Judith River/White River Fossils
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Identification of Late Cretaceous Dinosaur Teeth

The following article, written by Joseph LeBlanc, is reproduced here with the permission of Lynne Clos, editor/publisher of Fossil News.  It originally appeared in the January issue of Fossil News, a journal devoted to amateur paleontology.

 

While scrambling over Cretaceous hoodoos, I heard a loud cry from my wife, Nora. Alarm! Perhaps she had fallen into one of the yawning sinkholes that prey on the unwary hiker or.... had a disturbed rattlesnake lashed out at an exposed ankle? Fortunately, neither. Around an exposed outcrop she emerged, grinning ear to ear. A waving hand clenched a gleaming four-inch T. rex tooth. The cry was one of ecstasy. The serrated tyrannosaurid dagger is still a prize in our fossil collection.

The dinosaur tooth collector tackles the Cretaceous badlands with the same enthusiasm that gold-crazed prospectors flocked to the Yukon's Klondike. Teeth are great finds. Not only are they paleo masterpieces but are one of the few fossils that can often identify the dino host. The Late Cretaceous exposures of Western North America offer the determined collector a whole range of teeth.

It may be a 'no-brainer,' but the taxa of teeth found in a geologic formation will be the same as the dinosaurs deposited. No, you will not find Albertosaurus teeth in the latest Maastrichtian exposures of the Scollard Formation of Alberta. Yes, you will find T. rex teeth. No, you will not find Triceratops remains in the Campanian Judith River Formation of Montana. Yes, you will find other ceratopsians. This sounds simple. Unfortunately, the majority of dinosaur teeth (and other dino fossils) sold on the market are misidentified. The label says dromaeosaur (raptor), but could it be a small Daspletosaurus? The label says Edmontosaurus, but should it be its hadrosaurian kin Kritosaurus?

Dino teeth are common yet often left undiscovered in the field. Would you recognize a dino tooth if it were at your feet and taunting you to pick it up? The nasty predator teeth look like teeth and would be plucked instantly. What about the others? A half protruding Triceratops tooth...a root-first ankylosaur tooth...a worn hadrosaur crown: would these be passed by?

The following is a general guide to identification of Late Cretaceous dino teeth at the family level. Trying to identify isolated teeth to genus is a near impossibility without collecting information. With collecting information the task enters the realm of the possible. Much literature exists as to what genera of dinosaurs lived when and in which formations. Of course, the research is not complete, but in paleontology, it never is.

Theropod (fig.1): tyrannosaurids, raptors, Tro÷dons. (Ornithomimids were theropods but lacked teeth.)

 

Teeth are serrated. The number, depth and spacing of denticles are identification tools. If the tooth is not serrated, and does not appear worn, it is probably crocodile, fish or shark. Serrations, however, are often worn and not visible to the unaided eye. A finger rubbed over the edge may feel roughness and a microscope will reveal serration bases.
Teeth are almost always recurved (fig. 1a). The amount of curvature depends on the type of dino and the placement in the jaw. An exception is in the Latest Cretaceous deposits in which 'straight' raptor teeth are found.
Tooth serrations fade and run out before reaching the base of the tooth. If serrations are present at the base, the specimen is incomplete. It may be a tip only (fig. 1b). Caution! That 'complete raptor tooth' for sale may be the tip of a tyrannosaurid tooth!
Teeth with tips absent may be complete. Tips are often worn. Wear patterns appear as lighter or darker preservation on the tooth sides and distal (tip) end. What appears as 'half a tooth' may not be broken at all (fig. 1c). Worn teeth are prized by serious collectors; these worn teeth 'saw a lot of action'.
Teeth have a glossy enamel outer layer. If enamel is absent, the tooth may have been self-digested and the enamel dissolved by dino stomach acid. Shed teeth often 'went down the hatch' with dinner and exited in droppings. Such altered teeth are very difficult to identify with certainty.
Size of teeth is deceiving. For example: A T. rex jaw may contain teeth 3 cm to 15 cm in length. Is an isolated small tooth that of T. rex or a smaller raptor?
Larger teeth are often found fragmented or fractured along the vertical axis. Reconstruction is often necessary ('Crazy Glue' is the tooth collector's best friend).
Theropod teeth are common finds, yet theropod bones are rare. Many teeth cannot be identified to species because their host has never been found. Teeth are 'solid' whereas the skulls in which they grew are hollow or honeycombed and thus not readily preserved.

Ankylosaurs (fig. 2): 'Armored tanks' such as Panoplosaurus, Euplocephalus, Ankylosaurus.

 

Teeth are small. Unworn teeth are usually less than a half inch in length.
The enamel surface surrounds the tooth.
Unworn teeth are 'leaf-shaped' on a weak cylindrical base (figs. 2a, b). Often grooves run the length of the chewing surface.
Teeth which are unworn and stripped of enamel often exhibit a central ridge and may have been digested by a theropod (fig. 2c).
Shed teeth have degrees of flattened surfaces. They are often shapeless 'nubs' atop the remaining base (fig. 2d).
Both unworn and worn teeth are common finds in certain formations. Although still rare, teeth with roots are more common than in other families. Despite being delicate in life, teeth are usually found intact and suffer little from breakage. Identification to genus is difficult because the lack of skeletal remains of these animals.

Hadrosaurs (fig. 3): Edmontosaurus, Kritosaurus, Lambeosaurus and a host of others.

 

Teeth grew in batteries, 'conveyor belts' of exposed replacement teeth. Jaw sections are lined with parallel grooves where teeth grew.
Teeth have a center carina, or keel, with an enamelled face but usually a non-enamelled back.
Unworn crowns are from teeth freed from the jaw after death. These crowns are dull and 'v-shaped' (fig. 3a).
An angled, smooth surface reflects the direction of wear on the chewing surface (fig. 3b).
Worn teeth are usually sheds. These are small (1 cm). The chewing surface is often reduced to a sheared 'star-shaped' (fig. 3c). Roots are absent on sheds.
Jaws with teeth are extremely rare finds. Unworn teeth are uncommon. Worn 'star-shaped' teeth are numerous. The latter is expected, as the hadrosaur shed many thousands of teeth over a lifetime.

Ceratopsians (fig. 4): Triceratops, Centrosaurus, and other horned dinosaurs.

 

Teeth grew in batteries like in the hadrosaurs but only one row was 'in play' at a time. The ceratopsian had fewer teeth in its jaws.
Unworn teeth are 'U-shaped'. They are keeled. There is less enamel surface than in hadrosaurs. Small ridges (not serrations) often line the outer edge of these teeth (fig. 4a).
The teeth had double, bifurcated roots (fig. 4b). Other Cretaceous dinosaurs have single roots. These roots almost always broke of f when a worn tooth was shed.
Shed teeth lack distinct shape. There is almost no enamel chewing surface remaining (fig. 4c).
Unworn teeth are extremely rare finds. Worn teeth, numerous and recognizable only to family level.

Canadian winter nights are long and cold. On these nights I like to hold dino tooth specimens and dream of the sun-baked days of next collecting season. It's easy to get lost in reverie when one realizes that dino teeth are the 'real thing'. The enamel is too dense to be filled with mineral replacements. Their thrill lasts long after initial discovery. One can hold an actual Triceratops tooth that once munched on cycad fronds... and run a finger over the serrations of a Tyrannosaurus tooth that long ago pierced the hide of its hadrosaur victim.

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