SYNAPSIDA

PARENT CLADES:

Animalia: Vertebrata: Tetrapoda

CLADOGRAM:

—Synapsida “fused apses” =Theropsida
|–Caseasauria “Casea lizards”
| |–Caseidae
| `–Eothyrididae
`–Eupelycosauria “true pelycosaurs”
|–Varanopsidae
`–+–Ophiacodontidae
`–+–Edaphosauridae
`–Sphenacodontia “Sphenacodon‘s taxon”
|–Haptodus
`–+–Palaeohatteria
`–+–Pantelosaurus
`–+–Cutleria
`–Sphenacodontoidea
|–Sphenacodontidae (Dimetrodon, Sphenacoon, etc.)
`–Therapsida “beast apses” =Neotheropsida
|–Biarmosuchia
`–+–Dinocephalia “terrible heads” (Moschops, etc.)
`–+–Anomodontia
| |–Dromasauria
| |–Venyukiamorpha
| `–Dicynodontia
`–Theriodontia
|–Gorgonopsia (Lycaenops, etc.)
`–+–Therocephalia “beast heads”
`–Cynodontia “dog teeth”
|–Dviniidae
|–Galesauridae
|–Procynosuchidae
`–Eucynodontia “true cynodonts”
|–Cynognathidae
`–Probainognathia
|–Tritylodontoidea
`–+?-Eoraetia
|?-Kunminia
|–Chiniquodontidae
|–Tritheledontidae
`–Mammaliformes “Mammalia forms” =Mammalia sensu lato
|?-Adelobasilus
|?-Sinoconodon
|?-Theroteinus
|?-Tricuspes
|?-Gobiconodontidae
`–+?-Morganucodontidae
`–+?-Docodonta
`—->Mammalia

Once called mammal-like reptiles, the animals shown here are no longer considered reptiles. Instead, they were the non-mammalian members of a separate lineage. Their skin was probably not dry and scaly like true reptiles.
E
VOLUTIONARY DYNASTIES:Synapsids were the first terrestrial vertebrates to truly dominate the landscape. There were two main “waves”, the “pelycosaurs” (non-therapsid synapsids) in the Permian and then the early therapsids in the Triassic.
“Pelycosaurs” were probably cold-blooded. They ranged from large herbivores like Casea to snaggle-toothed, sail-backed predators like Dimetrodon. The advanced ones show the beginnings of the mammalian tooth pattern — incisors, canines, and molars.
Some (but probably not all) therapsids were warm-blooded, fur-covered, and milk-giving. They varied from the beaked, tusked, and herbivorous dicynodonts to the sleek, predatory Cynognathus. By the end of the Triassic, most of these forms had died out, replaced by archosaurs (including dinosaurs). Only a few small Probainognathia survived, including some of the earliest mammals.

BRENDAN SMITH