Ancient Comb Jelly Bones?

Comb jellies, soft-bodied marine creatures that swim by beating rows of cilia, may once have had a hard skeleton.

Jul 13, 2015
Jef Akst

Ctenophore Mnemiopsis leidyiWIKIMEDIA, BRUNO C. VELLUTINIModern ctenophores, or comb jellies, are entirely soft-bodied, consisting simply of a mass of jelly surrounded by a layer of cells. But comb jellies that lived more than 450 million years ago may have had some hard skeletal parts, according to a study published last week (July 10) in Science Advances.

Examining six ctenophore fossils from the Cambrian Period, researchers identified eight rigid plates at one end, surrounding a sensory organ that responds to the Earth’s gravitational pull, as well as eight spoke-like projections. “One of the species even had robust spines,” coauthor Quiang Ou, a paleobiologist at the China University of Geosciences, told The Verge.

The function of the hard plates and spokes remains unclear, though the authors speculated that the structures may have served as some sort of armor or a buffer against harsh environmental conditions. The ancient comb jellies also lacked the tentacles that are common in their modern counterparts. “This clade reveals a cryptic history and sheds new light on the early evolution of this basal animal phylum,” the authors wrote in their paper.