Sunday, June 22, 2014

Fossil shark teeth: Megalodon vs. Great White Shark

This post concerns large fossil-shark teeth belonging to the extinct Carcharocles megalodon (Agassiz, 1843), commonly called just "megalodon." Finding one of its teeth, which can be as large as 7 inches long, is something that tantalizes everyone from school kids to professional paleontologists. These teeth represent the largest shark teeth known, and they can be found in various parts of the world, including California.

Carcharocles megalodon, maximum height 13.5 cm (5.25 in),
early Pliocene age (about 5 million years old), southern California;
U.S. quarter for scale.

Carcharocles megalodon, maximum height 13 cm (5 in),
late Miocene age (about 14 million years old), south-central California;
U.S. quarter for scale.

The following diagram shows the comparative sizes between megalodon and the great white shark, whose official scientific name is Carharodon charcharias (Linnaeus, 1758). The car is about the size of a "mini-Cooper." Actual skeletons of megalodon are not preserved because they consist largely of cartilage, which easily decays away after death of the animal. The size of megalodon, therefore, cannot be directly determined. Estimates for the largest ones range from about 14 to 18 m (40 to 60 ft.) long. Only the hard enamel of the shark teeth are normally preserved.

Comparative sizes of megalodon, a modern great white shark, and a small car.

As shown in the following sketch, the mouth of megalodon was big enough to accommodate six adults.

Inferred reconstruction of the mouth of megalodon.

A single shark can produce thousands of teeth during its lifetime because there are rows upon rows of replacement-shark teeth inside the jaws of sharks. That is why shark teeth are common as fossils.

A section of a modern shark jaw. Length 25 cm (10 in).

"Conveyor-belt"apparatus that delivers new teeth to the front of  a shark's mouth when a tooth falls out.

Modern great white sharks are up to 7 m (23 ft.) long, and 
great white Shark teeth are never as large as than those of megalodon.

Carcharodon carcharias (great white shark) teeth.
On left, replica of a tooth, height 4.7 cm (1.85 in), Recent.
In middle, an actual tooth, height 4.5 cm (1.77 in), late Pliocene age (3 million years old), southern California.
U. S. quarter for scale.

In addition, the bottom (root) of a great white shark tooth is generally straight to slightly curved, whereas the tooth of megalodon has a deep indentation (see pictures at the beginning of this post).

The fossil record of Carcharocles megalodon ranges from the late Oligocene (25 mya = million years ago) to early Pleistocene (about 2 mya), whereas that of Carcharodon carcharias ranges from the middle Miocene to modern time. These two sharks apparently belong to separate families and evolved independently from one another. 

Thursday, June 19, 2014

More information about Campanile snail

This is the second part of my post on Campanile, the genus that includes the largest snail of all time = C. giganteum.

This sketch shows the aperture of this species. The aperture is the  the shell's anterior end, where the gastropod would have been able to extend its body out into the surrounding environment. In the previous blog, the illustrated specimen of this species showed the dorsal side of the shell, and most of the aperture was missing.

Sketch of ventral side of Campanile giganteum with its aperture intact.

The specimen shown in following picture is only the upper part of a very well preserved specimen of Cgiganteum from middle Eocene deposits in the Paris Basin, France. Notice that the axis (columella) of the shell bears two revolving features called folds or plaits. This type of morphologic feature is very important in the classification of gastropods.
upper part of shell of Campanile giganteum
height 22.5 cm

Fossil Campanile species have been found in Paleocene and Eocene deposits of California. The following picture is of an incomplete specimen (tip is missing) of Campanile dilloni Hanna and Hertlein, 1949 from a deposit of late Paleocene age in southern California. This species was not as large as C. giganteum

Campanile dilloni
height 15.5 cm

Today, Campanile is represented today by a single (relict) species, Campanile symbolicum Ireland, 1917, shown in the following picture. This snail crawls around on the seafloor in warm-shallow waters in the Perth area of southwestern Australia. This species is also known by the popular name "Bell Clapper" shell because of its overall shape. Also notice that the end of the columella (see above) is twisted and also has a narrow but distinct "spout." These features are also important in classification.

