Patterns of sclerobiont colonization on the rugose coral Schlotheimophyllum patellatum (Schlotheim, 1820) from the Silurian of Gotland, Sweden

Abstract

Analysis of mushroom‐shaped rugose corals Schlotheimophyllum patellatum (Schlotheim, 1820) from the Silurian (Upper Visby Beds, Lower Wenlock, Sheinwoodian) of Gotland, Sweden, showed that they were colonized on both the upper (exposed) and lower (cryptic) sides by a variety of encrusting and boring (sclerobiont) biotas, represented by 10 taxa and at least 23 species. Bryozoans and microconchid tubeworms, the most abundant encrusters, dominated on the cryptic undersides of the corals, while the dominant endobionts responsible for Trypanites borings overwhelmingly dominated the exposed surfaces. Except for cnidarian sphenothallids, which were exclusive colonizers of the underside of only one coral host, no other encrusters could be referred to as obligate cryptobionts. Because the upper surface of these corals was likely covered by soft‐tissues during life, in specimens lifted off the sea‐floor sclerobionts must have settled on the cryptic sides first. They could colonize the upper side only after the coral’s death, unless it was covered by sediment as could be the case in some flat specimens. With time, the space on the underside of the coral skeleton may have progressively been filled by sediment as well, precluding further colonization by sclerobionts. In that respect, the colonization patterns of these corals by encrusters and borers were controlled by the complex interplay of environmental factors, sclerobiont dynamics and coral growth in a given Silurian habitat. Compared with Silurian stromatoporoid hosts, the sclerobiont diversity and abundance noted on the Schlotheimophyllum corals may be regarded as representative for the Silurian as a whole.

Dead or alive? Brachiopods and other shells as substrates for endo- and sclerobiont activity in the early Devonian (Lochkovian) of the Barrandian (Czechia)

“…Encrusting rugose corals definitely growing on living hosts were described on crinoid stems (Głuchowski 2005, Berkowski & Klug 2012, Bohatý et al 2012 where caused stereomic reaction of a crinoid. Encrusting rugose corals or rugose corals as host substrate for sclerobionts were examined just recently by Vinn & Toom (2016) and Zatoń et al (2020). Rugose corals forming symbiotic associations with stromatoporoids are known from the Silurian (Kershaw 1987, Lebold 2000, Vinn & Wilson 2012, Vinn & Motus 2014, Vinn et al 2015, but as known to author, the rugose-brachiopod interaction is unsufficiently known in fossils records.…”