| Ductina Temporal range: | |
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| Ductina vietnamica | |
Scientific classification  | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Arthropoda |
| Class: | † Trilobita |
| Order: | † Phacopida |
| Family: | † Phacopidae |
| Genus: | † Ductina Richter and Richter, 1931 |
| Species | |
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Ductina is a genus of extinct, small to average sized, eyeless phacopid trilobite, that lived during the Devonian.
The body of Ductina is small to average (up to 5 centimetres (2.0 in)), 1¼ to 2 times as long as wide, blunted oval. Body without any adornment. The headshield (or cephalon) is 2 to 3 times as wide as it is long in the direction of the axis (or sagittally). The cephalic axis (or glabella) 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. [1] 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 has 10 segments, and the width of the axis is about ⅓ of the thorax. Tailpiece (or pygidium) is 20 to 35% of the length of the body. The pygidial axis (or rachis) is pointed (or acute), ending at the border. [2]
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 of China (Nandan Formation, Luofu, Nandan County, Guangxi Province 24°30′N115°36′E / 24.500°N 115.600°E , [3] and Hunan Province); and in the Pragian of Vietnam (Song Hiem, Mia Le Beds 22°12′N106°12′E / 22.200°N 106.200°E ). [4]
Fossils of D. ductifrons have been found in the Famennian [5] of the United Kingdom, Germany (Eskesberg, Nehden, Varresbeck, Archived 2012-04-26 at the Wayback Machine all near Wupperthal), Poland (near Psiarnia, in the Southern part of the Holy Cross Mountains 50°53′N20°55′E / 50.883°N 20.917°E ), [6] and the Western Urals in Russia. [6]
All phacopids were probably marine bottom-dwellers. D. vietnamica has been found with several open water species (Nandan Formation in Guanxi, China), indicating deep and dark waters, probably poor in oxygen near the bottom where Ductina lived. [3] It has also been found as part of a species rich community characteristic of a shallow coral sea. [4]
| 1 | Body symmetrically elliptic, 1¼ to 1½ times as long as wide, retaining the same width over the frontal half of the thorax. Glabellar furrow evenly shallow and discernible to the cephalic margin. Pygidium 2 times or more wider than long. Rachis has shallow but clear furrows, is narrowly triangular, with sides bending inward towards the back, to end at an angle of about 45° with the axis. Famennian. United Kingdom; Eifel and Thüringen, Germany; Holy Cross Mountains, Poland; West side of the Urals, Russia. → D. ductifrons |
|---|---|
| - | Body slightly reverse egg shaped, 1⅔ to 2 times as long as wide, widest at the back of the cephalon, the thorax slightly tapering backwards. Glabellar furrow quickly shallower and indiscernible near the cephalic margin. Pygidium 1¼ to 1½ times wider than long. Rachis has faint, hardly discernible furrows, is narrowly triangular with approximate straight sides along the length. Pragian to Eifelian. Guangxi and Hunan, Southern China; Vietnam. → D. vietnamica |
The Phacopina comprise a suborder of the trilobite order Phacopida. Species belonging to the Phacopina lived from the Lower Ordovician (Tremadocian) through the end of the Upper Devonian (Famennian). The one unique feature that distinguishes Phacopina from all other trilobites are the very large, separately set lenses without a common cornea of the compound eye.
Phacopidae is a family of phacopid trilobites that ranges from the Lower Ordovician to the Upper Devonian, with representatives in all paleocontinents.
Phacops is a genus of trilobites in the order Phacopida, family Phacopidae, that lived in Europe, northwestern Africa, North and South America and China from the Late Ordovician until the very end of the Devonian, with a broader time range described from the Late Ordovician. It was a rounded animal, with a globose head and large eyes, and probably fed on detritus. Phacops is often found rolled up ("volvation"), a biological defense mechanism that is widespread among smaller trilobites but further perfected in this genus.
Dalmanites is a genus of trilobite in the order Phacopida. They lived from the Late Ordovician to Middle Devonian.
Huntoniatonia is genus of trilobites, an extinct group of marine arthropods of average to large size.
