Modeling the ecology and evolution of biodiversity: Biogeographical cradles, museums, and graves

Abstract: Simulating South American biodiversity The emergence, distribution, and extinction of species are driven by interacting factors—spatial, temporal, physical, and biotic. Rangel et al. simulated the past 800,000 years of evolution in South America, incorporating these factors into a spatially explicit dynamic model to explore the geographical generation of diversity. Their simulations, based on a paleoclimate model on a 5° latitude-longitude scale, result in shifting maps of speciation, persistence, and extinction (or cradles, museums, and graves). The simulations culminate in a striking resemblance to contemporary distribution patterns across the continent for birds, mammals, and plants—despite having no target patterns and no empirical data parameterizing them. Science, this issue p. eaar5452 Mechanistic simulations of climate dynamics, speciation, and adaptive evolution yield realistic geographical patterns of biodiversity. INTRODUCTION Individual processes that shape geographical patterns of biodiversity are increasingly understood, but their complex interactions on broad spatial and temporal scales remain beyond the reach of analytical models and traditional experiments. To meet this challenge, we built a spatially explicit, mechanistic model that simulates the history of life on the South American continent, driven by modeled climates of the past 800,000 years. Operating at the level of geographical ranges of populations, our simulations implemented adaptation, geographical range shifts, range fragmentation, speciation, long-distance dispersal, competition between species, and extinction. Only four parameters were required to control these processes (dispersal distance, evolutionary rate, time for speciation, and intensity of competition). To assess the effects of topographic heterogeneity, we experimentally smoothed the climate maps in some treatments. RATIONALE The simulations had no target patterns. Instead, the study took a fundamental approach, relying on the realism of the modeled ecological and evolutionary processes, theoretical derivations of parameter values, and the climatic and topographic drivers to produce meaningful biogeographical patterns. The model encompassed only the Late Quaternary (last 800,000 years), with its repeated glacial-interglacial cycles, beginning at a time when South America was already populated with a rich biota, comprising many distinct lineages. Nonetheless, current consensus holds that the contemporary flora and vertebrate fauna of South America include numerous lineages that have undergone rapid diversification during the Quaternary, particularly in the Andes. In our model, over the course of each simulation, a complete phylogeny emerged from a single founding species. On the basis of the full historical records for each species range, at each 500-year interval, we recorded spatial and temporal patterns of speciation (“cradles”), persistence (“museums”), extinction (“graves”), and species richness. RESULTS Simulated historical patterns of species richness, as recorded by maps of the richness of persistent (museum) species, proved quite successful in capturing the broad features of maps of contemporary species richness for birds, mammals, and plants. Factorial experiments varying parameter settings and initial conditions revealed the relative impact of the evolutionary and ecological processes that we modeled, as expressed in spatial and temporal patterns of cradles, museums, graves, and species richness. These patterns were most sensitive to the geographical location of the founding species and to the rate of evolutionary adaptation. Experimental topographic smoothing confirmed a crucial role for climate heterogeneity in the diversification of clades, especially in the Andes. Analyses of temporal patterns of speciation (cradles) and extinction (graves) emerging from the simulations implicated Quaternary glacial-interglacial cycles as drivers of both diversification and extinction on a continental scale. CONCLUSION Our biogeographical simulations were constructed from the bottom up, integrating mechanistic models of key ecological and evolutionary processes, following well-supported, widely accepted explanations for how these processes work in nature. Despite being entirely undirected by any target pattern of real-world species richness and covering only a tiny slice of the past, surprisingly realistic continental and regional patterns of species richness emerged from the model. Our simulations confirm a powerful role for adaptive niche evolution, in the context of diversification and extinction driven by topography and climate. Observed species richness versus modeled (simulated) richness. Upper map: Contemporary South American bird richness (2967 species). Lower map: Simulated spatial pattern for the cumulative richness of persistent (museum) species, arising from the model. The map show results averaged over all parameter values for an Atlantic Rainforest founder, excluding the climate-smoothing experimental treatments. Simulated species richness is highly correlated with observed species richness for birds (r2 = 0.6337). Individual processes shaping geographical patterns of biodiversity are increasingly understood, but their complex interactions on broad spatial and temporal scales remain beyond the reach of analytical models and traditional experiments. To meet this challenge, we built a spatially explicit, mechanistic simulation model implementing adaptation, range shifts, fragmentation, speciation, dispersal, competition, and extinction, driven by modeled climates of the past 800,000 years in South America. Experimental topographic smoothing confirmed the impact of climate heterogeneity on diversification. The simulations identified regions and episodes of speciation (cradles), persistence (museums), and extinction (graves). Although the simulations had no target pattern and were not parameterized with empirical data, emerging richness maps closely resembled contemporary maps for major taxa, confirming powerful roles for evolution and diversification driven by topography and climate.

biodiversity
museum
grave
south america
planet


Gyrfalcon Falco rusticolus post‐glacial colonization and extreme long‐term use of nest‐sites in Greenland

Abstract: Gyrfalcons Falco rusticolus use the same nest-sites over long periods of time, and in the cold dry climate of Greenland, guano and other nest debris decay slowly. Nineteen guano samples and three feathers were collected from 13 Gyrfalcon nests with stratified faecal accumulation in central-west and northwest Greenland. Samples were 14 C dated, with the oldest guano sample dating to c. 2740‐2360 calendar years (cal yr) before present (BP) and three others were probably > 1000 cal yr BP. Feather samples ranged from 670 to 60 cal yr BP. Although the estimated age of material was correlated with sample depth, both sample depth and guano thickness gave a much less reliable prediction of sample age than use of radiocarbon dating on which the margin of error was less. Older samples were obtained from sites farther from the current Greenland Ice Sheet and at higher elevations, while younger samples were closer to the current ice sheet and at lower elevations. Values for d 13 C showed that Gyrfalcons nesting farther from the Greenland Ice Sheet had a more marine diet, whereas those nesting closer to the ice sheet (= further inland) fed on a more terrestrial diet. The duration of nest-site use by Gyrfalcons is a probable indicator of both the time at which colonization occurred and the palaeoenvironmental conditions and patterns of glacial retreat. Nowhere before has such extreme long-term to present use of raptor nest-sites been documented.


Paleontological baselines for evaluating extinction risk in the modern oceans

Abstract: Recognizing the threat of additive risk Humans are accelerating the extinction rates of species in both terrestrial and marine environments. However, species extinctions have occurred across time for a variety of other reasons. Finnegan et al. looked at the extinction rates across marine genera (groups of species) over the past 23 million years to determine intrinsic extinction rates and what traits or regions correspond to the highest rates. Combining patterns of intrinsic extinction with regions of high anthropogenic threat revealed taxa and areas, particularly in the tropics, where the risk of extinction will be especially high. Science, this issue p. 567 Fossils reveal patterns of extinction in marine species, past and present. Marine taxa are threatened by anthropogenic impacts, but knowledge of their extinction vulnerabilities is limited. The fossil record provides rich information on past extinctions that can help predict biotic responses. We show that over 23 million years, taxonomic membership and geographic range size consistently explain a large proportion of extinction risk variation in six major taxonomic groups. We assess intrinsic risk—extinction risk predicted by paleontologically calibrated models—for modern genera in these groups. Mapping the geographic distribution of these genera identifies coastal biogeographic provinces where fauna with high intrinsic risk are strongly affected by human activity or climate change. Such regions are disproportionately in the tropics, raising the possibility that these ecosystems may be particularly vulnerable to future extinctions. Intrinsic risk provides a prehuman baseline for considering current threats to marine biodiversity.

baseline
extinction risk
marine specie
biodiversity


Millennial‐Scale Changes in Bottom Water Temperature and Water Mass Exchange Through the Fram Strait 79°N, 63‐13 ka

Abstract: The Svalbard margin, in the eastern Fram Strait with its high sediment accumulation, form a key area for the reconstruction of water mass and heat exchange between the North Atlantic and Arctic Ocean in relation to abrupt climate changes as seen in glacial Greenland Interstadial and Greenland Stadial (GI‐GS) events. Here, we present a bottom water temperature (BWT) record from the northern Nordic Seas (79°N) at 1,273 m water depth based on benthic foraminiferal Mg/Ca. The BWT reconstructions, combined with benthic foraminiferal stable isotopes, benthic foraminiferal fauna compositions and ice‐rafted debris (IRD), reveal at least two distinctive scenarios for the GI‐GS events during the last glacial period (13–63 ka). During GIs, conditions were similar to modern with high productivity, low BWT and deep convection. During GS6, GS8, and GS15 and during Heinrich Stadials (HSs), BWT increased up to 5°C ± 1°C generally concomitant with low planktic and benthic δ18O. Our results suggest, that during some GSs and HSs, deep water generation was reduced, allowing the subsurface Atlantic water (AW) to thicken and deepen down to at least the core site depth. A strong halocline during HSs and GSs prevented heat release from the subsurface AW, which we can now trace from 45°N in the North Atlantic to the Arctic Ocean >79°N. Surfacing of the salty Atlantic subsurface water preconditioned the Nordic seas for convection. Release of the subsurface heat from this vast reservoir must have contributed to the large and abrupt atmospheric warmings at the start of GIs.

bottom water temperature
fram strait
arctic ocean


A Pliocene‐Pleistocene stack of 57 globally distributed benthic δ18O records

Abstract: [1] We present a 5.3-Myr stack (the “LR04” stack) of benthic δ18O records from 57 globally distributed sites aligned by an automated graphic correlation algorithm. This is the first benthic δ18O stack composed of more than three records to extend beyond 850 ka, and we use its improved signal quality to identify 24 new marine isotope stages in the early Pliocene. We also present a new LR04 age model for the Pliocene-Pleistocene derived from tuning the δ18O stack to a simple ice model based on 21 June insolation at 65°N. Stacked sedimentation rates provide additional age model constraints to prevent overtuning. Despite a conservative tuning strategy, the LR04 benthic stack exhibits significant coherency with insolation in the obliquity band throughout the entire 5.3 Myr and in the precession band for more than half of the record. The LR04 stack contains significantly more variance in benthic δ18O than previously published stacks of the late Pleistocene as the result of higher-resolution records, a better alignment technique, and a greater percentage of records from the Atlantic. Finally, the relative phases of the stack's 41- and 23-kyr components suggest that the precession component of δ18O from 2.7–1.6 Ma is primarily a deep-water temperature signal and that the phase of δ18O precession response changed suddenly at 1.6 Ma.

stack
benthic δ18o record
age model
benthic stack


The endemic radiodonts of the Cambrian Stage 4 Guanshan biota of South China

Abstract: The Guanshan Biota (South China, Cambrian, Stage 4) contains a diverse assemblage of biomineralizing and non-biomineralizing animals. Sitting temporally between the Stage 3 Chengjiang and Wuliuan Kaili Biotas, the Guanshan Biota contains numerous fossil organisms that are exclusive to this exceptional deposit. The Guanshan Konservat-Lagerstätte is also unusual amongst Cambrian strata that preserve non-biomineralized material, as it was deposited in a relatively shallow water setting. In this contribution we double the diversity of radiodonts known from the Guanshan Biota from two to four, and describe the second species of Paranomalocaris . In addition, we report the first tamisiocaridid from South China, and confirm the presence of a tetraradial oral cone bearing small and large plates in “Anomalocaris” kunmingensis , the most abundant radiodont from the deposit. All four radiodont species, and three genera, are apparently endemic to the Guanshan Biota. When considered in the wider context of geographically and temporally comparable radiodont faunas, endemism in Guanshan radiodonts is most likely a consequence of the shallower and more proximal environment in which they lived. The strong coupling of free-swimming radiodonts and benthic communities underlines the complex relationship between the palaeobiogeographic and environmental distributions of prey and predators. This local adaptation of radiodonts to their prey is highlighted by the frontal appendage morphology of the two species of Paranomalocaris , apparently specialised to different feeding modes, while the recognition of the limited geographic range of some radiodont faunas highlights the importance of exploring as many deposits as possible to fully understand this group.


