746


Journal of Paleontology 91(4):735–754


Figure 8. Large holotype (UCBL-FSL 712001) of Moroccodiscus smithi n. gen. n. sp. (1) Showing marginal ossicle arrangement; position of all double-pore ossicles marked. Note that paired double-pore ossicles all at subpentagonal corners. (2) Simplified diagram of the disk, showing the partly preserved pattern of ray branching. Scale bar = 10mm.


(~3.0mm wide), with two radial ducts through center, six in pairs, wide, trapezoidal, three unpaired, slightly narrower, trapezoidal; 24 ossicles narrower (~1.8mm wide, in 5–6 groups of 3–4) with only one radial duct; typical ossicle arrangement in each ray of large holotype and most other specimens is ‘22111121111’ (e.g., Figs. 3.1, 3.2, 8.1), in smaller paratypes ‘2211111111(1)’ (e.g., Figs. 3.3, 3.4, 3.8, 3.9, 4.2, 4.7, 7.9); marginal ossicles gently rounded on top, slightly tilted toward central disk with prominent overhang above duct entrances on distal edge (Fig. 9.1–9.4), separated by thin V-shaped gaps on rounded tops increasing in width distally (e.g., Fig. 7.5, 7.6); ossicles nearly flat on bottom surface with almost no gaps between them; ossicles having medium pustules on top, very small pustules (or stereom) on bottom; few marginal ossicles having slightly curved lateral sutures; one newly inserted ossicle present on paratype NPL 74385 (Fig. 4.4), wedge-shaped top edge does not reach distal edge of ring with gap partly filled by curved edges of adjacent ossicles. No obvious cupules with or without tubercules on distal side of marginal ossicles, which have slightly rounded lower edges sutured to frontals. Frontal plates (Fig. 9.1–9.5): separate, elongate-trapezoi-


dal, distally tapering, trough-shaped frontal plates attached to lower distal edge of a marginal ossicle (e.g., Fig. 9.1, 9.2, 9.4), each one leading to duct through a marginal (Figs. 7.6, 9.5); about 47 nearly complete frontals present (visible) in holotype UCBL-FSL 712001, 27 present in paratype UCBL-FSL 712000, and 33–34 complete frontals present in paratype NPL 62451; others covered, missing, or in stunted segments; frontals slightly shorter and much thinner than adjacent marginal ossicles, about 3.5mmlong and 1.5mmwide; laterally bounded (and underlain) by inner edge of imbricate peripheral skirt. Peripheral skirt (Fig. 9.6–9.8): edge of specimens gradually tapering in thickness, plated below with about 15 diagonal rows


of small to tiny, imbricate, arc-shaped to triangular plates decreasing in size outward, extending between (in V-shaped notches), below, and beyond frontal plates (e.g., Fig. 3.1, 3.4–3.6, 3.8, 3.9). Skirt easily damaged; in small paratype NPL 62451, about one-third of wide skirt missing near where several disrupted frontals present (e.g., Figs. 3.8, 3.9, 4.1, 4.2); plating widest on bottom where skirt about 6–7mm wide in small paratypes, up to 9.5mm wide in much larger holotype. Other features: several plate types (central disk plates,


marginal ossicles, frontal plates) show a frosted surface (possibly stereom or tiny pustular ornament) in smoked mold photos or CT scans. The apparent top of the mold is concave and the apparent bottom of the mold is slightly convex as preserved in the original concretion, implying that the original cyclocys- toid plating is convex on the top(?) surface and slightly concave on the bottom(?) surface. The central disk with its convex curvature often matches wispy, curved, white lines seen in several concretions (Fig. 10.1, 10.3).


Etymology.—Named for Andrew B. Smith, recently retired from the Natural History Museum, London, who revised the known cyclocystoids for a major monograph in the late 1970s to early 1980s and named many new genera and species (Smith and Paul, 1982; Smith and Wilson, 1995; Reich and Smith, 2008).


Discussion.—The shape and morphology of marginals and frontal plates distinguish this new genus and species from all other known cyclocystoid genera. During ontogeny, the mar- ginal ossicle arrangement apparently changed from 2211111111 (1) (e.g., Figs. 3.3, 3.4, 3.8, 3.9, 4.2, 4.7, 7.9) to 22111121111 (Figs. 3.1, 3.2, 8.1). The detailed arrangement of perforated marginals is clearly understudied in previously described


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