Early life strategies and juvenile mortality in Favosites (Anthozoa, Tabulata) from the Middle Devonian of the Mader Basin (Anti-Atlas, Morocco)

An exceptionally well-preserved population of numerous tiny, juvenile colonies of the tabulate coral Favosites goldfussi was discovered in the lower Eifelian of the Ouihlane section, Anti-Atlas, Morocco. The studied coralla provide a unique opportunity to reconstruct the details of the astogeny, i.e., the early growth of a colony, including the ontogeny of the protocorallite, and the process of offsetting of the first hysterocorallites. The investigated material afforded also an opportunity for the so far most detailed analysis of the early colony development in favositid corals. The studied population inhabited a relatively deep-water environment, with the colonies growing on a soft, muddy substrate exposed to constant unidirectional bottom currents. These environmental factors resulted in asymmetrical development of the colonies, which, starting from the early growth stages, developed specific, mud-sticker or mud-catcher growth strategies that stabilised their position on the seafloor. Despite their adaptation to the relatively unstable environment, including the dominance of the soft muddy substrate and exposure to unidirectional bottom currents, the studied favositid colonies were, however, apparently unable to cope with irregular events of high sediment influx, which resulted in their high juvenile mortality.