The hyoid arch and braincase anatomy of Acanthodes support chondrichthyan affinity of ‘acanthodians’

Abstract: Solving the evolutionary relationships of the acanthodians is one of the key problems in reconstructing ancestral anatomical conditions for the jawed vertebrates (gnathostomes). Current debate concerns whether acanthodians are an assemblage of stem chondrichthyans, or a more generalized grade encompassing some early stem osteichthyans. The skull anatomy of Acanthodes bronni has been pivotal in these debates, owing to tension between chondrichthyan- and osteichthyan-like models of reconstruction. We use computed tomography scanning and traditional palaeontological techniques to resolve the long-standing debate about the anatomy of the jaw suspension. We establish the correct length of the hyomandibula and show that it attaches to a process on the ventrolateral angle of the braincase below the jugular vein groove. This condition corresponds precisely to that in chondrichthyans. This character represents an unambiguously optimized synapomorphy with chondrichthyans given current gnathostome phylogenies, corroborating the growing consensus of the chondrichthyan affinity of acanthodians.

chondrichthyan affinity
acanthodian
stem osteichthyan


Evolution and the latitudinal diversity gradient: speciation, extinction and biogeography.

Abstract: A latitudinal gradient in biodiversity has existed since before the time of the dinosaurs, yet how and why this gradient arose remains unresolved. Here we review two major hypotheses for the origin of the latitudinal diversity gradient. The time and area hypothesis holds that tropical climates are older and historically larger, allowing more opportunity for diversification. This hypothesis is supported by observations that temperate taxa are often younger than, and nested within, tropical taxa, and that diversity is positively correlated with the age and area of geographical regions. The diversification rate hypothesis holds that tropical regions diversify faster due to higher rates of speciation (caused by increased opportunities for the evolution of reproductive isolation, or faster molecular evolution, or the increased importance of biotic interactions), or due to lower extinction rates. There is phylogenetic evidence for higher rates of diversification in tropical clades, and palaeontological data demonstrate higher rates of origination for tropical taxa, but mixed evidence for latitudinal differences in extinction rates. Studies of latitudinal variation in incipient speciation also suggest faster speciation in the tropics. Distinguishing the roles of history, speciation and extinction in the origin of the latitudinal gradient represents a major challenge to future research.

latitudinal diversity gradient
speciation
tropic
high rate


Fossil amphibians and reptiles from the Neogene locality of Maramena (Greece), the most diverse European herpetofauna at the Miocene/Pliocene transition boundary

Abstract: We herein describe the fossil amphibians and reptiles from the Neogene (latest Miocene or earliest Pliocene; MN 13/14) locality of Maramena, in northern Greece. The herpetofauna is shown to be extremely diverse, comprising at least 30 different taxa. Amphibians include at least six urodelan (Cryptobranchidae indet., Salamandrina sp., Lissotriton sp. [Lissotriton vulgaris group], Lissotriton sp., Ommatotriton sp., and Salamandra sp.), and three anuran taxa (Latonia sp., Hyla sp., and Pelophylax sp.). Reptiles are much more speciose, being represented by two turtle (the geoemydid Mauremys aristotelica and a probable indeterminate testudinid), at least nine lizard (Agaminae indet., Lacertidae indet., ?Lacertidae indet., aff. Palaeocordylus sp., ?Scincidae indet., Anguis sp., five morphotypes of Ophisaurus, Pseudopus sp., and at least one species of Varanus), and 10 snake taxa (Scolecophidia indet., Periergophis micros gen. et sp. nov., Paraxenophis spanios gen. et sp. nov., Hierophis cf. hungaricus, another distinct “colubrine” morphotype, Natrix aff. rudabanyaensis, and another distinct species of Natrix, Naja sp., cf. Micrurus sp., and a member of the “Oriental Vipers” complex). The autapomorphic features and bizarre vertebral morphology of Periergophis micros gen. et sp. nov. and Paraxenophis spanios gen. et sp. nov. render them readily distinguishable among fossil and extant snakes. Cryptobranchids, several of the amphibian genera, scincids, Anguis, Pseudopus, and Micrurus represent totally new fossil occurrences, not only for the Greek area, but for the whole southeastern Europe. The four different types of serration within the Varanus teeth from Maramena raise questions on the taxonomic importance or the variability of this feature. The large number of distinct amphibian and reptile taxa in Maramena makes this Greek locality by far the most diverse and speciose among all European localities across the latest Miocene and earliest Pliocene. An estimation of the palaeoprecipitation value of the locality is provided. The biogeographic origins of the Maramena herpetofauna are not fully resolved, though certain of its elements were previously only known from the early and middle Miocene of Central Europe. GEORGALIS ET AL.: FOSSIL HERPETOFAUNA MARAMENA 2 Georgios L. Georgalis. Dipartimento di Scienze della Terra, Università di Torino, Via Valperga Caluso 35, 10125 Torino, Italy. dimetrodon82@gmail.com Department of Geosciences, University of Fribourg / Freiburg, Chemin du Musée 6, 1700 Fribourg, Switzerland. Department of Ecology, Laboratory of Evolutionary Biology, Faculty of Natural Sciences, Comenius University in Bratislava, Mlynská dolina, 84215 Bratislava, Slovakia. Andrea Villa. Bayerische Staatssammlung für Paläontologie und Geologie, Richard-Wagner-Straße 10, 80333 Munich, Germany. a.villa@unito.it Dipartimento di Scienze della Terra, Università di Torino, Via Valperga Caluso 35, 10125 Torino, Italy. Martin Ivanov. Department of Geological Sciences, Faculty of Science, Masaryk University, Kotlářská 2, 611 37 Brno, Czech Republic. mivanov@sci.muni.cz Davit Vasilyan. JURASSICA Museum, Fontenais 21, 2900 Porrentruy, Switzerland. Department of Geosciences, University of Fribourg / Freiburg, Chemin du Musée 6, 1700 Fribourg, Switzerland. davitvasilyan@gmail.com Massimo Delfino. Dipartimento di Scienze della Terra, Università di Torino, Via Valperga Caluso 35, 10125 Torino, Italy. massimo.delfino@unito.it Institut Català de Paleontologia Miquel Crusafont, Universitat Autònoma de Barcelona, Edifici ICTA-ICP, Carrer de les Columnes s/n, Campus de la UAB, 08193 Cerdanyola del Vallès, Barcelona, Spain.

reptile
miocene
pliocene
fossil amphibian
south-eastern european region


Reproducible Digital Restoration of Fossils Using Blender

Abstract: Digital restoration of fossils based on computed tomographic (CT) imaging and other scanning technologies has become routine in paleontology. Digital restoration includes the retrodeformation and reconstruction of a fossil specimen. The former involves modification of the original 3D model to reverse post-mortem brittle and plastic deformation; and the latter involves the infilling of fractures, addition of missing pieces, and smoothing of the mesh surface. The restoration process often involves digital editing of the specimen in ways that are difficult to document and reproduce. To record all actions taken during the digital restoration of a fossil, we outline a workflow that generates both the restored bone and the sequence of steps involved in its retrodeformation and reconstruction. Our method can also generate an animation showing the transformation of the original digital model into its final form. We applied this method to a dorsal rib and frontal bone of a small-bodied Jurassic-age armored dinosaur from Africa, the digital restoration of which engaged all modalities of deformation (translation, rotation, scaling, distortion) and reconstruction (fracture infilling, adding missing bone, surface smoothing). Each bone was CT-scanned, segmented, and imported into Blender, an open-source 3D-graphics animation program. Blender has an animation tool called an “armature” that allows for precise control over portions of a surface mesh while keeping a record of manipulations. To retrodeform a fossil, an armature is created and then linked, or “rigged,” to the fossil in order to control the displacement and distortion of its fragments. After using the armature to perform retrodeformation, we use Blender to record the movement and distortion of each fragment and also record reconstructive modifications. By ensuring documentation and reproducibility in an open-source program, our workflow and output open a window onto the heretofore largely hidden process of digital restoration in paleontology.

digital restoration
blender
manipulation


The potential of sedimentary ancient DNA for reconstructing past sea ice evolution

Abstract: Sea ice is a crucial component of the Arctic climate system, yet the tools to document the evolution of sea ice conditions on historical and geological time scales are few and have limitations. Such records are essential for documenting and understanding the natural variations in Arctic sea ice extent. Here we explore sedimentary ancient DNA (aDNA), as a novel tool that unlocks and exploits the genetic (eukaryote) biodiversity preserved in marine sediments specifically for past sea ice reconstructions. Although use of sedimentary aDNA in paleoceanographic and paleoclimatic studies is still in its infancy, we use here metabarcoding and single-species quantitative DNA detection methods to document the sea ice conditions in a Greenland Sea marine sediment core. Metabarcoding has allowed identifying biodiversity changes in the geological record back to almost ~100,000 years ago that were related to changing sea ice conditions. Detailed bioinformatic analyses on the metabarcoding data revealed several sea-ice-associated taxa, most of which previously unknown from the fossil record. Finally, we quantitatively traced one known sea ice dinoflagellate in the sediment core. We show that aDNA can be recovered from deep-ocean sediments with generally oxic bottom waters and that past sea ice conditions can be documented beyond instrumental time scales. Our results corroborate sea ice reconstructions made by traditional tools, and thus demonstrate the potential of sedimentary aDNA, focusing primarily on microbial eukaryotes, as a new tool to better understand sea ice evolution in the climate system.

