''Hedstroemia '' is a

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

trilobite Trilobites (; meaning "three-lobed entities") are extinction, extinct marine arthropods that form the class (biology), class Trilobita. One of the earliest groups of arthropods to appear in the fossil record, trilobites were among the most succ ...

s in the order

Proetida Proetida is an order of trilobite that lived from the Ordovician to the Permian. It was the last surviving order of trilobite, dying out in the Permian-Triassic extinction event. Description These typically small trilobites resemble those of ...

known from the

Silurian period The Silurian ( ) is a geologic period and system spanning 23.5 million years from the end of the Ordovician Period, at million years ago ( Mya), to the beginning of the Devonian Period, Mya. The Silurian is the third and shortest period of t ...

of Europe, Asia, and North America.

Taxonomic history

The genus ''Hedstroemia'' was named in 1978. The

type species In International_Code_of_Zoological_Nomenclature, zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the spe ...

designated was ''Hedstroemia delicatus'', which had originally been described as ''Proetus delicatus'' in 1923. In 1990 the subgenus ''Pachyproetus'' was proposed to accommodate a single species, ''P. pachydermata.'' In 1994, the genus ''Milesdavis'' was proposed based on incomplete fossils consisting of the

pygidium The pygidium (: pygidia) is the posterior body part or shield of crustaceans and some other arthropods, such as insects and the extinct trilobites. In groups other than insects, it contains the anus and, in females, the ovipositor. It is compos ...

(rear segment) of three individuals. The genus was named after musician

Miles Davis Miles Dewey Davis III (May 26, 1926September 28, 1991) was an American jazz trumpeter, bandleader, and composer. He is among the most influential and acclaimed figures in the history of jazz and 20th century music, 20th-century music. Davis ado ...

, and the

, ''Milesdavis eldredgei'', was named in honor of the paleontologist

Niles Eldredge Niles Eldredge ( ; born August 25, 1943) is an American biologist and paleontologist, who, along with Stephen Jay Gould, proposed the theory of punctuated equilibrium in 1972. Education Eldredge began his undergraduate studies in Latin at Colum ...

. In 1997, ''Milesdavis'' and the subgenus ''Pachyproetus'' were recognized as

junior synonyms In taxonomy, the scientific classification of living organisms, a synonym is an alternative scientific name for the accepted scientific name of a taxon. The botanical and zoological codes of nomenclature treat the concept of synonymy differently. ...

of ''Hedstroemia'', by paleontologist Jonathan Adrain, who regarded the type species of both as ingroup ''Hedstroemia''.

Species

Several species of ''Hedstroemia'' are recognized, and other species are questionably assigned to the genus. Species names with the

authority Authority is commonly understood as the legitimate power of a person or group of other people. In a civil state, ''authority'' may be practiced by legislative, executive, and judicial branches of government,''The New Fontana Dictionary of M ...

in parentheses were originally described as a different genus. *''H. delicata'' (Hedström, 1923) *''H. eldredgei'' (Lieberman, 1994) *''H. kulchini'' Ludvigsen & Tripp, 1990 *''H. pachydermata'' (Barret, 1878) *''H. planedorsata'' (Schmidt, 1894) *''H. sourdoughi'' Ludvigsen & Tripp, 1990 *''H. sugiharensis'' (Kobayashi & Hamada, 1974) *''H. weedoni'' Adrain, 1997 Questionable species *?''H. channahonensis'' (Weller, 1907) *?''H. zlichoviana'' (Pribyl, 1966)

References

Proetidae Proetida genera Fossil taxa described in 1978 Silurian trilobites Prehistoric life of Europe {{proetida-stub