Paleocene IIJarðsaga 2

- Saga Lífs og Jarðar -Ólafur Ingólfsson

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Paleocene mammals• At the beginning of the Paleocene epoch, the worldwas practically without larger sized terrestrialanimals. This unique situation was the starting point for the great evolutionary success of the mammals.

• Only ten million years later, at the end of thePaleocene, they had occupied a large part of thevacant ecological niches. By this time, the landscape was teeming with small insectivorous and rodent-like mammals, medium sized mammals were searching the forests for any kind of food they could cope with, the first large (but not yet gigantic) mammals were browsing on the abundant vegetation, and carnivorous mammals were stalking their prey.

Rapid diversificationDespite the very rapid diver-sification, most Paleocenemammals are still on a primitivelevel of anatomy in comparisonto mammals of today. Oftenthey show only the beginning of specializations that character-ize their descendants from later epochs, such as optimi-zation of the teeth for a special kind of food or adap-tations of the limbs to fast running. The Paleocene mammalian fauna is therefore often called archaic.

Strange rooters and diggersThe Paleocene is known for its archaic, yet sometimes bizarrely adaptedgroups of mammals, which often lack any direct living counterparts.

Restoration of the advanced taeniodont Ectoganus, together with twolarge herbivores of the genus Pantolambda that belong to another extinct order of mammals, the Pantodonta. The scene is from the Middle Paleocene of the Rockies

The mammals soon lost their innocence...

... and turned to eating other animals

Mammals turn carnivorous...True carnivores of the order (ættbálkur)Carnivora (rándýr) appear first in the middle oreven early Paleocene of North America. They form an important component of many Paleocene faunasof this continent, which may be their place of origin. Members of the Carnivora remain small, generalized predators throughout the Paleocene and during much of the Eocene. The step towards the first meat-eating mammals is not such a dramatic one. Primitive mammals typically fed on insects, and there is a smooth transition between an insectivore that occasionally takes small vertebrates and a small predator. ..

Mesonychia

Mesonychia was a medium to large-sized, possiblydominant predator or scavenger of mid-Paleocene. It was an ungulate, and persisted until Oligocene.

The Creodonts

• Creodonts (“flesh-teeth”) were an order(ættbálkur) of meat-eating mammalsthat were very common roughly 60 to 30 MY ago; they were the dominantcarnivorous mammals during the Tertiary period. They lived in Asia, Europe, Africa, and North America, going extinct 7 MY ago, during the late Miocene.

Hyaenodon

Hyaenodon belongs to an extinct group of mammalscalled creodonts. Creodonts originated in Paleocenetimes, but were the predominant and most diverse group of mammalian predators during the Eocene and Oligocene.

HyaenodonThe hyaenodontids(hýenungar) were toppredators in thePaleocene. They soontook advantage of the plains all over Eurasia and North America and grew to large sizes.

Hyaenodon was particularly successful. There wereseven species ranging from the size of a fox to that of a small rhino, roaming the plains that became the Mongolian Hsanda Gol formation.

Carnivorous marsupialsIn South America, carnivorous marsupials like theborhyaenids developed during the Paleocene.

Slide 9 of 21

Jaws of a Bolivianmarsupial, Miocene

Carnivorous marsupialsThe marsupial carnivores developed basicallythe same tooth structure for cutting meat asthe true (placental) carnivores of thenorthern hemisphere. Unlike true carnivores, however, carnivorous marsupials did not develop particular adaptations for fast running. This may have been one reason for their decline and finally their extinction after the arrival of true carnivores in South America in late Cenozoic time. Carnivorous marsupials developed in Australia until the present day...

More than 40 living species of carnivorous marsupials...

The Tasmanian devil (Sarcophilusharrisii). Its spine-chilling screeches, black colour, and reputed bad-temper, led the early European settlers to call it The Devil. Although only the size of a small dog, it can sound and look incredibly fierce.

The tiger cat (Dasyurus maculatus) -is the second largest of the world's surviving carnivorous marsupials. The species has males measuring up to 130 cm long and 4 kg in weight.

During the Paleocene, birds began todiversify and occupy new niches.

