Fossil Hunting Trip

chrono_war01

Colossal Squid
Supporter
Joined
Oct 7, 2004
Messages
2,580
Reaction score
4
Tiny-weenie-itsy-bitsy speck of a fossil.
 

Phil

TONMO Supporter
Supporter
Joined
Nov 19, 2002
Messages
3,034
Reaction score
16
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?
 

Architeuthoceras

Architeuthis
Staff member
Moderator
Joined
Nov 19, 2002
Messages
2,417
Reaction score
111
Location
somewhere under the desert sky
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.
 

Phil

TONMO Supporter
Supporter
Joined
Nov 19, 2002
Messages
3,034
Reaction score
16
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!
 

Architeuthoceras

Architeuthis
Staff member
Moderator
Joined
Nov 19, 2002
Messages
2,417
Reaction score
111
Location
somewhere under the desert sky
RIGHT UNDER MY NOSE :oops:

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
Epizoans
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.
 

Architeuthoceras

Architeuthis
Staff member
Moderator
Joined
Nov 19, 2002
Messages
2,417
Reaction score
111
Location
somewhere under the desert sky
It finally cooled off enough I could get out and look for some fossils. Found this Forresteria alluaudi in a large concretion. The first pic shows it as found in the concretion, the phragmocone was filled with calcite that had started to crumble so I had to soak it with super-glue. The second pic shows the fossil after preparation. You can see the last chamber and the last suture. The third pic is just a view showing the side that was exposed.
 

Attachments

Architeuthoceras

Architeuthis
Staff member
Moderator
Joined
Nov 19, 2002
Messages
2,417
Reaction score
111
Location
somewhere under the desert sky
Some other fossils from the same concretion. Alot of Baculites mariasensis in the first pic. A bivalve (Inoceramus) in the second. And a view showing the concretion atop the teepee butte that formed around it.
 

Attachments

Phil

TONMO Supporter
Supporter
Joined
Nov 19, 2002
Messages
3,034
Reaction score
16
Very nice prep job Kevin.

Just how old is this ammonoid?
 

Architeuthoceras

Architeuthis
Staff member
Moderator
Joined
Nov 19, 2002
Messages
2,417
Reaction score
111
Location
somewhere under the desert sky
Forresteria alluaudi is an index fossil for the Middle Coniacian (Late Cretaceous) F. alluaudi Zone, aka Scaphites preventricosus Zone, about 88.5mya. In Europe it may be refered to the Peroniceras tridorsatum Zone.
This is another one of those "Polymorphic" forms having about 10 different genera, sub-genera and species as synonyms. The fossil shown was first described as Barroisiceras (Forresteria) forresteri, it is the more robust and strongly ornamented form, Barroisiceras (Alstadnites) sevierense was described as a medial form, and Barroisiceras (Harleites) castellense was descibed as the compressed, feebly ornamented form. It keeps me wondering why the Cardiocerids and Hoplitids are not lumped together into a single taxon, are there just more specimens to study or more studiers to the specimens, are the lumpers and splitters lumping and splitting 8-)
 

Similar threads




Latest posts

Forum statistics

Threads
19,591
Messages
203,047
Members
8,481
Latest member
718Cephalopod

Monty Awards

TONMOCON IV (2011): Terri
TONMOCON V (2013): Jean
TONMOCON VI (2015): Taollan
TONMOCON VII (2018): ekocak

About the Monty Awards
Top