ITEA-LIKE LEAVES FROM THE MIDDLE EOCENE REPUBLIC FLORA, WASHINGTON, USA

The Middle Eocene (ca. 49 mya) compression flora of Republic, Washington, is a mixed conifer and dicot flora thought to represent a unique temperate vegetation that occurred in highlands of the Pacific Northwest. This flora includes the oldest known records of several extant genera, among them leaves attributed to the extant genus Itea (Virginia willow), a North American-east Asian disjunct taxon of ca. 20 species. Originally described from only partial specimens, ca. 80 putative Itea leaf fossils are now known. In light of these new finds, a reexamination of the fossil leaves was undertaken in which they were compared with the leaves of extant Itea species. The leaf fossils are generally poorly preserved and all lack cuticle, though many have secondary and some have tertiary venation. The fossil leaves are consistent with the modern genus in the characters preserved, including: 1) shape, with acuminate to straight apices and convex to rounded bases; 2) type of secondary venation, semicraspedodromous; 3) type of tertiary venation, veins perpendicular or at an obtuse angle to the midrib and primarily parallel to one another; and 4) type of leaf margin, with simple serrate teeth. Although the fossil leaves seem to segregate roughly into two groups, with large leaves (75-111 x 42-64 mm) often being oblong in shape with strongly acuminate apices, like those known from extant I. macrophylla, and small leaves (12-91 x 10-40 mm) being highly variable in shape, like those known from I. virginica, intermediate types and lack of other unique characters or character combinations prevent distinction of two morphospecies. No other Itea-like remains (i.e., flowers, pollen) are currently known from the Republic locality.

Other fossils thought to have affinities to Itea are scarce in North America. A Turonian (ca. 90 mya) floral taxon, Divisestylus, thought to be a precursor to extant Itea, is known from a single locality in New Jersey. Fossil pollen attributed to Itea is known from the Oligocene of Vermont and Miocene of the Pacific Northwest and Alaska. The European record is more complete, extending from the Middle Eocene to the Pliocene, and is based primarily on palynological data. No fossils attributed to Itea are currently known from Asia, and, thus, the Republic fossils may help to explain the disjunct distribution of the extant genus.