Ptychagnostidae

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Ptychagnostidae
Temporal range: Wuliuan - Paibian
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Triplagnostus gibbus 2.jpg
Ptychagnostus gibbus
Ptychagnostus cuyanus.3 - Ordovicico.JPG
Ptychagnostus cuyanus
Scientific classification Red Pencil Icon.png
Kingdom: Animalia
Phylum: Arthropoda
Class:† Trilobita
Order:† Agnostida
Superfamily:† Agnostoidea
Family:†Ptychagnostidae
Kobayashi, 1939
Type genus
Ptychagnostus
Jaekel, 1909
Genera

See text.

Ptychagnostidae is a family of agnostid trilobites from the 5th Stage to the Paibian Age of the Cambrian (509 to 497 million years ago). [1] The family includes several important index fossils.

Family is one of the eight major hierarchical taxonomic ranks in Linnaean taxonomy; it is classified between order and genus. A family may be divided into subfamilies, which are intermediate ranks between the ranks of family and genus. The official family names are Latin in origin; however, popular names are often used: for example, walnut trees and hickory trees belong to the family Juglandaceae, but that family is commonly referred to as being the "walnut family".

Agnostida order of arthropods (fossil)

Agnostida is an order of arthropod which first developed near the end of the Early Cambrian period and thrived during the Middle Cambrian. They are present in the Lower Cambrian fossil record along with trilobites from the Redlichiida, Corynexochida, and Ptychopariida orders. The last agnostids went extinct in the Late Ordovician.

Trilobite class of arthropods (fossil)

Trilobites are a group of extinct marine arachnomorph 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 Atdabanian stage of the Early Cambrian period, and they flourished throughout the lower Paleozoic era before beginning a drawn-out decline to extinction when, during the Devonian, all trilobite orders except the Proetids died out. Trilobites disappeared in the mass extinction at the end of the Permian about 252 million years ago. The trilobites were among the most successful of all early animals, existing in oceans for almost 300 million years.

Contents

Description

Like all agnostids, ptychagnostids have cephalons and pygidia that are more or less uniform in size and shape (isopygous). The thorax is composed of two body segments (somites). They are completely blind. [2]

Pygidium

The pygidium is the posterior body part or shield of crustaceans and some other arthropods, such as insects and the extinct trilobites. It contains the anus and, in females, the ovipositor. It is composed of fused body segments, sometimes with a tail, and separated from thoracic segments by an articulation.

Thorax frontal part of an animals body, between its head and abdomen

The thorax or chest is a part of the anatomy of humans and various other animals located between the neck and the abdomen. The thorax includes the thoracic cavity and the thoracic wall. It contains organs including the heart, lungs, and thymus gland, as well as muscles and various other internal structures. Many diseases may affect the chest, and one of the most common symptoms is chest pain. The word thorax comes from the Greek θώραξ thorax "breastplate, cuirass, corslet" via Latin: thorax.

Somite division of the body of an animal or embryo

Somites are divisions of the body of an animal or embryo. The divisions are also known as metameric segments.

Distribution and age range

Ptychagnostidae has a cosmopolitan distribution. They existed during the 5th Stage of the Series 3 Epoch to the Paibian Age of the early Furongian Epoch in the Cambrian (509 to 497 million years ago). [1] The earliest member of the family is Ptychagnostus praecurrens from the Burgess Shale fauna. [3]

Cosmopolitan distribution biogeographic term

In biogeography, a taxon is said to have a cosmopolitan distribution if its range extends across all or most of the world in appropriate habitats. Such a taxon is said to exhibit cosmopolitanism or cosmopolitism. The opposite extreme is endemism.

In geochronology, an epoch is a subdivision of the geologic timescale that is longer than an age but shorter than a period. The current epoch is the Holocene Epoch of the Quaternary Period. Rock layers deposited during an epoch are called a series. Series are subdivisions of the stratigraphic column that, like epochs, are subdivisions of the geologic timescale. Like other geochronological divisions, epochs are normally separated by significant changes in the rock layers to which they correspond.

The Paibian is the lowest stage of Furongian series of the Cambrian. It follows the Guzhangian and is succeeded by the Jiangshanian stage. The base is defined as the first appearance of the trilobite Glyptagnostus reticulatus around 497 million years ago. The top, or the base of the Jiangshanian is defined as the first appearance of the trilobite Agnostotes orientalis around 494 million years ago.

