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Cow-Nosed Ray (Rhombodus laevis)

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Teeth

Lateroposterior tooth with two nutrient pores. This tooth has virtually no in vivo wear (which is unusual). It also has some somewhat unusual flattened lateral corners of the crown.

This lateroposterior tooth has some heavy in vivo wear, which is very typical.

This anterior tooth shows some light-medium in vivo wear. It also has some foramina on the lateral surfaces of the root next to the crown.

Another anterior tooth. It seems like anterior teeth have a more elongated root relative to the crown compared to lateroposterior teeth.

Dermal Denticles

This denticle is the most common classical type found.

The rays Rhombodus laevis, Brachyrhizodus wichitaensis, and Pseudohypolophus mcnultyi had denticles which were relatively large (~ 1/8 – ¾ inches, on average 1/2 inch). They were approximately tear-dropped in shape and had a protrusion around the middle, when looking at them in occlusal view. The denticles of B. wichitaensis were said to differ from R. laevis denticles by the presence of small dots on the surface. R. laevis supposedly had striations. These ideas are not entirely clear. The small dots/bumps fall off easily pre-fossilization. It might be that the denticles of both rays looked very similar. The denticles of P. mcnultyi are said to have resembled the denticles of B. wichitaensis. These denticles’ commonality is “very uncommon.” Associated remains need to be found in order to attribute the denticles to a specific type of ray.

Interesting wear pattern on this one.

Another denticle.

This denticle is very similar to the one above.

This one has a different surface texture/covering than the first dermal denticle presented. This one clearly has a surficial apatite dentine layer on collagen, while the first one seems to be composed of solely collagen (it doesn’t seem to be worn off).

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