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Ossinodus pueri Based on figure 11 of "New data on Ossinodus pueri, a stem tetrapod from the Early Carboniferous of Australia" by A. Warren Journal of Vertebrate Paleontology 27(4):850-862. Source: Wikipedia - Ossinodus |
While creationist doctrinal, evidence-free pseudoscience continues to insist that there are no transitional fossils, and certainly none showing the evolution of a major taxon such as the evolution of terrestrial tetrapods from bony fish, real, evidence-based science not only accepts the available evidence but has moved the debate on. The question is no longer 'if', but when, where and what?
As this new fossil from Queensland, Australia, now suggests, the first land vertebrates may have emerged from water earlier than we thought and not in what is now Europe, but in Gondwana before it split to become, in part, Australia. This, of course, is how science progresses. When new evidence is found, science changes its mind and always acknowledges that its current understanding is only as good as the currently available evidence.
Abstract
The origin of terrestrial tetrapods was a key event in vertebrate evolution, yet how and when it occurred remains obscure, due to scarce fossil evidence. Here, we show that the study of palaeopathologies, such as broken and healed bones, can help elucidate poorly understood behavioural transitions such as this. Using high-resolution finite element analysis, we demonstrate that the oldest known broken tetrapod bone, a radius of the primitive stem tetrapod Ossinodus pueri from the mid-Viséan (333 million years ago) of Australia, fractured under a high-force, impact-type loading scenario. The nature of the fracture suggests that it most plausibly occurred during a fall on land. Augmenting this are new osteological observations, including a preferred directionality to the trabecular architecture of cancellous bone. Together, these results suggest that Ossinodus, one of the first large (>2m length) tetrapods, spent a significant proportion of its life on land. Our findings have important implications for understanding the temporal, biogeographical and physiological contexts under which terrestriality in vertebrates evolved. They push the date for the origin of terrestrial tetrapods further back into the Carboniferous by at least two million years. Moreover, they raise the possibility that terrestriality in vertebrates first evolved in large tetrapods in Gondwana rather than in small European forms, warranting a re-evaluation of this important evolutionary event.
However, this new evidence is at best tentative and is based partly on the fact that a fossil femur normally associated with fully marine tetrapedal species has a healed fracture which is most likely to have occurred on land because the necessary forces are unlikely to be generated by a fall in water. This is also supported by an internal bone structure which shows a degree of remodelling during life in response to weight-bearing. More evidence is needed to support this view but if it is confirmed, this will show that this transition between major taxons occurred not in small marine tetrapods as we thought but some 2 million years earlier in larger species.
The problem creationists have, of course, is that, come what may, they must try to force-fit reality into their favourite Bronze Age creation myth, even at the expense of simply ignoring all the evidence to the contrary. If that's unfair, would any creationists be willing to try to explain why these supposedly non-existent fossils, showing the evolution of new taxons from ancestral ones, keep turning up so regularly?
Or is denialism to be the order of the day, still?
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