Quantitative assessment of tarsal morphology illuminates locomotor behaviour in Palaeocene mammals following the end-Cretaceous mass extinction

Abstract: Mammals exhibit vast ecological diversity, including a panoply of locomotor behaviours. The foundations of this diversity were established in the Mesozoic, but it was only after the end-Cretaceous mass extinction that mammals began to increase in body size, diversify into many new species and establish the extant orders. Little is known about the palaeobiology of the mammals that diversified immediately after the extinction during the Palaeocene, which are often perceived as ‘archaic’ precursors to extant orders. Here, we investigate the locomotor ecology of Palaeocene mammals using multivariate and disparity analyses. We show that tarsal measurements can be used to infer locomotor mode in extant mammals, and then demonstrate that Palaeocene mammals occupy distinctive regions of tarsal morphospace relative to Cretaceous and extant therian mammals, that is distinguished by their morphological robustness. We find that many Palaeocene species exhibit tarsal morphologies most comparable with morphologies of extant ground-dwelling mammals. Disparity analyses indicate that Palaeocene mammals attained similar morphospace diversity to the extant sample. Our results show that mammals underwent a post-extinction adaptive radiation in tarsal morphology relating to locomotor behaviour by combining a basic eutherian bauplan with anatomical specializations to attain considerable ecomorphological diversity.

tarsal morphology
locomotor behaviour
palaeocene mammal


Glesirhanis bercioi, a new genus and species from Baltic amber (Coleoptera: Endomychidae: Leiestinae) with a checklist and nomenclatural notes regarding fossil Endomychidae.

Abstract: A new genus and species of handsome fungus beetle, Glesirhanis bercioi gen. nov., sp. nov. (Coleoptera: Endomychidae: Leiestinae) is described from Baltic amber. The newly described genus is compared with all known extant and extinct genera of the subfamily. A key to the genera of Leiestinae including fossils and a checklist of fossil Endomychidae are provided. The status of two taxa previously placed in Endomychidae, Palaeoendomychus gymnus Zhang and Tetrameropsis mesozoica Kirejtshuk & Azar, is discussed, and a new status for the latter, elevating it to the family-level as Tetrameropseidae status nov., is proposed.

new genus
coleoptera
fossil endomychidae


Inferring locomotor behaviours in Miocene New World monkeys using finite element analysis, geometric morphometrics and machine-learning classification techniques applied to talar morphology

Abstract: The talus is one of the most commonly preserved post-cranial elements in the platyrrhine fossil record. Talar morphology can provide information about postural adaptations because it is the anatomical structure responsible for transmitting body mass forces from the leg to the foot. The aim of this study is to test whether the locomotor behaviour of fossil Miocene platyrrhines could be inferred from their talus morphology. The extant sample was classified into three different locomotor categories and then talar strength was compared using finite-element analysis. Geometric morphometrics were used to quantify talar shape and to assess its association with biomechanical strength. Finally, several machine-learning (ML) algorithms were trained using both the biomechanical and morphometric data from the extant taxa to infer the possible locomotor behaviour of the Miocene fossil sample. The obtained results show that the different locomotor categories are distinguishable using either biomechanical or morphometric data. The ML algorithms categorized most of the fossil sample as arboreal quadrupeds. This study has shown that a combined approach can contribute to the understanding of platyrrhine talar morphology and its relationship with locomotion. This approach is likely to be beneficial for determining the locomotor habits in other fossil taxa.

locomotor behaviour
geometric morphometric
talar morphology


Transformation of the quadrate (incus) through the transition from non-mammalian cynodonts to mammals

Abstract: ABSTRACT The quadrate (incus) bone underwent important evolutionary transformations through the cynodont-mammal transition. The following character transformations played crucial roles in modifying the cynodont quadrate into the mammalian incus: 1) progressively greater rotation of the dorsal plate relative to the trochlea; 2) the contact facet of the dorsal plate becomes concave; 3) development of a constricted neck between the dorsal plate and the trochlea; 4) simplification of the quadrate-cranium joint, resulting in better mobility of the joint; and 5) introduction of a stapedial process (crus longum). The dorsal plate rotation, the concave contact facet, the constricted neck, the mobile joint of the quadrate and the cranium are also present in some advanced non-mammalian cynodonts. Broad phylogenetic distributions of these features suggest that the major features of the incus of early mammals, as represented by Morganucodon, originated much earlier in phylogenetic history among non-mammalian cynodont...

quadrate
incus
non-mammalian cynodont
cranium
transformation


Wear facets and enamel spalling in tyrannosaurid dinosaurs

Abstract:
Numerous paleontologists have noted wear facets on tyrannosaurid lateral teeth over the past century. While several workers have proposed explanations for these features, there remains to this day no consensus concerning their etiology.
Here we report on an examination of wear surfaces on these teeth from the Upper Cretaceous (mid-Campanian) Judith River Group of southern Alberta, Canada. This study reveals two distinct types of wear features on the labial and lingual sides of tyrannosaurid lateral teeth: irregular "spalled" surfaces and wear facets. The irregular spalled surfaces typically extend to the apex of the tooth, which evidently reflects flaking of enamel resulting from forces produced during contact between tooth and food. These surfaces are often rounded, presumably from antemortem wear following spalling. Wear striations on these surfaces are oriented heterogeneously. The wear facets, in contrast, occur on only one side of the tooth and are typically elliptical in outline and evince parallel wear striations. Similar patterns of parallel wear striations in extant mammals reflect tooth-tooth contact. We therefore propose that wear facets in tyrannosaurids were formed by repeated tooth-tooth contact between the lingual side of maxillary teeth and labial side of dentary teeth. It remains unclear whether this contact was serendipitous or adaptive, though it appears to be unusual for reptiles, as we have found no evidence for wear facets in extant varanids and crocodilians.

facet
lingual side
parallel wear striation
dentary tooth


Extinction of fish-shaped marine reptiles associated with reduced evolutionary rates and global environmental volatility

Abstract: Despite their profound adaptations to the aquatic realm and their apparent success throughout the Triassic and the Jurassic, ichthyosaurs became extinct roughly 30 million years before the end-Cretaceous mass extinction. Current hypotheses for this early demise involve relatively minor biotic events, but are at odds with recent understanding of the ichthyosaur fossil record. Here, we show that ichthyosaurs maintained high but diminishing richness and disparity throughout the Early Cretaceous. The last ichthyosaurs are characterized by reduced rates of origination and phenotypic evolution and their elevated extinction rates correlate with increased environmental volatility. In addition, we find that ichthyosaurs suffered from a profound Early Cenomanian extinction that reduced their ecological diversity, likely contributing to their final extinction at the end of the Cenomanian. Our results support a growing body of evidence revealing that global environmental change resulted in a major, temporally staggered turnover event that profoundly reorganized marine ecosystems during the Cenomanian.

marine reptile
evolutionary rate
environmental volatility
ichthyosaur
early triassic


Direct and indirect effects of biological factors on extinction risk in fossil bivalves

Abstract: Biological factors, such as abundance and body size, may contribute directly to extinction risk and indirectly through their influence on other biological characteristics, such as geographic range size. Paleontological data can be used to explicitly test many of these hypothesized relationships, and general patterns revealed through analysis of the fossil record can help refine predictive models of extinction risk developed for extant species. Here, I use structural equation modeling to tease apart the contributions of three canonical predictors of extinction—abundance, body size, and geographic range size—to the duration of bivalve species in the early Cenozoic marine fossil record of the eastern United States. I find that geographic range size has a strong direct effect on extinction risk and that an apparent direct effect of abundance can be explained entirely by its covariation with geographic range. The influence of geographic range on extinction risk is manifest across three ecologically disparate bivalve clades. Body size also has strong direct effects on extinction risk but operates in opposing directions in different clades, and thus, it seems to be decoupled from extinction risk in bivalves as a whole. Although abundance does not directly predict extinction risk, I reveal weak indirect effects of both abundance and body size through their positive influence on geographic range size. Multivariate models that account for the pervasive covariation between biological factors and extinction are necessary for assessing causality in evolutionary processes and making informed predictions in applied conservation efforts.

indirect effect
biological factor
extinction risk
body size
range size


Global hydroclimatic response to tropical volcanic eruptions over the last millennium

Abstract: Significance Future large tropical volcanic eruptions will induce global hydroclimatic changes, superimposed on anthropogenic climate change. Understanding how volcanic eruptions affect global hydroclimate is therefore critically important. Tejedor et al. use a new paleoclimatic product, which combines information from high-resolution proxies and climate models, to estimate volcanic impacts on hydroclimate over the last millennium. They find that past eruptions caused severe drying in tropical Africa and across Central Asia and the Middle East and significantly wetter conditions over Oceania and the South American monsoon region, some of which persisted for a decade or longer. These proxy-based findings suggest that, relative to estimates from a state-of-the-art climate model, much larger and persistent hydroclimatic changes are possible across regions of important socioeconomic activity. Large tropical volcanic eruptions can affect the climate of many regions on Earth, yet it is uncertain how the largest eruptions over the past millennium may have altered Earth’s hydroclimate. Here, we analyze the global hydroclimatic response to all the tropical volcanic eruptions over the past millennium that were larger than the Mount Pinatubo eruption of 1991. Using the Paleo Hydrodynamics Data Assimilation product (PHYDA), we find that these large volcanic eruptions tended to produce dry conditions over tropical Africa, Central Asia and the Middle East and wet conditions over much of Oceania and the South American monsoon region. These anomalies are statistically significant, and they persisted for more than a decade in some regions. The persistence of the anomalies is associated with southward shifts in the Intertropical Convergence Zone and sea surface temperature changes in the Pacific and Atlantic oceans. We compare the PHYDA results with the stand-alone model response of the Community Earth System Model (CESM)-Last Millennium Ensemble. We find that the proxy-constrained PHYDA estimates are larger and more persistent than the responses simulated by CESM. Understanding which of these estimates is more realistic is critical for accurately characterizing the hydroclimate risks of future volcanic eruptions.

