[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

[dinosaur] Giant Stupendemys fossil + interpreting fossil feathers + Komodo dragon ecology



Ben Creisler
bcreisler@gmail.com

Some recent non-dino papers:

===

Free pdf:

E.-A. Cadena, T. M. Scheyer, J. D. Carrillo-BriceÃo, R. SÃnchez, O. A Aguilera-Socorro, A. Vanegas, M. Pardo, D. M. Hansen and M. R. SÃnchez-Villagra
The anatomy, paleobiology, and evolutionary relationships of the largest extinct side-necked turtle.
Science Advances Â6(7): eaay4593
DOI: 10.1126/sciadv.aay4593
https://advances.sciencemag.org/content/6/7/eaay4593

Free pdf:
https://advances.sciencemag.org/content/6/7/eaay4593/tab-pdf


Despite being among the largest turtles that ever lived, the biology and systematics of Stupendemys geographicus remain largely unknown because of scant, fragmentary finds. We describe exceptional specimens and new localities of S. geographicus from the Miocene of Venezuela and Colombia. We document the largest shell reported for any extant or extinct turtle, with a carapace length of 2.40 m and estimated mass of 1.145 kg, almost 100 times the size of its closest living relative, the Amazon river turtle Peltocephalus dumerilianus, and twice that of the largest extant turtle, the marine leatherback Dermochelys coriacea. The new specimens greatly increase knowledge of the biology and evolution of this iconic species. Our findings suggest the existence of a single giant turtle species across the northern Neotropics, but with two shell morphotypes, suggestive of sexual dimorphism. Bite marks and punctured bones indicate interactions with large caimans that also inhabited the northern Neotropics.

News:

https://phys.org/news/2020-02-extinct-giant-turtle-horned-shell.html

https://www.sciencemag.org/news/2020/02/battle-scarred-fossils-suggest-giant-turtles-fought-each-other-and-crocodiles-three

https://scitechdaily.com/absolutely-massive-extinct-turtle-weighed-2500-pounds-and-had-giant-horned-shell/
====

Georgios L. Georgalis, Gianni Insacco, Lorenzo Rook, Filippo Spadola & Massimo Delfino (2020)
Turtle remains from the late Miocene of the Cessaniti area, southern Italyâinsights for a probable Tortonian chelonian dispersal from Europe to Africa
Swiss Journal of Palaeontology 139(1): Â
https://doi.org/10.1186/s13358-020-00202-y
https://link.springer.com/article/10.1186/s13358-020-00202-y

Free pdf:

https://link.springer.com/content/pdf/10.1186/s13358-020-00202-y.pdf


We here describe turtle remains from the late Miocene (Tortonian) of Cessaniti (Calabria, southern Italy), an area that recently has been palaeogeographically reconstructed as being, at that time of the Neogene, directly connected (or at least rather proximate) to northern Africa, instead of Europe. The material pertains to three different turtle clades, i.e., pan-trionychids, pan-cheloniids, and pan-geoemydids. Although the material is incomplete, it nevertheless permits a more precise identification for the pan-trionychid specimens, which are referred to the species Trionyx pliocenicus, as well as the pan-geoemydid, which is attributed to the genus Mauremys. Especially for the case of T. pliocenicus, the new Cessaniti specimens expand its geographic and stratigraphic distribution and further comprise the sole existing material known for this species, considering that its holotype and so far only known material is currently lost. Overall, besides its taxonomic significance, the Cessaniti chelonian assemblage affords the potential for important biogeographic implications, attesting that the lineages of Trionyx and Mauremys could have potentially used the SicilyâCalabria arch for their dispersal from Europe to Africa during the Tortonian. The new turtle specimens further complement the associated mammal remains in envisaging the Cessaniti assemblage as a mosaic of both African and Eurasian (Pikermian) faunal elements.


====

Tao Zhao, Jianfang Hu, Liang Hu & Yanhong Pan (2020)
Experimental maturation of feathers: implications for interpretations of fossil feathers.
PALAIOS 35(2): 67-76
doi: https://doi.org/10.2110/palo.2019.064
https://pubs.geoscienceworld.org/sepm/palaios/article-abstract/35/2/67/580965/EXPERIMENTAL-MATURATION-OF-FEATHERS-IMPLICATIONS


