Ben Creisler
Some recent non-dino papers that may be of interest:
Not yet mentioned (English translation version not yet posted)...
Leptophora minima sp. nov.
V. V. Bulanov (2020)
New Species of the Genus Leptoropha (Kotlassiidae, Seymouriamorpha) from the Upper Urzhumian of European Russia.
Paleontological Journal 54(3): 80-86 (Russian Edition)
DOI: 10.31857/S0031031X20030058
https://elibrary.ru/item.asp?id=42725919New species of the genus Leptoropha (Kotlassiidae, Seymouriamorpha), L. minima sp. nov., is described on the basis of isolated teeth coming from the Upper Urzhumian of boundary-stratotype section of the Severodvinian Stage in the Monastery Ravine; Russia, Tatarstan Republic). The teeth from the type locality (Monastirsky Ovrag-D) allow to reconstruct the tooth shape modification from the tricuspid pattern in juveniles with skull length of about 30 mm to policuspid crowns bearing up to 14 complementary cusps at the cutting edges in adults (the skull is about 60 mm long), and forming in the anteriormost teeth the protocinguliar structures. Instead of type locality, the isolated teeth of Leptoropha minima have been confirmed from the Upper Urzhumian of South Cis-Ural Region (Orenburg Region, Yashkino locality) and lowermost Severodvinian of Viatka River basin (Kirov Region, Povoiska locality). The similarly arranged teeth collected in Sundyr-1 locality (Mari El Republic) prolong the stratigraphic distribution of Leptorophinae up to the Upper Severodvinian (Lower Putyatinian) and prove the presence of this subfamily in the last tetrapod fauna of Dinocephalian Superassemblage of the Eastern European (Sundyr Tetrapod Assemblage).
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The ontogeny of the paired appendages has been extensively studied in lungfishes and tetrapods, but remains poorly known in coelacanths. Recent work has shed light on the anatomy and development of the pectoral fin in Latimeria chalumnae. Yet, information on the development of the pelvic fin and girdle is still lacking. Here, we described the development of the pelvic fin and girdle in Latimeria chalumnae based on 3D reconstructions generated from conventional and Xâray synchrotron microtomography, as well as MRI acquisitions. As in other jawed vertebrates, the development of the pelvic fin occurs later than that of the pectoral fin in Latimeria . Many elements of the endoskeleton are not yet formed at the earliest stage sampled. The four mesomeres are already formed in the fetus, but only the most proximal radial elements (preâaxial radial 0â1) are formed and individualized at this stage. We suggest that all the preâaxial radial elements in the pelvic and pectoral fin of Latimeria are formed through the fragmentation of the mesomeres. We document the progressive ossification of the pelvic girdle, and the presence of a trabecular system in the adult. This trabecular system likely reinforces the cartilaginous girdle to resist the muscle forces exerted during locomotion. Finally, the presence of a preâaxial element in contact with the pelvic girdle from the earliest stage of development onwards questions the monoâbasal condition of the pelvic fin in Latimeria . However, the particular shape of the mesomeres may explain the presence of this element in contact with the girdle.
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ÂLarge nektonic suspension feeders have evolved multiple times. The apparent trend among apex predators for some evolving into feeding on small zooplankton is of interest for understanding the associated shifts in anatomy and behaviour, while the spatial and temporal distribution gives clues to an inherent relationship with ocean primary productivity and how past and future perturbations to these may impact on the different tiers of the food web. The evolution of large nektonic suspension feedersââgentle giantsââoccurred four times among chondrichthyan fishes (e.g. whale sharks, basking sharks and manta rays), as well as in baleen whales (mysticetes), the Mesozoic pachycormid fishes and at least twice in radiodontan stem group arthropods (Anomalocaridids) during the Cambrian explosion. The Late Devonian placoderm Titanichthys has tentatively been considered to have been a megaplanktivore, primarily due to its gigantic size and narrow, edentulous jaws while no suspension-feeding apparatus have ever been reported. Here, the potential for microphagy and other feeding behaviours in Titanichthys is assessed via a comparative study of jaw mechanics in Titanichthys and other placoderms with presumably differing feeding habits (macrophagy and durophagy). Finite-element models of the lower jaws of Titanichthys termieri in comparison to Dunkleosteus terrelli and Tafilalichthys lavocati reveal considerably less resistance to von Mises stress in this taxon. Comparisons with a selection of large-bodied extant taxa of similar ecological diversity reveal similar disparities in jaw stress resistance. Our results, therefore, conform to the hypothesis that Titanichthys was a suspension feeder with jaws ill-suited for biting and crushing but well suited for gaping ram feeding.
