The Acritarch Genus Veryhachium Deunff 1954: Taxonomic Evaluation and First Appearance

Abstract

Veryhachium Deunff 1954, originally described from the Ordovician of western France, is one of the most frequently recorded acritarch genera. Over 250 species and subspecies, from the Cambrian to the Neogene, have been attributed to the genus. This genus has a simple morphology; it displays a triangular, rectangular, or polygonal central vesicle, with a few, simple processes drawn out from the angles of the vesicle in a single plane, and sometimes with supplementary or auxillary processes arising from the vesicle body. Veryhachium has been emended and revised numerous times. The number of valid species is excessive: most are probably synonyms. To facilitate effective classification, only a few morphological categories should be retained. For the Lower Paleozoic, the use of two informal groups is proposed. These are the Veryhachium trispinosum group for triangular specimens, and the Veryhachium lairdii group for rectangular forms. Although generally abundant and widespread throughout the Phanerozoic, Veryhachium is of limited biostratigraphic, paleoecologic, or paleogeographic value. However, its First Appearance Datum (FAD) is of great importance for Ordovician stratigraphy; the first Veryhachium morphotypes appear in the Tremadocian Stage, making the genus an important biostratigraphic marker.

Palynostratigraphy of the Zorritas Formation, Antofagasta region, Chile: Insights on the Devonian/Carboniferous boundary in western Gondwana

“…octoaster (Staplin) Jardiné et al, 1972;7042e, J23/0. (16) Veryhachium trispinosum group Servais et al, 2007;7043e, G26/0. (17) Papulogabata annulata Playford and Dring, 1981; 7042e, Q42/3.…”

The palaeobiogeographical spread of the acritarchVeryhachiumin the Early and Middle Ordovician and its impact on biostratigraphical applications

“…Servais et al (2007) showed that the genus first appeared in the early Tremadocian and thus served to distinguish Ordovician from Cambrian rocks.…”

“…Morphotypes include triangular, rectangular or polygonal vesicles with three, four, or five and more processes respectively. Servais et al (2007) proposed a simple classification scheme in which all triangular specimens are attributed to the Veryhachium trispinosum group and all rectangular specimens to the Veryhachium lairdii group. In order to classify the numerous morphotypes of the Micrhystridium/Veryhachium complex in the Permian, Lei et al (2013) extended this approach and proposed a further informal group to include all Veryhachium morphotypes with ellipsoidal central body outlines, the Veryhachium cylindricum group.…”

“…Upper Cambrian forms previously attributed to the genus as Veryhachium dumontii are now interpreted as diacromorph acritarchs and are placed in the genus Ninadiacrodium Raevskaya & Servais, 2009. In addition, Servais et al (2007) considered a number of other Cambrian forms that had been assigned previously to Veryhachium, and concluded that none of them should be included the genus according to the emended diagnosis of Turner (1984). Among them is Veryhachium minutum Downie, 1958, which was transferred to the genus Dorsennidium Wicander, 1974, by Sarjeant andStancliffe (1994).…”

“…Elsewhere in North Africa, Combaz (1968) and Jardiné et al (1974) In addition to the Lake District record, the Veryhachium lairdii group has been recorded from messaoudensis-trifidum acritarch assemblages of south Wales, southern Ireland, Spain, Belgium, and the Czech Republic (for complete references see Molyneux et al 2007 andServais et al 2007). In At lower palaeolatitudes on the Gondwanan margin, for example in South China and Argentina, the first occurrence of the Veryhachium lairdii group is apparently in the lowermost Floian or higher ).…”