History of discovery
If you look at the outlines of continents - e.g. the east coast of South America and the west coast of Africa, you notice they fit together like a big jigsaw puzzle. In 1912 the father of the theory of continental drift, Alfred Wegner, cited geographical, geological, and paleontological evidence and proposed that some 200 million years ago the worlds continents were all joined into a single supercontinent which he called "Pangea" (all the Earth). As the sea floor spread Pangea broke up and the continents began to drift away from each another, finally assuming their present positions. Wegner's hypothesis languished until 1968, when empirical evidence of sea floor spreading was found, the old geological models overthrown, and a paradigm shift established continental drift as the mainstream understanding of the Earth.
The Formation of Pangea
The separate continents of the Paleozoic, after having drifted apart through the fragmentation of the supercontinent of Rodinia, around 650 million years ago (Ediacaran period) eventually drifted together again during the Paleozoic, colliding to form the supercontinent of Pangea during the Devonian and Carboniferous periods, some 350 million years ago. More specifically Pangea was assembled by the collisions of three main blocks, Gondwana, Euramerica, and Siberia, during Permo-Carboniferous time, around 350 to 260 million years ago. Various smaller blocks, especially in southeastern Asia, were late arrivals. In the initial collision between Gondwana and the northern continents, South America abutted central Euramerica. Modern Spain and central France are former pieces of Venezuela. Pangea was essentially complete by the Kungurian Age (late early Permian). A sliding motion then carried Gondwana 3500 kilometers westward, relative to the northern landmasses, until Africa was abutting North America by the Norian Age (Late Triassic), producing the classic Pangea configuration (E. Irving, Nature, Vol.270, 1977, p.304). [Nigel Calder, Timescale, p.264]
Pangea began to rift apart almost immediately. However, the process of separation was prolonged for some 250-300 million years, resulting in roughly the modern series of separate continental blocks in the early to Mid-Cretaceous, some 130-100 million years ago. However, for much of its long history the supercontinent was actually a series of large islands, separated from each other by shallow continental seas.
Name: Pangea
Status: Global Supercontinent
Time: from the early Permian to early Jurassic
Included: incorporating all the present day continents
Formed through collision of : Gondwana, Euramerica, and Siberia
Fragmented into: Gondwana and Laurasia (moreover, during the Jurassic and Cretaceous the low-lying areas were often submerged by shallow continental seas)
Indigenous biota: Animal life was largely uniform over much of its surface. However plants tended to be distinct in the northern and southern hemispheres
Pangean Animal Life - Permo-Triassic Tetrapods
A Triassic scene. The giant predatory pseudosuchian Saurosuchus menaces two Scaphonyx. The plants are the hardy pteridosperm Dicrodium. Following the extinction of the Permian therapsids due to the end Permian-extinction, most of the large animals that populated Pangea were archosaurs or archosauromorphs. Mammals, dinosaurs, and pterosaurs (flying reptiles) only appear towards the end of the Triassic.
Illustration © Greg S. Paul
The hundred million years and more of Pangean history saw a succession of cosmopolitan animal dynasties spread over the entire supercontinent. Different families of amphibians and reptiles would arise, flourish for a while, and then die out, before being replaced by a new biota. The hot arid conditions that persisted over much of the supercontinent for all this time favoured reptiles over therapsids and mammals; hence all the large-bodied (and most small-bodied) ecological niches were filled by eureptilia, especially archosaurs, with amphibians continuing only in rivers and ponds, and synapsids becoming progressively smaller and less diverse, and finally nocturnal. Only during the last days of Pangea, in the Jurassic, did conditions ameliorate and the tiny Mesozoic mammals diversify.
The following diagram is from Fig. 2. of R.T. Bakker, 1977 "Tetrapod Mass Extinctions - A model of the regulation of speciation rates and immigration by cycles of topographic diversity" in A. Hallam, ed. Patterns of Evolution as illustrated by the Fossil Record, Elsevier Scientific Publishing Company, Amsterdam, Oxford, New York, pp.439-68
Although subsequent research has modified some of the family rankings and stratigraphic correlations, the basic pattern remains.
Diversity of non-marine tetrapods, early Late Permian to Early Jurassic. Each bar represents one family. Narrow extensions of bars indicate that the family is present but very rare. Families known from only one formation are omitted. Roman numerals at top show the successive "dynasties". Biomass D has been calculated for each faunal level from the formation with the largest number of identifiable specimens. The faunal levels are represented by the following formations (the first named formation supplies the data for D, except for no.8, where two have been combined because of small sample size):
1, Tap Zone, Russian Zone II; 2, Ruhuhu, low Kistecephalus Zone; 3, upper Kistecephalus Zone, Madumabisa Mudatone; 4, low and middle Daptocephalus Zone, Kawinga; 5, upper Daptocephalus Zone; 6, Lystrosaurus Zone (South Africa); 7, Cynognathus Zone, ?Ur-Ma-Ying; 8, Omingonde Mudatone, Russian Zone VI; 9, Manda; 10, Santa Maria; 11, lschigualasto, lower Red Beds (South Africa); 12, Lower Chinle, lower Los Colorados, Wolfville; 13, upper Los Colorados, Stuben Sandstone; 14, Lufeng Beds, Knollenmergi, upper Red Beds (South Africa); 15, Forest Sandstone, Cave Sandstone, Portland Arkose. The South African and Russian "zones" correspond in rank to formation or series.
Family abbreviations:
Large Herbivores: A = titanosuchids; B = struthiocephalids; C = tapinocephalids; D = moschopids; E = styracocephalids; F = pareiasaurids; G = endothiodontids; H = oudenodontids; I = aulacephalodontids; J = whaitsiids; K = daptocephalids; L = lystrosaurids; M = diademodontids; N = kannemeyeriids; 0 = stahleckerilds; P = shansiodontids; Q = rhynchosaurids; R = traversodontids; S = aetosaurids; T = melanorosaurids; U = plateosaurids.
Large Carnivores: A = anteosaurids; B = hipposaurids; C = gorgonopsids; D = lycosuchids; E = pristerognathids; F = moschorhinida; G = proterosuchids; H = erythrosuchids and rauisuchids; I = cynognathids; J = herrerasaurids K = chiniquodontids; L = ornithosuchids; M = procompsognathids (including halticosaurs and dilophosaurs).
Small Terrestrial: A = dissorophids; B = dikopsids; C = scaloposaurids; D = emydopsids; E = nycteroleterids; F = kingoriids; G = procolophonids; H = kistecephalids; I = procynosuchids; J = galesaurids; K = prolacertids; L = trirachodontids; M = bauriids; N = sphenodontids; O = gracilosuchids; P = pedeticosaurids; Q = heterodontosaurids; R = anchisaurids; S = tritylodontids; T = fabrosaurids; U = ictidosaurids; V = icarosaurids; W = khuneotheriids; X = morganucondontids.
Fresh-Water Aquatics: A = archegosaurids; B = rhinesuchids; C = brachyopoids; D = benthosuchids; E = uranocentrodontids; F = rhytideosteids; G = sclerothoracids; H = lydekkerinids; I = trematosaurids; J = capitosaurids; K = metoposaurids; L = phtyosaurs; M = cerritosaurids.
Illustration & caption © Elsevier Scientific Publishing Company
