Marginocephalia

Marginocephalia
Name means “margin head”
Sister group to Ornithopoda
Most live during the Cretaceous (Only one from Jurassic)
Well-known (many complete skeletons)
Diagnosis of Marginocephalia
Shelf of bone extending back over occipital portion of skull

Shortened pubis

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Widely-spaced acetabula (hip sockets)

Shelf of bone extending back over occipital portion of skull
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Marginocephalia Clades
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Pachycephalosauria
Divided into two clades, which are?
“Bone heads”
Homocephalidae
and
Pachycephalosauridae
(Pachycephalosauria) Homocephalidae
Generally small

Flat, very bony heads

(Includes:
Micropachycephalosaurus
One of the smallest dinosaurs
One of the longest dinosaur names )

(Pachycephalosauria) Pachycephalosauridae
Domed heads

Extremely thick, boney skull

Diagnosis of CERATOPSIA
keratinous beak

frill formed by parietals

triangular shaped skull (when viewed dorsally)

high palate

Psittacosauridae
Parrot-like, toothless beak