Ammonite species from the "CALLOVIAN" stage (4 entries found)

Kosmoceras inner whorls are involute and the outer whorls becomes moderately evolute. The fine ribbing on the inner whorls tends to disappear on the body chamber. The ventral tubercles, separated by a smooth depression, disappear on the body chamber which presents a smooth venter. The periumbilical... [view details for full description]

Kosmoceras inner whorls are involute and the outer whorls becomes moderately evolute. The fine ribbing on the inner whorls persists on the body chamber and become wavy when approaching the aperture, announcing the lappets. The ventral tubercles, separated by a smooth depression also persists on the... [view details for full description]

Peltoceras marysae is an evolute species. The microconch only shows the first two stages of the macroconch: the inner whorls show fine, dense simple ribs, which then become a bit stronger and sometimes fork. The ammonite is terminated by two lappets.

Peltoceras marysae is an evolute species and its ornamentation changes a lot along its growth. The inner whorls show fine, dense simple ribs, which then become a bit stronger and sometimes fork. Then appears a bituberculated stage with very strong tubercles. The ornamentation becomes softer on the b... [view details for full description]