ALLEGED VERTEBRATE EGGS FROM UPPER CRETACEOUS REDBEDS, GOBI-DESERT, ARE FOSSIL INSECT (COLEOPTERA) PUPAL CHAMBERS - FICTOVICHNUS NEW ICHNOGENUS

Small egg-like structures from the Upper Cretaceous (Campanian) Djadok hta Formation of Mongolia were previously interpreted as casts of croc odile, lizard, and turtle eggs, or as inorganic nodules. Identical str uctures from coeval redbeds at Bayan Mandahu in northern China indicat e the structures are not vertebrate eggs, nor of vertebrate origin. Co mparisons with Recent and Quaternary beetle (Coleoptera) pupal chamber s show close similarities in size, shape, and the presence of a round to irregular exit hole for the adult beetle. Most importantly, the Cre taceous structures are enveloped by a thin clay-rich zone, which is ex pected if constructed by beetle larvae but inexplicable in any egg or inorganic nodule model. Additional evidence contradicting a vertebrate egg origin for the structures includes (i) the structures are too sma ll to have been laid by turtle or crocodile species occurring in the B ayan Mandahu redbeds; (ii) the structures are isolated, not in clutche s or pairs; and (iii) unlike newly hatched soft-shelled lizard eggs, t he Cretaceous structures are not collapsed and show a round to irregul ar exit hole rather than a slit. It is concluded that the egg-like str uctures are sand casts (steinkerns) of beetle pupal chambers, probably of Scarabaeidae, Tenebrionidae, or Curculionidae. The Cretaceous pupa l chambers are assigned to a new ichnogenus, Fictovichnus, and new ich nospecies, Fictovichnus gobiensis and Fictovichnus parvus.