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[dinosaur] Gobi dino egg isotope diagensis + Triassic archosauromorph bone pathology + Permian tetrapod tracks + more






Ben Creisler
bcreisler@gmail.com


Some recent mainly non-dino papers:


John Graf, Neil J. Tabor, Kurt Ferguson, Dale A. Winkler, Yuong-Nam Lee, Steven May & Louis L. Jacobs (2017)
Diagenesis of dinosaur eggshell from the Gobi Desert, Mongolia
Palaeogeography, Palaeoclimatology, Palaeoecology (advance online publication)
doi: https://doi.org/10.1016/j.palaeo.2017.11.011
http://www.sciencedirect.com/science/article/pii/S0031018217310702

Highlights

Stable isotopes in dinosaur eggshell are used to infer paleobiology and paleoenvironment.
However, porosity that facilitates movement of gases, makes fossil eggshells prone to diagenesis.
Î13C and Î18O in Mongolian Cretaceous eggshell from the Gobi Desert indicate rampant diagenesis.
Eggshell was subjected to shallow-burial, vadose and phreatic zone diagenesis.

Abstract

In order to test for paleoenvironmental and paleoecological parameters important in dinosaur evolution, thirty-four fragments of dinosaur eggshell, paleosol carbonates from six localities, and calcite crystals from inside a dinosaur femur were collected from the Campanian to Maastrichtian Baruungoyot and Nemegt formations, Gobi Desert, Mongolia. The samples were examined for diagenesis using light microscopy, SEM, and cathodoluminescence, and each was analyzed for Î13C and Î18O values. Eggshell isotope values plot along two trends of enrichment, with paleosol carbonate nodule values plotting along locality specific trends. Convergence of the trends suggests similar initial conditions among localities. Permian-age detrital zircons in the fossiliferous sediment suggest that enriched eggshell and paleosol carbonate nodule Î13C values may have been caused by phreatic zone diagenetic alteration by waters with an aqueous bicarbonate component derived from interaction and dissolution of Permian calcareous marine host rocks. Our hypothetical model for eggshell diagenesis assumes a stable carbon- and oxygen-isotope domain space delimited by three end members: (1) apparently unaltered eggshell with primary microstructure, (2) non-luminescent eggshell with no preserved microstructure, and (3) luminescent eggshell with no preserved microstructure. The two end members showing no preservation of microstructure indicate different phases of diagenetic alteration in the presence of vadose and phreatic waters. None of the samples analyzed can be shown to be sufficiently unaltered for analysis using standard techniques. Biologically, eggshell is porous to facilitate the movement of gases while an embryo is developing within the egg. Geologically, that same property allows the flow of diagenetic ground waters, which modifies the primary isotopic signature of eggshell.


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Saradee Sengupta (2017)

Fusion of cervical vertebrae from a basal archosauromorph from the Middle Triassic Denwa Formation, Satpura Gondwana Basin, India.

International Journal of Paleopathology (advance online publication)

doi: https://doi.org/10.1016/j.ijpp.2017.10.010

http://www.sciencedirect.com/science/article/pii/S1879981717300268

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This report describes two adjacent, longitudinally-fused anterior cervical vertebrae from a basal archosauromorph. The specimen was collected from the Denwa Formation, Satpura Gondwana Basin, India. The differential diagnosis of the fusion includes genetic or environmentally-mediated congenital malformations, nonspecific spondyloarthopathy, and various infectious agents. These observations represent the first published recognition of archosauromorph vertebral pathology from specimens that were discovered in India. The observations affirm that basal archosauromorphs suffered from disorders that have been observed in later dinosaurs and modern-day vertebrates. Considering the process of orderly differential diagnosis is an important aspect of understanding lesions of ancient bones.



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Martin G. Lockley, Josh A. Smith & M. Ryan King (2017)

First reports of turtle tracks from the Williams Fork Formation (âMesaverdeâ Group), Upper Cretaceous (Campanian) of western Colorado.

