Redlichiida

Redlichia takooensis from the Lower Cambrian Emu Bay Shale of South Australia's Kangaroo Island

• Worldwide

The Redlichiida are one of the nine orders of the extinct Trilobites ( Trilobita ). Together with the Agnostida, the Corynexochida and Ptychopariida they are one of the four older Trilobitenordnungen that occurred as early as the Cambrian.

• 5.1 subordination Olenellina Walcott, 1890
• 5.2 subordination Redlichiina Harrington, 1959

Etymology

The order of Redlichiida 1932 scientifically described by German paleontologist Rudolf Richter for the first time and named in honor of the Austrian geologist Karl August Redlich.

Description

( Morphological terms are explained in detail in the article trilobites )

Redlichiida have a primitive -sounding appearance. Your Cephalon ( head shield ) is large and semicircular, the glabella usually elongated, clearly segmented and usually forward broadening to. The strong genal spines are an extension of the tubular reinforced head plate edge. The hypostome is normally positioned konterminant. The rostral plate is usually quite wide. Her eyes are elongated and sickle-shaped above; they are of a significant move -shaped bulge - eyes strips - accompanied, which stretches up to the front edge of glabella. The thorax ( breastplate ) consists of many segments (there can be more than 90 available), their length in the direction of the pygidium ( tail sign ) decreases steadily; the pleura usually end in spikes. Sometimes a subdivision of the thorax in a broader prothorax and a narrower Ophistothorax is possible ( such as in the Emuelloidea ). The tiny pygidium often consists of just one or very few segments.

Redlichiida are very often armed with spines - these can start at the head shield ( genal spines ) on the glabella, the tail and in the thoracic segments ( pleural ). Unlike other Trilobitenordnungen to Redlichiida could not roll up for defense purposes most likely.

The Olenelliden own family as an identifying spines on the third thoracic segment. Some finds also appendages such as legs, antennae and gills, etc., were obtained. In number, arrangement and type this characteristic of trilobites pattern follow.

Distribution and occurrence

In the Cambrian faunal Redlichiida are common fossils global distribution. They were found in two known Konservatlagerstätten - in Emu Bay Shale in South Australia ( Kangaroo Island ) and in the Chengjiang Faunengemeinschaft in the People's Republic of China.

Faunal provinces

Within the Redlichiida representatives occur from the subordination Redlichiina only in Cambrian layer associations outside Laurentias, they find themselves in the Acadobaltischen faunal province - Avalonia, Baltica and Western Gondwana - as well as in the Oriental faunal province of East Gondwana. In contrast to the family of Olenelliden they have facial sutures, their fossils are often accompanied by the so-called Librigenae ( "free cheeks ").

The Olenelliden family, however, is on the Cambrian continent Laurentia - limited (North American faunal province North America and associated territories ). Olenelliden are quite common and likewise define the then expansion Laurentias. Her sudden disappearance defines the boundary between Lower and Middle Cambrian in their area of ​​distribution. Olenellide do not face seam.

Between the Olenelliden and Redlichiina a clearly developed exclusivity of their occurrence, only in Morocco and Western Mongolia occur both faunas on together. Highly endemic genera of Redlichiina also allow a further subdivision of the Oriental faunal province in the following sub- provinces:

• Lena Sayan
• Huangho
• Yangtze
• Eastern Mediterranean
• Zagros - Himalayas
• Australia
• Antarctic

History of development

Redlichiida are the first occurring trilobites in the fossil record at all. The oldest known trilobite comes from belonging to the family Redlichiida Fallotaspidae. Most scholars are of the view that in order Redlichiida or in their subordination Redlichiina the common ancestor of all other Trilobitenordnungen is to look - but one exception to this is the Agnostid. It is usually assumed that the orders Corynexochida and Ptychopariida developed during the Cambrian from the Redlichiina and Lichida then during the later Mittelkambriums emerged either from the Redlichiida or from the Corynexochida.

The Redlichiida died out before the end of the Middle Cambrian.

System

The order of Redlichiida is divided into two suborders - divided and five superfamilies - Olenellina and Redlichiina.

Subordination Olenellina Walcott, 1890

Superfamily Fallotaspidoidea

Families:

• Archaeaspidae
• Daguinaspidae - as Daguinaspinae now a subfamily of Fallotaspidae
• Fallotaspidae
• Judomiidae
• Neltneriidae
• Nevadiidae

Superfamily Olenelloidea

Families:

• Holmiidae
• Olenellidae

Subordination Redlichiina Harrington, 1959

Superfamily Emuelloidea

Families:

• Emuellidae
• Megapharanaspidae

Superfamily Paradoxidoidea

Families:

• Centropleuridae
• ( Hicksiidae )
• ( Lermontoviidae )
• Paradoxididae
• Xystriduridae

Superfamily Redlichoidea

Families:

• Abadiellidae
• Chengkouaspidae (including Bathynotidae )
• Dolerolenidae
• Gigantopygidae
• Kueichowiidae
• Mayiellidae
• Menneraspididae
• Metadoxididae
• Neoredlichiidae - as Neoredlichiinae subfamily of Redlichiidae
• Redlichiidae
• Redlichinidae
• Saukiandidae (including Despujolsiidae )
• Yinitidae (sometimes including Langduiidae, although these are usually conducted at the Corynexochida )
• Yunnanocephalidae - usually sent to the Ptychopariida

The systematic position of the relatively rare Bathynotiden is not yet clear, but they can be made to the Chengkouaspidae due to the similarities in their tank top. They had sutures and wore long spines on the head shield and the last thoracic segment.

The Ellipsocephalidae are occasionally performed as Redlichiida, although they actually belong to the Ptychopariida.