''Rhus malloryi'' is an

extinct Extinction is the termination of a kind of organism or of a group of kinds (taxon), usually a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and ...

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 ...

flowering plant Flowering plants are plants that bear flowers and fruits, and form the clade Angiospermae (), commonly called angiosperms. The term "angiosperm" is derived from the Greek words ('container, vessel') and ('seed'), and refers to those plants th ...

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 Eas ...

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 (geology), epoch that lasted from about 56 to 33.9 million years ago (mya). It is the second epoch of the Paleogene Period (geology), Period in the modern Cenozoic Era (geology), Era. The name ''Eocene' ...

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 Washington ...

, United States. The species was first described from a series of isolated

leaves in

shale Shale is a fine-grained, clastic sedimentary rock formed from mud that is a mix of flakes of clay minerals (hydrous aluminium phyllosilicates, e.g. kaolin, Al2 Si2 O5( OH)4) and tiny fragments (silt-sized particles) of other minerals, especial ...

. ''R. malloryi'' is one of four sumac species to be described from 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 ...

, and forms a hybrid complex with the other three species.

Taxonomy

''Rhus malloryi'' 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 (geology), age or lowest stage (stratigraphy), stratigraphic stage of the Eocene. It spans the time between , is preceded by the Thanetian Age (part of the Paleocene) and is followed by th ...

Republic A republic () is a "state in which power rests with the people or their representatives; specifically a state without a monarchy" and also a "government, or system of government, of such a state." Previously, especially in the 17th and 18th c ...

. 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 oc ...

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 30 ...

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''). ' ...

, but also having notable traces of

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

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 subfami ...

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 ...

, 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 (ba ...

. Fossils of ''Rhus malloryi'', along with fossil

Sapindaceae The Sapindaceae are a family of flowering plants in the order Sapindales known as the soapberry family. It contains 138 genera and 1858 accepted species. Examples include horse chestnut, maples, ackee and lychee. The Sapindaceae occur in tempera ...

leaves, were first published under the name ''"Dipteronia americana"'' by Roland W. Brown in 1935. The coeval fossil species ''

Rhus mixta 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 Eas ...

'' is noted to have a more linear shape and distinct secondary vein structure. The species was described from a

type specimen In biology, a type is a particular wiktionary:en:specimen, 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 a ...

, 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 several ...

leaf, number UWBM 39718, and a group of five

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). Of ...

specimens. The holotype and three of the paratypes are currently preserved in the paleobotanical collections of 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 ...

Seattle, Washington Seattle ( ) is a port, seaport city on the West Coast of the United States. It is the county seat, seat of King County, Washington, King County, Washington (state), Washington. With a 2020 population of 737,015, it is the largest city in bo ...

. 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 Jack A. Wolfe of the United States Geological Survey, Denver office and

Wesley C. Wehr Wesley Conrad Wehr (April 17, 1929 – April 12, 2004) was an American paleontology, paleontologist and artist best known for his studies of Cenozoic paleobotany, fossil floras in western North America, the Stonerose Interpretive Center, and as ...

of the Burke Museum. Wolfe and Wehr published their 1987

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 ...

for ''R. malloryi'' in the ''United states Geological Survey Bulletin 1597''. 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 Phonological chan ...

of the chosen specific name ''malloryi'' is in recognition of former chairman of the Burke Museum paleontology collections V. Standish Mallory. An additional three coeval species, '' Rhus boothillensis'', '' Rhus garwellii'' and '' Rhus republicensis'' were described by Flynn ''et al'' in 2019. They also provided a redescription of ''Rhus malloryi'' while noting that the Klondike Mountain Formation preserves a number of ''Rhus'' specimens which appear to be hybrids of the named species.

Description

Overall the leaflets of ''R. malloryi'' are elliptical to lanceolate, with a symmetrical shape, an asymmetrical base and a short petiolule. The

leaf A leaf ( : leaves) is any of the principal appendages of a vascular plant stem, usually borne laterally aboveground and specialized for photosynthesis. Leaves are collectively called foliage, as in "autumn foliage", while the leaves, ste ...

lets have a pinnate vein structure with the secondary veins display a gradually curving, looping structure typical of Anacardiaceae. The margins of the leaflets are serrated and have the simple teeth are spaced to one tooth per secondary vein loop. Veinlets from the secondary veins either enter the teeth centrally or enter the sinuses between teeth. Higher veins in the leaflets tend to thin rapidly or are indistinct, in contrast to the secondary vein structure of ''Rhus mixta'' which has stronger secondary veins.

References

{{Taxonbar, from=Q16758135 †malloryi Prehistoric angiosperms Plants described in 1987 Ypresian plants of North America Extinct flora of North America Fossil taxa described in 1987 Klondike Mountain Formation