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[dinosaur] Jurassic turtle reclassification + preen gland fossil + osteoderms + Nemegt strat map + more




Ben Creisler
bcreisler@gmail.com



Some recent non-dino papers:




Jérémy Anquetin, Christian Püntener & Walter G. Joyce (2017)
A Review of the Fossil Record of Turtles of the Clade Thalassochelydia.
Bulletin of the Peabody Museum of Natural History 58(2):317-369 
doi: 10.17605/OSF.IO/864T9
http://www.bioone.org/doi/10.3374/014.058.0205

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Post-print pdf for free here:

https://osf.io/preprints/paleorxiv/864t9/


The Late Jurassic (Oxfordian to Tithonian) fossil record of Europe and South America has yielded a particularly rich assemblage of aquatic pan-cryptodiran turtles that are herein tentatively hypothesized to form a monophyletic group named Thalassochelydia. Thalassochelydians were traditionally referred to three families, Eurysternidae, Plesiochelyidae, and Thalassemydidae, but the current understanding of phylogenetic relationships is insufficient to support the monophyly of either group. Given their pervasive usage in the literature, however, these three names are herein retained informally. Relationships with marine turtles from the Cretaceous have been suggested in the past, but these hypotheses still lack strong character support. Thalassochelydians are universally found in near-shore marine sediments and show adaptations to aquatic habitats, but isotopic evidence hints at a broad spectrum of specializations ranging from freshwater aquatic to fully marine. A taxonomic review of the group concludes that of 68 named taxa, 27 are nomina valida, 18 are nomina invalida, 18 are nomina dubia, and 5 nomina oblita.

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Lauren T. English (2017)
Variation in crocodilian dorsal scute organization and geometry with a discussion of possible functional implications.
Journal of Morphology (advance online publication)
DOI: 10.1002/jmor.20760
http://onlinelibrary.wiley.com/doi/10.1002/jmor.20760/full



Dermal ossifications, including osteoderms, are present in many vertebrates and are frequently interpreted as a defense against predators. Nevertheless, osteoderms remain ubiquitous in adult crocodilians while being absent in hatchlings, even though adults rarely experience predation. In other biological systems, increased variation, particularly fluctuating asymmetry, have proven useful for identifying biological structures likely to have evolved under relaxed selection, which in turn may inform their function. Therefore, using the keratinous scutes as proxies for the underlying osteoderm morphology, I investigated the average intraspecific variability of geometry and fluctuating asymmetry in dorsal scutes in five species of crocodilians. I first tested for differences in variability of scute length and width, then for differences in bilateral fluctuating asymmetry of scute number, before finally investigating scute distribution patterns for each species compared to hypothetical rectangular and hexagonal scute arrangements. The American crocodile, Crocodylus acutus, shows significantly more asymmetry than other species, which is consistent with relaxed selection on osteoderms in this species. A suspected decrease in intraspecific aggression within Crocodylus acutus, in conjunction with the inferred relaxed selection, suggests that, in general, crocodilian osteoderms function primarily as defensive armor in aggressive encounters with conspecifics. The smooth-fronted caiman, Paleosuchus trigonatus, exhibits increased variation in scute dimensions linked to the mediolateral offset of osteoderms in adjacent rows, possibly resulting in a more rigid carapace. Unfortunately, comparative data on crocodilian behavior, physiology, and development is extremely limited and restricts the ability to explore other potential explanations for the patterns observed, highlighting the need for more research on rare and cryptic crocodylians.




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Shane O'Reilly, Roger Summons, Gerald Mayr & Jakob Vinther (2017)
Preservation of uropygial gland lipids in a 48-million-year-old bird.
Proceedings of the Royal Society B  2017 284 20171050 
DOI: 10.1098/rspb.2017.1050
http://rspb.royalsocietypublishing.org/content/284/1865/20171050

Although various kinds of organic molecules are known to occur in fossils and rocks, most soft tissue preservation in animals is attributed to melanin or porphyrins. Lipids are particularly stable over time—as diagenetically altered ‘geolipids’ or as major molecular constituents of kerogen or fossil ‘geopolymers’—and may be expected to be preserved in certain vertebrate tissues. Here we analysed lipid residues from the uropygial gland of an early Eocene bird using pyrolysis gas chromatography mass spectroscopy. We found a pattern of aliphatic molecules in the fossil gland that was distinct from the host oil shale sediment matrix and from feathers of the same fossil. The fossil gland contained abundant n-alkenes, n-alkanes and alkylbenzenes with chain lengths greater than 20, as well as functionalized long-chain aldehydes, ketones, alkylnitriles and alkylthiophenes that were not detected in host sediment or fossil feathers. By comparison with modern bird uropygial gland wax esters, we show that these molecular fossils are likely derived from endogenous wax ester fatty alcohols and fatty acids that survived initial decay and underwent early diagenetic geopolymerization. These data demonstrate the high fidelity preservation of the uropygial gland waxes and showcase the resilience of lipids over geologic time and their potential role in the exceptional preservation of lipid-rich tissues of macrofossils.

