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Bathydraconidae (Notothenioidei) are a group of benthic fishes endemic to the Southern Ocean. Because of their recent evolutionary radiation and limited sampling efforts due to their occurrence in remote regions, their diversity is likely underestimated. Akarotaxis nudiceps, currently the only recognized member of its genus, is an especially poorly known bathydraconid. Although A. nudiceps has a circumpolar distribution on the Antarctic continental shelf, its deep habitat and rarity limit knowledge of its life history and biology. Using a combination of morphological and genetic analyses, we identified an undescribed species of this genus, herein named Akarotaxis gouldae sp. nov. (Banded Dragonfish). The separation of this species was initially identified from archived larval specimens, highlighting the importance of early life stage taxonomy and natural history collections. All currently known adult and larval A. gouldae sp. nov. specimens have been collected from a restricted ~400 km coastal section of the western Antarctic Peninsula, although this is possibly due to sampling bias. This region is targeted by the epipelagic Antarctic krill fishery, which could potentially capture larval fishes as bycatch. Due to the extremely low fecundity of A. gouldae sp. nov. and near-surface occurrence of larvae, we suggest the growing Antarctic krill fishery could negatively impact this speces.  

Abstract Although the Cretaceous is widely regarded as a time of great evolutionary transition for the freshwater fish fauna of North America, the fossil record of this period is notoriously poor, consisting mostly of fragments and isolated skeletal elements. Exceptions include the acipenseriforms, discussed in this paper, and some exceedingly rare teleosts. Here we describe two new species of well-preserved sturgeons (Acipenseridae) from the Tanis site in the Late Cretaceous Hell Creek Formation of North Dakota. The type and referred materials were preserved in a loosely consolidated matrix. † Acipenser praeparatorum n. sp. is represented by multiple body fossils (including the head and relatively complete postcranial remains) and a specimen of an intact, three dimensionally preserved skull and pectoral girdle. This taxon can be diagnosed based on features of the opercular elements (exceptionally tall and narrow branchiostegal). The second species, † Acipenser anisinferos n. sp., is represented by a partially preserved skull, and can be diagnosed by a relatively elongate preorbital region (i.e., snout) and the absence of thorn-like spines on the skull roofing bones. Most known sturgeon fossils from the Cretaceous are represented only by undiagnosable fragmentary remains (i.e., scutes and pectoral-fin spines) or poorly preserved partial skeletons (e.g., † Protoscaphirhynchus ), with † Priscosturion and † Anchiacipenser (both monotypic) being rare exceptions. Therefore, the newly discovered Tanis fossils give a rare glimpse into the evolution of Acipenseridae at a critical time in the phylogenetic history of acipenseriforms, and suggest significant morphological and taxonomic diversity early in the evolution of this group. UUID: http://zoobank.org/375b586a-2dd8-4a31-b6c4-42151e6e8fc8 

Abstract The recently discovered mass mortality of fishes from the Tanis Site in the North Dakota portion of the Late Cretaceous Hell Creek Formation contains many well-preserved, three-dimensional skeletons. Among these are representatives of two acipenseriform families, Acipenseridae (sturgeons) and Polyodontidae (paddlefishes). This paper describes two new monotypic polyodontid genera, expanding our knowledge of polyodontid diversity. The first of the new species described here is † Parapsephurus willybemisi n. gen. n. sp. It is distinguished from all other known species by having a combination of posteriorly elongate parietals, the middle fenestra longitudinalis bordered medially by the parietal and frontal and laterally by the dermopterotic, slender and numerous dorsal caudal fulcra, an elongate hyomandibula that is not hourglass shaped, and gill rakers that are short and widely spaced. The second polyodontid species described here is † Pugiopsephurus inundatus n. gen. n. sp. It is diagnosed by a combination of having stellate bones that are exceptionally poorly developed or absent and having a dermopalatine with a medial expansion and lacking an ectopterygoid process. The two species of paddlefishes described in this paper add to the morphological and taxonomic diversity of Polyodontidae. The presence of these taxa within the Hell Creek Formation hints at substantial diversity of polyodontids at this stage of their evolutionary history. UUID: http://zoobank.org/08cbf8c5-59ba-41fa-9265-8cb762cf7b13 

Abstract The notothenioid family Bathydraconidae is a poorly understood family of fishes endemic to the Southern Ocean. There is especially little information onAkarotaxis nudiceps, one of the deepest‐dwelling and least fecund bathydraconid species. Using genetic and morphological data, we document and describe the larval stages of this unique species, offer a novel characteristic to distinguish it from the morphologically similar bathydraconidPrionodraco evansiiand use the sampling locations to infer a possible spawning area ofA. nudicepsalong the western Antarctic Peninsula. These results provide important baseline information for locating, identifying and studying the biology ofA. nudiceps, an important component of the Southern Ocean ecosystem. 

Abstract Over the last half of the 20 th century, the western Antarctic Peninsula has been one of the most rapidly warming regions on Earth, leading to substantial reductions in regional sea ice coverage. These changes are modulated by atmospheric forcing, including the Amundsen Sea Low (ASL) pressure system. We utilized a novel 25-year (1993–2017) time series to model the effects of environmental variability on larvae of a keystone species, the Antarctic Silverfish ( Pleuragramma antarctica ). Antarctic Silverfish use sea ice as spawning habitat and are important prey for penguins and other predators. We show that warmer sea surface temperature and decreased sea ice are associated with reduced larval abundance. Variability in the ASL modulates both sea surface temperature and sea ice; a strong ASL is associated with reduced larvae. These findings support a narrow sea ice and temperature tolerance for adult and larval fish. Further regional warming predicted to occur during the 21st century could displace populations of Antarctic Silverfish, altering this pelagic ecosystem.