Catervaparmaster Systematic PalaeontologyType Specimens: Catervaparmaster pecularis Blake, 2000; original designation. Diagnosis: Asterozoan with asteroid-like body outline: Arms broad, triangular, tapering gradually, distal tip probably narrowly rounded, body profile probably low, interbrachial arc broadly rounded. Neither abactinal skeleton nor madreporite known. Ambital framework ossicles in single series; individual ossicles low, square to rectangular in outline, abutted rather than overlapping longitudinally, interossicular ossicular articular surface approximately perpendicular to arm margin. Ambital framework ossicular surfaces flat except for ridges that abut ambulacral transverse ridges. Framework ossicular ridges narrow, straight, sharp, more weakly developed medially but expanded abradially, which might indicate presence of lateral spines in life. Transverse ridges at adradial edge directed slightly ventrally to form an articular facet to ambulacral or possible ventral intermediary ossicles. Ossicles appearing pustulose, perhaps reflection an open stereom. Ambulacral ossicles rectangular, plate-like; ossicular boundaries approximately medial in basins. Transverse ridge sharp, narrow; podial pores lacking; radial water vascular channel narrow. First virgal or equivalent ossicles lacking, at least medially or distally on arm, rather ambital framework ossicles abut ambulacrals. Facets between ambulacrals and ambital framework ossicles small. No evidence of asteroid furrow nor deflection of edging ossicles as typically expressed by ophiuran laterals. Oral frame unknown. Remarks/Discussion: The Catervaparmasteridae originally was assigned to the Somasteroidea based on the form of the ambulacral ossicles (Blake, 2000, p. 90). Although no virgalseries ossicles were recognized, Spencer and Wright (1966) assigned the Archophiactinidae Spencer, 1927, to the Somasteroidea; however, full virgal series ossicles were not recognized in this family. Shackleton (2005) challenged inclusion of the only Ordovician archophiactinid genus in the somasteroids; Blake (2013) followed this interpretation and further excluded the Silurian and Devonian genera. No virgal series ossicles can be recognized in the interbrachial area of Catervaparmaster, although if none were present, interbrachial ambulacral ossicles would have to have been very wide. Following Blake (2013), lack of virgal-series ossicles is considered crucial for assignment to the Somasteroidea whereas the Stenuroidea is most readily recognized based on presence of two or three virgal-series ossicles throughout the full arm length. Asteroids and ophiuroids have a single ossicle aligned with the ambulacral and both are specialized in aspects of arm construction. Without evidence of virgalequivalent ossicles, and together with the unique construction of the ambital framework ossicles and the relationship of these ossicles to the ambulacrals, Catervaparmaster cannot be assigned to any of the recognized asterozoan classes; it is left in open nomenclature. Form and positioning of ambital framework ossicles and ambulacrals imply a capacity for facultative vaulting comparable to that of somasteroids and stenuroids. The facets at the adradial edge of the ambital framework ossicles appear directed slightly ventrally, which could indicate a ventrally directed, V–shaped vaulting for the facultative furrow. The broad, apparently flattened form of the ambital framework suggests limited dorsal arching in life. Some small possible ossicular debris could derive from the abactinal or actinal surfaces.Catervaparmaster appears to represent an asterozoan lineage apart from the main lines of asterozoan diversification, much as seems possible for the Phragmactinidae (Blake, 2014). The two families indicate a complex early asterozoan history with survival of comparatively few major lineages, a pattern reminiscent of the early history of the Blastozoa Sprinkle, 1973. It can only be hoped that additional material of Catervaparmaster will emerge to further elaborate and test the significance of this genus. Taphonomy & PalaeoecologyOccurrence: Two small fragments considered part and counterpart in Blake (2000) but both surfaces retaining impressions of the ventral surface, perhaps reflecting sediment compaction; only the better-preserved is illustrated here. Bardahessiagh Formation, Mitchell Siltstone Member, Caradoc and Shermanian, Ordovician, Pomeroy, County Tyrone, Northern Ireland.
