Ben Creisler
Some recent non-dino papers that may be interest (most with free pdfs):
Free pdf:
Roderick T. Wells & Aaron B. Camens (2018)
New skeletal material sheds light on the palaeobiology of the Pleistocene marsupial carnivore, Thylacoleo carnifex.Â
PLoS ONE 13(12): e0208020.Â
Free pdf:
The extinct marsupial 'lion' Thylacoleo carnifex was Australiaâs largest mammalian carnivore. Despite being the topic of more discussion than any other extinct Australian marsupial (excepting perhaps the Thylacine), basic aspects of its palaeobiology, including its locomotory repertoire, remain poorly understood. Recent discoveries allowed the first reconstruction of an entire skeleton including the first complete tail and hitherto-unrecognised clavicles. Here we describe these elements and re-assess the biomechanics of the postcranial skeleton via comparisons with a range of extant terrestrial, scansorial and arboreal Australian marsupials. Our analysis suggests that T. carnifex possessed: a relatively stiff tail comprising half of the vertebral column length; proximal caudal centra exhibiting a relatively high resistance to sagittal and lateral bending (RSB and RTB); relatively enlarged areas of origin for caudal flexors and extensors; a rigid lumbar spine; and a shoulder girdle braced by strong clavicles. The lever arms of major muscle/tendon systems controlling the axial and appendicular skeleton were identified and RSB and RTB calculated. The combination of these features compared most closely overall with those of the much smaller Tasmanian Devil (Sarcophilus harrisii), a hunter/scavenger capable of climbing. Similar locomotor behaviour is proposed for Thylacoleo carnifex. Orientation of articular facets and RSB stresses also indicate that T. carnifex may have held its tail in a dorsally-flexed position.
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News:Â
Related story about new discovery in underwater cave in Australia
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Free pdf:
Robin M. D. Beck and Charles Baillie (2018)
Improvements in the fossil record may largely resolve current conflicts between morphological and molecular estimates of mammal phylogeny.
Proceedings of the Royal Society B: Biological Sciences 285(1893): 20181632
Phylogenies of mammals based on morphological data continue to show several major areas of conflict with the current consensus view of their relationships, which is based largely on molecular data. This raises doubts as to whether current morphological character sets are able to accurately resolve mammal relationships. We tested this under a hypothetical âbest case scenarioâ by using ancestral state reconstruction (under both maximum parsimony and maximum likelihood) to infer the morphologies of fossil ancestors for all clades present in a recent comprehensive DNA sequence-based phylogeny of mammals, and then seeing what effect the subsequent inclusion of these predicted ancestors had on unconstrained phylogenetic analyses of morphological data. We found that this resulted in topologies that are highly congruent with the current consensus phylogeny, at least when the predicted ancestors are assumed to be well preserved and densely sampled. Most strikingly, several analyses recovered the monophyly of clades that have never been found in previous morphology-only studies, such as Afrotheria and Laurasiatheria. Our results suggest that, at least in principle, improvements in the fossil record--specifically the discovery of fossil taxa that preserve the ancestral or near-ancestral morphologies of the nodes in the current consensus--may be sufficient to largely reconcile morphological and molecular estimates of mammal phylogeny, even using current morphological character sets.
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Free pdf:
Jonathan D. Kennedy , Michael K. Borregaard , Petter Z. Marki , Antonin Machac , Jon Fjeldsà and Carsten Rahbek (2018)
Expansion in geographical and morphological space drives continued lineage diversification in a global passerine radiation.
Proceedings of the Royal Society B: Biological Sciences 285(1893): 20182181.
