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[dinosaur] Triassic-Jurassic tracks from Tunisia + ergs during Triassic-Jurassic of Utah + turtle and crocodile color vision + more




Ben Creisler
bcreisler@gmail.com


Some recent papers:



Grzegorz Niedźwiedzkia, Mohamed Soussib, Kamel Boukhalfac & Gerard D. Gierlińskid (2016)
Middle-Upper Triassic and Middle Jurassic tetrapod track assemblages of southern Tunisia, Sahara Platform.
Journal of African Earth Sciences (advance online publication)
http://dx.doi.org/10.1016/j.jafrearsci.2016.12.006
http://www.sciencedirect.com/science/article/pii/S1464343X16304046

Highlights

New tetrapod tracksites from Mesozoic of Tunisia are reported.
Middle-Late Triassic assemblages contain dinosaurian ichnotaxa.
Middle Jurassic ichnofauna shows similarity to dinosaur track assemblages from Africa, Europe and Asia.
These trace fossils represent the first tetrapod finds in the Triassic of Tunisia.

Abstract

Two tetrapod track assemblages from the early Mesozoic of southern Tunisia are reported. The strata exposed at the Tejra 2 clay-pit near the Medenine and Rehach site, located in the vicinity of Kirchaou, contain the first tetrapod tracks found in the Triassic of Tunisia. The Middle Jurassic (early Aalenian) dinosaur footprints are reported from the Mestaoua plain near Tataouine. In the Middle Triassic outcrop of the Tejra 2 clay-pit, tridactyl tracks of small and medium-sized dinosauromorphs, dinosauriforms (or basal theropods) were discovered. These tracks represent the oldest evidence of dinosaur-lineage elements in the Triassic ichnofauna of Tunisia. Similar tracks have been described from the Middle Triassic of Argentina, France and Morocco. An isolated set of the manus and pes of a quadrupedal tetrapod are referred to a synapsid tracemaker. The Middle Jurassic deposits of the Mestaoua plain reveal small and large tridactyl theropod dinosaur tracks (Theropoda track indet. A-C). Based on comparison with the abundant record of Triassic and Jurassic tetrapod ichnofossils from Europe and North America, the ichnofauna described here indicates the presence of a therapsid-dinosauromorph ichnoassociation (without typical Chirotheriidae tracks) in the Middle and Late Triassic, which sheds light on the dispersal of the Middle-Upper Triassic tetrapod ichnofaunas in this part of Gondwana. The reported Middle Jurassic ichnofauna show close similarities to dinosaur track assemblages from the Lower and Middle Jurassic of northwestern Africa, North America, Europe and also southeastern Asia. Sedimentological and lithostratigraphic data of each new tracksite have been defined on published data and new observations. Taken together, these discoveries present a tantalizing window into the evolutionary history of tetrapods from the Triassic and Jurassic of southern Tunisia. Given the limited early Mesozoic tetrapod record from the region, these discoveries are of both temporal and geographic significance.


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Lida Xing, Guangzhao Peng, Hendrik Klein, Yong Ye, Shan Jiang, Michael E Burns & Hao Ran (2016)
Middle Jurassic tetrapod burrows preserved in association with the large sauropod Omeisaurus jiaoi from the Sichuan Basin, China.
Historical Biology (advance online publication)
DOI: 10.1080/08912963.2016.1263627
http://www.tandfonline.com/doi/full/10.1080/08912963.2016.1263627


Here we report a Jurassic tetrapod burrow preserved in association with the partial skeleton of a large sauropod specimen of Omeisaurus jiaoi from Zigong, Sichuan Province, China. The ichnofossil can be divided into two parts, which may indicate two individual trace makers and some social behavior, although the possibility that they are two portions of one trace by a single trace maker cannot be ruled out. The burrow trace was examined via petrographic thin sections and carbonate analysis. Considering the spatial relationship of the burrows and the skeleton, it is likely that decomposition of the sauropod carcass preceded the formation of the burrows. It is possible that the process of decomposition improved the humus level of the soil, which would have attracted more soil-dwelling invertebrates and, by consequence, tetrapod predators thereof. The discovery of ZDM5051 has increased our understanding of global ichnofossil diversity.




