Abstract
Abundant tubular macrofossils occur in finely laminated siltstones and shales of the 548–542 Ma Schwarzrand Subgroup, Nama Group, Namibia. The Nama tubes occur in both the Vingerbreek and Feldschuhhorn members commonly in dense populations and always in fine-grained, lower shore-face lithologies deposited below fair-weather wave base. The tubes are preserved mostly as compressed casts and molds that range in width from 0.6 to 2.1 mm; apparently incomplete specimens reach lengths up to 10 cm. All specimens show sinuous bending and occasional brittle fracture, indicating an original construction of strong but flexible organic matter. Feldschuhhorn specimens preserve fine longitudinal pleats or folds that record pliant organic walls, but the older Vingerbreek populations do not. Similarly, some specimens in the Feldschuhhorn Member display branching, while Vingerbreek tubes do not. The abundant Feldschuhhorn tubes are assigned to the widespread Ediacaran problematicum Vendotaenia antiqua; however, the distinctive Vingerbreek population remains in open nomenclature. The most abundant fossils in Nama rocks, these tubes resemble populations in Ediacaran successions from Russia, China, Spain, and elsewhere. Beyond their local importance, then, such tubes may turn out to be the most abundant record of Ediacaran life.
Highlights
PALEONTOLOGISTS COMMONLY discuss Ediacaran life in terms of acritarchs and the distinctive Ediacara-type macrofossils so characteristic of much of the period
Traces versus Body Fossils. – Could the tubular fossils be trace fossils, or are they properly interpreted as body fossils? Feldschuhhorn tubes show several morphological features that immediately distinguish them from trace fossils, including the presence of folds and elevated levels of carbon (Figures 3.5, 7.2)
Documentation of widespread tubular macrofossils supports the hypothesis put forth by Droser et al (2005) that many of the bedding plane features originally interpreted as simple trace fossils in Ediacaran successions record body fossils of cylindrical or ribbon-like organisms
Summary
PALEONTOLOGISTS COMMONLY discuss Ediacaran life in terms of acritarchs and the distinctive Ediacara-type macrofossils so characteristic of much of the period. Simple macroscopic tubes have long been found as compression fossils in basinal shales of Neoproterozoic age These include simple cylindrical tubes, annulated cylindrical tubes, cylindrical tubes with transverse bands, cylindrical tubes with flanges, cylindrical tubes with transverse crosswalls, and cylindrical tubes with perforated cross-walls (Sokolov, 1968; Xiao and Dong 2006; Lui et al, 2008; Dong et al 2008 and references therein). The simplest of these fossils are often grouped as vendotaenids and commonly cover bedding planes in Ediacaran shales of the Eastern European Platform and elsewhere (Gnilovskaya et al, 1988). Along with comparable populations in coeval rocks from Europe and Asia, these tubes preserve what may have been among the most abundant and widespread of all Ediacaran macroorganisms
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