The genus contains a single species, Synophalos xynos, found in the Cambrian Stage 3-aged Chengjiang biota of Yunnan, China.

The body has approximately 6 (possibly 7) abdominal segments, which terminate in a forked unsegmented tail.

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 5.7 to 8.7 millimetres (0.22 to 0.34 in) 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.