Condylarth

Description
An extinct informal group but was previously considered an order of extinct placental mammals

Something
Cost: 50.75 Billion Entropy

Gives 1.25 Billion Entropy

Upgrades to get it

 * Bunodont teeth - Costs 1.5 Billion Entropy
 * Trigonids of lower molars - Costs 5.55 Billion Entropy
 * Lower third molar - Costs 20.25 Billion Entropy
 * Head of Astragalus - Costs 38.50 Billion Entropy