Lecture 6 - Skull diversity - vertpaleo.earth.indiana.edu

Indiana University | Earth and Atmospheric Sciences

© 2020 P. David Polly (or as otherwise noted)

E412/G512 Vertebrate Paleontology

Lecture 6 - Skull diversity




Exploded mammalian skull

Kardong, 1995, Vertebrates




Canis lupus (Grey wolf), TMM M-1709, from DigiMorph. CT scan by Pamela Owenhttp://www.digimorph.org/specimens/Canis_lupus_lycaon/




Coronal slices

Canis lupus (Grey wolf), TMM M-1709, from DigiMorph. CT scan by Pamela Owenhttp://www.digimorph.org/specimens/Canis_lupus_lycaon/




Grey fox skull

Evans, 1993, Anatomy of the Dog

Urocyon cinereoargenteus (photo by PD Polly)




Vertebrate phylogeny

Dinosauria

Bird

s

Icthyosaurs &

Plesiosaurs

Crurotarsi

Cro

codi

lia

Pter

osau

rs

Snak

es

Mam

mal

ia

SquamataChelonia

Archosauria

DiapsidaReptilia

Amniota

Tetrapoda

TemnospondylsTiktaalik

Placoderms

SynapsidaLissamphibia

Lung

fish

&C

oelo

cant

h

Hag

fish

ActinopterygiaChondricthyes

SarcopterygiaOsteicthyes

Gnathostomata

Vertebrata

“Agnatha”

Images from PhyloPic




TuataraSphenodon punctatus

YPM 9194, DigiMorpho CT scan rendering

Living diapsid (close relative of squamates) from New Zealand




A few hints…

tooth bearing bones• maxilla• premaxilla• vomer• palatine• pterygoid• dentary

jaw joint• quadrate (upper)• articular (lower)

except in mammals• squamosal (upper)• dentary (lower




supratemporal fenestra

infratemporal fenestra

nariz

orbit (with sclerotic ossicles)

TuataraSphenodon punctatus

YPM 9194, DigiMorpho CT scan rendering




Osteostracan skulls (agnatha)

Kiaeraspis internal anatomy reconstruction(from Carroll, 1996,Vertebrate Paleontology and Evolution)

Kiaeraspis dorsal anatomy

Osteostracan(from Long, 2011, Rise of Fishes)

Kiaeraspis dorsal anatomy(from Benton, 2005,Vertebrate Paleontology)




Black-nosed sharkCarcharinus acronatus

DigiMorpho CT scan rendering

chondricthyan features• cartilaginous skeleton• hyostylic jaw (suspended by

hyomandibula)• no dermal skull bones

Living chondricthyan shark, a gnathostome




Yellow perchPerca flavicens

actinopterygian features• lots of skull bones• hyper-kinetic (mobile) jaws• operculum covers gills

From Udo Savalli, Arizona State University

Living actinopterygian teleost fish




Bullfrog

Living lissamphibian frog

Rana catesbiana

lissamphibian features• reduced skull bones (especially

lateral bones)• huge orbits• small teeth

From Udo Savalli, Arizona State University




Natural World: Attenborough's Fabulous Frogs - BBC 2




Blood pythonPython curtus

Sues, 2019, The Rise of Reptiles

Living squamate (serpentes) from Sumatra




X-ray of a watersnake eating a fish (Duncan Irshick)

Kinetic skulls




RhynchosauriaTeyumbaita sulcognathus

Upper Triassic archosaur from Brazil

Sues, 2019, The Rise of Reptiles




Tyrannosaurus rex

Tyrannosaurus rex New Mexico Museum of Natural History (photo by PD Polly)

Late Cretaceous archosaur from North America




Evolutionary transformations of arches I & II


craniostyly – jaws fused to craniumhyostyly – suspension of the jaws by hyomandibulaeuautostyle – jaws not attached to craniumpaleostyly – no jaws







Developmental components of the skull

Dermatocranium (pink)Chondrocranium or neurocranium (blue)

Splanchnocranium (visceral or branchial arches) (yellow)





Göllner et al, 2001, Mechanisms of Development 106: 77-83.

bone (mostly dermatocranium)

cartilage (mostly chondrocranium + visceral arches)

eye tissue (brain outpocketing)




Drivers of skull evolutionDevelopmental gene expression

Depew et al., 1999, Development, 126: 3831-3846.DLX genes, “distal-less” in fruit flies

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Lecture 6 - Skull diversity - vertpaleo.earth.indiana.edu