''Lonchodomas'' is a

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 ...

trilobite Trilobites (; meaning "three lobes") are extinct marine arthropods that form the class Trilobita. Trilobites form one of the earliest-known groups of arthropods. The first appearance of trilobites in the fossil record defines the base of the At ...

s, that lived during the

Ordovician The Ordovician ( ) is a geologic period and System (geology), system, the second of six periods of the Paleozoic Era (geology), Era. The Ordovician spans 41.6 million years from the end of the Cambrian Period million years ago (Mya) to the start ...

. It was eyeless, like all raphiophorids, and had a long straight sword-like frontal spine, that gradually transforms into the relatively long

glabella The glabella, in humans, is the area of skin between the eyebrows and above the nose. The term also refers to the underlying bone that is slightly depressed, and joins the two brow ridges. It is a cephalometric landmark that is just superior to ...

. Both the glabellar spine and the backward directed genal spines are subquadrate in section. ''Lonchodomas'' has five thorax segments and the pleural area of the pygidium has two narrow furrows. ''Lonchodomas'' occurred in what are today

Argentina Argentina (), officially the Argentine Republic ( es, link=no, República Argentina), is a country in the southern half of South America. Argentina covers an area of , making it the second-largest country in South America after Brazil, th ...

Canada Canada is a country in North America. Its ten provinces and three territories extend from the Atlantic Ocean to the Pacific Ocean and northward into the Arctic Ocean, covering over , making it the world's second-largest country by tot ...

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Newfoundland Newfoundland and Labrador (; french: Terre-Neuve-et-Labrador; frequently abbreviated as NL) is the easternmost province of Canada, in the country's Atlantic region. The province comprises the island of Newfoundland and the continental region ...

Estonia Estonia, formally the Republic of Estonia, is a country by the Baltic Sea in Northern Europe. It is bordered to the north by the Gulf of Finland across from Finland, to the west by the sea across from Sweden, to the south by Latvia, a ...

Latvia Latvia ( or ; lv, Latvija ; ltg, Latveja; liv, Leţmō), officially the Republic of Latvia ( lv, Latvijas Republika, links=no, ltg, Latvejas Republika, links=no, liv, Leţmō Vabāmō, links=no), is a country in the Baltic region of ...

Norway Norway, officially the Kingdom of Norway, is a Nordic country in Northern Europe, the mainland territory of which comprises the western and northernmost portion of the Scandinavian Peninsula. The remote Arctic island of Jan Mayen and t ...

Sweden Sweden, formally the Kingdom of Sweden,The United Nations Group of Experts on Geographical Names states that the country's formal name is the Kingdom of SwedenUNGEGN World Geographical Names, Sweden./ref> is a Nordic country located on ...

, the

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Leningrad Oblast Leningrad Oblast ( rus, Ленинградская область, Leningradskaya oblast’, lʲɪnʲɪnˈgratskəjə ˈobləsʲtʲ, , ) is a federal subjects of Russia, federal subject of Russia (an oblast). It was established on 1 August 1927, a ...

A.V. Krylov (2003).
New data on trilobites from Hecker mud mounds (Ordovician) in the Leningrad region (in Russian)
. ''Vestnik Sankt-Petersburgskogo Universiteta, Seriya Geologiya i Geografiya'' 3(33):95-96) and the

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Oklahoma Oklahoma (; Choctaw language, Choctaw: ; chr, ᎣᎧᎳᎰᎹ, ''Okalahoma'' ) is a U.S. state, state in the South Central United States, South Central region of the United States, bordered by Texas on the south and west, Kansas on the nor ...

Virginia Virginia, officially the Commonwealth of Virginia, is a state in the Mid-Atlantic and Southeastern regions of the United States, between the Atlantic Coast and the Appalachian Mountains. The geography and climate of the Commonwealth ar ...

Distribution

* ''L. carinatus'' is found in the Upper Ordovician of the United States (Lower Member and Botetourt limestone Member, of the Edinburgh Formation, Shenandoah County, Virginia, 39.0° N, 78.4° W Blackriveran 460.9 - 449.5 Ma) * ''L. clavulus'' is present in the Middle Ordovician of Newfoundland, Canada (''

Histiodella kristinae ''Histiodella'' is an extinct genus of conodonts. ''Histiodella wuhaiensis'' is from the Ordovician of the Lower Klimoli Formation in China.Ordovician conodonts from Dashimen, Wuhai in Inner Mongolia and the significance of the discovery of th ...

