Crioceratites (Binelliceras) angulicostatus: 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 : 28

Crioceratites (Binelliceras) angulicostatus: This species

has four ornamental ontogenetic stages.

1. The first stage has two intermediate ribs to one thick rib with a lateral tubercle. Later, every second thick rib obtains an umbilical bulla; every other main rib becomes weak, loses its umbilical bulla, but still keeps its lateral tubercle. The two intermediate ribs unite into one ventrolateral tubercle (fibulation). This stage corresponds to stage one of C. (Bi.) angulicostatiformis , but it ends at a smaller diameter of 15 mm due to acceleration of the ontogeny in relation to C. (Bi.) angulicostatiformis .

2. The second stage consists of four intermediate ribs between every main rib. Fibulation is still present. From a diameter of 20 mm the lateral tubercles disappear. Between every two main ribs are 3-4 intermediate ribs. This stage is equivalent to stage two of C. (Bi.) angulicostatiformis , but ends earlier in the ontogeny, viz. at a diameter of 33 mm. This implies an acceleration of the ontogeny in relation to C. (Bi.) angulicostatiformis .

3. From a diameter of 33 mm, the number of intermediate ribs between every two main ribs is two. This third stage is equivalent to stage three of C. (Bi.) angulicostatiformis and ends at a diameter of 40 mm; it has accelerated in relation to the corresponding stage in C. (Bi.) angulicostatiformis .

4. From a diameter of 40 mm there are 1-2 intermediate ribs to one main rib. Forking occurs. Only just before the aperture, this number suddenly augments to three or four.