references for ammonite species ID by suture lines?


TONMO Supporter
Staff member
Mar 8, 2004
Hi, all.

When I was at the Hilo Farmers Market the a few weeks ago, the local hippie-crystal-cool-rock dealer had a number of ammonites for sale, and I bought 3 specimens I thought were nifty (although I couldn't really ID them particularly at all.) I chose 3 that had some view of the suture lines, although no complete suture all the way around.

Between Kevin's and Phil's articles and the Monks and Palmer Ammonites book, I know that there's a wide variety of complex suture lines in different species, and that there's a standard way to draw the suture line "unwrapped," but I'm wondering if there's an online reference that allows one to compare a suture line to species to find a match somehow? It looks like wikipedia is starting a big list-o-ammonites here: but it doesn't include suture lines and it's pretty spares except in the A's.

I assume that these are likely to be common and boring specimens, and I'm not sure if they were polished in a way that all you fossilhounds would scoff at, but I figured it'd be a good learning experience to try and ID them... she thought they were all from Madagascar, but wasn't positive... she tended to get Madagascar, Indonesia, and Malaysia mixed up...

I'm also curious if I got a good deal, or if these are a dime a dozen... I think I paid $80 for 3 prepared specimens: $15 for a small one that's the least prepared, $30 for a similar one that's cut into two halves down the center, and $35 for a big polished one that's got most of the shell polished away, but has much more visible suture lines. They might all be the same species, at least they're all planispiral, involute, oxycone, although the one that's cut in half seems to have less ribbing. They all have typical-looking complex septa showing in at least a small area. Ribbing is simple and slightly curved on the 2 that have a lot, like pictures of scaphites I've seen, and any lappets are long gone. There's some iridescence in the remaining shell parts.

(where do you measure diameter, anyway? the big one is 8cm perpendicular to the aperture, 10cm including the aperture. The others are around 2cm and 3cm)

more pics here.



Colossal Squid
Mar 23, 2005
I have a few, my biggest is 5" by 6". My others range from 1 1/2" by 2" to 3 1/2" by 4". They are all polished on the cut face, some polished on the outer surface, some not. The big one was $12.00, the smaller ones were $6.00 each. I wish I knew what happened to all the ones we dug out of our backyard in Texas. some of them were a foot across. Erich??? :earlyammo


Staff member
Nov 19, 2002
somewhere under the desert sky
monty;92110 said:
where do you measure diameter, anyway? the big one is 8cm perpendicular to the aperture, 10cm including the aperture. The others are around 2cm and 3cm
Measure the diameter across the widest part, from the end of the aperture on the ventral side, thru the umbilicus, to the opposite ventral side. The 10cm measurement would be the one to use.

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