Archosauria

Crown-clade Archosauria

OrnithodiraCrurotarsi

Ornithosuchidae

Pterosauria Dinosauria

“Rauisuchia”Crocodylomorpha

Basal archosaurs

Basal archosaur?Maybe... or it split off before archosauria

TanystropheusProlacertiform

Archosauria

prolacertiform?

Archosauromorpha

Archosauria: synapomorphies

Antorbital fenestra (in front of eye)Teeth with serrated marginsMandibular fenestra

ProterosuchusBasal Archosaur

Euparkeria (Facultative biped)Derived, Basal ArchosaurBony dermal plates down back

Faculatative biped vs. Obligate biped

Stances: sprawling <=> semi-erect <=> erect

aquatic <=> terrestrial

Rauisuchians-Pillar-Erect Posture

Locomotion(Pelvis)

Buttress-ErectOrnithodiransMammals

Archosauria

Crown-clade Archosauria

OrnithodiraCrurotarsi

Ornithosuchidae“Rauisuchia”Crocodylomorpha

Basal archosaurs

Pillar-ErectButtress-Erect

Buttress-Erect

Locomotion: Pelvic/Hind leg conditions:

Digitigradevs.Plantigrade

Barrel-like articulationConstrained ‘twisting’ motion to the plane parallel with its body

astragalus calcaneum

PM: Primitive Metatarsal

CN: Crocodyle NormalCrocodylomorphs/Rauisuchians

CR: Crocodyle ReversedOrnithosuchids

AM: Advanced MesotarsalPterosaurs, Dinosaurs

Hinge

Hinge

Rotation Rotation

Proterosuchus

The importance of a twisting ankle for animals with sprawling-erect posture

The importance of a twisting ankle for animals with sprawling-erect posture

Archosauria

Crown-clade Archosauria

OrnithodiraCrurotarsi

Ornithosuchidae“Rauisuchia”Crocodylomorpha

Basal archosaurs

Pillar-ErectRotation

Buttress-erect*Rotation

Buttress-erectRotation

Buttress-erectHinge

Sprawling/Semi-erectHinge

buttress-erect = parasagittal

CrocodylomorphaLate TriassicTerrestrisuchusSaltoposuchus

BIPEDAL!/TERRESTRIAL!

Saltoposuchus

Terrestrisuchus

Buttress-erect*Rotation

A return to aquatic environments was more recent for crocodylomorphs

Ornithodira

DinosauriaPterosauria(later)

Saurischia Ornithischia

Dinosaur expansion: multiple models

Competitive Replacement Scenario (Gradual)

Opportunistic Scenario (Abrupt)

DINOSAURS

Dinosaur synapomorphiesA) Crest on humerusB) Shelf on top surface of iliumC) Perforated acetabulumD) Tibia w/ expanded endE) Ascending astragular process on front surface of tibia

(parasagittal stance)

DINOSAURS

Herrerosaurus

Lagosuchus

Heterodontosaurus

Eoraptor

Herrerosaurus

Pisanosaurus

Basal Dinosaurs

Coelophysis

Ornithischians!

‘Cheeky’ saurs

Lesothosaurus

Heterodontosaurus

Shared, derived traits of skull

PredentaryLow jaw jointPalpebral bone: EAGLE EYE!Deep set cheek teeth

Head Tail

Hip shared, derived, trait

‘Opisthopubic pelvis’

Basal Ornithodiran condition

Heterodontosaurus

Shared, derived traits of skull

PredentaryLow jaw jointPalpebral bone: EAGLE EYE!Deep set cheek teeth

Head Tail

Hip shared, derived, trait

‘Opisthopubic pelvis’

Basal Ornithodiran condition

Other shared, derived traits

At least 5 sacral vertebraeOssified tendons above sacral regionFrontal process on illium

Lesothosaurus

How do mammals chew?Front: CroppingDiastem: Manipulation by tongueCheek teeth: Grinding (occluding)Coronoid Process ~ Muscle attachmentsInset molars for cheeks ~ keep food in mouth

How do mammals chew?Front: CroppingDiastem: Manipulation by tongueCheek teeth: Grinding (occluding)Coronoid Process ~ Muscle attachmentsInset molars for cheeks ~ keep food in mouth

How did Ornithischians chew? In very similar waysFront: Cropping: carried out by keratin RAMPHOTHECADiastem: Manipulation by tongueCheek teeth: Grinding! Dental BatteriesCoronoid Process ~ Different shape, different muscle attachmentsInset molars for cheeks ~ keep food in mouth

EdmontosaurusOrnithopod

How did Ornithischians chew? The Angle of the jaw. Scissors vs. Pliers

Traveling forceSmall area, large force

Broadly distributed force

Large area, less force

Basal Ornithischians

Pisanosaurus Lesothosaurus

Everything else in Ornithischiais in Genasauria Chewing

‘Cheeky’ saurs

Lesothosaurus

Heterodontosauridae

Heterodontosaurids: Not Primitive... unique chewing.

Three kinds of teethAnterior: Snipping/CroppingPosterior: ChewingTusks: Potentially display/courtship

Heterodontosaurids: Not Primitive... unique chewing.

Three kinds of teethAnterior: Snipping/CroppingPosterior: ChewingTusks: Potentially display/courtship

Chevrotain