Epizoans immured in the heterocoral Oligophylloides maroccanus Weyer, 2017: a unique record from the Famennian (Upper Devonian) of Morocco

Abstract

Exceptionally well‐preserved proximal parts of colonies of the late Famennian heterocoral Oligophylloides maroccanus Weyer, 2017 with immured epizoans are described here from the Jebel Bou Ifarherioun ridge of the eastern Anti‐Atlas, Morocco. This is the first evidence of unique syn vivo interactions between a heterocoral and numerous epizoans, that is the colonial tabulate corals Zemmourella? sp. and Aulopora? sp.; solitary rugose corals Czarnockia? sp. and Gorizdronia? sp.; and other juvenile, undeterminable solitary rugosans, crinoids, as well as microbial structures. Detailed analysis of sectioned specimens allowed mutual interactions to be traced during growth of the host and infesting encrusting taxa. The studied associations show that the epizoans must have settled on the proximal parts of Oligophylloides in places devoid of soft tissue. The encrusted proximal portions of the colonies show that soft tissue of the heterocoral could have retracted and expanded again, fouling and immuring dead epizoans. The process of bioimmuration is perfectly marked by thin layers of microbial encrustations developing on the epibiont skeletons prior to their overgrowth by the skeleton of the heterocoral. The studied encrustations seem to be widespread, but the association provided the epizoans with additional substrate for encrustation, as well as an elevated position above the seafloor, beneficial for access to nutrients. We suggest that the host bioimmured the encrusters after their death, because of noticeable microbial encrustations and veneers of sediment, a lack of malformations, relatively rapid growth and aggressive activity of epizoans.

Early development and coloniality in Oligophylloides from the Devonian of Morocco—Are Heterocorallia Palaeozoic octocorals?

“…These characteristic basal parts of heterocorals are strikingly different from those of the basal parts of all septate corals described to date. Moreover, [ 6 ] and [ 17 ] described more advanced root-like holdfasts, which were named paracolonies. Such big basal parts could be formed as an effect of multiple larval settlement and/or formation of additional branches on the root-like holdfast.…”

“…In rare cases, representatives of Oligophylloides also formed complex holdfasts, such as those shown by Weyer (2017, pl. 10, Fig 16) [ 6 ] and [ 17 ]. Holdfasts showing the same complex structure are known from extant and subfossil representatives of the genus Keratoisis [ 32 ].…”

“…Furthermore, the basal part attached to the substrate represents a structure and origin that is different from that of a ’true’ talon developed in rugose corals, for which the term ’attachment body’ was proposed [ 4 ]. More massive, proximal parts of Oligophylloides coralla, composed of many individual branches united within a common thick protoheterotheca (paracolonies sensu Weyer 2017), have been described from the Famennian of Morocco [ 5 , 6 , 17 ].…”

3D morphology of post mortem acrothoracican borings in Famennian heterocorals – a morphological diversification or a continuum ichnospecies?

“…The entire skeleton was presumably covered by soft tissue with numerous polyps (Berkowski et al, 2021). Most heterocorals, and especially Oligophylloides, inhabited environments interpreted as oxygen-depleted and relatively deep-water (mesophotic and aphotic; e.g., Weyer, 2016;Dworczak et al, 2020). The genus Oligophylloides Różkowska, 1969 is characterised by a thick wall of protoheterotheca type and a central core with septal apparatus that is composed of dichotomously dividing septa.…”

“…The limestone contains pelagic organisms, especially abundant cephalopods, ostracods, conodonts (see, e.g., Korn and Bockwinkel, 2017), and reworked fragments of crinoids, bivalves, gastropods, and trilobites. Corals are represented by well-preserved small, undissepimented, solitary rugosans, tabulates (Weyer, 2002) and heterocorals with abundant epizoans (Dworczak et al, 2020). The studied material is housed at the Institute of Geology, Adam Mickiewicz University, Poznań, Poland.…”