Tetracentron hopkinsii

Tetracentron hopkinsii; Temporal range: Ypresian PreꞒ Ꞓ O S D C P T J K Pg N ↓
	Fossil leaf, Klondike Mountain Formation
Scientific classification
Kingdom:	Plantae
Clade:	Tracheophytes
Clade:	Angiosperms
Clade:	Eudicots
Order:	Trochodendrales
Family:	Trochodendraceae
Genus:	Tetracentron
Species:	†T. hopkinsii
Binomial name
	†Tetracentron hopkinsii; Pigg et al, 2007

Last updated November 13, 2021

Tetracentron hopkinsii is an extinct species of flowering plant in the family Trochodendraceae. The species is known from fossil leaves found in the early Eocene deposits of northern Washington state, United States and south Central British Columbia. The species was first described from fossil leaves found in the Allenby Formation. T. hopkinsii are possibly the leaves belonging to the extinct trochodendraceous fruits Pentacentron sternhartae .

Distribution and paleoenvironment

Tetracentron hopkinsii was initially described from two leaves, both recovered from the Early Eocene, Ypresian ^[1] Allenby Formations One Mile Creek outcrop 8 km (5.0 mi) north of Princeton, British Columbia.^[2]^[3] The one mile creek site is notable for being dominated by fossils of Betula leopoldae though Acer species, Rosaceae species, Tsukada davidiifolia , and Ulmus okanaganensis are also present.^[4]

The Allenby Formation preserves an upland temperate flora which was first interpreted as being distinctly microthermal,^[5] however further study has shown the flora to be more upper microthermal to lower mesothermal in nature, with few to no days below freezing in a year.^[1] Analysis of pollen samples shows plant community preserved at the site was mesic mixed conifer–broadleaf forest, with large pollen elements of birch and golden larch, but also having notable traces of fir, spruce, cypress, and palm.^[1] The plants and animals are preserved in a finely layered light greenish-gray lacustrine shale as compression-impression fossils.

Pigg et al noted in 2007 that one leaf assignable to Tetracentron had been found in the Klondike Mountain Formation of Republic, Washington, but was not complete enough to confidently attribute it to T. hopkinsii. The recovery of additional leaves deposited in the Stonerose Interpretive Center allowed Manchester et al to assign the Republic flora specimens to T. hopkinsii in 2018, expanding the confirmed distribution of the species.^[3]

Taxonomy

Examination of the species was performed by Kathleen Pigg, Richard Dillhoff, Melanie DeVore and Wesley Wehr based on the study of the holotype "UWBM 54185" and paratype "UWBM 56700ab" leaves. Both specimens were part of the in the Burke Museum of Natural History and Culture paleobotanical collections at the time of description.^[2] Pigg et al published their 2007 type description of the species in the International Journal of Plant Sciences along with the type description of Trochodendron drachukii . They chose the specific epithet hopkinsii as a patronym honoring Donald Q. Hopkins in recognition for his collecting efforts at both the One Mile Creek site and other sites in the Okanagan highlands floras.^[2]

Along with the 2008 description of Tetracentron atlanticum from the Mid to Late Miocene of Iceland, Grímsson et al documented and figured Tetracentron pollen recovered from the Princeton Chert locality of the Allenby Formation.^[6]

T. hopkinsii is one of between three and four trochodendraceous species that have been described from the Klondike Mountain Formation. Broadly circumscribed, three other species have been identified in the Republic flora, Paraconcavistylon wehrii , Pentacentron sternhartae , and Trochodendron nastae . Additionally the species Trochodendron drachukii is known from related Kamloops group shales at the McAbee Fossil Beds near Cache Creek, British Columbia. Manchester et al 2018 noted that Tr. drachukii is likely the fruits of Tr. nastae, while Pe. sternhartae are likely the fruits of Te. hopkinsii. If fossils of the fruits and foliage in attachment are found, that would bring the species count down to three whole plant taxa.^[3]

