Precambrian acritarcha: A cautionary note

Extensive studies have shown that acritarch-like artifacts, ‘pseudomicrofossils’, may be easily produced during acid maceration of samples. Such acritarch-like forms may also be found in rocks and in modern ecological settings. The most common pseudomicrofossils are microstructures which have specific gravities less than unity. Such ‘light-microfossils’ have been described previously by A.C. Lopuchin and coworkers (1978). Experiments have more recently been conducted, including microscopic observations and scanning electron microscopy, the results revealing that these ‘light-microfossils’ actually consist of finely-dispersed organic substances and that pseudomicrofossils can be formed during each step of the customary maceration processes. Consequently, care must be taken when referring to certain published taxa, particularly to forms resembling Trachysphaeridium, Asperatopsophosphaera, Pseudozonosphaera, Trematosphaeridium, Taeniatum and the Polyporata morphotypes, because they may include artifacts. The purpose of this preliminary report is to point out that, while there are many real acritarchs described and carefully diagnosed in the literature, a number of reports of artifacts merely resembling acritarchs have also been published inadvertently. In a broader sense, during the past 50 years numerous morphotypes assumed to be the remnants of organisms have been described from Precambrian strata. Many of the Precambrian microstructures are, in fact, not microfossils at all but various microstructures unrelated to syngenetic microorganisms.