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Auge M.L.,CNRS Center for Research on Palaeobiodiversity and Palaeoenvironments
Palaeobiodiversity and Palaeoenvironments | Year: 2012

In this paper, part of the amphisbaenian fossil record from the european Eocene is revised. There is no evidence for the existence of amphisbaenian lizards in Europe or on other continents during the Late Cretaceous. Crown amphisbaenians were present in Europe in the early Paleocene and throughout the Paleogene, with the notable exception of the middle Eocene. In particular, they were not found at Messel. European fossil taxa previously assigned to the amphisbaenians are briefly reviewed, and a description of some representative specimens from the Eocene fossil record is presented: dentary and vertebrae from Mutigny (early Eocene, France) are referred to the North American genus Anniealexandria; fossils from the late Eocene of the Phosphorites du Quercy (France) are attributed to Blanidae, and they are the earliest secure occurrence of Blanidae in the fossil record; and dentaries and maxillae from Grisolles (middle-late Eocene, Paris Basin, France) are referred to a new species, Louisamphisbaena ferox. Global distribution of fossil amphisbaenians in the Eocene reveals at least one episode of dispersal between North America and Europe during the early Eocene. Finally, some explanations are suggested for the absence of crown amphisbaenians at Messel and in the European middle Eocene. © Senckenberg Gesellschaft für Naturforschung and Springer 2012.


Rage J.-C.,CNRS Center for Research on Palaeobiodiversity and Palaeoenvironments
Palaeobiodiversity and Palaeoenvironments | Year: 2012

The fauna of amphibians and squamates during the Eocene in western Europe resulted initially from the addition of an old, ante-Eocene fauna, and of a new fauna that arrived as a big wave of dispersals at the beginning of the Eocene (MP 7). These dispersals were likely favoured by the tropical climate. The fauna, as a whole, included taxa with Laurasian affinities, some of which indicate relationships with North America. However, some taxa showed South American affinities. The subsequent fauna (MP 8+9 and MP 10) developed from that of MP 7 and was not affected by peculiar events. The fauna of the MP 11-MP 15 interval (middle Eocene) is poorly known. The last interval (MP 16-MP 19+20, latest middle and late Eocene) is characterised by a rich and diverse fauna, despite temperatures lower than that of the early Eocene. This fauna perhaps partly originated during the preceding interval. Richness and diversity resulted from dispersals and local radiations; autochthonous forms were apparently rather frequent. This fauna still included taxa with South and North American affinities. At the end of the Eocene, there occurred a prominent extinction event, the 'Grande Coupure'. Most taxa were eliminated, at least in western Europe; they survived elsewhere, permitting subsequent repopulation. The Grande Coupure was a pivotal event. Before it, the faunas were indicative of warm climates and included American components; after the Grande Coupure, the faunas that progressively repopulated Europe were indicative of less warm climates and no longer included American forms. © Senckenberg Gesellschaft für Naturforschung and Springer 2012.


Laurin M.,CNRS Center for Research on Palaeobiodiversity and Palaeoenvironments
Frontiers in Genetics | Year: 2012

Dating the Tree of Life (TOL) has become a major goal of biological research. Beyond the intrinsic interest of reconstructing the history of taxonomic diversification, time-calibrated trees (timetrees for short, as used throughout below) are required in many types of comparative analyses, where branch lengths are used to assess the conservation importance of lineages, correlation between characters, or to assess phylogenetic niche conservatism, among other uses. Improvements in dating theTOL would thus benefit large segments of the biological community, ranging from conservation biology and ecology through functional biology and paleontology. Recently, progress has been made on several fronts: in compiling databases and supertrees incorporating paleontological data, in computing confidence intervals on the true stratigraphic range of taxa, and in using birthand-death processes to assess the probability distribution of the time of origin of specified taxa. Combined paleontological and molecular dating has also progressed through the insertion of extinct taxa into data matrices, which allows incorporation of their phylogenetic uncertainty into the dating analysis. © 2012 Laurin.


Tassy P.,CNRS Center for Research on Palaeobiodiversity and Palaeoenvironments
Journal of Zoological Systematics and Evolutionary Research | Year: 2011

Phylogenetic trees published before Darwin's On the Origin of Species are scarce. Lamarck (1809) and Barbançois (1816; J Phys Chim Hist Nat Arts 82, 444) are the first and only trees devoted to illustrating the genealogical connections between organisms of different species and different higher taxa. In the late 18th and early 19th centuries, most of the trees depicted in papers dealing with natural history were classifications; classifications in the shape of trees, but classifications nonetheless. Those published by Bronn (1858) are a good example. After Darwin, phylogenetic trees incorporating the time dimension flourished. In the first half of the 20th century, the Modern Synthesis failed to renew and rejuvenate the intuitive construction of trees. It wasn't until the appearance of Hennig's phylogenetic systematics that the real nature of the connection between phylogeny and the pre-Darwinian concept of homology was made clear. © 2010 Blackwell Verlag GmbH.


