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[dinosaur] Carinodens (Mosasauridae) from Denmark + turtle cranial evolution + more






Ben Creisler
bcreisler@gmail.com


Some recent non-dino papers:


Jesper MilÃn, John W.M. Jagt, Johan Lindgren & Anne S. Schulp (2017)

First record of Carinodens (Squamata, Mosasauridae) from the uppermost Maastrichtian of Stevns Klint, Denmark.

Alcheringa (advance online publication)

doi: https://doi.org/10.1080/03115518.2017.1391878ÂÂ

Âhttp://www.tandfonline.com/doi/full/10.1080/03115518.2017.1391878

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Here we report on an important addition to the Late Cretaceous fossil record of marine reptiles from Denmark: a tooth crown of the rare durophagous mosasaur Carinodens minalmamar found in the uppermost Maastrichtian strata at the UNESCO World Heritage Site Stevns Klint. The tooth was found within the uppermost few metres of the Maastrichtian chalk placing it within the latest 50.000 years prior to the K/Pg boundary. The new find is a shed crown probably representing a tooth from the 11th to 13th position in the jaw. The tooth represents the northernmost occurrence of the genus Carinodens. Previous mosasaur finds from Denmark have all been from the hypercarnivorous mosasaurids Mosasaurus hoffmannii and Plioplatecarpus sp., thus our specimen adds a new trophic niche exploited by marine tetrapods in the food web of the latest Maastrichtian of Denmark.

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Free pdf:

Christian Foth, Eduardo Ascarrunz & Walter G. Joyce (2017)

Still slow, but even steadier: an update on the evolution of turtle cranial disparity interpolating shapes along branches.

Royal Society Open Science 4: 170899

DOI: 10.1098/rsos.170899

http://rsos.royalsocietypublishing.org/content/4/11/170899

http://rsos.royalsocietypublishing.org/content/royopensci/4/11/170899.full.pdf


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In a previous study, we estimated the cranial disparity of turtles (Testudinata) through time using geometric morphometric data from both terminal taxa and hypothetical ancestors to compensate for temporal gaps in the fossil record. While this method yielded reasonable results for the Mesozoic and the early Cenozoic, we found a large drop in cranial disparity for the Miocene, for which we found no correlation with known environmental changes or extinction events. Instead, we speculated that the Miocene dip was a result of poor sampling of fossils or ancestors in this time bin. To countervail this problem, we here updated our original dataset and interpolated changes of shape along the branch lengths and compared them with the previous data. We furthermore explored the impact of topological and temporal uncertainty, demonstrating that the Miocene dip, indeed, is a sampling artefact. All remaining conclusions of the previous study could be more or less supported, nevertheless, including an apparent correlation with global biogeographic events, a minor correlation between cranial disparity and global temperature, and resilience across the K/T extinction event.

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LucÃLia GonÃalves Vieira, Fabiano Campos Lima, SÃnia Helena Santesso Teixeira MendonÃa, Lorena TannÃs Menezes, LÃria Queiroz Luz Hirano and Andrà Luiz Quagliatto Santos (2017)

Ontogeny of the Postcranial Axial Skeleton of Melanosuchus niger (Crocodylia, Alligatoridae).

The Anatomical Record (advance online publication)

DOI: 10.1002/ar.23722

http://onlinelibrary.wiley.com/doi/10.1002/ar.23722/full




This study proposes the description of the development of the postcranial axial skeleton, including vertebrae, gastralium, ribs, sternum, and interclavicle, in Melanosuchus niger. Six nests were marked and two eggs removed from each nest at 24-hr intervals until hatching. For posthatching evaluation, 30 hatchlings were kept in captivity and one exemplar was euthanized at three-day intervals. Samples were diaphanized using potassium hydroxide (KOH), alizarin red S, and Alcian blue. A routinely generally used method was applied for histological evaluation. It was difficult to define in which vertebrae the development of cartilaginous centers began, but it was possible to observe that this condensation advanced in the craniocaudal direction. The condensation started in the vertebral arches and was visibly stronger in the cervical and dorsal regions, advancing to the lumbar, sacral and, last, to the caudal region. The atlas showed a highly different morphology compared with the other cervical vertebrae, with a short intercenter, two neural arches, and a proatlas. The ossification process began in the body of cervical vertebrae III to VIII and alizarin retention decreased in the last vertebrae, indicating a craniocaudal direction in bone development, similar to cartilage formation. In the histological sections of gastralium and interclavicles of M. niger at several development stages, it was possible to observe that these elements showed intramembranous development.



