Hydroceras Dawson & Hinde, 1889 Hydnoceras is an extinct genus of sponges that existed from the Upper Devonian through the end of the Pennsylvanian.

Hydnoceras fossils' entire surfaces are typically covered by coarse and fine rectangular patterns of narrow, threadlike ridges.

[1] Fossils of Hydnoceras sponges have been found in rock formations in the United States, mainly in New York, Pennsylvania, and West Virginia.

[1][2] Hydnoceras species were suspension feeders, and likely remained attached to a single substrate for their entire lives, as typical for a sponge.

[3] Unlike modern glass sponges, which typically live in deep marine environments, these sponges lived throughout the marine water column.