| Phytophilaspis Temporal range: | |
|---|---|
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Scientific classification  | |
| Kingdom: | Animalia |
| Phylum: | Arthropoda |
| (unranked): | † Artiopoda |
| Subphylum: | † Trilobitomorpha |
| (unranked): | † Xandarellida |
| Genus: | † Phytophilaspis Ivantsov, 1999 [1] |
| Species | |
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Phytophilaspis is a phosphatized [2] genus of trilobite-like arthropod with eyes, found in association with algal remains. [1] It dwelt in well-lit, shallow waters. [3]
Phytophilaspis has several features in common with trilobites, including: tripartite division of the dorsal shield; presence of prominent pygidium; large eyes, situated on the pleural area of the cephalon; facial sutures, and shape of the hypostome. However, it differs from trilobites in many ways, including a reduced thorax, thoracic pleura fused to each other and to the cephalon and pygidium, facial sutures not crossing the eyes, and weak original mineralization of the cuticle. [1] Because of these differences, Phytophilaspis was originally assigned to the Artiopodan subclass Concilliterga, in an undetermined order and family. [1] It was later considered by Bergström and Hou as a xandarellid, along with Cindarella , Xandarella and Sinoburius . [4] A position that was supported in subsequent studies. [5]
Agnostida are an order of extinct arthropods which have classically been seen as a group of highly modified trilobites, though some recent research has doubted this placement. Regardless, they appear to be close relatives as part of the Artiopoda. They are present in the Lower Cambrian fossil record along with trilobites from the Redlichiida, Corynexochida, and Ptychopariida orders, and were highly diverse throughout the Cambrian. Agnostidan diversity severely declined during the Cambrian-Ordovician transition, and the last agnostidans went extinct in the Late Ordovician.
Naraoiidae is a family, of extinct, soft-shelled trilobite-like arthropods, that belongs to the order Nectaspida. Species included in the Naraoiidae are known from the second half of the Lower Cambrian to the end of the Upper Silurian. The total number of collection sites is limited and distributed over a vast period of time: Maotianshan Shale and Balang Formation (China), Burgess Shale and Bertie Formation (Canada), the Šárka Formation, Emu Bay Shale (Australia), Idaho and Utah (USA). This is probably due to the rare occurrence of the right circumstances for soft tissue preservation, needed for these non-calcified exoskeletons.
Trilobites 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 Atdabanian stage of the Early Cambrian period and they flourished throughout the lower Paleozoic before slipping into a long decline, when, during the Devonian, all trilobite orders except the Proetida died out. The last extant trilobites finally disappeared in the mass extinction at the end of the Permian about 252 million years ago. Trilobites were among the most successful of all early animals, existing in oceans for almost 270 million years, with over 22,000 species having been described.
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.
Naraoia is a genus of small to average size marine arthropods within the family Naraoiidae, that lived from the early Cambrian to the late Silurian period. The species are characterized by a large alimentary system and sideways oriented antennas.
Misszhouia is a genus of small to average sized marine arthropods within the Naraoiidae family, that lived during the early Cambrian period. The only species presently known is Misszhouia longicaudata and the holotype was discovered in 1984.
Asaphus is a genus of trilobites that is known from the Lower and Middle Ordovician of northwestern Europe.
Yunnanocephalus is a genus of ptychopariid trilobite. It lived during the late Atdabanian and Botomian stages, in what are currently Antarctica, Australia and China. It was a "moderately common" member of the Chengjiang Fauna. Yunnanocephalus is the only genus currently assigned to the Yunnanocephalidae family.
Acanthomeridion is an extinct arthropod found in the Chengjiang fauna deposits of China. In 1997, it was placed in its own, monotypic family, Acanthomeridiidae. It is known from eight specimens, all found in China.
Cindarella is genus of trilobite-like Cambrian arthropod known from the Chengjiang biota of China. It is classified in the stem group of trilobites (Artiopoda) in the clade Xandarellida, along with Phytophilaspis, Sinoburius, and Xandarella.
Panlongia was a small-sized marine arthropod, with an oval-shaped non-calcified exoskeleton. Both the head shield and the tail shield are semi-circular. In between the cephalon and pygidium are four thoracic body segments (somites). The cephalon occupies approximately ⅓ of the body length, the thorax ¼ and pygidium about 45%. Panlongia lived during the late Lower Cambrian (Botomian) in what is today South China. In Panlongia spinosa the edge of the exoskeleton carries several small sawtooth-like spines, that are absent in P. tetranodusa.
The cephalon is the head section of an arthropod. It is a tagma, i.e., a specialized grouping of arthropod segments. The word cephalon derives from the Greek κεφαλή (kephalē), meaning "head".
Emucarididae is an extinct family of soft-shelled trilobite-like arthropods (nektaspids) from the Lower Cambrian of South Australia and South China. It contains only two genera – Emucaris and Kangacaris. Two species were described in 2010 from specimens recovered from Emu Bay Shale Lagerstätte, one species in 2012 from the Maotianshan Shales. It is classified under the order Nektaspida, and is a sister-group to the families Liwiidae and Naraoiidae.
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.
Marocconus is an extinct genus from a well-known class of fossil marine arthropods, the trilobites. It is still debated if it lived at the very end of the Lower Cambrian or at the very beginning of the Middle Cambrian. Marocconus notabilis is the only known species in this genus.
Tricrepicephalus is an extinct genus of ptychopariid trilobites of the family Tricrepicephalidae with species of average size. Its species lived from 501 to 490 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°.
Squamacula is an extinct artiopodan arthropod from the Cambrian Series 2. The type species S. clypeata was described in 1997 from the Chengjiang biota of Yunnan, China. At the time of description there were only two known specimens of S. clypeata, but now there are at least six known specimens. In 2012 a second species S. buckorum was described from the Emu Bay Shale of Australia.
Sinoburius is an extinct genus of xandarellid artiopodan known from the Cambrian aged Chengjiang Biota of China. It is only known from the type species S. lunaris, which was described in 1991. It is a rare fossil within the Chengjiang assemblage. Like other Xandarellids, Sinoburius has an unmineralised exoskeleton. Adult individuals are around 7-8 millimetres in length, with stalked eyes present on the ventral side. Unusually among artiopods, the antennae are strongly reduced in size.
Xandarella is an extinct genus of xandarellid artiopodan known from the Cambrian of China and Morocco, the type species Xandarella spectaculum was described in 1991 from the Cambrian Stage 3 aged Chengjiang Biota in China. An additional species Xandarella mauretanica was described from the Cambrian Stage 5 Tatelt Formation in Morocco in 2017, which preserved only the ventral anatomy. Like other Xandarellids, the exoskeleton is unmineralised. The cephalon has pronounced eye slits, presumably derived from ancestral ventral stalked eyes.
Retifacies is an extinct arthropod, that lived in the lower Cambrian. Its fossil remains have been found in the Maotianshan Shales of Yunnan, China. It is a member of the Artiopoda.
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