Vendian faunas - Vendian faunas The Vendian Faunas -- Vendazoa are ancient lifeforms found in rocks a bit older than the Cambrian faunas that represent the oldest fossils of classical paleontology. The original descriptions came from the Ediacaran faunas of South Australia. It later turned out that similar faunus had been described previously from Namibia, but their great age had not been appreciated. Subsequent discoveries have found similar fossils in Brazil, Antarctica, Newfoundland, The Canadian Maritimes, North Carolina, England, Canada's Northwest Territories, The Western US, Scandanavia, The White Sea region of Russia, and Poland, and other places. The Vendian 'animals' (assuming that they were animals) are probably too large and complex to be single celled. They universally lack mouths, any organs, or appendages. Symmetries may be two, three, four,.
Ediacaran - fossils have been found in South Australia. Additional fossils have been found in dozens of outcrops on all continents. Especially important deposits have been found in the White Sea area of Russia, in SouthWest Africa, in Northwest Canada, and in Newfoundland. As time has passed, the Ediacaran faunas have, if anything, become more rather than less enigmatic. A few fossils such as Kimberella, Bomakellia, and Xenusion seem to be possible for precursors to Cambrian forms. Close to the Cambrian boundary, worm tracks, and various hard shelled forms - especially a collection of small forms known as the 'small shelly fauna' also appear to be probable precursors of Cambrian life. On the other hand, many of the best known Ediacaran creatures appear to be immobile blobs, disks, fronds, and air matress like.
Doushantuo Formation - to be older. The formation is of particular interest because it appears to cover the boundary between the problematic Ediacaran organisms and the more famous Cambrian Explosion. The formation ranges from early Vendian age – about 590 Ma at its base to about 565 Ma at its top, predating by perhaps 5 million years (Ma) the earliest of the 'classical' Ediacaran faunas from Mistaken Point, Newfoundland, and recording conditions a good 40 to 50 million years before the Cambrian explosion. The whole sequence sits on an unconformity with the underlying Liantuo Formation, which is free of fossils, an unconformity usually being interpreted as a period of erosion. On that lie tillites, (the Nantuo Formation) cemented glacial till formed of glacial deposits of cobbles and gravel laid down at the end of.
Precambrian - Western Australia. Probable fossils 100 million years older have been found in the same area. There is a fairly solid record of bacterial life throughout the remainder of the Precambrian. Excepting a few dubious reports of much older forms from Texas and India, the first complex multicelled lifeforms seem to have appeared roughly 600 million years before the present. A quite diverse collection of soft-bodied forms is known from a variety of locations worldwide between 600 and 544 million years ago. These are referred to as Ediacaran or Vendian faunas. Hard-shelled creatures appeared toward the end of that timespan. A very diverse collection of forms appeared around 544 million years before the present starting in the latest Precambrian with a poorly understood "small shelly fauna" and ending in the very early.
Neoproterozoic - century, paleontologists started finding fossils of multicellular animals that predated the Cambrian boundary. A complex fauna was found in South West Africa in the 1920s but was misdated. Another was found in South Australia in the 1940s but was not thoroughly examined until the late 1950s. Other possible early fossils were found in Germany, Arizona, Ontario, and elsewhere. Some were determined to be pseudo fossils, but others were revealed to be members of rather complex faunas that are still poorly understood. At least 20 regions worldwide yielded metazoan fossils prior to the classical Cambrian boundary. A few of the early animals appear possibly to be ancestors of modern animals. Most fall into ambiguous groups of frond-like animals(?); discoids that might be holdfasts for stalked animals(?) ("medusoids"); mattress-like forms; small calcaerous tubes;.
Vendian Biota - Vendian Biota Vendian Biota or fauna are a group of what may be very early forms of animal life. These now extinct forms are generally flat, segmented, or frondlike with no visible organs other than holdfasts in some varieties. Many of these fossils are difficult to interpret, and trace fossils are common. They are probably entirely late precambrian although some possible Vendian forms have been identified in the Cambrian. Many believe that some or all of the Vendians are precursors to one or more modern phyla that arose in the Cambrian. The Vendian biota are also collectively known as Ediacarian fauna. See also Ediacarian..
Kimberella - Kimberella quadrata is a fossil animal from the Ediacaran or Vendian fauna. This fossil varies from 3mm to 10 cm in size. It is oval in shape with larger ones being elongated more. The long axis has a raised ridge, and the edge is crenulated or scalloped with 44 lobes, though some always appear missing. The organism that caused this fossil is believed to be a bilaterian organism, with bilateral symmetry. As such it is the earliest known bilaterian animal. It may represent the ancestor of all bilaterian animals including humans or may be a lophotrochozoan ancestor. It has been interpreted as a mollusc with a non mineralised shell. It may be the cause of the long trails found in the Ediacaran strata. It was first described by Glaessner & Daily.
