Eocene-Oligocene 1 - paradise lost -

Jarðsaga 2 - Saga Lífs og Jarðar - Ólafur Ingólfsson Háskóli Íslands Climate started cooling towards the end of

Global climate during the Late Eocene was still warm, but on a cooling trend. Glaciers begun to form in Antarctica. Oligocene (“almost recent”) • The Oligocene is the third epoch of the Cenozoic, 34 -23 MY. • Global cooling marked the start of the Oligocene, an environmental shift that led to changes in the flora and fauna. Global temperature dropped as much as 10° C, shrinking forests and introducing the grassy plains that would come to dominate in the . •Herbivorous adapted to eating grass and carnivores adapted to hunting out in the open. Both groups evolved better eyesight to see predators and prey as well as elongated limbs to increase speed over open terrain. • During this epoch archaic species of the early Cenozoic were replaced by modern , such as , camels and deer, and carnivores such as cats and dogs. Oligocene World Oligocene Ocean Currents

When Antarctica became isolated in a South Pole position, the coastal seas of Antarctica began to freeze, changing the ocean currents dramatically. Cold water and icebergs flowed north. Warm currents circulated around the equatorial continents. Oligocene climate

During the Oligocene, glacial ice covered the South Pole but not the North Pole. Seasonal sea ice may have formed there. Increased pole-equator temperature gradients. Oxygen isotope records show cooling and growth of glaciers go marine Whales evolved and diversified during the Eocene and Oligocene, and the two groups of Mysticetes (“skíð- hvalir”) and Odonto- cetes (“tannhvalir”) originated between 40-35 MY ago Mesonychide – ancestors of whales and hippos

Whales evolved from wolf-like creatures which 60-55 MY ago began searching for food in the water.

Andrewsarchus, the biggest , has a skull of about 83cm which would make it about 1.8m high and 5m long - the largest meat-eating land ever.

Lived in , and America. The Mesonychians were a group of carnivorous hoofed . These animals might have been solitary hunters/scavengers along river banks and tide lines.

http://www.visindavefur.hi.is/svar.asp?id=3556

http://www.pbs.org/wgbh/evolution/library/03/4/quicktime/l_034_05.html Archaeocetes: Early Whales, Dolphins/Porpoises Six families (ættir) of cetaceans (hvalir) are commonly included in Archaeocetes (fornhvalir): These archaeocete families - Pakicetidae document that the Eocene -Ambulocetidae cetacean evolution is - Remingtonocetidae characterized by increasing aquatic adaptations, starting - at amphibious early whales - (pakicetids, ambulocetids) to -Dorudontidae more marine protocetids (frumhvalir). Pakicetidae

- Early-to-middle Eocene, ca. 50 MY ago, in India and Pakistan. Fossils found in fresh-water deposits, most represent shallow streams in arid climate - Although pakicetids were land mammals, they are related to whales and dolphins based on a number of specializations of the ear. Skeletons of and Ichthyolestes

- Dozens of fossils known, but none consist of complete skeletons. Mostly skulls, teeth, and jaw fragments. How do we know this was “a whale”?

A 50 million year old earbone of Pakicetus lies between poppy seeds that show its tiny size. Photo taken with a scanning electron microscope. The hearing organ of Eocene whales was not spec- ialized as that of modern cetaceans. Instead it represents a compromise of adaptations relating to underwater sound reception and a hearing system used for listening to sounds in air. Ambulocetidae

- Known from Eocene (49 MY) rocks in northern India and Pakistan - Fewer than 10 described fossils; one nearly complete skeleton ( natans). - A. natans skeleton suggest it was probably slow on land and an ambush hunter which attacks prey in or near shallow water (like modern crocodiles). - Only known from nearshore marine environments, including bays and estuaries. Ambulocetidae

in action Copyright Carl Buell Remingtoncetidae

Illustration by Carl Buell and taken from http://www.neoucom.edu/Depts/Anat/Remi.html. - Only known from India and Pakistan, ca 46-43 MY (middle Eocene). It was a small animal, no bigger than a river otter. - Dozens of fossils described, most document morphology of skull and lower jaw - Most fossils known from marine, nearshore deposits; may have lived in bays and saltwater swamps Birthplace of whales: The Tethys Seaway Protocetidae

Some protocetids were probably the ancestor of all later cetaceans (including the modern groups). They are the first whales found outside of Indo-Pakistan, and are known from and . Protocetids are only found in sediments deposited in shallow seas. Protocetids were the first whale group to develop tail flukes and most were probably agile and quick aquatic hunters who preyed on small animals.Their teeth were reduced and most prey was probably swallowed whole. Protocetidae -frumhvalir -

An artist's rendering of a largely aquatic early whale of the Rod- hocetus. This mammal, which was the size of a sea lion, lived near the shores of the Tethys Sea, between Asia and the South Asian sub- continent, about 47 MY ago. J. Klausmeyer /Science http://www.pbs.org/wgbh/evolution/library/03/4/quicktime/l_034_05.html Basilosauridae (“king Lizzard”)

