User:Slate Weasel/sandbox

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Besanosaurus

Corosaurus

The initial specimen of Corosaurus was found in the summer 1935 by

Natrona County. After the initial excavation, more of the specimen was collected by Allsen and Horace Thomas. Extracting the specimen was complicated, as it was found in a quarry dump and fragmented. To expose the specimen from the hard calcareous concretions that it was embedded in, the matrix was ground down using a silicon carbide bit.[1]

Knight asked

E.C. Case to determine what the specimen was, and sent it to him so he could study it. In a 1936 publication, Case determined that it represented a new genus and species of nothosaur, and named it Corosaurus alcovensis, with Corus meaning 'northwest quarter'.[1]

"Callawayia" wolonggangense

History of study

There are two known specimens of "Callawyia" wolonggangense, the

Callawayia neoscapularis, and therefore assigned it to that genus, thereby extending both the geographic and temporal range of the genus. However, there were differences between C. neoscapularis and the new Chinese material, so the authors named a new species, C. wolonggangense, to contain these new fossils. The name of the species refers to a hill, Wolonggang, rich in well-preserved fossils.[2]

The assignment of this species to the genus Callawayia was contested by Michael Masich in 2010. Furthermore, he noted that the species was differentiated by the configuration of bones in the skull, which can be influenced by the quality of a specimen's preservation and how well it was

Guizhouichthyosaurus tangae, another ichthyosaur from the same place and time,[2] but refrained from synonymizing them, provisionally reassigning "C." wolonggangense to Guizhouichthyosaurus wolonggangense until it could be studied in more detail.[3] In a 2012 study, Shang Qing-Hua and coauthors restudied the anatomy of the skull of Guizhouichthyosaurus tangae, which they assigned to the geuns Shastasaurus as S. tangae, an assignment not accepted by other authors.[3][4] They considered "Callawayia" wolonggangense to be quite similar to G. tangae and also proposed that the two species were synonymous.[5] In a subsequent paper, Shang and Li Chun reaffirmed this synonymy, finding "C." wolonggangense to fall within the range of variation of G. tangae.[6]

However, "C." wolonggangense has also been considered a distinct species. Cheng Ji and coauthors conducted a phylogenetic study of ichthyosaurs in 2015, including "C." wolonggangense in their analysis. Their work further rejected the assignment of this species to Callawayia, failing to find unique features linking it to C. neoscapularis. However, they also found it to not be assignable to Guizhouichthyosaurus either.[4]

Description

"Callawayia" wolonggangense is a medium-sized ichthyosaur, based on the size of its lower jaw, measuring about 70 centimetres (2.3 ft) long.

roots implanted into sockets.[2]

The configuration of the skull bones is preserved in the specimens, but it is uncertain how accurately.

squamosals from reaching the rim. Each parietal was described by Chen and coauthors as bearing a prominent ridge, behind which there is a shelf-like surface.[2] However, Ji and coauthors stated in 2015 that this feature was not present in "C." wolonggangense.[4]

The trunk of the holotype of "C." wolonggangense is about 1.5 metres (4.9 ft) long. Exactly how many vertebrae the trunk contained is not certain, but Chen and coauthors estimated that there were between 46 and 65. The

humeri are short, wide bones with a strong ridge on their upper sides. Each foreflipper contains four digits. The front edges of the bones in the frontmost digit bear notches.[2]

Classification

While recognized as a

Shonisauridae, alonside Shonisaurus and Himalayasaurus.[3]

In their 2015 phylogenetic analysis, Ji and coauthors found "C." wolonggangense to belong to Shastasauridae, in turn part of a larger group called Merriamosauria. Guizhouichthyosaurus was also found to belong to this group, though Callawayia was not.[4] A modified version of this analysis run by Gabriele Bindellini and coauthors in 2021, who found different configurations for the classification of the shastasaurids. Some of their analyses found shastasaurids to form a natural group like that of Ji an colleagues; however, the relationships within this group were uncertain. "C. wolonggangense was sometimes found to form part of a small group in Shastasauridae along with Guizhouichthyosaurus and Besanosaurus, though this was not always the case. Furthermore, other analyses run by these authors found shastasaurids to not be a natural grouping, instead being a series of branches each more closely related to other merriamosaurs.[7]

  1. ^ a b Case, E.C. (1936). "A nothosaur from the Triassic of Wyoming" (PDF). University of Michigan Contributions from the Museum of Paleontology. 5 (1): 1–36.
  2. ^ a b c d e f g h i j Chen, X.H.; Cheng, L.; Sander, P.M. (2007). "A new species of Callawayia (Reptilia: Ichthyosauria) from the Late Triassic in Guanling, Guizhou" (PDF). Geology in China. 34 (6): 974–982.
  3. ^ a b c d e Maisch, M. W. (2010). "Phylogeny, systematics, and origin of the Ichthyosauria – the state of the art" (PDF). Palaeodiversity. 3: 151–214.
  4. ^
    S2CID 85621052
    .
  5. doi:10.1360/zd-2012-42-5-773
    .
  6. ^ Shang, Q. H.; Li, C. (2013). "On the sexual dimorphism of Shastasaurus tangae (Reptilia: Ichthyosauria) from the Triassic Guanling Biota, China" (PDF). Vertebrata PalAsiatica. 51 (4): 253–264.
  7. PMID 33996277
    .
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