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[dinosaur] Eocyclotosaurus + Rotten Hill Triassic bonebed + Permian Siberian eruption + more





Ben Creisler
bcreisler@gmail.com



Some recent Triassic items not yet mentioned:

Free pdf:

G. Warrington (2017)
Triassic literature — 2015. 
Albertiana 44: 12-48
Comprehensive compilation of Triassic literature published in 2015 with additional (pre-2015) titles not listed in previously in Albertiana.
http://albertiana-sts.org/2017/07/31/triassic-literature-2015/
http://albertiana-sts.org/wp-content/uploads/2017/07/44-3-Warrington.pdf


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These two will probably be free pdfs online in another year or so.


L. F. Rinehart and S. G. Lucas (2017) [2016] 
Eocyclotosaurus appetolatus, a Middle Triassic amphibian: Osteology, life history, and paleobiology by 
New Mexico Museum of Natural History and Science, Bulletin 70: 1-118
http://albertiana-sts.org/2017/06/06/publication-announcement-eocyclotosaurus-appetolatus-a-middle-triassic-amphibian-osteology-life-history-and-paleobiology-by-l-f-rinehart-and-s-g-lucas/

This 97-page volume presents a complete analysis of the taphonomy, composition and paleobiology of a Late Triassic bonebed, including a large population sample of the temnospondyl amphibian Koskinonodon. If you are interested in ordering Bulletin 70, it costs $20 and you can contact Beth Ricker, Store Manager for the NMMNH&S, at beth@ naturalhistoryfoundation.org to place orders.

Abstract—Eocyclotosaurus appetolatus is a recently named Middle Triassic (Perovkan: early Anisian) amphibian (Temnospondyli: Capitosauroidea: Cyclotosauridae) from the Moenkopi Formation of New Mexico. Here, we study a population of these animals from a single locality, the Tecolotito bonebed in San Miguel County, north-central New Mexico. This sample provides the first nearly complete postcranial skeletal material of E. appetolatus to be described and illustrated. This disarticulated, attritional assemblage reflects an all-adult population comprising animals in the 1.2 to 2.5 meter length range, and averaging 1.7 meters. The body proportions, and skull and jaw morphology of E. appetolatus was alligator-like, implying that they filled an ecological niche similar to that of some modern crocodilians. Our functional morphology study shows that they were generalist feeders; they probably took fish in the lakes and rivers that they inhabited and small- to medium-sized prey along the shorelines. Data indicate that juveniles grew quickly to sexual maturity in three to four years, after which their growth rate continuously slowed until death. Survivorship analysis indicates that mortality was probably high in the juveniles, was very low in mid-life, and continuously increased in old age. Very few individuals reached the ultimate age of perhaps 30 to 40 years. Based on limb bone allometry and stress-strength analysis, juveniles probably had significant terrestrial capability, allowing dispersal of the species, whereas the adults likely formed breeding populations that became increasingly water-bound. Well-preserved otic regions in some skulls allowed us to determine that impedance matching in the middle ear was excellent, but the high mass of the stapes and large area of the tympanum may have limited hearing to the low end of the audio spectrum, probably extending into the infrasound region.



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S. G. Lucas, L. F. Rinehart, A. B. Heckert, A. P. Hunt and J. A. Spielmann (2017) [2016] 
Rotten Hill: A Late Triassic bonebed in the Texas Panhandle, USA
New Mexico Museum of Natural History and Science Bulletin 72: 1-97
http://albertiana-sts.org/2017/06/06/publication-announcement-rotten-hill-a-late-triassic-bonebed-in-the-texas-panhandle-usa/

This 118-page volume presents a complete osteology and paleobiological analysis of a large population sample of the Triassic temnospondyl amphibian Eocyclotosaurus from a bonebed in northern New Mexico. If you are interested in ordering Bulletin 72, it costs $20 and you can contact Beth Ricker, Store Manager for the NMMNH&S, at beth@ naturalhistoryfoundation.org to place orders.

