History. Fallot (1920) described a small ammonite from the Aptian-Albian marls of Majorca (Balearic Islands). It is smooth, with a narrow ventral groove between two fine keels. He assigned it to genus Waagenia, although this genus is jurassic. With Termier (1923), he also found this ammonite in Ibiza and created for it the genus Trochleiceras and the type species T. balearense. Collignon (1950) reported a similar ammonite in the Lower Albian of Madagascar but, unaware of the work of Fallot and Termier, proposed a new genus Magneticeras and the species M. magneti. In 1951, he recognized that his specimen was a Trochleiceras balearense.
Species. Following the creation of T. balearense by Fallot and Termier, Collignon added two new Aptian species in fascicle IX (Aptian) of his Atlas of Characteristic Fossils of Madagascar (1962): T. ambanjabense, with thin riblets on the external region and a very attenuated ventral groove, and T. termieri, with broader riblets and a distinct groove, with rounded rather than keeled edges. Etayo-Serna (1979) created two more from the Lower Albian of Colombia: T. juliverti with ribs appearing suddenly on the body chamber, and T. hoffstetteri, with a very faint ventral groove hidden under the test.
Age and distribution. A very rare genus from Upper Aptian and Lower Albian. Reported in the Balearic Islands, Madagascar, and Colombia. The vertical extension is uncertain: the T. balearense specimens of Collignon would come from the Douvilleiceras inaequinodum zone of the Malagasy Lower Albian.