Wednesday, November 23, 2011

Pterosaur teeth are like bird teeth

Pterosaur teeth:
http://1.bp.blogspot.com/_RdSbs0-97Pw/S5oAy1xtuxI/AAAAAAAAB2s/jYQ-GusuYVE/s400/PterosaurTeeth.jpg



Here is a theropod dinosaur tooth:
http://australianmuseum.net.au/image/Theropod-dinosaur-tooth/
"SEM of theropod dinosaur tooth, showing serrated edge."





http://www.palaeodiversity.org/pdf/03/Palaeodiversity_Bd3_Nesbitt.pdf
The presence of an external mandibular fenestra, along with morphological evidence elsewhere in the body of pterosaurs (serrated teeth, antorbital fossa present, fourth trochanter on the femur present), supports a placement of Pterosauria within Archosauriformes and is consistent with a position within Archosauria.

In several pterosaurs the medial or first premaxillary tooth was procumbent
[excessive inclination of the incisor teeth toward the lips]. It angled forward as well as downward. In B St 1967 I 276 (No. 6 of Wellnhofer 1970), the tiniest pterosaur, the anterior premaxillary tooth was procumbent. 

 http://en.wikipedia.org/wiki/Deinonychosauria
The teeth of deinonychosaurs were curved and serrated, but not blade-like except in some advanced species such as Dromaeosaurus albertensis. The serrations on the front edge of deinonychosaur teeth were very small and fine, while the back edge had serrations which were very large and hooked.[3] 
https://en.wikipedia.org/wiki/Oviraptorosauria
The most primitive members have four pairs of teeth in the premaxillae, such as in Caudipteryx[9] and in Incisivosaurus they are enlarged and form bizarrely prominent bucktoothed [procumbent] incisors.

http://blogs.scientificamerican.com/tetrapod-zoology/yi-qi-is-neat-but-might-not-have-been-the-black-screaming-dino-dragon-of-death/
The scansoriopterygid skull is short-faced and robust, the anterior end of the lower jaw is slightly downturned, and the teeth are procumbent.
http://en.wikipedia.org/wiki/Yi_(dinosaur)
[Yi qi] Like other scansoriopterygids, the head was short and blunt-snouted, with a downturned lower jaw. Its few teeth were present only in the tips of the jaws, with the four upper front teeth per side being the largest and slightly forward-pointing, and the front lower teeth being angled even more strongly forward.[1] 
https://en.wikipedia.org/wiki/Oviraptorosauria
The most primitive members have four pairs of teeth in the premaxillae, such as in Caudipteryx[9] and in Incisivosaurus they are enlarged and form bizarrely prominent bucktoothed incisors

9 comments:

  1. http://www.scientificamerican.com/article.cfm?id=mutant-chicken-grows-alli
    The mutant chickens Harris studied bear a recessive trait dubbed talpid2. This trait is lethal, meaning that such mutants are never born, but some incubate in eggs as long as 18 days. During that time, the same two tissues from which teeth develop in mammals come together in the jaw of the mutant embryo--and this leads to nascent teeth, a structure birds have lacked for at least 70 million years.
    "They don't make a molar," explains development biologist John Fallon, who oversaw Harris's work. "What they make is this conical, saber-shaped structure that is clearly a tooth. The other animal that has a tooth like that is an alligator."

    ReplyDelete
  2. What can make this confusing is that some fossils that had serrated teeth are incorrectly labeled as maniraptors.
    This misclassification is made solely due to the assumption that that they were related to dinosaurs that had serrated teeth.
    Those fossils labeled as "maniraptors" would not (and should not) be classified as maniraptors.

    This is a quite common tendency. Researchers classify fossils based solely on the ASSUMPTION of their lineage.

    Frances James makes exactly this point in her very insightful article:
    http://www.bio.fsu.edu/James/Ornithological%20Monographs%202009.pdf


    Also for reference:
    http://www.encyclopediajr.com/wikiarticle/c/a/u/caudipteryx.php
    While most scientists consider Caudipteryx hard evidence for the dinosaurian ancestry of birds, some scientists (e.g. Alan Feduccia) claim that Caudipteryx (along with all other maniraptorans) are not dinosaurs at all, but birds which evolved from a non-dinosaurian ancestor. They note that oviraptorosaurian fossils (and Caudipteryx in particular) have short tails, similar to the bird Confuciusornis, and skulls which show many birdlike features that are not found in theropods. Stomach stones were present in the Caudipteryx fossil, which indicate that these were herbivores, resembling Enantiornithes and flightless birds. The fossils also lack the serrated teeth typical of theropods. Feduccia and mammalian paleontologist Larry Martin believe these fossils are the remains of flightless birds that evolved from a flying ancestor, probably Archaeopteryx (Martin & Czerkas, 2000). This view is supported by other researchers who consider birds to be descendents of dinosaurs, most notably Gregory S. Paul (2002), Lu et al. (2002), and Maryanska et al. (2002).

