Convergent Evolution in Amblyopsid Cavefishes and the Age of Eastern North American Subterranean Ecosystems.

Genomes provide tools for reconstructing organismal evolution and larger Earth system processes. Although genome sequences have been jointly analyzed with geological data to understand links between biological evolution and geological phenomena such as erosion and uplift, genomic and natural history observations have seldom been leveraged to reconstruct the timescale of landscape change in cases where traditional methods from the Earth sciences cannot. Here, we reconstruct the genomic evolution of cave-adapted amblyopsid fishes.

Night lizards survived the Cretaceous-Palaeogene mass extinction near the asteroid impact.

Discovering traits that facilitate survival through mass extinctions is of great interest to scholars of macroevolution. Here, we show that the common ancestry of xantusiid night lizards, a species-poor lineage with conserved anatomy, precedes the Cretaceous-Palaeogene boundary. We reconstruct the geographic distribution of the stem lineages of three living genera, and the monospecific , as surrounding the Gulf of Mexico, identifying as the only tetrapod crown clade currently known to have survived the Cretaceous-Palaeogene mass extinction proximal to the site of the bolide impact on the Yucatan Peninsula.

The many origins of extremophile fishes.

Extremophiles survive in environments that are considered uninhabitable for most living things. The evolution of extremophiles is of great interest because of how they may have contributed to the assembly of ecosystems, yet the evolutionary dynamics that drive extremophile evolution remain obscure. Here, we investigate the evolution of extremophiles in , a lineage of over 300 species of fishes that have colonized both poles, the deep sea, and hydrothermal vents.

Phylogenomics establishes an Early Miocene reconstruction of reef vertebrate diversity.

Oceans blanket more than two-thirds of Earth's surface, yet marine biodiversity is disproportionately concentrated in coral reefs. Investigating the origins of this exceptional diversity is crucial for predicting how reefs will respond to anthropogenic disturbances. Here, we use a genome-scale dataset to reconstruct the evolutionary history of the wrasses and parrotfishes (), which rank among the most species-rich and ecologically diverse lineages of reef fishes.

Undescribed and imperiled vertebrate biodiversity near an American urban center.

Urban expansion threatens biodiversity hotspots and endemic species. In this study, we describe two imperiled new species of fishes belonging to the vermilion darter () complex. These new species are restricted to individual stream systems surrounding the city of Birmingham, Alabama, USA, and are at risk of extinction due to anthropogenic development.

Cenozoic evolutionary history obscures the Mesozoic origins of acanthopterygian fishes.

Sister lineage comparisons provide a valuable tool for understanding evolutionary origins of species-rich clades and the role of habitat transitions in lineage diversification. Percomorpha, comprising over 18,900 species, includes nearly one third of living vertebrates. However, the phylogenetic resolution of its sister lineage remains unclear, obscuring whether contrasts in histories of diversification provide insights into the factors that gave rise to this clade's high diversity.

The Palaeozoic assembly of the holocephalan body plan far preceded post-Cretaceous radiations into the ocean depths.

Among cartilaginous fishes, represents the species-depauperate, morphologically conservative sister to sharks, rays and skates and the last survivor of a once far greater Palaeozoic and Mesozoic diversity. Currently, holocephalan diversity is concentrated in deep-sea species, suggesting that this lineage might contain relictual diversity that now persists in the ocean depths. However, the relationships of living holocephalans to their extinct relatives and the timescale of their diversification remain unclear.

Colonization of the ocean floor by jawless vertebrates across three mass extinctions.

Background: The deep (> 200 m) ocean floor is often considered to be a refugium of biodiversity; many benthic marine animals appear to share ancient common ancestry with nearshore and terrestrial relatives. Whether this pattern holds for vertebrates is obscured by a poor understanding of the evolutionary history of the oldest marine vertebrate clades. Hagfishes are jawless vertebrates that are either the living sister to all vertebrates or form a clade with lampreys, the only other surviving jawless fishes.

Synergistic innovations enabled the radiation of anglerfishes in the deep open ocean.

Major ecological transitions are thought to fuel diversification, but whether they are contingent on the evolution of certain traits called key innovations is unclear. Key innovations are routinely invoked to explain how lineages rapidly exploit new ecological opportunities. However, investigations of key innovations often focus on single traits rather than considering trait combinations that collectively produce effects of interest.

A juvenile bird with possible crown-group affinities from a dinosaur-rich Cretaceous ecosystem in North America.

