Re: Paronychodon-related questions

[Sam Girouard <sampgir@premier1.net>]

Phil Bigelow wrote:

>I don't know; however you might be interested to know that
>some pterosaur teeth are found in marine facies rocks.
>Some of these pterosaur teeth *vaguely* resemble plesiosaur teeth
>(see my response and ref. to your #7, below).

        I have a hunch that a lot of teeth called pterosaur teeth in marine
sediments are just really big Enchodus teeth, but a few of them look pretty
pterosaur-ish.

>I am sure someone has already beat me to the punch on mentioning
>Spinosaurids as possessing multiple longitudinal ridges on their
>enamel (see a ref. below).
>I don't know about Baryonyx. Perhaps someone else knows.

        Yup, Baryonyx has the ridges (more on that further on down this post).

>Many species of fossil crocs and 'gators also have
>very strongly developed multiple longitudinal
>ridges on their teeth, but the chances of confusing
>these teeth with those from other taxa is quite low.

        Agreed. These ridges are very fine, and nothing like those in 
Paronychodon.

>Spinosaurids often have extremely fine denticles, some so fine
>in fact, that some teeth appear to be serration-less
>without magnification. Kellner and Mader (1997) found a tooth with
>(supposadly) no serrations.

        I picked up that paper today, and I have no idea how they decided that 
the
tooth was spinosaurid as opposed to a sarcosuchid crocodile. The tooth was
"elliptical in cross section," and unserrated to boot. But they could well
be right.

>The following is only speculation on my part, but I wonder if
>there is a relationship between the evolution of
>multiple longitudinal ridges on enamel and a general evolutionary
>fining (or loss) of denticles on the carinae.

        Could very well be, Baryonyx has "fluting" on the lingual sides of its
teeth, and it has "very fine" denticles, (Charig and Milner, 1986);
Ceratosaurus has the ridges but has rather medium-grade denticles (see the
pic in any of Glut's books), Euronychodon has the striations but lacks
denticles altogether(Antunes and Sigogneau-Russell, 1991), and the list
goes on...
        My question is, what is the reason for having ornamented crowns and
smaller/no denticles? From an engineering standpoint, I could see how the
longitudinal striations could strengthen the tooth. Examples would be the
internal structure of packing cardboard, corrugated steel sheets, aircraft
parts (look at the fuselage of the old German Junkers 52 transports, or
even the wings of the SR-71), and last but not least plastic tequila
bottles... (yay!)

>>9. Does anyone know of any isolated theropod teeth occurring in marine
>>sediments?>>
>
>Horner's (1979) census of the Dinosauria from the marine Bearpaw Shale
>contained no theropod material.  I am not aware of any updates to
>this now rather dated list.

        None that have been published, to my knowledge. I have a copy of that
particular paper, it's not just on the Bearpaw but all marine occurrences
of dinosaurs known at the time (a pretty short list). Off the top of my
head, I can think of a few marine occurrences of theropods since Horner's
paper; Irritator from South America (Martill et al., 1996), the "Montgomery
Theropod" (the albertosaur from the Mooreville Chalk in Alabama), several
sites in the eastern U.S., I think a couple of scraps from Japan too.

References:

(as a few of you may of noticed, only socially pathological retrobates like
Phil and I have the time to reference our postings!)

Antunes, M. T., et Sigogneau-Russell, D., 1991. Nouvelles donnees sur les
Dinosaures du Cretace superieur du Portugal. Comptes Rendusdes Seances de
l'Academie des Sciences, Paris, 212, Serie II, pp. 113-119.

Charig, A. J., and Milner, A. C., 1986. Baryonyx, a remarkable new theropod
dinosaur. Nature, 324, pp. 359-361.

Horner, J. R. 1979. Upper Cretaceous dinosaurs from the Bearpaw shale
(marine) of south-central Montana with a checklist of upper Cretaceous
dinosaur remains from marine sediments in North America. Journal of
Paleontology, volume 53(3):566-577.

Kellner, A. and Mader, B.J. 1997.  Archosaur teeth from the Cretaceous of
Morocco. Journal of Paleontology 71(3):525-527.

Martill, D. M. et many al, 1996. A new crested maniraptoran dinosaur from
the Santana Formation (Lower Cretaceous) of Brazil. Journal of the
Geological Scoeity, London, 153 pp. 5-8.