Reptiles Guide

Placodonts  Fossil range: Triassic
Scientific classification
Kingdom: Animalia   Phylum: Chordata   Class: Sauropsida   Superorder: Sauropterygia   Order: Placodontia Cope, 1871
Families
Paraplacodontidae Placodontidae Henodontidae Cyamodontidae Placochelyidae

Placodonts were a group of marine reptiles that lived during the Triassic period, becoming extinct at the end of the period. It is believed that they were related to the Sauropterygia, the group that includes Plesiosaurs. Placodonts were generally between one to two metres in length, with some of the largest measuring three metres long.

In appearance, they resembled some of today's large bottom-feeding mammals such as walruses or dugongs, others looking more turtle-like due to large bony plates on their backs. They had short limbs and were highly robust.

Because of their dense bone and heavy armour plating, these creatures would have been too heavy to float in the ocean and would have used a lot of energy to reach the water surface. For this reason and because of the type of sediment found accompanying fossils it is suggested they lived in shallow waters and not in deep oceans.

Their diet consisted of marine bivalves, brachiopods, and other invertebrates. They were notable for their large, flat, often protruding teeth which they used to crush molluscs and brachiopods, which they hunted on the sea bed (another way in which they were similar to walruses). The Palate teeth were extremely thick and large enough to crush thick shell.

The first specimen was discovered in 1830, and they have since been discovered throughout Europe and the Middle East.

Classification

• Class Sauropsida
  • Superorder Sauropterygia
    • ORDER PLACODONTIA
      • Genus Saurosphargis
      • Family Paraplacodontidae
        • Genus Paraplacodus
      • Family Placodontidae
        • Genus Placodus
      • Superfamily Cyamodontoidea
        • Family Henodontidae
          • Genus Henodus
        • Family Cyamodontidae
          • Genus Cyamodus
        • Genus Protenodontosaurus
        • Family Placochelyidae
          • Genus Placochelys
          • Genus Psephoderma

External links

• http://www.oceansofkansas.com/placodnt.html
• http://users.unimi.it/vertpal/galleriafossili/best-retilli/PSEPHODERMAMORFFUNZ.html
• http://rainbow.ldgo.columbia.edu/courses/v1001/9.html
• http://palaeos.com/Vertebrates/Units/220Lepidosauromorpha/220.100.html#Placodontia
• Oceans of Kansas Palaeontology Mike Everhart