page_title: Diadectomorpha
section_title: Reproduction and the origin of Amniota
hierarchical_section_title: Diadectomorpha / Reproduction and the origin of Amniota
caption_attribution_description: Diadectes
context_page_description: Diadectomorpha are a clade of large tetrapods that lived in Euramerica during the Carboniferous and Early Permian periods and in Asia during Late Permian, They have typically been classified as advanced reptiliomorphs close to the ancestry of the Amniota, though some paleontologists consider them basal synapsids. They include both large carnivorous and even larger herbivorous forms, some semi-aquatic and others fully terrestrial. The Diadectomorpha seem to have evolved during late Mississippian times, although they only became common after the Carboniferous rainforest collapse and flourished during the Late Pennsylvanian and Early Permian periods.
context_section_description: The reproduction of the Diadectomorphs has been the matter of some debate. If their group lay within the Amniota as has at times been assumed, they would have laid an early version of the amniote egg. Current thinking favours the amniote egg being evolved in very small animals, like Westlothiana or Casineria, leaving the bulky Diadectomorphs just on the amphibian side of the divide.
  This would indicate the large and bulky Diadectomorphs laid anamniote eggs (in water). However, no unambiguously diadectomorph tadpole is known. Whether this is due to an actual lack of tadpole stage or taphonomy (many diadectomorphs were upland creatures where tadpoles would have a poor probability of being fossilized) is uncertain. Alfred Romer indicated that the anamniote/amniote divide might not have been very sharp, leaving the question of the actual mode of reproduction of these large animals unanswered. Possible reproductive modes include full amphibian spawning with aquatic tadpoles, internal fertilization with or without ovoviviparity, aquatic eggs with direct development or some combination of these. The reproductive mode might also have varied within the group.
caption: Life restoration of Diadectes
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