An Australian fossil is forcing scientists to rethink on our ancestors' emergence onto land.
Queensland University of Technology paleontologists say that the 333million-year-old broken bone is causing fossil scientists to reconsider the evolution of land-dwelling vertebrate animals.
Analysis of a fractured and partially healed radius (front-leg bone) from Ossinodus pueri, a large, primitive, four-legged (tetrapod), salamander-like animal, found in Queensland, pushes back the date for the origin of demonstrably terrestrial vertebrates by two million years, said researcher Matthew Phillips.
Phillips added that previously described partial skeletons of Ossinodus suggest this species could grow to more than 2m long and perhaps to around 50kg, noting that its age raises the possibility that the first animals to emerge from the water to live on land were large tetrapods in Gondwana in the southern hemisphere, rather than smaller species in Europe.
He noted that the evolution of land-dwelling tetrapods from fish is a pivotal phase in the history of vertebrates because it called for huge physical changes, such as weight bearing skeletons and dependence on air-breathing.
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Phillips noted that the three findings taken together suggest that Ossinodus spent a significant part of its life on land. This is augmented by its exceptional degree of ossification, which is also consistent with weight bearing away from the buoyancy of water.
He said the findings highlighted the value of combining studies on palaeontology, biomechanics and pathology to understand how extinct organisms lived.
The study is published in journal PLOS ONE.
