Phanerozoic survivors: Actinopterygian evolution through the Permo‐Triassic and Triassic‐Jurassic mass extinction events

Abstract: Actinopterygians (ray‐finned fishes) successfully passed through four of the big five mass extinction events of the Phanerozoic, but the effects of these crises on the group are poorly understood. Many researchers have assumed that the Permo‐Triassic mass extinction (PTME) and end‐Triassic extinction (ETE) had little impact on actinopterygians, despite devastating many other groups. Here, two morphometric techniques, geometric (body shape) and functional (jaw morphology), are used to assess the effects of these two extinction events on the group. The PTME elicits no significant shifts in functional disparity while body shape disparity increases. An expansion of body shape and functional disparity coincides with the neopterygian radiation and evolution of novel feeding adaptations in the Middle‐Late Triassic. Through the ETE, small decreases are seen in shape and functional disparity, but are unlikely to represent major changes brought about by the extinction event. In the Early Jurassic, further expansions into novel areas of ecospace indicative of durophagy occur, potentially linked to losses in the ETE. As no evidence is found for major perturbations in actinopterygian evolution through either extinction event, the group appears to have been immune to two major environmental crises that were disastrous to most other organisms.

actinopterygian evolution
mass extinction event
phanerozoic


The fossil Osmundales (Royal Ferns)—a phylogenetic network analysis, revised taxonomy, and evolutionary classification of anatomically preserved trunks and rhizomes

Abstract: The Osmundales (Royal Fern order) originated in the late Paleozoic and is the most ancient surviving lineage of leptosporangiate ferns. In contrast to its low diversity today (less than 20 species in six genera), it has the richest fossil record of any extant group of ferns. The structurally preserved trunks and rhizomes alone are referable to more than 100 fossil species that are classified in up to 20 genera, four subfamilies, and two families. This diverse fossil record constitutes an exceptional source of information on the evolutionary history of the group from the Permian to the present. However, inconsistent terminology, varying formats of description, and the general lack of a uniform taxonomic concept renders this wealth of information poorly accessible. To this end, we provide a comprehensive review of the diversity of structural features of osmundalean axes under a standardized, descriptive terminology. A novel morphological character matrix with 45 anatomical characters scored for 15 extant species and for 114 fossil operational units (species or specimens) is analysed using networks in order to establish systematic relationships among fossil and extant Osmundales rooted in axis anatomy. The results lead us to propose an evolutionary classification for fossil Osmundales and a revised, standardized taxonomy for all taxa down to the rank of (sub)genus. We introduce several nomenclatural novelties: (1) a new subfamily Itopsidemoideae (Guaireaceae) is established to contain Itopsidema, Donwelliacaulis, and Tiania; (2) the thamnopteroid genera Zalesskya, Iegosigopteris, and Petcheropteris are all considered synonymous with Thamnopteris; (3) 12 species of Millerocaulis and Ashicaulis are assigned to modern genera (tribe Osmundeae); (4) the hitherto enigmatic Aurealcaulis is identified as an extinct subgenus of Plenasium; and (5) the poorly known Osmundites tuhajkulensis is assigned to Millerocaulis. In addition, we consider Millerocaulis stipabonettiorum a possible member of Palaeosmunda and Millerocaulis estipularis as probably constituting the earliest representative of the (Todea-)Leptopteris lineage (subtribe Todeinae) of modern Osmundoideae.

fossil osmundales
evolutionary classification
trunk


Early Paleocene tropical forest from the Ojo Alamo Sandstone, San Juan Basin, New Mexico, USA

Abstract: Abstract. Earliest Paleocene megafloras from North America are hypothesized to be low diversity and dominated by long-lived cosmopolitan species following the Cretaceous/Paleogene (K/Pg) mass extinction. However, megafloras used to develop this hypothesis are from the Northern Great Plains (NGP) of North America, and relatively little is known about floras from southern basins. Here, we present a quantitative analysis of an earliest Paleocene megaflora (<350 kyr after K/Pg boundary) from the Ojo Alamo Sandstone in the San Juan Basin (SJB), New Mexico. The megaflora, comprising 53 morphotypes, was dominated by angiosperms, with accessory taxa composed of pteridophytes, lycophytes, and conifers. Diversity analyses indicate a species-rich, highly uneven, and laterally heterogeneous flora. Paleoclimate estimates using multivariate and univariate methods indicate warm temperatures and relatively high precipitation consistent with a modern tropical seasonal forest. When compared with contemporaneous floras from the Denver Basin (DB) of Colorado and the Williston Basin (WB) of North Dakota, the SJB flora had significantly higher species richness but lower evenness. Paleoclimate estimates from the SJB were 7–14°C warmer than the estimates for the DB and WB, indicating a shift from a temperate forest in the NGP to a tropical forest in the SJB. These results demonstrate the presence of a latitudinal floral diversity and paleoclimatic gradient during the earliest Paleocene in western North America. We hypothesize that the warm, wet conditions in the earliest Paleocene SJB drove rapid rates of speciation following the K/Pg boundary, resulting in a diverse and heterogeneous flora.

tropical forest
ojo alamo sandstone
san juan basin


Variation of atmospheric CO2 by ventilation of the ocean's deepest water

Abstract: A new box model for glacial-interglacial changes in atmospheric CO2 produces lower levels of atmospheric CO 2 without changes in biological production or nutrient chemistry. The model treats the boundary between middepth water and deep water as a chemical divide that separates low-CO 2 water above from high-CO 2 water below. Atmospheric CO 2 is reduced 21 ppm by reduced ventilation of the deep water below the divide. A further reduction of 36 ppm is due to CaCO 3 compensation in response to lower CO3 = below the divide. Colder surface temperatures account for an additional 23 ppm of CO 2 reduction. The new mechanism leaves the glacial atmosphere lighter in õ13C than in preindustrial time, as seen in ice cores and fossil plant material. Bottom water below the divide becomes strongly depleted in õ13C without a change in nutrient concentrations.


Abstract: Darragh, T.A., 2002. A revision of the Australian genus Umbilia (Gastropoda: Cypraeidae). Memoirs of Museum Victoria 59(2): 355–392. Umbilia, an endemic Australian genus of cool-water cowry, comprises 11 species ranging in age from Late Oligocene to Recent, of which four species are known only in the living fauna. Fossil species occur in the Eucla, St Vincent, Murray, Otway, Bass and Gippsland Basins, and living species range from Western Australia to central Queensland. Species of the genus probably have no free-swimming larval stage, so that there is considerable morphological variability which has led to the creation of many synonyms. Two subgenera are recognised here, Umbilia (Umbilia), with ten species, U. prosila sp. nov., U. leptorhyncha, U. petilirostris sp. nov., U. platyrhyncha, U. angustior, U. eximia (= brevis, maccoyi, frankstonensis, montismarthae and sphaerodoma), U. hesitata (= beddomei, cera, howelli and tatei?), U. siphonata (= breviplicata), U. armeniaca and U. capricornica, and U. (Palliocypraea) with one species, U.(P.) gastroplax. A possible ancestor of Umbilia, Palaeocypraea? eripnides, from the Upper Paleocene–Lower Eocene, of the Chatham Is, New Zealand, is newly described. Rhynchocypraea Cossmann, 1898 (type species Cypraea leptorhyncha McCoy) is synonymised with Umbilia.

revision
australian genus umbilia
cypraeidae


Seawater chemistry and biomineralization: did trepostome bryozoans become hypercalcified in the ‘calcite sea’ of the Ordovician?

Abstract: Secular variations in the proportion of Mg and Ca ions in seawater during the Phanerozoic have driven alternations between calcite seas (Mg:Ca<2) and aragonite seas (Mg:Ca>2). There is mounting evidence that these changes in seawater chemistry have impacted the evolution of marine organisms constructing calcareous skeletons, favouring calcite as the CaCO 3 biomineral during times of calcite seas but aragonite during times of aragonite seas. It has been suggested that some organisms became hypercalcified when the mineralogy of their skeletons matched seawater type. This paper tests the proposal that calcitic trepostome bryozoans ('stony bryozoans') became hypercalcified in the calcite sea of the Ordovician. Data on two independent hypercalcification proxies-the diameter of branches, and exozonal wall thickness-have been compiled from the literature for ramose trepostome species from the Ordovician (calcite sea), Devonian (calcite sea) and Permian (aragonite sea). No significant difference was found in branch diameter between the calcite and aragonite sea periods, whereas wall thickness was found to be greater in the Permian than in the Ordovician and Devonian, counter to expectations. Either these two parameters are inadequate as proxies for hypercalcification or, more likely, trepostomes did not become hypercalcified in the calcite sea of the Early Palaeozoic, probably because they exerted a higher degree of control over their biomineralization than some other groups such as corals.


Abstract: Li, Y., Liu, X., Ren, D., Li, X. & Yao, Y., June 2016. First report of Cixiidae insect fossils from the Miocene of the northeastern Tibetan Plateau and their palaeoenvironmental implications. Alcheringa 41, xxx–xxx. ISSN 0311-5518. A new insect species, Cixius discretus (Hemiptera, Fulgoromorpha), from the Lower Miocene Garang Formation of Zeku County, Qinghai Province (northeastern Tibetan Plateau) is described. This species can be assigned to Cixiidae and represents the first fossil representative of this family from Qinghai Province. Based on the recent single-origin hypothesis and the distribution of tectonic plates in the Cretaceous, we consider that ancient Cixius had dispersed globally prior to the Cretaceous. Through analysis of the habitats of extant Cixius, the palaeoclimate and fossil flora of the Zeku area during the Miocene, we interpret the climate of Zeku in the early Miocene to have been warm-temperate and mildly arid. The new species constitutes evidence of wooded and shrubby habitats in Zeku during the Miocene. Yi Li [liy0124@sina.com], XiaoHui Liu [liuxh8917@163.com], Dong Ren [rendong@mail.cnu.edu.cn] and YunZhi Yao [yunzhi@cnu.edu.cn], College of Life Sciences, Capital Normal University, Xisanhuanbeilu 105, Haidian District, Beijing 100048, PR China; XiangChuan Li [lzulixiangchuan@163.com], College of Earth Sciences and Resources & Key Laboratory of Western Mineral Resources and Geological Engineering of the Ministry of Education, Chang’an University, Xi’an 710054, PR China.

cixiidae insect fossil
miocene
palaeoenvironmental implication


Ignoring stratigraphic age uncertainty leads to erroneous estimates of species divergence times under the fossilized birth–death process

