Dental Morphology, Palaeoecology and Palaeobiogeographic Significance of a New Species of Requiem Shark (Genus Carcharhinus) from the Lower Miocene of Peru (East Pisco Basin, Chilcatay Formation)

Abstract

Nowadays, the requiem sharks comprise one of the most diverse and widespread families of selachians, i.e., Carcharhinidae. Among the carcharhinids, the genus Carcharhinus has the largest number of living species, namely, at least 35. Known from fossils as old as the Cretaceous, the requiem sharks did not significantly radiate before the Eocene (when Carcharhinus also appeared), and their diversification mainly occurred in Neogene times. Here, we describe a new species of requiem shark, Carcharhinus dicelmai sp. nov., based on fossil teeth from Lower Miocene (18.4–18.1 Ma) strata of the Chilcatay Formation of the East Pisco Basin (southern Peru). Upper teeth of C. dicelmai sp. nov. are typically provided with a slender, smooth-edged cusp; a marked coronal twist; and a distal heel that bears 1–5 coarse, angularly lobate serrae that become more prominent toward the base of the cusp. The dentition of C. dicelmai sp. nov. appears less akin to that of most other carcharhines to the cutting-clutching type, and seemingly testifies to the development of more predominantly clutching adaptations. A carcharhinid tooth from the Burdigalian to lower Langhian Cantaure Formation of Venezuela is reassigned to C. dicelmai sp. nov., suggesting a trans-Panamanian distribution for this extinct shark species.

A new platyrostrine sperm whale from the Early Miocene of the southeastern Pacific (East Pisco Basin, Peru) supports affinities with the southwestern Atlantic cetacean fauna

“…Strengthening previous suggestions of vertebrate faunal flow between the Chilcatay palaeobiotopes and the Atlantic realm (Peri et al 2019; Collareta et al 2022), the shared presence of the genera Diaphorocetus and Notocetus Moreno, 1892 evokes the existence of a dispersal route between the east and west coasts of South America during the Early Miocene (note that the genus Kentriodon Kellogg, 1927 is more widely distributed, so that its South American records do not imply any specific biogeographic link; Kimura & Hasegawa 2019). Furthermore, the many morphotypes shared by the Chilcatay and Gaiman/Monte Leon cetacean assemblages may point to similarities in the structuring of the local odontocete communities.…”

“…Other localities where the Burdigalian portion of the Chilcatay Formation is exposed have so far yielded further forms of cetaceans (Bianucci et al 2018a, 2020; Lambert et al 2018, 2020, 2021; Di Celma et al 2019), elasmobranchs (Shimada et al 2017; Di Celma et al 2019; Landini et al 2019; Collareta et al 2022, 2023), sea birds (Acosta-Hospitaleche & Stucchi 2005), and bony fishes (Di Celma et al 2019). In particular, another physeteroid species, Rhaphicetus valenciae , has recently been described from the highly fossiliferous locality of Zamaca, and specifically from deposits belonging the Ct1a stratal package (Lambert et al 2020) (Fig.…”

A Review of the Paleobiology of Some Neogene Sharks and the Fossil Records of Extant Shark Species

“…This newly described species is known from the Lower Miocene Chilcatay Formation of Peru (type locality) and from the Lower-to mid-Miocene (Burdigalian to Lower Langhian) Cantaure Formation of Venezuela. The latter locality suggests a trans-Panamanian distribution for this ancient species [73]. Given the dimensions of its teeth, †C.…”

A Review of the Palaeobiology of Some Neogene Sharks and the Fossil Record of Extant Shark Species

“…The latter locality suggests a trans-Panamanian distribution for this ancient species (Collareta et al 2022a). Given the dimensions of the teeth, C. dicelmai was likely a diminutive carcharhinid and may have relied on small-sized prey items (including, e.g., small bony fishes and invertebrates) that were individually captured and ingested through feeding actions that involved clutching (Collareta et al 2022a). Following the latter authors, C. dicelmai may also have been an essentially thermophilic and very littoral shark.…”

“…Carcharhinus dicelmai Collareta, Kindlimann, Baglioni, Landini, Sarti, Altamirano, Urbina & Bianucci, 2022 This newly described species is known from the Lower Miocene Chilcatay Formation of Peru (type locality) and from the Lower-to mid Miocene (Burdigalian to lower Langhian) Cantaure Formation of Venezuela. The latter locality suggests a trans-Panamanian distribution for this ancient species (Collareta et al 2022a). Given the dimensions of the teeth, C. dicelmai was likely a diminutive carcharhinid and may have relied on small-sized prey items (including, e.g., small bony fishes and invertebrates) that were individually captured and ingested through feeding actions that involved clutching (Collareta et al 2022a).…”