Ammonite Food Viewed by X-ray Eyes

Authors Kruta et al (2011, the Role of Ammonites in the Mesozoic Marine Food Web Revealed by Jaw Preservation, Science, vol. 331, p. 70-72; also see Tanabe, 2011, The Feeding Habits of Ammonites, Science, vol. 331, p. 37-38) utilize synchrotron x-ray microtomography, the newest wonder-tool of palaeontology - to examine the innards of a small handful of Baculites, a squid-like creature with an external shell, extremely common in Late Cretaceous deposits of North America but with a much earlier origin. What they find is the buccal mass - the upper and lower jaw, and radula - which is considerably less preserved. Within one, they "document a larval shell of a gastropod and three fragments of crustaceans." Based on jaw morphology (which is often related to diet) they are able to determine that "are incompatible with biting and tearing large prey". The "buccal apparatus in Baculites" they contend "is an adaptation for capturing and eating small organisms in the water column" rather than the more aggressive snagging and consuming large prey. Favoring small organisms may have been their downfall at the end of the Cretaceous Period with "the marked ... decline in several groups of plankton."
It will be interesting to see if 1) synchrotron x-ray microtomography has the same capabilities across a wider spectrum of ammonoid species, and 2) if the feeding strategy remains the same. Whatever, this new 'paleo-toy' has great potential.