Nooxobeia gracilis gen. et sp. nov.Â
Bryan M. Gee, Diane Scott & Robert R. Reisz (2018)
Reappraisal of the Permian dissorophid Fayella chickashaensis.
Canadian Journal of Earth Sciences 55(10): 1103-1114,
The Permian temnospondyl Fayella chickashaensis from Oklahoma, a purported member of the intriguing clade of terrestrially adapted dissorophids, has been difficult to contextualize within the clade because of uncertainties related to the holotype, an isolated and badly weathered neurocranium. However, postcranial material that has been attributed to this taxon is particularly important for furthering our broader understanding of the patterns of temnospondyl evolution as it relates to their terrestrial diversification at the same time as the diversification of amniotes. Here we present a reevaluation of all material assigned to Fayella. Our examination of the holotype indicates that it is not referable below Temnospondyli indet., and Fayella chickashaensis is hence designated as a nomen dubium. Significant postcranial and the partial cranial material from a different locality than the holotype was referred to the taxon and is sufficiently diagnostic to be associated with the olsoniforms, the clade of large-bodied terrestrial dissorophoids. The presence of osteoderms and the absence of a subdivided naris exclude trematopids. This specimen can be differentiated from other dissorophid taxa by the proportions of the limbs and the elongation of the intercentra and is herein designated as the holotype of Nooxobeia gracilis gen. et sp. nov. The gracile limb proportions of Nooxobeia are particularly exaggerated relative to other olsoniforms and indicate an unusually active, agile predator that is interpreted here as an advanced stage of terrestrial adaptation among dissorophid temnospondyls.
Abstract
It is crucial to determine whether rapid eye movement (REM) sleep and slow-wave sleep (SWS) (or non-REM sleep), identified in most mammals and birds, also exist in lizards, as they share a common ancestor with these groups. Recently, a study in the bearded dragon (P. vitticeps) reported states analogous to REM and SWS alternating in a surprisingly regular 80-s period, suggesting a common origin of the two sleep states across amniotes. We first confirmed these results in the bearded dragon with deep brain recordings and electro-oculogram (EOG) recordings. Then, to confirm a common origin and more finely characterize sleep in lizards, we developed a multiparametric approach in the tegu lizard, a species never recorded to date. We recorded EOG, electromyogram (EMG), heart rate, and local field potentials (LFPs) and included data on arousal thresholds, sleep deprivation, and pharmacological treatments with fluoxetine, a serotonin reuptake blocker that suppresses REM sleep in mammals. As in the bearded dragon, we demonstrate the existence of two sleep states in tegu lizards. However, no clear periodicity is apparent. The first sleep state (S1 sleep) showed high-amplitude isolated sharp waves, and the second sleep state (S2 sleep) displayed 15-Hz oscillations, isolated ocular movements, and a decrease in heart rate variability and muscle tone compared to S1. Fluoxetine treatment induced a significant decrease in S2 quantities and in the number of sharp waves in S1. Because S2 sleep is characterized by the presence of ocular movements and is inhibited by a serotonin reuptake inhibitor, as is REM sleep in birds and mammals, it might be analogous to this state. However, S2 displays a type of oscillation never previously reported and does not display a desynchronized electroencephalogram (EEG) as is observed in the bearded dragons, mammals, and birds. This suggests that the phenotype of sleep states and possibly their role can differ even between closely related species. Finally, our results suggest a common origin of two sleep states in amniotes. Yet, they also highlight a diversity of sleep phenotypes across lizards, demonstrating that the evolution of sleep states is more complex than previously thought.
Author summary
Until recently, the general understanding about sleep was that only mammals and birds show two sleep states: slow-wave sleep and rapid eye movement (REM) sleep. Consequently, it was thought that these two states appeared independently in these warm-blooded animals. However, a recent paper reported the presence of these two states in the bearded dragon lizard (Pogona vitticeps), suggesting that these two states arose with the common ancestor of mammals, birds, and reptiles. We confirmed the presence of two sleep states in the bearded dragon and compared its sleep with that of another lizard, the Argentine tegu (Salvator merianae). Our results show that both lizard species have two sleep states with similarities to the two sleep states observed in mammals and birds. Additionally, our study of behavioral and physiological parameters as well as the brain activity associated with sleep in these lizards allowed us to also show important differences between these two species of lizards and between lizards, birds, and mammals. Our findings indicate that sleep in lizards is more complex than previously thought and raise further questions about the nature, function, and evolution of these two sleep states.