tropical volcanic eruption
last millennium
global hydroclimatic response


Larval ecology and morphology in fossil gastropods

Abstract: The shell of marine gastropods conserves and reflects early ontogeny, including embryonic and larval stages, to a high degree when compared with other marine invertebrates. Planktotrophic larval development is indicated by a small embryonic shell (size is also related to systematic placement) with little yolk followed by a multiwhorled shell formed by a free‐swimming veliger larva. Basal gastropod clades (e.g. Vetigastropoda) lack planktotrophic larval development. The great majority of Late Palaeozoic and Mesozoic ‘derived’ marine gastropods (Neritimorpha, Caenogastropoda and Heterobranchia) with known protoconch had planktotrophic larval development. Dimensions of internal moulds of protoconchs suggest that planktotrophic larval development was largely absent in the Cambrian and evolved at the Cambrian–Ordovician transition, mainly due to increasing benthic predation. The evolution of planktotrophic larval development offered advantages and opportunities such as more effective dispersal, enhanced gene flow between populations and prevention of inbreeding. Early gastropod larval shells were openly coiled and weakly sculptured. During the Mid‐ and Late Palaeozoic, modern tightly coiled larval shells (commonly with strong sculpture) evolved due to increasing predation pressure in the plankton. The presence of numerous Late Palaeozoic and Triassic gastropod species with planktotrophic larval development suggests sufficient primary production although direct evidence for phytoplankton is scarce in this period. Contrary to previous suggestions, it seems unlikely that the end‐Permian mass extinction selected against species with planktotrophic larval development. The molluscan classes with highest species diversity (Gastropoda and Bivalvia) are those which may have planktotrophic larval development. Extremely high diversity in such groups as Caenogastropoda or eulamellibranch bivalves is the result of high phylogenetic activity and is associated with the presence of planktotrophic veliger larvae in many members of these groups, although causality has not been shown yet. A new gastropod species and genus, Anachronistella peterwagneri, is described from the Late Triassic Cassian Formation; it is the first known Triassic gastropod with an openly coiled larval shell.


Orbitally tuned timescale and astronomical forcing in the middle Eocene to early Oligocene

Abstract: Abstract. Deciphering the driving mechanisms of Earth system processes, including the climate dynamics expressed as paleoceanographic events, requires a complete, continuous, and high-resolution stratigraphy that is very accurately dated. In this study, a robust astronomically calibrated age model was constructed for the middle Eocene to early Oligocene interval (31–43 Ma) in order to permit more detailed study of the exceptional climatic events that occurred during this time, including the middle Eocene climate optimum and the Eocene–Oligocene transition. A goal of this effort is to accurately date the middle Eocene to early Oligocene composite section cored during the Pacific Equatorial Age Transect (PEAT, IODP Exp. 320/321). The stratigraphic framework for the new timescale is based on the identification of the stable long eccentricity cycle in published and new high-resolution records encompassing bulk and benthic stable isotope, calibrated XRF core scanning, and magnetostratigraphic data from ODP Sites 171B-1052, 189-1172, 199-1218, and 207-1260 as well as IODP Sites 320-U1333, and 320-U1334 spanning magnetic polarity Chrons C12n to C20n. Subsequently orbital tuning of the records to the La2011 orbital solution was conducted. The resulting new timescale revises and refines the existing orbitally tuned age model and the geomagnetic polarity timescale from 31 to 43 Ma. The newly defined absolute age for the Eocene–Oligocene boundary validates the astronomical tuned age of 33.89 Ma identified at the Massignano, Italy, global stratotype section and point. The compilation of geochemical records of climate-controlled variability in sedimentation through the middle-to-late Eocene and early Oligocene demonstrates strong power in the eccentricity band that is readily tuned to the latest astronomical solution. Obliquity driven cyclicity is only apparent during 2.4 myr eccentricity cycle minima around 35.5, 38.3, and 40.1 Ma.

tuning
timescale
eocene
oligocene
eccentricity cycle


Pre-Gondwanan-breakup origin of Beauprea (Proteaceae) explains its historical presence in New Caledonia and New Zealand

Abstract: The tropical shrub Beauprea was already present in Gondwana when Zealandia drifted away from Antarctica 82 million years ago. New Caledonia and New Zealand belong to the now largely submerged continent Zealandia. Their high levels of endemism and species richness are usually considered the result of transoceanic dispersal events followed by diversification after they re-emerged from the Pacific Ocean in the mid-Cenozoic. We explore the origin and evolutionary history of Beauprea (Proteaceae), which is now endemic to New Caledonia but was once spread throughout eastern Gondwana, including New Zealand. We review the extensive Beauprea-type pollen data in the fossil records and analyze the relationship of these fossil taxa to extant genera within Proteaceae. We further reconstruct the phylogenetic relations among nine extant species of Beauprea and estimate the age of the Beauprea clade. By incorporating extinct taxa into the Beauprea phylogenetic tree, we reconstruct the ancient distribution of this genus. Our analysis shows that Beauprea originated c. 88 Ma (million years ago) in Antarctica–Southeastern Australia and spread throughout Gondwana before its complete breakup. We propose that Beauprea, already existing as two lineages, was carried with Zealandia when it separated from the rest of Gondwana c. 82 Ma, thus supporting an autochthonous origin for Beauprea species now in New Caledonia and historically in New Zealand up to 1 Ma. We show that the presence of Beauprea through transoceanic dispersal is implausible. This means that neither New Caledonia nor New Zealand has been entirely submerged since the Upper Cretaceous; thus, possible vicariance and allopatry must be taken into account when considering the high levels of endemism and species richness of these island groups.

proteaceae
new caledonia
new zealand
endemism


Out of the tropics, but how? Fossils, bridge species, and thermal ranges in the dynamics of the marine latitudinal diversity gradient

Abstract: Latitudinal diversity gradients are underlain by complex combinations of origination, extinction, and shifts in geographic distribution and therefore are best analyzed by integrating paleontological and neontological data. The fossil record of marine bivalves shows, in three successive late Cenozoic time slices, that most clades (operationally here, genera) tend to originate in the tropics and then expand out of the tropics (OTT) to higher latitudes while retaining their tropical presence. This OTT pattern is robust both to assumptions on the preservation potential of taxa and to taxonomic revisions of extant and fossil species. Range expansion of clades may occur via “bridge species,” which violate climate-niche conservatism to bridge the tropical-temperate boundary in most OTT genera. Substantial time lags (∼5 Myr) between the origins of tropical clades and their entry into the temperate zone suggest that OTT events are rare on a per-clade basis. Clades with higher diversification rates within the tropics are the most likely to expand OTT and the most likely to produce multiple bridge species, suggesting that high speciation rates promote the OTT dynamic. Although expansion of thermal tolerances is key to the OTT dynamic, most latitudinally widespread species instead achieve their broad ranges by tracking widespread, spatially-uniform temperatures within the tropics (yielding, via the nonlinear relation between temperature and latitude, a pattern opposite to Rapoport’s rule). This decoupling of range size and temperature tolerance may also explain the differing roles of species and clade ranges in buffering species from background and mass extinctions.

tropic
bridge specie
latitudinal diversity gradient
marine bivalve
ott


Abstract: Martins-Neto, R.G., Gallego, O.F. & Zavattieri, A.M., June, 2007. A new Triassic insect fauna from Cerro Bayo, Potrerillos (Mendoza Province, Argentina) with descriptions of new taxa (Insecta: Blattoptera and Coleoptera). Alcheringa 31, 199‐213. ISSN 0311-5518. This contribution describes new fossil insect taxa from the early Late Triassic Potrerillos Formation (lower section), at quebrada del puente, Cerro Bayo, Mendoza Province, Argentina. A new family, three new genera, and four new species of Blattoptera are described: Anablatta compacta gen. et sp. nov., Potrerilloblatta stipanicici gen. et sp. nov. (Subioblattidae Schneider), Delpuenteblatta dangeloi gen. et sp. nov. and Lariojablatta neiffi sp. nov. (Delpuenteblattidae fam. nov.); and a new coleopteran species, Delpuentesyne menendezi sp. nov. (Permosynidae Tillyard). These findings extend the stratigraphic distribution of the typical Triassic coleopteran taxa. The new assemblage shares the genus Lariojablatta with the Los Rastros fauna. The Blattoptera and Coleoptera genera differ from those typical of the Australian and South African Triassic biota (Ademosyne for Coleoptera and Triassoblatta and Samaroblatta for Blattoptera) and appear to be endemic to Argentina (Delpuentesyne, Potrerilloblatta and Delpuenteblatta).

triassic insect fauna
new taxa
blattoptera


Merging paleobiology with conservation biology to guide the future of terrestrial ecosystems

