The Body Chamber Length Variations and Muscle and Mantle Attachments in Ammonoids

2015 ◽  
pp. 545-584 ◽  
Author(s):  
Larisa A. Doguzhaeva ◽  
Royal H. Mapes
Keyword(s):  
The Body ◽  
Chamber Length ◽  
Body Chamber

VI.—Note on Ephippioceras clitellarium, J. de C. Sowerby, sp., and E. costatum, A. H. Foord

1900 ◽  
Vol 7 (12) ◽  
pp. 560-561
Author(s):  
G. C. Crick
Keyword(s):  
New Species ◽  
New Genus ◽  
British Museum ◽  
Acute Angle ◽  
The Body ◽  
Museum Collection ◽  
Body Chamber ◽  
Coal Measures ◽  
A New Species

The name Nautilus clitellarius was given by J. de C. Sowerby to a Nautiloid from the Coal-measures, Coalbrookdale, Shropshire, and the description was accompanied by three figures, each representing a different specimen. In 1884 the species was included by Professor Hyatt in his new genus Ephippioceras. In 1891 Dr. A. H. Foord found a new species, Ephippioceras costatum, which was said to be “distinguished from E. clitellarium (to which it is, however, very closely related) by the character of the septa and by the surface ornaments. The septa in E. costatum do not form such an acute lobe upon the periphery as do those of E. clitellarium, and they are also a little wider apart in the former species than they are in the latter. Moreover, E. costatum is provided with prominent transverse costæ, which are strongest upon the sides of the shell where they swell out into heavy folds. These costæ are directed obliquely backwards, and cross the septa at an acute angle, passing across the periphery and forming a shallow sinus in the middle. None of the specimens in the British Museum have the test preserved, so that the ribbing has only been observed upon casts. The costæ are equally well developed upon the body-chamber and upon the septate part of the shell in the adult, but they were either very feeble or altogether absent in the young.” A re-examination of the specimens in the Museum collection shows that the separation of the two forms is quite justifiable.

Jaws and radula of the Carboniferous ammonoid Cravenoceras

1995 ◽  
Vol 69 (4) ◽  
pp. 703-707 ◽  
Author(s):  
Kazushige Tanabe ◽  
Royal H. Mapes
Keyword(s):  
The Body ◽  
Anterior Portion ◽  
Phylogenetic Affinity ◽  
Body Chamber ◽  
Lower Jaw ◽  
Upper Jaw ◽  
Marginal Plates ◽  
Buccal Space

A well-preserved mouth apparatus consisting of jaws and a radula was found in situ within the body chamber of the goniatite Cravenoceras fayettevillae Gordon, 1965 (Neoglyphiocerataceae: Cravenoceratidae), from the middle Chesterian (Upper Mississippian) of Arkansas. Both upper and lower jaws consist of a black material. The lower jaw is characterized by a widely opened larger outer lamella and a shorter inner lamella. The upper jaw is fragmental. The radula is preserved in the anterior portion of the buccal space and comprises a series of tooth elements. Each transverse tooth row consists of seven teeth (a rhachidian and pairs of two lateral and one marginal teeth), with a pair of marginal plates. This arrangement is typical of radulae of other ammonoids of Carboniferous to Cretaceous age, coleoids, and the orthoconic “nautiloid” Michelinoceras (Silurian, Michelinocerida), suggesting a phylogenetic affinity among them.

Form and function of orthoconic cephalopod shells with concave septa

Paleobiology ◽  
1977 ◽  
Vol 3 (3) ◽  
pp. 300-321 ◽  
Author(s):  
G. E. G. Westermann
Keyword(s):  
Calcium Carbonate ◽  
Relative Length ◽  
The Body ◽  
Neutral Buoyancy ◽  
Spherical Cap ◽  
Apical Angle ◽  
Form And Function ◽  
Body Chamber ◽  
Septal Thickness ◽  
Horizontal Stability