Why diversification rates vary so extensively across the tree of life remains an important yet unresolved issue in biology. Two prominent and potentially independent factors proposed to explain these trends reflect the capacity of lineages to expand into new areas of (i) geographical or (ii) ecological space. Here, we present the first global assessment of how diversification rates vary as a consequence of geographical and ecological expansion, studying these trends among 15 speciose passerine families (together approximately 750 species) using phylogenetic path analysis. We find that relative slowdowns in diversification rates characterize families that have accumulated large numbers of co-occurring species (at the 1Â scale) within restricted geographical areas. Conversely, more constant diversification through time is prevalent among families in which species show limited range overlap. Relative co-occurrence is itself also a strong predictor of ecological divergence (here approximated by morphological divergence among species); however, once the relationship between co-occurrence and diversification rates have been accounted for, increased ecological divergence is an additional explanatory factor accounting for why some lineages continue to diversify towards the present. We conclude that opportunities for prolonged diversification are predominantly determined by continued geographical range expansion and to a lesser degree by ecological divergence among lineages.
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Pay-walled:
Kyung Soo Kim, Martin G.Lockley, Jong Deok Lim & Dong Hee Kim (2018)
The oldest known anuran (frog) trackways from the Jinju Formation, Lower Cretaceous, Korea.
Cretaceous Research (advance online publication)
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Newly discovered frog tracks from the Lower Cretaceous (upper-Aptian-lower Albian) Jinju Formation, South Korea, represent only the second report from Asia, and only the third global report from the Mesozoic. They are also the oldest reported from the fossil record, and can be assigned to Ranipes isp. indet. These tracks add to the rapidly growing list of small tetrapod tracks recovered from large excavations in the Jinju Formation, in Jinju City. Such small tracks owe their preservation to an abundance of fine-grained lacustrine sediments suitable for registration of small tetrapod tracks that are generally very rare or absent from most facies. The trackways indicate hopping locomotion.
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Free pdf:
Emanuell Ribeiro, Aaron M. Davis, Rafael A. Rivero-Vega, Guillermo Ortà and Ricardo Betancur-R (2018)
Post-Cretaceous bursts of evolution along the benthic-pelagic axis in marine fishes
Proceedings of the Royal Society B: Biological Sciences 285(1893): 20182010
Ecological opportunity arising in the aftermath of mass extinction events is thought to be a powerful driver of evolutionary radiations. Here, we assessed how the wake of the CretaceousâPalaeogene (K-Pg) mass extinction shaped diversification dynamics in a clade of mostly marine fishes (Carangaria), which comprises a disparate array of benthic and pelagic dwellers including some of the most astonishing fish forms (e.g. flatfishes, billfishes, remoras, archerfishes). Analyses of lineage diversification show time-heterogeneous rates of lineage diversification in carangarians, with highest rates reached during the Palaeocene. Likewise, a remarkable proportion of Carangaria's morphological variation originated early in the history of the group and in tandem with a marked incidence of habitat shifts. Taken together, these results suggest that all major lineages and body plans in Carangaria originated in an early burst shortly after the K-Pg mass extinction, which ultimately allowed the occupation of newly released niches along the benthic-pelagic habitat axis.
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Free pdf:
Chad M. Eliason and Julia A. Clarke (2018)
Metabolic physiology explains macroevolutionary trends in the melanic colour system across amniotes.
Proceedings of the Royal Society B: Biological Sciences 285(1893): 20182014
Metabolism links organisms to their environment through its effects on thermoregulation, feeding behaviour and energetics. Genes involved in metabolic processes have known pleiotropic effects on some melanic colour traits. Understanding links between physiology and melanic colour is critical for understanding the role of, and potential constraints on, colour production. Despite considerable variation in metabolic rates and presumed ancestral melanic coloration in vertebrates, few studies have looked at a potential relationship between these two systems in a comparative framework. Here, we test the hypothesis that changes in melanosome shape in integumentary structures track metabolic rate variation across amniotes. Using multivariate comparative analyses and incorporating both extant and fossil taxa, we find significantly faster rates of melanosome shape evolution in taxa with high metabolic rates, as well as both colour- and clade-specific differences in the relationship between metabolic rate and melanosome shape. Phylogenetic tests recover an expansion in melanosome morphospace in maniraptoran dinosaurs, as well as rate shifts within birds (in songbirds) and mammals. These findings indicate another core phenotype influenced by metabolic changes in vertebrates. They also provide a framework for testing clade-specific gene _expression_ patterns in the melanocortin system and may improve colour reconstructions in extinct taxa.