Pliocene

The Pliocene ( /ˈplaɪəˌsiːn/;[2][3] also Pleiocene[4]) Epoch is the epoch in the geologic timescale that extends from 5.333 million to 2.58[5] million years BP. It is the second and youngest epoch of the Neogene Period in the Cenozoic Era. The Pliocene follows the Miocene Epoch and is followed by the Pleistocene Epoch. Prior to the 2009 revision of the geologic time scale, which placed the four most recent major glaciations entirely within the Pleistocene, the Pliocene also included the Gelasian stage, which lasted from 2.588 to 1.806 million years ago, and is now included in the Pleistocene.[6]

As with other older geologic periods, the geological strata that define the start and end are well identified but the exact dates of the start and end of the epoch are slightly uncertain. The boundaries defining the Pliocene are not set at an easily identified worldwide event but rather at regional boundaries between the warmer Miocene and the relatively cooler Pliocene. The upper boundary was set at the start of the Pleistocene glaciations.

System/
Period
Series/
Epoch
Stage/
Age
Age (Ma)
Quaternary Pleistocene Gelasian younger
Neogene Pliocene Piacenzian 2.58 3.600
Zanclean 3.600 5.333
Miocene Messinian 5.333 7.246
Tortonian 7.246 11.63
Serravallian 11.63 13.82
Langhian 13.82 15.97
Burdigalian 15.97 20.44
Aquitanian 20.44 23.03
Paleogene Oligocene Chattian older
Subdivision of the Neogene Period
according to the ICS, as of 2017.[1]

Etymology

Charles Lyell (later Sir Charles) gave the Pliocene its name in Principles of Geology (volume 3, 1833).[7]

The word pliocene comes from the Greek words πλεῖον (pleion, "more") and καινός (kainos, "new" or "recent")[8] and means roughly "continuation of the recent", referring to the essentially modern marine mollusc fauna.

H.W. Fowler called the term Pliocene (like other geological jargon such as pleistocene and miocene) a "regrettable barbarism" and an indication that even "a good classical scholar" such as Lyell should have requested a philologist's help when coining words.[9]

To summarize the usage of these "regrettable barbarisms" in the labelling of the Cenozoic ("recent life") era (from youngest to oldest):

Epoch Literally First Element Second Element
Greek Transliteration Meaning Greek Transliteration Meaning
Holocene whole-new ὅλος holos "whole" or "entire" καινός kainós
(Latinized as cænus)
"new"
Pleistocene most-new πλεῖστος pleīstos "most"
Pliocene more-new πλεῖον pleion "more"
Miocene less-new μείων meiōn "less"
Oligocene few-new ὀλίγος oligos "few"
Eocene dawn-new ἠώς ēṓs "dawn"
Paleocene old-new παλαιός palaios "old(er)"

with the understanding that these are all new relative to the Mesozoic ("middle life" - the age of dinosaurs) and Paleozoic ("old life" - Trilobites, coal forests, and the earliest Synapsida) eras.

Subdivisions

In the official timescale of the ICS, the Pliocene is subdivided into two stages. From youngest to oldest they are:

The Piacenzian is sometimes referred to as the Late Pliocene, whereas the Zanclean is referred to as the Early Pliocene.

In the system of

In the Paratethys area (central Europe and parts of western Asia) the Pliocene contains the Dacian (roughly equal to the Zanclean) and Romanian (roughly equal to the Piacenzian and Gelasian together) stages. As usual in stratigraphy, there are many other regional and local subdivisions in use.

In Britain the Pliocene is divided into the following stages (old to young): Gedgravian, Waltonian, Pre-Ludhamian, Ludhamian, Thurnian, Bramertonian or Antian, Pre-Pastonian or Baventian, Pastonian and Beestonian. In the Netherlands the Pliocene is divided into these stages (old to young): Brunssumian C, Reuverian A, Reuverian B, Reuverian C, Praetiglian, Tiglian A, Tiglian B, Tiglian C1-4b, Tiglian C4c, Tiglian C5, Tiglian C6 and Eburonian. The exact correlations between these local stages and the ICS stages is still a matter of detail.[10]

Climate

Pliocene sst anomaly
Mid-Pliocene reconstructed annual sea surface temperature anomaly
Landscape of the Pliocene epoch - showing environment at the time of men's appearance - drawn by Riou
19th century artist's impression of a Pliocene landscape

The global average temperature in the mid-Pliocene (3.3–3 mya) was 2–3 °C higher than today,[11] carbon dioxide levels were the same as today,[12] and global sea level was 25 m higher.[13] The northern hemisphere ice sheet was ephemeral before the onset of extensive glaciation over Greenland that occurred in the late Pliocene around 3 Ma.[14] The formation of an Arctic ice cap is signaled by an abrupt shift in oxygen isotope ratios and ice-rafted cobbles in the North Atlantic and North Pacific ocean beds.[15] Mid-latitude glaciation was probably underway before the end of the epoch. The global cooling that occurred during the Pliocene may have spurred on the disappearance of forests and the spread of grasslands and savannas.[16]

Paleogeography

Great American Biotic Interchange examples
Examples of migrant species in the Americas after the formation of the Isthmus of Panama. Olive green silhouettes denote North American species with South American ancestors; blue silhouettes denote South American species of North American origin.

