Acer beckianum
| Acer beckianum Temporal range:
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|---|---|
Scientific classification 
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| Kingdom: | Plantae |
| Clade: | Tracheophytes |
| Clade: | Angiosperms |
| Clade: | Eudicots |
| Clade: | Rosids |
| Order: | Sapindales |
| Family: | Sapindaceae |
| Genus: | Acer |
| Species: | A. beckianum
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| Binomial name | |
| Acer beckianum Prakash & Barghoorn, 1961
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Acer beckianum is an extinct maple species in the family Sapindaceae described from a single fossil wood section. The species is solely known from the Middle Miocene sediments exposed in central Washington State, USA. It is one of three Washington state Acer species described in 1961 from petrified wood.
History and classification
The type specimen was part of a collection compiled by Jay O'Leary, who was then a student of Harvard College, in 1954 from the west bank of the Columbia river in the area of Vantage, Washington.[1] The petrified woods of the area are preserved in an interbed area between the older Grande Ronde Basalt and the younger Wanapum basalts, with the interbed overlain by the Ginkgo Flow,[2] the oldest segment of the Frenchman Springs Member of the Wanapum basalts. K–Ar dating performed on the Grande Ronde Basalts gives an age of 15.6 million years old, and dating of the Frenchman Springs Member gives a date of 15.3 million years old.[3] This places the vantage woods as from the Langhian stage of the Miocene.[2] Mean annual temperature estimates for the vantage paleoclimate were made based on analysis of the fossil wood. Based on a series of wood anatomy characters, a temperature range between 15.8–16.2 °C (60.4–61.2 °F). This is distinctly warmer then the modern mean annual temperature of 8.4 °C (47.1 °F).[3]
The species was described from the 4 cm × 2.5 cm × 3 cm (1.57 in × 0.98 in × 1.18 in) section of mature secondary xylem designated the holotype. The type specimen, number 55226, was preserved in the paleobotanical collections of Harvard College.[1] and was studied by paleobotanists Uttam Prakash of the Birbal Sahni Institute of Palaeobotany and Elso Barghoorn of Harvard University. Prakash and Barghoorn published their 1961 type description for A. beckianum in the Journal of the Arnold Arboretum.[1] The etymology of the chosen specific name beckianum is a patronym honoring George F. Beck, a resident of Yakima, Washington who pioneered the interest and study of the Vantage petrified woods.[1] The species was one of three Acer species described by Prakash and Barghoorn in the paper, along with Acer olearyi and Acer puratanum. Based on the wood anatomy, A. beckianum is closest in structure to Acer negundo, while A. olearyi is closer to Acer grandidentatum and A. puratanum is closest to Acer circinatum.[1]
Description
The wood shows distinct growth rings which are separated from each other by between one and two layers of thick walled flattened fibers. The vessels in the wood are mostly solitary, though can be present in groups of up to five.[1]
References
- ^ a b c d e f Prakash, U.; Barghoorn, E. S. (1961). "Miocene fossil woods from the Columbia Basalts of central Washington". Journal of the Arnold Arboretum. 42 (2): 165–203.
- ^ a b [1] Accessed 17 June 2019
- ^ a b Wiemann, M. C.; Manchester, S. R.; Wheeler, E. A. (1999). "Paleotemperature estimation from dicotyledonous wood anatomical characters". Palaios. 14 (5): 459–474.