Arimasia
| Arimasia Temporal range: Ediacaran
| |
|---|---|
Scientific classification 
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| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Porifera |
| Genus: | †Arimasia Runnegar et al., 2024 |
| Species: | †A. germsi
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| Binomial name | |
| †Arimasia germsi Runnegar et al., 2024
| |
Arimasia germsi is an extinct sponge from the late Ediacaran, with possible affinities to the Archaeocyatha clade. Estimated to be about 543 million years old, A. germsi has been identified as possibly being the oldest known Archaeocyath to date. Its fossil material was found between 1993 and 1996 from the Nama Group in Namibia.[1]
Discovery and name
[edit]The fossil material of Arimasia was found from the Nama Group of Namibia during the years of 1993, 1995 and 1996, and officially described in 2024.[1]
The generic name Arimasia is derived from the place name of Arimas farm, the type locality of the fossil material. The specific name germsi is derived from the surname of Gerard J.B. Germs, celebrating the 50th anniversary of his Ph.D. dissertation on The stratigraphy and paleontology of the lower Nama Group, South West Africa.[1]
Description
[edit]Arimasia germsi is possibly the earliest known Archaeocyath sponge to be found in the Ediacaran, with possible relations to the Monocyathida order, partially sharing certain features seen in the clade, although missing a couple of key details.
It has a conical form, which grew up to a max of 20 mm (0.8 in) in height. It features a sealed rounded base, with a circular opening at the top, which extends into the cone. It bears eight irregular rugae on the lower part of its body, the body itself being granular in nature, forming a mesh-like appearance.[1]
Some specimens on a particular slab are oriented in a certain direction, suggesting that Arimasia may have been tethered to the substrate.[1] Arimasia has also been noted to pass the criteria for being classified as a sponge as set out by Antcliffe et al.,[2] with the meshed body being similar to that of Archaeolynthus contractus, but does not feature the minerlised bodies that all sponges have. As such, it has been suggested that Arimasia is a unmineralised, single-walled Archaeocyath, perhaps even a stem-group Demosponge, along with possibly being related to vauxiid sponges, which are known to have unmineralised bodes. [1][3]
See also
[edit]References
[edit]- ^ a b c d e f Runnegar, Bruce; Gehling, James G.; Jensen, Sören; Saltzman, Matthew R. (October 2024). "Ediacaran paleobiology and biostratigraphy of the Nama Group, Namibia, with emphasis on the erniettomorphs, tubular and trace fossils, and a new sponge, Arimasia germsi n. gen. n. sp". Journal of Paleontology. 98 (S94): 1–59. Bibcode:2024JPal...98S...1R. doi:10.1017/jpa.2023.81.
- ^ Antcliffe, Jonathan B.; Callow, Richard H. T.; Brasier, Martin D. (November 2014). "Giving the early fossil record of sponges a squeeze". Biological Reviews. 89 (4): 972–1004. doi:10.1111/brv.12090. PMID 24779547.
- ^ Wei, Fan; Zhao, Yang; Chen, Ailin; Hou, Xianguang; Cong, Peiyun (September 2021). "New vauxiid sponges from the Chengjiang Biota and their evolutionary significance". Journal of the Geological Society. 178 (5). Bibcode:2021JGSoc.178..162W. doi:10.1144/jgs2020-162.