Abstract: Fossil information is essential for estimating species divergence times, and can be integrated into Bayesian phylogenetic inference using the fossilized birth–death (FBD) process. An important aspect of palaeontological data is the uncertainty surrounding specimen ages, which can be handled in different ways during inference. The most common approach is to fix fossil ages to a point estimate within the known age interval. Alternatively, age uncertainty can be incorporated by using priors, and fossil ages are then directly sampled as part of the inference. This study presents a comparison of alternative approaches for handling fossil age uncertainty in analysis using the FBD process. Based on simulations, we find that fixing fossil ages to the midpoint or a random point drawn from within the stratigraphic age range leads to biases in divergence time estimates, while sampling fossil ages leads to estimates that are similar to inferences that employ the correct ages of fossils. Second, we show a comparison using an empirical dataset of extant and fossil cetaceans, which confirms that different methods of handling fossil age uncertainty lead to large differences in estimated node ages. Stratigraphic age uncertainty should thus not be ignored in divergence time estimation and instead should be incorporated explicitly.

stratigraphic age uncertainty
specie divergence time
prior


Middle Jurassic Monte Fallano Plattenkalk (Campania, southern Italy): first report on terrestrial plants, decapod crustaceans and fishes

Abstract: A new Jurassic fossiliferous Plattenkalk has been discovered at Monte Fallano (Caserta, Campania, southern Italy). Biostratigraphic analyses indicate a Bajocian/Bathonian age (Middle Jurassic). The fossil assemblage consists of terrestrial plants, invertebrates (bivalves, gastropods, decapod crustaceans, isopods and insect larvae) and vertebrates (fishes). This study takes terrestrial plants, fishes, and decapod crustaceans into account, giving systematic, taphonomic and palaeoenvironmental considerations. The land flora consists of impressions of sterile and fertile shoots of microphyllous conifers; leaves with parallel venation of unknown taxonomy are also present. The genera Cupressinocladus, Brachyphyllum and Araucarites are documented and their microscopical characters are examined. Plant remains possibly represent a stable biotope, as floral composition presents no variation along the section studied. Taphonomic considerations on plant fossils suggest parautochtonous deposition. The study of the rich decapod crustacean fauna includes Acanthochirana liburiaensis n. sp. (Aegeridae Burkenroad, 1963), Casertanus sabellicus n. gen., n. sp. (Sergestidae dana, 1852), Eryma osciensis (Erymidae Van Straelen, 1925) and Tethyseryon campanicus n. gen., n. sp. (Eryonidae de Haan, 1841). Casertanus sabellicus n. gen., n. sp. is the oldest representative of Sergestidae in the fossil record, extending the stratigraphic range of this family into the Middle Jurassic. Tethyseryon campanicus n. gen., n. sp. is the earliest species in which juveniles have been identified within the Eryonidae; the presence of both juveniles and adults in the depositional environment of Monte Fallano suggests that this species was autochthonous or parautochthonous. Preliminary data on fossil fishes sample have lead to the identification of leptolepid, macrosemiid among which Notagogus (Neonotagogus) denticulatus, pleuropholid (Pleuropholis) and pycnodontid fishes; other primitive teleosts and incomplete and indeterminate “ganoid” fishes are also reported. Based on the sedimentological data and the characteristics of decapod crustaceans and fishes, the investigated record of the Monte Fallano section represents the product of depositional process in shallow water carbonate platform settings.

campania
terrestrial plant
decapod crustacean


Formation binning: a new method for increased temporal resolution in regional studies, applied to the Late Cretaceous dinosaur fossil record of North America

Abstract: The advent of palaeontological occurrence databases has allowed for detailed reconstruction and analyses of species richness through deep time. While a substantial literature has evolved ensuring that taxa are fairly counted within and between different time periods, how time itself is divided has received less attention. Stage‐level or equal‐interval age bins have frequently been used for regional and global studies in vertebrate palaeontology. However, when assessing diversity at a regional scale, these resolutions can prove inappropriate with the available data. Herein, we propose a new method of binning geological time for regional studies that intrinsically incorporates the chronostratigraphic heterogeneity of different rock formations to generate unique stratigraphic bins. We use this method to investigate the diversity dynamics of dinosaurs from the Late Cretaceous of the Western Interior of North America prior to the Cretaceous–Palaeogene mass extinction. Increased resolution through formation binning pinpoints the Maastrichtian diversity decline to between 68 and 66 Ma, coinciding with the retreat of the Western Interior Seaway. Diversity curves are shown to exhibit volatile patterns using different binning methods, supporting claims that heterogeneous biases in this time‐frame affect the pre‐extinction palaeobiological record. We also show that the apparent high endemicity of dinosaurs in the Campanian is a result of non‐contemporaneous geological units within large time bins. This study helps to illustrate the utility of high‐resolution, regional studies to supplement our understanding of factors governing global diversity in deep time and ultimately how geology is inherently tied to our understanding of past changes in species richness.

new method
resolution
late cretaceous
north america
western interior seaway


Ephemeroid wing venation based upon new gigantic Carboniferous mayflies and basic morphology, phylogeny, and metamorphosis of pterygote insects (Insecta, Ephemerida)

Abstract: Gigantic as well as very large mayflies from the middle Upper Carboniferous (Westphalian) strata of Europe and North America are described: the adult and nymph of Bojophlebia prokopi n. gen., n. sp. (Bojophlebiidae n. fam.) and the nymphs of Lithoneura piecko n. sp. and Lithoneura clayesi n. sp. (Syntonopteridae). Evolution of ephemerid wing venation during 300 million years is summarized. Autapomorphic, apomorphic, and plesiomorphic character states of venation are categorized. Venational nomenclature of Recent Ephemerida is emended based on its evolutionary changes. Evidence that wing veins occurred primitively as a pair of fluted sectors is documented in Carboniferous mayflies in the costa, subcosta, radius, anal, and jugal. Ephemeroids and odonatoids are sister groups that share the veinal anal brace AA fused with CuP at an area important for flight. Ancestral Odonatoephemerida are the sister group of the extinct haustellate Paleoptera. The Carboniferous nymphs bear three pairs of almost homonomous th...

wing venation
carboniferous mayfly
mayfly


Ontogenetic trajectories of septal spacing in Early Jurassic belemnites from Germany and France, and their palaeobiological implications

Abstract: Based on well‐preserved belemnites, the ontogenetic trajectories of septal spacing between succeeding chambers were analysed. In the examined species (Passaloteuthis laevigata, Parapassaloteuthis zieteni and Pseudohasitites longiformis) that come from Buttenheim, Germany, and Lixhausen, France, the ontogenetic trajectories of septal spacing follow exponentially increasing trends with no decreasing phase of septal crowding during the earliest ontogenetic stage. The absence of a decreasing trend at the earliest ontogenetic stage is a unique character in contrast with those in modern cuttlefish and ancient and modern nautiloids, in which the decreasing trends are related to hatching events. These ontogenetic septal spacing trends suggest that the belemnite hatchlings had only a protoconch with no chamber. These belemnite hatchlings with no chamber and therefore small embryonic shell diameter are similar to those of ammonoids. Significant difference in a statistical test that compared the protoconch size between the two localities, might suggest that there was limited transportation at the embryonic stage, although it could also just indicate differences in regional environmental conditions, age and/or degree of time averaging which might differ between the examined taxa.

septal spacing
germany
ontogenetic trajectory


Modified perichondral ossification and the evolution of paddle-like limbs in ichthyosaurs and plesiosaurs

Abstract: ABSTRACT Evolution of paddle-like limbs in ichthyosaurs and plesiosaurs is correlated with loss of perichondral bone from the shafts of long bones. Among ichthyosaurs, loss of perichondral bone is first observed on the shafts of digit bones of Early Triassic taxa. Late Triassic ichthyosaurs show perichondral bone loss on the postaxial margins of the ulna and fibula. Among plesiosaurs, loss of perichondral bone is first observed on the postaxial margins of the ulna and fibula of Lower Jurassic taxa. In geologically later species of both groups, perichondral bone is progressively lost on all margins of the ulna and radius, and fibula and tibia. Late Triassic and Jurassic ichthyosaurs show an absence of perichondral ossifications on all limb bones distal to the humerus and femur. Delayed ossification of the mesopodium is not observed in ichthyosaurs. Evolutionary changes to the ossification of perichondral tissues appear to affect the sequence of limb ossification as long bones lose perichondral bone. Limb b...

perichondral ossification
paddle-like limb
ichthyosaur


Calibrating the zenith of dinosaur diversity in the Campanian of the Western Interior Basin by CA-ID-TIMS U–Pb geochronology

Abstract: The spectacular fossil fauna and flora preserved in the Upper Cretaceous terrestrial strata of North America’s Western Interior Basin record an exceptional peak in the diversification of fossil vertebrates in the Campanian, which has been termed the ‘zenith of dinosaur diversity’. The wide latitudinal distribution of rocks and fossils that represent this episode, spanning from northern Mexico to the northern slopes of Alaska, provides a unique opportunity to gain insights into dinosaur paleoecology and to address outstanding questions regarding faunal provinciality in connection to paleogeography and climate. Whereas reliable basin-wide correlations are fundamental to investigations of this sort, three decades of radioisotope geochronology of various vintages and limited compatibility has complicated correlation of distant fossil-bearing successions and given rise to contradictory paleobiogeographic and evolutionary hypotheses. Here we present new U–Pb geochronology by the CA-ID-TIMS method for 16 stratigraphically well constrained bentonite beds, ranging in age from 82.419 ± 0.074 Ma to 73.496 ± 0.039 Ma (2σ internal uncertainties), and the resulting Bayesian age models for six key fossil-bearing formations over a 1600 km latitudinal distance from northwest New Mexico, USA to southern Alberta, Canada. Our high-resolution chronostratigraphic framework for the upper Campanian of the Western Interior Basin reveals that despite their contrasting depositional settings and basin evolution histories, significant age overlap exists between the main fossil-bearing intervals of the Kaiparowits Formation (southern Utah), Judith River Formation (central Montana), Two Medicine Formation (western Montana) and Dinosaur Park Formation (southern Alberta). Pending more extensive paleontologic collecting that would allow more rigorous faunal analyses, our results support a first-order connection between paleoecologic and fossil diversities and help overcome the chronostratigraphic ambiguities that have impeded the testing of proposed models of latitudinal provinciality of dinosaur taxa during the Campanian.

dinosaur diversity
campanian
western interior basin


Fossil marine vertebrates of Cerro Los Quesos: Distribution of cetaceans, seals, crocodiles, seabirds, sharks, and bony fish in a late Miocene locality of the Pisco Basin, Peru

Abstract: ABSTRACT One-hundred and ninety-two fossil marine vertebrate specimens, preserved as bone elements cropping out at Cerro Los Quesos (Pisco Basin, Peru), are identified and reported on a 1:4,000 scale geological map and in the corresponding stratigraphic section. All the fossils originate from the Pisco Formation, which is dated in this area to the late Miocene (from 7.55 Ma to ≥6.71 Ma, based on 40Ar/39Ar analyses of three volcanic ash layers along the section). Specimens are particularly concentrated near the top of the two main hills, where the geologically youngest portion of the examined section crops out. The impressive fossil assemblage includes cetaceans (91.6%), represented by mysticetes (balaenopteroids and cetotheriids) and odontocetes (phocoenids, physeteroids, and ziphiids, including the holotype of Nazcacetus urbinai). Seals, a crocodile, a seabird, bony fish, and sharks are also reported. Isolated large teeth of Carcharocles and Cosmopolitodus are common and, in several instances, associated to mysticete skeletons. Together with a similar work recently published for the other late Miocene locality of Cerro Colorado, this work represents a case study for the detailed inventory of the extraordinary paleontological heritage of the Pisco Basin. As such, it constitutes the basis for future taphonomic, paleoecological, and systematic studies, as well as for a much-needed conservation effort.


