Evidence of shark-on-shark trophic interactions in the Miocene of Costa Rica, Southern Central America

Evidencia de interacciones tróficas entre tiburones en el Mioceno de Costa Rica, América Central Meridional

Daniela Araya-Gamboa1, César A. Laurito2*, Cristian Calvo2 & Ana L. Valerio2

1 Panthera Costa Rica ORG, Montes de Oca, San José, Costa Rica

2 Independent Researchers, Vázquez de Coronado, San José, Costa Rica

*Corresponding author: Eremotherium1961@gmail.com

(Recibido: 06/09/2025; aceptado: 03/02/2026)

Revista Geológica de América Central, 74, 2026, doi: https://doi.org/10.15517/sz9r7m18

ISSN: 0256-7024

Abstract: The trophic interactions of many extant shark species are well known. When examining the fossil record, the evidence is weak, often indirect, and subject to interpretation, almost always limited to bite marks on bones. However, the record of shark teeth embedded in skeletal remains, although rare in the fossil record, constitutes direct evidence of predation and/or scavenging. Even rarer is the record of trophic interactions type Shark-on-Shark. Here, we describe the discovery of a fossil that provides direct evidence of trophic interaction between a Hemigaleid shark on Carcharhinid shark, from inner neritic sediments of the Santa Teresa Formation of Miocene age.

Keywords: Carcharhinidae; Hemigaleidae; scavenging; Santa Teresa Fm.; Miocene; Puntarenas province.

Resumen: Las interacciones tróficas de muchas especies de tiburones actuales son bien conocidas. Al examinar el registro fósil, la evidencia es débil, a menudo indirecta y sujeta a interpretación, casi siempre limitada a marcas de mordeduras en huesos. Sin embargo, el registro de dientes de tiburón incrustados en restos óseos, aunque poco frecuente en el registro fósil, constituye evidencia directa de depredación y/o carroñeo, pero aún más raro es el registro de interacciones tróficas entre tiburones. Acá describimos el hallazgo de un fósil que aporta evidencia directa de interacción trófica entre un tiburón Hemigaleidae y un Carcharhinidae, procedente de sedimentos neríticos internos de la Formación Santa Teresa, de edad Mioceno.

Palabras clave: Carcharhinidae, Hemigaleidae, carroñeo, Fm. Santa Teresa, Mioceno, provincia de Puntarenas.

Introduction

It is not uncommon to find direct or indirect evidence in the fossil record of the trophic interaction of sharks with other marine organisms (Ehret et al., 2009), and even with organisms that inhabited lake environments with a predominance of freshwater (Kriwet et al., 2008). Such evidence consists primarily of bite marks preserved in skeletal remains; loose teeth associated with fossil skeletal remains of other vertebrates; less frequently, the record of detached teeth embedded in fossilized bones; even rarer, the record of fossilized skeletal, dental, or scales remains preserved in areas associated with a shark’s digestive tract, corresponding to soft-body structures that are rarely preserved; and even rarer inclusions in coprolites.

The trophic interaction of sharks in the past, as well as today, was not limited solely to the vertebrate group, but also involves many invertebrates as part of their diet. Always focusing on vertebrates, the Paleozoic fossil record highlights the predation of amphibians by batrachophagous sharks (Soler-Gijón, 1995; Kriwet et al., 2008). In the Mesozoic, we have frequent records of sharks feeding on mosasaur and plesiosaur reptiles (Dortangs et al., 2002; Everhart, 2004; Rothschild, et al., 2005; Hamm & Shimada, 2007), pterosaurs, †Pteranodon spp. (Hone et al., 2018; Ehret & Harrell, 2018), turtles (Shimada & Hooks, 2004; Almafitano et al., 2017), Crocodyliformes Hyposaurinae (Hill et al., 2015), Hesperornithiformes birds (Shimada & Hanks, 2020) and Dinosauria of the families Hadrosauridae (Everhart & Ewell, 2006; Shein & Poole, 2014) and Nodosaurinidae that inhabited coastal environments in the Late Cretaceous (Everhart & Hamm, 2005).

