Marsupials and Relatives Metatheria All have pouches for young Can be distinguished from placentals by: ñ 2 epipubic bones – to do with pelvis structure as they do not give birth to large young ñ general dental formula of three premolars and four molars Placentals and Relatives Eutheria Distinguished by: ñ absence of epipubic bones ñ wide pelvic opening for birth of well-developed young ñ four premolars, three molars ñ long gestation period ñ different type of ankle joint Most diverse and widespread group From tiny ground-dwellers and bats to blue whales Origin of Placental Mammals Most placental orders appear to have originated after the K-Pg boundary, mostly within 400ka, or in the late part of the Creataceous Protoungluatum (first ungulate) possibly first placental mammal, stem eutherian Purgatorius is a stem primate Both found close to K-Pg boundary 4 Broad Groups of Mammals Afrotheria Opecia – basal to most Afrotherians ñ thought to have been a browser ñ first found in Paleocene Major radiation of Afrotheria in Paleocene leading to: ñ elephants, ñ elephant shrews, ñ golden moles, ñ hyraxes, ñ aardvarks, ñ manatees Xenarthra First to split off from other groups Major radiation demonstrated in South America ñ modern sloths, anteaters, armadillos, ñ extinct pampatheres, ground sloths, and glyptodonts Eurachontoglires Cosmopolitan Laurasiatheria From the super-continent Laurasia Includes: ñ Perissodactyls – odd-toed ungulates, e.g. horses, tapirs, rhinoceroses ñ Artiodactyls – even-toed ungulates, e.g. camels, pigs, hippos, ruminants, cetaceans ñ Carnivorans ñ Pholidota – pangolins ñ Chiroptera – bats ñ Rodentia – rodents ñ Eulipotyphyla – hedgehogs, moles, shrews, Solenodon Madagascar Isolated from Africa for 115my, from India for 88my Shows major radiation of Lemuridae (Primates), Tenrecidae (Lipotphyla), Eupleridae ñ Genetic analysis indicates single colonisation event for each group Series of rafting events responsible for animals ending up on Madagascar ñ Mostly small mammals able to store fat and enter torpor There were hippos – but they were smaller than mainland African hippos, and became extinct after European arrival ñ Up to 3 species Also, a giant lemur – 1.6m tall Africa Major radiation of Afrotheria outlined above Africa was separated from northern continents for much of early Cenozoic Made contact with Eurasia about 30mya Lagomorphs, ungulates, insectivorans entered Africa ñ this includes much of the current charismatic large fauna o e.g. rhinos, giraffes, many antelope South America Major radiation of Xenarthra outlined above Also, major radiation of marsupials ¼ of extant marsupials live in the Americas Diversification of Notoungluates, litopterns, astrapotheres, pyrotheres The Great American Interchange Large-scale faunal swap when N. America became joined with S. America by the Isthmus of Panama ~ 3mya Resulted in specialised placental carnivores reaching S. America New Zealand Terrestrial mammals absent today (except a small amount of ground-feeding bats) There was a fully terrestrial mammal present in the Miocene – possibly a multituberculate relative due to teeth marks on fossil bird bones Australian Mammal Evolution Australia is good for fossils because we have a broad geographical background But there are many gaps in the fossil record because some areas are not suitable for some time periods So molecular phylogenies are used to extrapolate relationships Early Mammals of Australia Early Cretaceous Early monotremes – Steropodon, Kollikodon Kollikodon largest monotreme ~1m Multituberculates – Corriebaatar Ausktribosphenids – not sure where they belong, but closer to marsupials than monotremes or eutherians Eocene Djartha – Australdelphian group (incl. all Aus. Marsupials, and microbiotheres of South America) Possible Peramelemorph – early bilby Microbiotheres – generalised insectivore Archaeonothos – basal to marsupials and unrelated to current marsupials Several Polydoploids present – group of South American marsupials (incl. Chulpasia and Thylacotinga) Australian Mammal Dentition Radiation Tooth morphology is good indicator because teeth are often well preserved Form one of the main interactions between an animal and its environment – useful for paleobiological relationships Every single detail in a tooth has a name .