''Palaeoagaracites'' is an

extinct Extinction is the termination of a kind of organism or of a group of kinds (taxon), usually a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and ...

monotypic In biology, a monotypic taxon is a taxonomic group (taxon) that contains only one immediately subordinate taxon. A monotypic species is one that does not include subspecies or smaller, infraspecific taxa. In the case of genera, the term "unispec ...

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...

of gilled

fungus A fungus ( : fungi or funguses) is any member of the 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, separately from th ...

in the order Agaricales. It contains the single

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 ...

''Palaeoagaracites antiquus''. The genus is solely known from the

Lower Cretaceous Lower may refer to: *Lower (surname) *Lower Township, New Jersey *Lower Receiver (firearms) *Lower Wick Lower Wick is a small hamlet located in the county of Gloucestershire, England. It is situated about five miles south west of Dursley, eig ...

, Upper Albian stage (about 100 Ma),

Burmese amber Burmese amber, also known as Burmite or Kachin amber, is amber from the Hukawng Valley in northern Myanmar. The amber is dated to around 100 million years ago, during the latest Albian to earliest Cenomanian ages of the mid-Cretaceous period. The ...

deposits in

Myanmar Myanmar, ; UK pronunciations: US pronunciations incl. . Note: Wikipedia's IPA conventions require indicating /r/ even in British English although only some British English speakers pronounce r at the end of syllables. As John C. Wells, Joh ...

. ''Palaeoagaracites'' is one of only five known agaric fungal species known in the fossil record, the oldest to be described, and only genus from Burmese amber.

History and classification

The genus is known only from the single

holotype A holotype is a single physical example (or illustration) of an organism, known to have been used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of several ...

, number "''AB-368''", a single partial

fruiting body The sporocarp (also known as fruiting body, fruit body or fruitbody) of fungi is a multicellular structure on which spore-producing structures, such as basidia or asci, are borne. The fruitbody is part of the sexual phase of a fungal life cy ...

specimen. When described the

mushroom A mushroom or toadstool is the fleshy, spore-bearing fruiting body of a fungus, typically produced above ground, on soil, or on its food source. ''Toadstool'' generally denotes one poisonous to humans. The standard for the name "mushroom" is t ...

was in the private collection of Ron Buckley of

Florence, Kentucky Florence is a home rule-class city in Boone County, Kentucky, United States. Florence is the second largest city located in Northern Kentucky, after Covington, and part of the Greater Cincinnati Metropolitan Area. The population was 31,946 at ...

, United States. The collection has since been sold and is now owned by Deniz Erin of

Istanbul, Turkey ) , postal_code_type = Postal code , postal_code = 34000 to 34990 , area_code = +90 212 (European side) +90 216 (Asian side) , registration_plate = 34 , blank_name_sec2 = GeoTLD , blank_in ...

.Fossil page of Ron Buckley
Retrieved 7 December 2010 ''AB-368'' was collected from one of the amber mines in the

Hukawng Valley The Hukawng Valley ( my, ဟူးကောင်းချိုင့်ဝှမ်း; also spelt Hukaung Valley) is an isolated valley in Myanmar, roughly in area. It is located in Tanaing Township in the Myitkyina District of Kachin State ...

area southwest of Maingkhwan,

Kachin State Kachin State ( my, ကချင်ပြည်နယ်; Kachin: ), also known by the endonym Kachinland, is the northernmost state of Myanmar. It is bordered by China to the north and east (Tibet and Yunnan, specifically and respectively); Sh ...

, Northern

. It was first studied by a pair of researchers led by Dr George Poinar from

Oregon State University Oregon State University (OSU) is a public land-grant, research university in Corvallis, Oregon. OSU offers more than 200 undergraduate-degree programs along with a variety of graduate and doctoral degrees. It has the 10th largest engineering co ...

who worked with Ron Buckley. Poinar and Buckley published their 2007

type description A species description is a formal description of a newly discovered species, usually in the form of a scientific paper. Its purpose is to give a clear description of a new species of organism and explain how it differs from species that have be ...

in '' Mycological Research'', a journal of the

British Mycological Society The British Mycological Society is a learned society established in 1896 to promote the study of fungi. Formation The British Mycological Society (BMS) was formed by the combined efforts of two local societies: the Woolhope Naturalists' Field ...

. The genus has been assigned the

MycoBank MycoBank is an online database, documenting new mycological names and combinations, eventually combined with descriptions and illustrations. It is run by the Westerdijk Fungal Biodiversity Institute in Utrecht. Each novelty, after being screened ...

number ''MB510456'', and the species number ''MB510465''. The genus name ''Palaeoagaracites'' is

Greek Greek may refer to: Greece Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group. *Greek language, a branch of the Indo-European language family. **Proto-Greek language, the assumed last common ancestor ...

in derivation and is a combination of the words ''palaeo'' meaning "old" and ''agaricon'', which means "fungus". The specific epithet ''antiquus'' is

Latin Latin (, or , ) is a classical language belonging to the Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through the power of the ...

for "old". When published, ''Palaeoagaracites antiquus'' was the fifth species of extinct agaric fungus to be described, and the oldest. The three species '' Aureofungus yaniguaensis'', ''

Coprinites dominicana ''Coprinites'' is an extinct monotypic genus of gilled fungus in the Agaricales family Agaricaceae. At present it contains the single species ''Coprinites dominicana''. The genus is solely known from the early Miocene, Burdigalian stage, Dom ...

