''Rhus republicensis'' 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 ...

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 ...

. The species is known from

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 ...

leaves found in the early

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'', " ...

deposits of northern

Washington state Washington (), officially the State of Washington, is a state in the Pacific Northwest region of the Western United States. Named for George Washington—the first U.S. president—the state was formed from the western part of the Washingto ...

in the United States. The species was first described from

leaves found in the

Klondike Mountain Formation The Klondike Mountain Formation is an Early Eocene (Ypresian) geological formation located in the northeast central area of Washington state. The formation, named for the type location designated in 1962, Klondike Mountain north of Republic, Wash ...

. ''R. republicensis'' likely hybridized with the other Klondike Mountain formation sumac species '' Rhus boothillensis'', '' Rhus garwellii'', and '' Rhus malloryi''.

Distribution and paleoenvironment

''Rhus republicensis'' is known from specimens which are recovered from an outcrop of the early Eocene,

Ypresian In the geologic timescale the Ypresian is the oldest age or lowest stratigraphic stage of the Eocene. It spans the time between , is preceded by the Thanetian Age (part of the Paleocene) and is followed by the Eocene Lutetian Age. The Ypresian i ...

in Republic. The Klondike Mountain Formation preserves an upland temperate flora which was first interpreted as being

microthermal In climatology, the term microthermal is used to denote the continental climates of Eurasia and North America. Etymology The word ''microthermal'' is derived from two Greek words meaning "small" and "heat". This is misleading, however, since the t ...

, however further study has shown the flora to be more

mesothermal In climatology, the term mesothermal is used to refer to certain forms of climate found typically in the Earth's temperate zones. It has a moderate span of temperature, with winters not cold enough to sustain snow cover. Summers are warm within o ...

in nature. The plant community preserved in the Klondike Mountain formation is a mixed conifer–broadleaf forest with large pollen elements of

birch A birch is a thin-leaved deciduous hardwood tree of the genus ''Betula'' (), in the family Betulaceae, which also includes alders, hazels, and hornbeams. It is closely related to the beech- oak family Fagaceae. The genus ''Betula'' contains 3 ...

and

golden larch ''Pseudolarix amabilis'' is a species of coniferous tree in the pine family Pinaceae. The species is commonly known as golden larch, but being more closely related to ''Keteleeria'', ''Abies'' and ''Cedrus'', is not a true larch (''Larix''). ''P ...

, but also having notable traces of

fir Firs (''Abies'') are a genus of 48–56 species of evergreen coniferous trees in the family Pinaceae. They are found on mountains throughout much of North and Central America, Europe, Asia, and North Africa. The genus is most closely related to ...

spruce A spruce is a tree of the genus ''Picea'' (), a genus of about 35 species of coniferous evergreen trees in the family Pinaceae, found in the northern temperate and boreal ( taiga) regions of the Earth. ''Picea'' is the sole genus in the sub ...

cypress Cypress is a common name for various coniferous trees or shrubs of northern temperate regions that belong to the family Cupressaceae. The word ''cypress'' is derived from Old French ''cipres'', which was imported from Latin ''cypressus'', the la ...

, and

palm Palm most commonly refers to: * Palm of the hand, the central region of the front of the hand * Palm plants, of family Arecaceae ** List of Arecaceae genera * Several other plants known as "palm" Palm or Palms may also refer to: Music * Palm (b ...

Taxonomy

The species was described from a

type specimen 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 the ...

, 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 ...

leaf, number SR 10-29-20 A&B, plus a pair

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, SR 92-05-05 and SR 97-03-15 A&B. The type series specimens are currently preserved in the

paleobotanical 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 ...

collections of the

Stonerose Interpretive Center The Stonerose Interpretive center & Eocene Fossil Site is a 501c(3) non-profit public museum and fossil dig located in Republic, Washington. The center was established in 1989 and houses fossils that have been featured in ''National Geographic ...

Republic, Washington Republic is a city in Ferry County, Washington, United States. The population was 1,073 at the 2010 census, a 12.5% increase over the 2000 census. It is the county seat of Ferry County. It was the largest mining camp in the Republic Mining Di ...

. The 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 ...

s Soon Flynn and Kathleen Pigg of

Arizona State University Arizona State University (Arizona State or ASU) is a public research university in the Phoenix metropolitan area. Founded in 1885 by the 13th Arizona Territorial Legislature, ASU is one of the largest public universities by enrollment in t ...

with Melanie DeVore of

Georgia College and State University Georgia College & State University (Georgia College or GC) is a public liberal arts university in Milledgeville, Georgia. The university enrolls approximately 7,000 students and is a member of the University System of Georgia and the Council o ...

. They published their 2019

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. republicensis'' in the ''

International Journal of Plant Sciences The ''International Journal of Plant Sciences'' covers botanical research including genetics and genomics, developmental and cell biology, biochemistry and physiology, morphology and structure, systematics, plant-microbe interactions, paleobotany ...

''. The

etymology Etymology () The New Oxford Dictionary of English (1998) – p. 633 "Etymology /ˌɛtɪˈmɒlədʒi/ the study of the class in words and the way their meanings have changed throughout time". is the study of the history of the form of words ...

of the chosen specific name ''republicensis'' is a reference to Republic, Washington where the collecting site is located. In addition to ''Rhus republicensis'' Flynn ''et al'' also provided descriptions of the coeval species '' Rhus boothillensis'' and '' Rhus garwellii'' and gave a redescription of '' Rhus malloryi'' in the 2019 paper. They noted that the Klondike Mountain Formation preserves a number of ''Rhus'' specimens which appear to be hybrids of the named species.

Description

''Rhus republicensis'' leaves are

pinnately compound Pinnation (also called pennation) is the arrangement of feather-like or multi-divided features arising from both sides of a common axis. Pinnation occurs in biological morphology, in crystals, such as some forms of ice or metal crystals, and in ...

on a long petiole, with a possible total length of for full leaves. The subopposite leaflets are

sessile Sessility, or sessile, may refer to: * Sessility (motility), organisms which are not able to move about * Sessility (botany), flowers or leaves that grow directly from the stem or peduncle of a plant * Sessility (medicine), tumors and polyps that ...

on the

rachis In biology, a rachis (from the grc, ῥάχις [], "backbone, spine") is a main axis or "shaft". In zoology and microbiology In vertebrates, ''rachis'' can refer to the series of articulated vertebrae, which encase the spinal cord. In this c ...

between the flared wings that bracket the midvein. The leaflets are obovoid to ovoid in outline, tapering from the wide middle to both the base and apex. They have a width of and a length to width ratio of up to 3.1:1. The midveins of the leaflets are narrow and pass all the way to the leaflet apex, with smaller secondary veins branching off the midvein at acute angles. The narrow secondaries are spaced on the midvein unevenly and group closer together near the leaflet tip, while usually branching once near the leaflet margin. The branches of the secondaries enter a tooth or the sinus between two teeth. The teeth are rounded on their tips with convex basal and apical sides running towards variable sinuses. The teeth become more developed and closer spaced towards the tip of the leaflet. The leafy wings of the rachis have secondary veins that angle steeply towards the leaf tip and occasionally forking.

References

{{Taxonbar, from=Q96401734 †republicensis Prehistoric angiosperms Plants described in 2019 Ypresian plants of North America Extinct flora of North America Fossil taxa described in 2019 Klondike Mountain Formation