Cretaceous Research (advance online publication)

doi: https://doi.org/10.1016/j.cretres.2017.11.001

http://www.sciencedirect.com/science/article/pii/S019566711730383X

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Tetrapod footprints from the coal-bearing, Upper Cretaceous beds of Colorado, Wyoming and Utah, loosely known as the âMesaverdeâ Group, have been reported and collected, mostly for Utah and Colorado institutions since the 1920s. However, it has only been in recent decades that the track assemblages have been reexamined in any detail. The results of such work indicate that the assemblages are more diverse than hitherto recognized. Here we report the first assemblages of turtle tracks that come from an important locality in the Williams Fork Formation in western Colorado, which also yields diverse dinosaur tracks. Collectively the turtle track-dominated assemblages reveal more than 150 swim tracks registered on a total surface area of â3 m2, indicating a density of â50 tracks/m2, and a fauna in which turtles were a significant component. The swim tracks mostly show strong preferred orientations suggesting the influence of directional currents. The co-occurrence of turtle tracks swim tracks and dinosaur tracks in the local facies indicates a mosaic of subaqueous and emergent wetland substrates consistent with the interpretation of these track-rich, coal- and plant-rich sequences as swampy, coastal plain habitats. Current evidence suggests these Upper Cretaceous tracks are typically larger than those known from the âmidâ and Lower Cretaceous in North America and elsewhere. Thus, the Williams Fork paleoenvironments may have represented settings conducive to habitation by large turtles.


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Free pdf

Lorenzo Marchetti, Matteo Belvedere, and Paolo Mietto (2017)
Lopingian tetrapod footprints from the Venetian Prealps, Italy: New discoveries in a largely incomplete panorama.
Acta Palaeontologica Polonica (in press)
available online 07 Nov 2017Â
doi: https://doi.org/10.4202/app.00392.2017
http://app.pan.pl/article/item/app003922107.html

Free pdf:
http://app.pan.pl/archive/published/app62/app003922017.pdf

After new studies were carried out in the Lopingian Val Gardena Sandstone of northern Italy, in the Recoaro area (Venetian Prealps, NE Italy), the following tetrapod ichnotaxa are identified: cf. Capitosauroides isp., cf. Merifontichnus isp., Pachypes isp., Paradoxichnium isp., and Rynchosauroides isp., probably corresponding to ?parareptile, captorhinid eureptile, pareiasaurid parareptile, archosauromorph neodiapsid, and lacertoid neodiapsid trackmakers, respectively. An undetermined track shows features consistent with possible therapsid producers. These are the first possible records of Merifontichnus and Capitosauroides in the Lopingian (late Permian) and one of the few records of Paradoxichnium worldwide. The paleoecology of the ichnoassociation highlights a relatively high diversity in the floodplain lithofacies, a monospecific association of Rhynchosauroides in distal floodplain/sabkha environments and the occurrence of Paradoxichnium isp. and cf. Capitosauroides only in the lagoon lithofacies, suggesting different habits of the trackmakers. The tetrapod ichnoassociation is characterized by eureptile and parareptile tracks, and differs from the classic Lopingian tetrapod ichnoassociation of the Dolomites mainly because of the absence of chirotheriid and small parareptile ichnotaxa. A comparison of the Italian tetrapod ichnoassociation with other Lopingian non-eolian ichnofaunas suggests a possible preference for marginal marine settings by the archosauromorph and therapsid trackmakers at low-latitudes of Pangaea.


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Mauro LuÃs Triques & Martin Lindsey Christoffersen (2017)
Arguments for replacing the concept of preadaptation by exaptation at the origin of terrestriality in Vertebrata.
Biological Journal of the Linnean Society, blx119 (advance online publication)
doi:Â https://doi.org/10.1093/biolinnean/blx119
https://academic.oup.com/biolinnean/article-abstract/doi/10.1093/biolinnean/blx119/4599944


A simplified cladogram of Sarcopterygii was used to analyse preadaptations compared with exaptations at the origin of terrestriality in Vertebrata. The cladogram contains Neotetrapoda â the crown group of the terrestrial sarcopterygians â and its sister group, Actinopterygii. The concept of preadaptation is considered unsuitable because (1) the term etymologically presupposes occurrence prior to adaptation, which does not correspond to our findings; (2) it is a concept that is historically pervaded by gradualism or continuism; (3) it can only be verified when its corresponding exaptation is found; (4) preadaptations only became exaptations jointly with other characters, not on their own; (5) in an evolutionary context, the terms preadaptation and preaptation are operationally analogous to plesiomorphies in cladistics; their analytical value is null, because they do not lead to future evolutionary changes; (6) supposed âpreadaptationsâ were noted in several lineages that never attained terrestriality and (7) both preadaptation and preaptation are terms that make the reader infer that evolution is continuous; yet we found discontinuity. Thus, âpreadaptationâ and âpreaptationâ lend unfounded support to adaptationism in the case we studied. Only a polyphyletic crown group (Neotetrapoda) would enable argumentation contrary to our reasoning. Guidelines are provided for such a study.

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