A new cuspidate ptychodontid shark (Chondrichthyes; Elasmobranchii), from the Upper Cretaceous of Morocco with comments on tooth functionalities and replacement patterns

The extinct shark, Ptychodus (Elasmobranchii, Ptychodontidae) in the Upper Cretaceous of central-western Russia—The road to easternmost peri-Tethyan seas

“…Regardless of possible differences in dentition efficiency and functionalities between cuspidate and un-cuspidate species, the different morphologies identified in Ptychodus from Russia, as well as from other European localities, confirm a complex and intricate scenario for the trophic ecology of this marine predator (see also Amadori et al, 2019bAmadori et al, , 2020bAmadori et al, , 2022. Moreover, the various degrees of tooth wear documented for cuspidate and un-cuspidate Ptychodus from numerous other localities around the world indicate durophagy as one of the main feeding strategies for this extinct predatory elasmobranch, reaching even a high degree of specialization in some species (e.g., Woodward, 1887Woodward, , 1912Shimada, 2012;Diedrich, 2013;Amadori et al, 2019bAmadori et al, , 2020aAmadori et al, , 2022Hamm, 2020a;present paper). In Ptychodus, diversification in tooth morphology and, consequently, in diet preferences could therefore have reduced competition for food (e.g., shell-covered prey) within the genus (niche specialization), as well as with other possible durophagous groups.…”

The oldest Gondwanan record of the extinct durophagous hybodontiform chondrichthyan, Strophodus from the Bajocian of Morocco

“…Potential causes underlying the species decline and subsequent demise of Strophodus remain elusive but are likely to be multifactorial, perhaps involving both fluctuations in the relative availability of preferred food resources (note that marine hard-shelled invertebrates declined across the Jurassic/Cretaceous boundary; see Tennant et al, 2017, and references therein) and an increasing competitive overlap with crown group elasmobranchs (i.e., sharks and rays), which rapidly diversified during the Jurassic and Cretaceous (Guinot & Cavin, 2016;Kriwet et al, 2009;Underwood, 2006). Interestingly, the final demise of Strophodus coincides with the appearance of the giant durophagous shark Ptychodus Agassiz, 1834 (see Cappetta, 2012, andreferences therein), which quickly diversified into many different species soon after it first appeared during the Albian to become the most dominant Cretaceous durophagous predator to have ever lived (e.g., Shimada et al, 2009Shimada et al, , 2010Amadori et al, 2020Amadori et al, , 2022Amadori et al, , 2023Jambura & Kriwet, 2020). This suggests that Ptychodus might have benefitted from the freed ecospace that was left in the wake of Strophodus' extinction.…”

Enameloid‐bound δ15N reveals large trophic separation among Late Cretaceous sharks in the northern Gulf of Mexico

“…Paleontologists have inferred the clutching‐type dentition of Meristodonoides (Cappetta, 1987) to be successful at crushing (Whitenack & Motta, 2010) and/or restraining fast‐swimming prey (e.g., Ciampagalio et al., 2005), suggesting that it potentially had a diversified diet (including, e.g., weakly armored prey, small fishes, squid). The crushing‐type dentition of Ptychodus suggests durophagy, or a diet of primarily hard‐shelled macroinvertebrates (Amadori et al., 2022; Shimada, 2012). By the Late Cretaceous, lamniforms dominated the marine realm, and hybodontiforms were increasingly restricted to more nearshore habitats (e.g., Maisey, 2012).…”