- bactritids.
Orthocones existed from the Late
Cambrian to the Late Tri****ic, but they were most
common in the
early Paleozoic.
Revivals of the
orthocone design...
- shapes,
including coiled morphologies and
giant straight-s****ed
forms (
orthocones). No
orthoconic and only a
handful of
coiled species, the nautiluses,...
- over 470
million years ago. The Bactritida, a Devonian–Tri****ic
group of
orthocones, are
widely held to be
paraphyletic without the
coleoids and ammonoids...
-
Orthoceras referred to all
nautiloids with a straight-s****,
called an "
orthocone" (Fenton &
Fenton 1958:40). But
later research on
their internal structures...
- Baculites,
which has a
nearly straight s****
convergent with the
older orthocone nautiloids.
Still other species' s**** are
coiled helically (in two dimensions)...
- Antarctica.
These are
straight s**** that
closely resemble those of the
orthocones,
although they are
thought to have been
internal akin to
those of certain...
-
dominant marine arthropods (e.g. eurypterids) and
cephalopod molluscs (e.g.
orthocones),
producing some of the
first and most
infamous vertebrate apex predators...
- gap of
nearly 50
million years occurs between Bactroceras and the next
orthocones with a
spherical apex and
ventral siphuncle. Bactritids,
especially the...
-
Phragmoteuthids Early forms the
earliest cephalopod group Ellesmerocerida Orthocones: Endocerida, Orthocerida,
Actinocerida Brevicones: Ascocerida, Oncocerida...
-
diameter and
thickness of a
calciosiphonate connecting ring and
shape of
orthocone siphuncles.
Orthocerida may thus be a
polyphyletic group,
having arisen...