Hesperornis: A flighless Cretaceous bird

The Jurassic and Cretaceousbird forms were either poorlyadapted to flight or could not fly at all. The Paleocene bird record is very sparse...

Archaeopteryx: Pigeon-sized extremely primitive bird, probably capable of flight.

Two evolutionary lines:Palaeognathae –Flightless birds

• Today these are mostlya Gondwana group, butfossil evidence suggests they originated in the Northern Hemisphere.

•Include todays emus, ostriches, kiwis etc, aswell as the extinct moa birds of New Zealand

Neognathae – All other modern birds

• Includes almost allmodern birds, ~ 8500 species.

• Most have recordsgoing back to the Eocene

Paleocene birdsPrayed on mammals...?

Large flightless birds havebeen found in Paleocenerocks in some parts of theworld, like Gastornis in Europe, and could have hunted mammals.

Gastornis (and its Americancousin Diatryma) was ca. 1.75 m tall, with enormous beak. Probably hid in forest undergrowth and ambushed small animals

GastornisRemains of the giantbird Gastornis werefirst discovered nearParis in 1855, by thephysicist Gaston Planté(who later invented thelead battery still used incars). Gastornis parisiensis was not only a giant bird, it was also one of the oldest known birds at that time (Archaeopteryx had not yet been described).

Diatryma – american giant birdDiatryma is of late Paleocene-early Eocene age, ca. 55 MY. It was up to 2.4 m high. One huge duck!!!

Diatrymareconstructions

Who did eat whom?Flighless Diatryma try todefend their chicks against a pack of Pachyaena

Pachyaena was a latestPaleocene to Eocenewolf- to bear-sized meateater (creodont). This animal is thought to be amongst the ancestors to the whale.

First owls appear in late Paleocene

The earliest representatives of the owls, which typicallyhunt mammals, are Ogygoptynx and Berruornis from the late Paleocene of the U. S.A. and France respectively.

Paleocene birds

Among other groups of birds that appear during thePaleocene are Gaviiformes (skarfar og lómar), Podicipedi-formes (goðar), Pelecaniformes (pelikanar), Ciconiiformes (hegrar og storkar), and Charadriiformes (vaðfuglar og máfar)

Early CenozoicPenguins

Penguins have a longnatural history; theyprobably started toevolve already in latePaleocene or early Eocene times. Huge (>1.5 m long) fossil penguins discovered in Antarctica

Seymour Islands giant penguins

PaleoceneOcean

CurrentsThe Palaeocenewas characterizedby globally warm seas

Northern Hemisphere - Warm shallow sea currentscirculated around the Northern Supercontinent. Southern Hemisphere - Warm shallow seas circulatedbetween Antarctica, Africa, Australia, South America and India.

Paleocene Planktonic foraminiferaOnly three species of planktonic foraminifera(götungar) survived the K/T mass extinction. But within 100.000 years of Paleocene time, 17 new species appeared.

Calcareous nannoplankton(dvergsvif), which hadsuffered greatly during the K/T extinction, also rediversified rapidly during early Tertiary.

Early Tertiary Corals haveproblems building reefs

Rudists (bivalves) were the most important reef buildersduring the Cretaceous. They demise at the K/T boundary.

Corals failed to takeadvantage of the rudistdecline. They built no largereefs during early Tertiary(Paleocene, Eocene), only small and scattered reefs. Probably the low magnesium-calcium ratio in seawater during early Tertiary impended the ability of corals to form reefs.

Septastrea, Tertiary coral Fossil

Paleocene bivalves and gastropods...Paleocene gastropods (sniglar) and bivalves (samlokur)were very similar to modern forms. Soft-bodied squid(smokkar) replaced the hard-shelled ammonites as the leading molluscs. New kinds of sea urchins (sægúrkur)replaced Mesozoic types that had been killed off in the great terminal Cretaceous extinction.Marine invertebrates were advantaged bythe disappearance of Mesozoic predators such as the ammonites.

Fossil Echinoid(ígulker): Linthia

Teleost fishes (beinfiskar) developand diversify rapidly

By Cenozoic times fishes had already gone through themajor evolutionary steps leading towards modern fishes. These include: (a) jaw development; (b) development of fins and reducement in armour; (c) skeletal and body-shape adjustments to reduce wight and increase speed; (d) developing ways of coping with water-pressure and buyoancy.

