The Upper Homerian (Silurian) machaerid sclerite from Lithuania

Abstract

Machaerids are a branch of Lophotrochozoans closely related to the Annelids known from the Early Ordovician to the Mid Permian marine environments. One specimen of machaerid sclera was found in the Viduklė-61 well, Siesartis Formation, at the depth of 1 285.1 m. Along with the specimen, the graptolite species of Colonograptus deubeli (Jaeger) was found, which is a mark of the Late Homerian, Gėluva Age. Brachiopod fauna shows that at this time there was an anaerobic, low turbulence and low shelf marine environment, i. e. BA 4–5 zone of the benthic brachiopod assemblage. Machaerid studies have shown that it belongs to the Plumulites genus. Without a full animal print with all sclerites we cannot accurately describe these fossils. This is the first specimen which was found in Lithuania, Gėluva Regional Stage. This finding will give more information about fauna recovery after extinction in the Early Gėluva Regional Stage, also known as the ludgreni Event. With the help of machaerid findings, we also could reconstruct palaeoenviroments and autecology.