Cornulitida

Cornulitida is an extinct order of marine invertebrates belonging to the phylum Annelida. These organisms are characterized by their distinctive conical, tubular shells, which are typically found as fossils. The shells are composed of organic material, often chitin, and can be straight or slightly curved. They are sessile, meaning they lived attached to a substrate, such as other shells, rocks, or seaweed.

Fossils of Cornulitida are known from the Cambrian period through the Permian period, with the majority of discoveries dating to the Silurian and Devonian periods. Their distribution appears to have been global. The exact lifestyle and ecological role of cornulitids are subjects of ongoing research. Some evidence suggests they may have been filter feeders, drawing water through an opening at the top of their shells. Others propose a predatory or scavenging lifestyle.

The taxonomic placement of Cornulitida has been debated for a long time. While they possess some features similar to other annelid groups, their unique shell structure has led some to consider them a separate phylum or class. However, recent molecular and morphological analyses increasingly support their inclusion within Annelida, though their precise relationship to other annelid groups remains uncertain. Their fossil record provides valuable insights into the diversity of early marine life and the evolution of sessile invertebrates.