The last group we’re looking at this month are the brachiozoans, a lineage that includes modern horseshoe worms and brachiopods along with the extinct hyoliths.
Horseshoe worms, or phoronids, are represented by about 15 living species and are usually considered to be their own phylum, but some analyses classify them as a sub-group of brachiopods instead. Like other lophophorates they have a “crown” of filter-feeding tentacles around their mouths, and similarly to some bryozoans they build protective chitinous tubes around their bodies.
There are no definite body fossils of phoronids at all, although there are a few possible trace fossils of their tubes and the enigmatic fossil hederelloids might be related to them.
But some Cambrian fossils might give us a hint about their evolutionary history.Continue reading “Cambrian Explosion Month #29: Phylum Phoronida & Early Brachiozoans”