Definition that contains atop
- tier one of two or more layers one atop another
- triceratops huge ceratopsian dinosaur having three horns and the neck heavily armored with a very solid frill
- frill (paleontology) a bony plate that curves upward behind the skull of many ceratopsian dinosaurs
- velociraptor small active carnivore that probably fed on protoceratops; possibly related more closely to birds than to other dinosaurs
- keratoconus abnormal cone-shaped protrusion of the cornea of the eye; can be treated by epikeratophakia
- genus ceratophyllum constituting the family Ceratophyllaceae: hornworts
- ceratophyllum constituting the family Ceratophyllaceae: hornworts
- spermatophyta seed plants; comprises the Angiospermae (or Magnoliophyta) and Gymnospermae (or Gymnospermophyta); in some classification systems Spermatophyta is coordinate with Pteridophyta (spore producing plants having vascular tissue and roots) and Bryophyta (spore producing plants lacking vascular tissue and roots)
- suborder marginocephalia includes boneheaded (pachycephalosaurs) and horned (ceratopsian) dinosaurs
- amber lily plant having basal grasslike leaves and a narrow open cluster of starlike yellowish-orange flowers atop a leafless stalk; southwestern United States; only species of Anthericum growing in North America