acritarch

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acritarch

[′ak·rə‚tark]
(paleontology)
A unicellular microfossil of unknown or uncertain biological origin that occurs abundantly in strata from the Precambrian and Paleozoic.
References in periodicals archive ?
Diachronous recovery patterns in early Silurian corals, graptolites and acritarchs.
Cambrian-Ordovician acritarchs in the Meguma terrane, Nova Scotia, Canada: Resolution of early Paleozoic stratigraphy and implications for paleogeography.
Most specimens consist of amorphous material of indeterminate origin, but a few are densely packed with sphaeromorphic acritarchs (Fig.
The scientists found that diverse assemblages of microscopic organic-walled fossils called acritarchs, which dominate the fossil record of this time, are present in lower rocks of the Chuar Group, but are absent from higher strata.
Other acid-resistant microfossils encountered during this study include acritarchs, foraminiferans, melanoscleritoids, chitinous hydroids, and graptolite siculae, but these were not studied quantitatively.
Marine oil shales are composed of lipid-rich organic matter derived from marine algae, acritarchs (unicellular organisms of questionable origin), and marine dinoflagellates (one-celled organisms with a flagellum).
In addition, palynologic analysis reveals the presence of land spores, acritarchs, chitinozoans, and scolecodonts.
Palynodebris Characteristics Amorphous organic matter Unstructured, irregularly-shaped, light brown to medium brown masses; usually gel- like (Figure 2A) Marine palynomorphs Scolecodonts (chitinous mouth parts of marine annelid worms) and acritarchs (cysts of marine algal phytoplankton, Figure 2G) Black debris Opaque particles with sharp angular outlines; lath-shaped, sometimes more equidimensional (Figure 2E) Yellow-brown debris Structureless particles of yellow to light brown color; attributable to highly degraded herbaceous material (Figure 2A) Black-brown debris Unstructured dark brown to nearly black particles; attributable to highly degraded woody material Cuticles Platy epidermal fragments of leaves, roots, etc.
Paleontologists call these acritarchs, a catch-all category of unicellular eukaryotic fossils.
5 m) and the samples from 905 m upwards yielded no or very few, poorly preserved acritarchs (see Table 1).
Some acritarchs possess a similar reticulate texture, which has been described as a taxonomic feature.
Acritarchs are also sparse and rather monotonous: in addition to leiosphaerids, rare Globosphaeridium cf.