The turtles of the Purbeck Limestone Group of Dorset, southern England

The turtles from the Purbeck Limestone are revised and it is concluded that there are four shell-based cryptodire species present, namely Pleurosternon bullockii, ‘Glyptops’typocardium comb. nov., Helochelydra anglica comb. nov.,Hylaeochelys latiscutata. There is also one skull-based species, Dorsetochelys delairi, which may prove to be the skull of ‘Glyptops’, Hylaeochelys or an unknown shell-type. All other taxa are junior synonyms except ‘Chelone’obovata Owen, 1842 and Tretosternon punctatum Owen, 1842 which are nomina dubia, the material being unfigured and either lost or incorrectly associated. Other taxonomic conclusions are that (1) because Tretosternon is a nomen dubium, the next senior name for this Purbeck–Wealden genus is Helochelydra Nopcsa, 1928; (2) ‘Pleurosternon’typocardium and ‘Glyptops’ruetimeyeri are synonymous, the senior combination being ‘Glyptops’typocardium; (3) the Purbeck ‘Tretosternon’ material is combined with the holotype and only specimen of Platychelys? anglica as Helochelydra anglica comb. nov.; (4) Hylaeochelys emarginata and H. sollasi are junior synonyms of Hylaeochelys latiscutata; (5) one of Owen's ‘lost’ syntypes of ‘Tretosternon punctatum’ has been recognised and is a plastron of Hylaeochelys latiscutata

The tetrapod Caerorhachis bairdi Holmes and Carroll from the Lower Carboniferous of Scotland

The tetrapod Caerorhachis bairdi, probably from the Pendleian Limestone Coal Group in the Scottish Midland Valley, is redi agnosed and redescribed, and its affinities are discussed. Caerorachis was originally interpreted as a temnospondyl amphibian, based on characters that are now regarded as primitive for tetrapods, or of uncertain polarity. Several features of Caerorhachis (e.g. gastrocentrous vertebrae, curved trunk ribs, reduced dorsal iliac blade, L-shaped tarsal intermedium) are observed in certain primitive amniotes. In particular, Caerorhachis resembles ‘anthracosaurs’, generally considered to be among the most primitive of stem-group amniotes. The phylogenetic position of Caerorhachis is considered in the light of recently published cladistic analyses of Palaeozoic tetrapods. Most analyses place Caerorhachis at the base of, or within, ‘anthra- cosaurs’. When multiple, equally parsimonious solutions are found, its ‘anthracosaur’ affinities are shown in at least some trees, and are supported by several informative and, generally, highly consistent characters. Alternative phylogenetic placements (e.g. sister taxon to temnospondyls) are usually less well corroborated. If the fundamental evolutionary split of most early tetrapods into stem-group lissamphibians (e.g. temnospondyl s) and stem-group amniotes (e.g. ‘anthracosaurs’) is accepted, then the revised interpretation of Caerorhachi s sheds light on near-ancestral conditions for Amniota

New Basal Iguanodonts from the Cedar Mountain Formation of Utah and the Evolution of Thumb-Spiked Dinosaurs

BACKGROUND: Basal iguanodontian dinosaurs were extremely successful animals, found in great abundance and diversity almost worldwide during the Early Cretaceous. In contrast to Europe and Asia, the North American record of Early Cretaceous basal iguanodonts has until recently been limited largely to skulls and skeletons of Tenontosaurus tilletti. METHODOLOGY/PRINCIPAL FINDINGS: Herein we describe two new basal iguanodonts from the Yellow Cat Member of the Cedar Mountain Formation of eastern Utah, each known from a partial skull and skeleton. Iguanacolossus fortis gen. et sp. nov. and Hippodraco scutodens gen. et sp. nov. are each diagnosed by a single autapomorphy and a unique combination of characters. CONCLUSIONS/SIGNIFICANCE: Iguanacolossus and Hippodraco add greatly to our knowledge of North American basal iguanodonts and prompt a new comprehensive phylogenetic analysis of basal iguanodont relationships. This analysis indicates that North American Early Cretaceous basal iguanodonts are more basal than their contemporaries in Europe and Asia

Acherontiscus caledoniae: the earliest heterodont and durophagous tetrapod.

