''Quercus hiholensis'' is an extinct

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...

oak An oak is a tree or shrub in the genus ''Quercus'' (; Latin "oak tree") of the beech family, Fagaceae. There are approximately 500 extant species of oaks. The common name "oak" also appears in the names of species in related genera, notably ''L ...

in the Fagaceae genus ''Quercus''. The species is known from Middle Miocene

fossil A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...

s found in Central

Washington Washington commonly refers to: * Washington (state), United States * Washington, D.C., the capital of the United States ** A metonym for the federal government of the United States ** Washington metropolitan area, the metropolitan area centered o ...

Description

''Q. hiholensis'' acorns range in size from to with an umbo on the tip of some nuts, but absent on others. Of the 26 identified ''Q. hiholensis'' acorns, only one specimen has a nut emerging from the cupule, while in the others only the perianth and styles, or umbo show. The exteriors of the cupules comprise helically arranged scales that have a papery tip and range up to with the papery tip extending up to further. The cupule has patches of

sclereid Sclereids are a reduced form of sclerenchyma cells with highly thickened, lignified cellular walls that form small bundles of durable layers of tissue in most plants.Evert, Ray F; Eichhorn, Susan E. Esau's Plant Anatomy: Meristems, Cells, and T ...

s scattered through it with some of the sclereids that are associated with scale bases organized into white star shaped patches. The fruits have an ovoid to ovoid-conical shape, ranging between to in size. The smaller, less mature fruits show the distinct structuring of styles and perianth. The styles have flared tips and are short, while the perianth has distinct lobes that are closely placed to the styles. As is typical for acorns of section ''Quercus'', the youngest specimens still have the aborted second ovule and dividing septum present near the base of the developing fruit.

History and classification

At the time of study, the

holotype A holotype is a single physical example (or illustration) of an organism, known to have been used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of sever ...

acorn, specimen UWBM 45-I, and a series of paratype specimens were preserved in the

Burke Museum of Natural History and Culture The Burke Museum of Natural History and Culture (Burke Museum) is a natural history museum in Seattle, Washington, in the United States. Established in 1899 as the Washington State Museum, it traces its origins to a high school naturalist club fo ...

, while additional examined fossils that were not part of the type series were part of the paleobotanical collections at Arizona State University. The specimens represent a range of preservation conditions, ranging from exposed on weathered surfaces of the chert, totally weathered out of the chert, and as hollow chert casts of the acorns. A total of 42 specimens in chert were studied by

paleobotanist Paleobotany, which is also spelled as palaeobotany, is the branch of botany dealing with the recovery and identification of plant remains from geological contexts, and their use for the biological reconstruction of past environments (paleogeogr ...

s Sandra Borgardt and Kathleen Pigg, with their 1999

type description A species description is a formal description of a newly discovered species, usually in the form of a scientific paper. Its purpose is to give a clear description of a new species of organism and explain how it differs from species that have be ...

being published in the ''

American Journal of Botany The ''American Journal of Botany'' is a monthly peer-reviewed scientific journal which covers all aspects of plant biology. It has been published by the Botanical Society of America since 1914. The journal has an impact factor of 3.038, as of 2019 ...

''. Borgardt and Pigg chose the specific epithet ''hiholensis'' as a reference to the "Hi'' ''hole" locality that is the type locality of the species. Based on the acorn and floral morphology, Borgardt and Pigg placed the species into the oak subgenus ''Quercus'' section ''Quercus'', which includes living

white oak The genus ''Quercus'' contains about 500 species, some of which are listed here. The genus, as is the case with many large genera, is divided into subgenera and sections. Traditionally, the genus ''Quercus'' was divided into the two subgenera ''C ...

s. As ''Q. hiholensis'' was the first oak to be described from anatomically preserved acorns, they chose to place the fossils into a new species rather than describe them as fossils belonging to the living species, or acorns belonging to an already described fossil species.

Distribution and paleoecology

The species was first described from specimens of

silicified In geology, petrifaction or petrification () is the process by which organic material becomes a fossil through the replacement of the original material and the filling of the original pore spaces with minerals. Petrified wood typifies this proce ...

acorns preserved in

chert Chert () is a hard, fine-grained sedimentary rock composed of microcrystalline or cryptocrystalline quartz, the mineral form of silicon dioxide (SiO2). Chert is characteristically of biological origin, but may also occur inorganically as a ...

of the "Yakima Canyon Flora". The chert was recovered from the "Hi'' ''hole" site, one of the "county line hole" fossil localities of the "Yakima Canyon Flora" located north of

Interstate 82 Interstate 82 (I-82) is an Interstate Highway in the Pacific Northwest region of the United States that travels through parts of Washington and Oregon. It runs from its northwestern terminus at I-90 in Ellensburg, Washington, to its southeaste ...

Yakima County, Washington Yakima County is a county in the U.S. state of Washington. As of the 2020 census, its population was 256,728. The county seat and largest city is Yakima. The county was formed out of Ferguson County in January 1865 and is named for the Yakama ...

. The "Hi'' ''hole" site works strata which was thought to be part of the Museum Flow Package within the interbeds of the Sentinel Bluffs Unit of the central Columbia Plateau N₂ Grande Ronde Basalt,

Columbia River Basalt Group The Columbia River Basalt Group is the youngest, smallest and one of the best-preserved continental flood basalt province on Earth, covering over mainly eastern Oregon and Washington, western Idaho, and part of northern Nevada. The basalt grou ...

. The Museum Flow Package interbeds, designated the type locality, are dated to the middle Miocene and are approximately 15.6'' ''million years old. Later of the "hi'' ''hole" site indicated that the site is included into a basalt flow, rather than part of the interbedded Museum flow package. The evaluation suggested the basalt is part of the Wanapum Basalt and that the fossils are possibly a little younger than formerly reported. Dating reported in 2007 of a related site near

Ellensburg, Washington Ellensburg is a city in and the county seat of Kittitas County, Washington, United States. It is located just east of the Cascade Range near the junction of Interstate 90 and Interstate 82. The population was 18,666 at the 2020 census. and was ...

, confirmed that the deposits worked are pockets within the basalt flows, and the 15.6'' ''million-year-old date was accurate. Borgardt and Pigg noted that a number of the acorns show signs of probable insect damage, with preserved bore tunnels, possible

frass Frass refers loosely to the more or less solid excreta of insects, and to certain other related matter. Definition and etymology ''Frass'' is an informal term and accordingly it is variously used and variously defined. It is derived from the ...

, and possible larvae in some acorns. The overall damage is similar to damage by beetles in modern acorns, and the finds in ''Q. hiholensis'' suggest an oak/insect relationship extending at least back to the Miocene.

References

{{Taxonbar, from=Q21397177 hiholensis Plants described in 1999 Fossil taxa described in 1999 Miocene plants Flora of North America Extinct flora of North America † †