Introduction to the Vertebrata

And their relatives

1. Animals with a hollow dorsal nerve cord, notochord, and pharyngeal gill slits. 2. Brain encapsulated, or at least partially so, by a cartilaginous or bony cranium. Vertebrae, associated with or replace notochord. First duplication of genome (1R).3. Loss of vertebrae.4. Mineralized bone. Second duplication of the genome (2R).5. Head shield of dermal bone; bony scales.6. Paired spines or fins.7. Neurocranium encloses brain dorsally.8. Mouth formed by articulated jaws.9. Teeth erupt from dental lamina.10. Paired fin radials barely extend beyond body.11. Gills covered by an operculum.12. Pectoral and pelvic girdles anchored to vertebral column.13. Digits reduced to 5 or fewer; radius as long as the ulna. Operculum lost.14. Premaxilla less than 2/3 skull width.15. Egg with an outer amnion membrane.16. One temporal fenestra formed by the squamosal and jugal bones.17. Large post-temporal fenestra; suborbital foramen in palate.18. Two temporal fenestrae; upper one formed by the squamosal and postorbital bones.19. Trunk ribs single-headed, end of humerus robust.

General Animal Life Cycle

Vertebrate Development

Defining VertebratesThey posses the following characters at some point in their lives:• Pharyngial gill slits• Notochord• Hollow dorsal nerve cord• Vertebrae

Distribution of living groups of vertebrates

Myxinomorphithe hagfish

A cladogram based on Benton (2005), shows the agnathan taxa as a paraphyletic group. Myllokunmingida and Mixini, considered classes here, are sisters within a clade, the Myxinomorphi, that is sister to the Petromyzontomorphi (lampreys). Together, the lampreys and hagfishes form the Cyclostomata. Myllokunmingiida is in red because it has no extant members.

Hagfish

• The minimal vertebrate• Hagfish, cyclostomes without vertebrae

Hagfish Pacific hagfish feeding

Petromyzontomorphithe lampreys

A cladogram that illustrates the position of the two classes of the Petromyzontomorphi in the jawless fishes is based primarily on Benton (2005). However, Petromyzontida (the lampreys) are presented as sisters to the Euphaneropsids as proposed by Janvier (2008a). Here, they are shown as a sister group to the hagfish and basal within the Vertebrata in a clade called Cyclostomata (the round mouths). Euphaneropsida is in red because it has no living members.

Lampreys

ChondrichthyesSharks, Skates, Rays, & Chimeras

A cladogram of the gnathostome fishes according to Benton (2005). The two major clades of the Chondrichthyes: Euchondrocephali and Elasmobranchii both have extant taxa.

1) Jaws fused to cranium; 2) jaws not fused; 3) multiple, separate gill slits; 4) no anal fin

Chimeras

RatfishSpotted ratfish

ElasmobranchsSharks, Skates, & Rays

Great White Shark

Basking Shark

Eagle Ray

Spiny Dogfish Shark

Cladoselache

Osteichthyesthe bony fishes

A cladogram that illustrates the relative position of the Osteichthyes (Actinopterygii + Sarcopterygii) in the gnathostome fishes. 1. ray-finned fishes; 2. basal ray-fins; 3-4. remnants

of earlier radiations; 5. teleosts; 10. lobe-fins + tetrapods

Bony Fishesremnants of early radiations

BowfinLong-nosed Gar

Volga Sturgeon

Bichir

Bony Fishesremnants of early teleost groups

Arapaima Common Carp

Blue Catfish

Bony Fishteleosts

Atlantic Cod

Rainbow Trout

Basal teleosts, note separation of pectoral and pelvic fins

Cods are among the most primitive of the spiny-rayed fish, note that the pelvic fins have moved far forward

Bony Fisheshigher teleosts

Guppies

SargassumSeahorse

Long-ear Sunfish

African Jewel Cichlid

Mola

Blue-fin Tuna

Lobe-fin Fishes

AfricanLungfish

Australian Lungfish

Coelocanth

Batrachomorphathe amphibians

Frogs, Toads, & SalamandersStrawberry PoisonDart Frog Hellbender

African clawed frog

Axolotl

Mammaliaanimals with hair

• Hair• Single tooth-bearing

lower jaw bone• Teeth replaced one

time• Mammary glands• Teeth with

differentiation

Dimetrodon

Non-placental mammals

Platypus

Virginia Possum

Kangaroo

Placental mammals I

Tenrec

African elephant

Nine-banded armadillo

Three-toed sloth

Placental mammals II

Golden-crowned fruit bat

Mole

Przewalski’s horse

Least weasel

White-tailed deer

Blue whale

Placental mammals III

Aye-aye

Snow monkeys

Capybara

Cottontail rabbit

Anapsidaturtles

Scutosaurus

Turtles

Malamata

Sea turtle

Softshell turtle

Aldabra tortoise

Lepidosauromorphalizards & snakes

Plesiosaur

Diapsid skull

Lizards & Snakes

Iberian worm lizard

Glass lizard

Blue-tongued skink

Leopard gecko

Green tree iguana

Indian python

Spectacled cobra

LepidosauromorphaCrocs, Birds, & Dinosaurs

Archaeopteryx

Crocodilians

American alligator

Euparkeria, a stem archosaur from the mid-Triassic

Dinosaurs

Deinonichus, TheropodDiplodocus, Sauropod

Triceratops, CeratopsianCamptosaurus, Hadrosaur

Birds

• Basal clades (12 & 14)

• Waterbird assemblage (15)

• Owl-Cuckoo assemblage (16)

• Perching birds (17), including the songbirds (18)

Basal Clades

Turkey

Ostrich

Wood Duck

Waterbird Assemblage

Whooping Crane

Peregrine Falcon

Owl-Cuckoo Assemblage

Barn Owl

Cockatiel

Perching Bird AssemblagePileated Woodpecker

Scissor-tailed Flycatcher

Rook

Raggiana Bird-of-Paradise

House SparrowBlack-capped Chickadee

Barn Swallow

Galapagos Finch

Vertebrates

• OVER CLASSIFIED…

• Why?

Vertebrates

• OVER CLASSIFIED– Degree of difference between orders of birds

DOES NOT APPROACH that observed between orders of insects!!!

Vertebrates comprise a group within Chordates

– Hollow dorsal nerve cord– Notochord– Pharyngeal Gill Slits

• Other Chordates:– Cephalochordates

– Tunicates

Evo-Devo• Literally means evolution by means of changes

in development• Discovery of HOX genes in the 1980s• These are genes that regulate the on-off

switch for genes in development and determine timing

• Arranged in linear arrays that correspond to anterior-posterior axis

Major Events in the Evolution of the Vertebrates

• The evolution of jaws

Entelognathus (419 MYA), Zhu et al. 2013. Nature. 502:188-193. Earliest known fish with jaws. These were more similar to jaws of bony fishes that sharks

Major Events in the Evolution of the Vertebrates

• The evolution of a weight-bearing appendicular skeleton

Tiktaalik

Acanthostega

Major Events in the Evolution of the Vertebrates

• The evolution of the amniotic egg • This would be the point of transition between

amphibians and reptilesMoschops

Seymouria

Major Events in the Evolution of the Vertebrates

Archaeopteryx

Major Events in the Evolution of the Vertebrates