Edlund, D.R.L.Burge & S.A.Spaulding 2017 Category: Symmetrical biraphid
BASIONYM: Navicula cuspidata var. obtusa R.M.Patrick (nom. illegit.) 1966
REPORTED AS: Navicula halophila var. maior (Héribaud (in Boyer 1927))
Contributor: Mark Edlund - January 2017
Length Range: 101-162 µm
Width Range: 22.5-26.7 µm
Striae in 10 µm: transverse striae 11.9-14.3; longitudinal striae 20.0-23.8
There are three valve types found for this taxon: vegetative, “heribaudii”, and craticula forms. The three forms are produced as a cellular strategy for surviving inimical conditions such as desiccation (Schmid 1979). Two craticula are formed within the vegetative frustule and subsequently the “heribaudii” cell is formed within the craticula. The heribaudii cell usually has different ornamentation compared to vegetative cell.
Vegetative valves are fusiform-lanceolate, with acutely rounded (shorter valves) to pointed apices (longer valves), never protracted. The axial area is narrow and strongly silicified. The central area is only slightly expanded. Raphe filiform to slightly lateral. Proximal raphe ends curve slightly to same side of valve and terminate in a small hook. Terminal raphe fissures are sickle-shaped and hooked toward the same side of the valve. Slit-like and apically elongate areolae arranged in both transapical and longitudinal striae, with transapical striae more prominent. Transapical striae are parallel throughout the valve, becoming slightly convergent near the apices. Longitudinal striae arranged in slightly wavy rows.
“Heribaudii” forms have similar shape, size, and raphe features as vegetative valves. Slit-like and apically elongate areolae (21 in 10 µm) are arranged only in transapical striae. Transapical striae radiate (1.9-11.6 in 10 µm) becoming parallel to convergent only at the valve ends.
The craticula forms have similar shape and size as the vegetative valves, but are very heavily silicified and comprise a central sternum, parallel transapical ribs (1.5-1.8/10 µm), a thick margin, and circular to oval to quadrilateral openings.
Basionym: Navicula cuspidata var. obtusa
Author: R.M.Patrick (nom. illegit.) 1966
Length Range: 127-146 µm
Width Range: 23-29 µm
Striae in 10 µm: 14-17 transverse, 24-28 longitudinal
Valve linear-lanceolate, gradually tapering to acute, rounded ends. Axial area narrow, distinct. Central area not clearly differentiated from the axial area. Striae parallel throughout the valve; punctate, the puncta forming longitudinal and transverse lines. Transverse lines, 15 in 10 µ. Longitudinal lines, 24-28 in 10 µ. Length, 127-146 µ. Breadth, 23-29 µ.
Boyer, C.S. (1927). Synopsis of North American Diatomaceae, Part II. – Naviculatae, Surirellatae. Proceedings of The Academy of Natural Sciences of Philadelphia 79: 229– 583.
Edlund, M.B., Burge, R.L. and Spaulding, S.A. (2017). The transfer of Navicula cuspidata var. obtusa to Craticula (Bacillariophyceae). Notulae algarum 19: (14 January 2017) ISSN 2009-8987.
Grunow, A. (1860). Uber neue oder ungenügend gekannte Algen. Verhandlungen der Kaiserlich-Königlichen Zoologisch-Botanischen Gesellschaft in Wein, 10: 503-582.
Héribaud, J. (1903). Les Diatomées Fossiles d’Auvergne (Second Mémoire). Librairie des Sciences Naturelles, Paris. pp. v-x, 1-166, pls 9-12.
Patrick, R.M. and Reimer, C.W. (1966). The Diatoms of the United States exclusive of Alaska and Hawaii, V. 1. Monographs of the Academy of Natural Sciences of Philadelphia 13.
Schmid, A.M. (1979). Influence of environmental factors on the development of the valve in diatoms. Protoplasma 99: 99-115. 10.1007/BF01274072
Craticula coloradensis is known only from its type locality, Radford Peak, Colorado. Associated taxa include Hantzschia amphioxys.
The basionym of this taxon, Navicula cuspidata var. obtusa R.M.Patrick nom. illegit. (1966) is a later homonym of Navicula cuspidata var. obtusa Grunow (1860). Edlund et al. (2017) formally proposed the transfer of Navicula cuspidata var. obtusa R.M.Patrick to Craticula with a new name and with species status as Craticula coloradensis Edlund, D.R.L.Burge & S.A.Spaulding. From May 2015 until January 2017, this taxon appeared on this site as Navicula cuspidata var. obtusa R.M.Patrick. - M.B. Edlund