Madagascar's ephemeral palaeo-grazer guild: who ate the ancient C4 grasses?

Abstract: Madagascar today is 65% grassland. Its grassy biomes were widely interpreted as ‘anthropogenic’ before Bond et al. [[1][1]] challenged that view, claiming that grasses colonized Madagascar during the Miocene. Through an analysis of grass clade endemism and specialization, Vorontsova et al. [[2][


Squamation and ecology of thelodonts

Abstract: Thelodonts are an enigmatic group of Paleozoic jawless vertebrates that have been well studied from taxonomical, biostratigraphic and paleogeographic points of view, although our knowledge of their ecology and mode of life is still scant. Their bodies were covered by micrometric scales whose morphology, histology and the developmental process are extremely similar to those of extant sharks. Based on these similarities and on the well-recognized relationship between squamation and ecology in sharks, here we explore the ecological diversity and lifestyles of thelodonts. For this we use classic morphometrics and discriminant analysis to characterize the squamation patterns of a significant number of extant shark species whose ecology is well known. Multivariate analyses have defined a characteristic squamation pattern for each ecological group, thus establishing a comparative framework for inferring lifestyles in thelodonts. We then use this information to study the squamation of the currently described 147 species of thelodonts, known from both articulated and disarticulated remains. Discriminant analysis has allowed recognizing squamation patterns comparable to those of sharks and links them to specific ecological groups. Our results suggest a remarkable ecological diversity in thelodonts. A large number of them were probably demersal species inhabiting hard substrates, within caves and crevices in rocky environments or reefs, taking advantage of the flexibility provided by their micromeric squamations. Contrary to classical interpretations, only few thelodonts were placed among demersal species inhabiting sandy and muddy substrates. Schooling species with defensive scales against ectoparasites could be also abundant suggesting that social interactions and pressure of ectoparasites were present in vertebrates as early the Silurian. The presence of species showing scales suggestive of low to moderate speed and a lifestyle presumably associated with open water environments indicates adaptation of thelodonts to deep water habitats. Scale morphology suggests that some other thelodonts were strong-swimming pelagic species, most of them radiating during the Early Devonian in association with the Nekton Revolution.


Paleoenvironments of the evolving Pliocene to early Pleistocene foreland basin in northwestern Taiwan: An example from the Dahan River section

Abstract: The overriding of the Luzon volcanic arc atop the underlying Chinese rifted‐continental margin has caused the formation of the Taiwan mountain belts and a peripheral foreland basin west of the orogen since the late Miocene. In this study, lithofacies analysis and calcareous nannofossil biostratigraphic investigations of the Dahan River section in northwestern (NW) Taiwan were performed. Our results offer insights into the temporal evolution of the sedimentary environments and the competing effects of the sedimentation and basin tectonics of the NW Taiwan foreland basin from the Pliocene to early Pleistocene. Nannofossil biostratigraphic studies showed that the upper Kueichulin Formation and the overlying Chinshui Shale can be assigned to the NN15 biozone of the Pliocene age, and the Cholan Formation pertains to NN16–NN18 of the early Pleistocene. The NN15–NN16 boundary coincides roughly with the boundary of the Chinshui Shale and Cholan Formation. We recognized three major sedimentary environments in the studied foreland succession comprising the upper Kueichulin Formation, Chinshui Shale, Cholan Formation and Yangmei Formation, in ascending order. During the deposition of the upper Kueichulin Formation in the early Pliocene, the dominant environment was a wave‐ and tide‐influenced open marine setting. During the late Pliocene, the environment deepened to an outer‐offshore setting when the sediments of Chinshui Shale were accumulated. In the Pleistocene, the environment then shallowed to wave‐dominated estuaries during the deposition of the lower Cholan Formation, and the basin was rapidly filled, generating a meandering and sandy braided river environment during the deposition of the upper Cholan to the Yangmei Formation. In summary, the evolution of sedimentary environments in the studied succession shows a deepening then a shallowing and coarsening upward trend during the period from the Pliocene to the Pleistocene, spanning the age from approximately 4 to 1 Ma.

pleistocene
foreland basin
dahan river section


Morphological and ecological disparity in Naraoiids (Arthropoda) from the Early Cambrian Chengjiang fauna, China

Abstract: Misszhouia longicaudata (Zhang & Hou) from the Chengjiang lagerstatte is separated from Naraoia Walcott by its antennular orientation, its smaller cephalic caeca and gut, lanceolate distal exopod lobe, and partial fusion of the exopod and first endopodal podomere. Naraoia spinosa Zhang & Hou (also from Chengjiang) shares derived characters with the type species, N. compacta. Deposit feeding is suggested for Naraoia spinosa by both morphology and preservational circumstances. New material shows previously unknown features in Misszhouia longicaudata, including frontal organs anterior to a sclerotised lobe of the hypo stomal complex, the position of the mouth opening, details of antennule and biramous limb attachments, morphology of the sternites and limb rami, and the structure of the ventral cuticle in the cephalon and pleural areas. CHEN, JUN-YUAN, GREGORY D. EDGECOMBE & LARS RAMSKOLD, 1997. Morphological and ecological disparity in naraoiids (Arthropoda) from the Early Cambrian Chengjiang fauna, China. Records of the Australian Museum 49(1): 1-24. The systematic status of Naraoia Walcott, 1912, and several allied non-mineralised arthropods has most recently been reviewed by Fortey & Theron (1994). These workers provided evidence that Naraoiidae Walcott, 1912, could be defined as a monophyletic group that unites the Lower-Middle Cambrian Naraoia, the Lower Cambrian Liwia Dzik & Lendzion, 1988, the Ordovician Tariccoia Hammann et al., 1990, and the Upper Ordovician Soomaspis Fortey & Theron, 1994. Among a range of Early Palaeozoic Arachnata that are known from exceptionally-preserved faunas, naraoiids are of particular significance because they have been regarded as a possible sister or stem-group to trilobites (Fortey & Theron, 1994; Shu et al., 1995).

ecological disparity
arthropoda
cambrian chengjiang fauna


Statistical approach for inferring ecology of Mesozoic birds

Abstract: The ability to identify the ecological role an organism plays is fundamental to modern ecology and is an important goal of palaeontological studies. Morphometrics has the potential to be a statistically robust means of furthering this goal, identifying ecomorphological trends within a group of organisms. The dramatic morphological and ecological diversity of modern and fossil birds makes them ideal for ecomorphological studies, and the vast increase in known Mesozoic avian diversity opens numerous possibilities for applying modern ecomorphology to enhance our understanding of avian diversification in the Mesozoic. This study presents a large morphometric database of modern birds analysed using a multivariate statistical approach, in order to identify correlations between ecology and morphology. These relationships were also examined in a number of Mesozoic birds in order to investigate both the ecological diversification of early birds as a whole and the specific ecological roles individual taxa may have played.

ecology
mesozoic bird
statistical approach


Gauging benthic recovery from 20th century pollution on the southern California continental shelf using bivalves from sediment cores

Abstract: Urbanization of coasts creates stresses on adjacent marine communities, but the full impact is seldom known owing to scarce historical records. Paleoecological analysis of sediment cores can be a powerful means of reconstructing baseline benthic communities, but is particularly challenging for continental shelves where dead-shell assemblages are prone to greater time-averaging than in natural sediment sinks such as deltas, coastal bays, and estuaries. We compared temporal changes in the composition of bivalve shell assemblages collected from box cores on the Palos Verdes (southern California, USA) shelf to a 40 yr time series of annually collected living benthic assemblages in the same area in order to calibrate bivalve core assemblages to known changes in community composition during wastewater remediation. Older (pre-1970) core assemblages were then used to reveal the nature of bivalve communities from the early 20th century and the extent to which present-day communities match, i.e. have recovered to, early urban baselines. Deep bioturbation and only moderate sedimentation rates (0.2 cm yr−1) damp the magnitude and rapidity of changes in core assemblage composition. Despite the geological complexity, bivalve core assemblages (1) detect known late 20th century dynamics in broad outline, (2) reveal the undocumented rise of chemosymbiont-bearing bivalves during the early 20th century, and (3) establish that the present-day community is largely but not fully recovered to its pre-effluent, early urban (1900−1930) baseline. Thus, cores capture the nature, timing, and duration of macrobenthic response to 20th century wastewater, validating this approach for shelf settings with scarce or no historical data.

southern california
continental shelf
sediment core


Making sense of ‘lower’ and ‘upper’ stem‐group Euarthropoda, with comments on the strict use of the name Arthropoda von Siebold, 1848

Abstract: The ever‐increasing number of studies that address the origin and evolution of Euarthropoda – whose extant representatives include chelicerates, myriapods, crustaceans and hexapods – are gradually reaching a consensus with regard to the overall phylogenetic relationships of some of the earliest representatives of this phylum. The stem‐lineage of Euarthropoda includes numerous forms that reflect the major morphological transition from a lobopodian‐type to a completely arthrodized body organization. Several methods of classification that aim to reflect such a complex evolutionary history have been proposed as a consequence of this taxonomic diversity. Unfortunately, this has also led to a saturation of nomenclatural schemes, often in conflict with each other, some of which are incompatible with cladistic‐based methodologies. Here, I review the convoluted terminology associated with the classification of stem‐group Euarthropoda, and propose a synapomorphy‐based distinction that allows ‘lower stem‐Euarthropoda’ (e.g. lobopodians, radiodontans) to be separated from ‘upper stem‐Euarthropoda’ (e.g. fuxianhuiids, Cambrian bivalved forms) in terms of the structural organization of the head region and other aspects of overall body architecture. The step‐wise acquisition of morphological features associated with the origins of the crown‐group indicate that the node defining upper stem‐Euarthropoda is phylogenetically stable, and supported by numerous synapomorphic characters; these include the presence of a deutocerebral first appendage pair, multisegmented head region with one or more pairs of post‐ocular differentiated limbs, complete body arthrodization, posterior‐facing mouth associated with the hypostome/labrum complex, and post‐oral biramous arthropodized appendages. The name ‘Deuteropoda’ nov. is proposed for the scion (monophyletic group including the crown‐group and an extension of the stem‐group) that comprises upper stem‐Euarthropoda and Euarthropoda. A brief account of common terminological inaccuracies in recent palaeontological studies evinces the utility of Deuteropoda nov. as a reference point for discussing aspects of early euarthropod phylogeny.

