''Equisetum similkamense'' is an extinct horsetail

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 Equisetaceae described from a group of whole plant

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 ...

s including rhizomes, stems, and leaves. The species is known from

Ypresian In the geologic timescale the Ypresian is the oldest age (geology), age or lowest stage (stratigraphy), stratigraphic stage of the Eocene. It spans the time between , is preceded by the Thanetian Age (part of the Paleocene) and is followed by th ...

sediments exposed in

British Columbia British Columbia (commonly abbreviated as BC) is the westernmost province of Canada, situated between the Pacific Ocean and the Rocky Mountains. It has a diverse geography, with rugged landscapes that include rocky coastlines, sandy beaches, ...

, Canada. It is one of several extinct species placed in the living genus ''Equisetum''.

History and classification

Fossils of ''Equisetum similkamense'' were collected during field work in 1877 from outcrops of the Allenby Formation along Nine Mile Creek near Princeton. These were examined and described by John William Dawson (1879) as a new species based on stems, leaves, and rhizomes. Dawson did not give an etymology for the species name in the type description, though the type locality of Nine Mile Creek is a tributary of Whipsaw Creek, a tributary in turn of the

Similkameen River The Similkameen River runs through southern British Columbia, Canada, eventually discharging into the Okanagan River near Oroville, Washington, in the United States. Through the Okanagan River, it drains to the Columbia River. The river is said ...

. Dawson (1890) reprinted his description of the species with some elaboration of the details and included drawn illustrations of representative fossils. Dawson (1879) notes ''E. similkamense'' to be most similar to varieties of the Miocene species '' Equisetum winkleri'' from

Tjörnes Tjörnes () is a peninsula situated at the northeast of Iceland, between the fjords of Öxarfjörður and Skjálfandi. Tjörnes is known for its particularly dense population of Rock Ptarmigan and the rich fossil record of Miocene - Pliocene ag ...

, Iceland and '' Equisetum limosellum'' from Öhningen, Germany. Dawson (1890) also suggested the possibility of '' Equisetum globulosum'', described by Lesquereux from Paleocene Alaskan fossils, might be of the same species. However Dawson cited the incomplete nature of the Alaskan fossils and the more globose nature of the rhizomes there as reason not to make a firm comparison.

Distribution and paleoecology

''Equisetum similkamense'' is known from a series of specimens which were recovered from a single formation in the Eocene Okanagan Highlands, outcrops of the

Allenby Formation around

Princeton, British Columbia Princeton (originally Vermilion Forks) is a town in the Similkameen region of southern British Columbia, Canada."The rich history of Princeton or how Vermilion Forks made it on the map...", Princeton 2008 Visitors Guide, p. 4. It lies just east o ...

. In addition to the type locality on Nine Mile Creek, an additional find of ''E. similkamense'' was reported by Melcon (1975) from outcrops of

brecciated Breccia () is a rock composed of large angular broken fragments of minerals or rocks cemented together by a fine-grained matrix. The word has its origins in the Italian language, in which it means "rubble". A breccia may have a variety of di ...

shale Shale is a fine-grained, clastic sedimentary rock formed from mud that is a mix of flakes of clay minerals (hydrous aluminium phyllosilicates, e.g. kaolin, Al2 Si2 O5( OH)4) and tiny fragments (silt-sized particles) of other minerals, especial ...

near Glacier Lake in Cathedral Provincial Park. The Allenby Formation preserves an upland lake system surrounded by a mixed conifer–broadleaf forest with nearby volcanism. The highlands likely had a mesic upper microthermal to lower mesothermal climate, in which winter temperatures rarely dropped low enough for snow, and which were seasonably equitable. The Okanagan Highlands paleoforest surrounding the lakes have been described as precursors to the modern temperate broadleaf and mixed forests of Eastern North America and Eastern Asia. Based on the fossil biotas the lakes were higher and cooler than the

coeval {{Short pages monitor