The Illaenidae are a family of

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 in the order

Corynexochida Corynexochida is an order of trilobite that lived from the Lower Cambrian to the Late Devonian. Like many of the other trilobite orders, Corynexochida contains many species with widespread characteristics. The middle region of the cephalon (the ...

. 223 currently accepted species in 24 genera are known from the Ordovician. Some scholars include the

Panderiidae ''Panderiidae'' is a family of trilobites in the order Corynexochida. These nektobenthic carnivores lived in the Ordovician period, from 488.3 to 443.7 Ma. Genera *'' Hemibarrandia'' *'' Panderia'' Distribution Fossils of this genus have been ...

in the Illaenidae, but this is not generally supported.

Distribution

''Illaenus? priscus'' from Salair and ''Illaenus? berkutensis'' from the Malyi Karatau, Kazakhstan (both Lower

Tremadocian The Tremadocian is the lowest stage of Ordovician. Together with the later Floian Stage it forms the Lower Ordovician Epoch. The Tremadocian lasted from to million years ago. The base of the Tremadocian is defined as the first appearance of the ...

), are both very poorly known and it remains uncertain to which family they could best be assigned. The first certain Illaenid is ''I. hinomotoensis'' from the Upper Tremadocian of North China and South Korea. The earliest species known from

Laurentia Laurentia or the North American Craton is a large continental craton that forms the 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, although ...

(western Ireland) is ''I. weaveri'', probably latest

Floian The Floian is the second stage of the Ordovician Period. It succeeds the Tremadocian with which it forms the Lower Ordovician epoch. It precedes the Dapingian Stage of the Middle Ordovician. The Floian extended from to million years ago. The lowe ...

. These early occurrences are from the tropics, but during the

Darriwilian The Darriwilian is the upper stage of the Middle Ordovician. It is preceded by the Dapingian and succeeded by the Upper Ordovician Sandbian Stage. The lower boundary of the Darriwilian is defined as the first appearance of the graptolite species '' ...

the family spread over southern

Gondwana Gondwana () was a large landmass, often referred to as a supercontinent, that formed during the late Neoproterozoic (about 550 million years ago) and began to break up during the Jurassic period (about 180 million years ago). The final stages ...

, and became

cosmopolitan Cosmopolitan may refer to: Food and drink * Cosmopolitan (cocktail), also known as a "Cosmo" History * Rootless cosmopolitan, a Soviet derogatory epithet during Joseph Stalin's anti-Semitic campaign of 1949–1953 Hotels and resorts * Cosmopoli ...

for the remainder of the Ordovician, although most genera had limited distributions. The genus ''Stenopareia'' survived the

Ordovician–Silurian extinction events The Late Ordovician mass extinction (LOME), sometimes known as the end-Ordovician mass extinction or the Ordovician-Silurian extinction, is the first of the "big five" major Extinction event, mass extinction events in Earth's history, occurring ro ...

and the family slightly rebounded with 26 species divided over three genera during the Silurian. ''Quadratillaenus tewoensis'' from North China is the youngest species known ( Přídolí).

Genera

*'' Bumastoides'' Whittington 1954 *'' Cryptonymus'' Eichwald 1825 *''

Deucalion In Greek mythology, Deucalion (; grc-gre, Δευκαλίων) was the son of Prometheus; ancient sources name his mother as Clymene, Hesione, or Pronoia.A scholium to ''Odyssey'' 10.2 (='' Catalogue'' fr. 4) reports that Hesiod called Deucalion ...

'' Shtsheglov 1827 *'' Dysplanus'' Burmeister 1843 *'' Ectillaenus'' Salter 1867 *'' Harpillaenus'' Whittington 1963 *'' Hyboaspis'' Raymond 1920 *'' Hydrolaenus'' Salter 1867 *''

Illaenus ''Illaenus'' is a genus of trilobites from Russia and Morocco, from the middle Ordovician The Ordovician ( ) is a geologic period and system, the second of six periods of the Paleozoic Era. The Ordovician spans 41.6 million years from the end ...

'' Dalman 1827 *'' Nanillaenus'' Jaanusson 1954 *'' Octillaenus'' Salter 1867 *'' Parillaenus'' Jaanusson 1954 *'' Platillaenus'' Jaanusson 1954 *'' Ptilillaenus'' Lu 1962 *''

Rhodope Rhodope may refer to: * Rhodope (mythology), a figure of Greek mythology * Rhodope Mountains, in Bulgaria and Greece * Rhodope (regional unit), of Greece * Rhodope (province), a Roman and Byzantine province * 166 Rhodope, an asteroid * Rhodope (genu ...

'' Angelin 1854 *'' Stenopareia'' Holm 1886 *'' Thaleops'' Conrad 1843 *'' Ulugtella'' Petrunina 1975 *'' Zbirovia'' Snajdr 1956 *'' Zdicella'' Snajdr 1956 *'' Zetillaenus'' Snajdr 1957

References

Ordovician trilobites Illaenina Trilobite families {{Corynexochida-stub