Fish otoliths from the early Miocene of Chile: a window into the evolution of marine bony fishes in the Southeast Pacific

Abstract

Few fossil fish otolith associations have been described from the Pacific side of the Americas and, except for a single species (Steindachneria svennielseni), none have been described from Pacific South America south of the Central American tropical region. Here, we describe a rich otolith assemblage obtained from fifteen early Miocene outcrop locations along the Chilean coast from about 33°S to about 45°S. More than 2,000 specimens were studied resulting in the recognition of 67 species, with 27 being new to science. This assemblage represents an important new data point distant from any previously known otolith-based fish fauna, with the nearest coeval associations being from the Caribbean Province in Venezuela, which lies about 5000 km to the north, and New Zealand, which is about 9000 km to the west. The fauna represents a mixture of offshore and shallow water fishes and is rich in myctophids, paralichthyids (Citharichthys), ophidiids (Lepophidium), steindachneriids, and macrourids. Typical tropical American fishes are nearly completely absent, with the exception of Steindachneria and certain anguilliforms. The mesopelagic faunal component, chiefly Myctophidae, shows a striking resemblance to the well-known coeval fish fauna from New Zealand, and both are interpreted as representing an early South Pacific mesopelagic bioprovince. The strong correlation with the mesopelagic otolith-based fish fauna from New Zealand constricts the time interval of the sampled sediments to the middle Burdigalian (approximately 17.5 to 18.5 Ma). All otoliths obtained from the early Miocene of Chile relate to extant fish groups of the area and few exotic components not currently present in the East Pacific. The sole exception is a morpho-type described as Navidadichthys which has an unresolved relationship, possibly with the Prototroctidae, a family that is today endemic to the freshwater and nearshore marine environments of Australia and New Zealand. The new taxa are in the sequence of taxonomic description: Pterothrissus transpacificus n. sp., Pythonichthys panulus n. sp., Chiloconger chilensis n. sp., Gnathophis quinzoi n.sp., Rhynchoconger chiloensis n. sp., Navidadichthys mirus n. gen. et n. sp., Maurolicus brevirostris n. sp., Polyipnus bandeli n. sp., Lampanyctus ipunensis n. sp., Physiculus pichi n. sp., Coelorinchus fidelis n. sp., Coelorinchus rapelanus n. sp., Nezumia epuge n. sp., Paracarapus chilensis n. gen. et n. sp., Lepophidium chonorum n. sp., Lepophidium mapucheorum n. sp., Sirembola supersa n. sp., Spectrunculus sparsus n. sp., Pseudonus humilis n. sp., Capromimus undulatus n. sp., Agonopsis cume n. sp., Cottunculus primaevus n. sp., Kuhlia orientalis n. sp., Citharichthys parvisulcus n. sp., Citharichthys vergens n. sp., Achirus australis n. sp., Achirus chungkuz n. sp.

Ancient DNA from the extinct New Zealand grayling (Prototroctes oxyrhynchus) reveals evidence for Miocene marine dispersal

“…Extant retropinnids are restricted to south-eastern Australia and New Zealand, but a possible fossil retropinnid—with closest affinities to Prototroctes —has also been described from the Miocene of Chile ( Navidadichthys miru ; Schwarzhans et al, 2021). This exclusively Southern Hemisphere distribution suggests that Gondwanan vicariance may have played a role in determining the distribution of retropinnid lineages.…”

“…The New Zealand grayling is generally considered to be the sister-species to the endangered Australian grayling ( Prototroctes maraena ), which is presently restricted to south-eastern Australia and Tasmania. Although the genus Prototroctes has sometimes been attributed to a distinct family—the Prototroctidae (McDowall, 1969; McDowall, 1976; Nelson, 1994; Schwarzhans et al, 2021)—it is currently considered to belong to a subfamily (Prototroctinae) within Retropinnidae (Waters et al, 2002). The Retropinnidae (southern smelts and graylings) constitute a monophyletic group sister to the Osmeridae (northern smelts; Li et al, 2010), sharing a common ancestor ∼80 million years ago (Mya; Burridge et al, 2012).…”

Lanternfish otoliths (Myctophidae, Teleostei) from the Miocene of Japan

“…Diogenichthys aguilerai was apparently widespread during the early Miocene (Aquitanian and Burdigalian) but usually not common, with the exception of a recent find in the late Burdigalian of Chile (Schwarzhans and Nielsen 2021). It was originally described from Angola (Schwarzhans 2013b) but is also known from New Zealand (Schwarzhans 2019) and possibly also from the Caribbean (as Diogenichthys sp.…”

“…Myctophum murbani (Weinfurter, 1952) is a widely distributed tropical to subtropical species that occurred in the late Burdigalian to Langhian in the Caribbean, the Mediterranean, the Paratethys, and now also in Japan. Thus far, no coeval Myctophum otoliths are known from the southern hemisphere (i.e., New Zealand or Chile; see Schwarzhans 2019 andNielsen 2021).…”

“…Discussion. For a detailed description, see Schwarzhans ( 2019) and the subsequent update in Schwarzhans and Nielsen (2021). Protomyctophum ahunga is a typical and rather common species in the late Burdigalian of New Zealand and Chile but has not been found in coeval sediments of the Caribbean (Trinidad or Venezuela).…”