Olladiscoaster bordii Varol & Bowman, 2024
From Latin olla, jar – referring to its shape in side view
An asterolith with the segments having quasi-arms or no arms. Pronounced sutural ridges are created by deep cavities and capped by the distal cover on the distal side. A proximally bulged central area with proximal ridges characterises the proximal side.
Distinct sutural ridges, distal cover, and deep cavities ornament the distal side of all Olladiscoaster species. Prominent ridges run along the segments on the proximal side, and they may develop a platform-like structure over the proximally bulged central area. The ridges may produce a hexagon-stellate, petaloid or radiating proximal knob in the middle of the central area. A species consists of five to six segments with quasi-arms or no arms. At the plan view, Olladiscoaster is non-birefringent, but at the side view, it is strongly birefringent with a tangential c-axis. According to the characteristics of the segments, we recognised two groups of Olladiscoaster (Figures 7-8).
Olladiscoaster is primarily distinguished from the Discoaster virginianus group of Discoaster by having qua-si-arms or no arms. Olladiscoaster further differs from all other Discoaster (Discoaster virginianus group) by having distal covers over distinct sutural ridges and deep cavities. Our current interpretation of Catinaster is also developed from Discoaster with the extreme proximal curvature of segments until the ends of the segments converge.
The taxonomic problems existing within the ollasdiscoasters are primarily caused by typically settling randomly in side-view or plan-view due to the similar height-width ratio. Many species of olladiscoasters display noticeable taxonomic differences and may appear superficially similar in particular views. We applied the mobile mount technique on all samples and successfully mapped the different profiles of all olladiscoasters. Based on our rigorous experience, we strongly recommend utilising the mo-bile mount technique while examining Middle to Late Miocene samples. However, all the species cited in this study may be easily identified with the help of Figures 4, 7-9.
Varol, O. & Bowman, A. R. 2024. The New Middle Miocene Genus Olladiscoaster, and Related and Associated Discoasters. Grzybowski Foundation Special Publication, 28: 1-103 pp.