Insect egg ovipositions on leaves from the Upper Triassic from northern Chile

GNAEDINGER, S.; ADAMI-RODRIGUES, K.; GALLEGO, O.F.

Florianópolis, Brasil

Simposio; XII Simpósio Brasileiro de Paleobotânica e Palinologia; 2008

Asociación Latinoamericana de Paleobotánica y Palinología

According to recent contributions the knowledge of animal-plant interactions has increased noticeably in the last decade. Such evidences indicate the presence of organisms that are absent from burials and provide exceptional information about ancient ecological relationships. The geological record of the insect ovipositions includes several foundings, which range from the Paleozoic (Carboniferous) through the Cenozoic (Paleogene-Neogene?). This paper reports the first record of Triassic insect egg ovipositions from southern South America. They are recorded on leaves and leaf fragment from Heidiphyllum Retallack, Taeniopteris Brongniart and Pseudoctenis Autor, from the Upper Triassic from La Ternera and Las Breas formations, from northern Chile. These traces are ovate and lenticulate in outline showing the characteristic ovipositor scar, arranged in longitudinal rows, near the leaf base, parallel to the leaf venation/veins. Comparisons morphological characters (shape, size) with other world records and with various oviposition types on plants are made. They are tentatively assigned to the Order Odonatoptera (damselflies) based on the morphologic characteristics, host plants, paleoenvironmetal interpretations of fossil records of those units. The host plants Heidiphyllum was probably a relatively low-growing shrubby voltzialean conifer that formed dominant to monospecific thickets in areas of higher water table on a floodplain, or on sandbars within the braided river channels. Cycadacean as Pseudoctenis were related to environments as forst or woodland, other as Taeniopteris grown as shrub to small tree forst to woodland. Cycadacean were herbaceous or shrublike (bushlike) habit, that growth up (or that develop) as grove or thicket in areas without trees. And their leaves brought a favourable/suitable place for the oviposition of the ancient odonata.