Giants of the Past

Reconstruction of Arthropleura amata by Jordan and Meyer*

The maximum size of arthropods has increased and decreased in the distant past in response to changing composition of earth’s atmosphere. 300 million years ago, the oxygen concentration in earth’s atmosphere may have been greater than 30% (compared to about 21% today). The higher level of oxygen allowed arthropods to attain a much larger size. When the oxygen concentration dropped, these giant went extinct.

One large species of terrestrial arthropod was Arthropleura, a centipede like creature that measured 6 feet in length and around a foot in width. This creature had one pair of legs per segment like modern centipedes. Material in the gut of Arthropleura fossils indicates that it consumed lycopods and other plants like modern millipedes.  Arthropleura is considered to be a myriapod since every segment has a pair of appendages. However, its legs have more segments than extant centipedes and millipedes so it is placed in its own taxonomic group.

The evolution and extinction of Arthropleura is linked to changes in atmospheric gas concentrations. What new species might evolve and what extant species might go extinct due to anthropogenic changes to earth’s atmosphere?

W. D. IAN ROLE and J. K. INGHAM.  Limb structure, affinity and diet of the Carboniferous  ‘centipede’ Arthropleura.  Scott. J. Geol. 3 (1), 118-124, 1967.