Article: Three-dimensionally mineralized insects and millipedes from the Tertiary of Riversleigh, Queensland, Australia
An assemblage of three-dimensionally preserved insects and millipedes from the lale Oligocene/early Miocene limestones of Riversleigh (north-west Queensland) augments a sparse Tertiary insect record from Australia. The fauna includes four species of Coleoptera, one of Trichopiera represented only by the larva, and a myriapod. The arthropods are uncompacted and have been replicated in calcium phosphate. Early phosphatization has preserved original structures such as the overlapping layers and helicoidal pore canals of the procuticle, and wrinkles in the arthrodial membrane. The most remarkable preservation is of the ocular apparatus. The hexagonal lenses and their rhabdom emplacements are preserved in the Coleoptera. The trichopteran larva displays an unusual form of compound eye, consisting of large, separate circular lenses. Where the cornea has been lost, an irregular lattice of 'cups' is exposed. This is the first example of this 'schizochroal'-type eye reported in a fossil insect. Bacteria and fungi associated with the decay of the insects are themselves mineralized.