stem‐group euarthropoda
chelicerate
deuteropoda
euarthropod


Tectonic history of the western Tethys since the Late Triassic

Abstract: The tectonic history of the western Tethys since the Late Triassic is illustrated through a set of computer-generated plate reconstructions, which are based on a rigorous plate motions model of this region. The model is constrained by the Atlantic plate kinematics and on-land geologic evidence and defines 13 tectonic phases, spanning the time interval from the late Ladinian (230 Ma) to the present. The kinematics associated with the Late Triassic western Tethyan rifts produced the detachment of a large composite fragment from the northern margin of Gondwana. It can be considered as the eastern propagation of the central Pangea breakup. During the Early Jurassic these rift zones became inactive, while new zones of extension formed along the southern margin of Eurasia, the eastern margin of Iberia, and within the rifted northern Gondwana fragment itself. Plate motions associated with the first two extensional centers can still be considered as an eastern branch of the central Atlantic plate kinematics. Conversely, the kinematic parameters of the latter rift result from the composition of the Euler rotation describing the central Pangea breakup and the Euler pole of closure of the paleo–Tethys ocean. The Late Triassic–Early Jurassic rifting phases determined the formation of a number of independent microplates at the interface between Africa and Eurasia. Starting from the Early Cretaceous, convergence between Africa and Eurasia triggered further deformation within the dispersed continental fragments and the formation of backarc basins at the active margins, ultimately leading to an increase in the number of tectonic elements that were moving independently in the western Tethyan region during the Late Cretaceous and the Cenozoic. The proposed tectonic evolution of the western Tethys area is compatible with both global-scale plate kinematics and geological constraints from on-land data observed across the present-day mosaic of displaced terranes surrounding the Mediterranean region.

western tethys
late triassic
tectonic history


Permian spiriferellid brachiopods from northern Pangaea: taxonomy, biostratigraphy, macroevolution and implications for palaeoenvironmental and palaeobiogeographical reconstructions

Abstract: This study reports diverse spiriferellid brachiopods from the Permian rocks of Svalbard and adjacent areas (Arctic Canada and Subpolar Urals of Russia) located at the northern margin of Pangaea. In total, 11 brachiopod species in four genera are recognized and described in detail, including two new species (Spiriferella protodraschei and Arcullina? enokiani). According to our taxonomic investigation, morphological characteristics of the ventral sulcus and dorsal fold are relatively stable within each species, in spite of considerable intraspecific variations in shell outline and macro-ornamentation. In addition, both the arrangement of pustules, as a shell surface micro-ornamentation, and the development of delthyrial coverings are shown to be significant features for inferring phylogenetic relationships and for defining species. The best-known but still questionable taxon, Spiriferella keilhavii, is here identified as an endemic species restricted to Bjørnøya and, possibly, to central East Greenland; it is phylogenetically closest to S. loveni. Following the taxonomic revision, the stratigraphical ranges of the spiriferellids within the Kapp Starostin Formation in Spitsbergen are fully refined: three species, S. protodraschei, A. polaris and Timaniella wilczeki, are confined to the lowermost Vøringen Member (late Artinskian–early Kungurian), whereas S. loveni dominates the overlying members with a much longer stratigraphical range (late Kungurian–Lopingian?). This abrupt compositional change, along with comparable changes in other taxonomic groups, can be explained by a palaeoclimatic shift from cool to cold conditions between the Vøringen Member and the overlying Svenskeegga member. A similar biotic transition is identified between the Hambergfjellet and Miseryfjellet formations in Bjørnøya. On the other hand, S. loveni is abundant in the Late Permian strata of central East Greenland, but there it appears to be more costate in plication compared to its counterpart from Spitsbergen. It is suggested that this alteration in shell ornamentation may represent a possible response (adaptation) to warming arising from the southward migration of the species. http://zoobank.org/urn:lsid:zoobank.org:pub:85B863D2-DB42-4835-940A-2DE852C82178

spiriferellid brachiopod
pangaea
northern margin
kapp starostin formation


Therian mammals experience an ecomorphological radiation during the Late Cretaceous and selective extinction at the K–Pg boundary

Abstract: It is often postulated that mammalian diversity was suppressed during the Mesozoic Era and increased rapidly after the Cretaceous–Palaeogene (K–Pg) extinction event. We test this hypothesis by examining macroevolutionary patterns in early therian mammals, the group that gave rise to modern placentals and marsupials. We assess morphological disparity and dietary trends using morphometric analyses of lower molars, and we evaluate generic level taxonomic diversity patterns using techniques that account for sampling biases. In contrast with the suppression hypothesis, our results suggest that an ecomorphological diversification of therians began 10–20 Myr prior to the K–Pg extinction event, led by disparate metatherians and Eurasian faunas. This diversification is concurrent with ecomorphological radiations of multituberculate mammals and flowering plants, suggesting that mammals as a whole benefitted from the ecological rise of angiosperms. In further contrast with the suppression hypothesis, therian disparity decreased immediately after the K–Pg boundary, probably due to selective extinction against ecological specialists and metatherians. However, taxonomic diversity trends appear to have been decoupled from disparity patterns, remaining low in the Cretaceous and substantially increasing immediately after the K–Pg extinction event. The conflicting diversity and disparity patterns suggest that earliest Palaeocene extinction survivors, especially eutherian dietary generalists, underwent rapid taxonomic diversification without considerable morphological diversification.

ecomorphological radiation
selective extinction
therian mammal


The diet of Metaschizotherium bavaricum (Chalicotheriidae, Mammalia) from the MN 5 of Sandelzhausen (Germany) implied by the mesowear method

Abstract: The genus Metaschizotherium is a Miocene member of the Schizotheriinae (Chalicotheriidae, Perissodactyla) and appears in the MN 5 of Southern Germany with the species M. bavaricum. The Chalicotheriidae have mostly been reconstructed as browsers. In this study, the mesowear method is applied to 11 upper premolars and molars of M. bavaricum from the Upper Freshwater Molasse locality of Sandelzhausen (MN 5). With this method the amount of abrasive and attritive dental wear is investigated and thus it provides a time-averaged signature of food abrasiveness of ungulates. Principal components analysis is performed on mesowear variables of M. bavaricum. This species is found to classify closest to extant mixed feeding ruminants. This indicates that the diet of M. bavaricum essentially included nonabrasive browse but also a certain amount of abrasive plant material. The composition of the diet of extant reference species indicates that this abrasiveness was most likely imposed by bark and whole branches. In the palaeoecological context of Sandelzhausen M. bavaricum occupied the dietary niche of a mixed feeder or an abrasion-dominated browser. A high degree of similarity is recognised between the mesowear patterns of M. bavaricum from Sandelzhausen and M. fraasi from the MN 6 of the Franconian Alb. This is interpreted as reflecting a similar dietary niche of the two species.

chalicotheriidae
sandelzhausen
mesowear method
ecological niche
chalicothere


Paleogene deepwater mass composition of the tropical Pacific and implications for thermohaline circulation in a greenhouse world

Abstract: The Pacific Ocean likely exerted the greatest marine influence on climate during the greenhouse interval of the Paleogene. The first step toward assessing the role of Pacific deepwater circulation in global heat transport is a comprehensive reconstruction of deepwater mass composition and circulation patterns. We present new deepwater mass Nd isotope data from ODP Leg 199 Sites 1215, 1217, 1219, and 1221 to augment the existing coverage provided by ferromanganese crust and fossil fish debris data. The new data corroborate the notion that the Pacific Ocean operated in a bimodal pattern with deepwater sources in both the Southern Ocean and North Pacific for much of the early to middle Paleogene. In addition, the data indicate that there was little to no influence of Atlantic waters on the deepwater composition of the tropical Pacific. The available deepwater Nd isotope data provide refined constraints on the geographic and depth range of influence of both a Southern Ocean and North Pacific deepwater mass. From ∼65 to ∼45 Ma, the deep tropical Pacific was the mixing location of deep waters sourced from the Southern Ocean and the North Pacific. The Southern Ocean deepwater mass extended from ∼1800 m to abyssal depths. Until 53.6 Ma it circulated northward in the western Pacific at least as far as the paleolocation of Fe‐Mn Crust CLD01 (∼5°N paleolatitude) and in the eastern portion of the Pacific as far as Site 1215 (∼10°N paleolatitude). A North Pacific deepwater mass extended from at least ∼2400 m to 2900 m water depth from ∼65 to 54 Ma, south to Shatsky Rise (paleolatitude ∼10–15°N), and possibly as far as Site 1215, 700 km to the south of Shatsky Rise Sites 1209 and 1211.

deepwater mass composition
tropical pacific
paleogene


Paleobiogeography and biodiversity of Late Maastrichtian dinosaurs: how many dinosaur species went extinct at the Cretaceous-Tertiary boundary?

