- An
orthocone is the long, cone-shaped s****
belonging to
several species of
ancient nautiloid cephalopod—the
prehistoric ancestors of today's
marine cephalopod...
-
Orthoceras referred to all
nautiloids with a straight-s****,
called an "
orthocone" (Fenton &
Fenton 1958:40). But
later research on
their internal structures...
-
diameter and
thickness of a
calciosiphonate connecting ring and
shape of
orthocone siphuncles.
Orthocerida may thus be a
polyphyletic group,
having arisen...
- species, A. nordenskjoeldi. It is
either considered the last of the "
orthocone"-type cephalopods, the only
member of its
subclass Paracoleoidea & a descendant...
- 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...
-
during the
entire Ordovician period. Like
other endocerids, it was an
orthocone,
meaning that its s**** was
fairly straight and pointed. It was particularly...
- Baculites,
which has a
nearly straight s****
convergent with the
older orthocone nautiloids.
Still other species' s**** are
coiled helically (in two dimensions)...
- end, and the
opening itself is
usually called the
apical aperture. In
orthocone cephalopods, the
pointed end of the s**** is
called the apex, and s****...
- shapes,
including coiled morphologies and
giant straight-s****ed
forms (
orthocones). No
orthoconic and only a
handful of
coiled species, the nautiluses,...
-
deposits are
referred to semi-formally as "belemnite battlefields" (cf. "
orthocone orgies"). It
remains unclear whether these deposits represent post-mating...
