Description. Type species Mortoniceras (Cantabrigites) cantabrigense Spath, 1933. Spath created Cantabrigites as a subgenus of Mortoniceras, but Wright (1996) prefers a separate genus within the Mortoniceratinae. According to these authors, these are small ammonites (50–60 mm maximum), with a slightly compressed to slightly depressed rectangular section, a ventral keel, and ribs bifurcated at first but tending to become simple, mostly without tubercles. They are distinguished from other Mortoniceratinae by a simplified suture, with a square S with a small median incision, and L1 shorter than L, with a rectangular trunk ending in three teeth and bearing another tooth on the ventral side. According to Wright, the genus is perhaps more closely related to Hysteroceras (Brancoceratinae). Lower Cretaceous, Upper Albian. England, Belgium, Hungary, France, Switzerland.
Some species. C. cantabrigense Spath, 1933, is evolute (O/D = 0.35-0.45), with a moderately compressed section (H/T = 0.84–0.90), with low, simple or bifid, straight or slightly flexuous ribs bearing a small umbilical bulla and projecting forward on venter. C. minor Spath, 1933, is more evolute (O/D = 0.42–47), with a square section, barely compressed to slightly depressed, and higher ribs bearing prominent umbilical and ventrolateral bullae. More or less visible lateral tubercles may be present. The photos on the right (Jattiot et al., 2021), show the holotype from Cambridge Greensand. C. spinosum (Pervinquière, 1907) is evolute too (O/D = 0.41-0.48), but with whorls increasing slowly in height and strongly bituberculate ribs.
Remarks. Species of Cantabrigites are illustrated in Spath (1933), Kennedy (2004), Kennedy et al. (2008), and Jattiot et al. (2021). It is clear that despite the diagnosis of genus by Spath and then Wright, distinctly tuberculate forms exist. The trituberculate morphs even resemble young Mortoniceras (Mortoniceras) fallax, but the simplified suture allows for a clear distinction. Jattiot et al. (2021) illustrate numerous specimens from the fallax zone of Salazac (Gard) and emphasize their variability. Scholz (1979) even proposed to assign all existing species to Cantabrigites cantabrigense.
| Cantabrigites (1) | minor |