Earliest fossil record of Burseraceae from the Deccan Intertrappean Beds of Central India and its biogeographic implications

Abstract

Premise of research. Burseraceae is represented by a large number of fossils from the Cenozoic sedimentary succession and has a disjunct distribution today in the southern part of North America, Africa, Europe, and Asia. However, the family has a poor fossil record in deep time, making hypotheses concerning its origin and dispersal difficult to evaluate. Here, we report the occurrence of reproductive organs (fruit and flower) attributable to modern Burseraceae from the probable latest Maastrichtian (Late Cretaceous) to earliest Danian (early Paleocene) sediments of the Mandla Lobe of the Deccan Intertrappean beds of Madhya Pradesh, Central India. Methodology. X-ray micro–computed tomography was used to observe three-dimensional structures. The reconstruction software takes the 2D projection images acquired by the X-ray detector and generates a 3D image represented by gray values distributed in a volumetric space. The present fruit and flower fossils are identified through morphological comparison with another fossil and extant Burseraceae. Pivotal results. The fossil pyrene corresponds in morphology with that of Burseraceae (particularly some genera of Protieae and Bursereae), while the fossil flower, with the pentamerous organization of sepals and petals and ovary and 10 stamens arranged in two whorls around a prominent intrastaminal nectary disk, is particularly similar to Protium. The fossil fruit is here described as a new species of the fossil genus Bursericarpum Reid et Chandler as Bursericarpum indicum Kumar, Manchester et Khan sp. nov. and the fossil flower as Debursera indica Kumar, Manchester, Judd et Khan sp. nov. Conclusions. The present discoveries represent the oldest reliable fossil records of Burseraceae supporting its Gondwanan origin. These fossils also provide important information for tracing possible migration pathways of Burseraceae from India to Europe after the docking of the Indian subcontinent with Eurasia during the early Eocene (55±10 Ma), supporting an “out-of-India” dispersal hypothesis. Based on earlier and present records we suggest that the family might have reached Europe from India and then colonized North America (during the Eocene) in areas where it is now regionally extinct.