Notes on selected Cretaceous echinoids from south-central Sakhalin, Far East Russia

From Albian, Santonian and Campanian strata in south-central Sakhalin, four echinoid taxa are described, illustrated and discussed. In Far East Russia, echinoids are rare constituents amongst mid-and Late Cretaceous macrofaunal assemblages in which inoceramid and non-inoceramid bivalves, plus heteromorph and non-heteromorph ammonites predominate. The sole regular species in the present lot is represented by an incomplete external mould of a primary spine of a rhabdocidarid, Polycidaris(?) sp., from the lower Campanian. Irregular taxa include a fragmentary, specifically indeterminate 'pygurid', Echinopygus(?) sp., of late Albian age, as well as two spatangoids. One of these, a toxasterid of late Campanian age, is assigned to Niponaster cf. hokkaidensis (Lambert in Lambert & Thiery, 1924). The other is a new hemiasterid with a semi-ethmophract apical disc, a peripetalous fasciole with diffuse boundaries (parafasciole) and posterior petals that are near-equal in length to anterior ones, from lowermost Campanian strata. For this, the name Palhemiaster natalyae n. sp. is introduced. Comparisons with coeval echinoid faunas from nearby Hokkaido (northern Japan) are hampered by the generally poor preservation of the latter. However, with the exception of Niponaster cf. hokkaidensis, none of the forms recorded in the present paper appears to be represented in those Japanese assemblages.