Fossil Hunting Trip


Staff member
Moderator (Staff)
Nov 19, 2002
somewhere under the desert sky
Hi Folks,
When it gets too hot in the great western desert, we go fossil hunting in the great Rocky Mts (about 105F in the valley and about 75F on the mountain). This spot is in the Wasatch Range, I find fossil cephalopod molds (first picture) right at the place this picture was taken(second picture).

After a few hours hunting I decided to do my Croc Hunter impression, that's why the third picture is blurry.

I fill the molds I find with liquid latex to get a cast of the shell. The nice thing about liquid latex is it has .6% ammonia added as a drying agent, so I can imagine myself working alongside Steve and Kat while they are playing with a big squid.



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As Steve Irwin would say, "Crikey mate! Ripper!" Kevin, you are the 'Ammonite Hunter'.

That rattlesnake is a very impressive. I'm not surprised the picture is a bit blurry; you've got steadier nerves than me! I think I would have cleared off like lightning. How large was it? How close did you get? And that scenery looks beautiful.

I've managed to find out a little bit of information about Eumorphoceras. This cephalopod is known from both North America and Europe, especially the Texas Barnett formation and examples are known from Yorkshire in the UK. Actually, Europe and North America were very close at this point in time and were actually converging to form part of the later supercontinent Pangea. This goniatite would have inhabited part of the south-west Paleo-Tethys ocean, an area that was diminishing in size.

This animal existed for about 19 million years from 342-323milion years ago which places it in the early to mid Carboniferous period. It has a very discoid shape with thick whorls and a simple suture. This goniatite, (subfamily: Dimorphoceratacea, family Girtyoceratidea) is usually preserved in aragonite.

If anyone is interested in how the surface of the earth has changed via continental drift and wondered where land masses were located in relation to each other at any point in time, this is the place to go:

Paleomap Project

Fascinating stuff!
The nice thing about liquid latex is it has .6% ammonia added as a drying agent, so I can imagine myself working alongside Steve and Kat while they are playing with a big squid.

I think I would have cleared off like lightning.
Right on, that snake looks ready to pounce!

Phil, that link is great -- it even shows outlines for the US states to show where they were way back when! Hard to tell which is which after a while, since they themselves obviously went through land changes as well.

Great pictures Architeuthoceras, thanks!
The little cutey was only about 2 feet (60cm) long. There were three of us surrounding the snake, but, for some reason it kept coming towards me, maybe it could sense something, seeing me stooped over trying to take a picture, walking backwards about to trip over a fallen tree. This is only the third rattler I have run across, and the first time I have had a camera with me to take a picture.
That is some great information on Eumorphoceras Phil, heres some more:

Emorphoceras girtyi Elias 1956, is an index fossil for the middle Arnsbergian stage (Early Carboniferous or Late Mississippian). That means as you work your way up thru rock strata, the first appearance of E. girtyi marks the rocks of Middle Arnsbergian age. Higher up in the rock strata another form of ammonoid will take the place of E. girtyi. E. bisulcatum is the next Eumorphoceras in line but is not used as an index fossil for a variety of reasons, so another form is used, in the Western US this would be Cravenoceratoides nititoides which, like E. bisulcatum, is also found in the UK, so the two areas can be correlated and the rocks dated. This process is used to create biozones, so rocks from all over the world can be correlated and dated.
Rocks of this age in the UK provide a higher resolution for zonation than most other areas, so some are proposing to make those rocks a Global Stratotype, or a place where all other rock strata can be refered to. See Riley, N.J. et. al., 1994, Geochronometry and geochemistry of the European mid-Carboniferous boundary global stratotype proposal, Stonehead Beck, North Yorkshire, UK: Annales de la Societe Geologique de Belgique, v. 116 p. 275-289.
The following picture file of a correlation chart showing where E. girtyi fits into things comes from Titus, A. L., 2000, Late Mississippian (Arnsbergian Stage E2 Chronozone) Ammonoid Paleontology and Biostratigraphy of the Antler Foreland Basin, California, Nevada, Utah, UGS Bull. 131


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Wow! Thanks for the detail.

I had no idea that UK rocks are potentially to be used as a form of baseline in global stratigraphy. Is this because lowland UK has had a very turbulent geological history, with many periods of flooding by shallow seas? Zonation must be very well defined, I suppose.

Do you by any chance have a similar chart for the Albian in the early Cretaceous? I'd be quite curious to see this as most of the ammonites I find are datable to 100mya and are mostly Hoplites and other members of the Hoplitidae.

Cheers as ever!
Got out in the desert yesterday and thought I would post a couple of pics just to show how things went.

The Ammonoid is Girtyoceras meslerianum, about 327my old. From a concretion that contained a few other ammonoids. The formation it was found in is the Lower Carboniferous (Upper Mississippian) Chainman Shale, it lies just above the Joana Limestone, which is pictured with my truck in the photo below.

Also caught this pic of a blue bird as I got close to it's nest, never did see the nest, but the bird wouldnt leave me alone. :biggrin2:


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Spectacular pictures as always Kevin. That's a very striking bird, any idea what it is?
Another Girtyoceras, but this one retains some of the shell. And also a bus for scale (the space took up by the pixel used for the dot is probably about 10x the actual size of the fossil :wink:)


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Ha ha! Great picture there Kevin. That really puts the fossil into perspective!

Those growth lines are really well preserved; have any conclusions been drawn as to how long goniaties may have lived based on examinations of these features?
Phil said:
have any conclusions been drawn as to how long goniaties may have lived based on examinations of these features?
Ive been looking for something Phil, no luck. Studies have been done on Nautilus, and judging from some of the repaired shells of other ammonoids on the ammonoid pathology thread, i would have to think that it didnt take very long for an ammonoid to grow a shell. The baby snails in my garden are full grown by the end of summer. I dont know if ammonoids would have lived as long as nautiloids, or grew shells as fast as snails, but I imagine they would be mature within a year and live for at least two years, some of the larger ones living longer (no proof or evidence, just speculation :wink: ) I'll keep looking.
Thanks very much for checking for me Kevin. This is just a thought but perhaps if ammonoids generally lived nearer the surface in warmer waters with more sunlight than the deep water Nautilus, perhaps their metabolism worked at a faster rate? Perhaps then their growth rate would be faster and average lifespan would be shorter than Nautilus? Perhaps also the early orthocone nautiloids grew much quicker than Nautilus as they also tended to live in shallower water and inhabited a greater variety of habitats in varied forms.

I'm sure I read once that ammonoid lifespan has been estimated at anywhee between 4-36 years but I can't find the reference right now. I will report back if I can find it.

Thanks as ever!

Bucher, H., J. Guex, N. H. Landman, and S. M. Klofak. 1996. Mode and rate of growth in ammonoids. in Landman, N. H., K. Tanabe, and R. A Davis (eds.), Ammonoid Paleobiology, Plenum Press, New York, pp. 408-463.

A summary

Time to reach maturity (from several studies)

Periodicity of ornamentation
1-20 years avg. 5
Seasonality (septal spacing)
1-7 years
Size classes
5-6 years
1-7.5 years

Water Depth

Shallow @ 5 years
Deep @ 10-15 years

Length of life after maturity

Shallow water forms: possibly semelparous died after reaching maturity and mating
Deep water forms: iteroparous possibly mated several times and lived several years after.

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