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Protura (Insecta) and Brazil during 400 million years of continental drift

1978; Taylor & Francis; Volume: 13; Issue: 1 Linguagem: Inglês

10.1080/01650527809360530

1744-5140

S. L. Tuxen,

Paleontology and Stratigraphy of Fossils

Summary The present paper continues my paper on the ecology and zoogeography of the Brazilian Protura, especially its fig. 9, the map of distribution. It builds on the assumptions that the Protura are of Devonian origin (as sister group to Collembola known as fossils from the Middle Devonian), that their evolution in time is a very slow process (since they are still fairly uniform in appearance) as is also their distribution in space (i.a. because of their susceptibility to desiccation). It attempts to correlate their phylogenetical evolution with recent theories on moving continents. That the Southern Atlantic opened‐up progressively from South during the Cretaceous period was shown on purely geological reasoning by Beurlen (1961, 1970). Proceeding from this experience a survey is given of the modern and ultramodern views on the movements of the continents from a Devonian Pangaea to their recent position. The following chapter deals with the possible phylogeny of Protura built upon recent systematics. The two suborders Eosentomoidea and Acerentomoidea have reliable synapomorphous characters and so have the families Acerentomidae and Protentomidae. Within the families, however, I have hitherto not been able to erect a trustworthy cladogram of the 37 genera known till now, and so I have been obliged to use trends of probable lines of evolution from "primitive"; to "highly developed"; genera. If these trends are related to paleogeography we arrive at the following picture. The Eosentomoidea having most plesiomorphous characters have a Pan‐gaean distribution. Among Protentomidae the genera around Hesperentomon have most characters in common with eosentomoids; they are distributed in Laurasia with extreme development in the Far East. The other genera are Laurasian or Gondwanian or both. Within Acerentomoidea four trends are distinguishable. 1: From the Pangaean Acerentulus is derived the Gondwanian Australentulus and probably also the highly developed Acerentomon which is exclusively European. 2: From the Pangaean Gracilentulus issued the purely Gondwanian Delamarentulus‐complex and the genera Baculentulus and Berberentulus. These two genera seem to be separated by the "Wallace line"; which may mark the closure of the Tethys Sea. 3: The Silvestridia‐complex which is purely Gondwanian. And 4: The Acerella‐complex which is purely Laurasian. Among the distribution of the Brazilian Protura that of Delamarentulus tristani is of the highest interest. This species is common in northern South America and in tropical West Africa and found nowhere else and so must have its origin from Turonian time before the breaking‐up of the "Pernambuco Querstruktur";. It must therefore be more than 100 million years old. It is also ecologically little selective since it is found in tropical rain forest a few metres above sea level and in Andesian paramo at a height of 3500 m; it may even have ascended with the upheaval of the Andes. The same holds true of an Amazonian Eosentomon species, curupira, which, however, underwent speciation in the paramo. The Gondwanian relationship also of the other Brazilian species — the same or related species elsewhere in "Gondwana"; — is pointed out. Interesting is also the common occurrence in Melanesia of a species otherwise known only from Brazil (Rio de Janeiro). In an epilogue a retrospective vision of the simultaneous evolution of the Protura and the continents is given; from their Pangaean origin the Protura were induced to further development by the break‐up in Laurasia and Gondwana, specializing in attaining new characters in Laurasia, in reduction in Gondwana.