Cyathidium undetermined

Cyathidium sp. Figures 8D–E, Table 5 Synonymy. Cyathidium gastaldii Manni & Pacioni, 2021: 68–69, fig. 3 (non Michelin, 1851). Material examined. Four aboral cups from Cengio dell’Orbo quarry (Cava Boschetto) in the Chiampo Valley, north-eastern Italy: three (MGP-PD 31469 to 71) figured by Manni & Pacioni (2021, fig. 3) (Fig. 8D–E) and one (MGP-PD 33231) not figured. Description of the specimens. All specimens without ornamentation and with very variable cup shape from depressed (H/D 0.36) to taller than wide (H/D 1.15), H/h 1.10 to 3.67, D/Db 0.54 to 1.19, D/Dcs 0.79 to 1.38 (Table 5). Three bioeroded and worn aboral cups with Db>D from MGP-PD collection described in Manni and Pacioni (2021) with only adoral faces figured. Additional data on quantitative characters listed in Table 5 and side views illustrated in Fig. 8D–E. Two cups MGP-PD 31469 (D 3.9 mm) and MGP-PD 31470 (D 3.5 mm) larger than holotype of C. chiampoensis sp. nov., strongly depressed, showing one thin growth band above attachment surface (Fig. 8D). Cup MGP-PD 31471 is smaller (D 2.2 mm) with adoral face poorly preserved and two thick growth bands without marked ornamentation (except for short, faint granules) above attachment surface (Fig. 8E). Smallest specimen MGP-PD 33231 with Db<D, bioeroded and slightly worn without growth line, slight constriction (D/Dcs 1.38), two interradial processes preserved, and cup base broken just above attachment surface. Remarks. Do all Cyathidium cups from the Cengio dell’Orbo quarry belong to the same species? The four specimens described here resemble C. championensis sp. nov. except for the absence of ornamentation and growth lines and appear to fall within the range of variation of quantitative characters. Bioerosion and wear may have erased the fine wrinkles on the cups’ surface, perpendicular to the growth lines, that characterize C. chiampoensis sp. nov. In the absence of ornamentation, and given their intraspecific morphological plasticity, the different Cyathidium species cannot be easily distinguished based solely on the external morphology of the aboral cup (see above). The presence of short, faint granules on the cup MGP-PD 31471 led Manni and Pacioni (2021) to attribute these specimens to C. gastaldii, although this character, which develops variably in different species of Holopodidae, is not a discriminating feature (see below and above). Moreover, it seems unlikely that two Cyathidium species would cohabit in the same biotope. However, the fossil association of the Chiampo deposit includes both well-preserved specimens and others that are biocorroded or worn, suggesting a mixture of ossicles from different biotopes, possibly with reworked elements (see Taphonomy below). Thus, the existence of two Cyathidium species cannot be ruled out, one living in the depositional environment (C. chiampoensis sp. nov.), the other from a different ecological niche. As a result, we leave these specimens that lack observable discriminating characters in open nomenclature. Occurrence. Cengio dell’Orbo quarry (Cava Boschetto) in the Chiampo Valley, north-eastern Italy, lower Lutetian.