''Acer kenaicum'' is an extinct

maple ''Acer'' () is a genus of trees and shrubs commonly known as maples. The genus is placed in the family Sapindaceae.Stevens, P. F. (2001 onwards). Angiosperm Phylogeny Website. Version 9, June 2008 nd more or less continuously updated since http ...

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 ...

in the family

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 ...

described from a pair of

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

and a

samara Samara ( rus, Сама́ра, p=sɐˈmarə), known from 1935 to 1991 as Kuybyshev (; ), is the largest city and administrative centre of Samara Oblast. The city is located at the confluence of the Volga and the Samara (Volga), Samara rivers, with ...

. The species is known solely from the

Oligocene The Oligocene ( ) is a geologic epoch of the Paleogene Period and extends from about 33.9 million to 23 million years before the present ( to ). As with other older geologic periods, the rock beds that define the epoch are well identified but the ...

sediments found exposed in central coastal

Alaska Alaska ( ; russian: Аляска, Alyaska; ale, Alax̂sxax̂; ; ems, Alas'kaaq; Yup'ik: ''Alaskaq''; tli, Anáaski) is a state located in the Western United States on the northwest extremity of North America. A semi-exclave of the U.S., ...

, US. It is one of several extinct species belonging to the living

section Section, Sectioning or Sectioned may refer to: Arts, entertainment and media * Section (music), a complete, but not independent, musical idea * Section (typography), a subdivision, especially of a chapter, in books and documents ** Section sign ...

'' Rubra''.

Taxonomy

''Acer kenaicum'' is known from a pair of leaf specimens and a solitary samara which were recovered from two different outcrops of Early Oligocene strata. The Redoubt Point Flora is part of the

Tyonek Formation The Tyonek Formation is a geologic formation in Alaska. It preserves fossils dating back to the Neogene period. See also * List of fossiliferous stratigraphic units in Alaska * Paleontology in Alaska Paleontology in Alaska refers to paleontolo ...

, while the Tsadaka Canyon belongs to the Tsadaka Formation. While hundreds of fossil leaves were examined from the Redoubt Point flora, only one ''A. kenaicum'' leaf and one samara fossil was identified. In the Tsadaka Canyon flora a single ''A. kenaicum'' leaf was found. An additional leaf fragment, which was to fragmentary to describe to species, but showing morphology seen in the modern ''Acer'' section ''Spicata'' species. The type specimens for ''A. kenaicum'' are 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

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 ...

and paratype fruit from Redoubt point, and the paratype leaf from Tsadaka Canyon, all of which are part slab fossils. At the time of description, all three were preserved in the paleobotanical collections housed at the

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 ...

, part of the Smithsonian. 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 Toshimasa Tanai of

Hokkaido University , or , is a Japanese national university in Sapporo, Hokkaido. It was the fifth Imperial University in Japan, which were established to be the nation's finest institutions of higher education or research. Hokkaido University is considered ...

. Wolfe and Tanai 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 ''A. kenaicum'' in the ''Journal of the Faculty of Science, Hokkaido University''. 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 ''kenaicum'' is a reference to the type locality of the species within the Kenai Group. Based on the characters seen in the leaves and fruits of ''Acer kenaicum'', Wolfe and Tanai suggested the species was a probable ancestral maple for the modern ''

Acer saccharinum ''Acer saccharinum'', commonly known as silver maple, creek maple, silverleaf maple, soft maple, large maple, water maple, swamp maple, or white maple, is a species of maple native to the eastern and central United States and southeastern Canad ...

'' (silver maple). Acer-saccharinum-leaves-e

Description

Leaves of ''Acer kenaicum'' are simple in structure, with perfectly actinodromous vein structure and are widely

ovate Ovate may refer to: *Ovate (egg-shaped) leaves, tepals, or other botanical parts *Ovate, a type of prehistoric stone hand axe *Ovates, one of three ranks of membership in the Welsh Gorsedd *Vates In modern English, the nouns vates () and ovat ...

in shape. The leaves are five-lobed with upper lateral lobes that are two thirds as long as the median lobe. All the lateral lobes are triangular in outline while the medial lobe is elliptic in outline. The leaves have five primary veins, five secondary veins that diverge from the lateral primary veins and six medial secondary vein pairs. The samara of ''A. kenaicum'' has a moderately inflated nutlet and smoothly diverging veins which rarely

anastomise An anastomosis (, plural anastomoses) is a connection or opening between two things (especially cavities or passages) that are normally diverging or branching, such as between blood vessels, leaf veins, or streams. Such a connection may be norma ...

. The overall shape of the nutlet is elliptic with a rounded tip and approximate length of and a wing width of . The paired samaras of the species have a 25° attachment angle and have seven veins originating in the attachment scar of the samara that run the length of the wing.

References

{{Taxonbar, from=Q19871471 kenaicum Plants described in 1987 Fossil taxa described in 1987 Oligocene plants Flora of Alaska Extinct flora of North America