Testing the effect of the rock record on diversity: a multidisciplinary approach to elucidating the generic richness of sauropodomorph dinosaurs through time

Abstract: The accurate reconstruction of palaeobiodiversity patterns is central to a detailed understanding of the macroevolutionary history of a group of organisms. However, there is increasing evidence that diversity patterns observed directly from the fossil record are strongly influenced by fluctuations in the quality of our sampling of the rock record; thus, any patterns we see may reflect sampling biases, rather than genuine biological signals. Previous dinosaur diversity studies have suggested that fluctuations in sauropodomorph palaeobiodiversity reflect genuine biological signals, in comparison to theropods and ornithischians whose diversity seems to be largely controlled by the rock record. Most previous diversity analyses that have attempted to take into account the effects of sampling biases have used only a single method or proxy: here we use a number of techniques in order to elucidate diversity. A global database of all known sauropodomorph body fossil occurrences (2024) was constructed. A taxic diversity curve for all valid sauropodomorph genera was extracted from this database and compared statistically with several sampling proxies (rock outcrop area and dinosaur‐bearing formations and collections), each of which captures a different aspect of fossil record sampling. Phylogenetic diversity estimates, residuals and sample‐based rarefaction (including the first attempt to capture ‘cryptic’ diversity in dinosaurs) were implemented to investigate further the effects of sampling. After ‘removal’ of biases, sauropodomorph diversity appears to be genuinely high in the Norian, Pliensbachian–Toarcian, Bathonian–Callovian and Kimmeridgian–Tithonian (with a small peak in the Aptian), whereas low diversity levels are recorded for the Oxfordian and Berriasian–Barremian, with the Jurassic/Cretaceous boundary seemingly representing a real diversity trough. Observed diversity in the remaining Triassic–Jurassic stages appears to be largely driven by sampling effort. Late Cretaceous diversity is difficult to elucidate and it is possible that this interval remains relatively under‐sampled. Despite its distortion by sampling biases, much of sauropodomorph palaeobiodiversity can be interpreted as a reflection of genuine biological signals, and fluctuations in sea level may account for some of these diversity patterns.

rock record
richness
sampling
ornithischian
neosauropod


Ediacaran distributions in space and time: testing assemblage concepts of earliest macroscopic body fossils

Abstract: Abstract. The mid-late Ediacaran Period (∼579–541 Ma) is characterized by globally distributed marine soft-bodied organisms of unclear phylogenetic affinities colloquially called the “Ediacara biota.” Despite an absence of systematic agreement, previous workers have tested for underlying factors that may control the occurrence of Ediacaran macrofossils in space and time. Three taxonomically distinct “assemblages,” termed the Avalon, White Sea, and Nama, were identified and informally incorporated into Ediacaran biostratigraphy. After ∼15 years of new fossil discoveries and taxonomic revision, we retest the validity of these assemblages using a comprehensive database of Ediacaran macrofossil occurrences. Using multivariate analysis, we also test the degree to which taphonomy, time, and paleoenvironment explain the taxonomic composition of these assemblages. We find that: (1) the three assemblages remain distinct taxonomic groupings; (2) there is little support for a large-scale litho-taphonomic bias present in the Ediacaran; and (3) there is significant chronostratigraphic overlap between the taxonomically and geographically distinct Avalonian and White Sea assemblages ca. 560–557 Ma. Furthermore, both assemblages show narrow bathymetric ranges, reinforcing that they were paleoenvironmental—ecological biotopes and spatially restricted in marine settings. Meanwhile, the Nama assemblage appears to be a unique faunal stage, defined by a global loss of diversity, coincident with a noted expansion of bathymetrically unrestricted, long-ranging Ediacara taxa. These data reinforce that Ediacaran biodiversity and stratigraphic ranges of its representative taxa must first statistically account for varying likelihood of preservation at a local scale to ultimately aggregate the Ediacaran macrofossil record into a global biostratigraphic context.


Required Levels of Catalysis for Emergence of Autocatalytic Sets in Models of Chemical Reaction Systems

Abstract: The formation of a self-sustaining autocatalytic chemical network is a necessary but not sufficient condition for the origin of life. The question of whether such a network could form “by chance” within a sufficiently complex suite of molecules and reactions is one that we have investigated for a simple chemical reaction model based on polymer ligation and cleavage. In this paper, we extend this work in several further directions. In particular, we investigate in more detail the levels of catalysis required for a self-sustaining autocatalytic network to form. We study the size of chemical networks within which we might expect to find such an autocatalytic subset, and we extend the theoretical and computational analyses to models in which catalysis requires template matching.

catalysis
autocatalytic chemical network
sufficient condition


Fossil biogeography: a new model to infer dispersal, extinction and sampling from palaeontological data

Abstract: Methods in historical biogeography have revolutionized our ability to infer the evolution of ancestral geographical ranges from phylogenies of extant taxa, the rates of dispersals, and biotic connectivity among areas. However, extant taxa are likely to provide limited and potentially biased information about past biogeographic processes, due to extinction, asymmetrical dispersals and variable connectivity among areas. Fossil data hold considerable information about past distribution of lineages, but suffer from largely incomplete sampling. Here we present a new dispersal–extinction–sampling (DES) model, which estimates biogeographic parameters using fossil occurrences instead of phylogenetic trees. The model estimates dispersal and extinction rates while explicitly accounting for the incompleteness of the fossil record. Rates can vary between areas and through time, thus providing the opportunity to assess complex scenarios of biogeographic evolution. We implement the DES model in a Bayesian framework and demonstrate through simulations that it can accurately infer all the relevant parameters. We demonstrate the use of our model by analysing the Cenozoic fossil record of land plants and inferring dispersal and extinction rates across Eurasia and North America. Our results show that biogeographic range evolution is not a time-homogeneous process, as assumed in most phylogenetic analyses, but varies through time and between areas. In our empirical assessment, this is shown by the striking predominance of plant dispersals from Eurasia into North America during the Eocene climatic cooling, followed by a shift in the opposite direction, and finally, a balance in biotic interchange since the middle Miocene. We conclude by discussing the potential of fossil-based analyses to test biogeographic hypotheses and improve phylogenetic methods in historical biogeography.

dispersal
des
fossil occurrence
phylogenetic tree
extinction rate


Eggshell geochemistry reveals ancestral metabolic thermoregulation in Dinosauria

Abstract: All major groups of Mesozoic dinosaurs exhibited metabolically mediated thermoregulation based on clumped isotopes in eggshells. Studying the origin of avian thermoregulation is complicated by a lack of reliable methods for measuring body temperatures in extinct dinosaurs. Evidence from bone histology and stable isotopes often relies on uncertain assumptions about the relationship between growth rate and body temperature, or the isotopic composition (δ18O) of body water. Clumped isotope (Δ47) paleothermometry, based on binding of 13C to 18O, provides a more robust tool, but has yet to be applied across a broad phylogenetic range of dinosaurs while accounting for paleoenvironmental conditions. Applying this method to well-preserved fossil eggshells demonstrates that the three major clades of dinosaurs, Ornithischia, Sauropodomorpha, and Theropoda, were characterized by warm body temperatures. Dwarf titanosaurs may have exhibited similar body temperatures to larger sauropods, although this conclusion is provisional, given current uncertainties in taxonomic assignment of dwarf titanosaur eggshell. Our results nevertheless reveal that metabolically controlled thermoregulation was the ancestral condition for Dinosauria.


The usefulness of caries frequency, depth, and location in determining cariogenicity and past subsistence: a test on early and later agriculturalists from the Peruvian coast.

Abstract: Dental markers have been used to unravel particularities of paleodiet, subsistence, social structure, and health. This article aims to compare oral pathology among four pre-Columbian groups with different degrees of agricultural and socio-cultural development but comparable ecological conditions who lived on the coastal desert of Peru. Three of these groups are assigned to distinct phases of the Formative Period (2500-1 BC), a time critical for our understanding of the development of agriculture and social complexity. The fourth group corresponds to the Late Intermediate Period (1000-1470 AD), when agriculture had its apogee and society was highly stratified. In this study we test whether there is an increase (1) in the frequency of carious lesions and (2) in caries depth, and (3) if there is a shift from occlusal to extra-occlusal caries locations with the development of agriculture. Therefore, we analyze the frequencies of carious lesions and antemortem tooth loss (AMTL), the caries distributions by age, sex, and type of tooth, as well as the tissues affected by, and the location of the carious lesions. Since there are no significant differences in the frequencies of carious lesions and AMTL between the groups, we reject hypothesis 1. In contrast, caries depth does increase, and caries location changes from occlusal to extra-occlusal sites with agricultural development. However, we can only corroborate hypothesis 2 and 3 when taking into consideration dental wear. Thus, we recommend that caries depth and locations should be used with evaluations of dental wear to reconstruct subsistence in ancient populations.

location
subsistence
carious lesion
tissue


An analysis of dinosaurian biogeography: evidence for the existence of vicariance and dispersal patterns caused by geological events

Abstract: As the supercontinent Pangaea fragmented during the Mesozoic era, dinosaur faunas were divided into isolated populations living on separate continents. It has been predicted, therefore, that dinosaur distributions should display a branching (‘vicariance’) pattern that corresponds with the sequence and timing of continental break‐up. Several recent studies, however, minimize the importance of plate tectonics and instead suggest that dispersal and regional extinction were the main controls on dinosaur biogeography. Here, in order to test the vicariance hypothesis, we apply a cladistic biogeographical method to a large dataset on dinosaur relationships and distributions. We also introduce a methodological refinement termed ‘time‐slicing’, which is shown to be a key step in the detection of ancient biogeographical patterns. These analyses reveal biogeographical patterns that closely correlate with palaeogeography. The results provide the first statistically robust evidence that, from Middle Jurassic to mid‐Cretaceous times, tectonic events had a major role in determining where and when particular dinosaur groups flourished. The fact that evolutionary trees for extinct organisms preserve such distribution patterns opens up a new and fruitful direction for palaeobiogeographical research.


Evolutionary biomechanics: hard tissues and soft evidence?

