Fossils Found on the Potomac in MD & VA

Fossils here include:

Shark Teeth, Other Shark Parts, Skates and Rays, Reptiles, Gastropods,

(The smallest divisions in the ruler are 1/8")

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Shark Teeth

Carcharias hopei (Agassiz, 1843b) (Sand tiger shark) Sand tiger teeth are very hard to identify, the key to identifying this species from the other sand tigers in the sedements is their smooth enamel. (no striations).

These teeth are abundant. The left most tooth is a profile view. All teeth are anteriors except the rightmost one, which is a lateral. The top tooth is a lingual view, all others are labial views. Formation: Aquia Formation, Piscataway Member Age: Paleocene, ~56-59 m.y. Location: Potomac river, Charles Co., MD Size: Largest one is ~1 1/2" (36mm)

Cretolamna sp. (appendiculata?) (Mackerel-type shark)

This tooth is very small and a little to worn to make a posative identification, but it probably is a C. appendiculata. Formation: Aquia Formation, Piscataway Member Age: Paleocene, ~56-59 m.y. Location: Potomac River, Charles Co., MD Size: ~5/16" (10mm)

Otodus obliquus (Agassiz, 1843b) (Giant Mackerel-type shark) These self evident teeth are the second most sought after teeth in the Aquia formation (the first is the rare Palaeocarcharodon orientalis, which I sadly have not found.) O. obliquus teeth can reach slant heights of up to 4", however anything over 2.5" is rare for this location. However, small teeth (~1") are fairly common. To some, Otodus is thought to have evolved into the ancestor of Carcharocles spp., including the final species, C. megalodon. However, Purdy et al (2001) suggests the megalodons and the Great whites are related, and therefore both placed in the Carcharodon genus. This means the Otodus genus did not give rise to the megalodons, and instead, the megalodons and Great whites (in fact all Carcharodon genus) came from the Carcharodon orientalis aka Paleocarcharodon orientalis.

Most teeth found in this area are around this size. Formation: Aquia Formation, Piscataway Member Age: Paleocene, ~56-59 m.y. Location: Potomac River, Charles Co., MD Size: ~1 - 1 1/2" (25-33mm)

Paleohypotodus rutoti (Winkler, 1874b) (Sand tiger/Mackerel-type shark)

These teeth can be identified by their broad crowns, elongated root lobes, and two-three triangular cusplets. The first is a posterior, the second is a lateral Formation: Aquia Formation, Piscataway Member Age: Paleocene, ~56-59 m.y. Location: Potomac River, Charles Co., MD Size: They can get up to an inch in length, the posterior one is ~ 5/8" (32mm)

Striatolamia striata (Winkler, 1874b) (Sand tiger Shark) The key to identifying Striatolamia sp. from Carcharias hopei is that Striatolamia sp. have striations on their enamel, where Carcharias hopei do not.

These are abundant, especially small ones of < 1" Formation: Aquia Formation, Piscataway Member Age: Paleocene, ~56-59 m.y. Location: Potomac River, Charles Co., MD Size: Largest one is ~ 1 5/8" (41mm)

This is the largest sand tiger I found. It is actually, the largest Striatolamia I have ever seen! It was the 1st nice tooth found with the glass-bottom bucket. Click here to see a pic of when it was found. Formation: Aquia Formation Age: Paleocene, ~56-59 m.y. Location: Belvedere beach, Potomac River, VA Size: ~ 2 1/4" (57mm) Date: Fall 2002

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Other Shark parts

(Shark Verteberal Centrum)

Vertebra from sharks Formation: Aquia Formation, Piscataway Member Age: Paleocene, ~56-59 m.y. Location: Potomac River, Charles Co., MD Size: Largest one is ~5/8" (16mm)

Myliobatiformes order (Rays) Rays are related to Sharks and Skates, as they are all in the Chondrichthyes Class. Fish in this class have a skeleton made of cartilage instead of true bone. What this means for the fossil collector is bones from these animals seldom fossilize. Occasionally a vertebra may be found, however mostly the hard shark teeth and ray crushing plates are found.