Abstract: The global Late Maastrichtian non-avian dinosaur apparent biodiversity is extensively surveyed for the first time. It amounts to 104 species (including unnamed forms) in 2010. The real biodiversity being obscured by taphonomical biases and the scarcity of the continental fossil record, a species-area relationship is used to estimate it. The results show that several hundreds (between 628 and 1078) non-avian dinosaur species were alive in the Late Maastrichtian, which is almost an order of magnitude above previous estimates. Because of the complex Late Cretaceous palaeobiogeography, discussions about dinosaur extinction should be based on this estimated real global biodiversity, not on the apparent biodiversity of a single area. Given the mean duration of dinosaur genera (7.7 Ma), the presence of so many dinosaur species in the Latest Cretaceous is consistent with the termination of most lineages at the Cretaceous-Tertiary boundary (the Late Maastrichtian sub-stage is 2.8 m.y. long). The Late Maastrichtian dinosaurian biodiversity is therefore consistent with the sudden extinction of the group following the Chicxulub impact.

biodiversity
dinosaur specie
cretaceous-tertiary boundary


Permian–Triassic Osteichthyes (bony fishes): diversity dynamics and body size evolution

Abstract: The Permian and Triassic were key time intervals in the history of life on Earth. Both periods are marked by a series of biotic crises including the most catastrophic of such events, the end‐Permian mass extinction, which eventually led to a major turnover from typical Palaeozoic faunas and floras to those that are emblematic for the Mesozoic and Cenozoic. Here we review patterns in Permian–Triassic bony fishes, a group whose evolutionary dynamics are understudied. Based on data from primary literature, we analyse changes in their taxonomic diversity and body size (as a proxy for trophic position) and explore their response to Permian–Triassic events. Diversity and body size are investigated separately for different groups of Osteichthyes (Dipnoi, Actinistia, ‘Palaeopterygii’, ‘Subholostei’, Holostei, Teleosteomorpha), within the marine and freshwater realms and on a global scale (total diversity) as well as across palaeolatitudinal belts. Diversity is also measured for different palaeogeographical provinces. Our results suggest a general trend from low osteichthyan diversity in the Permian to higher levels in the Triassic. Diversity dynamics in the Permian are marked by a decline in freshwater taxa during the Cisuralian. An extinction event during the end‐Guadalupian crisis is not evident from our data, but ‘palaeopterygians’ experienced a significant body size increase across the Guadalupian–Lopingian boundary and these fishes upheld their position as large, top predators from the Late Permian to the Late Triassic. Elevated turnover rates are documented at the Permian–Triassic boundary, and two distinct diversification events are noted in the wake of this biotic crisis, a first one during the Early Triassic (dipnoans, actinistians, ‘palaeopterygians’, ‘subholosteans’) and a second one during the Middle Triassic (‘subholosteans’, neopterygians). The origination of new, small taxa predominantly among these groups during the Middle Triassic event caused a significant reduction in osteichthyan body size. Neopterygii, the clade that encompasses the vast majority of extant fishes, underwent another diversification phase in the Late Triassic. The Triassic radiation of Osteichthyes, predominantly of Actinopterygii, which only occurred after severe extinctions among Chondrichthyes during the Middle–Late Permian, resulted in a profound change within global fish communities, from chondrichthyan‐rich faunas of the Permo‐Carboniferous to typical Mesozoic and Cenozoic associations dominated by actinopterygians. This turnover was not sudden but followed a stepwise pattern, with leaps during extinction events.

bony fish
diversity dynamic
predator
early triassic
actinopterygian


The future of the carbon cycle: review, calcification response, ballast and feedback on atmospheric CO2

Abstract: The operation of the carbon cycle forms an important part of the processes relevant to future changes in atmospheric carbon dioxide. The balance of carbon between terrestrial and oceanic reservoirs is an important factor and here we focus in particular on the oceans. Future changes in the carbon cycle that may affect air–sea partitioning of CO2 are difficult to quantify but the palaeoceanographic record and modern observational studies provide important evidence of what variations might occur. These include changes in surface nutrient use, the oceanic inventory of nutrients, and the elemental composition and rain–rate ratio of marine particles. Recent work has identified two inter–linked processes of potential importance that we consider in some detail: the response of marine calcification to changes in surface water CO2 and the association of particulate organic carbon with ballast minerals, in particular biogenic calcite. We review evidence from corals, coccolithophores and foraminifera, which suggests that the response of reduced calcification provides a negative feedback on rising atmospheric CO2. We then use a box model to demonstrate how the calcification response may affect the organic carbon rain rate through the ballast effect. The ballast effect on export fluxes of organic and inorganic carbon acts to counteract the negative calcification response to increased CO2. Thus, two oceanic buffers exert a significant control on ocean–atmosphere carbonate chemistry: the thermodynamic CO2 buffer; and the ballast/calcification buffer. Just how tightly coupled the rain–rate ratio of CaCO3/Corg is to fluxes of ballast minerals is an important question for future research.

carbon cycle
calcification response
atmospheric co2


Late Pleistocene/Holocene craniofacial morphology in Mesoamerican Paleoindians: implications for the peopling of the New World.

Abstract: Several studies on craniofacial morphology showed that most Paleoindians, who were the first settlers of the New World, clearly differ from modern Amerindians and East Asians, their supposed descendants and sister group, respectively. Here we present new evidence supporting this view from the Late Pleistocene/Early Holocene horizon from Mexico, as well as from the most complete set of dated Paleoindian remains. We analyzed the phenotypic resemblance of early Mexicans with other South Paleoamerican and modern human series. Two independent approaches to the data were used. In the first case, individual specimens were tested for morphological similarity with a set of modern reference samples. In the second analysis, Mexican specimens were treated as a sample in order to compute minimum genetic distances. Results from both approaches tend to associate early Mexican skulls with Paleoindians from Brazil, an Archaic sample from Colombia, and several circum-Pacific populations. These results give support to a model in which morphologically generalized groups of non-Northeast Asian descent (the so-called Paleoamericans) entered the continent first, and then dispersed from North to South America through Central America. The large geographic dispersal of Paleoamericans, and their presence in Mexico in the Early Holocene, raise new issues about the continent's settlement scenario.

craniofacial morphology
new world
late pleistocene


THE ECOLOGY OF LATE PLEISTOCENE AND RECENT MICROTUS FROM SOUTH-CENTRAL AND SOUTHWESTERN NEW MEXICO

Abstract: Four species of voles (Microtus pennsylvanicus, M. mexicanus, M. mont-nus and M. ochrogaster) are reported from Late Pleistocene and Recent cave deposits in southcentral and southwestern New Mexico. Identification of isolated molars was achieved by multivariate statistics. Aspects of paleoecology for each locality are given and late pluvial to Recent conditions of southern New Mexico are discussed. Rodents of the genus Microtus have long been favorites of Pleisto- cene paleontologists because of their complex dentition and their high degree of habitat specificity. Despite voluminous literature on molar patterns and variations, most isolated microtine molars are not reliably identifiable to species. Extensive microtine remains from five caves in southcentral and southwestern New Mexico gave me the impetus to develop a new method for the identification of microtine teeth and to reconstruct aspects of late Pleistocene paleoecology in southern New Mexico based upon the identifications. METHODS. Material was taken from two previously known sites (Shelter Cave and Howell's Ridge Cave) and two new sites (The Khulo and Anthony Cave). Material from Conkling's Cavern was borrowed. Locations of sites are shown in Fig. 1. When excavated, the sizes of test pits varied from site to site, but only 10 cm levels were removed at a time unless a clearly defined layer was observed, in which case the natural stratification was followed. At each locality a general survey of the present day ecology and geology was made. Microtine material consisted of isolated teeth and some partial jaws. Modern skeletal material of five species of Microtus now living in the Southwest

pleistocene
microtus
southwestern new mexico


A specimen-level phylogenetic analysis and taxonomic revision of Diplodocidae (Dinosauria, Sauropoda)

Abstract: Diplodocidae are among the best known sauropod dinosaurs. Several species were described in the late 1800s or early 1900s from the Morrison Formation of North America. Since then, numerous additional specimens were recovered in the USA, Tanzania, Portugal, and Argentina, as well as possibly Spain, England, Georgia, Zimbabwe, and Asia. To date, the clade includes about 12 to 15 nominal species, some of them with questionable taxonomic status (e.g., ‘Diplodocus’ hayi or Dyslocosaurus polyonychius), and ranging in age from Late Jurassic to Early Cretaceous. However, intrageneric relationships of the iconic, multi-species genera Apatosaurus and Diplodocus are still poorly known. The way to resolve this issue is a specimen-based phylogenetic analysis, which has been previously implemented for Apatosaurus, but is here performed for the first time for the entire clade of Diplodocidae. The analysis includes 81 operational taxonomic units, 49 of which belong to Diplodocidae. The set of OTUs includes all name-bearing type specimens previously proposed to belong to Diplodocidae, alongside a set of relatively complete referred specimens, which increase the amount of anatomically overlapping material. Non-diplodocid outgroups were selected to test the affinities of potential diplodocid specimens that have subsequently been suggested to belong outside the clade. The specimens were scored for 477 morphological characters, representing one of the most extensive phylogenetic analyses of sauropod dinosaurs. Character states were figured and tables given in the case of numerical characters. The resulting cladogram recovers the classical arrangement of diplodocid relationships. Two numerical approaches were used to increase reproducibility in our taxonomic delimitation of species and genera. This resulted in the proposal that some species previously included in well-known genera like Apatosaurus and Diplodocus are generically distinct. Of particular note is that the famous genus Brontosaurus is considered valid by our quantitative approach. Furthermore, “Diplodocus” hayi represents a unique genus, which will herein be called Galeamopus gen. nov. On the other hand, these numerical approaches imply synonymization of “Dinheirosaurus” from the Late Jurassic of Portugal with the Morrison Formation genus Supersaurus. Our use of a specimen-, rather than species-based approach increases knowledge of intraspecific and intrageneric variation in diplodocids, and the study demonstrates how specimen-based phylogenetic analysis is a valuable tool in sauropod taxonomy, and potentially in paleontology and taxonomy as a whole.

phylogenetic analysis
diplodocidae
north america
apatosaurus


The early Aurignacian dispersal of modern humans into westernmost Eurasia

Abstract: Significance We report the remarkable discovery of an early Aurignacian occupation, ∼5,000 years older than any Upper Paleolithic site in westernmost Eurasia. The archaeological and radiocarbon data provide definitive evidence that modern humans were in western Iberia at a time when, if present at all, Neanderthal populations would have been extremely sparse. This discovery has important ramifications for our understanding of the process of modern human dispersal and replacement of Neanderthal populations. The results support a very rapid, unimpeded dispersal of modern humans across western Eurasia and support the notion that climate and environmental change played a significant role in this process. Documenting the first appearance of modern humans in a given region is key to understanding the dispersal process and the replacement or assimilation of indigenous human populations such as the Neanderthals. The Iberian Peninsula was the last refuge of Neanderthal populations as modern humans advanced across Eurasia. Here we present evidence of an early Aurignacian occupation at Lapa do Picareiro in central Portugal. Diagnostic artifacts were found in a sealed stratigraphic layer dated 41.1 to 38.1 ka cal BP, documenting a modern human presence on the western margin of Iberia ∼5,000 years earlier than previously known. The data indicate a rapid modern human dispersal across southern Europe, reaching the westernmost edge where Neanderthals were thought to persist. The results support the notion of a mosaic process of modern human dispersal and replacement of indigenous Neanderthal populations.

dispersal
modern human
westernmost eurasia


Mg/Ca–temperature proxy in benthic foraminifera: New calibrations from the Florida Straits and a hypothesis regarding Mg/Li

