Krammer 1991 Category: Centric
BASIONYM: Aulacoseira crassipunctata Krammer 1991
Contributor: Marina Potapova - December 2010
Length Range: 4-12 µm
Width Range: 9-18 µm
Striae in 10 µm: 5.5-9
Frustules are cylindrical and form colonies. Valves are 4-12 µm in diameter, with a mantle height of 9-18 µm. The ratio of the mantle height to valve diameter is greater than 1. The mantle has straight sides and the valve face is strongly concave or convex. Rows of mantle areolae are straight, 5.5-9 in 10 µm, with 5-10 round areolae in 10 µm. The height of the collum is approximately 1/3-1/4 of the mantle height. The valve face is covered by areolae. The spines are thin, often bifurcated, and irregular in shape. The ringleiste is solid, broad and shallow.
Basionym: Aulacoseira crassipunctata
Author: Krammer 1991
Length Range: 6-10 µm
Width Range: 10-17 µm
Striae in 10 µm: 6-9
Frustules cylindrial, linked into short straight or curved chains; valves 6-10 μm in diameter, mantle height 10-17 μm, ratio height/diameter 0,8-1,5, varies not only throughout the division cycle, but also between sibling valves and even between valves of a single frustule (fig. 72). Outer and inner mantle lines straight and parallel; discus distinctly convex (fig. 76) or concave (fig. 79, in sibling valves, convex and concave disci fit into each another); pseudosulcus a broad but flat furrow. Cell wall thick; linking spines short; separating spines not observed, the broad collum bears on its inside a very broad Ringleiste (figs. 73, 74). The disci have varied patterns of medium-seized areolae, sometimes being dispersed and irregularly distributed (figs. 75, 79), in completely areolated disci the areolae sometimes arranged in tangential rows. Nearly every pervalvar mantle rib bears a very small, somewhat irregularly shaped linking spine with bifid anchors (figs. 76-78). The mantle areolae vary in size (fig. 76), are very large and appear pearl-like in the LM (figs. 71, 72). SEM reveals very irregular areolae foramina (figs. 76-78). The pervalvar rows (6-9/10 μm) run parallel or slightly oblique to the pervalvar axis. The areola arrangement here is somewhat irregular with the consequence that transverse rows are either absent (figs. 71, 78) or indistinct (figs. 72, 76).
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.
Krammer, K. (1991). Morphology and taxonomy of some taxa in the genus Aulacoseira Thwaites (Bacillariophyceae). I. Aulacoseira distans and similar taxa. Nova Hedwigia 52(1-2):89-112.
Siver, P.A. and Kling, H. (1997). Morphological observations of Aulacoseira using scanning electron microscopy. Can. J. Bot. 75: 1807–1835.
Aulacoseira crassipunctata was reported from 2 sites in the western EMAP survey, 1998SIDFB124 and WIDP99-069. Potapova examined 2 slides from site WIDP99-0697, but failed to confirm the presence of A. crassipunctata. The EMAP distribution and data plots were removed from this page. A fragment of the fossil A. canadensis may have been present, misidentified as A. crassipunctata. - S. Spaulding