The enigmatic tetrapod Acherontiscus caledoniae from the Pendleian stage of the Early Carboniferous shows heterodontous and durophagous teeth, representing the earliest known examples of significant adaptations in tetrapod dental morphology. Tetrapods of the Late Devonian and Early Carboniferous (Mississippian), now known in some depth, are generally conservative in their dentition and body morphologies. Their teeth are simple and uniform, being cone-like and sometimes recurved at the tip. Modifications such as keels occur for the first time in Early Carboniferous Tournaisian tetrapods. Acherontiscus, dated as from the Pendleian stage, is notable for being very small with a skull length of about 15 mm, having an elongate vertebral column and being limbless. Cladistic analysis places it close to the Early Carboniferous adelospondyls, aïstopods and colosteids and supports the hypothesis of 'lepospondyl' polyphyly. Heterodonty is associated with a varied diet in tetrapods, while durophagy suggests a diet that includes hard tissue such as chitin or shells. The mid-Carboniferous saw a significant increase in morphological innovation among tetrapods, with an expanded diversity of body forms, skull shapes and dentitions appearing for the first time.NER

Compositionality, stochasticity and cooperativity in dynamic models of gene regulation

We present an approach for constructing dynamic models for the simulation of gene regulatory networks from simple computational elements. Each element is called a ``gene gate'' and defines an input/output-relationship corresponding to the binding and production of transcription factors. The proposed reaction kinetics of the gene gates can be mapped onto stochastic processes and the standard ode-description. While the ode-approach requires fixing the system's topology before its correct implementation, expressing them in stochastic pi-calculus leads to a fully compositional scheme: network elements become autonomous and only the input/output relationships fix their wiring. The modularity of our approach allows to pass easily from a basic first-level description to refined models which capture more details of the biological system. As an illustrative application we present the stochastic repressilator, an artificial cellular clock, which oscillates readily without any cooperative effects.Comment: 15 pages, 8 figures. Accepted by the HFSP journal (13/09/07

Eye movements and hazard perception in active and passive driving

Differences in eye movement patterns are often found when comparing passive viewing paradigms to actively engaging in everyday tasks. Arguably, investigations into visuomotor control should therefore be most useful when conducted in settings that incorporate the intrinsic link between vision and action. We present a study that compares oculomotor behaviour and hazard reaction times across a simulated driving task and a comparable, but passive, video-based hazard perception task. We found that participants scanned the road less during the active driving task and fixated closer to the front of the vehicle. Participants were also slower to detect the hazards in the driving task. Our results suggest that the interactivity of simulated driving places increased demand upon the visual and attention systems than simply viewing driving movies. We offer insights into why these differences occur and explore the possible implications of such findings within the wider context of driver training and assessment

Morphology and distribution of scales, dermal ossifications, and other non-feather integumentary structures in non-avialan theropod dinosaurs

Modern birds are typified by the presence of feathers, complex evolutionary innovations that were already widespread in the group of theropod dinosaurs (Maniraptoriformes) that include crown Aves. Squamous or scaly reptilian-like skin is, however, considered the plesiomorphic condition for theropods and dinosaurs more broadly. Here, we review the morphology and distribution of non-feathered integumentary structures in non-avialan theropods, covering squamous skin and naked skin as well as dermal ossifications. The integumentary record of non-averostran theropods is limited to tracks, which ubiquitously show a covering of tiny reticulate scales on the plantar surface of the pes. This is consistent also with younger averostran body fossils, which confirm an arthral arrangement of the digital pads. Among averostrans, squamous skin is confirmed in Ceratosauria (Carnotaurus), Allosauroidea (Allosaurus, Concavenator, Lourinhanosaurus), Compsognathidae (Juravenator), and Tyrannosauroidea (Santanaraptor, Albertosaurus, Daspletosaurus, Gorgosaurus, Tarbosaurus, Tyrannosaurus), whereas dermal ossifications consisting of sagittate and mosaic osteoderms are restricted to Ceratosaurus. Naked, non-scale bearing skin is found in the contentious tetanuran Sciurumimus, ornithomimosaurians (Ornithomimus) and possibly tyrannosauroids (Santanaraptor), and also on the patagia of scansoriopterygids (Ambopteryx, Yi). Scales are surprisingly conservative among non-avialan theropods compared to some dinosaurian groups (e.g. hadrosaurids); however, the limited preservation of tegument on most specimens hinders further interrogation. Scale patterns vary among and/or within body regions in Carnotaurus, Concavenator and Juravenator, and include polarised, snake-like ventral scales on the tail of the latter two genera. Unusual but more uniformly distributed patterning also occurs in Tyrannosaurus, whereas feature scales are present only in Albertosaurus and Carnotaurus. Few theropods currently show compelling evidence for the co-occurrence of scales and feathers (e.g. Juravenator, Sinornithosaurus), although reticulate scales were probably retained on the mani and pedes of many theropods with a heavy plumage. Feathers and filamentous structures appear to have replaced widespread scaly integuments in maniraptorans. Theropod skin, and that of dinosaurs more broadly, remains a virtually untapped area of study and the appropriation of commonly used techniques in other palaeontological fields to the study of skin holds great promise for future insights into the biology, taphonomy and relationships of these extinct animals.Fil: Hendrickx, Christophe Marie Fabian. Fundación Miguel Lillo; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico - Tucumán. Unidad Ejecutora Lillo; ArgentinaFil: Bell, Phil R.. University Of New England; AustraliaFil: Pittman, Michael. Colegio Universitario de Londres; Reino UnidoFil: Milner, Andrew R. C.. No especifíca;Fil: Cuesta Fidalgo, Elena. Bayerische Staatssammlung für Paläontologie und Geologie; AlemaniaFil: O'Connor, Jingmai. No especifíca;Fil: Loewen, Mark. No especifíca;Fil: Currie, Philip J.. University of Alberta; CanadáFil: Mateus, Octávio. Universidade Nova de Lisboa; PortugalFil: Kaye, Thomas G.. Foundation For Scientific Advancement; Estados UnidosFil: Delcourt, Rafael. Universidade Estadual de Campinas; Brasi

