Boletus fibrillosus is a basidiomycete

Basidiomycota

Basidiomycota is one of two large phyla that, together with the Ascomycota, comprise the subkingdom Dikarya within the Kingdom Fungi...

 fungus

Fungus

A fungus is a member of a large group of eukaryotic organisms that includes microorganisms such as yeasts and molds , as well as the more familiar mushrooms. These organisms are classified as a kingdom, Fungi, which is separate from plants, animals, and bacteria...

 of the genus

Genus

In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...

 Boletus

Boletus

Boletus is a genus of mushroom, comprising over 100 species. The genus Boletus was originally broadly defined and described by Elias Magnus Fries in 1821, essentially containing all fungi with pores...

found in western North America

North America

North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...

. The fruiting bodies

Basidiocarp

In fungi, a basidiocarp, basidiome or basidioma , is the sporocarp of a basidiomycete, the multicellular structure on which the spore-producing hymenium is borne. Basidiocarps are characteristic of the hymenomycetes; rusts and smuts do not produce such structures...

 are found in mixed coastal forests in the fall. The cap

Pileus (mycology)

The pileus is the technical name for the cap, or cap-like part, of a basidiocarp or ascocarp that supports a spore-bearing surface, the hymenium. The hymenium may consist of lamellae, tubes, or teeth, on the underside of the pileus...

 is up to 17 cm wide, buff to brown to dark brown in color, and has a wrinkled to finely fibrous texture. The tubes are yellow, while the flesh is white to buff and does not stain when cut. The stem

Stipe (mycology)

thumb|150px|right|Diagram of a [[basidiomycete]] stipe with an [[annulus |annulus]] and [[volva |volva]]In mycology a stipe refers to the stem or stalk-like feature supporting the cap of a mushroom. Like all tissues of the mushroom other than the hymenium, the stipe is composed of sterile hyphal...

 is yellow at the top, brown otherwise, and has a reticulate texture. 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...

 was collected in Mendocino County, California

Mendocino County, California

Mendocino County is a county located on the north coast of the U.S. state of California, north of the greater San Francisco Bay Area and west of the Central Valley. As of the 2010 census, the population was 87,841, up from 86,265 at the 2000 census...

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Phylogenetic

Phylogenetics

In biology, phylogenetics is the study of evolutionary relatedness among groups of organisms , which is discovered through molecular sequencing data and morphological data matrices...

 analysis has shown B. fibrillosus as a member of a clade

Clade

A clade is a group consisting of a species and all its descendants. In the terms of biological systematics, a clade is a single "branch" on the "tree of life". The idea that such a "natural group" of organisms should be grouped together and given a taxonomic name is central to biological...

, or closely related group, with B. pinophilus

Boletus pinophilus

Boletus pinophilus, commonly known as the pine bolete or pinewood king bolete, is a basidiomycete fungus of the genus Boletus found throughout Europe. The large, edible fruiting bodies known as mushrooms appear under pine trees, generally in summer and autumn...

, B. regineus

Boletus regineus

Boletus regineus, commonly known as the queen bolete, is an edible and highly regarded fungus of the Boletus family that inhabits southwestern North America. It was considered a variant of the similarly edible B. edulis for many years until declared a unique species in 2008. Phylogenetic analysis...

, B. rex-veris

Boletus rex-veris

Boletus rex-veris, commonly known as the spring king bolete, is a basidiomycete fungus of the genus Boletus found in western North America. The large, edible fruiting bodies known as mushrooms appear under pine trees, generally in May to June. It has a pinkish to brownish cap and its stem is often...

, B. subcaerulescens

Boletus subcaerulescens

Boletus subcaerulescens is a basidiomycete fungus of the genus Boletus found in northeastern North America. The fruiting bodies are found associated with pine and spruce. The cap is up to 18 cm wide, convex to flat, and brown in color. The tubes are yellow and stain blue when bruised, while...

, and Gastroboletus subalpinus

Gastroboletus subalpinus

Gastroboletus subalpinus is a species of fungus in the family Boletaceae. The species was first described scientifically in 1969 by American mycologists Harry Delbert Thiers and James M. Trappe. It is found in California and Oregon....

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