Diversification trajectories and paleobiogeography of Neogene chondrichthyans from Europe

Despite the rich fossil record of Neogene chondrichthyans (chimaeras, sharks, rays, and skates) from Europe, little is known about the macroevolutionary processes that generated their current diversity and geographical distribution. We compiled 4368 Neogene occurrences comprising 102 genera, 41 families, and 12 orders from four European regions (Atlantic, Mediterranean, North Sea, and Paratethys) and evaluated their diversification trajectories and paleobiogeographic patterns. In all regions analyzed, we found that generic richness increased during the early Miocene, then decreased sharply during the middle Miocene in the Paratethys, and moderately during the late Miocene and Pliocene in the Mediterranean and North Seas. Origination rates display the most significant pulses in the early Miocene in all regions. Extinction rate pulses varied across regions, with the Paratethys displaying the most significant pulses during the late Miocene and the Mediterranean and North Seas during the late Miocene and early Pliocene. Overall, up to 27% and 56% of the European Neogene genera are now globally and regionally extinct, respectively. The observed pulses of origination and extinction in the different regions coincide with warming and cooling events that occurred during the Neogene globally and regionally. Our study reveals complex diversity dynamics of Neogene chondrichthyans from Europe and their distinct biogeographic composition despite the multiple marine passages that connected the different marine regions during this time

Neogene Bony Fishes from the Bahía Inglesa Formation, Northern Chile

Despite being one of the richest Neogene deposits of marine fossil vertebrates along the Pacific coast of South America, no detailed study of bony fishes from the Bahía Inglesa Formation has been carried out. Through the revision of historical collections of the Caldera Paleontological Museum, we describe 27 fossil remains of bony fishes. Fossils described here are distributed in 13 taxa. Among these, Sardinops sp. cf. S. sagax (Clupeidae) represents the first fossil record of the genus for Chile, Labrodon sp. (Labridae) and Stelliferinae (Sciaenidae) are the first respective records for the southeast Pacific Ocean, Sarda sp. (Scombridae) represents the first fossil record for South America, Semicossyphus sp. (Labridae) and Anisotremus sp. (Haemulidae) are the first respective records for the Southern Hemisphere. Gymnosarda sp. (Scombridae) is described for the first time for the Neogene. We performed a paleobathymetric analysis of fossil fishes, including elasmobranchs, to understand the paleoenvironment followed by a similarity analysis that compares the faunal composition of the Bahía Inglesa Fm. with other fossil assemblages for the Pacific of South America. Our results show that the fish fauna from the Bahía Inglesa Fm. likely represents a depth range of 98 to 382 m with a mean depth range of 252 m in an uppermost bathyal environment. The assemblage from the Bahía Inglesa Fm. shows low taxonomic similarity levels with other Neogene geological units from the southeast Pacific Ocean. The study represents the first paleoecological and paleobiogeographic analysis of the fossil fish fauna from the Southeast Pacific. Key words. Atacama region. Clupeiformes. Eastern Pacific. Paleoenviroments. Perciformes. Ophidiiformes

¿Qué sabemos de los peces óseos marinos del neógeno en Chile? Diversidad e implicaciones biogeográficas

