with six branches, M with two branches before stem MA1 fused with RP, and short CuA almost vertical against the posterior margin. This fossil represents the earliest definitive record of the family Elcanidae and the first orthopteran described from the Triassic of North America. Scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) analyses show that the veins and a pterostigma-like structure on the wing of C. virginiana n. gen. n. sp. are preserved as carbonaceous compressions. The presence of a pterostigma-like structure in elcanids indicates that they may have evolved a particular flight mechanism distinct from those of other orthopterans.


Libysiren sickenbergi, gen. et sp. nov.: A New Sirenian (Mammalia, Protosirenidae) from the Middle Eocene of Libya

Abstract:
ABSTRACT
 Fossil sirenian specimens collected in 1964 by the late R. J. G. Savage's expeditions in north-central Libya are described. They come from early middle Eocene (lower Lutetian, 47.8–43.6 Ma) deposits at the locality of Bu el Haderait and represent a new genus and species, Libysiren sickenbergi. This animal is the largest known protosirenid, and the largest Eocene sirenian known to date (condylobasal length >420 mm). Its dental formula was apparently 3.1.5.3, with five premolar loci as in all other Eocene sirenians, but the teeth are mostly not preserved. Its postcranial skeleton is unknown except for the atlas, a thoracic vertebra, and rib fragments. Stable isotopes indicate a mostly seagrass diet and a habitat of fully marine salinity. The Protosirenidae presently comprise the genera Protosiren, Ashokia, and Libysiren, with their interrelationships unresolved. Together, they are most parsimoniously regarded as a paraphyletic group basal to both Trichechidae and Dugongidae. However, as more of their morphology and diversity are revealed, they may prove to be more closely allied to the former and may shed crucial light on the still-mysterious origins of the trichechids (manatees).


TAPHONOMIC VARIABILITY OF FOSSIL INSECTS: A BIOSTRATINOMIC STUDY OF PALAEONTINIDAE AND TETTIGARCTIDAE (INSECTA: HEMIPTERA) FROM THE JURASSIC DAOHUGOU LAGERSTÄTTE

Abstract: ABSTRACT Various intrinsic as well as extrinsic factors significantly control the preservation of insects. Few studies have presented a quantitative comparison of biostratinomic patterns in different groups, especially at the familial level. Here, we systematically investigated the preservation of 277 specimens of Palaeontinidae and 113 of Tettigarctidae, two hemipterous families from the Jurassic Daohugou beds lacustrine Konservat-Lagerstätte. We carried out quantitative analyses of their size and taphonomic characters, including body orientation, articulation, and preservational quality, and also performed a preliminary experiment to understand the floating and decay process of cicadas. Our statistical analyses reveal significant differences in both body orientation and preservational quality between the two families. Palaeontinidae experienced longer flotation time (mostly over one month) before settling through the water column due to their high SM index (wing surface/body mass ratio) and unfolded wings, increasing the opportunity to decompose on the water surface and resulting in the dorsoventral preservation position with lower preservational quality. In contrast, Tettigarctidae have a comparatively low SM index and overlapping wings, so that their drifting period on the water surface might have been short (mostly within 2 weeks), leading to the lateral preservation position with higher preservational quality. Our results show that the wing-folding behavior and relative size of wings (SM index) influence the buoyancy times and significantly control the preservation patterns of both groups.


The origin of annelids

Abstract: Annelids are a phylum of segmented bilaterian animals that have become important components of ecosystems spanning terrestrial realms to the deep sea. Annelids are remarkably diverse, possessing high taxonomic diversity and exceptional morphological disparity, and have evolved numerous feeding strategies and ecologies. Their interrelationships and evolution have been the source of much controversy over the past century with the composition of the annelid crown group, the relationship of major groups and the body plan of the ancestral annelid having undergone major recent revisions. There is a convincing body of molecular evidence that polychaetes form a paraphyletic grade and that clitellates are derived polychaetes. The earliest stem group annelids from Cambrian Lagerstätten are errant, epibenthic polychaetes, confirming that biramous parapodia, head appendages and diverse, simple chaetae are primitive for annelids. Current evidence from molecular clocks and the fossil record suggest that crown group annelids are a Late Cambrian – Ordovician radiation, with clitellates radiating in the Late Palaeozoic. Their body fossil record is largely confined to deposits showing exceptional preservation and is punctuated by the acquisition of hard parts in major groups. The discovery of an Ordovician fossil with soft tissues has shown that machaeridians are in fact a clade of crown polychaetes. They were in existence for more than 200 million years and possess unique calcitic dorsal armour, allowing their mode of life and phylogeny to be interpreted in the context of the annelid body plan. We identify a novel clade of machaeridians, the Cuniculepadida, which exhibit a series of adaptations for burrowing.

