Acer hillsi
Encyclopedia
Acer hillsi is an extinct maple
species
in the family Sapindaceae
described from a single fossil
samara
. The species is solely known from the Early Eocene sediments exposed in south central British Columbia
, Canada adjacent to northeast Washington State, USA. It is one of only two species belonging to the extinct section Stewarta.
location UWBM A0307, an outcrop of the early Eocene, Ypresian
Klondike Mountain Formation
in Republic
. The UWBM A0307 site is known as the "Corner lot" locality. The section Stewarta is known only from A. hillsi and the related species A. stewarti
described from the Ypresian Allenby Formation exposed near Princeton, British Columbia
. Both the Allenby and Klondike Mountain Formations preserve upland temperate floras which were first interpreted as being microthermal
, however further study has shown them to be more mesothermal
in nature. The plant community preserved in the Klondike Mountain formation is a mixed conifer–broadleaf forest with large pollen elements of birch
and golden larch, but also having notable traces of fir
, spruce
, cypress
, and palm
. The Allenby formation is similar with the birch and golden larch as strong pollen signals and traces of fir and spruce, however the cypress and palm are not distinct signals. The species were known only from the Republic and Princeton fossil localities respectively when first described. Of the two species, A. hillsi is only known from the samara fossils while A. stewarti has been described from both leaves and samaras. The two are among a number of Acer species described from the Republic and Princeton sites by Wolfe and Tanai.
The species was described from a solitary type specimen, the holotype
samara, number UWBM 56260 A, B, which is currently preserved in the paleobotanical
collections housed at the Burke Museum, part of the University of Washington
in Seattle. The specimen was studied by paleobotanists Jack A. Wolfe
of the United States Geological Survey, Denver office
and Toshimasa Tanai of Hokkaido University
. Wolfe and Tanai published their 1987 type description for A. hillsi in the Journal of the Faculty of Science, Hokkaido University. The etymology
of the chosen specific name
hillsi is in recognition L. V. Hills who allowed Wolf and Tanai access to his extensive fossil collection and for his contributions to paleobotany and palynology.
. While very similar in morphology to A. stewarti, the two related species can be separated by the overall nutlet morphology, with A. hillsi having an asymmetrically inflated nutlet of more ovoid outline while A. stewarti has a fully inflated nutlet of circular outline.
Maple
Acer is a genus of trees or shrubs commonly known as maple.Maples are variously classified in a family of their own, the Aceraceae, or together with the Hippocastanaceae included in the family Sapindaceae. Modern classifications, including the Angiosperm Phylogeny Group system, favour inclusion in...
species
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
in the family Sapindaceae
Sapindaceae
Sapindaceae, also known as the soapberry family, is a family of flowering plants in the order Sapindales. There are about 140-150 genera with 1400-2000 species, including maple, horse chestnut and lychee....
described from a single fossil
Fossil
Fossils are the preserved remains or traces of animals , plants, and other organisms from the remote past...
samara
Samara (fruit)
A samara is a type of fruit in which a flattened wing of fibrous, papery tissue develops from the ovary wall. A samara is a simple dry fruit and indehiscent . It is a winged achene...
. The species is solely known from the Early Eocene sediments exposed in south central British Columbia
British Columbia
British Columbia is the westernmost of Canada's provinces and is known for its natural beauty, as reflected in its Latin motto, Splendor sine occasu . Its name was chosen by Queen Victoria in 1858...
, Canada adjacent to northeast Washington State, USA. It is one of only two species belonging to the extinct section Stewarta.
Taxonomy
Acer hillsi is known from one single specimen which was recovered from the the Burke Museum of Natural History and CultureBurke Museum of Natural History and Culture
The Burke Museum of Natural History and Culture has been a Washington state museum since 1899. It is located at the University of Washington campus at the intersection of N.E. 45th Street and 17th Avenue N.E. in Seattle, Washington, USA, in the University District. It is the only major natural...
location UWBM A0307, an outcrop of the early Eocene, Ypresian
Ypresian
In the geologic timescale the Ypresian is the oldest age or lowest stratigraphic stage of the Eocene. It spans the time between and , is preceded by the Thanetian age and is followed by the Eocene Lutetian age....
Klondike Mountain Formation
Klondike Mountain Formation
The Klondike Mountain Formation is an early Eocene geologic formation that records the sedimentation in the southern most of a string of highland subtropical/Temperate lakes in Washington state and British Columbia. The formation is best known for exceptionally well preserved plant and insect fossils...
in Republic
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.-History:...
. The UWBM A0307 site is known as the "Corner lot" locality. The section Stewarta is known only from A. hillsi and the related species A. stewarti
Acer stewarti
Acer stewarti is an extinct maple species in the family Sapindaceae described from a series of fossil leaves and samaras. The species is solely known from the Early Eocene sediments exposed in south central British Columbia, Canada adjacent to northeast Washington State, USA...
described from the Ypresian Allenby Formation exposed near Princeton, British Columbia
Princeton, British Columbia
Princeton is a small town in the Similkameen region of southern British Columbia, Canada. It lies just east of the Cascade Mountains, which continue south into Washington, Oregon and California. The Tulameen and Similkameen Rivers converge here...
