The only known fossil specimen is from the Lower Cretaceous Hekou Group, part of the larger Lanzhou-Minhe Basin.

In 2016, their discovery was described as a new oogenus and oospecies, Polyclonoolithus yangjiagouensis, by Chinese paleontologists Xie Jun-Fang, Zhang Shu-Kang, Jin Xing-Sheng, Li Da-Qing, and Zhou Ling-Qi.

[1] Polyclonoolithus is only known from one specimen: ZMNH M1849, an incomplete egg (made up of several fragments) housed in the Zhejiang Museum of Natural History.

Due to the poor preservation, the size and shape of a complete egg are unknown, but Polyclonoolithus was likely less than 10 centimetres (3.9 in) in diameter.

It lacks the reticulate structure seen in dictyoolithids, and unlike similifaveoloolithids and dendroolithids, the eggshell units vary in thickness.