annelid
phylum
polychaete
chaeta
exceptional preservation


Macroevolutionary patterns in Rhynchocephalia: is the tuatara (Sphenodon punctatus) a living fossil?

Abstract: The tuatara, Sphenodon punctatus, known from 32 small islands around New Zealand, has often been noted as a classic ‘living fossil’ because of its apparently close resemblance to its Mesozoic forebears and because of a long, low‐diversity history. This designation has been disputed because of the wide diversity of Mesozoic forms and because of derived adaptations in living Sphenodon. We provide a testable definition for ‘living fossils’ based on a slow rate of lineage evolution and a morphology close to the centroid of clade morphospace. We show that through their history since the Triassic, rhynchocephalians had heterogeneous rates of morphological evolution and occupied wide morphospaces during the Triassic and Jurassic, and these then declined in the Cretaceous. In particular, we demonstrate that the extant tuatara underwent unusually slow lineage evolution, and is morphologically conservative, being located near the centre of the morphospace for all Rhynchocephalia.

rhynchocephalia
sphenodon punctatus
new zealand
morphology


The earliest primates

Abstract: Remarkable new fossil discoveries and intensive study of fossil evidence has led, during the past decade, and particularly the last few years, to exceptional advances and modifications in our understanding of early primate evolution. New insights have also come from research on extant primates, especially detailed anatomical, functional, and molecular studies. This review, however, focuses on the paleontological evidence. New fossils are spawning novel, sometimes controversial ideas about the relationships within and among primates and their allies—a situation that has caused temporary instability, but should eventually lead to elucidation, if not resolution, of outstanding problems.


New Carnivoraforms from the Latest Paleocene of Europe and Their Bearing on the Origin and Radiation of Carnivoraformes (Carnivoramorpha, Mammalia)

Abstract:
ABSTRACT
 We report the discovery of the earliest European carnivoraforms, based on two new taxa from the latest Paleocene of France and Romania. A new species of Vassacyon, V. prieuri, from the locality of Rivecourt (MP6b; Oise, France) (MP = Mammalian Paleogene reference levels) is described based on a dentary fragment and isolated teeth. This species displays several primitive features compared with species of Vassacyon known from the early Eocene of North America and Europe. A second Paleocene carnivoraform, cf. Gracilocyon sp., is described based on fragmentary specimens from the locality of Jibou (MP6b; Transylvania, Romania). Carnivoraformes were previously unknown in Europe before the Eocene, and Vassacyon prieuri and cf. Gracilocyon sp. are their oldest records in Europe. These discoveries favor the hypothesis of a dispersal of these two genera from Europe to North America during the Paleocene-Eocene Thermal Maximum. Vassacyon prieuri and cf. Gracilocyon sp. strengthen support for the level MP6b and its correlation with the Clarkforkian. The geographic origin of the Carnivoraformes remains unknown. However, based on the observed biochronological and geographic distributions of the carnivoraforms, we infer a possible Asian origin for this group. In this scenario, Gracilocyon and Vassacyon dispersed to Europe during the Clarkforkian MP6b time, probably together with rodent taxa, whereas Uintacyon dispersed from Asia to North America shortly after rodents and tillodonts.

carnivoraformes
europe
carnivoramorpha
late paleocene


Paleogenomic data suggest mammal‐like genome size in the ancestral amniote and derived large genome size in amphibians

