Calthropella Sollas 1888

Type material available to us has a flattened (Fig. 31A left), rounded shape, size 1×1×0.2 cm. It is a fragment of a larger holotype specimen (3.5×3×2.5 cm) that is massively rounded and may have a large central oscule (Fig. 31A right). Colour very pale green or dirty white. Skeleton: an irregular mass of large triaenes covered at the periphery by a thick layer of ataxasters / microrhabds, which are also strewn in the interior. Loose oxeas of widely different sizes present in moderate quantities, considered foreign. Spicules: calthrops, spheroxyasters, ataxasters. Calthrops (Fig. 31B) variable in size and thickness, mostly with straight cladi, often one cladus slightly shorter, occasionally curved at the ends; cladi 133–412.3–708 × 15–37.4–71 µm, cladome 233–626.8–1180 µm. Spheroxyasters (Fig. 31C), thick-centred with smooth conical rays, many of which appear underdeveloped causing an irregular aspect; extreme cases are the medusa-like forms such as pictured at lower right inFig 31C, showing a deformed aster with rays present only at one side; diameter (including rays) 15–18.1–24 µm (centre approx. 10 µm diameter). Ataxasters (Figs 31D–E), typically pyriform (pointed one-sidely), occasionally ovate or rounded, microspined all over, but spines tend to be grouped; no branching shapes were found, making the term ‘ataxaster’ inappropriate for these spicules, but their homology to the ataxasters ofPachataxa lithistinais nevertheless obvious; size 7–20.5–31 µm, measured along the longest axis.

Lobate mass (Fig. 27A), size 6×5×5cm, microhispid surface, rough to the touch. Colour pinkish brown. Two oscule type openings are located on the rounded upper surface, 3–4 mm in diameter. Consistency hard. Skeleton: a dense crust of asterose microscleres at the surface covers a dense mass of calthrops. Asters are also crowded in the choanosome. The skeleton is densely confused and there are few canals or cavities; some broken monaxone spicules were present. Spicules: calthrops, globular tuberculate asters, oxyspherasters, oxeas?. Calthrops (Fig. 27B) in an extremely wide range of sizes and shapes, cladi 44–238.2–587 × 5–40.8–101 µm, cladome 62–344.3–820 µm. Broken monaxonic spicules (oxeas?) measured up to 700 × 10 µm. Oxyasters (Fig. 27C), with a discrete rounded center and rays often ill developed or partly missing, range from 8 to 21, possibly in two size categories, the larger (Fig. 27D) with fewer rays, 15–16.9–21 (8 rays) and smaller (Fig. 27E) with more numerous rays, 8–9.7–10 µm (12–14 rays), but some overlap is present. Globular tuberculated spherasters (Fig. 27C) or ‘silica balls’, appearing to be derived from the normal euasters by heavy silicification, in a wide size range, 6–27 µm, possibly in two size categories, larger (Fig. 27F) 18–21.3–27 µm and smaller (Fig. 27G) 6–8.3–10 µm.

NE of Santa Cruz Island, Galapagos, East Pacific.

Known only from the type locality, E of the island of Komodo, Nusa Tengara (southern island chain bordering the Banda Sea).