Paleocene developments in the OceanThe present marine ecosystem is for the most part populated by groups of animals, plants and single-celled organisms that survived the K/T extinction event

Sharks became the top predators of the Palaeocene oceans, as the marine reptiles had disappeared.

All modern sharks were developed by the Paleocene, and have changedlittle since. Ancestors of the great white shark appeared in the

Paleocene.

Ancestors of theGreat White Shark

Eocene-Pliocene sharks grew toenormous sizes: Megalodon ("GiantTooth”) (Miocene-Pliocene) was 16 m long, with a gap of >2 m! Carcharodon carcharias

Early Tertiary reptilesThe marine reptiles suffered heavilyduring the K/T extinctions, and thehuge marine predators (like the greatmososaurs) went extinct. Crocodilians, chelonians (“skjaldbökur”) and lizards were affected only mildly by the K-T boundary events.

Chelonians survived the K-T extinctionbetter than any other reptilian groups. Where 15 species were known to havehad lived to the end of the Cretaceous eight of them survived to move on into the Tertiary. Still a hard hit, but slightly more than half survived.

Early Tertiary crocodilesPerhaps because of theirectothermic metabolism(which makes it possible togo without food for longperiods) and their relianceon the fresh water carrion- based or the terrestrial plant-based foodchains, the crocodiles were unaffected by the K/T mass extinction that eliminated most forms of life on Earth.

In the absence of large competi-tors during the Paleocene, thecocodiles evolved into large fully terrestrial preditors (Sebeco-suchids, Pristochampsids).

Paleocene crocodiles – ruling predators in swamp and river environments

http://www.crocsrule.org/immersions.html

Tertiary crocodilesThe crocodiles from the Late Cretaceous are quite similarto modern crocodiles. With the disappearance of thedinosaurs, crocodiles became among the most important predators in the warm climates of early Tertiary.

Diplocynodon – an earlyTertiary crocodile

Croc’s ruled until end of Eocene...The crocodiles continued toevolve and diversify throughthe Paleocene, and in theabsence of large competitors evolved into large fully terrestrial preditors.

The global cooling trend that began in the Oligoceneepoch and accelerated in the Miocene and Pliocene wascatastrophic for the crocodiles. Many types died out, unable to cope with the increasing cold, and the survivors retreated to the tropics and a life in swamps.

Summing up the Paleocene• The climate was warm from pole-to-pole.

• Continental drift and break-up of Pangea led to the relativeisolation of South America, Africa, Australia-Antarctica and India. First phase of the Laramide orogeny.

• Flowering plants diversify. First appearance of pines, cacti and palms

• Mammals diversify rapidly and occupy most niches. Mammalian carnivores

• Birds diversify rapidly. The two evolutionary lines (flightless and flying birds) become established

• Sharks become top predators in the sea, crocodiles are top predators on land

• Teleost fishes develop and diversify rapidly

References for lectures on PaleoceneStanley: Earth System History. Arnold, London

Fortey: Life. A Natural History of the First Four Billion Years on Earth. Vintage, New York.www.ucmp.berkeley.edu/diapsids/birds/www.palaeos.com/Vertebrateswww.bbc.co.uk/beasts/changing/paleocene/mammals.shtmlwww.carlwozniak.com/earth/Life.htmlwww.paleocene-mammals.de/index.htmwww.ucmp.berkeley.edu/www.il-st-acad-sci.org/kingdom/bird001z.htmlwww.peabody.yale.edu/www.scotese.com/www.karencarr.com/index.htmlwww2.nature.nps.gov/geology/parks/grte/www.molndal.se/BIBL/xuge.htmwww.dmclf.org/evolution/fossil-penguins.htmlwww.news.nationalgeographic.com/news/2001/05/0524_paperclipmammal.htmlwww.crocsrule.org/immersions.htmlwww.dpiwe.tas.gov.au/inter.nsf/WebPages/BHAN-5372FN?openwww.palaeos.com/Vertebrates/Units/Unit290/290.300.html#Sebecosuchidae