Stuart S. SumidaBiology 342

Phylogeny of Basal Amniota

What we used to think...

Amphibians

PRIMITIVEREPTILES

“Mammal-like Reptiles”

Mammals Birds

Um.........NO.

Amphibians

PRIMITIVEREPTILES

“Mammal-like Reptiles”

Mammals Birds

Panderichthyid Most ReptiliaSarcoptrygians Amphibians Diadectomorpha Synapsida (including Aves)

Panderichthyid Most Synapsida ReptiliaSarcoptrygians Amphibians Diadectomorpha (Mammals) (including Aves)

AMNIOTA (FOR SURE)

Panderichthyid Most Synapsida ReptiliaSarcoptrygians Amphibians Diadectomorpha (Mammals) (including Aves)

AMNIOTA (FOR SURE)

Amniota?

Panderichthyid Most Synapsida ReptiliaSarcoptrygians Amphibians Diadectomorpha (Mammals) (including Aves)

AMNIOTA (FOR SURE)

Amniota?

TETRAPODA

Panderichthyid Most Synapsida ReptiliaSarcoptrygians Amphibians Diadectomorpha (Mammals) (including Aves)

AMNIOTA (FOR SURE)

Amniota?

Other Sarcopterygians

Panderichthyids

Ichthyostegalia

Dissorophoids

Lissamphibia

Anthracosauria

Seymouriamorpha

Diadectomorpha

Amniota

Sarcopterygii

Tetrapoda

The road to reptiles

Advanced Seymouriamorpha Amphibian:Seymouria sanjuanensis – from the Early Permian of Europe and the U.S.

Amniotes: have four embryonic structures that reside outside the embryo to help it survive:

•Amnion•Yolk sac•Chorion•Allantois

Other Sarcopterygians

Panderichthyids

Ichthyostegalia

Dissorophoids

Lissamphibia

Anthracosauria

Seymouriamorpha

Diadectomorpha

Amniota

Sarcopterygii

Tetrapoda

The road to reptiles

Diadectomorpha:•No intertemporal bone like other amniotes•Very terrestrially adapted

Orobates pabsti, a new genus of diadectomorph– found in both North America and central Germany

10 cm

Orobates pabsti, a new genus of diadectomorph– found in both North America and central Germany

1 cm

Orobates pabsti, a new genus of diadectomorph– found in both North America and central Germany

Diadectes – this genus found in Utah, New Mexico, Texas, Oklahoma, and central Germany

“Amphibia” Amniota

Seymouriamorpha Diadectomorpha Synapsida Parareptilia Captorhinidae Diapsida Archosauromorpha

Amniota

Reptilia

Amniotes: have four embryonic structures that reside outside the embryo to help it survive:

•Amnion•Yolk sac•Chorion•Allantois

Remember, we’re studying AMNIOTES.

Defined by:

EMBRYOLOGICAL FEATURES: amnion, chorion, allantois, yolk sac.

ANATOMICAL FEATURES: lack of an intertemporal bone.

ALSO, FUNCTIONAL FEATURES: • Costal breathing (inhaling using movement of the ribs).• Active exhalation using movement of ribs to push air out.

“Amphibia” Amniota

Seymouriamorpha Diadectomorpha Synapsida Parareptilia Captorhinidae Diapsida Archosauromorpha

Amniota

Reptilia

Basal Synapsida (“Pelycosauria”): A single opening on side of skull

“Amphibia” Amniota

Seymouriamorpha Diadectomorpha Synapsida Parareptilia Captorhinidae Diapsida Archosauromorpha

Amniota

Reptilia

PARAREPTILIA Includes:

•Mesosauria•Bolosauridae•Procolophonia•Paraiesauria

Mesosaurus: A member of Mesosauria

Eudibamus cursoris (a bolosaur)The earliest known bipedal vertebrateFrom the Early Permian (~280 million years old) of central Germany.

Bradysaurus: A member of the Parieasauria

Parieasaurs have lumpy, bumpy skulls

Scutosaurus

“Amphibia” Amniota

Seymouriamorpha Diadectomorpha Synapsida Parareptilia Captorhinidae Diapsida Archosauromorpha

Amniota

Reptilia

Basal Captorhinid: Eocaptorhinus

1 cm

New taxon: (Albright, in prep) New, miniature, captorhinid with three rows of dentary and maxillary teeth.

1 cm

New taxon

Size Range in Captorhinid Reptiles

(All specimens collected by Everett C. Olson.)

1 cm

“Amphibia” Amniota

Seymouriamorpha Diadectomorpha Synapsida Parareptilia Captorhinidae Diapsida Archosauromorpha

Amniota

Reptilia

Basal Diapsid: Petrolacosaurus

Note: TWO holes (fenestrae) on side of skull

Known back to Late Pennsylvanian

Diapsida includes:•Many extinct forms•Squamata•Archosauromorpha

Squamata includes living lizards and snakes.