lecture 2 mammals

What are the 2 evolutionary trends in Xenarthra?

1. loss of teeth/ant eating

2. extra teeth with homodonty, no enamel, peg teeth

Bradypodidae has symbiotic relationships with…

beetles, algae, and moths

Eulipotyphla orders

Soricomorpha

Erinaceomorphora

shrews, hedgehogs, gymnures

fat and blind

Chiroptera are the only mammals capable of

powered flight

Chiroptera have delayed

fertilization

Light bones for flight do not

fossilize well

Chiroptera in tropical areas means fossiles are

less likely to be found

First chiroptera fossils were found in

Wyoming and India

Chiroptera clades divereged

60 mya

Chiroptera wings have

-elongation of fingers - main body between 4 digits of hand

-membrane extends down sides of bodies and attaches to hind legs

-uropatagium

-robust thoracic region for flight muscles

Uropatagium definition

membrane between hind legs that encloses the tail in chiroptera

Chiroptera were previously subdivided into

Microchiroptera and Megachiroptera

Megachiroptera

feed on plant materia

large bats

NO ECHOLOCATION

Microchiroptera

diversity of food (fruits, bugs, nectar, blood, frogs)

ALL ECHOLOCATE

Yinpterochiroptera

pteropodidae + 5 echolocating families

Yangochiroptera

all other echolocating bats

Did echolocation evolve multiple times?

1. evolved once from common ancestor and lost in fruit bats

2. evolved 2 times independently (there are small differences between them)

New studies show that echolocation in chiroptera

evolved twice!

Pholidota

(pangolin)

Convergence on ant eating behavior

lack teeth

long muscular tongue

pyloric stomach thickened and muscular with keratinous spines

What are carnivora derived from?

creodonta

when were carnivora dominant?

in the late cretaceous to the miocene because the dinosaurs were gone there were large carnivores

Carnivora possibly evolved in response to

a new food source (herbivores)

all modern carnivorans have

carnassial teeth or are derived from ancestor that did

by the eocene all carnivorans are defined by

presence of carnassial pair (p4/m1) or ancestor with one

phocidae (seals) secondarily evolved

homodont teeth

creodonta were out competed by

the daughter group carnivora

Not all carnivorans are __ and not all carnivorous mammals _

1. carnivous

2. belong to the order carnivora

Fissipedia

terrestrial

pinnipedia

aquatic

is pinnipedia monophyletic?

yes

Condylathra are the

archaic ungulates

Perissodactyla evolved from

condylarthra-like mammals

Perissodactyla do not

ruminate

Hindgut fermentation

expanded cecum - feed on fibrous vegetation OF POOR QUALITY, can eat quickly but have to eat a lot to get nutrients

Digestive efficiency of a horse (perissodactyla) is about __ of a cow

70%

Perissodactyla are __ toed

Odd toed ungulates - decrease to 3 digits or 1 digit (2, 3, 4) most have 3 digits on hind and 3-4 on forefoot

weight on middle toe

what does a groove in the astragalus do?

creates a pulley-like surface that limits the limbs to forward-backward movement

helps with fast and efficient terrestrial locomotion

Paraceratherium

extinct ancient rhino that was one of the largest land mammals ever

Rhinos were once widespread and evolved in

north america and eurasia

Horses used to be

small and foxlike in the eocene in north america

Evolutionary trends of equidae

• increasing body size and lengthening of legs with emphasis on the middle toe

• grasslands evolved and increased lophodonty and hypsodonty

In the pleistocene every horse

in north america went extinct

they survived in europe and were reintroduced in 1500s

artiodactyla are __ toed

even toed - reduced to 2-5 - symmetry between 3&4 toe

seems to have lead to longer legs

Artyodactly have __ limbs and are often _ to __

1. lengthened

2. digitigrade

3. increase speed

How did artiodactyla get much more diverse than perissodactyla?

1. evolution of double pulley arrangement in lower leg

2. ruminant digestion (foregut)

What does the double pulley arrangement achieve?

tendon extends across tip of leg bones creating a spring which increased speed and allows them to run faster than perissodactyla

Ruminant digestion

Foregut fermentation - animal chews food multiple times (cud)

Advantage of ruminant digestion

can eat low energy food items and multiple chewing gets all of the energy out

-4 chamber stomachs and microorganism decompose cellulose into digestible components

-can watch for predators unlike perisso who have their heads down

These adaptations allowed artidactyla to

go to open areas, fill up with food, go to safe place to chew (perisso had to chew where they eat and could be attacked)

Cetacea early ancestors were

terrestrial (oldest fossils from pakistan in eocene) then moved to completely obligate aquatic life form