Durante el Neógeno ocurren intensos eventos, oceanográficos y climáticos, que influyeron sobre la fauna marina de Chile desde el pasado hasta la actualidad. Estudios enfocados en la evaluación del efecto de estos eventos sobre la diversidad de mamíferos, aves y tiburones han sido previamente abordados. Sin embargo, las interacciones de estos eventos con los peces óseos como grupo de estudio no han sido analizados en detalle. Este trabajo compara la diversidad de peces óseos del Neógeno con la actualidad y da a conocer lo que sabemos de su diversidad. Se procesaron los datos disponibles de la presencia de peces óseos marinos en formaciones neógenas de Chile y la actualidad. Se comparó la composición del registro fósil de peces neógenos con el registro de peces actuales a 3 niveles taxonómicos distintos (familia, género y especie). Finalmente, se analizaron los rangos de distribución de los taxa fósiles que sobrevivieron con el objetivo de realizar aproximaciones de las dinámicas paleobiogeográficas. Nuestros resultados muestran que la diversidad actual de peces óseos marinos en Chile es de 624 géneros (1.196 especies), mientras que para el Neógeno se han reportado 65 géneros (46 especies). Comparado con la diversidad actual, el registro fósil de peces es representado por un 3,9% a nivel de especie, 10,4% a nivel de género y 23,4% a nivel de familias, lo que puede ser relacionado con la baja cantidad de estudios enfocados en fósiles de este grupo. Del total de 46 especies fósiles reportadas, sólo una se encuentra actualmente presente en las costas de Chile. A nivel genérico, un 38,5% se encuentra actualmente ausente en la región y un 61,5% sobrevive. En relación a los géneros ausentes actualmente, un 20% corresponde a extinción global y un 80% a extinción regional. Estos cambios en las dinámicas biogeográficas de peces óseos del pasado al reciente, podrían estar relacionadas con los intensos eventos climáticos y oceanográficos que han ocurrido en los últimos 23 millones de años. Los análisis de rarefacción y de extrapolación de especies confirman que a pesar de que han aumentado los trabajos sobre peces óseos en los últimos años, todavía se podrían encontrar un mayor número de taxa si se aplica un mayor esfuerzo de muestreo. Estudios futuros podrían ayudarnos a comprender de mejor manera el efecto de los cambios climáticos y oceanográficos sobre los peces del Neógeno de Chile.Durant el Neogen ocorren intensos esdeveniments, oceanogràfics, i climàtics, que van influir sobre la fauna marina de Xile des del passat fins a l’actualitat. Estudis enfocats en l’avaluació de l’efecte d’aquests esdeveniments sobre la diversitat de mamífers, ocells i taurons han sigut prèviament abordats. No obstant això, les interaccions d’aquests esdeveniments amb els peixos ossis com a grup d’estudi no han sigut analitzats detalladament. Aquest treball analitza la diversitat de peixos ossis del Neogen comparat amb l’actualitat i dona a conéixer que sabem de la seua diversitat. Es van analizar les dades disponibles de la presència de peixos ossis marins en formacions neógenas de Xile i l’actualitat. Es va comparar la composició del registre fòssil de peixos neògens amb el registre de peixos actuals a 3 nivells taxonòmics diferents (família, gènere i espècie). Finalment, es van analizar els rangs de distribució dels taxa fòssils que van sobreviure amb la finalitat de realitzar aproximacions de les dinàmiques paleobiogeográficas. Els nostres resultats mostren que la diversitat actual de peixos ossis marins a Xile és de 624 gèneres (1.196 espècies), mentre que per al Neogen s’han reportat 65 gèneres (46 espècies). Comparat amb la diversitat actual, el registre fòssil de peixos és representat per un 3,9% a nivell d’espècie, 10,4% a nivell de gènere i 23,4% a nivell de famílies, la qual cosa pot ser relacionat amb la baixa quantitat d’estudis enfocats en fòssils d’aquest grup. Del total de 46 espècies fòssils reportades, només un 4% es troba actualment present en les costes de Xile. A nivell genèric, un 38.5% es troba actualment absent a la regió i un 61.5% sobreviu. En relació als gèneres absents actualment, un 20% correspon a extinció global i un 80% a extinció regional. Aquests canvis en les dinàmiques biogeogràfiques de peixos ossis del passat al recent, podrien estar relacionades amb els intensos esdeveniments climàtics i oceanogràfics que han ocorregut en els últims 23 milions d’anys. Les anàlisis de rarefacció i d’extrapolació d’espècies confirmen que a pesar que han augmentat els treballs sobre el grup en els últims anys, encara es podrien trobar un major número de taxa si s’aplica un major esforç de mostreig. Estudis futurs podrien ajudar-nos a comprendre de millor manera l’efecte dels canvis climàtics i oceanogràfics sobre els peixos del Neogen de Xile.During the Neogene occurred intense oceanographic and climatic events which had an effect on the marine fauna from the past to the present. Studies focused on the evaluation of the effect of these events on the diversity of mammals, birds and sharks have been previously addressed. However, the interactions of these events with bony fishes as a study group have not been analyzed in detail. This work analyzes the diversity of bony fishes from the Neogene compared to today and reveals what we know about their diversity. We analyzed the available data on the presence of marine bony fishes from Neogene formations in Chile and today. The composition of the fossil record of Neogene fishes was compared to the current fish record at 3 different taxonomic levels (family, genus, and species). Lastly, the distribution ranges of the surviving fossil taxa were analyzed in order to make approximations of the paleobiogeographic dynamics. Our results show that the current diversity of marine bony fish in Chile is composed of 624 genera (1,196 species), whereas from the Neogene 65 genera (46 species) have been reported. Compared to the current diversity, the fossil record of fishes is represented by 3.9% at the species level, 10.4% at the genus level and 23.4% at the family level, which can be related to the low number of studies focused on fossils of this group. Of the total of 46 fossil species reported, only 4% is currently present along the coast of Chile. At a generic level, 38.5% are currently absent in the region whereas 61.5% survived. In relation to the genera currently absent in the region, 20% are globally extinct and 80% regional extinct. These changes in the biogeographic dynamics of bony fishes from the past to the recent could be related to the intense climatic and oceanographic events that have occurred in the last 23 million years. The rarefaction and extrapolation analyses confirm that although the studies focused on the group have increased in the last years, a higher number of taxa could still be found if the sampling effort is increased. Future studies could help us to a better understanding of the effects of climatic and oceanographic changes on the group during the Neogene of Chile