Background: Living birds comprise the most speciose and anatomically diverse clade of flying vertebrates, but their poor early fossil record and the lack of resolution around the relationships of the major clades have greatly obscured extant avian origins.

Results: Here, I describe a Late Cretaceous bird from North America based on a fragmentary skeleton that includes cranial material and portions of the forelimb, hindlimb, and foot and is identified as a juvenile based on bone surface texture. Several features unite this specimen with crown Aves, but its juvenile status precludes the recognition of a distinct taxon.

A Morrison stem gekkotan reveals gecko evolution and Jurassic biogeography.

Geckos are a speciose and globally distributed clade of (lizards, including snakes and amphisbaenians) that are characterized by a host of modifications for nocturnal, scansorial and insectivorous ecologies. They are among the oldest divergences in the lizard crown, so understanding the origin of geckoes () is essential to understanding the origin of , the most species-rich extant tetrapod clade. However, the poor fossil record of gekkotans has obscured the sequence and timing of the assembly of their distinctive morphology.

The affinities of the Late Triassic and the age of crown squamates.

Most living reptile diversity is concentrated in Squamata (lizards, including snakes), which have poorly known origins in space and time. Recently, † from the Late Triassic of the United Kingdom was described as the oldest crown squamate. If true, this result would push back the origin of all major lizard clades by 30-65 Myr and suggest that divergence times for reptile clades estimated using genomic and morphological data are grossly inaccurate.

A late-surviving phytosaur from the northern Atlantic rift reveals climate constraints on Triassic reptile biogeography.

Background: The origins of all major living reptile clades, including the one leading to birds, lie in the Triassic. Following the largest mass extinction in Earth's history at the end of the Permian, the earliest definite members of the three major living reptile clades, the turtles (Testudines), crocodylians and birds (Archosauria), and lizards, snakes, amphisbaenians, and Tuatara (Lepidosauria) appeared. Recent analyses of the Triassic reptile fossil record suggest that the earliest diversifications in all three of these clades were tightly controlled by abrupt paleoclimate fluctuations and concordant environmental changes.

Phylogenetics and the Cenozoic radiation of lampreys.

The development of a movable jaw is one of the most important transitions in the evolutionary history of animals. Jawed vertebrates rapidly diversified after appearing approximately 470 million years ago. Today, only lampreys and hagfishes represent the once dominant jawless grade and comprise less than 1% of living vertebrate species.

Hidden species diversity in an iconic living fossil vertebrate.

Ancient, species-poor lineages persistently occur across the Tree of life. These lineages are likely to contain unrecognized species diversity masked by the low rates of morphological evolution that characterize living fossils. Halecomorphi is a lineage of ray-finned fishes that diverged from its closest relatives before 200 Ma and is represented by only one living species in eastern North America, the bowfin, Linnaeus.

Evolutionary origins of the prolonged extant squamate radiation.

Squamata is the most diverse clade of terrestrial vertebrates. Although the origin of pan-squamates lies in the Triassic, the oldest undisputed members of extant clades known from nearly complete, uncrushed material come from the Cretaceous. Here, we describe three-dimensionally preserved partial skulls of two new crown lizards from the Late Jurassic of North America.

Species delimitation and coexistence in an ancient, depauperate vertebrate clade.

Background: A major challenge to understanding how biodiversity has changed over time comes from depauperons, which are long-lived lineages with presently low species diversity. The most famous of these are the coelacanths. This clade of lobe-finned fishes occupies a pivotal position on the vertebrate tree between other fishes and tetrapods.

Giant gar from directly above the Cretaceous-Palaeogene boundary suggests healthy freshwater ecosystems existed within thousands of years of the asteroid impact.

The Cretaceous-Palaeogene (K-Pg) mass extinction was responsible for the destruction of global ecosystems and loss of approximately three-quarters of species diversity 66 million years ago. Large-bodied land vertebrates suffered high extinction rates, whereas small-bodied vertebrates living in freshwater ecosystems were buffered from the worst effects. Here, we report a new species of large-bodied (1.

High morphological disparity in a bizarre Paleocene fauna of predatory freshwater reptiles.

Background: The consequences of the K-Pg mass extinction are reflected across present biodiversity, but many faunas that appeared immediately after the extinction event were very different from current ones. Choristodera is a clade of reptiles of uncertain phylogenetic placement that have an extremely poor fossil record throughout their 150-million-year history. Yet, choristoderes survived the K-Pg event and persisted until the Miocene.