If you're reading this, you probably know what an ammonite is. You might even have an automatic response along the lines of "extinct squid-like cephalopods in coiled chambered shells" queued up. To be perfectly fair, most ammonites did go for the flat spiral look. A handful, though, rebelled. Most of them conveniently belong to the same suborder, the Ancyloceratina. These non-conformist cephalopods are called heteromorph ammonites, "other forms". They are particularly a feature of all of those Cretaceous-age shallow continental seas. Here are a few examples.
|Baculites grandis, image from Wikimedia Commons.|
|Hamites as restored by Neale Monk, image from Wikimedia Commons.|
|Hyphantoceras orientale, image from Wikimedia Commons.|
|Several Nipponites mirabilis, image from Wikimedia Commons.|
|Nostoceras malagasyense, image from Wikimedia Commons.|
|Scaphites, from Wikimedia Commons.|
|Turrilites costatus, about as unfair a fossil as you'd ever want to see; image from Wikimedia Commons.|
Some of these heteromorph ammonites are easier to figure than others. Baculites, for example, could probably do more or less what the orthoconic nautiloids of the Paleozoic did, and Turrilites seems to have cleverly combined the powers of a squid with the powers of a snail. Others are more difficult. What in the world was Nipponites up to? Presumably, whatever the stranger heteromorphs were doing did not rely on speed and streamlined forms.
By the way, if you're in the neighborhood in a couple of weeks, I'll be doing an event for the Minnesota side of Interstate State Park at 10 AM, September 23. We'll be looking at the Cambrian rocks, so be prepared to hear me say "Mazomanie" a lot.
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