- umbilicus,
arched to
acute venter, and
typically at some
growth stage,
falcoid ribs that
spring in
pairs from
umbilical tubercles,
usually disappearing...
- but also
members of
genera Protogrammoceras and Harpoceras. Ribs are
falcoid and in
small sizes of s**** are bifurcating,
later they are single. On...
- in section.
Inner whorls are smooth,
outer mature whorl develops co****
falcoid ribs that
arise near the
umbilical rim but to not p**** over the rounded...
- convex,
converge toward a
narrowly ached venter.
Inner whorls have
sharp falcoid ribs,
outer are smooth.
Umbilical tubercles are lacking.
Similar related...
- s**** of
which are
typically oxycones with a
tricarinate venter and
falcoid ribbing,
commonly divided by a
median lateral groove or fillet. The median...
- is elliptical, with
rounded umbilical edge and
sloping umbilical wall.
Falcoid, or
sinuous ribs are weak, or
moderate on
inner whorls,
while on outer...
- of
oppeliids from the
Middle and
Upper Jur****ic
typically with
strong falcoid or
falcate ribbing that
covers whorl sides completely.
Venters are usually...
- and compressed.
Whorl sides are flat and
there is
strong keel. Ribs are
falcoid or
falcate and thus biconcave,
strong and projected. Sometimes, ribs can...
- whorls,
venter has been sharp, but then it
became rounded.
Faint ribs had
falcoid shape, but sometimes, ribs
could absent. S****
could have been
large in...
- by 3 to 5 crawlings.
Umbilicus took
about 30—40% of diameter. Ribs were
falcoid and weak.
Suture has been the same as in the case of
young Oxynoticeras...
