Trochleiceras balearense  Fallot & Termier, 1923

Measurements	D mm	H/D	HI/D	T/D	O/D	H/T
Collignon 1950	11	0.33	--	0.33	0.33	1.00
CP-75	25	0.30	--	0.28	0.46	1.07

Age	Origin
D. inaequinodum Malagasy zone Lower Albian	Komihevitsy Boeny Region Madagascar

Description. A small, fully septate ammonite, very evolute, with a nearly complete test and a slightly compressed oval whorl section. The low umbilical wall slopes at 45° and is joined to the flank by an almost angular edge. The test is smooth at first, then adorned with very faint, thin, closely spaced, slightly flexuous riblets, some bifurcated. These are interrupted on venter by a narrow groove bordered by two very low, thin carinae. The groove and carinae are attenuated on the test. Faint spiral lirae are also visible at the beginning of last whorl. The suture line is surprisingly simple for a Cretaceous ammonite and resembles that of a nautilus. As shown in Collignon's drawing on the right (1950), it comprises only two broad, rounded saddles and three narrow lobes, the last one forming an acute angle on the umbilical wall.

Remarks. A strange and extremely rare species looking like a Planorbis. We have never seen it again among the Malagasy ammonites at fossil exhibitions. Our specimen was a gift of an exhibitor for the purchase of other ammonites. He thought it was a gastropod! It conforms to the centimeter-sized pyritic specimens found by Fallot and Termier in the Balearic Islands. Otherwise, the species is known only from Komihevitra (also spelled Komehavitra or Komihevitsy) in Madagascar, where Collignon (1950) named it Magneticeras magneti, before recognizing it in 1951 as the ammonite of Fallot and Termier. We should point out an error in the suture line given by Fallot & Termier (1923): the ventral and umbilical sides are reversed!