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Eunotia is the largest and most diverse genus within the family Eunotiaceae, a primarily freshwater group of diatoms often found in dilute, acidic and humic-stained environments. Species in this genus are characterized by being asymmetric along their apical axis, symmetric about the transapical axis, and with a simple and reduced raphe system situated largely on the mantle and restricted to the apical ends of the valve. In addition, Eunotia taxa have one or more rimoportula per valve, usually close to the apex. Because of their reduced raphe system, coupled with the presence of rimoportulae, Eunotia and its relatives are often viewed as the oldest lineage of raphe-bearing diatoms. To date, the oldest remains of Eunotia species have been reported from the early to middle Eocene, including from the Giraffe Pipe locality, an ancient Eocene fossil site located in northern Canada near the Arctic Circle. Rocks from this site contain a large and diverse assemblage of Eunotia taxa. The purpose of this study is to begin to characterize this assemblage with descriptions of three new species, Eunotia giraffensis sp. nov., E. petasum sp. nov. and E. pseudonaegelii sp. nov. The new species, representing the longest specimens found at the Giraffe Pipe locality, each possess characteristics common to Eunotia making them easily assigned to this genus. Because the Eunotia lineage was well established by the early part of the Eocene, it is likely to be significantly older.
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This content will become publicly available on June 12, 2025
Light and Scanning Observations on a Denticula species reported from South Africa and endemism of the diatom genus Tetralunata (Rhopalodiales, Bacillariophyceae)
Denticula costata Hustedt was originally described from fossil material from Sumatra and later assigned to the genus Tetralunata. Although Tetralunata was thought to be endemic to Indonesia, D. costata has been reported from wetwalls from South Africa. This disparity in locality prompted us to investigate the D. costata in South Africa further. D. costata (now T. costata) specimens and the species reported from South Africa were different in size, shape, and structure of the raphe system. These differences, as well as comparisons to other Denticula species, allowed us to determine that the South African specimens have not been described previously. Valve ultrastructure, including the canal raphe, areolae with volate occlusions, and presence/structure of the septa suggest this new species belongs to the genus Tetralunata. This is the first report of Tetralunata from outside of Indonesia. Herein, we describe Tetraluanata schoemanii sp. nov. and its systematic placement close to, but separate from, Epithemia. This first report of Tetralunata from outside of Indonesia, increases our understanding of the genus range and displays a unique biogeographical pattern that warrants further investigation in the future.
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- Award ID(s):
- 2222945
- PAR ID:
- 10516830
- Publisher / Repository:
- Magnolia Press
- Date Published:
- Journal Name:
- Phytotaxa
- Volume:
- 652
- Issue:
- 4
- ISSN:
- 1179-3155
- Page Range / eLocation ID:
- 284 to 292
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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