Dikelocephalidae

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Dikelocephalidae
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Trilobita
Order: Asaphida
Superfamily: Dikelocephaloidea
Family:Dikelocephalidae
Miller, 1889

Dikelocephalidae is a family of trilobites, that lived during the Upper Cambrian. Relatively large eyes close to the glabella, is a shared characteristic. [1] The following genera have been assigned to this family: [2]

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".

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 over 300 million years.

<i>Dikelocephalus</i> genus of trilobites

Dikelocephalus is a genus of very large trilobites of up to 50 cm (20 in) long, that lived during the last 3 million years of the Cambrian (Sunwaptan). Their fossils are commonly found as disarticulated sclerites, in the upper Mississippi Valley and in Canada (Alberta). The exoskeleton is rounded anteriorly, with the thorax and sides of the tailshield slightly tapering to about ⅔× of the width across the base of the spines at the back of the headshield. At the side corners of the pygidium there may be triangular or hooked spines, pointing backwards, while between the spines the posterior margin is at a 30-75° angle with the lateral margin, gently convex or nearly straight. If pygidial spines are lacking, the margin is gradually rounded. The thorax has 12 segments.

Taebaeksaukia spinata is a species of trilobites in the family Dikelocephalidae, which existed in what is now Korea during the upper Furongian period. It was described in 2011, and is the only species in the genus Taebaeksaukia.

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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.

The Ordovician is a geologic period and system, the second of six periods of the Paleozoic Era. The Ordovician spans 41.2 million years from the end of the Cambrian Period 485.4 million years ago (Mya) to the start of the Silurian Period 443.8 Mya.

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.

Emu Bay Shale Basal conglomerate with fine sandstone and mudstone (containing the fossil Lagerstatte within basal 10 m) above; sandstone and conglomerate above.

The Emu Bay Shale is a geological formation in Emu Bay, South Australia, containing a major Konservat-Lagerstätten. It is one of two in the world containing Redlichiidan trilobites. The Emu Bay Shale is dated as Cambrian Series 2, Stage 4, correlated with the upper Botomian Stage of the Lower Cambrian.

<i>Naraoia</i> genus of Nektaspida arthropod (fossil)

Naraoia is a genus of small to average size marine arthropods within the family Naraoiidae, that lived from the early Cambrian to the late Silurian period. The species are characterized by a large alimentary system and sideways oriented antennas.

The Dresbachian is a Maentwrogian regional stage of North America, lasting from 501 to 497 million years ago. It is part of the Upper Cambrian and is defined by four trilobite zones. It overlaps with the ICS-stages Guzhangian, Paibian and the lowest Jiangshanian.

Trilobites are used as index fossils to subdivide the Cambrian period. Assemblages of trilobites define trilobite zones. The Olenellus-zone has traditionally marked the top of the Lower Cambrian, and is followed by the Eokochaspis zone.

Odontopleurida order of arthropods (fossil)

Odontopleurida is an order of very spinose trilobites closely related to the trilobites of the order Lichida. Some experts group the Odontopleurid families, Odontopleuridae and Damesellidae, within Lichida. Odontopleurids tend to have convex, bar-shaped cephalons, and lobed, knob-shaped glabella that extend to, or almost to the anterior margin. Many, if not almost all odontopleurids have long spines that are derived either from the margins of the exoskeleton, or from granular or tubercular ornamentation, or both. Many odontopleurids are so spinose so as to be described as having "spines on (their) spines." Odontopleurids have 8 to 13 thoracic segments, with Odontopleuridae odontopleurids having no more than 10, and Damesellidae odontopleurids having no more than 13. The pygidium tends to be very small, and invariably has long spines emanating from it in all known genera.

Asaphidae family of arthropods (fossil)


Asaphidae is a family of asaphid trilobites. Although the first genera originate in Upper Cambrian marine strata, the family becomes the most widely distributed and most species-rich trilobite family during the Ordovician. 754 species assigned to 146 genera are included in Asaphidae.

