Taxon Account

Ulnaria (Kützing) P. Compère; 2001; 100

Key references

Williams D.M. 2011. Ulnaria: definitions and descriptions - a partial resolution. Diatom Research. 26(1-2): 149-153.


Cells typically long and thin, lying in valve or girdle view; valves linear or linear-lanceolate, with rounded, rostrate, capitate or swollen ends.

Frustules isopolar, isovalvar, bilaterally symmetrical.

Striae uniseriate, parallel; areolae small, circular. Marginal spines absent. Both apices with a large area of small pores (apical pore field) through which mucilage is secreted. In addition, a rimoportula is found close to each apex.

Axial area narrow. Central area variable; often forming a broad almost plain transverse area (fascia) though faint ‘ghost striae’ may be present within it.

Girdle of several bands including some closed hoops.

Two elongate chloroplasts per cell, located along the valves, though in unhealthy material these may split up, giving the appearance of many small discoid chloroplasts.


References are given in chronological order.

Compère P. 2001. Ulnaria (Kützing) Compère, a new genus name for Fragilaria subgen. Alterasynedra Lange-Bertalot with comments on the typification of Synedra Ehrenberg. Jahn R., Kociolek J.P., Witkowski A., Compère P. (eds) Lange-Bertalot-Festschrift: Studies on Diatoms. Dedicated to Prof. Dr. Dr. h.c. Horst Lange-Bertalot on the occassion of his 65th Birthday. A.R.G. Gantner Verlag. K.G. 97-102 pp Taxonomy
Williams D.M. 2011. Ulnaria: definitions and descriptions - a partial resolution. Diatom Research. 26(1-2): 149-153. ; Taxonomy; Morphology
Morales E.A., Rivera P., Wetzel C.E., Novais M.H., Hamilton P.B., Hofmann G., Ector L. 2013. New epiphytic araphid diatoms in the genus Ulnaria (Bacillariophyta) from Lake Tititaca, Bolivia. Diatom Research. 29(1): 41-54. Morphology; Illustrations; Taxonomy
Lange-Bertalot H., Ulrich S. 2014. Contributions to the taxonomy of needle-shaped Fragilaria und Ulnaria species. Lauterbornia. 78: 1-73. Type Illustration; Morphology; Taxonomy
Van de Vijver B., De Haan M., Mertens A., Cocquyt C. 2017. Ulnaria verhaegeniana, a new diatom (Bacillariophyta) species from Belgium. Phytotaxa. 326(3): 221-226. Morphology; Taxonomy; Type Illustration
Liu B., Williams D.M., Tan L. 2017. Three new species of Ulnaria (Bacillariophyta) from the Wuling Mountains Area, China. Phytotaxa. 306(4): 241-258. Morphology; Taxonomy; Illustrations
Liu B., Williams D.M., Liu Q., Yang X. 2019. Three species of Ulnaria (Bacillariophyceae) from China, with reference to the valve central area and apices. Diatom Research . Morphology; Illustrations
Williams D.M., Blanco S. 2020. Studies on type material from Kützing's diatom collection II: Synedra acus Kützing, Synedra arcus Kützing, their morphology, types and nomenclature. Diatom Research DOI: 10.1080/0269249X.2020.1711534. Morphology; Illustrations; Taxonomy
This page should be cited as:

Jüttner I., Mann D. G. Ulnaria (Kützing) P. Compère; 2001; 100. In: Jüttner I., Carter C., Cox E.J., Ector L., Jones V., Kelly M.G., Kennedy B., Mann D.G., Turner J. A., Van de Vijver B., Wetzel C.E., Williams D.M.. Freshwater Diatom Flora of Britain and Ireland. Amgueddfa Cymru - National Museum Wales. Available online at [Accessed:  ].

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Record last modified: 27/12/2020