Abstract: Looking back to move forward The current impacts of humanity on nature are rapid and destructive, but species turnover and change have occurred throughout the history of life. Although there is much debate about the best approaches to take in conservation, ultimately, we need to permit or enhance the resilience of natural systems so that they can continue to adapt and function into the future. In a Review, Barnosky et al. argue that the best way to do this is to look back at paleontological history as a way to understand how ecological resilience is maintained, even in the face of change. Science, this issue p. eaah4787 BACKGROUND The pace and magnitude of human-caused global change has accelerated dramatically over the past 50 years, overwhelming the capacity of many ecosystems and species to maintain themselves as they have under the more stable conditions that prevailed for at least 11,000 years. The next few decades threaten even more rapid transformations because by 2050, the human population is projected to grow by 3 billion while simultaneously increasing per capita consumption. Thus, to avoid losing many species and the crucial aspects of ecosystems that we need—for both our physical and emotional well-being—new conservation paradigms and integration of information from conservation biology, paleobiology, and the Earth sciences are required. ADVANCES Rather than attempting to hold ecosystems to an idealized conception of the past, as has been the prevailing conservation paradigm until recently, maintaining vibrant ecosystems for the future now requires new approaches that use both historical and novel conservation landscapes, enhance adaptive capacity for ecosystems and organisms, facilitate connectedness, and manage ecosystems for functional integrity rather than focusing entirely on particular species. Scientific breakthroughs needed to underpin such a paradigm shift are emerging at the intersection of ecology and paleobiology, revealing (i) which species and ecosystems will need human intervention to persist; (ii) how to foster population connectivity that anticipates rapidly changing climate and land use; (iii) functional attributes that characterize ecosystems through thousands to millions of years, irrespective of the species that are involved; and (iv) the range of compositional and functional variation that ecosystems have exhibited over their long histories. Such information is necessary for recognizing which current changes foretell transitions to less robust ecological states and which changes may signal benign ecosystem shifts that will cause no substantial loss of ecosystem function or services. Conservation success will also increasingly hinge on choosing among different, sometimes mutually exclusive approaches to best achieve three conceptually distinct goals: maximizing biodiversity, maximizing ecosystem services, and preserving wilderness. These goals vary in applicability depending on whether historical or novel ecosystems are the conservation target. Tradeoffs already occur—for example, managing to maximize certain ecosystem services upon which people depend (such as food production on farm or rangelands) versus maintaining healthy populations of vulnerable species (such as wolves, lions, or elephants). In the future, the choices will be starker, likely involving decisions such as which species are candidates for managed relocation and to which areas, and whether certain areas should be off limits for intensive management, even if it means losing some species that now live there. Developing the capacity to make those choices will require conservation in both historical and novel ecosystems and effective collaboration of scientists, governmental officials, nongovernmental organizations, the legal community, and other stakeholders. OUTLOOK Conservation efforts are currently in a state of transition, with active debate about the relative importance of preserving historical landscapes with minimal human impact on one end of the ideological spectrum versus manipulating novel ecosystems that result from human activities on the other. Although the two approaches are often presented as dichotomous, in fact they are connected by a continuum of practices, and both are needed. In most landscapes, maximizing conservation success will require more integration of paleobiology and conservation biology because in a rapidly changing world, a long-term perspective (encompassing at least millennia) is necessary to specify and select appropriate conservation targets and plans. Although adding this long-term perspective will be essential to sustain biodiversity and all of the facets of nature that humans need as we continue to rapidly change the world over the next few decades, maximizing the chances of success will also require dealing with the root causes of the conservation crisis: rapid growth of the human population, increasing per capita consumption especially in developed countries, and anthropogenic climate change that is rapidly pushing habitats outside the bounds experienced by today’s species. Fewer than 900 mountain gorillas are left in the world, and their continued existence depends upon the choices humans make, exemplifying the state of many species and ecosystems. Can conservation biology save biodiversity and all the aspects of nature that people need and value as 3 billion more of us are added to the planet by 2050, while climate continues to change to states outside the bounds that most of today’s ecosystems have ever experienced? Photo: E. A. Hadly, at Volcanoes National Park, Rwanda Conservation of species and ecosystems is increasingly difficult because anthropogenic impacts are pervasive and accelerating. Under this rapid global change, maximizing conservation success requires a paradigm shift from maintaining ecosystems in idealized past states toward facilitating their adaptive and functional capacities, even as species ebb and flow individually. Developing effective strategies under this new paradigm will require deeper understanding of the long-term dynamics that govern ecosystem persistence and reconciliation of conflicts among approaches to conserving historical versus novel ecosystems. Integrating emerging information from conservation biology, paleobiology, and the Earth sciences is an important step forward on the path to success. Maintaining nature in all its aspects will also entail immediately addressing the overarching threats of growing human population, overconsumption, pollution, and climate change.

paleobiology
conservation biology
future
global change
million


Correlated terrestrial and marine evidence for global climate changes before mass extinction at the Cretaceous–Paleogene boundary

Abstract: Terrestrial climates near the time of the end-Cretaceous mass extinction are poorly known, limiting understanding of environmentally driven changes in biodiversity that occurred before bolide impact. We estimate paleotemperatures for the last ≈1.1 million years of the Cretaceous (≈66.6–65.5 million years ago, Ma) by using fossil plants from North Dakota and employ paleomagnetic stratigraphy to correlate the results to foraminiferal paleoclimatic data from four middle- and high-latitude sites. Both plants and foraminifera indicate warming near 66.0 Ma, a warming peak from ≈65.8 to 65.6 Ma, and cooling near 65.6 Ma, suggesting that these were global climate shifts. The warming peak coincides with the immigration of a thermophilic flora, maximum plant diversity, and the poleward range expansion of thermophilic foraminifera. Plant data indicate the continuation of relatively cool temperatures across the Cretaceous–Paleogene boundary; there is no indication of a major warming immediately after the boundary as previously reported. Our temperature proxies correspond well with recent pCO2 data from paleosol carbonate, suggesting a coupling of pCO2 and temperature. To the extent that biodiversity is correlated with temperature, estimates of the severity of end-Cretaceous extinctions that are based on occurrence data from the warming peak are probably inflated, as we illustrate for North Dakota plants. However, our analysis of climate and facies considerations shows that the effects of bolide impact should be regarded as the most significant contributor to these plant extinctions.

global climate change
mass extinction
cretaceous–paleogene boundary


Phylogeny of Basal Iguanodonts (Dinosauria: Ornithischia): An Update

Abstract: The precise phylogenetic relationships of many non-hadrosaurid members of Iguanodontia, i.e., basal iguanodonts, have been unclear. Therefore, to investigate the global phylogeny of basal iguanodonts a comprehensive data matrix was assembled, including nearly every valid taxon of basal iguanodont. The matrix was analyzed in the program TNT, and the maximum agreement subtree of the resulting most parsimonious trees was then calculated in PAUP. Ordering certain multistate characters and omitting taxa through safe taxonomic reduction did not markedly improve resolution. The results provide some new information on the phylogeny of basal iguanodonts, pertaining especially to obscure or recently described taxa, and support some recent taxonomic revisions, such as the splitting of traditional “Camptosaurus” and “Iguanodon”. The maximum agreement subtree also shows a close relationship between the Asian Probactrosaurus gobiensis and the North American Eolambia, supporting the previous hypothesis of faunal interchange between Asia and North America in the early Late Cretaceous. Nevertheless, the phylogenetic relationships of many basal iguanodonts remain ambiguous due to the high number of taxa removed from the maximum agreement subtree and poor resolution of consensus trees.


Data from: On the probabilities of branch durations and stratigraphic gaps in phylogenies of fossil taxa when rates of diversification vary over time

Abstract: The time separating the first appearances of species from their divergences from related taxa affects assessments of macroevolutionary hypotheses about rates of anatomical or ecological change. Branch durations necessarily posit stratigraphic gaps in sampling within a clade over which we have failed to sample predecessors (ancestors) and over which there are no divergences leading to sampled relatives (sister taxa). The former reflects only sampling rates, whereas the latter reflects sampling, origination, and extinction rates. Because all three rates vary over time, the probability of a branch duration of any particular length will differ depending on when in the Phanerozoic that branch duration spans. Here, I present a birth-death-sampling model allowing interval-to-interval variation in diversification and sampling rates. Increasing either origination or sampling rates increases the probability of finding sister taxa that diverge both during and before intervals of high sampling/origination. Conversely, elevated extinction reduces the probability of divergences from sampled sister taxa before and during intervals of elevated extinction. In the case of total extinction, a Signor-Lipps will reduce expected sister taxa leading up to the extinction, with the possible effect stretching back many millions of years when sampling is low. Simulations indicate that this approach provides reasonable estimates of branch duration probabilities under a variety of circumstances. Because current probability models for describing morphological evolution are less advanced than methods for inferring diversification and sampling rates, branch duration priors allowing for timevarying diversification could be a potent tool for phylogenetic inference with fossil data.

branch duration
stratigraphic gap
phylogeny


Asteroid impact, not volcanism, caused the end-Cretaceous dinosaur extinction

Abstract: Significance We present a quantitative test of end-Cretaceous extinction scenarios and how these would have affected dinosaur habitats. Combining climate and ecological modeling tools, we demonstrate a substantial detrimental effect on dinosaur habitats caused by an impact winter scenario triggered by the Chicxulub asteroid. We were not able to obtain such an extinction state with several modeling scenarios of Deccan volcanism. We further show that the concomitant prolonged eruption of the Deccan traps might have acted as an ameliorating agent, buffering the negative effects on climate and global ecosystems that the asteroid impact produced at the Cretaceous–Paleogene boundary. The Cretaceous/Paleogene mass extinction, 66 Ma, included the demise of non-avian dinosaurs. Intense debate has focused on the relative roles of Deccan volcanism and the Chicxulub asteroid impact as kill mechanisms for this event. Here, we combine fossil-occurrence data with paleoclimate and habitat suitability models to evaluate dinosaur habitability in the wake of various asteroid impact and Deccan volcanism scenarios. Asteroid impact models generate a prolonged cold winter that suppresses potential global dinosaur habitats. Conversely, long-term forcing from Deccan volcanism (carbon dioxide [CO2]-induced warming) leads to increased habitat suitability. Short-term (aerosol cooling) volcanism still allows equatorial habitability. These results support the asteroid impact as the main driver of the non-avian dinosaur extinction. By contrast, induced warming from volcanism mitigated the most extreme effects of asteroid impact, potentially reducing the extinction severity.

volcanism
dinosaur extinction
asteroid impact


Non‐enzymatic glycolysis and pentose phosphate pathway‐like reactions in a plausible Archean ocean

Abstract: The reaction sequences of central metabolism, glycolysis and the pentose phosphate pathway provide essential precursors for nucleic acids, amino acids and lipids. However, their evolutionary origins are not yet understood. Here, we provide evidence that their structure could have been fundamentally shaped by the general chemical environments in earth's earliest oceans. We reconstructed potential scenarios for oceans of the prebiotic Archean based on the composition of early sediments. We report that the resultant reaction milieu catalyses the interconversion of metabolites that in modern organisms constitute glycolysis and the pentose phosphate pathway. The 29 observed reactions include the formation and/or interconversion of glucose, pyruvate, the nucleic acid precursor ribose‐5‐phosphate and the amino acid precursor erythrose‐4‐phosphate, antedating reactions sequences similar to that used by the metabolic pathways. Moreover, the Archean ocean mimetic increased the stability of the phosphorylated intermediates and accelerated the rate of intermediate reactions and pyruvate production. The catalytic capacity of the reconstructed ocean milieu was attributable to its metal content. The reactions were particularly sensitive to ferrous iron Fe(II), which is understood to have had high concentrations in the Archean oceans. These observations reveal that reaction sequences that constitute central carbon metabolism could have been constrained by the iron‐rich oceanic environment of the early Archean. The origin of metabolism could thus date back to the prebiotic world.

glycolysis
reaction
archean ocean
pentose phosphate pathway


Breaking down the lithification bias: the effect of preferential sampling of larger specimens on the estimate of species richness, evenness, and average specimen size

