HOME | DD

Description

Carcharocles chubutensis is the second last chronospecies in the obliquus-megalodon lineage. This large Lamniform shark appeared in the latest Chattian stage of the late Oligocene and survived until the Langhian stage of the middle Miocene. The teeth of C. chubutensis can be identified by a triangular, mesial-laterally broadened main crown, a convex lingual crown face, a mildly convex to flat labial crown face that slightly overhangs the labial face of the root, a finely and regularly serrated cutting edge, a robust root with a less concave “V” shaped root interlobe, a faint lingual protuberance of the root, and a tall chevron scar on the lingual face. C. chubutensis can be distinguished from the younger C. megalodon by the presence of small lateral cusplets, which are not separated from the main crown by a distinct notch as in the earlier C. angustidens (Cappetta, 1987) (Purdy et al., 2001).

Agassiz (1839) assigned the name C. subauriculatus to three large triangular teeth, one from a museum in Stuttgart, Germany and two from the Paris Museum, France. In his description, Agassiz admitted it difficult to distinguish this species from C. megalodon but claimed the marginal sides of the C. subauriculatus teeth were straighter and less convex or flared. The name C. chubutensis was instead used by Ameghino (1901) and has since become the preffered name by researchers despite C. subauriculatus having seniority. Occasionally the teeth of juvenile C. megalodon possess lateral cusplets and rarely even adult teeth can retain them as a vestige, making distinguishing C. chubutensis teeth from C. megalodon teeth difficult at times (Perez et al., 2019).

The transition from C. chubutensis to C. megalodon is so smooth that it is difficult to discern an exact point in time when one species merged into the next. As noted by Perez et al. (2019), in the lower Miocene beds of the Calvert Formation (20.2 - 17 mya) cuspleted teeth are more common than uncuspleted teeth, suggesting C. chubutensis was only beginning to transition into C. megalodon. In the middle Miocene beds (16.4 - 14 mya) there is an increase in uncuspleted teeth, suggesting C. megalodon definitively begins at this point in time. By 10.4 mya, teeth possessing lateral cusplets are virtually absent, indicating C. chubutensis becomes extinct.

While not as large as its immediate descendant C. chubutensis was a gigantic shark, the largest specimen described by Perez et al. (2021) yielded a total length estimate of between 11.2 and 16.7 metres, the average estimate for this specimen being 13.3 metres. The increase in body size for the Carcharocles species in the Oligocene and Miocene, was likely in part due to the appearance of baleen whales (Mysticeti) which provided a much greater food source.

References:

Agassiz, L. (1843). “Recherches Sur Les Poissons Fossiles. (Tome III).” Imprimérie de Petitpierre.

Ameghino, F. (1901) “L’age des formations sédimentaires de Patagonie.” Anales de la Sociedad Científica Argentina, 51: 20-91.

Cappetta, H. (1987). “Chondrichthyes II : Mesozoic and Cenozoic Elasmobranchii.” In: Schultze, H. P, (ed). “Handbook of paleoichthyology (Volume 3B).” Verlag Dr. Gustav Fischer, 1-193.

Perez, V. J., Godfrey, S. J., Kent, B. W., Weems, R. E., Nance, J. R. (2019). “The Transition between Carcharocles Chubutensis and Carcharocles Megalodon (Otodontidae, Chondrichthyes): Lateral Cusplet Loss Through Time.” Journal of Vertebrate Paleontology, 38(6), e1546732-.

Perez, V. J., Leder, R. M., Badaut, T. (2021). “Body length estimation of Neogene macrophagous lamniform sharks (Carcharodon and Otodus) derived from associated fossil dentitions.” Palaeontologia Electronica.

Purdy, R. W., Schneider, V. P., Applegate, S. P., Mclellan, J. H., Meyer, R. L., Slaughter, R. (2001). “The Neogene sharks, rays, and bony fishes from Lee Creek Mine, Aurora, North Carolina.” In: Ray, C. E. R., Bohaska, D. J. (2001). “Geology and paleontology of the Lee Creek Mine, North Carolina, III.” Smithsonian Contributions to Paleobiology, 90: 71-202.

