Morphological and taxonomic descriptions of a new genus and species of killifishes (Teleostei: Cyprinodontiformes) from the high Andes of northern Chile

Abstract

A new genus and species, Pseudorestias lirimensis, is described from the southern part of the Chilean Altiplano. While sharing several characters that clearly align the new species with Orestias, this new fish is characterized by numerous autapomorphies: the Meckel cartilage is a continuous cartilage that broadly expands posteriorly (in large specimens, it keeps its anterior part and is resorbed posteriorly), the basibranchials are fused into one long element, the second pharyngobranchial is not displaced dorsally over pharyngobranchial tooth plate 3+4, but they are aligned, the anterior and posterior ceratohyals are closely articulated keeping a scarce amount of cartilage between both bones and ventral to them, ossified middle and distal dorsal radials are present in females as well as ossified middle and distal anal radials. Pseudorestias lirimensis presents strong sexual dimorphism associated to size. Females are almost twice as large and long than males, neuromast lines are absent in males, a mesethmoid is present in males, squamation on head is reduced in males, and ossified middle and distal radial of dorsal fin are cartilaginous in males. Pseudorestias and Orestias are suggested as the sole members of the tribe Orestiini. A list of characters diagnosing the tribe is provided. The presence of the new genus is interpreted as a possible result of the ecosystem isolation where the fish is living from surrounding basins—as early as possibly from the Miocene-Pliocene times—and its physical and chemical characteristics. Small populations, living conditions, small habitat, and reduced distribution make this species a strong candidate to be considered critically endangered, a situation already established for all other Chilean species living in the Altiplano. There is high probability it will become extinct due to water demands and climate change in the region.

Platyfish bypass the constraint of the caudal fin ventral identity in teleosts

“…A recently described new species of Cyprinodontiformes, named Pseudorestias lirimensis, forms an articulation between the first principal ray and epural. 59 Interestingly, the Cyprinodontiform fossil from the oligocene in France, †Prolebias delphinensis, reveals a configuration, in which the upper non-branched principal ray articulated with the neural spine. 60,61 In this extinct species, the caudal fin consisted of 12 branched rays, whereby the upper-most branched ray connected to the epural.…”

“…The Cyprinodontiformes can be unambiguously recognized by the presence of a single, blade-like epural that mirrors the parhypural, and the widened neural and hemal spines. [58][59][60][66][67][68][69] Consistently, the next level of the caudal endoskeletal symmetry in platyfish and guppies is represented by these structures. In both these species, the dorsal and ventral counterpart bones of preural centra display mirrored appearance and they symmetrically support upper and lower principal rays.…”

“…This observation is consistent with the main feature of Cyprinodontiformes, which evolved enhanced symmetry of its caudal endoskeleton, as reported for various species. [58][59][60][66][67][68][69] In this order, the upper and lower hypural plates can stay separate or fuse to provide a more rigid support for the principal rays. Consistently, our developmental analysis of platyfish demonstrated that the hypural plate derives from two separate elements, namely a lower hypural plate (ie, hypurals 1 + 2 in zebrafish) and an upper hypural plate (ie, hypurals 3 + 4 + 5).…”

First record sheds light on the distribution of the cyprinodontiform genus Jenynsia (Günther, 1866) in the High Andean Plateau

“…This landscape is dominated by non‐marine brines accumulated in sedimentary basins during Neogene, where ecological heterogeneity is expressed by an array of aquatic ecosystems that include numerous extensive salars and lagoons – such as Antofalla and Laguna Colorada – as well as geothermal springs and other high‐altitude wetlands (Alonso et al ., 1991; Benzaquen et al ., 2017). Within the entire HAP, which stretches along 1800 km from southern Perú Altiplano plain to northwestern Argentina Puna, only four native fish genera were recorded above 3 km: Astroblepus (climbing catfish), Orestias and Pseudorestias (pupfish) and Trichomycterus (pencil catfish) (Arratia et al ., 2017; Arraya et al ., 2009; Barra et al ., 2009; Cruz‐Jofré et al ., 2014; Fernández & Andreoli Bize, 2018; Fernández & Andreoli Bize, 2017; Schaefer, 2011). The Orestiini ( sensu Arratia et al ., 2017) is recognized as the sole cyprinodontiform clade found in the HAP.…”

“…Within the entire HAP, which stretches along 1800 km from southern Perú Altiplano plain to northwestern Argentina Puna, only four native fish genera were recorded above 3 km: Astroblepus (climbing catfish), Orestias and Pseudorestias (pupfish) and Trichomycterus (pencil catfish) (Arratia et al ., 2017; Arraya et al ., 2009; Barra et al ., 2009; Cruz‐Jofré et al ., 2014; Fernández & Andreoli Bize, 2018; Fernández & Andreoli Bize, 2017; Schaefer, 2011). The Orestiini ( sensu Arratia et al ., 2017) is recognized as the sole cyprinodontiform clade found in the HAP. By comparison, the complementary distribution of Anablepidae is considered the outcome of a Neogene diversification in South American coastal marine habitats (Amorim & Costa, 2018; Nelson et al ., 2016).…”