Australasian Science: Australia's authority on science since 1938

The Rise of Arthropods

By John Long

Spectacular arthropod fossils have shed light on their early anatomy, and might one day help resolve the mystery of their distant origins.

The full text of this article can be purchased from Informit.

Arthropods are joint-legged animals, one of the most successful animal groups on the planet. They include insects, crustaceans, spiders, scorpions, millipedes, centipedes and many other kinds of living and extinct animals, all of which share segmented jointed legs and an outer exoskeleton of a special kind of chitin, which they moult to grow.

Love them (prawns, crayfish) or hate them (spiders, ticks, cockroaches), they form an integral part of our daily lives, as much of our food depends upon their behaviour. One-third of all the food plants we eat relies upon pollination by bees, and at various times our crops are devastated by swarms of hungry locusts.

The arthropods account for approximately 80% of all known described species of animals, yet some scientists estimate there are perhaps 5–10 million undescribed forms. However, the really big question for evolutionary biologists is: when did arthropods first arise, and how?

The fossil record of arthropods is now very well-known, ranging from the many species of trilobites living in Palaeozoic seas through to superb 3-D insects preserved in amber.

Our earliest examples of arthropods come from the beginning of the Cambrian Period about 530 million years ago. This was a time when many arthropods, such as the first trilobites, had developed the hard chitinous exoskeleton, yet there was also a great...

The full text of this article can be purchased from Informit.