Chotecops is a genus of trilobites from the order Phacopida, suborder Phacopina, family Phacopidae. It was initially erected as a subgenus of Phacops but some later authors thought it distinctive enough to raise its status. Species assigned to this genus occur between the Emsian and the Famennian. Chotecops is the most abundant trilobite in the Hunsrück Slate and due to the excellent preservation, often soft tissue such as antennae and legs have been preserved as a thin sheet of pyrite.
Trimerocephalus is a genus of eyeless trilobites from the order Phacopida, family Phacopidae. It lived during the final stage of the Devonian, the Famennian, and became extinct at the end of this stage, together with all other trilobites with the exception of some Proetida. It can be found in Australia, the Czech Republic, France, Germany, Iran, Kazakhstan, Morocco, Poland, the Russian Federation (Urals), Spain, and the United Kingdom (England).
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 2⁄3× 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.
Meteoraspis is an extinct genus of ptychopariid trilobites of the family Tricrepicephalidae. The various species lived from 501 to 497 million years ago during the Dresbachian faunal stage of the late Cambrian Period. Fossils of Meteoraspis are characteristic of Late Cambrian strata in North America, though they are found in Late Cambrian strata elsewhere in the world, such as M. nevensis from Victoria Land, Antarctica.
Erbenochile is a genus of spinose phacopid trilobite, of the family Acastidae, found in Lower to Middle Devonian age rocks from Algeria and Morocco. Originally described from an isolated pygidium, the first complete articulated specimen of E. erbeni revealed the presence of extraordinarily tall eyes:
"Straight-sided towers of lenses... with [up to] 18 lenses in a vertical file"
Nephrolenellus is an extinct genus of trilobite, fossil marine arthropods, of relatively small size. Currently two species are attributed to it. Nephrolenellus lived at the end of the Lower Cambrian. Species are known from the Great Basin of California, Nevada and Arizona, with one specimen from Canada.
Morocconites malladoides is an average size trilobite, which lived during the Devonian period, in what is now southern Morocco. This species is assumed to be a close relative of Acastoides. The most conspicuous feature is the very long upcurved frontal medial spine, a bit like an avocet bill. It is the only known species in this genus.
Mallagnostus Howell, 1935, is a trilobite genus belonging to the family Weymouthiidae Kobayashi T. (1943), Order Agnostida Salter (1864) according to Whittington et al. 1997. It lived during the late Lower Cambrian, with remains found in USA, Canada (Newfoundland), Spain, England, Russia, Mongolia, and the early Middle Cambrian as reported from China and Russia (Yakutia).
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.
Psychopyge is a genus of trilobite, that lived during the upper Emsian and has been found in Germany and Morocco. It is characterized by the swordlike extension from the front of the head.
Cedaria is an extinct genus of trilobites from the late Cambrian.
Kendallina is a genus of parabolinoidid trilobite with an inverted egg-shaped outline, a wide headshield, small eyes, small deflected spines, 12 thorax segments and a small, short tailshield. It lived during the Late Cambrian in what are today Canada and the United States.
Orygmaspis is a genus of asaphid trilobite with an inverted egg-shaped outline, a wide headshield, small eyes, long genal spines, 12 spined thorax segments and a small, short tailshield, with four pairs of spines. It lived during the Upper Cambrian in what are today Canada and the United States.
Tricrepicephalus is an extinct genus of ptychopariid trilobites of the family Tricrepicephalidae with species of average size. Its species lived from 501 to 497 million years ago during the Dresbachian faunal stage of the late Cambrian Period. Fossils of Tricrepicephalus are widespread in Late Cambrian deposits in North America, but is also known from one location in South America. Tricrepicephalus has an inverted egg-shaped exoskeleton, with three characteristic pits in the fold that parallels the margin of the headshield just in front of the central raised area. The articulating middle part of the body has 12 segments and the tailshield carries two long, tubular, curved pygidial spines that are reminiscent of earwig's pincers that rise backwards from the plain of the body at approximately 30°.
Viaphacops is a genus of trilobites in the order Phacopida, family Phacopidae, that lived during the Middle Devonian, and is known from North and South America, Asia.