Kellan Korcheck and M. Royce
In this artist’s reconstruction we see, from left to right, a Wooly Mammoth behind an apple tree , early horses in the background, a Terror Bird, a flying insect, a Big Brown Bat, a crocodile in the pond, a Saber-tooth Cat on the shore, and Ground Sloths in the forest.
23.03 Million years ago to the Present
The Neogene* encompasses two epochs, beginning with the Miocene (23.03-5.33 Mya) and followed by the Pliocene (5.33-1.806 Mya). The Pleistocene (the "Ice age", 1.806-0.0115 Mya) and the current epoch, the Holocene, beginning eleven thousand five hundred years ago are now (2009) included in the Quaternary Period. Though traditionally the Holocene is treated separately, it may in fact just be the latest interglacial of the Pleistocene. This display includes the Miocene through the Pleistocene Epochs of the Neogene and Quaternary Periods.
The Neogene Period started with the replacement of vast areas of forest by grasslands and savannahs. New food sources and niches on the grasslands and savannahs fostered further evolution of mammals and birds. Whales diversified in the seas, and sharks reached their largest size during the Miocene. Complex patterns of mammalian evolution resulted from changing climates and continental separations. More modern mammals evolved as grasslands became widespread and the climate cooled and dried. Additional information about the mammals of these epochs can be found in our Prehistoric Mammals of the Cenozoic exhibits. The Neogene saw a gradual closing of the Tethys Sea as the continents moved into their modern positions. The dramatic cooling phases of the Neogene lead to more distinctive latitudinal biotic zones.
The Miocene comprised most of the Neogene Period making it the second longest Epoch of the Cenozoic Era. Wide expanses of grasslands formed across the Northern Hemisphere and supported a variety of new types of mammals. Horses moved from browsing in forests and meadows to grazing (eating grass) in grasslands. In the oceans the first known kelp forests appeared. Ocean circulations changed to form large gyres (circular patterns) in both the Northern and Southern hemispheres. The new circulation patterns in turn lead to the evolution and spread of diverse marine mammals including a variety of toothed and baleen whales, sea lions, seals, walruses and sea cows. Non-mammalian predators included marine crocodiles and the largest known shark, Carcharodon megalodon. Marine invertebrates were similar to today, in fact half of the species are unchanged.The Miocene began with a short warming, followed by a return to the general Cenozoic cooling trend. The once great Tethys ocean was reduced to the Mediterranean Sea and closed at both ends, bringing the circumglobal circulation of warm waters to an end.
The mural above emphasizes the variety of mammals that evolved to occupy the grasslands and savannahs of North America in the Miocene epoch. On the far left are the giant (8' at the shoulder) perrisodactyl Moropus, a clawed herbivore related to horses, confronting Daphoenodon dogs. In front of them are a group of ruminant oreodonts (Merychyus). Next to them in the foreground is a herd of extinct horses, Parahippus, that was evolving from a browsing habit to a grazing (eating grass) one. A group of semiaquatic Promerycochoerus are in the background and behind them a Daeodon, a large (12 ft long) pig-like scavenger or predator. Finally, on the right of this panel is a group of the small camelid Stenomylus.**
A dramatic event at the beginning of the Pliocene was the catastrophic filling of the Mediterranian sea. The collisions of the African and Eurasian continents during the Miocene had closed the Mediterannian basin both in the east and at the Straits of Gibraltar resulting in the basin drying up and converting to grasslands. When the barrier on the western end was breached it refilled catastrophically from the Atlantic ocean. Also during the Pliocene the Panamanian bridge was formed between North and South America allowing for the migration of animals both north and south in what is known as the “Great American Faunal Interchange.” Giant ground sloths, armadillos and marsupials among others came north, while cats, dogs, bears, camels and others went south. Many of the South American species were replaced by northern species and eventually went extinct. Bringing the two continents together also stopped the exchange between the Caribbean and the Pacific allowing these faunal provinces to evolve apart. In Africa early hominids appear for the first time in the fossil record. Famous hominid fossils such as "Lucy" a female Australopithecus aferensis and footprints from a pair of hominids alive 3Ma have been found in Pliocene deposits in Africa. Marine and freshwater aquatic Pliocene fossils are now numerous around the globe.
