Melanosclerites: first North American report of these problematic microfossils and discussion of their affinity

Abstract

Melanosclerites are rod-shaped, pseudochitinous microfossils of problematic affinity. They have not been widely studied. The first North American discovery of melanosclerites is here reported; Melanostylus coronifer and Melanosteus acutus (the latter with two subspecies), of Devonian (Late Siegenian) age, were discovered in the Indian Cove Formation of the Upper Gaspé Limestones from the Gaspé Peninsula, Quebec, Canada.These melanosclerites bear a strong resemblance to the modern cubomedusa polyp Carybdea alata and the planula stages of the hydrozoan Pennaria tiarella. They are interpreted as being the embryonic planula and early polyp stages of scyphozoans, cubozoans, and hydrozoans.Consequently, Semenola semen Schallreuter, 1981, is considered an early growth stage of M. acutus anceps and thus a junior synonym; similarly, Eichbaumia incus is a junior synonym of Melanostylus coronifer; while, on the basis of their three-fold symmetry, Orthopelta? femuralis Eller, 1945, and Menola os Schallreuter, 1981, are treated as junior synonyms of Melanofurca neptuni Eisenack, 1963. Melanosclerites could represent the planula and polyp stages of any of the three classes of Cnidaria; therefore, the order Melanoscleritoitidea Eisenack, 1963, and the family Melanoscleritoitidae are here rejected because the supposed family crosses the boundaries of classes. The new subspecific combinations Melanosteus acutus acutus, M. acutus filiformis, and M. acutus anceps are proposed, their diagnoses being emended; the diagnosis of Melanostylus coronifer is also emended.Melanosclerites appear to be strongly facies controlled and thus may have potential for paleoenvironmental and paleogeographical reconstructions.