'' conodont zone,

Table Cove Formation The Table Cove Formation is a geologic formation in Newfoundland and Labrador. It preserves fossils dating back to the Ordovician period Period may refer to: Common uses * Era, a length or span of time * Full stop (or period), a punctuation m ...

; Table Point, "Middle Table Head" and Table Cove). * ''L. mcgeheei'' is present in the Upper Ordovician of Oklahoma, United States (

Bromide Formation The Bromide Formation is a geological formation in Oklahoma, USA. It is well known for its diverse echinoderm and trilobite fossil fauna. Location The Bromide Formation crops out in the Arbuckle and Wichita Mountains and in the Criner Hills ...

, Sandbian). * ''L. retrolatus'' was collected from the Ordovician of Nevada (Eureka Quartzite, sandy limestone, 60–90 ft above base, Ranger Mountains, Nevada Test Site)) * ''L. rostratus'' is known from the Upper Ordovician of Estonia (Narva open pit, and Lasnamägi, Kukruse Stage, Sandbian) and Latvia (Remte 3 borehole, and Adze 6 borehole, Kukruse Stage,

Sandbian The Sandbian is the first stage of the Upper Ordovician. It follows the Darriwilian and is succeeded by the Katian. Its lower boundary is defined as the first appearance datum of the graptolite species '' Nemagraptus gracilis'' around million yea ...

). * ''L. suriensis'' was excavated from the Middle Ordovician of Argentina (Portillo del Cajón, Cerro Morado; Cerro Suri; Puesto El Despacho; Las Pircas; all

La Rioja La Rioja () is an autonomous community and province in Spain, in the north of the Iberian Peninsula. Its capital is Logroño. Other cities and towns in the province include Calahorra, Arnedo, Alfaro, Haro, Santo Domingo de la Calzada, and N� ...

) * ''L. volborthi'' occurs in the Lower Ordovician of the Russian Federation (Volkhovian level,

Syas River The Syas () is a river in Lyubytinsky District of Novgorod Oblast and Tikhvinsky and Volkhovsky Districts of Leningrad Oblast, Russia. The Syas flows from the Valdai Hills north into Lake Ladoga. The town of Syasstroy is located at its mouth. It ...

, Putilovo and Babino quarries, St.Petersburg region). It was originally described as ''Ampyx volborthi'' but assigned to ''Lonchodomas'' in 1952 by Steinar Skjeseth.Steinar Skjeseth, 1952.
On the lower Didymograptus zone (3B) at Ringsaker, and contemporaneous deposits in Scandinavian
: ''Norsk geol. tidsskr''., v. 30, p. 138 — 182.

Description

Like all raphiophorids, ''Lonchodomas'' is eyeless. The headshield (or

cephalon Cephalon, Inc. was an American biopharmaceutical company co-founded in 1987 by pharmacologist Frank Baldino, Jr., neuroscientist Michael Lewis, and organic chemist James C. Kauer—all three former scientists with the DuPont Company. Baldino s ...

) and tailshield (or

pygidium The pygidium (plural 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 compo ...

) are subtriangular in outline. ''Lonchodomas'' looks a lot like

Ampyx In Greek mythology, Ampyx (Ancient Greek: Ἄμπυξ) or Ampycus (Ἄμπυκος ''Ampykos'' means 'woman's diadem, frontlet') was the name of the following figures: * Ampyx, also called Ampycus or AmpyceHesiod, ''Shield of Heracles'' 180 was a ...

but the glabella is diamond-shaped in outline, and it has a ridge along the midline (it is carinate). The glabella gradually transforms into the spine, which makes it difficult to determine where the spine begins. The long median glabellar spine is subquadrate in section and is directed horizontally forward, from the frontal tip of the glabella. The glabella has 2 pairs of muscle scars. The genal spines are also subquadrate in section. The thorax has 5 segments. The pleural regions of pygidium have 2 pairs of narrow pleural furrows.

References

{{Taxonbar, from=Q6669670 Raphiophoridae Asaphida genera Ordovician trilobites Fossils of Argentina Fossils of Estonia Fossils of Latvia Fossils of Norway Fossils of Russia Fossils of the United States Bromide Formation Paleozoic life of Newfoundland and Labrador Paleozoic life of the Northwest Territories Paleozoic life of Quebec Paleozoic life of Yukon