Biology of a leaf miner (Coleoptera) on Liaoningocladus boii (Coniferales) from the Early Cretaceous of northeastern China and the leaf-mining biology of possible insect culprit clades

Specimens of the broad-leaved conifer, Liaoningocladus boii Sun, Zheng & Mei 2000 were evaluated from the mid Early Cretaceous Yixian Formation occurring overwhelmingly at Dawangzhangzi, Liaoning Province, NE China. Arthropod-mediated plant damage types (DTs) were categorized for 343 specimens of this host; one of these DTs represented a distinctive leaf-mine, DT280, established as Fossafolia offae Ding, Labandeira & Ren, ichnogen. et ichnosp. nov. A comparison of DT280 to analogous modern leaf mines was based on: (1) leaf-mine features observed in modern leaf mines; (2) likelihood of a particular leaf-mine culprit lineage being present, given phylogenetic evidence; and (3) body fossils of the candidate culprit occurring in the same or a spatiotemporally proximal deposit. Evidence from these three and other sources of information indicate the most likely miner of F. offae was an extinct species of Buprestidae (Coleoptera), perhaps similar to modern leaf-mining tribe Trachyini. Much less likely affiliations were Mordellidae, Chrysomelidae and Curculionoidea. Fossafolia offae leaf mines were produced by a larva that consisted of four instars, engaged in full-depth tissue feeding, partitioned into a linear, earlier-phase mine with a distinctive frass trail and a more blotch-like, later-phase mine. Adults of this leaf miner likely fed on L. boii, producing linear patches of intercostal window feeding, assigned to DT103, or less likely, may have been a pollinator. The adult female likely laid eggs singly into leaf tissues between adjacent major veins, resulting in DT101 ovipositional damage. This study provides for the use of multiple damage-types to document life-history feeding traits for a single herbivore species. Consequently, we introduce the damage-type suite concept to refer to two or more different damage types genetically linked to the same culprit herbivore that issue from different developmental stages (larvae, adult), or are produced by different tissue-penetrating insect organs (ovipositors, mouthparts). In addition, we provide a basis for using three types of general evidence necessary to elucidate identification of the culprit.