Abstract: An unsolved question in evolutionary genomics is whether amniote genomes have been expanding or contracting since the common ancestor of this diverse group. Here, we report on the polarity of amniote genome size evolution using genome size estimates for 14 extinct tetrapod genera from the Paleozoic and early Mesozoic Eras using osteocyte lacunae size as a correlate. We find substantial support for a phylogenetically controlled regression model relating genome size to osteocyte lacunae size (P of slopes < 0.01, r2 = 0.65, phylogenetic signal (λ) = 0.83). Genome size appears to have been homogeneous across Paleozoic crown‐tetrapod lineages (average haploid genome size 2.9–3.7 pg) with values similar to those of extant mammals. The differentiation in genome size and underlying architecture among extant tetrapod lineages likely evolved in the Mesozoic and Cenozoic Eras, with expansion in amphibians, contractions along the diapsid lineage, and no directional change within the synapsid lineage leading to mammals.


Origin of human bipedalism: The knuckle-walking hypothesis revisited.

Abstract: Some of the most long-standing questions in paleoanthropology concern how and why human bipedalism evolved. Over the last century, many hypotheses have been offered on the mode of locomotion from which bipedalism originated. Candidate ancestral adaptations include monkey-like arboreal or terrestrial quadrupedalism, gibbon- or orangutan-like (or other forms of) climbing and suspension, and knuckle-walking. This paper reviews the history of these hypotheses, outlines their predictions, and assesses them in light of current phylogenetic, comparative anatomical, and fossil evidence. The functional significance of characteristics of the shoulder and arm, elbow, wrist, and hand shared by African apes and humans, including their fossil relatives, most strongly supports the knuckle-walking hypothesis, which reconstructs the ancestor as being adapted to knuckle-walking and arboreal climbing. Future fossil discoveries, and a clear understanding of anthropoid locomotor anatomy, are required to ultimately test these hypotheses. If knuckle-walking was an important component of the behavioral repertoire of the prebipedal human ancestor, then we can reject scenarios on the origin of bipedalism that rely on a strictly arboreal ancestor. Moreover, paleoenvironmental data associated with the earliest hominins, and their close relatives, contradict hypotheses that place the agents of selection for bipedality in open savanna habitats. Existing hypotheses must explain why bipedalism would evolve from an ancestor that was already partly terrestrial. Many food acquisition and carrying hypotheses remain tenable in light of current evidence.

bipedalism
knuckle-walking hypothesis
climbing
pan


Bipedalism, flight, and the evolution of theropod locomotor diversity

Abstract: ABSTRACT The evolution of theropod flight has been characterized as a shift from one to three locomotor modules. Basal theropods, which were terrestrial bipeds, had a single locomotor module composed of the hind limb and tail. In birds, aerial locomotion was acquired with the origination of the wing module and a decoupling of the hind limb and tail into separate pelvic and caudal modules. This increase in modularity is thought to have granted birds more locomotor “options” than non-avian theropods. More specifically, an aerial locomotor system could have eased constraints on the hind limb and allowed specialization for habitats and lifestyles unavailable to non-birds. If so, bird hind limbs should be more disparate than those of non-avian theropods. We addressed this hypothesis by visualizing one aspect of limb design, the proportions of the three main segments, using ternary diagrams. Our results show that avian hind limb proportions are much more disparate than those of non-avian theropods. This broad r...


A small ichthyosaur from the Clearwater Formation (Alberta, Canada) and a discussion of the taxonomic utility of the pectoral girdle

Abstract: Albian sedimentary successions of northwestern Canada have yielded a diverse assemblage of Mesozoic marine vertebrates, and ichthyosaurs form an important component of these faunas. Here, we describe a partial postcranial skeleton of a small (estimated at less than 3 m total body length) ichthyosaur from the Wabiskaw Member of the Clearwater Formation (lowermost Albian). The semi-articulated specimen includes much of the presacral vertebral column, dorsal ribs and gastralia. Most significantly, it possesses an articulated pectoral girdle and humerus, and also preserves the pelvic girdle, allowing new insights into girdle evolution in ichthyosaurs. Whereas both sets of girdles are thought to exhibit large amounts of intraspecific variation, the pectoral girdle of ophthalmosaurids appears to evolve very slowly, remaining essentially unchanged from the Middle Jurassic onwards. In contrast, the pelvic girdle shows taxonomically informative changes within Ophthalmosauridae. The variable and poorly known nature of girdle morphology in Cretaceous ichthyosaurs precludes generic referral of the specimen.