Abstract:
Abstract.
 Lithification, the transition of unconsolidated sediments to fully indurated rocks, can potentially bias estimates of species richness, evenness, and body size distribution derived from fossil assemblages. Fossil collections made from well-indurated rocks consistently exhibit lower species richness, lower evenness, and larger average specimen size relative to collections made from unconsolidated sediments, even when collections are drawn from the same assemblage. This phenomenon is known as “lithification bias.” While the bias itself has been demonstrated empirically, much less attention has been paid to its causes. Proposed causes include taphonomic processes (e.g., destruction of small specimens during early diagenesis) and methodological differences (e.g., sieving vs. counting specimens on outcrops, bedding surfaces, or mechanically split surfaces). Here we investigate the potential effects of preferential intersection that could also result in a methodologically related bias: the preferential sampling of larger specimens relative to smaller ones when fossils are counted on rock surfaces. We used an analogue model to simulate preferential intersection (fossil collection via splitting fossiliferous rocks) and compare the results with a random-draw model that approximates the effects of sieving. The model was parameterized using nine different combinations of species abundance and species size distributions. The results show that, with rare exceptions, species richness is 5–23% lower, evenness 5–25% lower, and average specimen size 24–150% larger in preferential-intersection than in random-draw simulations. We conclude that preferential intersection can impose a significant bias independent of other mechanisms (e.g., preferential destruction of smaller specimens during diagenetic or sampling processes), that the magnitude of this bias is partially dependent on the species abundance and size distributions, and that this bias alone does not fully account for empirically observed lithification bias on species richness (i.e., other sources of bias are also at work).

lithification bias
preferential sampling
average speciman size


Multifactorial determination of skeletal age at death: a method and blind tests of its accuracy.

Abstract: Traditional methods of estimating skeletal age at death have relied solely on the pubic symphyseal face or on this indicator combined with others in nonsystematic ways. A multifactorial method is presented that uses a principal components weighting of five indicators (public symphyseal face, auricular surface, radiographs of proximal femur, dental wear, and suture closure). This method has been tested by completely blind assessment of age in two samples from the Todd collection carefully screened for accuracy of stated age at death. Results show a marked superiority of the multifactorial method over any single indicator with respect to both bias and accuracy. This represents the first truly blind test of an age-at-death indicator or system, as the test populations were independent of the system(s) being tested, and the age, sex, and ethnogeographic origin of the individuals being assessed (as well as the compositions of the test samples with respect to these variables) were completely unknown until the tests were completed. Implications for paleodemography are discussed.


mapDamage2.0: fast approximate Bayesian estimates of ancient DNA damage parameters

Abstract: Motivation: Ancient DNA (aDNA) molecules in fossilized bones and teeth, coprolites, sediments, mummified specimens and museum collections represent fantastic sources of information for evolutionary biologists, revealing the agents of past epidemics and the dynamics of past populations. However, the analysis of aDNA generally faces two major issues. Firstly, sequences consist of a mixture of endogenous and various exogenous backgrounds, mostly microbial. Secondly, high nucleotide misincorporation rates can be observed as a result of severe post-mortem DNA damage. Such misincorporation patterns are instrumental to authenticate ancient sequences versus modern contaminants. We recently developed the user-friendly mapDamage package that identifies such patterns from next-generation sequencing (NGS) sequence datasets. The absence of formal statistical modeling of the DNA damage process, however, precluded rigorous quantitative comparisons across samples. Results: Here, we describe mapDamage 2.0 that extends the original features of mapDamage by incorporating a statistical model of DNA damage. Assuming that damage events depend only on sequencing position and post-mortem deamination, our Bayesian statistical framework provides estimates of four key features of aDNA molecules: the average length of overhangs (λ), nick frequency (ν) and cytosine deamination rates in both double-stranded regions () and overhangs (). Our model enables rescaling base quality scores according to their probability of being damaged. mapDamage 2.0 handles NGS datasets with ease and is compatible with a wide range of DNA library protocols. Availability: mapDamage 2.0 is available at ginolhac.github.io/mapDamage/ as a Python package and documentation is maintained at the Centre for GeoGenetics Web site (geogenetics.ku.dk/publications/mapdamage2.0/). Contact: jonsson.hakon@gmail.com Supplementary information: Supplementary data are available at Bioinformatics online.

ancient dna
adna
mapdamage
deamination
dna damage pattern


A new species of Cricosaurus (Thalattosuchia, Metriorhynchidae) based upon a remarkably well-preserved skeleton from the Upper Jurassic of Germany

Abstract: Herein we describe a new and exceptionally well-preserved skeleton of the metriorhynchid thalattosuchian Cricosaurus from the upper Kimmeridgian Torleite Formation of Painten in Bavaria (Southern Germany). The specimen is articulated, shows soft-tissue preservation, and represents one of the most complete metriorhynchid skeletons known. The exceptional preservation allows us to explore the morphological variation of the tail region in the Metriorhynchidae, a part of the skeleton that has long been neglected. Based on our description and phylogenetic analyses, we name this specimen Cricosaurus albersdoerferi sp. nov. Our phylogenetic analyses recover a Cricosaurus subclade composed of four species from Southern Germany and one from Argentina. We provide revised diagnoses for the Southern German members of this subclade, revealing the presence of at least four closely-related Cricosaurus species in the upper Kimmeridgian-early Tithonian of Southern Germany. Interestingly, within this subclade there is evidence of rapid change in tail construction and feeding ecology. However, there is no evidence of sympatry between these taxa, and the two species known from the same ammonite subzone are exclusively found in different northernTethys lagoons. Most interesting, however, is the variation in the skulls, dorsal neural spines, the tail displacement units, and flukes between these different species. This previously unexplored variation within Metriorhynchidae hints to differences in locomotory abilities between different species. Sven Sachs. Naturkunde-Museum Bielefeld, Abteilung Geowissenschaften, Adenauerplatz 2, 33602 Bielefeld, Germany, and Im Hof 9, 51766 Engelskirchen, Germany. Sachs.Pal@gmail.com Mark T. Young. School of GeoSciences, Grant Institute, University of Edinburgh, James Hutton Road, Edinburgh, EH9 3FE, UK. Mark.Young@ed.ac.uk Pascal Abel. Senckenberg Centre for Human Evolution and Palaeoenvironment, Eberhard-KarlsUniversität Tübingen, Sigwartstraße 10, 72076 Tübingen, Germany pascal.abel@ifg.uni-tuebingen.de], Heinrich Mallison. Palaeo3D, Dorfstr. 11, 86641 Rain am Lech, Germany and CeNak, Universität SACHS ET AL.: A NEW Cricosaurus SPECIES 2 Hamburg, Martin-Luther-King-Platz 3, 20146 Hamburg, Germany. mallison@palaeo3d.com

metriorhynchidae
well-preserved skeleton
germany
skull


Improvements in the fossil record may largely resolve current conflicts between morphological and molecular estimates of mammal phylogeny

Abstract: Phylogenies of mammals based on morphological data continue to show several major areas of conflict with the current consensus view of their relationships, which is based largely on molecular data. This raises doubts as to whether current morphological character sets are able to accurately resolve mammal relationships. We tested this under a hypothetical ‘best case scenario’ by using ancestral state reconstruction (under both maximum parsimony and maximum likelihood) to infer the morphologies of fossil ancestors for all clades present in a recent comprehensive DNA sequence-based phylogeny of mammals, and then seeing what effect the subsequent inclusion of these predicted ancestors had on unconstrained phylogenetic analyses of morphological data. We found that this resulted in topologies that are highly congruent with the current consensus phylogeny, at least when the predicted ancestors are assumed to be well preserved and densely sampled. Most strikingly, several analyses recovered the monophyly of clades that have never been found in previous morphology-only studies, such as Afrotheria and Laurasiatheria. Our results suggest that, at least in principle, improvements in the fossil record—specifically the discovery of fossil taxa that preserve the ancestral or near-ancestral morphologies of the nodes in the current consensus—may be sufficient to largely reconcile morphological and molecular estimates of mammal phylogeny, even using current morphological character sets.

conflict phylogeny dna laurasiatheria improvement


Relationships between bone growth rate, body mass and resting metabolic rate in growing amniotes: a phylogenetic approach

Abstract: We explored the factors that explain the variation in resting metabolic rates (RMR) in growing amniotes by using the phylogenetic comparative method. For this, we measured raw RMR (mL O2 h−1), body mass, body mass growth rate, and periosteal bone growth rate in a sample of 44 growing individuals belonging to 13 species of amniotes. We performed variation partitioning analyses, which showed that phylogeny explains a significant fraction of the variation of mass-specific RMR (mL O2 h−1 g−1), and that the cost of growth is much higher than the cost of maintenance. Moreover, we tested the hypothesis of the independence of energy allocation, and found that maintenance metabolism and growth rates are not significantly related. Finally, we calculated the statistical parameters of the relationship between geometry-corrected RMR (mL O2 h−1 g−0.67) and bone growth rate. This relationship could potentially be used in palaeobiology to infer RMR from bone tissue samples of fossil species by assuming Amprino’s rule (according to which bone tissue types reflect bone growth rates). These estimates would be especially interesting for Mesozoic non-avian theropod dinosaurs and Permian and Triassic therapsids to investigate, respectively, the origin of avian and mammalian endothermy. © 2007 The Linnean Society of London, Biological Journal of the Linnean Society, 2007, 92, 63–76.


