(Hustedt) Simonsen 1979 Category: Centric
BASIONYM: Melosira canadensis Hustedt 1952
Contributor: Loren Bahls - March 2012
Diameter: 5-16 µm
Mantle Height: 13-22 µm
Rows of areolae in 10 µm: 6-11
Frustules are cylindrical and form colonies. Valves are 5-16 µm in diameter, with a mantle height of 13-22 µm. The ratio of mantle height to valve diameter is >1. The mantle has straight sides, but sides may be curved in smaller diameter cells. Rows of mantle areolae are straight, 6-11 in 10 µm, with 5-10 very large blocky or oblong areolae in 10 µm. In smaller diameter cells areolae may be disorganized and more widely spaced. The height of the collum varies between 1/3 and 1/10 of the mantle height. The valve face is usually covered by areolae, but in some specimens there are areolae only at the periphery of the valve face. Linking spines are present. The ringleiste is solid and located on the border between the collum and the part of the mantle containing areolae.
Basionym: Melosira canadensis
Author: Hustedt 1952
Rows of areolae in 10 µm:
Bahls, L., Potapova, M., Fallu, M.A. and Pienitz, R. (2009). Aulacoseira canadensis and Aulacoseira crassipunctata (Bacillariophyta) in North America. Nova Hedwigia, Beiheft 135: 167-184.
Hustedt, F. (1952). Neue und wenig bekannte Diatomeen. IV. Botaniska Notiser 1952:366-410.
Simonsen, R. (1979). The diatom system: ideas on phylogeny. Bacillaria 2: 9-71.
Simonsen, R. (1987). Atlas and Catalogue of the Diatom Types of Friedrich Hustedt. J. Cramer, Berlin & Stuttgart 1: 525 pp.
When found in abundance, Aulacoseira canadensis is associated with freshwater lacustrine deposits of Miocene age, and none of the preserved material that we have examined contains protoplasm or plastids (Bahls et al. 2009). We therefore conclude that this taxon is probably extinct. Geological processes have redistributed fossil material throughout much of the interior Northwest (map), where occasional cells may appear in a wide variety of habitats.
Distribution of Aulacoseira canadensis in western North America. “Q” marks the type locality at Quesnel, British Columbia. Other letters represent known fossil deposits.
Credit/Source: Bahls et al. 2009.