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Christian Foth, MarÃa Victoria Fernandez Blanco, Paula Bona and Torsten M. Scheyer (2017)

Cranial shape variation in jacarean caimanines (Crocodylia, Alligatoroidea) and its implications in the taxonomic status of extinct species: The case of Melanosuchus fisheri.

Journal of Morphology (advance online publication)

DOI: 10.1002/jmor.20769

http://onlinelibrary.wiley.com/doi/10.1002/ar.23722/full



This study proposes the description of the development of the postcranial axial skeleton, including vertebrae, gastralium, ribs, sternum, and interclavicle, in Melanosuchus niger. Six nests were marked and two eggs removed from each nest at 24-hr intervals until hatching. For posthatching evaluation, 30 hatchlings were kept in captivity and one exemplar was euthanized at three-day intervals. Samples were diaphanized using potassium hydroxide (KOH), alizarin red S, and Alcian blue. A routinely generally used method was applied for histological evaluation. It was difficult to define in which vertebrae the development of cartilaginous centers began, but it was possible to observe that this condensation advanced in the craniocaudal direction. The condensation started in the vertebral arches and was visibly stronger in the cervical and dorsal regions, advancing to the lumbar, sacral and, last, to the caudal region. The atlas showed a highly different morphology compared with the other cervical vertebrae, with a short intercenter, two neural arches, and a proatlas. The ossification process began in the body of cervical vertebrae III to VIII and alizarin retention decreased in the last vertebrae, indicating a craniocaudal direction in bone development, similar to cartilage formation. In the histological sections of gastralium and interclavicles of M. niger at several development stages, it was possible to observe that these elements showed intramembranous development.


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Amanda R. Falk, stephen T. Hasiotis, Enpu Gong, Jong-Deock Lim, and Erika D. Brewer (2017)

A new experimental setup for studying avian neoichnology and the effects of grain size and moisture content on tracks: trials using the domestic chicken (Gallus gallus).

PALAIOS 32(11):689-707. 2017

https://doi.org/10.2110/palo.2017.022

http://www.bioone.org/doi/abs/10.2110/palo.2017.022


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A new experimental setup using a collapsible wooden tray, monopod, and digital video camera is used to observe and collect modern bird tracks. This setup is unique because it simultaneously captures tracemaker behavior, trace morphology, and media consistency (i.e., grain size and moisture content), and can be used in the laboratory and in natural environments. Here we provide examples produced by domestic chickens (Gallus gallus). Using this setup we determined that bird track morphology varies in a predictable manner with respect to sediment grain size and the percent of water present. The finer the sediment grain size, the more detail is likely to be preserved. If the sediment is completely dry, no track details will be preservedââdigit impressions will be broad and will not taper at the tips; digit impression length will be longer than the actual digit lengths. If the sediment is wet (8.8%â6.7%), digit impressions will taper to points, will not be as wide as in dry sediment, and will not preserve pad impressions. If the sediment is variably moist (5.3%â3.2%), the detail level of pad or scale impressions, depending on the grain size, may be present. Within this study, we propose a sinuosity index that allows for quantification of sinuous avian trackways, and quantify the trackway parameters of behaviors, including start-stop walking, walking, running, takeoff, and landing. Both takeoff and landing traces are significantly deeper than the proceeding or following walking and running traces. Start-stop walking does not always result in side-by-side paired tracks, and often the bird will pause in midstride. Linking behavior and morphology of tracks can be used to better interpret ancient behavior and the depositional environment in which ancient tracks were produced.

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