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[dinosaur] Yunguisaurus juvenile + Early Triassic Jurong fish fauna + camouflage




Ben Creisler
bcreisler@gmail.com

Recent papers not yet mentioned

Xue Wang, Hao Lua, Da-Yong Jiang, Min Zhou & Zuo-Yu Sun (2019)
A new specimen of Yunguisaurus (Reptilia; Sauropterygia) from the Ladinian (Middle Triassic) Zhuganpo Member, Falang Formation, Guizhou, China and the restudy of Dingxiaosaurus.
Palaeoworld (advance online publication)
doi: https://doi.org/10.1016/j.palwor.2019.05.006
https://www.sciencedirect.com/science/article/pii/S1871174X1830180X


A new articulated juvenile specimen of Yunguisaurus liae (GMPKU-P-1528) from the Ladinian (Middle Triassic) Zhuganpo Member, Falang Formation, Xingyi, Guizhou, China presents new morphological information on the relatively complete atlas and axis. The comparison of the all four Y. liae skeletons with the holotype (DMK 8) of Dingxiaosaurus luyinensis reveals that there is no morphological difference between the two species. The similarities include the similar orientation of the tarsals, the same value of the ratio of the distal width to the proximal width of the tibia and the ratio of the fibula length to the tibia length. The taxonomy of D. luyinensis, however, remains controversial. It cannot be distinguished from other pistosauroid taxa due to the lack of comparative portions of the skeletons preserved (e.g., Chinchenia, Kwangsissaurus). It may turn out that D. luyinensis and Y. liae stand for the same species when more complete materials become available.


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Xincheng Qiu, Yaling Xu, Zhong-Qiang Chen, Michael J. Benton, Wen Wen & Yuangeng Huang (2019)
The Early Triassic Jurong fish fauna, South China: Age, anatomy, taphonomy, and global correlation.
Global and Planetary Change (advance online publication)
doi: https://doi.org/10.1016/j.gloplacha.2019.05.012
https://www.sciencedirect.com/science/article/pii/S0921818118307197

Free pdf:
http://palaeo.gly.bris.ac.uk/Benton/reprints/2019Jurong.pdf


Highlights

The Jurong fishes represent the earliest marine vertebrate fauna in Triassic in China.
The Jurong fishes resemble the Early Triassic faunas from Chaohu and Madagascar.
Collagen layers of fish scales, fins, organ walls and cartilages are well-preserved.
The fish fauna was buried in an euxinic environment indicated by pyrite framboids.
A four-step taphonomic process is recognized for the formation of the fish nodule.

Abstract

As the higher trophic guilds in marine food chains, top predators such as larger fishes and reptiles are important indicators that a marine ecosystem has recovered following a crisis. Early Triassic marine fishes and reptiles therefore are key proxies in reconstructing the ecosystem recovery process after the end-Permian mass extinction. In South China, the Early Triassic Jurong fish fauna is the earliest marine vertebrate assemblage in the recovery period. It is constrained as mid-late Smithian in age based on both conodont biostratigraphy and carbon isotopic correlations. The Jurong fishes are all preserved in calcareous nodules embedded in black shale of the Lower Triassic Lower Qinglong Formation, and the fauna comprises at least three genera of Paraseminotidae and Perleididae. The phosphatic fish bodies often show exceptionally preserved interior structures, including network structures of possible organ walls and cartilages. Microanalysis reveals the well-preserved micro-structures (i.e. collagen layers) of teleost scales and fish fins. Abundant small pyrite framboids, 2â5âÎm in diameter, are detected from the nodules and fish body surfaces, indicating a calm, euxinic burial environment. Coccoid-like microspheroids are also very abundant in the host rocks and near the fish fossil surfaces, implying that microbes may have participated in the burial process of the fishes. Taphonomic analysis uncovers the four-step formation process of the fish nodules. (1) Fishes lived in the oxic seawater in the upper ocean, and (2) their bodies sank to the anoxic seabed after death, with the body surface being wrapped by bacteria. (3) Microbial biofilms sealed body surfaces to prevent or delay the decay of the fleshy body. The decomposition of the body cavity and interior organs produced some CO2 and H2S gases. The former formed bicarbonate ions in seawater and attracted calcium ions to facilitate the precipitation of calcium carbonate, while the H2S combined with iron ions in seawater to form pyrite framboids. (4) The fish nodule gradually grew by precipitation of calcium carbonate in layers and embedding with pyrite framboids, and later the fish fossil nodule was compacted during diagenesis. Global faunal correlations indicate that the Jurong fishes are closely related to the Early Triassic fish faunas from Chaohu, Anhui Province and Madagascar.


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Free pdf:

J. G. Fennell, L. Talas, R. J. Baddeley, I. C. Cuthill and N. E. Scott-Samuel (2019)
Optimizing colour for camouflage and visibility using deep learning: the effects of the environment and the observer's visual system.
Journal of the Royal Society Interface 16(154): 20190183
doi: Âhttps://doi.org/10.1098/rsif.2019.0183.
https://royalsocietypublishing.org/doi/10.1098/rsif.2019.0183

Free pdf:
https://royalsocietypublishing.org/doi/pdf/10.1098/rsif.2019.0183


Avoiding detection can provide significant survival advantages for prey, predators, or the military; conversely, maximizing visibility would be useful for signalling. One simple determinant of detectability is an animal's colour relative to its environment. But identifying the optimal colour to minimize (or maximize) detectability in a given natural environment is complex, partly because of the nature of the perceptual space. Here for the first time, using image processing techniques to embed targets into realistic environments together with psychophysics to estimate detectability and deep neural networks to interpolate between sampled colours, we propose a method to identify the optimal colour that either minimizes or maximizes visibility. We apply our approach in two natural environments (temperate forest and semi-arid desert) and show how a comparatively small number of samples can be used to predict robustly the most and least effective colours for camouflage. To illustrate how our approach can be generalized to other non-human visual systems, we also identify the optimum colours for concealment and visibility when viewed by simulated redâgreen colour-blind dichromats, typical for non-human mammals. Contrasting the results from these visual systems sheds light on why some predators seem, at least to humans, to have colouring that would appear detrimental to ambush hunting. We found that for simulated dichromatic observers, colour strongly affected detection time for both environments. In contrast, trichromatic observers were more effective at breaking camouflage.

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