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Leslie F. NoÃ, Marcela GÃmez-PÃrez & Robert Nicholls (2018)
Mary Anning, Alfred Nicholson Leeds and Steve Etches. Comparing the three most important UK 'amateur' fossil collectors and their collections.
Proceedings of the Geologists' Association (advance online publication)
Mary Anning, Alfred Nicholson Leeds and Steve Etches form part of a long line of individuals who furnished a substantial addition to our understanding of marine and terrestrial ecosystems through collecting significant numbers of superb fossils. For all three collectors, fossils became a factor that dominated their lives, and their fossil collecting led to the discovery of numerous taxa new to science. Extensive collecting was made possible by the fortunate circumstances of living 'in the right place at the right time', close to fine-grained UK Jurassic deposits (LagerstÃtten) with well-preserved large Jurassic marine reptiles. All three were highly-motivated and developed a considerable skill sets for discovering, collecting, preparing, conserving and displaying fossils. They developed personal and professional interactions with family and friends, and university and museum professionals, although their collecting resulted in variable recognition of their work. Each collector can be considered a complex mix of amateur and professional: Mary Anning, a professional fossil collector and amateur palaeontologist; Alfred Leeds transitioned from amateur to professional fossil collector, but remained an amateur palaeontologist; and Steve Etches has remained an amateur fossil collector and palaeontologist. However, all three exhibited an entirely professional outlook to collecting, and should be considered professionals of the highest degree. The impact of Mary Anning, Alfred Nicholson Leeds and Steve Etches has been critical for the development of Palaeontology as a science, and without whom palaeontology, with all its associated benefits to a wide scientific and non-scientific audience, would not be as rich as we currently know it.
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Graham E. Budd & Richard P. Mann (2018)
History is written by the victors: The effect of the push of the past on the fossil record
Evolution (advance online publication)
Survivorship biases can generate remarkable apparent rate heterogeneities through time in otherwise homogeneous birthâdeath models of phylogenies. They are a potential explanation for many striking patterns seen in the fossil record and molecular phylogenies. One such bias is the "push of the past": clades that survived a substantial length of time are likely to have experienced a high rate of early diversification. This creates the illusion of a secular rate slowâdown through time that is, rather, a reversion to the mean. An extra effect increasing early rates of lineage generation is also seen in large clades. These biases are important but relatively neglected influences on many aspects of diversification patterns in the fossil record and elsewhere, such as diversification spikes after mass extinctions and at the origins of clades; they also influence rates of fossilization, changes in rates of phenotypic evolution and even molecular clocks. These inevitable features of surviving and/or large clades should thus not be generalized to the diversification process as a whole without additional study of small and extinct clades, and raise questions about many of the traditional explanations of the patterns seen in the fossil record.
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Yanhong Pan, Liang Hu & Tao Zhao (2018)
Applications of chemical imaging techniques in paleontology.Â
National Science Review: nwy107 (advance online publication)
Chemical imaging techniques, based on a combination of microscopy and spectroscopy, are designed to analyze the composition and spatial distribution of heterogeneous chemical complexes within a sample. Over the last few decades, it became an increasingly popular tool for characterizing trace elements, isotopic information, and organic biomarkers (molecular biosignatures) found in fossils. Here we introduce the analytical principle of each technique and the interpretation of the chemical signals, followed by a review of the main applications of these techniques in paleontology. We also demonstrate that each technique is associated with pros and cons, and the current limitations and obstacles associated with the use of each specific technique should be taken into account before being applied to fossil samples. Finally, we propose that due to the rapid advances in the available technology and overall trends towards more multi-disciplinary studies in paleontology, chemical imaging techniques can be expected to have broad applications in paleontology in the near future.
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