Description

Carcharocles chubutensis is the second last chronospecies in the obliquus-megalodon lineage. This large Lamniform shark appeared in the latest Chattian stage of the late Oligocene and survived until the Langhian stage of the middle Miocene. The teeth of C. chubutensis can be identified by a triangular, mesial-laterally broadened main crown, a convex lingual crown face, a mildly convex to flat labial crown face that slightly overhangs the labial face of the root, a finely and regularly serrated cutting edge, a robust root with a less concave “V” shaped root interlobe, a faint lingual protuberance of the root, and a tall chevron scar on the lingual face. C. chubutensis can be distinguished from the younger C. megalodon by the presence of small lateral cusplets, which are not separated from the main crown by a distinct notch as in the earlier C. angustidens (Cappetta, 1987) (Purdy et al., 2001).

Agassiz (1839) assigned the name C. subauriculatus to three large triangular teeth, one from a museum in Stuttgart, Germany and two from the Paris Museum, France. In his description, Agassiz admitted it difficult to distinguish this species from C. megalodon but claimed the marginal sides of the C. subauriculatus teeth were straighter and less convex or flared. The name C. chubutensis was instead used by Ameghino (1901) and has since become the preffered name by researchers despite C. subauriculatus having seniority. Occasionally the teeth of juvenile C. megalodon possess lateral cusplets and rarely even adult teeth can retain them as a vestige, making distinguishing C. chubutensis teeth from C. megalodon teeth difficult at times (Perez et al., 2019).

The transition from C. chubutensis to C. megalodon is so smooth that it is difficult to discern an exact point in time when one species merged into the next. As noted by Perez et al. (2019), in the lower Miocene beds of the Calvert Formation (20.2 - 17 mya) cuspleted teeth are more common than uncuspleted teeth, suggesting C. chubutensis was only beginning to transition into C. megalodon. In the middle Miocene beds (16.4 - 14 mya) there is an increase in uncuspleted teeth, suggesting C. megalodon definitively begins at this point in time. By 10.4 mya, teeth possessing lateral cusplets are virtually absent, indicating C. chubutensis becomes extinct.

While not as large as its immediate descendant C. chubutensis was a gigantic shark, the largest specimen described by Perez et al. (2021) yielded a total length estimate of between 11.2 and 16.7 metres, the average estimate for this specimen being 13.3 metres. The increase in body size for the Carcharocles species in the Oligocene and Miocene, was likely in part due to the appearance of baleen whales (Mysticeti) which provided a much greater food source.

References:

Agassiz, L. (1843). “Recherches Sur Les Poissons Fossiles. (Tome III).” Imprimérie de Petitpierre.

Ameghino, F. (1901) “L’age des formations sédimentaires de Patagonie.” Anales de la Sociedad Científica Argentina, 51: 20-91.

Cappetta, H. (1987). “Chondrichthyes II : Mesozoic and Cenozoic Elasmobranchii.” In: Schultze, H. P, (ed). “Handbook of paleoichthyology (Volume 3B).” Verlag Dr. Gustav Fischer, 1-193.

Perez, V. J., Godfrey, S. J., Kent, B. W., Weems, R. E., Nance, J. R. (2019). “The Transition between Carcharocles Chubutensis and Carcharocles Megalodon (Otodontidae, Chondrichthyes): Lateral Cusplet Loss Through Time.” Journal of Vertebrate Paleontology, 38(6), e1546732-.

Perez, V. J., Leder, R. M., Badaut, T. (2021). “Body length estimation of Neogene macrophagous lamniform sharks (Carcharodon and Otodus) derived from associated fossil dentitions.” Palaeontologia Electronica.

Purdy, R. W., Schneider, V. P., Applegate, S. P., Mclellan, J. H., Meyer, R. L., Slaughter, R. (2001). “The Neogene sharks, rays, and bony fishes from Lee Creek Mine, Aurora, North Carolina.” In: Ray, C. E. R., Bohaska, D. J. (2001). “Geology and paleontology of the Lee Creek Mine, North Carolina, III.” Smithsonian Contributions to Paleobiology, 90: 71-202.