Melanie L. DeVore

A brief review of the fossil history of the family Rosaceae with a focus on the Eocene Okanogan Highlands of eastern Washington State, USA, and British Columbia, Canada

Many of the oldest definitive members of the Rosaceae are present in the Eocene upland floras of the Okanogan Highlands of northeastern Washington State and British Columbia, Canada. Over a dozen rosaceous taxa representing extant and extinct genera of all four traditionally recognized subfamilies are known from flowers, fruits, wood, pollen, and especially leaves. The complexity seen in Eocene Rosaceae suggests that hybridization and polyploidy may have played a pivotal role in the early evolution of the family. Increased species diversity and the first appearance of additional modern taxa occur during the Late Paleogene in North America and Europe. The Rosaceae become increasingly important components of fossil floras during the Neogene, with taxa adapted to many habitats.

New Diversity among the Trochodendraceae from the Early/Middle Eocene Okanogan Highlands of British Columbia, Canada, and Northeastern Washington State, United States

Newly recognized fossil infructescences and leaves of the Trochodendraceae are described from the Early/Middle Eocene McAbee and One Mile Creek sites of British Columbia, Canada, and Republic, eastern Washington State, United States. Trochodendron drachukii Pigg, Dillhoff, DeVore, & Wehr sp. nov., from McAbee, is an infructescence similar to that of extant Trochodendron aralioides Sieb. & Zucc. but strongly paniculate rather than racemose. This new species is larger and more robust than those of the Eocene flora of Republic, Washington, and has attached fruits quite similar to both extant Trochodendron Sieb. & Zucc. and Miocene fossils from Asia and western North America. Associated leaves are similar to those of extant Trochodendron except for sometimes bearing short basal auriculate extensions of the lamina. They differ from Trochodendron nastae Pigg, Wehr, & Ickert‐Bond leaves from Republic that have palmate rather than pinnate venation. Tetracentron hopkinsii Pigg, Dillhoff, DeVore, & Wehr sp. nov. from One Mile Creek and Tetracentron sp. from Republic have leaves remarkably like those of extant Tetracentron Oliver, firmly establishing the presence of this genus in the Eocene. This study demonstrates that within the Trochodendraceae, a poorly understood group within the eudicot grade, both extinct forms as well as plants with quite modern‐appearing fruits and leaves were present by the Eocene in northwestern North America.

Paleoactaea gen. nov. (Ranunculaceae) fruits from the Paleogene of North Dakota and the London Clay

Paleoactea nagelii Pigg & DeVore gen. et sp. nov. is described for a small, ovoid ranunculaceous fossil fruit from the Late Paleocene Almont and Beicegel Creek floras of North Dakota, USA. Fruits are 5-7 mm wide, 4.5-6 mm high, 10-13 mm long, and bilaterally symmetrical, containing 10-17 seeds attached on the upper margin in 2-3 rows. A distinctive honeycomb pattern is formed where adjacent seeds with prominent palisade outer cell layers abut. Seeds are flattened, ovoid, and triangular. To the inside of the palisade cells, the seed coat has a region of isodiametric cells that become more tangentially elongate toward the center. The embryo cavity is replaced by an opaline cast. This fruit bears a striking resemblance to extant Actaea, the baneberry (Ranunculaceae), an herbaceous spring wildflower of North Temperate regions. A second species, Paleoactaea bowerbanki (Reid & Chandler) Pigg & DeVore nov. comb., is recognized from the Early Eocene London Clay flora, based on a single fruit. This fruit shares most of the organization and structure of P. nagelii but is larger and has a thicker pericarp. This study documents a rare Paleocene occurrence of a member of the buttercup family, a family that is today primarily herbaceous, and demonstrates a North Atlantic connection for an Actaea-like genus in the Paleogene.

Fruits of Icacinaceae (Tribe Iodeae) from the Late Paleocene of western North America

The Icacinaceae occur pantropically today, but are well represented by fossil fruits of the warm Early Middle Eocene, when tropical plants that currently occupy low latitudes were more widely distributed in higher latitudes. Members of this family are first known in the Late Cretaceous; however, fossil fruits of tribe Iodeae are quite rare before the Eocene. In this paper we describe the first formally recognized Late Paleocene icacinaceous taxa from western North America. We name two new species of Icacinicarya based on anatomically preserved fruits and establish a new genus, Icacinicaryites, for impressions with a strong similarity to Icacinicarya that lack anatomical preservation. These new records from the Almont/Beicegel Creek flora in North Dakota and several localities in Wyoming, Colorado, and Montana complement records known from the Early Eocene of England and document an increased diversity of Iodeae and related forms in the Paleogene of western North America.

