Cladaster rudis Verrill 1899

FIGURE 10A–E

Verrill 1899: 175; Fisher 1911: 223; 1940: 125; Bernasconi 1963: 14; Halpern 1970: 180; Clark & Downey 1992: 240; Mah 2020: 220.

Diagnosis & Summary Description

Body stellate, (R/r=1.9–2.1), arms triangular, interradial arcs curved (Figs 10A, B, D). Abactinal plates irregular to polygonal in shape on disc extending to proximal region on arms (Fig. 10A–B). Pedicellariae, paddle-shaped abundant on abactinal surface (Fig. 10B, C). Superomarginal plates, two to three pairs, abutted over midline distally (Fig. A-B). Abactinal and marginal plates covered by deciduous round granules, with shallow to distinct convexities on each plate. Superomarginal plates tumid, approximately 13–14 per interradius. Small peripheral granules present around each marginal plate. Actinal plates covered by widely spaced granules, 1–8 per plate surface. Furrow spines 2–4 per plate, spatulate to flat. One enlarged subambulacral spine, at least 2 to 3X the thickness, length of the furrow spines (Fig. 10E). Subambulacral granules 1 to 3, small present on each plate. Pedicellariae present, small paddle-shaped, approximately the size of two granules, present on actinal surface (Fig. 10D, E).

Comments

USNM 1674028 represents a dramatic range extension for this species, which had previously been known only from western tropical Atlantic settings off Florida and the Blake Plateau (Mah 2020). It is similar to previously reported specimens sharing consistent R/r ratios, granulation, superomarginals joined over mid radius, plate shape, and similar furrow spine shape and number. The most significant character difference in this specimen versus those specimens studied from the western tropical Atlantic is the presence of 40–50 small paddle-shaped pedicellariae (Fig. B–C), each sitting on an abactinal plate but widely distributed from one another, primarily occurring on plates around the distal edge of the disc adjacent to the contact with the superomarginal plates. Pedicellariae have been used to diagnose species among asteroids, but their use, such as in Hippasteria or Gilbertaster, has been dependent on pedicellariae type as well as consistent presence and position. Pedicellariae in this specimen appear variable in their position on the disc surface.

Occurrence

Off Florida, Stetson Mesa North and West, Blake Plateau, Yucatan Channel.

New occurrence. Mid Atlantic Ridge, Rendonda, Azores (40’ 27” 9.9N 29’ 54” 26.1” W). 150– 900 m. 1133 m (Fig. 10A–E).

Material Examined

USNM 1674028 Rendonda, Azores, North Atlantic Ocean. 40’ 27” 9.9N 29’ 54” 26.1” W, 1133 m. Coll. Okeanos Explorer & Deep Discoverer, 27 July 2022. 1 wet specimen R= 2.2 cm r= 1.1 cm.