''Synophalos'' is an extinct genus of bivalved

arthropod Arthropods ( ) are invertebrates in the phylum Arthropoda. They possess an arthropod exoskeleton, exoskeleton with a cuticle made of chitin, often Mineralization (biology), mineralised with calcium carbonate, a body with differentiated (Metam ...

. The genus contains a single species, ''Synophalos xynos'', found in the

Cambrian Stage 3 Cambrian Stage 3 is the still unnamed third stage of the Cambrian. It succeeds Cambrian Stage 2 and precedes Cambrian Stage 4, although neither its base nor top have been formally defined. The plan is for its lower boundary to correspond approxima ...

-aged

Chengjiang biota The Maotianshan Shales () are a series of Early Cambrian sedimentary deposits in the Chiungchussu Formation or Heilinpu Formation, famous for their '' Konservat Lagerstätten'', deposits known for the exceptional preservation of fossilized orga ...

Yunnan Yunnan; is an inland Provinces of China, province in Southwestern China. The province spans approximately and has a population of 47.2 million (as of 2020). The capital of the province is Kunming. The province borders the Chinese provinces ...

, China. The body has approximately 6 (possibly 7) abdominal segments, which terminate in a forked unsegmented tail. The holotype specimen is around long. It is noted for having been found in unusual chain-like associations where up to 20 individuals were connected via the insertion of the tail into the head carapace of the preceding individual. While the linking behaviour of ''Synophalos'' is unique among known arthropods living or extinct, other animals do form lines for a variety of purposes, such as the migratory queues of the Caribbean spiny lobster (''Palinurus argus''). Individuals found in chains are around in length, smaller than the max size. The purpose of the chaining behaviour in ''Synophalos'' is uncertain, but could have served for reproduction, migration, or protection. The authors of the describing paper considered migration the most likely candidate. The describers tentatively referred ''Synophalos'' to

Waptiidae Hymenocarina is an order of extinct marine arthropods known from the Cambrian. They possess bivalved carapaces, typically with exposed posteriors. Members of the group are morphologically diverse and had a variety of ecologies, including as filte ...

Etymology

''Synophalos'' comes from ancient Greek Synodia meaning "company of travellers" and Hyphalos meaning "under the sea" or "submerged."

References

{{Taxonbar, from=Q115801595 Cambrian arthropods Fossil taxa described in 2009 Hymenocarina