Janvier P.,CNRS Center for Research on Palaeobiodiversity and Palaeoenvironments
Current Biology | Year: 2011

In contrast to lampreys and jawed vertebrates, hagfishes were thought to lack vertebrae. Now, long overlooked vertebral rudiments have been analysed in hagfish, suggesting that vertebrae existed in the last common ancestor of all vertebrates. © 2011 Elsevier Ltd. All rights reserved.


Vincent P.,CNRS Center for Research on Palaeobiodiversity and Palaeoenvironments
Journal of Vertebrate Paleontology | Year: 2011

The holotype and only known specimen of the pliosauroid plesiosaur Hauffiosaurus zanoni O'Keefe is a substantially complete and almost entirely articulated skeleton from the Toarcian Posidonien-Schiefer (Upper Lias, Lower Jurassic) of Holzmaden (Baden-Württemberg), Germany. The original description of this specimen was preliminary, and this paper presents a detailed re-description and revised diagnosis of the specimen, thus adding significant, new anatomical information. Characters such as the presence of a lateral palatal fenestra and the absence of a contact between the internal nares and the palatines are examples of phylogenetically relevant characters. The specimen presents a novel and unique combination of characters and body proportions, including a long ilium, short ischia, and propodials longer than any of their associated girdle bones, that separate it from all other pliosauroid taxa. Its elongate snout and long, slender teeth imply that this species most likely had a prey preference of fish. © 2011 by the Society of Vertebrate Paleontology.


Houssaye A.,CNRS Center for Research on Palaeobiodiversity and Palaeoenvironments
Biological Reviews | Year: 2013

Bone mass increase (BMI; i.e. osteosclerosis with possible additional pachyostosis) is characteristically displayed by many Late Cretaceous squamates that adapted to shallow marine environments-plesiopelvic mosasauroids, stem-ophidians and pachyophiids. A combined morphological and microanatomical analysis of vertebrae and, to a lesser extent, ribs of these fossil squamates provides new data about the distribution and variability of this osseous specialization in these taxa. Classical thin sections and third generation synchrotron microtomography and laminography were used for the microanatomical analysis. Following the explanation of the likely involvement of this specialization in the control of buoyancy, body trim and Carrier's constraint, new palaeoecological inferences and new hypotheses about the locomotor abilities and life environment of these organisms are produced. The taxa displaying BMI are considered to have undertaken long dives, hovering slowly and maintaining a horizontal trim, in shallow and protected water environments. Conversely, marine stem-ophidians deprived of this specialization are regarded as slow surface swimmers able to live in more open marine environments. This study highlights the importance of microanatomical data for palaeoecological studies. It also discusses the significance of the use of this specialization as a character in phylogenetic studies. © 2012 Cambridge Philosophical Society.


Argot C.,CNRS Center for Research on Palaeobiodiversity and Palaeoenvironments
Journal of Mammalian Evolution | Year: 2013

The postcranial skeleton of the late Paleocene Arctocyon primaevus is described based on a sub-complete associated specimen. A comparison with arboreal or scansorial and fossorial extant taxa shows that on the forelimb, several features suggest arboreal capabilities, including the development of abductors and adductors, the development of digital flexors, which allows grasping/manipulative ability, as well as the highly mobile articulations, the convex ulna, and the pentadactyl, plantigrade foot. In contrast with the highly mobile joints of the limbs, Arctocyon had a rigid posterior thoracic area, characterized by revolute zygapophyses unknown in extant mammals. The morphology of the most anterior caudal vertebra indicates that the tail was long, powerful, muscular, and rigid at its base, and that it played an important role in locomotion. The morphology of the hind limb is congruent with that of the forelimb, the development of the adductors, flexors, and rotators of the mobile hip joint being emphasized. Although the femoral trochlea is longer and better defined than in highly arboreal taxa, Arctocyon probably moved in a controlled fashion. A comparison with South American borhyaenoids shows that Arctocyon is morphologically more similar to some predator-like Miocene metatherians than to any living mammal. It represents an interesting mix between Prothylacinus and Borhyaena in overall size and proportions, and shows a development of crests and processes of the humerus similar to those of Prothylacinus. Arctocyonidae, which evolved towards incipient saber-toothed canines combined with cheek teeth compatible with an omnivorous diet, and which show a postcranium that is morphologically more similar to carnivorans than to ungulates, represent a mosaic of features that is of particular interest in the evolution of mammals. © 2012 Springer Science+Business Media, LLC.


