Lecture 1: what is a dinosaur

Question 1

Clade

Answer 1

grouping of organisms made on the basis of their hypothesized evolutionary history
- consisting of a common ancestor and all of its descendants

Question 2

cladogram

Answer 2

a diagram showing the evolutionary relationships between organisms
- an evolutionary tree made from cladistics analysis

Question 3

demitrodon

Answer 3

• misidentified as a dinosaur; has two measures of teeth
• Had only 1 hole behind eye socket, more closely related to living mammals than dinos
• Is a synapsid!!

Question 4

dinosaur

Answer 4

• terrible lizard; defined by principle and best established representatives
• 3 extinct organisms grouped together based on similarities in their skeletons
  
  • Megalosaurus
  • Iguanodon
  • Hylaeosaurus
• Dinosauria represented a distinct tribe grouped together for convenience
• Scientists now recognize these traits as coming from a common ancestor
• Birds are a part of the dinosauria clade

Question 5

subclade

Answer 5

• members of the same subclade are more closely related to each other
• makes up a clade

Question 6

synapomorphy

Answer 6

• shared traits unique to a group (defines clades)
• The number of holes behind the eye socket is a synapomorphy separating synapsids from diapsids
  
  • Diapsids (birds and reptiles and dinos) have 2 holes
  • Synapsids (mammals) have 1 hole