Description

The elliptical Tetracentron hopkinsii type specimen leaves have a length to width ratio of 1.3:1, being up to 9.5 cm (3.7 in) in length and up to 7.5 cm (3.0 in). The venation is palmate with one thin midvein and two to three sets of lateral primaries which curve upwards towards the apex. The outermost set of lateral primaries are thin, branching off from the midvein at a 90° angle. Conversely the inter one to two sets of lateral primaries are thicker and arch towards the leaf apex.^[2] The secondary veins which branch off the midvein are thin, and fork out from the midvein at 32°–40° angles before meeting secondaries from the lateral primaries and forming chevrons. The tertiary veins and quaternary veins are percurrent forking at 60° to 70° angles. The margin has regular teeth formed by a convex basal side and a convex apical side which may divide into a subtooth. A persistent gland is present in the tooth tip and which is supplied by a central vein and two converging lateral veins. The robust 4.3 cm (1.7 in) long petiole starts wide at its base, and gradually thins along its length before meeting the leaf in the center of the cordate leaf base.^[2]

Related Research Articles

Trochodendron is a genus of flowering plants with one living species, Trochodendron aralioides, and six extinct species known from the fossil record. It was often considered the sole genus in the family Trochodendraceae, though botanists now also include the distinct genus Tetracentron in the family.

Tetracentron is a genus of flowering plant with a sole living species being Tetracentron sinense and several extinct species. It was formerly considered the sole genus in the family Tetracentraceae, though it is now included in the family Trochodendraceae together with the genus Trochodendron.

Trochodendraceae is the only family of flowering plants in the order Trochodendrales. It comprises two extant genera, each with a single species along with up to five additional extinct genera and a number of extinct species. The living species are native to south east Asia. The two living species both have secondary xylem without vessel elements, which is quite rare in angiosperms. As the vessel-free wood suggests primitiveness, these two species have attracted much taxonomic attention.

Trochodendron nastae is an extinct species of flowering plant in the family Trochodendraceae known from fossil leaves found in the early Eocene Ypresian stage Klondike Mountain Formation deposits of northern Washington state. T. nastae is one of the oldest members of the genus Trochodendron, which includes the living species T. aralioides, native to Japan, southern Korea and Taiwan and the coeval extinct species T. drachukii from the McAbee Fossil Beds near Cache Creek, British Columbia.

Trochodendron drachukii is an extinct species of flowering plants in the family Trochodendraceae known from a fossil fruiting structure found in the early Ypresian age Eocene fossils found in British Columbia, Canada. T. drachukii is one of the oldest members of the genus Trochodendron, which includes the living species T. aralioides, native to Japan, southern Korea and Taiwan and the coeval extinct species T. nastae from Washington state, United States.

Neviusia dunthornei is an extinct species of flowering plants in the family Rosaceae. The species is solely known from the early Eocene, Ypresian stage, Allenby Formation Lacustrine deposits near the town of Princeton, British Columbia.

The Klondike Mountain Formation is an Early Eocene (Ypresian) geological formation located in the northeast central area of Washington state. The formation, named for the type location designated in 1962, Klondike Mountain north of Republic, Washington, is composed of volcanic rocks in the upper unit and volcanics plus lacustrine (lakebed) sedimentation in which a lagerstätte with exceptionally well-preserved plant and insect fossils has been found, along with fossil epithermal hot springs.

Corylopsis reedae is an extinct species of flowering plant in the family Hamamelidaceae known from fossil leaves found in the early Eocene Klondike Mountain Formation deposits of northern Washington state. C. readae is one of the oldest occurrences of the winter-hazel genus Corylopsis, which includes between seven and thirty species, all found in Asia. Fossils from two other occurrences are of similar age to C. readae, with Paleocene specimens from Greenland being placed in the form taxon Corylopsiphyllum and an Eocene Alaskan fossil being included in Corylopsis without species placement.

The McAbee Fossil Beds is a Heritage Site that protects an Eocene Epoch fossil locality east of Cache Creek, British Columbia, Canada, just north of and visible from Provincial Highway 97 / the Trans-Canada Highway. The McAbee Fossil Beds, comprising 548.23 hectares, were officially designated a Provincial Heritage Site under British Columbia's Heritage Conservation Act on July 19, 2012. The site is part of an old lake bed which was deposited about 52 million years ago and is internationally recognised for the diversity of plant, insect, and fish fossils found there. Similar fossil beds in Eocene lake sediments, also known for their well preserved plant, insect and fish fossils, are found at Driftwood Canyon Provincial Park near Smithers in northern British Columbia, on the Horsefly River near Quesnel in central British Columbia, and at Republic in Washington, United States. The Princeton Chert fossil beds in southern British Columbia are also Eocene, but primarily preserve an aquatic plant community. A 2016 review of the early Eocene fossil sites from the interior of British Columbia discusses the history of paleobotanical research at McAbee, the Princeton Chert, Driftwood Canyon, and related Eocene fossil sites such as at Republic.

