[citation needed] Species also occur in the Chengjiang biota,[7] Siberia,[8] and in Upper Ordovician strata of Morocco.

[9] It takes the form of a round, medusoid disk (which originally led to suggestions of a jellyfish affinity)[7] with a C-shaped gut trace.

[10] A specimen from the Lower Ordovician Madaoyu Formation in Hunan, South China, can be interpreted as the incomplete body of Eldonia or the similar animal.

[12] Alternative affinities to be suggested, which did not stand the test of time, included the siphonophores[13][14][15] and a coelenterate medusa.

[17] The organism is frequently found in association with the lobopod Microdictyon, which is presumed to have fed on Eldonia.