F.Y.I. The name "Campanile" is Italian, meaning "bell tower." There is tall tower, called "Campanile" on the campus of University of California, Berkeley. 

Campanile symbolicum
height 15.5 cm

Sunday, June 15, 2014

Link to another interesting blog site dealing with paleontology

This post is intended to let you know about another blog site that caters to paleontology, as well as to zoology and other natural history subjects.

The link is

Thursday, June 12, 2014

LARGEST snail of all time

The fossil snail (gastropod) Campanile giganteum (Lamarck, 1804) is truly a giant among gastropods. Specimens can reach a height of 1 meter (= 100 cm = 3.28 ft = 39 in), thereby, making this species the largest snail of all time.

The specimen on the left side of the picture below pretty much represents the maximum size of this snail. The specimen is Campanile sp., cf. C. giganteum of middle Eocene age (about 45 million years ago) from the small island of St. Bartholomew in the Caribbean Sea. The letters "cf." indicate that the identification as to species is tentative because of imperfect preservation. 

100-cm high Campanile sp., cf Cgiganteum (on the left)
 versus 53-cm high Syrinx aruanus (on the right);
measuring stick is 36 inches long = 91.5 cm

The picture on the left is modified from an illustration by Jung (1987, pl. 2) in the journal Ecologae geologic Helvetiae, v. 80, no. 1, pp. 889–896.

A picture of Syrinx aruanus (Linnaeus, 1758) from shallow-marine waters along the northern coast of Australia (i.e., primarily in Queensland) is included in the above picture for comparative purposes. Syrinx aruanus reportedly can reach a height of approximately 60 cm. Although the specimen shown here is only 53 cm (21 in.) in height, it is representative of a rather large-adult specimen. I have only seen a few specimens that are slightly larger. 

Campanile had wide distribution in the world during the warm times of the Paleocene and Eocene, especially from 60 to 40 million years ago. The genus became very restricted afterward because of global cooling of the oceans. In my next blog, I shall comment on some additional interesting details about this genus.

Friday, June 6, 2014

World's biggest fossil single-celled organisms

This post concerns Foraminifera (also called "forams"). They are single-celled organisms and are classified as protozoans. Most forams are so small (amoeba-size) that a microscope is necessary to see them. There are some exceptionally large fossil forams, however, that are coin size (see below).

Large forams belong to the orbitoids, which has three families:
1) discocyclinds (Late Cretaceous to Eocene)
2) nummulitids (Paleocene to Eocene)
3) lepidocyclinids (Eocene to Miocene)

Orbitoids are indicative of ancient
 warm, shallow seas.

Pseudophragmina clarki
maximum diameter 6.5 mm
Discocyclinids can be so abundant as to make discocyclinid limestones or sandstones (especially in Baja California Sur, Mexico). Compared to the other two orbitoids, discocyclinids are smaller and resemble lentils. The earliest known discocylinids found along the west coast of North America are of early Eocene age. 

Nummulites gizehensis
maximum diameter 25.5 mm
Nummulitids are larger than discocyclinids. Nummulites (note: nummulus is Latin, meaning small coin) is a common genus, and one of its species, Nummulites gizehensis (Lamarck, 1801) is a major component of the limestones that make up the Eygptian pyramids. This species, which can be as large as 30 mm in diameter) represents the largest known cells of all time. This species
Comparison between a specimen of N. gizehensis and a
 USA quarter (23 mm dimeter)
was a bottom dweller (benthic organism) in seas during the middle Eocene (about 45 million years ago). It most likely had a symbiotic relationship with a green alga, which probably accounted for the large size of the foram. For more details about
Nummulites and pictures showing their very complicated interior, the link is HERE
cross-section of the interior of Nummulites from Egypt
maximum diameter of foram 18 mm

Lepidocycylina californica (one corner broken off)
maximum diameter 24 mm
Lepidocyclinids can be found locally in southern California and in Baja California Sur, Mexico. Lepidocyclina californica, of early Miocene age (about 20 million years old) is known from the Santa Ynez River valley, northern Santa Barbara County.