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Free pdf:

Brooks B. Britt, Daniel J. Chure, George F. Engelmann & Jesse Dean Shumway (2016)
Rise of the erg—paleontology and paleoenvironments of the Triassic-Jurassic transition in northeastern Utah
Geology of the Intermountain West [S.l.] 3: 1-32, 
http://www.utahgeology.org/openjournal/index.php/GIW/article/view/6


This field trip focuses on the Late Triassic-Early Jurassic transition in northeastern Utah. This transition records one of the most striking terrestrial environmental transformations in the history of North America, wherein the fluvio-lacustrine Chinle Formation is transgressed by the vast erg system of the Nugget (Wingate+Navajo)/Navajo/Aztec Sandstones. Exposures in northeastern Utah are ideal for studying this transition as they are closely spaced and accessible. The uppermost Chinle Formation beds are lacustrine/fluvial fine-grained sediments which are overlain by increasingly drier, sandy, transitional beds. The non-eolian basal beds of the Nugget Sandstone preserve a Late Triassic ichnofauna, with some sites including Brachychirotherium tracks. Large-scale dune deposits comprise most of the Nugget Sandstone and contain vertebrate (Brasilichnium) tracks and a diverse invertebrate ichnofauna. Interdunal, carbonate, spring mounds, as much as 3 m tall, fed carbonate freshwater lake deposits containing gastropod body fossils and invertebrate ichnofossils.
Another lacustrine deposit, located at the Saints & Sinners Quarry, is on the shoreline of a non-carbonate interdunal lake/oasis. Over 11,500 bones have been collected from the site and represent two theropod dinosaur taxa, sphenodonts, sphenosuchians, a pterosaur, and drepanosaurs (with many complete, three-dimensional, articulated skeletons). In addition to bones, dinosaur trackways are also preserved in shoreline and other interdunal beds. The fauna shows that this interdunal area of the Nugget Sandstone was the site of intense biological activity. The drepanosaurs are chronologically significant in that they are restricted globally to the Late Triassic, indicating that at least the lower one-fourth to one-third of the formation is Late Triassic in age.


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Christopher A. Emerling (2016)

Archelosaurian color vision, parietal eye loss and the crocodylian nocturnal bottleneck

Molecular Biology and Evolution (advance online publication)

doi: 10.1093/molbev/msw265

http://mbe.oxfordjournals.org/content/early/2016/12/06/molbev.msw265.abstract

 

Vertebrate color vision has evolved partly through the modification of five ancestral visual opsin proteins via gene duplication, loss and shifts in spectral sensitivity. While many vertebrates, particularly mammals, birds and fishes, have had their visual opsin repertoires studied in great detail, testudines (turtles) and crocodylians have largely been neglected. Here I examine the genomic basis for color vision in four species of turtles and four species of crocodylians, and demonstrate that while turtles appear to vary in their number of visual opsins, crocodylians experienced a reduction in their color discrimination capacity after their divergence from Aves. Based on the opsin sequences present in their genomes and previous measurements of crocodylian cones, I provide evidence that crocodylians have co-opted the rod opsin (RH1) for cone function. This suggests that some crocodylians might have reinvented trichromatic color vision in a novel way, analogous to several primate lineages. The loss of visual opsins in crocodylians paralleled the loss of various anatomical features associated with photoreception, attributed to a ‘nocturnal bottleneck’ similar to that hypothesized for Mesozoic mammals. I further queried crocodylian genomes for non-visual opsins and genes associated with protection from ultraviolet light, and found evidence for gene inactivation or loss for several of these genes. Two genes, encoding parietopsin and parapinopsin, were additionally inactivated in birds and turtles, likely co-occurring with the loss of the parietal eye in these lineages.



News

http://scienmag.com/how-turtles-and-crocodiles-lost-parietal-eye-and-differing-color-vision-adaptations/



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Free pdf:

Eric Buffetaut (2016)
A reassessment of the giant birds Liornis floweri Ameghino, 1895 and Callornis giganteus Ameghino, 1895, from the Santacrucian (late Early Miocene) of Argentina.
Palaeovertebrata 40 (2)-e3
doi: 10.18563/pv.40.2.e3
http://www.palaeovertebrata.com/Articles/view/359



The status of the giant bird taxa Liornis floweri and Callornis giganteus from the Santa Cruz Formation (late Early Miocene) of Patagonia, first described by Ameghino (1895) is reassessed on the basis of a re-examination of the type material at the Natural History Museum, London. Liornis floweri, which lacks a Pons supratendineus on the tibiotarsus and has an unbifurcated Canalis interosseus distalis on the tarsometatarsus, is clearly a brontornithid and is considered as a junior synonym of Brontornis burmeisteri. Ameghino’s replacement of Callornis by Eucallornis is unjustified. Callornis giganteus is a chimera based on a phorusrhacid tarsometatarsus (probably belonging to Phorusrhacos longissimus) and a brontornithid tibiotarsus. The latter can be considered as the lectotype of Callornis giganteus, which may represent a small morph of Brontornis burmeisteri or a distinct taxon. It is referred to here as Brontornithidae indet. The tarsometatarsus described by Dolgopol de Saez (1927a,b) as Liornis minor and considered by her as a gracile brontornithid apparently has a bifurcated Canalis interosseus distalis and should therefore be placed among the Phorusrhacidae.