Taxonomy

Ptychagnostidae is classified under the superfamily Agnostoidea of the suborder Agnostina, order Agnostida. The family was first established by the Japanese paleontologist Teiichi Kobayashi in 1939. Its name comes from the type genus, Ptychagnostus . It includes the following genera (with their taxonomic synonyms): [2]

In biological classification, the order is

  1. a taxonomic rank used in the classification of organisms and recognized by the nomenclature codes. Other well-known ranks are life, domain, kingdom, phylum, class, family, genus, and species, with order fitting in between class and family. An immediately higher rank, superorder, may be added directly above order, while suborder would be a lower rank.
  2. a taxonomic unit, a taxon, in that rank. In that case the plural is orders.

Japanese people are an ethnic group that is native to the Japanese archipelago and modern country of Japan, where they constitute 98.5% of the total population. Worldwide, approximately 129 million people are of Japanese descent; of these, approximately 125 million are residents of Japan. People of Japanese ancestry who live outside Japan are referred to as nikkeijin(日系人), the Japanese diaspora. The term ethnic Japanese is often used to refer to mainland Japanese people, specifically Yamato people. Japanese people are one of the largest ethnic groups in the world.

Type genus term in zoological nomenclature (also non-officially in botanical nomenclature)

In biological classification, especially zoology, the type genus is the genus which defines a biological family and the root of the family name.

= Miagnostus
= Agnostonymus
<i>Ptychagnostus</i> genus of trilobites (fossil)

Ptychagnostus is an extinct genus of blind trilobite that lived during the Cambrian period, part of the order Agnostida. Ptychagnostidae generally do not exceed ten millimetres in length. Their remains are sometimes found in the otherwise empty tubes of the polychaete worm Selkirkia. It probably lived in the water column. Its major characteristics are lack of eyes, two lobes on the glabella, and three lobes on the pygidium.

=Triplagnostus, Huarpagnostus, Solenagnostus, Pentagnostus, Aristarius, Aotagnostus, Acidusus, Canotagnostus, Zeteagnostus

Related Research Articles

The Furongian is the fourth and final series of the Cambrian. It lasted from 497 to 485.4 million years ago. It succeeds the Miaolingian series of the Cambrian and precedes the Lower Ordovician Tremadocian stage. It is subdivided into three stages: the Paibian, Jiangshanian and the unnamed 10th stage of the Cambrian.

<i>Agnostus</i> genus of trilobites (fossil)

Agnostus is a genus of agnostid trilobites that lived during the upper Middle Cambrian–lower Upper Cambrian. It is the type genus of the family Agnostidae. It is subdivided into two subgenera, Agnostus and Homagnostus.

<i>Acidiscus</i>

Acidiscus is an extinct genus of eodiscinid agnostid trilobites. It lived during the Botomian stage of the Cambrian period.

Acadagnostus is a genus of trilobite from the Middle Cambrian, with 7 species currently recognized. The type species A. acadicus has the widest distribution known from any peronopsid and has been found in North America, Greenland, England, Western Europe, Eastern Europe, Central Asia, the Altai Mountains, the Siberian shield, China, and Australia.

<i>Peronopsis</i> genus of trilobites (fossil)

Peronopsis is a genus of trilobite restricted to the Middle Cambrian. Its remains have been found in Asia, Australia, Europe, and North America.

Wheeler Shale

The Wheeler Shale is a Cambrian (c. 507 Ma) fossil locality world-famous for prolific agnostid and Elrathia kingii trilobite remains and represents a Konzentrat-Lagerstätten. Varied soft bodied organisms are locally preserved, a fauna and preservation style normally associated with the more famous Burgess Shale. As such, the Wheeler Shale also represents a Konservat-Lagerstätten.

<i>Pagetia</i> genus of trilobites

Pagetia is a genus of very small, agnostid trilobites, assigned to the family Eodiscidae, and that had a global distribution during the Middle Cambrian. The genus contains 55 currently recognized species, each with a limited spatial and temporal distribution.

The Guzhangian is an uppermost stage of the Miaolingian Series of the Cambrian. It follows the Drumian Stage and precedes the Paibian Stage of the Furongian Series. The base is defined as the first appearance of the trilobite Lejopyge laevigata around 500.5 million years ago. The Guzhangian-Paibian boundary is marked by the first appearance of the trilobite Glyptagnostus reticulatus around 497 million years ago.

