Biology:Xenobrachyops
Xenobrachyops is an extinct monotypic genus of brachyopid temnospondyl amphibian from the Arcadia Formation of Queensland, Australia. The type species is Xenobrachyops allos.[1]
History of study
Material of Xenobrachyops was first collected from the Duckworth Creek locality in exposures of what was then considered the Rewan Formation (now the Arcadia Formation of the Rewan Group).[2] The holotype skull of Xenobrachyops allos, the type species, was collected from a red mudstone. Howie (1972) originally placed the species in Brachyops, although some concerns were expressed with existing quantitative (non-phylogenetic) methods for differentiating taxa.
Warren (1981) described a pair of hemimandibles from Duckworth Creek that were referred to Brachyops allos on the basis of similar curvature, size, and dentition.[3]
Later work by Warren & Hutchinson (1983) recovered 'Brachyops allos' as being distantly related to Brachyops laticeps within Brachyopoidea, leading them to propose the new genus Xenobrachyops from the Greek xenos ("strange") and Brachyops.
The holotype was subsequently restudied by Damiani & Warren (1996),[4] who identified several additional diagnostic features of the taxon.
The review of Brachyopoidea by Warren & Marsicano (2000) also lists an undescribed fragmentary clavicle and an undescribed fragmentary interclavicle as referred specimens, although these specimens were not listed in Schoch & Milner's (2014) review.[5][6]
Anatomy
The diagnosis of X. allos has been relatively unchanged, with Schoch & Milner listing only two features, denticles on the parasphenoid at the base of the cultriform process and a posteriorly expanded ectopterygoid that extends along the margin of the subtemporal fossa.[6] Previous workers have remarked on features that were unusual or unique at the time of study. Warren & Marsicano (2000) noted several plesiomorphic features, such as an angled medial margin of the subtemporal fossa (not parallel to the skull midline), the absence of a palatoquadrate fissure between the squamosal and the palate, and the posteriorly truncated quadrate ramus of the pterygoid.[5] Damiani & Warren (1996) considered the posteriorly expanded ectopterygoid to be an autapomorphy, though they noted that this feature is present to a lesser extent in Batrachosuchus and Batrachosuchoides.[4] They also considered a tripartite anterior palatal vacuity to be autapomorphic. An ossified septomaxilla and a lateral exposure of the palatine (LEP) are other features not always observed in brachyopids.[4]
Phylogenetic relationships
Phylogenetic analyses usually recover Xenobrachyops at or near the base of Brachyopidae.[5][7]
References
- ↑ Warren, A.A. & Hutchinson, M.N., (1983). The last labyrinthodont? A new brachyopoid (Amphibia, Temnospondyli) from the Early Jurassic Evergreen Formation of Queensland, Australia. Philosophical Transactions of the Royal Society of London B 303, 1–62.
- ↑ Howie, A. (1972). "A brachyopid labyrinthodont from the Lower Trias of Queensland". Proceedings of the Linnean Society of New South Wales 96: 268–277. https://www.biodiversitylibrary.org/part/47790.
- ↑ Warren, Anne A. (1981). "The lower jaw of the labyrinthodont family Brachyopidae.". Memoirs of the Queensland Museum, Nature 20 (2): 285–289. https://search.informit.org/doi/abs/10.3316/informit.T2025093000001490091672575.
- ↑ 4.0 4.1 4.2 Damiani, Ross J.; Warren, Anne (January 1996). "A new look at members of the superfamily Brachyopoidea (Amphibia, Temnospondyli) from the Early Triassic of Queensland and a preliminary analysis of brachyopoid relationships" (in en). Alcheringa: An Australasian Journal of Palaeontology 20 (4): 277–300. doi:10.1080/03115519608619472. ISSN 0311-5518. Bibcode: 1996Alch...20..277D. http://www.tandfonline.com/doi/abs/10.1080/03115519608619472.
- ↑ 5.0 5.1 5.2 Warren, Anne; Marsicano, Claudia (2000-09-25). [0462:apotbt2.0.co;2 "A phylogeny of the Brachyopoidea (Temnospondyli, Stereospondyli)"]. Journal of Vertebrate Paleontology 20 (3): 462–483. doi:10.1671/0272-4634(2000)020[0462:apotbt2.0.co;2]. ISSN 0272-4634. https://doi.org/10.1671/0272-4634(2000)020[0462:apotbt]2.0.co;2.
- ↑ 6.0 6.1 Schoch, Rainer R.; Milner, Andrew R. (2014), Sues, Hans-Dieter, ed., Handbuch der Paläoherpetologie = Encyclopedia of paleoherpetology. Temnospondyli I / by Rainer R. Schoch & Andrew R. Milner, München: Verlag Dr. Friedrich Pfeil, ISBN 978-3-89937-170-3
- ↑ Hart, Lachlan J.; Gee, Bryan M.; Smith, Patrick M.; McCurry, Matthew R. (2022-12-14). "A new chigutisaurid (Brachyopoidea, Temnospondyli) with soft tissue preservation from the Triassic Sydney Basin, New South Wales, Australia". Journal of Vertebrate Paleontology 42 (6). doi:10.1080/02724634.2023.2232829. ISSN 0272-4634. Bibcode: 2022JVPal..42E2829H. https://doi.org/10.1080/02724634.2023.2232829.
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