Unlike living anapsids (turtles), all of the main groups of stem anapsids retained teeth, and the structure of their teeth yields clues about their diet. The earliest anapsids (millerettids, Acleistorhinus, lanthanosuchids, nycteroletorids, and the first procolophonoids) had a fairly unelaborated dentition consisting of sharp, conical teeth. This suggests that these animals were insectivorous or carnivorous. Pareiasaurs had leaf-shaped teeth that suggest that they were herbivorous, and procolophonids (a Triassic group of procolophonoids) had transversely broad, bulbous teeth that are likely indicative of a herbivorous or durophagous (hard food such as shelled mollusks, arthropods, etc.) diet.
Restored environment of Proganochelys (the oldest known turtle) during the Late Triassic in Germany. A few early sauropodomorph dinosaurs (Plateosaurus) can be seen above Proganochelys. Painting by Frank Ippolito, copyright 1987 American Museum of Natural History.
All extant anapsids are oviparous, and most extinct anapsids were probably also oviparous, because this condition is apparently primitive for reptiles.
Extant anapsids (i.e. turtles) include fully terrestrial, amphibious, freshwater, and marine taxa. However, all known groups of extinct stem anapsids appear to have been terrestrial, with the possible exception of lanthanosuchids. If early anapsids occasionally ventured into the water, they have no skeletal specializations suggesting aquatic habits.