Uncus dzaugisi
| Uncus dzaugisi Temporal range:
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| Artist's interpretation of U. dzaugisi | |
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| Genus: | †Uncus Hughes et al., 2024
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| Species: | †U. dzaugisi
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| Uncus dzaugisi Hughes et al., 2024
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Uncus dzaugisi is an extinct species of animal which lived approximately 560 to 550 Ma ago during the late Ediacaran of Southern Australia. Its morphology suggests that it was a member of Ecdysozoa, which would make it the oldest member of the clade known so far.[1] It is currently the only member of the genus Uncus.
Discovery and name
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The team's excavation, led by Mary Droser, began in 2018 at the Nilpena Ediacara National Park which is known for its well preserved Ediacaran fossils.[2] During the excavation, the team noted the presence of hook-shaped indentations in the rock. At first, it was not looked into with much interest, but after discovering dozens of specimens they began to investigate the true identity of the indentations in the rock. The discovery of trace fossils in nearby sediment supported the fact that their findings were indeed fossils of a previously unknown organism.[1][2]
The generic name that was chosen, Uncus, is derived directly from the Latin word Uncus, meaning "hooked", in reference to the shape of many specimens. The specific name dzaugisi is the Latinisation of the surname of Mary, Matthew and Peter Dzaugis, made in honor of their contributions to fieldwork at the Nilpena Ediacara National Park.[1]
Description
[edit]Uncus is a soft-bodied, smooth cylindrical organism growing from 6 to 30 millimeters in length. The specimens have varying degrees of curvature to them with one end being wider than the other. The wider end is suspected as being the posterior end as seen in other ecdysozoans. Unlike most other Ediacaran organisms, it possibly had a sturdy external membrane, as evidenced by 77 out of the 82 specimens showing little to no deformation.[1]
The sharpness of the edges also shows that Uncus was free from the organic mats that covered the seabeds of Ediacaran Australia, showing that it may have most likely been motile, unlike sessile organisms which are preserved having softer margins due to the organic mat growing onto them. This is further supported with the existence of the ichnogenus Multina on one of the fossil beds where Uncus specimens were found, which it is proposed to be the maker of. Several specimens have also been found overlaying other Ediacaran organisms, such as felled Funisia, and even the feeding traces of other motile organisms such as Dickinsonia.[1]
Affinity
[edit]The sturdy membrane around the organism is possibly evidence of an early cuticle. This in addition to its body shape and motile lifestyle suggests Uncus was a member of Ecdysozoa, with possible relations to nematoids.[1] Many molecular clocks have estimated the origin of Ecdysozoa in the Ediacaran,[3][4][5] but no definitive ecdysozoans have been found. If Uncus is indeed an ecdysozoan, it would be the first Ediacaran example found and would finally bridge the gap between the early bilaterians of the Ediacaran and ecdysozoans like arthropods and priapulids otherwise first known from the Cambrian.
References
[edit]- ^ a b c d e f Hughes, Ian V.; Evans, Scott D.; Droser, Mary L. (18 November 2024). "An Ediacaran bilaterian with an ecdysozoan affinity from South Australia". Current Biology. doi:10.1016/j.cub.2024.10.030.
- ^ a b Nightingale, Sarah (18 November 2024). "Tiny worm makes for big evolutionary discovery". UC Riverside News.
- ^ Reis, Mario dos; Thawornwattana, Yuttapong; Angelis, Konstantinos; Telford, Maximilian J.; Donoghue, Philip C.J.; Yang, Ziheng (21 November 2024). "Uncertainty in the Timing of Origin of Animals and the Limits of Precision in Molecular Timescales". Current Biology. doi:10.1016/j.cub.2015.09.066. hdl:1983/829338e6-fcd5-4794-8028-3924ecba0929.
- ^ Rehm, Peter; Borner, Janus; Meusemann, Karen; von Reumont, Björn M.; Simon, Sabrina; Hadrys, Heike; Misof, Bernhard; Burmester, Thorsten (December 2011). "Dating the arthropod tree based on large-scale transcriptome data". Molecular Phylogenetics and Evolution. 61 (3): 880–887. doi:10.1016/j.ympev.2011.09.003.
- ^ Howard, Richard J.; Giacomelli, Mattia; Lozano-Fernandez, Jesus; Edgecombe, Gregory D.; Fleming, James F.; Kristensen, Reinhardt M.; Ma, Xiaoya; Olesen, Jørgen; Sørensen, Martin V.; Thomsen, Philip F.; Wills, Matthew A.; Donoghue, Philip C. J.; Pisani, Davide (July 2022). "The Ediacaran origin of Ecdysozoa: integrating fossil and phylogenomic data". Journal of the Geological Society. 179 (4). doi:10.1144/jgs2021-107. hdl:2445/186596.