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Bristolia
''Bristolia'' is an extinct genus of trilobite, fossil marine arthropods, with eight or more small to average size species. It is common in and limited to the Lower Cambrian (Upper ''Olenellus''-zone) shelf deposits across the southwestern US, which constitutes part of the former paleocontinent of Laurentia. Taxonomy ''Bristolia'' can be separated into two distinct groups: one consisting of ''B. insolens'' and ''B. anteros'', the other comprising a gradual spectrum of morphologies including ''B. mohavensis'', ''B. harringtoni'', and ''B. bristolensis'' morphotypes. The second group reveals a dynamic morphological trend. From the oldest species ''B. mohavensis'', the lineage undergoes gradational increase in intergenal angle and advancement of the genal spines, progressing through ''B. harringtoni'', culminating in ''B. bristolensis''. Younger specimens show a trend back to more acute intergenal angles and less advanced genal spines typical of ''B. fragilis''. This development ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bristolia Bristolensis Cephalon Negative CRF
''Bristolia'' is an extinct genus of trilobite, fossil marine arthropods, with eight or more small to average size species. It is common in and limited to the Lower Cambrian (Upper ''Olenellus''-zone) shelf deposits across the southwestern US, which constitutes part of the former paleocontinent of Laurentia. Taxonomy ''Bristolia'' can be separated into two distinct groups: one consisting of ''B. insolens'' and ''B. anteros'', the other comprising a gradual spectrum of morphologies including ''B. mohavensis'', ''B. harringtoni'', and ''B. bristolensis'' morphotypes. The second group reveals a dynamic morphological trend. From the oldest species ''B. mohavensis'', the lineage undergoes gradational increase in intergenal angle and advancement of the genal spines, progressing through ''B. harringtoni'', culminating in ''B. bristolensis''. Younger specimens show a trend back to more acute intergenal angles and less advanced genal spines typical of ''B. fragilis''. This development ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Trilobite Zone
Trilobites are used as index fossils to subdivide the Cambrian period. Assemblages of trilobites define trilobite zones. The ''Olenellus''-zone has traditionally marked the top of the Lower Cambrian, and is followed by the '' Eokochaspis'' zone. The last two zones of the Middle Cambrian are the '' Bathyuriscus– Elrathina''-zone (contemporaneous with the Burgess Shale) and the subsequent '' Bolaspidella''-zone (starting at the base of the Drumian stage). These are overlain by the lowermost Upper Cambrian ''Cedaria''-zone. Alternative zoning names place the Burgess Shale in the ''Peronopsis bonnerensis''-zone, which is underlain by the ''Oryctocephalus indicus''-zone (e.g. Spence Shale) and overlain (perhaps not directly) by the ''Ptychagnostus punctuosus''-zone. The lower Middle Cambrian '' Glossopleura''-zone (Spence Shale) is above the '' Albertella''-zone. The '' Elvinia''-zone is upper Cambrian. Subdivision of the ''Olenellus''-zone Recently, it has been proposed to ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bristoliinae
The Bristoliinae is an extinct subfamily of trilobites, fossil marine arthropods, with species of small to average size. Species belonging to this subfamily lived during the Botomian and Toyonian stage (''Olenellus''-zone), 522-513 million years ago, in the former continent of Laurentia, including what are today Mexico, the Appalachian Mountains and the south-western United States, and Canada (Northwest Territories). Etymology The Bristoliinae are named for the type species '' Bristolia bristolensis''. Description The headshield (or cephalon) carries spines (called genal spines) of approximately 4-8 thorax segments long (measured parallel to the midline). The genal spines are attached in front of the back of the headshield. The central raised portion of the cephalon that represents the axis in the cephalon (or glabella) touches the flattened ledge that borders the cephalon. The furrows that separate border, eye ridges, glabella and its lobes are distinct. Communalities an ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bolbolenellus
''Bolbolenellus'' is an extinct genus of trilobites, fossil marine arthropods, with five species attributed to it currently. It can be easily distinguished from all other trilobites by the combination of the absence of dorsal sutures in the head shield like all Olenellina (which in all other trilobite suborders assist in moulding by splitting open), and a distinctly bulbous frontal lobe (L4) of the raised axial area in the head (or cephalon) called glabella. The species lived at the end of the Lower Cambrian. Etymology ''Bolbolenellus'' is the combination of Greek (, “plant with round swelling on underground stem”), and ''Olenellus'', the rather distantly related genus to which all of the species were previously assigned. This refers to the bulb-like swelling of the frontal lobe of the glabella. The names of the species have the following derivations. * ''B. altifrons'' from the Latin altus (“high”) and from Latin frons (“forehead”), to express the species has a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lochmanolenellus
''Lochmanolenellus'' is an extinct genus of trilobites, fossil marine arthropods, with one small species, ''L. mexicana''. It lived during the Botomian stage (''Olenellus''-zone), 522–513 million years ago, in the South-West of the former continent of Laurentia, in what are today Mexico, and the South-Western United States. Etymology ''Lochmanolenellus'' is named in honor of C. Lochman, who initially described the fossils that are assigned to this genus, and for its likeness to ''Olenellus'' a distantly related genus. The species epithet ''mexicana'' refers to Mexico, where the first specimen was found. Taxonomy ''L. mexicana'' was first described as ''Wanneria mexicana prima''. There are however so many differences, that it is highly unlikely ''L. mexicana'' is more than distantly related. Later scholars assigned the species to ''Laudonia''. Although ''Laudonia'' is much more related than ''Wanneria'', ''L. mexicana'' must be considered an early representative of the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fremontella
