Neopterygii

Since Darwin, biologists have been struck by the extraordinary diversity of teleost fishes, particularly in contrast to their closest " living fossil " holostean relatives. Hypothesized drivers of teleost success include innovations in jaw mechanics, reproductive biology and, particularly at present, genomic architecture, yet all scenarios presuppose enhanced phenotypic diversification in teleosts. We test this key assumption by quantifying evolutionary rate and capacity for innovation in size and shape for the first 160 million y (Permian–Early Cretaceous) of evolution in neopterygian fishes (the more extensive clade containing teleosts and holosteans). We find that early teleosts do not show enhanced phenotypic evolution relative to holosteans. Instead, holostean rates and innovation often match or can even exceed those of stem-, crown-, and total-group teleosts, belying the living fossil reputation of their ex-tant representatives. In addition, we find some evidence for hetero-geneity within the teleost lineage. Although stem teleosts excel at discovering new body shapes, early crown-group taxa commonly display higher rates of shape evolution. However, the latter reflects low rates of shape evolution in stem teleosts relative to all other neopterygian taxa, rather than an exceptional feature of early crown teleosts. These results complement those emerging from studies of both extant teleosts as a whole and their sublineages, which generally fail to detect an association between genome duplication and significant shifts in rates of lineage diversification.

Angular One of the bones forming the lower jaw. Articular One of jaw joint bones of the lower jaw-articulates with the quadrate. Autocentrum or vertebral autocentrum Part of the centrum that develops as a direct ossification. Branchiostegal rays Series of bones attached to the anterior and/or posterior ceratohyals. Ceratohyal Part of the hyoid arch supporting branchiostegal rays. Two elements: anterior and posterior ceratohyal. Circumorbital series Series of bones forming the orbit such as antorbital, infraorbitals, supraorbital(s), and dermosphenotic. Chordacentrum or vertebral chordacentrum Part of the centrum that develops as mineralization of the notochordal sheath. Clavicle One of the bones forming the secondary shoulder girdle supporting the pectoral fin. It articulates with the anteroventral margin of cleithrum. Cleithrum One of the dermal bones forming the secondary shoulder girdle supporting the pectoral fin. Coracoid One of the bones forming the primary shoulder girdle supporting the pectoral fin. Dentary One of the bones forming the anterior part of the lower jaw. Epiotic Bone at the dorsoposterior face of the braincase. Epural Median element of the caudal fin commonly supporting procurrent rays. Haemal spine Spine of a vertebral centrum in ventral position and bearing an arch where major blood vessels are placed. Hyomandibula Most dorsal element of the suspensorium supporting the lower jaw and articulating with the braincase. Hypural Median element of the caudal fin or modified haemal spine supporting principal rays. Hypural plate Median element resulting of fusion of hypurals. Incertae sedis An uncertain position of a taxon in the classification. Branchial camera Interopercle One of the bones forming the opercular region protecting the branchial camera. Opercle One of the bones forming the opercular region protecting the branchial camera. Paired fins Bilateral fins including the pectoral and pelvic fins. Palatoquadrate Dorsal region of the palate arch including the autopalatine anteriorly and the metapterygoid and quadrate posteriorly. Bones, such as the dermal dermopalatine, entopterygoid and ectopterygoid, are associated with this arch, as well as tooth plates in some taxa. Parasphenoid One of the bones forming the base of the braincase. Preopercle One of the bones forming the opercular cover of the branchial chamber that in addition is tightly attached to the bones of the suspensorium of the lower jaw.

The Permian and Triassic were key time intervals in the history of life on Earth. Both periods are marked by a series of biotic crises including the most catastrophic of such events, the end-Permian mass extinction, which eventually led to a major turnover from typical Palaeozoic faunas and floras to those that are emblematic for the Mesozoic and Cenozoic. Here we review patterns in Permian-Triassic bony fishes, a group whose evolutionary dynamics are understudied. Based on data from primary literature, we analyse changes in their taxonomic diversity and body size (as a proxy for trophic position) and explore their response to Permian-Triassic events. Diversity and body size are investigated separately for different groups of Osteichthyes (Dipnoi, Actinistia, 'Palaeopterygii', 'Subholostei', Holostei, Teleosteomorpha), within the marine and freshwater realms and on a global scale (total diversity) as well as across palaeolatitudinal belts. Diversity is also measured ...

