Last day… working our way through the phylum Chordata

Class Crocodilia - Crocodilians Part of group known as archosaurs, early crocodilians were small & terrestrial - Cretaceous crocs up to 12 m, modern spp m - 23 species in tropical & warm regions - top predators, but also good parents Nile CrocodileSiamese Crocodile

Class Aves - Birds Another group of archosaurs, closest living relative of dinosaurs - thought by most to be descended from theropod dinosaurs (though some skeptics remain...) Archaeopteryx from Jurassic (about 150 MYA) - has feathers (defining feature of birds), but also teeth, many tail tail vertebrae, etc.

Recently, fossil of Anchiornis described, older than Archaeopteryx (155 MYA), assigned to Troodontidae - feathers of 2 nd specimen allowed determination of color patterns

Currently, most diverse terrestrial vertebrates (about 10,000 spp.) - found virtually anywhere on planet Often abundant & conspicuous (because diurnal, use use vocal & visual signals) Rainbow Lorikeet Emperor Penguin Ostrich

Brown-backed Needletail Peregrine Falcon Success of birds probably largely due to superior flight abilities: Peregrine Falcon over 200 kph in dives, some birds in level flight 60+ kph? Flight allows safety from terrestrial predators, fast & efficient transport, ability to use scattered resources (short-term or seasonally)

Many features of birds related to flight: lightweight flexible feathers w. interlocking flat vanes & hollow quill - bipedalism, large flight muscles, wings acting as effective airfoils & propellers, hollow bones & air sacs (a) wing (b) Bone structure Finger 1 (c) Feather structure Shaft Barb Barbule Hook Vane Shaft Forearm Wrist Palm Finger 3 Finger 2

Other avian features also related to flight: lack of teeth, possession of gizzard (muscular grinding stomach), excellent vision, small size

Why birds are better than mammals... Higher metabolism - maintain body temperatures around 40º C - enables greater speed & power, faster nerve transmission, activity at cold temperatures More efficient respiration - lungs with one-way flow, maximizes O 2 exchange

Live longer than most mammals of same size Birds are even smarter than (non-human) mammals (arguably...) New Caledonian CrowAfrican Grey Parrot (Alex)

Synapsids Ancestral amniote Reptiles Diapsids Archosaurs Saurischians Lepidosaurs Dinosaurs Parareptiles Turtles Crocodilians Pterosaurs Ornithischian dinosaurs Saurischian dinosaurs other than birds Birds Plesiosaurs Ichthyosaurs Tuatara Squamates Mammals Next groups on another major branch: Lepidosaurs

Class Rhynchocephalia - Tuataras Common Tuatara Only 2 surviving species of group common in Mesozoic, found in New Zealand (now basically on offshore islands - due to introduced rats) - resemble lizards, but many unspecialized anatomical traits (diapsid skull, gastralia, parietal eye)

Class Squamata – Lizards & Snakes Squamates are quite diverse & numerous – almost 5,100 lizard spp. and 3,150 snakes - most numerous in tropical & warm temperate areas Lizards are not monophyletic if snakes excluded - snakes evolved from lizards related to monitor lizards Gila Monster Coral Snake

Most lizards small (to 16 mm), though Komodo Dragon to 3 m - small species insectivorous, large spp. often herbivores Jaragua Sphaero Green Iguana Usambara Three- horned Chameleon Chameleons highly specialized w. prehensile tail, long sticky tongue, independently swivelling eyes, etc.

Snakes range from tiny (10 cm) burrowers to constrictors near 10m - all? carnivorous, but ‘only’ 500 venomous? Reticulated Python (& minor celebrities) Common Egg-eating Snake - flexible connections in skull & mandibles important for swallowing large diameter prey

Grass Snake Snakes and some lizards sample odors w. tongue, then contact paired vomeronasal organs in roof of mouth - may detect odor gradient?

Synapsids Ancestral amniote Reptiles Diapsids Archosaurs Saurischians Lepidosaurs Dinosaurs Parareptiles Turtles Crocodilians Pterosaurs Ornithischian dinosaurs Saurischian dinosaurs other than birds Birds Plesiosaurs Ichthyosaurs Tuatara Squamates Mammals Final group - a little familiar...

Class Mammalia - the Mammals A moderately diverse & successful group – about 5400 spp. - average larger than most vertebrates, but ~2300 rodents & 1100 bats, so most quite small Little Brown BatNorthern Red-backed Vole Humpback Whale

Lineage leading to mammals - the Synapsida - branched off from other amniotes early, but not considered mammals yet Dimetrodon, a synapsid Dicynodon, a therapsid - later stages included the therapsids before ‘true’ mammals evolved in the Triassic or Jurassic

Mammalian characters include hair (may be sparse!), mammary glands for nursing young, endothermy, four-chambered heart & muscular diaphragm - varied dentition is important in feeding & ecological specialization Manatee

Mammalian jaw evolution – Biarmosuchus is early synapsid, has jaw joint between quadrate & articular ‘True’ mammals have those bones evolve into incus & malleus of middle ear

Monotremes Monotremes - the platypus & 4 spp. of echidnas - only living mammals that lay eggs Reptile-like egg contains enough yolk to nourish the developing embryo. Platypus Short- beaked Echidna Monotremes have hair, & females produce milk in specialized glands After hatching, baby sucks milk from mother’s fur because she lacks nipples

Marsupials Marsupials include opossums, kangaroos, bandicoots, koalas, etc. Unlike monotremes, marsupials have higher metabolic rate, nipples for milk, & live young. Koala (or 2) Marsupials born very early in development &, in most spp., complete development while nursing in maternal pouch, the marsupium Marsupials existed worldwide in Mesozoic but now are restricted to Australia & the Americas

Newborn kangaroo in marsupium

Marsupial mammals Eutherian mammals Plantigale Marsupial mole Sugar glider Wombat Tasmanian devil Kangaroo Deer mouse Mole Woodchuck Flying squirrel Wolverine Patagonian cavy Convergent evolution between marsupial and eutherian mammals

Eutherian Mammals Compared to marsupials, eutherian mammals have longer gestation period (pregnancy) Young eutherians complete embryonic development in uterus, joined to mother by placenta Cougar Eutherians often called ‘placental mammals’ - placentas more complex than marsupials, provide more intimate, long-lasting association between mother & young

A Phylogenetic Tree for Mammals

One group (Afrotheria) diverged in Africa while isolated African Elephant Rock HyraxWest Indian Manatee Cape Golden MoleAardvarkBlack-and-rufous Elephant Shrew

Xenarthra are restricted to the Americas Brown-throated Three-toed Sloth Giant Anteater Nine-banded Armadillo

Another group (Laurasiatheria) evolved on the northern landmass about 95 MYA Plains ZebraKiller Whale Gray-headed Flying Fox Ground PangolinPolar BearStar-nosed Mole

Final group (Euarchontoglires) evolved in Laurasia too Terrestrial Large Tree Shrew Black-tailed Jackrabbit a colugo (or 2)Homo sapiens Norway Rat