'' and '' Protomycena electra'' are known from the

Burdigalian The Burdigalian is, in the geologic timescale, an age (geology), age or stage (stratigraphy), stage in the early Miocene. It spans the time between 20.43 ± 0.05 annum, Ma and 15.97 ± 0.05 Ma (million years ago). Preceded by the Aquitanian (sta ...

amber mines of the

Dominican Republic The Dominican Republic ( ; es, República Dominicana, ) is a country located on the island of Hispaniola in the Greater Antilles archipelago of the Caribbean region. It occupies the eastern five-eighths of the island, which it shares wit ...

, while the fourth species '' Archaeomarasmius leggeti'' is from the slightly younger

Turonian The Turonian is, in the ICS' geologic timescale, the second age in the Late Cretaceous Epoch, or a stage in the Upper Cretaceous Series. It spans the time between 93.9 ± 0.8 Ma and 89.8 ± 1 Ma (million years ago). The Turonian is preceded b ...

age

New Jersey Amber New Jersey Amber, sometimes called Raritan amber, is amber found in the Raritan and Magothy Formations of the Central Atlantic (Eastern) coast of the United States. It is dated to the Late Cretaceous, Turonian age, based on pollen analysis of t ...

Description

The holotype of ''Palaeoagaracites'' is a single, partly decomposed

fruit body In botany, a fruit is the seed-bearing structure in flowering plants that is formed from the ovary after flowering. Fruits are the means by which flowering plants (also known as angiosperms) disseminate their seeds. Edible fruits in particu ...

without any associated structures preserved in a rectangular piece of yellow amber approximately by by . The pileus is in diameter and has a convex shape. The

flesh Flesh is any aggregation of soft tissues of an organism. Various multicellular organisms have soft tissues that may be called "flesh". In mammals, including humans, ''flesh'' encompasses muscles, fats and other loose connective tissues, but ...

is a bluish-gray color, hairy, and radially furrowed with sixteen grooves visible on the intact section of pileus. The margin is curved slightly inward. The

lamellae Lamella (plural lamellae) means a small plate or flake in Latin, and in English may refer to: Biology * Lamella (mycology), a papery rib beneath a mushroom cap * Lamella (botany) * Lamella (surface anatomy), a plate-like structure in an animal * ...

, or gills, though slightly decomposed, are subdivided into short sections ranging from 85 μm to 110 μm in length. The stipe was not preserved with the cap. The

basidiospore A basidiospore is a reproductive spore produced by Basidiomycete fungi, a grouping that includes mushrooms, shelf fungi, rusts, and smuts. Basidiospores typically each contain one haploid nucleus that is the product of meiosis, and they are ...

s, present as both light and dark colored spores on the gill sides, are smooth and oval. Each basidiospore is approximately 3 to 4.5 μm long. While mature light colored spores are present in many agarics, darker colored mature spores are found in some genera. ''Palaeoagaracites'' presents the oldest, and only, evidence of fungal

parasitism Parasitism is a Symbiosis, close relationship between species, where one organism, the parasite, lives on or inside another organism, the Host (biology), host, causing it some harm, and is Adaptation, adapted structurally to this way of lif ...

by other fungi in the fossil record. The fossil displays a complex interrelationship between three different fungal genera. The preserved ''P. antiquus'' cap is host to both a mycoparasitic fungus and a hypermycoparasitic fungus. The surface of the ''Palaeoagaracites'' specimen hosts the extinct

necrotroph A fungus ( : fungi or funguses) is any member of the 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, separately from t ...

fungus '' Mycetophagites atrebora''. The

mycelia Mycelium (plural mycelia) is a root-like structure of a fungus consisting of a mass of branching, thread-like hyphae. Fungal colonies composed of mycelium are found in and on soil and many other substrates. A typical single spore germinates ...

of ''Mycetophagites'' are found across the surface of the ''P. antiquus'' pileus, and the hyphae penetrate into the ''P. antiquus'' tissues themselves forming necrotic areas. ''Mycetophagites'' is in turn host to a hypermycoparasitic necrotrophic fungus species '' Entropezites patricii''. Hyphae of ''Entropezites'' are preserved penetrating the ''Mycetophagites'' hyphae, forming areas of decomposing tissue. ''Entropezites'' also displays a range of growth stages for probable

zygospore A zygospore is a diploid reproductive stage in the life cycle of many fungi and protists. Zygospores are created by the nuclear fusion of haploid cells. In fungi, zygospores are formed in zygosporangia after the fusion of specialized budding struc ...

s. The combined distinguishable characters of ''Palaeoagaracites'' were not enough for Poinar and Buckley to place the genus further than Agaricales ''

incertae sedis ' () or ''problematica'' is a term used for a taxonomic group where its broader relationships are unknown or undefined. Alternatively, such groups are frequently referred to as "enigmatic taxa". In the system of open nomenclature, uncertain ...

''. The overall size, shape of the spores, and structure of the cap hint at a relationship to the genera ''

Mycena ''Mycena'' is a large genus of small saprotrophic mushrooms that are rarely more than a few centimeters in width. They are characterized by a white spore print, a small conical or bell-shaped cap, and a thin fragile stem. Most are gray or br ...

'', ''

Marasmius ''Marasmius'' is a genus of mushroom-forming fungi in the family Marasmiaceae. It contains about 500 species of agarics, of which a few, such as '' Marasmius oreades'', are edible. However, most members of this genus are small, unimpressive ...

'' and '' Collybia''.

References

{{Taxonbar, from=Q21078887, from2=Q7126386 †Palaeoagaracites Agaricales enigmatic taxa †Palaeoagaracites Prehistoric fungi Fossil taxa described in 2007 Natural history of Myanmar Cretaceous fungi Burmese amber Fossils of Myanmar Taxa named by George Poinar Jr.