The antiarch fish Asterolepis orcadensis from the Scottish Middle Devonian

Abstract

The Givetian (Middle Devonian) antiarch Asterolepis orcadensis was first described in 1932 based on a limited amount of material. Newly collected material has allowed the head to be described in more detail, especially the premedian plate which has an embayment at the centre of the anterior edge. Also, the anterior section of supra-orbital sensory line has been identified on the premedian plate. Other elements newly described include the pectoral appendages which are shown to be quite broad at their proximal ends. The anterior ventro-lateral plate has been described in detail for the first time, particularly structures associated with the attachment of pectoral appendages. The posterior median dorsal plate has been shown not to have had a more pointed posterior edge as depicted in the 1932 description, but a flatter posterior edge reminiscent of Asterolepis saevesoederberghi which is shown to be closely related to A. orcadensis. The shortness of the posterior median dorsal plate has emphasised the broadness of the whole armour, making A. orcadensis one of the broadest species of Asterolepis. Whilst A. orcadensis is endemic to the Orcadian Basin of northern Scotland, it fits into a biostratigraphical column at the same level as A. saevesoederberghi so strengthening the evidence of a close relationship between these two forms.

Fossils From the Arctic in the Collections of the Natural History Museum in Oslo, Norway

“…Recent and ongoing research has clarified the type locality of several of the Devonian plant species described by Høeg (1942) (e.g., Berry and Marshall 2015), enhanced the collection with new material during several field seasons since 2016, and led to new findings about a low tropical diversity during Devonian plant evolution (Wellman et al 2022). Investigations of Devonian fishes from Spitsbergen in the NHMO collection, and the collection and description of new specimens during the last years, have added valuable type specimens to the collection (Newman, Burrow, and den Blaauwen 2019, 2020; Newman et al 2021; Newman, den Blaauwen, and Leather 2019). During field work in 2010 and 2013 the first Devonian (Famennian) tetrapod remains on Svalbard were discovered and collected (Lindemann, Volohonsky, and Marshall 2013).…”

Late Devonian antiarch remains (placoderm fish) from the Gilberton Formation, north Queensland

“…They also had different stratigraphic ranges: Bothriolepis was first described from the Famennian of Russia, and Asterolepis from the Frasnian of the Baltic (Eichwald 1840). Asterolepis was later discovered in many Middle Devonian localities (for a recent summary of the history of this genus see Newman et al 2019). The replacement and stratigraphic overlap of Asterolepis by Bothriolepis, near or just above the Middle-Late Devonian boundary, became recognized as an important biostratigraphic horizon in the fishbearing non-marine Devonian strata of western Europe (Young 1974).…”