Cetaceans had a vast increase in body size because

water is cold so it is advantageous to be bigger to retain body heat

example blubber

Cetaceans had a

decrease in hindlimbs and evolution of flippers, streamlines bodies to reduce drag, telescoped skulls, echolocation

Odontoceti are _ and mysteceti are -

1. tooth whales

2. baleen whales

both derived from archaeoceti (extinct)

whale earwax can study

biogeography

hormone levels (sexual maturity)

pollutants

Dermoptera (colugo) have a extensive

patagium - furred membrane all over their body

Dermoptera use membrane

as an air break

plesiadapiformes

early primates

shared derived primate characters

stereoscope vision, brain, reproduction, dentition, auditory, locomotion

Auditory characters in primates led to

arboreal lifestyle

Primates went from terrestrial insectivores to

arboreal omnivores then some went terrestrial again

Strepsirrhini have a

biocornuate uterus and epitheliochorial placenta

haplorrhini have an

invasive hemochorial form of a placenta

How do we have such a wide distribution of haplorrhini?

35-40mya they got to the western hemisphere by raft from the east (land mass went east to west)

We can infer that ancestral haplorrhini were active at dawn/dusk because

tarsiers had trichomatic vision (lots of colors)

Archaeoidris

giant sloth sized lemur

Lagomorpha are

corophagous (survive on low quality vegetation; hindgut fermenter)

Rodents evolved in

isolation from multituberculates

they later came into contact and outcompeted them

rodents are _ fermenters

hindgut (coprophagous- eat their own fecal)

Biological species concept

Species are groups of interbreeding populations which are reproductively isolated from other groups

Prezygotic mechanisms of isolation

habitat, seasonal, behavioral, mechanical, gametic mortality

Postzygotic isolation

hybrid inviability - hybrid dies

hybrid sterility - cant reproduce

Phylogenetic species concept

irreducible cluster of organisms diagnosably distinct from other clusters and there is a parental pattern of ancestry

Why do species matter?

They are the conservation unit - how we apply conservation to a specific population

Current research species

peromyscus maniculatus - can cause lots of disease and could differ by east or west coast on how they carry it

hair is dead epidermal cells

strengthened with keratin

hair structure

arrector pili

• allow hair to stand up (goosebumps)

• can thicken and give warmth

• can give bigger appearance do defend yourself

accessory follicles

increase density

hair cross section

medulla hollow to trap air to stay warm and trap air to float

Where did hair come from?

• first early synapsis have scales not flexible

• scales separate/lost and expose skin for better movement/flex

• follicles formed in the sensory pit

• de novo evolution of hair gives sensory pit increased ability to sense environment

alpha keratin is

distinctly mammalian

evolution of fur

1. increase number of follicles/sensory pit

2. increase number of hairs in each follicle

functions of increasing density of hair

• insulation - retain heat

• tactile - sensory

• protect skin

• protection (quills)

• visual (distract/conceal) ex zebra or white fur in snow

types of hair

• guard hairs - guard under fur (protection, wind break, buoyancy)

• wool hairs - (dense) insulation, buoyancy

• vibrissae (whisker)

• spines/quills

evolution of spines is

convergent (rodents and hedgehog, tenrec, echidna) of modified guard hairs

Hair is tied closely to

endothermy - allows mammals to live in cold environments, or deserts (hot in day cold in night), aquatic environments

Hair pigmentation functions

mechanichal function

visual function

Mechanical function of pigment

strength - darker = stronger

reflect heat - light fure

reflect UV

Visual functions of pigment

concealing - matching, counter, or disruptive coloration (breakup outline) ex zebras/hide eyes

conspicuous coloration - aposematic (warning b/w), ocelli (false eyes), weapon automimicry (lines extend antlers), intraspecific communication (white tail deer the tail is warning, age, etc)

Why aren’t mammals green?

Mammals only have pigment for brown/black and yellow/red, most mammals can not see green and brown/orange appears similar to the foilage.

Angora hair growth type

continual growth

Definitive growth type

determinate growth - there is a max where hair will stop and hair has to be replaced with molt

Continual molt

lose and replace as needed

Periodic molt

all hair is replaced all over the body

• ontogenetic/postjuvenile - molting several times from baby to juvenile to adult (color and quality change) not all at once

• seasonal - shed to come in with different quality or color for season (white long fur for winter/short brown for spring)

• annual

Keratinized structures

paws, claws, nails, hooves

hooves

give leverage against the ground for running

True horn is

only in bovidae - boney core covered by a sheath of keratin - unbranched

Pronghorn

branched, sheath, shed and regrow every year

giraffe

boney projection, covered by hair

rhino

horn is hair like fibers, not shed, lots of blood flow