Continents continued to drift, moving from positions possibly as far as 250 km from their present locations to positions only 70 km from their current locations. South America became linked to North America through the Isthmus of Panama during the Pliocene, making possible the Great American Interchange and bringing a nearly complete end to South America's distinctive large marsupial predator and native ungulate faunas. The formation of the Isthmus had major consequences on global temperatures, since warm equatorial ocean currents were cut off and an Atlantic cooling cycle began, with cold Arctic and Antarctic waters dropping temperatures in the now-isolated Atlantic Ocean.

Africa's collision with Europe formed the Mediterranean Sea, cutting off the remnants of the Tethys Ocean. The border between the Miocene and the Pliocene is also the time of the Messinian salinity crisis.

Sea level changes exposed the land bridge between Alaska and Asia (Beringia).

Pliocene marine rocks are well exposed in the Mediterranean, India, and China. Elsewhere, they are exposed largely near shores.

During the Pliocene parts of southern Norway and southern Sweden that had been near sea level rose. In Norway this rise elevated the Hardangervidda plateau to 1200 m in the Early Pliocene.[17] In Southern Sweden similar movements elevated the South Swedish highlands leading to a deflection of the ancient Eridanos river from its original path across south-central Sweden into a course south of Sweden.[18]

Flora

The change to a cooler, dry, seasonal climate had considerable impacts on Pliocene vegetation, reducing tropical species worldwide. Deciduous forests proliferated, coniferous forests and tundra covered much of the north, and grasslands spread on all continents (except Antarctica). Tropical forests were limited to a tight band around the equator, and in addition to dry savannahs, deserts appeared in Asia and Africa.

Fauna

Both marine and continental faunas were essentially modern, although continental faunas were a bit more primitive than today. The first recognizable hominins, the australopithecines, appeared in the Pliocene.

The land mass collisions meant great migration and mixing of previously isolated species, such as in the Great American Interchange. Herbivores got bigger, as did specialized predators.

Oliva sayana

The gastropod Oliva sayana, from the Pliocene of Florida.

Cladocora

The coral Cladocora from the Pliocene of Cyprus.

CyprusPlioceneGastropod

A gastropod and attached serpulid wormtube from the Pliocene of Cyprus.

Turritellatricarinata

The gastropod Turritella carinata from the Pliocene of Cyprus.

SpondylusPliocene

The thorny oyster Spondylus right and left valve interiors from the Pliocene of Cyprus.

SpondylusArticulated

Articulated Spondylus from the Pliocene of Cyprus.

Diodoraitalica

The limpet Diodora italica from the Pliocene of Cyprus.

DentaliumPliocene

The scaphopod Dentalium from the Pliocene of Cyprus.

Aporrhais from Pliocene

The gastropod Aporrhais from the Pliocene of Cyprus.

AnadaraPliocene

The arcid bivalve Anadara from the Pliocene of Cyprus.

Amusium cristatum Cyprus

The pectenid bivalve Ammusium cristatum from the Pliocene of Cyprus.

Petaloconchus Cyprus Pliocene

Vermetid gastropod Petaloconchus intortus attached to a branch of the coral Cladocora from the Pliocene of Cyprus.

Mammals

In North America, rodents, large mastodons and gomphotheres, and opossums continued successfully, while hoofed animals (ungulates) declined, with camel, deer and horse all seeing populations recede. Rhinos, three toed horses (Nannippus), oreodonts, protoceratids, and chalicotheres became extinct. Borophagine dogs and Agriotherium became extinct, but other carnivores including the weasel family diversified, and dogs and short-faced bears did well. Ground sloths, huge glyptodonts, and armadillos came north with the formation of the Isthmus of Panama.

In Eurasia rodents did well, while primate distribution declined. Elephants, gomphotheres and stegodonts were successful in Asia, and hyraxes migrated north from Africa. Horse diversity declined, while tapirs and rhinos did fairly well. Cows and antelopes were successful, and some camel species crossed into Asia from North America. Hyenas and early saber-toothed cats appeared, joining other predators including dogs, bears and weasels.

Human evolution during the Pliocene
Pliocene
Pliocene mammals of North America

Africa was dominated by hoofed animals, and primates continued their evolution, with australopithecines (some of the first hominins) appearing in the late Pliocene. Rodents were successful, and elephant populations increased. Cows and antelopes continued diversification and overtaking pigs in numbers of species. Early giraffes appeared. Horses and modern rhinos came onto the scene. Bears, dogs and weasels (originally from North America) joined cats, hyenas and civets as the African predators, forcing hyenas to adapt as specialized scavengers.

