Palæos: Paleozoic		Guadalupian Epoch
PERMIAN PERIOD		Roadian Age

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The Roadian Age

The Roadian Age of the Guadalupian Epoch: 271 to 268 million years ago

Tetrapods

The Biarmosuchian - Estemennosuchian Terrestrial empire

Estemmenosuchus mirabilis
illustration by Gregory S. Paul

Habitat: Terrestrial
Productivity: probably somewhat low to average
Time: Early Middle Permian period
Distribution: so far known only from Eastern Europe, but probably much wider distribution

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, but I cannot agree with Dr Bakker that they were already partially or fully endothermic. 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.

Stratigraphy of Tetrapods from East Europe

The following stratigraphic table, based mostly on information in Olson, 1962, King, 1990 and Chernykh 2002 , catalogues the occurrence of Roadian tetrapods in East Europe.

sketch © 2001 by Vince R Ward - Prehistoric Pages

Suborder "Biarmosuchia"
"Eotitanosuchia"
Family Eotitanosuchidae

Eotitanosuchus olsoni Chudinov 1960

Horizon: Upper Kazanian
Locality: Echovo locality, Ocher Province, Perm Region, Russia
Length (skull): juvenile: 35 cm; large adult : 1 meter
Length (total): 5 to 6 meters?
Size: the size of a large bull
Diet: large tetrapods
Comments: Without doubt the dominant animal of its environment. Found preserved in flood deposits (once coastal bogs) containing many skeletons of estemmenosuchids, and it is likely that this large predator was an excellent swimmer, possibly semi-aquatic or frequenting marshy ground. Their legs are quite long, and the animals were probably quite agile in spite of their size. The name means "Dawn giant crocodile"
References: Sigogneau-Russell 1989
Links: Eotitanosuchus page

Suborder Dinocephalia
Plesion Anteosauria
Family Brithopodidae
Subfamily Brithopodinae?

Archaesyodon praeventor Chudinov 1960

Horizon: Upper Kazanian ("Zone I")
Locality: from Ochersky area, near Ezhovo locality. Kazanian, Cis-Uralian, Russia
Length (skull): holotype skull about 30 cm long
Length (total): 1.7 to 2 meters?
Diet: medium-sized tetrapods
Comments: An unspecialized early brithopodid. As Archaeosyodon is known only from the skull, and the contemporary brithopodid Chthomaloporus only from postcrania, it is not unlikely that these two thus represent the same animal. If so, this is the earliest known member of the anteosaurian lineage of carnivorous dinocephalians. This was a reasonably large animal, probably filling an ecological role of a medium-sized carnivore, intermediate between the dog-sized Biarmosuchus and the gigantic Eotitanosuchus.
References: Olson, 1962, King 1988