Abstract: Biomechanical modelling is a powerful tool for quantifying the evolution of functional performance in extinct animals to understand key anatomical innovations and selective pressures driving major evolutionary radiations. However, the fossil record is composed predominantly of hard parts, forcing palaeontologists to reconstruct soft tissue properties in such models. Rarely are these reconstruction approaches validated on extant animals, despite soft tissue properties being highly determinant of functional performance. The extent to which soft tissue reconstructions and biomechanical models accurately predict quantitative or even qualitative patterns in macroevolutionary studies is therefore unknown. Here, we modelled the masticatory system in extant rodents to objectively test the ability of current muscle reconstruction methods to correctly identify quantitative and qualitative differences between macroevolutionary morphotypes. Baseline models generated using measured soft tissue properties yielded differences in muscle proportions, bite force, and bone stress expected between extant sciuromorph, myomorph, and hystricomorph rodents. However, predictions from models generated using reconstruction methods typically used in fossil studies varied widely from high levels of quantitative accuracy to a failure to correctly capture even relative differences between macroevolutionary morphotypes. Our novel experiment emphasizes that correctly reconstructing even qualitative differences between taxa in a macroevolutionary radiation is challenging using current methods. Future studies of fossil taxa should incorporate systematic assessments of reconstruction error into their hypothesis testing and, moreover, seek to expand primary datasets on muscle properties in extant taxa to better inform soft tissue reconstructions in macroevolutionary studies.

modelling
tissue reconstruction
muscle
macroevolutionary morphotype


Deep drilling reveals massive shifts in evolutionary dynamics after formation of ancient ecosystem

Abstract: A volatile assemblage of short-lived endemic species developed into a stable community of long-lived species in Lake Ohrid. The scarcity of high-resolution empirical data directly tracking diversity over time limits our understanding of speciation and extinction dynamics and the drivers of rate changes. Here, we analyze a continuous species-level fossil record of endemic diatoms from ancient Lake Ohrid, along with environmental and climate indicator time series since lake formation 1.36 million years (Ma) ago. We show that speciation and extinction rates nearly simultaneously decreased in the environmentally dynamic phase after ecosystem formation and stabilized after deep-water conditions established in Lake Ohrid. As the lake deepens, we also see a switch in the macroevolutionary trade-off, resulting in a transition from a volatile assemblage of short-lived endemic species to a stable community of long-lived species. Our results emphasize the importance of the interplay between environmental/climate change, ecosystem stability, and environmental limits to diversity for diversification processes. The study also provides a new understanding of evolutionary dynamics in long-lived ecosystems.

evolutionary dynamic
ecosystem
limit
speciation


Taxonomic status of the caturid genera (Halecomorphi, Caturidae) and their Late Jurassic species

Abstract: Caturids are among the best-known predatory ray-finned fishes of the Mesozoic. Although there is consensus about their sister-group relationship to Amiidae (Holostei, Amiiformes), their diversity, ingroup phylogenetic relationships and evolutionary history are still very poorly understood. Caturidae is currently restricted to Caturus and Amblysemius, each with two species. Among them, C. furcatus has become the wastebasket taxon for the group. Our revision of nearly 40 species based on the original descriptions, type and referred material led to significant results changing the picture of caturid diversity in the Late Jurassic. Four specific names are unavailable. Due to insufficient information in the original descriptions, lack of diagnostic features in the type material, or the complete lack of type material, 13 nominal species are nomina dubia. Two species currently considered junior synonyms represent distinct taxa. Strobilodus giganteus is removed from Caturidae. Caturus cliftoni, Thlattodus and Ditaxiiodus are tentatively referred to Strobilodus. The fossil record of Caturoidea is restricted to the Jurassic and earliest Cretaceous. The group apparently underwent significant diversification during the Late Jurassic, as indicated by the increase in the number of taxa and the dispersal of the group outside Europe, which had already begun in the Middle Jurassic.

halecomorphi caturidae amiiformes caturoidea diversification


Anatomy and relationships of Haptodus garnettensis, a Pennsylvanian synapsid from Kansas

Abstract: ABSTRACT New, well-preserved specimens of the Upper Pennsylvanian synapsid Haptodus garnettensis from Garnett, Kansas, represent more mature individuals than those available previously and indicate that H. garnettensis is diagnosed by several autapomorphies: septomaxilla with small facial exposure; prefrontal pocket shallow; pineal ridge present; supratemporal notched; anterior end of angular overlapped dorsally and ventrally by splenial; robust, chisel-shaped teeth; teeth present on palatal ramus of premaxilla. A phylogenetic analysis of early synapsids indicates that H. garnettensis is not a sphenacodontid.


Microstructural diversity of the stylophyllid (Scleractinia) skeleton

Abstract: Coralla of the three species of solitary corals described herein from the Sinemurian (Lower Jurassic) of Sicily, i.e., Haimeicyclus haimei (Chapuis and Dewalque, 1853), Stylophyllopsis sp. cf. S. rugosa (Duncan and Wright, 1867), and Stylophyllopsis sp. A., conform to the overall stylophyllid morphology. Their septa consist of spines that are increasingly covered with sclerenchyme and low in the calice form compact blades. The pattern of diagenetic alteration of septa is diverse but consistent within particular taxa. It suggests that the spectrum of the original microstructures is wider than traditionally suggested for stylophyllids. In H. haimei, the septa are covered with dense granulations and completely recrystallized. Granulations also cover septal faces of Stylophyllopsis cf. rugosa and have rod-like foundations. In Stylophyllopsis sp. A., vestiges of the narrow mid-septal zone (similar to that in minitrabecular corals) occur in the proximal part of larger septa, whereas septal spines which are similar to those in Stylophyllopsis cf. rugosa occur in their distal parts. Similar diversity of microstructures is reported also in Triassic stylophyllids that have aragonitic coralla. The presence of distinct septal spines along with wide-ranging microstructural diversity of traditional Triassic-Jurassic stylophyllids, casts light on their possible evolutionary relationships, and can be a useful criterion for further revision of the group. For example, Jurassic thecocyathids, considered ancestral to caryophylliinans, share similar spiny/lobate septa with stylophyllids. Also Recent deep-water anthemiphylliids with spiny/lobate septa are strikingly similar to stylophyllids. Although this may be another example of parallel evolution, the separation of anthemiphylliids from other scleractinian clades on a mitochondrial 16S RNA tree topology suggests their ancient roots and enable us to suggest a stylophyllid ancestry. The supposed cyclic pattern of protoseptal insertion in Early Jurassic H. haimei supports the hypothesis of scleractinian-like (and not rugosan) ancestory of the stylophyllid evolutionary lineage.

stylophyllid
scleractinia
coral
deep-water
microstructural diversity


A New Anisian (Middle Triassic) Eosauropterygian (Reptilia, Sauropterygia) from Panzhou, Guizhou Province, China

Abstract: ABSTRACT Eosauropterygians rapidly diversified in the Anisian (Middle Triassic), a period by which the invertebrates had already completely recovered from the end-Permian mass extinction. The Pelsonian (Anisian) deposits of the small Panxian and Luoping intraplatform basins in southwestern China alone yielded seven or more eosauropterygian taxa. A new Middle Triassic sauropterygian, Panzhousaurus rotundirostris, gen. et sp. nov., is here described based on an almost complete skeleton from the middle Anisian (Middle Triassic) of Panzhou (Guizhou Province, southwestern China). The upper temporal fenestra smaller than the orbit, the broad and flat parietal table, the cervical ribs with two proximal articular heads, the pachyostotic proximal ends of the dorsal ribs, and the unexpanded sacral ribs indicate that the specimen is a pachypleurosaur-like eosauropterygian. The new species also shows some differences from all other eosauropterygians, such as a rounded and shortened snout, 24 cervical and 20 dorsal vertebrae, a straight ulna with a concave posterior margin, and four distal carpals. Phylogenetic analysis also reveals that Panzhousaurus is an eosauropterygian, closely related to pachypleurosaur-like forms. The discovery of Panzhousaurus enriches our knowledge of the diversity of the Panxian fauna and provides new information to test phylogenetic relationships among known eosauropterygians.

middle triassic
eosauropterygian
southwestern china


A new species of Plesiodimylus (Dimylidae, Eulipotyphla, Mammalia) from the Early Miocene of Spain

Abstract: Abstract We report a new dimylid species, Plesiodimylus ilercavonicus sp. nov., from the Early Miocene locality of Mas d’Antolino B-5 (Ribesalbes-Alcora, Castelló, Spain). This new species of Plesiodimylus is an amblyodont form of the genus and exhibits some primitive characters. The phylogenetic and palaeoenvironmental implications of this southern occurrence of Plesiodimylus in Lower Miocene sediments are discussed. http://zoobank.org/lsid:zoobank.org:pub:E78DB979-6552-4BE2-BEC9-FA2EA05B7B39


Phylogeny of the Ichthyopterygia Incorporating Recent Discoveries from South China

Abstract:
ABSTRACT
 During the last decade, abundant ichthyopterygian material has been found from the Triassic of South China as well as the Upper Jurassic and Lower Cretaceous of Europe and South America, significantly expanding our knowledge of ichthyopterygian diversity through the Mesozoic. Previous phylogenetic hypotheses of the group no longer account for these extensive additions, necessitating a new phylogenetic framework for the entire Ichthyopterygia to enable evolutionary studies of the group. We present here a comprehensive phylogenetic hypothesis for Ichthyopterygia based on cladistic analysis of 163 characters coded for 59 ingroup and five outgroup taxa. The monophyly of Ichthyopterygia is strongly supported by a Bremer index value of 7. Five major groups of Ichthyopterygia during the Triassic, viz., Grippioidea, Cymbospondylidae, Mixosauridae, Shastasauridae, and Toretocnemidae, are well supported by Bremer index values between 3 and 5. Major clades that evolved in the Triassic, including Merriamosauria, Euichthyosauria, and Parvipelvia, are also robustly supported, whereas most post-Triassic clades are very weakly supported with a Bremer index value of 1, with a few exceptions, such as Thunnosauria and Ophthalmosauridae. The traditional Shastasauridae is expanded to comprise six genera but excludes Callawayia, which is more closely related to Parvipelvia than to Shastasauridae. ‘C.’ wolonggangensis is a shastasaurid but does not form a monophyletic clade with Callawayia neoscapularis or Guizhouichthyosaurus tangae as previously asserted. The new phylogenetic hypothesis is generally consistent with the stratigraphic occurrences of each taxon especially for the Triassic taxa.