The Allenby formation is a sedimentary rock formation in British Columbia which was deposited during the Ypresian stage of the Early Eocene. It consists of conglomerates, sandstones with interbedded with shales and coal. The shales contain an abundance of insect, fish and plant fossils known from 1877 and onward, while the Princeton Chert was first indented in the 1950's and is known from anatomically preserved plants.

Rhus malloryi is an extinct species of flowering plant in the sumac family Anacardiaceae. The species is known from fossil leaves found in the early Eocene deposits of northern Washington state, United States. The species was first described from a series of isolated fossil leaves in shale. R. malloryi is one of four sumac species to be described from the Klondike Mountain Formation, and forms a hybrid complex with the other three species.

Tsukada is an extinct genus of flowering plant in the family Nyssaceae related to the modern "dove-tree", Davidia involucrata, containing the single species Tsukada davidiifolia. The genus is known from fossil leaves found in the early Eocene deposits of northern Washington state, United States and a similar aged formation in British Columbia, Canada.

Betula leopoldae is an extinct species of birch in the family Betulaceae. The species is known from fossil leaves, catkins, and inflorescences found in the early Eocene deposits of northern Washington state, United States, and similar aged formations in British Columbia, Canada. The species is placed as basal in Betula, either as a stem group species, or an early divergent species.

Rhus boothillensis is an extinct species of flowering plant in the sumac family Anacardiaceae. The species is known from fossil leaves found in the early Eocene deposits of northern Washington State, United States. The species was first described from fossil leaves found in the Klondike Mountain Formation. Rhus boothillensis likely hybridized with the other Klondike Mountain formation sumac species Rhus garwellii, Rhus malloryi, and Rhus republicensis.

Rhus garwellii is an extinct species of flowering plant in the sumac family Anacardiaceae. The species is known from fossil leaves found in the early Eocene deposits of northern Washington State, United States. The species was first described from fossil leaves found in the Klondike Mountain Formation. R. garwellii likely hybridized with the other Klondike Mountain formation sumac species R. boothillensis, R. malloryi, and R. republicensis.

Rhus republicensis is an extinct species of flowering plant in the sumac family, Anacardiaceae. The species is known from fossil leaves found in the early Eocene deposits of northern Washington state in the United States. The species was first described from fossil leaves found in the Klondike Mountain Formation. R. republicensis likely hybridized with the other Klondike Mountain formation sumac species Rhus boothillensis, Rhus garwellii, and Rhus malloryi.

Pentacentron is an extinct genus of flowering plant in the family Trochodendraceae, consisting of the single species Pentacentron sternhartae. The genus is known from fossil fruits found in the early Eocene deposits of northern Washington state, United States. P. sternhartae are possibly the fruits belonging to the extinct trochodendraceous leaves Tetracentron hopkinsii.

Trochodendron postnastae is an extinct species of flowering plant in the family Trochodendraceae. The species is known from fossils found in Middle Miocene deposits of central Oregon. T. postnastae are possibly the leaves belonging to the extinct trochodendraceous fruits Trochodendron rosayi.

Paraconcavistylon is an extinct genus of flowering plant in the family Trochodendraceae comprises a single species, Paraconcavistylon wehrii. The genus is known from fossil fruits and leaves found in the early Eocene deposits of northern Washington state, United States, and southern British Columbia, Canada. The species was initially described as a member of the related extinct genus Concavistylon as "Concavistylon" wehrii, but subsequently moved to the new genus Paraconcavistylon in 2020 after additional study.

Carpinus perryae is an extinct species of hornbeam known from fossil fruits found in the Klondike Mountain Formation deposits of northern Washington state, dated to the early Eocene Ypresian stage. Based on described features, C. perryae is the oldest definite species in the genus Carpinus.