Abstract: [1] Over the past decade, the ratio of Mg to Ca in foraminiferal tests has emerged as a valuable paleotemperature proxy. However, large uncertainties remain in the relationships between benthic foraminiferal Mg/Ca and temperature. Mg/Ca was measured in benthic foraminifera from 31 high-quality multicore tops collected in the Florida Straits, spanning a temperature range of 5.8° to 18.6°C. New calibrations are presented for Uvigerina peregrina, Planulina ariminensis, Planulina foveolata, and Hoeglundina elegans. The Mg/Ca values and temperature sensitivities vary among species, but all species exhibit a positive correlation that decreases in slope at higher temperatures. The decrease in the sensitivity of Mg/Ca to temperature may potentially be explained by Mg/Ca suppression at high carbonate ion concentrations. It is suggested that a carbonate ion influence on Mg/Ca may be adjusted for by dividing Mg/Ca by Li/Ca. The Mg/Li ratio displays stronger correlations to temperature, with up to 90% of variance explained, than Mg/Ca alone. These new calibrations are tested on several Last Glacial Maximum (LGM) samples from the Florida Straits. LGM temperatures reconstructed from Mg/Ca and Mg/Li are generally more scattered than core top measurements and may be contaminated by high-Mg overgrowths. The potential for Mg/Ca and Mg/Li as temperature proxies warrants further testing.

benthic foraminifera
new calibration
florida straits


Lower Ordovician (Chewtonian to Castlemainian) Radiolarians of Spitsbergen

Abstract: Synopsis Diverse and well‐preserved radiolarian faunas are found in a biostratigraphically precisely dated succession in the Lower Ordovician of Spitsbergen. The faunas are from the Didymograptellus bifidus and Isograptus victoriae lunatus graptolite Biozones. They document the transition from the Upper Cambrian to Lower Ordovician spicular dominated to spumellarian dominated Middle and Upper Ordovician faunas and yield important data for a more precise biostratigraphical use of Ordovician radiolarians. The faunas are dominated by early spumellarians of the Antygoporidae and Aspiculumidae, while the Protoentactiniidae and Palaeospiculumidae are rare elements surviving from the earlier Palaeozoic. Members of the Echidninidae have not been found. The precise definition of a number of important structural characters of early Palaeozoic radiolarians is discussed. The early spumellarians of the family Antygoporidae possess a distinct microsphere formed from a number of curved bars and provided on the outside with a variable number of outer spines, representing the oldest known type of microsphere. The development of the spherical skeletons of spumellarian and entactinarian radiolarians is developed in a number of different ways that are important for phylogen‐etic considerations. The following taxa are new: Svalbardospiculum gen. nov., Svalbardospiculum arenigium sp. nov., Protoentactinia bifurcata sp. nov., Sphaeroentactiniidae fam. nov.,Sphaeroentac‐tinia gen. nov., S. hexaspinosa sp. nov., S. bispinosa sp. nov., S. integrata sp. nov., Nyfrieslandia gen. nov., N. sphaeroidea sp. nov., N. complicata sp. nov., Parechidnina densa sp. nov., Antygoporidae fam. nov., Antygopora bella sp. nov., A. compacta sp. nov., A. microspina sp. nov., A. labyrinthina sp. nov., Labyrinthia gen. nov., Labyrinthia inexpectata sp. nov.

radiolarians
spitsbergen
radiolarian faunas
upper cambrian
low ordovician


Bivalve network reveals latitudinal selectivity gradient at the end-Cretaceous mass extinction

Abstract:
Biogeographic patterns of survival help constrain the causal factors responsible for mass extinction. To test whether biogeography influenced end-Cretaceous (K-Pg) extinction patterns, we used a network approach to delimit biogeographic units (BUs) above the species level in a global Maastrichtian database of 329 bivalve genera. Geographic range is thought to buffer taxa from extinction, but the number of BUs a taxon occurred in superseded geographic range as an extinction predictor. Geographically, we found a latitudinal selectivity gradient for geographic range in the K-Pg, such that higher latitude BUs had lower extinction than expected given the geographic ranges of the genera, implying that (i) high latitude BUs were more resistant to extinction, (ii) the intensity of the K-Pg kill mechanism declined with distance from the tropics, or (iii) both. Our results highlight the importance of macroecological structure in constraining causal mechanisms of extinction and estimating extinction risk of taxa.
ass extinctions have disproportionately shaped the evolutionary history of life 1 . During these rare, geologically rapid events, the rules of selectivity that prevail in background extinctions do not always clearly apply 2 . To delimit what may be independent selection processes and constrain possible causal factors, paleontologists have sought biologically meaningful patterns of survivorship in mass extinctions 3, 4 . In the marine realm, there are some taxon-specific cases where survivorship is linked to ecological traits -for example, in the K-Pg mass extinction event, reliance on photosymbiosis among scleractinian corals severely reduced survivorship 5 and sea urchin feeding strategy correlates positively with survivorship 6 . However, more often, survivorship in mass extinctions appears to be linked to increased geographic range size above the species level 7 , suggesting that biogeographic history of a taxon plays a vital role in sorting survivors from victims.
The correlation of geographic range at the lineage level with lineage survival, but apparent lack of physiological mechanisms in determining survivorship, suggests that lineages with similar biogeographic histories should have similar chances to survive mass extinction. Histories of ocean surface currents, plate tectonics, and environments shape biogeographic patterns above the species level by allowing lineages (genera) dispersal opportunities. Here, we explore whether these emergent biogeographic regions impact our understanding of extinction processes.
Here we employ a network approach to test whether biogeographic structure above the species level 8-11 correlates with bivalve survivorship in the K-Pg. Network methods have been useful in a broad range of applications, for example, to model the transmission of disease in social networks 12 , to describe the structure of scholarly communication 13 , and to model the stability of ecosystems in response to extinction 14 . A network approach can also reveal spatial patterns of taxa from geographic range data 15 . We generated a Maastrichtian network from the bivalve dataset, and used stratigraphic ranges from the Paleobiology Database to determine which genera survived the K-Pg mass extinction event 16 . We adapt a network-based clustering approach 13 to reveal biogeographic units (BUs) from patterns of geographic ranges (see methods).
The K-Pg event (ca. 66 Ma) is an ideal case to test whether biogeography influences survival in mass extinctions. It was geologically abrupt and was associated with significant changes to marine productivity and ocean chemistry, dramatic restructuring of marine and terrestrial communities, long-term effects on evolutionary rates and biogeography 17, 18 , and the extinction of up to 76% of all species 19 . As the most recent of the ''big five'' mass extinctions, the quantity, quality, and spatial resolution of the geological and paleontological data for the K-Pg interval are also better than those available for more ancient mass extinctions 22 . Bivalves have emerged as a model

latitudinal selectivity gradient
mass extinction
survival
network approach
unit


A model for variation in the chemistry of planktonic foraminifera due to secondary calcification and selective dissolution

Abstract: A quantitative model for describing the within-population variation in planktonic foraminifer shell chemistry that results from secondary calcification and selective dissolution is presented. The objective is to construct a basis for inferring the chemistries of different shell components and estimating the extent of shell dissolution. Variation is modeled as mixtures of two kinds of shell calcite, a primary calcite that forms the chambers and a secondary calcite that forms crust. Bulk shell chemistries are intermediate between the chemistries of these calcites and lie on mixing lines between them. For two component systems, mass balance relationships can be reformulated as a linear regression and solved for the chemistries of the primary and secondary calcites and for the uncertainties associated with these estimates. To apply this model, one needs measurements of bulk shell chemistries and estimates of the relative proportions of secondary and primary calcites. For most planktonic foraminifer species the proportion of secondary calcite can be estimated from differences in the relationship between shell size and mass before and after crusting. Preliminary results are consistent with previous work showing that secondary calcites are added at depth. However, even deep-dwelling species appear to grow most of their primary shell in surface waters and some surface-dwelling species add secondary calcite in the deep ocean. In contrast to the model's simple description of secondary calcification, the variation in chemistry from selective dissolution is more complicated because undissolved shells are themselves mixtures of primary and secondary calcites and therefore present a wide range of initial shell compositions. Nevertheless, the model allows both the compositions of different components to be inferred and the amount of dissolution to be estimated. Preliminary results indicate that dissolution of planktonic foraminifera is apparent nearly 2 km above the foraminifer lysocline and even apparently well-preserved shells may be over 50% dissolved.

planktonic foraminifera
secondary calcification
selective dissolution


Genetic evidence for patrilocal mating behavior among Neandertal groups

Abstract: The remains of 12 Neandertal individuals have been found at the El Sidrón site (Asturias, Spain), consisting of six adults, three adolescents, two juveniles, and one infant. Archaeological, paleontological, and geological evidence indicates that these individuals represent all or part of a contemporaneous social group of Neandertals, who died at around the same time and later were buried together as a result of a collapse of an underground karst. We sequenced phylogenetically informative positions of mtDNA hypervariable regions 1 and 2 from each of the remains. Our results show that the 12 individuals stem from three different maternal lineages, accounting for seven, four, and one individual(s), respectively. Using a Y-chromosome assay to confirm the morphological determination of sex for each individual, we found that, although the three adult males carried the same mtDNA lineage, each of the three adult females carried different mtDNA lineages. These findings provide evidence to indicate that Neandertal groups not only were small and characterized by low genetic diversity but also were likely to have practiced patrilocal mating behavior.

patrilocal mating behavior
neandertal group
genetic evidence


First spalacotheriid and dryolestid mammals from the Cretaceous of Germany

Abstract: The new spalacotheriid “symmetrodontan” Cifellitherium suderlandicum gen. et sp. nov. from the Barremian–Aptian of the Balve locality in northwestern Germany is the first record of spalacotheriids in Central Europe. The new taxon is based on one lower and two upper molars. Cifellitherium is similar to Spalacotherium, but differs by smaller stylocone and larger paraststyle on the upper molars, and a labially interrupted cingulid on the lower molar. The new dryolestid Minutolestes submersus gen. et sp. nov. is based on one lower and two upper molars of small size. Phylogenetic analysis revealed it as sister taxon of the clade comprising Laolestes, Krebsotherium, Dryolestes, and Guimarotodus. A dryolestid mandible with unevenly rooted molars and extremely worn down teeth cannot be attributed to Minutolestes submersus gen. et sp. nov. due to possessing molars twice as large in size. The mandible is assigned to a new dryolestid taxon, Beckumia sinemeckelia gen. et sp. nov., and has the dental formula 3i, 1c, 4p, 8m and a fully reduced Meckel’s groove. The mandible lacks any trace of a coronoid or splenial. In the phylogenetic analysis, it appears as sister taxon of a clade comprising Achyrodon, Phascolestes, Crusafontia, and Hercynodon. The new mammals are the stratigraphically youngest European representatives of their clades. The late survival of Beckumia sinemeckelia gen. et sp. nov. and Minutolestes submersus gen. et sp. nov. is possibly the result of isolated evolution in an Early Cretaceous island environment. This finding of new spalacotheriid and dryolestid mammals from Central Europe adds to an emerging paleobiogeographic pattern that Europe was distinct from Asia in the constituents of mammalian faunas during the Barremian–Aptian.

spalacotheriid
dryolestid mammal
germany


The Earliest-Known Fin Whale, Balaenoptera physalus, from the Early Pleistocene of Northern California, U.S.A.

