Euhystrichoceras and Algericeras, the last mortoniceratine ammonites
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Euhystrichoceras Spath, 1923, Algericeras Spath, 1925, of which Prionocydoides Spath, 1925 is regarded as a synonym and Sakondryella Collignon, 1964 a subgenus, are the last, Cenomanian, members of the typically Upper Albian subfamily Mortoniceratinae. They are believed to have evolved from the diminutive Cantabrigites Spath, 1932 and are diminutive taxa of paedomorphic origin. The type and other poorly understood species are revised and a new species, Euhystrichoceras baylissi, the largest and youngest known, is described from the Upper Cenomanian of Devon.
Palaeontology - Volume 24 Part 2 Pages 417-435Palaeontology - Volume 24 Part 2 Pages 417-435
Citations
KENNEDY, W. J., WRIGHT, C. W. 1981. Euhystrichoceras and Algericeras, the last mortoniceratine ammonites. Palaeontology, 24, 2, 417–435.