Geologic timescale - of geologic and paleontologic events immediately prior to the Cambrian. The nomenclature has not stabilized. The term Neoproterozoic is used here, but other writers might equally well have used one or more of the terms 'Ediacarian', 'Vendian', 'Varangian', 'Precambrian', 'Protocambrian', 'Eocambrian', or might have extended the Cambrian further back in time. All of these terms are usually treated as a subset of the Proterozoic rather than a period between the Paleozoic and the Proterozoic. 3) Dates are slightly uncertain with differences of a few percent between various sources being common. This is largely due to uncertainties in radiometric dating and the problem that deposits suitable for radiometric dating seldom occur exactly at the places in the geologic column where we would most like to have them. Dates with an * are.
Gondwanatheria - been a lively place. The fossils and the geological conditions of the site suggest a near-by forest populated by a diverse fauna, which had many similarities with the slightly earlier residents of Patagonia; small, arboreal, fruit and insect eating possums, 10kg sloths, middle to largish grazers (sparnotheriodontids and Trigonostylops), falcons, ratites (rheass and the like, aka big, flightless birds) and penguins. At the end of the Eocene the climate seems to have taken a turn for the worse... With thanks for Martin Jehle for the notification and interesting abstract and David Marjanovic for digging out the paper. Link [1]Marsupial teeth from Antarctica Page references: Kielan-Jaworowska Z & Hurum JH (2001), Phylogeny and Systematics of multituberculate mammals. Paleontology 44, p.389-429. Reguero MA, Sergio AM & Santillana SN (2002), Antarctic Peninsula and South.
Faunal stage - stages are regional. They often include many formations of differing rock types that were being laid down in different environments at the same time. In recent years, regional and global correlations of rock sequences have become relatively certain and there is less need for faunal labels to refine the age of formations. There has been a tendency to use European and, to a lesser extent, Asian, stage names for the same time period world wide even though the faunas in other regions may have little in common with the stage as originally defined. A summary of most commonly used marine faunal stage names can be found at http://flatpebble.nceas.ucsb.edu/public/harland.html.
Ectypodus - 1921 Place: Mason Pocket, Colorado Country: USA Age: Torrejonian, Upper Paleocene Remarks: A macho version, weighing in at around 30g. Reference: Species: Ectypodus powelli Jepsen GL, 1940 Place: Princeton Quarry, Wyoming Country: USA Age: Torrejonian-Tiffanian, Middle-Upper Paleocene Remarks: At least some of this material has been referred to Microcosmodon conus Jepsen, 1930. Weight guestimate, 20g. Reference: Jepsen (1940), Paleocene faunas of the Polecat Bench formation, Park County, Wyoming. Pro. Amer. Philos. Soc, 83, p.217-340, 21 figs., 5pls. Species: Ectypodus szalayi Sloan RE, 1981 Place: New Mexico & Gidley Quarry, Montana & Wyoming Country: USA Age: Mid Paleocene Remarks: 15g of furry fun. Reference: Sloan (1981), Systematics of Paleocene multituberculates from the San Juan Basin, New Mexico, p. 127-160, in Lucas et al (eds), Advances in San Juan Basin paleontology. University of.
Emmonaspis - as well. Descriptions are somewhat vague and confusing. It was interpreted by Walcott in 1911 as a Polychaete worm. Conway Morris suggested in 1993 that it might be a Cambrian descendant of the Vendian form Pteridinium. Some paleontologists regard it as an early chordate alied with Pikaia et. al. Emmonaspis is described as a tadpole-like or worm-like animal. It is apparently segmented, but no trace of a spinal cord is present. It is said to have at least 46 segments with two filamentous branches (walking legs?) on the body segments. Faint jointed appendages are said to extend forward from the front of the head. The fossil apparently has not been restudied. No modern interpretation is available. There are two species: Emmonaspis Worthanella Emmonaspis Cambriensis Walcott(?) 1886(?) 1911(?).
Eocene - a major extinction event that may be related to the impact of (a) large extraterrestrial object(s) in Siberia and in what is now Chesapeake Bay. Table of contents showTocToggle("show","hide") 1 Eocene naming 2 Eocene dating 3 Eocene subdivisions 4 Eocene climate 5 Eocene paleogeography 6 Eocene fauna Eocene naming The name Eocene refers to the dawn of modern ('new') mammalian faunas that appeared during the epoch. Eocene dating As with other older geologic periods, the strata that define the start and end are well identified, but their exact dates are slightly uncertain. Eocene subdivisions The Eocene is usually broken into Lower and Upper subdivisions. The Faunal stages from youngest to oldest are: Ypresian/(Lower Claiborne) Lutetian/(Lower Claiborne) Bartonian/Auversian (Upper Claiborne) Priabonian/Jackson (Upper Claiborne) Eocene climate Marking the start of the Eocene, the.