Laurin M.,CNRS Center for Research on Palaeobiodiversity and Palaeoenvironments
Systematic Biology | Year: 2010

Some of the most basic questions about the history of life concern evolutionary trends. These include determining whether or not metazoans have become more complex over time, whether or not body size tends to increase over time (the Cope-Depéret rule), or whether or not brain size has increased over time in various taxa, such as mammals and birds. Despite the proliferation of studies on such topics, assessment of the reliability of results in this field is hampered by the variability of techniques used and the lack of statistical validation of these methods. To solve this problem, simulations are performed using a variety of evolutionary models (gradual Brownian motion, speciational Brownian motion, and Ornstein-Uhlenbeck), with or without a drift of variable amplitude, with variable variance of tips, and with bounds placed close or far from the starting values and final means of simulated characters. These are used to assess the relative merits (power, Type I error rate, bias, and mean absolute value of error on slope estimate) of several statistical methods that have recently been used to assess the presence of evolutionary trends in comparative data. Results show widely divergent performance of the methods. The simple, nonphylogenetic regression (SR) and variance partitioning using phylogenetic eigenvector regression (PVR) with a broken stick selection procedure have greatly inflated Type I error rate (0.123-0.180 at a 0.05 threshold), which invalidates their use in this context. However, they have the greatest power. Most variants of Felsenstein's independent contrasts (FIC; five of which are presented) have adequate Type I error rate, although two have a slightly inflated Type I error rate with at least one of the two reference trees (0.064-0.090 error rate at a 0.05 threshold). The power of all contrastbased methods is always much lower than that of SR and PVR, except under Brownian motion with a strong trend and distant bounds. Mean absolute value of error on slope of all FIC methods is slightly higher than that of phylogenetic generalized least squares (PGLS), SR, and PVR. PGLS performs well, with low Type I error rate, low error on regression coefficient, and power comparable with some FIC methods. Four variants of skewness analysis are examined, and a new method to assess significance of results is presented. However, all have consistently low power, except in rare combinations of trees, trend strength, and distance between final means and bounds. Globally, the results clearly show that FIC-based methods and PGLS are globally better than nonphylogenetic methods and variance partitioning with PVR. FIC methods and PGLS are sensitive to the model of evolution (and, hence, to branch length errors). Our results suggest that regressing raw character contrasts against raw geological age contrasts yields a good combination of power and Type I error rate. New software to facilitate batch analysis is presented. © The Author(s) 2010.


Rage J.-C.,CNRS Center for Research on Palaeobiodiversity and Palaeoenvironments
Palaeobiodiversity and Palaeoenvironments | Year: 2013

Squamates first appeared in Europe in the Middle Jurassic. They were lizards that already included some crown-group members. Faunas of the Late Jurassic and Early Cretaceous were more or less a continuation of the Middle Jurassic assemblage. The early Late Cretaceous was characterised by a peculiar fauna of marine pythonomorphs, while terrestrial forms were rare. In the subsequent levels of the Late Cretaceous, marine forms were mainly mosasaurids; terrestrial assemblages heralding modern ones began to take form during the Campanian-Maastrichtian. The Cretaceous-Tertiary event did not strongly affect squamates in Europe. After poor Paleocene faunas, a big wave of dispersals reached Europe during a marked rise in temperature at the beginning of the Eocene (MP 7). The Eocene fauna was rich, diverse and of tropical type. In western Europe, a sharp extinction event ('Grande Coupure') eliminated most squamates at the end of the Eocene, but its impact in central and eastern Europe is unknown. The Oligocene fauna was transitional between the 'old' Eocene and the modern Miocene faunas. By the late early Miocene (MN 3-MN 4), the fauna markedly changed when an important wave of dispersals entered Europe during a climatic optimum. From the late middle Miocene onward, the temperature has dropped. As a consequence, faunas became less rich and regionalisation occurred. Numerous extinctions and withdrawals took place during the late Pliocene and early Pleistocene, leaving an impoverished fauna in Europe. © 2013 Senckenberg Gesellschaft für Naturforschung and Springer-Verlag Berlin Heidelberg.

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