Ben Creisler
Some recent non-dino papers:
Mathias M. Pires, Brian D. Rankin, Daniele Silvestro & Tiago B. Quental (2018)
Diversification dynamics of mammalian clades during the KâPg mass extinction.
Biology Letters 14(9): 2018045Â
DOI: 10.1098/rsbl.2018.0458.Â
The Cretaceous/Palaeogene (KâPg) episode is an iconic mass extinction, in which the diversity of numerous clades abruptly declined. However, the responses of individual clades to mass extinctions may be more idiosyncratic than previously understood. Here, we examine the diversification dynamics of the three major mammalian clades in North America across the KâPg. Our results show that these clades responded in dramatically contrasting ways to the KâPg event. Metatherians underwent a sudden rise in extinction rates shortly after the KâPg, whereas declining origination rates first halted diversification and later drove the loss of diversity in multituberculates. Eutherians experienced high taxonomic turnover near the boundary, with peaks in both origination and extinction rates. These findings indicate that the effects of geological episodes on diversity are context dependent and that mass extinctions can affect the diversification of clades by independently altering the extinction regime, the origination regime or both.
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Evan P. Kingsley, Chad M. Eliason, Tobias Riede, Zhiheng Li, Tom W. Hiscock, Michael Farnsworth, Scott L. Thomson, Franz Goller, Clifford J. Tabin, and Julia A. Clarke (2018)
Identity and novelty in the avian syrinx
In its most basic conception, a novelty is simply something new. However, when many previously proposed evolutionary novelties have been illuminated by genetic, developmental, and fossil data, they have refined and narrowed our concept of biological "newness." For example, they show that these novelties can occur at one or multiple levels of biological organization. Here, we review the identity of structures in the avian vocal organ, the syrinx, and bring together developmental data on airway patterning, structural data from across tetrapods, and mathematical modeling to assess what is novel. In contrast with laryngeal cartilages that support vocal folds in other vertebrates, we find no evidence that individual cartilage rings anchoring vocal folds in the syrinx have homology with any specific elements in outgroups. Further, unlike all other vertebrate vocal organs, the syrinx is not derived from a known valve precursor, and its origin involves a transition from an evolutionary "spandrel" in the respiratory tract, the site where the trachea meets the bronchi, to a target for novel selective regimes. We find that the syrinx falls into an unusual category of novel structures: those having significant functional overlap with the structures they replace. The syrinx, along with other evolutionary novelties in sensory and signaling modalities, may more commonly involve structural changes that contribute to or modify an existing function rather than those that enable new functions.
News:
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Luca Natali, Alessandro Blasetti & Giuseppe Crocetti (2018)
Detection of Lower Cretaceous fossil impressions of a marine tetrapod on Monte Conero (Central Italy).
Cretaceous Research (advance online publication)
Inside the Conero Natural Park, in Central Italy, on the top layers of the Maiolica Formation belonging to the Umbria-Marche succession, we discovered 11 depressions identified as a fossil trackway in an area forbidden to the public for safety reasons. We collected data about their dimensional and morphological characteristics, together with photographic documentation and cast collection, in an area difficult to reach. This data, with the characteristic alternation and the almost straight line of the depressions, together with the nature of the sediment on which they were imprinted, lead us to believe that we have found imprints constituting a trackway generated on a deep seabed. Furthermore, the results of our studies allow us to hypothesize that the series of tracks may have been impressed by the fore-paddles of a Lower Cretaceous marine tetrapod, a reptile not yet identified. According to current knowledge, the examined tracks seem to be unique for this period and rare for the deep seabed paleoenvironment.
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Christofer J. Clemente & Nicholas C. Wu (2018)
Body and tail-assisted pitch control facilitates bipedal locomotion in Australian agamid lizards.
Journal of the Royal Society Interface 15(146): 20180276
DOI: 10.1098/rsif.2018.0276
Certain lizards are known to run bipedally. Modelling studies suggest bipedalism in lizards may be a consequence of a caudal shift in the body centre of mass, combined with quick bursts of acceleration, causing a torque moment at the hip lifting the front of the body. However, some lizards appear to run bipedally sooner and for longer than expected from these models, suggesting positive selection for bipedal locomotion. While differences in morphology may contribute to bipedal locomotion, changes in kinematic variables may also contribute to extended bipedal sequences, such as changes to the body orientation, tail lifting and changes to the ground reaction force profile. We examined these mechanisms among eight Australian agamid lizards. Our analysis revealed that angular acceleration of the trunk about the hip, and of the tail about the hip were both important predictors of extended bipedal running, along with increased temporal asymmetry of the ground reaction force profile. These results highlight important dynamic movements during locomotion, which may not only stabilize bipedal strides, but also to de-stabilize quadrupedal strides in agamid lizards, in order to temporarily switch to, and extend a bipedal sequence.
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Pujatodon ektopos, gen. et sp. nov.ÂÂ
Francisco J. Goin, Emma C. Vieytes, Javier N. Gelfo, Laura Chornogubsky, Ana N. Zimicz & Marcelo A. Reguero (2018)
New Metatherian Mammal from the Early Eocene of Antarctica
Journal of Mammalian Evolution (advance online publication)
A new Paleogene metatherian from locality IAA 1/90, Marambio (Seymour) Island in the Antarctic Peninsula is described. Pujatodon ektopos, gen. et sp. nov., is recognized on the basis of a tiny lower left molar recovered from early Eocene (late Ypresian) levels of the Cucullaea I Allomember, La Meseta Formation. The tooth is characterized by its small size, bunoid aspect, short trigonid with closely set paraconid and metaconid, wide and long talonid, the development of an incipient cingulid at the labial base of the crown between the trigonid and talonid, and an expanded posterior cingulid. Body mass estimations for the new taxon range from 83.13 to 153.15 g. Its enamel microstructure shows the earliest evidence among metatherians of aligned prisms, as well as of interprismatic sheets of matrix. The analysis of other parameters, like body mass, molar morphometric index, and wear facets, suggests that the molars of Pujatodon were primarily adapted to the processing of fruits, nuts, seeds, and/or hard insects. Several features suggest the allocation of this specimen among basal polydolopimorphians (Prepidolopidae or, more probably, Glasbiidae). The discovery of the specimen MLP 14-I-10-20 could offer new insights on the origins and early diversification of Australidelphian marsupials in southern (and northern?) continents. It also adds significant information on the diversity of Antarctic Paleogene mammals, their evolution, habits, and historical biogeography.
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Free pdf:
Tatsuya Hirasawa & Shigeru Kuratani (2018)
Evolution of the muscular system in tetrapod limbs.
Zoological Letters 4:27
Free pdf:
While skeletal evolution has been extensively studied, the evolution of limb muscles and brachial plexus has received less attention. In this review, we focus on the tempo and mode of evolution of forelimb muscles in the vertebrate history, and on the developmental mechanisms that have affected the evolution of their morphology. Tetrapod limb muscles develop from diffuse migrating cells derived from dermomyotomes, and the limb-innervating nerves lose their segmental patterns to form the brachial plexus distally. Despite such seemingly disorganized developmental processes, limb muscle homology has been highly conserved in tetrapod evolution, with the apparent exception of the mammalian diaphragm. The limb mesenchyme of lateral plate mesoderm likely plays a pivotal role in the subdivision of the myogenic cell population into individual muscles through the formation of interstitial muscle connective tissues. Interactions with tendons and motoneuron axons are involved in the early and late phases of limb muscle morphogenesis, respectively. The mechanism underlying the recurrent generation of limb muscle homology likely resides in these developmental processes, which should be studied from an evolutionary perspective in the future.
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