ichthyopterygia
south china
phylogenetic framework
thunnosauria
early triassic


Temporal and phylogenetic evolution of the sauropod dinosaur body plan

Abstract: The colossal size and body plan of sauropod dinosaurs are unparalleled in terrestrial vertebrates. However, to date, there have been only limited attempts to examine temporal and phylogenetic patterns in the sauropod bauplan. Here, we combine three-dimensional computational models with phylogenetic reconstructions to quantify the evolution of whole-body shape and body segment properties across the sauropod radiation. Limitations associated with the absence of soft tissue preservation in fossils result in large error bars about mean absolute body shape predictions. However, applying any consistent skeleton : body volume ratio to all taxa does yield changes in body shape that appear concurrent with major macroevolutionary events in sauropod history. A caudad shift in centre-of-mass (CoM) in Middle Triassic Saurischia, associated with the evolution of bipedalism in various dinosaur lineages, was reversed in Late Triassic sauropodomorphs. A craniad CoM shift coincided with the evolution of quadrupedalism in the Late Triassic, followed by a more striking craniad shift in Late Jurassic–Cretaceous titanosauriforms, which included the largest sauropods. These craniad CoM shifts are strongly correlated with neck enlargement, a key innovation in sauropod evolution and pivotal to their gigantism. By creating a much larger feeding envelope, neck elongation is thought to have increased feeding efficiency and opened up trophic niches that were inaccessible to other herbivores. However, we find that relative neck size and CoM position are not strongly correlated with inferred feeding habits. Instead the craniad CoM positions of titanosauriforms appear closely linked with locomotion and environmental distributions, potentially contributing to the continued success of this group until the end-Cretaceous, with all other sauropods having gone extinct by the early Late Cretaceous.

sauropod
com
striking craniad shift
jurassic–cretaceous titanosauriform
body mass


A new species of Clevosaurus (Lepidosauria: Rhynchocephalia) from the Upper Triassic of Rio Grande do sul, Brazil

Abstract: Abstract:  Well‐preserved cranial remains of a small sphenodontian lepidosaur from the Upper Triassic Caturrita Formation of Rio Grande do Sul, Brazil, are the first record of the genus Clevosaurus Swinton, 1939 from South America. They represent a new species, Clevosaurus brasiliensis, which is distinguished by a very short antorbital region of the skull (corresponding to about 20 per cent of skull length) and the presence of teeth in addition to two longitudinal rows on the pterygoid. C. brasiliensis most closely resembles C. bairdi from the Lower Jurassic of Nova Scotia (Canada) and C. mcgilli from the Lower Jurassic of Yunnan (China). The discovery of Clevosaurus in the Upper Triassic of southern Brazil provides a significant range extension of this widely distributed sphenodontian genus. Along with other recent finds, it also suggests that there may have been less biotic provincialism among terrestrial vertebrates during the Late Triassic than has previously been assumed.


On the origin of modern humans: Asian perspectives

Abstract: The peopling of Asia In recent years, there has been increasing focus on the paleoanthropology of Asia, particularly the migration patterns of early modern humans as they spread out of Africa. Bae et al. review the current state of the Late Pleistocene Asian human evolutionary record from archaeology, hominin paleontology, geochronology, genetics, and paleoclimatology. They evaluate single versus multiple dispersal models and southern versus the northern dispersal routes across the Asian continent. They also review behavioral and environmental variability and how these may have affected modern human dispersals and interactions with indigenous populations. Science, this issue p. eaai9067 BACKGROUND The earliest fossils of Homo sapiens are located in Africa and dated to the late Middle Pleistocene. At some point later, modern humans dispersed into Asia and reached the far-away locales of Europe, Australia, and eventually the Americas. Given that Neandertals, Denisovans, mid-Pleistocene Homo, and H. floresiensis were present in Asia before the appearance of modern humans, the timing and nature of the spread of modern humans across Eurasia continue to be subjects of intense debate. For instance, did modern humans replace the indigenous populations when moving into new regions? Alternatively, did population contact and interbreeding occur regularly? In terms of behavior, did technological innovations and symbolism facilitate dispersals of modern humans? For example, it is often assumed that only modern humans were capable of using watercraft and navigating to distant locations such as Australia and the Japanese archipelago—destinations that would not have been visible to the naked eye from the departure points, even during glacial stages when sea levels would have been much lower. Moreover, what role did major climatic fluctuations and environmental events (e.g., the Toba volcanic super-eruption) play in the dispersal of modern humans across Asia? Did extirpations of groups occur regularly, and did extinctions of populations take place? Questions such as these are paramount in understanding hominin evolution and Late Pleistocene Asian paleoanthropology. ADVANCES An increasing number of multidisciplinary field and laboratory projects focused on archaeological sites and fossil localities from different areas of Asia are producing important findings, allowing researchers to address key evolutionary questions that have long perplexed the field. For instance, technological advances have increased our ability to successfully collect ancient DNA from hominin fossils, providing proof that interbreeding occurred on a somewhat regular basis. New finds of H. sapiens fossils, with increasingly secure dating associations, are emerging in different areas of Asia, some seemingly from the first half of the Late Pleistocene. Cultural variability discerned from archaeological studies indicates that modern human behaviors did not simply spread across Asia in a time-transgressive pattern. This regional variation, which is particularly distinct in Southeast Asia, could be related at least in part to environmental and ecological variation (e.g., Palearctic versus Oriental biogeographic zones). OUTLOOK Recent findings from archaeology, hominin paleontology, geochronology, and genetics indicate that the strict “out of Africa” model, which posits that there was only a single dispersal into Eurasia at ~60,000 years ago, is in need of revision. In particular, a multiple-dispersal model, perhaps beginning at the advent of the Late Pleistocene, needs to be examined more closely. An increasingly robust record from Late Pleistocene Asian paleoanthropology is helping to build and establish new views about the origin and dispersal of modern humans. Map of sites with ages and postulated early and later pathways associated with modern humans dispersing across Asia during the Late Pleistocene. Regions of assumed genetic admixture are also shown. ka, thousand years ago. The traditional “out of Africa” model, which posits a dispersal of modern Homo sapiens across Eurasia as a single wave at ~60,000 years ago and the subsequent replacement of all indigenous populations, is in need of revision. Recent discoveries from archaeology, hominin paleontology, geochronology, genetics, and paleoenvironmental studies have contributed to a better understanding of the Late Pleistocene record in Asia. Important findings highlighted here include growing evidence for multiple dispersals predating 60,000 years ago in regions such as southern and eastern Asia. Modern humans moving into Asia met Neandertals, Denisovans, mid-Pleistocene Homo, and possibly H. floresiensis, with some degree of interbreeding occurring. These early human dispersals, which left at least some genetic traces in modern populations, indicate that later replacements were not wholesale.

modern human
africa
late pleistocene
subject


The evolution of the modern avian digestive system: insights from paravian fossils from the Yanliao and Jehol biotas

Abstract: The avian digestive system, like other aspects of avian biology, is highly modified relative to other reptiles. Together these modifications have imparted the great success of Neornithes, the most diverse clade of amniotes alive today. It is important to understand when and how aspects of the modern avian digestive system evolved among neornithine ancestors in order to elucidate the evolutionary success of this important clade and to understand the biology of stem birds and their closest dinosaurian relatives: Mesozoic Paraves. Although direct preservation of the soft tissue of the digestive system has not yet been reported, ingested remains and their anatomical location preserved in articulated fossils hint at the structure of the digestive system and its abilities. Almost all data concerning direct evidence of diet in Paraves comes from either the Upper Jurassic Yanliao Biota or the Lower Cretaceous Jehol Biota, both of which are known from deposits in north‐eastern China. Here, the sum of the data gleaned from the thousands of exceptionally well‐preserved fossils of paravians is interpreted with regards to the structure and evolution of the highly modified avian digestive system and feeding apparatus. This information suggests intrinsic differences between closely related stem lineages implying either strong homoplasy or that diet in each lineage of non‐ornithuromorph birds was highly specialized. Regardless, modern digestive capabilities appear to be limited to the Ornithuromorpha, although the complete set of derived feeding related characters is restricted to the Neornithes.

avian digestive system
biology
stem bird


Insect herbivory, plant defense, and early Cenozoic climate change

Abstract: Insect damage on fossil leaves from the Central Rocky Mountains, United States, documents the response of herbivores to changing regional climates and vegetation during the late Paleocene (humid, warm temperate to subtropical, predominantly deciduous), early Eocene (humid subtropical, mixed deciduous and evergreen), and middle Eocene (seasonally dry, subtropical, mixed deciduous and thick-leaved evergreen). During all three time periods, greater herbivory occurred on taxa considered to have short rather than long leaf life spans, consistent with studies in living forests that demonstrate the insect resistance of long-lived, thick leaves. Variance in herbivory frequency and diversity was highest during the middle Eocene, indicating the increased representation of two distinct herbivory syndromes: one for taxa with deciduous, palatable foliage, and the other for hosts with evergreen, thick-textured, small leaves characterized by elevated insect resistance. Leaf galling, which is negatively correlated with moisture today, apparently increased during the middle Eocene, whereas leaf mining decreased.


Paleobiology of the Latest Tithonian (Late Jurassic) Ammonite Salinites grossicostatum Inferred from Internal and External Shell Parameters

Abstract: Based on material from the uppermost Tithonian La Caja Formation at Puerto Piñones, northeastern Mexico, the complete ontogenetic development (protoconch to adult) of the ammonite Salinites grossicostatum is outlined by a detailed morphometrical shell analysis. The embryonic stage, consisting of a small ellipsoid protoconch and ammonitella, ends at about 0.6 mm. Four major morphological changes are differentiated throughout ontogeny based on internal features such as reduced septal spacing and siphuncle position. Sexual dimorphism is reflected by shell size, siphuncular diameter, differences in the morphology of the apophysis, and by two distinct general trends in septal spacing. In addition, macroconchs are characterized by septal crowding at different stages, followed by the return to normal septum distances. Our analysis indicates a change in the mode of life after the neanic stage. A change in habitat preference is inferred for adult individuals. While microconchs persisted at Puerto Piñones, large mature macroconchs temporarily migrated to other areas, possibly for egg deposition. Salinites grossicostatum is endemic to the ancient Gulf of Mexico and is there restricted to outer continental shelf environments.

ammonite salinites grossicostatum
ammonoid
two-dimensional measurement


The birth of a dinosaur footprint: Subsurface 3D motion reconstruction and discrete element simulation reveal track ontogeny

