A New Cheiracanthid Acanthodian Species from the Aruküla Regional Stage (Middle Devonian, Givetian) of the Eastern Main Devonian Field

Abstract

A new cheiracanthid acanthodian species, Cheiracanthus flabellicostatus sp. nov., is described based on scales found in the beds of the Aruküla Regional Stage of Siverskiy and Zaitsevo localities of the Leningrad Region. It is distinguished from other members of the genus in the presence of a V-shaped eminence in the medial part of the scale crown and 8-10 large ribs branching into smaller ribs in the anterior part of the crown; large lacunas are observed at crossings of circular and ascending canals in the middle part of the scale neck.

A redescription of the three longest-known species of the acanthodian Cheiracanthus from the Middle Devonian of Scotland

“…Flat or concave based dermal tesserae from the head region have a lamellar base and areal-growth Figure 6.6 for map of sections): 1, slice II before grinding (corresponds to sections 6, 7), arrow indicates dorsal direction; 2, NMS G. 2019.3.3.7, scapulocoracoid, long section mid-shaft;3, NMS G.2019.3.3.12, TS pectoral spine at insertion/exertion boundary; 4, NMS G. 2019.3.3.10, TS of spine close to insertion; 5, NMS G. 2019.3.3.6, close up of leading edge ridge structure of pectoral spine, midspine; 6, NMS G.2019.3.3.2, TS pectoral spine near the tip. 7-10, NMS G. 2018.28.26, TS pectoral spines: 7, 20188, 2018.28.26.7, midspine;9, 10, 2018.28.26.5, towards tip, with closeup of infilling dentine. 11-14, NMS G.2019.3.7 TS pectoral spine, near insertion, and flange of scapulocoracoid: 11, NMS G. 2019.3.7.8;12, NMS G.2019.3.7.9;13-14, NMS G.2019.3.7.10, outer side of spine with thin sharp ridges.…”

“…Cheiracanthus spp. were abundant in Middle Devonian vertebrate faunal assemblages of northern Europe, with isolated scales described from the Baltic countries and Russia (e.g., Valiukevičius, 1985Valiukevičius, , 1988Glinskiy and Pinakhina, 2018;Pinakhina, 2018;Pinakhina and Märss, 2018), and articulated fish from Scotland and Spitsbergen (Agassiz, 1835;Egerton, 1861;McCoy, 1848;Newman et al, 2019). Only one valid new species based on articulated specimens, C. peachi den Blaauwen, Newman and Burrow, 2019, from Scotland, has been described since the nineteenth century.…”