Neosilesites maximus  Collignon, 1963

Measurements	D mm	H/D	T/D	O/D	H/T
David Jolly	30	0.25	0.27	0.52	0.88
Holotype Collignon	56	0.33	0.33	0.47	1.00

Age	Origin
A. besairiei Malagasy zone Lower Albian	Ambatolafia Boeny Region Madagascar

Description. A beautiful, flat ammonite with barely overlapping whorls that increase in height very slowly. The whorls are subcircular in cross-section and slightly flattened on the flanks. The umbilicus is very wide, with a very low wall. The fine, sharp, closely spaced ribs emerge from the umbilical suture. Initially radial, they become slightly convex and rursiradiate on the last whorl. Most of them bifurcate in the outer third of the flanks, and there are about a hundred ribs on the venter, which they cross perpendicularly to the siphonal line. There are five deep, narrow constrictions. This specimen is very similar to the type illustrated by Collignon, except that it is a bit more compressed.

Remarks. This species, currently known only from Madagascar, is easily distinguished from the other Neosilesites by its slightly depressed cross-section, wider umbilicus, very pronounced constrictions, and larger maximum size. In N. nepos (see its entry), the constrictions are less distinct and, on the test, are reduced to an intercostal space that is slightly wider and deeper than the others. Thanks to David Jolly for lending me his specimen!