Allaire et al.—Early Ordovician eocrinoids from Morocco
the second radial plate is split in two elements forming two spines (Fig. 12.6). As far as plate ornamentation is concerned, Chauvel (1971)
pointed out the presence of continuous longitudinal ridges on infralateral and lateral plates. These ridges correspond to ornamen- tation folds andwere observed in several specimens (e.g., Fig. 13.4– 13.7). In specimen AA-TISa-OI-27a (Fig. 13.4),which corresponds to a partially preserved theca (aboral partmissing), all plates exhibit ornamentation folds, some of which are continuous on several plates. The stem and the basal of some specimens also possess this type of folds, which form continuous ridges from the stem to the infralaterals (e.g., Fig. 13.5–13.7). Some specimens do not show this kind of ornamentation (e.g., Fig. 13.8–13.10), but this absence may result from their different preservation (the surfaces of their tests seem to be more weathered). The proximal part of the stem is preserved in connection
with the theca in a few specimens (e.g., Figs. 11.6, 11.9, 12.3, 12.8, 13.5–13.7). It seems to be made up of cylindrical columnals of various sizes (alternation of short and longer columnals). The longest ones are swollen (nodal-shaped) and can show small longitudinal ridges, which are little pronounced (e.g., Fig. 13.6, 13.7). As in R. grandis, the plates of the lateral area show a
characteristic pattern resulting from a growth mode by intercalation of new elements (Sprinkle and Guensburg, 2001; e.g., Figs. 11.3–11.5, 11.8, 12.3, 12.7). The plates exhibiting spine-shaped protuberances seem to be the primary plates (P), which formed the initial organization of the theca into transversal circlets. The secondary plates are smaller, not ornamented, and their shape is more irregular. Therefore, the growth by intercalation of plates seems to begin from a theca constituted of different primary circlets: a basal circlet (one plate), one circlet of infralaterals (four plates), several circlets of spine-shaped laterals, and three circlets of radials. The morphology of the oral surface of R. havliceki (rarely
preserved) is comparable to that of R. destombesi (e.g., Fig. 7.10). However, the ambulacra seem to be composed of a larger number of
plates.According to the specimenAA-TISa-OI-22g (Figs. 12.4, 13.3), the ambulacra of R. havliceki seemto be constituted of eight brachioliferous plates, and the oral surface is apparently flattened, in contrast to the situation in other species, which have a more convex oral surface. The posterior interradial area (with the periproct) and the peristomial area have not been observed.
Materials.—Several poorly preserved latex casts of original specimens examined by Chauvel (1978), corresponding to external molds of incomplete thecae: 2082a, 2082b (locality 2082; Fig. 1), 1725h4.5 (holotype), and 1725e' (locality
707
809 = 1157 = 1725; Fig. 1). Numerous original samples containing about 100 external molds of thecae, coming from the localities Z-F1 (AA.TAM.OI.1–80) and Z-F12c (AA.TISa. OI.22, 23, AA.TISa.OI.25–27) (Fig.1).
Remarks.—The species Rhopalocystis C, left in open nomen- clature by Chauvel (1978, text-fig. 11o, p), was created for only one specimen (2082a) coming from locality 2082. This speci- men corresponds to a fragmentary theca, with only the lateral area preserved. However, the presence of spine-shaped protuberances on several plates is a diagnostic feature of R. havliceki. Therefore, R. sp. C is here identified as a junior synonym of R. havliceki. As far as the ornamentation of R. havliceki is concerned,
some differences can be observed between the populations coming from localities Z-F1 and Z-F12c. In specimens from Z-F12c, infralaterals can have one, two, or three rounded protuberances (e.g., Figs. 12.1–12.3, 12.5–12.8, 13.4, 13.5, 13.7), while in specimens from Z-F1, these plates exhibit only one protuberance, which can be elongated and spine-shaped (e.g., Figs. 11.2, 11.4, 11.6, 11.9, 13.8–13.10). The diagnosis of R. havliceki was completed, thanks to the
observation of the new material, in order to bring out more accurately the morphological characteristics of this species.
Rhopalocystis zagoraensis Chauvel, 1971 Figures 4.3, 5.3–5.8, 5.12, 5.18–5.20, 14, 15
1971 Rhopalocystis zagoraensis Chauvel, p. 45, pl. 1, fig. 6; pl. 2 fig. 2.
1978 Rhopalocystis zagoraensis; Chauvel, p. 52, fig. 11a–e. 1986 Rhopalocystis lehmani; Chauvel and Régnault, p. 866, pl. 1, figs. 9, 10, text-fig. 3I–N.
1986 Rhopalocystis zagoraensis; Chauvel and Régnault, p. 865, text-fig. 3O; p. 867, specimen M.1725f.
2015 Rhopalocystis zagoraensis; Allaire et al., p. 24, text- fig. 2E, G.
2016b Rhopalocystis zagoraensis,Lefebvre et al., p. 10, text-fig.8B.
Holotype.—Specimen 1725g from the Fezouata Shale, Zagora area, locality 809 (=1157 = 1725; Fig. 1), Anti-Atlas, Morocco (Chauvel, 1971, pl. 1, fig. 6; pl. 2, fig. 2).
Diagnosis.—Rhopalocystis with a theca composed of six primary circlets of plates, one basal, one circlet of infralaterals (four plates), one circlet of laterals (four to six plates), and three circlets of radials (perradial areas consisting of columns of three plates); additional secondary plates between infralaterals and laterals (up to three circlets of plates), between laterals and
Figure 12. Rhopalocystis havliceki from the locality Z-F12c, late Tremadocian (A. murrayi Zone), drawings realized under a stereomicroscope with a camera lucida. (1) AA-TISa-OI-22j; (2) AA-TISa-OI-22h. (1, 2) Large thecae; several spine-shaped radials are preserved; some laterals exhibit a spine-shaped umbo more or less rounded; the infralaterals seem to have several rounded protuberances (three in (2)). (3) AA-TISa-OI-23a, relatively small theca; a radius is partially exposed; the first radial is missing; the second one is spine-shaped; the third one is convex; the infralaterals and the largest laterals have a small umbo. (4) AA-TISa-OI-22g, aboral fragment of theca; a part of the oral surface is preserved; some spine-shaped radials are visible; the ambulacra seem to have eight brachioliferous plates; numerous epispires are located within the interradial area, which has been preserved. (5) AA-TISa-OI-22i, large theca partially complete; some laterals exhibit a small umbo; infralaterals have two or three protuberances; some ambulacra are preserved; they seem constituted of eight brachioliferous plates; a radial with a small umbo can be observed. (6) AA-TISa-OI-22l, large fragment of theca; one radius is partially preserved; the first radial is spine-shaped; the second one seems to be split in two plates also spine-shaped; some laterals exhibit a small protuberance. (7) AA-TISa-OI-22a, theca partially complete; two disconnected radials can be observed; they are spine-shaped. (8) AA-TISa-OI-22e, adoral part of theca with a relatively large portion of stem conserved in connection with the theca; it is constituted of columnals of different sizes; one of them is particularly swollen (nodal-shaped); the infralaterals possess several rounded protuberances, and some laterals have a small umbo. Scale bar = 1 cm.
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