An unusual and exceptionally well preserved cryptic community of cnidarians, crinoids, sponges, and microbes developed in a submarine cavity of Middle Devonian age in the Hamar Laghdad area (Morocco). The biota encrusted the cavity roof and grew predominantly in an upside-down position, forming spectacular “hanging gardens.” The investigated assemblage differs strikingly from both its Paleozoic and modern analogues; it constitutes one of a very few known examples of fossil cryptic assemblages developed in relatively deep water settings, and is the first report of a cryptic paleoecosystem dominated by rugose corals. The results support the view that during the middle Paleozoic there was no distinct polarization between open-surface and cryptic faunas in deep-water environments, but keen competition for space already existed in Devonian cryptic assemblages. The regional species pool seems to have been the main determinant of the ecological succession and structure of this cryptic community.

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