South America was invaded by North American species for the first time since the Cretaceous, with North American rodents and primates mixing with southern forms. Litopterns and the notoungulates, South American natives, were mostly wiped out, except for the macrauchenids and toxodonts, which managed to survive. Small weasel-like carnivorous mustelids, coatis and short-faced bears migrated from the north. Grazing glyptodonts, browsing giant ground sloths and smaller caviomorph rodents, pampatheres, and armadillos did the opposite, migrating to the north and thriving there.

The marsupials remained the dominant Australian mammals, with herbivore forms including wombats and kangaroos, and the huge Diprotodon. Carnivorous marsupials continued hunting in the Pliocene, including dasyurids, the dog-like thylacine and cat-like Thylacoleo. The first rodents arrived in Australia. The modern platypus, a monotreme, appeared.

Birds

Titanis07DB
Titanis

The predatory South American phorusrhacids were rare in this time; among the last was Titanis, a large phorusrhacid that migrated to North America and rivaled mammals as top predator. Other birds probably evolved at this time, some modern, some now extinct.

Reptiles and amphibians

Alligators and crocodiles died out in Europe as the climate cooled. Venomous snake genera continued to increase as more rodents and birds evolved. Rattlesnakes first appeared in the Pliocene. The modern species Alligator mississippiensis, having evolved in the Miocene, continued into the Pliocene, except with a more northern range; specimens have been found in very late Miocene deposits of Tennessee. Giant tortoises still thrived in North America, with genera like Hesperotestudo. Madtsoid snakes were still present in Australia. The amphibian order Allocaudata became extinct.

Oceans

Oceans continued to be relatively warm during the Pliocene, though they continued cooling. The Arctic ice cap formed, drying the climate and increasing cool shallow currents in the North Atlantic. Deep cold currents flowed from the Antarctic.

The formation of the Isthmus of Panama about 3.5 million years ago cut off the final remnant of what was once essentially a circum-equatorial current that had existed since the Cretaceous and the early Cenozoic. This may have contributed to further cooling of the oceans worldwide.

The Pliocene seas were alive with sea cows, seals, sea lions and sharks.

Supernovae

In 2002, Narciso Benítez et al. calculated that roughly 2 million years ago, around the end of the Pliocene epoch, a group of bright O and B stars called the Scorpius-Centaurus OB association passed within 130 light-years of Earth and that one or more supernova explosions gave rise to a feature known as the Local Bubble.[19] Such a close explosion could have damaged the Earth's ozone layer and caused the extinction of some ocean life (at its peak, a supernova of this size could have the same absolute magnitude as an entire galaxy of 200 billion stars).[20][21]

See also

References

  1. ^ "ICS Timescale Chart". www.stratigraphy.org.
  2. ^ "Pliocene". Merriam-Webster Dictionary.
  3. ^ "Pliocene". Dictionary.com Unabridged. Random House.
  4. ^ "Pleiocene". Dictionary.com Unabridged. Random House.
  5. ^ See the 2014 version of the ICS geologic time scale Archived 2014-05-30 at the Wayback Machine
  6. ^ Ogg, James George; Ogg, Gabi; Gradstein F. M. (2008). The Concise Geologic Time Scale. Cambridge University Press. pp. 150–1. ISBN 9780521898492.
  7. ^ See:
  8. ^ "Pliocene". Online Etymology Dictionary.
  9. ^ Fowler, H.W. (2009). David Crystal, ed. A Dictionary of Modern English Usage: The Classic First Edition (Reissue ed.). USA: Oxford University Press. ISBN 978-0-19-953534-7.
  10. ^ Kuhlmann, G.; C.G. Langereis; D. Munsterman; R.-J. van Leeuwen; R. Verreussel; J.E. Meulenkamp; Th.E. Wong (2006). "Integrated chronostratigraphy of the Pliocene-Pleistocene interval and its relation to the regional stratigraphical stages in the southern North Sea region" (PDF). Netherlands Journal of Geosciences. 85: 19–35. doi:10.1017/S0016774600021405.
  11. ^ Robinson, M.; Dowsett, H.J.; Chandler, M.A. (2008). "Pliocene role in assessing future climate impacts". Eos, Transactions, American Geophysical Union. 89 (49): 501–502. Bibcode:2008EOSTr..89..501R. doi:10.1029/2008eo490001.
  12. ^ "Solutions: Responding to Climate Change". Climate.Nasa.gov. Retrieved 1 September 2016.
  13. ^ Dwyer, G.S.; Chandler, M.A. (2009). "Mid-Pliocene sea level and continental ice volume based on coupled benthic Mg/Ca palaeotemperatures and oxygen isotopes". Phil. Trans. Royal Soc. A. 367 (1886): 157–168. Bibcode:2009RSPTA.367..157D. doi:10.1098/rsta.2008.0222. PMID 18854304.
  14. ^ Bartoli, G.; et al. (2005). "Final closure of Panama and the onset of northern hemisphere glaciation". Earth Planet. Sci. Lett. 237 (1–2): 3344. Bibcode:2005E&PSL.237...33B. doi:10.1016/j.epsl.2005.06.020.
  15. ^ Van Andel (1994), p. 226.
  16. ^ "The Pliocene epoch". University of California Museum of Paleontology. Retrieved 2008-03-25.
  17. ^ Japsen, Peter; Green, Paul F.; Chalmers, James A.; Bonow, Johan M. (17 May 2018). "Mountains of southernmost Norway: uplifted Miocene peneplains and re-exposed Mesozoic surfaces". Journal of the Geological Society. 175 (5): 721–741. doi:10.1144/jgs2017-157.
  18. ^ Lidmar-Bergström, Karna; Olvmo, Mats; Bonow, Johan M. (2017). "The South Swedish Dome: a key structure for identification of peneplains and conclusions on Phanerozoic tectonics of an ancient shield". GFF.
  19. ^ Narciso Benítez, Jesús Maíz-Apellániz, and Matilde Canelles et al. (2002). "Evidence for Nearby Supernova Explosions". Phys. Rev. Lett. 88 (8): 081101. arXiv:astro-ph/0201018. Bibcode:2002PhRvL..88h1101B. doi:10.1103/PhysRevLett.88.081101. PMID 11863949.CS1 maint: Uses authors parameter (link)
  20. ^ Katie Pennicott (Feb 13, 2002). "Supernova link to ancient extinction". physicsworld.com. Retrieved 16 July 2012.
  21. ^ Comins & Kaufmann (2005), p. 359.

