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Mollisoniida
Mollisoniida is an extinct order of chelicerates, living from the mid-Cambrian to Early Ordovician. The clade is united by the presence of various characteristics. These include an elongated dorsal exoskeleton, seven articulating tergites and similarly sized cephalic and pygidial shields, in addition to only having three pairs of walking legs and the rest of the limbs being used as gills (which likely places them nearest to Euchelicerata, due to sharing similar arrangements of limbs). The clade is relatively diverse, containing three (possibly four) genera. '' Mollisonia'' and '' Thelxiope'' are both known from four species extending from Cambrian to Ordovician, with ''Thelxiope'' being very spiny and often with a shortened body. ''Mollisonia'', on the other hand, barely has any spines at all, and (with the exception of ''Mollisonia plenovenatrix'' and ''Mollisonia sinica'', which are similarly shaped to ''Thelxiope'') has a relatively elongated body. '' Corcorania'' is purely ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Urokodia
''Urokodia'' is an extinct genus of marine arthropod from the early Cambrian. The only known species is ''Urokodia aequalis'' from the Maotianshan Shales of China based on some 15 specimens. Description ''Urokodia'' is an elongated arthropod measuring up to 3.5 cm. The dorsal exoskeleton (tergite) is composed of a cephalon (head) and a pygidium (tail shield) of subequal size. Both were initially thought to be nearly identical, possessing 4 pairs of large lateral spikes. However, subsequent studies revealed that the pygidium had a distinct triangular shape and a parallel row of tiny posterior spikes. Between the cephalon and pygidium was an elongated thorax of 14 or 15 segments. It possesses a pair of stalked eyes and stubby antennae below the front of its head. The remaining ventral region possesses subequal appendages with annulated bases and lamellar (lobe-like) outer branches, 3 pairs under both cephalon and pygidium and 1 pair under each thoracic segment. All but the pygid ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chelicerates
The subphylum Chelicerata (from Neo-Latin, , ) constitutes one of the major subdivisions of the phylum Arthropoda. Chelicerates include the sea spiders, horseshoe crabs, and arachnids (including harvestmen, scorpions, spiders, solifuges, ticks, and mites, among many others), as well as a number of extinct lineages, such as the eurypterids (sea scorpions) and chasmataspidids. Chelicerata split from Mandibulata by the mid-Cambrian, as evidenced by stem-group chelicerates like Habeliida and '' Mollisonia'' present by this time. The surviving marine species include the four species of xiphosurans (horseshoe crabs), and possibly the 1,300 species of pycnogonids (sea spiders), if the latter are indeed chelicerates. On the other hand, there are over 77,000 well-identified species of air-breathing chelicerates, and there may be about 500,000 unidentified species. Like all arthropods, chelicerates have segmented bodies with jointed limbs, all covered in a cutic ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chelicerate Orders
The subphylum Chelicerata (from Neo-Latin, , ) constitutes one of the major subdivisions of the phylum Arthropoda. Chelicerates include the sea spiders, horseshoe crabs, and arachnids (including Opiliones, harvestmen, scorpions, spiders, Solifugae, solifuges, Tick, ticks, and Mite, mites, among many others), as well as a number of extinct lineages, such as the eurypterids (sea scorpions) and chasmataspidids. Chelicerata split from Mandibulata by the mid-Cambrian, as evidenced by stem-group chelicerates like Habeliida and ''Mollisonia'' present by this time. The surviving marine species include the four species of xiphosurans (horseshoe crabs), and possibly the 1,300 species of Pycnogonida, pycnogonids (sea spiders), if the latter are indeed chelicerates. On the other hand, there are over 77,000 well-identified species of air-breathing chelicerates, and there may be about 500,000 unidentified species. Like all arthropods, chelicerates have Segmentation (biology), ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