Reconstruction of cetoides .From: http://darla.neoucom.edu/DEPTS/ANAT/BasilAndDor.htm A Carnivorous early whale - ate fish, sharks and molluscs. It was huge, 15- 18 m long. This Eocene whale (40-36 MY ago) is well known from a large number of fossils. It must have been common in the warm shallow sea between Africa and Europe, and around North America. Basilosaurus

The narrow skull contained 44 teeth of various shapes: pointed, conical teeth in front, and saw-edged teeth in the back. This configuration made it possible for Basilo- saurus to catch and eat fish, hard-shelled mollusks, and crustaceans. One fossil had a ball of fish and sharks inside it, the remains of its last meal. The skeletons also show a pair of tiny legs. Dorudontidae (“spear-toothed”)

Basilosaurids and Dorudontids lived at the same time, and fossils are mainly known from the eastern USA and from Egypt (but were probably worldwide in their distribution). While Basilosaurids had snake-like bodies, with a tail fluke, Dorudontids were proportionally more like dolphins. An Eocene killer Whale

The Dorudontides were carnivorous, ate fish and molluscs. They were ca 5 m long. A famous fossil locality in Egypt has preserved many of them in ancient shallow-bay sedi- ments, along with their babies. Perhaps they calved in bays for protection like some modern whales. Familytreeof Whales Not only whales grew large and vicious... Coling and shrink- ing tropical forests towards the end of the Eocene opened up the landscape. This created space for larger Tropical rainforests withdraw towards herbivores and, the equatorial regins; conifers and later consequently, grasslands/steppes expand at higher latitudes larger carnivores Oligocene vegetation • By the Oligocene the major evolution and dispersal of modern types of angiosperms had occurred. •The vegetation of the higher latitudes in the northern hemisphere changed from tropical evergreen forest such as had typified the Eocene, to a temperate deciduous woodland of evergreen and broad-leaved trees. • Grasses, which appeared for the first time as plants of water margins in the Eocene, became more common in open habitats. Laurasian fauna

The brontotheres were common and widespread Herds of large, herbivorous 40 MY ago, when warm (shrubs, tree branches, soft forests were opening vegetation) brontotheres into drier plains. They (“Thunder beast”) lived on the are related to rhinos, N American and Asian plains. tapirs and horses. Indricothere (“indrik beast”)

The indricotheres (30-25 MY) were huge herbivores - browsing on upper branches of deciduous trees. Their closest living relatives are the Rhinos. The largest males were 4.5m at the shoulder, weighing 15 tonnes. The largest land mammals – ever!

Indricotheres were the largest land mammals ever to live.

The indricotheres had very large nasal passages meaning they had a very good sense of smell. They were related to the Rhinoceros, but browsed the tops of trees like a giraffe. Another strange giant...

...the Chaligotherium (“pebble beast”), 45- 3 MY. had the face of a , the neck of an ox, the arms and shoulders of a massive ape, the front claws of an anteater and short rear legs to support its massive bulk. A Tertiary “Panda” Fossils of a Chalicotherium arefoundintheOligocene of Asia, but fossils are rare.

They had no front teeth in the upper jaw, and even the back teeth show little wear from use. They must have Hebivorous - Soft shoots been fussy eaters – picking only, thank you! only the freshest shoots and putting them straight Closest living relatives are into the back of their Rhinos, tapirs and horses mouths like modern pandas.

http://www.pbs.org/wgbh/evolution/library/03/4/quicktime/l_034_04.html References used for this lecture

Stanley: Earth System History. Arnold, London Fortey: Life. A Natural History of the First Four Billion Years on Earth. Vintage, New York. http://www.sci.tamucc.edu/tmmsn/extinct/archaeocetes.html http://www.cetaceen.de/images/zeichnungen/EvolutionWale.png http://www1.thdo.bbc.co.uk/beasts/factfiles/index_all.shtml http://www.palaeos.com/Vertebrates/Units/520Cetartiodactyla/520.120.html# http://www.sciencenews.org/20010922/fob1.asp http://www.kokogiak.com/megafauna/strange.asp http://darla.neoucom.edu/DEPTS/ANAT/BasilAndDor.htm http://www.pbs.org/wgbh/evolution/library/03/4/quicktime/l_034_05.html http://www.ucmp.berkeley.edu/mammal/eutheria/creodonta.html http://www.flmnh.ufl.edu/natsci/vertpaleo/fhc/mesoh1.htm http://www.copyrightexpired.com/earlyimage/prehistoriclifeafterkt/index.html http://www.ucmp.berkeley.edu/tertiary/oli/olilife.html http://www.clas.ufl.edu/users/emartin/GLY3074S03/lecturenotes/cenozoicclimate.htm http://www.palaeoentomolog.ru/Publ/PALJ153.pdf http://www.pbs.org/wgbh/evolution/library/03/4/quicktime/l_034_04.html http://www.nature-source.com/turtles.htm http://sorcerer.ucsd.edu/tauxe/pdfs/shackleton00.pdf