Prunus and Oemleria (Rosaceae) Flowers from the Late Early Eocene Republic Flora of Northeastern Washington State, U.S.A.

Two genera of Rosaceae are described from the latest early Eocene Republic flora of northeastern Washington State, United States. Prunus cathybrownae sp. nov. (Rosaceae: subfamily Spiraeoideae, tribe Amygdaleae sensu Potter et al.) is based on eight flowers, including one containing in situ pollen and two immature fruits. Flowers are actinomorphic, perigynous, and pentamerous, with a campanulate hypanthium bearing five sepals. The gynoecium is unicarpellate and consists of a distally flared, bilobed stigma; an elongate style; and an ellipsoid, bilaterally asymmetric ovary. Two whorls of stamens—an inner one in which stamens are reflexed and an outer whorl of extended stamens—are both inserted into the hypanthium. Pollen from the outer whorl is 20 μm in diameter and tricolporate with a striately ornamented exine; clusters of smaller, presumably immature grains 7 μm long and 4 μm wide lacking distinctive ornamentation were recovered from the inner whorl. Immature fruits differ from the flowers in either having a senescent style or lacking one entirely and having fewer remnants of perianth parts and a larger and more symmetrical ovary. A second flower, Oemleria janhartfordae sp. nov. (Rosaceae: subfamily Spiraeoideae, tribe Osmaronieae sensu Potter et al.) is actinomorphic and perigynous and has five free pistils that each resemble the solitary pistil of Prunus. These include a flattened, bilobed stigma and an ellipsoid, bilaterally asymmetric ovary. The fossil has the laterally fixed, elongate style characteristic of the genus. These fossils are the oldest known floral examples of these two genera and demonstrate that both Prunus and Oemleria were present in the latest early Eocene in western North America. The Okanogan Highlands floristic province provides the earliest fossil evidence to date for the first major radiation of the Rosaceae, an important mostly temperate, mostly Northern Hemisphere family.

Hamawilsonia boglei gen. et sp. nov. (Hamamelidaceae) from the Late Paleocene Almont flora of central North Dakota

Hamawilsonia boglei Benedict, Pigg & DeVore gen. et sp. nov. (Hamamelidaceae) is described from the Late Paleocene Almont flora of central North Dakota. The infructescence is an anatomically preserved spike with up to 20 sessile, robust, cuboidal to ovoid capsules borne on an elongate, thick axis up to \documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \usepackage[OT2,OT1]{fontenc} \newcommand\cyr{ \renewcommand\rmdefault{wncyr} \renewcommand\sfdefault{wncyss} \renewcommand\encodingdefault{OT2} \normalfont \selectfont} \DeclareTextFontCommand{\textcyr}{\cyr} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} \landscape

Shirleya grahamae gen. et sp. nov. (Lythraceae), Lagerstroemia-like fruits from the middle Miocene Yakima Canyon flora, central Washington State, USA

9.2\,\mathrm{cm}\,\,\mathrm{long}\,\times 0.5\,\mathrm{cm}\,\,\mathrm{wide}\,

Paleosecuridaca curtisii gen. et sp. nov., Securidaca‐Like Samaras (Polygalaceae) from the Late Paleocene of North Dakota and Their Significance to the Divergence of Families within the Fabales

\end{document} . Individual fruits are 10–12 mm across and bilocular, with paired persistent, recurved styles borne on the distal carpel face. One locule is often larger than the other. Anatomically, the fruit wall is composed of a sclerified endocarp and a poorly preserved exocarp. Seeds are elliptical to slightly obovate with a sclerotic seed coat. Hamawilsonia is an extinct Late Paleocene genus with a combination of characters not seen in any extant hamamelid genus. Hamawilsonia is similar to the Asian endemic genus Sinowilsonia in its elongate spikelike infructescence, resembles the witch hazel Hamamelis in fruit and seed morphology, and has seed anatomy that combines features found in several extant genera. Affinities with Sinowilsonia are further supported by the co‐occurrence of associated pollen catkins and in situ tricolpate pollen with a distinctive reticulate sculpturing. Like several other Almont taxa (Amersinia, Beringiaphyllum, Davidia, and Palaeocarpinus), Hamawilsonia is a genus with strong North American–Asian affinities.