Abstract: Citation for this article: Tsai, C.-H., and R. W. Boessenecker. 2017. The earliest-known fin whale, Balaenoptera physalus, from the Early Pleistocene of Northern California, U.S.A. Journal of Vertebrate Paleontology. DOI: 10.1080/02724634.2017.1306536.

earliest-known fin whale
balaenoptera physalus
pleistocene


Variations in the strontium isotopic ratio of seawater during the Miocene: Stratigraphic and geochemical implications

Abstract: A composite strontium isotopic seawater curve was constructed for the Miocene between 24 and 6 Ma by combining 87Sr/86Sr measurements of planktonic foraminifera from Deep Sea Drilling Project sites 289 and 588. Site 289, with its virtually continuous sedimentary record and high sedimentation rates (26 m/m.y.), was used for constructing the Oligocene to mid-Miocene part of the record, which included the calibration of 63 biostratigraphic datums to the Sr seawater curve using the timescale of Cande and Kent (1992). Across the Oligocene/Miocene boundary, a brief plateau occurred in the Sr seawater curve (87Sr/86Sr values averaged 0.70824) which is coincident with a carbon isotopic maximum (CM-O/M) from 24.3 to 22.6 Ma. During the early Miocene, the strontium isotopic curve was marked by a steep rise in 87Sr/86Sr that included a break in slope near 19 Ma. The rate of growth was about 60 ppm/m.y. between 22.5 and 19.0 Ma and increased to over 80 ppm/m.y. between 19.0 and 16 Ma. Beginning at ∼16 Ma (between carbon isotopic maxima CM3 and CM4 of Woodruff and Savin (1991)), the rate of 87Sr/86Sr growth slowed and 87Sr/86Sr values were near constant from 15 to 13 Ma. After 13 Ma, growth in 87Sr/86Sr resumed and continued until ∼9 Ma, when the rate of 87Sr/86Sr growth decreased to zero once again. The entire Miocene seawater curve can be described by a high-order function, and the first derivative (d87Sr/86Sr/dt) of this function reveals two periods of increased slope. The greatest rate of 87Sr/86Sr change occurred during the early Miocene between ∼20 and 16 Ma, and a smaller, but distinct, period of increased slope also occurred during the late Miocene between ∼12 and 9 Ma. These periods of steepened slope coincide with major phases of uplift and denudation of the Himalayan-Tibetan Plateau region, supporting previous interpretations that the primary control on seawater 87Sr/86Sr during the Miocene was related to the collision of India and Asia. The rapid increase in 87Sr/86Sr values during the early Miocene from 20 to 16 Ma imply high rates of chemical weathering and dissolved riverine fluxes to the oceans. In the absence of another source of CO2, these high rates of chemical weathering should have quickly resulted in a drawdown of atmospheric CO2 and climatic cooling through a reversed greenhouse effect. The paleoclimatic record, however, indicates a warming trend during the early Miocene, culminating in a climatic optimum between 17 and 14.5 Ma. We suggest that the high rates of chemical erosion and warm temperatures during the climatic optimum were caused by an increase in the contribution of volcanic CO2 from the eruption of the Columbia River Flood Basalts (CRFB) between 17 and 15 Ma. The decrease in the rate of CRFB eruptions at 15 Ma and the removal of atmospheric carbon dioxide by increased organic carbon burial in Monterey deposits eventually led to cooling and increased glaciation between ∼14.5 and 13 Ma. The CRFB hypothesis helps to explain the significant time lag between the onset of increased rates of organic carbon burial in the Monterey at 17.5 Ma (as marked by increased δ13C values) and the climatic cooling and glaciation during the middle Miocene (as marked by the increase in δ18O values), which did not begin until ∼14.5 Ma.


Abstract:
Perez-Huerta, A., Cusack, M. & Mendez, C.A. 2011: Preliminary assessment of the use of electron backscatter diffraction (EBSD) in conodonts. Lethaia, Vol. 45, pp. 253–258.

Conodonts are extensively used as ‘geochemical tools’ in palaeoenvironmental reconstructions in Palaeozoic and Triassic strata. The retention of a primary geochemical signal is substantially dependent on the ultrastructural integrity and crystallinity after diagenesis. Direct assessments of the preservation potential of the polycrystalline matrix are scarce with the exception of the application of transmission electron microscopy (TEM). The possible application of electron backscatter diffraction (EBSD) is introduced for well-preserved Pennsylvanian platform conodont elements as a novel in situ technique based on successful previous results for biogenic carbonates. EBSD shows the presence of no diffraction in central regions of all studied elements of Idiognathodus and Adetognathus, with possible implications for geochemistry analysis. The absence of diffraction could be attributed to the existence of an amorphous phase, water (+OH) or a process of hypocalcification related to the development of ‘growth cavities’ in the lamellar crown tissue. Overall results indicate the suitability of using EBSD to extract crystallographic information from conodonts and potentially for other apatite (micro-) fossils. □Conodont, diagenesis, EBSD, geochemistry, Pennsylvanian.

assessment
electron backscatter diffraction
conodont


An optimized method for the extraction of ancient eukaryote DNA from marine sediments

Abstract: Marine sedimentary ancient DNA (sedaDNA) provides a powerful means to reconstruct marine palaeo‐communities across the food web. However, currently there are few optimized sedaDNA extraction protocols available to maximize the yield of small DNA fragments typical of ancient DNA (aDNA) across a broad diversity of eukaryotes. We compared seven combinations of sedaDNA extraction treatments and sequencing library preparations using marine sediments collected at a water depth of 104 m off Maria Island, Tasmania, in 2018. These seven methods contrasted frozen versus refrigerated sediment, bead‐beating induced cell lysis versus ethylenediaminetetraacetic acid (EDTA) incubation, DNA binding in silica spin columns versus in silica‐solution, diluted versus undiluted DNA in shotgun library preparations to test potential inhibition issues during amplification steps, and size‐selection of low molecular‐weight (LMW) DNA to increase the extraction efficiency of sedaDNA. Maximum efficiency was obtained from frozen sediments subjected to a combination of EDTA incubation and bead‐beating, DNA binding in silica‐solution, and undiluted DNA in shotgun libraries, across 45 marine eukaryotic taxa. We present an optimized extraction protocol integrating these steps, with an optional post‐library LMW size‐selection step to retain DNA fragments of ≤500 base pairs. We also describe a stringent bioinformatic filtering approach for metagenomic data and provide a comprehensive list of contaminants as a reference for future sedaDNA studies. The new extraction and data‐processing protocol should improve quantitative paleo‐monitoring of eukaryotes from marine sediments, as well as other studies relying on the detection of highly fragmented and degraded eukaryote DNA in sediments.

extraction
eukaryote dna
marine sediment


A complete magnetic-polarity stratigraphy of the Miocene continental deposits of Mae Moh Basin, northern Thailand, and a reassessment of the age of hominoid-bearing localities in northern Thailand

Abstract: Northern Thailand comprises more than 40 Tertiary intermontane basins. These basins, tectonically interpreted as grabens or half grabens, have yielded hominoid fossils and rich Neogene mammal faunas. Relative ages provided by biochronological studies are controversial and neither absolute ages nor correlations with marine deposits are available. A precise temporal framework provided by magnetic-polarity stratigraphy is therefore crucial to understand the evolution of these Southeast Asian mammalian faunas, to estimate the timing and duration of basin formation, and finally to allow correlations with other Neogene hominoid localities of the Old World. A complete magnetostratigraphic study, which significantly extends previous paleomagnetic investigations, has been conducted in the Miocene sequence of Mae Moh Basin, Lampang Province, northern Thailand. Based on the biostratigraphic constraints, the 15 polarity zones recognized from the composite section have been correlated with Chrons C5ACr–C5r.3r, between 14.1 and 12.0 Ma. The present study provides a high-resolution magnetostratigraphic reference for the continental middle Miocene of all Southeast Asia. By correlation with the Miocene sequence of the nearby basin of Chiang Muan, the large-bodied hominoid ( Khoratpithecus chiangmuanensis )–bearing levels can be precisely dated between 12.4 and 12.2 Ma.

magnetic-polarity stratigraphy
mae moh basin
northern thailand


Knoetschkesuchus langenbergensis gen. nov. sp. nov., a new atoposaurid crocodyliform from the Upper Jurassic Langenberg Quarry (Lower Saxony, northwestern Germany), and its relationships to Theriosuchus

Abstract: We report a new, small-sized atoposaurid crocodyliform from the Upper Jurassic of Langenberg, Northeastern Germany. Atoposaurids are small-sized Mesozoic crocodyliforms of mainly European distribution, which are considered to be phylogenetically close to the origin of Eusuchia. Knoetschkesuchus langenbergensis gen. nov. sp. nov. is represented by two well-preserved skulls and additional cranial and postcranial remains representing different ontogenetic stages. 3D reconstructions of a juvenile skull based on micro-computed tomography allow the most detailed description of cranial remains of any atoposaurid hitherto presented. Our new analysis contradicts previous preliminary assignment of the Langenberg atoposaurids to Theriosuchus. Knoetschkesuchus gen. nov. is characterized in particular by the presence of two dental morphotypes in the maxilla and dentary, slit-like secondary choanae within a narrow groove on the surface of the pterygoid, absence of lacrimonasal contact, presence of an antorbital foramen and an external mandibular fenestra, and proportional characters of the interorbital and intertemporal region. A similar combination of characters allows attribution of Theriosuchus guimarotae to Knoetschkesuchus, forming the new combination Knoetschkesuchus guimarotae. Our analysis provides an osteological basis for the separation of Theriosuchus and Knoetschkesuchus and helps further delineate generic differences in other closely related crocodylomorphs. Our phylogenetic analysis corroborates inclusion of Knoetschkesuchus into Atoposauridae and supports a position of Atoposauridae within Eusuchia.

atoposaurid crocodyliform
theriosuchus
knoetschkesuchus langenbergensis gen


Cladistic tests of monophyly and relationships of biostratigraphically significant conodonts using multielement skeletal data –Lochriea homopunctatus and the genus Lochriea

