Where the outer whorl of an ammonite shell largely covers the preceding whorls, the specimen is said to be involute (e.g., Anahoplites). Where it does not cover those preceding, the specimen …

Shell shapes of ammonoids. Most ammonoids had tightly-coiled planispiral (coiled in a single plane) shells, though heteromorph ammonoids deviated from this style of coiling (see …

The Grypoceratidae are characterized by evolute to involute shells that may have some modification to the venter (the outer rim) varying from flattened to subangular, or bearing a …

Mar 10, 2019 · Shells with a wide umbilicus are termed Evolute and shells with a narrow umbilicus are termed Involute. The umbilical Seam is where the shell wall attaches to the preceding …

Finally, some species have shells that are involute: the youngest whorls completely (or almost completely) cover all of the earlier whorls (as observed in the shell of Nautilus). Planispiral …

Jun 13, 2013 · If the outer whorl of an ammonite shell largely covers the preceding whorls, the specimen is said to be ‘involute’ (for example, Anahoplites). If it does not, the specimen is said …

Finally, some species have shells that are involute: the youngest whorls completely (or almost completely) cover all of the earlier whorls (as observed in the shell of Nautilus).

Placenticeras has a very involute shell with slightly convex sides and a very narrow venter. Side are smooth or with faint sinuous ribs. Early whorls have umbilical tubercles that in later whorls …

The modern chambered nautilus belongs to the Nautilida group, which characteristically have "closely coiled, widely umbilicate to convolute and involute" (Teichert and Moore, 1964a, p. …

May 8, 2018 · involute Having edges that roll under or inwards. Applied to those coiled cephalopods (Cephalopoda) where the final whorl of the shell envelops earlier ones. The …