Hoffmanigraptus n. gen., a new retiolitine (Graptolithina), an early member of the Plectograptus lineage from the Silurian of Baltica, Poland

Abstract

Most upper Homerian and Ludfordian retiolitines have a tubarium with hexagonal meshes and a zigzag pattern in the middle part of their lateral walls, a shallow ancora umbrella, and a free nema. Hoffmanigraptus varsoviensis n. gen., n. sp. is described from isolated, three-dimensional material, from the upper part of the Colonograptus praedeubeli Biozone (upper Homerian, Silurian) of Poland, Baltica, and represents one of the earliest forms with this construction. This type of tubarium is represented by the upper Homerian Doliograptus Lenz & Kozłowska-Dawidziuk, 2002 and Spinograptus Bouček & Münch, 1952, differing from Hoffmanigraptus n. gen. mainly in larger proximal lateral orifices, pattern of clathrial lists on lateral walls, as well as size and shape of tubaria. Hoffmanigraptus n. gen. has a tubarium widening medially, tapering towards the distal end and forming a finite tubarium, with a possible three-vaned nematularium. Flattened specimens Plectograptus? ovatus Kozłowska, Lenz & Štorch, 2001 and Plectograptus? karlsteinensis Kozłowska, Lenz & Štorch, 2001, preserved on a rock surface from the Barrandian area are assigned to the new genus. They are of the same upper Homerian age, and show the main features of the new form. Hoffmanigraptus n. gen. is regarded as an early member of the Plectograptus clade.