Origin of Dinosaurs

How Diversity is studied

Phylogenetics

Hypthesizing Relationships

A (vague) evolutionary tree

Something more precise

Cladogram

A cladogram for dinosaurs and relatives

A cladogram for advanced theropod dinosaurs

Cladogram for group of North American stream fishes

SMN’s ground-breaking work on African anabantid fishes

Supraorbital pores of the cephalic lateralis

Deep time – dinosaur ancestors

Tetrapods are terrestrial adapted vertebrates – they have legs with feet

First dinosaurs First tetrapods

Tetrapods come out of the fish world † Eusthenopteron

Modifications of skull Tetrapoda Neotetrapoda “Fishes” Temnospondyli Lissamphibia Actinistia (coelacanth) Dipneusti (lungfish) Amniota (see Fig. 26.2) Anura Gymnophiona Urodela Diverse tetrapod groups† *Diverse Devonian groups† Ichthyostegans† Diverse temnospondyl groups† Characteristics of jaw, skull Modifications of skull bones (tentative) Three-lobed tail; ossified swim bladder; double jaw articulation Tetrapods

† Panderichthys

Tetrapod Origins Ray Troll

Towards terrestrial tetrapods aquatic Semi-terrestrial

Early tetrapod (fish-like) Later tetrapod (more terrestrial)

† Acanthostega Early tetrapod trackway

aquatic Semi-terrestrial Eusthenopteron

aquatic Semi-terrestrial Panderichthys

aquatic Semi-terrestrial Tiktaalik

aquatic Semi-terrestrial Acanthostega

aquatic Semi-terrestrial Ichthyostega

“Fishes” (more or less) Pederpes Not a fish Ichthyostega Acanthostega “Fishes” (more or less) Tiktaalik Panderichthys Eusthenopteron

Nelson (2006): Tetrapods are a “divergent sideline within the fishes that ascends onto land and into the air and secondarily returns to water.”

Early terrestrial tetrapods

Very rich Paleozoic diversity of these creatures

Carboniferous Era Great time to be an early terrestrial tetrapod

Carboniferous 360-300 mya

Very rich Paleozoic diversity of these creatures CENOZOIC MESOZOIC PALEOZOIC Carboniferous Devonian Coelacanth 395 252 66 Geologic time (MY ago) Permian Caecilians Salamanders Lissamphibians Anthracosauria Lepospondyli Ichthyostega Dipneusti Sarcopterygian ancestor Frogs and toads Diverse temnospondyl groups (includes Eusthenopteron, Tiktaalik, and Acanthostega) Diverse Devonian groups Amniota Amniotes

Reptiles / Mammals Amphibians Most gone – Two groups survived Amniotes Frogs and toads Anthracosauria Lepospondyli Amniota Amphibians Salamanders Ichthyostega Lissamphibians Caecilians Dipneusti Diverse temnospondyl groups (includes Eusthenopteron, Tiktaalik, and Acanthostega) Diverse Devonian groups Sarcopterygian ancestor Coelacanth Devonian Carboniferous Permian PALEOZOIC MESOZOIC CENOZOIC 395 252 66 Geologic time (MY ago)

Very rich Paleozoic diversity of these creatures CENOZOIC MESOZOIC PALEOZOIC Carboniferous Devonian Coelacanth 395 252 66 Geologic time (MY ago) Permian Caecilians Salamanders Lissamphibians Anthracosauria Lepospondyli Ichthyostega Dipneusti Sarcopterygian ancestor Frogs and toads Diverse temnospondyl groups (includes Eusthenopteron, Tiktaalik, and Acanthostega) Diverse Devonian groups Amniota Amniotes

on our way to amphibians

Class Amphibia

Very rich Paleozoic diversity of these creatures CENOZOIC MESOZOIC PALEOZOIC Carboniferous Devonian Coelacanth 395 252 66 Geologic time (MY ago) Permian Caecilians Salamanders Lissamphibians Anthracosauria Lepospondyli Ichthyostega Dipneusti Sarcopterygian ancestor Frogs and toads Diverse temnospondyl groups (includes Eusthenopteron, Tiktaalik, and Acanthostega) Diverse Devonian groups Amniota Amniotes

