Diapsid Evolutionary Tree

The Mesozoic Era is popularly known as 'The Age of Reptiles'. It comprises three periods: Triassic, Jurassic, and Cretaceous - but reptiles were already present during the preceding Carboniferous and Permian periods. These were the last periods of the Palaeozoic Era (Table 1). (Palaeozoic means 'ancient life', Mesozoic 'middle life' and Cenozoic, which followed it and continues to the present, 'recent life'.)

Life probably began in the sea, and terrestrial plants and animals did not appear until the Ordovician period: this followed the Cambrian and preceded the Silurian. Terrestrial vegetation during the Ordovician consisted mainly of simple, non-vascular plants (which probably included mosses, liverworts, lichens, and fungi), while the fossil soils contain burrows presumably made by worms and arthropods. Land plants diversified during the Silurian period, while the fauna consisted mainly of millipedes, centipedes, and tiny, fungus-eating microarthropods. Thus, even then, there was the beginning of a terrestrial food web consisting of primary producers, decomposers, secondary consumers, and predators. Nearly all the terrestrial animals of the Devonian period were arthropods. The phylum Arthropoda diversified considerably at that time; mites and springtails (Collembola) appeared, and the first amphibians crawled onto the land (Benton and Harper 1997).

■ Table 1. Periods of the Palaeozoic, and Mesozoic Eras

Period

Approximate date (millions of years) before the present

Approximate duration (millions of years)

Cretaceous

145-65

80

Jurassic

205-145

60

Triassic

250-205

45

Permian

270-250

20

Carboniferous

350-270

80

Devonian

400-350

50

Silurian

440-400

40

Ordovician

480-440

40

Cambrian

550-480

70

Collembola Chart

Fig. 1. Phylogenetic tree of the diapsid reptiles and turtles, showing postulated phylogenetic relationships of the main groups (dashed lines), known fossil records of each (vertical time dimension) and their relative abundance through time (horizontal axis). Mass extinctions and possible mass extinctions are noted with asterisks on the left. (Benton 2004)

Fig. 1. Phylogenetic tree of the diapsid reptiles and turtles, showing postulated phylogenetic relationships of the main groups (dashed lines), known fossil records of each (vertical time dimension) and their relative abundance through time (horizontal axis). Mass extinctions and possible mass extinctions are noted with asterisks on the left. (Benton 2004)

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