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Fossils from Monmouth County, New Jersey

Hybodont (Meristodonoides sp. aka Hybodus sp. Hybodus ?novojerseyensis)

Age – Late Cretaceous; Commonality – teeth: Uncommon, cephalic claspers / fin spines: very uncommon; Size – teeth: 1/8 – 3/8 inches, cephalic claspers: ¾ – 1 ¼ inches, fin spines: 4 – 7 inches (when complete)

The teeth of this more ancient and primitive extinct shark are triangular with some basal wrinkles present on some teeth. The root is porous and is almost never fossilized. The cusplets are far from the crown, separated by lateral extensions of the enamel along the root margins, which explains why the teeth are usually found without the cusplets. Some teeth did not possess cusplets. The cephalic claspers were used for mating. Typically four of them would be located on a male shark’s head. Modern sharks don’t possess cephalic claspers. Instead, they have two pelvic claspers that are located in between their pelvic fins. Other sharks of the time also had cephalic claspers, but they did not fossilize. The difference between Hybodont claspers and ratfish claspers is that the Hybodont ones have lobes that are usually smaller than the root, while the ratfish clasper has two lobes that are significantly larger than the root. The ratfish hook is also angled much more than the Hybodont one which is curved. The ratfish claspers are larger than the Hybodont claspers. The Hybodonts also had two fin spines- one in front of the primary dorsal fin, and one in front of the secondary dorsal fin. There appears to be significant variation in the Hybodont spines. Some have faint lines running on the surface and faint tubercles with no trailing edge of spikes, others have prominent tubercles, a trailing edge of spikes, and no lines on the surface. Still others have faint lines and prominent tubercles. A possibility is that some belong to Lonchidion babulskii, and the rest belong to Hybodus sp. The difference between ratfish fin spines and Hybodus fin spines is that ratfish spines have a trailing edge of two rows of spikes, while Hybodont spines only have one row of spikes. The ratfish spines also have a smooth outer surface unlike the Hybodont spines which are studded. Both the Hybodont spines and claspers are more common than the spines and claspers of ratfish.

Anterior Tooth - Labial View

Same Tooth - Lingual View

Lateral Tooth - Labial View

Hybodont Shark Cretaceous (Meristodonoides sp.) Lateral tooth, New Jersey

Same Tooth - Lingual View

Same Tooth - Profile View of Mesial Side

The first two images are of an anterior tooth, shown in labial and lingual views, respectively. The third through fifth images are of a lateral tooth shown in labial, then lingual, and finally profile (showing the mesial carina) views. Both teeth are missing roots and cusplets.

Lateral Tooth - Labial View

Same Tooth - Lingual View

Same Tooth - Profile View of Mesial Side

Anterior Tooth (most likely) - Labial View

Same Tooth - Lingual View

These two teeth have a single cusplet still attached. The first tooth is shown in labial, then lingual, and finally profile (showing the mesial cutting edge) views. The second tooth is shown in labial view and in lingual view.

Anterior Tooth - Lingual View

Hybodont Shark Cretaceous ((Meristodonoides sp.) Anterior tooth, New Jersey

Same Tooth - Labial View

Anterior Tooth - Lingual View

Same Tooth - Labial View

These two teeth have roots. The first tooth is my only complete specimen so far (it did not possess cusplets by the small look of it and short enamel ledges running along its root) and is shown in lingual and labial views. The second tooth is shown in lingual and labial views. I almost threw it away when I found it since it resembled a worn Enchodus jaw section.

Cephalic Claspers

Occlusal View

Profile View

Hybodont Shark Cretaceous (Meristodonoides sp.) Cephalic Clasper, New Jersey

Occlusal View

Basal View

This is one of my best Hybodont cephalic claspers. It is shown in occlusal, profile, slanted occlusal, and basal views.

Occlusal View

Profile View

Oblique View

Basal View

Another awesome cephalic clasper. It has some strange wrinkles on it (this can be seen in the occlusal and profile views) around its hook and body. It is shown in occlusal, profile, slanted profile, and basal views.

Fin Spine Fragments

Fragment 1 - Lateral View

Fragment 1 - Basal View

Fragment 2 - Lateral View

Fragment 2 - Lateral View (of opposite side)

Fragment 2 - Oblique Occlusal View

Fragment 3 - Lateral View

Fragment 4 - Posterior View (View of Trailing Edge)

Fragment 4 - Anterior View (View of Leading Edge)

Fragment 5 - Anterior View (View of Leading Edge)

Fragment 5 - Posterior View (View of Trailing Edge)

Fragment 6 - Lateral View

Fragment 6 - Anterior View (View of Leading Edge)

Fragment 6 - Posterior-Lateral View (Side View of Trailing Edge)

Fragment 6 - Posterior-Basal-Lateral View (Side View of the Base of the Trailing Edge)

Fragment 7 - Anterior View (View of Leading Edge)

Hybodont Shark Cretaceous (Meristodonoides sp.) Fin Spine, New Jersey

Fragment 7 - Posterior View (View of Trailing Edge)

Fragment 7 - Lateral View

These are partial Hybodont fin spines. The first 3 fragments are the tips of fin spines of the type that has many tubercles and no striations. The 4th fragment is a specimen which has both tubercles and striations. Fragments 5 and 6 are a type of fin spine that has strong striations and very faint tubercles. The eleventh image shows the side of a spine with some visible tubercles and striations. The twelfth image shows the leading edge of the spine; the thirteenth and fourteenth images are views of the hollow trailing part of this fin spine type. Fragment 7   (1 3/8 inches) has relatively strong striations and prominent tubercles. In general, the spine type pictured in the first six images is more delicate in comparison to the others.

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