On our way to mammals / reptiles

Amniotes Reptiles Mammals Other

Reptiles / Mammals Amphibians Most gone – Two groups survived Amniotes CENOZOIC MESOZOIC PALEOZOIC Carboniferous Devonian Coelacanth 395 252 66 Geologic time (MY ago) Permian Caecilians Salamanders Lissamphibians Anthracosauria Lepospondyli Ichthyostega Dipneusti Sarcopterygian ancestor Frogs and toads Diverse temnospondyl groups (includes Eusthenopteron, Tiktaalik, and Acanthostega) Diverse Devonian groups Amniota Amniotes Reptiles / Mammals Amphibians

Carboniferous 360-300 mya

Before we get to the Mesozoic, we have to survive the Permian Carboniferous

Permian – it all almost ends

Permian – cooler and drier

A new, drier, world favors a new type of tetrapod Amniotes

Amniotes Amniotes CENOZOIC MESOZOIC PALEOZOIC Carboniferous Devonian Coelacanth 395 252 66 Geologic time (MY ago) Permian Caecilians Salamanders Lissamphibians Anthracosauria Lepospondyli Ichthyostega Dipneusti Sarcopterygian ancestor Frogs and toads Diverse temnospondyl groups (includes Eusthenopteron, Tiktaalik, and Acanthostega) Diverse Devonian groups Amniota Amniotes Amniotes

Amniota

Amnoita (living)

Deriving Amniotes

Carboniferous terrestrial habitats

Permian – cooler and drier

Post-Paleozoic is the age of amniotes

The Mesozoic was really cool

AGE OF AMNIOTES

Adapting to the new conditions

Moving away from water

Amnoites Amniotes CENOZOIC MESOZOIC PALEOZOIC Carboniferous Devonian Coelacanth 395 252 66 Geologic time (MY ago) Permian Caecilians Salamanders Lissamphibians Anthracosauria Lepospondyli Ichthyostega Dipneusti Sarcopterygian ancestor Frogs and toads Diverse temnospondyl groups (includes Eusthenopteron, Tiktaalik, and Acanthostega) Diverse Devonian groups Amniota Amniotes Amnoites

Amniota What’s going on at the beginning?

Amniotic Egg

Amniotic Egg 65

Fish Amphibian Amniote

Internal Fertilization

No more gill breathing – even in larvae amphibian larvae

Body covering Dry and dead

Respiration

Anamniotes – Positive Pressure Breathing

Amniotes – negative pressure breathing

Patterns in Skull Evolution

Pre-Amniote Diadectes

Pre-Amniote

Skulls Anapsid Pre-Amniote Synapsid Diapsid

anapsid skull and jaw muscles pre-amniote

anapsid skull and jaw muscles pre-amniote

foramen pre-amniote amniote

Skulls Anapsid Synapsid Diapsid

foramen present No foramen

Anapsid Synapsid Diapsid

Reptiles, birds, dinosaurs, etc. Mammals and ancestors Amniote ancestor Anapsid Diapsid Synapsid Reptiles, birds, dinosaurs, etc. Mammals and ancestors

Anapsid anamniotes, stem amniotes

Synapsid

Synapsid Dimetrodon

Synapsid Modern mammal

Synapsid fenestra joined with orbit Modern mammal orbit

Diapsid

Diapsid orbit orbit

Diapsid tuatara orbit

Diapsid Modern Lizard

Diapsid Modern snake

Diapsid Modern bird orbit

Diapsid orbit Mesozoic reptiles orbit

Turtles

Turtles are diapsids with a (secondarily acquired) anapsid skull

Fenestration

Clear proof of diapsids on Mars NASA Photos (Science Education is important)

Jaw rearrangements Fig. 26.11

The big split anapsid anamniote diapsid synapsid

The big split

The big split

Synapsid lineage

Diapsid radiation

The big split

Synapsids – only mammals remain All this is extinct

Diapsids – many fossil groups, but many groups remain

Some interesting parallels in evolution

Endothermy warm-bloodedness Living Amniotes Diapsid Synapsid

Endothermy warm-bloodedness Diapsids Synapsids

Both groups Greater Mobility

Greater Mobility Higher metabolism More heat generation better respiration better circulation waste heat elimination heat conservation / utilization diet / digestion

What do we do with the heat?

Diet

Respiration ancestor towards mammals towards birds

Circulation

Some interesting parallels in evolution

Reptiles and Diapsids