Abstract: Significance We reconstructed the 3D foot movements of guineafowl traversing a granular substrate from biplanar X-rays, and then incorporated those kinematics into a discrete element simulation. Digital track models permitted visualization of in vivo track formation at the surface and at virtual bedding planes for the first time. Application of these volumetric data to fossil dinosaur tracks uncovered the developmental origin of previously enigmatic features. A “track ontogeny” perspective helps integrate limb and substrate dynamics into the interpretation of track morphology, from which foot anatomy cannot be read directly. Locomotion over deformable substrates is a common occurrence in nature. Footprints represent sedimentary distortions that provide anatomical, functional, and behavioral insights into trackmaker biology. The interpretation of such evidence can be challenging, however, particularly for fossil tracks recovered at bedding planes below the originally exposed surface. Even in living animals, the complex dynamics that give rise to footprint morphology are obscured by both foot and sediment opacity, which conceals animal–substrate and substrate–substrate interactions. We used X-ray reconstruction of moving morphology (XROMM) to image and animate the hind limb skeleton of a chicken-like bird traversing a dry, granular material. Foot movement differed significantly from walking on solid ground; the longest toe penetrated to a depth of ∼5 cm, reaching an angle of 30° below horizontal before slipping backward on withdrawal. The 3D kinematic data were integrated into a validated substrate simulation using the discrete element method (DEM) to create a quantitative model of limb-induced substrate deformation. Simulation revealed that despite sediment collapse yielding poor quality tracks at the air–substrate interface, subsurface displacements maintain a high level of organization owing to grain–grain support. Splitting the substrate volume along “virtual bedding planes” exposed prints that more closely resembled the foot and could easily be mistaken for shallow tracks. DEM data elucidate how highly localized deformations associated with foot entry and exit generate specific features in the final tracks, a temporal sequence that we term “track ontogeny.” This combination of methodologies fosters a synthesis between the surface/layer-based perspective prevalent in paleontology and the particle/volume-based perspective essential for a mechanistic understanding of sediment redistribution during track formation.

discrete element simulation
track ontogeny
foot
substrate
depth


Devonian events: examples from the eastern Palaeotethys (Si Phai section, NE Vietnam)

Abstract:
Recent study of Middle to Upper Devonian deposits in the Dong Van area, northeast Vietnam, has revealed new, more detailed information of both the stratigraphic record of the Si Phai section and global Devonian bioevents. Four possible equivalents of well-known Devonian events of different magnitude were found in Vietnam, an area which is underrepresented in that respect: the (?) Kačák Event, the (?)pumilio Events, the late Middle Givetian Taghanic Event and the Frasnian/Famennian Kellwasser Event. The stratigraphic framework of the Si Phai section allows us to recognise and assess the timing of global Devonian bioevents in Vietnam even though the section is not continuous. An overview of the sedimentological development of the Si Phai section is discussed briefly where carbonates in the section are composed of argillaceous limestones suggesting relatively deep, off-shore conditions. Due to the facies setting, the macrofauna is generally rare and the conodont record is likewise limited in some parts. Nevertheless, it is possible to pinpoint some global event intervals for the first time in Vietnam.
Keywords Devonian events . Palaeotethys . Vietnam .
This article is a contribution to the special issue BClimate change and biodiversity patterns in the mid-Palaeozoic*

dong van area
devonian event
southeast asia
chinese border
more data


Evolution of retiolitid graptolites-a synopsis

Abstract: Twenty million years of retiolitid evolution reflect environmental changes, the most severe being the Silurian Cyrtograptus lundgreni Event. Five biostratigraphically and morphologically constrained retiolitid faunas are distinguished and characterized according to their rhabdosomal modifications: (1) the oldest and long-ranging Llandovery group of mostly large and morphologically complex rhabdosomes, (2) the less diverse Telychian-Sheinwoodian group, (3) the Cyrtograptus lundgreni Biozone varied group of intermediate size, and two short-ranged (4) late Homerian, and (5) early Ludlow groups with small rhabdosomes. Although the evolutionary history of retiolitids was complex and not linear, a common tendency toward reduction of rhabdosome size in most lineages is observed. The greatest reduction in both number and volume of thecae, and in skeletal elements is demonstrated in the Gothograptus and Plectograptus faunas. Contrary to the thecal decrease, a distinctive increase of sicula size is observed in retiolitids. Two types of colonies are distinguished: L-colonies with a small sicula and numerous large thecae of similar size, and S-colonies with a long sicula and a few, small thecae. These changes imply modification of the soft body: an increase in siculozooid length and a decrease in the size of the zooids. Thus, the siculozooid probably produced great amounts of morphogen inhibiting zooid growth. In consequence the phenomenon of colony reduction occurred. The most extreme stages of rhabdosome reduction in Ludlow retiolitids can be seen in Plectodinemagraptus gracilis of the Plectograptus lineage and in the new species Holoretiolites helenaewitoldi, possibly representing the last stage of skeletal reduction in the Gothograptus lineage; the next hypothetical stage would be its total loss. The sicula length of Holoretiolites, about 2 mm, is reported herein for the first time.

silurian
holoretiolites
tubarium construction


New perspectives on pterosaur palaeobiology

Abstract: Abstract Pterosaurs were the first vertebrates to evolve powered flight and occupied the skies of the Mesozoic for 160 million years. They occurred on every continent, evolved their incredible proportions and anatomy into well over 100 species, and included the largest flying animals of all time among their ranks. Pterosaurs are undergoing a long-running scientific renaissance that has seen elevated interest from a new generation of palaeontologists, contributions from scientists working all over the world and major advances in our understanding of their palaeobiology. They have especially benefited from the application of new investigative techniques applied to historical specimens and the discovery of new material, including detailed insights into their fragile skeletons and their soft tissue anatomy. Many aspects of pterosaur science remain controversial, mainly due to the investigative challenges presented by their fragmentary, fragile fossils and notoriously patchy fossil record. With perseverance, these controversies are being resolved and our understanding of flying reptiles is increasing. This volume brings together a diverse set of papers on numerous aspects of the biology of these fascinating reptiles, including discussions of pterosaur ecology, flight, ontogeny, bony and soft tissue anatomy, distribution and evolution, as well as revisions of their taxonomy and relationships.

pterosaur
palaeobiology
first vertebrate
world


Early dinosaurs: A phylogenetic study

Abstract: Synopsis Early dinosaur evolution has been the subject of several phylogenetic studies and the position of certain basal forms is currently debated. This is the case for the oldest known members of the group, excavated from the Late Triassic Ischigualastian beds of South America, such as Herrerasaurus, Eoraptor, Pisanosaurus, Saturnalia and Staurikosaurus. A new cladistic analysis of the early dinosaur radiation was performed to assess the relationships among the three major clades (Ornithischia, Sauropodomorpha and Theropoda) and to define the phylogenetic position of the basal members of the group. The most parsimonious hypothesis has Silesaurus opolensis as the sister taxon to a dichotomy including monophyletic Saurischia and Ornithischia. The latter includes Pisanosaurus mertii, and the former all other well‐known Triassic dinosaurs. Saurischia is composed of two major monophyletic groups: Herrerasauridae (including Herrerasaurus ischigualastensis and Staurikosaurus pricei) and Eusaurischia (including the theropod and sauropodomorph lineages), while Eoraptor lunensis appears to represent the sister taxon to Eusaurischia. Saturnalia tupiniquim is a stem‐taxon to Sauropodomorpha and Guaibasaurus candelariensis might belong to the theropod branch. Some of these hypotheses are, however, not strongly supported. Especially uncertain are the affinities of Silesaurus and Guaibasaurus. The latter can only be safely regarded as a saurischian, while the former might belong to the ornithischian lineage. The dinosaurian affinities of Eoraptor and Herrerasauridae are strongly supported. Yet, the possibility that they (especially Eoraptor) represent basal theropods, rather than basal saurischians, cannot be dismissed. In fact, basal saurischian evolution is still too poorly understood for a definitive hypothesis of relationships to be presented.

phylogenetic study
late triassic
silesaurus
archosaur


The trilobite Redlichia from the lower Cambrian Emu Bay Shale Konservat-Lagerstätte of South Australia: systematics, ontogeny and soft-part anatomy

Abstract: The trilobite Redlichia Cossmann, 1902 is an abundant element of the lower Cambrian (Series 2, Stage 4) Emu Bay Shale (EBS) Konservat-Lagerstätte on Kangaroo Island, South Australia. Well-preserved, fully articulated specimens from this deposit are known to reach lengths of up to 25 cm, representing one of the largest known Cambrian trilobites. Until now, all Redlichia specimens from the EBS have been referred to Redlichia takooensis Lu, 1950, a species originally described from South China. Previous work recognized considerable differences in exoskeletal morphology among specimens of varying sizes, which was attributed to ontogeny. However, close examination of a large collection of recently acquired specimens shows that this variation actually represents two distinct morphs, interpreted here as separate species: R. takooensis, and a large, new species, Redlichia rex sp. nov. An analysis of morphological variation in holaspides (‘adults’) of the more common R. takooensis reveals considerable ontogenetic change occurred even during this later phase of growth. Some specimens of both Redlichia species from the EBS also exhibit exceptionally preserved soft-part anatomy, particularly the antennae and biramous appendages. Here, appendages (antenniform and biramous) and digestive structures are described, and biramous appendage reconstructions of R. rex sp. nov. are presented, which show a striking resemblance to some early Cambrian trilobites from South China. In particular, R. rex has a tripartite exopodite, as well as a dorsoventrally deep protopodite with gnathobasic spines used to shred or crush food items. Based on recent phylogenetic analyses, it is possible that an exopodite with tripartite subdivisions represents the plesiomorphic condition for Artiopoda (trilobites and kin). The digestive system of R. takooensis exhibits a series of paired digestive glands in the cephalon and anterior thorax, similar to those described for a number of other Cambrian and Ordovician trilobites. http://zoobank.org/urn:lsid:zoobank.org:pub:507BEAFC-4AFA-43F4-A5C4-49E4B58C658E

emu bay shale
south australia
ontogeny
soft-part anatomy
morphology


The brachiopod Eoobolus from the Early Cambrian Mural Formation (Canadian Rocky Mountains)