First evidence of a palaeo-nursery area of the great white shark

Shark nurseries are essential habitats for shark survival. Notwithstanding the rich fossil record of the modern great white shark (Carcharodon carcharias, GWS), its use of nursery areas in the fossil record has never been assessed before. Here, we analysed the fossil record of the GWS from three South American Pliocene localities, assessed body size distributions and applied previously established criteria to identify palaeo-nurseries. We found that juveniles dominate the Coquimbo locality (Chile), whereas subadults and adults characterize Pisco (Peru) and Caldera (Chile), respectively. These results, summed to the paleontological and paleoenvironmental record of the region, suggest that Coquimbo represents the first nursery area for the GWS in the fossil record. Our findings demonstrate that one of the top predators in today’s oceans has used nursery areas for millions of years, highlighting their importance as essential habitats for shark survival in deep time

Diversity and paleoenvironmental implications of an elasmobranch assemblage from the Oligocene–Miocene boundary of Ecuador

The occurrence and diversity of elasmobranchs from the Oligocene–Miocene boundary from Tropical America is poorly known in comparison with the paleodiversity from younger Neogene intervals of the region. Here we describe a new elasmobranch assemblage from the rich fossil site of Montañita-Olón (Dos Bocas Formation, Santa Elena, Ecuador), where other vertebrates have already been described: for example, sea turtles and cetaceans. We report a total of 27 elasmobranch taxa, 19 of which are new fossil records for Ecuador, 10 new records for the Central Eastern Pacific and four new records for South America. Additionally, in order to reconstruct the environment where these marine remains were deposited, we performed abundance, paleobathymetric and habitat preference analyses, concluding that they were likely deposited in an outer neritic (open shelf) environment. The study of Oligocene and early Miocene marine elasmobranchs faunas in Tropical America is key to addressing the issues in the evolutionary history of this group

The Neogene fossil record of Aetomylaeus (Elasmobranchii, Myliobatidae) from the south-eastern Pacific

The presence of eagle rays of the genus Aetomylaeus in the Neogene of the Temperate Pacific coast of South America (TPSA) still is ambiguous, although the fossil record of elasmobranch fishes (sharks, rays, and skates) from this area is quite good. Here, we present the first unmistakable fossil remains of Aetomylaeus from the Neogene of the TPSA. The material comprises 13 dental plates from one site in Peru and six localities in Chile ranging in age from Miocene to Pliocene and was compared with dental plates of extant species. Our study reveals that the number of tooth rows and the shape of lateral teeth in extant species are seemingly very variable and need to be established before fossil specimens can be confidently identified. Consequently, we do not assign the fossil specimens from the Neogene of the TPSA to any species but leave them as Aetomylaeus. Moreover, we recognized that only the shape of medial teeth provides reliable diagnostic characters in our material, whereas the shape and number of lateral teeth are highly variable, similar to the condition seen in extant species

Late Neogene Elasmobranch Fauna From The Coquimbo Formation, Chile

Artículo de publicación ISINeogene marine sediments from Chilean geological formations contain a diverse marine fossil fauna. In Chile, the "Norte Chico" (27 degrees S to 32 degrees S) is composed of two important sedimentary marine deposits, the Bahia Inglesa and Coquimbo formations. Diverse vertebrate taxa including fish, birds, mammals and abundant chondrichthyans have been described from Bahia Inglesa Formation. However, the vertebrate fauna from Coquimbo Formation has been poorly documented. Based upon field trips and the analysis of collections from the Coquimbo Formation, the elasmobranch fossil fauna is composed of at least nine taxa, two of which are extinct (Carcharocles megalodon and Carcharodon plicatilis). The rest of the taxa are related with living elasmobranch species that are inhabitants of the Eastern Pacific Ocean and Tropical America coast

Diversity and paleoenvironmental implications of an elasmobranch assemblage from the Oligocene-Miocene boundary of Ecuador

Altres ajuts: Research Groups CSIC 64 1538 and CAM-UCM910607The occurrence and diversity of elasmobranchs from the Oligocene-Miocene boundary from Tropical America is poorly known in comparison with the paleodiversity from younger Neogene intervals of the region. Here we describe a new elasmobranch assemblage from the rich fossil site of Montañita-Olón (Dos Bocas Formation, Santa Elena, Ecuador), where other vertebrates have already been described: for example, sea turtles and cetaceans. We report a total of 27 elasmobranch taxa, 19 of which are new fossil records for Ecuador, 10 new records for the Central Eastern Pacific and four new records for South America. Additionally, in order to reconstruct the environment where these marine remains were deposited, we performed abundance, paleobathymetric and habitat preference analyses, concluding that they were likely deposited in an outer neritic (open shelf) environment. The study of Oligocene and early Miocene marine elasmobranchs faunas in Tropical America is key to addressing the issues in the evolutionary history of this group