Further reading

  • Comins, Niel F.; William J. Kaufmann III (2005). Discovering the Universe (7th ed.). New York, NY: Susan Finnemore Brennan. ISBN 978-0-7167-7584-3.
  • Gradstein, F.M.; Ogg, J.G. & Smith, A.G.; 2004: A Geologic Time Scale 2004, Cambridge University Press.
  • Ogg, Jim (June 2004). "Overview of Global Boundary Stratotype Sections and Points (GSSP's)". Archived from the original on 2006-04-23. Retrieved 2006-04-30.
  • Van Andel, Tjeerd H. (1994). New Views on an Old Planet: a History of Global Change (2nd ed.). Cambridge: Cambridge University Press. ISBN 978-0-521-44243-5.

External links

Anomalomyidae

Anomalomyidae is a family of extinct muroid rodents from Europe.

Apodiformes

Traditionally, the bird order Apodiformes contained three living families: the swifts (Apodidae), the treeswifts (Hemiprocnidae), and the hummingbirds (Trochilidae). In the Sibley-Ahlquist taxonomy, this order is raised to a superorder Apodimorphae in which hummingbirds are separated as a new order, Trochiliformes. With nearly 450 species identified to date, they are the most diverse order of birds after the passerines.

Australopithecus

Australopithecus ( OS-trə-lo-PITH-i-kəs; from Latin australis, meaning 'southern', and Greek πίθηκος (pithekos), meaning 'ape', informal australopithecine or australopith (although the term australopithecine has a broader meaning as a member of the subtribe Australopithecina,  which includes this genus as well as the Paranthropus, Kenyanthropus, Ardipithecus, and Praeanthropus genera)  is a 'genus' of hominins.

From paleontological and archaeological evidence, the genus Australopithecus apparently evolved in eastern Africa around 4 million years ago before spreading throughout the continent and eventually becoming extinct two million years ago. Australopithecus is not literally extinct (in the sense of having no living descendants) as the Kenyanthropus, Paranthropus and Homo genera probably emerged as sister of a late Australopithecus species such as A. Africanus and/or A. Sediba. During that time, a number of australopithecine species emerged, including Australopithecus afarensis, A. africanus, A. anamensis, A. bahrelghazali, A. deyiremeda (proposed), A. garhi, and A. sediba.

For some hominid species of this time – A. robustus, A. boisei and A. aethiopicus – some debate exists whether they truly constitute members of the genus Australopithecus. If so, they would be considered 'robust australopiths', while the others would be 'gracile australopiths'. However, if these more robust species do constitute their own genus, they would be under the genus name Paranthropus, a genus described by Robert Broom when the first discovery was made in 1938, which makes these species P. robustus, P. boisei and P. aethiopicus.

Australopithecus species played a significant part in human evolution, the genus Homo being derived from Australopithecus at some time after three million years ago.