Abstract: The Early Cambrian brachiopod, Eoobolus, is one of the first representatives of the superfamily, Linguloidea, the defining characteristics of which include the classical morphology of oval shells and a pedicle that emerges from between the two valves. The material described here from the Mural Formation (Jasper National Park, Canadian Rocky Mountains) provides well-preserved muscle scars and larval shells that allow a discussion of the muscle system and the larval morphology of Eoobolus. The dorsal larval shell exhibits a morphology similar to other Cambrian linguloids, but also to paterinids, Mickwitzia muralensis, and some rhynchonelliforms. This suggests that there was a lesser degree of disparity among brachiopod larvae in the Cambrian than there is today. The muscle system of Eoobolus is similar to other linguloids, but differs from that of Recent lingulids and discinids by having one or two more pairs of oblique muscles. New data on the distribution of features characteristic of the family Eoobolidae question the validity of this family.

brachiopod
eoobolus
mural formation
canadian rocky mountains
larvae


Greenhouse- and orbital-forced climate extremes during the early Eocene

Abstract: The Palaeocene–Eocene Thermal Maximum (PETM) was a significant global warming event in Earth's deep past (56 Mya). The warming across the PETM boundary was driven by a rapid rise in greenhouse gases. The event also coincided with a time of maximum insolation in Northern Hemisphere summer. There is increased evidence that the mean warming was accompanied by enhanced seasonality and/or extremes in precipitation (and flooding) and drought. A high horizontal resolution (50 km) global climate model is used to explore changes in the seasonal cycle of surface temperature, precipitation, evaporation minus precipitation and river run-off for regions where proxy data are available. Comparison for the regions indicates the model accurately simulates the observed changes in these climatic characteristics with North American interior warming and drying, and warming and increased river run-off at other regions. The addition of maximum insolation in Northern Hemisphere summer leads to a drier North America, but wetter conditions at most other locations. Long-range transport of atmospheric moisture plays a critical role in explaining regional changes in the water cycle. Such high-frequency variations in precipitation might also help explain discrepancies or misinterpretation of some climate proxies from the same locations, especially where sampling is coarse, i.e. at or greater than the frequency of precession. This article is part of a discussion meeting issue ‘Hyperthermals: rapid and extreme global warming in our geological past’.


Five hundred million years of extinction and recovery: a phanerozoic survey of large‐scale diversity patterns in fishes

Abstract: Abstract:  Fishes include more than half of all living animals with backbones, but large‐scale palaeobiological patterns in this assemblage have not received the same attention as those for terrestrial vertebrates. Previous surveys of the fish record have generally been anecdotal, or limited either in their stratigraphic or in their taxonomic scope. Here, we provide a broad overview of the Phanerozoic history of fish diversity, placing a special emphasis on intervals of turnover, evolutionary radiation, and extinction. In particular, we provide in‐depth reviews of changes during, and ecological and evolutionary recovery after, the end‐Devonian (Hangenberg) and Cretaceous–Palaeogene (K–Pg) extinctions.

recovery
fish diversity
diversification
devonian


The stratigraphy of mass extinction

Abstract: Patterns of last occurrences of fossil species are often used to infer the tempo and timing of mass extinction, even though last occurrences generally precede the time of extinction. Numerical simulations with constant extinction demonstrate that last occurrences are not randomly distributed, but tend to cluster at subaerial unconformities, surfaces of forced regression, flooding surfaces and intervals of stratigraphical condensation, all of which occur in predictable stratigraphical positions. This clustering arises not only from hiatuses and non‐deposition, but also from changes in water depth. Simulations with intervals of elevated extinction cause such clusters of last occurrences to be enhanced within and below the interval of extinction, suggesting that the timing and magnitude of extinctions in these instances could be misinterpreted. With the possible exception of the end‐Cretaceous, mass extinctions in the fossil record are characterized by clusters of last occurrences at these sequence stratigraphical horizons. Although these clusters of last occurrences may represent brief pulses of elevated extinction, they are equally likely to form by stratigraphical processes during a protracted period (more than several hundred thousand years) of elevated extinction rate. Geochemical proxies of extinction causes are also affected similarly, suggesting that many local expressions of mass extinction should be re‐evaluated for the timing of extinction and its relation to environmental change. We propose three tests for distinguishing pulses of extinction from clusters of last occurrences produced by stratigraphical processes.

mass extinction
simulation
cluster
regression
stratigraphic architecture


The overlooked aquatic green algal component of early terrestrial environments: Triskelia scotlandica gen. et sp. nov. from the Rhynie cherts

Abstract: As a large majority of modern green algae are freshwater rather than marine, it can be hypothesized that algae were an important component of early terrestrial environments. However, this component remains overlooked as algal affinities are difficult to decipher, due to the lack of distinctive characters observable in standard light microscopy. Herein, we use a new approach to studying microfossils from the Devonian (407 Ma) Rhynie cherts, renowned as one of the earliest exceptionally preserved terrestrial ecosystem. Using data from confocal laser scanning microscopy, the microfossils were reconstructed in 3D allowing us to gather information on morphological and physiological traits. We document Triskelia scotlandica gen. et sp. nov., which is the resting stage of a new species of microalgae. Numerous individuals were discovered preserved inside the remains of a flooded plant aerial axis. They are shown to be spheroidal to ellipsoidal walled cells, with a pseudo‐reticulate surface ornamentation and occasional large openings probably resulting from the germination process. We draw comparison with fossil and modern microorganisms demonstrating morphological convergences in wall ornament and physiological traits, especially with zygospores of modern Chlorophyta. Our description of Triskelia leads us to critically evaluate the Rhynie chert fossils Cymatiosphaera and Pterospermella. We conclude that it is unlikely that the Rhynie cherts contained prasinophycean algae of these types. We suggest that our microfossils are Chlorophyta (green algae) incertae sedis that were highly adapted to the special ecological conditions encountered in a geothermal wetland.

early terrestrial environment
green algae
chlorophyta


The Late Palaeozoic relations between Gondwana and Laurussia

Abstract: Abstract Reconstructions based on biogeography, palaeomagnetism and facies distributions indicate that, in later Palaeozoic time, there were no wide oceans separating the major continents. During the Silurian and Early Devonian time, many oceans became narrower so that only the less mobile animals and plants remained district. There were several continental collisions: the Tornquist Sea (between Baltica and Avalonia) closed in Late Ordovician time, the Iapetus Ocean (between Laurentia and the newly merged continents of Baltica and Avalonia) closed in Silurian time, and the Rheic Ocean (between Avalonia and Gondwana and the separate parts of the Armorican Terrane Assemblage) closed (at least partially) towards the end of Early Devonian time. Each of these closures was reflected by migrations of non-marine plants and animals as well as by contemporary deformation. New maps, based on palaeomagnetic and faunal data, indicate that Gondwana was close to Laurussia during the Devonian and Carboniferous periods, with fragments of Bohemia and other parts of the Armorican Terrane Assemblage interspersed between. It follows that, after Early Devonian time, the Variscan oceans of central Europe can never have been very wide. The tectonic evolution of Europe during Devonian and Carboniferous time was thus more comparable with the present-day Mediterranean Sea than with the Pacific Ocean.


Fruits, seeds, and flowers from the Warman clay pit (middle Eocene Claiborne Group), western Tennessee, USA

Abstract: In this report, we examine fossil plant reproductive materials from the Warman clay pit in western Tennessee. The investigation of about 600 specimens has resulted in the recognition of 60 species and morphotypes. Based upon comparisons of gross morphology of these specimens with available extant plant materials and the literature, we have been able to assess their affinities with 16 extant families. We are able to relate 36 species and morphotypes to the following families: Altingiaceae, Annonaceae, Araceae, Araliaceae, Bignoniaceae, Euphorbiaceae, Fabaceae, Fagaceae, Hamamelidaceae, Juglandaceae, Lauraceae, Magnoliaceae, Malpighiaceae, Moraceae, Oleaceae, and Theaceae. In addition, 24 morphotypes are not assigned to any family due to the limited number of diagnostic characters. This report represents a comprehensive review on the reproductive materials from a single locality of the Claiborne Group of the southeastern United States. Compared to traditional investigations focused primarily on leaves, this study provides a different perspective for understanding plant diversity for the middle Eocene Claiborne Group. Hongshan Wang. Florida Museum of Natural History, University of Florida, Gainesville, Florida 32611, USA hwang@flmnh.ufl.edu Jane Blanchard. Florida Museum of Natural History, University of Florida, Gainesville, Florida 32611, USA Ojjhblanchard@aol.com David L. Dilcher. Departments of Biology and Geology, Indiana University, Bloomington, Indiana 47405, USA dilcher@indiana.edu

warman clay pit
western tennessee
usa
reproductive material
morphotype


Dating the late prehistoric dispersal of Polynesians to New Zealand using the commensal Pacific rat

Abstract: The pristine island ecosystems of East Polynesia were among the last places on Earth settled by prehistoric people, and their colonization triggered a devastating transformation. Overhunting contributed to widespread faunal extinctions and the decline of marine megafauna, fires destroyed lowland forests, and the introduction of the omnivorous Pacific rat (Rattus exulans) led to a new wave of predation on the biota. East Polynesian islands preserve exceptionally detailed records of the initial prehistoric impacts on highly vulnerable ecosystems, but nearly all such studies are clouded by persistent controversies over the timing of initial human colonization, which has resulted in proposed settlement chronologies varying from ≈200 B.C. to 1000 A.D. or younger. Such differences underpin radically divergent interpretations of human dispersal from West Polynesia and of ecological and social transformation in East Polynesia and ultimately obfuscate the timing and patterns of this process. Using New Zealand as an example, we provide a reliable approach for accurately dating initial human colonization on Pacific islands by radiocarbon dating the arrival of the Pacific rat. Radiocarbon dates on distinctive rat-gnawed seeds and rat bones show that the Pacific rat was introduced to both main islands of New Zealand ≈1280 A.D., a millennium later than previously assumed. This matches with the earliest-dated archaeological sites, human-induced faunal extinctions, and deforestation, implying there was no long period of invisibility in either the archaeological or palaeoecological records.

dispersal
new zealand
east polynesia
people


Time and taphonomy: quantitative estimates of time-averaging and stratigraphic disorder in a shallow marine habitat

