''Shirleya'' 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 ...

genus in the

crape myrtle ''Lagerstroemia'' (), commonly known as crape myrtle (also spelled crepe myrtle or crêpe myrtle), is a genus of around 50 species of deciduous and evergreen trees and shrubs native to the Indian subcontinent, southeast Asia, northern Australia ...

family,

Lythraceae Lythraceae is a family of flowering plants, including 32 genera, with about 620 species of herbs, shrubs, and trees. The larger genera include ''Cuphea'' (275 spp.), ''Lagerstroemia'' (56), ''Nesaea'' (50), ''Rotala'' (45), and ''Lythrum'' (35). ...

, which contains a single species, ''Shirleya grahamae''. The genus and species are known from

Middle Miocene The Middle Miocene is a sub-epoch of the Miocene Epoch made up of two stages: the Langhian and Serravallian stages. The Middle Miocene is preceded by the Early Miocene. The sub-epoch lasted from 15.97 ± 0.05 Ma to 11.608 ± 0.005 Ma (million y ...

fossils found in Central Washington.

History and classification

The species was first described from specimens of silicified fruits preserved in chert of the "Yakima Canyon Flora". The chert was recovered from the type locality "Hi hole" site, one of the "county line hole" fossil localities of the "Yakima Canyon Flora" located north of Interstate 82 in Yakima County, Washington. The "Hi hole" site works strata was formerly 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 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 ...

, Columbia River Basalt Group. The Museum Flow Package interbeds are dated to the

middle Miocene The Middle Miocene is a sub-epoch of the Miocene Epoch made up of two stages: the Langhian and Serravallian stages. The Middle Miocene is preceded by the Early Miocene. The sub-epoch lasted from 15.97 ± 0.05 Ma to 11.608 ± 0.005 Ma (million y ...

and are approximately 15.6 million years old. Later re-evaluation of the "Hi hole" site indicated that the site is included into a basalt flow, having deposited into pockets and crevasses on the surface of the flow, rather than being 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 confirmed that the deposits worked are pockets within the basalt flows, and the 15.6 million year old date was accurate. At the time of study, the holotype fruit, specimen UWBM 55134, and a series of paratype specimens were preserved in the Burke Museum of Natural History and Culture while additional paratypes, and examined fossils that were not part of the type series, were part of the paleobotanical collections at

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 the ...

. 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 fully enclosed fruits in chert. A total of over 24 specimens in or preserved by chert were studied by paleobotanists Kathleen Pigg and Melanie DeVore, with their 2005

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''. Pigg and DeVore coined the genus name ''Shirleya'' and 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 ...

''grahamae'' as a

matronym A matronymic is a personal name based on the given name of one's mother, grandmother, or any female ancestor. It is the female equivalent of a patronymic. Around the world, matronymic surnames are far less common than patronymic surnames. In som ...

honoring Shirley A. Graham, then of the Missouri Botanical Garden in

St. Louis, Missouri St. Louis () is the second-largest city in Missouri, United States. It sits near the confluence of the Mississippi River, Mississippi and the Missouri Rivers. In 2020, the city proper had a population of 301,578, while the Greater St. Louis, ...

for her work and "significant contributions" to the family Lythraceae. Based on similarities to the living genus ''

Lagerstroemia ''Lagerstroemia'' (), commonly known as crape myrtle (also spelled crepe myrtle or crêpe myrtle), is a genus of around 50 species of deciduous and evergreen trees and shrubs native to the Indian subcontinent, southeast Asia, northern Australia ...

'', Pigg and DeVore placed ''Shirleya'' into Lythraceae, with no indication of a subfamily assignment. While ''Shirleya'' has a number of features that are similar to ''Lagerstroemia'', there are also several distinct features. The fruits have a thicker pericarp that is similar to the genera '' Duabanga'' and '' Sonneratia'' which have berry-like fruits, but ''Shirleya'' fruits were

dehiscent Dehiscence is the splitting of a mature plant structure along a built-in line of weakness to release its contents. This is common among fruits, anthers and sporangia. Sometimes this involves the complete detachment of a part; structures that op ...

, unlike the berry-like fruits, as indicated by several isolated silicified fruit valves. The seeds in ''Shirleya'' fruits develop near the tops of the fruit gynoecium with wings extending down towards the gynoecium base, while in ''Lagerstroemia'' the seeds develop in reverse position, with the wing extending from the seed towards the top of the gynoecium. These differences lead Pigg and DeVore to place the fossils in a new genus.

Description

The fruits of ''Shirleya'' range up to long and have a diameter of up to giving a subglobose outline. The central axis of the fruit is mostly a

parenchyma Parenchyma () is the bulk of functional substance in an animal organ or structure such as a tumour. In zoology it is the name for the tissue that fills the interior of flatworms. Etymology The term ''parenchyma'' is New Latin from the word π ...

tous pith that forms a star shape. The fruits have between five and seven wedge shaped

locule A locule (plural locules) or loculus (plural loculi) (meaning "little place" in Latin) is a small cavity or compartment within an organ or part of an organism (animal, plant, or fungus). In angiosperms (flowering plants), the term ''locule'' usu ...

s or minute chambers surrounding the central axis and narrow dehiscence slits which split on maturity, breaking the fruit into sections of two locule halves and the joining septum. Each locule contains between five and seven mature seeds plus occasional smaller seeds. The seeds are tightly packed into each locule and hang down from the apical area of the locule with wings curving out from the axis. The seeds are up to in length with a tail or hook on both the

proximal and distal Standard anatomical terms of location are used to unambiguously describe the anatomy of animals, including humans. The terms, typically derived from Latin or Greek roots, describe something in its standard anatomical position. This position ...

ends, and a wing that make up approximately two-thirds of the seed length. The seed wings each have a central bilobed parenchymatous mass that surrounds a central cavity.

References

{{Taxonbar, from=Q21397193 Extinct flora of North America Flora of North America

† A dagger, obelisk, or obelus is a typographical mark that usually indicates a footnote if an asterisk has already been used. The symbol is also used to indicate death (of people) or extinction (of species). It is one of the modern descendan ...

Fossil taxa described in 2005 Lythraceae Lythraceae genera Miocene plants Plants described in 2005 Monotypic Myrtales genera