The cover of New Mexico Bureau of Mines & Mineral Resources Memoir 32 (1977), and the description from inside the front cover (below) (both used with permission from the New Mexico Bureau of Geology and Mineral Resources). Showing the contented and smiling face of an orthoconic cephalopod with cameral (or siphonal) deposits counterweighting the gas-filled phragmocone letting it float horizontally and getting its face "out of the mud". The non-counterweighted forms with disgusted frowns floating vertically (or about to). I've had a smile on my face ever since first seeing this paper over 30 years ago just thinking of how happy the nautiloids on the cover were.
All that changed the other day when I got a copy of Peterman & Ritterbush 2021 Vertical escape tactics and movement potential of orthoconic cephalopods PeerJ 9:e11797. Which lead to: Peterman, D.J., Barton, C.C., and Yacobucci, M.M., 2019 The hydrostatics of Paleozoic ectocochleate cephalopods (Nautiloidea and Endoceratoidea) with implications for modes of life and early colonization of the pelagic zone Palaeontologia Electronica Article number: 22.2.24
Needless to say, I now have to re-arrange the thoughts of horizontal nautiloids having smiles and put the smile on the vertical nautiloid.
This might be just as hard as giving up the Geosynclinal Theory I was taught back in 1972.
:)