ichthyosaur
clearwater formation
pectoral girdle


Mineralization of Alvinella polychaete tubes at hydrothermal vents

Abstract: Alvinellid polychaete worms form multilayered organic tubes in the hottest and most rapidly growing areas of deep‐sea hydrothermal vent chimneys. Over short periods of time, these tubes can become entirely mineralized within this environment. Documenting the nature of this process in terms of the stages of mineralization, as well as the mineral textures and end products that result, is essential for our understanding of the fossilization of polychaetes at hydrothermal vents. Here, we report in detail the full mineralization of Alvinella spp. tubes collected from the East Pacific Rise, determined through the use of a wide range of imaging and analytical techniques. We propose a new model for tube mineralization, whereby mineralization begins as templating of tube layer and sublayer surfaces and results in fully mineralized tubes comprised of multiple concentric, colloform, pyrite bands. Silica appeared to preserve organic tube layers in some samples. Fine‐scale features such as protein fibres, extracellular polymeric substances and two types of filamentous microbial colonies were also found to be well preserved within a subset of the tubes. The fully mineralized Alvinella spp. tubes do not closely resemble known ancient hydrothermal vent tube fossils, corroborating molecular evidence suggesting that the alvinellids are a relatively recent polychaete lineage. We also compare pyrite and silica preservation of organic tissues within hydrothermal vents to soft tissue preservation in sediments and hot springs.

polychaete tube
hydrothermal vent
mineralization


Assessing ontogenetic maturity in extinct saurian reptiles

Abstract: Morphology forms the most fundamental level of data in vertebrate palaeontology because it is through interpretations of morphology that taxa are identified, creating the basis for broad evolutionary and palaeobiological hypotheses. Assessing maturity is one of the most basic aspects of morphological interpretation and provides the means to study the evolution of ontogenetic changes, population structure and palaeoecology, life‐history strategies, and heterochrony along evolutionary lineages that would otherwise be lost to time. Saurian reptiles (the least‐inclusive clade containing Lepidosauria and Archosauria) have remained an incredibly diverse, numerous, and disparate clade through their ~260‐million‐year history. Because of the great disparity in this group, assessing maturity of saurian reptiles is difficult, fraught with methodological and terminological ambiguity. We compiled a novel database of literature, assembling >900 individual instances of saurian maturity assessment, to examine critically how saurian maturity has been diagnosed. We review the often inexact and inconsistent terminology used in saurian maturity assessment (e.g. ‘juvenile’, ‘mature’) and provide routes for better clarity and cross‐study coherence. We describe the various methods that have been used to assess maturity in every major saurian group, integrating data from both extant and extinct taxa to give a full account of the current state of the field and providing method‐specific pitfalls, best practices, and fruitful directions for future research. We recommend that a new standard subsection, ‘Ontogenetic Assessment’, be added to the Systematic Palaeontology portions of descriptive studies to provide explicit ontogenetic diagnoses with clear criteria. Because the utility of different ontogenetic criteria is highly subclade dependent among saurians, even for widely used methods (e.g. neurocentral suture fusion), we recommend that phylogenetic context, preferably in the form of a phylogenetic bracket, be used to justify the use of a maturity assessment method. Different methods should be used in conjunction as independent lines of evidence when assessing maturity, instead of an ontogenetic diagnosis resting entirely on a single criterion, which is common in the literature. Critically, there is a need for data from extant taxa with well‐represented growth series to be integrated with the fossil record to ground maturity assessments of extinct taxa in well‐constrained, empirically tested methods.


