Fossils of large terrestrial arthropods from the Lower Devonian of Canada

Article Abstract:

Impression fossils and some organic cuticle remains of millipeds, arthropleurids and a scorpion from the Emsian sediments are obtained from New Brunswick and Quebec, Canada. These are from Lower Devonian age and represent one of the earliest fauna of North America. A milliped fossil show the presence of two pairs of slender legs per segment. Organically preserved cuticle of a scorpion indicates the overall length of the insect to be about 9 cm and the presence of air breathing in them. The presence of macroarthropods fossils is peculiar of this Canadian site.

Canada, Natural history, Paleontology, Devonian period

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End of the 'Uniramia' taxon

Article Abstract:

A new analysis of insect fossils indicates that the arthropods' evolutionary origin was from an arthropod common ancestor (monophyletic) rather than from two or more non-arthropod ancestors (polyphyletic). The arthropods are a highly diverse group of invertebrates that comprises insects, spiders, crabs and related forms. Jarmila Kukalova-Peck examined the leg anatomy of several well-preserved insect fossils and concluded the taxon Uniramia, a fundamental component of the polyphyletic theory, never existed.

Origin, Fossil insects

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Taxon sampling revisited

Article Abstract:

Phylogenies having long, unbranched lineages are difficult to reconstruct, and added taxa can decrease accuracy. It has been argued that this negative impact, known as long-branch attraction, is lessened if slowly evolving lineages are included to subdivide long branches. Computer simulations have shown that adding characters can be favourable, and that the addition of slowly evolving taxa can reduce accuracy.

Models, Phylogeny

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