The importance of muscle architecture in biomechanical reconstructions of extinct animals: a case study using Tyrannosaurus rex

Abstract: Functional reconstructions of extinct animals represent a crucial step towards understanding palaeocological interactions, selective pressures and macroevolutionary patterns in the fossil record. In recent years, computational approaches have revolutionised the field of ‘evolutionary biomechanics’ and have, in general, resulted in convergence of quantitative estimates of performance on increasingly narrow ranges for well studied taxa. Studies of body mass and locomotor performance of Tyrannosaurus rex – arguably the most intensively studied extinct animal – typify this pattern, with numerous independent studies predicting similar body masses and maximum locomotor speeds for this animal. In stark contrast to this trend, recent estimates of maximum bite force in T. rex vary considerably (> 50%) despite use of similar quantitative methodologies. Herein we demonstrate that the mechanistic causes of these disparate predictions are indicative of important and underappreciated limiting factors in biomechanical reconstructions of extinct organisms. Detailed comparison of previous models of T. rex bite force reveals that estimations of muscle fibre lengths and architecture are the principal source of disagreement between studies, and therefore that these parameters represents the greatest source of uncertainty in these reconstructions, and potentially therefore extinct animals generally. To address the issue of fibre length and architecture estimation in extinct animals we present data tabulated from the literature of muscle architecture from over 1100 muscles measured in extant terrestrial animals. Application of this dataset in a reanalysis of T. rex bite force emphasises the need for more data on jaw musculature from living carnivorous animals, alongside increased sophistication of modelling approaches. In the latter respect we predict that implementing limits on skeletal loading into musculoskeletal models will narrow predictions for T. rex bite force by excluding higher‐end estimates.

muscle architecture
biomechanical reconstruction
extinct animal


Ancient Egyptian mummy genomes suggest an increase of Sub-Saharan African ancestry in post-Roman periods

Abstract: Egypt, located on the isthmus of Africa, is an ideal region to study historical population dynamics due to its geographic location and documented interactions with ancient civilizations in Africa, Asia and Europe. Particularly, in the first millennium BCE Egypt endured foreign domination leading to growing numbers of foreigners living within its borders possibly contributing genetically to the local population. Here we present 90 mitochondrial genomes as well as genome-wide data sets from three individuals obtained from Egyptian mummies. The samples recovered from Middle Egypt span around 1,300 years of ancient Egyptian history from the New Kingdom to the Roman Period. Our analyses reveal that ancient Egyptians shared more ancestry with Near Easterners than present-day Egyptians, who received additional sub-Saharan admixture in more recent times. This analysis establishes ancient Egyptian mummies as a genetic source to study ancient human history and offers the perspective of deciphering Egypt's past at a genome-wide level.

genome
ancestry
new kingdom
roman period


Thresholds of temperature change for mass extinctions

Abstract: Climate change is a critical factor affecting biodiversity. However, the quantitative relationship between temperature change and extinction is unclear. Here, we analyze magnitudes and rates of temperature change and extinction rates of marine fossils through the past 450 million years (Myr). The results show that both the rate and magnitude of temperature change are significantly positively correlated with the extinction rate of marine animals. Major mass extinctions in the Phanerozoic can be linked to thresholds in climate change (warming or cooling) that equate to magnitudes >5.2 °C and rates >10 °C/Myr. The significant relationship between temperature change and extinction still exists when we exclude the five largest mass extinctions of the Phanerozoic. Our findings predict that a temperature increase of 5.2 °C above the pre-industrial level at present rates of increase would likely result in mass extinction comparable to that of the major Phanerozoic events, even without other, non-climatic anthropogenic impacts.

temperature change
mass extinction
threshold


The Jehol Biota, an Early Cretaceous terrestrial Lagerstätte: new discoveries and implications

Abstract: The study of the Early Cretaceous terrestrial Jehol Biota, which provides a rare window for reconstruction of a Lower Cretaceous terrestrial ecosystem, is reviewed with a focus on some of the latest progress. A newly proposed definition of the biota based on paleoecology and taphonomy is accepted. Although the Jehol fossils are mainly preserved in two types of sedimentary rocks, there are various types of preservation with a complex mechanism that remains to be understood. New discoveries of significant taxa from the Jehol Biota, with an updated introduction of its diversity, confirm that the Jehol Biota represents one of the most diversified biotas of the Mesozoic. The evolutionary significance of major biological groups (e.g. dinosaurs, birds, mammals, pterosaurs, insects, and plants) is discussed mainly in the light of recent discoveries, and some of the most remarkable aspects of the biota are highlighted. The global and local geological, paleogeographic, and paleoenvironmental background of the Jehol Biota have contributed to the unique composition, evolution, and preservation of the biota, demonstrating widespread faunal exchanges between Asia and other continents caused by the presence of the Eurasia-North American continental mass and its link to South America, and confirming northeastern China as the origin and diversification center for a variety of Cretaceous biological groups. Although some progress has been made on the reconstruction of the paleotemperature at the time of the Jehol Biota, much more work is needed to confirm a possible link between the remarkable diversity of the biota and the cold intervals during the Early Cretaceous. Finally, future directions for the study of the Jehol Biota are proposed that highlight the great potential of more comprehensive and multidisciplinary studies to further our understanding of the biological and geological implications of the Jehol Lagerstatte.

jehol biota
new discovery
cretaceous terrestrial ecosystem
taphonomy
vertebrate


Mind the Outgroup and Bare Branches in Total-Evidence Dating: a Case Study of Pimpliform Darwin Wasps (Hymenoptera, Ichneumonidae)

Abstract: Abstract Taxon sampling is a central aspect of phylogenetic study design, but it has received limited attention in the context of total-evidence dating, a widely used dating approach that directly integrates molecular and morphological information from extant and fossil taxa. We here assess the impact of commonly employed outgroup sampling schemes and missing morphological data in extant taxa on age estimates in a total-evidence dating analysis under the uniform tree prior. Our study group is Pimpliformes, a highly diverse, rapidly radiating group of parasitoid wasps of the family Ichneumonidae. We analyze a data set comprising 201 extant and 79 fossil taxa, including the oldest fossils of the family from the Early Cretaceous and the first unequivocal representatives of extant subfamilies from the mid-Paleogene. Based on newly compiled molecular data from ten nuclear genes and a morphological matrix that includes 222 characters, we show that age estimates become both older and less precise with the inclusion of more distant and more poorly sampled outgroups. These outgroups not only lack morphological and temporal information but also sit on long terminal branches and considerably increase the evolutionary rate heterogeneity. In addition, we discover an artifact that might be detrimental for total-evidence dating: “bare-branch attraction,” namely high attachment probabilities of certain fossils to terminal branches for which morphological data are missing. Using computer simulations, we confirm the generality of this phenomenon and show that a large phylogenetic distance to any of the extant taxa, rather than just older age, increases the risk of a fossil being misplaced due to bare-branch attraction. After restricting outgroup sampling and adding morphological data for the previously attracting, bare branches, we recover a Jurassic origin for Pimpliformes and Ichneumonidae. This first age estimate for the group not only suggests an older origin than previously thought but also that diversification of the crown group happened well before the Cretaceous-Paleogene boundary. Our case study demonstrates that in order to obtain robust age estimates, total-evidence dating studies need to be based on a thorough and balanced sampling of both extant and fossil taxa, with the aim of minimizing evolutionary rate heterogeneity and missing morphological information. [Bare-branch attraction; ichneumonids; fossils; morphological matrix; phylogeny; RoguePlots.]

outgroup
total-evidence
ichneumonidae
early cretaceous


Mitochondrial Phylogenomics of Modern and Ancient Equids

Abstract: The genus Equus is richly represented in the fossil record, yet our understanding of taxonomic relationships within this genus remains limited. To estimate the phylogenetic relationships among modern horses, zebras, asses and donkeys, we generated the first data set including complete mitochondrial sequences from all seven extant lineages within the genus Equus. Bayesian and Maximum Likelihood phylogenetic inference confirms that zebras are monophyletic within the genus, and the Plains and Grevy’s zebras form a well-supported monophyletic group. Using ancient DNA techniques, we further characterize the complete mitochondrial genomes of three extinct equid lineages (the New World stilt-legged horses, NWSLH; the subgenus Sussemionus; and the Quagga, Equus quagga quagga). Comparisons with extant taxa confirm the NWSLH as being part of the caballines, and the Quagga and Plains zebras as being conspecific. However, the evolutionary relationships among the non-caballine lineages, including the now-extinct subgenus Sussemionus, remain unresolved, most likely due to extremely rapid radiation within this group. The closest living outgroups (rhinos and tapirs) were found to be too phylogenetically distant to calibrate reliable molecular clocks. Additional mitochondrial genome sequence data, including radiocarbon dated ancient equids, will be required before revisiting the exact timing of the lineage radiation leading up to modern equids, which for now were found to have possibly shared a common ancestor as far as up to 4 Million years ago (Mya).


Amniotes through major biological crises: faunal turnover among Parareptiles and the end‐Permian mass extinction

Abstract: Abstract:  The Parareptilia are a small but ecologically and morphologically diverse clade of Permian and Triassic crown amniotes generally considered to be phylogenetically more proximal to eureptiles (diapsids and their kin) than to synapsids (mammals and their kin). A recent supertree provides impetus for an analysis of parareptile diversity through time and for examining the influence of the end‐Permian mass extinction on the clade’s origination and extinction rates. Phylogeny‐corrected measures of diversity have a significant impact on both rates and the distribution of origination and extinction intensities. Time calibration generally results in a closer correspondence between origination and extinction rate values than in the case of no time correction. Near the end‐Permian event, extinction levels are not significantly higher than origination levels, particularly when time calibration is introduced. Finally, regardless of time calibration and/or phylogenetic correction, the distribution of rates does not differ significantly from unimodal. The curves of rate values are discussed in the light of the numbers and distributions of both range extensions and ghost lineages. The disjoint time distributions of major parareptile clades (e.g. procolophonoids and nycteroleterids‐pareiasaurs) are mostly responsible for the occurrence of long‐range extensions throughout the Permian. Available data are not consistent with a model of sudden decline at the end‐Permian but rather suggest a rapid alternation of originations and extinctions in a number of parareptile groups, both before and after the Permian/Triassic boundary.

parareptile
mass extinction
origination
correction


Semicircular canals in Anolis lizards: ecomorphological convergence and ecomorph affinities of fossil species