References

1 2 3 Moss, P. T.; Greenwood, D. R.; Archibald, S. B. (2005). "Regional and local vegetation community dynamics of the Eocene Okanagan Highlands (British Columbia – Washington State) from palynology". Canadian Journal of Earth Sciences. 42 (2): 187–204. Bibcode:2005CaJES..42..187M. doi:10.1139/E04-095.
1 2 3 4 5 Pigg, K.B.; Dillhoff, R.M.; DeVore, M.L.; Wehr, W.C. (2007). "New diversity among the Trochodendraceae from the Early/Middle Eocene Okanogan Highlands of British Columbia, Canada, and Northeastern Washington State, United States". International Journal of Plant Sciences. 168 (4): 521–532. doi:10.1086/512104. S2CID 86524324.
1 2 3 Manchester, S.; Pigg, K. B.; Kvaček, Z; DeVore, M. L.; Dillhoff, R. M. (2018). "Newly recognized diversity in Trochodendraceae from the Eocene of western North America". International Journal of Plant Sciences. 179 (8): 663–676. doi:10.1086/699282. S2CID 92201595.
↑ Dillhoff, R.M.; Dillhoff, T.A.; Greenwood, D.R.; DeVore, M.L.; Pigg, K.B. (2013). "The Eocene Thomas Ranch flora, Allenby Formation, Princeton, British Columbia, Canada". Botany. 91 (8): 514–529. doi:10.1139/cjb-2012-0313.
↑ Wolfe, J.A.; Tanai, T. (1987). "Systematics, Phylogeny, and Distribution of Acer (maples) in the Cenozoic of Western North America". Journal of the Faculty of Science, Hokkaido University. Series 4, Geology and Mineralogy. 22 (1): 1–246.
↑ Grímsson, F.; Denk, T.; Zetter, R. (2008), "Pollen, fruits, and leaves of Tetracentron (Trochodendraceae) from the Cainozoic of Iceland and western North America and their palaeobiogeographic implications", Grana, 73 (2)

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[Moss2005-1] 1 2 3 Moss, P. T.; Greenwood, D. R.; Archibald, S. B. (2005). "Regional and local vegetation community dynamics of the Eocene Okanagan Highlands (British Columbia – Washington State) from palynology". Canadian Journal of Earth Sciences. 42 (2): 187–204. Bibcode:2005CaJES..42..187M. doi:10.1139/E04-095.

[Pigg2007-2] 1 2 3 4 5 Pigg, K.B.; Dillhoff, R.M.; DeVore, M.L.; Wehr, W.C. (2007). "New diversity among the Trochodendraceae from the Early/Middle Eocene Okanogan Highlands of British Columbia, Canada, and Northeastern Washington State, United States". International Journal of Plant Sciences. 168 (4): 521–532. doi:10.1086/512104. S2CID 86524324.

[Pentacentron-3] 1 2 3 Manchester, S.; Pigg, K. B.; Kvaček, Z; DeVore, M. L.; Dillhoff, R. M. (2018). "Newly recognized diversity in Trochodendraceae from the Eocene of western North America". International Journal of Plant Sciences. 179 (8): 663–676. doi:10.1086/699282. S2CID 92201595.

[Thomasranch-4] Dillhoff, R.M.; Dillhoff, T.A.; Greenwood, D.R.; DeVore, M.L.; Pigg, K.B. (2013). "The Eocene Thomas Ranch flora, Allenby Formation, Princeton, British Columbia, Canada". Botany. 91 (8): 514–529. doi:10.1139/cjb-2012-0313.

[Wolfe_&_Tanai_1987-5] Wolfe, J.A.; Tanai, T. (1987). "Systematics, Phylogeny, and Distribution of Acer (maples) in the Cenozoic of Western North America". Journal of the Faculty of Science, Hokkaido University. Series 4, Geology and Mineralogy. 22 (1): 1–246.

[iceland2008-6] Grímsson, F.; Denk, T.; Zetter, R. (2008), "Pollen, fruits, and leaves of Tetracentron (Trochodendraceae) from the Cainozoic of Iceland and western North America and their palaeobiogeographic implications", Grana, 73 (2)

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