Assertion: sponge's spicule | /r/AtLocation | the carboniferous period
Facets:
Source sentences:
text: That these morphological differences are accompanied by important embryological differences is supported by the facts that the oldest Demospongiae, from the Cambrian, are monaxonid (with only oxeas) and that the four-rayed spicule originates later, in the Carboniferous Period.