In addition, they were the first hominids to possess certain genes, known as the duplicated SRGAP2, which increased the length and ability of neurons in the brain. One of the australopith species evolved into the genus Homo in Africa around two million years ago (e.g. Homo habilis), and eventually modern humans, H. sapiens sapiens.In January 2019, scientists reported that Australopithecus sediba is distinct from, but shares anatomical similarities to, both the older Australopithecus africanus, and the younger Homo habilis.

Cormorant

Phalacrocoracidae is a family of approximately 40 species of aquatic birds commonly known as cormorants and shags. Several different classifications of the family have been proposed recently, and the number of genera is disputed. The great cormorant (P. carbo) and the common shag (P. aristotelis) are the only two species of the family commonly encountered on the British Isles, and "cormorant" and "shag" appellations have been later assigned to different species in the family somewhat haphazardly.

Cormorants and shags are medium-to-large birds, with body weight in the range of 0.35–5 kilograms (0.77–11.02 lb) and wing span of 45–100 centimetres (18–39 in). The majority of species have dark feathers. The bill is long, thin and hooked. Their feet have webbing between all four toes. All species are fish-eaters, catching the prey by diving from the surface. They are excellent divers, and under water they propel themselves with their feet with help from their wings; some cormorant species have been found to dive as deep as 45 metres (150 ft). They have relatively short wings due to their need for economical movement underwater, and consequently have the highest flight costs of any flying bird.Cormorants nest in colonies around the shore, on trees, islets or cliffs. They are coastal rather than oceanic birds, and some have colonised inland waters – indeed, the original ancestor of cormorants seems to have been a fresh-water bird. They range around the world, except for the central Pacific islands.

Hagerman Fossil Beds National Monument

Hagerman Fossil Beds National Monument near Hagerman, Idaho, contains the largest concentration of Hagerman horse fossils in North America. The fossil horses for which the monument is famous have been found in only one locale in the northern portion of the monument called the Hagerman Horse Quarry. The 4,351-acre (17.61 km2) monument is internationally significant because it protects the world's richest known fossil deposits from the late Pliocene epoch, 3.5 million years ago. These plants and animals represent the last glimpse of that time that existed before the Ice Age, and the earliest appearances of modern flora and fauna. This is also significant because the fossils present during this period of the Pliocene represent species which were alive during the early stages in the evolution of man, albeit on a different continent. The fossil beds were designated a National Natural Landmark in 1975.

List of fossil bird genera

Birds evolved from certain feathered theropod dinosaurs, and there is no real dividing line between birds and dinosaurs, except of course that some of the former survived the Cretaceous–Paleogene extinction event while the latter did not. For the purposes of this article, a 'bird' is considered to be any member of the clade Aves sensu lato. Some dinosaur groups which may or may not be true birds are listed below under Proto-birds.

This page contains a listing of prehistoric bird taxa only known from completely fossilized specimens. These extinctions took place before the Late Quaternary and thus took place in the absence of significant human interference. While the earliest hominids had been eating birds and especially their eggs, human population and technology was simply insufficient to seriously affect healthy bird populations until the Upper Paleolithic Revolution. Rather, reasons for the extinctions listed here are stochastic abiotic events such as bolide impacts, climate change due to orbital shifts, mass volcanic eruptions etc. Alternatively, species may have gone extinct due to evolutionary displacement by successor or competitor taxa – it is notable that an extremely large number of seabirds have gone extinct during the mid-Tertiary; this seems at least partly due to competition by the contemporary radiation of marine mammals.

The relationships of these taxa are often hard to determine, as many are known only from very fragmentary remains and due to the complete fossilization precluding analysis of information from DNA, RNA or protein sequencing. The taxa listed in this article should be classified with the Wikipedia conservation status category "Fossil".

Before the late 19th century, when minerals were still considered one of the kingdoms of binomial nomenclature, fossils were often treated according to a parallel taxonomy. Rather than assigning them to animal or plant genera, they were treated as mineral genera and given binomial names typically using Osteornis ("bone-bird") or Ornitholithus ("bird fossil") as "genus". The latter name, however, is still in use for an oogenus of fossil bird eggs. Also, other animals (in particular pterosaurs) were placed in these "genera". In sources pre-dating the Linnean system, the above terms are also seen in the more extensive descriptions used to name taxa back then.

List of fossil sites

This list of fossil sites is a worldwide list of localities known well for the presence of fossils. Some entries in this list are notable for a single, unique find, while others are notable for the large number of fossils found there. Many of the entries in this list are considered Lagerstätten (sedimentary deposits that exhibits extraordinary fossils with exceptional preservation—sometimes including preserved soft issues). Lagerstätten are indicated by a note () in the noteworthiness column.

