-
known taxa were
discovered in
sediments dating back to the Cambrian.
Helicoplacoid skeletons consist of
small platelets arranged like
those of asteroids...
-
other echinoderms) and
Helicocystis (seen as
bridging the
triradial helicoplacoids and the
pentaradial crown group). They cite
research indicating that...
- J. (2000). "Evolutionary
paleoecology of the
earliest echinoderms:
Helicoplacoids and the
Cambrian substrate revolution". Geology. 28 (9): 839–842. Bibcode:2000Geo...
-
December 2021. Durham, J. W. (1993). "Observations on the
Early Cambrian Helicoplacoid Echinoderms".
Journal of Paleontology. 67 (4): 590–604. ISSN 0022-3360...
-
Zamora et al., 2022 Not all of the
echinoderms are
edrioasteroids with some
being Edrioasteroids, Blastozoa, Crinoids,
Helicocystoid and
Helicoplacoid)....
-
including brachiopods, hyolithids, trilobites, archeocyathids, and
helicoplacoids,
which are
often articulated. Non-mineralized
components of
these fossils...
- J. (2000). "Evolutionary
paleoecology of the
earliest echinoderms:
Helicoplacoids and the
Cambrian substrate revolution". Geology. 28 (9): 839–842. Bibcode:2000Geo...
- survive.
Early sessile echinoderms were
mostly "mat stickers". The
helicoplacoids failed to
adapt to the new
conditions and died out; the edrioasteroids...
