Jaws were also more complex than expected.
A tiny tooth plate of the 410 million year old fossil fish Romundina stellina indicates that teeth evolved earlier in the tree of life than recently thought.
That is a while back.
The tooth plate of just some millimeters in size had been in a box for more than 40 years, without being recognized after the discovery and preparation of the fish it belonged to.
Because no one expected to find anything like that. And few had any special desire to
Everyone knows evolution is a long, slow process of natural selection acting on random mutation (Darwinian evolution). Every third rate biology teacher teaches that, and so do first raters, because they don’t dare teach anything else, even though they would have to know better by now.
Philip Donoghue from the University of Bristol in the UK explains: “We show that the earliest teeth were like our own — but also structured like body scales in primitive fishes. This supports the view that teeth evolved from scales, which arose much earlier in vertebrate evolution.”
Rücklin adds: “Our results suggest that teeth originated deeper in the tree of life than we thought. We will have to look into more basal jawed vertebrates and also jawless fossils. Earliest jaws and teeth seem to be less integrated than we thought and teeth look more complex than expected. I am very happy that my research and our collaboration will be supported by the Vidi-grant of the Netherlands Organization for Scientific Research (NWO) in the next five years, enabling us to investigate these early stages of teeth and how the complex system of our own jaws and teeth evolved.” More.
The basic problem this earlier than thought/more complex than thought stuff represents for Darwinian evolution is that it continually diminishes the time frame within which things could somehow just happen by chance. So it is better to just report the facts and flee the scene.
Here’s the abstract:
Theories on the origin of vertebrate teeth have long focused on chondrichthyans as reflecting a primitive condition—but this is better informed by the extinct placoderms, which constitute a sister clade or grade to the living gnathostomes. Here, we show that ‘supragnathal’ toothplates from the acanthothoracid placoderm Romundina stellina comprise multi-cuspid teeth, each composed of an enameloid cap and core of dentine. These were added sequentially, approximately circumferentially, about a pioneer tooth. Teeth are bound to a bony plate that grew with the addition of marginal teeth. Homologous toothplates in arthrodire placoderms exhibit a more ordered arrangement of teeth that lack enameloid, but their organization into a gnathal, bound by layers of cellular bone associated with the addition of each successional tooth, is the same. The presence of enameloid in the teeth of Romundina suggests that it has been lost in other placoderms. Its covariation in the teeth and dermal skeleton of placoderms suggests a lack of independence early in the evolution of jawed vertebrates. It also appears that the dentition—manifest as discrete gnathal ossifications—was developmentally discrete from the jaws during this formative episode of vertebrate evolution. (Public access) – M. Rucklin, P. C. J. Donoghue. Romundina and the evolutionary origin of teeth. Biology Letters, 2015; 11 (6): 20150326 DOI: 10.1098/rsbl.2015.0326
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