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Retifacies
''Retifacies'' (''Retifacies abnormalis'') is an extinct arthropod, that lived in the lower Cambrian (about 518 million years ago). Its fossil remains have been found in the Maotianshan Shales of Yunnan, China. It is a member of the Artiopoda. Description This large animal could reach 55 centimeters in length, even though most of the specimens found were smaller. The cephalic shield was short, and was followed by a dozen tergites that overlapped each other. The rear part of the body consisted of a large shield and a long segmented tail. All the tergites had a surface made up of irregular polygons, unknown among other Maotianshan arthropods. Ventrally there were probably no eyes placed on peduncles, and immediately alongside there were two long antennae with short bristles. Like many primitive arthropods, this animal also had the classic biramous appendages, eighteen pairs in number. Three of these were positioned under the head, ten corresponded to the thoracic wipes and five ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Retifacies Diagram
''Retifacies'' (''Retifacies abnormalis'') is an extinct arthropod, that lived in the lower Cambrian (about 518 million years ago). Its fossil remains have been found in the Maotianshan Shales of Yunnan, China. It is a member of the Artiopoda. Description This large animal could reach 55 centimeters in length, even though most of the specimens found were smaller. The cephalic shield was short, and was followed by a dozen tergites that overlapped each other. The rear part of the body consisted of a large shield and a long segmented tail. All the tergites had a surface made up of irregular polygons, unknown among other Maotianshan arthropods. Ventrally there were probably no eyes placed on peduncles, and immediately alongside there were two long antennae with short bristles. Like many primitive arthropods, this animal also had the classic biramous appendages, eighteen pairs in number. Three of these were positioned under the head, ten corresponded to the thoracic wipes and fi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Retifacies
''Retifacies'' (''Retifacies abnormalis'') is an extinct arthropod, that lived in the lower Cambrian (about 518 million years ago). Its fossil remains have been found in the Maotianshan Shales of Yunnan, China. It is a member of the Artiopoda. Description This large animal could reach 55 centimeters in length, even though most of the specimens found were smaller. The cephalic shield was short, and was followed by a dozen tergites that overlapped each other. The rear part of the body consisted of a large shield and a long segmented tail. All the tergites had a surface made up of irregular polygons, unknown among other Maotianshan arthropods. Ventrally there were probably no eyes placed on peduncles, and immediately alongside there were two long antennae with short bristles. Like many primitive arthropods, this animal also had the classic biramous appendages, eighteen pairs in number. Three of these were positioned under the head, ten corresponded to the thoracic wipes and five ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Artiopoda
The Artiopoda is a grouping of extinct arthropods that includes trilobites and their close relatives. It was erected by Hou and Bergström in 1997 to encompass a wide diversity of arthropods that would traditionally have been assigned to the Trilobitomorpha. Hou and Bergström used the name Lamellipedia as a superclass to replace Trilobitomorpha that was originally erected at the subphylum level, which they considered inappropriate. Trilobites, in part due to their mineralising exoskeletons, are by far the most diverse and long lived members of the clade, with most records of other members, which lack mineralised exoskeletons, being from Cambrian deposits. Description According to Stein and Selden (2012) artiopods are recognised by the possession of filiform antennulae, limbs with bilobate exopods, with the proximal lobe being elongate and bearing a lamella, while the distal lobe is paddle-shaped and setiforous (bearing hair-or bristle like structures). The limb endopod has se ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pygmaclypeatus
''Pygmaclypeatus'' is a genus of trilobite-like arthropod from the Cambrian aged Chengjiang biota of southern China. It is less than 20 mm in length. The carapace is flat and broad, and slightly shorter than it is wide. The trunk has 6 tergites, along with a terminal pygidium associated with a segmented short tailspine. The well developed paddle-like exopodites on the trunk limbs along with its small size suggests that it was an effective swimmer with a strong power stroke, and that it probably had a nektobenthic mode of life, swimming close to the ocean floor. Given its delicate spinose endites on the limbs it likely only consumed soft food and organic particles. It is considered to be closely related to ''Retifacies'' from the same deposit with shared characters including a segmented tailspine. It has been placed as a member of Artiopoda, possibly along with ''Retifacies'' the earliest diverging lineage of the Trilobitomorpha The Artiopoda is a grouping of extinct arthropods th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cambrian Stage 3
Cambrian Stage 3 is the still unnamed third stage of the Cambrian. It succeeds Cambrian Stage 2 and precedes Cambrian Stage 4, although neither its base nor top have been formally defined. The plan is for its lower boundary to correspond approximately to the first appearance of trilobites, about million years ago, though the globally asynchronous appearance of trilobites warrants the use of a separate, globally synchronous marker to define the base. The upper boundary and beginning of Cambrian Stage 4 is informally defined as the first appearance of the trilobite genera ''Olenellus'' or '' Redlichia'' around million years ago. Naming The International Commission on Stratigraphy has not officially named the 3rd stage of the Cambrian. The stage approximately corresponds to the "Atdabanian", which is used by geologists working in Siberia. Biostratigraphy The oldest trilobite known is ''Lemdadella'' which appears at the beginning of the '' Fallotaspis'' zone. The Cambrian radiati ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Arthropod
