Varanopidae was a family of 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...

 "pelycosaur

Pelycosaur

The pelycosaurs are an informal grouping composed of basal or primitive Late Paleozoic synapsid amniotes. Some species were quite large and could grow up to 3 meters or more, although most species were much smaller...

s" that resembled monitor lizard

Monitor lizard

Monitor lizards are usually large reptiles, although some can be as small as in length. They have long necks, powerful tails and claws, and well-developed limbs. Most species are terrestrial, but arboreal and semiaquatic monitors are also known...

s and might have had the same lifestyle, hence their name. No known varanopids developed a sail like Dimetrodon

Dimetrodon

Dimetrodon was a predatory synapsid genus that flourished during the Permian period, living between 280–265 million years ago ....

. Their size varied from lizard-sized to dog-sized creatures. Varanopids already showed some advanced characteristics of true pelycosaurs such as their deep, narrow, elongated skulls. Their jaws were long and their teeth were sharp. However, they were still primitive by 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...

ian standards. Like many other pelycosaur families, they evolved from an 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....

-like synapsid in the Late Carboniferous

Carboniferous

The Carboniferous is a geologic period and system that extends from the end of the Devonian Period, about 359.2 ± 2.5 Mya , to the beginning of the Permian Period, about 299.0 ± 0.8 Mya . The name is derived from the Latin word for coal, carbo. Carboniferous means "coal-bearing"...

. They had long tails, lizard

Lizard

Lizards are a widespread group of squamate reptiles, with nearly 3800 species, ranging across all continents except Antarctica as well as most oceanic island chains...

-like body, and thin legs. The varanopids were mostly carnivorous, but as they were reduced in size, their diets changed from a carnivorous to an insectivorous lifestyle. Compared to the other animals in Early Permian, varanopids were agile creatures. But the last of the varanopids were outcompeted, having been replaced by the evolving diapsid

Diapsid

Diapsids are a group of reptiles that developed two holes in each side of their skulls, about 300 million years ago during the late Carboniferous period. Living diapsids are extremely diverse, and include all crocodiles, lizards, snakes, and tuatara...

s and by the end of the Middle Permian, they became extinct. A varanopid from the latest Middle Permian Pristerognathus Assemblage Zone

Pristerognathus Assemblage Zone

The Pristerognathus Assemblage Zone is a geological stratum and a faunal zone of the Beaufort Group, of the South African Karoo. The name refers to Pristerognathus, a genus of Therocephalian mammal-like reptile, whose fossils have been found in that structure....

 is the youngest known varanopid and the last member of the "pelycosaur" group of synapsids.

Taxonomy and Phylogeny

• Class Synapsida
• Order Pelycosauria
  • Eupelycosauria
    Eupelycosauria
    The Eupelycosauria originally referred to a suborder of 'pelycosaurs' , but has been redefined to designate a clade of synapsids that includes most pelycosaurs, as well as all therapsids and mammals...
    
    
    • Family Varanopidae
      • Archaeovenator
      • Basicranodon
      • Thrausmosaurus
        Thrausmosaurus
        Thrausmosaurus is a genus of synapsid pelycosaurs from the extinct family Varanopidae. Like all that resemble members of Varanopidae, Thrausmosaurus most likely resembled the modern monitor lizard and may have had the same lifestyle. The type and only species was described by R. C. Fox in 1962,...
        
        
      • Varanosaurus
        Varanosaurus
        Varanosaurus is an extinct genus of early pelycosaur synapsid that lived during the early Permian .As its name implies, Varanosaurus looked very similar to present-day monitor lizards...
        
        
      • Subfamily Mycterosaurinae
        • Mesenosaurus
          Mesenosaurus
          Mesenosaurus is an extinct genus of non-mammalian synapsid, the only know species within this genus in the Mesenosaurus romeri.-References:*...
          
          
        • Mycterosaurus
          Mycterosaurus
          Mycterosaurus was a pelycosaur belonging to the family Varanopidae of the subfamily Mycterosaurinae. Mycterosaurus is the most primitive member of its family. It lacks some features that its advanced relatives have....
          
          
      • Subfamily Varanodontinae
        • Aerosaurus
          Aerosaurus
          Aerosaurus is an extinct genus within Varanopidae, a family of non-mammalian synapsids. It lived from the Late Carboniferous to Early Permian in North America.-References:...
          
          
        • Elliotsmithia
          Elliotsmithia
          Elliotsmithia is an extinct genus of non-mammalian synapsid.-References:*...
          
          
        • Varanodon
          Varanodon
          Varanodon was a pelycosaur of the family Varanopidae.- References :* E. C. Olson. 1965. New Permian vertebrates from the Chickasha Formation in Oklahoma. Circular Oklahoma Geological Survey 70:1-70....
          
          
        • Varanops
          Varanops
          Varanops is an extinct genus of Early Permian varanopid synapsid known from Texas and Oklahoma of the United States. It was first named by Samuel Wendell Williston in 1911 as a second species of Varanosaurus, Varanosaurus brevirostris. In 1914, Samuel W. Williston reassigned it to its own genus and...
          
          

External links

• Varanopseidae - at Palaeos