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Shark Evolution

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Fish on Evolution's Fast Track - Scientific American

Whatever else we might say about , it is a fish. In a review article on (appearing in the same issue of the scientific journal that reported the discovery of ), fish evolution experts, Ahlberg and Clack concede that “in some respects and are straightforward fishes: they have small pelvic fins, retain fin rays in their paired appendages and have well-developed gill arches, suggesting that both animals remained mostly aquatic.”

The evolutionary history of bony vertebrates remains an outstanding problem in the Tree of Life. Osteichthyes, the group inclusive of ray-finned fishes (Actinopterygii) and lobe-finned fishes plus tetrapods (Sarcopterygii), contains all extant vertebrates except chondrichthyans and agnathans, yet our understanding of phylogenetic patterns and divergence times of many early-branching lineages remains incomplete. Phylogenetic resolution is vital for understanding vertebrate biology, including recent investigations of genome duplications , development and evolution of appendages , diversification rates associated with habitat preferences , reproductive systems , sensory and communication systems , hormone receptors , sodium channels , and developmental genes and regulatory elements . However, sarcopterygian relationships are notoriously contentious and much of the current view of ray-finned fish evolution remains based on morphological studies conducted nearly four decades ago . Resolving the phylogenetic branching order close to the base of the fish tree has been particularly challenging. Over the past 30 years numerous studies using morphological and molecular data have yielded conflicting results, contributing to persistent phylogenetic and taxonomic uncertainty (see ). Although recent studies have employed larger character sets to address some of these issues, their data sets are restricted to ray-finned fishes and do not include all lineages relevant to addressing relationships among bony fishes.

Toxic Avengers: Pollution Drove Fish Evolution : NPR

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    Have you ever wished you could have the entire 150 million years of spiny-rayed fish evolution in convenient poster form? Well, wait no longer. Your happy day is here! Trust me . . . this is one poster featuring mullets you will not be embarrassed to display.

    To provide for a more robust hypothesis of osteichthyan phylogeny and more accurate times of diversification, we conducted the first comprehensive analysis of bony fish evolution. We generated a data set of nearly 20,000 nucleotides from 21 loci from 61 species representing all major extant osteichthyan lineages plus chondrichthyan outgroups. Divergence dating employed an original set of 24 fossil calibrations that are chronologically proximal to focal divergence events. The resulting phylogenetic hypothesis and evolutionary time scale provide new insights on fish diversification and establish a framework for understanding their many evolutionary innovations.