Nuevos datos sobre el género Sucocystis (Cincta, Echinodermata) en el Cámbrico medio de España: Implicaciones biostratigráficas y filogenéticas

New material of the carpoid class Cincta is described from the middle Cambrian of the Iberian Chains (Spain). Material consists of the dorsal surface of a well preserved individual belonging to the genus Sucocystis; this spe-cimen comprises a complete theca and a partial stele. The marginal ring (cinctus) is composed of twelve margi-nal plates (M6r-M5l). Two well-defined grooves run from the mouth around the outer face of the marginal ring: the right groove is short, terminating in M2r; the left one is longer, ending in the medial part of M2l. The lintel is composed of four suropercular plates, which are larger than other supracentral ossicles. The shape of the the¬ca, length of the left marginal groove and structure of the lintel allow Sucocystis sp. A to be differentiated from other members of the Sucocystidae. The specimen was found in Mesones de Isuela (Zaragoza, Spain), in levels from the upper part of the Murero Formation (lower Languedocian), which correspond to the Solenopleuropsis thorali zone. It is one of the oldest representatives of the genus and expands the stratigraphic range of Sucocys-tis in the middle Cambrian of Spain. Sucocystis sp. A is unique among the Sucocystidae in the length of the left marginal groove, which reaches plate M2l. Comparisons with other species of Sucocystis (sensu Friedrich, 1993) demonstrate that there was considerable variation in the length and number of food grooves within the genus, suggesting that Sucocystis may be a paraphyletic group.