Grasslands and savannahs continued to be commonplace as shown in the mural above emphasizing common Pliocene American mammals. In the background a herd of gomphotheres, Amebelodon (a primitive proboscidian with flattened shovel-like lower tusks) amble across the plain next to extinct grazing rhinoceros, teloceres. In the foreground three extinct deer-like artiodactyls with multiple horns, (Cranioceras) are seen next to a pair of Synthetoceras, artiodactyls with large forked horns on the snout. On the ground in front of them are a group of horned gophers (Ceratogaulus) the smallest known horned mammal and the only known horned rodent. A prehistoric horse can also be seen at the upper right.**
Modern humans including Homo erectus, H. neanderthalensis and H. sapiens evolved during the Pleistocene. The first recorded migrations of humans out of Africa occurred during this epoch. At least 20 cycles of glaciations occurred during the Pleistocene, with some glaciations covering up to 30% of Earth's surface. North American ice sheets in the Wisconsin glaciation of 18,000 year ago were over 3900 meters (2.4 miles) thick. These and other massive ice sheets tied up so much water that sea levels dropped 140 meters. Many large mammals went extinct near the end of the Pleistocene (~11,000 years ago), leaving our modern flora and fauna. Though controversial, a widely held theory explains these extinctions as a result of human hunters in both Europe and the Americas.
The illustration above shows some animals of ice-age Spain. A small herd of horses moves off to the left while a group of wooly mammoths marches towards us up the center over a light dusting of snow. In the foreground lions protect their kill under the gaze of a wooly rhinoceros.
* The term Neogene comes from the grouping by Hornes (1853) of the Miocene, the Pliocene and the Pleistocene into the “Neogen Stufe.”
** The names and information concerning the animals in these murals are taken from the original legends in the 1964 Time-Life book, The Land and Wildlife of North America, and may be outdated.
Two Pliocene crabs, Trichopeltarion greggi,Galena bispinosa, a Miocene crab, Tumidocarcinus giganteus, and a Pliocene lobster, show the modern appearance of Neogene crustaceans.
Barnacles (Theostraca) are represented by a barnacle covered scallop.
barnacle covered scallop
Echinoderms in this display include two echinoids (Echinoidea), a Lower Miocene sea urchin, Tripnuestes parkinsoni Agassiz, and a Pliocene sand dollar, Dendraster diegoensis.
Tripnuestes parkinsoni Agassiz
A tooth of the giant Miocene shark, Carcharodon megalodon is displayed. These giant "white" sharks could reach lengths of perhaps 80 feet with teeth exceeding 7 inches in diagonal length. It was one of the most formidable predator to ever live, feeding on small whales as well as fish etc.
Carcharodon megalodon tooth life reconstruction of a Megalodon shark pursuing Eobalaenoptera whales
Ray-finned fish (Actinopterigii), Teleost fish (teleosti), are represented by pharyngeal teeth from a Cyprinid.
Reptiles are represented by a Miocene jaw fragment with two teeth from Gavialoschus sp.
Gavialoschus sp. jaw
Birds (Aves<Dinosauria [Birds and Dinosaurs]). A group of Pliocene bird bones, with the slender look of modern forms are shown.
Mammals are represented in this display by fossils from a variety of marine organisms: a tooth and a tusk of the Miocene sea cow, Desmostylus hesperus, an unusual marine mammal common in the North Pacific with legs adapted for both land and swimming; some teeth from the sea lion, Aledesmus kernensis; a whale ear bone, and the vertebra of a Miocene whale.
Sea cow (Desmostylus hesperus)
tooth tusk life reconstruction
ear bone vertebra
Bivalves (bivalvia) are represented by a barnacle covered scallop and a Pliocene clam, Arca scalarina. Numerous bivalves can be seen, along with a few gastropods, in the sample of Pliocene coquina, a form of loose limestone composed mostly of fossil shells.
Casts from the Miocene boring bivalve shipworm, Kuphus calamus Lea, are also displayed.
Kuphus calamus Lea
Gastropods (Gastropoda): A variety of gastropods are on display: the Pliocene snails, Busycon contrarium,Ecphora quadricostata, and Triplofusus scalorina. ; the Pliocene olive snail, Oliva sayana, the Pliocene turret snail, Vermicularia weberi, and finally a group of Pliocene slipper snails of the genus Crepidula. A number of gastropods can be seen along with numerous bivales in the sample of Pliocene coquina, a form of loose limestone composed mostly of fossil shells.
Corals are represented by a 'braincoral,' Mancinia sp. from the Pliocene.
©1998, HSU NHM | Last modified 30 October 2012