- Devonian. The
heterostracans differed from
other Paleozoic agnathan taxa both in the
arrangement and
histology of
their scales. Most
heterostracans had two...
-
ventral plate forming the
edges of the
mouth suggest that
pteraspidiform heterostracans were filter-feeders that
selectively filtered specific sized plankton...
- groups, the more
primitive heterostracans and the cephalaspids. The
cephalaspids were more
advanced than the
heterostracans in that they had
lateral stabilizers...
- or begin. Some
experts regard it as
being descended from the
basal heterostracans of the Silurian. Haaramo,
Mikko (2007). "†Pteraspidomorphi". Mikko's...
- by a
small fin web. This tail
structure clearly differs from that of
heterostracans,
which are
currently grouped with
arandaspids and
astraspids in the...
- skeleton, they were
first regarded as
heterostracans. Now, we know that they are
widely different from
heterostracans, in
particular in
retaining about ten...
-
Protaspis is an
extinct genus of
pteraspidid heterostracan agnathan which lived during the
Early Devonian of the
United States, with
fossils found in...
-
Poraspis is an
extinct genus of
heterostracan.
Fossils are
found in Late
Silurian and
Early Devonian marine strata of Norway,
Canada and the
United States...
-
Drepanaspis from the Hunsrück lagerstätte. The
Psammosteids were the only
heterostracans that
survived the
Upper Frasnian extinction event during the Late Devonian...
- to that of
heterostracans that to that of astraspids. This is the only
argument to
place them, as the
closest relatives to
heterostracans,
among the Ordovician...