sedimentary ancient dna
dna
sea ice evolution
marine sediment


Slow dynamics of the Northern Hemisphere glaciation

Abstract: [1] Unraveling the dynamics of the Northern Hemisphere glaciation (NHG) in the Pliocene is a key step toward a quantitative theory of the climate transition from a greenhouse to an icehouse world. Extracting the ice volume signal from marine oxygen isotope (δ18O) records corrupted with “temperature noise” can be accomplished using statistical time series analysis. We use 45 δ18O records from benthic and planktonic foraminifera and globally distributed sites to reconstruct the dynamics of NHG initiation. We compare δ18O amplitudes with those of temperature proxy records and estimate a global ice volume–related increase of 0.4‰, equivalent to an overall sea level lowering of 43 m. We find the NHG started significantly earlier than previously assumed, as early as 3.6 Ma, and ended at 2.4 Ma. This long-term increase points to slow, tectonic forcing such as closing of ocean gateways or mountain building as the root cause of the NHG.

dynamic
northern hemisphere glaciation
pliocene
climate transition


Dental enamel ultrastructure in Ochotona and Prolagus (Mammalia: Lagomorpha: Ochotonidae) from three late Miocene localities in Ukraine

Abstract: The comparison of the dental enamel of late Miocene ochotonids from the Ukraine shows only very subtle differences. The ultrastructure of premolars, molars, and incisors of pikas: Ochotona and Prolagus (Lagomorpha, Ochotonidae) from three localities (Popovo 3, MN 11; Verkhnya Krynytsya 2, MN 12; Lobkove, MN 12/13) is mainly multilayered. In cheek teeth it is composed of a radial (up to 60% of total enamel thickness) and an irregular layer (up to 40%). There is almost no difference in the enamel ultrastructure between remains of different geological age and tooth position (premolars, molars). However, the lower incisor of Ochotona differs from the upper one in having a radial enamel and a HSB layer, whereas the upper have a radial and a tangential enamel. Minor differences between the various species of Ochotona and Prolagus could be recognised in the arrangement of the prisms.

enamel ultrastructure
lagomorpha
ochotonidae


Clonal growth, algal symbiosis, and reef formation by corals

Abstract: The occurrence of zooxanthellae in Recent scleractinian corals is strongly correlated with their growth form, corallite size, and degree of morphological integration of corallites. The great majority of zooxanthellate corals are multiserial with small, highly integrated corallites, whereas most corals lacking zooxanthellae are solitary or uniserial colonial forms with large, poorly integrated corallites. Beginning in the Jurassic, fossil scleractinian faunas are morphologically similar to Recent faunas dominated by zooxanthellate species, strongly implying that most scleractinians contained zooxanthellae by that time. Evidence for Siluro–Devonian tabulates and Triassic scleractinians is equivocal but still suggests the presence of zooxanthellae in these corals. In contrast, morphological evidence suggests that rugosan corals lacked zooxanthellae. Most populations of Recent zooxanthellate corals contribute to reef formation, but many do not. Similarly, fossil corals interpreted to contain zooxanthellae on morphological grounds did not always form reefs. Recent reef formation depends upon a host of environmental factors that have little to do with the possession of zooxanthellae per se. Coral morphology should be a better predictor of the presence of zooxanthellae in fossil corals than their association with reefs.

reef formation
coral
growth form
zooxanthellate coral


The hatching mechanism of 130‐million‐year‐old insects: an association of neonates, egg shells and egg bursters in Lebanese amber

Abstract: Hatching is a pivotal moment in the life of most animals. Diverse chemical, behavioural and mechanical methods have evolved in metazoans to break the egg membranes. Among them, many arthropod and vertebrate embryos hatch using ephemeral, frequently convergent structures known as egg bursters. However, the evolutionary processes by which hatching mechanisms and related embryonic structures became established in deep time are poorly understood due to a nearly complete absence from the fossil record. Herein we describe an exceptional c. 130‐million‐year‐old association in Lebanese amber composed of multiple neonate green lacewing larvae, Tragichrysa ovoruptora gen. et sp. nov. (Neuroptera, Chrysopoidea), and conspecific egg remains. Egg bursters with a serrated blade bearing a short process are attached to three longitudinally split egg shells. Embryos of extant green lacewing relatives (Chrysopidae) utilize this egg burster morphotype to open a vertical slit on the egg, after which the burster is moulted and left joined to the empty egg shell. Additionally, the new larval species has extremely elongate dorsal tubercles, an adaptation to carry exogenous debris for protection and camouflage also known from other Cretaceous chrysopoids but absent in modern relatives. The present discovery demonstrates that the hatching mechanism of modern green lacewings was established in the chrysopoid lineage by the Early Cretaceous and proves through direct fossil evidence how some morphological traits related to hatching and linked behaviours, at least in insect embryos, have been subject to a high degree of evolutionary conservatism.

insect
egg shell
lebanese amber
chrysopoidea


A nomenclature for vertebral laminae in sauropods and other saurischian dinosaurs

Abstract: ABSTRACT The vertebrae of sauropods are characterized by numerous bony struts that connect the costovertebral and intervertebral articulations, centrum, and neural spine of the presacral, sacral, and anterior caudal vertebrae. A nomenclature for sauropod vertebral laminae is proposed that: 1) utilizes the morphological landmarks connected by the laminae (rather than their spatial orientation); and 2) provides the same name for serial homologues. This landmark-based nomenclature for vertebral laminae, which establishes the first criterion of homology (similarity), is the first step towards interpreting their phylogenetic significance. Nineteen different neural arch laminae are identified in sauropods, although all are never present in a single vertebra. Vertebral laminae can be divided into four regional categories, with each distinct lamina abbreviated with a simple four-letter acronym: diapophyseal laminae; parapophyseal laminae; zygapophyseal laminae; and spinal laminae. The distribution of neural arch ...

nomenclature
vertebral laminae
sauropod
neural arch


High concentration of long‐snouted beaked whales (genus Messapicetus) from the Miocene of Peru

Abstract: Abstract:  Eight skulls of beaked whales (Cetacea, Odontoceti, Ziphiidae), in six cases associated with elements of the mandible, were collected from a limited area (about 1.5 km2) and roughly from the same stratigraphic horizon at Cerro Colorado, 35 km south‐south‐west of the city of Ica (Peru), where the late Middle Miocene basal strata of the Pisco Formation crop out. They represent the highest concentration reported of fossil Ziphiidae. These finely preserved Cerro Colorado fossils are described and assigned to a new species Messapicetus gregarius, together with another specimen collected from sediments of the same age at Cerro la Bruja (33 km south‐east to Cerro Colorado). Messapicetus gregarius shares with M. longirostris Bianucci, Landini and Varola, 1992 (Tortonian of Italy), an extremely elongated rostrum, but is clearly different from the Italian species in the more distinct maxillary tubercle and prominential notch, the more robust premaxillary crest, and the abrupt ventrolateral descent of the medial margin of the maxilla from the vertex. A parsimony analysis reveals that Messapicetus belongs to a basal clade, which includes other ziphiids with a dorsally closed mesorostral groove and prenarial basin. The high concentration of specimens belonging to the same species (some of them tentatively identified as adult males and females), combined with the presence of a calf, supports the hypothesis of site fidelity; these cetaceans might have lived in a limited region for a long period for both breeding and feeding. Besides the eight specimens of M. gregarius, strata at Cerro Colorado include many other cetacean remains (with several specimens of the pontoporiid Brachydelphis including a foetus), pinnipeds, turtles, fishes, and birds.


A palaeolimnological perspective to understand regime-shift dynamics in two Yangtze-basin lakes

Abstract: Natural and human disturbances have caused widespread regime shifts in shallow lakes of the lower Yangtze basin (LYB, China) resulting in a severe decline of ecosystem services. Improved understanding of the relationship between environmental forcing and ecosystem response, and the mechanisms behind regime shifts has significant implications for management. However, the patterns of these regime shifts and the underlying internal mechanisms are less known. In this study, two typical lakes (Chaohu and Zhangdu) from the LYB were selected to determine the trajectories of ecological regime shifts, both of which transitioned from vegetation- to plankton-dominated states several decades ago. Ecological trajectories since the 1900s in both lakes were reconstructed using palaeolimnological proxies, mainly diatom assemblages. Although results show that regime shifts occurred in both lakes in the 1970s and the 1950s, respectively, their inherent mechanisms were different. In Lake Zhangdu, altered hydrological conditions pushed the ecosystem across an ecological threshold, providing an example of a driver-mediated regime shift. In Lake Chaohu, ongoing nutrient loading influenced ecosystem processes and drove the lake to an alternative stable state, potentially presenting an example of a critical transition after a loss of resilience. This research indicates that palaeolimnological perspectives can provide insights into regime shift changes, as well as important information regarding which restoration methods should be tailored to individual lakes.

palaeolimnological perspective
lake
diatom assemblage


Barium distributions in teeth reveal early life dietary transitions in primates

Abstract: Early life dietary transitions reflect fundamental aspects of primate evolution and are important determinants of health in contemporary human populations1,2. Weaning is critical to developmental and reproductive rates; early weaning can have detrimental health effects but enables shorter inter-birth intervals, which influences population growth3. Uncovering early life dietary history in fossils is hampered by the absence of prospectively-validated biomarkers that are not modified during fossilisation4. Here we show that major dietary shifts in early life manifest as compositional variations in dental tissues. Teeth from human children and captive macaques, with prospectively-recorded diet histories, demonstrate that barium (Ba) distributions accurately reflect dietary transitions from the introduction of mother’s milk and through the weaning process. We also document transitions in a Middle Palaeolithic juvenile Neanderthal, which shows a pattern of exclusive breastfeeding for seven months, followed by seven months of supplementation. After this point, Ba levels in enamel returned to baseline prenatal levels, suggesting an abrupt cessation of breastfeeding at 1.2 years of age. Integration of Ba spatial distributions and histological mapping of tooth formation enables novel studies of the evolution of human life history, dietary ontogeny in wild primates, and human health investigations through accurate reconstructions of breastfeeding history.

dietary transition
primate
neanderthal
tooth
barium


Changes in the Western Boundary Undercurrent Outflow since the Last Glacial Maximum, from smectite/illite ratios in deep Labrador Sea sediments

