| Paradoxididae Temporal range: | |
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| Paradoxides | |
Scientific classification  | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Arthropoda |
| Class: | † Trilobita |
| Order: | † Redlichiida |
| Suborder: | † Redlichiina |
| Superfamily: | † Paradoxidoidea Hawle & Corda, 1847 |
| families | |
The Paradoxidoidea Hawle & Corda 1847, [1] are a superfamily of trilobites, a group of extinct marine arthropods. They occurred during the late Lower Cambrian (Toyonian) and disappeared at the end of the Middle Cambrian.
Species in this superfamily can be average (under 10 cm) to very large (over 30 cm), are relatively flat, have an inverted egg-shaped outline, a glabella that in early genera has parallel sides and expands forward in later representatives, and approaches or reaches the frontal border. All species have an almost semicircular headshield (or cephalon) with long backward directed genal spines. The facial suture in front of the eye diverges forward and outward in the Paradoxididae, while in the Centropleuridae it runs outward and even a bit backward (or retrodivergent). The articulate middle part of the body (or thorax) consists of 14 to 21 segments ending in sickle-shaped spines that to the back curve increasingly further backwards (Paradoxididae) or in bluntly truncated tips (Centropleuridae). While in the Paradoxididae the frontal two segments may be more robust, the thorax of the Centropleuridae is characterize by longer backward directed sickle shaped spines on the three rear thoracic segments. The tailshield (or pygidium) is typically small with an entire margin or pair of spines in Paradoxididae, and medium-sized with 2 or 3 pairs of marginal spines in the Centropleuridae. [2]
| 1 | Thorax with 15-21 segments tipped with sickle-shaped spines, frontal two may be enlarged. Pygidium small with an entire margin. → Paradoxididae |
|---|---|
| - | Thorax with 14-16 segments with rounded or truncated tips, except for the three next to the pygidium which are tipped with sickle-shaped spines. Pygidium medium-sized with two or three pairs of marginal spines. → Centropleuridae |
Redlichiida is an order of trilobites, a group of extinct marine arthropods. Species assigned to the order Redlichiida are among the first trilobites to appear in the fossil record, about halfway during the Lower Cambrian. Due to the difficulty to relate sediments in different areas, there remains some discussion, but among the earliest are Fallotaspis, and Lemdadella, both belonging to this order. The first representatives of the orders Corynexochida and Ptychopariida also appear very early on and may prove to be even earlier than any redlichiid species. In terms of anatomical comparison, the earliest redlichiid species are probably ancestral to all other trilobite orders and share many primitive characters. The last redlichiid trilobites died out before the end of the Middle Cambrian.
Paradoxides is a genus of large to very large trilobite found throughout the world during the Middle Cambrian period. One record-breaking specimen of Paradoxides davidis, described by John William Salter in 1863, is 37 cm (15 in). The cephalon was semicircular with free cheeks ending in long, narrow, recurved spines. Eyes were crescent shaped providing an almost 360° view, but only in the horizontal plane. Its elongate thorax was composed of 19–21 segments and adorned with longish, recurved pleural spines. Its pygidium was comparatively small. Paradoxides is a characteristic Middle-Cambrian trilobite of the 'Atlantic' (Avalonian) fauna. Avalonian rocks were deposited near a small continent called Avalonia in the Paleozoic Iapetus Ocean. Avalonian beds are now in a narrow strip along the East Coast of North America, and in Europe.
Agnostus is a genus of agnostid trilobites, belonging to the family Agnostidae, that lived during the late Middle Cambrian – early Upper Cambrian. It is the type genus of the family Agnostidae and is subdivided into two subgenera, Agnostus and Homagnostus.
The Paradoxididae are a family of trilobites, a group of extinct marine arthropods. They occurred during the late Lower Cambrian (Toyonian) and disappeared at the end of the Middle Cambrian. Representatives of this family have been found in the paleocontinents of Avalonia, Baltica, and Gondwana, now Canada, USA, England, Wales, Morocco, Spain, Czech Republic, Poland, Russia, Mongolia, and Turkey. Species in this family can typically grow large to very large, are relatively flat, have an inverted egg-shaped outline, opisthoparian sutures, a glabella that in early genera has parallel sides and expands forward in later representatives, and approaches or reaches the frontal border. All species have an almost semicircular headshield with long backward-directed genal spines. The articulate middle part of the body consists of 15 to 21 segments ending in sickle-shaped spines that to the back curve increasingly further backwards. The tailshield is small.
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.
