The earliest burst of necrophagous dung beetles in South America revealed by the Cenozoic record of Coprinisphaera

Abstract

New ichnological, sedimentological and palaeobotanical information from a Miocene palaeosol succession from Patagonia bearing abundant fossil brood balls of dung beetles (Coprinisphaera) allow inferring novel aspects of the evolutionary history, biology and feeding habits of Scarabaeinae, along with the palaeoenvironmental and palaeoclimatic conditions in which they nested. Coprinisphaera tonnii and Coprinisphaera akatanka, both attributed to necrophagous dung beetles, represent 40.2% of the specimens. Considering their scarce or null record in older Cenozoic units from South America, these high values reveal that the first burst of necrophagous Scarabaeinae took place during the Miocene. Some Coprinisphaera preserve characters that indicate the developmental stage of the ball occupant and the adult emergence success. Both ichnospecies show the egg chamber isolated from the provision chamber, which was associated with a higher preference of cleptoparasites for necrophagous balls. The comparison among the abundance of traces of nest intruders in Coprinisphaera attributed both to necrophagous and to coprophagous beetles from different units of South America indicates that the presence of such intruders would be independent of the nature of the organic matter contained within the balls. Phytolith analyses performed in Coprinisphaera and extant necrophagous and coprophagous balls indicate that the comparison between the relative abundance of phytoliths in the wall of the brood ball, their infilling and the bearing palaeosol is a useful tool for inferring the feeding behaviour of the trace makers and support the attribution of Coprinisphaera tonnii and Coprinisphaera akatanka to necrophagous Scarabaeinae. Sedimentary and palaeosol analyses indicate that the beetles would have nested in well‐drained soils showing mollic‐like features, in grass‐dominated habitats, under a seasonal sub‐humid, temperate–warm climate.

Comprehensive total evidence phylogeny of chinchillids (Rodentia, Caviomorpha): Cheek teeth anatomy and evolution

“…For several early and middle Miocene units, a grass-dominated environment with subordinated trees and seasonal sub-humid to temperate-warm climate was also proposed (e.g. Cantil et al, 2020). Nevertheless, other studies suggest that grasses were not dominant during the early and middle Miocene in Patagonia (Palazzesi et al, 2014).…”

“…Formation), a grass-dominated environment with subordinated trees and seasonal sub-humid to temperate-warm climate was proposed (e.g. Cantil et al, 2020). The main cause of this change was the rising of the Patagonian Cordillera since middle Miocene (e.g.…”

An assemblage of large-sized insect traces in paleosols from the middle Miocene of northern Patagonia related to the climatic optimum

“…Climate and resulting biota can be assessed by several preserved pedofeatures. Silicified ferruginous crusts in some Andisols result from silica releasing during weathering of volcanic ash in dry soils (Chadwick et al, 1987;Buol et al, 2011), a process enhanced by earthworm activity (Cantil et al, 2020). Lack of carbonates and the presence of clay skins, ferruginous nodules and high biomass (at least below-ground) inferred by abundant trace fossils and the diffuse boxwork ichnofabric, suggest temperate-warm, seasonal subhumid conditions.…”

“…Insect trace fossils in paleosols in combination with pedogenic features is one of the most powerful tools that has been used in the last years to disentangle ecological and climatic conditions of terrestrial paleoecosystems (Genise et al, 2000;Sánchez et al, 2010;Bellosi et al, 2016;Genise, 2016;Sarzetti et al, 2017;Cantil et al, 2020). South American ichnology of paleosols has a long history and tradition arising in the first half of the last century (Sauer, 1955;Frenguelli, 1938Frenguelli, , 1939Roselli, 1939) and it has been contributing a lot since then to interpret paleoenvironments from different areas of the region (Verde et al, 2007;Genise and Farina, 2011;Cantil et al, 2013;Sánchez et al, 2013;Catena et al, 2016;Genise et al, 2016;do Nascimento et al, 2019).…”

“…Particularly, Patagonia has been one of the most studied areas, which has been favored by extensive outcrops with paleosols spanning from the Jurassic to the Miocene (Bedatou et al, 2008;Genise et al, 2008Genise et al, , 2017Genise et al, , 2020Genise, 2016). In this context, recent ichnological research on the middle Miocene La Pava Formation of northern, extra-Andean Patagonia (Nullo, 1978) has resulted in significant information on the evolution of necrophagous habitats in dung beetles (Cantil et al, 2020), the appearance and evolution of Diphaglossinae bees producing curved cells (Sarzetti et al, 2014(Sarzetti et al, , 2017 and paleoenvironmental reconstructions (Cantil et al, 2015(Cantil et al, , 2020Sarzetti et al, 2017;Sánchez et al, 2018). This research on new localities of the La Pava Formation in the Rio Negro province of Patagonia, in combination with previous information for this unit allows us to present herein the ichnology of paleosols formed during the Middle Miocene Climatic Optimum.…”