Abstract: High-resolution mineralogical studies were performed on late glacial and deglacial sediments from two deep piston cores from the Labrador Sea, located at the inlet (SW Greenland Rise) and outlet (Labrador Rise) of the Western Boundary Undercurrent (WBUC) gyre. At the two sites, smectites transported from the eastern Iceland and Irminger basins by the WBUC are observed. Clay mineral changes are used as proxies for the paleointensity reconstruction of the WBUC. On the Greenland Rise, a clay mineral index (smectite/illite (S/I) ratio) is defined. A S/I ratio of ∼1 characterized the Last Glacial Maximum. It increased after ∼17 ka. and reached a maximum value of 4 during the early Holocene. The mineralogical changes are gradual and do not show any reversal during the Younger Dryas. This pattern, which is confirmed by first-order estimations of smectite and illite fluxes, suggests gradually increasing sedimentary fluxes and WBUC intensity since the Last Glacial Maximum. A peak in the velocity of the WBUC at ∼9 ka, as recorded by clay assemblages, is consistent with other regional studies based on pollen, foraminifera, or grain-size measurements. A massive dilution of smectites by illite and chlorite (S/I ≈ 3) occurs at ∼8.5 ka. It corresponds to a period of rapid sediment accumulation and reflects an intensified illite-rich detrital supply by meltwaters from the southern Greenland Ice Margin. On the Labrador Rise, the smectite content varies between 20 and 60% with no obvious trend through time. The mineralogical composition is strongly influenced by ice-rafted deposition and by the abundance of fast deposit units (cf. Heinrich layers in the North Atlantic) which contain abundant detrital carbonates spilled-over from the North-West Atlantic Mid-Ocean Channel. In such layers, smectites are present but are diluted by the addition of illites, chlorites, and kaolinites. This provides evidence for a discrete and continuous WBUC supply of fine particles from the Irminger and Iceland Basins as far as the southeastern part of the Labrador Basin. Early deglacial smectite-rich layers (up to 60%) are also observed at this site. They indicate an increase in the outflow of the WBUC at ∼13.5 ka. (Bolling-Allerod), as previously reported from grain size or foraminiferal assemblage studies.


Evolution of ecospace occupancy by Mesozoic marine tetrapods

Abstract: Ecology and morphology are different, and yet in comparative studies of fossil vertebrates the two are often conflated. The macroevolution of Mesozoic marine tetrapods has been explored in terms of morphological disparity, but less commonly using ecological‐functional categories. Here we use ecospace modelling to quantify ecological disparity across all Mesozoic marine tetrapods. We document the explosive radiation of marine tetrapod groups in the Triassic and their rapid attainment of high ecological disparity. Late Triassic extinctions led to a marked decline in ecological disparity, and the recovery of ecospace and ecological disparity was sluggish in the Early Jurassic. High levels of ecological disparity were again achieved by the Late Jurassic and maintained during the Cretaceous, when the ecospace became saturated by the Late Cretaceous. Sauropterygians, turtles and ichthyosauromorphs were the largest contributors to ecological disparity. Throughout the Mesozoic, we find that established groups remained ecologically conservative and did not explore occupied or vacant niches. Several parts of the ecospace remained vacant for long spans of time. Newly evolved, radiating taxa almost exclusively explored unoccupied ecospace, suggesting that abiotic releases are needed to empty niches and initiate diversification. In the balance of evolutionary drivers in Mesozoic marine tetrapods, abiotic factors were key to initiating diversification events, but biotic factors dominated the subsequent generation of ecological diversity.

mesozoic
marine tetrapod
diversification
sea


A new time tree reveals Earth history’s imprint on the evolution of modern birds

Abstract: Estimates of the timing of evolution of modern birds reveals the influence of paleogeography and paleoclimate on diversification. Determining the timing of diversification of modern birds has been difficult. We combined DNA sequences of clock-like genes for most avian families with 130 fossil birds to generate a new time tree for Neornithes and investigated their biogeographic and diversification dynamics. We found that the most recent common ancestor of modern birds inhabited South America around 95 million years ago, but it was not until the Cretaceous-Paleogene transition (66 million years ago) that Neornithes began to diversify rapidly around the world. Birds used two main dispersion routes: reaching the Old World through North America, and reaching Australia and Zealandia through Antarctica. Net diversification rates increased during periods of global cooling, suggesting that fragmentation of tropical biomes stimulated speciation. Thus, we found pervasive evidence that avian evolution has been influenced by plate tectonics and environmental change, two basic features of Earth’s dynamics.

new time tree
modern bird
diversification
neornithes


Population Genomic Analysis of Ancient and Modern Genomes Yields New Insights into the Genetic Ancestry of the Tyrolean Iceman and the Genetic Structure of Europe

Abstract: Genome sequencing of the 5,300-year-old mummy of the Tyrolean Iceman, found in 1991 on a glacier near the border of Italy and Austria, has yielded new insights into his origin and relationship to modern European populations. A key finding of that study was an apparent recent common ancestry with individuals from Sardinia, based largely on the Y chromosome haplogroup and common autosomal SNP variation. Here, we compiled and analyzed genomic datasets from both modern and ancient Europeans, including genome sequence data from over 400 Sardinians and two ancient Thracians from Bulgaria, to investigate this result in greater detail and determine its implications for the genetic structure of Neolithic Europe. Using whole-genome sequencing data, we confirm that the Iceman is, indeed, most closely related to Sardinians. Furthermore, we show that this relationship extends to other individuals from cultural contexts associated with the spread of agriculture during the Neolithic transition, in contrast to individuals from a hunter-gatherer context. We hypothesize that this genetic affinity of ancient samples from different parts of Europe with Sardinians represents a common genetic component that was geographically widespread across Europe during the Neolithic, likely related to migrations and population expansions associated with the spread of agriculture.

new insight
genetic structure
europe
migration


Serpens endocrania symmetrica (SES): a new term and a possible clue for identifying intrathoracic disease in skeletal populations.

Abstract: This paper describes a phenomenon in the endocranial plate, which we have termed "serpens endocrania symmetrica" (SES), and discusses its value as a diagnostic tool. The affected discolored bone area exhibits disruption of the endocranial surface, lending it a maze-like appearance. Histological sections demonstrate that the process is limited to the most superficial portion of the endocranium, with no diploic and ectocranial involvement (sinus areas excepted). Adult skulls (n = 1,884) from the Hamann-Todd collection (HTH), housed at the Cleveland Museum of Natural History, were utilized for the present study. SES was recognized in 32 of the 1,884 skulls studied (1.7%). The frequency of SES among individuals reported to have died from tuberculosis (TB) was 4.4%. The rate of SES in the non-TB sample was only 0.53%. The locations were as follows: limited to sinus area, 28.1%; calvarium (excluding the sinuses), 46.9%; sinus + calvarium, 25.0%. SES was bilateral in 90.9% of cases. Twenty-five of the 32 individuals (78.1%) with SES in the HTH collection had tuberculosis specifically listed as the cause of death. Six of the other 7 individuals had infections other than TB. In 29 of the 32 individuals with SES, infection involved structures within the thorax. As SES was also associated with another osteological phenomenon known to represent pulmonary disease, i.e., hypertrophic osteoarthropathy (HOA; 68.0% of SES individuals also had HOA), SES may be of diagnostic value in paleopathology for the recognition of intrathoracic disease, and perhaps tuberculosis.

ses
intrathoracic disease
disease
ectocranial involvement
serpen endocrania symmetrica


Pteropods are excellent recorders of surface temperature and carbonate ion concentration

Abstract: Pteropods are among the first responders to ocean acidification and warming, but have not yet been widely explored as carriers of marine paleoenvironmental signals. In order to characterize the stable isotopic composition of aragonitic pteropod shells and their variation in response to climate change parameters, such as seawater temperature, pteropod shells (Heliconoides inflatus) were collected along a latitudinal transect in the Atlantic Ocean (31° N to 38° S). Comparison of shell oxygen isotopic composition to depth changes in the calculated aragonite equilibrium oxygen isotope values implies shallow calcification depths for H. inflatus (75 m). This species is therefore a good potential proxy carrier for past variations in surface ocean properties. Furthermore, we identified pteropod shells to be excellent recorders of climate change, as carbonate ion concentration and temperature in the upper water column have dominant influences on pteropod shell carbon and oxygen isotopic composition. These results, in combination with a broad distribution and high abundance, make the pteropod species studied here, H. inflatus, a promising new proxy carrier in paleoceanography.

excellent recorder
carbonate ion concentration
paleoceanography
pteropod


Nonmineralized triradial conulariids from the lowermost Cambrian Stage 2 of the Olenek Uplift, Siberian Platform

Abstract: Abstract. In the early Cambrian fossil record, triradial symmetry is typical for anabaritids and occurs among carinachitids. The former are an extinct group of minute benthic cnidarians covered with a calcareous tubular exoskeleton. The origin of the anabaritids is poorly understood, but previously reported triradial pyramid-shaped steinkerns and molds of the oldest conulariids, Vendoconularia, from the upper Ediacaran of the White Sea region suggested the anabaritids were closely related to conulariids. However, triradial symmetry could originate independently in different lineages in the late Ediacaran and early Cambrian. Herein we describe a new taxon, Ilankirus kessyusensis new genus new species, from the base of the Cambrian Stage 2 of the Olenek Uplift (Siberian Platform). These fossils occur as ornamented steinkerns in the shape of trilateral pyramids and lack any relics of a mineralized exoskeleton. Abundant plastic deformations and fractures of the casts suggest the organism was weakly if at all mineralized. The steinkerns are encrusted with a thin patina of iron-rich chlorite (chamosite) formed because of a multistage diagenetic replacement of authigenic glauconite (glauconite–berthierine–chamosite) under reducing conditions of oxygen-depauperate pore- and seawater. Both lacking two major autapomorphies of the crown-group conulariids (mineralized periderm and quadrate cross section of the oral region of the periderm), the late Ediacaran triradial Vendoconularia and Terreneuvian Ilankirus represent stem-group conulariids.