Olenelloides armatus is an extinct, small sized olenelloid redlichiid trilobite arthropod. It lived during the later part of the Botomian stage, which lasted from approximately 524 to 518.5 million years ago. This faunal stage was part of the Cambrian Period. The most conspicuous feature is the hexagonal head shield that carries 6 ray-like spines..
Wanneria is an extinct genus from a well-known class of fossil marine arthropods, the trilobites. It lived during the later part of the Botomian stage, which lasted from approximately 524 to 518.5 million years ago. This faunal stage was part of the Cambrian Period. Wanneria walcottana is the only known species in this genus.
Acadagnostus is a genus of trilobite from the Middle Cambrian, with 7 species currently recognized. The type species A. acadicus has the widest distribution known from any peronopsid and has been found in North America, Greenland, England, Western Europe, Eastern Europe, Central Asia, the Altai Mountains, the Siberian shield, China, and Australia.
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.
Mesonacis is an extinct genus of trilobite that lived during the Botomian, found in North-America, and the United Kingdom. Some of the species now regarded part of Mesonacis, have previously been assigned to Angustolenellus or Olenellus (Angustolenellus). Angustolenellus is now regarded a junior synonym of Mesonacis.
Fallotaspis is a genus of redlichiid trilobites found in Early Cambrian-aged strata of the United States and Morocco.
Biceratops is an extinct genus of olenelloid redlichiid trilobites, of average size, with the largest specimen 8 centimetres or 3.1 inches long, not including the huge pleural spines of the 3rd segment of the thorax. It lived during the Toyonian stage, in what is today the South-Western United States. Biceratops can easily be distinguished from other members of Biceratopsidae by the absence of genal spines, in combination with effaced features of the raised axial area of the head shield, that is bordering the two horn-like projections that carry the eyes. Biceratops nevadensis is the only known species in this genus.
Mesolenellus is an extinct genus of trilobites that lived during the lower Cambrian (Botomian), found in Greenland and Spitsbergen.
Conocoryphe is a genus of primarily eyeless trilobites belonging to the family Conocoryphidae. They lived during the Middle Cambrian period, about 505 million years ago. These arthropods lived on the sea bottom (epifaunal) and lived off dead particulate organic matter.
Bolbolenellus is an extinct genus of trilobites, fossil marine arthropods, with five species attributed to it currently. It can be easily distinguished from all other trilobites by the combination of the absence of dorsal sutures in the head shield like all Olenellina, and a distinctly bulbous frontal lobe (L4) of the raised axial area in the head called glabella. The species lived at the end of the Lower Cambrian.
Eodiscina is trilobite suborder. The Eodiscina first developed near the end of the Lower Cambrian period and became extinct at the end of the Middle Cambrian. Species are tiny to small, and have a thorax of two or three segments. Eodiscina includes six families classified under one superfamily, Eodiscoidea.
The Condylopygidae Raymond (2013) are a family of small trilobites that lived during the Middle Cambrian, and found in Canada, the Czech Republic, Germany, France, Spain, England, Wales, Sweden, and the Russian Federation (Siberia). They uniquely differ from all other Agnostina in having the frontal glabellar lobe wider than the rear lobe. The Condylopygidae are the only family assigned to the Condylopygoidea superfamily.
Diplorrhina Hawle and Corda (1847) is a genus of trilobite belonging to Order Agnostida. It lived during the early Middle Cambrian in what are now the Czech Republic and the North Siberian plateau. as in members of the family Peronopsidae it lacks a preglabellar furrow. Both cephalon and pygidium lack spines. It is difficult to distinguish Diplorrhina from many other peronopsids.
Cyclopygidae is a family of asaphid trilobites from the Ordovician. Cyclopygids had an extratropical distribution, and there is evidence that they lived in darker parts of the water column. Cyclopygids are characterized by enlarged eyes, with a wide angle of view, both horizontal and vertical, reminiscent of the eyes of dragonflies. These typically touch the glabella directly on the side. Cyclopygids all lack genal spines, but Symphysops carries a forward directed frontal spine on the glabella. It is presumed that at least the members of the genus Pricyclopyge swam upside down and had bioluminescent organs on the third thorax segment. Cyclopygids had between 7 and 5 thorax segments, a wide and stout axis, and short side lobes.
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 Late Cambrian in what are today Canada and the United States.
Data related to Paradoxidoidea at Wikispecies
Media related to Paradoxidoidea at Wikimedia Commons  | This Redlichiida-related article is a stub. You can help Wikipedia by expanding it. |