allochoans

Allochoans are a diverse group of extinct marine invertebrates that lived during the Cambrian period, approximately 541 to 485.4 million years ago. They are characterized by their segmented bodies and, in many species, a pair of appendages extending from each segment. These appendages likely served various functions, including locomotion and feeding. Allochoans exhibit a wide range of morphologies, with some species possessing simple, unadorned bodies while others developed elaborate spines, plates, or other protective structures. Their exact phylogenetic placement remains a subject of ongoing research, but they are generally considered to be stem-arthropods or closely related to the arthropod lineage.

Fossil evidence for allochoans is primarily found in Lagerstätten deposits, such as the Burgess Shale in Canada and the Chengjiang biota in China, which preserve soft-bodied organisms in exceptional detail. These fossils reveal a variety of ecological roles, with some allochoans appearing to be deposit feeders, consuming organic matter from the seafloor, while others may have been predators or scavengers. The study of allochoans provides valuable insights into the early diversification of animal life during the Cambrian explosion, a period of rapid evolutionary innovation. Their unique body plans and evolutionary relationships contribute to our understanding of the origins of major animal phyla.