Birbal Sahni Institute of Palaeosciences, Lucknow, 226007, India.
Department of Biology, University of Florida, Gainesville, FL, 32611, USA.
Am J Bot. 2021 May;108(5):883-892. doi: 10.1002/ajb2.1651. Epub 2021 May 20.
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.
Remains of tiny flowers in amber were studied by micro-CT scanning, reflected light, and epifluorescence microscopy.
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 µm). The combined characters indicate a position within the grade known as subfamily Rauvolfioideae.
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.
印度古吉拉特邦坎贝褐煤的早始新世琥珀以其多样的昆虫群和分散的花粉而闻名，但其中包含的花朵受到的关注有限。夹竹桃科的化石记录相对较少，该科特有的花部特征以前在化石记录中尚未得到识别。
通过微 CT 扫描、反射光和荧光显微镜研究琥珀中微小花朵的遗骸。
Maryendressantha succinifera gen. et. sp. n. 的花朵具有辐射对称、五瓣、管状的花冠，宽 2.2-2.3 毫米，深 1.7-2.1 毫米，具有左旋覆瓦状排列，雄蕊轮生，由 5 个花丝附着在花冠管的下半部分组成。花药为卵形，基部圆形，顶端逐渐变细，连接体彼此会聚成圆锥形。花粉为球形、具粒状纹饰、三孔沟，非常小（10-11 µm）。综合特征表明其位于 Rauvolfioideae 亚科的等级内。
这些化石作为 Rauvolfioids 的最古老遗骸，补充了来自其他地区的夹竹桃科和萝藦科化石种子的化石记录，表明夹竹桃科在早始新世已经得到很好的建立，这与该科系统发育的先前分歧估计基本一致。保存在坎贝琥珀中的潜在传粉者包括蚊子、蚋、小蛾和无刺蜜蜂。