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News:
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Eloy GÃlvezâLÃpez (2020)
Quantifying morphological adaptations using direct measurements: the carnivoran appendicular skeleton as a case study.
The Anatomical Record (advance online publication)
doi:
https://doi.org/10.1002/ar.24453https://anatomypubs.onlinelibrary.wiley.com/doi/10.1002/ar.24453Here, I study whether locomotor adaptations can be detected in limb bones using a univariate approach, and whether those results are affected by size and/or shared evolutionary history. Ultimately, it tests whether classical papers on locomotor adaptations should be trusted. To do that, I analyzed the effect of several factors (size, taxonomic group and locomotor habit) on limb bone morphology using a set of 43 measurements of the scapula, long bones, and calcaneus, of 435 specimens belonging to 143 carnivoran species. Size was the main factor affecting limb morphology. Sizeâcorrected analyses revealed artifactual differences between various locomotionârelated categories in the analyses of raw data. Additionally, several betweenâgroup differences were new to the sizeâcorrected analyses, suggesting that they were masked by the sizeâeffect. Phylogeny had also an important effect, although it only became apparent after removing the effect of size, probably due to the strong covariation of both factors. Regarding locomotor adaptations, locomotor type was used to represent locomotor specialization, and utilised habitat as an indicator of the capacity to adopt different modes of locomotion (running, swimming, climbing and digging) and thus maximize resource exploitation by being capable of navigating all the substrates in the habitat they use. Locomotor type produced better results than utilised habitat, suggesting that carnivorans use locomotor specialization to minimize locomotion costs. The characteristic limb bone morphology for each locomotor type studied is described, including several adaptations and trends that are novel to the present study. Finally, the results presented here support the hypothesis of a "viverridâlike", forestâdwelling carnivoran ancestor, either arboreal or terrestrial.
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Duncan J. E. Murdock (2020)
The 'biomineralization toolkit' and the origin of animal skeletons.
Biological Reviews (advance online publication)
doi:
https://doi.org/10.1111/brv.12614https://onlinelibrary.wiley.com/doi/10.1111/brv.12614From pdf:
https://onlinelibrary.wiley.com/doi/pdf/10.1111/brv.12614Biomineralized skeletons are widespread in animals, and their origins can be traced to the latest Ediacaran or early Cambrian fossil record, in virtually all animal groups. The origin of animal skeletons is inextricably linked with the diversification of animal body plans and the dramatic changes in ecology and geosphereâbiosphere interactions across the Ediacaran-Cambrian transition. This apparent independent acquisition of skeletons across diverse animal clades has been proposed to have been driven by coâoption of a conserved ancestral genetic toolkit in different lineages at the same time. This 'biomineralization toolkit' hypothesis makes predictions of the early evolution of the skeleton, predictions tested herein through a critical review of the evidence from both the fossil record and development of skeletons in extant organisms. Furthermore, the distribution of skeletons is here plotted against a timeâcalibrated animal phylogeny, and the nature of the deep ancestors of biomineralizing animals interpolated using ancestral state reconstruction. All these lines of evidence point towards multiple instances of the evolution of biomineralization through the coâoption of an inherited organic skeleton and genetic toolkit followed by the stepwise acquisition of more complex skeletal tissues under tighter biological control. This not only supports the 'biomineralization toolkit' hypothesis but also provides a model for describing the evolution of complex biological systems across the Ediacaran-Cambrian transition.