Stylophorans

Stylophorans were a group of extinct marine animals belonging to the phylum Stylophora, which lived during the Cambrian to Silurian periods. They are characterized by a unique body plan featuring a flattened, shield-like trunk, often referred to as a thalloid body, and a single, large appendage called a rhipidion. This rhipidion was typically fan-shaped and could be extended or retracted.

The exact taxonomic placement of stylophorans has been a subject of considerable debate among paleontologists. Historically, they were considered a distinct phylum, but more recent research, particularly based on fine anatomical details revealed by advanced imaging techniques, has suggested possible affinities with echinoderms. Some studies propose they represent an early, extinct lineage within the echinoderm stem group.

Stylophorans are known from fossilized remains found in marine sedimentary rocks worldwide. Their fossils often preserve the distinctive thalloid body and the prominent rhipidion. The function of the rhipidion is not fully understood, with hypotheses suggesting roles in feeding, locomotion, or sensory perception. Their lifestyle is believed to have been benthic, meaning they lived on the seafloor. The extinction of stylophorans occurred by the end of the Silurian period, leaving no known direct descendants. Their unusual morphology and uncertain evolutionary relationships continue to make them a fascinating group for paleontological study.