''Ductina'' is a

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nomencla ...

extinct Extinction is the termination of a kind of organism or of a group of kinds (taxon), usually a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and ...

, small to average sized, eyeless phacopid

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 ...

, that lived during the

Devonian The Devonian ( ) is a geologic period and system of the Paleozoic era, spanning 60.3 million years from the end of the Silurian, million years ago (Mya), to the beginning of the Carboniferous, Mya. It is named after Devon, England, whe ...

Description

The body of ''Ductina'' is small to average (up to ), 1¼ to 2 times as long as wide, blunted oval. Body without any adornment. The headshield (or

cephalon Cephalon, Inc. was an American biopharmaceutical company co-founded in 1987 by pharmacologist Frank Baldino, Jr., neuroscientist Michael Lewis, and organic chemist James C. Kauer—all three former scientists with the DuPont Company. Baldino s ...

) is 2 to 3 times as wide as it is long in the direction of the axis (or sagittally). The cephalic axis (or

glabella The glabella, in humans, is the area of skin between the eyebrows and above the nose. The term also refers to the underlying bone that is slightly depressed, and joins the two brow ridges. It is a cephalometric landmark that is just superior ...

) is strongly widening forward with shallow furrows, the front curving downward to end at an approximate straight angle to the plain of the axis. Another shallow furrow (the occipital furrow), with left and right a deep pit (apodemal pit), crosses to the back of the glabella to define a narrow band (or occipital ring), and just in front left and right a small lobe is defined by shallow furrows and a deep pits. The back of the cephalon is often broken, obscuring the features of the occipital ring. Eyes and eye ridges ( palpebral lobes) are absent. The natural fracture lines (sutures) of the cephalon coincide with its margin (unique with the Phacopidae), so there are no free cheeks (or librigenae). The genal angles are rounded, not truncated, no genal spine. The

thorax The thorax or chest is a part of the anatomy of humans, 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 divisions of the crea ...

has 10 segments, and the width of the axis is about ⅓ of the thorax. Tailpiece (or

pygidium The pygidium (plural 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 compo ...

) is 20 to 35% of the length of the body. The pygidial axis (or rachis) is pointed (or acute), ending at the border.

Distribution

The species of the genus ''Ductina'' lived during the Devonian in Europe and South-East Asia. Fossils of ''D. vietnamica'' have been found in the

Eifelian The Eifelian is the first of two faunal stages in the Middle Devonian Epoch. It lasted from 393.3 ± 1.2 million years ago to 387.7 ± 0.8 million years ago. It was preceded by the Emsian Stage and followed by the Givetian Stage. North American ...

of China (Nandan Formation, Luofu, Nandan County, Guangxi Province ,Wang, Y., A. J. Boucot, J.Y. Rong and X.C. Yang. Community paleoecology as a geologic tool: the Chinese Ashgillian-Eifelian (latest Ordovician through early Middle Devonian) as an example. Geological Society of America Special Paper 211:1-100. 1987 and Hunan Province); and in the

Pragian The Pragian is one of three faunal stages in the Early Devonian Epoch. It lasted from 410.8 ± 2.8 million years ago to 407.6 ± 2.8 million years ago. It was preceded by the Lochkovian Stage and followed by the Emsian Stage. The most important La ...

of Vietnam (Song Hiem, Mia Le Beds ).Tong-Dzuy, E. T., T. H. Dang, D. H. Nguyen, D. K. Nguyen, H. H. Nguyen, T. D. Nguyen, H. P. Ta, K. N. Pham, and N. T. Doan. 1988. Stratigrafiya i tselenteraty Dewona W'etnama, 1: Stratigrafiya evonian stratigraphy and coelenterata of Vietnam, 1: Stratigraphy5-184 Fossils of ''D. ductifrons'' have been found in the

Famennian The Famennian is the latter of two faunal stages in the Late Devonian Epoch. The most recent estimate for its duration estimates that it lasted from around 371.1 million years ago to 359.3 million years ago. An earlier 2012 estimate, still used b ...

Brauckman, C. and B. Famennian Trilobites: An Outline of their Stratigraphical Importance. Belgian Ministry of Economic Affairs, Administration of Mines, Belgian Geological Survey, T109, pp. 9-17. 198

/ref> of the United Kingdom, Germany (Eskesberg, Nehde

Varresbec

all near Wupperthal), Poland (near Psiarnia, in the Southern part of the Świętokrzyskie Mountains, Holy Cross Mountains ),Osmolska, H. Famennian Phacopidae from the Holy Cross Mountains (Poland). Acta Palaeontologica Polonica, Volume 3, nr. 2, 195

/ref> and the Western Urals in Russia.

Habitat

All phacopids were probably marine bottom-dwellers. ''D. vietnamica'' has been found with several pelagic zone, open water species (Nandan Formation in Guanxi, China), indicating deep and dark waters, probably poor in oxygen near the bottom where ''Ductina'' lived. It has also been found as part of a species rich community characteristic of a shallow coral sea.

Key to the species

File:Ductina ductifrons.jpg, ''Ductina ductifrons'', from Wupperthal, Germany File:Ductina vietnamica 2 lateral.jpg, ''Ductina vietnamica'', lateral view File:Ductina vietnamica 2 frontal.jpg, ''Ductina vietnamica'', frontal view File:Ductina vietnamica dorsal.jpg, ''Ductina vietnamica'', dorsal view

References

{{Taxonbar, from=Q5311610 Phacopidae Devonian trilobites of Europe Fossils of China Fossils of Germany Fossils of Poland Fossils of Russia Fossils of Sweden Fossils of Great Britain Fossils of Vietnam Early Devonian first appearances Famennian extinctions Devonian trilobites of Asia