Flowers of Apocynaceae in amber from the early Eocene of India

Premise Early Eocene ambers of the Cambay lignite in Gujarat, India, are well known for their diverse insect fauna and dispersed pollen, but the included flowers have received limited attention. The fossil record of Apocynaceae is relatively poor, and the distinctive floral characters of this family have not been recognized in the fossil record before. Methods Remains of tiny flowers in amber were studied by micro-CT scanning, reflected light, and epifluorescence microscopy. Results Flowers of Maryendressantha succinifera gen. et. sp. n. have actinomorphic, pentamerous, tubular corollas 2.2-2.3 mm wide, and 1.7-2.1 mm deep with sinistrorse aestivation and androecia consisting of a whorl of five stamens attached by short filaments to the lower half of the corolla tube. Anthers are ovate, rounded basally and apically tapered with their connectives convergent with one another in a conical configuration. The pollen is globose, psilate, tricolporate, and very small (10-11 mu m). The combined characters indicate a position within the grade known as subfamily Rauvolfioideae. Conclusions These fossils, as the oldest remains of Rauvolfioids, complement the fossil records of Apocynoid and Asclepioid fossil seeds from other regions, demonstrating that the Apocynaceae were well established by the early Eocene, mostly consistent with prior divergence estimates for the phylogeny of this family. Potential pollinators, also preserved in the Cambay amber, include mosquitos, gnats, small moths, and stingless bees.

Automated summary

Early Eocene ambers from Gujarat, India, have revealed a new fossil flower, Maryendressantha succinifera, which represents the oldest remains of Rauvolfioids. This finding complements the fossil records of other Apocynoid and Asclepioid seeds, indicating the well-established presence of Apocynaceae by the early Eocene. The fossilized flowers also provide insights into potential pollinators present in the Cambay amber, such as mosquitos, gnats, small moths, and stingless bees.