Models of “ideal” orthoconic shells having simple concave septa with minimal weight and maximal strength and analysis of 72 species of fossil orthocones and cyrtocones yield important insights into the physical principles underlying cephalopod shell design. The ideal septum is a spherical cap weighing only 77% of a hemispherical septum of equal strength. The septa of most longicones approximate this ideal shape while those of brevicones are less curved, probably owing to buoyancy problems. Increase in septal strength leads to weight increase unless the shell becomes more logiconic or septal spacing increases or both. However, increased spacing requires more cameral liquid for septum formation, thus reducing buoyancy. In ideal longicones, septal spacing resembles the cone radius for thick, strong septa but declines to half of the cone radius for thin, weak septa. In ideal intermediates and brevicones, spacings are respectively reduced by factors of about 2 and 4, with similar additional dependence on septal thickness. Most real septa resemble these ideal models.The relative length of the body chamber to the phragmocone varies greatly between about 0.2 and 1.5, depending mainly on the wall thickness and to a lesser degree on the septal thickness, apical angle and body density. Removal of cameral liquid in the adult must be compensated for by additional growth to retain neutral buoyancy. The conditions for neutral equilibrium calculated for longicones with different “counterweights” indicate that: (1) cameral liquid only is least feasible; (2) half-and-half calcium carbonate and liquid results in one-third length and one-quarter volume reduction of the body chamber; (3) with calcium carbonate only, body chamber reduction is minimal. Real ‘counterweights’ appear to be intermediate between (2) and (3), providing the animal with horizontal stability, which is missing in (3). Most uncalcified siphuncles reduce the body chamber only slightly although they improve horizontal stability. If the wall attains full thickness only at the apical end of body chamber, the liquid-only ‘counterweight’ becomes feasible.

New Pennsylvanian coleoids (Cephalopoda) from Nebraska and Iowa, USA

2017 ◽  
Vol 92 (2) ◽  
pp. 146-156 ◽  
Author(s):  
Royal H. Mapes ◽  
Larisa A. Doguzhaeva
Keyword(s):  
New Species ◽  
New Genus ◽  
The Body ◽  
New Genera ◽  
Shell Material ◽  
Body Chamber ◽  
Evolutionary Radiation

AbstractFour rare Pennsylvanian (Stark Shale: Pennsylvanian, Missourian [=Kasimovian]) coleoids from Nebraska and Iowa, which are preserved as flattened partial phragmocones and body chambers associated with three-dimensionally fossilized ink sacs, are herein described as Pabianiconus starkensis new genus new species, Nebraskaconus whitei new genus new species, and Starkites compressus new genus new species. One specimen that is missing most of the phragmocone, is provisionally assigned to Donovaniconus. The fossils are assigned to the Coleoidea because of the presence of ink-filled sacs in the body chamber region of the conch. Additionally, eight fragmented and flattened phragmocones and body-chamber clusters with similar morphologies, including some with ink fragments and arm hooks, are assigned to the Coleoidea, but are not named because of their fragmentary condition. On most of the eight specimens, the shell material is associated with other unidentified finely macerated material, which suggests these fossils are probably either ejectoid masses or coprolites from coleoid predators and/or scavengers. However, the new genera named above appear to have been deposited as complete animals, based on the presence of the ink-filled sacs that are in the body chambers. With their body chamber and phragmocone morphologies, these rare coleoid taxa provide valuable information about conch variability within the Carboniferous evolutionary radiation of coleoids.

Mosasaur tooth marks on the ammonite Placenticeras from the Upper Cretaceous of Alberta, Canada

1990 ◽  
Vol 27 (3) ◽  
pp. 469-472 ◽  
Author(s):  
R. A. Hewitt ◽  
G. E. G. Westermann
Keyword(s):  
Upper Cretaceous ◽  
The Body ◽  
Shell Wall ◽  
Flexible Support ◽  
Body Chamber ◽  
Tooth Marks

Mosasaur tooth marks were found in the body chamber and phragmocone of the Campanian ammonite Placenticeras meeki Boehm from the Bearpaw Formation of the St. Mary River area near Lethbridge. They imply that the shell wall of the ammonite buckled around point loads and did not break into fragments like the shell of Nautilus. The complex septal sutures provided a strong but marginally flexible support for the shell wall. The shells were probably attacked near the surface, perhaps during initial postmortem drift of corpses.

