L20 - Modern Birds: Origins, Diversification, and Specializations

naming birds - four nodes

• Avialae

• Ornithurae

• pygostylia

• Aves

naming birds - Avialae

birds in the broad sense

• Archaeoptergy, living birds, and everything in between; memebership shifts when the tree starts

naming birds - pygostylia

congucisornis + crown birds + all descendants

• name for pygostyle; node based

naming birds - ornithurae

Hesperonis + icthryonis + crown birds; node based

naming birds - Aves

Neornithes (crown birds)

• last common ancestor of all living birds + all descendants

Confuciusornis =

the best known mesozoic bird

Confuciusornis - huge sample

one surgery collect 603 specimens

Confuciusornis - a beak but

not a modern beak

• toothless keratin beak that evolved independently of the crown-bird beak y

Confuciusornis - short tail

an early pygostylian

Confuciusornis - males with streamers?

medullary bone shows that individuals without long tail streamers include egg-laying females

Confuciusornis - fast growth

adult size within a year, unlike enantiornithines

Jeholornis

long bony tail fo 20-24 vertebrae with a feather fan

• seed-eater

Sapeornis

rod-like pygostyle

• only a few teeth, at the front of the upper jaw

Zhongjianornis

fully toothless

• first placed near the base of Avialae; later moved crown ward

Enantiornithes =

opposite birds

Enantiornithes - cretaceous lineages

• most abundant and diverse

• revered joint

• alula

• slow growth

• navaornis

Enantiornithes - reversed joint

scapula-coracoid articulation opposite to ours

Enantiornithes - slow growth

precocial hatchlings; most took several years to mature

Enantiornithes - navaornis

toothless, with a crown-like skull

Ornithuromorpha leads to

living birds

Ornithuromorpha - cretaceous lineages

• early waders

• swimmers

• fish-eaters

• divers

• fast growth

two cretaceous lineages - split early

diverged before 131 ma and coexisted for 65 myr

mosaic heads - ichthyornis

teeth plus a small beak at the jaw tips; a modern brain and mobile palate; and old-fashioned temple region

mosaic heads - Janavis

toothed, yet its palate bone matches chickens and ducks

mosaic heads - overturned

the ostrich-type palate of palaeognaths is derived, not primitive

mosaic heads - lesson

the bird skull modernized piece by piece, like the body

teeth were lost

repeatedly, not progressively

at least five toothless lineages

• Confuciusornithids

• Some enantiornithines (e.g., Navaornis)

• Two separate ornithuromorph lineages

• Crown birds

teeth lost - no trend

toothless and toothed birds both coexisted for 60 myr

teeth lost - survivor effects

all crown birds lack teeth because a toothless lineage happened to survive the K-pg

teeth lost - one loss in the crown line

but when? gene evidence: 116 ma; fossil-based tree: 90 ma

the K-pg bottleneck - only

crown birds survived

the K-pg bottleneck - total loss

outside the crown

• enantiornithines and toothed ornithurines vanished at 66 Ma

the K-pg bottleneck - asteroid impact killed the

forests

• dust, soot and sulfate from the Chicxlub impact blocked sunlight; ground-dwelling birds survived; tree-dwellers re-evolved as forests regrew

inherited from earlier ancestors - Archosaurs

one-way airflow in the lungs

inherited from earlier ancestors - theropods

hollow bones, furcula

inherited from earlier ancestors - maniraptorans

folding wrists, enlarged forebrain

inherited from earlier ancestors - pennaraptorans

vaned feathers, brooding, colored eggs

inherited from earlier ancestors - avialans and beyond

flapping flight, pygostyle, keel

new characteristics in crown birds

• toothless beak (in every species)

• syrinx

• adult size in <1 year

• highest metabolism rates among vertebrates

syrinx

a new vocal organ

a bird is a nested set of

dinosaur clades and their characters; few traits are unique to the crown

where “bird” traits first appear - ornithodira

upright two-legged gait, hinge ankle

where “bird” traits first appear - theropods

hollow bones, furcula, three-toed foot

where “bird” traits first appear - tetaurae

three-fingered hand

where “bird” traits first appear - coelurosaurian

filament feathers

where “bird” traits first appear - maniraptora

folding wrist, enlarged forebrain

where “bird” traits first appear - pennaraptora

vaned feathers, brooding, colored eggs

where “bird” traits first appear - avialae

flapping flight, tertials

where “bird” traits first appear - pygostylia

pygostyle

where “bird” traits first appear - ornithuromorpha

full keel, fast growth

where “bird” traits first appear - ornithurae

beak tip, mobile palate

where “bird” traits first appear - nzorithes

toothless beak, syrinx

where “bird” traits first appear - neoakves

phallus lost

crown birds before the asteroid - vegavis

near complete skull: toothless pointed beak, large brain

• a crown duck relative; foot-propelled diver

crown birds before the asteroid - asterionis

“winder chicken”: near or within the chicken-duck clade

• lived alongside toothed Janavis

How old are crown birds? near the K-Pg (majority)

