Reproductive and vegetative remains of an eucalypt (Myrtaceae) from the early Eocene of India

Abstract

Eucalypt fossils were widely reported from the Cenozoic deposits across the Southern Hemisphere (Australia, New Zealand, and Argentina). However, no attached reproductive and vegetative fossil remains of this myrtaceous clade have been discovered till now. We report and describe for the first time a fossil eucalypt twig with attached foliage, flower buds, and mature flowers from the early Eocene (~55–52 Ma) sediments (Palana Formation) of Rajasthan, western India. As both vegetative and reproductive organs are in organic connection, they clearly represent the same species. In addition, here we also introduce fossil materials of isolated leaves, flower buds, inflorescence, and flowers recovered from the same stratigraphic level. Our Eocene fossils and extant members of the eucalypt clade are related morphologically by means of robust, thick petiolate lanceolate-shaped leaves with intramarginal secondary veins; operculate flower buds consisting of imbricate petals with discernable margins; solitary inflorescence with three flowers per umbellaster, epigynous and bisexual flowers. Based upon combined characteristics of leaf, flower, and bud morphology, these fossils conform to the Eucalypt clade and are recognized as a new fossil genus and species: Hindeucalyptus eocenicus Patel, R.F. Almeida, Ali et Khan gen. nov. et sp. nov. We also compare it with extant and extinct eucalypts using morphological phylogeny and character mapping analyses. In addition, we briefly discuss its phytogeographic and paleoclimatic implications regarding the distribution and habitat of fossil and modern eucalypts.

Keywords

early Eocene / eucalypt / flower buds / flowers / foliage / fossil twig / India / phytogeography

RIGHTS & PERMISSIONS

2024 Institute of Botany, Chinese Academy of Sciences.