''Tilia johnsoni'' 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 of

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 family

Malvaceae Malvaceae, or the mallows, is a family of flowering plants estimated to contain 244 genera with 4225 known species. Well-known members of economic importance include okra, cotton, cacao and durian. There are also some genera containing familiar ...

that, as a member of the genus ''

Tilia ''Tilia'' is a genus of about 30 species of trees or bushes, native throughout most of the temperateness, temperate Northern Hemisphere. The tree is known as linden for the European species, and basswood for North American species. In Britain a ...

'', is related to modern lindens (called "limes" in Britain and "

basswood ''Tilia americana'' is a species of tree in the family Malvaceae, native to eastern North America, from southeast Manitoba east to New Brunswick, southwest to northeast Oklahoma, southeast to South Carolina, and west along the Niobrara River to ...

s" in the US). 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 and a similar aged formation in

British Columbia British Columbia (commonly abbreviated as BC) is the westernmost province of Canada, situated between the Pacific Ocean and the Rocky Mountains. It has a diverse geography, with rugged landscapes that include rocky coastlines, sandy beaches, ...

, Canada.

History and classification

''Tilia johnsoni'' leaf fossils have been identified from two locations in Western North America, the 49 million year old

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 ...

near

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 Distr ...

and at the Quilchena locality near

Merritt, British Columbia Merritt is a city in the Nicola Valley of the south-central Interior of British Columbia, Canada. It is northeast of Vancouver. Situated at the confluence of the Nicola and Coldwater rivers, it is the first major community encountered after ...

. Fossil pollen identified as from the genus ''Tilia'' has been identified from a greater range of

Okanagan Highland The Okanagan Highland is an elevated hilly plateau area in British Columbia, Canada, and the U.S. state of Washington (where it is spelled Okanogan Highlands). Rounded mountains with elevations up to above sea level and deep, narrow valleys are ...

fossil sites, having been found in the

Allenby Formation The Allenby formation is a sedimentary rock formation in British Columbia which was deposited during the Ypresian stage of the Early Eocene. It consists of conglomerates, sandstones with interbedded shales and coal. The shales contain an abun ...

near

Princeton, British Columbia Princeton (originally Vermilion Forks) is a town in the Similkameen region of southern British Columbia, Canada."The rich history of Princeton or how Vermilion Forks made it on the map...", Princeton 2008 Visitors Guide, p. 4. It lies just east o ...

, at the Falkland fossil site near Falkland, the

McAbee Fossil Beds The McAbee Fossil Beds is a Heritage Site that protects an Eocene Epoch fossil locality east of Cache Creek, British Columbia, Canada, just north of and visible from Provincial Highway 97 / the Trans-Canada Highway ( Highway 1). The McAbee Fos ...

near

Kamloops Kamloops ( ) is a city in south-central British Columbia, Canada, at the confluence of the South flowing North Thompson River and the West flowing Thompson River, east of Kamloops Lake. It is located in the Thompson-Nicola Regional District, w ...

, the Hat Creek Amber and

Driftwood Canyon Provincial Park Driftwood Canyon Provincial Park is a provincial park in British Columbia, Canada. Driftwood Canyon Provincial Park covers 23 ha of the Bulkley River Valley, on the east side of Driftwood Creek, a tributary of the Bulkley River, 10 km nort ...

near

Smithers Smithers is a surname of English origin. It derives from the Middle English term "smyther", referring to a metalsmith, and is thus related to the common occupational surname Smith. The name Smither is related. People *Alan Smithers (born 1938), ...

. Of the Okanagan Highlands sites, ''Tilia'' microfossils and macrofossils have not been identified from the Horsefly fossil beds near the unincorporated community of Horsefly. The age for the Okanagan Highland locations is, in general,

Early Eocene 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 ...

