How are the Mighty Fallen

Contents Updated: Monday, September 13, 1999

• Greatest Puzzle
• Table: Genera surviving the Late Cretaceous extinctions

Greatest Puzzle

"Learn to see in another's calamity the ills which you should avoid."

The extinction of the dinosaurs is the greatest of all titillating puzzles according to writer, John Noble Wilford.

Something unusual certainly happened at the end of the Cretaceous Period. Many genera of all kinds died off. Any terrestrial creature weighing more than 50 pounds as an adult became extinct; sea organisms of all sizes were devastated, including many minute sea creatures like the foraminifera; many of the sea bottom filter feeders such as bivalves disappeared; only about 30 per cent of sponges remained.

But not all living things were equally affected:

• marine genera were badly affected but not freshwater ones;
• tropical plants suffered more than those in more northerly climes;
• pterosaurs died but not birds;
• most mammals survived but few marsupials;
• squid survived but their relatives the ammonites died;
• dinosaurs died but not crocodiles ;
• mammals, which were all small, and small lizards mostly survived but even the smallest dinosaurs died out.

Though the Cretaceous mass extinction was bad, the earlier Permo-Triassic mass extinction, when 70 per cent of all known types of animal became extinct, was worse.

The Permian extinction is explained by the theory of pl