Abstract: We examined the radiocarbon age, taphonomic condition and stratigraphic position of shells of the venerid bivalve Chione spp. from the tidal flats of Bahia la Choya, Sonora, Mexico. Shells in Bahia la Choya are time-averaged. Thirty shells yielded radiocarbon dates from modern (A.D. 1950 or younger) to 3569 years before present. The median calendar age of inner flat shells is 483 years; the median age of tidal channel shells is 427 years. We interpret such long shell survival to be the result of frequent shallow burial. Such burial retards bioerosion of shells. The taphonomic condition of shells varied with environment. Shells from the surface of the inner flats were better preserved than shells from the tidal channel. Shells are more likely to be physically worn and biologically degraded in the waters of the channel than on the quieter and more frequently exposed inner tidal flat. Taphonomic condition is an unreliable indicator of a shell's time-since-death. Poorly-preserved shells on the inner flats tended to be old, but in general shell condition was much more variable than shell age. A shell's condition is more likely the result of its total residence time on the surface than its time-since-death (surface time plus burial time). Two composite short (44 cm and 50 cm) cores revealed varying degrees of stratigraphic disorder (the departure from perfect correlation between relative stratigraphic position and relative age). One of eight shells in the inner flats core was disordered; four of nine shells in the tidal channel were disordered. The actual age range of surface shells approximates the age range of shells in cores. Stratigraphic disorder is a consequence of both time-averaging and physical and biogenic mixing. Time-averaging controls the degree of precision possible in paleoecological studies. Environmental changes and ecological phenomena occurring within a span of 3500 years would not be recognized in deposits like those of Bahia la Choya. Time-averaging and stratigraphic disorder also constrain the temporal resolution possible in microstratigraphic studies of evolution. The extent of time-averaging and stratigraphic disorder will dictate an appropriate sample interval. In order to prevent temporal overlap between successive samples in deposits like Bahia la Choya, sample spacing should not be less than approximately 0.5 m.

time-averaging
stratigraphic disorder
mixing
fossil assemblage


Smithian-Spathian boundary event: Evidence for global climatic change in the wake of the end-Permian biotic crisis

Abstract: One of the most important carbon cycle perturbations following the end-Permian mass extinction event straddles the Smithian-Spathian boundary (SSB) (Olenekian, Early Triassic). This anomaly is characterized by a prominent positive carbon isotope excursion known from Tethyan marine rocks. Its global signifi cance is established here by a new high paleolatitude record (Spitsbergen). Paleontological evidence, such as Boreal palynological data (Barents Sea, Norway) and global patterns of ammonoid distribution, indicates a synchronous major change in terrestrial and marine ecosystems near the SSB. The reestablishment of highly diverse plant ecosystems, including the rise of woody gymnosperms and decline of the formerly dominating lycopods, is interpreted as an effect of a major climate change. This hypothesis is supported by modeling of ammonoid paleobiogeography, the distribution patterns of which are interpreted as a proxy for sea surface temperatures (SST). The latest Smithian thus appears to have been a time of a warm and equable climate as expressed by an almost fl at pole to equator SST gradient. In contrast, the steep Spathian SST gradient suggests latitudinally differentiated climatic conditions. We propose that this drastic climate change and the global carbon cycle perturbation were triggered by a massive end-Smithian CO2 injection. The SSB event could therefore represent one of the causes for stepwise and delayed recovery of marine and terrestrial biotas in the wake of the end-Permian biotic crisis.

end-permian biotic crisis
early triassic
smithian-spathian boundary


Functional anatomy of the cervical region in the late Miocene amphicyonid Magericyon anceps (Carnivora, Amphicyonidae): implications for its feeding behaviour

Abstract: We describe the skull and neck morphology of the late Miocene amphicyonid Magericyon anceps, focusing on aspects related to functional anatomy. This species, recorded only from the Vallesian sites of Batallones‐1 and Batallones‐3 (Madrid, Spain), is the last known amphicyonid in the fossil record of Western Europe, with the Batallones populations being one of the best‐known of the family. The morphology of its skull and cervical vertebrae allows us to infer aspects of its associated musculature, such as muscle strength and range of movement. Magericyon anceps had well‐developed neck muscles, suited for providing the head with a high capacity for lateral and rotatory movements, as well as for playing an important role in the extension and stabilization of the head and neck, improving its efficiency in killing and consuming prey. Magericyon anceps shared its habitat with other large carnivorans, which would have strongly influenced its behaviour. Rapid killing and processing of prey would have been an advantage for avoiding kleptoparasitism by other large predators, as well as reducing consumption time, during which M. anceps would have been more vulnerable to attack from competitors.


Reassessment of the Evidence for Postcranial Skeletal Pneumaticity in Triassic Archosaurs, and the Early Evolution of the Avian Respiratory System

Abstract: Uniquely among extant vertebrates, birds possess complex respiratory systems characterised by the combination of small, rigid lungs, extensive pulmonary air sacs that possess diverticula that invade (pneumatise) the postcranial skeleton, unidirectional ventilation of the lungs, and efficient crosscurrent gas exchange. Crocodilians, the only other living archosaurs, also possess unidirectional lung ventilation, but lack true air sacs and postcranial skeletal pneumaticity (PSP). PSP can be used to infer the presence of avian-like pulmonary air sacs in several extinct archosaur clades (non-avian theropod dinosaurs, sauropod dinosaurs and pterosaurs). However, the evolution of respiratory systems in other archosaurs, especially in the lineage leading to crocodilians, is poorly documented. Here, we use µCT-scanning to investigate the vertebral anatomy of Triassic archosaur taxa, from both the avian and crocodilian lineages as well as non-archosaurian diapsid outgroups. Our results confirm previous suggestions that unambiguous evidence of PSP (presence of internal pneumatic cavities linked to the exterior by foramina) is found only in bird-line (ornithodiran) archosaurs. We propose that pulmonary air sacs were present in the common ancestor of Ornithodira and may have been subsequently lost or reduced in some members of the clade (notably in ornithischian dinosaurs). The development of these avian-like respiratory features might have been linked to inferred increases in activity levels among ornithodirans. By contrast, no crocodile-line archosaur (pseudosuchian) exhibits evidence for unambiguous PSP, but many of these taxa possess the complex array of vertebral laminae and fossae that always accompany the presence of air sacs in ornithodirans. These laminae and fossae are likely homologous with those in ornithodirans, which suggests the need for further investigation of the hypothesis that a reduced, or non-invasive, system of pulmonary air sacs may be have been present in these taxa (and secondarily lost in extant crocodilians) and was potentially primitive for Archosauria as a whole.

postcranial skeletal pneumaticity
pterosaur
outgroup
foramina
ornithodira


The systematic position of Anourosoricini (Soricidae, Mammalia): paleontological and molecular evidence

Abstract: ABSTRACT Two late middle Miocene to early late Miocene (12–11 Ma) soricid populations from Spain and Germany are re-described and assigned to Crusafontina and Darocasorex, gen. et sp. nov., primitive genera within the Anourosoricini. The relatively advanced morphology of these oldest Anourosoricini genera known suggest a much earlier date for the origin of the tribe. Molecular phylogenetics support an early origin (∼15 Ma), but ages up to ∼18 Ma are possible after re-evaluating the calibration points that use early–middle Miocene occurrences of Soricinae and their potential ancestors. Both molecular phylogenetics and paleontology consistently point to Anourosoricini being the sister clade of the combined Nectogalini and Notiosoricini. Synapomorphies in morphology relate to the condylar structure, the morphology of the lower premolar (p4) and reduction of the upper antemolars. The phylogenetic roots of the Anourosoricini within the Soricinae will remain elusive until more early–middle Miocene rests are found. The paucity of fossils is probably related to the lack of terrestrial sedimentary rocks at northern latitudes, where primitive Anourosoricini and their soricine ancestors might have been residing during the early–middle Miocene thermal optimum.


Bayesian models of episodic evolution support a late precambrian explosive diversification of the Metazoa.

Abstract: Multicellular animals, or Metazoa, appear in the fossil records between 575 and 509 million years ago (MYA). At odds with paleontological evidence, molecular estimates of basal metazoan divergences have been consistently older than 700 MYA. However, those date estimates were based on the molecular clock hypothesis, which is almost always violated. To relax this hypothesis, we have implemented a Bayesian approach to describe the change of evolutionary rate over time. Analysis of 22 genes from the nuclear and the mitochondrial genomes under the molecular clock assumption produced old date estimates, similar to those from previous studies. However, by allowing rates to vary in time and by taking small species-sampling fractions into account, we obtained much younger estimates, broadly consistent with the fossil records. In particular, the date of protostome-deuterostome divergence was on average 582 +/- 112 MYA. These results were found to be robust to specification of the model of rate change. The clock assumption thus had a dramatic effect on date estimation. However, our results appeared sensitive to the prior model of cladogenesis, although the oldest estimates (791 +/- 246 MYA) were obtained under a suboptimal model. Bayes posterior estimates of evolutionary rates indicated at least one major burst of molecular evolution at the end of the Precambrian when protostomes and deuterostomes diverged. We stress the importance of assumptions about rates on date estimation and suggest that the large discrepancies between the molecular and fossil dates of metazoan divergences might partly be due to biases in molecular date estimation.


Recovery of benthic marine communities from the end‐Permian mass extinction at the low latitudes of eastern Panthalassa

Abstract: Based on the quantitative community analysis using species‐level identifications, we track the restoration of benthic ecosystems after the end‐Permian mass extinction throughout the Lower Triassic of the western USA. New data on the palaeoecology of the Thaynes Group and Sinbad Formation are provided, which fill a gap between the recently studied palaeoecology of the Griesbachian–Dienerian Dinwoody Formation and the Spathian Virgin Formation. In the Sinbad Formation and Thaynes Group, 17 species (12 genera) of bivalves, 7 species and genera of gastropods and 2 species and genera of brachiopods are recognized. The new bivalve genus Confusionella (Pteriidae) is described. A comprehensive review of the whole Lower Triassic succession of benthic ecosystems of the western USA indicates that mid‐ and inner shelf environments show incipient recovery signals around the Griesbachian–Dienerian transition, during the Smithian and, most profound, during the early Spathian. Ecological data from youngest strata of the Dinwoody Formation as well as stratigraphic ranges of species suggest that the late Dienerian was likely a time interval of environmental stress for benthic ecosystems. Despite some evidence for short‐term environmental disturbances (e.g. shift of dominant taxa, transient drop in alpha‐diversity) during the Smithian–Spathian transition, benthic ecosystems did not show any notable taxonomic turnover at that time, in contrast to the major crisis that affected ammonoids and conodonts. Whereas alpha‐diversity of benthic communities generally increased throughout the Early Triassic, beta‐diversity remained low, which reflects a persistently wide environmental range of benthic species. This observation is in accordance with a recently proposed model that predicts a time lag between increasing within‐habitat diversity (alpha‐diversity) and the onset of taxonomic differentiation between habitats (beta‐diversity) during biotic recoveries from mass extinction events. The observation that beta‐diversity had not significantly increased during the Early Triassic might also provide an explanation for the comparably sluggish increase in benthic diversity during that time, which has previously been attributed to persistent environmental stress.