Abstract: Anolis lizards are a model system for the study of adaptive radiation and convergent evolution. Greater Antillean anoles have repeatedly evolved six similar forms or ecomorphs: crown-giant, grass-bush, twig, trunk, trunk-crown and trunkground. Members of each ecomorph category possess a specific set of morphological, ecological and behavioural characteristics which have been acquired convergently. Here we test whether the semicircular canal system-the organ of balance during movement-is also convergent among ecomorphs, reflecting the shared sensory requirements of their ecological niches. As semicircular canal shape has been shown to reflect different locomotor strategies, we hypothesized that each Anolis ecomorph would have a unique canal morphology. Using three-dimensional semilandmarks and geometric morphometrics, semicircular canal shape was characterized in 41 Anolis species from the Greater Antilles and the relationship between canal shape and ecomorph grouping, phylogenetic history, size, head dimensions, and perch characteristics was assessed. Further, canal morphology of modern species was used to predict the ecomorph affinity of five fossil anoles from the Miocene of the Dominican Republic. Of the covariates tested, our study recovered ecomorph as the single-most important covariate of canal morphology in modern taxa; although phylogenetic history, size, and head dimensions also showed a small, yet significant correlation with shape. Surprisingly, perch characteristics were not found to be significant covariates of canal shape, even though they are important habitat variables. Using

anolis lizard
ecomorph affinity
canal shape
modern specie
semicircular canal


Devonian deposits of the Baruunhuurai Terrane, Western Mongolia (IGCP 596 Field Workshop)

Abstract: IGCP 596 (2011-2015) has a primary focus on climate change and biodiversity patterns in the Mid-Paleozoic (Early Devonian to Late Carboniferous). As a part of this project, we conducted a field workshop in western Mongolia in the summer of 2012. The goal was to locate fossiliferous sections that expose the stage boundaries from the Eifelian/Givetian boundary (Middle Devonian) to the Devonian/Carboniferous boundary to expand our knowledge of the key Devonian biotic and geochemical events such as the Frasnian/Famennian extinction event and the Kacak, Kellwasser and Hangenberg oceanographic events. During the field workshop, we examined sections in the Nariinhar Formation, Baruunhuurai Formation and Samnuuruul Formation from the Baruunhuurai Terrane.

baruunhuurai terrane
western mongolia
field workshop
volcaniclastic rock
carbonate facie


Testing the molecular clock using mechanistic models of fossil preservation and molecular evolution

Abstract: Molecular sequence data provide information about relative times only, and fossil-based age constraints are the ultimate source of information about absolute times in molecular clock dating analyses. Thus, fossil calibrations are critical to molecular clock dating, but competing methods are difficult to evaluate empirically because the true evolutionary time scale is never known. Here, we combine mechanistic models of fossil preservation and sequence evolution in simulations to evaluate different approaches to constructing fossil calibrations and their impact on Bayesian molecular clock dating, and the relative impact of fossil versus molecular sampling. We show that divergence time estimation is impacted by the model of fossil preservation, sampling intensity and tree shape. The addition of sequence data may improve molecular clock estimates, but accuracy and precision is dominated by the quality of the fossil calibrations. Posterior means and medians are poor representatives of true divergence times; posterior intervals provide a much more accurate estimate of divergence times, though they may be wide and often do not have high coverage probability. Our results highlight the importance of increased fossil sampling and improved statistical approaches to generating calibrations, which should incorporate the non-uniform nature of ecological and temporal fossil species distributions.

molecular clock
mechanistic model
fossil preservation


Hyainailourine and teratodontine cranial material from the late Eocene of Egypt and the application of parsimony and Bayesian methods to the phylogeny and biogeography of Hyaenodonta (Placentalia, Mammalia)

Abstract: Hyaenodonta is a diverse, extinct group of carnivorous mammals that included weasel- to rhinoceros-sized species. The oldest-known hyaenodont fossils are from the middle Paleocene of North Africa and the antiquity of the group in Afro-Arabia led to the hypothesis that it originated there and dispersed to Asia, Europe, and North America. Here we describe two new hyaenodont species based on the oldest hyaenodont cranial specimens known from Afro-Arabia. The material was collected from the latest Eocene Locality 41 (L-41, ∼34 Ma) in the Fayum Depression, Egypt. Akhnatenavus nefertiticyon sp. nov. has specialized, hypercarnivorous molars and an elongate cranial vault. In A. nefertiticyon the tallest, piercing cusp on M1–M2 is the paracone. Brychotherium ephalmos gen. et sp. nov. has more generalized molars that retain the metacone and complex talonids. In B. ephalmos the tallest, piercing cusp on M1–M2 is the metacone. We incorporate this new material into a series of phylogenetic analyses using a character-taxon matrix that includes novel dental, cranial, and postcranial characters, and samples extensively from the global record of the group. The phylogenetic analysis includes the first application of Bayesian methods to hyaenodont relationships. B. ephalmos is consistently placed within Teratodontinae, an Afro-Arabian clade with several generalist and hypercarnivorous forms, and Akhnatenavus is consistently recovered in Hyainailourinae as part of an Afro-Arabian radiation. The phylogenetic results suggest that hypercarnivory evolved independently three times within Hyaenodonta: in Teratodontinae, in Hyainailourinae, and in Hyaenodontinae. Teratodontines are consistently placed in a close relationship with Hyainailouridae (Hyainailourinae + Apterodontinae) to the exclusion of “proviverrines,” hyaenodontines, and several North American clades, and we propose that the superfamily Hyainailouroidea be used to describe this relationship. Using the topologies recovered from each phylogenetic method, we reconstructed the biogeographic history of Hyaenodonta using parsimony optimization (PO), likelihood optimization (LO), and Bayesian Binary Markov chain Monte Carlo (MCMC) to examine support for the Afro-Arabian origin of Hyaenodonta. Across all analyses, we found that Hyaenodonta most likely originated in Europe, rather than Afro-Arabia. The clade is estimated by tip-dating analysis to have undergone a rapid radiation in the Late Cretaceous and Paleocene; a radiation currently not documented by fossil evidence. During the Paleocene, lineages are reconstructed as dispersing to Asia, Afro-Arabia, and North America. The place of origin of Hyainailouroidea is likely Afro-Arabia according to the Bayesian topologies but it is ambiguous using parsimony. All topologies support the constituent clades–Hyainailourinae, Apterodontinae, and Teratodontinae–as Afro-Arabian and tip-dating estimates that each clade is established in Afro-Arabia by the middle Eocene.

parsimony
hyaenodonta
character-taxon matrix
hyainailouroidea


Influence of tidal‐range change and sediment compaction on Holocene relative sea‐level change in New Jersey, USA

Abstract: We investigated the effect of tidal‐range change and sediment compaction on reconstructions of Holocene relative sea level (RSL) in New Jersey, USA. We updated a published sea‐level database to generate 50 sea‐level index points and ten limiting dates that define continuously rising RSL in New Jersey during the Holocene. There is scatter among the index points, particularly those older than 7 ka. A numerical model estimated that paleotidal range was relatively constant during the mid and late Holocene, but rapidly increased between 9 and 8 ka, leading to an underestimation of RSL by ∼0.5 m. We adjusted the sea‐level index points using the paleotidal model prior to assessing the influence of compaction on organic samples with clastic deposits above and below (an intercalated sea‐level index point). We found a significant relationship (p = 0.01) with the thickness of the overburden (r = 0.85). We altered the altitude of intercalated index points using this simple stratigraphic relationship, which reduced vertical scatter in sea‐level reconstructions. We conclude that RSL rose at an average rate of 4 mm a−1 from 10 ka to 6 ka, 2 mm a−1 from 6 ka to 2 ka, and 1.3 mm a−1 from 2 ka to AD 1900. Copyright © 2013 John Wiley & Sons, Ltd.

tidal‐range change
sediment compaction
holocene


A Review of the Fossil Record of Turtles of the Clade Baenidae

Abstract: Abstract The fossil record of the turtle clade Baenidae ranges from the Early Cretaceous (Aptian—Albian) to the Eocene. The group is present throughout North America during the Early Cretaceous, but is restricted to the western portions of the continents in the Late Cretaceous and Paleogene. No credible remains of the clade have been reported outside of North America to date. Baenids were warmadapted freshwater aquatic turtles that supported high levels of diversity at times through niche partitioning, particularly by adapting to a broad range of dietary preferences ranging from omnivorous to molluscivorous. Current phylogenies place Baenidae near the split of crown-group Testudines. Within Baenidae three more inclusive, named clades are recognized: Baenodda, Palatobaeninae and Eubaeninae. A taxonomic review of the group concludes that of 49 named taxa, 30 are nomina valida, 12 are nomina invalida and 7 are nomina dubia.


THE MORPHOLOGY OF HYOLITHIDS AND ITS FUNCTIONAL IMPLICATIONS

Abstract: Abstract:  The exceptionally preserved hyolithids Gompholites striatulus, Maxilites robustus, Maxilites snajdri and Maxilites sp. are described with particular emphasis on helen and muscle scar morphology. These two aspects of hyolithid morphology have remained controversial. In life position, each helen curved ventrally. When the operculum closed the aperture of the conch, each helen was locked at the commissure slit with its dorsal edge tilted forward. Inside the conch, it was held in the dorsal apertural plane and clear of the inner surface of the operculum. Previously unidentified muscle scars are described from both the operculum and the conch. Dorsal scars on the conch aperture held muscles directed to the operculum. Comparative study of the muscle insertion pattern indicates that hyolithids did not have serially arranged muscles and that all hyolithids may have had a common skeleto‐muscular system. The arrangement of the muscle scars with respect to the helens suggests that the latter were capable of relatively complex movements and could have been used to propel the organism over the substrate. The general morphology and orientation of the helens suggests that in addition they functioned to stabilize the organism on the sea‐floor.

morphology
hyolithid
operculum
conch
lateral spine


Dispersal and diversity in the earliest North American sauropodomorph dinosaurs, with a description of a new taxon

Abstract: Sauropodomorph dinosaurs originated in the Southern Hemisphere in the Middle or Late Triassic and are commonly portrayed as spreading rapidly to all corners of Pangaea as part of a uniform Late Triassic to Early Jurassic cosmopolitan dinosaur fauna. Under this model, dispersal allegedly inhibited dinosaurian diversification, while vicariance and local extinction enhanced it. However, apomorphy-based analyses of the known fossil record indicate that sauropodomorphs were absent in North America until the Early Jurassic, reframing the temporal context of their arrival. We describe a new taxon from the Kayenta Formation of Arizona that comprises the third diagnosable sauropodomorph from the Early Jurassic of North America. We analysed its relationships to test whether sauropodomorphs reached North America in a single sweepstakes event or in separate dispersals. Our finding of separate arrivals by all three taxa suggests dispersal as a chief factor in dinosaurian diversification during at least the early Mesozoic. It questions whether a ‘cosmopolitan’ dinosaur fauna ever existed, and corroborates that vicariance, extinction and dispersal did not operate uniformly in time or under uniform conditions during the Mesozoic. Their relative importance is best measured in narrow time slices and circumscribed geographical regions.

