Opsoonina

Opsoonina is a genus of small, extinct marine invertebrates belonging to the phylum Mollusca. These fossils are primarily found in the Cambrian period, dating back approximately 520 to 500 million years ago. Opsoonina fossils are rare and have been discovered in various Lagerstätten, which are fossil sites known for exceptional preservation. The exact taxonomic placement of Opsoonina within Mollusca has been a subject of debate among paleontologists due to its unusual morphology and limited fossil record.

The body plan of Opsoonina is characterized by a cap-like shell, often described as conical or limpet-like, and a soft body that is rarely preserved. The shell typically exhibits a circular or oval outline and can vary in size, though most specimens are small, measuring only a few millimeters to a couple of centimeters in length. Unlike many other shelled mollusks, Opsoonina appears to have lacked a distinct foot for locomotion or a well-developed radula for feeding. Some researchers suggest a sessile lifestyle, attached to the substrate, or a very slow-moving existence.

The ecological role of Opsoonina in Cambrian seas is not well understood. Its small size and simple structure suggest it may have occupied a niche as a detritivore or a grazer on microbial mats. The rarity of its fossils indicates it may not have been abundant, or its delicate structure made it less likely to fossilize. The discovery of Opsoonina has contributed to our understanding of early mollusk evolution and the diversity of life during the Cambrian explosion.