, with the sites that have current uranium-lead or argon–argon radiometric dates being of

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 ...

age, while the undated sites or those given older dates being possibly slightly younger and

Lutetian The Lutetian is, in the geologic timescale, a stage or age in the Eocene. It spans the time between . The Lutetian is preceded by the Ypresian and is followed by the Bartonian. Together with the Bartonian it is sometimes referred to as the Midd ...

in age. ''Tilia johnsoni'' was described from a single

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 ...

, a leaf, 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 ...

being UW 39712, 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

Burke Museum 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 ...

, and its

counterpart Counterpart or Counterparts may refer to: Entertainment and literature * "Counterparts" (short story), by James Joyce * Counterparts, former name for the Reel Pride LGBT film festival * ''Counterparts'' (film), a 2007 German drama * ''Counterp ...

UCMP 9291 in the

University of California Museum of Paleontology The University of California Museum of Paleontology (UCMP) is a paleontology museum located on the campus of the University of California, Berkeley. The museum is within the Valley Life Sciences Building (VLSB), designed by George W. Kelham and ...

California California is a U.S. state, state in the Western United States, located along the West Coast of the United States, Pacific Coast. With nearly 39.2million residents across a total area of approximately , it is the List of states and territori ...

. Working from this specimen, collected in the Republic, Washington area in the early 1980s, the fossil was studied by Jack A. Wolfe of the

University of California The University of California (UC) is a public land-grant research university system in the U.S. state of California. The system is composed of the campuses at Berkeley, Davis, Irvine, Los Angeles, Merced, Riverside, San Diego, San Francisco, ...

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. They 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 the species in a

United States Geological Survey The United States Geological Survey (USGS), formerly simply known as the Geological Survey, is a scientific agency of the United States government. The scientists of the USGS study the landscape of the United States, its natural resources, ...

monograph A monograph is a specialist work of writing (in contrast to reference works) or exhibition on a single subject or an aspect of a subject, often by a single author or artist, and usually on a scholarly subject. In library cataloging, ''monograph ...

on the North Eastern Washington dicot fossils. 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 ...

''johnsoni'' is a

patronym A patronymic, or patronym, is a component of a personal name based on the given name of one's father, grandfather (avonymic), or an earlier male ancestor. Patronymics are still in use, including mandatory use, in many countries worldwide, alt ...

recognizing the help provided to Wolfe and Wehr by a young

Kirk Johnson Kirk Cyron Johnson (born June 29, 1972) is a Canadian former professional boxer who competed from 1993 to 2010, and challenged once for the World Boxing Association, WBA heavyweight title in 2002. Amateur career Johnson represented Canada at ...

, now director of the Smithsonian's

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 7 ...

. Wolfe and Wehr noted that, at the time of publication, ''T. johnsoni'' was the oldest macrofossil occurrence for the genus to be described,; older microfossil records of pollen date near to the Paleocene – Eocene boundary, and fruits of an extinct ''Tilia'' relative are known from the Eocene of England.

Description

The type leaf of ''Tilia johnsoni'' is palmate in venation with an overall orbicular shape, cordate blade base and acute blade tip. The central primary vein is flanked by three pairs of lateral primary veins and the margin of the leaf has evenly spaced, distinctly shaped teeth with rounded

sinuses Paranasal sinuses are a group of four paired air-filled spaces that surround the nasal cavity. The maxillary sinuses are located under the eyes; the frontal sinuses are above the eyes; the ethmoidal sinuses are between the eyes and the sphenoid ...

separating them. The inner most set of lateral primary veins run parallel to the median secondary veins, broadly curving upwards and with three secondary veins branching off the exterior side. The branched secondaries run parallel to the next lateral primary vein. The tertiary veins run perpendicular to the secondary veins with an even spacing, while the quaternary veins are orthogonal to the tertiaries forming reticulated pattern of pentagonal and quadrangular spaces.

References

{{Taxonbar, from=Q7802148 Ypresian plants of North America Extinct flora of North America Flora of North America † † Fossil taxa described in 1987 Plants described in 1987 johnsoni Klondike Mountain Formation