In most of the cited cases, trophic interaction, predation and/or scavenging, was caused, indirectly or directly, by Lamniformes sharks, primarily by †Cretoxyrhina mantelli (Agassiz), an apex predator of the food chain in the Late Cretaceous seas (Shimada, 1997a) that probably stabbed and anchored its food with large anterior teeth, and cut food primarily with its more distally located teeth (Shimada, 1997b).

In the Cenozoic, the fossil remains of cetaceans among all marine mammals, constitute the group of vertebrates that provides the greatest evidence of trophic activity attributed to sharks, due to their remarkable size, high diversity and cosmopolitan distribution (Aguilera et al. 2008; Bianucci et al., 2000; Cicimurri & Knight, 2009; Cigala Fulgosi, 1990; Cortés et al., 2019; Cozzuol & Aguilera, 2008; Collareta et al., 2017; Freschi, 2017; Freschi & Cau, 2020; Govender & Chinsamy, 2013; Govender, 2015; Noriega et al. 2007; Takakuwua, 2014). It is striking that attacks on cetaceans by predation or possible scavenging during the Miocene and Pliocene, due to the size and configuration of the bite marks and shark teeth associated with the bone remains, are attributed or are directly related to sharks of the Otodontoidea family, such as †Otodus (Megaselachus) chubutensis and †Otodus (Megaselachus) megalodon (Godfrey et al., 2021); while during the later Pliocene and until the Recent, sharks of the Lamnidae family, particularly the genus Carcharodon and the species Carcharodon carcharias, are attributed most of the trophic activity towards cetaceans (Deméré and Cerutti, 1982; Cigala-Fulgosi, 1990; Bianucci et al., 2000; Freschi, 2017; Freschi and Cau, 2020), all species of sharks corresponding to apex predators.

In addition to the cetacean record, there is fossil evidence of trophic interactions between sharks and other marine mammals. This is particularly true of Sirenia, where dugongs provide the most significant evidence of shark predation or scavenging (Benites-Palomino et al., 2023; Merella et al., 2021: Feichtinger et al., 2021; Rateau et al., 2009), followed by the record of Pinnipedia (Bigelow, 1994, Collareta et al., 2017; Govender, 2021; Godfrey et al., 2018; Godfrey et al., 2024a).

On the other hand, fossil evidence of trophic interaction between sharks and bony fish is even scarcer; one notable example is a specimen of †Xiphactinus audax from the Niobrara Chalk (Upper Cretaceous) of western Kansas that contains an embedded tooth of †Cretoxyrhina mantelli (Shimada & Everhart, 2004).

Shark-on-shark trophic interactions have existed for hundreds of millions of years (Perez et al., 2021), despite this, their fossil record is extremely rare, for example Shark remains present within the gut contents of the Devonian shark Cladoselache represent the oldest documented evidence of shark-on-shark predation (Williams, 1990). In the Cretaceous, the discovery of †Pseudocorax and †Squalicorax teeth associated with a semi-articulated skeleton of †Cretoxyrhina mantelli is a remarkable fact, which was interpreted by Shimada, 1997b, as evidence of scavenging.

In addition to evidence of predation or scavenging, resulting from trophic interactions between sharks and other vertebrates, including other sharks, there is evidence in the fossil record of teeth bearing marks that may have been involuntarily self-inflicted, resulting from one tooth striking another in the opposing jaw during forced occlusion, collateral damage from feeding, or aggressive behavior (Godfrey et al., 2024b; Perez, 2020; Purdy et al., 2001).

Among the Neogene records of shark-on-shark trophic interactions, the following stand out: the discovery of several vertebral centra from the Atlantic Coastal Plain, collected in Miocene sediments of North Carolina and Maryland, which present bite marks attributed to Galeocerdo cuvier (Péron & Lesueur, 1822); an incomplete vertebral centrum of an indeterminate carcharhinid was described from the Calvert Formation in Chesapeake Beach, Maryland, which contains two embedded shark teeth of Carcharhinidae indet. (both cases reported by Perez et al., 2021); and the record of two shark vertebral centra associated with a Carcharodon carcharias tooth from the Pliocene of the Po Basin, Italy, considered a case of trophic interaction between sharks (Rondelli et al., 2024). Here we report the first fossil record of a Shark-on-shark trophic interactions found in Central America and the Caribbean Region.

