The mystery of hyoliths seems to be solved

Hyolitha was a group of shelled, cone-shaped animals that lived during the Paleozoic, some 536 to 252 million years ago, since the early phases of the Cambrian, until the very end of the Permian.

Hyoliths have usually been associated with mollusks but no conclusive evidence was presented to support their close connections, even though they’ve been known to science for over 175 years.

Due to their unique appearance and problematic origin, scientists have keenly awaited a study that will solve the mysteries surrounding these fascinating creatures. And the time has apparently come.

A team of researchers led by Joseph Moysiuk from the University of Toronto published a paper based on a detailed study of more than 1 500 specimens belonging to a mid-Cambrian hyolith Haplophrentis from the Burgess Shale and Spence Shale Lagerstätten. The material includes exceptionally preserved soft tissues that enable to reconstruct anatomical features that have as yet been undiscovered in hyoliths.

The new study shows that Haplophrentis had a specific organ surrounding a central mouth. It was gullwing-shaped and bore tentacles. The researchers interpreted it as a lophophore. The lophophore is a feeding organ that is typical for a clade named Lophophorata. This clade contains the brachiopods, bryozoans, and phoronids.

If the authors interpreted the anatomy correctly, hyoliths were most likely lophophorates, most closely related to the brachiopods.

Featured image © Danielle Dufault, Royal Ontario Museum.

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