Moulting, ontogeny and sexual dimorphism in the Cambrian ptychopariid trilobite Strenuaeva inflata from the northern Swedish Caledonides

Abstract: Abstract:  Three thousand seven hundred disarticulated remains together with several articulated specimens of the Cambrian Series 2 ptychopariid trilobite Strenuaeva inflata Ahlberg and Bergström, 1978 have been collected from the Torneträsk area, northern Sweden. The material provides significant new data on the morphology, ontogeny, moulting and enrolment of the species. Two distinct morphotypes, possibly an expression of sexual dimorphism, are recognized. The morph with a pair of bulbs in the frontal area, interpreted as brood pouches, is considered to represent females. Statistical treatment of the length/width ratio in cranidia reveals isometric growth during ontogeny for both morphotypes. The transition from the meraspid to holaspid ontogenetic period has been established through recognition of the successive development of the number of thoracic segments in articulated late meraspides. Throughout its life cycle, S. inflata went through 11 meraspid degrees and at least 17 holaspid growth stages. Inferred moult ensembles and exuviae reveal the successive opening of cephalic sutures and the function of the rostral plate during exuviation. As in other ellipsocephalid trilobites in which enrolment is known, the pygidium and two or three thoracic segments of S. inflata are concealed beneath the cephalon (spiral enrolment) during complete enrolment.

sexual dimorphism
ptychopariid trilobite strenuaeva
moulting


New information on Brasilodon and Brasilitherium (Cynodontia, Probainognathia) from the Late Triassic, southern Brazil

Abstract: New discoveries of articulated skulls and lower jaws of Brasilodon and Brasilitherium from the Late Triassic of Brazil provide additional information on these small cynodonts, allowing us to establish the family Brasilodontidae nov. The basicranium, lateral wall of the braincase, primary and secondary palates and the quadrate of Brasilitherium are described, as well as the basicranium, primary palate and lower jaw of Brasilodon. Brasilitherium exhibits more derived characters than Brasilodon in the periotic, the promontorium, and the articular process of the dentary. Brasilodon is more derived in the lower dentition, the mode of tooth replacement, and the vascular features in the stapedial recess. Both genera have interpterygoid vacuities that are considered here as possibly derived or reversed characters of the mammalian primary palate. The new phylogenetic analysis presented here corroborates the position of both genera as sister-group of mammals as previously proposed.


SPIERS and VAXML; A software toolkit for tomographic visualisation and a format for virtual specimen interchange

Abstract: Virtual palaeontology', the study of fossils through the medium of digital models, is an increasingly important palaeontological technique. The vast majority of such work is tomographic, based around serial-slice datasets generated either physically or via scanning technologies. There are, however, no general-purpose software packages for tomographic reconstruction that are freely available and tuned to the needs of palaeontological data. In addition to its value in the primary study of specimens, virtual palaeontology has the potential to become a powerful medium for online data-dissemination, greatly increasing the degree to which palaeontologists are able to inspect each other's data. The absence of a standardised data-format for these datasets, however, has been a primary factor impeding such data exchange. We describe here solutions to both problems. The SPIERS software suite is a complete, free, multi-platform and fully documented software toolkit for the reconstruction of any tomographic data into threedimensional models. While capable of rapid reconstruction, it is especially well suited to the production of carefully prepared models from difficult data. We argue that virtualspecimen dissemination should take the form of triangle-mesh datasets, which can be generated from a maximally broad range of data sources. We introduce here the VAXML data format for such datasets, a candidate for a standard dissemination format for virtual specimens, both palaeontological and biological. The SPIERS suite includes a package capable of both visualising and exporting VAXML files, designed to support the viewing of complex datasets on relatively low-powered systems.

software toolkit
tomographic dataset
virtual fossil


A new avian species with tubercle-bearing cervical vertebrae from the Middle Eocene of Messel (Germany). In Proceedings of the VII International Meeting of the Society of Avian Paleontology and Evolution, ed. W.E. Boles and T.H. Worthy

