Evolution What the Fossils Say and Why it Matters

FIGURE 12.7. The evolutionary tree of the horned dinosaurs from Yinlong and other primitive marginocephalans.
(Drawing by Carl Buell)

Yinlong

Psittacosaurus

Graciliceratops

Protoceratops

Leptoceratops

Zuniceratops

Pachyrhinosaurus

Styracosaurus

Centrosaurus

Monoclonius

Chasmosaurus

Anchiceratops

Arrhinoceratops

Pentaceratops

Torosaurus

Triceratops

125 112 100 93 70 65

Jurassic

Aptian Albian CenomanianTuronianConiacianSantonianCampanian Maastrichtian

Cretaceous Cenozoic

90 86 84

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