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Panderichthys—a fish with fingers?

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Published: 9 December 2008(GMT+10)

Image by Boisvert et al., ref. 3, p. 1.

Panderichthys’ fin

Figure 1. CT scans of Panderichthys’ fin show that it has a fin structure like Tiktaalik.

Once more, fish-to-tetrapod evolution is paraded around,1,2 this time with a study suggesting that Tiktaalik, the ‘poster boy’ of fish–tetrapod evolution, is not quite all it’s cracked up to be. There’s a new kid on the block, the 90–130-cm-long Panderichthys rhombolepis. Except, Panderichthys isn’t exactly new; it was actually named in 1941.3 And it’s supposedly older too: 385 million years (Ma) old in comparison to Tiktaalik, which is supposedly 380 Ma old. However, a recent study has suggested that Panderichthys’ fin may be closer to tetrapods in morphology than Tiktaalik, 4 although evolutionary theory would predict that tetrapod characteristics would be more recent.

Fishing for fingers

Boisvert et al. have based their analysis on the pectoral fin of one particular Panderichthys fossil, which they reconstructed from a CT scan study of the fossil, which they then used to reconstruct a 3D image of the fossil fin. Panderichthys was found to have multiple ‘digits’ at the end of the bony part of the pectoral fin similar to Tiktaalik’s, which Boisvert et al. made out to be homologous with digits on tetrapod limbs (figure 1). Aside from the general biological5 and theological6 problems with excluding common design, Panderichthys is still unequivocally a fish with fins.

The small distal bones found between Panderichthys and Tiktaalik are nothing in comparison to the changes that need to be made between either of them and a limb, as one of the co-authors of the Nature paper, Per Ahlberg, has admitted before:

‘Although these small distal bones bear some resemblance to tetrapod digits in terms of their function and range of movement, they are still very much components of a fin. There remains a large morphological gap between them and digits as seen in, for example, Acanthostega: if the digits evolved from these distal bones, the process must have involved considerable developmental repatterning.’7

They do not claim that the digits themselves in Panderichthys are any more advanced than Tiktaalik; but they do claim that some of the features of the so-called ‘wrist’ and the positioning of the digits are more tetrapod-like. However, they also acknowledge that Panderichthys and Tiktaalik are close in pectoral fin morphology, exhibiting largely the same bones in comparable proportions. The problem is that neither of them are anything like a tetrapod limb because the wrist morphology is all wrong.8

As Luskin points out, there are a number of things that need to radically change from Tiktaalik to get a proper tetrapod wrist/hand:

  1. ‘Shrink Tiktaalik’s [and Panderichthys’] radius and reposition it so that it articulates other bones further down the limb.
  2. ‘Evolve a radiale [a third bone alongside the ulnare and intermedium that articulates with the radius].
  3. ‘Dramatically repattern, reposition, and transform the existing radials by lining them up, separating them out to form digits.
  4. ‘Evolve metacarpals and phalanges so that there are real digits extending distally from the radius.
  5. ‘Evolve the ‘lotsa blobs’, i.e. evolve other carpal bones between the radius, ulna, and the now-aligned digits to form a real wrist. In other words, evolve the bulk of the wrist-bones.’8

Another important consideration is function. Since these particular fins have never been seen in live operation, there is no reason to suggest that they provide evidence for fish–tetrapod evolution. Coelacanth is a prime example. Before it was known that its limbs were used for deft manoeuvring of the fin, the coelacanth’s limbs were thought to be evidence of the fish–tetrapod transition. Now we know better.9 The situation is no different in Panderichthys.

The illusion of evolution

Boisvert et al. are at the end of the day rather confused as to how and where to place Panderichthys in the evolutionary series:

‘It is difficult to say whether this character distribution implies that Tiktaalik is autapomorphic,10 that Panderichthys and tetrapods are convergent,11 or that Panderichthys is closer to tetrapods than Tiktaalik. At any rate, it demonstrates that the fish–tetrapod transition was accompanied by significant character incongruence in functionally important structures.’4

However, there are no lineages—merely the comparing of finished products to come up with the illusion of a lineage.