Exceptionally preserved fossil feathers and feather-like integumentary structures provide valuable insights into the early evolution of feathers and flight, but taphonomic biases often make interpretations at the microstructural and ultrastructural levels ambiguous. Maturation experiments have been demonstrated to be useful for investigating the taphonomic alterations of soft tissues, including feathers, during diagenesis. However, experimentally matured feathers resembling fossil feathers preserving keratinous matrix have not yet been obtained. Here we employ experimental maturation to obtain feathers corresponding to different degradation stages, and compare these matured feathers with untreated feathers and fossil feathers at the macroscopic, microstructural, and ultrastructural levels. Results show that several features of thermally matured feathers are similar to those found in fossil feathers. The fusion of barbules that occurred in thermally matured feathers suggests that such a process could occur during diagenesis, making barbules difficult to identify in fossil feathers. Under the most extreme experimental condition, the keratinous matrix can partially survive when the whole feather is turned into ash-like remains and many melanosomes are exposed. Moreover, our results show that the keratinous matrix immediately surrounding melanosomes appears to be more resistant to degradation than the unpigmented keratinous matrix, supporting the hypothesis that melanin can act as a fixative agent to prevent the degradation of keratin.


===

Tim S. Jessop, Achmad Ariefiandy, David M. Forsyth, Deni Purwandana,Craig R. White, Yunias Jackson Benu, Thomas Madsen, Henry J. Harlow & Mike Letnic (2020)
Komodo dragons are not ecological analogs of apex mammalian predators.
Ecology (advance online publication)
doi: Âhttps://doi.org/10.1002/ecy.2970
https://esajournals.onlinelibrary.wiley.com/doi/10.1002/ecy.2970

Apex predators can have substantial and complex ecological roles in ecosystems. However, differences in speciesâspecific traits, population densities, and interspecific interactions are likely to determine the strength of apex predatorsâ roles. Here we report complementary studies examining how interactions between predator per capita metabolic rate and population density influenced the biomass, population energy use, and ecological effects of apex predators on their large mammalian prey. We first investigated how large mammal prey resources and field metabolic rates of terrestrial apex predators, comprising large mammals and the Komodo dragon (Varanus komodoensis), influenced their biomass densities and population energy use requirements. We next evaluated whether Komodo dragons, like apex mammalian predators, exerted topâdown regulation of their large mammal prey. Comparison of results from field studies demonstrates that Komodo dragons attain mean population biomass densities that are 5.75â231.82 times higher than that of apex mammalian predator species and their guilds in Africa, Asia, and North America. The high biomass of Komodo dragons resulted in 1.96â108.12 times greater population energy use than that of apex mammalian predators. Nevertheless, substantial temporal and spatial variation in Komodo dragon population energy use did not regulate the population growth rates of either of two large mammal prey species, rusa deer (Rusa timorensis) and wild pig (Sus scrofa). We suggest that multiple processes weaken the capacity of Komodo dragons to regulate large mammal prey populations. For example, a low per capita metabolic rate requiring an infrequent and inactive hunting strategy (including scavenging), would minimize lethal and nonlethal impacts on prey populations. We conclude that Komodo dragons differ in their predatory role from, including not being the ecological analogs of, apex mammalian predators.

==

Free pdf:

Shawn A. Hamm (2020)
Stratigraphic, Geographic, and Paleoecological Distribution of the Late Cretaceous Shark Genus Ptychodus within the Western Interior Seaway, North America.
New Mexico Museum of Natural History & Science Bulletin 81: 94 pp.
https://econtent.unm.edu/digital/collection/bulletins/id/7316/rec/3


Presented here is a comprehensive monograph of all the members of the Late Cretaceous shark family Ptychodontidae. It is composed of two genera, Paraptychodus and Ptychodus, with 15 valid species of Ptychodus, 13 of which are found in deposits throughout the Western Interior Seaway of North America. Based on stratigraphic occurrences, modification in dental morphology within the family illustrates continuous specialization, which may be an indication of dietary preferences and niche partitioning. Dental characteristics indicate a common ancestor in the late Albian and that the high crowned species arose repeatedly and separately from low crowned sister species. Skeletal elements associated with Ptychodus include differentiated dermal and oral denticles, circular vertebral centra, mandibular cartilages, a plesodic pectoral fin and a dorsal fin, and suggest that member of the genus Ptychodus had a fusiform body. Its co-occurrence with large lamniform shark taxa in contemporaneous deposits suggests that Ptychodus were large-bodied predators, with lengths of up to 10 m and capable of moving at fast speeds, while occupying the apex of the food chain. Three dimensional morphometric analyses was used to diagnose the variability in each species and specify the tooth file position of individual teeth within a dentition that can contain up to 10 tooth files. Based on all the available data, the systematic position of the family Ptychodontidae should be placed within its own order, the Ptychodontiformes with the Neoselachii at the base of the Superorder Galea.