• genomes - nerves splits predate 66 ma

• 9,072 species tree - rapid radiation from 70.6 ma

• fossils - a tree-dwelling mousebird relative and a flightless penguin by 62 ma

How old are crown birds? late cretaceous (minority)

• basal neoakves split

• 15 orders before the k-pg

• linked to the rise of flowering plants

How old are crown birds? calibration, not data

the oldest age for fossil calibration drives the result

the first genome-scale bird tree

• 48 genomes

• 41.8 million aligned base pairs

• >400 years of single-processor computing

• 0 gene trees matched the species tree

the first genome-scale bird tree - resolves

core landlords and waterbirds, at full support

• explosive radiation

the first genome-scale bird tree - gene-tree conflict

short deep branches show incomplete lineage sorting

the first genome-scale bird tree - coding gene mislead

they grouped birds by liftstyle; noncoding DNA tracked ancestry better

the first genome-scale bird tree - data scale

rapid rapidations need whole genomes, not a few genes

the first genome-scale bird tree - convergence

vocal learning and raptor habits evolved more than once

Palaeognathae =

ostrich, kiwi, tinamous

Galloanserae =

chickens and ducks

Mirandornithes =

flamingos and grebes

Columbaves =

pigeons, cuckoos, bustards

Elementaves

waterbirds, shorebirds, hummingbirds

Afroaves =

hawks, owls, kingfishers

Australaves =

falcons, parrots, songbirds

the current tree of living birds is

still open

palaeognaths - ratites are not

a clade

palaeognaths - nested fliers

flying tinamous are closet to the extinct Mao

palaeognaths - odd pairs

Madagascar’s elephants birds closest to New Zealand’s kiwi

palaeognaths - flight lost

3-6 times; mostly by convergent changes in gene regulation

palaeognaths - dispersal, not drift

flying ancestors spread out’ the continental-breakup story is outdated

flacons are not

hawks

raptors are

polyphyletic

• hooked beaks and talons evolved separately in falcons and in hawks and owls

the core-land bird ancestor may have been a

predator; the habit was then lost repeatedly

similar ecology is a poor guide to

ancestry

flaconiformes old grouping

hawks, eagles, falcons, new world vultures

flaconiformes current placement

falcons only, beside parrots and songbirds

• hawks and eagles = accipitriformes

Ciconiiformes out grouping

storks, herons, flamingos

Ciconiiformes current placement

storks only

• herons join pelicans

• flamingos pair with grebes Pelecaniformes

Pelecaniformes out grouping

pelicans, cormorants, gannets

Pelecaniformes new grouping

pelicans, herons, ibises

• cormorants and gannets in their own order

Gruiformes old grouping

cranes, rails, seriemans, bistards

Gruiformes surrent placement

cranes and rials

• seriemas near falcons; bustards near cuckoos

Apodiformes old grouping

swifts, hummingbirds

• still together

the old orders grouped birds by

shared lifestyle, which genomes shoe evolved repeatedly

passerines

a young radiation from australisa

• young, two big branches, 60% of living birds species

Paleocene birds - giants

• Gastornis

• Waimanu

• Tsidiiyazhi

• terror birds

• Kumimanu fordycei

• Pelagornis sandersi

how many bird species?

it depends on the list

• 11,131 species, 252

where the species are (bird families)

1. tyrant flycatchers = 441

2. tanagers = 384

3. hummingbirds = 363

4. pigeons and doves = 353

5. old world flycatchers = 345

where the species are (bird families) - what it shows

• the top three families are mainly central and South American

  • passerines dominate (3/5 top)

birds in trouble

• 12.8% species threatened

• 61% of species declining

• >187 species extinct since 1500

• 50 billion alive

birds in trouble groups

islands, albatrosses and cranes, and flightless birds

bird skeleton

fused, rigid frame: keel, furcula, synsacrum, pygostyle, and and ankle fusions