They don’t know which of their smorgasboard of just-so evolutionary ‘explanations’ they should use, so they leave the reader with a few possible ones to give the illusion that evolution has it all worked out, even if we don’t. However, there are no lineages—merely the comparing of finished products to come up with the illusion of a lineage. The story as Daeschler et al. described it remains true:

‘Major elements of the tetrapod body plan originated as a succession of intermediate morphologies that evolved mosaically and in parallel among sarcopterygians closely related to tetrapods, allowing them to exploit diverse habitats in the Devonian [emphases added]’12

The problem of mosaic and parallel evolution is that they occur to parts of organisms rather than the whole (mosaic) and that the same thing evolves more than once independently (parallel). Both of these are excuses that are used when common descent fails, and are extremely unlikely to happen.9,13

Conclusion

For all the complex 3D imaging that went into this paper, there really is not much in it. It further confirms that Tiktaalik is an unequivocal fish, related to Panderichthys, and it tells us that fish–tetrapod evolution is a mess. This is not a surprise from a biblical perspective, because evolution fails to explain the evidence, and these fish were created fully functional.

Recommended Resources


References

  1. Primordial fish had rudimentary fingers, PhysOrg.com, 22 September 2008. Return to text.
  2. Bowden, R., Discovery of fish with fingers gives evolution new twist, The Tech Herald, 21 September 2008 Return to text.
  3. Gross, W., Über den Unterkiefer einiger devonischer Crossopterygier (About the lower jaw of some Devonian crossopterygians), Abhandlungen der preußischen Akademie der Wissenschaften Jahrgang 1941 (Treatises of the Prussian Academy of Sciences Year 1941). Return to text.
  4. Boisvert, C.A., Mark-Kurik, E. and Ahlberg, P.E., The pectoral fin of Panderichthys and the origin of digits, Nature, doi:10.1038/nature07339, Published online: 21 September 2008. Return to text.
  5. Sarfati, J., Refuting Evolution 2, Master Books, Green Forest AR, 2002. See chapter 6: Argument: Common design points to common ancestry. Return to text.
  6. Holding, J.P., Not to be used again : homologous structures and the presumption of originality as a critical value, Journal of Creation 21(1):13–14, 2007. Return to text.
  7. Ahlberg, P.E. and Clack, J.A., Palaeontology: A firm step from water to land, Nature 440(7085):747–749, 6 April 2006. Return to text.
  8. Luskin, C., An ulnare and an intermedium a wrist do not make: a response to Carl Zimmer, Discovery Institute, 1 August 2008. Return to text.
  9. Jaroncyk, R. and Doyle, S., Gogonasus: a fish with human limbs? Journal of Creation 21(1):48–52, 2007. Return to text.
  10. Autapomorphy is a cladistic term for a characteristic that is unique to the group, found neither in the groups said to be closest relatives nor in their supposed common ancestor. Features supposedly derived from an autapomorphy in a common ancestor are called synapomorphies. Return to text.
  11. I.e. their common features cannot be explained by inheritance from a common ancestor with such a feature, which would then have been an autapomorphy; such common features are called homoplasies, which are ubiquitous in many alleged transitional series. Return to text.
  12. Daeschler, E.B., Shubin, N.H. and Jenkins Jr, F.A., A Devonian tetrapodlike fish and the evolution of the tetrapod body plan, Nature 440(7085):757–763, 6 April 2006. Return to text.
  13. ReMine, W.J., The Biotic Message: Evolution versus Message Theory, St Paul Science, St Paul, MN, pp. 289–290, 344–346, 1993; and review: Batten, D., Journal of Creation (CEN Tech. J.) 11(3):292–298, 1997. Return to text.

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