Fossils may be found either associated with a geological formation or at a single geographic site. Geological formations consist of rock that was deposited during a specific period of time. They usually extend for large areas, and sometimes there are different important sites in which the same formation is exposed. Such sites may have separate entries if they are considered to be more notable than the formation as a whole. In contrast, extensive formations associated with large areas may be equivalently represented at many locations. Such formations may be listed either without a site, with a site or sites that represents the type locality, or with multiple sites of note. When a type locality is listed as the site for a formation with many good outcrops, the site is flagged with a note (). When a particular site of note is listed for an extensive fossil-bearing formation, but that site is somehow atypical, it is also flagged with a note ().

Many formations are for all practical purposes only studied at a single site, and may not even be named. For example, sites associated with hominin, particularly caves, are frequently not identified with a named geologic formation. Therefore, some sites are listed without an associated formation.

Mastodon

Mastodons (Greek: μαστός "breast" and ὀδούς, "tooth") are any species of extinct proboscideans in the genus Mammut (family Mammutidae), distantly related to elephants, that inhabited North and Central America during the late Miocene or late Pliocene up to their extinction at the end of the Pleistocene 10,000 to 11,000 years ago. Mastodons lived in herds and were predominantly forest-dwelling animals that fed on a mixed diet obtained by browsing and grazing with a seasonal preference for browsing, similar to living elephants.

M. americanum, the American mastodon, and M. pacificus, the Pacific mastodon, are the youngest and best-known species of the genus. Mastodons disappeared from North America as part of a mass extinction of most of the Pleistocene megafauna, widely believed to have been caused by overexploitation by Clovis hunters.

Megalodon

Megalodon (Carcharocles megalodon), meaning "big tooth", is an extinct species of shark that lived approximately 23 to 3.6 million years ago (mya), during the Early Miocene to the end of the Pliocene. It was formerly thought to be a member of the family Lamnidae, making it closely related to the great white shark (Carcharodon carcharias). However presently there is near unanimous consensus that it belongs to the extinct family Otodontidae, which diverged from the ancestry of the great white shark during the Early Cretaceous. Its genus placement is still debated, authors placing it in either Carcharocles, Megaselachus, Otodus, or Procarcharodon.

Scientists suggest that megalodon looked like a stockier version of the great white shark, though some experts believe it may have looked similar to the basking shark (Cetorhinus maximus) or the sand tiger shark (Carcharias taurus). Regarded as one of the largest and most powerful predators to have ever lived, fossil remains of megalodon suggest that this giant shark reached a maximum length of 18 meters (59 ft) with the average size being 10.5 meters (34 ft). Their large jaws could exert a bite force of up to 110,000 to 180,000 newtons (25,000 to 40,000 lbf). Their teeth were thick and robust, built for grabbing prey and breaking bone.

Megalodon probably had a major impact on the structure of marine communities. The fossil record indicates that it had a cosmopolitan distribution. It probably targeted large prey, such as whales, seals, and sea turtles. Juveniles inhabited warm coastal waters and fed on fish and small whales. Unlike the great white, which attacks prey from the soft underside, megalodon probably used its strong jaws to break through the chest cavity and puncture the heart and lungs of its prey.

The animal faced competition from whale-eating cetaceans, such as Livyatan and other macroraptorial sperm whales, and smaller ancestral killer whales such as Orcinus citoniensis. As the shark preferred warmer waters, it is thought that oceanic cooling associated with the onset of the ice ages, coupled with the lowering of sea levels and resulting loss of suitable nursery areas, may have also contributed to its decline. A reduction in the diversity of baleen whales and a shift in their distribution toward polar regions may have reduced megalodon's primary food source. More recently, evidence has come forward that competition from the modern great white shark may have also contributed to the extinction of megalodon, coupled with range fragmentation resulting in a gradual, asynchronous extinction as a result of cooling oceans around 3.6-4 million years ago, far earlier than previously assumed. The extinction of the shark appeared to affect other animals; for example, the size of baleen whales increased significantly after the shark had disappeared.

Megatherium

Megatherium ( meg-ə-THEER-ee-əm from the Greek mega [μέγας], meaning "great", and therion [θηρίον], "beast") was a genus of elephant-sized ground sloths endemic to South America, sometimes called the giant ground sloth, that lived from the Early Pliocene through the end of the Pleistocene. Only a few other land mammals equaled or exceeded Megatherium in size, such as large proboscideans and the giant rhinoceros Paraceratherium.

Miocene

The Miocene ( ) is the first geological epoch of the Neogene Period and extends from about 23.03 to 5.333 million years ago (Ma). The Miocene was named by Charles Lyell; its name comes from the Greek words μείων (meiōn, “less”) and καινός (kainos, “new”) and means "less recent" because it has 18% fewer modern sea invertebrates than the Pliocene. The Miocene is preceded by the Oligocene and is followed by the Pliocene.

As the earth went from the Oligocene through the Miocene and into the Pliocene, the climate slowly cooled towards a series of ice ages. The Miocene boundaries are not marked by a single distinct global event but consist rather of regionally defined boundaries between the warmer Oligocene and the cooler Pliocene Epoch.