Geological setting

The vertebral centra presented here, was collected on the surface of Santa Teresa beach at coordinates 9°38’42.85”N and 85°10’18.04”W, south of the Nicoya Peninsula in the Province of Puntarenas, Costa Rica (Fig. 1). From the natural color of this concretion it most likely comes from sediments of the Santa Teresa Formation of Miocene to Early Pliocene age. The sedimentology of the Santa Teresa Formation suggests shallow marine, sublittoral and proximal neritic paleo-environments (Calvo,1987).

Material

A concretion containing four articulated shark vertebral centra, and associated with the vertebrae are the remains of three shark teeth. The material is housed at the rocks, minerals and fossils collection of the National Museum of Costa Rica under the code CFM-5496. It was collected with the collaboration of Manú Salom Araya and Lucas Pérez Rojas, students from the CATIE Inter-American School.

Description

The vertebral centra measure approximately 48 mm at their widest point, 45 mm high, and 20 mm thick. Both the anterior and posterior surfaces of the exposed vertebrae are broken, and their phosphate corpus is missing. However, the central point of the birth ring can be seen on both surfaces, as well as its internal structures, such as the basidorsal and basiventral attachments of the neural and hemal arches. Both the neural and hemal arches were not preserved, as is natural due to their lack of ossification. In the inner vertebrae, the rim of the external growth ring is well preserved. The cavities or foramina for the basiventral insertions are also visible, although they are filled with cemented material precipitated during diagenesis, the oval and slightly elongated outline of the foramina can be seen. The vertebrae exhibit structural characteristics such as well-defined vertebral centra aseptate. The overall width of the vertebral centrum is greater than its thickness. The vertebral centrum has a well-defined and spacious phosphated nucleus, and the intermediate zone is surrounded by a mineralized band.

On the other hand, the vertebrae carry three fossilized dental fragments belonging to sharks. Two of the three preserved crowns are characterized by a high triangular outline, measuring 18 mm and 20 mm in height, with a prominent apex inclined toward the commissure, and edges with prominent serrations, the commissural serrations being thicker than the mesial ones. The serrations increase in size toward the apex. Both crowns have a wide triangular groove on their lower half.

The third crown fragment is very small, its observable length reaches 5.5 mm, and it has a slightly inflated concave labial surface with smooth edges on the sides.

Discussion and conclusions

Vertebral centra are among the most commonly preserved shark remains in the fossil record, after oral and dermal teeth. This is because neural and hemal arches are less mineralized than vertebral centra, so they are not usually preserved. The vertebral centra also allow differentiation between different lineages, which makes them of taxonomic value (Burris, 2004; Ehret et al., 2009; Kozuch & Fitzgerald, 1989; Medeiros et al., 2024; Welton & Farish, 1993).

The fossil vertebral centra here analyzed are characterized by thick basidorsal and basihemal insertions, surrounded by dense intermedialia (see figures 2c, d and d´), without the lamellar structures of Lamniformes. These characteristics are typical of the vertebral centra of Carcharhiniformes (sensu Welton & Farish, 1993 and Burris 2004). Additionally, the basidorsal insertion foramen is slightly elongated and oval in shape (see Fig. 2b), condition that is also observed into the family Carcharhinidae. Beyond this, it is not possible to determine the genus.

The occurrence of teeth embed¬ded in prey substrate offers unequivocal evidence of trophic interactions and, generally, allow one to more confidently identify the predator than bite marks alone (cf. Godfrey et al., 2024a). In this case the triangular tooth crowns embedded between the vertebrae are typical of sharks of the species †Hemipristis serra of the Hemigaleidae family. hese crowns correspond to two upper consecutive left lateral teeth that, in our case, became detached when trying to cut the soft tissue surrounding the vertebrae. Something that commonly happens to sharks, because the teeth are anchored by connective tissue fibers in the mucosa covering the jaws (Cappetta, 2012).

There is evidence of a change in the upper teeth of †Hemipristis serra during the Miocene: they increased in size and their edges became almost completely serrated (Chandler et al., 2006). Also, adults of †Hemipristis serra in the Miocene are estimated to have reached dimensions of up to 6 m, typical of a giant (Pimiento et al., 2019).

