Framework built by corals (diverse) and rudists (one species only).
Corals encrusted by red algae.
Buildup dimensions 20x50x1 m.

Abstract of ref. 743:
A coral-rudist limestone was newly discovered in the Lower Cretaceous (upper Aptian) sequence of the Miyako Group. It is small in scale but contains abundant frame-building organisms, notably autochthonous corals and rudists. Though vertical succession was not recognized, in some parts of the limestone, large and massive corals make a rigid framework, whereas in other parts the main frame-builder is Praecaprotina yaegashii (Yehara), a caprotinid rudist, which often forms clusters but does not show dense packing. This paper is the first concrete description of carbonate buildup in the Cretaceous of East Asia. Existence of coral-rudist buildup indicates that the northern limit of tropical-subtropical realm reached north Japan in late Aptian time. The influx of abundant clastic material may have prevented the buildup from the development of large-scale reefs, but small-scale buildups could grow, though temporarily or episodically, on the rocky shore in a transgressive stage.