Abstract—The Rotten Hill bonebed is a Late Triassic fossil locality in the Texas Panhandle discovered by Floyd V. Studer in 1926, and collected primarily by WPA-funded excavations during the late 1930s and early 1940s. This locality is in the lower part of the Tecovas Formation (Chinle Group) and is of Adamanian (late Carnian) age. Forensic taphonomic analysis indicates it is a mass death assemblage that was hydraulically concentrated. The Rotten Hill bonebed is a low diversity multitaxic and monodominant bonebed; the vast majority of the bones are of the metoposaurid Koskinonodon perfectum.

It closely resembles other Chinle Group metoposaurid-dominated bonebeds that suggest aggregation of a group of metoposaurids, followed by catastrophic mortality, complete disarticulation and disassociation of the skeletons, culminated by rapid transport and burial. Fossil taxa from the Rotten Hill bonebed are the unionoidan bivalve Plesioelliptio sp., the coprolite ichnogenera Alacocopros, Eucoprus and Heteropolacopros; various fishes known from ichtyoliths; a rhynchosaur; a sphenodontid; the archosauriform Vancleavea; the trilophosaurs Trilophosaurus and Spinosuchus; the phytosaur Smilosuchus; a probable poposaurid (cf. Postosuchus), the aetosaurs Desmatosuchus and cf. Stagonolepis; a shuvosaurid; and the metoposaurids Apachesaurus gregorii and K. perfectum. K. perfectum is represented by numerous skulls, lower jaws, vertebrae, girdle and limb bones representing a minimum number of 68 individuals based on recovered interclavicles. We describe the osteology and variation of these bones, which allows us to present a revised diagnosis of Koskinonodon that employs new postcranial characters to differentiate it from other metoposaurid genera. We also compiled and analyzed a morphometric database of the Rotten Hill Koskinonodon to conclude that bone growth varied from isometry to allometry and suggests a loss in limb robustness during ontogeny that likely indicates a transition from a partly terrestrial to a more aquatic lifestyle. Probability plotting to test for size groups in the Rotten Hill Koskinodonon identifies 10-11 groups that we interpret as yearly age cohorts and use to plot a growth curve. This indicates indeterminate growth in K. perfectum and that the Rotten Hill sample represents a population of breeding adults, some of which survived at least 10-11 years after reaching sexual maturity. This is a growth curve also characteristic of some living salamanders. We infer that K. perfectum employed some mechanism, such as disparate feeding strategies, or another ecological factor that enforced separation of adults and juveniles, to reduce predation on juveniles by conspecifics and minimize the competition for food resources between the ontogenetic stages.

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Also free:


S. D. Burgess, J. D. Muirhead & S. A. Bowring (2017)

Nature Communications 8, Article number: 164 (2017)

Initial pulse of Siberian Traps sills as the trigger of the end-Permian mass extinction.

doi:10.1038/s41467-017-00083-9

https://www.nature.com/articles/s41467-017-00083-9

https://www.nature.com/articles/s41467-017-00083-9.pdf




Mass extinction events are short-lived and characterized by catastrophic biosphere collapse and subsequent reorganization. Their abrupt nature necessitates a similarly short-lived trigger, and large igneous province magmatism is often implicated. However, large igneous provinces are long-lived compared to mass extinctions. Therefore, if large igneous provinces are an effective trigger, a subinterval of magmatism must be responsible for driving deleterious environmental effects. The onset of Earth’s most severe extinction, the end-Permian, coincided with an abrupt change in the emplacement style of the contemporaneous Siberian Traps large igneous province, from dominantly flood lavas to sill intrusions. Here we identify the initial emplacement pulse of laterally extensive sills as the critical deadly interval. Heat from these sills exposed untapped volatile-fertile sediments to contact metamorphism, likely liberating the massive greenhouse gas volumes needed to drive extinction. These observations suggest that large igneous provinces characterized by sill complexes are more likely to trigger catastrophic global environmental change than their flood basalt- and/or dike-dominated counterparts.



News:


https://phys.org/news/2017-07-geologists-clues-world-greatest-extinction.html