These two preserved teeth of †Hemipristis serra are relatively small and slender, corresponding to mesial rather than commissural lateral teeth (compare with figures 1 and 7 of Jambura et al., 2018). Another important feature is that the mesial and commissural edges are completely serrated and the cusplets of the commissural edges are well developed, confirming that this was an adult individual. Although the roots were not preserved, it can be speculated that the total length of the teeth was around 20 and 22 mm and that the commissural edge was composed of 9 to 11 cusplets.

These dental dimensions are 25 % larger than those recorded for adult individuals of the current species Hemipristis elongata, 196 cm long and with teeth lengths of 15.10 mm (Baranes & Ben-Tuvia, 1979), so it can be speculated that the teeth embedded in the vertebrae centra corresponded to a specimen of around 2 m in length, even slightly larger.

All the characteristics described above allow us to conclude that the morpho-dental development corresponds to forms of †Hemipristis serra from the Middle Miocene. This age coincides with ages suggested for the Santa Teresa Formation. This is consistent with the temporal range of †Hemipristis serra, which spanned the Miocene to the early Pleistocene and had a nearly global distribution (Cappetta, 2012).

Laurito (1999) considered †Hemipristis serra, based on its fossil record, as a shark with nektonic and epipelagic habits, which inhabited insular and continental platforms in warm seas during the Neogene. This paleobiogeographic distribution pattern is also consistent with the sedimentology of the Santa Teresa Formation.

There is no doubt that this shark was an important predator, although stating with certainty what its diet was, given that it is a fossil species, is debatable. One way to resolve this is to turn to what is known about the trophic interactions of extant species with fossil representatives from the Neogene or, as in the case analyzed, to consider direct evidence from the fossil record as a snapshot of trophic interactions. The genus Hemipristis is currently represented by the species Hemipristis elongata, whose biogeographic distribution is limited to the western Pacific, the Indian Ocean and the Red Sea (Carpenter et al., 1997; Compagno, 1998; Ebert et al., 2021). With maximum corporal dimensions of 2.40 m (Compagno, 1984), its diet does not differ from that of other sharks of the same size that share its habitat. This diet includes bony fish, cartilaginous fish such as Carcharhinus spp. and Gymnura sp., as well as cephalopods (Compagno, 1984, 1998; Ebert et al., 2021; Chappell & Serét, 2020).

Fossil CFM-5496 provides compelling evidence that Carcharhinidae sharks were part of the diet of †Hemipristis serra in the Miocene.

Whether the trophic interaction evidenced by the fossil clearly corresponds to predation or scavenging is difficult to determine. However, given that †Hemipristis serra was a significant predator, we could assume that the trophic interaction occurred “perimortem,” that is, during a predation event.

Acknowledgements

We thank Gerardo González Barba, Natural History Museum at Universidad Autónoma de Baja California Sur for his suggestions that improved the manuscript.

References

Aguilera, O. A., García, L., & Cozzuol, M. A. (2008). Giant-toothed White sharks and cetacean trophic interaction from the Pliocene Caribbean Paraguaná Formation. Paläontologische Zeitschrift, 82(2), 204–208. https://doi.org/10.1007/BF02988410

Amalfitano, J., Dalla Vecchia, F. M., Giusberti, L., Fornaciari, E., Luciani, V., & Roghi, G. (2017). Direct evidence of trophic interaction between a large lamniform shark, Cretodus sp., and a marine turtle from the Cretaceous of northeastern Italy. Palaeogeography, Palaeoclimatology, Palaeoecology, 469, 104–121. https://doi.org/10.1016/j.palaeo.2016.12.044

Baranes, A., & Ben-Tuvia, A. (1979). Two rare carcharhinids, Hemipristis elongatus and Iago omanensis, from the northern Red Sea. Israel Journal of Zoology, 28(1), 39-50

Benites-Palomino, A., Aguirre-Fernández, G., Velez-Juarbe, J., Carrillo-Briceño, J. D., Sánchez, R., & Sánchez-Villagra, M. R. (2023). Trophic interactions of sharks and crocodylians with a sea cow (Sirenia) from the Miocene of Venezuela. Journal of Vertebrate Paleontology, 43 (6). https://doi.org/10.1080/02724634.2024.2381505

Bianucci, G., Bisconti, M., Landini, W., Storai, T., Zuffa, M., Giuliani, S., & Mojetta, A. (2000). Trophic interactions between white sharks (Carcharodon carcharias) and cetaceans: a comparison between Pliocene and recent data. In M. Vacchi, G. La Mesa, F. Serena, & B. Sèret (Eds.), Proceedings 4th Meeting of the European Elasmobranc Association, Livorno (Italy). 33–48. Imprimerie F. Paillart.

