Most recent additions (18 entries found)

Pavlovia is an evolute genus. The ribs are strong and well spaced. They are simple on the periumbilical region and on the flank. They generally bifurcate, and sometimes trifurcate, just before running over the venter.

The shell is made of a succession of straight parallel shafts. A given shaft can grow just enough to encompass the previous one or, like in the photographed specimen, it can get much longer than the previous one. The simple ribs are quite smooth on the early stage and get stronger when approaching t... [view details for full description]

Sphenodiscus is highly involute with an extremely compressed whorl section. The surface of the shell is smooth and the venter is very sharp. The suture pattern is complex with many lobes and saddles.

Prolyelliceras is highly evolute. It has strong, simple and well spaced ribs which run straight over the venter. On the venter, the ribs bear tubercles on ventral and lateral-ventral positions. The ornamentation is completed by a lateral row of tubercles.

Australiceras is an heteromorph genus with whorls very close to each others and simple ribbing. On the juvenile whorls, smooth ribs alternate with ribs bearing conical tubercles. The tubercles get smaller with the growth of the shell until they disappear on the body chamber.

Compressed whorl section with a round venter. Simple ribs on the periumbilical region, which fork at the start of the flank and then run straight across the venter. The shell is terminated with a simple peristome.

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]

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]

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]

Dactylioceras is highly evolute and has strong slightly inclined forward ribs. The ribs run over the venter and sometimes fork on its outer edge. Dactylioceras commune can be distinguished by its almost perfectly round whorl section. The fine ribbing in the inner whorls becomes sparser on the outer... [view details for full description]

The juvenile whorls form a tightly coiled helical spire covered with a fine ribbing. The body chamber then rolls away from the juvenile whorls before turning back towards them in a 'U' turn. The ribbing gets stronger on the body chamber. The aperture of the body chamber is right underneath the spire... [view details for full description]

Quite thick Involute genus with strong ribbing on the inner whorls and a smooth keel. The ribbing tends to disappear on the body chamber which represents about 90% of the last whorl.

Planispiral heteromorphic genus. Strong simple ribs distinctly spaced. Aegocrioceras capricornu can be distinguished by its tight coiling and the thickness of the whorl.

Planispiral heteromorphic genus. Strong simple ribs distinctly spaced. Aegocrioceras capricornu can be distinguished by its loose coiling and the very slow growth of the width of the whorl.

Planispiral heteromorphic genus. Strong simple ribs distinctly spaced. Aegocrioceras capricornu can be distinguished by its loose coiling and the very slow growth of the width of the whorl.

The early whorls, planispirally coiled and highly evolute, are followed by a more or less straight section. The senile stage is materialized by a section of shell that turns back on itself in a hook like shape. Ornamentation based on straight, radial and simple ribs, with sporadic constrictions. At... [view details for full description]

Small involute species. The last whorl shows two elbows (a round one followed by a pinched one) and narrow flanks. The thin ribs start above a flat periumbilical zone and they generally divide into two ribs at mid-flank. The umbilicus has a rectangular shape with rounded angles. The rostrum is prece... [view details for full description]