The Evolution and Development of Cephalopod Chambers and Their Shape

摘要: The Ammonoidea is a group of extinct cephalopods ideal to study evolution through deep time. the planispiral shell and complexly folded septa in ammonoids has been thought have increased functional surface area chambers permitting enhanced metabolic functions such as: chamber emptying, rate mineralization growth rates throughout ontogeny. Using nano-computed tomography synchrotron radiation based micro-computed tomography, we present first ontogenetic changes volume ratios phragmocone several phylogenetically distant extant cephalopods. Contrary initial hypothesis, do not possess persistently high relative area. Instead, higher earliest ontogeny when compared Spirula spirula. quicker potential emptying chamber; would theoretically permit faster growth. This supported by siphuncular ratio collected for ammonite Amauroceras sp. either S. spirula or nautilids. We demonstrate that curvature increases with greater septal complexity increasing refilling rates. further show unique relationship between ammonoid shape size does exist view function also implications internal coleoids, relating this event decoupling soft-body