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News

https://phys.org/news/2017-10-fatty-bird-gland-million-years.html

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F. Fanti, L. Cantelli & L. Angelicola (2017)

High-resolution maps of Khulsan and Nemegt localities (Nemegt Basin, southern Mongolia): Stratigraphic implications.

Palaeogeography, Palaeoclimatology, Palaeoecology (advance online publication)

doi: https://doi.org/10.1016/j.palaeo.2017.10.015

http://www.sciencedirect.com/science/article/pii/S0031018217306259




Highlights


We provide the first topographic maps of the Khulsan and Nemegt localities of southern Mongolia

The Baruungoyot and Nemegt formations are mapped, including their ‘interfingering’ interval

We provide a single stratigraphic framework for the Khulsan and Nemegt localities

GIS-based dataset allow to include historic sites, geological sections and newly discovered fossil localities in a single framework



Abstract



Since the discovery of fossil-rich exposures at the Khulsan and Nemegt localities (Nemegt Basin, southern Mongolia), tens of paleontological expeditions returned to these exposures, which are considered some of the richest Cretaceous units in the world. However, limited data on the local geology and cartography have been limiting our comprehension on correlations between different sites and the stratigraphic occurrence of vertebrate remains. Although informative, hand-drawn maps from the 1940s still represent the sole tool for researchers to provide a framework for locating access path, quarries and major geological sections. In 2016, we started a project for the realization of high-resolution topographic maps of key localities within the Nemegt Basin based on drone-acquired images. Several tests were performed at pivotal localities such as Altan Uul 2 and 3, Tsagaan Khushuu, and Ulaan Khushuu providing partial maps of such localities, whereas the Nemegt and Khulsan localities were fully covered. Photogrammetric elaboration of high-resolution images resulted in digital surface models used to obtain high-resolution topographic maps and orthophotos. Rock cairns used in the 1940s for triangulation were relocated and painted with vivid colors in order to represent reliable ground control points. In this study, we introduce new topographic maps for both Khulsan and Nemegt localities as well as comprehensive geological maps. In so doing, we provide additional stratigraphic and geographic data on the approximately 25 m thick interfingering interval that characterize the transition from the Baruungoyot and overlying Nemegt formations. Data presented in this study provide a solid framework in which detailed geological and paleontological investigations can be referred in order to significantly improve our comprehension on the Late Cretaceous Nemegt ecosystems.

 

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Free pdf:

Chris Mays,  David J. Cantrill  &  Joseph J. Bevitt (2017)

Polar wildfires and conifer serotiny during the Cretaceous global hothouse

Geology (advance online publication)

DOI: https://doi.org/10.1130/G39453.1

https://pubs.geoscienceworld.org/geology/article/doi/10.1130/G39453.1/519369/Polar-wildfires-and-conifer-serotiny-during-the



 

Several highly effective fire-adaptive traits first evolved among modern plants during the mid-Cretaceous, in response to the widespread wildfires promoted by anomalously high atmospheric oxygen (O2) and extreme temperatures. Serotiny, or long-term canopy seed storage, is a fire-adaptive strategy common among plants living in fire-prone areas today, but evidence of this strategy has been lacking from the fossil record. Deposits of abundant fossil charcoal from sedimentary successions of the Chatham Islands, New Zealand, record wildfires in the south polar regions (75°–80°S) during the mid-Cretaceous (ca. 99–90 Ma). Newly discovered fossil conifer reproductive structures were consistently associated with these charcoal-rich deposits. The morphology and internal anatomy as revealed by neutron tomography exhibit a range of serotiny-associated characters. Numerous related fossils from similar, contemporaneous deposits of the Northern Hemisphere suggest that serotiny was a key adaptive strategy during the high-fire world of the Cretaceous.


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News

https://phys.org/news/2017-10-early-global-greenhouse-event-gave.html

 



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