The PRISM (Pliocene palaeoclimate) reconstruction: time for a paradigm shift

Abstract: Global palaeoclimate reconstructions have been invaluable to our understanding of the causes and effects of climate change, but single-temperature representations of the oceanic mixed layer for data–model comparisons are outdated, and the time for a paradigm shift in marine palaeoclimate reconstruction is overdue. The new paradigm in marine palaeoclimate reconstruction stems the loss of valuable climate information and instead presents a holistic and nuanced interpretation of multi-dimensional oceanographic processes and responses. A wealth of environmental information is hidden within the US Geological Survey's Pliocene Research, Interpretation and Synoptic Mapping (PRISM) marine palaeoclimate reconstruction, and we introduce here a plan to incorporate all valuable climate data into the next generation of PRISM products. Beyond the global approach and focus, we plan to incorporate regional climate dynamics with emphasis on processes, integrating multiple environmental proxies wherever available in order to better characterize the mixed layer, and developing a finer time slice within the Mid-Piacenzian Age of the Pliocene, complemented by underused proxies that offer snapshots into environmental conditions. The result will be a proxy-rich, temporally nested, process-oriented approach in a digital format—a relational database with geographic information system capabilities comprising a three-dimensional grid representing the surface layer, with a plethora of data in each cell.


Palaeozoic, Mesozoic and contemporaneous megaspores from the Tertiary of southern England: indicators of sedimentary provenance and ancient vegetation

Abstract: Megaspores are recorded from several localities in the Thanet and Reading Beds (upper Palaeocene) of southern England. Evidence from their taxonomic affinity, colour, compression and state of preservation indicates three separate groups: two reworked from lower Westphalian Coal Measures and Lower Cretaceous sequences, respectively, and one of contemporaneous forms. Mesozoic megaspores redeposited in the British Tertiary have not previously been recorded. Isolated Carboniferous forms have been found before but their possible value in provenance studies has not been fully explored. The new material includes a diverse assemblage of numerous Westphalian and Lower Cretaceous forms from a single horizon in the Thanet Beds. Of possible source areas it seems most likely that these spores were reworked from the Moray Firth Basin, and elsewhere near the present eastern coast of Scotland, by means of longshore drift following a roughly N–S palaeocoastline. Evidence from other studies of heavy mineral assemblages and palaeogeography also indicates derivation of Thanet Beds sediments by this means. The Cenozoic megaspores include an Azolla (water fern) and two distinct lycopsid forms, one probably of selaginellalean and one of isoetalean affinity. These latter provide the first clear evidence of lycopsids in British Tertiary floras and expand our knowledge of freshwater macrophytes of that time. The assemblages of Minerisporites show morphological trends which may prove to be of biostratigraphic value.

megaspore
southern england
minerisporites


Middle Cambrian through lowermost Ordovician conodonts from Hunan, South China

Abstract: Abstract Since 1986, samples with a total mass of more than 14,000 kg, mainly from three key sections in western Hunan, South China, have been processed for conodonts. Previous work mainly focused on biostratigraphy, but the taxonomy has been performed only on the faunas of the middle Cambrian. Described herein are conodonts of the upper Cambrian (Furongian Series) through lowermost Ordovician from Hunan, South China. Conodonts of the middle Cambrian are redescribed, based on material that has been recovered for more than three decades. The fauna consists of 82 species belonging to 36 genera. Newly established genera are Lugnathus n. gen., Miaognathus n. gen., Millerodontus n. gen., Tujiagnathus n. gen., Wangcunella n. gen. and Wangcunognathus n. gen. New species are Coelocerodontus hunanensis n. sp., Furnishina wangcunensis n. sp., Laiwugnathus hunanensis n. sp., Laiwugnathus transitans n. sp., Lugnathus hunanensis n. gen. n. sp., Miaognathus multicostatus n. gen. n. sp., Millerodontus intermedius n. gen. n. sp., Prosagittodontus compressus n. sp., Tujiagnathus gracilis n. gen. n. sp., Wangcunella conicus n. gen. n. sp., Wangcunognathus elegans n. gen. n. sp., Westergaardodina dimorpha n. sp., Westergaardodina gigantea n. sp., and Westergaardodina sola n. sp. The taxonomy of some conodont genera is revised. In the light of histological investigation, genera are assigned to euconodonts, paraconodonts, or protoconodonts. The 13 conodont zones previously proposed in the middle Cambrian through lowermost Ordovician remain the same, but taxa within these conodont zones are documented more clearly because of the revised taxonomy proposed herein.


Cranial anatomy and taxonomy of the erythrosuchid archosauriform ‘Vjushkovia triplicostata’ Huene, 1960, from the Early Triassic of European Russia

Abstract: Erythrosuchidae are a globally distributed and important group of apex predators that occupied Early and Middle Triassic terrestrial ecosystems following the Permo-Triassic mass extinction. The stratigraphically oldest known genus of Erythrosuchidae is Garjainia Ochev, 1958, which is known from the late Early Triassic (late Olenekian) of European Russia and South Africa. Two species of Garjainia have been reported from Russia: the type species, Garjainia prima Ochev, 1958, and ‘Vjushkovia triplicostata’ von Huene, 1960, which has been referred to Garjainia as either congeneric (Garjainia triplicostata) or conspecific (G. prima). The holotype of G. prima has received relatively extensive study, but little work has been conducted on type or referred material attributed to ‘V. triplicostata’. However, this material includes well-preserved fossils representing all parts of the skeleton and comprises seven individuals. Here, we provide a comprehensive description and review of the cranial anatomy of material attributed to ‘V. triplicostata’, and draw comparisons with G. prima. We conclude that the two Russian taxa are indeed conspecific, and that minor differences between them result from a combination of preservation or intraspecific variation. Our reassessment therefore provides additional information on the cranial anatomy of G. prima. Moreover, we quantify relative head size in erythrosuchids and other early archosauromorphs in an explicit phylogenetic context for the first time. Our results show that erythrosuchids do indeed appear to have disproportionately large skulls, but that this is also true for other early archosauriforms (i.e. proterosuchids), and may reflect the invasion of hypercarnivorous niches by these groups following the Permo-Triassic extinction.

erythrosuchid
vjushkovia triplicostata
russia
holotype
cranial anatomy


Cavity-dwelling microorganisms from the Ediacaran and Cambrian of North Greenland (Laurentia)

Abstract: Abstract. Records of diagenetically mineralized, filamentous, cavity-dwelling microorganisms extend back to strata from the early Paleoproterozoic (2400 Ma). In North Greenland (Laurentia), they are first known from the Ediacaran (Neoproterozoic; ca. 600 Ma) Portfjeld Formation of southern Peary Land, in association with a biota similar to that of the Doushantuo Formation of China. The Portfjeld Formation cavity dwellers are compared with more widespread occurrences in Cambrian (Series 2, Stage 4, Miaolingian Series) strata from the same region in which assemblages in postmortal shelter structures within articulated acrotretoid brachiopods and other invertebrates are common. All specimens were recovered by digestion of carbonate samples in weak acids. The described fossils are preserved as mineral encrusted threads but this diagenetic phosphatization unfortunately obscures their biological identity.


Dynamic evolutionary change in post-Paleozoic echinoids and the importance of scale when interpreting changes in rates of evolution

Abstract: Significance Biodiversification studies have often relied on constant-rate models of diversification. More recently, however, there has been an effort to identify changes in diversification rates within clades. This effort has largely focused on models of declining rates because many clades appear to have high initial rates, followed by slow-downs as ecological space fills. Here we provide an example of a 265 million-year-old marine invertebrate clade where evolutionary rates show a net increase over time instead. This is punctuated by intervals of high rates of morphological evolution, coinciding with major shifts in lifestyle and the evolution of new subclades. This study demonstrates the dynamic nature of evolutionary change within major clades. How ecological and morphological diversity accrues over geological time has been much debated by paleobiologists. Evidence from the fossil record suggests that many clades reach maximal diversity early in their evolutionary history, followed by a decline in evolutionary rates as ecological space fills or due to internal constraints. Here, we apply recently developed methods for estimating rates of morphological evolution during the post-Paleozoic history of a major invertebrate clade, the Echinoidea. Contrary to expectation, rates of evolution were lowest during the initial phase of diversification following the Permo-Triassic mass extinction and increased over time. Furthermore, although several subclades show high initial rates and net decreases in rates of evolution, consistent with “early bursts” of morphological diversification, at more inclusive taxonomic levels, these bursts appear as episodic peaks. Peak rates coincided with major shifts in ecological morphology, primarily associated with innovations in feeding strategies. Despite having similar numbers of species in today’s oceans, regular echinoids have accrued far less morphological diversity than irregular echinoids due to lower intrinsic rates of morphological evolution and less morphological innovation, the latter indicative of constrained or bounded evolution. These results indicate that rates of evolution are extremely heterogenous through time and their interpretation depends on the temporal and taxonomic scale of analysis.


Abstract:
Martinez, J.-N. & Sudre, 1. 1995 11 30 The astragalus of Paleogene artiodactyls: comparative morphology, variability and prediction of body mass. Lethaia, Vol. 28, pp. 197–209. Oslo. ISSN 0024–1164.

The morphology of the astragalus is analysed in nineteen Paleogene artiodactyls (suborders Palaeodonta, Suina, Ancodonta and Ruminantia). This morphology is related to the functional adaptations of the appendicular skeleton, but some diagnostic characters can be seen at the family level. For the populations examined, the proportions of this bone show a low intraspecific variability, which does not allow detection of any dimorphism. An allometric relationship between the dimensions of the astragalus and the body mass has been established for extant species, allowing estimates for the fossil species. In most cases, the interval between the two extreme estimations using the astragalus includes the estimated body mass using M/1 area. The limits of this method are discussed, and it is suggested that the dimensions of the astragalus give a better estimation of the body mass than the dental area. □Artiodactyls, astragalus, comparative morphology, body mass, allometry, Paleogene.

astragalus
artiodactyls
morphology
body mass


Extinction Vulnerability and Selectivity: Combining Ecological and Paleontological Views

Abstract: ▪ Abstract Extinction is rarely random across ecological and geological time scales. Traits that make some species more extinction-prone include individual traits, such as body size, and abundance. Substantial consistency appears across ecological and geological time scales in such traits. Evolutionary branching produces phylogenetic (as often measured by taxonomic) nesting of extinction-biasing traits at many scales. An example is the tendency, seen in both fossil and modern data, for higher taxa living in marine habitats to have generally lower species extinction rates. At lower taxononomic levels, recent bird and mammal extinctions are concentrated in certain genera and families. A fundamental result of such selectivity is that it can accelerate net loss of biodiversity compared to random loss of species among taxa. Replacement of vulnerable taxa by rapidly spreading taxa that thrive in human-altered environments will ultimately produce a spatially more homogenized biosphere with much lower net diversity.

