Clepsydrops was a primitive amniote

Amniote

The amniotes are a group of tetrapods that have a terrestrially adapted egg. They include synapsids and sauropsids , as well as their fossil ancestors. Amniote embryos, whether laid as eggs or carried by the female, are protected and aided by several extensive membranes...

 from the early Late Carboniferous that was related to Archaeothyris

Archaeothyris

Archaeothyris was a very early mammal-like reptile, which lived in the late Carboniferous period. Dated to 306 million years ago, it is the oldest undisputed synapsid known....

and the synapsid

Synapsid

Synapsids are a group of animals that includes mammals and everything more closely related to mammals than to other living amniotes. They are easily separated from other amniotes by having an opening low in the skull roof behind each eye, leaving a bony arch beneath each, accounting for their name...

s—the ancestors of mammal

Mammal

Mammals are members of a class of air-breathing vertebrate animals characterised by the possession of endothermy, hair, three middle ear bones, and mammary glands functional in mothers with young...

s. Like many other terrestrial early amniote

Amniote

The amniotes are a group of tetrapods that have a terrestrially adapted egg. They include synapsids and sauropsids , as well as their fossil ancestors. Amniote embryos, whether laid as eggs or carried by the female, are protected and aided by several extensive membranes...

s, it had the diet of insect

Insect

Insects are a class of living creatures within the arthropods that have a chitinous exoskeleton, a three-part body , three pairs of jointed legs, compound eyes, and two antennae...

s and smaller animal

Animal

Animals are a major group of multicellular, eukaryotic organisms of the kingdom Animalia or Metazoa. Their body plan eventually becomes fixed as they develop, although some undergo a process of metamorphosis later on in their life. Most animals are motile, meaning they can move spontaneously and...

s. It also laid eggs on land rather than in the water, as most of its ancestors

Tetrapod

Tetrapods are vertebrate animals having four limbs. Amphibians, reptiles, birds and mammals are all tetrapods; even snakes and other limbless reptiles and amphibians are tetrapods by descent. The earliest tetrapods evolved from the lobe-finned fishes in the Devonian...

 did. Its jaws were slightly more advanced than Paleothyris

Paleothyris

Paleothyris was a small, agile, anapsid reptile which lived in the Middle Pennsylvanian epoch in Nova Scotia . Paleothyris had sharp teeth and large eyes, meaning that it was a nocturnal hunter. It was about a foot long. It probably fed on insects and other smaller animals found on the floor of its...

, and Hylonomus

Hylonomus

Hylonomus was a very early reptile. It lived 312 million years ago during the Late Carboniferous period.It is the earliest unquestionable reptile ....

.

See also

• List of pelycosaurs
• Evolution of mammals
  Evolution of mammals
  __FORCETOC__The evolution of mammals within the synapsid lineage was a gradual process that took approximately 70 million years, beginning in the mid-Permian. By the mid-Triassic, there were many species that looked like mammals, and the first true mammals appeared in the early Jurassic...
  
  
• Carboniferous tetrapods
  Carboniferous tetrapods
  Carboniferous Tetrapods include amphibians and reptiles that lived during the Carboniferous Period.During this time, amphibians were the predominant tetrapods, and included the Temnospondyli, Lepospondyli, and Reptiliomorpha/Batrachosauria...
  
  
• List of transitional fossils