The Drumian is a stage of the Miaolingian Series of the Cambrian. It succeeds the Wuliuan and precedes the Guzhangian. The base is defined as the first appearance of the trilobite Ptychagnostus atavus around 504.5 million years ago. The top is defined as the first appearance of another trilobite Lejopyge laevigata around 500.5 million years ago.

<i>Ptychagnostus atavus</i> species of agnostid trilobite (fossil)

Ptychagnostus atavus is a species of agnostid trilobite. It belongs to the genus Ptychagnostus in the family Ptychagnostidae. It was originally described by Swedish paleontologist Sven Axel Tullberg as Agnostus atavus in 1880. It is used in biostratigraphy as an index fossil. Its first appearance at the GSSP section in the Wheeler Shale of Utah is defined as the beginning of the Drumian Age of the Miaolingian.

<i>Lejopyge laevigata</i> species of trilobite (fossil)

Lejopyge laevigata is a species of agnostid trilobite belonging to the genus Lejopyge. It existed during the Guzhangian to the Paibian Age of the Cambrian. It has a cosmopolitan distribution and is an important index fossil in biostratigraphy.

<i>Pentagnostus</i> genus of trilobites (fossil)

Pentagnostus is a genus of trilobites restricted to the Middle Cambrian. Its remains have been found in Siberia, Australia, North America, Scandinavia, and Kazakhstan.

The Miaolingian is the third Series of the Cambrian period, and was formally named in 2018. It lasted from about 509 to 497 million years ago and is divided into 3 stages: the Wuliuan, the Drumian, and the Guzhangian. The Miaolingian is preceded by the unnamed Cambrian Series 2 and succeeded by the Furongian series.

<i>Glyptagnostus reticulatus</i> species of trilobite (fossil)

Glyptagnostus reticulatus is a species of agnostid trilobite belonging to the genus Glyptagnostus. It existed during the Paibian Age of the Cambrian. It has a cosmopolitan distribution and is an important index fossil in biostratigraphy. It was characterized by an unusual net-like pattern of furrows on both the cephalon and the pygidium.

Agnostotes orientalis is a species of agnostid trilobite belonging to the genus Agnostotes. It existed during the Jiangshanian Age of the Cambrian. It is an important index fossil in biostratigraphy.

Peronopsidae family of trilobites (fossil)

The Peronopsidae comprise the earliest family of the Agnostina suborder. Species of this family occurred on all paleocontinents. The earliest representatives of this family first occur just before the start of the Middle Cambrian, and the last disappeared just after the start of the Upper Cambrian.

<i>Condylopyge</i> genus of arthropods (fossil)

Condylopyge is a genus of very small trilobites, that lived during the latest Early and the early Middle Cambrian, in what are today Canada, Czech Republic, England and Wales, France, Germany, Italy, Morocco, the Russian Federation, Spain, Turkey and Sweden. It can easily be distinguished from all other Agnostida because the frontal lobe of the central raised area of the headshield is wider than the rear lobe. It looks like Pleuroctenium but the frontal glabellar lobe does not fold around the rear lobe, as it does in Pleuroctenium.

Eodiscidae family of arthropods (fossil)

Eodiscidae is a family of agnostid trilobites that lived during the final Lower Cambrian and the Middle Cambrian. They are small or very small, and have a thorax of two or three segments. Eodiscidae includes nine genera.

<i>Genevievella</i> genus of arthropods (fossil)

Genevievella is a genus of trilobites with a short inverted egg-shaped outline, a wide headshield, small eyes, and long genal spines. The backrim of the headshield is inflated and overhangs the first of the 9 thorax segments. The 8th thorax segment from the front bears a backward directed spine that reaches beyond the back end of the exoskeleton. It has an almost oval tailshield with 5 pairs of pleural furrows. It lived during the Upper Cambrian in what are today Canada and the United States.

References

  1. 1 2 "Ptychagnostidae". Paleobiology Database. Retrieved 18 November 2012.
  2. 1 2 Samuel M. Gon III. "Agnostida Fact Sheet". A Guide to the Orders of Trilobites. Retrieved 18 November 2012.
  3. ↑ Richard A. Robison (1984). "Cambrian trilobites of east-central Alaska". Cambrian Agnostida of North America and Greenland: Part I: Ptychagnostidae. The University of Kansas Paleontological Contributions: Paper 109. Paleontological Institute, University of Kansas. pp. 1–60. ISSN   0075-5052.
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