BSCI 392 Lecture Notes - Lecture 24: Mosasaur, Durophagy, Fractal Dimension
29 Mar 2017
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Bsci392 lecture 24: a diverse lot of shelled cephalopods. Straight or planispiral external shell: chambers separated by septa, siphuncle = siphonal tube adjusts gas to buoyancy of shell. Carnivorous: grasping tentacles, radula to scrape things off of rocks, beak characteristic of molluscs, though some slugs have evolved it. Nautiloids = most diverse paraphyletic group, stem group leading to more derived forms like ammonoids. External shell of ammoinoid has been lost, so much more complex attachment functions. Aptychi = beak, heavily calcified: unique: dual function for feeding and protection, the shape of the aptychi perfectly matches the shape of the opening of the shell. Huge, exploited planispiral growth more effectively than nautiloids: first photo is not the whole shell, the body cavity would extend even further out in a ring. Something about ammoinoids allowed them to have more diverse body shapes: fractal geometry.