end‐permian mass extinction
smithian
benthic specie


Tiny individuals attached to a new Silurian arthropod suggest a unique mode of brood care

Abstract: Significance The paper reports a remarkable arthropod from the Silurian Herefordshire Lagerstätte of England. The fossil reveals a unique association in an early Paleozoic arthropod involving tethering of 10 tiny individuals each by a single thread to the tergites so that their appearance is reminiscent of kites. The evidence suggests that these are juveniles and that the specimen records a unique brooding strategy. This is part of a diversity of complex brooding behaviors in early arthropods heralding the variety that occurs today. The possibility that the small individuals represent a different arthropod, possibly parasitic, which colonized the larger individual, seems less likely. The ∼430-My-old Herefordshire, United Kingdom, Lagerstätte has yielded a diversity of remarkably preserved invertebrates, many of which provide fundamental insights into the evolutionary history and ecology of particular taxa. Here we report a new arthropod with 10 tiny arthropods tethered to its tergites by long individual threads. The head of the host, which is covered by a shield that projects anteriorly, bears a long stout uniramous antenna and a chelate limb followed by two biramous appendages. The trunk comprises 11 segments, all bearing limbs and covered by tergites with long slender lateral spines. A short telson bears long parallel cerci. Our phylogenetic analysis resolves the new arthropod as a stem-group mandibulate. The evidence suggests that the tethered individuals are juveniles and the association represents a complex brooding behavior. Alternative possibilities—that the tethered individuals represent a different epizoic or parasitic arthropod—appear less likely.

arthropod
brood care
juvenile
mandibulate
tiny individual


Diversity dynamics and evolutionary patterns of Devonian Bryozoa

Abstract: Bryozoan diversity during the Devonian period displays a persistent rise from the Pragian to the early Givetian, significantly dropping in the late Givetian in the wake of the Taghanic Event. In contrast, two other important events during the Devonian, the Frasne/Famenne Event and the Hangenberg Event at the Devonian/Carboniferous boundary, were less significant and resulted mainly in shifts in faunal composition. Diversity dynamics of Devonian Bryozoa was apparently controlled by extrinsic and intrinsic factors. Global palaeogeographic settings influenced faunal provincialism to which bryozoans seem to be sensitive. Sealevel fluctuations and subsequent changes in suitability of habitats influenced biodiversification processes in bryozoans. Intrinsically, bryozoans show some patterns consistent with diffuse co-evolution with potential predators and, possibly, prey. Observed trends in the morphological evolution of Devonian bryozoans include some obvious anti-predator adaptations (protective structures, strengthened skeletal walls). Moreover, Devonian bryozoans often developed various internal modifications, which apparently influenced the activity of polypides. This pattern is regarded here as apparent improvement of feeding, possibly as a response to diminishing food in the course of the mid-Palaeozoic Phytoplankton Blackout.

devonian bryozoa
diversity dynamic
shallow-water habitat
palaeoenvironmental setting
echinoderm


New Ctenodactyloid Rodents from the Erlian Basin, Nei Mongol, China, and the Phylogenetic Relationships of Eocene Asian Ctenodactyloids

Abstract: ABSTRACT During the last decade, numerous ctenodactyloid rodent fossils have been systematically collected from at least six horizons of the strata that are distributed from the upper part of the Nomogen Formation to the lower part of the Irdin Manha Formation in the Huheboerhe-Nuhetingboerhe area of the Erlian Basin, Nei Mongol (Inner Mongolia). The ages of these fossiliferous horizons range from the Earliest Eocene to the Middle Eocene. These fossils represent the best-known ctenodactyloid assemblages with a high species diversity and reliable stratigraphic and chronological constraints from one locality in central Asia. The fossils show a relatively continuous record of ctenodactyloids and the earliest radiation of rodents in central Asia beginning from the earliest Eocene. These data are important for biostratigraphic correlation of the Paleogene in central Asia and for understanding the taxonomy of Asian ctenodactyloids and the earliest diversity and evolution of rodents. Among the new fossils, we recognized 10 species that belong to six genera and three morphotypes. Of these taxa, three new genera and species, Chenomys orientalis, gen. et sp. nov., Simplicimys bellus, gen. et sp. nov., and Yongshengomys extensus, gen. et sp. nov., are described. In addition, three new species of Tamquammys, T. robustus, sp. nov., T. longus, sp. nov., and T. fractus, sp. nov., and one new species of Yuomys, Y. huheboerhensis, sp. nov., are also named. With these new materials, we are able to briefly review some existing problems in the taxonomy of early ctenodactyloids, which has remained a difficult task in the study of this Asian rodent group. In light of the new material and taxonomic review, we conducted phylogenetic analyses of ctenodactyloids using a data matrix that contains 38 taxa and 81 characters. Our analysis shows that Chenomys, Tamquammys, and Simplicimys are placed at the base of the clade that contains the extant Ctenodactylus. Yongshengomys is the only taxon that is deeply placed within the clade containing the extant Ctenodactylus and clustered with Chuankueimys and Tsinlingomys. Our analysis supports Gobiomyidae and Ctenodactylidae as monophyletic groups, respectively, but shows that other families and subfamilies traditionally recognized, such as Cocomyinae, Advenimurinae, Tamquammyidae, Yuomyidae, and Chapattimyidae, are probably paraphyletic.

erlian basin
asian ctenodactyloid
paleogene


Neoselachians (Chondrichthyes, Elasmobranchii) from the Lower and lower Upper Cretaceous of north-eastern Spain

Abstract: Extensive sampling of several Barremian and Albian–Cenomanian levels across the Aguilon, Oliete and Aliaga subbasins of the Iberian Basin, north-east Spain, yielded abundant material of new or so far poorly known neoselachians. The faunas consist of 16 different species, five of which represent new species and two new genera: Cantioscyllium brachyplicatum sp. nov., Platypterix venustulus gen. et sp. nov., Ptychotrygon pustulata sp. nov., Ptychotrygon striata sp. nov. and Iberotrygon plagiolophus gen. et sp. nov. In addition, teeth of Heterodontus cf. H. carerens, Lamniformes indet., Pteroscyllium sp., Scyliorhinidae indet., Rhinobatos sp., Spathobatis sp., Belemnobatis sp., Ptychotrygon geyeri, Ptychotrygon sp. and Celtipristis herreroi are described. The new family Ptychotrygonidae is defined. The localities comprise palaeoenvironments ranging from lacustrine and shallow lake to open marine settings. Neoselachians are almost completely absent from continental settings in the Barremian, as a result of prevailing freshwater conditions, but became more abundant in marine strata. The Albian–Cenomanian selachian assemblage is the most profuse and diverse of the three assemblages studied. It is dominated by small, benthic and near-coastal taxa, for instance Cantioscyllium and Ptychotrygon, and contains several new species, including an endemic batoid, Iberotrygon plagiolophus gen. et sp. nov. © 2009 The Linnean Society of London, Zoological Journal of the Linnean Society, 2009, 155, 316–347.

selachian assemblage
iberian chondricthyan
extensive fossil record
other cretaceous sediment


Rapid Asia-Europe-North America geographic dispersal of earliest Eocene primate Teilhardina during the Paleocene-Eocene Thermal Maximum.

Abstract: True primates appeared suddenly on all three northern continents during the 100,000-yr-duration Paleocene-Eocene Thermal Maximum at the beginning of the Eocene, approximately 55.5 mya. The simultaneous or nearly simultaneous appearance of euprimates on northern continents has been difficult to understand because the source area, immediate ancestors, and dispersal routes were all unknown. Now, omomyid haplorhine Teilhardina is known on all three continents in association with the carbon isotope excursion marking the Paleocene-Eocene Thermal Maximum. Relative position within the carbon isotope excursion indicates that Asian Teilhardina asiatica is oldest, European Teilhardina belgica is younger, and North American Teilhardina brandti and Teilhardina americana are, successively, youngest. Analysis of morphological characteristics of all four species supports an Asian origin and a westward Asia-to-Europe-to-North America dispersal for Teilhardina. High-resolution isotope stratigraphy indicates that this dispersal happened in an interval of approximately 25,000 yr. Rapid geographic dispersal and morphological character evolution in Teilhardina reported here are consistent with rates observed in other contexts.

geographic dispersal
primate
paleocene-eocene thermal maximum
north america


Molecular fossils within bitumens and kerogens from the ~ 1 Ga Lakhanda Lagerstätte (Siberia, Russia) and their significance for understanding early eukaryote evolution

Abstract: The emergence and diversification of eukaryotes during the Proterozoic is one of the most fundamental evolutionary developments in Earth's history. The ca. 1-billion-year-old Lakhanda Lagerstätte (Siberia, Russia) contains a wealth of eukaryotic body fossils and offers an important glimpse into their ecosystem. Seeking to complement the paleontological record of this remarkable lagerstätte, we here explored information encoded within sedimentary organic matter (total organic carbon = 0.01-1.27 wt.%). Major emphasis was placed on sedimentary hydrocarbons preserved within bitumens and kerogens, including molecular fossils (or organic biomarkers) that are specific to bacteria and eukaryotes (i.e. hopanes and regular steranes, respectively). Programmed pyrolysis and molecular organic geochemistry suggest that the organic matter in the analyzed samples is about peak oil window maturity and thus sufficiently well preserved for detailed molecular fossil studies that include hopanes and steranes. Together with petrographic evidence as well as compositional similarities of the bitumens and corresponding kerogens, the consistency of different independent maturity parameters establishes that sedimentary hydrocarbons are indigenous and syngenetic to the host rock. The possible presence of trace amounts of hopanes and absence of steranes in samples that are sufficiently well preserved to retain both types of compounds evidences an environment dominated by anaerobic bacteria with no or very little inputs by eukaryotes. In concert with the paleontological record of the Lakhanda Lagerstätte, our study adds to the view that eukaryotes were present but not significant in Mesoproterozoic ecosystems.

bitumen
eukaryote
mesoproterozoic ecosystem
molecular fossil


A Late Triassic Dinosauromorph Assemblage from New Mexico and the Rise of Dinosaurs

