Early Ordovician stromatoporoid Pulchrilamina spinosa from South China: Geobiological significance and implications for the early development of skeletal-dominated reefs

The thin, laminar to low domical, encrusting stromatoporoid Pulchrilamina spinosa is reported from the Tremadocian-Floian in Hubei and Guizhou provinces, South China. The Chinese Pulchrilamina appeared earlier (late Tremadocian-early Floian) than North American equivalents (early Floian), which possess large domical forms and are the main framework-builders. Pulchrilamina appeared much earlier than the observed diversification of other stromatoporoids. These skeletal reef-builders thus provide excellent clues for understanding the initial evolution of the stromatoporoids and the subsequent development of the skeletal-dominated (especially stromatoporoid-dominated) reefs that reached their first acme in the late Middle-Late Ordovician.