The Hyolithida are lophophorates, one of the two orders of hyolithid, the other being the Orthothecida. Most of our knowledge of the hyolithids comes from studies on the Hyolithida.^[2] 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.^[2]

Hyolithida Temporal range: Early Cambrian – Upper Permian[1] PreꞒ Ꞓ O S D C P T J K Pg N
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Superphylum:	Lophotrochozoa
Class:	†Hyolitha
Order:	†HyolithidaSussoiev, 1957 Families See text References edit ^ Malinky, J. M. (2009). "Permian Hyolithida from Australia: The Last of the Hyoliths?". Journal of Paleontology. 83 (1): 147–152. Bibcode:2009JPal...83..147M. doi:10.1666/08-094R.1. ^ a b Marek, Ladislav; Yochelson, Ellis L. (1976). "Aspects of the biology of Hyolitha (Mollusca)". Lethaia. 9 (1): 65–82. doi:10.1111/j.1502-3931.1976.tb00952.x. Further reading edit Malinky, John M. (1989). "New Early Paleozoic Hyolithida and Orthothecida (Hyolitha) from North America". Journal of Paleontology. 63 (3): 302–319. Bibcode:1989JPal...63..302M. doi:10.1017/S0022336000019454. JSTOR 1305500. S2CID 132877043. Marek, Ladislav (1976). "On the ontogeny in Hyolithida". Časopis pro mineralogii a geologii. 21 (3): 277–283.