Biotic Interactions Between Conulariids and Epibionts From the Silurian Waukesha Biota

Abstract

Here we describe an epibiont association between conulariids and holdfast producers, with attachment scars resembling those of the tubular epibiont, Sphenothallus, from the Silurian (late Telychian Series) Brandon Bridge Formation, Wisconsin. The conulariid population represents the most abundant sessile organisms in the Waukesha Biota and consists of two species, Conularia niagarensisHall, 1852 and Metaconularia cf. manni (Roy, 1935). Attachment scars present on the conulariid test offer a unique glimpse into the paleoecology of this Silurian benthic assemblage. However, body fossils of the attached epibiont are scarce and have not been observed attached or near conulariid specimens. This study evaluates the identity and paleoecological relationship between the conulariids and their enigmatic epibionts. Statistical analyses of attachment trace size, frequency, and distribution on the conulariid test gives insight to the nature of their symbiotic relationship. Our results did not find any significant support for a parasitic relationship. However, commensalism cannot be ruled out and serves as an alternative explanation for the relationship between these two organisms.

Rhabdopleurid epibionts from the Ordovician Fezouata Shale biota and the longevity of cross-phylum interactions

“…In some cases, the ecology of some organisms will facilitate the fossilization of biotic interactions, such as the case of epibionts that require a hard substrate to metamorphose from the larval to the adult stage, as in the case of some sessile echinoderms 16 and benthic pterobranchs 17 , 18 . Although post-Cambrian Paleozoic sites also contain evidence of biotic interactions 19 , 20 , Burgess Shale-type preservation becomes much rarer after the Miaolingian and thus restricts access to this type of valuable ecological data.…”

“…It was deposited under the fair-weather wave base, however, the majority of the most exceptional fossil preservation is restricted to below the storm-weather wave base, underscoring the complex depositional setting of the locality 22 – 25 . The biodiversity of the Fezouata Shale biota combines faunal elements from Cambrian Burgess Shale-type biotas (e.g., marrellomorphs, radiodonts; palaeoscolecids) 26 – 28 , alongside more “modern” groups, more typical of the Paleozoic evolutionary fauna (e.g., asterozoans, synziphosurans, machaeridians) 20 , 29 , 30 . The Tremadocian-Floian age of the Fezouata Shale biota makes it the best available view into the early Ordovician world, both in terms of its evolution and ecology.…”