Phylogenetic analysis shows the general diversification pattern of deep-sea notacanthiforms (Teleostei: Elopomorpha)

7 pages, 2 tables, 2 figuresThe Notacanthiformes is an ancient group of deep-sea ray-finned fishes comprising 27 species in two families; Halosauridae and Notacanthidae. Although many studies have tried to reconstruct the phylogenetic relationships among the major clades of Elopomorpha, little is known about the evolutionary history of notacanthiforms. Molecular and morphological data were used to test previous hypotheses regarding the phylogenetic relationships among notacanthiform taxa, and to unravel the origin and evolution of this group. The molecular analyses of notacanthids showed similar results to those previously obtained employing osteological data, which proposed the existence of the Lipogenyinae (Lipogenys) and Notacanthinae (Notacanthus + Polyacanthonotus) subfamilies. Nevertheless, when the external morphology data is considered Lipogenys is more related to Notacanthus than Polyacanthonotus. The analyses could not fully resolve the inner relationships of the halosaurids. The time-calibrated tree of the order Notacanthiformes shows a long process of diversification spanning from the upper Cretaceous, to 50 million years after the K-Pg extinction, with the gradual emergence of all the modern families and genera of the group. This is the first specific phylogeny of the order Notacanthiformes, combining different analyses and data in order to obtain a wider perspective of the evolution and diversification of this group of fishesThis investigation was partially founded by the Spanish Ministry of Environment (research project ECOMARG 3), by the EC LIFE+ ‘Nature Biodiversity’ INDEMARES project (07/NAT/E/000732) and received additional funding from the Research Line BlueSensors, integrated in the Structured Program of R&D&I CORAL – Sustainable Ocean Exploitation: Tools and Sensors (reference NORTE-01-0145-FEDER-000036), funded by the Northern Regional Operational Programme (NORTE2020) through the European Regional Development Fund (ERDF). EF was supported by the Portuguese Foundation for Science and Technology (FCT) under grant SFRH/BPD/108445/2015Peer reviewe