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Cow-Nosed Ray (Rhombodus laevis)

Age – Late Cretaceous; Commonality – Teeth: very common, Possible Vertebrae or Dermal Denticles: uncommon; Size – teeth: ~5mm, Possible Vertebrae: 1/4-11/8 inches, Possible Dermal Denticles: 1/4-3/4 inches

This was a common type of ray. Its teeth are the most common elements recovered. They had a crown that is the shape of a rhombus (hence their genus name) and a bilobate root which possesses foramina in between the root lobes and on the sides.

The vertebrae and dermal denticles are probably found, but it would be difficult or impossible to attribute them to this specific ray because of no associated remains.

Teeth

Basal View

Occlusal View

Lingual View

Cow-Nosed Ray (Rhombodus laevis) Tooth, Cretaceous, New Jersey

Labial View

Side View

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.

Basal View

Occlusal View

Lingual View

Labial View

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

Basal View

Occlusal View

Lingual View

Labial View

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.

Basal View

Occlusal View

Lingual View

Labial View

Labial View

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

Dermal Denticles

Occlusal View

Basal View

Side View

Anterior View

Posterior View

Oblique View

Cow-Nosed Ray (Rhombodus laevis) Dermal Denticle, Cretaceous, New Jersey 2

This denticle is the most common classical type found.

The rays Rhombodus laevisBrachyrhizodus wichitaensis, and Pseudohypolophus mcnultyi had denticles which were relatively large (~ 1/8 – ¾ inches). 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 had striations. The denticles of P. mcnultyi are said to have resembled the denticles of B. wichitaensis. These ideas are not entirely clear. There is a chance that the small dots/bumps fell off easily pre-fossilization, similar to Hybodont spines which may have lost their tubercles in a similar manner (information from Steve B.). It might be that the denticles of the rays looked very similar. These denticles’ commonality is “very uncommon.” Associated remains need to be found in order to attribute the denticles to a specific type of ray.

Occlusal View

Basal View

Side View

Anterior View

Posterior View

Oblique View

Cow-Nosed Ray (Rhombodus laevis) Dermal Denticle, Cretaceous, New Jersey 1
Interesting wear pattern on this one.

Occlusal View

Basal View

Side View

Anterior View

Posterior View

Oblique View

Another denticle.

Occlusal View

Basal View

Side View

Anterior View

Posterior View

Oblique View

This denticle is very similar to the one above.

Occlusal View

Basal View

Side View

Anterior View

Posterior View

Oblique View

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, but could be). Information from: http://www.elasmo-research.org/education/white_shark/scales.htm

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