sauropodomorph dinosaur
new taxon
dispersal


Abstract: Edgecombe, G.D. 2010. Palaeomorphology: fossils and the inference of cladistic relationships. —Acta Zoologica (Stockholm) 91: 72–80 Twenty years have passed since it was empirically demonstrated that inclusion of extinct taxa could overturn a phylogenetic hypothesis formulated upon extant taxa alone, challenging Colin Patterson’s bold conjecture that this phenomenon ‘may be non-existent’. Suppositions and misconceptions about missing data, often couched in terms of ‘wildcard taxa’ and ‘the missing data problem’, continue to cloud the literature on the topic of fossils and phylogenetics. Comparisons of real data sets show that no ap riori(or indeed a posteriori) decisions can be made about amounts of missing data and most properties of cladograms, and both simulated and real data sets demonstrate that even highly incomplete taxa can impact on relationships. The exclusion of fossils from phylogenetic analyses is neither theoretically nor empirically defensible.

inference
cladistic relationship
palaeomorphology


AUTECOLOGY AND THE FILLING OF ECOSPACE: KEY METAZOAN RADIATIONS

Abstract: Abstract:  All possible combinations of six tiering positions in relation to the substratum/water interface, six motility levels and six feeding strategies define a complete theoretical ecospace of 216 potential modes of life for marine animals. The number of modes of life actually utilized specifies realized ecospace. Owing to constraints of effectiveness and efficiency the modern marine fauna utilizes only about half the potential number of modes of life, two‐thirds of which (62 of 92) are utilized by animals with readily preserved, mineralized hard parts. Realized ecospace has increased markedly since the early evolution of animal ecosystems. The Ediacaran fauna utilized at most 12 modes of life, with just two practised by skeletal organisms. A total of 30 modes of life are recorded in the Early and Middle Cambrian, 19 of which were utilized by skeletal organisms. The other 11 are documented from soft‐bodied animals preserved in the Chengjiang and Burgess Shale Konservat‐Lagerstätten. The number of modes of life utilized by skeletal organisms increased by more than 50 per cent during the Ordovician radiation to a Late Ordovician total of 30. Between the Late Ordovician and the Recent the number of utilized modes of life has doubled again. The autecological and taxonomic diversity histories of the marine metazoa appear to be broadly parallel, and future studies of theoretical ecospace utilization should provide more detailed tests of pattern and process in the ecological history of the metazoa.

ecospace
marine fauna
cambrian
complexity
life mode


Inferring palaeoecology in extinct tremarctine bears (Carnivora, Ursidae) using geometric morphometrics

Abstract: In this study we explore the ecomorphological patterns of extinct tremarctine bears in South America during the Great American Biotic Interchange (GABI). These patterns are used to derive palaeoautoecological inferences in extinct tremarctines and their palaeosinecological relationships within Plio-Pleistocene ecosystems. We used geometric morphometrics of landmark data to recover the shape of the craniomandibular skeleton of bears. The results reveal different ecomorphological specializations in extinct tremarctines during the Plio-Pleistocene of South America. Indeed, these bears could have increased the percentage of plant matter in their diets according with the increased diversity of large carnivores in South America after the GABI. Omnivorous bears retain the ability to behave as carnivores or herbivores depending on resource availability. This fact strongly supports that bears are one of the most ecologically and morphologically adaptable members of the large carnivore guild. Moreover, their skull morphology could reflect ecological adaptations under different selection pressures with the required evolutionary time. h Evolution, GABI, geometric morphometrics, palaeoecology, Tremarctinae.

palaeoecology
extinct tremarctine bear
geometric morphometric


The Extent of the Preserved Feathers on the Four-Winged Dinosaur Microraptor gui under Ultraviolet Light

Abstract: Background The holotype of the theropod non-avian dinosaur Microraptor gui from the Early Cretaceous of China shows extensive preservation of feathers in a halo around the body and with flight feathers associated with both the fore and hindlimbs. It has been questioned as to whether or not the feathers did extend into the halo to reach the body, or had disassociated and moved before preservation. This taxon has important implications for the origin of flight in birds and the possibility of a four-winged gliding phase. Methodology/Principal Findings Examination of the specimen under ultraviolet light reveals that these feathers actually reach the body of the animal and were not disassociated from the bones. Instead they may have been chemically altered by the body tissues of the animal meaning that they did not carbonise close into the animal or more likely were covered by other decaying tissue, though evidence of their presence remains. Conclusions/Significance These UV images show that the feathers preserved on the slab are genuinely associated with the skeleton and that their arrangement and orientation is likely correct. The methods used here to reveal hidden features of the specimen may be applicable to other specimens from the fossil beds of Liaoning that produced Microraptor.


Comparative osteology and phylogenetic relationships of Miocaperea pulchra, the first fossil pygmy right whale genus and species (Cetacea, Mysticeti, Neobalaenidae)

Abstract:
A fossil pygmy right whale (Cetacea, Mysticeti, Neobalaenidae) with exquisitely preserved baleen is described for the first time in the history of cetacean palaeontology, providing a wealth of information about the evolutionary history and palaeobiogeography of Neobalaenidae. This exquisitely preserved specimen is assigned to a new genus and species, Miocaperea pulchra gen. et sp. nov., and differs from Caperea marginata Gray, 1846, the only living taxon currently assigned to Neobalaenidae, in details of the temporal fossa and basicranium. A thorough comparative analysis of the skeleton of M. pulchra gen. et sp. nov. and C. marginata is also provided, and forms the basis of an extensive osteology-based phylogenetic analysis, confirming the placement of M. pulchra gen. et sp. nov. within Neobalaenidae as well as the monophyly of Neobalaenidae and Balaenidae; the phylogenetic results support the validity of the superfamily Balaenoidea. No relationship with Balaenopteroidea was found by the present study, and thus the balaenopterid-like morphological features observed in C. marginata must have resulted from parallel evolution. The presence of M. pulchra gen. et sp. nov. around 2000 km north from the northernmost sightings of C. marginata suggests that different ecological conditions were able to support pygmy right whale populations in what is now Peru, and that subsequent environmental change caused a southern shift in the distribution of the living neobalaenid whales.

© 2012 The Linnean Society of London, Zoological Journal of the Linnean Society, 2012, 166, 876–911.


Improving access to endogenous DNA in ancient bones and teeth

Abstract:
Poor DNA preservation is the most limiting factor in ancient genomic research. In the majority of
ancient bones and teeth, endogenous DNA molecules represent a minor fraction of the whole DNA
extract, rendering shot-gun sequencing inefficient for obtaining genomic data. Based on ancient
human bone samples from temperate and tropical environments, we show that an EDTA-based enzymatic
‘pre-digestion’ of powdered bone increases the proportion of endogenous DNA several
fold. By performing the pre-digestion step between 30 min and 6 hours on five bones,
we observe an asymptotic increase in endogenous DNA content, with a 2.7-fold average increase
reached at 1 hour. We repeat the experiment using a brief pre-digestion (15 or
30 mins) on 21 ancient bones and teeth from a variety of archaeological contexts and observe
an improvement in 16 of these. We here advocate the implementation of a brief pre-digestion step as
a standard procedure in ancient DNA extractions. Finally, we demonstrate on 14 ancient teeth that by
targeting the outer layer of the roots we obtain up to 14 times more endogenous DNA than when using
the inner dentine. Our presented methods are likely to increase the proportion of ancient samples
that are suitable for genome-scale characterization.


Cranial Morphology of the Brachystelechid ‘Microsaur’ Quasicaecilia texana Carroll Provides New Insights into the Diversity and Evolution of Braincase Morphology in Recumbirostran ‘Microsaurs’

Abstract: Recumbirostran ‘microsaurs,’ a group of early tetrapods from the Late Carboniferous and Early Permian, are the earliest known example of adaptation to head-first burrowing in the tetrapod fossil record. However, understanding of the diversity of fossorial adaptation within the Recumbirostra has been hindered by poor anatomical knowledge of the more divergent forms within the group. Here we report the results of μCT study of Quasicaecilia texana, a poorly-known recumbirostran with a unique, broad, shovel-like snout. The organization of the skull roof and braincase of Quasicaecilia is found to be more in line with that of other recumbirostrans than previously described, despite differences in overall shape. The braincase is found to be broadly comparable to Carrolla craddocki, with a large presphenoid that encompasses much of the interorbital septum and the columella ethmoidalis, and a single compound ossification encompassing the sphenoid, otic, and occipital regions. The recumbirostran braincase conserves general structure and topology of braincase regions and cranial nerve foramina, but it is highly variable in the number of ossifications and their extent, likely associated with the reliance on braincase ossifications to resist compression during sediment compaction and mechanical manipulation by epaxial and hypaxial musculature. Expansion of the deep ventral neck musculature in Quasicaecilia, autapomorphic among recumbirostrans, may reflect unique biomechanical function, and underscores the importance of future attention to the role of the cervical musculature in contextualizing the origin and evolution of fossoriality in recumbirostrans.


