''Coryloides'' is an

extinct Extinction is the termination of an organism by the death of its Endling, last member. A taxon may become Functional extinction, functionally extinct before the death of its last member if it loses the capacity to Reproduction, reproduce and ...

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

flowering plant Flowering plants are plants that bear flowers and fruits, and form the clade Angiospermae (). The term angiosperm is derived from the Ancient Greek, Greek words (; 'container, vessel') and (; 'seed'), meaning that the seeds are enclosed with ...

s in the

hazelnut The hazelnut is the fruit of the hazel tree and therefore includes any of the nuts deriving from species of the genus '' Corylus'', especially the nuts of the species ''Corylus avellana''. They are also known as cobnuts or filberts according to ...

family,

Betulaceae Betulaceae, the birch family, includes six genera of deciduous nut-bearing trees and shrubs, including the birches, alders, hazels, hornbeams, hazel-hornbeam, and hop-hornbeams, numbering a total of 167 species. They are mostly natives of ...

, containing the single species ''Coryloides hancockii''. The species is solely known from the

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

sediments exposed in north central

Oregon Oregon ( , ) is a U.S. state, state in the Pacific Northwest region of the United States. It is a part of the Western U.S., with the Columbia River delineating much of Oregon's northern boundary with Washington (state), Washington, while t ...

and 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 preserve ...

nuts 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 prec ...

History and classification

''Coryloides hancockii'' has been identified from a single location in the

Clarno Formation John Day Fossil Beds National Monument is a National monument (United States), U.S. national monument in Wheeler County, Oregon, Wheeler and Grant County, Oregon, Grant counties in east-central Oregon. Located within the John Day River basin an ...

, the Clarno nut beds, type locality 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 middle Eocene in age, based on averaging zircon fission track

radiometric dating Radiometric dating, radioactive dating or radioisotope dating is a technique which is used to Chronological dating, date materials such as Rock (geology), rocks or carbon, in which trace radioactive impurity, impurities were selectively incorporat ...

which yielded an age of 43.6 and 43.7 ± 10

million years ago Million years ago, abbreviated as Mya, Myr (megayear) or Ma (megaannum), is a unit of time equal to (i.e. years), or approximately 31.6 teraseconds. Usage Myr is in common use in fields such as Earth science and cosmology. Myr is also used w ...

and

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

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 co ...

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 genus and species was described from a series of type specimens, the

holotype A holotype (Latin: ''holotypus'') is a single physical example (or illustration) of an organism used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of s ...

specimen UF 8497, which is currently preserved in the paleobotanical collections of the

University of Florida The University of Florida (Florida or UF) is a public university, public land-grant university, land-grant research university in Gainesville, Florida, United States. It is a senior member of the State University System of Florida and a preem ...

and thirty-seven

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 (biology), isotype ...

specimens. Eight of the paratypes are also in the University of Florida collections, while twenty-five are in the

National Museum of Natural History The National Museum of Natural History (NMNH) 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. With 4.4 ...

collections, two are deposited at the

Burke Museum of Natural History and Culture The Burke Museum of Natural History and Culture (commonly as Burke Museum) is a natural history museum on the campus of the University of Washington, in Seattle, Washington, United States. It is administered by the UW College of Arts and Scien ...

and the remaining specimen is part of the

University of Michigan The University of Michigan (U-M, U of M, or Michigan) is a public university, public research university in Ann Arbor, Michigan, United States. Founded in 1817, it is the oldest institution of higher education in the state. The University of Mi ...

, Museum of Paleontology. The fossils were part of a group of approximately 20,000 specimens collected from 1942 to 1989 by Thomas Bones, Alonzo W. Hancock, R. A. Scott, Steven R. Manchester, and a number of high school students. The ''Coryloides'' specimens were studied by

paleobotanist Paleobotany or palaeobotany, also known as paleophytology, is the branch of botany dealing with the recovery and identification of plant fossils from geological contexts, and their use for the biological reconstruction of past environments (pale ...

Steven R. Manchester of the University of Florida. He published his 1994 type description for ''C. hancockii'' in the journal '' Palaeontographica Americana''. In his type description Manchester noted the generic name is derived from similarity of the fossils to the nuts of ''

Corylus Hazels are plants of the genus ''Corylus'' of deciduous trees and large shrubs native to the temperate Northern Hemisphere. The genus is usually placed in the birch family, Betulaceae,Germplasmgobills Information Network''Corylus''Rushforth, ...

''. The

specific epithet In Taxonomy (biology), taxonomy, binomial nomenclature ("two-term naming system"), also called binary nomenclature, is a formal system of naming species of living things by giving each a name composed of two parts, both of which use Latin gramm ...

''hancockii'' was chosen in honor of the amateur paleobotanist Alonzo W. Hancock, for his work establishing the field station next to the Clarno Nut Beds. Though originally informally identified as palm fruits, ''Coryloides'' is considered either to have been a sister genus of the hazelnuts in ''Corylus'', or as an example of parallel evolution in the subfamily

Coryloideae Coryloideae is a subfamily in the woody angiosperm family Betulaceae, commonly known as the birch family, and consists of four extant genera - '' Corylus'' L., '' Ostryopsis'' Decne., ''Carpinus'' L., and ''Ostrya'' Scop. These deciduous trees an ...

Description

The nuts of ''Coryloides hancockii'' are nearly perfectly spherical and rounded at both the apex and base. The nuts have an overall length ranging between and a diameter between . The nuts are unilocular in structure, containing a solitary nut. The nuts have an outer hull showing strong ribbing from base to apex and which are spaced about apart at the nut equator. The wall of the nut is thick and a large vascular bundle corresponds to each of the external ribs. The base is dominated by a circular basal scar in diameter and a stylar protrusion in diameter at the apex. The vascular bundles, unilocular nut and fruit, and circular detachment scar on the nut base are all features seen in the modern genus ''Corylus'', but the larger nut size and the nearly perfectly spherical nature of the nut are not seen in ''Corylus''.

References

{{Taxonbar, from=Q16752104 Betulaceae Prehistoric angiosperm genera Fossil taxa described in 1994 Eocene plants Flora of Oregon Monotypic Fagales genera Extinct flora of North America Prehistoric plants of North America Clarno Formation