Fossils of comb-jelly ancestors show signs of rigid, skeletal spokes and plates, unlike their living, soft-bodied descendants.

Credit: Qiang Ou et al.

All 150 known species of modern comb jellies, known as ctenophores, lack skeletons and use eight rows (or combs) of hair-like structures to swim. Qiang Ou of the China University of Geosciences in Beijing and his colleagues identified three new species of comb jelly from roughly 520-million-year-old Cambrian deposits in south China, and reanalysed these and other comb-jelly fossils. The fossils had combs and a similar basic body plan to living ctenophores, but also had radiating spokes and rigid plates (reconstructed models pictured), which probably provided support or served as armour.

The intense interactions of ancient comb jellies with their predators and prey may have led to this burst of diverse body types in the Cambrian period, the authors suggest.

Sci. Adv. 1, e1500092 (2015)