They are found in shallow marine carbonates across widely separated areas, such as Croatia, Tunisia, Oman, Afghanistan, Iran, Thailand, Malaysia, Philippines, Japan, Alaska and South China.

[3][1] In 1968, Shikamaia akasakaensis from Japan, named after palaeontologist Shikama Tokio, is described, but due to its unique shape and fragmentary fossil preservation, it was originally classified as Animalia incertae sedis.

[1] It is theorized that one genus in this family, Shikamaia, formed symbiotic relationships with photosynthetic or chemosynthetic microbes for sustenance, like modern Corculum cardissa.

It suggests that Shikamaia possibly pumped up seawater that contain hydrogen sulfide from deeper sediment layers to nourish chemosynthetic bacteria within the animal's soft tissue, like modern lucinid bivalve.

[7] However, later study questioned that theory, because it is unclear whether the Kamura event actually happened, for example climatic cooling inconsistent with the conodont apatite oxygen isotope records.