Deep‐water cirripedes colonizing dead shells of the cephalopod Nautilus macromphalus from New Caledonian waters

Abstract

Fossil cephalopods are frequently encrusted by epibionts; however, determining whether encrustation occurred prior to or post‐mortem to the host, and whether the final environment of deposition corresponds to the habitat of encrustation is complex. The present paper describes cirripede epibionts, their calcareous bases and their attachment scars on 6 post‐mortem shells of Nautilus macromphalus, collected from deep water off New Caledonia. The cirripedes have left both cemented calcareous bases of Hexelasma and scars associated with bioerosion and discoloration produced by verrucomorph barnacles. Live cirripedes included a Metaverruca recta, with articulated opercular plates and organic tissue (on a shell that had been exposed on the sea floor for at least 150 years), and specimens of Hexelasma velutinum, one of which was partly attached to an internal surface of a shell. The disposition of verrucomorphs indicates that most Nautilus shells were colonized post‐mortem rather than during a floating stage. However, as cirripedes are known to have colonized living Nautilus, some Hexelasma, preserved only as calcareous eroded bases, may represent specimens that settled on a living Nautilus. The degree of bioerosion and discoloration induced by verrucomorph barnacles varies according to the surface preservation of Nautilus shells, with deeper and discolored traces preserved on old and degraded shells. Traces made by verrucomorphs described here are ellipsoidal and a new ichnotaxon, Anellusichnus ellipticus, is proposed to accommodate them. Importantly, verrucomorphs and other cirripede taxa with membranous bases that were attached to pristine shells may not leave any substantial scars, and, thus, will be difficult to detect in the fossil record.

The occurrence of the coronuloid barnacle Chelonibia Leach, 1817 as an encruster on mammalian bone in the central Mediterranean Sea

“…They consist of oval patches where the outer cortical surface is seemingly well preserved and appears as slightly lifted above the partly abraded surrounding areas. These traces superficially recall the barnacle attachment marks that have been classified under the ichnogeneric name Anellusichnus (SANTOS et al, 2005;BUCKERIDGE et al, 2019), and especially Anellusichnus circularis Santos, Mayoral & Muñiz, 2005. A few traces still exhibit shreds of soft tissues (i.e., the membranous basis of the barnacle) attached to them, which in one case also reveal the dense pattern of longitudinal internal parietal septa that is typical of Chelonibia (Fig.…”

Thatchtelithichnus on a Pliocene grey whale mandible and barnacles as possible tracemakers

“…Such a reappraisal of the scope and content of Anel lusichnus is nevertheless beyond the purposes of the present paper, and substrate is not taken into account herein when distinguishing between the aforementioned ichnogenera. Thus, for the moment being, the below described ichnofossils are recognised as belonging to Thatchtelithichnus based on the observation of a distinct boss or pedestal in the central portion of these traces -a morphological feature that characterises the type series of T. holmani (Zonneveld et al 2015) while not being present (or at least not apparent) in the three ichnospecies of Anellusichnus that have been described so far (Santos et al 2005;Buckeridge et al 2019).…”

Fossil barnacles from the Antarctic Peninsula: refining ways of exploring the nature of rare and/or delicate specimens employing X-ray Computer Tomography (CT)

“…Seilacher (2005) assessed the mechanism by which Coronula attached to cetaceans, and concluded that embedding within the whale skin was achieved by a narrow ring of sutural tissue at the base of the barnacle shell during its cypris larval stage that evolved to clean surfaces prior to attachment of sessile cirripedes. The ability of barnacles to excavate (and dissolve) substrate was noted as early as Darwin (1854); more recent observations of this phenomenon are provided in Santos et al (2005, p. 184), Buckeridge and Newman (2017, p. 229), and Buckeridge et al (2019b). In combination with shell growth, this sutural tissue has the ability to penetrate the skin of the whale sufficiently deeply to avoid dislodgment during periods of skin shedding.…”