Roadian

From Wikipedia, the free encyclopedia

The Roadian (also known as Ufimian) is the first stage of the Guadalupian epoch of Permian period. It spans the time between 270.6 ± 0.8 Ma and 268 ± 0.7 Ma (million years ago).

During this period the low diversity caseid fauna that characterized the Kungurian age is supplanted (and for the most part replaced) by a rich range of early therapsids. It is not unlikely that these early therapsids may have had the beginnings of metabolic development towards the mammalian condition. In any case, these animals quickly radiated into an extraordinary variety of large and small terrestrial herbivores and carnivores. The Early Permian ectothermic families died out early during, or perhaps prior to, this time.

The therapsids belonged to several distinct (albeit related) lineages, none with clear antecedents. These include the modest-sized Biarmosuchidae, relatively long-limbed lightly-built hunters of small game (a kind of therapsid dog perhaps), representing a persisting primitive lineage from which the other groups may have developed, the huge carnivorous eotitanosuchians (essentially biarmosuchids grown large), the bizarre estemmenosuchids, herbivores that seem to have frequented a marshy environment, and possessing strange bony head growths, not unlike antlers, and the large brithopodids, representing another carnivorous lineage, more heavily built than the biarmosuchids. Note that apart from the estemennosuchids, which replaced the cotolyhunchines as great lumbering herbivores, all these animals were carnivores. As with the Early Permian pelycosaur-dominated fauna, this was a primitive ecosystem with a preponderance of meat-eaters over herbivores.

Although the Roadian age was ruled by large and small primitive therapsids, these were also accompanied by a rich fauna of stem tetrapods and unspecialized reptiles.

The tetrapods were mostly large semi-aquatic fish-eaters, superficially crocodile-like in appearance, although there were also a selection of smaller aquatic and fully terrestrial types. Apart from the aquatic batrachosaurs, all belong to the Order Temnospondyli.

Various other types of stem tetrapods and reptiles are well-represented in the Belebei-Mezen Cotylosaur Complex, which is difficult to correlate stratigraphically because of a paucity of shared faunas. It can be assumed however that numerous small lizard-like insectivorous Anapsida were an important part of the ecosystem. The Pelycosaurs may (or may not) be represented by a single femur, Phreatosaurus aenigmaticum Efremov (1954), which Efremov assigns to the family Phraetosuchidae (probably an artificial group based on scrappy postcrania), but Olson, 1962 argues is really a member of the Family Caseidae, a group that is well represented from the Artinskian to the Wordian ages.