Sclerobionts associated with Orbiramus from the Early Ordovician of Hubei, China, the oldest known trepostome bryozoan

Abstract

In addition to a marked rise in marine biodiversity, the Ordovician witnessed the most profound increase in the complexity of marine ecosystems in the history of the earth, including the expansion of tiering and enhanced biotic interactions. In order to understand these changes, it is important to study palaeoecological relationships among organisms at the commencement of the Great Ordovician Biodiversification Event (GOBE). Here, we describe sclerobionts associated with one of the earliest bryozoans in the fossil record, the oldest known trepostome, Orbiramus from the Fenhsiang Formation (late Tremadocian) of Hubei Province, China. These sclerobionts are diverse and include borings (e.g. Trypanites and Sanctum), bioclaustrations of vermiform organisms, and syn‐vivo fouling by the putative black coral Sinopathes and other bryozoans. Diverse sclerobiotic associations and intricate palaeoecological relationships had already been established between bryozoans and other metazoans by the Tremadocian, showing the early onset of the ‘hard substrate revolution’ during the GOBE.

Rise of clathrodictyid stromatoporoids during the Great Ordovician Biodiversification Event: insights from the Upper Ordovician Xiazhen Formation of South China

“…in the Cambrian Burgess Shale of Canada (Topper et al, 2015). The earliest known intergrowth association involved the early bryozoan Orbiramus and diverse sclerobionts reported from the Early Ordovician of South China (Ma et al, 2021). Bryozoans commonly hosted various endobionts, such as cornulitid tubeworms and rugose corals, in the subsequent stages of the Ordovician (e.g., Vinn and Mõtus, 2012; Vinn et al, 2014, 2016, 2017, 2018a, b, 2019) and later (e.g., Plusquellec and Bigey, 2019; Sendino et al, 2019).…”

Bryozoan–cnidarian mutualism triggered a new strategy for greater resource exploitation as early as the Late Silurian

“…These earliest bryozoan symbiotic endobionts were solitary animals with unknown biological affinities. However, phosphatic tubes are characteristics of the presumed cnidarian Sphenothallus known from the Tremadoc, though the tubes described by Ma et al 64 are slightly too small for Sphenothallus . Nevertheless, tubicolous morphology and Sphenothallus -like composition could indicate a cnidarian affinity.…”

“…Bryozoans are known to have formed symbiotic associations with other invertebrates since the Tremadoc 64 . Endobiotic invertebrates with phosphatic tubes and some with entirely soft bodies formed symbiotic associations with the trepostome Orbiramus in the Tremadoc of China 64 . These earliest bryozoan symbiotic endobionts were solitary animals with unknown biological affinities.…”

Sclerobiosis: A Term for Colonization of Marine Hard Substrates

“…The terms 'sclerobiotic' and 'sclerobiosis' have been used by some authors as derived words from 'sclerobiont' by Taylor and Wilson (2002). In several studies, sclerobiontic and even sclerobiont were used as one word-adjective, e.g., sclerobiotic or sclerobiont assemblages (see Toscano & Raspini, 2005;Brett et al, 2011;Barclay et al, 2013;Schneider, 2013;Moissette et al, 2013;Brezina et al, 2017;Luci et al, 2021;Ma et al, 2021). While the use of the term sclerobiotic is the same in all works, that does not occur with the use and meaning of the word sclerobiosis.…”