Attachment of the Body to the Shell in Ammonoids

Non-invasive imaging methods applied to neo- and paleo-ontological cephalopod research

“…Applied to the extinct ammonoids, exact morphological data become available for the description of features of the ammonitella, the ammonite hatchling shell, or muscle attachment sites of the soft body to the shell wall (Doguzhaeva and Mutvei, 1996;Shigeta, 1993). Morphology of the ammonitella was used to distinguish between major ammonoid groups based on protoconch size and shape, fixator length and position, position of the siphuncle, length/angle of the ammonitella and the nepionic constriction.…”

“…External shell features like crenulation as shown for Spirula (Fig. 9), which are also present on juvenile gastropod shells (Bandel, 1982), can be traced and used for the discussion if ammonoids had an internal or external shell (Doguzhaeva and Mutvei, 1996). However, the high scan resolution makes the nano-CT a useful tool for microfossils like Foraminifera or Ostracoda with complex internal shell structures (Briguglio et al, 2011;Görög et al, 2012;Hohenegger and Briguglio, 2012).…”

Scaphites of the “Nodosus Group” from the Upper Cretaceous (Campanian) of the Western Interior of North America

“…Scaphites lack large retractor muscles, which would have provided the propulsive power necessary for strong swimming. Such muscles may have existed in other ammonites based on the presence of scars on the internal surfaces of the shells (Doguzhaeva and Mutvei, 1996). In scaphites, there are only two types of muscle scars, the paired dorsal muscle scars and the unpaired midventral muscle scar ( fig.…”

The Body Chamber Length Variations and Muscle and Mantle Attachments in Ammonoids

“…In the Early Carboniferous goniatite (?Rhadinites or ?Anthracoceras), Landman et al (2010) documented "a spiral red band that extends from midway in the body chamber to the apical end of the jaw (Figs 3A,B,F). The position of this feature matches that of the cephalic retractor muscle illustrated in the reconstruction of Cretaceous ammonoids by Doguzhaeva and Mutvei (1996, Fig. 7)".…”

“…14.4a,14.11). This distance is shorter or equal to the length of the circumsiphonal invagination of the posterior portion of the body where the formation of the new segment of the siphonal tube began Doguzhaeva and Mutvei 1996). Ventral marks produced earlier in the ontogeny are often visible between the septa in the phragmocone; every chamber has a solo mark (Fig.…”