Postcephalic segmentation and spines of the Siluro-Devonian odontopleurine trilobites Leonaspis Richter & Richter and Kettneraspis Prantl & Přibyl, with description of Bruthansovaspis gen. nov. from the Wenlock to Ludlow of the Prague Basin

Abstract

Species of the odontopleurine trilobites Leonaspis Richter & Richter, 1917 and Kettneraspis Prantl & Přibyl, 1949 from the Silurian and the Devonian have been studied. Dorsal tubercle and spine patterns are highly variable and deemed of restricted use. The pygidial segmentation of Leonaspis is consistent among species in the development of a rudimentary inner pleural ridge or wide space between the pleural ridge and the axis. In Kettneraspis, an inner pleural ridge is never developed but the primitive condition is to have a space here. The formation of this ridge and an auxiliary interior border spine pair was arrested prematurely during ontogeny in species assigned to Kettneraspis at present. The type species of the monotypic Rupbachella Alberti, 2021 is regarded as a juvenile Leonaspis. Bruthansovaspis gen. nov. (type species: Acidaspis roemeri Barrande, 1852) is proposed for a Silurian clade of former Kettneraspis species from peri-Gondwana, that are principally distinct in lacking the combination of stunted anterior and macropleural posterior, thoracic segments synapomorphic of Kettneraspis and Leonaspis. The types of Bruthansovaspis roemeri, Bruthansovaspis dormitzeri (Hawle & Corda, 1847), Bruthansovaspis dumortieri (Hawle & Corda, 1847), Kettneraspis propinqua (Barrande, 1852), Kettneraspis lindackeri (Hawle & Corda, 1847) and Bruthansovaspis zenkeri (Hawle & Corda, 1847) (= B. dormitzeri) from the Silurian of the Barrandian, all of which had previously been lumped as dormitzeri, are figured and their classifications revisited. Exceptionally well-preserved odontopleurine material from the Devonian in the Tafilalt (southern Morocco) is described as Kettneraspis freitagi sp. nov. Leonaspis? strix Lütke, 1965 from the Devonian of the Harz Mountains is in need of revision; a previously tentatively assigned pygidium does not belong in that genus.