Bigelow, P. K. (1994). Occurrence of a squaloid shark (Chondrichthyes: Squaliformes) with the pinniped Allodesmus from the Upper Miocene of Washington. Journal of Paleontology, 68(3), 680-684. https://doi.org/10.1017/s0022336000026032

Burris, J. H. (2004). Morphology and phylogenetic implications of Recent and fossil carcharhiniform shark vertebral centra (PhD Dissertation). Michigan State University.

Calvo, C. (1987). Las Calizas neríticas de la Vertiente Pacífica del Norte de Costa Rica y Sur de Nicaragua: Épocas y Sistemas Asociados con la apertura y evolución del margen convergente de la América Central meridional. (Bachelor Thesis). Universidad de Costa Rica.

Cappetta, H. (2012). Chondrichthyes II: Mesozoic and Cenozoic Elasmobranchii: teeth. In H. P. Schulze (Ed.), Handbook of Paleoichthyology (3E, pp. 1-512). Verlag Dr. Friedrich Pfeil.

Carpenter, K. E., Krupp, F., Jones, D. A., & Zajonz, U. (1997). FAO species identification guide for fishery purposes. The living marine resources of Kuwait, Eastern Saudi Arabia, Bahrain, Qatar, and the United Arab Emirates. FAO.

Chandler, R. E., Chiswell, K. E., & Faulkner, G. D. (2006). Quantifying a Possible Miocene Phyletic Change in Hemipristis (Chondrichthyes) teeth. Palaeontologia Electronica, 9(1), 4A:1-14. https://palaeo-electronica.org/2006_1/teeth/teeth.pdf

Chappell, A., & Séret, B. (2020). Functional Morphology of the Feeding Apparatus of the Snaggletooth Shark, Hemipristis elongate (Carcharhiniformes: Hemigaleidae). Journal of Anatomy, 238(2), 288–307. https://doi.org/10.1111/joa.13313

Cicimurri, D. J., & Knight, J. L. (2009). Two Shark bitten Whale Skeletons from Coastal Plain Deposits of South Carolina. Southeastern Naturalist, 8(1), 71–82. JSTOR. https://doi.org/10.2307/25599297

Cigala Fulgosi, F. (1990). Predation (or possible scavenging) by a great White shark on an extinct species of bottlenosed dolphin in the Italian Pliocene. Tertiary Research, 12, 17–36.

Collareta, A., Lambert, O., Landini, W., Di Celma, C., Malinverno, E., Varas-Malca, R., Urbina, M., & Bianucci, G. (2017). Did the giant extinct shark Carcharocles megalodon target small prey? Bite marks on marine mammal remains from the late Miocene of Peru. Palaeogeography, Palaeoclimatology, Palaeoecology, 469, 84–91. https://doi.org/10.1016/j.palaeo.2017.01.001

Compagno, L. J. V. (1984). FAO Species Catalogue, volume 4, part 1, Sharks of the world: an annotated and illustrated catalogue of shark species known to date. United Nations Development Program. Roma. https://openknowledge.fao.org/server/api/core/bitstreams/1b650fd0-3675-43cc-adcf-876cdc5a001f/content

Compagno, L. J. V. (1998). Hemigaleidae, weasel sharks. In Carpenter, K.E., & Niem, V.H. (Eds.), FAO species identification guide for fishery purposes. The living marine resources of the Western Central Pacific. Volume 2, Cephalopods, crustaceans, holothurians and sharks (pp. 1305-1311). https://openknowledge.fao.org/server/api/core/bitstreams/40a8028a-042a-46fc-b573-eb1700b3d85c/content

Cortés, D., De Gracia, C., Carrillo-Briceño, J. D., Aguirre-Fernández, G., Jaramillo, C., Benites-Palomino, A., & Atencio-Araúz, J. E., (2019). Shark-cetacean trophic interactions during the late Pliocene in the Central Eastern Pacific (Panama). Palaeontologia Electronica, 22(2). https://doi.org/10.26879/953

Cozzuol, M. A., & Aguilera, O. A. (2008). Cetacean remains from the Neogene of northwestern Venezuela. Paläontologische Zeitschrift, 82(2), 196–203. https://doi.org/10.1007/bf02988409

Deméré, T. A., & Cerutti, R. A. (1982). A Pliocene shark attack on a cetotheriid whale. Journal of Paleontology, 56, 1480–1482.

