Rugosphaeraster ruegensis Gale 2021, sp. nov.
Creators: name: Gale, Andrew Scott
Publisher: name: Zenodo
Year: 2021
Subjects: Biodiversity
Taxonomy
Animalia
Echinodermata
Asteroidea
Valvatida
Sphaerasteridae
Rugosphaeraster
Rugosphaeraster ruegensis

description: Rugosphaeraster ruegensis sp. nov.
(Fig. 26A–Q)
Types. The group of associated ossicles, including abactinals and several poorly preserved ambulacrals, plus a single adambulacral (Fig. 26A), is the holotype (SNSB-BGSP 2020 XLV4); the other figured ossicles are paratypes (SNSB-BGSP 2020 XLV5-18). All are from the Lower Maastrictian of Rugen, Germany.
Derivation of name. After the Island of Rugen, Germany, where the species is common in Lower Maastrichtian chalks.
Material. There are over 200 isolated abactinal ossicles in the M. Kutscher Collection (SNSB-BGSP) from the Lower Maastrichtian of Rugen, and three adambulacrals, collected by picking natural beach residues. A single abactinal is known from the Campanian of Ivo Klack, Skåne, southern Sweden (NHMUK EE 17698).
Occurrence. Lower Maastrichtian of Rugen, Germany, and the Campanian of Ivo Klack, Skåne, southern Sweden.
Description. All abactinals are robust (height approximately half maximum breadth) and are of even thickness, with no taper to the margins. The lateral surfaces bear oval articulation surfaces (e.g. Fig. 26F, J), which carry centrally positioned small holes that probably bore ligaments to attach adjacent plates. Broad papular notches, with rounded margins, are present between the articular surfaces. Some plates (e.g. Fig. 26A, central ossicle, G, L) bear a deep depression at one end, unique to this taxon. The external surfaces of the ossicles are flat, and bear coarse rugosities (Fig. 26C, G), or radially to transversely arranged ridges of imperforate stereom (Fig. 26B, C, E, H, I, K).
Abactinal plates (Fig. 26B–L) fall into a number of discrete categories. Plates originally from the central portion of the disc (Fig. 26D, G) are rounded in abactinal outline and have five to six short lobes of even size, and bear rounded rugosities arranged radially. Oval plates (Fig. 26C, E) were probably positioned on the sides of the body, with the pointed end directed actinally. Plates of irregular outline, bearing strips of raised stereom (Fig. 26K–N) were also likely to have been positioned laterally. Rhombic plates, in which the low ridges are parallel with the long axis, are analogous to the ‘I plates' developed in taxa such as Eosphaeraster amellagensis gen. et sp. nov. (Fig. 17K, L) and Podosphaeraster pulvillus (Fig. 1C) and would have been positioned on the central part of the actinal surface. Irregularly rhombic plates, with significant imbrication (slanting sides) and with deep grooves between the ridges (Fig. 26H, K, N), were also actinal in position and comparable with actinal plates of Sphaeraster tabulatus (Fig. 9E) and Echinosphaeraster scutatus (Fig. 15A, B). Tall ossicles with one straight margin (Fig. 26M) were probably positioned on the actinal surface, in articulation with the adambulacrals.
The adambulacrals (Fig. 26O–Q) are rectangular in abradial aspect, and taller than broad. The actinal surface is square, and carries a single row of small furrow spine bases, and large, irregularly arranged, bifid subambulacral spine bases (Fig. 26O, P). In proximal:distal aspect, a deep-set ligament pit is present (Fig. 26P) in place of adadm. In abactinal aspect (Fig. 26Q), padam is well developed, and dadam is replaced by a ligament pit. Ada1a, b are strongly inclined to the ambital surface, and ada2 and ada3 are horizontal.
description: Published as part of Gale, Andrew Scott, 2021, Taxonomy and phylogeny of the ' football stars' (Asteroidea, Sphaerasteridae), pp. 691-741 in Journal of Systematic Palaeontology 19 (10) on page 739, DOI: 10.1080/14772019.2021.1960911, http://zenodo.org/record/10949919