Family: Unicells or cells loosely attached forming hyphae; cell body varied in shape, a constriction at the center in most species; cell walls consisting of two or more parts, with small pores and various ornaments (Illustrations of The Japanese Fresh-water Algae, 1977).
Genus:

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From Arthrodesmus section Tetracanthum: Lateral margins lack spiny projections
Semicells elliptical in shape
S. subulatus var. subaequalis or A. rhomboides ? 38 x 27 μm USA, 1999	S. subulatus var. nordstedtii 31 x 31 μm Uruguay, 1999	S. convergens 4 samples 31-33 x 33-38 μm 2006-2008
Semicells inverted semicircle/hexagonal		Semicells inverted trapezoid
S. incus 17 samples 15-25 x 13-23 μm 199?-2007		S. controversus ? 18 x 15 μm Tenbo marsh Tsugaike highland Nagano, 2005
Semicells inverted quadrangular		Semicells inverted triangular
S. extensus 10 samples 15-26 x 13-27 μm 1999-2007		S. triangularis 5 samples var. latiusculum ? 17-22 μm 2004-2007	S. triangularis 5 samples var. acuminatum ? 17-22 μm 2004-2007
From Staurastum section Spinastrum: With spiny projections at corners, cell wall smooth
S. longispinum ? 3 samples 60-78 x 60-65 μm Ushidome-ike Norikura highland Nagano, 2005-7	S. connatus 26 samples 18-39 x μm 1998-2008	S. apiculatus 2 samples 19 x 20 μm spines μm 1999-2006	S. dickiei 3 samples 21-31 x μm spines μm 199-2005
S. cuspidatus 7 samples 18-25 x μm 2004-2007	S. bifidum ? 4 samples x 30-31 μm 1998-2008	Staurastrum sp. S. pseudobiretum ? small var. 24 x 25 μm Uruguay, 1999
S.leptodermum ? x 31 μm Onnenai Kushiro marsh Hokkaido, 2005	S.subscolopacinum 19 x 16 μm spines 5 μm Koshigaya Saitama, 2001	S. dejectus 20 x 20 μm spines 7 μm 4 arms Otto-Numa Ibaraki, 2002	Staurastrum sp. S. dejectum ? 3 arms Otto-Numa Ibaraki, 2002
S. wandae v. brevispinum 11 samples 23-30 μm 2005-2008	S. contectum v. inevolutum 36 x 34 μm Onnenai Kushiro marsh Hokkaido, 2005

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