Denyer, P., Aguilar, T., & Montero, W. (2013). Mapa geológico de la hoja Cabuya (3144-I). Escala 1:50 000. UCR-MINAE.

Dortangs, R. W., Schulp, A. S., Mulder, E. W. A, Jagt, J. W. M., Peeters, H. H. G., & de Graaf, D. T. (2002). A large new mosasaur from the Upper Cretaceous of The Netherlands. Netherlands Journal of Geosciences, 81, 1-8. https://doi.org/10.1017/S0016774600020515

Ebert, D. A., Dando, M., & Fowler, S. (2021). Sharks of the World: A Complete Guide. Princeton University Press, Wildenature Press.

Ehret, D. J., MacFadden, B. J., Jones, D. S., DeVries, T. J., & Salas-Gismondi, R. (2009). Caught in the act: trophic interactions between a 4-million-year-old white shark (Carcharodon) and mysticete whale from Peru. PALAIOS, 24(5), 329–333. https://doi.org/10.2110/palo.2008.p08-077r

Ehret, D. J., & Harrell, T. L. (2018). Feeding traces on a Pteranodon (Reptilia: Pterosauria) bone from the Late Cretaceous (Campanian) Mooreville Chalk in Alabama, USA. PALAIOS, 33(9), 414-418. https://doi.org/10.2110/palo.2018.024

Everhart, M. J. (2004). Late Cretaceous interaction between predators and prey: Evidence of feeding by two species of shark on a mosasaur. PalArch Vertebrate Palaeontology Series, 1(1), 1–7.

Everhart, M. J., & Ewell, K. (2006). Shark-bitten dinosaur (Hadrosauridae) caudal vertebrae from the Niobrara Chalk (Upper Coniacian) of western Kansas. Transactions of the Kansas Academy of Science, 10 (1/2), 27-35.

Everhart, M. J., & Hamm, S. A. (2005). A new nodosaur specimen (Dinosauria: Nodosauridae) from the Smoky Hill Chalk (Upper Cretaceous) of western Kansas. Transactions of the Kansas Academy of Science, 108(1), 15-21. https://doi.org/10.1660/0022-8443(2005)108[0015:ANNSDN]2.0.CO;2

Feichtinger, I., Fritz, I., & Göhlich, U. B. (2021). Tiger shark feeding on sirenian–first fossil evidence from the middle Miocene of the Styrian Basin (Austria). Historical Biology, 34(2), 193–200. https://doi.org/10.1080/08912963.2021.1906665

Freschi, A. (2017). New Carcharodon scavenging evidence on Pliocene whale bones remains from Northern Appennines. Quaderni del Museo Civico di Storia Naturale di Ferrara, 5, 33-36. https://storianaturale.comune.fe.it/modules/core/lib/d.php?c=jklo5

Freschi, A., & Cau, S. (2020). Nuovi segni d’interazione trofica tra Charcharodon carcharias ed un odontoceto dal bacino Plio-Pleistocenico di Castell’Arquato (Piacenza, Apennino Settentrionale). Parva Naturalia, 15, 133-156.

Godfrey, S. J., Ellwood, M., Groff, S., & Verdin, M. S. (2018). Carcharocles-bitten odontocete caudal vertebrae from the Coastal Eastern United States. Acta Palaeontologica Polonica, 63(3), 463–468. https://doi.org/10.4202/app.00495.2018

Godfrey, S. J., Nance, J. R., & Riker, N. L. (2021). Otodus-bitten sperm whale tooth from the Neogene of the Coastal Eastern United States. Acta Palaeontologica Polonica, 66(3), 599–603. https://doi.org/10.4202/app.00820.2020

Godfrey, S. J., Murdoch, P., Dewaele, L., Perez, V. J., & Schumaker, C. (2024a). First report in the fossil record of a shark tooth embedded in a pinniped bone. Comptes Rendus Palevol, 23(8), 107-118. https://doi.org/10.5852/cr-palevol2024v23a8

