Fossil wood with dimorphic fibers from the Deccan Intertrappean Beds of India - The oldest fossil Connaraceae?

Abstract

Wood of Connaroxylon dimorphum (Connaraceae, Oxalidales) from the Deccan Intertrappean Beds of India (KPg Boundary 65-67 MY BP) is described. It is characterized by parenchyma-like fiber bands alternating with normal fibers, septate and nonseptate fibers, vessel-ray pits with strongly reduced borders, uniseriate rays of square and upright cells, and radial tubules in the center of ray cells that are arranged in a herringbone pattern. The overall wood anatomy strongly resembles Melastomataceae p. p., Lagerstroemia p. p. (Lythraceae) and Connarus (Connaraceae). However, the shared radial tubules of Connarus and the fossil strongly tilt the evidence of botanical affinities towards this genus. This would represent the second and by far the oldest fossil wood record of the Connaraceae, also considerably older than the earliest fossil records of the family's other plant parts, and one of the oldest fossils of the order Oxalidales.