Vertebrate Palaeoecology of the Pisco Formation (Miocene, Peru): Glimpses into the Ancient Humboldt Current Ecosystem

Abstract

The northward-flowing Humboldt Current hosts perpetually high levels of productivity along the western coast of South America. Here, we aim to elucidate the deep-time history of this globally important ecosystem based on a detailed palaeoecological analysis of the exceptionally preserved middle–upper Miocene vertebrate assemblages of the Pisco Formation of the East Pisco Basin, southern Peru. We summarise observations on hundreds of fossil whales, dolphins, seals, seabirds, turtles, crocodiles, sharks, rays, and bony fishes to reconstruct ecological relationships in the wake of the Middle Miocene Climatic Optimum, and the marked cooling that followed it. The lowermost, middle Miocene Pisco sequence (P0) and its vertebrate assemblage testify to a warm, semi-enclosed, near-shore palaeoenvironment. During the first part of the Tortonian (P1), high productivity within a prominent upwelling system supported a diverse assemblage of mesopredators, at least some of which permanently resided in the Pisco embayment and used it as a nursery or breeding/calving area. Younger portions of the Pisco Formation (P2) reveal a more open setting, with wide-ranging species like rorquals increasingly dominating the vertebrate assemblage, but also local differences reflecting distance from the coast. Like today, these ancient precursors of the modern Humboldt Current Ecosystem were based on sardines, but notably differed from their present-day equivalent in being dominated by extremely large-bodied apex predators like Livyatan melvillei and Carcharocles megalodon.

Sperm whales (Physeteroidea) from the Pisco Formation, Peru, and their trophic role as fat sources for late Miocene sharks

“…Shark bite marks on marine mammal bones have been previously reported from late Miocene strata of Peru, either inflicted by Carcharodon or Otodus [9,57,65,66]. The materials here reported indicate that these events were not uncommon within the ancient Pisco ecosystems, and are congruent with previous reports of feeding behaviour by large sharks [9].…”

“…The sperm whale remains discussed herein were collected from the upper strata of the Pisco Fm. Research carried out in the coastal desert of Peru during the last 30 years revealed that during the Late Miocene the region was a hotspot for marine biodiversity, including a wide diversity of typical Miocene faunal elements along with early representatives of modern families [37,57]. Sharks and cetaceans constitute the most representative finds in the upper Pisco strata.…”

An Early Miocene kentriodontoid (Cetacea: Odontoceti) from the western North Pacific, and its implications for their phylogeny and paleobiogeography

“…Further analysis could improve the current reconstruction of their paleobiogeography when even more specimens could be added to the cladogram. Recently, many specimens of delphinidans including kentriodontoids have been reported such as those undescribed specimens discovered in Peru [ 50 , 51 ].…”

Paleoceanographic Implications of Diatom Seasonal Laminations in the Upper Miocene Pisco Formation (Ica Desert, Peru) and Their Clues on the Development of the Pisco Fossil‐Lagerstätte

“…(2016), Bianucci, Di Celma, Landini, et al. (2016), where the authors list more than 300 specimens preserved as bone elements belonging mostly to cetaceans at the site of Cerro Colorado (Pisco Fossil Lagerstätte Ica Desert, Peru) and 192 fossils of marine vertebrates preserved as bone elements at CLQ; (b) the exceptional preservation of the specimens, both in terms of completeness and details of delicate features such as baleens (e.g., Bosio et al., 2021a; Collareta et al., 2021; Esperante et al., 2015), and; (c) the scientific relevance of this findings by recalling that the Miocene represents a pivotal moment in the evolution of marine vertebrates (Marx & Uhen, 2010).…”

“…As a second step, we have wanted to test the possibility of getting indications of the role played by the flux of diatoms to the sea bed in preserving the carcasses and thus leading to the formation of the Lagerstätte. We can get a glimpse of the importance of this Lagerstätte in terms of: (a) number of findings by citing the data reported by Bianucci, Di Celma, Collareta, et al (2016), , where the authors list more than 300 specimens preserved as bone elements belonging mostly to cetaceans at the site of Cerro Colorado (Pisco Fossil Lagerstätte Ica Desert, Peru) and 192 fossils of marine vertebrates preserved as bone elements at CLQ; (b) the exceptional preservation of the specimens, both in terms of completeness and details of delicate features such as baleens (e.g., Bosio et al, 2021a;Collareta et al, 2021;Esperante et al, 2015), and; (c) the scientific relevance of this findings by recalling that the Miocene represents a pivotal moment in the evolution of marine vertebrates (Marx & Uhen, 2010). Recently, researches have investigated the mechanisms that have favored the fossilization of all these organisms.…”