''Rhus rooseae'' is an extinct

species In biology, a species is the basic unit of Taxonomy (biology), 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 ...

flowering plant Flowering plants are plants that bear flowers and fruits, and form the clade Angiospermae (), commonly called angiosperms. They include all forbs (flowering plants without a woody stem), grasses and grass-like plants, a vast majority of ...

s in the

sumac Sumac ( or ), also spelled sumach, is any of about 35 species of flowering plants in the genus ''Rhus'' and related genera in the cashew family (Anacardiaceae). Sumacs grow in subtropical and temperate regions throughout the world, including Ea ...

family,

Anacardiaceae The Anacardiaceae, commonly known as the cashew family or sumac family, are a family of flowering plants, including about 83 genera with about 860 known species. Members of the Anacardiaceae bear fruits that are drupes and in some cases produce ...

, solely known from the

middle Eocene The Eocene ( ) Epoch is a geological epoch that lasted from about 56 to 33.9 million years ago (mya). It is the second epoch of the Paleogene Period in the modern Cenozoic Era. The name ''Eocene'' comes from the Ancient Greek (''ēṓs'', "d ...

sediments exposed in north central

Oregon Oregon () is a state in the Pacific Northwest region of the Western United States. The Columbia River delineates much of Oregon's northern boundary with Washington, while the Snake River delineates much of its eastern boundary with Idah ...

. The species was first described from a series of isolated

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 ...

seeds 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 ...

History and classification

''Rhus rooseae'' has been identified from a single location in the

Clarno Formation Clarno may refer to: Locations *Clarno, Oregon *Clarno, Wisconsin **Clarno (community), Wisconsin *Clarno Township, Lake County, South Dakota Other * Clarno Formation, an Eocene geologic formation in Central Oregon * Beverly Clarno Beverly A. ...

, the Clarno nut beds,

type locality Type locality may refer to: * Type locality (biology) * Type locality (geology) See also * Local (disambiguation) * Locality (disambiguation) {{disambiguation ...

for both the formation and the species. The nut beds are approximately east of the unincorporated community of Clarno, Oregon, and currently considered to be

in age, based on averaging zircon fission track

radiometric dating Radiometric dating, radioactive dating or radioisotope dating is a technique which is used to date materials such as rocks or carbon, in which trace radioactive impurities were selectively incorporated when they were formed. The method compares t ...

which yielded an age of 43.6 and 43.7 ± 10

million years ago The abbreviation Myr, "million years", is a unit of a quantity of (i.e. ) years, or 31.556926 teraseconds. Usage Myr (million years) is in common use in fields such as Earth science and cosmology. Myr is also used with Mya (million years ago). ...

and

Argon–argon dating Argon–argon (or 40Ar/39Ar) dating is a radiometric dating method invented to supersede potassiumargon (K/Ar) dating in accuracy. The older method required splitting samples into two for separate potassium and argon measurements, while the newer ...

which yielded a 36.38 ± 1.31 to 46.8 ± 3.36 mya date. The average of the dates resulted in an age range of 45 to 43 mya. The beds are composed of silica and calcium carbonate cemented

tuff Tuff is a type of rock made of volcanic ash ejected from a vent during a volcanic eruption. Following ejection and deposition, the ash is lithified into a solid rock. Rock that contains greater than 75% ash is considered tuff, while rock ...

aceous sandstones, siltstones, and conglomerates which preserve either a lake delta environment, or alternatively periodic floods and volcanic mudflows preserved with hot spring activity. The species was described from a series of

type specimens In biology, a type is a particular specimen (or in some cases a group of specimens) of an organism to which the scientific name of that organism is formally attached. In other words, a type is an example that serves to anchor or centralizes th ...

, 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 seve ...

specimen USNM 355036, which is currently preserved in the paleobotanical collections of the

National Museum of Natural History The National Museum of Natural History is a natural history museum administered by the Smithsonian Institution, located on the National Mall in Washington, D.C., United States. It has free admission and is open 364 days a year. In 2021, with ...

Washington, D.C. ) , image_skyline = , image_caption = Clockwise from top left: the Washington Monument and Lincoln Memorial on the National Mall, United States Capitol, Logan Circle, Jefferson Memorial, White House, Adams Morgan, ...

and nine

paratype In zoology and botany, a paratype is a specimen of an organism that helps define what the scientific name of a species and other taxon actually represents, but it is not the holotype (and in botany is also neither an isotype nor a syntype). O ...

specimens which are in the

University of Florida The University of Florida (Florida or UF) is a public land-grant research university in Gainesville, Florida. It is a senior member of the State University System of Florida, traces its origins to 1853, and has operated continuously on its ...

collections. The fossils were part of approximately 20,000 specimens collected from 1942 to 1989 by Thomas Bones, A. W. Hancock, R. A. Scott, Steven R. Manchester, and a number of high school students. The ''Rhus rooseae'' specimens 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 ...

Steven R. Manchester of the University of Florida. He published his 1994

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 ...

for ''R. rooseae'' in the Journal '' Palaeontographica Americana''. The

specific epithet In taxonomy, binomial nomenclature ("two-term naming system"), also called nomenclature ("two-name naming system") or binary nomenclature, is a formal system of naming species of living things by giving each a name composed of two parts, bot ...

''rooseae'' was chosen in recognition of work done by Carrie L. Roose during the preparation of Clarno flora project.

Description

The fruits of ''Rhus rooseae'' are bilaterally symmetrical with an subelliptic shape and both the tip and base rounded. The seeds have an overall length ranging between and a width between . The seeds are identified as belonging to a ''Rhus'' species by the exterior morphology and by the structure of the vascular supply system. The

mesocarp Fruit anatomy is the plant anatomy of the internal structure of fruit. Fruits are the mature ovary or ovaries of one or more flowers. They are found in three main anatomical categories: aggregate fruits, multiple fruits, and simple fruits. A ...

of the fruit hosts between 25 and 30 prominent vascular bundles which run longitudinally along the fruit surface. Also, as is typical of ''Rhus'' species, the fruits are flattened along the plane of symmetry and elliptic in cross section. The funicular depression where the petiole would have attached is located in the plane of symmetry, and so is a corresponding bulge on the opposite side of the fruit.

References

{{Taxonbar, from=Q16758136 †rooseae Prehistoric angiosperms Plants described in 1994 Fossil taxa described in 1994 Eocene plants Flora of Oregon Extinct flora of North America Clarno Formation