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[dinosaur] Metoposaurus skull ornamentation + Aust Cliff Triassic bone bed (free pdfs)




Ben Creisler
bcreisler@gmail.com


Some recent non-dino papers:



Free pdf:

Mateusz Antczak & Adam Bodzioch (2018)
Ornamentation of dermal bones of Metoposaurus krasiejowensis and its ecological implications.Â
PeerJ 6:e5267
doi: https://doi.org/10.7717/peerj.5267
https://peerj.com/articles/5267/


Background

Amphibians are animals strongly dependent on environmental conditions, like temperature, water accessibility, and the trophic state of the reservoirs. Thus, they can be used in modern palaeoenvironmental analysis, reflecting ecological condition of the biotope.

Methods

To analyse the observed diversity in the temnospondyl Metoposaurus krasiejowensis from Late Triassic deposits in KrasiejÃw (Opole Voivodeship, Poland), the characteristics of the ornamentation (such as grooves, ridges, tubercules) of 25 clavicles and 13 skulls were observed on macro- and microscales, including the use of a scanning electron microscope for high magnification. The different ornamentation patterns found in these bones have been used for taxonomical and ecological studies of inter- vs. intraspecific variation.

Results

Two distinct types of ornamentation (fine, regular and sparse, or coarse, irregular and dense) were found, indicating either taxonomical, ecological, individual, or ontogenetic variation, or sexual dimorphism in M. krasiejowensis.

Discussion

Analogies with modern Anura and Urodela, along to previous studies on temnospondyls amphibians and the geology of the KrasiejÃw site suggest that the differences found are rather intraspecific and may suggest ecological adaptations. Sexual dimorphism and ontogeny cannot be undoubtedly excluded, but ecological variation between populations of different environments or facultative neoteny (paedomorphism) in part of the population (with types of ornamentations being adaptations to a more aquatic or a more terrestrial lifestyle) are the most plausible explanations.

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Samuel R. R. Cross, Nikola Ivanovski, Christopher J. Duffin, Claudia Hildebrandt, Adam Parker & Michael J.Benton (2018)
Microvertebrates from the basal Rhaetian Bone Bed (latest Triassic) at Aust Cliff, S.W. England.
Proceedings of the Geologists' Association (advance online publication)
doi: https://doi.org/10.1016/j.pgeola.2018.06.002Â
https://www.sciencedirect.com/science/article/abs/pii/S0016787818300944


Free pdf:
http://palaeo.gly.bris.ac.uk/Benton/reprints/2018Aust.pdf




The famous Aust Cliff section, on the east bank of the River Severn, S.W. England, includes one of the first documented successions through the Rhaetian stage (latest Triassic) and a classic Triassic-Jurassic boundary section, and, historically, the first ever mention and description of the Rhaetian bone bed, dating back to the 1820s. The larger fossils, abraded vertebrae and limb bones of marine reptiles, have been widely reported, but the microvertebrates from the Aust Cliff Rhaetian basal bone bed have been barely noted, after the classic works of Louis Agassiz, who named 17 fish taxa from Aust in the 1830s, of which eight are still regarded as valid taxa. Here we describe the extensive microvertebrate fauna, including six species of chondrichthyans identified from their teeth, featuring the second ever report of Parascylloides turnerae from the UK, as well as numerous examples of three morphotypes of chondrichthyan placoid scales (denticles). In addition, we report four species of osteichthyans based on their teeth, Gyrolepis, Severnichthys, Sargodon, and Lepidotes, as well as numerous isolated scales, fin rays, and gill rakers, and the second occurrence of cephalopod hooklets from the British Rhaetian. Four types of coprolites are noted, probably produced by these fishes, and these, with evidence from teeth, allow us to present a food web for the classic Rhaetian bone bed seas.


News:

Classic Late Triassic fossil site re-explored in undergraduate project

http://www.bristol.ac.uk/news/2018/july/aust-cliff-fossils-.html


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