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Mongolitubulus
''Mongolitubulus'' is a form genus encapsulating a range of ornamented conical small shelly fossils of the Cambrian period. It is potentially synonymous with ''Rushtonites'', ''Tubuterium'' and certain species of '' Rhombocorniculum'', and owing to the similarity of the genera, they are all dealt with herein. Organisms that bore ''Mongolitubulus''-like projections include trilobites, bradoriid arthropods and hallucigeniid lobopodians. Morphology The fossils consist of round, slender, pointed, spines with a slight curvature, and are covered with short rhomboid processes that spiral around the spine surface, forming a regular mosaic with a 60° angle of intersection. Spines vary from sub-millimetric up to two centimetres in length, but do not show any growth lines, suggesting that they were moulted and replaced. Species are defined on the basis of the ornamentation, which may of course be convergent. Spines of ''Rhombocorniculum cancellatum'' have a similar surface ornamenta ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Small Shelly Fossil
The small shelly fauna, small shelly fossils (SSF), or early skeletal fossils (ESF) are mineralized fossils, many only a few millimetres long, with a nearly continuous record from the latest stages of the Ediacaran to the end of the Early Cambrian Period. They are very diverse, and there is no formal definition of "small shelly fauna" or "small shelly fossils". Almost all are from earlier rocks than more familiar fossils such as trilobites. Since most SSFs were preserved by being covered quickly with phosphate and this method of preservation is mainly limited to the late Ediacaran and early Cambrian periods, the animals that made them may actually have arisen earlier and persisted after this time span. Some of the fossils represent the entire skeletons of small organisms, including the mysterious '' Cloudina'' and some snail-like molluscs. However, the bulk of the fossils are fragments or disarticulated remains of larger organisms, including sponges, molluscs, slug-like halkierii ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bradoriid
Bradoriids are an extinct order of small marine arthropods with a bivalved carapace, and were globally distributed, forming a significant portion of the Cambrian and Early Ordovician soft-bodied communities. Affinity Whilst the Bradoriida were traditionally considered as relatives of the modern bivalved arthropod group Ostracoda, the anatomy of their appendages does not support such a relationship; neither are they related to the Cambrian bivalved arthropod group Phosphatocopida. Rather, they are most probably related to the Eucrustacea at a stem-group level. An in-depth phylogenetic analysis of Panarthropoda included two bradoriid genera, '' Kunyangella'' and '' Kunmingella'', and recovered them as the most basal stem- mandibulates. Occurrence Bradoriida are geographically widespread, and first occur in the fossil record shortly before the earliest trilobite Trilobites (; meaning "three lobes") are extinct marine arthropods that form the class Trilobita. Trilob ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rhombocorniculum
''Rhombocorniculum'' is a species of small shelly fossil comprising twisted ornamented cones. It has been described from the Comely limestone and elsewhere. ''R. cancellatum'' straddles the Atdabanian/Botomian boundary. The structure of its inner layer suggests that its phosphatic fibres formed within a flexible organic matrix. Taxonomy Three species are recognized — in stratigraphic succession: ''R. insolutum'', ''R. cancellatum'' (=''R. walliseri''), and ''R. spinosus'' (=''Rushtonites spinosus''). Landing (1995) refers ''R. insolutum'' to the strictocorniculids, along with '' Rushtonites''. Hinz (1987) considers ''insolutum'' to fall within the variability seen in ''cancellatum''. Affinity Based on details of the ornament and construction, ''Rhombocorniculum'' is interpreted as the spines of a ''Hallucigenia''-like lobopodian worm. See also *''Mongolitubulus ''Mongolitubulus'' is a form genus encapsulating a range of ornamented conical small shelly fossils ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bradoriid
Bradoriids are an extinct order of small marine arthropods with a bivalved carapace, and were globally distributed, forming a significant portion of the Cambrian and Early Ordovician soft-bodied communities. Affinity Whilst the Bradoriida were traditionally considered as relatives of the modern bivalved arthropod group Ostracoda, the anatomy of their appendages does not support such a relationship; neither are they related to the Cambrian bivalved arthropod group Phosphatocopida. Rather, they are most probably related to the Eucrustacea at a stem-group level. An in-depth phylogenetic analysis of Panarthropoda included two bradoriid genera, '' Kunyangella'' and '' Kunmingella'', and recovered them as the most basal stem- mandibulates. Occurrence Bradoriida are geographically widespread, and first occur in the fossil record shortly before the earliest trilobite Trilobites (; meaning "three lobes") are extinct marine arthropods that form the class Trilobita. Trilob ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Form Genus
Form classification is the classification of organisms based on their morphology, which does not necessarily reflect their biological relationships. Form classification, generally restricted to palaeontology, reflects uncertainty; the goal of science is to move "form taxa" to biological taxa whose affinity is known. Form taxonomy is restricted to fossils that preserve too few characters for a conclusive taxonomic definition or assessment of their biological affinity, but whose study is made easier if a binomial name is available by which to identify them. The term "form classification" is preferred to "form taxonomy"; taxonomy suggests that the classification implies a biological affinity, whereas form classification is about giving a name to a group of morphologically-similar organisms that may not be related. A "parataxon" (not to be confused with parataxonomy), or "sciotaxon" (Gr. "shadow taxon"), is a classification based on incomplete data: for instance, the larval stage ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Acid Maceration
