Belenocarpa tertiara (Berry) gen. et comb. nov. (Euphorbiaceae): Fossil Fruits with Carunculate Seeds from the Oligocene of Peru

Premise of research. Three-dimensionally preserved fruits and seeds of Jatropha tertiara Berry from the early Oligocene of Peru have been reinvestigated on the basis of type material supplemented by more complete recently collected specimens.Methodology. The fossils were recovered by fracturing the weakly consolidated sediment. Extant and fossil fruits were studied with reflected light and by micro-computed tomography scanning.Pivotal results. The fruits are thin-walled prolate trilocular capsules that are hexagonal in cross section with prominent loculicidal and septicidal keels. The seeds are ovate in dorsiventral view, lenticular in cross section, and fitted with a large caruncle about half the length of the seed body. The large size and six-keeled aspect of the fruit distinguish this fossil from extant species of Jatropha and lead us to exclude it from the extant genus. We transfer this fossil species to the new genus Belenocarpa.Conclusions. Similarities to other genera, particularly some species of Manihot, indicate likely affinities between Belenocarpa and Euphorbiaceae subfamily Crotonoideae. The well-preserved, relatively large caruncles on these seeds, making up about one-third of the full seed length, are comparable to those seen on extant seeds known to be dispersed by ants and suggest that similar insect-plant associations were already present in South America by the Oligocene.

Automated summary

This study reinvestigated the three-dimensionally preserved fruits and seeds of Jatropha tertiara Berry from the early Oligocene of Peru. The results showed that the fossils belong to a new genus, Belenocarpa, and likely have affinities with Euphorbiaceae subfamily Crotonoideae. The well-preserved caruncles on these seeds suggest that insect-plant associations similar to those seen in the present were already present in South America by the Oligocene.