Hybosorus ocampoi: the first hybosorid from the Cretaceous Myanmar amber (Coleoptera: Scarabaeoidea)

Abstract

The Hybosoridae is a cosmopolitan family of Scarabaeoidea that is most diverse in the tropics. Up to now, all published Mesozoic hybosorids were compression fossils, except for one from Lebanon amber which is incomplete. A new species, Hybosorus ocampoi Bai et Zhang sp. nov., of Hybosoridae (Scarabaeoidea) is described and illustrated based on one well-preserved Myanmar amber specimen. The phylogenetic position of H. ocampoi was analyzed by employing 117 morphological characters and 44 extant/extinct species. The documented features are discussed and analyzed with respect to the phylogenetic placement of the species which may have a strong impact on the evolution in Hybosoridae and greatly expand our knowledge on the early evolution of Scarabaeoidea. Our finding provides solid evidence to prove the very old origin of the genus Hybosorus which is the type genus of Hybosoridae. Furthermore, this finding not only supports the hypothesis of Mesozoic origin of most families in Scarabaeoidea but also supports some genera of Scarabaeoidea might have already appeared in the Mesozoic. The palaeobiogeography of Hybosoridae and its palaeoenvironmental implications are also discussed.