Myliobatidae family (Eagle Rays)

Myliobatis sp Ray crushing plates Rays have modified teeth that form flat crushing plates. These crushing plates are adapted for eating mollusks and crustaceans on the sea floor. They suck their prey up like a vacuum and simply crush them between their upper and lower crushing plates.

The first one is the central part of a ray dental plate, the second is one broken in half. Formation: Aquia Formation, Piscataway Member Age: Paleocene, ~56-59 m.y. Location: Potomac River, Charles Co., MD Size: The complete one is ~1 1/4" by 1 1/2" (30x37mm)

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Reptiles

Crocodilia order (Crocodiles)

Thecachampsa sp. (crocodile teeth) Crocodile teeth come in all shapes and sizes, and are usually black

Croc teeth are very common along the beach Formation: Aquia Formation, Piscataway Member Age: Paleocene, ~56-59 m.y. Location: Potomac River, Charles Co., MD Size: largest one is ~1 5/8" (40mm)

Thecachampsa sp. (crocodile scute fragment) Crocodile scutes are a common find in the paleocene deposits along the river. Scutes serve as a kind of body armor. They are bone plates just under the skin throughout most of a crocdiles head, neck, back, and upper half of the tail. Scutes also serve to warm the crocodiles blood (as crocs are cold blooded animals). Blood collects in the little dimples on the scutes, when the crocodile basks in the sun, the blood in the dimples warm up and circulate through the crocodiles body. Crococile scutes can be differentiated from turtle scutes, as the dimples in crocodile scutes are much deeper than in turtle scutes.

This is half of a little scute. Due to the shape, it is probably either a scute from the back or upper tail. Formation: Aquia Formation, Piscataway Member Age: Paleocene, ~56-59 m.y. Location: Potomac River, Charles Co., MD Size: ~ 1.75" (45mm) Date: June 2002

Thecachampsa sp. (crocodile femur fragment) Bone fragments from crocodiles are very common, however identifiable fragments are less common.

This is probably the end of a femur from a very big crocodile. Formation: Aquia Formation, Piscataway Member Age: Paleocene, ~56-59 m.y. Location: Potomac River, Charles Co., MD Size: ~ 3" (75mm)

Testudine order (Turtles) Turtle material is common in this formation.

Turtle plastron fragment

This is a scute from of the bottom of a turtle shell (the plastron). There are no patterns on the plastron, so it is very difficult to determine what type of turtle this came from. Formation: Aquia Formation, Piscataway Member Age: Paleocene, ~56-59 m.y. Location: Potomac River, Charles Co., MD Size: ~5 1/4" (134mm)

Trionychidae family (Softshell Turtles)

Trionyx sp. Freshwater turtle Scutes from the carapace of Trionyx are readily identifiable by their deep intricate patterns (which can be seen in both images). They are different from crocodile scutes in that the dimples in a crocodile scute are much deeper.

This is a carapace scute from the top of the turtle shell (the carapace). Notice the ligament-like attachment protruding in the side view of the scute. Formation: Aquia Formation, Piscataway Member Age: Paleocene, ~56-59 m.y. Location: Potomac River, Charles Co., MD Size: ~2" (50mm)

This is another Trionychid scute fragment from the carapace. Notice the self evident pattern, making these scutes easy to identify. Formation: Aquia Formation, Piscataway Member Age: Paleocene, ~56-59 m.y. Location: Potomac River, Charles Co., MD Size: ~2" (50mm)

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Gastropods

Turritella sp. (Gastropod internal mold)

At times, entire cliffsides are composed of these molds Formation: Aquia Formation, Piscataway Member Age: Paleocene, ~56-59 m.y. Location: Potomac River, Charles Co., MD Size: range from ~1"-5" (26-126mm)