selectivity
extinction vulnerability
high taxa


A one-billion-year-old multicellular chlorophyte

Abstract: Chlorophytes (which represent a clade within the Viridiplantae and a sister group of the Streptophyta) probably dominated marine export bioproductivity and played a key role in facilitating ecosystem complexity before the Mesozoic diversification of phototrophic eukaryotes such as diatoms, coccolithophorans, and dinoflagellates. Molecular clock and biomarker data indicate that chlorophytes diverged in the Mesoproterozoic or early Neoproterozoic, followed by their subsequent phylogenetic diversification, multicellular evolution, and ecological expansion in the late Neoproterozoic and Paleozoic. This model, however, has not been rigorously tested with paleontological data because of the scarcity of Proterozoic chlorophyte fossils. Here we report abundant millimeter-sized, multicellular, and morphologically differentiated macrofossils from ~1,000 Ma rocks. These fossils are described as Proterocladus antiquus new species and are interpreted as benthic siphonocladalean chlorophytes, suggesting that chlorophytes acquired macroscopic size, multicellularity, and cellular differentiation nearly a billion years ago, much earlier than previously thought.

chlorophyte
diversification
proterocladus antiquus


Paleoneurology of Teyumbaita sulcognathus (Diapsida: Archosauromorpha) and the sense of smell in rhynchosaurs

Abstract: Rhynchosaurs were a group of archosauromorphs that dominated the guild of herbivores during the early Late Triassic. Despite the large number of specimens available, paleobiological studies are rare in the literature, especially concerning the South American species. The present study analyzes the paleoneurology of Teyumbaita sulcognathus, a Brazilian hyperodapedontine rhynchosaur, along with its nasal cavity, based on tomographic images of the specimen UFRGS-PV-0232-T. Although the endocast only reveals the morphology of the posterior half of the encephalon due to the incompletely ossified braincase, it is possible to infer the presence of great olfactory bulbs because of their impressions left on the ventral surface of the frontals. Although the snout is relatively short, the areas of the nasal cavity probably devoted to olfaction were also large and, along with the size of the olfactory bulbs, it is possible to infer that olfaction was important for the behavior and ecology of T. sulcognathus, as previously proposed for Hyperodapedon.

teyumbaita sulcognathus
rhynchosaur
late triassic
paleoneurology


Abstract: Shen, Y. & Wang, X.L., July 2016. Howchinia Cushman, 1927 (Foraminifera) from the Mississippian Bei’an Formation and its distribution in South China. Alcheringa 40, xxx–xxx. ISSN 0311-5518. Howchinia Cushman is a useful biostratigraphic marker for Mississippian rocks. In South China, Howchinia has been reported from four sections: the Bei’an, Baping, Naqing and Yashui sections; with high species diversity in the Bei’an section. Ten species from the Mississippian Bei’an Formation in the Bei’an section are described in this paper: Howchinia bradyana, H. beleutensis, H. gibba, H. plana, H. convexa, H. subconica, H. subplana, Howchinia sp. A, Howchinia sp. B. and Howchinia beianensis sp. nov. Howchinia ranges from late Visean to early Bashkirian in South China. Howchinia species inhabited both shallow-water and relatively deep-water environments. Yang Shen [shenybj@126.com] and Xun-Lian Wang [wxl@cugb.edu.cn], State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences, 29 Xueyuan Road, Beijing 100083, PR China.

foraminifera
south china
howchinia cushman


Sedimentary phosphorus record from the Oman margin: New evidence of high productivity during glacial periods

Abstract: [1] The northern region of the Arabian Sea is one of the biologically most fertile regions of the world oceans, with present productivity rates varying between 150 and 2500 mgC/m2 × day [Madhupratap et al., 1996]. This is related to the influence of the southwesterly summer monsoon which causes vigorous upwelling along the Oman margin. Upwelling ceases during northeasterly winter monsoon activity; productivity rates, however, remain relatively high (about 800 mgC/m2 × day), related to deep water mixing [Madhupratap et al., 1996]. The goal of this study is to verify if during the last glacial period, a period in which winter monsoon conditions prevailed, productivity rates were similarly high. With an analysis of phosphorus phases, stable nitrogen isotopes, organic matter content, and bulk mineralogy of the upper 10 m of the cores of ODP Hole 724C (corresponding to the last 140,000 years, sample resolution is ∼5 kyr), we provide new evidence of high productivity during this last glacial period (marine isotopic stages 2, 3, and 4). This was probably related to the combined effect of (1) increased eolian input of iron-containing dust due to dryness on the adjacent continent and stronger winter monsoon, and (2) regeneration and diffusion of dissolved phosphorus from the sediments to the water column due to variations in the position and intensity of the Oxygen Minimum Zone. These findings suggest that there is no one-to-one relationship between summer monsoon activity and productivity, which emerges to be a quasi-persistent phenomenon across glacial and interglacial stages.

new evidence
glacial period
winter monsoon


Ignoring Fossil Age Uncertainty Leads to Inaccurate Topology and Divergence Time Estimates in Time Calibrated Tree Inference

Abstract: Time calibrated trees are challenging to estimate for many extinct groups of species due to the incompleteness of the rock and fossil records. Additionally, the precise age of a sample is typically not known as it may have occurred at any time during the time interval spanned by the rock layer. Bayesian phylogenetic approaches provide a coherent framework for incorporating multiple sources of evidence and uncertainty. In this study, we simulate datasets with characteristics typical of Palaeozoic marine invertebrates, in terms of character and taxon sampling. We use these datasets to examine the impact of different age handling methods on estimated topologies and divergence times obtained using the fossilized birth-death process. Our results reiterate the importance of modeling fossil age uncertainty, although we find that the relative impact of fossil age uncertainty depends on both fossil taxon sampling and character sampling. Sampling the fossil ages as part of the inference gives topology and divergence time estimates that are as good as those obtained by fixing ages to the truth, whereas fixing fossil ages to incorrect values results in higher error and lower coverage. The relative effect increases with increased fossil and character sampling. Modeling fossil age uncertainty is thus critical, as fixing incorrect fossil ages will negate the benefits of improved fossil and character sampling.

fossil age uncertainty
topology
birth-death process


Biological evidence supports an early and complex emergence of the Isthmus of Panama

Abstract: Significance The formation of the Isthmus of Panama, which linked North and South America, is key to understanding the biodiversity, oceanography, atmosphere, and climate in the region. Despite its importance across multiple disciplines, the timing of formation and emergence of the Isthmus and the biological patterns it created have been controversial. Here, we analyze molecular and fossil data, including terrestrial and marine organisms, to show that biotic migrations across the Isthmus of Panama began several million years earlier than commonly assumed. An earlier evolution of the Isthmus has broad implications for the mechanisms driving global climate (e.g., Pleistocene glaciations, thermohaline circulation) as well as the rich biodiversity of the Americas. The linking of North and South America by the Isthmus of Panama had major impacts on global climate, oceanic and atmospheric currents, and biodiversity, yet the timing of this critical event remains contentious. The Isthmus is traditionally understood to have fully closed by ca. 3.5 million years ago (Ma), and this date has been used as a benchmark for oceanographic, climatic, and evolutionary research, but recent evidence suggests a more complex geological formation. Here, we analyze both molecular and fossil data to evaluate the tempo of biotic exchange across the Americas in light of geological evidence. We demonstrate significant waves of dispersal of terrestrial organisms at approximately ca. 20 and 6 Ma and corresponding events separating marine organisms in the Atlantic and Pacific oceans at ca. 23 and 7 Ma. The direction of dispersal and their rates were symmetrical until the last ca. 6 Ma, when northern migration of South American lineages increased significantly. Variability among taxa in their timing of dispersal or vicariance across the Isthmus is not explained by the ecological factors tested in these analyses, including biome type, dispersal ability, and elevation preference. Migration was therefore not generally regulated by intrinsic traits but more likely reflects the presence of emergent terrain several millions of years earlier than commonly assumed. These results indicate that the dramatic biotic turnover associated with the Great American Biotic Interchange was a long and complex process that began as early as the Oligocene–Miocene transition.


Enamel microstructure of Recent and fossil Canidae (Carnivora: Mammalia)

Abstract: ABSTRACT The tooth enamel of living and fossil Canidae has been studied to test the hypothesis that a special type of Hunter-Schreger bands (HSB), termed zigzag HSB, is associated with bone consumption. It is shown that in the enamel of Canidae, as in other Carnivora, three types of HSB occur: (1) undulating, (2) acute-angled, and (3) zigzag HSB. Mapping the occurrence of these different types on to the proposed phylogeny of the Canidae indicates that zigzag HSB were derived from undulating bands. Undulating HSB, which have a three-dimensional simple structure, are associated with an insectivorous to carnivorous diet, whereas zigzag HSB occur in taxa that consume bone. Complex three-dimensional zigzag HSB increase the resistance of enamel to formation and propagation of cracks under greater loading of the teeth during bone crushing.


Strontium and carbon isotopic evidence for decoupling of pCO2 from continental weathering at the apex of the late Paleozoic glaciation