Godfrey, S. J., Bennett, M., & Perez, V. J. (2024b). Taphonomic and ecological insights from conspecific bite marks on Otodus megalodon teeth. Acta Palaeontologica Polonica, 69(4), 731–736. https://doi.org/10.4202/app.01188.2024

Govender, R., & Chinsamy, A. (2013). Early Pliocene (5 Ma) shark-cetacean trophic interaction from Langebaanweg, western coast of South Africa. PALAIOS, 28, 270-277. https://doi.org/10.2110/palo.2012.p12-058r

Govender R. (2015). Shark–Cetacean trophic interaction, Duinefontein, Koeberg, (5 Ma), South Africa. South African Journal of Science, 111(11/12), 1-7. http://dx.doi.org/10.17159/ sajs.2015/20140453

Govender, R. (2021). Shark-seal interaction off South Africa’s west coast during the early Pliocene (5 Ma). South African Journal of Science, 117(3/4), 123-129. https://doi.org/10.17159/sajs.2021/8837

Hamm, S. A., & Shimada, K. (2007). The Late Cretaceous anacoracid shark, Pseudocorax laevis (Leriche), from the Niobrara Chalk of western Kansas. Transactions of the Kansas Academy of Science, 110(1/2), 1-15.

Hill, R. V., Roberts, E. M., Tapanila, L., Bouaré, M. L., Sissoko, F., & O’Leary, M. A. (2015). Multispecies shark feeding in the Trans-Saharan seaway: Evidence from late cretaceous dyrosaurid (crocodyliformes) fossils from northeastern Mali. PALAIOS, 30(7), 589–596. https://doi.org/10.2110/palo.2014.109

Hone, D. W. E., Witton, M. P., & Habib, M. B. (2018). Evidence for the Cretaceous shark Cretoxyrhina mantelli feeding on the pterosaur Pteranodon from the Niobrara Formation. PeerJ, 6, e6031. https://doi.org/10.7717/peerj.6031

Jambura, P. L, Pfaff, C., Underwood, C. J., Ward, D. J., & Kriwet, J. (2018). Tooth mineralization and histology patterns in extinct and extant snaggletooth sharks, Hemipristis (Carcharhiniformes, Hemigaleidae) Evolutionary significance or ecological adaptation? PLoS ONE, 13(8), e0200951. https://doi.org/10.1371/journal.pone.0200951

Kozuch, L., & Fitzgerald, C. (1989). A guide to identifying shark centra from southeastern archaeological sites. Southeastern Archaeology, 8, 146–157.

Kriwet, J., Witzmann, F., Klug, S., & Heidtke, U. H. J. (2008). First direct evidence of a vertebrate three-level trophic chain in the fossil record. Proceedings of the Royal Society of London, B275, 181-186.

Laurito, C. (1999). Los seláceos fósiles de la localidad de Alto Guayacán (y otros ictiolitos asociados). CIIPALEOGEO.

Medeiros, S., Francischini, H., Oddone, M. C., Cardoso, L. G., & Dentzien-Dias, P. (2024). Shark (Neoselachii) vertebral centra from the Quaternary of southern Brazil. Revista Brasileira de Paleontologia, 27(2), e20240439. https://doi.org/10.4072/rbp.2024.2.0439

Merella, M., Collareta, A., Casati, S., Di Cencio, A., & Bianucci, G. (2021). An unexpected deadly meeting: deep-water (hexanchid) shark bite marks on a sirenian skeleton from Pliocene shoreface deposits of Tuscany (Italy). Neues Jahrbuch für Geologie und Paläontologie - Abhandlungen, 301(3), 295–305. https://doi.org/10.1127/njgpa/2021/1012

Noriega, J. I., Cione, A. L., & Aceñolaza, F. G. (2007). Shark tooth marks on Miocene balaenopterid cetacean bones from Argentina. Neues Jahrbuch Für Geologie Und Paläontologie - Abhandlungen, 245(2), 185–192. https://doi.org/10.1127/0077-7749/2007/0245-0185

Perez, V. J. (2020). Self-bitten snaggletooth. Ecphora, 35, 12.