The new neopterygian genusTicinolepis, including two new speciesT. longaevaandT. crassidensis described from Middle Triassic carbonate platform deposits of the Monte San Giorgio. The anatomy of this fish shows a mosaic of halecomorph and ginglymodian characters and, thus, the new taxon probably represents a basal holostean. During the latest Anisian to earliest Ladinian the two new species coexisted in the intraplatform basin represented by the uppermost Besano Formation, but onlyT. longaevasp. nov. inhabited the more restricted basin represented by the Ladinian Meride Limestone (except for the Kalkschieferzone). The more widely distributed type species shows interesting patterns of intraspecific variation including ontogenetic changes and morphological variation over time. The second species presents anatomical features that strongly indicate a strictly durophagous diet. The different distribution of the species is interpreted as a result of habitat partitioning and different adapt...

Comprising Holostei and Teleostei, the ~32,000 species of neopterygian fishes are anatomically disparate and represent the dominant group of aquatic vertebrates today. However, the pattern by which teleosts rose to represent almost all of this diversity, while their holostean sister-group dwindled to eight extant species and two broad morphologies, is poorly constrained. A geometric morphometric approach was taken to generate a morphospace from more than 400 fossil taxa, representing almost all articulated neopterygian taxa known from the first 150 million years—roughly 60%—of their history (Triassic‒Early Cretaceous). Patterns of morphospace occupancy and disparity are examined to: (1) assess evidence for a phenotypically “dominant” holostean phase; (2) evaluate whether expansions in teleost phenotypic variety are predominantly abrupt or gradual, including assessment of whether early apomorphy-defined teleosts are as morphologically conservative as typically assumed; and (3) compare diversification in crown and stem teleosts. The systematic affinities of dapediiforms and pycnodontiforms, two extinct neopterygian clades of uncertain phylogenetic placement, significantly impact patterns of morphological diversification. For instance, alternative placements dictate whether or not holosteans possessed statistically higher disparity than teleosts in the Late Triassic and Jurassic. Despite this ambiguity, all scenarios agree that holosteans do not exhibit a decline in disparity during the Early Triassic‒Early Cretaceous interval, but instead maintain their Toarcian‒Callovian variety until the end of the Early Cretaceous without substantial further expansions. After a conservative Induan‒Carnian phase, teleosts colonize (and persistently occupy) novel regions of morphospace in a predominantly gradual manner until the Hauterivian, after which expansions are rare. Furthermore, apomorphy-defined teleosts possess greater phenotypic variety than typically assumed. Comparison of crown and stem teleost partial disparity indicates that, despite a statistically significant increase in crown teleost disparity between the Late Jurassic and earliest Cretaceous, stem teleosts remained important long-term contributors to overall teleost disparity during this time.

Fishes have evolved to exploit multiple ecological niches. Extant fishes in both marine (e.g., rabbitfishes, surgeonfishes) and freshwater systems (e.g., haplochromine cichlids, characiforms) have evolved specialized, scoop-like, multidenticulate teeth for benthic scraping, feeding primarily on algae. Here, I report evidence of the oldest example of specialized multidenticulate dentition in a ray-finned fish, †Hemicalypterus weiri, from the Upper Triassic Chinle Formation of southeastern Utah (∼210–205 Ma), USA. †H. weiri is a lower actinopterygian species that is phyloge- netically remote from modern fishes, and has evolved special- ized teeth that converge with those of several living teleost fishes (e.g., characiforms, cichlids, acanthurids, siganids), with a likely function of these teeth being to scrape algae off a rock substrate. This finding contradicts previously held no- tions that fishes with multicuspid, scoop-like dentition were restricted to teleosts, and indicates that ray-finned fishes were diversifying into different trophic niches and exploring differ- ent modes of feeding earlier in their history than previously thought, fundamentally altering our perceptions of the ecolog- ical roles of fishes during the Mesozoic.

The lagerstätten in the Monte San Giorgio have provided excellent fossils representing one of the most important windows to the marine life during the Triassic. Among these fossils, fishes are abundant and extraordinarily well preserved. Most of these fishes represent extinct lineages and were difficult to understand and classify during the early years after discovery. These difficulties usually led to a mixture of species under the same taxonomic name. This is the case of fishes referred to the genus Archaeosemionotus. The name bearing type of A. connectens, the type species of this genus, represents a basal halecomorph, but most other fishes referred to this genus represent basal ginglymodians. Therefore, we conducted this study to clarify the taxonomic status and phylogenetic relationships of A. connectens, which is a member of the family Furidae (Halecomorphi, Ionoscopiformes) representing the second cladistically supported evidence of ionoscopiforms in the Triassic and it is th...