Abstract: It has generally been thought that the first dinosaurs quickly replaced more archaic Late Triassic faunas, either by outcompeting them or when the more archaic faunas suddenly became extinct. Fossils from the Hayden Quarry, in the Upper Triassic Chinle Formation of New Mexico, and an analysis of other regional Upper Triassic assemblages instead imply that the transition was gradual. Some dinosaur relatives preserved in this Chinle assemblage belong to groups previously known only from the Middle and lowermost Upper Triassic outside North America. Thus, the transition may have extended for 15 to 20 million years and was probably diachronous at different paleolatitudes.

late triassic
new mexico
archosaur
terrestrial ecological niche
ecological dominance


Conservation Paleobiology: Leveraging Knowledge of the Past to Inform Conservation and Restoration

Abstract: Humans now play a major role in altering Earth and its biota. Finding ways to ameliorate human impacts on biodiversity and to sustain and restore the ecosystem services on which we depend is a grand scientific and societal challenge. Conservation paleobiology is an emerging discipline that uses geohistorical data to meet these challenges by developing and testing models of how biota respond to environmental stressors. Here we (a) describe how the discipline has already provided insights about biotic responses to key environmental stressors, (b) outline research aimed at disentangling the effects of multiple stressors, (c) provide examples of deliverables for managers and policy makers, and (d) identify methodological advances in geohistorical analysis that will foster the next major breakthroughs in conservation outcomes. We highlight cases for which exclusive reliance on observations of living biota may lead researchers to erroneous conclusions about the nature and magnitude of biotic change, vulnerabili...

past
biodiversity
biotic response
conservation paleobiology
degradation


Radiation of Extant Cetaceans Driven by Restructuring of the Oceans

Abstract: Abstract The remarkable fossil record of whales and dolphins (Cetacea) has made them an exemplar of macroevolution. Although their overall adaptive transition from terrestrial to fully aquatic organisms is well known, this is not true for the radiation of modern whales. Here, we explore the diversification of extant cetaceans by constructing a robust molecular phylogeny that includes 87 of 89 extant species. The phylogeny and divergence times are derived from nuclear and mitochondrial markers, calibrated with fossils. We find that the toothed whales are monophyletic, suggesting that echolocation evolved only once early in that lineage some 36–34 Ma. The rorqual family (Balaenopteridae) is restored with the exclusion of the gray whale, suggesting that gulp feeding evolved 18–16 Ma. Delphinida, comprising all living dolphins and porpoises other than the Ganges/Indus dolphins, originated about 26 Ma; it contains the taxonomically rich delphinids, which began diversifying less than 11 Ma. We tested 2 hypothesized drivers of the extant cetacean radiation by assessing the tempo of lineage accumulation through time. We find no support for a rapid burst of speciation early in the history of extant whales, contrasting with expectations of an adaptive radiation model. However, we do find support for increased diversification rates during periods of pronounced physical restructuring of the oceans. The results imply that paleogeographic and paleoceanographic changes, such as closure of major seaways, have influenced the dynamics of radiation in extant cetaceans.

restructuring
cetacea
diversification
extant specie


The Good, the Bad, and the Ugly: The Influence of Skull Reconstructions and Intraspecific Variability in Studies of Cranial Morphometrics in Theropods and Basal Saurischians

Abstract: Several studies investigating macroevolutionary skull shape variation in fossil reptiles were published recently, often using skull reconstructions taken from the scientific literature. However, this approach could be potentially problematic, because skull reconstructions might differ notably due to incompleteness and/or deformation of the material. Furthermore, the influence of intraspecific variation has usually not been explored in these studies. Both points could influence the results of morphometric analyses by affecting the relative position of species to each other within the morphospace. The aim of the current study is to investigate the variation in morphometric data between skull reconstructions based on the same specimen, and to compare the results to shape variation occurring in skull reconstructions based on different specimens of the same species (intraspecific variation) and skulls of closely related species (intraspecific variation). Based on the current results, shape variation of different skull reconstructions based on the same specimen seems to have generally little influence on the results of a geometric morphometric analysis, although it cannot be excluded that some erroneous reconstructions of poorly preserved specimens might cause problems occasionally. In contrast, for different specimens of the same species the variation is generally higher than between different reconstructions based on the same specimen. For closely related species, at least with similar ecological preferences in respect to the dietary spectrum, the degree of interspecific variation can overlap with that of intraspecific variation, most probably due to similar biomechanical constraints.

influence
skull reconstruction
deformation


A review of paleontological finite element models and their validity

Abstract: Abstract Finite element analysis (FEA) is a powerful quantitative tool that models mechanical performance in virtual reconstructions of complex structures, such as animal skeletons. The unique potential of FEA to elucidate the function, performance, and ecological roles of extinct taxa is an alluring prospect to paleontologists, and the technique has gained significant attention over recent years. However, as with all modeling approaches, FE models are highly sensitive to the information that is used to construct them. Given the imperfect quality of the fossil record, paleontologists are unlikely to ever know precisely which numbers to feed into their models, and it is therefore imperative that we understand how variation in FEA inputs directly affects FEA results. This is achieved through sensitivity and validation studies, which assess how inputs influence outputs, and compare these outputs to experimental data obtained from extant species. Although these studies are restricted largely to primates at present, they highlight both the power and the limitations of FEA. Reassuringly, FE models seem capable of reliably reproducing patterns of stresses and strains even with limited input data, but the magnitudes of these outputs are often in error. Paleontologists are therefore cautioned not to over-interpret their results. Crucially, validations show that without knowledge of skeletal material properties, which are unknowable from fossilized tissues, absolute performance values such as breaking stresses cannot be accurately determined. The true power of paleontological FEA therefore lies in the ability to manipulate virtual representations of morphology, to make relative comparisons between models, and to quantitatively assess how evolutionary changes of shape result in functional adaptations.

finite element analysis
fea
mechanical performance
complex structure
stress


Olson's Gap or Olson's Extinction? A Bayesian tip-dating approach to resolving stratigraphic uncertainty

Abstract: Adaptive radiations and mass extinctions are of critical importance in structuring terrestrial ecosystems. However, the causes and progress of these transitions often remain controversial, in part because of debates surrounding the completeness of the fossil record and biostratigraphy of the relevant fossil-bearing formations. The early–middle Permian, when a substantial faunal turnover in tetrapods coincided with a restructuring of the trophic structure of ecosystems, is such a time. Some have suggested the transition is obscured by a gap in the tetrapod fossil record (Olson's Gap), while others suggest a correlation between North American and Russian tetrapod-bearing formations allows the interval to be documented in detail. The latter biostratigraphic scheme has been used to support a mass extinction at this time (Olson's Extinction). Bayesian tip-dating methods used frequently in phylogenetics are employed to resolve this debate. Bayes factors are used to compare the results of analyses incorporating tip age priors based on different stratigraphic hypotheses, to show which stratigraphic scheme best fits the morphological data and phylogeny. Olson's Gap is rejected, and the veracity of Olson's Extinction is given further support. Tip-dating approaches have great potential to resolve debates surrounding the stratigraphic ages of critical formations where appropriate morphological data is available.


New occurrence of the Guanshan Lagerstätte (Cambrian Series 2, Stage 4) in the Kunming area, Yunnan, southwest China, with records of new taxa

Abstract: Abstract As a classic Burgess-Shale-Type Konservat-Lagerstätte, the Guanshan biota is well known for its abundant soft-bodied fossils with high taxonomic diversity. Here, we report a new locality of the Guanshan biota in the Kunming area, Yunnan, South China with several new forms being first documented. In particular: a naraoiid euarthropod, the dorsal exoskeleton of which has characters of both naraoiids and Emucaris; and a discoidal animal, identified as a small eldonioid-like metazoan, which has a counterpart from the Emu Bay Shale Lagerstätte of South Australia, and which further strengths the biogeographic connection between the early Cambrian biotas of South China and Australia. Our new discoveries not only expand the palaeogeographic distribution of the Guanshan biota, but also reveal that its biodiversity is much higher than previously thought, and can be justifiably regarded as a community successor to the Chengjiang biota. Jun Zhao [zhaojunpaleo@126.com], Yunnan Key Laboratory for Palaeobiology, Institute of Palaeontology, Yunnan University, Kunming, Yunnan, 650091, China; Yunnan Key Laboratory of International Rivers and Transboundary Eco-Security, Yunnan University, Kunming 650091, China; MEC International Joint Laboratory for Palaeobiology and Palaeoenvironment, Institute of Palaeontology, Yunnan University, Kunming, Yunnan, 650091, China; Yujing Li [yujingli@ynu.edu.cn], Yunnan Key Laboratory for Palaeobiology, Institute of Palaeontology, Yunnan University, Kunming, Yunnan, 650091, China; MEC International Joint Laboratory for Palaeobiology and Palaeoenvironment, Institute of Palaeontology, Yunnan University, Kunming, Yunnan, 650091, China; Paul A. Selden [selden@ku.edu], Department of Geology, University of Kansas, 1457 Jayhawk Boulevard, Lawrence, KS 66045, USA; Natural History Museum, Cromwell Road, London SW7 5BD, UK; Peiyun Cong [cong@ynu.edu.cn], Yunnan Key Laboratory for Palaeobiology, Institute of Palaeontology, Yunnan University, Kunming, Yunnan, 650091, China; MEC International Joint Laboratory for Palaeobiology and Palaeoenvironment, Institute of Palaeontology, Yunnan University, Kunming, Yunnan, 650091, China.


Ontogenetic histology of Apatosaurus (Dinosauria: Sauropoda): New insights on growth rates and longevity

Abstract: ABSTRACT The bone microstructure of an ontogenetic series of Apatosaurus radii, ulnae, and scapulae suggests that Apatosaurus underwent three distinct osteogenic phases. Primary laminar to plexiform fibro-lamellar bone tissue, devoid of lines of arrested growth (LAG), occurs in individuals up to 91% adult size. LAGs and longitudinally vascularized lamellar tissue are deposited for the first time in the external cortices of sub-adult individuals. Slow growth and additional deposition of accretionary lamellar bone occurs in adulthood, and indicates attainment of maximum size in Apatosaurus. All scapulae examined show cyclicity in vascularity indicative of regular variation in speeds of osteogenesis. In contrast, Apatosaurus radii and ulnae show consistent bone depositional rates throughout ontogeny. Despite inter-element variability, all Apatosaurus bones sampled corroborate the hypothesis of sustained rapid growth rates for most of ontogeny, followed by gradual decline with attainment of maximum size. Esti...

apatosaurus
growth rate
ontogenetic series
tissue