Sublethal injury and shell repair in Upper Mississippian ammonoids

Paleobiology ◽  
1989 ◽  
Vol 15 (4) ◽  
pp. 414-428 ◽  
Author(s):  
Paul N. Bond ◽  
W. Bruce Saunders
Keyword(s):  
Shell Thickness ◽  
Physical Parameters ◽  
Selective Predation ◽  
Chamber Length ◽  
Body Chamber ◽  
Interspecific Differences ◽  
Sublethal Injury ◽  
Shell Damage ◽  
Shell Repair ◽  
Northwest Arkansas

Sublethal injuries recorded in the shells of five Upper Mississippian ammonoid species from the Imo Formation of northwest Arkansas are manifested as repaired shell breaks, which can be categorized as minor, moderate, massive, deep-acute, or as perforations. Overall, 15% of the ammonoids exhibit some form of repaired break. The injuries are distributed as follows: Anthracoceras discus 9%; Fayettevillea bransoni 13%; Fayettevillea friscoense 21%; Rhadinites miseri 24%; Richardsonites mapesi 38%. These figures are substantially lower than in living Nautilus, in which more than one-half of adult specimens exhibit repaired shell breaks. The different frequencies of injuries may reflect species-selective predation, differential abilities to sustain and to repair shell damage, or they may be due to interspecific differences in physical parameters such as shell thickness and body chamber length. The most likely possible perpetrators of the injuries include sharks, other fishes, and cephalopods.

Large heteromorph ammonites from the Upper Cretaceous of Seymour Island, Antarctica

1989 ◽  
Vol 63 (5) ◽  
pp. 626-636 ◽  
Author(s):  
Eduardo B. Olivero ◽  
William J. Zinsmeister
Keyword(s):  
Upper Cretaceous ◽  
Flat Surface ◽  
Center Of Mass ◽  
The Body ◽  
Total Density ◽  
Nacreous Layer ◽  
Shell Wall ◽  
Body Chamber ◽  
Large Size ◽  
Seymour Island

Two species of the heteromorph ammonite genus Diplomoceras Hyatt are described from the Upper Cretaceous of the James Ross–Seymour Islands area, Antarctica. The late Campanian–early Maastrichtian D. lambi Spath has a relatively high rib density, whereas D. maximum n. sp. has a lower rib density and is known only from the uppermost Maastrichtian of the Lopez de Bertodano Formation on Seymour Island. Both species attain an exceptionally large size with the body chamber of D. maximum n. sp. attaining a length in excess of one meter. The structure of the shell wall in Diplomoceras is characterized by the thickening of the nacreous layer below the ribs. The shell thickening results in an inner flat surface and a smooth phragmocone. Reconstruction of the shell suggests at least four parallel shafts and three U-connectives. Estimates of the total density, center of buoyancy, and center of mass in this reconstructed shell indicate a slightly positive buoyant shell with a relatively unstable floating position.

III.—On Jurassic Ammonites

1889 ◽  
Vol 6 (5) ◽  
pp. 200-203 ◽  
Author(s):  
S. S. Buckman
Keyword(s):  
Natural History ◽  
Type Specimen ◽  
The Body ◽  
Natural History Museum ◽  
History Museum ◽  
Body Chamber ◽  
Ventral Area

In a former communication (Geol. Mag. Dec. III. Vol. IV. No. 9, p. 396, 1887), when pointing out how Reinecke's Amm. serpentinus had been misunderstood, I gave as a synonym, but with a query, Sowerby's Amm. Strangewaysi. As I have, since then, examined the type-specimen of the latter species contained in the collection of the Natural History Museum, and as Mr. E. Walford kindly forwarded me for my determination a capital specimen from Byfield, I have been able to satisfactorily settle the identity of these forms. Except being evolute carinate Ammonites, the two species have hardly a feature in common.Discoidal, compressed, hollow-carinate. Whorls flattened, ornamented with genuine sickle-shaped ribs, which, though less conspicuous in size on the body-chamber, are there more distinctly bent. Ventral area marked by the prolonged forward sweep of the ribs, and surmounted by a well-marked hollow-carina.

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