Fossil flowers of Lachnociona camptostylus sp. nov., a second record for the genus in mid-Cretaceous Myanmar Amber

Abstract

Two flowers embedded in a single block of amber from Myanmar are here proposed as a second species of the previously described fossil genus Lachnociona. The mid-Cretaceous age of the fossils was earlier established through paleontological and U-Pb isotope dating methods. Because they lie within millimeters of each other in the amber, the flowers are assumed to have come from the same parent plant. One flower is hermaphrodite while the other is functionally pistillate. They differ by the number of styles—4 in the perfect flower and 5 in the unisexual one—and most notably by the presence, in the perfect flower, of 10 conspicuous nectar glands forming a disc above the whorl of stamens. The pistillate flower has no such glands. In the new species, the arched styles are widely divergent and the ovary is fully inferior, while in the earlier-described Lachnociona terriae, the flower is functionally pistillate, with styles that are erect and connivent or connate. It could not be determined whether the ovary is superior or half-inferior. The best-preserved anther in the perfect flower of L. camptostylus resembles, in its dorsal filament attachment and hooked filament tip, a vestigial anther present in the flower of L. terriae. Pollen of the new species is tri- or tetracolpate. As proposed in the previous paper, the genus may have participated in the early diversification of the rosid clade of eudicots.