The Apes first evolved, arose, and diversified during the early Miocene (Aquitanian and Burdigalian stages), becoming widespread in the Old World. By the end of this epoch and the start of the following one, the ancestors of humans had split away from the ancestors of the chimpanzees to follow their own evolutionary path during the final Messinian stage (7.2 - 5.3 mya) of the Miocene. As in the Oligocene before it, grasslands continued to expand and forests to dwindle in extent. In the seas of the Miocene, kelp forests made their first appearance and soon became one of Earth's most productive ecosystems.The plants and animals of the Miocene were recognizably modern. Mammals and birds were well-established. Whales, pinnipeds, and kelp spread.

The Miocene is of particular interest to geologists and palaeoclimatologists as major phases of the geology of the Himalaya occurred during the Miocene, affecting monsoonal patterns in Asia, which were interlinked with glacial periods in the northern hemisphere.

Neogene

The Neogene ( ) (informally Upper Tertiary or Late Tertiary) is a geologic period and system that spans 20.45 million years from the end of the Paleogene Period 23.03 million years ago (Mya) to the beginning of the present Quaternary Period 2.58 Mya. The Neogene is sub-divided into two epochs, the earlier Miocene and the later Pliocene. Some geologists assert that the Neogene cannot be clearly delineated from the modern geological period, the Quaternary. The term "Neogene" was coined in 1853 by the Austrian palaeontologist Moritz Hörnes (1815–1868).During this period, mammals and birds continued to evolve into roughly modern forms, while other groups of life remained relatively unchanged. Early hominids, the ancestors of humans, appeared in Africa near the end of the period. Some continental movement took place, the most significant event being the connection of North and South America at the Isthmus of Panama, late in the Pliocene. This cut off the warm ocean currents from the Pacific to the Atlantic Ocean, leaving only the Gulf Stream to transfer heat to the Arctic Ocean. The global climate cooled considerably over the course of the Neogene, culminating in a series of continental glaciations in the Quaternary Period that follows.

Piacenzian

The Piacenzian is in the international geologic time scale the upper stage or latest age of the Pliocene. It spans the time between 3.6 ± 0.005 Ma and 2.588 ± 0.005 Ma (million years ago). The Piacenzian is after the Zanclean and is followed by the Gelasian (part of the Pleistocene).

The Piacenzian is roughly coeval with the European land mammal age MN 16, overlaps the late Chapadmalalan and early Uquian South American land mammal age and falls inside the more extensive Blancan North American land mammal age. It also correlates with the Astian, Redonian, Reuverian and Romanian regional stages of Europe. Some authorities describe the British Red Crag Formation and Waltonian stage as late Piacenzian, while others regard them as early Pleistocene.

Piciformes

Nine families of largely arboreal birds make up the order Piciformes, the best-known of them being the Picidae, which includes the woodpeckers and close relatives. The Piciformes contain about 71 living genera with a little over 450 species, of which the Picidae (woodpeckers and relatives) make up about half.

In general, the Piciformes are insectivorous, although the barbets and toucans mostly eat fruit and the honeyguides are unique among birds in being able to digest beeswax (although insects make up the bulk of their diet). Nearly all Piciformes have parrot-like zygodactyl feet—two toes forward and two back, an arrangement that has obvious advantages for birds that spend much of their time on tree trunks. An exception are a few species of three-toed woodpeckers. The jacamars aside, Piciformes do not have down feathers at any age, only true feathers. They range in size from the rufous piculet at 8 centimetres in length, and weighing 7 grams, to the toco toucan, at 63 centimetres long, and weighing 680 grams. All nest in cavities and have altricial young.

Pika

A pika ( PY-kə; archaically spelled pica) is a small mammal, with short limbs, very round body, rounded ears, and no external tail. They resemble their close cousin the rabbit, but with shorter ears. They live in mountainous countries in Asia, and there are also two species in North America. Most pikas prefer rocky slopes. The large-eared pika of the Himalayas and nearby mountains is one of the highest living mammals; it is found at heights of more than 6,000 metres (20,000 ft). Pikas graze on a range of plants, mostly grasses, flowers and young stems. In the autumn, they pull hay, soft twigs and other stores of food into their burrows to eat during the long, cold winter. The name "pika" is used for any member of the Ochotonidae, a family within the order of lagomorphs; the latter also includes the Leporidae (rabbits and hares). One genus, Ochotona, is recognised within the family, and it includes 30 species. It is also known as the "whistling hare" due to its high-pitched alarm call when diving into its burrow. In the United States, the pika is colloquially called a "coney", a nonspecific term also used for rabbits, hares, and hyraxes. The name "pika" appears to be derived from the Tungus piika and the scientific name Ochotona is from the Mongolian word ogdoi which means pika.