Perez, V. J., Godfrey, S. J., & Chapman, P. F. (2021). Rare evidence of shark-on-shark trophic interactions in the fossil record. Acta Palaeontologica Polonica, 66(4), 847-856. https://doi.org/10.4202/app.00911.2021

Pimiento, C., Cantalapiedra, L. J., Shimada, K., Field, D., & Smaers, J. (2019) Evolutionary pathways toward gigantism in sharks and rays. Evolution, 73, 588-599. https://doi.org/10.1111/evo.13680

Purdy, R. W., Schneider, V. P., Applegate, S. P., McLellan, J. H., Meyer, R. L., & Slaughter, B. H. (2001). The Neogene sharks, rays, and bony fishes from Lee Creek Mine, Aurora, North Carolina. In C. E. Ray & D. J. Bohaska. (Eds.), Geology and Paleontology of the Lee Creek Mine, North Carolina (vol. 90, pp. 71–202). Smithsonian Contributions to Paleobiology.

Rondelli, R., Borghi, E., & Borghi, M. (2024) Denti di Elasmobranchii nel Piacenziano della Cava di Campore (Appennino Parmense). Notiziario della Società Reggiana di Scienze Naturali, 2024, 148-178. https://srsnsite.wordpress.com/wp-content/uploads/2025/01/n2024-art11-denti-di-eelasmobranchi-nel-piacenziano.pdf

Rothschild, B. M., Martin, L. D., & Schulp, A. S. (2005). Sharks eating mosasaurs, dead or alive?. Netherlands Journal of Geosciences, 84, 335-340. https://doi.org/10.1017/S0016774600021119

Rateau, R., Gagnaison, C., & Gelot, V. (2009). Un Metaxytherium medium (Mammalia, Sirenia) attaqué par des requins dans les faluns miocènes de Channay-sur-lathan (37, France). Symbioses, Nouvelle Série, 23, 1-12.

Schein, J. P., & Poole, J. C. (2014). A shark-bitten dinosaur (Hadrosauridae) femur from the latest Maastrichtian basal Hornerstown Formation, New Jersey, U.S.A. The Mosasaur, 8, 15–22.

Shimada, K. (1997a). Paleoecological relationships of the Late Cretaceous lamniform shark, Cretoxyrhina mantelli (Agassiz). Journal of Paleontology, 71(5), 926 - 933. https://doi.org/10.1017/S002233600003585X

Shimada, K. (1997b). Dentition of the Late Cretaceous lamniform shark, Cretoxyrhina mantelli, from the Niobrara Chalk of Kansas. Journal of Vertebrate Paleontology, 17(2), 269-279.

Shimada, K., & Everhart, M. J. (2004). Shark-bitten Xiphactinus audax (Teleostei: Ichthyodectiformes) from the Niobrara Chalk (Upper Cretaceous) of Kansas. The Mosasaur, 7, 35-39.

Shimada, K., & Hooks, G. E. (2004). Shark-bitten protostegid turtles from the Upper Cretaceous Mooreville Chalk, Alabama. Journal of Paleontology, 78(1), 205–210.

Shimada, K., & Hanks, H. D. (2020). Shark-Bitten Hesperornithiform Bird Bone from a Turonian (Upper Cretaceous) Marine Deposit of Northeastern South Dakota, U.S.A. Transactions of the Kansas Academy of Science, 123(3-4), 414-418. https://doi.org/10.1660/062.123.0310

Soler-Gijón, R. (1995). Evidence of predator-prey relationship in xenacanth sharks of the Upper Carboniferous (Stephanian C) from Puertollano; Spain. Geobios, 28, 151–156. https://doi.org/10.1016/s0016-6995(95)80104-9

Takakuwa, Y. (2014). A dense occurrence of teeth of fossil “mako” shark (“Isurus”: Chondrichthyes, Lamniformes), associated with a balaenopterid-whale skeleton of the Late Miocene Pisco Formation, Peru, South America. Bulletin of Gunma Museum of Natural History, 18, 77-86.

Welton, B. J., & Farish, R. F. (1993). The collector’s guide to fossil sharks and rays from the Cretaceous of Texas (1st ed.). Before Time.

Williams, M. E. (1990). Feeding behavior in Cleveland shale fishes. In A. J. Boucot (Ed.), Evolutionary paleobiology of behavior and coevolution (pp. 273–287). Elsevier.