#psephochelys

[vickysaurus]

Henodus and Psephochelys, two placodonts from the Triassic.

[extinctworld-ua]

Psephochelys

Psephochelys — вимерлий рід плакодонтів з пізнього тріасу Китаю. Представлений єдиним видом — Psephochelys polyosteoderma, названим у 2002 році на основі єдиного часткового скелета, знайденого у відслоненні формації Фалун карнійського віку в провінції Гуйчжоу.

Повний текст на сайті "Вимерлий світ":

https://extinctworld.in.ua/psephochelys/

[wtf-triassic]

Odontochelys semitestacea

By @alphynix​

Etymology: Toothed Turtle

First Described By: Lie et al., 2008 

Classification: Biota, Archaea, Proteoarchaeota, Asgardarchaeota, Eukaryota, Neokaryota, Scotokaryota, Opimoda, Podiata, Amorphea, Obazoa, Opisthokonta, Holozoa, Filozoa, Choanozoa, Animalia, Eumetazoa, Parahoxozoa, Bilateria, Nephrozoa, Deuterostomia, Chordata, Olfactores, Vertebrata, Craniata, Gnathostomata, Eugnathostomata, Osteichthyes, Sarcopterygii, Rhipidistia, Tetrapodomorpha, Eotetrapodiformes, Elpistostegalia, Stegocephalia, Tetrapoda, Reptiliomorpha, Amniota, Sauropsida, Eureptilia, Romeriida, Diapsida, Neodiapsida, Sauria, Archosauromorpha?, Archelosauria, Pantestudines, Odontochelyidae  

Time and Place: Around 232 million years ago, in the Carnian age of the Late Triassic

Odontochelys is known from the Lower Member of the Xiaowa Formation of China, commonly known as the Guanling Fauna

Physical Description: Odontochelys is one of the earliest known turtles - preceded by one, possibly two, precursors other than stem members of the family group - and it showcases how this extremely unique group managed to evolve in the chaos that was the Triassic Explosion. It was simultaneously similar to and very different from living turtles, a true transitional organism. Like other reptiles, it had teeth embedded in its jaws, rather than the toothless beak found in turtle mouths. Like turtles, it had the lower plastron extending from its ribs, but unlike living turtles it had no upper shell - instead, it just had widened ribs and no bony shell around its body. The ribs and the vertebrae were put together differently from modern turtles as well, and its skull was more stretched out compared to its living relatives. It didn’t have fused tail bones, and its scapulae were very different from living turtles. It had short limbs and long, thick fingers, as well as a decently sized shell. It was about forty centimeters long from snout to tail tip. 

Diet: The diet of Odontochelys is fairly uncertain, despite us having its teeth; though they are small and peg like, we can’t really extrapolate a function since we don’t actually know its precise ecology! They may have been used for stripping plants, but it’s also possible they were used to chipp up algae and other aquatic water plants, or even invertebrates! So, more research there is clearly needed. 

Behavior: The life history of Odontochelys is actually a big mystery. It was found in a marine environment, leading initial studies to indicate it was marine. However, it had the hands of a fresh water organism, including fresh water turtles today. Furthermore, studies of other early turtles indicate that turtles first arose on the land, rather than in the water, and later groups would adapt to water life; the limbs of Odontochelys share similarities with tortoises and support a terrestrial lifestyle. So, the ecology of Odontochelys has been a constant battle. That said, there is some evidence that it was actually marine - and may represent an early experiment in ocean life by turtles. One fossil of Odontochelys indicates that it had completely messed up shoulder bones, likely due to a problem in life rather than destruction of the fossil. This pattern resembles decompression sickness, aka the bends, aka the condition caused by a diving animal coming up much too fast from a lower depth. Modern turtles have complex behavioral adaptations to avoid the bends, so Odontochelys may be an early experiment in marine life in a group mostly adapted for terrestrial life. In this transition to ocean life, it not only lacked better physical adaptations for the ocean, but also better behavioral ones, and was stricken with the bends on its trip back to the surface. So, as we try to determine its ecology and behavior, these clued paint a rich tapestry of the world’s most transitional turtle. A pioneer! 

Ecosystem: Odontochelys was found in - and thus, the null hypothesis is that it lived in - an ocean environment near the coast of the Tethys sea. This was a deep, open ocean - pelagic, hence the bends and problems Odontochelys faced trying to deal with the ocean. It was a very fertile ecosystem as well, with a variety of Triassic marine animals showcasing the rapid evolution of these groups. Among the invertebrates, there were many different types of Ammonites, plenty of bivalves, brachiopods, and crinoids & sea cucumbers as well. Still, the fascinating part of the ecosystem was the sheer number of marine reptiles. There were Thalattosaurs such as Anshusaurus and Xinpusaurus; Placodonts like Psephochelys and Sinocyamodus; and Ichthyosaurs like Qianicthyosaurus, Guizhouichthyosaurus, Guanlingsaurus, and Callawayia. One of many beautiful deposits of marine animals from this Period - and the many Ichthyosaurs would have been major predators of the relative n00b Odontochelys. 

Other: Odontochelys also just looks really weird because it basically looks like your usual turtle except it doesn’t have a freaking shell so here we are with this oddity. It’s transitional in shape, transitional in ecology, transitional in behavior, and just. What the heck. What the heck, Odontochelys. If you need more proof for evolution despite knowing about the dinosaur - bird transition, have I got a friend for you. 

~ By Meig Dickson 

Sources Under the Cut

Anquetin, J. 2012. Reassessment of the phylogenetic interrelationships of basal turtles (Testudinata). Journal of Systematic Palaeontology 10(1):3-45. 

Bradley Shaffer, H., E. McCartney-Melstad, T. J. Near, G. G. Mount, P. Q. Spinks. 2017. Phylogenomic analyses of 539 highly informative loci dates a fully resolved time tree for the major clades of living turtles (Testudines). Molecular Phylogenetics and Evolution 115: 7 - 15. 

Feldmann, R. M., C. E. Schweitzer, S. Hu, J. Huang, Q. Zhang, C. Zhou, W. Wen, T. Xie, E. P. Maguire. 2017. A new Middle Triassic (Anisian) cyclidan crustacean from the Luoping Biota, Yunnan Province, China: morphologic and phylogenetic insights. Journal of Crustacean Biology 37 (4): 406 - 412. 

Gilbert, S. F. 2007. How the turtle gets its shell. Biology of Turtles: The Structures to Strategies of Life. 

Heiss, E. 2010. Functionality and plasticity of turtle-feeding with special emphasis on oropharyngeal structures. Universitat Wien Doctoral Dissertation. 

Hess, H., W. Etter, and H. Hagdorn. 2016. Roveacrinida (Crinoidea) from Late Triassic (early Carnian) black shales of Southwest China. Swiss Journal of Paleontology 135(2):249-274. 

Joyce, W. G. 2015. The origin of turtles: A paleontological perspective. Journal of Experimental Zoology Part B: Molecular and Developmental Evolution 324 (3): 181 - 193. 

Lee, M. S. Y. 2013. Turtle origins: Insights from phylogenetic retrofitting and molecular scaffolds. Journal of Evolutionary Biology 26 (12): 2729 - 2738. 

Lemell, P., N. Natchev, C. J. Beisser, E. Heiss. 2019. Feeding in Turtles: Understanding Terrestrial and Aquatic Feeding in a Diverse but Monophyletic Group. Feeding in Vertebrates: 611 - 642. 

Li, C., and O. Rieppel. 2002. A new cyamodontid placodont from Triassic of Guizhou, China. Chinese Science Bulletin 47(5):403-407. 

Li, C., X. C. Wu, O. Rieppel, L. T. Wang, and L. J. Zhao. 2008. An ancestral turtle from the Late Triassic of southwestern China. Nature 456:497-501. 

Lu, H., D.-Y. Jiang, R. Motani, P.-G. Ni, Z.-Y. Sun, A. Tintori, S.-Z. Xiao, M. Zhou, C. Ji, W.-L. Fu. 2018. Middle Triassic Xingyi Fauna: Showing turnover of marine reptiles from coastal to oceanic environments. Palaeoworld 27 (1): 107 - 116. 

Luo, M., Y.-M. Gong, G. R. Shi, Z.-Q. Chen, J. Huang, S. Hu, X. Feng, Q. Zhang, C. Zhou, W. Wen. 2018. Palaeoecological Analysis of Trace Fossil Sinusichnus sinuosus from the Middle Triassic Guanling Formationin Southwestern China. Journal of Earth Science 29: 854 - 863. 

Meredith, R. W., J. Gatesy, M. S. Springer. Molecular decay of enamel matrix protein genes in turtles and other edentulous amniotes. BMC Evolutionary Biology 13: 20. 

Neenan, J. M., N. Klein, T. M. Scheyer. 2013. European origin of placodont marine reptiles and the evolution of crushing dentition in Placodontia. Nature Communications 4: 1621. 

Nicholls, E. L., C. Wei, and M. Manabe. 2002. New material of Qianichthyosaurus Li, 1999 (Reptilia, Ichthyosauria) from the Late Triassic of southern China, and implications for the distribution of Triassic icthyosaurs. Journal of Vertebrate Paleontology 22(4):759-765. 

Reisz, R. R., J. J. Head. 2008. Palaeontology: Turtle origins out to sea. Nature 456 (7221): 450 - 451. 

Rothschild, B. M., V. Naples. 2015. Decompression syndrome and diving behavior in Odontochelys, the first turtle. Acta Palaeontologica Polonica 60 (1): 163 - 167. 

Schoch, R. R., H.-D. Sues. 2015. A Middle Triassic stem-turtle and the evolution of the turtle body plan. Nature 523 (7562): 584 - 587. 

Shang, Q.-H., and C. Li. 2009. On the occurrence of the ichthyosaur Shastasaurus in the Guanling biota (Late Triassic), Guizhou, China. Vertebrata PalAsiatica 47(3):178-193. 

Vermeij, G. J., R. Motani. 2017. Land to sea transitions in vertebrates: the dynamics of colonization. Paleobiology 44 (2): 237 - 250. 

Wang, X., G. H. Bachmann, H. Hagdorn, P. M. Sanders, G. Cuny, X. Chen, C. Wang, L. Chen, L. Cheng, F. Meng, and G. Xu. 2008. The Late Triassic black shales of the Guanling area, Guizhou province, south-west China: a unique marine reptile and pelagic crinoid fossil lagerstätte. Palaeontology 51(1):27-61. 

Wang, X., X. Chen, C. Wang, L. Cheng. 2009. The Triassic Guanling Fossil Group - A Key GeoPark from a barren mountain, Guizhou Province, China. Notebooks on Geology 3: Chapter 2: 11 - 28. 

[wtf-triassic]

Traumatocrinus caudex

By @stolpergeist​

Etymology: Wounded lily 

First Described By: Woehrmann, 1889

Classification: Biota, Archaea, Proteoarchaeota, Asgardarchaeota, Eukaryota, Neokaryota, Scotokaryota Opimoda, Podiata, Amorphea, Obazoa, Opisthokonta, Holozoa, Filozoa, Choanozoa, Animalia, Eumetazoa, Parahoxozoa, Bilateria, Nephrozoa, Deuterostomia, Ambulacraria, Echinodermata, Crinozoa, Crinoidea, Articulata, Encrinida

Status: Extinct 

Time and Place: 235 to 221.5 million years ago, from the Carnian to the Norian of the Late Triassic.

Traumatocrinus is known from Austria, China, Germany, India, Indonesia, Iran, and Italy.

Physical Description: Traumatocrinus was very similar in appearance to modern crinoids, also known as sea lilies. A crinoid is a relative of sea stars and sea urchins. The mouth faces upwards and is surrounded by a bunch of arms, each bearing many filtering appendages called pinnules. A stalk extends from the body, and at the end is a holdfast that roots the crinoid on the seafloor. Almost like kelp. Crinoids have planktonic larvae, in contrast to sedentary adults. Traumatocrinus had ten pairs of major arms around the mouth, and mostly differs from living crinoids physically in being huge - the largest can have stalks up to 11 meters (36 feet) long.

Diet: Like other crinoids, Traumatocrinus would have filter-fed, filtering plankton and tiny particles of food floating in the water with its arms.

Behavior: Most crinoids have the decency to at least root on the seafloor. But nope, not Traumatocrinus. Traumatocrinus has to live up to its trauma-envoking name. No, Traumatocrinus is specialized for rooting on floating driftwood. Yeah. It’s straight-up pseudoplanktonic. A single floating trunk could sustain up to 150 Traumatocrinus. As crinoid numbers increased, they tended to cluster around each end of the log. Imagine swimming in the Triassic seas and you see this log floating by that has an entire forest of eleven-meter-long crinoids on it.

Ecosystem: Traumatocrinus lived on wood floating in the open ocean. The seafloor in the area was richly populated by bivalves, but they don’t seem to have shared the driftwood with Traumatocrinus. Small fish and ammonites were also present where Traumatocrinus lived, and if I may speculate, it’s possible they may have even found shelter among the floating crinoid forests. Witnesses to the Eldritch mass of crinoids floating by included ichthyosaurs such as Guizhouichthyosaurus and Qianichthyosaurus, placodonts like Psephochelys and Placodus, and thalattosaurs like Anshunsaurus, Sinocyamodus, and Xinpusaurus. 

Other: Surprisingly enough Traumatocrinus is not the only log-loving crinoid. The later, unrelated crinoids Seirocrinus and Pentacrinus also adapted to root on driftwood, and appear to have outcompeted the larger Traumatocrinus. They went extinct in the Jurassic, possibly due to the appearance of wood-boring bivalves that took over the floating logs.

~ By Henry Thomas

Sources under the Cut

Hagdorn, H., Wang, X., Wang, C. 2007. Palaeoecology of the pseudoplanktonic Triassic crinoid Traumatocrinus from Southwest China. Palaeogeography, Palaeoclimatology, Palaeoecology 247 (3-4): 181-196.

Hagdorn, H., Wang, X. 2015. The pseudoplanktonic crinoid Traumatocrinus from the Late Triassic of Southwest China - Morphology, ontogeny, and taphonomy. Palaeoworld 24 (4): 479-496.