Crioceratites (Balearites) balearis: This

Hoedemaeker, Philip, 2013, Genus Pseudothurmannia Spath, 1923 and related subgenera Crioceratites (Balearites) Sarkar, 1954 and C. (Binelliceras) Sarkar, 1977 (Lower Cretaceous Ammonoidea), Revue de Paléobiologie 32 (1), pp. 1-209 : 15

Crioceratites (Balearites) balearis: This species is

regarded as the ancestral aperamorphic species of this

mosaïc heterochronocline. Two ornamental ontogenetic

stages could be defined.

1. A first fine uniformly ribbed stage with lateral tubercles and uniform ventrolateral tubercles on every rib up to a diameter of 7 mm.

2. A long second stage characterized by fine dense uniform ribbing without lateral tubercles up to a diameter of 40 mm, but with uniform ventrolateral tubercles on every rib up to a diameter of 30-40 mm.

3. The adult growth stage with distantly spaced constrictions lined by thick ribs appearing amidst the fine dense uniform ribbing up to the aperture. The constrictions with thick ribs are here interpreted as an ‘adult variation,’ because this ornamentation remains restricted to the adult in the descendants, and does not exhibit heterochrony. In many other species of Crioceratites this type of ornamentation is present in the adult stage.

As for the ontogeny of the shape of the conch; the whorl

height equals the umbilical width at a diameter of c.

50 mm. At smaller diameters the umbilicus is narrower

than the whorl height, at larger diameters wider. The

largest specimen has a diameter of 101 mm.