Mongolitubulus Temporal range: | |
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Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Arthropoda |
Order: | † Bradoriida |
Genus: | † Mongolitubulus Missarzhevsky, 1977 [2] |
Species | |
Synonyms | |
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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, [1] [4] [5] they are all dealt with herein. Organisms that bore Mongolitubulus-like projections include trilobites, bradoriid arthropods and hallucigeniid lobopodians. [6]
The fossils consist of round, slender, pointed, spines with a slight curvature, [1] and are covered with short rhomboid processes that spiral around the spine surface, forming a regular mosaic with a 60° angle of intersection. [5] 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. [7] Species are defined on the basis of the ornamentation, which may of course be convergent.
Spines of Rhombocorniculum cancellatum have a similar surface ornamentation and are also curved, sometimes in two dimensions to form a 'screw'; they had an inner and outer organic layer that surrounded a layer of pillar-like apatite crystals; these enclosed a honeycomb-like structure of narrow edge-parallel chambers. [8] This genus is a useful biostratigraphic marker of the Lower Cambrian. The rhomboid ornament uniformly covers all the spine, with the exception (in some cases) of the smooth-surfaced tip. [9]
Mongolitubulus has a comparable structure; phosphatic fossils show that there was a smooth outer layer about 2–3.5 μm thick, a 10–15 μm-thick inner layer comprising axis-parallel fibres that are each ~1 μm wide, and a large cavity in the centre of the spine. [5]
Species | Distinguishing features | Probable affinity |
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M. henrikseni Skovsted & Peel, 2001 | Ornament of rounded conical protrusions, sometimes associated with faint ridges, at high angle to spine, irregularly arranged at low density. Spines circular in cross-section, straight to gently curved, more parallel-sided than M. squamifer. Tip of spine may be truncated or bifurcate slightly. Original microstructure unknown, but apparently formed two layers. Flaring of base, which is attached to bradoriid carapace. [1] [10] | Bradoriid |
M. squamifer Missarzhevsky, 1977 (type) | Regular ornament of rhomboidal to rounded projections arranged in spirals at 60° angle to form regular pattern; these lift slightly from the surface of the spine, directed towards its tip; their intensity fades at the tip, which is generally smooth-walled. Fibrous internal layer with high organic content. [1] Further, very thin layer within this, no structure apparent. [11] Spines are straight or gently curved; the pointed tip is always straight. Circular cross-section. Reaching 2.3 mm in length. [3] Base does not flare. [12] | Trilobite? [13] |
M. spinosus (Hinz, 1987) [14] | Described as Rushtonites and since synonymized. Incomplete fragments reach 3 mm in length. Apical angle 5°. Base unknown. Gentle curvature. Spine ornament of rhombi with rounded tips, arrangement slightly deviates from regular pattern, with adjacent rhombi in places so close as to seem to merge. Wall in two layers, microstructure unknown. | Unknown |
"Rushtonites" astiaca [15] | Spinose processes, not scales. [1] | Unknown |
M. unispinosa Topper et al.. 2007 [3] (=Spinella unialata) [12] | Carapaces with a single central spine. Ornament irregularly distributed, comprising short cones or pustules at steep angle to spine. Spine straight or slightly curved, with pointed tip. Cross-section circular. Base flares to join with carapace. | Bradoriid |
M. reticulatus Kouchinsky et al., 2010 | Flaring base. Parallel edged near base, becoming highly curved in final quarter of length near tip. Pointed tip and circular cross-section. Two mineralogical layers (both calcium phosphate); inner layer bears transverse lineations, resembling growth lines, not entirely straight. Outer layer bears a polygonal network, grading into a more linear, axis-parallel fabric near the base. Up to 2.5 mm long. Observed attached to carapaces. | Bradoriid |
M. henrikseni has been shown to be part of the carapace of a bivalved bradoriid arthropod. [10] However, the affinity of M. squamifer is still unresolved; the genus may transpire to be a form taxon, which would require M. henrikseni to be re-classified into a new genus. [10] Unlike the spines of M. henrikseni, which flare out at the base where they attach to the cuticle, the spines of M. squamifer are more parallel-sided, with the fossil material becoming thinner towards the base: consistent with their attachment to non-mineralized cuticle. [7] M. squamifer spines appear to have formed in pairs, owing to their symmetry; on this basis they have been likened to the spines of certain armoured lobopods known from Burgess shale-type deposits. [7] This speculative claim has been substantiated for some material attributed to Mongolitubulus, based on similarities with the spines of the hallucigeniid lobopodians. [6]
The trilobite Hupeidiscus orinentalis has spinose projections with a rhomboidal ornamentation that resembles that seen in Mongolitubulus, so some Mongolitubulus material may represent trilobites. [13]
The spines often comprise layers of phosphate, with a central void often infilled with diagenetic phosphate. [7] Similar spines have been recovered from acid macerations, where they are preserved as films of organic carbon. [16]
Mongolitubulus is known from the Botomian to the lower strata of the Middle Cambrian, [1] and have a worldwide distribution, [7] being found on every continent including Antarctica. [3]
Rhombocorniculum is known from a variety of localities, including England [17] and Massachusetts. [18]
Lobopodians are members of the informal group Lobopodia, or the formally erected phylum Lobopoda Cavalier-Smith (1998). They are panarthropods with stubby legs called lobopods, a term which may also be used as a common name of this group as well. While the definition of lobopodians may differ between literatures, it usually refers to a group of soft-bodied, marine worm-like fossil panarthropods such as Aysheaia and Hallucigenia.