Abstract: A new avian species, Perplexicervix microcephalon n.gen. and n.sp., is described from the Middle Eocene of Messel in Germany. It is most unusual in that the cervical vertebrae of five of the six known specimens bear numerous bony tubercles. Such tubercles were also reported from another avian fossil from the Messel deposits, which is a representative of the extinct taxon Idiornithidae. Although the osteology of P. microcephalon is not known well enough for a reliable phylogenetic assignment, the new species clearly does not belong to the Idiornithidae. Compared to extant birds, it agrees with Anhimidae and Cathartidae in some osteological features. The origin of the vertebral tubercles remains mysterious. The fact that these structures are now known from two unrelated avian taxa supports previous assumptions, that they represent a pathologic condition. Not in line with this assumption, however, is their occurrence in all specimens referred to P. microcephalon, in which cervical vertebrae are preserved.

new avian specie
cervical vertebrae
middle eocene


Testing Equid Body Mass Estimate Equations on Modern Zebras—With Implications to Understanding the Relationship of Body Size, Diet, and Habitats of Equus in the Pleistocene of Europe

Abstract: The monodactyl horses of the genus Equus originated in North America during the Pliocene, and from the beginning of the Pleistocene, they have been an essential part of the large ungulate communities of Europe, North America and Africa. Understanding how body size of Equus species evolved and varied in relation to changes in environments and diet thus forms an important part of understanding the dynamics of ungulate body size variation in relation to Pleistocene paleoenvironmental changes. Here we test previously published body mass estimation equations for the family Equidae by investigating how accurately different skeletal and dental measurements estimate the mean body mass (and body mass range) reported for extant Grevy's zebra (Equus grevyi) and Burchell's zebra (Equus quagga). Based on these tests and information on how frequently skeletal elements occur in the fossil record, we construct a hierarchy of best practices for the selection of body mass estimation equations in Equus. As a case study, we explore body size variation in Pleistocene European Equus paleopopulations in relation to diet and vegetation structure in their paleoenvironments. We show a relationship between diet and body size in Equus: very large-sized species tend to have more browse-dominated diets than small and medium-sized species, and paleovegetation proxies indicate on average more open and grass-rich paleoenvironments for small-sized, grazing species of Equus. When more than one species of Equus co-occur sympatrically, the larger species tend to be less abundant and have more browse-dominated diets than the smaller species. We suggest that body size variation in Pleistocene Equus was driven by a combined effect of resource quality and availability, partitioning of habitats and resources between species, and the effect of environmental openness and group size on the body size of individuals.


Morphofunctional Analysis of the Quadrate of Spinosauridae (Dinosauria: Theropoda) and the Presence of Spinosaurus and a Second Spinosaurine Taxon in the Cenomanian of North Africa.

Abstract: Six quadrate bones, of which two almost certainly come from the Kem Kem beds (Cenomanian, Upper Cretaceous) of south-eastern Morocco, are determined to be from juvenile and adult individuals of Spinosaurinae based on phylogenetic, geometric morphometric, and phylogenetic morphometric analyses. Their morphology indicates two morphotypes evidencing the presence of two spinosaurine taxa ascribed to Spinosaurus aegyptiacus and? Sigilmassasaurus brevicollis in the Cenomanian of North Africa, casting doubt on the accuracy of some recent skeletal reconstructions which may be based on elements from several distinct species. Morphofunctional analysis of the mandibular articulation of the quadrate has shown that the jaw mechanics was peculiar in Spinosauridae. In mature spinosaurids, the posterior parts of the two mandibular rami displaced laterally when the jaw was depressed due to a lateromedially oriented intercondylar sulcus of the quadrate. Such lateral movement of the mandibular ramus was possible due to a movable mandibular symphysis in spinosaurids, allowing the pharynx to be widened. Similar jaw mechanics also occur in some pterosaurs and living pelecanids which are both adapted to capture and swallow large prey items. Spinosauridae, which were engaged, at least partially, in a piscivorous lifestyle, were able to consume large fish and may have occasionally fed on other prey such as pterosaurs and juvenile dinosaurs.

spinosauridae
cenomanian
jaw mechanic
morphofunctional analysis


The importance of sampling standardization for comparisons of insect herbivory in deep time: a case study from the late Palaeozoic

