Acritarchs are microorganisms of uncertain affinity, having a hollow shell of highly varied shape (spherical, ellipsoidal, discoidal, elongate, or polygonal) composed of an organic substance or substances. Their size is between 7 and 1000 μm, most often less than 150 μm. The shell may be pitted, granular, or entirely smooth; it may be unornamented or may bear spines or other processes, raised ridges (crests), pits, or granules. The distribution of the ornament may be quite random or it may show a consistent positional relationship—e.g., confinement to, or arrangement around, the poles of an ellipsoidal shell. Sometimes the shell is multiple, consisting of two separate, roughly concentric membranes of comparable thickness; sometimes the main shell is partially or entirely surrounded by a much more tenuous, often incomplete outer membrane; sometimes the shell bears a median flange or wing. (Fig. 1.)
Fossil acritarchs.
A, Subgroup Herkomorphitae,...
This is a preview of subscription content, log in via an institution.
Buying options
Tax calculation will be finalised at checkout
Purchases are for personal use only
Learn about institutional subscriptionsReferences
Deflandre, G., and M., 1964. Notes sur les Acritarches, Rev. Micropaléont., 7, 111–114.
Downie C., 1973. Observations on the nature of the acritarchs, Palaeontology, 16, 239–260.
Downie, C., and Sarjeant, W. A. S., 1964. Bibliography and index of fossil dinoflagellates and acritarchs, Geol. Soc. Amer. Mem. 94, 180p.
Downie, C.; Evitt, W. R.; and Sarjeant, W. A. S., 1963. Dinoflagellates, hystrichospheres and the classification of the acritarchs, Stanford Univ. Publ., Geol. Sci., 7(3), 1–16.
Downie, C.; Jardine, S.; and Visscher, eds., 1974. Acritarchs, Rev. Palaeobot. Palynol., 18, 1–186.
Evitt, W. R., 1963. A discussion and proposals concerning fossil dinoflagellates, hystrichospheres and acritarchs, Proc. Nat. Acad. Sci., 49, 158–164, 298–302.
Harland, R., and Sarjeant, W. A. S., 1970. Fossil fresh-water plankton (dinoflagellates and acritarchs) from Flandrian (Holocene) sediments of Victoria and Western Australia, Proc. Roy. Soc. Victoria, 13, 211–234.
Naumova, S. N., and Pavlovsky, E. V., 1961. The discovery of plant remains (spores) in the Torridonian shales of Scotland (in Russian), Doklady Akad. Nauk SSSR, 141, 181–182.
Norris, G., and Sarjeant, W. A. S., 1965. A descriptive index of genera of fossil Dinophyceae and Acritarcha, New Zealand Geol. Surv. Palaeont. Bull. 40, 72p.
Sarjeant, W. A. S., 1965. The Xanthidia; the solving of a palaeontological problem, Endeavour, 24(91), 33–9.
Sarjeant, W. A. S., 1970. Xanthidia, palinospheres and “Hystrix.” A review of the study of fossil microplankton with organic cell walls, Microscopy; J. Quekett Microsc. Club, 31, 221–253.
Timofeyev, B. V., 1965. Phytoplankton of the late Proterozoic and early Palaeozoic seas (in Russian), Tez. Doklad. K Perv. Vses. Paleoalgo. Sov., Novosibirsk, 1965, 112–114. (Translation available in Russian Translating Programme R.T.S. 4006. Boston Spa, England: National Lending Library.)
Wall, D., 1962. Evidence from recent plankton regarding the biological affinities of Tasmanites Newton, 1975, and Leiosphaeridia Eisenack, 1958, Geol. Mag., 99, 36–62.
Cross-references
Rights and permissions
Copyright information
© 1979 Dowden, Hutchinson & Ross, Inc.
About this entry
Cite this entry
Sarjeant, W.A.S. (1979). Acritarchs . In: Paleontology. Encyclopedia of Earth Science. Springer, Berlin, Heidelberg. https://doi.org/10.1007/3-540-31078-9_1
Download citation
DOI: https://doi.org/10.1007/3-540-31078-9_1
Publisher Name: Springer, Berlin, Heidelberg
Print ISBN: 978-0-87933-185-6
Online ISBN: 978-3-540-31078-5
eBook Packages: Springer Book Archive