. Both the Allenby and Klondike Mountain Formations preserve upland temperate floras which were first interpreted as being microthermal
Microthermal
In climatology, the term microthermal is used to denote the continental climates of Eurasia and North America.The word microthermal is derived from two Greek words meaning "having little heat." This is misleading, however, since the term is intended to describe only the temperature conditions that...
, however further study has shown them to be more mesothermal
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 amount of heat, with winters not cold enough to sustain snow cover...
in nature. The plant community preserved in the Klondike Mountain formation is a mixed conifer–broadleaf forest with large pollen elements of birch
Birch
Birch is a tree or shrub of the genus Betula , in the family Betulaceae, closely related to the beech/oak family, Fagaceae. The Betula genus contains 30–60 known taxa...
and golden larch, but also having notable traces of fir
Fir
Firs are a genus of 48–55 species of evergreen conifers in the family Pinaceae. They are found through much of North and Central America, Europe, Asia, and North Africa, occurring in mountains over most of the range...
, spruce
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 regions of the earth. Spruces are large trees, from tall when mature, and can be distinguished by their whorled branches and conical...
, cypress
Taxodium
Taxodium is a genus of one to three species of extremely flood-tolerant conifers in the cypress family, Cupressaceae...
, and palm
Arecaceae
Arecaceae or Palmae , are a family of flowering plants, the only family in the monocot order Arecales. There are roughly 202 currently known genera with around 2600 species, most of which are restricted to tropical, subtropical, and warm temperate climates...
. The Allenby formation is similar with the birch and golden larch as strong pollen signals and traces of fir and spruce, however the cypress and palm are not distinct signals. The species were known only from the Republic and Princeton fossil localities respectively when first described. Of the two species, A. hillsi is only known from the samara fossils while A. stewarti has been described from both leaves and samaras. The two are among a number of Acer species described from the Republic and Princeton sites by Wolfe and Tanai.
The species was described from a solitary type specimen, the holotype
Holotype
A holotype is a single physical example of an organism, known to have been used when the species was formally described. It is either the single such physical example or one of several such, but explicitly designated as the holotype...
samara, number UWBM 56260 A, B, which is currently preserved in the paleobotanical
Paleobotany
Paleobotany, also spelled as palaeobotany , is the branch of paleontology or paleobiology dealing with the recovery and identification of plant remains from geological contexts, and their use for the biological reconstruction of past environments , and both the evolutionary history of plants, with a...
collections housed at the Burke Museum, part of the University of Washington
University of Washington
University of Washington is a public research university, founded in 1861 in Seattle, Washington, United States. The UW is the largest university in the Northwest and the oldest public university on the West Coast. The university has three campuses, with its largest campus in the University...
in Seattle. The specimen was studied by paleobotanists Jack A. Wolfe
Jack A. Wolfe
Jack Albert Wolfe was an American paleontologist best known for his studies of Tertiary climate in western North America through analysis of fossil angiosperm leaves.-External links:...
of the United States Geological Survey, Denver office
United States Geological Survey
The United States 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, and the natural hazards that threaten it. The organization has four major science disciplines, concerning biology,...
and Toshimasa Tanai of Hokkaido University
Hokkaido University
Hokkaido University is one of the most prestigious universities in Japan. It can be seen in the several rankings such as shown below.-General Rankings:...
. Wolfe and Tanai published their 1987 type description for A. hillsi in the Journal of the Faculty of Science, Hokkaido University. The etymology
Etymology
Etymology is the study of the history of words, their origins, and how their form and meaning have changed over time.For languages with a long written history, etymologists make use of texts in these languages and texts about the languages to gather knowledge about how words were used during...
of the chosen specific name
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
hillsi is in recognition L. V. Hills who allowed Wolf and Tanai access to his extensive fossil collection and for his contributions to paleobotany and palynology.
Description
The samaras of A. hillsi have an indistinct flange along the notably asymmetrically inflated nutlet and acutely diverging veins which rarely anastomise. The general shape of the nutlet is ovoid. The overall length of the samara is approximately 2.5 centimetre (0.984251968503937 in) and a wing width of 1 centimetre (0.393700787401575 in). The paired samaras of the species have a 40° attachment angle and the distal region region of the nutlet and wing forming a broad sulcusSulcus
Sulcus may refer to:* Sulcus , a groove, crevice or furrow in medicine, botany, and zoology* Sulcus , a long parallel groove on a planet or a moon-See also:...
. While very similar in morphology to A. stewarti, the two related species can be separated by the overall nutlet morphology, with A. hillsi having an asymmetrically inflated nutlet of more ovoid outline while A. stewarti has a fully inflated nutlet of circular outline.