Captorhinidae

From Palaeos

o Eureptilia
|--o-- Diapsida
|  `== †"Protorothyrididae"
`--+-- †Thuringothyris
   `--o †Captorhinidae
      |-- †Concordia
      `--+--o †Romeria
         |  `--+-- †R. texana
         |     `-- †R. prima
         `--+-- †Protocaptorhinus
            `--+-- †Rhiodenticulatus
               `--+-- †Saurorictus
                  |?- †Acrodenta
                  |?- †Baeotherates
                  `--+--o †Captorhinus
                     |  `--+-- †C. laticeps
                     |     `--+-- †C. aguti
                     |        `-- †C. magnus
                     `--+-- †Captorhinikos
                        `--+-- †Labidosaurus
                           `--o †Moradisaurinae
                              |-- †Labidosaurikos
                              `--+-- †Gecatogomphius
                                 |-- †Kahneria
                                 |?- †Rothianiscus
                                 `-- †Moradisaurus

The Captorhinidae (in former times considered as 'stem reptiles') were one of the earliest and most primitive reptiles. They first occured in the Late Carboniferous of North America. In Upper Permian times they spread throughout the world but dissapeared from the North American fossil record, and finally they became extinct by the end of the Permian. Captorhinid fossils today are known from all continents with the exception of Antarctica and Australia.
Captorhinids have an anapsid skull which is triangular in dorsal view and more or less heavily ornamented with a honeycomb-like pattern of ridges and pits, similar to that of numerous Late Paleozoic amphibians or, to a certain degree, modern crocodiles. Their body size ranges from that of a modern lizard up to that of a medium-sized modern alligator or the large Komodo Island monitor.
It has been mistakenly said that multiple tooth rows are a characteristic trait of captorhinids. This is not true and related to the fact that Captorhinus aguti, a representative with multiple rows of teeth, is the by far most common captorhinid. In reality captorhinids are divided into basal, rather small, lightly built forms with single rows of teeth, and into derived, larger forms with multiple rows of teeth. The most derived multiple-tooth-rowed forms form a clade referred to as subfamily Moradisaurinae. Cladistic analyses reveal that the evolution of multiple tooth rows took place at least three times independently within captorhinids: in Captorhinus, Captorhinikos and within the moradisaurines.
There is little doubt that the basal single-tooth-rowed forms were most likely feeding on insects and/or small vertebrates. The more robust built multiple-tooth-rowed forms seem to have fed on fibrous plants but an omnivorous diet or a diet consisting of hard-shelled invertebrates, such as clams or crabs, cannot be ruled out.