CICTERRA   20351
CENTRO DE INVESTIGACIONES EN CIENCIAS DE LA TIERRA
Unidad Ejecutora - UE
artículos
Título:
Evolutionary history of Cambrian spiculate sponges: implication for the Cambrian evolutionary fauna.
Autor/es:
CARRERA, M.G., Y BOTTING, J.,
Revista:
PALAIOS
Editorial:
SEPM Society for sedimentary Geology
Referencias:
Lugar: Kansas; Año: 2008 vol. 23 p. 124 - 138
ISSN:
0883-1351
Resumen:
Broad-scale analyses of Cambrian spiculate sponges are scarce. The
apparent differences between Cambrian and Ordovician sponge faunas
were included in Sepkoskis concept of evolutionary faunas; in
these, sponges were regarded as minor contributors to the Paleozoic
and modern faunas and insignificant in the Cambrian Evolutionary
Fauna. More recent published occurrences of Cambrian and Ordovician
spiculate sponges and the inclusion of archaeocyaths in the
phylum Porifera, however, have altered our understanding of the
significance of sponges among Cambrian faunas. The majority of
Cambrian occurrences appear to be segregated into two major associations:
lower Cambrian sponges in China, and middle Cambrian
sponges in North America, primarily British Columbia and Utah.
The main associations of spiculate sponges are in siliciclastic deposits
from middle-to-deep muddy shelf and basin environments, whereas
orchoclad demosponges are associated with shallow carbonate environments.
Four main aspects of sponge biology are considered potential
factors dictating the distribution of sponges in the Cambrian:
their trophic requirements, hydrodynamic constraints, possible biogeochemical
constraints, and the sponge-sediment relationship. A series
of critical steps in sponge evolutionary history occurred during
the interval from the Proterozoic-Cambrian boundary to the middle
late Ordovician. The lowermiddle Cambrian faunas are considered
to be a Cambrian evolutionary sponge fauna, with archaeocyaths and
diverse monaxonid demosponges as distinctive components. There
was a transitional fauna in the upper CambrianLower Ordovician,
with orchoclad lithistids dominating shallow environments. Hexactinellids
began to colonize nearshore siliciclastic settings during this
time. The third interval, MiddleUpper Ordovician, corresponds to
the Paleozoic Evolutionary Fauna, which is the interval during which
lithistids diversified in several suborders and families and the stromatoporoid
and sphinctozoan calcified sponges experienced their first radiation.