Genome analysis of a simultaneously predatory and prey-independent, novel Bdellovibrio bacteriovorus from the River Tiber, supports in silico predictions of both ancient and recent lateral gene transfer from diverse bacteria

Background: Evolution equipped Bdellovibrio bacteriovorus predatory bacteria to invade other bacteria, digesting and replicating, sealed within them thus preventing nutrient-sharing with organisms in the surrounding environment. Bdellovibrio were previously described as “obligate predators” because only by mutations, often in gene bd0108, are 1 in ~1x107 of predatory lab strains of Bdellovibrio converted to prey-independent growth. A previous genomic analysis of B. bacteriovorus strain HD100 suggested that predatory consumption of prey DNA by lytic enzymes made Bdellovibrio less likely than other bacteria to acquire DNA by lateral gene transfer (LGT). However the Doolittle and Pan groups predicted, in silico, both ancient and recent lateral gene transfer into the B. bacteriovorus HD100 genome. Results: To test these predictions, we isolated a predatory bacterium from the River Tiber- a good potential source of LGT as it is rich in diverse bacteria and organic pollutants- by enrichment culturing with E. coli prey cells. The isolate was identified as B. bacteriovorus and named as strain Tiberius. Unusually, this Tiberius strain showed simultaneous prey-independent growth on organic nutrients and predatory growth on live prey. Despite the prey-independent growth, the homolog of bd0108 did not have typical prey-independent-type mutations. The dual growth mode may reflect the high carbon content of the river, and gives B. bacteriovorus Tiberius extended non-predatory contact with the other bacteria present. The HD100 and Tiberius genomes were extensively syntenic despite their different cultured-terrestrial/freshly-isolated aquatic histories; but there were significant differences in gene content indicative of genomic flux and LGT. Gene content comparisons support previously published in silico predictions for LGT in strain HD100 with substantial conservation of genes predicted to have ancient LGT origins but little conservation of AT-rich genes predicted to be recently acquired. Conclusions: The natural niche and dual predatory, and prey-independent growth of the B. bacteriovorus Tiberius strain afforded it extensive non-predatory contact with other marine and freshwater bacteria from which LGT is evident in its genome. Thus despite their arsenal of DNA-lytic enzymes; Bdellovibrio are not always predatory in natural niches and their genomes are shaped by acquiring whole genes from other bacteria

Amine Dynamics in Diamine-Appended Mg2(dobpdc) Metal-Organic Frameworks.

Variable-temperature 15N solid-state NMR spectroscopy is used to uncover the dynamics of three diamines appended to the metal-organic framework Mg2(dobpdc) (dobpdc4- = 4,4'-dioxidobiphenyl-3,3'-dicarboxylate), an important family of CO2 capture materials. The results imply both bound and free amine nitrogen environments exist when diamines are coordinated to the framework open Mg2+ sites. There are rapid exchanges between two nitrogen environments for all three diamines, the rates and energetics of which are quantified by 15N solid-state NMR data and corroborated by density functional theory calculations and molecular dynamics simulations. The activation energy for the exchange provides a measure of the metal-amine bond strength. The unexpected negative correlation between the metal-amine bond strength and CO2 adsorption step pressure reveals that metal-amine bond strength is not the only important factor in determining the CO2 adsorption properties of diamine-appended Mg2(dobpdc) metal-organic frameworks