Monday, December 20, 2010

A Christmas Caudipteryx Chapter III



In spite of recent finds, there are still several coelurosaur ghost lineages. Using phylogenetics, it's possible to predict whether a certain clade existed at a certain point in time. If phylogenetic analyses are correct (and they might not be), we know that clade simply must have been around at that time. However, we may not find any actual fossils of that clade from that time period. When this happens, we end up with a ghost lineage.

For a long time, Archaeopteryx was the oldest known maniraptor, dating from the Late Jurassic. But Archaeopteryx was an avialian, one of the most derived maniraptors. If avialians were around in the Jurassic, where were all the other Jurassic maniraptor groups? The BAND jumped on this fact, calling it the "temporal paradox" and using it as "evidence" that birds couldn't have descended from dinosaur ancestors. But the BAND were wrong (and still are). The real answer to the "paradox" was that we simply hadn't found the other Jurassic maniraptors. Throughout the last ten years or so these ghost lineages have slowly been filled up. We now have Jurassic deinonychosaurs (Anchiornis, as well as some teeth and an undescribed troodont nicknamed "Lori"), alvarezsauroids (Haplocheirus), and even a possible therizinosaur from the Early Jurassic (Eshanosaurus). The odd group out is the oviraptorosaurs. What did Jurassic oviraptorosaurs look like? Only time will tell.

5 comments:

  1. Hmm. I thought Avimimus was considered an early Oviraptor? Forgive me, I don't know much about Avimimus (aside from the fact that it's portrait in _PDOTW_ is one of the ugly-cutest things ever.)

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  2. Avimimus is a weird, basal oviraptorosaur, but it's from the Late Cretaceous.

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  3. Wait, I'm confused. The characters are typically shown in a modern setting, in which case 100 million years ago would be the Early Cretaceous - Late Cretaceous boundary. Oviraptorosaurs are known from this time. What's up with that?

    - Spinosegnosaurus77/SpongeBobFossilPants

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    1. I remember now. When I began the comic, the characters (besides Skull) were supposed to be actual living animals that had somehow been transported to present day, so 100 million years ago was meant to be 100 million years from the time of Caudipteryx. (That would put things in the Triassic, prior to the appearance of any maniraptors, but Savape was probably rounding up.) Chalk it up to early installment weirdness.

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  4. Uh, I had a reason for that but now I forget. Probably just a miscalculation. Or a really huge error margin.

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