Abstract: Abstract:  Since the 1960s, huge progress has been made in reconstructing the multielement skeletons of conodont species and developing a biologically defensible taxonomy. Nevertheless, a widespread prejudice remains that certain parts of the conodont skeleton, particularly the P1 elements, are more informative than others with regard to taxonomy and evolutionary relationships. Here, we test these views. A new partial multielement reconstruction of the skeleton of the biostratigraphically significant conodont originally described as Gnathodus commutatus homopunctatus allows us to conduct a cladistic test of the alternative hypotheses of phylogenetic placement of this species. Our analysis also provides the first test of the hypothesis that Lochriea– species of which are markers for global correlation – is monophyletic and tests hypotheses concerning the origins of the genus. Our results demonstrate that homopunctatus is a species of Lochriea and that the genus is monophyletic. The widely held view that Lochriea arose from a species of Bispathodus is not supported. Our results show that it is difficult to predict a priori which parts of the conodont skeleton carry phylogenetic signal, and provide strong support for the hypothesis that similarity in the morphology of conodont P1 elements alone is not a reliable guide to relationships and taxonomic groupings of conodont species. This is because P1 elements with similar morphologies are convergently acquired in multiple conodont clades, because reliance on the characters of only one of the six or seven morphologically distinct elements of the conodont skeleton ignores phylogenetically significant data and because P1 elements can lack characters that might seem to be diagnostic of a genus. Conodonts are no different to other organisms: ignoring data that have the potential to be phylogenetically informative is unlikely to produce the most reliable hypotheses of evolutionary relationships. We suggest that other biostratigraphically significant hypotheses of relationship between conodont taxa that are based on P1 elements alone should be subject to cladistic testing.


Extreme weather events recorded by daily to hourly resolution biogeochemical proxies of marine giant clam shells

Abstract: Significance Reconstructing past extreme weather events, such as tropical cyclones and cold surges, using natural paleoclimate archives can lengthen the instrumental data and help us have a broader understanding of the range of weather variability not evident in instrumental record. However, the time resolution of current paleoarchives, from millennial to monthly at best, is usually too low to explore past weather events. Here we found that the Tridacna shells from South China Sea, western Pacific, have continuous daily growth bands, and several daily to hourly resolution biogeochemical proxy records were developed. Our results demonstrate that these records can record nearby tropical cyclones and cold surges, indicating that Tridacna shells have the potential to be an unprecedented ultra-high-resolution archive for paleoweather reconstructions. Paleoclimate research has built a framework for Earth’s climate changes over the past 65 million years or even longer. However, our knowledge of weather-timescale extreme events (WEEs, also named paleoweather), which usually occur over several days or hours, under different climate regimes is almost blank because current paleoclimatic records rarely provide information with temporal resolution shorter than monthly scale. Here we show that giant clam shells (Tridacna spp.) from the tropical western Pacific have clear daily growth bands, and several 2-y-long (from January 29, 2012 to December 9, 2013) daily to hourly resolution biological and geochemical records, including daily growth rate, hourly elements/Ca ratios, and fluorescence intensity, were obtained. We found that the pulsed changes of these ultra-high-resolution proxy records clearly matched with the typical instrumental WEEs, for example, tropical cyclones during the summer−autumn and cold surges during the winter. When a tropical cyclone passes through or approaches the sampling site, the growth rate of Tridacna shell decreases abruptly due to the bad weather. Meanwhile, enhanced vertical mixing brings nutrient-enriched subsurface water to the surface, resulting in a high Fe/Ca ratio and strong fluorescence intensity (induced by phytoplankton bloom) in the shell. Our results demonstrate that Tridacna shell has the potential to be used as an ultra-high-resolution archive for paleoweather reconstructions. The fossil shells living in different geological times can be built as a Geological Weather Station network to lengthen the modern instrumental data and investigate the WEEs under various climate conditions.

resolution
giant clam shell
daily growth band
biogeochemical proxy record
extreme weather event


Canadia spinosa and the early evolution of the annelid nervous system

Abstract: Exceptional fossils reveal annelid nervous system evolution. Annelid worms are a disparate, primitively segmented clade of bilaterians that first appear during the early Cambrian Period. Reconstructing their early evolution is complicated by the extreme morphological diversity in early diverging lineages, rapid diversification, and sparse fossil record. Canadia spinosa, a Burgess Shale fossil polychaete, is redescribed as having palps with feeding grooves, a dorsal median antenna and biramous parapodia associated with the head and flanking a ventral mouth. Carbonaceously preserved features are identified as a terminal brain, circumoral connectives, a midventral ganglionated nerve cord and prominent parapodial nerves. Phylogenetic analysis recovers neuroanatomically simple extant taxa as the sister group of other annelids, but the phylogenetic position of Canadia suggests that the annelid ancestor was reasonably complex neuroanatomically and that reduction of the nervous system occurred several times independently in the subsequent 500 million years of annelid evolution.

early evolution
nervous system
canadia spinosa


Quantifying intra- and interspecific variability in trilobite moulting behaviour across the Palaeozoic

Abstract: Moulting of a protective exoskeleton is a defining characteristic of Euarthropoda, and its evolution can be explored through analysing moults preserved in the fossil record. Our most complete record comes from the Trilobita, which were uniquely flexible in moulting compared to other arthropod groups. This study presents the first broad-scale quantitative analysis of trilobite moulting. Trends in moulting variability with taxonomy and through the Palaeozoic are explored by looking at the occurrences of six moulting characteristics: opening of the facial and ventral sutures; and disarticulation of the cephalon, cranidium, thorax, and pygidium. Significant differences in moulting across taxonomic and temporal groups were identified using chi-squared analyses, and biases with sampling and diversity identified through correlation analyses. Occurrences of facial and ventral suture opening, and cephalic disarticulation, significantly varied between orders and Epochs. These likely result from the prevalence of ventral suture moulting in Redlichiida and cephalic disarticulation in Phacopida, and their relevant diversity patterns. The data show high levels of intraspecific variability in moulting; ~40% of species showed multiple moulting characteristics. Redlichiida and the early Cambrian are the most intraspecifically variable, with greater variability likely an adaptation to the initial radiation and establishment of trilobites into new niches. The longest-lived group, Proetida, showed the lowest levels of intraspecific variability, which may suggest greater specialism later in the Palaeozoic. Ultimately, datasets such as this advocate the need to study behaviours in the fossil record on a broad-scale, because they help us build a comprehensive picture of extinct groups as living animals. Harriet B. Drage. Department of Zoology, University of Oxford, South Parks Road, Oxford, United Kingdom, OX1 3PS. harriet.drage@zoo.ox.ac.uk

trilobite behaviour palaeozoic exoskeleton cephalon


An unusual new archosauriform from the Middle–Late Triassic of southern Brazil and the monophyly of Doswelliidae

Abstract:
Until now the Doswelliidae was considered a monospecific family including Doswellia kaltenbachi from the Late Triassic of North America. The phylogenetic position of this taxon remained enigmatic until recently, when a sister-group relationship with the Proterochampsidae was suggested. In the present contribution we describe the new doswelliid species Archeopelta arborensis gen. et sp. nov. from the Middle–Late Triassic of Brazil. A cladistic analysis recovered Archeopelta, Doswellia, and Tarjadia within a monophyletic group of basal archosauriforms, the Doswelliidae. The monophyly of this family is supported by the presence of osteoderm ornamentation that is coarse, incised, and composed of regular pits and the presence of an unornamented anterior articular lamina. Archeopelta is more closely related to Doswellia than to other archosauriforms by the presence of basipterygoid processes anterolaterally orientated, dorsal centra with a convex surface, width of the neural arch plus ribs of the first primordial sacral that are three times the length of the neural arch, and iliac blade laterally deflected, with strongly convex dorsal margin, and a length less than three times its height. The phylogenetic analysis indicates that Doswellidae is the closest large monophyletic entity to Archosauria, which achieved a wide palaeolatitudinal distribution during the late Middle and Late Triassic time span.

© 2011 The Linnean Society of London, Zoological Journal of the Linnean Society, 2011, 161, 839–871.

archosauriform
middle–late triassic
monophyly


Mid-Cretaceous amber fossils illuminate the past diversity of tropical lizards

Abstract: Exquisitely preserved fossil lizards from 99-million-year-old Burmese amber provide new insights into paleotropical diversity. Modern tropical forests harbor an enormous diversity of squamates, but fossilization in such environments is uncommon and little is known about tropical lizard assemblages of the Mesozoic. We report the oldest lizard assemblage preserved in amber, providing insight into the poorly preserved but potentially diverse mid-Cretaceous paleotropics. Twelve specimens from the Albian-Cenomanian boundary of Myanmar (99 Ma) preserve fine details of soft tissue and osteology, and high-resolution x-ray computed tomography permits detailed comparisons to extant and extinct lizards. The extraordinary preservation allows several specimens to be confidently assigned to groups including stem Gekkota and stem Chamaleonidae. Other taxa are assignable to crown clades on the basis of similar traits. The detailed preservation of osteological and soft tissue characters in these specimens may facilitate their precise phylogenetic placement, making them useful calibration points for molecular divergence time estimates and potential keys for resolving conflicts in higher-order squamate relationships.


The St George Group (Lower Ordovician) of western Newfoundland: tidal flat island model for carbonate sedimentation in shallow epeiric seas

Abstract:
The St George Group consists of peritidal carbonate rocks deposited on the continental shelf of North America bordering the ancient Iapetus Ocean. These Lower Ordovician rocks are similar to other lower Palaeozoic limestones and dolostones that accumulated in epeiric seas and veneer cratonic areas worldwide. A wide variety of facies in the St George is grouped into seven lithotopes, interpreted to represent supratidal, intertidal and shallow, high- and low-energy subtidal environments. Rapid lateral facies changes can be observed in some field exposures, and demonstrated by correlation of closely spaced sections. The stratigraphic array of these lithotopes, although too irregular to be simplified into shallowing-upward cycles, suggests that they were deposited as small tidal flat islands and banks. Shallow subtidal areas around islands generated sediment and permitted tidal exchange. Tidal flat islands were somewhat variable in character at any one time, and evolved with changing regional hydrographic conditions.

The St George rocks suggest an alternative theory of carbonate sedimentation in large, shallow epeiric seas, namely as small islands and banks built by processes that operated in a tidal regime. Furthermore, this island model provides a framework for a mechanism of cyclic carbonate sedimentation, by which small-scale, peritidal cycles represent tidal flat islands that accreted vertically and migrated laterally as local sediment supply from neighbouring subtidal areas waxed and waned during relatively constant subsidence.

island model
carbonate sedimentation
shallow epeiric sea