LYRE-SHAPED HORNERID BRYOZOAN COLONIES - HOMEOMORPHY IN COLONY FORM BETWEEN PALEOZOIC FENESTRATA AND CENOZOIC CYCLOSTOMATA

Reticulate Hornera reteramae (Bryozoa, order Cyclostomata) have been d iscovered as free-lying, lyre-shaped colonies in the Castle Hayne Lime stone (Eocene) in North Carolina. These specimens represent a striking instance of homeomorphy in colony form with the Late Mississippian ge nera Lyropora and Lyroporella of the order Fenestrata. Bryozoans with reticulate growth habit most commonly develop upright colonies. Living representatives generally grow in quiet environments or microenvironm ents, and fossils are generally found in situ in quiet-water deposits. However, lyre-shaped Hornera reteramae occur in skeletal packstones i nferred to have been deposited in a moderate-energy, shallow, open she lf environment near normal wave base. Upper Mississippian lyre-shaped colonies are preserved in skeletal packstones and grainstones in local ized channels or on upper surfaces of low-angle cross-bedded sheets in terpreted as high-energy, marine shoal deposits. Modification of the r eticulate growth habit to low, peripherally weighted, free-lying struc tures apparently allowed invasion of higher energy sand bottoms, both in Mississippian and Eocene times.