<i>Olenus</i> (trilobite) fossil genus of trilobites

Olenus is a genus of Upper Cambrian ptychopariid trilobite.

<i>Biceratopsinae</i> subfamily of trilobites (fossil)

The Biceratopsinae is an extinct subfamily of redlichiid trilobites within the family Biceratopsidae, with species of small to average size. Species belonging to this subfamily lived during the Toyonian stage, 516-513 million years ago, in the former continent of Laurentia, including what are today the South-Western United States and Canada.

Stage 10 of the Cambrian is the still unnamed third and final stage of the Furongian series. It follows the Jiangshanian and precedes the Ordovician Tremadocian stage. The proposed lower boundary is the first appearance of the trilobite Lotagnostus americanus around 489.5 million years ago, but other fossils are also being discussed. The upper boundary is defined as the appearance of the conodont Iapetognathus fluctivagus which marks the beginning of the Tremadocian and is radiometrically dated as 485.4 million years ago.

<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.

Cambrian Stage 3 is the still unnamed third stage of the Cambrian. It succeeds Cambrian Stage 2 and precedes Cambrian Stage 4, although neither its base nor top have been formally defined. The plan is for its lower boundary to correspond approximately to the first appearance of trilobites, about 521 million years ago, though the globally asynchronous appearance of trilobites warrants the use of a separate, globally synchronous marker to define the base. The upper boundary and beginning of Cambrian Stage 4 is informally defined as the first appearance of the trilobite genera Olenellus or Redlichia around 514 million years ago.

Cambrian Stage 4 is the still unnamed fourth stage of the Cambrian and the upper stage of Cambrian Series 2. It follows Cambrian Stage 3 and lies below the Wuliuan. The lower boundary has not been formally defined by the International Commission on Stratigraphy. One proposal is the first appearance of two trilobite genera, Olenellus or Redlichia. Another proposal is the first appearance of the trilobite species Arthricocephalus chauveaui. Both proposals will set the lower boundary close to 514 million years ago. The upper boundary corresponds to the beginning of the Wuliuan.

Rosas rule

Rosa's rule, also known as Rosa's law of progressive reduction of variability, is a biological rule that observes the tendency to go from character variation in more primitive representatives of a taxonomic group or clade to a fixed character state in more advanced members. An example of Rosa's rule is that the number of thoracic segments in adults may vary in Cambrian trilobite species, while from the Ordovician the number of thoracic segments is constant in entire genera, families, and even suborders. Thus, a trend of decreasing trait variation between individuals of a taxon as the taxon develops across evolutionary time can be observed. The rule is named for Italian paleontologist Daniele Rosa.

The Collier Shale is a geologic formation in the Ouachita Mountains of Arkansas and Oklahoma. Dating from the Late Cambrian to Early Ordovician periods, the Collier Shale is the oldest stratigraphic unit exposed in Arkansas. First described in 1892, this unit was not named until 1909 by Albert Homer Purdue in his study of the Ouachita Mountains of Arkansas. Purdue assigned the type locality to the headwaters of Collier Creek in Montgomery County, Arkansas, but did not designate a stratotype. As of 2017, a reference section for this unit has yet to be designated.

Entomaspididae family of arthropods (fossil)

Entomaspididae is a family of harpetid trilobites that ranges from the Upper Cambrian to Lower Ordovician of marine strata in China and the United States.

References

  1. ↑ Hughes, Nigel C. (1994). "Ontogeny, Intraspecific Variation, and Systematics of the Late Cambrian Trilobite Dikelocephalus". Smithsonian Contributions to Paleobiology. 79.
  2. ↑ S. M. Gon III. "Order Asaphida" . Retrieved November 14, 2010.
  3. ↑ Seung-Bae Lee & Duck K. Choi (2011). "Dikelocephalid trilobites from the Eosaukia fauna (Upper Furongian) of the Taebaek Group, Korea". Journal of Paleontology . 85 (2): 279–297. doi:10.1666/10-034.1.


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