Inoceramids 

Giant clams of the Cretaceous 

Copyright © 2011 by Mike Everhart

Page Created 11/28/2011

Last revised 11/28/2011

LEFT: A large and relatively uncrushed lower valve of Volviceramus grandis from the Late Coniacian Smoky Hill Chalk of Trego County, Kansas.

"Fragments of thick shell of a fibrous structure: The doubts expressed respecting the nature of this shell, and the observations made with regard to it, offer another strong point of agreement between the shells of the two strata. The shell here alluded to is most probably that represented Org. Rem. vol. III. pl. V.-fig. 3; the structure of which agrees exactly with that mentioned as found in the French stratum of- chalk. That shell is however described as being of a tubular form; it is therefore right to observe, that fossil that represented Org. Rem. vol. III. pl. V.-fig. 3; the structure of which agrees exactly with that mentioned as found in the French stratum of- chalk. That shell is however described as being of a tubular form; it is therefore right to observe, that fossil pinnae do sometimes possess this peculiar structure."

LEFT: Figure 3 from Plate V in Parkinson's Organic Remains of a Former World (1811a).

Sowerby, J. 1822. On a fossil shell of a fibrous structure, the fragments of which occur abundantly in the chalk strata and in the flints accompanying it. Transactions of the Linnean Society of London XIII: 453-458. Plate XXV.

RIGHT: James Sowerby (1757-1822) portrait in Volume 7. His son, James De Carle Sowerby (1787-1871)  continued the publication of Sowerby's conchology books starting with Volume 5. Volume 7 was never finished.

"Fig. 10, A, E, F, G, H, I. Catillus cuvieri, A. BR. (p.15) Inoceramus cuvieri, SOW., PARK. The name Inoceramus has been given to shells which seem to me show so numerous and striking differences that I could not decide to keep them together, breaking the law I imposed myself to bring no change in the shells division (family), such as it had been established by the specialists. One has just to compare the fossil shells that I unite here under the name of Catillus with Inoceramus, fig.11 and 12, pl. VI, to be stricken by this difference. The species of both these genera are found in the chalk, but they are located in very distant strata.

It has seemed logical for me to keep the name Inoceramus for the gender composed of  the shells that M. Parkinson made known and drew under this name in the first volume of the Transactions of Geol. Soc. of London., that M. Sowerby established and presented under this same name at the Linnaean Soc. of London in 1814, of which figures he just published in plates 305 and 306 in Conchology, and I have preferred give a new name to the species for which I see no description nor precise figure anywhere.

"The name Inoceramus, from [unreadable] (fibra) and ϰέραμος (testa) is justly objected to by scholars, as an improperly formed word, and not expressive of "fibrous shell" which it was intended to signify; it therefore ought to be changed, but it bas been in use so long, that it has become general; and, if I were even inclined to act the part of an innovator, to do so would, I think, only be adding to the confusion already existing in consequence of Brongniart's naming the type of the Genus, Catillus, a name not applicable to the whole of the species."

RIGHT: A juvenile V. grandis lower valve with attached P. congesta oysters. This shell measures about 2.5 by 2.0 inches. The shell crushing shark, Ptychodus, most likely fed on shells that were about this size.

RIGHT: A field photograph of a fairly complete V. grandis shell from the lower chalk of Trego County with the upper (right) valve still in place, and completely covered with Pseudoperna congesta oysters.   The bottom of this specimen was also completely covered with oysters.

LEFT: A field photo from 1996 showing the edge of a large Cladoceramus undulatoplicatus eroding from the edge of a gully in the lower Smoky Hill Chalk, Gove County, Kansas. This shell was near a Pteranodon sternbergi specimen discovered by Pam Everhart and helped to establish the age of those remains.

LEFT:  The exhibit specimen of Platyceramus platinus (FHSM IP-532) at the Sternberg Museum. This shell is about 3 ft. wide and 3.5 feet long (Scale = 10 cm). As collected by G.F. Sternberg, this would have been the lower side of the specimen as discovered (Here in a 1960s photo,  Dr. L.D. Wooster looks on as George Sternberg points out a colony of oysters.)

RIGHT: My concept of a giant (> 1m) Platyceramus platinus resting on the sea floor with a rather large area of the rim of the lower shell exposed above the sediment... a great location for oysters looking for a home.

RIGHT: Platyceramus platinus shells were so large that they provided shelter for schools of small fish. Sometimes the fish were trapped inside the clam's shell when it died.  This picture shows skeletal fragments of small fish that were preserved inside a Platyceramus platinus shell from the Smoky Hill Chalk.

RIGHT: The remains of two small fish preserved in the same shell as the eel (left).

LEFT: Several views of a giant fossil pearl I discovered in the lower Smoky Hill Chalk, Gove County, Kansas.  The specimen is the size of half a golf ball. (Scale = cm)

RIGHT:  A side view of an inoceramid "blister" pearl showing the underlying inoceramid shell.

Another group of pearls and a close-up of a large pearl from the Smoky Hill Chalk. (Scale =mm)

PEARLS FROM OTHER FORMATIONS IN KANSAS

LEFT: Two small pearls (4-5 mm) from the base of the Lincoln Limestone Member of the Greenhorn Limestone Formation (Upper Cenomanian) in Russell County, Kansas. (Scale = mm)

RIGHT: A cross section of the larger pearl shown at left showing. the concentric layers.

"INVERTEBRATES.

Of the Mollusca, Ostrea congesta is of very great abundance in the Rudistes beds, but much less common in the Hesperornis beds. They are found attached to other shells, and it may perhaps be in consequence of the fewness of large shells in the upper strata that their comparative rarity- may be ascribed. Several species of Inoceramus are apparently found in all horizons, but the Haploscaphas are abundant only in the lower horizons, and I never have found H. grandis or those allied to that species in the upper horizons. On the Smoky Hill River near the mouth of the Hackberry [Creek] there are places where these shells can be gathered by the wagon load, often distorted, but not rarely in extraordinary perfection. A very thin shelled Inoceramid [Platyceramus platinus] measuring in the largest specimens forty-four by forty-six or eight inches is not rare over a large part of the exposures. Invariably where exposed, as they sometimes are in their entirety on low fiat mounds of shale, they are broken into innumerable pieces. For that reason, I have never known of one being collected complete, or even partially complete. Notwithstanding their great size the shell substance is not more than an eighth of an inch in thickness."