Major issues in the origins of ray‐finned fish ( A ctinopterygii) biodiversity

Ray‐finned fishes ( A ctinopterygii) dominate modern aquatic ecosystems and are represented by over 32000 extant species. The vast majority of living actinopterygians are teleosts; their success is often attributed to a genome duplication event or morphological novelties. The remainder are ‘living fossils’ belonging to a few depauperate lineages with long‐retained ecomorphologies: P olypteriformes (bichirs), H olostei (bowfin and gar) and C hondrostei (paddlefish and sturgeon). Despite over a century of systematic work, the circumstances surrounding the origins of these clades, as well as their basic interrelationships and diagnoses, have been largely mired in uncertainty. Here, I review the systematics and characteristics of these major ray‐finned fish clades, and the early fossil record of A ctinopterygii, in order to gauge the sources of doubt. Recent relaxed molecular clock studies have pushed the origins of actinopterygian crown clades to the mid‐late P alaeozoic [ S ilurian– C arboniferous; 420 to 298 million years ago ( M a)], despite a diagnostic body fossil record extending only to the later M esozoic (251 to 66 M a). This disjunct, recently termed the ‘ T eleost G ap’ (although it affects all crown lineages), is based partly on calibrations from potential P alaeozoic stem‐taxa and thus has been attributed to poor fossil sampling. Actinopterygian fossils of appropriate ages are usually abundant and well preserved, yet long‐term neglect of this record in both taxonomic and systematic studies has exacerbated the gaps and obscured potential synapomorphies. At the moment, it is possible that later P alaeozoic‐age teleost, holostean, chondrostean and/or polypteriform crown taxa sit unrecognized in museum drawers. However, it is equally likely that the ‘ T eleost G ap’ is an artifact of incorrect attributions to extant lineages, overwriting both a post‐ P alaeozoic crown actinopterygian radiation and the ecomorphological diversity of stem‐taxa.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/109271/1/brv12086.pd

Sampling diverse characters improves phylogenies:craniodental and postcranial characters of vertebrates often imply different trees

This is the author accepted manuscript. The final version is available from Wiley via http://dx.doi.org/10.1111/evo.12884Morphological cladograms of vertebrates are often inferred from greater numbers of characters describing the skull and teeth than from postcranial characters. This is either because the skull is believed to yield characters with a stronger phylogenetic signal (i.e., contain less homoplasy), because morphological variation therein is more readily atomized, or because craniodental material is more widely available (particularly in the palaeontological case). An analysis of 85 vertebrate datasets published between 2000 and 2013 confirms that craniodental characters are significantly more numerous than postcranial characters, but finds no evidence that levels of homoplasy differ in the two partitions. However, a new partition test, based on tree-to-tree distances (as measured by the Robinson Foulds metric) rather than tree length, reveals that relationships inferred from the partitions are significantly different about one time in three, much more often than expected. Such differences may reflect divergent selective pressures in different body regions, resulting in different localized patterns of homoplasy. Most systematists attempt to sample characters broadly across body regions, but this is not always possible. We conclude that trees inferred largely from either craniodental or postcranial characters in isolation may differ significantly from those that would result from a more holistic approach. We urge the latter.This work was supported by a University of Bath URS award to RCPM, Leverhulme Trust Grant F/00351/Z and BBSRC grant BB/K015702/1 to MAW, JTF Grant 43915 to Mark Wilkinson and MAW, and NERC fellowship NE/I020253/1 to RSS

Southern Gondwanan Late Jurassic continental teleosts (Actinopterygii, Teleostei): phylogeny and biogeography

During the Jurassic the teleost fishes went through their first important radiation and colonization of continental environments. Due to a bias in the geological record, Jurassic fresh-water deposits are very scarce, and only three continental fish faunas of Late Jurassic age are known worldwide: the Almada Fauna from the Cañadón Calcáreo Formation in central Chubut, Argentina, the Talbragar Fauna from the Australian Talbragar Beds and the fish assemblages from the Morrison Formation in USA. The Almada and Talbragar faunas show strong similarities. Regarding their taxonomic composition, both faunas share one genus of coccolepid and the presence of halecomorphs and basal teleosts. Concerning their geological settings and taphonomic background, each fauna occur in a single horizon within the stratigraphic column, representing mass mortality events, probably related to volcanic activity. To date, the Almada Fauna includes two species of teleosts: "Tharrias" feruglioi (Bordas) and Luisiella inexcutata Bocchino. Interestingly, "T". feruglioi shares very similar morphological features with Cavenderichthys talbragarensis (Woodward), the only valid species of teleost from Talbragar. A previous phylogenetic analysis showed a sister group relationship between these two species. Strengthening the resemblance between the Almada and Talbragar faunas, this result suggested close biogeographic relationships between the Argentinean and Australian localities. Here we present a new phylogenetic analysis including other taxa of fresh-water teleosts and new characters, the results of which support this hypothesis of close biogeographic connection.Sesiones libresFacultad de Ciencias Naturales y Muse