Tracing the effects of eutrophication on molluscan communities in sediment cores: outbreaks of an opportunistic species coincide with reduced bioturbation and high frequency of hypoxia in the Adriatic Sea

Abstract:
Abstract.
 Estimating the effects and timing of anthropogenic impacts on the composition of macrobenthic communities is challenging, because early twentieth-century surveys are sparse and the corresponding intervals in sedimentary sequences are mixed by bioturbation. Here, to assess the effects of eutrophication on macrobenthic communities in the northern Adriatic Sea, we account for mixing with dating of the bivalve Corbula gibba at two stations with high accumulation (Po prodelta) and one station with moderate accumulation (Isonzo prodelta). We find that, first, pervasively bioturbated muds typical of highstand conditions deposited in the early twentieth century were replaced by muds with relicts of flood layers and high content of total organic carbon (TOC) deposited in the late twentieth century at the Po prodelta. The twentieth century shelly muds at the Isonzo prodelta are amalgamated but also show an upward increase in TOC. Second, dating of C. gibba shells shows that the shift from the early to the late twentieth century is characterized by a decrease in stratigraphic disorder and by an increase in temporal resolution of assemblages from ~ 25–50 years to ~ 10–20 years in both regions. This shift reflects a decline in the depth of the fully mixed layer from more than 20 cm to a few centimeters. Third, the increase in abundance of the opportunistic species C. gibba and the loss of formerly abundant, hypoxia-sensitive species coincided with the decline in bioturbation, higher preservation of organic matter, and higher frequency of seasonal hypoxia in both regions. This depositional and ecosystem regime shift occurred in ca. A.D. 1950. Therefore, the effects of enhanced food supply on macrobenthic communities were overwhelmed by oxygen depletion, even when hypoxic conditions were limited to few weeks per year in the northern Adriatic Sea. Preservation of trends in molluscan abundance and flood events in cores was enhanced by higher frequency of hypoxia that reduced bioturbation in the late twentieth century.

eutrophication
sediment core
bioturbation


Sex and the shifting biodiversity dynamics of marine animals in deep time

Abstract: Significance Fertilization mechanisms explain broad patterns in the taxonomic distribution of diversity in marine animals, as argued previously for land plants. We argue that fertilization via copulation (or some other significant interaction among adults) permits additional mechanisms of reproductive isolation and smaller population sizes relative to fertilization via the broadcasting of sperm into the water, thus enhancing diversification potential. Maximum-likelihood modeling of paleontological data indicates that the diversity of sperm broadcasters has been limited by diversity-dependent factors for the last 450 million years. In contrast, animals that copulate, etc., were also limited until the Cretaceous and then radiated dramatically, coincident with apparent major changes in marine productivity. Fertilization may have acted synergistically with ecological specialization in promoting diversification, particularly in predators. The fossil record of marine animals suggests that diversity-dependent processes exerted strong control on biodiversification: after the Ordovician Radiation, genus richness did not trend for hundreds of millions of years. However, diversity subsequently rose dramatically in the Cretaceous and Cenozoic (145 million years ago–present), indicating that limits on diversification can be overcome by ecological or evolutionary change. Here, we show that the Cretaceous–Cenozoic radiation was driven by increased diversification in animals that transfer sperm between adults during fertilization, whereas animals that broadcast sperm into the water column have not changed significantly in richness since the Late Ordovician (∼450 million years ago). We argue that the former group radiated in part because directed sperm transfer permits smaller population sizes and additional modes of prezygotic isolation, as has been argued previously for the coincident radiation of angiosperms. Directed sperm transfer tends to co-occur with many ecological traits, such as a predatory lifestyle. Ecological specialization likely operated synergistically with mode of fertilization in driving the diversification that began during the Mesozoic marine revolution. Plausibly, the ultimate driver of diversification was an increase in food availability, but its effects on the fauna were regulated by fundamental reproductive and ecological traits.

marine animal
fertilization
diversification
water column


Developmental and evolutionary novelty in the serrated teeth of theropod dinosaurs

Abstract:
Tooth morphology and development can provide valuable insights into the feeding behaviour and evolution of extinct organisms. The teeth of Theropoda, the only clade of predominantly predatory dinosaurs, are characterized by ziphodonty, the presence of serrations (denticles) on their cutting edges. Known today only in varanid lizards, ziphodonty is much more pervasive in the fossil record.
Here we present the first model for the development of ziphodont teeth in theropods through histological, SEM, and SR-FTIR analyses, revealing that structures previously hypothesized to prevent tooth breakage instead first evolved to shape and maintain the characteristic denticles through the life of the tooth. We show that this novel complex of dental morphology and tissues characterizes Theropoda, with the exception of species with modified feeding behaviours, suggesting that these characters are important for facilitating the hypercarnivorous diet of most theropods. This adaptation may have played an important role in the initial radiation and subsequent success of theropods as terrestrial apex predators.

tooth
valuable insight
feeding behaviour
extinct organism


The effects of locomotion on the structural characteristics of avian limb bones

Abstract: Despite the wide range of locomotor adaptations in birds, little detailed attention has been given to the relationships between the quantitative structural characteristics of avian limb bones and bird behaviour. Possible differences in forelimb relative to hindlimb strength across species have been especially neglected. We generated cross-sectional, geometric data from peripheral quantitative computed tomography scans of the humerus and femur of 127 avian skeletons, representing 15 species of extant birds in 13 families. The sample includes terrestrial runners, arboreal perchers, hindlimb-propelled divers, forelimb-propelled divers and dynamic soarers. The hindlimb-propelled diving class includes a recently flightless island form. Our results demonstrate that locomotor dynamics can be differentiated in most cases based on cross-sectional properties, and that structural proportions are often more informative than bone length proportions for determining behaviour and locomotion. Recently flightless forms, for example, are more easily distinguished using structural ratios than using length ratios. A proper phylogenetic context is important for correctly interpreting structural characteristics, especially for recently flightless forms. Some of the most extreme adaptations to mechanical loading are seen in aquatic forms. Penguins have forelimbs adapted to very high loads. Aquatic species differ from non-aquatic species on the basis of relative cortical thickness. The combination of bone structural strength and relative cortical area of the humerus successfully differentiates all of our locomotor groups. The methods used in this study are highly applicable to fossil taxa, for which morphology is known but behaviour is not. The use of bone structural characteristics is particularly useful in palaeontology not only because it generates strong signals for many locomotor guilds, but also because analysing such traits does not require knowledge of body mass, which can be difficult to estimate reliably for fossil taxa. © 2008 The Linnean Society of London, Zoological Journal of the Linnean Society, 2008, 153, 601‐624.

locomotion
structural characteristic
avian limb bone


Bone histology of Proneusticosaurus (Diapsida, Eosauropterygia) from the Middle Triassic of Poland reveals new insights into taxonomic affinities

Abstract: The status of Proneusticosaurus silesiacus from the Lower Muschelkalk (lower Anisian) of Poland is controversially discussed. Its femur was histologically sampled to learn more about its taxonomic affinities and life style. It shows a reduced central medullary cavity surrounded by a narrow medullary region and followed by a thick compact cortex, displaying strong osteosclerosis. The tissue type can be summarized as lamellar-zonal. The inner third of the cortex consists of well vascularized parallel-fibred bone and is interpreted as a phase of juvenile growth, whereas the middle and outer cortex is made of highly organized parallel-fibred to lamellar bone. Except for the inner cortex and local accumulations of longitudinally primary osteons in the middle cortex, the femur is widely avascular. The cortex of P. silesiacus is regularly stratified by rest lines. Altogether seven annual growth cycles are counted. The very low growth rate of P. silesiacus, as deduced from tissue type, makes taxonomical affinities to Nothosaurus spp. or basal pistosauroids (i.e., humeri of aff. Cymatosaurus sp.) very unlikely. Proneusticosaurus silesiacus femoral histology does also not match any of the here studied femora of Eosauropterygia indet. Proneusticosaurus silesiacus shares similar low growth rates, the osteosclerotic femur, as well as pachyostotic vertebrae and ribs with the pachypleurosaurs Dactylosaurus gracilis and Neusticosaurus spp. and with the nothosaur Lariosaurus sp. These features are, however, most likely convergent and reflect the degree of secondary aquatic adaptation in shallow marine inhabitants. The high organized and low vascularized tissue, the implied low growth rate, the plesiomorphic femur morphology, and the strongly inclined zygapophyses of the vertebrae (contra roughly horizontal zygapophyses in other Eosauropterygia), makes P. silesiacus unique and evidence that this genus represents a valid genus within early Eosauropterygia. Proneusticosaurus silesiacus might represent one of the most basal members of Eosauropterygia so far known.

proneusticosaurus
eosauropterygia
taxonomic affinity
pachypleurosaur


The skull and taxonomy of Mixosaurus (Ichthyopterygia)

Abstract: Mixosaurus, a Middle Triassic ichthyopterygian, has traditionally been recognized as a typically primitive ichthyopterygian, but this view was recently questioned. Examination of the skull of Mixosaurus revealed many features to confirm this doubt. Its cranial characters, such as the parietal ridge and short supratemporal process of the parietal, are shared with derived ichthyopterygians from the Jurassic. Mixosaurus also has features that are derived within the Ichthyopterygia and unique to the genus, such as a long sagittal crest reaching the nasal, and an expanded anterior terrace of the upper temporal fenestra that also reaches the nasal. Phalarodon, Contectopalatus, and Sangiorgiosaurus are all considered as junior synonyms of Mixosaurus. The supratemporal, squamosal, and quadratojugal are all present in Mixosaurus atavus, as in basal ichthyopterygians. Because all basal ichthyopterygians, and even some derived ichthyopterygians from the Jurassic, have these three elements, the absence of the squamosal in Ichthyosaurus and Platypterygius should be considered derived if it is not preservational.


Comparing cal3 and other a posteriori time-scaling approaches in a case study with the pterocephaliid trilobites

Abstract: Abstract. Reconstructing the tree of life involvesmore than identifying relationships among lineages; it also entails accurately estimating when lineages diverged. Paleontologists typically scale cladograms to time a posteriori by direct reference to first appearances of taxa in the stratigraphic record. Some approaches use probabilistic models of branching, extinction, and sampling processes to date samples of trees, such as the recently developed cal3 method, which stochastically draws divergence dates given a set of rates for those processes. However, these models require estimates of the rates of those processes, which may be hard to obtain, particularly for sampling. Here, we contrast the use of cal3 and other a posteriori time-scaling approaches by examining a previous study that documented a decelerating rate of morphological evolution in pterocephaliid trilobites. Although aspects of the data set make estimation of branching, extinction, and sampling rates difficult, we use a multifaceted approach to calculate and evaluate the rate estimates needed for applying cal3. In agreement with previous simulation studies, we find that the choice of phylogenetic dating method impacts downstream macroevolutionary conclusions. We also find contradictory evolutionary inferences between analyses on ancestor—descendant contrasts (based on ancestor trait reconstruction methods) and maximum-likelihood parameter estimates. Ancestral taxon inference in cal3 corroborates previously hypothesized ancestor—descendant sequences, but cal3 suggests greater support for budding cladogenesis than anagenesis. This case study demonstrates the potential and wide applicability of the cal3 method and the benefits afforded by choosing cal3 over simpler a posteriori time-scaling approaches.

cal3
posteriori time-scaling approach
case study