Abstract: Earth’s penultimate icehouse (ca. 340–285 Ma) was a time of low atmospheric pCO2 and high pO2, formation of the supercontinent Pangaea, dynamic glaciation in the Southern Hemisphere, and radiation of the oldest tropical rainforests. Although it has been long appreciated that these major tectonic, climatic, and biotic events left their signature on seawater 87Sr/86Sr through their influence on Sr fluxes to the ocean, the temporal resolution and precision of the late Paleozoic seawater 87Sr/86Sr record remain relatively low. Here we present a high-temporal-resolution and high-fidelity record of Carboniferous–early Permian seawater 87Sr/86Sr based on conodont bioapatite from an open-water carbonate slope succession in south China. The new data define a rate of long-term rise in 87Sr/86Sr (0.000035/m.y.) from ca. 334–318 Ma comparable to that of the middle to late Cenozoic. The onset of the rapid decline in 87Sr/86Sr (0.000043/m.y.), following a prolonged plateau (318–303 Ma), is constrained to ca. 303 Ma. A major decoupling of 87Sr/86Sr and pCO2 during 303–297 Ma, coincident with the Paleozoic peak in pO2, widespread low-latitude aridification, and demise of the pan-tropical wetland forests, suggests a major shift in the dominant influence on pCO2 from continental weathering and organic carbon sequestration (as coals) on land to organic carbon burial in the ocean. INTRODUCTION Seawater 87Sr/86Sr has long been used as a tool for chronostratigraphic correlation (e.g., McArthur et al., 2012), and, in combination with global seawater δ13C, to constrain the timing and magnitude of tectonic events, continental weathering, and paleoclimate change (e.g., Kump and Arthur, 1997; Goddéris et al., 2017). For the middle to late Cenozoic, the highresolution seawater 87Sr/86Sr curve has provided robust chronostratigraphic constraints and insight into the interlinked processes of the Earth system during our modern icehouse (e.g., Zachos et al., 1999). The late Paleozoic ice age (LPIA, ca. 340–285 Ma) is one of two major icehouses of the Phanerozoic, and records the only greenhouse gas–forced transition from an icehouse with complex terrestrial ecosystems to a fully greenhouse world (Montañez and Poulsen, 2013). The LPIA was a time of very low atmospheric pCO2 (Montañez et al., 2016) and high pO2 (Glasspool et al., 2015), dynamic glaciation on Gondwana (Isbell et al., 2012), global tectonic reconfiguration (Veevers, 2013), and the evolution and radiation of the oldest tropical rainforests (DiMichele, 2014). The fingerprints of these events should have been recorded in seawater 87Sr/86Sr given they collectively influenced continental weathering, and thus Sr flux to the late Paleozoic oceans. The existing Carboniferous–early Permian seawater 87Sr/86Sr record derived using calcitic brachiopods (Bruckschen et al., 1999; Korte et al., 2006) remains only moderately resolved, reflecting stratigraphic uncertainties, relatively low temporal resolution, and possible diagenetic alteration. Here, we present a 87Sr/86Sr record of unprecedented temporal resolution (105 yr) for ~38 m.y. of the LPIA, built using conodont bioapatite from an open-water carbonate slope succession (Naqing, south China) of the eastern Paleo-Tethys Ocean (Fig. DR1 in the GSA Data Repository1). Our record refines the structure of the middle Mississippian to early Permian seawater 87Sr/86Sr curve and places more precise temporal constraints on the timing of major shifts and rates of change. Integrated conodont apatite 87Sr/86Sr and carbonate δ13C records provide insight into the relative roles of orogenic uplift, pan-tropical aridification, and the evolution of the paleo-tropical wetland rainforests on continental weathering and atmospheric pCO2 during Earth’s penultimate icehouse. GEOLOGIC SETTING AND METHODS During the Carboniferous–Permian, the South China Block was a nearly isolated terrain located at the interface of the Paleo-Tethys Ocean (west) and Panthalassic Ocean (east) (Fig. DR1). The Carboniferous– Permian Naqing succession in the Guizhou Province consists of thinbedded lime mudstones intercalated with intraclast-bearing bioclastic wackestones to packstones (Fig. 1), and contains abundant conodonts with complete evolutionary lineages (Qi et al., 2014). The succession records near-continuous, hemipelagic deposition on a carbonate slope episodically punctuated by turbidity currents and debris flows in the Qian-Gui Basin that defined an open-water seaway to the Paleo-Tethys Ocean (Buggisch et al., 2011; Chen et al., 2016). Sr was isolated from conodonts (n = 99) and carbonates (n = 22), collected from the Naqing section, using Eichrom exchange resin (50– 100 μm) in pipette-tip columns attached to a Watson Marlow 205U Peristaltic pump (detailed methods are provided in the Data Repository). The 87Sr/86Sr ratios were measured on a Nu Plasma HR (Nu032) multicollector–inductively coupled plasma–mass spectrometer (MC-ICPMS) at the University of California–Davis (USA). Analytical precision (2 standard deviations [SD] = ±0.000026) is based on repeated 87Sr/86Sr analysis of 1 GSA Data Repository item 2018128, analytical methods, age calibration, revision of pCO2 estimates, Figures DR1 and DR2, and Tables DR1 and DR2, is available online at http://www.geosociety.org/datarepository/2018/, or on request from editing@geosociety.org. *E-mail: jtchen@nigpas.ac.cn GEOLOGY, May 2018; v. 46; no. 5; p. 395–398 | GSA Data Repository item 2018128 | https://doi.org/10.1130/G40093.1 | Published online 1 March 2018 © 2018 The Authors. Gold Open Access: This paper is published under the terms of the CC-BY license. Downloaded from https://pubs.geoscienceworld.org/gsa/geology/article-pdf/4134043/395.pdf by guest on 31 October 2019 396 www.gsapubs.org | Volume 46 | Number 5 | GEOLOGY strontium carbonate isotopic standard SRM 987 (avg. of 0.710251; n = 44) over the study period. All data are normalized to a SRM 987 value of 0.710249. RESULTS AND DISCUSSION Refined Seawater 87Sr/86Sr Conodont apatite 87Sr/86Sr values from the Naqing section delineate three phases during the middle Mississippian to early Permian (Fig. 1; Fig. DR2). First, after a brief decline from 0.70780 to 0.70769 during the Middle Mississippian (ca. 336–334 Ma), 87Sr/86Sr values increase rapidly (avg. of 0.000035/m.y.) over a 16 m.y. period (334–318 Ma) to 0.70827. Second, the 87Sr/86Sr values define an ~15 m.y. plateau throughout much of the Pennsylvanian (318–303 Ma). Third, 87Sr/86Sr values decline, at an average rate of 0.000043/m.y., from ca. 303 Ma through to the end of the record in the early Permian (ca. 298 Ma). The 87Sr/86Sr values of diagenetically screened micrite from the Naqing section are overall higher, by up to 0.00029, than co-existing conodonts and exhibit greater scatter (Fig. 1). The Naqing conodont 87Sr/86Sr record largely agrees with a published first-order 87Sr/86Sr trend (Bruckschen et al., 1999; Korte et al., 2006), but with significantly less scatter and greater continuity (Fig. 2B). The Naqing data, with minimal stratigraphic uncertainty and higher temporal resolution (105 yr), refine the trend and fill in existing gaps. Notably, the Naqing 87Sr/86Sr values are comparable, within analytical uncertainty, with those of brachiopods from Panthalassic open-ocean settings (Brand et al., 2009) and of conodonts from the highprecision U-Pb calibrated Russian succession (Henderson et al., 2012). Seawater 87Sr/86Sr represents a mixture of two main sources: a continent-derived, more-radiogenic weathering flux, and mantle-derived, lessradiogenic volcanic and hydrothermal fluxes. The rise in 87Sr/86Sr during ca. 334–318 Ma likely records the increased 87Sr/86Sr ratio of the riverine flux due to exposure and weathering of uplifted radiogenic basement rocks (Goddéris et al., 2017) driven by the Hercynian orogeny (ca. 340–260 Ma; Hatcher, 2002; Veevers, 2013). The subsequent protracted (15 m.y.) 87Sr/86Sr plateau (318–303 Ma) is interpreted to record sustained high87Sr/86Sr riverine flux due to westward progression of maximum elevations and subsequent rapid denudation of the highlands in the paleo-tropics. The new 87Sr/86Sr record indicates a rate of rise comparable to that of last 34 m.y. of the Cenozoic icehouse (0.000040/m.y.; McArthur et al., 2012, and references therein), suggesting that increased global weatherability due to orogenic uplift may be a common driver of these icehouses (cf. Kump and Arthur, 1997). Conversely, the rapid, near-linear decline in 87Sr/86Sr ca. 303–285 Ma likely records decreased continental (silicate) weathering. This raises a paradox, as the potential for tectonically driven weatherability most likely remained unchanged through the early Permian (cf. Goddéris et al., 2017) with continued orogenesis to ca. 260 Ma (Hatcher, 2002). We hypothesize that continental weathering likely decreased during this time based on two other factors. First, the onset of widespread aridification in pan-tropical regions that began in the late Moscovian and intensified with time eastward across Pangaea through to the early Permian (Tabor and Poulsen, 2008; Michel et al., 2015) would have dramatically decreased silicate weathering. Second, the Euramerican tropical wetland forests underwent permanent turnover toward the close of the Carboniferous to dryland forests with less weathering potential (Wilson et al., 2017). Moreover, weathering of less-radiogenic basaltic provinces, which were emplaced initially in the latest Carboniferous and throughout the early Permian opening of the Neo-Tethys (e.g., Liao et al., 2015), may have contributed to declining 87Sr/86Sr. The relative contribution of basalt weathering on global seawater 87Sr/86Sr, however, was likely small in the latest Carboniferous–earliest Permian, as early basaltic province emplacement was limited in volume and occurred primarily in mid-latitude regions (Liao et al., 2015) where weathering rates would have been lower, in particular during


Bringing Dicynodonts Back to Life: Paleobiology and Anatomy of a New Emydopoid Genus from the Upper Permian of Mozambique

Abstract: Dicynodontia represent the most diverse tetrapod group during the Late Permian. They survived the Permo-Triassic extinction and are central to understanding Permo-Triassic terrestrial ecosystems. Although extensively studied, several aspects of dicynodont paleobiology such as, neuroanatomy, inner ear morphology and internal cranial anatomy remain obscure. Here we describe a new dicynodont (Therapsida, Anomodontia) from northern Mozambique: Niassodon mfumukasi gen. et sp. nov. The holotype ML1620 was collected from the Late Permian K5 formation, Metangula Graben, Niassa Province northern Mozambique, an almost completely unexplored basin and country for vertebrate paleontology. Synchrotron radiation based micro-computed tomography (SRµCT), combined with a phylogenetic analysis, demonstrates a set of characters shared with Emydopoidea. All individual bones were digitally segmented allowing a 3D visualization of each element. In addition, we reconstructed the osseous labyrinth, endocast, cranial nerves and vasculature. The brain is narrow and the cerebellum is broader than the forebrain, resembling the conservative, “reptilian-grade” morphology of other non-mammalian therapsids, but the enlarged paraflocculi occupy the same relative volume as in birds. The orientation of the horizontal semicircular canals indicates a slightly more dorsally tilted head posture than previously assumed in other dicynodonts. In addition, synchrotron data shows a secondary center of ossification in the femur. Thus ML1620 represents, to our knowledge, the oldest fossil evidence of a secondary center of ossification, pushing back the evolutionary origins of this feature. The fact that the specimen represents a new species indicates that the Late Permian tetrapod fauna of east Africa is still incompletely known.