    ReplyDelete
  3. Here is an example:
    http://news.bbc.co.uk/2/hi/science/nature/3659783.stm
    "Seven fossil dinosaur teeth unearthed on the Isle of Wight belong to raptors
    The teeth represent only the second example of velociraptorines in the UK and suggest the animals from which they came were surprisingly large.
    Mr Sweetman, a postgraduate student at Portsmouth University, found the first tooth in 1972. Since then he has collected three more. A further three teeth came from a private collector."

    http://en.wikipedia.org/wiki/Velociraptorinae
    While most velociraptorines were generally small animals, at least one species may have achieved gigantic sizes comparable to those found among the dromaeosaurines. So far, this unnamed giant velociraptorine is known only from isolated teeth found on the Isle of Wight, England. The teeth belong to an animal the size of dromaeosaurines of the genus Utahraptor, but they appear to belong to a velociraptorine, judging by the shape of the teeth and the anatomy of their serrations.[3]

    ReplyDelete
  4. http://en.wikipedia.org/wiki/Utahraptor
    This evidence comes from phylogenetic bracketing, which allows paleontologists to infer traits that exist in a clade based on the existence of that trait in a more basal form.

    This is all based on ASSUMPTIONS. If those assumptions are wrong this gives an incorrect result of course. It is not based on evidence.

    ReplyDelete
  5. Let's begin with the idea that the following are not maniraptors:
    - the unnamed giant velociraptorine based on isolated serrated teeth found on the Isle of Wight, England.
    - Utahraptor
    - Achillobator
    - Dromaeosaurus

    Here is the assertion that needs to be analyzed:
    http://en.wikipedia.org/wiki/Dromaeosauridae
    The dromaeosaurid body plan includes a relatively large skull, serrated teeth, narrow snout, and forward-facing eyes which indicate some degree of binocular vision.[6]

    ReplyDelete
  6. Some pterosaurs had serrated teeth.
    http://www.palaeodiversity.org/pdf/03/Palaeodiversity_Bd3_Nesbitt.pdf

    So the issue is not serrated teeth. It is the other aspects of the tooth.
    In the development from pterosaur to primitive bird to modern bird the teeth are no longer expressed. But when artificially forced to express they are similar to pterosaur teeth. For example the nature of the roots and being "saber-shaped".

    http://www.jstor.org/pss/4085810
    Avian dentitions also pose a problem for the dinosaur hypothesis. While theropod teeth are serrated and have straight roots, avian teeth, like those of crocodilians, are unserrated, with constricted bases and expanded roots.

    ReplyDelete
  7. http://www.jstor.org/pss/4085810
    According to this reference, for a long time, folks thought that birds evolved from "pseudosuchian archosaurs".
    Then that fell from fvour and was replaced by "a direct derivation of birds from theropod dinosaurs".

    When that was shown to be untenable, some folks moved to the idea that birds evolved from crocodiles. (Yes, crocodiles).
    But then that idea fell from favour and the folks moved back to some purported vague dinosaur ancestry. But they do not give any specifics so that it could never be evaluated.

    Perhaps someone could do us all a favour and tell us what the current thinking is about the purported dino to bird lineage.

    I have proposed a lineage. What is the alternative?

    ReplyDelete
  8. http://www.jstor.org/pss/4085810
    According to this reference, for a long time, folks thought that birds evolved from "pseudosuchian archosaurs".
    Then that fell from favour and was replaced by a purported "direct derivation of birds from theropod dinosaurs".

    When that was shown to be untenable, some folks moved to the idea that birds evolved from crocodile type ancestors. (Yes, crocodiles).
    But then that idea fell from favour and the folks moved to some purported vague dinosaur ancestry. But they do not give any specifics so that it could never be evaluated.

    Perhaps someone could do us all a favour and tell us what the current thinking is about the purported dino to bird lineage.

    I have proposed a lineage. What is the alternative?

    ReplyDelete
  9. If anyone wishes to comment, please include a made-up name if you wish to use "Anonymous".

    ReplyDelete