''Fremontella'' is an extinct genus from a well-known class of fossil marine arthropods, the trilobites. It lived during the part of the Toyonian stage. This faunal stage was part of the Cambrian Period. ''Fremontella'' shares with the other genera of the Bristoliinae The Bristoliinae is an extinct subfamily of trilobites, fossil marine arthropods, with species of small to average size. Species belonging to this subfamily lived during the Botomian and Toyonian stage (''Olenellus''-zone), 522-513 million years ... subfamily, Lochmanolenellus and Bristolia conspicuous and long curved spines (called genal spines) on the headshield (or cephalon). These reach back equal to 4-5 thorax segments (measured parallel to the midline). The furrows that separate border, eye ridges, glabella and its lobes are distinct (unlike in the Biceratopsinae). The area outside of the axis (or pleural lobes) of the third segment of the thorax is enlarged, and carries large trailing spine on each side. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Paleocontinent
A paleocontinent or palaeocontinent is a distinct area of continental crust that existed as a major landmass in the geological past. There have been many different landmasses throughout Earth's time. They range in sizes, some are just a collection of small microcontinents while others are large conglomerates of crust. As time progresses and sea levels rise and fall more crust can be exposed making way for larger landmasses. The continents of the past shaped the evolution of organisms on Earth and contributed to the climate of the globe as well. As landmasses break apart, species are separated and those that were once the same now have evolved to their new climate. The constant movement of these landmasses greatly determines the distribution of organisms on Earth's surface. This is evident with how similar fossils are found on completely separate continents. Also, as continents move, mountain building events (orogenies) occur, causing a shift in the global climate as new rock is expo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Geology Of The Death Valley Area
The exposed geology of the Death Valley area presents a diverse and complex set of at least 23 formations of sedimentary units, two major gaps in the geologic record called unconformities, and at least one distinct set of related formations geologists call a group. The oldest rocks in the area that now includes Death Valley National Park are extensively metamorphosed by intense heat and pressure and are at least 1700 million years old. These rocks were intruded by a mass of granite 1400 Ma (million years ago) and later uplifted and exposed to nearly 500 million years of erosion. Marine deposition occurred 1200 to 800 Ma, creating thick sequences of conglomerate, mudstone, and carbonate rock topped by stromatolites, and possibly glacial deposits from the hypothesized Snowball Earth event. Rifting thinned huge roughly linear parts of the supercontinent Rodinia enough to allow sea water to invade and divide its landmass into component continents separated by narrow straits. A pa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cephalon (arthropod Head)
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". Insects In insects, ''head'' is a preferred term. The insect head consists of five segments, including three (the labial, maxillary and mandibular) necessary for food uptake, which are altogether known as the gnathocephalon and house the suboesophageal ganglion of the brain, as well as the antennal segment, and an ocular segment, as well as a non segmented fused section of the head where the archicerebrum is housed known as the acron. See also arthropod head problem. Chelicerates and crustaceans In chelicerates and crustaceans, the cephalothorax is derived from the fusion of the cephalon and the thorax, and is usually covered by a single unsegmented carapace. In relation with the arthropod head problem, phylogeny studies show that members of the Malacostraca class of cru ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mojave Desert
The Mojave Desert ( ; mov, Hayikwiir Mat'aar; es, Desierto de Mojave) is a desert in the rain shadow of the Sierra Nevada mountains in the Southwestern United States. It is named for the indigenous Mojave people. It is located primarily in southeastern California and southwestern Nevada, with small portions extending into Arizona and Utah. The Mojave Desert, together with the Sonoran, Chihuahuan, and Great Basin deserts, forms a larger North American Desert. Of these, the Mojave is the smallest and driest. The Mojave Desert displays typical basin and range topography, generally having a pattern of a series of parallel mountain ranges and valleys. It is also the site of Death Valley, which is the lowest elevation in North America. The Mojave Desert is often colloquially called the "high desert", as most of it lies between . It supports a diversity of flora and fauna. The desert supports a number of human activities, including recreation, ranching, and military training. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bristol Dry Lake
Bristol Lake is a dry lake in the Mojave Desert of San Bernardino County, California, northeast of Twentynine Palms. Bristol Lake is located southeast of Amboy, California, Amboy and U.S. Route 66 in California, U.S. Route 66, and is also south of Cadiz, California, Cadiz. Amboy Crater and the Bullion Mountains are to the west, and Old Woman Mountains to the east. The lake is approximately long and at its widest point. Geological setting Bristol Lake is located in San Bernardino County's Mojave Desert. It is a playa lake in the Basin and Range Province and is the northernmost member of a northwest-southeast trending playa lake system that includes Cadiz Lake and Danby Lake.Hanford, C. Robertson. "Sedimentology and Evaporite Genesis in a Holocene Continental-sabkha Playa Basin-Bristol Dry Lake, California." Sedimentology, 29.2 (1982): 239–253. Mineralogy Bristol Lake's mineralogy is described as having a bullseye pattern of minerals with lithofacies consisting of halite a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Laudonia
''Laudonia'' is an extinct genus of trilobites that lived during the early 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 The Cambrian Period ( ; sometimes symbolized C with bar, 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 .... There are currently two named species assigned to it. Distribution * ''L. bispinata'' has been collected from the Early Cambrian of Alberta ( Lower ''Olenellus'' zone, Mural Formation, Mumm Peak Section, immediately west of Mumm Peak and north of Mount Robson Provincial Park, near Mural Glacier) and of British Columbia (Cinnamon Peak-Whitehorn Mtn. Section: Dyeran) Canada.W. H. Fritz. 1992. Walcott's Lower Cambrian Olenellid trilobite collection 61k, Mount Robson Area, Canadian Rocky Mountains. Geological Survey of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
