In Cretaceous, 150 million years ago to 100 million years ago, small, nocturnal insect-eaters {placental mammal}| (Placentalia) evolved.
anatomy: placenta
Tissue {placenta}, in which mother blood vessels commingle with embryo vessels, surrounds embryo inside uterus, allowing food and waste exchange. This allows more embryo growth, by improving nutrition and respiration.
anatomy: senses
First Eutheria had large ears and good hearing. They had vibrissae and good smell sense. They had small eyes, on head sides.
anatomy: nervous system
First Eutheria had larger brains than same-size reptiles.
biology: signal
Mammals other than primates have 10 to 40 different signals.
biology: children
All Eutheria have live birth. Eutheria have fewer births per mother, birth at later stage, and more care of young. Culture transmission requires relatively few young. Adults must outnumber young to preserve culture.
types
The 23 placental-mammal orders include bats, carnivores, cetacea, edentates, hooved, insectivores, primates, proboscids, rodents, scienia, and simple hooved. Carnivores include cat, dog, bear, and seal. Edentates include sloth, anteater, and armadillo. Insectivores include hedgehog, insectivore shrew, and mole. Primates include tree shrew, lemur, tarsier, and monkey. Lemurs and tarsiers are similar.
clades
Placental mammals have four clades. Clade I {Afrotheria} includes elephants, manatees, aardvarks, and elephant shrews. Clade II {Xenarthra} includes sloths, anteaters, and armadillos. Clade III {Euarchontoglires} {Supraprimates} includes rodents, primates, flying lemurs, and tree shrews. Clade IV {Laurasiatheria} includes cetaceans, bats, carnivores, hedgehogs, insectivore shrews, and moles.
clades: evolution
Afrotheria was first. Afrotheria and Xenarthra, clades I and II, split 103 to 105 million years ago, in Cretaceous, perhaps from South America and Africa separation.
Early superorder {Boreoeutheria}, of clades III Euarchontoglires and IV Laurasiatheria, split from Xenarthra 84 to 95 million years ago.
Euarchontoglires and Laurasiatheria {Epitheria} split 60 million years ago.
clades: I Afrotheria
Afrotheria is in Africa and includes golden mole (Chrysochloridae), otter shrew/tenrec, elephant shrew/sengi (Macroscelidea), aardvark (Tubulidentata), hyrax (Hyracoidea), mantee/dugong (Sirenia), and elephant (Proboscidea).
Tenrec (Tenrecidae) and otter shrew (Potamogalinae) have cloaca and can look like shrews, hedgehogs, mice, or otters. Golden mole lives in south Africa, eats insects, burrows, and looks like moles. Golden mole and otter shrew/tenrec are order (Afrosoricida).
Elephant shrew or jumping shrew (Macroscelididae) has long nose and looks like shrews.
Hyrax, mantee/dugong, and elephant are clade (Paenungulata). Hyrax lives in Africa and Middle East, looks like rabbit or guinea pig, and ferments food in cecum {copraphage}.
clades: II Xenarthra
Xenarthra developed in South America and includes armadillo (Cingulata), anteater (Vermilingua), and tree sloth (Folivora), which have strange joints {xenarthra}. Anteater includes silky anteater, giant anteater, and tamandua. Tree sloth includes two-toed and three-toed sloths. Anteater and tree sloth are group (Pilosa).
clades: III Euarchontoglires
Squirrel, mouse, and other rodents (Rodentia); rabbit, hare, and pika (Lagomorpha); treeshrew (Scandentia); coluga (Dermoptera); and primates are superorder (Euarchontoglires) (Supraprimates).
Coluga (Cynocephalidae) or cobego or flying lemur can glide from trees and lives in southeast Asia. Coluga, primate, and treeshrew are order (Euarchonta).
Pika (Ochotonidae), rock rabbit, or coney is like hamsters and squeaks {whistling hare}. Rodents and lagomorphs are order (Glires).
clades: IV Laurasiatheria
Laurasiatheria developed in Laurasia and are bats, hedgehogs, cetaceans, even-toed ungulates, odd-toed ungulates, carnivores, and scaly anteaters.
Hedgehogs (Erinaceinae) live in Eurasia and Africa. Gymnures or moonrats live in southeast Asia. Hedgehogs and gymnures are early order (Erinaceomorpha).
Shrews (Soricidae) include white-toothed shrews, red-toothed shrews, and African white-toothed shrews. Moles (Talpidae) include Talpinae, Scalopinae, and Uropsilinae. Solenodons (Solenodontidae) look like large shrews, are insectivores, and live in Cuba and Haiti. Moles, shrews, and solenodons (Soricomorpha) are order.
Artiodactyla order of even-toed ungulates includes pigs, hippopotamus, camels, giraffe, deer, antelope, cattle, sheep, and goats. Cetacea order includes whales, dolphins, and porpoises. Cetaceans probably evolved from hippopotamus (Whippomorpha) (Cetancodonta). Cetaceans and even-toed ungulates are order (Cetartiodactyla).
Even-toed and odd-toed ungulates are a group.
Order (Pegasoferae) is in Africa and south Asia and includes pangolins or scaly anteaters (Pholidota), carnivores (Carnivora), bats (Chiroptera), and odd-toed ungulates (Perissodactyla), such as horses. Carnivores and scaly anteaters are group (Ferae).
Mammals accept that individuals can have authority, resulting in different ranks {dominance hierarchy}|. Animals in groups have ranks or roles, relatively dominant or subordinate. Older males typically dominate.
authority
Different species use different authority symbols.
hierarchy
All societies have status hierarchies and/or resource controls.
change
Primates form alliances based on obligations and contact, to gain higher rank. Ranks are always shifting. Dominance fights are not deadly. Animals can try to act differently than rank. Others must catch and punish offenders. Animals can try to deceive, but only higher apes seem to try to make others' beliefs be wrong.
effects
Dominance hierarchy causes hostility to strangers, maintains peace in society, decreases new behaviors, and causes threats from younger males toward older males.
factors
Dominance behaviors increase at breeding times. Dominance behaviors increase at higher population densities.
Only humans laugh {laughter, human}, but other mammals appear happy.
Fat layer {blubber}| can protect body from cold.
Insectivores have hands with opposing thumb across from fingers {grasping hand}|, which allows better grip and more hand-eye coordination.
Some whales have oil {spermaceti}.
Proboscids have long trunk {trunk}| from nose.
Proboscids have elongated incisor teeth {tusk}|.
Insectivores have eyes facing front {forward vision}|, rather than on side, allowing better vision and eye-hand coordination and more space for brain frontal lobes.
Some echolocating bats, like horseshoe bat, scan for sound and then focus sound using nose structures {nose leaves}.
Cats have mirror-like layer {tapetum} behind retina to reflect light back through retina.
Individuals at rank must know to do some things and not do other things {deontic reasoning}.
Individuals in society attend to and remember rule breaking and act on previous-situation knowledge {indicative reasoning}.
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Date Modified: 2022.0225