The Hyolithida are
lophophorate
The Lophophorata are a Lophotrochozoan clade consisting of the Brachiozoa and the Bryozoa. They have a lophophore. Molecular phylogenetic analyses suggest that lophophorates are protostomes
Protostomia () is the clade of animals once though ...
s, one of the two orders of
hyolithid
Hyoliths are animals with small conical shells, known as fossils from the Palaeozoic era. They are at least considered as lophotrochozoan, and possibly being lophophorates, a group which includes the brachiopods, while others consider them as b ...
, the other being the
Orthothecida
The orthothecids are one of the two hyolith orders.
Marek diagnoses the order thus: Conchs with a flat or concave ventral surface — opercula with large, flat cardinal processes but without clavicles – tightly sigmoidal, sediment-filled
intes ...
. Most of our knowledge of the hyolithids comes from studies on the Hyolithida.
Both orders had an
operculum that was not hinged to the conch. However, the Hyolithida are distinct from the Orthothecida in having additional paired, curved, whiskerlike appendages. The Hyolithida were probably bottom feeders living in shallow water, and had tentacules.
References
Further reading
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Paleozoic invertebrates
Prehistoric animal orders
Hyolitha
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