Arthropods (, (gen. ποδός)) are invertebrate animals with an exoskeleton, a Segmentation (biology), segmented body, and paired jointed appendages. Arthropods form the phylum Arthropoda. They are distinguished by their jointed limbs and Arthropod cuticle, cuticle made of chitin, often Mineralization (biology), mineralised with calcium carbonate. The arthropod body plan consists of segments, each with a pair of appendages. Arthropods are bilaterally symmetrical and their body possesses an exoskeleton, external skeleton. In order to keep growing, they must go through stages of moulting, a process by which they shed their exoskeleton to reveal a new one. Some species have wings. They are an extremely diverse group, with up to 10 million species. The haemocoel, an arthropod's internal cavity, through which its haemolymph – analogue of blood – circulates, accommodates its interior Organ (anatomy), organs; it has an open circulatory system. Like their exteriors, the internal or ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Maotianshan Shales
The Maotianshan Shales are a series of Cambrian, Early Cambrian deposits in the Chiungchussu Formation, famous for their ''Lagerstätte, Konservat Lagerstätten'', deposits known for the exceptional preservation of fossilized organisms or traces. The Maotianshan Shales form one of some forty Cambrian fossil locations worldwide exhibiting exquisite preservation of rarely preserved, non-mineralized soft tissue, comparable to the fossils of the Burgess Shale. They take their name from Maotianshan Hill (, Literal meaning: Hat Sky Mountain) in Chengjiang County, Yunnan Province, China. The most famous assemblage of organisms are referred to as the Chengjiang biota for the multiple scattered fossil sites in Chengjiang. The age of the Chengjiang Lagerstätte is locally termed Qiongzhusian, a stage correlated to the late Atdabanian Stage in Siberian sequences of the middle of the Early Cambrian. The shales date to ≤. The shales also contain the slightly younger Guanshan biota from Mal ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tergites
A ''tergum'' (Latin for "the back"; plural ''terga'', associated adjective tergal) is the dorsal ('upper') portion of an arthropod segment other than the head. The anterior edge is called the 'base' and posterior edge is called the 'apex' or 'margin'. A given tergum may be divided into hardened plates or sclerites commonly referred to as tergites. In a thoracic segment, for example, the tergum may be divided into an anterior notum and a posterior scutellum. Lateral extensions of a tergite are known as paranota (Greek for "alongside the back") or ''carinae'' (Latin for "keel"), exemplified by the flat-backed millipedes of the order Polydesmida. Kinorhynchs have tergal and sternal plates too, though seemingly not homologous with those of arthropods. Tergo-tergal is a stridulatory mechanism in which fine spines of the abdominal tergites are rubbed together to produce sound. This process is known as abdominal telescoping. Examples File:Andrena spiraeana abdomen.jpg , Abdominal t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Arthropod Leg
The arthropod leg is a form of jointed appendage of arthropods, usually used for walking. Many of the terms used for arthropod leg segments (called podomeres) are of Latin origin, and may be confused with terms for bones: ''coxa'' (meaning hip, plural ''coxae''), ''trochanter'', ''femur'' (plural ''femora''), ''tibia'' (plural ''tibiae''), ''tarsus'' (plural ''tarsi''), ''ischium'' (plural ''ischia''), ''metatarsus'', ''carpus'', ''dactylus'' (meaning finger), ''patella'' (plural ''patellae''). Homologies of leg segments between groups are difficult to prove and are the source of much argument. Some authors posit up to eleven segments per leg for the most recent common ancestor of extant arthropods but modern arthropods have eight or fewer. It has been argued that the ancestral leg need not have been so complex, and that other events, such as successive loss of function of a ''Hox''-gene, could result in parallel gains of leg segments. In arthropods, each of the leg segments ar ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Helmetia
''Helmetia'' is an extinct genus of arthropod from the middle Cambrian. Its fossils have been found in the Burgess Shale of Canada and the Jince Formation of the Czech Republic. Fossils are both rare and poorly known; the genus was described by Walcott in 1918 and has not been reexamined, though it was briefly reviewed in the 1990s and has been included in a number of cladistic analyses. It has been lumped with the arachnomorphs. One analysis has resolved the Helmetiiida as a robust clade and the closest relatives of trilobites. The most complete specimen of ''Helmetia'' is 19 cm long, and has six thoracic segments. There is a head shield and a large tail shield, making the animal leaf-shaped. Unlike trilobites, the margin of the head shield is concave, ending in a spine on each corner. There is an oval structure with two spots at the anterior center of the head shield, behind which are two eyes. The whole animal is broad and flat with a thin exoskeleton. The central region ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Naraoia
''Naraoia'' is a genus of small to average size (about 2-4½ cm long) 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. Etymology The name is derived from Narao, the name of a group of small lakes in Cataract Brook canyon, above Hector on the Canadian Pacific Railway, British Columbia, Canada.Walcott, C.D. Middle Cambrian Branchiopoda, Malacostraca, Trilobita, and Merostomata. In: Cambrian Geology and Paleontology II. Smithsonian. 1914. s:Cambrian Geology and Paleontology/Volume 2/Middle Cambrian Branchiopoda, Malacostraca, Trilobita, and Merostomata History of the classification When the fossil was first discovered in Canada's Burgess Shale, it was believed to be a crustacean, such was the difference between this and other trilobites. Its continuous shield hid most of its structure, interfering with proper classification. Wh ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Emeraldella
''Emeraldella'' is a genus of arthropod known from the Middle Cambrian of North America. The type species ''E. brocki'' was described in 1912 from the Burgess Shale. 21 specimens of ''Emeraldella'' are known from the Greater Phyllopod bed, where they comprise < 0.1% of the community. A re-study on the species was done in 2012. A second species ''E. brutoni'' is known from the Wheeler Shale, which was described in 2011. An additional specimen of ''E. brutoni'' was described in 2019, which revealed more of the anatomy. It has been placed as part of the Artiopoda, a group of arthropods containing Trilobite, trilobites and their relatives. Description Caudal flaps are present on the terminal tergite, alongside an elongated spine.''Emeraldella'' ''brocki'' ''E. brocki'' is at least 60 mm in length, it possesses 12 tergites in t ...[...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
