''Elrathia'' is a genus of
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 ...
belonging to
Ptychopariacea
Ptychoparioidea is a superfamily of the Ptychopariida order of trilobites.Pour M. G., Popov L. E. (2009) Silicified Middle Cambrian trilobites from Kyrgyzstan, Palaeontology, 1039-1056 Taxonomy
*Family Acrocephalitidae
*Family Alokistocaridae
...
known from the mid-
Cambrian
The Cambrian ( ) is the first geological period of the Paleozoic Era, and the Phanerozoic Eon. The Cambrian lasted 51.95 million years from the end of the preceding Ediacaran period 538.8 Ma (million years ago) to the beginning of the Ordov ...
of
Laurentia
Laurentia or the North American craton is a large continental craton that forms the Geology of North America, ancient geological core of North America. Many times in its past, Laurentia has been a separate continent, as it is now in the form of ...
(North America). ''E. kingii'' is one of the most common trilobite
fossils
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 ...
in the USA
locally found in extremely high concentrations within the
Wheeler Formation
The Wheeler Shale (named by Charles Doolittle Walcott, Charles Walcott) is a Cambrian ( 507 Annum, Ma) fossil locality world-famous
for prolific agnostid and ''Elrathia kingii'' trilobite remains (even though many areas are barren of fo ...
in the U.S. state of
Utah
Utah is a landlocked state in the Mountain states, Mountain West subregion of the Western United States. It is one of the Four Corners states, sharing a border with Arizona, Colorado, and New Mexico. It also borders Wyoming to the northea ...
.
''E. kingii'' has been considered the most recognizable trilobite. Commercial quarries extract ''E. kingii'' in prolific numbers,
with just one commercial collector estimating 1.5 million specimens extracted in a 20-year career.
1950 specimens of ''Elrathia'' are known from the Greater
Phyllopod bed
The Phyllopod bed, designated by USNM locality number 35k, is the most famous fossil-bearing member of the Burgess Shale fossil ''Lagerstätte''. It was quarried by Charles Walcott from 1911–1917 (and later named Walcott Quarry), and was ...
, where they comprise 3.7% of the community.
Etymology
Even though the generic name ''Elrathia'' was first published in the combination ''E. kingii'', a species from the
House Range
The House Range is a north-south trending mountain range in Millard County, of west-central Utah. The House Range was named in 1859 by James H. Simpson. It was named by Simpson because "...of its well-defined stratification and the resemblan ...
,
Utah
Utah is a landlocked state in the Mountain states, Mountain West subregion of the Western United States. It is one of the Four Corners states, sharing a border with Arizona, Colorado, and New Mexico. It also borders Wyoming to the northea ...
, the name, itself, is derived from Elrath, Cherokee County, Alabama.
Description
''E. kingii'' is a medium-sized trilobite with a smooth sub-ovate carapace that is tapered towards the rear.
Thorax
The thorax (: thoraces or thoraxes) or chest is a part of the anatomy of mammals and other tetrapod animals located between the neck and the abdomen.
In insects, crustaceans, and the extinct trilobites, the thorax is one of the three main di ...
is usually 13 segments.
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 ...
has four axial rings and a long terminal piece. Posterior margin of the pygidium has a long broad medial notch.
In contrast, ''E. marjumi'' usually has 12 segments, 5 axial rings, lacks a notched posterior margin and possess incipient antero-lateral spines.
The British Columbian species, ''E. permulta'', is much smaller, averaging about only 20 millimeters, and has up to thoracic 14 segments. Because ''E. permulta'' lacks several diagnostic features of the genus it may even represent a distinct genus.
See also
*
Hypoxia (environmental)
Hypoxia (''hypo'': 'below', ''oxia'': 'oxygenated') refers to low oxygen conditions. Hypoxia is problematic for air-breathing organisms, yet it is essential for many anaerobic organisms. Hypoxia applies to many situations, but usually refers t ...
*
Paleobiota of the Burgess Shale
This is a list of the Biota (ecology), biota of the Burgess Shale, a Cambrian lagerstätte located in Yoho National Park in Canada.
The Burgess Shale is a fossil-bearing deposit exposed in the Canadian Rockies of British Columbia, Canada. It is fa ...
References
External links
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{{Taxonbar, from=Q26146
Burgess Shale fossils
Alokistocaridae
Cambrian trilobites
Fossils of British Columbia
Fossils of the United States
Fossils of Georgia (U.S. state)
Cambrian genus extinctions
Wheeler Shale
Paleozoic life of Newfoundland and Labrador