Fossil preparation is the act of preparing fossil specimens for use in paleontological research or for exhibition, and involves removing the surrounding rocky matrix and cleaning the fossil. Techniques Acid maceration Acid maceration is a technique to extract organic microfossils from a surrounding rock matrix using acid. Hydrochloric acid or acetic acid may be used to extract phosphatic fossils, such as the small shelly fossils, from a carbonate matrix. Hydrofluoric acid is also used in acid macerations to extract organic fossils from silicate rocks. Fossiliferous rock may be immersed directly into the acid, or a cellulose nitrate film may be applied ( dissolved in amyl acetate), which adheres to the organic component and allows the rock to be dissolved around it. Film pull The film pull technique is a means of recovering carbonaceous compression fossils for study under transmitted light microscopy. An acid is applied to the surface of the rock to etch away the matrix from ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Controversial Taxa
Controversy is a state of prolonged public dispute or debate, usually concerning a matter of conflicting opinion or point of view. The word was coined from the Latin ''controversia'', as a composite of ''controversus'' – "turned in an opposite direction". Legal In the jurisprudence, theory of law, a controversy differs from a legal case; while legal cases include all suits, Criminal law, criminal as well as civil law (common law), civil, a controversy is a purely civil proceeding. For example, the Case or Controversy Clause of Article Three of the United States Constitution (Article Three of the United States Constitution#Section 2: Judicial power, jurisdiction, and trial by jury, Section 2, Clause 1) states that "the judicial Power shall extend ... to Controversies to which the United States shall be a Party". This clause has been deemed to impose a requirement that United States federal courts are not permitted to cases that do not pose an actual controversy—th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Prehistoric Crustacean Genera
Prehistory, also known as pre-literary history, is the period of human history between the use of the first stone tools by hominins 3.3 million years ago and the beginning of recorded history with the invention of writing systems. The use of symbols, marks, and images appears very early among humans, but the earliest known writing systems appeared 5000 years ago. It took thousands of years for writing systems to be widely adopted, with writing spreading to almost all cultures by the 19th century. The end of prehistory therefore came at very different times in different places, and the term is less often used in discussing societies where prehistory ended relatively recently. In the early Bronze Age, Sumer in Mesopotamia, the Indus Valley Civilisation, and ancient Egypt were the first civilizations to develop their own scripts and to keep historical records, with their neighbors following. Most other civilizations reached the end of prehistory during the following Iron Age. T ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Arthropod Enigmatic Taxa
Arthropods (, (gen. ποδός)) are invertebrate animals with an exoskeleton, a segmented body, and paired jointed appendages. Arthropods form the phylum Arthropoda. They are distinguished by their jointed limbs and cuticle made of chitin, often 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 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 organs; it has an open circulatory system. Like their exteriors, the internal organs of arthropods are generally built of repeated segments. Their nervous system is "ladder- ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cambrian Arthropods
The Cambrian Period ( ; sometimes symbolized Ꞓ) was the first geological period of the Paleozoic Era, and of the Phanerozoic Eon. The Cambrian lasted 53.4 million years from the end of the preceding Ediacaran Period 538.8 million years ago (mya) to the beginning of the Ordovician Period mya. Its subdivisions, and its base, are somewhat in flux. The period was established as "Cambrian series" by Adam Sedgwick, who named it after Cambria, the Latin name for 'Cymru' (Wales), where Britain's Cambrian rocks are best exposed. Sedgwick identified the layer as part of his task, along with Roderick Murchison, to subdivide the large "Transition Series", although the two geologists disagreed for a while on the appropriate categorization. The Cambrian is unique in its unusually high proportion of sedimentary deposits, sites of exceptional preservation where "soft" parts of organisms are preserved as well as their more resistant shells. As a result, our understanding of the Cambrian biolo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Form Taxon
Form classification is the classification of organisms based on their morphology, which does not necessarily reflect their biological relationships. Form classification, generally restricted to palaeontology, reflects uncertainty; the goal of science is to move "form taxa" to biological taxa whose affinity is known. Form taxonomy is restricted to fossils that preserve too few characters for a conclusive taxonomic definition or assessment of their biological affinity, but whose study is made easier if a binomial name is available by which to identify them. The term "form classification" is preferred to "form taxonomy"; taxonomy suggests that the classification implies a biological affinity, whereas form classification is about giving a name to a group of morphologically-similar organisms that may not be related. A "parataxon" (not to be confused with parataxonomy), or "sciotaxon" (Gr. "shadow taxon"), is a classification based on incomplete data: for instance, the larval stage o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Burgess Shale-type Deposit
The Burgess Shale of British Columbia is famous for its exceptional preservation of mid-Cambrian organisms. Around 69 other sites have been discovered of a similar age, with soft tissues preserved in a similar, though not identical, fashion. Additional sites with a similar form of preservation are known from the Ediacaran and Ordovician periods. These various shales are of great importance in the reconstruction of the ecosystems immediately after the Cambrian explosion. The taphonomic regime results in soft tissue being preserved, which means that organisms without hard parts that could be conventionally fossilised can be seen; also, we gain an insight into the organs of more familiar organisms such as the trilobites. The most famous localities preserving organisms in this fashion are the Canadian Burgess Shale, the Chinese Chengjiang fauna, and the more remote Sirius Passet in north Greenland. However, a number of other localities also exist. Distribution Burgess Shale-type biota ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