Abstract: Sampling standardization has not been fully addressed for the study of insect herbivory in the fossil record. The effects of sampling within a single locality were explored almost a decade ago, but the importance of sampling standardization for comparisons of herbivory across space and time has not yet been evaluated. Here, we present a case study from the Permian in which we evaluate the impact of sampling standardization on comparisons of insect herbivory from two localities that are similar in age and floral composition. Comparisons of insect damage type (DT) diversity change dramatically when the number of leaves examined is standardized by surface area. This finding suggests that surface area should always be taken into account for comparisons of DT diversity. In addition, the three most common metrics of herbivory—DT diversity, proportion of leaves herbivorized and proportion of leaf surface area herbivorized—are inherently decoupled from each other. The decoupling of the diversity and intensity of insect herbivory necessitates a reinterpretation of published data because they had been conflated in previous studies. Future studies should examine the divergent ecological factors that underlie these metrics. We conclude with suggestions to guide the sampling and analysis of herbivorized leaves in the fossil record.

standardization
insect herbivory
case study


Digital imaging and public engagement in palaeontology

Abstract: Public engagement and the promotion of science to a wider non‐academic audience form an integral role of the professional scientist in the twenty‐first century. The high level of public interest in palaeontology means that the Earth's prehistoric past can provide an important medium through which to communicate information concerning contemporary scientific issues. Here we explain how modern computer techniques can be used to enhance public understanding of complex palaeontological issues.


The earliest modern humans outside Africa

Abstract: Earliest modern humans out of Africa Recent paleoanthropological studies have suggested that modern humans migrated from Africa as early as the beginning of the Late Pleistocene, 120,000 years ago. Hershkovitz et al. now suggest that early modern humans were already present outside of Africa more than 55,000 years earlier (see the Perspective by Stringer and Galway-Witham). During excavations of sediments at Mount Carmel, Israel, they found a fossil of a mouth part, a left hemimaxilla, with almost complete dentition. The sediments contain a series of well-defined hearths and a rich stone-based industry, as well as abundant animal remains. Analysis of the human remains, and dating of the site and the fossil itself, indicate a likely age of at least 177,000 years for the fossil—making it the oldest member of the Homo sapiens clade found outside Africa. Science, this issue p. 456; see also p. 389 Fossilized mouthparts indicate the presence of Homo sapiens in the Levant 160,000 years ago. To date, the earliest modern human fossils found outside of Africa are dated to around 90,000 to 120,000 years ago at the Levantine sites of Skhul and Qafzeh. A maxilla and associated dentition recently discovered at Misliya Cave, Israel, was dated to 177,000 to 194,000 years ago, suggesting that members of the Homo sapiens clade left Africa earlier than previously thought. This finding changes our view on modern human dispersal and is consistent with recent genetic studies, which have posited the possibility of an earlier dispersal of Homo sapiens around 220,000 years ago. The Misliya maxilla is associated with full-fledged Levallois technology in the Levant, suggesting that the emergence of this technology is linked to the appearance of Homo sapiens in the region, as has been documented in Africa.


Palaeogenomics of pterosaurs and the evolution of small genome size in flying vertebrates

Abstract: The two living groups of flying vertebrates, birds and bats, both have constricted genome sizes compared with their close relatives. But nothing is known about the genomic characteristics of pterosaurs, which took to the air over 70 Myr before birds and were the first group of vertebrates to evolve powered flight. Here, we estimate genome size for four species of pterosaurs and seven species of basal archosauromorphs using a Bayesian comparative approach. Our results suggest that small genomes commonly associated with flight in bats and birds also evolved in pterosaurs, and that the rate of genome-size evolution is proportional to genome size within amniotes, with the fastest rates occurring in lineages with the largest genomes. We examine the role that drift may have played in the evolution of genome size within tetrapods by testing for correlated evolution between genome size and body size, but find no support for this hypothesis. By contrast, we find evidence suggesting that a combination of adaptation and phylogenetic inertia best explains the correlated evolution of flight and genome-size contraction. These results suggest that small genome/cell size evolved prior to or concurrently with flight in pterosaurs. We predict that, similar to the pattern seen in theropod dinosaurs, genome-size contraction preceded flight in pterosaurs and bats.