In the Anaspidea there is a tendency for parapodia to enlarge and, together with the mantle, to enclose the fragile shell (with increasingly reduced and involute spire).
Both the evolute and involute of a cycloid is an identical cycloid.
Distinguishing characteristics are fully double, involute florets that are narrow and pointed.
Most contemporary goniatitids had an involute shell with compressed whorls.
They evolved in the Devonian, comprising evolute to involute planispirally coiled conchs quite similar to that of the contemporaneous nautiloids.
They were found to comprise at least three different traits: involute leaves, early flowering, and Apetala flowers.
This mutant displayed involute leaves and early flowering, although less than clf and icu2 mutants (20 days after sowing).
Although no equatorial sections were recovered, the present specimens exhibit a likely involute initial stage followed by biserial, uncoiled later stage in which chambers are more flattened.
The evolute and the involute of an equiangular spiral is an identical equiangular spiral.
The fundamental structure of the proloculus is the innermost part of the spirally arranged shell; it resembles the involute type of planispirally arranged foraminifera tests.