Figure 4 - uploaded by John St James Stewart Buckeridge
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UBGD 30735 -Nautilus macromphalus with Hexelasma velutinum Hoek, 1913. (a) Top view of operculum of H. velutinum, showing base of H. velutinum as the second epibiont, attached over an agglutinated foraminifer (scale bar 10 mm); (a1) carinal view of H. velutinum (scale bar 1 mm); (a2) base of H. velutinum (scale bar 1 mm); (a1a) opercular view of H. velutinum, (scale bar 1 mm). (a1b) View of base (scale bar 1 mm); (a1c) view of the cirripede base overgrowing agglutinated foraminifers (the primary epibiont) (scale bar 1 mm).
Source publication
Fossil cephalopods are frequently encrustated by epibionts; however determining whether encrustation occurred prior to, or post‐mortem the host, and whether the final environment of deposition corresponds to the habitat of encrustation is complex. This paper describes cirripede epibionts, their calcareous bases and their attachment scars on six pos...
Contexts in source publication
Context 1
... velutinum Hoek, 1913: 246;Broch, 1931: 53;Hiro, 1933: 79;Utinomi, 1968: 30;Newman & Ross, 1971: 155;Newman & Ross, 1976: 46;Foster, 1981: 356-358;Jones 2000: 273, fig. 64, tabs 28-31; Liu & Ren 2007: 328, fig. 146;Chan et al. 2009: 183- 184, figs 155-157;Chan et al. 2010, p. 41-43, fig. 29- ...
Context 2
... UBGD 30750 -stn DW 08 (20°34′21″S, 166°53′53.88″E); depth 435 m; 1 specimen with opercula, attached inside the broken body chamber, near the umbilical area (Fig. 2a, a1); UBGD 30735 -stn CP 45 (22°47′20.4″S, 167°14′37.32″E); depth 430 m; 1 specimen (without opercula) attached on the ventral side and 1 hexelasmatine base (Fig. 4); Calcareous bases preserved on two other specimens may also belong to this species: UBGD 30741 -stn CP 45 (22°47′20.4″S, 167°14′37.32″E); depth 430 m; two ?hexelasmatine bases (Fig. 5b, b1); UBGD 30748 -stn DW 44/2 (22°47′17.88″S, 167°14′17.88″E); depth 440-450 m; one ?hexelasmatine base ( 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 ...
Context 3
... quickly lose soft tissue and opercula after their death. The compartments may detach from the base, which can be either calcareous or membranous. Two types of cirripede attachment were observed on these Nautilus shells. The first type is represented by calcareous, non-porous, very thin bases typical of hexelasmatines, such as H. velutinum (Fig. 4a1c). The second type is represented by etching scars typical of cirripedes that lack a mineralized base, such as with the Verrucomorpha and most of the Chthamalidae. This type of attachment can corrode the substrate encrusted by the barnacle (Buckeridge & Newman 2017), depending on the degree of substrate preservation and its strength. ...
Citations
The ichnogenus Thatchtelithichnus Zonneveld, Bartels, Gunnell & McHugh was created for ring-shaped, roughly circular grooves affecting the outer surface of plastral bones of Eocene geoemydid turtles. Such traces were assumed to be attachment scars of aquatic ectoparasites (possibly ticks, leeches or liver flukes). Despite its well-distinctive aspect, Thatchtelithichnus has only been reported subsequently by few works and mostly from the plastron-bottom of freshwater turtles. Here we provide the first record of Thatchtelithichnus from a fossil mammal bone, namely, a partial grey whale mandible from the Belgian Pliocene. Thatchtelithichnus traces from this cetacean fossil commonly penetrate into the outermost portion of the cancellous bone, achieving a maximum depth of about 2 mm. The external margin of these grooves is sharply defined and commonly follows an elliptical, somewhat festooned path. A scrutiny of recent literature in palaeontological and forensic taphonomy as well as new first-hand observations reveal that Thatchtelithichnus-like structures can be produced by the attachment of barnacles on the surface of mammal bones that suffered long-lasting exposure on the seafloor. When encrusting bare bones in marine settings, barnacles can thus produce a variety of traces, including Anellusichnus Santos, Mayoral & Muñiz, Thatchtelithichnus and, possibly, Karethraichnus lakkos Zonneveld, Bartels, Gunnell & McHugh. The modes of trace formation are still largely to be understood, but observations on how barnacles damage paint coatings during growth might help us in envisaging how this kind of process works.
Assessment of unique and potentially significant fossils may be considerably compromised by surrounding matrix. This paper assesses a fossil barnacle group from the mid to late Eocene of Seymour Island, off the Antarctic Peninsula, that potentially has very significant phylogenetic importance. It discusses why the specimen could be significant, and describes and applies as a proof of concept an advanced imaging technique, using X-ray Computed Tomography (CT), that was effectively employed to confirm systematic taxonomy with virtual 3-D sections through the specimen. In this case, the Antarctic barnacle's complex internal plate morphologies were resolved by advanced 3-D imaging, such that a taxonomic attribution could be made to either the Archaeobalanidae or Austrobalanidae, excluding the initial assessment of Coronulidae, which would have otherwise been allusive.
