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Journal of Paleontology 91(4):672–684
because of the presence of both brachioles and sutural pores and the similar morphology of their attachment disc (holdfast). He diagnosed the order Imbricata on the basis of the well-marked differentiation between the tessellate plating of the oral surface and the imbricate plating of the aboral region (Sprinkle, 1973, p. 60). However, several other echinoderms exhibit a comparable combination of imbricate and tessellate platings (e.g., Camptostroma Ruedemann, 1933; several edrioasteroids, primitive solutans). The discovery of Felbabkacystis n. gen. confirms that the order Imbricata Sprinkle, 1973 was mostly described on plesiomorphic characters (e.g., imbricate plating, sutural pores). Therefore, the order Imbricata is not considered here as a valid taxonomic entity, and the family Lepido- cystoidae, with a diagnosis emended from Durham (1968), is retained as a basal blastozoan family. Lepidocystoids possess one single apomorphy of the subphylum (presence of bra- chioles), but they lack all other apomorphies present in more advanced taxa (e.g., theca, spout-like oral area, holomeric stem). The particular morphology of the lepidocystoids recalls the bipartite body-wall organization (disc-like oral surface and elongate aboral cup; Fig. 2) also occurring in other primitive echinoderms (camptostromatoids, basal crinoids, edrioasteroids, etc.). The body wall of the lepidocystoids is therefore called here a ‘calyx’ by comparison to the structure observed in many other basal echinoderms (see Nardin et al., 2009 for further discussion). The family Lepidocystoidae contains the three closely
Figure 2. Photographs of selected specimens representing the Family Lepidocystoidae Durham, 1968. (1) Holotype MCZ 581 of Kinzercystis durhami Sprinkle, 1973 (Kinzers Formation, Pennsylvania) showing the circular oral disc, composed of large adjacent plates bearing roundish epispires and bearing the periproct laterally, overlapping the conical aboral cup; (2) plesiotype MCZ 588A of Lepidocystis wanneri Foerste, 1938 (Kinzers Formation, Pennsylvania) showing narrow oral surface composed of small platelets bearing small epispires and damaged periproct, few brachioles attached to the ambulacra; (3, 4) specimens of Vyscystis ubaghsi Fatka and Kordule, 1990 for comparison (Jince Formation, Příbram-Jince Basin, Czech Republic); (3) partial small specimen NML28665 showing long imbricate plates and adjacent plates pierced by small roundish epispires, embedded ambulacral flooring plates bearing brachiole facets; (4) holotype NML 28664, showing disarticulated imbricate plates and epispire-bearing adjacent plates with five coiled brachioles. Latex casts have been whitened with ammonium chloride. Scale bars = 5mm.
Remarks.—This family, based on the genus Lepidocystis Foerste, 1938, was initially assigned to an independent class (Lepidocystoidea Durham, 1968). Durham (1968) differentiated lepidocystoids from eocrinoids on three main features: (1) the restriction of the epispires-bearing surface to the oral surface, (2) the imbricate plating on the aboral region, and (3) the circlet of ‘free arms’ (brachioles) on the oral surface and their mode of attachment. With the description of a second genus (Kinzercystis Sprinkle, 1973), Sprinkle (1973) suggested that these differences were not supported by the new discoveries and not sufficiently grounded to maintain the class Lepidocystoidea. Accordingly, he decided to assign lepidocystoids to the new order Imbricata, within the class Eocrinoidea, and to synony- mize the class Lepidocystoidea with the new order Imbricata. Sprinkle (1973) interpreted lepidocystoids as eocrinoids
related genera Lepidocystis and Kinzercystis (both from the Cambrian Stage 4 Kinzers Formation of Pennsylvania, USA) and Vyscystis Fatka and Kordule, 1990 (from the Drumian Jince Formation of Czech Republic).
Family Felbabkacystidae new family
Type genus.—Felbabkacystis new genus Diagnosis.—As for type species by monotypy.
Remarks.—The presence of brachioles supports the assignment of felbabkacystids to the subphylum Blastozoa. The combi- nation of plesiomorphic (e.g., imbricate plating, sutural pores) and derived characters (vaulted oral surface, tessellate region extended beyond the body wall edge, elongate epispires, lateral location of the periproct) is not present among members of the family Lepidocystoidae (Fig. 2). It therefore justifies the erection of a new family, which occupies a relatively basal position within blastozoans (see the following for an extended explanation). Felbabkacystids differ from lepidocystoids by: (1) the higher ratio between tessellate/imbricate regions of the body wall, associated with the overgrowth of the tessellate region not only restricted to the oral disc; and (2) the strongly indented shape of the plates, the length of the epispires, and the location of the periproct high in the lateral tessellate area (Figs. 3, 4). They share with lepidocystoids the presence of an elongate aboral region (cup and stalk)made of imbricate elements.
Genus Felbabkacystis new genus Figures 3–5
Type species.—Felbabkacystis luckae n. gen. n. sp.
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