Generic revision of holocystitid blastozoans
Brightonicystis is a valid genus characterised by nine or more oral plates, with two in the B and D ambulacra not reaching the inner mouth edge; five ambulacral facets shared by oral and facetal plates; two generations of smooth thecal plates with buried humatipores. Brightonicystis contains two...
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| Main Author: | |
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| Format: | Article |
| Language: | English |
| Published: |
Institute of Paleobiology PAS
2025-03-01
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| Series: | Acta Palaeontologica Polonica |
| Subjects: | |
| Online Access: | https://www.app.pan.pl/archive/published/app70/app012122024.pdf |
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| Summary: | Brightonicystis is a valid genus characterised by nine or more oral plates, with two in the B and D ambulacra not reaching
the inner mouth edge; five ambulacral facets shared by oral and facetal plates; two generations of smooth thecal plates
with buried humatipores. Brightonicystis contains two named species, Brightonicystis gregaria and Brightonicystis sal
moensis, with other unnamed taxa known from Canada and Sweden, all of which are Hirnantian. All other holocystitid
genera are Silurian. A review of the Holocystitidae confirms the established genera Holocystites and Brightonicystis both
characterised by five ambulacra with shared facets, as well as Trematocystis, Pustulocystis, and Paulicystis all character
ised by four ambulacra. The hypothesis that the differences between Pentacystis (without orals) and Osgoodicystis (with
two or six orals) are taphonomic is reviewed and rejected. The peristome border and food grooves should be absent in
Pentacystis if the oral plates on which they occur were lost during preservation. Pentacystis species show both features
developed on facetal plates. Osgoodicystis is reinstated as a valid genus with six narrow orals. Moyacystis gen. nov.,
type species Osgoodicystis cooperi, bears only two orals (O1 and O6) and facetal plates with oral pores in the peristome
border. Pentacystis, Osgoodicystis, and Moyacystis gen. nov., all possess five ambulacral facets restricted to single
facetal plates and a smooth thecal surface. The Australian genus Austrocystites is a junior synonym of Trematocystis.
Holocystitid subfamilies and subgenera introduced by Frest and Strimple (in Frest et al. 2011) are not discussed herein. |
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| ISSN: | 1732-2421 |