Attached leaves and fruits of myrtaceous affinity from the Middle Eocene of Colorado

Abstract

A new myrtaceous genus, Syzygioides Manchester, Dilcher et Wing, gen. nov., is established based upon compressed twigs showing the attachment of leaves, with axillary panicles of flowers and fruits from the Eocene of the Rocky Mountain region. The new combination Syzygioides americana (Lesquereux) Manchester, Dilcher et Wing, comb. nov. applies to leaves that formerly were attributed to Eucalyptus and Eugenia. The opposite, decussately arranged leaves are similar in architecture to those of extant Syzygium fluviatilis (Hemsley) Merrill et Perry and S. jambos (L.) Alston, but the attached leathery fruits, with incurved persistent calyx and short capitate stigmas, are unlike those of extant Eucalyptus, Syzygium, Eugenia and other extant genera. Syzygioides americana first appears in the Lower Eocene of the Rocky Mountain region and is common in the Middle Eocene. The improved understanding of this fossil shows the presence of an extinct myrtaceous genus in the Eocene and demonstrates the need for caution in attempting to identify isolated fossil leaves to extant genera of the Myrtaceae.