Hallucigenia is a genus of lobopodian known from Cambrian aged fossils in Burgess Shale-type deposits in Canada and China, and from isolated spines around the world. The generic name reflects the type species' unusual appearance and eccentric history of study; when it was erected as a genus, H. sparsa was reconstructed as an enigmatic animal upside down and back to front. Lobopodians are a grade of Paleozoic panarthropods from which the velvet worms, water bears, and arthropods arose.
Opabinia regalis is an extinct, stem group arthropod found in the Middle Cambrian Burgess Shale Lagerstätte of British Columbia. Opabinia was a soft-bodied animal, measuring up to 7 cm in body length, and its segmented trunk had flaps along the sides and a fan-shaped tail. The head shows unusual features: five eyes, a mouth under the head and facing backwards, and a clawed proboscis that probably passed food to the mouth. Opabinia probably lived on the seafloor, using the proboscis to seek out small, soft food. Fewer than twenty good specimens have been described; 3 specimens of Opabinia are known from the Greater Phyllopod bed, where they constitute less than 0.1% of the community.
Microdictyon is an extinct armoured worm-like panarthropod coated with net-like scleritic plates, known from the Early Cambrian Maotianshan shale of Yunnan China and other parts of the world. Microdictyon is part of the ill-defined taxon – Lobopodia – that includes several other odd worm-like animals that resembling worm with legs, such as Hallucigenia, Onychodictyon, Cardiodictyon, Luolishania, and Paucipodia. The isolated sclerites of Microdictyon are known from other Lower Cambrian deposits. Microdictyon sclerites appear to have moulted; one sclerite seems to have been preserved during ecdysis.
Sidneyia is an extinct arthropod known from fossils found from the Early to the Mid Cambrian of China and the Mid Cambrian Burgess Shale of British Columbia, Canada.
Dinocaridida is a proposed fossil taxon of basal arthropods that flourished in the Cambrian period with occasional Ordovician and Devonian records. Characterized by a pair of frontal appendages and series of body flaps, the name of Dinocaridids refers to the suggested role of some of these members as the largest marine predators of their time. Dinocaridids are occasionally referred to as the 'AOPK group' by some literatures, as the group compose of Radiodonta, Opabiniidae, and the "gilled lobopodians" Pambdelurion and Kerygmachelidae. It is most likely paraphyletic, with Kerygmachelidae and Pambdelurion more basal than the clade compose of Opabiniidae, Radiodonta and other arthropods.
The Emu Bay Shale is a geological formation in Emu Bay, South Australia, containing a major Konservat-Lagerstätte. It is one of two in the world containing Redlichiidan trilobites. The Emu Bay Shale is dated as Cambrian Series 2, Stage 4, correlated with the upper Botomian Stage of the Lower Cambrian.
Shelly limestone is a highly fossiliferous limestone, composed of a number of fossilized organisms such as brachiopods, bryozoans, crinoids, sponges, corals and mollusks. It varies in color, texture and hardness. Coquina is a poorly indurated form of shelly limestone.
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.
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.
The Cambrian explosion is an interval of time approximately 538.8 million years ago in the Cambrian period of the early Paleozoic when there was a sudden radiation of complex life, and practically all major animal phyla started appearing in the fossil record. It lasted for about 13 to 25 million years and resulted in the divergence of most modern metazoan phyla. The event was accompanied by major diversification in other groups of organisms as well.
The Mount Cap Formation is a geologic formation exposed in the Mackenzie Mountains, northern Canada. It was deposited in a shallow shelf setting in the late Early Cambrian, and contains an array of Burgess Shale-type microfossils that have been recovered by acid maceration.
Bradoriida, also called bradoriids, are an extinct order of small marine arthropods with a bivalved carapace, which globally distributed, forming a significant portion of the Cambrian and Early Ordovician soft-bodied communities.
Diania is an extinct genus of lobopodian panarthropod found in the Lower Cambrian Maotianshan shale of China, represented by a single species - D. cactiformis. Known during its investigation by the nickname "walking cactus", this organism belongs to a group known as the armoured lobopodians, and has a simple worm-like body with robust, spiny legs. Initially, the legs were thought to have a jointed exoskeleton and Diania was suggested to be evolutionarily close to early arthropods, but many later studies have rejected this interpretation.
Mickwitziids are a Cambrian group of shelly fossils with originally phosphatic valves, belonging to the Brachiopod stem group, and exemplified by the genus Mickwitzia – the other genera are Heliomedusa and Setatella. The family Mickwitziidae is conceivably paraphyletic with respect to certain crown-group brachiopods.
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.
Onychomicrodictyon is a genus of Toyonian net-like small shelly fossil that probably belonged to a lobopodian resembling Onychodictyon or Microdictyon; the plates have a honeycomb structure with nodal flanges and an apical spinose extension. It is considered a junior synonym of Onychodictyon by some authors.
This list of fossil arthropods described in 2019 is a list of new taxa of trilobites, fossil insects, crustaceans, arachnids and other fossil arthropods of every kind that are scheduled to be described during the year 2019, as well as other significant discoveries and events related to arthropod paleontology that are scheduled to occur in the year 2019.
Acinocricus is a genus of extinct panarthropod belonging to the group Lobopodia and known from the middle Cambrian Spence Shale of Utah, United States. As a monotypic genus, it has one species Acinocricus stichus. The only lobopodian discovered from the Spence Shale, it was described by Simon Conway Morris and Richard A. Robison in 1988. Owing to the original fragmentary fossils discovered since 1982, it was initially classified as an alga, but later realised to be an animal belonging to Cambrian fauna.
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