50
6
November
1327
1333
10.1111/j.1475-4983.2007.00708.x
MUTVEI, H., ZHANG, Y., DUNCA, E. 2007. Late Cambrian plectronocerid nautiloids and their role in cephalopod evolution. Palaeontology, 50, 6, 1327–1333.
Harry Mutvei, Yun-Bai Zhang and Elena Dunca Numerous plectronocerid nautiloids appear in the Upper Cambrian of China. We have restudied their siphuncular structure, first described some 20 years ago. The siphuncle is characterized by: (1) long and holochoanitic septal necks dorsally but short and recurved necks laterally and ventrally; (2) strongly expanded connecting rings laterally; (3) two calcified layers in each connecting ring, outer spherulitic-prismatic and inner compact, the latter perforated by numerous pore canals; and (4) highly oblique siphuncular segments. The strongly expanded lateral sides of the connecting rings, together with the highly oblique course of the siphuncular segments, considerably enlarged the surface area of the connecting rings in each chamber, thereby increasing the transport capacity of cameral liquid. Thus, from their first appearance, plectronocerid nautiloids had developed a siphuncle for the replacement of cameral liquid with gases, and this system had a better and a more sophisticated design than that seen in stratigraphically younger nautiloids. However, their small orthoconic or slightly cyrtoconic shells were not well adapted for jet-powered swimming.- CHAMBERLAIN, J. and MOORE, W. 1982. Rupture strength and flow rate of Nautilus siphuncular tube. Paleobiology, 8, 408–425.
- CHEN JUN-YUAN and TEICHERT, C. 1983. Cambrian Cephalopoda of China. Palaeontographica, A, 181, 1–102.
- CHEN, J. Y., TSOU, S. P., CHEN, T. E. and QI, D. L. 1979. Late Cambrian cephalopods of North China: Plectronocerida, Protactinocerida (ord. nov.) and Yanhecerida (ord. nov.). Acta Palaeontologica Sinica, 18, 1–24.
- FLOWER, R. H. 1964. The nautiloid order Ellesmeroceratida. New Mexico Institute of Mining and Technology, Memoir, 12, 234 pp.
- FLOWER, R. H. and KUMMEL, B. 1950. A classification of the Nautiloidea. Journal of Paleontology, 24, 604–616.
- FREY, R. C. 1995. Middle and Upper Ordovician cephalopods of the Cincinnati region of Kentucky, Indiana and Ohio. United States Geological Survey, Professional Paper, 1066, P1–P119.
- FURNISH, W. M. and GLENISTER, B. F. 1964. Nautiloidea – Ellesmerocerida. K129–K159. In MOORE, R. C. (ed.). Treatise of invertebrate paleontology, Mollusca (3). Geological Society of America, Boulder, CO, and the University of Kansas Press, Lawrence, KS, 519 pp.
- KRÖGER, B. and MUTVEI, H. 2005. Nautiloids with multiple paired muscle scars from Lower–Middle Ordovician of Baltoscandia. Palaeontology, 48, 781–791.
- MUTVEI, H. 1964. On the secondary internal calcareous lining of the wall of the siphonal tube in certain fossil ‘nautiloid’ cephalopods. Arkiv för Zoologi, 16, 375–424.
- MUTVEI, H. 1971. The siphonal tube in Jurassic Belemnitida and Aulacocerida (Cephalopoda: Coleoidea). Bulletin of the Geological Institutions of the University of Uppsala, New Series, 3, 27–36.
- MUTVEI, H. 1997a. Characterization of actinoceratoid cephalopods by their siphuncular structure. Lethaia, 29, 339–348.
- MUTVEI, H. 1997b. Siphuncular structure in Ordovician endocerid cephalopods. Acta Palaeontologica Polonica, 42, 375–390.
- MUTVEI, H. 1998. Siphuncular structure in Silurian narthecoceratid nautiloid from the Island of Gotland. Geologiska Föreningens i Stockholm Förhandlingar, 120, 373–378.
- MUTVEI, H. 2002a. Nautiloid systematics based on siphuncular structure and position of muscle scars. Abhandlungen der Geologischen Bundesanstalt, 57, 379–392.
- MUTVEI, H. 2002b. Connecting ring structure and its significance for classification of the orthoceratid cephalopods. Acta Palaeontologica Polonica, 47, 157–168.
- MUTVEI, H. and DONOVAN, D. 2006. Siphuncular structure in some fossil coleoids and Recent Spirula. Palaeontology, 49, 685–691.
- MUTVEI, H. and STUMBUR, H. 1971. Remarks on the genus Pictetoceras (Cephalopoda: Ellesmerocerida). Bulletin of the Geological Institutions of the University of Uppsala, New Series, 2, 117–122.
- MUTVEI, H., WEITSCHAT, W., DOGUZHAEVA, L. A. and DUNCA, E. 2004. Connecting ring with pore canals in two genera of Mesozoic ammonoids. Mitteilungen aus dem Geologisch-Palontologischen Institut der Universitt Hamburg, 87, 135–144.
- STUMBUR, H. and MUTVEI, H. 1983. A new Middle Ordovician torticonic nautiloid. Geologiska Föreningens i Stockholm Förhandlingar, 105, 43–47.
- WALCOTT, C. D. 1905. Cambrian faunas of China. Proceedings of the United States National Museum, 29, 1–106.
- WARD, P. D. 1987. The natural history of Nautilus. Allen and Brown, Boston, MA, 267 pp.