Ben Creisler
Some recent non-dino papers and earlier posted papers now free:
Highlights
We reconstruct palaeoecology of mosasaurs from coeval Kansas and Alabama chalk.
Oxygen isotopes in pristine fossil tooth enamel record changing aquatic habitats.
Two adults and one juvenile show a pattern of bi-weekly migration to freshwater.
Freshwater consumption suggests osmoregulation similar to living sea snakes.
Abstract
Mosasaurs were widespread predators of the vast Cretaceous seas, and it is debated whether these extinct marine reptiles migrated to coastal environments to feed or reproduce. Here we investigate the potential for migration and palaeobiology of mosasaurs through a novel combination of high-resolution sclerochronology and palaeoecological interpretation that samples incremental growth lines in fossil teeth and extracts oxygen isotopes from pristine enamel. Oxygen isotope trends of consecutive teeth are spliced to reconstruct one to seven month-long life histories of Platecarpus tympaniticus and Clidastes propython mosasaurs, respectively, collected from time-equivalent chalk deposits of the Western Interior Seaway and Mississippi Embayment of North America. The records of all individualsâtwo adults and one juvenileâare characterized by semi-regular depletions in oxygen isotope values, indicating travel from marine to freshwater coastal environments. Weekly to bi-weekly consumption of freshwater by two genera at diverse life stages implies that mosasaur osmoregulatory function was similar to their living sea snake relatives that drink freshwater periodically.
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Brain allometry across higher macroevolutionary hierarchies in snakes seems conserved.
In lizards the macroevolutionary brain allometry at higher hierarchies is variable.
Brain size in Crotalinae pit-vipers evolved without anatomical energetic trade-offs.
Body design could drive conservation of macroevolutionary brain allometry in snakes.
Abstract
Despite historical interest in brain size evolution in vertebrates, few studies have assessed variation in brain size in squamate reptiles such as snakes and lizards. Here, we analyzed the pattern of brain allometry at macroevolutionary scale in snakes and lizards, using body mass and snout vent length as measures of body size. We also assessed potential energetic trade-offs associated with relative brain size changes in Crotalinae vipers. Body mass showed a conserved pattern of brain allometry across taxa of snakes, but not in lizards. Body length favored changes of brain allometry in both snakes and lizards, but less variability was observed in snakes. Moreover, we did not find evidence for trade-offs between brain size and the size of other organs in Crotalinae. Thus, despite the contribution of body elongation to changes in relative brain size in squamate reptiles, snakes present low variation in brain allometry across taxa. Although the mechanisms driving this conserved pattern of brain size allometry in our snake sample are unknown, we hypothesize that the snake body plan plays an important role in balancing the energetic demands of brain and body size increase at macroevolutionary scales. We encourage future research on the evolution of brain and body size in snakes to test this hypothesis.
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This new paper posted yesterday now has a free pdf:
Free pdf:
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Highlights
The first occurrence of Acresuchus pachytemporalis in Venezuela is presented.
Acresuchus pachytemporalis is an unusual crocodylian with âhorn-likeâ eminences.
It is the first occurrence of the taxon outside of Brazil, where it was discovered.
Our knowledge on the anatomy and geographic distribution of the taxon is increased.
A review of the fossil crocodylian fauna of northern South America is provided.
Abstract
The late Miocene Urumaco Formation of Venezuela has one of the richest and ecologically diverse crocodylian fossil faunas of the Cenozoic of South America. This diversity includes several different genera and species of crocodylians that held many distinct ecological niches, such as those of generalist predators, durophagous predators, giant predators and longirrostrine piscivorous, among others. This paper offers a significant addition to this already remarkable fauna by describing the first occurrence of Acresuchus pachytemporalis Souza-Filho et al.,2018 for the Urumaco Formation. This record consists of the specimen MCNUSB-PB-02FU-RS43, which is a posterior portion of the skull, consisted mostly by the skull table and the braincase, with incomplete mandibular rami associated. The specimen also represents the first occurrence of A. pachytemporalis outside the late Miocene SolimÃes Formation of Brazil, from which it has been originally described. As such, the occurrence of A. pachytemporalis in the Urumaco Formation recorded by this contribution is another evidence of the large taxonomical and paleoecological similarity between the crocodylian faunas of this unit and the SolimÃes Formation, which share many similar taxa at generic and specific levels and exhibit similar ecological niches being hold by fossil crocodylians.
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Recent discoveries of Mammaliamorph teeth in the Keuper of southern Poland have extended the global record of eucynodonts in the Late Triassic and revealed a significant diversity of the group at that time. Here, we expand on this record with the description of new cynodont postcanine teeth from the KrasiejÃw bone bed. They show the dental morphology typical for Dromatheriidae, with a single root and crown without cingulum. We assigned them to Polonodon woznikensis, described from WoÅniki. None of the 38 teeth from KrasiejÃw and WoÅniki exhibit signs of serious wear, potentially indicating a very fast rate of tooth replacement in Polonodon.
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Jeremy E. Martin, Guillaume Suan, Baptiste SuchÃras-Marx, Louis Rulleau, Jan SchlÃgl, Kevin Janneau, Matt Williams, Alex LÃna, Anne-Sabine Grosjean, Estel Sarroca, Vincent Perrier, ÂVincent Fernandez, Anne-Lise Charruault, ÂErin E. Maxwell and Peggy Vincent (2021)
Stenopterygiids from the lower Toarcian of Beaujolais and a chemostratigraphic context for ichthyosaur preservation during the Toarcian Oceanic Anoxic Event.
Geological Society London Special Publications 514 Carbon Cycle and Ecosystem Response to the Jenkyns Event in the Early Toarcian (Jurassic)
doi:
https://doi.org/10.1144/SP514-2020-232https://sp.lyellcollection.org/content/early/2021/02/25/SP514-2020-232
We report new ichthyosaur material excavated in lower Toarcian levels of the LafargeHolcim Val d'Azergues quarry in Beaujolais, SE France. A partially articulated skull and a smaller, unprepared but likely subcomplete skeleton preserved in a carbonate concretion are identified as stenopterygiids, a family of wide European distribution during the Early Jurassic. These specimens are among the finest preserved Toarcian exemplars known from Europe and in one of them, soft tissue preservation is suspected. Their state of preservation is attributed to the combination of prolonged anoxic conditions near the water-sediment interface and early carbonate cementation resulting from the activity of sulfate-reducing bacteria. We also present carbon and strontium isotope values obtained from the study site that allow detailed temporal comparisons with other Toarcian vertebrate-yielding sites and environmental perturbations associated with the Toarcian Oceanic Anoxic Event (T-OAE). These comparisons suggest that the relatively high abundance and good preservation state of Toarcian vertebrates was favoured by a prolonged period of low bottom water oxygenation and accumulation rates. The environmental conditions that prevailed during the T-OAE were probably responsible for the extensive nature of LagerstÃtte-type deposits with exceptional preservation of marine organisms. Whether the T-OAE had a biological impact on marine vertebrates requires a precise chemostratigraphic context of the fossil record spanning the Pliensbachian-Toarcian interval.
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Posted earlier but now with free pdf:
Free pdf: