Guizhouichthyosaurus

Guizhouichthyosaurus ("Guizhou fish lizard") is an extinct genus of Ichthyosaur which existed during the lower Carnian stage of the Late Triassic in southwest China. The genus contains the single species Guizhouichthyosaurus tangae.[1] It had been referred to the genus Shastasaurus in the past, but later study showed that it is likely distinct, since it lacks the characteristically short snout of that genus. The ichthyosaurs Cymbospondylus asiaticus, named in 2002, and Panjiangsaurus epicharis, named in 2003, are junior synonyms of this genus.[2]

Guizhouichthyosaurus Temporal range: Middle Triassic, 235–221 Ma PreꞒ Ꞓ O S D C P T J K Pg N
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Reptilia
Order:	†Ichthyosauria
Genus:	†Guizhouichthyosaurus
Species:	†G. tangae
Binomial name
†Guizhouichthyosaurus tangae Cao & Luo, 2000 (type)
Synonyms
Cymbospondylus asiaticus Li & You, 2002 Panjiangsaurus epicharis Chen & Chang, 2003

Appearance

Following the Permian-Triassic extinction event (also colloquially known as The Great Dying), the decline and disappearance of eugeneodonts and giant nautiloids left an environmental niche empty that many marine reptiles began to fill. Guizhouichthyosaurus was one of the largest marine vertebrates of the time, whose only predators composed of large macro-predatory Ichthyosaurs (that of which preferred to hunt smaller ichthyosaurs). The rise of the shelled cephalopods (ammonites that survived the Permian-Triassic extinction event, along with the appearance of belemnites) gave ichthyosaurs an abundant food supply with little competition. Guizhouichthyosaurus and other ichthyosaurs began to adapt to hunting these cephalopods through larger eyes, and thick bodies, to handle the pressures of diving deep to hunt for their prey.

Paleobiology

Unlike other Triassic ichthyosaurs, which were small fast-moving pursuit predators, the Guizhouichthyosaurus had a body build to Shastasaurus and was assumed to have had a similar feeding strategy. Guizhouichthyosaurus was believed to have been a very large suction-feeder, gaining assistance in hunting invertebrates, soft-shelled cephalopods and fish with its narrowed snout. Guizhouichthyosaurus was originally assumed to have inhabited an ecological niche similar to modern-day humpback whales, their caudal fins being reduced and its head remaining small in comparison to its body.[3] However, discoveries from China suggest that it was an apex predator. In 2020, a fossil specimen of Guizhouichthyosaurus measuring roughly 5 m (16 ft) was described after being discovered in 2010 by Motani et al., with a fossil thalattosaur of the genus Xinpusaurus measuring 4 m (13 ft) in its stomach. The ichthyosaur is believed to have died from asphyxiation while swallowing the thalattosaur. The bones of the Xinpusaurus show no signs of decay or decomposition, suggesting that the Guizhouichthyosaurus had attacked and consumed its intended target while it was still alive. Until this discovery, it had been assumed that large ichthyosaurs with peg-like teeth such as Guizhouichthyosaurus only preyed upon soft-bodied small animals like squid and ammonites, but comparisons with modern marine predators such as killer whales suggest large, serrated teeth were not a necessity in ichthyosaurs for hunting large prey and that megapredation was more common in ichthyosaurs than was previously assumed.[4][5][6]

Disappearance

Near the end of the Triassic deadly marine biocalcification began to occur, along with oceanic acidification, sea-level fluctuations and the Central Atlantic Magmatic Province(CAMP) releasing carbon dioxide, sulfur dioxide and aerosols. These environmental catastrophes caused the extinction of the conodonts and 34% of other marine genera to disappear.[7] With the amount of pressure upon the Guizhouichthyosaurus food supply, and the amount of competition it had with other larger ichthyosaurs at the time, it became less and less common reaching towards the Jurassic, and after the Triassic-Jurassic extinction event it became extinct. Other ichthyosaurs however adapted to its lifestyle, and many larger species emulated its body shape and hunting style.

See also

• List of ichthyosaurs
• Timeline of ichthyosaur research

References

1. Cranial Osteology of Guizhouichthyosaurus tangae (Reptilia: Ichthyosauria) From the Upper Triassic of China (2006). By Michael W. Maisch, Xin-Ru Pan, Zuo-Yu Sun, Tao Cai, Da-Peng Zhang, Jia-Lin Xie.
2. Sander, P.M.; Chen, X.; Cheng, L.; Wang, X. (2011). "Short-Snouted Toothless Ichthyosaur from China Suggests Late Triassic Diversification of Suction Feeding Ichthyosaurs". PLoS ONE. 6 (5): e19480. doi:10.1371/journal.pone.0019480. PMC 3100301. PMID 21625429.
3. http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0019480 "Short-Snouted Toothless Ichthyosaur from China Suggests Late Triassic Diversification of Suction Feeding" Retrieved September 9, 2014
4. http://www.sci-news.com/paleontology/thalattosaur-xinpusaurus-xingyiensis-stomach-triassic-ichthyosaur-guizhouichthyosaurus-08774.html
5. https://gizmodo.com/incredible-fossil-shows-a-sea-monster-in-the-belly-of-a-1844776009?fbclid=IwAR0u7tNsNzh6kriYTk53mg0IAqqpFqO-7-CU3m4qslyzev22yGfYieichmE
6. https://www.nationalgeographic.com/science/2020/08/ancient-marine-reptile-ichthyosaur-preyed-on-large-sea-creature-thalattosaur/
7. Graham Ryder; David E. Fastovsky; Stefan Gartner (1996). The Cretaceous-Tertiary Event and Other Catastrophes in Earth History. Geological Society of America. p. 19. ISBN 9780813723075.