A new transitional fossil

April 23, 2009 • 11:03 am

In the latest issue of Nature is a report on a pretty amazing transitional fossil: Pulija darwini, a relative of modern seals, but one that was a “pre-seal” in that it walked on land.  It was related to but not on the direct line of ancestry to modern pinnipeds. Pujila appears to have been much like a large otter.  It’s already been covered amply on several other blogs, so I’ll just refer you to the official Pujila website (be sure to manipulate the three-dimensional model and the three dimensional skull), which has all the information, and a disquisition on the beast on Ed Yong’s blog Not Exactly Rocket Science.


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Reconstuction of animal from Pujila website, reconstruction of skeleton from Nature paper

A semi-aquatic Arctic mammalian carnivore from the Miocene epoch and origin of Pinnipedia

Natalia Rybczynski, Mary R. Dawson & Richard H. Tedford

Summary of the article: Modern pinnipeds (seals, sea lions and the walrus) are semi-aquatic, generally marine carnivores the limbs of which have been modified into flippers. Recent phylogenetic studies using morphological and molecular evidence support pinniped monophyly, and suggest a sister relationship with ursoids (for example bears) or musteloids (the clade that includes skunks, badgers, weasels and otters). Although the position of pinnipeds within modern carnivores appears moderately well resolved, fossil evidence of the morphological steps leading from a terrestrial ancestor to the modern marine forms has been weak or contentious. The earliest well-represented fossil pinniped is Enaliarctos, a marine form with flippers, which had appeared on the northwestern shores of North America by the early Miocene epoch. Here we report the discovery of a nearly complete skeleton of a new semi-aquatic carnivore from an early Miocene lake deposit in Nunavut, Canada, that represents a morphological link in early pinniped evolution. The new taxon retains a long tail and the proportions of its fore- and hindlimbs are more similar to those of modern terrestrial carnivores than to modern pinnipeds. Morphological traits indicative of semi-aquatic adaptation include a forelimb with a prominent deltopectoral ridge on the humerus, a posterodorsally expanded scapula, a pelvis with relatively short ilium, a shortened femur and flattened phalanges, suggestive of webbing. The new fossil shows evidence of pinniped affinities and similarities to the early Oligocene Amphicticeps from Asia and the late Oligocene and Miocene Potamotherium from Europe. The discovery suggests that the evolution of pinnipeds included a freshwater transitional phase, and may support the hypothesis that the Arctic was an early centre of pinniped evolution.

11 thoughts on “A new transitional fossil

  1. Puijila darwini (pronounced: pew yee lah) might go well as an appetizer for Paella (pie eh ya) if it is not too chewy.

  2. This biblical creationist loves when fossils of water mammals are found showing a original land connection.
    All water mammals are in fact post flood creatures from off the ark that quickly adapted to living in the water. These are not intermediate fossils but rather another variety of the kind still living more on land then present ones. No evolution but rather instant adaptation to niches.
    Its a poverty of evolution to grasp at water mammals to show actual anatomical change between species when if evolution was true it would be the most common thing in the fossil record. Its clear to this creationist that water mammals came from the land.
    It fits fine in creationist models of speciation even if many creationists see it differently.

    1. Robert Byers, you clearly have no knowledge of evidence and no capacity for logic or critical thinking. Your statements are incoherent.

      I suggest you first learn how to read the English language and then actually read an article before you comment on it.

  3. @Robert Byers:

    You either:

    a) have an incomplete knowledge of paleontology, molecular biology and cladistics
    b) didn’t read the article
    c) all of the above
    d) none of the above

    Which is it? If you claim option d, I suggest you back that up with something other than your special pleads about “instant adaptation” to make plausible your delusion about a god-inspired boat.

    If in fact the answer is a, b or c (and my money is on the latter option), I suggest you read up on the actual sicence behind this discovery before you comment any further. You’d be doing not only us, but also yourself (actually your entire movement) a huge favor. Thanks!

  4. Arne
    I say the biblical boundaries are solid as evidence in determining the past.
    Then there is the data in the field.
    These fossils are above the k-t line and to this creationist clearly post flood.
    So these creatures must only be from leaving the land after the flood.
    Indeed there are no fossils below the k-t line.
    Then it requires special cases for fossilization.
    Therefore these cases would be few or one. Therefore its just a snapshot.
    So one must conclude its just a variety of seal living alongside the other types.
    No evolution but mere adaptation.
    So this adaptation must be instant and allow these creatures to occupy niches as found.
    Flippers or feet are a minor change.

    Creationism can accept fine water mammals having a land origin. I welcome it.
    Instant adaptation can explain their quick sea bourne life without intermediates being a factor. However there would be varieties all along the way from landlover to sealover.

    1. @Robert Byers:

      I’m sorry, but your preposterous flood hypothesis flies in the face of every geological and paleontological finding from the last century or so. Despite all your handwaving I still contend that you have only a superficial understanding of the current evidence in support of the theory of evolution, but again I welcome you to prove me wrong.

      I can only repeat my original suggestion that you pick up a book. Oh, and please check out the text as well as the pretty pictures before you make your decision. Best of luck to you!

    2. I repeat my statements that Robert Byers’ statements are incoherent and illogical. It appears that he is cutting and pasting from documents for which he clearly has no understanding. What I now wonder is whether he is really this ignorant or is this just a ruse by malicious creationist.

  5. You’ve missed Robert Byer’s explanation that mammals became marsupials because “after the flood” they were “in a hurry”

    To claim he doesn’t make sense, is a very polite way putting it.

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