Pleistocene

The Pleistocene ( , often colloquially referred to as the Ice Age) is the geological epoch which lasted from about 2,588,000 to 11,700 years ago, spanning the world's most recent period of repeated glaciations. The end of the Pleistocene corresponds with the end of the last glacial period and also with the end of the Paleolithic age used in archaeology.

The Pleistocene is the first epoch of the Quaternary Period or sixth epoch of the Cenozoic Era. In the ICS timescale, the Pleistocene is divided into four stages or ages, the Gelasian, Calabrian, Middle Pleistocene (unofficially the 'Chibanian') and Upper Pleistocene (unofficially the 'Tarantian'). In addition to this international subdivision, various regional subdivisions are often used.

Before a change finally confirmed in 2009 by the International Union of Geological Sciences, the time boundary between the Pleistocene and the preceding Pliocene was regarded as being at 1.806 million years Before Present (BP), as opposed to the currently accepted 2.588 million years BP: publications from the preceding years may use either definition of the period.

Suinae

Suinae is a subfamily of artiodactyl mammals that includes several of the extant members of Suidae and their closest relatives—the domestic pig and related species, such as babirusas. Several extinct species within the Suidae are classified in subfamilies other than Suinae. However, the classification of the extinct members of the Suoidea-the larger group that includes the Suidae, the peccary family (Tayassuidae), and related extinct species—is controversial, and different classifications vary in the number of subfamilies within Suidae and their contents. Some classifications, such as the one proposed by paleontologist Jan van der Made in 2010, even exclude from Suinae some extant taxa of Suidae, placing these excluded taxa in other subfamilies.In their 1997 Classification of Mammals, Malcolm C. McKenna and Susan K. Bell classify the Suinae as:

Tribe Suini

Genus †Eumaiochoerus (Miocene)

Genus †Hippopotamodon (Miocene to Pleistocene)

Genus †Korynochoerus (Miocene to Pliocene)

Genus †Microstonyx (Miocene)

Genus Porcula

Genus Sus (Miocene to Recent)

Tribe Potamochoerini

Genus †Celebochoerus (Pliocene to Pleistocene)

Genus Hylochoerus (Pleistocene to recent)

Genus †Kolpochoerus (Pliocene to Pleistocene)

Genus Potamochoerus (Miocene to recent)

Genus †Propotamochoerus (Miocene to Pliocene)

Tribe †Hippohyini

Genus †Hippohyus (Pliocene)

Genus †Sinohyus (Pliocene)

Genus †Sivahyus (Pliocene)

Tribe Phacochoerini

Genus †Metridiochoerus (Pliocene to Pleistocene)

Genus Phacochoerus (Pliocene to recent)

Genus †Potamochoeroides (Pliocene, possibly Pleistocene)

Genus †Stylochoerus (Pleistocene)

Tribe Babyrousini

Genus Babyrousa (Pleistocene to recent)In the 2005 third edition of Mammal Species of the World, which treats only recent forms, Peter Grubb followed this classification.

Tertiary

Tertiary is a widely used term for the geologic period from 66 million to 2.6 million years ago, a timespan that occurs between the Mesozoic Era and the Quaternary, although no longer recognized as a formal unit by the International Commission on Stratigraphy. The span of the Tertiary is subdivided into the Paleocene Epoch (56 – 66 million years BP), the Eocene Epoch (33.9 – 56 million years BP), the Oligocene Epoch (23 – 33.9 million years BP), the Miocene Epoch (5.3 – 23 million years BP) and the Pliocene Epoch (2.6 – 5.3 million years BP), extending to the first stage of the Pleistocene Epoch, the Gelasian stage.The period began with the demise of the non-avian dinosaurs in the Cretaceous–Paleogene extinction event, at the start of the Cenozoic Era, and extended to the beginning of the Quaternary glaciation at the end of the Pliocene Epoch.

Zanclean

The Zanclean is the lowest stage or earliest age on the geologic time scale of the Pliocene. It spans the time between 5.332 ± 0.005 Ma and 3.6 ± 0.005 Ma (million years ago). It is preceded by the Messinian age of the Miocene epoch, and followed by the Piacenzian age.

The Zanclean can be correlated with regionally used stages, such as the Tabianian or Dacian of Central Europe. It also corresponds to the late Hemphillian to mid-Blancan North American Land Mammal Ages. In California, the Zanclean roughly corresponds to the mid-Delmontian Californian Stage of from 7.5 To 2.9 Ma ago.

Cenozoic era
(present–66.0 Mya)
Mesozoic era
(66.0–251.902 Mya)
Paleozoic era
(251.902–541.0 Mya)
Proterozoic eon
(541.0 Mya–2.5 Gya)
Archean eon (2.5–4 Gya)
Hadean eon (4–4.6 Gya)

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