Evaluating the influences of temperature, primary production, and evolutionary history on bivalve growth rates

Abstract: Organismal metabolic rates reflect the interaction of environmental and physiological factors. Thus, calcifying organisms that record growth history can provide insight into both the ancient environments in which they lived and their own physiology and life history. However, interpreting them requires understanding which environmental factors have the greatest influence on growth rate and the extent to which evolutionary history constrains growth rates across lineages. We integrated satellite measurements of sea-surface temperature and chlorophyll-a concentration with a database of growth coefficients, body sizes, and life spans for 692 populations of living marine bivalves in 195 species, set within the context of a new maximum-likelihood phylogeny of bivalves. We find that environmental predictors overall explain only a small proportion of variation in growth coefficient across all species; temperature is a better predictor of growth coefficient than food supply, and growth coefficient is somewhat more variable at higher summer temperatures. Growth coefficients exhibit moderate phylogenetic signal, and taxonomic membership is a stronger predictor of growth coefficient than any environmental predictor, but phylogenetic inertia cannot fully explain the disjunction between our findings and the extensive body of work demonstrating strong environmental control on growth rates within taxa. Accounting for evolutionary history is critical when considering shells as historical archives. The weak relationship between variation in food supply and variation in growth coefficient in our data set is inconsistent with the hypothesis that the increase in mean body size through the Phanerozoic was driven by increasing productivity enabling faster growth rates.

influence
evolutionary history
growth rate
metabolic rate


Inferring skeletal production from time-averaged assemblages: skeletal loss pulls the timing of production pulses towards the modern period

Abstract: Abstract. Age-frequency distributions of dead skeletal material on the landscape or seabed—information on the time that has elapsed since the death of individuals—provide decadal- to millennial-scale perspectives both on the history of production and on the processes that lead to skeletal disintegration and burial. So far, however, models quantifying the dynamics of skeletal loss have assumed that skeletal production is constant during time-averaged accumulation. Here, to improve inferences in conservation paleobiology and historical ecology, we evaluate the joint effects of temporally variable production and skeletal loss on postmortem age-frequency distributions (AFDs) to determine how to detect fluctuations in production over the recent past from AFDs. We show that, relative to the true timing of past production pulses, the modes of AFDs will be shifted to younger age cohorts, causing the true age of past pulses to be underestimated. This shift in the apparent timing of a past pulse in production will be stronger where loss rates are high and/or the rate of decline in production is slow; also, a single pulse coupled with a declining loss rate can, under some circumstances, generate a bimodal distribution. We apply these models to death assemblages of the bivalve Nuculana taphria from the Southern California continental shelf, finding that: (1) an onshore-offshore gradient in time averaging is dominated by a gradient in the timing of production, reflecting the tracking of shallow-water habitats under a sea-level rise, rather than by a gradient in disintegration and sequestration rates, which remain constant with water depth; and (2) loss-corrected model-based estimates of the timing of past production are in good agreement with likely past changes in local production based on an independent sea-level curve.

skeletal production
production
death assemblage


Systematic taxonomy of the Trilobatus sacculifer plexus and descendant Globigerinoidesella fistulosa (planktonic foraminifera)

Abstract: The extant morphospecies of the Trilobatus sacculifer plexus (T. sacculifer, T. quadrilobatus, T. immaturus and T. trilobus) have widespread biogeographical distributions and long stratigraphical ranges, and are thus routinely utilized in palaeoceanographical studies. The descendant morphospecies Globigerinoidesella fistulosa is comparatively short-ranging (Pliocene–Pleistocene) and an important biostratigraphical marker. However, taxonomic concepts of these morphospecies are inconsistently applied between workers, leading to loss of information and incomparable datasets. We present a taxonomic appraisal of each morphospecies, including detailed taxonomic histories and refinement of their morphological concepts, using a combined population-based and typological approach. Morphometric data and scanning electron microscopy are used to illustrate morphological intergradation in the Trilobatus sacculifer plexus. The distinctive morphology of Globigerinoidesella fistulosa is shown to develop from T. sacculifer (as previously documented), but also from the other morphospecies in the plexus, providing the first fossil evidence demonstrating that the four morphospecies of the T. sacculifer plexus are the same species. Our new analyses support culturing and molecular genetic evidence from extant specimens that suggests the four T. sacculifer plexus morphospecies are the same biological species. However, we advocate using the four morphospecies concepts (T. sacculifer, T. quadrilobatus, T. immaturus and T. trilobus) and G. fistulosa, here refined, to increase their palaeoecological and biostratigraphical value.

trilobatus sacculifer plexus
globigerinoidesella fistulosa
morphospecie


Extreme carpal variability in Teleoceras (Rhinocerotidae, Mammalia)

Abstract: ABSTRACT A large population of the common American Miocene rhinoceros, Teleoceras, shows extreme variability in the shape of the magnum and unciform. A small number of the specimens show a de novo posterior (volar) articulation between these two carpals. The new articulation may have been formed as an early stage in the fusion of the two bones. It is suggested that in order to evolve a complex new structure, a population will sometimes produce more variation in the affected elements than is actually necessary to form the structure.


Quantifying ecological impacts of mass extinctions with network analysis of fossil communities

Abstract: Significance The geologic record provides evidence of repeated diversification events and mass extinctions, which entailed benchmark changes in biodiversity and ecology. For insights into these events, we explore the fossil record of marine animal communities using a network-based approach to quantifying ecological change over time. The major radiations and mass extinctions of the Phanerozoic Eon resulted in the biggest ecological changes, as they involved the rise and decline of interrelated communities in relative dominance. Our analyses provide support for an ecological severity ranking of mass extinctions and illuminate the long-term consequences of the Ordovician radiation and Devonian mass depletion of biodiversity. Our work highlights the potential for irreversible ecosystem changes with species losses, both previously documented and predicted in the future. Mass extinctions documented by the fossil record provide critical benchmarks for assessing changes through time in biodiversity and ecology. Efforts to compare biotic crises of the past and present, however, encounter difficulty because taxonomic and ecological changes are decoupled, and although various metrics exist for describing taxonomic turnover, no methods have yet been proposed to quantify the ecological impacts of extinction events. To address this issue, we apply a network-based approach to exploring the evolution of marine animal communities over the Phanerozoic Eon. Network analysis of fossil co-occurrence data enables us to identify nonrandom associations of interrelated paleocommunities. These associations, or evolutionary paleocommunities, dominated total diversity during successive intervals of relative community stasis. Community turnover occurred largely during mass extinctions and radiations, when ecological reorganization resulted in the decline of one association and the rise of another. Altogether, we identify five evolutionary paleocommunities at the generic and familial levels in addition to three ordinal associations that correspond to Sepkoski’s Cambrian, Paleozoic, and Modern evolutionary faunas. In this context, we quantify magnitudes of ecological change by measuring shifts in the representation of evolutionary paleocommunities over geologic time. Our work shows that the Great Ordovician Biodiversification Event had the largest effect on ecology, followed in descending order by the Permian–Triassic, Cretaceous–Paleogene, Devonian, and Triassic–Jurassic mass extinctions. Despite its taxonomic severity, the Ordovician extinction did not strongly affect co-occurrences of taxa, affirming its limited ecological impact. Network paleoecology offers promising approaches to exploring ecological consequences of extinctions and radiations.

ecological impact
mass extinction
network analysis
evolutionary faunas
taxonomic severity


Development of cyclic shedding teeth from semi-shedding teeth: the inner dental arcade of the stem osteichthyan Lophosteus

Abstract: The numerous cushion-shaped tooth-bearing plates attributed to the stem group osteichthyan Lophosteus superbus, which are argued here to represent an early form of the osteichthyan inner dental arcade, display a previously unknown and presumably primitive mode of tooth shedding by basal hard tissue resorption. They carry regularly spaced, recumbent, gently recurved teeth arranged in transverse tooth files that diverge towards the lingual margin of the cushion. Three-dimensional reconstruction from propagation phase-contrast synchrotron microtomography (PPC-SRµCT) reveals remnants of the first-generation teeth embedded in the basal plate, a feature never previously observed in any taxon. These teeth were shed by semi-basal resorption with the periphery of their bases retained as dentine rings. The rings are highly overlapped, which evidences tooth shedding prior to adding the next first-generation tooth at the growing edge of the plate. The first generation of teeth is thus diachronous. Successor teeth at the same sites underwent cyclical replacing and shedding through basal resorption, producing stacks of buried resorption surfaces separated by bone of attachment. The number and spatial arrangement of resorption surfaces elucidates that basal resorption of replacement teeth had taken place at the older tooth sites before the addition of the youngest first-generation teeth at the lingual margin. Thus, the replacement tooth buds cannot have been generated by a single permanent dental lamina at the lingual edge of the tooth cushion, but must have arisen either from successional dental laminae associated with the individual predecessor teeth, or directly from the dental epithelium of these teeth. The virtual histological dissection of these Late Silurian microfossils broadens our understanding of the development of the gnathostome dental systems and the acquisition of the osteichthyan-type of tooth replacement.

inner dental arcade
tooth
basal resorption


Recognising moulting behaviour in trilobites by examining morphology, development and preservation: Comment on Błażejowski et al. 2015

Abstract: A 365 million year‐old trilobite moult‐carcass assemblage was described by Błażejowski et al. (2015) as the oldest direct evidence of moulting in the arthropod fossil record. Unfortunately, their suppositions are insufficiently supported by the data provided. Instead, the morphology, configuration and preservational context of the highly fossiliferous locality (Kowala Quarry, Poland) suggest that the specimen consists of two overlapping, queued carcasses. The wider fossil record of moulting actually extends back 520 million years, providing an unparalleled opportunity to study behaviour, ecology and development in early animals. Taking cues from modern analogues, it is possible to quantify precise details about moulting behaviour to determine broad‐scale evolutionary trends, ontogenetic sequences and morphological selection pressures. In this review, we argue that this rich source of data has been underused in evolutionary studies, though has great potential for investigating the life history and evolution of arthropods in deep time.


Dental evidence for ontogenetic differences between modern humans and Neanderthals

Abstract: Humans have an unusual life history, with an early weaning age, long childhood, late first reproduction, short interbirth intervals, and long lifespan. In contrast, great apes wean later, reproduce earlier, and have longer intervals between births. Despite 80 y of speculation, the origins of these developmental patterns in Homo sapiens remain unknown. Because they record daily growth during formation, teeth provide important insights, revealing that australopithecines and early Homo had more rapid ontogenies than recent humans. Dental development in later Homo species has been intensely debated, most notably the issue of whether Neanderthals and H. sapiens differ. Here we apply synchrotron virtual histology to a geographically and temporally diverse sample of Middle Paleolithic juveniles, including Neanderthals, to assess tooth formation and calculate age at death from dental microstructure. We find that most Neanderthal tooth crowns grew more rapidly than modern human teeth, resulting in significantly faster dental maturation. In contrast, Middle Paleolithic H. sapiens juveniles show greater similarity to recent humans. These findings are consistent with recent cranial and molecular evidence for subtle developmental differences between Neanderthals and H. sapiens. When compared with earlier hominin taxa, both Neanderthals and H. sapiens have extended the duration of dental development. This period of dental immaturity is particularly prolonged in modern humans.

ontogenetic difference
modern human
neanderthals
dental development
tooth