Body Chamber (body + chamber)

Distribution by Scientific Domains
Earth and Environmental Science100%

Selected Abstracts

Morphogenetic significance of the conchal furrow in nautiloids: evidence from early embryonic shell development of Jurassic Nautilida

LETHAIA, Issue 3 2003
RéGIS CHIRAT
As reported by many workers over the past two centuries, the inner part of the shell of various straight and coiled Palaeozoic to tertiary nautiloid taxa bears a continuous mid-ventral furrow that extends into the phragmocone and the body chamber nearly to the aperture. Study of the early embryonic shell development of Jurassic Nautilida shows that the most apical part of this so-called conchal furrow originates from the inner part of the initial, calcified shell apex, in line with the inner ventral termination of the central linear depression of the cicatrix, the initial site of shell deposition. The conchal furrow corresponds to a morphological feature arising as a developmental by-product. Rare specimens of scattered ammonoid species (and possibly of bactritoids) display a similar feature, whereas their protoconch lacks a cicatrix. However, the protoconch of recent cuttlefish, Sepia officinalis, often displays a longitudinal fold of the primary shell epithelium. A longitudinal groove or a pair of grooves appears connected with this cicatrix-like structure. Although the mid-ventral ridge in ammonoids must probably be viewed as an incidental ,fabricational noise', whether or not it originates from a so far undocumented optional ridge on the protoconch or from some other structure related to shell development remains an open question. [source]

SOME LESSER KNOWN FEATURES OF THE ANCIENT CEPHALOPOD ORDER ELLESMEROCERIDA (NAUTILOIDEA, CEPHALOPODA)

PALAEONTOLOGY, Issue 3 2007
BJÖRN KRÖGER
Abstract:, Three specimens of the small breviconic ellesmeroceratid Paradakeoceras minor Flower, 1964 from the Tremadocian of the New York area preserve the annular elevation and muscle scars in moulds of the body chamber. The annular elevation is positioned at the base of the body chamber and is wider on the convex side of the shell than on the concave side. Multiple paired muscle scars can be seen within this annular elevation. A well-preserved body chamber of the breviconic ellesmeroceratid Levisoceras cf. edwardsi Ulrich, Foerste and Miller is described. Its body chamber shows a strong anterior,posterior asymmetry, which is common within the Ellesmeroceratida. The shape of the body chamber and of the soft body attachment structures has led to a reconstruction of an ellesmeroceratid soft body that is organized like a primitive conchiferan mollusc. Based on this reconstruction, a tryblidian cephalopod ancestor is supported. An evolutionary scenario is reconstructed from an ancestral nautiloid that is stretched along the anterior,posterior axis, and has serially arranged shell muscles and a small mantle cavity, towards a modern cephalopod with a dorsal,ventral body orientation, reduced number of shell muscles and a large mantle cavity. [source]

Soft-tissue imprints in fossil and Recent cephalopod septa and septum formation

LETHAIA, Issue 4 2008
CHRISTIAN KLUG
Several soft-tissue imprints and attachment sites have been discovered on the inside of the shell wall and on the apertural side of the septum of various fossil and Recent ectocochleate cephalopods. In addition to the scars of the cephalic retractors, steinkerns of the body chambers of bactritoids and some ammonoids from the Moroccan and the German Emsian (Early Devonian) display various kinds of striations; some of these striations are restricted to the mural part of the septum, some start at the suture and terminate at the anterior limit of the annular elevation. Several of these features were also discovered in specimens of Mesozoic and Recent nautilids. These structures are here interpreted as imprints of muscle fibre bundles of the posterior and especially the septal mantle, blood vessels as well as the septal furrow. Most of these structures were not found in ammonoids younger than Middle Devonian. We suggest that newly formed, not yet mineralized (or only slightly), septa were more tightly stayed between the more numerous lobes and saddles in more strongly folded septa of more derived ammonoids and that the higher tension in these septa did not permit soft-parts to leave imprints on the organic preseptum. It is conceivable that this permitted more derived ammonoids to replace the chamber liquid faster by gas and consequently, new chambers could be used earlier than in other ectocochleate cephalopods, perhaps this process began even prior to mineralization. This would have allowed faster growth rates in derived ammonoids. [source]