Devonian period - Devonian was called the “greenhouse age.” Widespread reefs indicated that the climate was mild and warm, as well as generally dry. Devonian fauna Sea levels in the Devonian were generally high. Fish were abundant and diverse. The first sharks appeared early in the period. Bony fish, many of substantial size appeared shortly thereafter. Small land plants appeared early in the period. By the end of the period forests of primitive plants existed. Both vertebrates and arthropods were solidly established on the land. Marine faunas continued to be dominated by bryozoa, brachiopods and corals. Trilobites were still fairly common, but less diverse than in earlier periods. ..
Anconodon - it's within the Suborder of Cimolodonta, and possibly the family Cimolodontidae. Genus: Anconodon Jepsen GL, 1940 Aka: Ectopodon Russell, 1967; Ectypodus (partly); Liotomus (partly); Ptilodus (partly) Reference: Jepsen (1940), Paleocene faunas of the Polecat Bench formation, Park County, Wyoming. Pro. Amer. Philos. Soc, 83, p.217-340, 21 figs., 5pls. Species: Anconodon cochranensis (Russell, 1929) Van Valen & Sloan, 1966 Aka: A. russelli (Simpson, 1935) Jepsen, 1940; Ectopodon cochranensis Russel, 1967; Ectypodus cochranensis Simpson, 1937a; Ectypodus russelli Simpson, 1935d; Liotomus russelli; Ptilodus cochranensis Russell, 1929 Place: Alberta & Montana & Wyoming Country: Canada & USA Age: Tiffanian, Middle-Upper Paleocene Remarks: Has been cited as a descendant of A. gidleyi. The holotype is in the University of Alberta collection. Body mass of about two standard mice, (55g). Reference: Species: Anconodon gidleyi (Simpson GG, 1935).
Arkarua - the internal structure. There is no sign of the Calcium Carbonate stereoms (plates) that are diagnostic of echinoderms. Neither can a mouth be identified. The earliest well studied echinoderm -- Helioplacus -- is somewhat younger. It is not radially symmetric and does not possess five fold symmetry. McMenamin/Sielacher have proposed 'Arkarua' as a conventional main line member of the Vendazoa with five fold symmetry and non-iterated cell families. For pictures, see http://www.ucmp.berkeley.edu/vendian/arkaru.html.
Ausia - depressions ("windows") that taper into ovals toward the conical point. Ausia Fenestrata, named for the town of Aus in Namibia, is the only Vendian animal with pores although there is some question whether the depressions completely penetrate the animal's wall. It may be a primitive sponge..
Burgess shale - Several poorly understood fossils were found to be body parts of a predatory form known as Anomalocaris More recent (late 1990s) work by Derek Briggs and Richard Fortey has placed many of the "peculiar" Burgess Shale fossils within the arthropoda, but many animals such as Amiskwia remain enigmatic. A popular account of the 1980s analysis of the Burgess Shale is given in Wonderful Life by Stephen Jay Gould. The diversity and exotic nature of the Burgess fauna has caused a great deal of controversy in paleontology with regard to the reasons for and nature of what has come to be called the Cambrian Explosion. Further investigations showed that the Burgess Shale extends for many miles in isolated outcrops and the various faunas are preserved in different places. The deposits appear to.
Cambrian - the definitive age for the start of the Phanerozoic. Report on the Amthor et al. paper in Geology 2003. Cambrian subdivisions A radiometric date from New Brunswick puts the end of the first stage of the Cambrian around 511 million years. This leaves only 21 million years for the other two periods of the Cambrian. The Cambrian is usually broken into Lower (Caerfai or Waucoban), Middle (St Davids or ALbertian) and Upper (Merioneth or Croixan) subdivisions. The faunal stages from youngest to oldest are: Franconian/Trempealeauan/Dolgellian (Upper) Dresbachian/Maentwrogian (Upper) Solvan (Middle), Menevian (Middle) Toyonian/Lenian/Botomian (Lower) Atdabanian (Lower) Tommatian (Lower) Cambrian palaeogeography The Cambrian continents are thought to have resulted from the breakup of a Neoproterozoic supercontinent called Rodinia. It is thought that Cambrian climates were significantly warmer than those of preceding times.
Xenusion - a spine on each body bump and faint transverse parallel striations on the annulations on the legs. The legs of the foremost (?) segments are either missing or not preserved. The head(?) is missing or poorly preserved. If Xenusion is an arthropod/onychophore it is one of the oldest currently known fossils of a mobile, modern animal. Xenusion has been reinterpreted as a Vendian frond animal by Tarlo and a convincing drawing of that interpretation has been presented by McMenamin. If the creature is actually an onychophore, the original specimen would appear to be part of an onychophore about 20cm in length which is much larger than most modern species. The photograph in The Treatise of Invertebrate Paleontology Volume O looks more like the original interpretation. The presence of 'worm tubes' Skolithes.
