Subepidermal Emsian “auloporids” on crinoids from Hamar Laghdad (Anti-Atlas, Morocco)

The late Emsian outcrops of Hamar Laghdad, Morocco, yielded crinoid stalks encrusted by auloporid tabulates, Cladochonus-like cnidarians, or with swellings of unknown cause. In one case, the auloporid skeleton is preserved in the gall, showing the tracemaker; also, circumferential openings of the cysts suggest an “auloporid” nature of the infester. In the case of Cladochonus-like infestations, the symbiont skeleton is usually not preserved, but the host’s stereom mimics the symbiont’s external morphology, thus allowing the assignment. In all analysed specimens, the infestation took place syn vivo as demonstrated by skeletal intergrowths of the involved crinoids and cnidarians. The interaction between these organisms can be classified as parasitism, as the cnidarian parasite benefited from the elevation above the seafloor, thus profiting from stronger currents and less competition, while the host was harmed or at least disturbed by this infestation; in most cases it had to produce extra skeletal material for the cyst, which was energy demanding. Such an infestation also affected stem flexibility, making it prone to breakage in strong currents.