First buckthorn (Rhamnaceae) fossil flowers from India

Abstract

Fossil leaves, fruits, and woods assigned to Rhamnaceae have been recorded from India, however, there are no previous reports of rhamnaceous fossil flowers from India. Here, we report the first fossil flowers in appreciable numbers from the early Eocene (Palana Formation) sedimentary sequences of Gurha Lignite Mine, Rajasthan, western India, and show that they are attributable to Rhamnaceae. We examined variation in flower morphology among extant and extinct rhamnaceous species as a basis for interpreting our fossil flowers. The specimens are small star-like, pentamerous, actinomorphic, gamosepalous flowers with triangular, keeled sepals with acute apices, spathulate, short-clawed petals alternating with sepals, shallow, five-lobed nectary disc with prominent pentagonal outer margin, and a centrally placed globose ovary with stigma scar. The flowers co-occur with ziziphoid leaves and are recognized as a new species Eopaliura indica Patel, Rana & Khan sp. nov. Because of aforesaid characteristics, fossil flowers are easily identifiable as Rhamnaceae and should provide a reliable means of documenting the evolutionary history of this family during the Cenozoic.

Keywords

early Eocene / fossil flowers / paleoecology / Rajasthan / Rhamnaceae / western India

RIGHTS & PERMISSIONS

2023 Institute of Botany, Chinese Academy of Sciences.