The impact of paleoclimatic changes on body size evolution in marine fishes.

Body size is an important species trait, correlating with life span, fecundity, and other ecological factors. Over Earth's geological history, climate shifts have occurred, potentially shaping body size evolution in many clades. General rules attempting to summarize body size evolution include Bergmann's rule, which states that species reach larger sizes in cooler environments and smaller sizes in warmer environments, and Cope's rule, which poses that lineages tend to increase in size over evolutionary time. Tetraodontiform fishes (including pufferfishes, boxfishes, and ocean sunfishes) provide an extraordinary clade to test these rules in ectotherms owing to their exemplary fossil record and the great disparity in body size observed among extant and fossil species. We examined Bergmann's and Cope's rules in this group by combining phylogenomic data (1,103 exon loci from 185 extant species) with 210 anatomical characters coded from both fossil and extant species. We aggregated data layers on paleoclimate and body size from the species examined, and inferred a set of time-calibrated phylogenies using tip-dating approaches for downstream comparative analyses of body size evolution by implementing models that incorporate paleoclimatic information. We found strong support for a temperature-driven model in which increasing body size over time is correlated with decreasing oceanic temperatures. On average, extant tetraodontiforms are two to three times larger than their fossil counterparts, which otherwise evolved during periods of warmer ocean temperatures. These results provide strong support for both Bergmann's and Cope's rules, trends that are less studied in marine fishes compared to terrestrial vertebrates and marine invertebrates.

Fossilized cell structures identify an ancient origin for the teleost whole-genome duplication.

Teleost fishes comprise one-half of all vertebrate species and possess a duplicated genome. This whole-genome duplication (WGD) occurred on the teleost stem lineage in an ancient common ancestor of all living teleosts and is hypothesized as a trigger of their exceptional evolutionary radiation. Genomic and phylogenetic data indicate that WGD occurred in the Mesozoic after the divergence of teleosts from their closest living relatives but before the origin of the extant teleost groups. However, these approaches cannot pinpoint WGD among the many extinct groups that populate this 50- to 100-million-y lineage, preventing tests of the evolutionary effects of WGD. We infer patterns of genome size evolution in fossil stem-group teleosts using high-resolution synchrotron X-ray tomography to measure the bone cell volumes, which correlate with genome size in living species. Our findings indicate that WGD occurred very early on the teleost stem lineage and that all extinct stem-group teleosts known so far possessed duplicated genomes. WGD therefore predates both the origin of proposed key innovations of the teleost skeleton and the onset of substantial morphological diversification in the clade. Moreover, the early occurrence of WGD allowed considerable time for postduplication reorganization prior to the origin of the teleost crown group. This suggests at most an indirect link between WGD and evolutionary success, with broad implications for the relationship between genomic architecture and large-scale evolutionary patterns in the vertebrate Tree of Life.

Confronting Sources of Systematic Error to Resolve Historically Contentious Relationships: A Case Study Using Gadiform Fishes (Teleostei, Paracanthopterygii, Gadiformes).

Reliable estimation of phylogeny is central to avoid inaccuracy in downstream macroevolutionary inferences. However, limitations exist in the implementation of concatenated and summary coalescent approaches, and Bayesian and full coalescent inference methods may not yet be feasible for computation of phylogeny using complicated models and large data sets. Here, we explored methodological (e.g., optimality criteria, character sampling, model selection) and biological (e.g., heterotachy, branch length heterogeneity) sources of systematic error that can result in biased or incorrect parameter estimates when reconstructing phylogeny by using the gadiform fishes as a model clade. Gadiformes include some of the most economically important fishes in the world (e.g., Cods, Hakes, and Rattails). Despite many attempts, a robust higher-level phylogenetic framework was lacking due to limited character and taxonomic sampling, particularly from several species-poor families that have been recalcitrant to phylogenetic placement. We compiled the first phylogenomic data set, including 14,208 loci ($>$2.8 M bp) from 58 species representing all recognized gadiform families, to infer a time-calibrated phylogeny for the group. Data were generated with a gene-capture approach targeting coding DNA sequences from single-copy protein-coding genes. Species-tree and concatenated maximum-likelihood (ML) analyses resolved all family-level relationships within Gadiformes. While there were a few differences between topologies produced by the DNA and the amino acid data sets, most of the historically unresolved relationships among gadiform lineages were consistently well resolved with high support in our analyses regardless of the methodological and biological approaches used. However, at deeper levels, we observed inconsistency in branch support estimates between bootstrap and gene and site coefficient factors (gCF, sCF). Despite numerous short internodes, all relationships received unequivocal bootstrap support while gCF and sCF had very little support, reflecting hidden conflict across loci. Most of the gene-tree and species-tree discordance in our study is a result of short divergence times, and consequent lack of informative characters at deep levels, rather than incomplete lineage sorting. We use this phylogeny to establish a new higher-level classification of Gadiformes as a way of clarifying the evolutionary diversification of the order. We recognize 17 families in five suborders: Bregmacerotoidei, Gadoidei, Ranicipitoidei, Merluccioidei, and Macrouroidei (including two subclades). A time-calibrated analysis using 15 fossil taxa suggests that Gadiformes evolved $\sim $79.5 Ma in the late Cretaceous, but that most extant lineages diverged after the Cretaceous-Paleogene (K-Pg) mass extinction (66 Ma). Our results reiterate the importance of examining phylogenomic analyses for evidence of systematic error that can emerge as a result of unsuitable modeling of biological factors and/or methodological issues, even when data sets are large and yield high support for phylogenetic relationships. [Branch length heterogeneity; Codfishes; commercial fish species; Cretaceous-Paleogene (K-Pg); heterotachy; systematic error; target enrichment.].

Phylogenomics and Historical Biogeography of Seahorses, Dragonets, Goatfishes, and Allies (Teleostei: Syngnatharia): Assessing Factors Driving Uncertainty in Biogeographic Inferences.

The charismatic trumpetfishes, goatfishes, dragonets, flying gurnards, seahorses, and pipefishes encompass a recently defined yet extraordinarily diverse clade of percomorph fishes-the series Syngnatharia. This group is widely distributed in tropical and warm-temperate regions, with a great proportion of its extant diversity occurring in the Indo-Pacific. Because most syngnatharians feature long-range dispersal capabilities, tracing their biogeographic origins is challenging. Here, we applied an integrative phylogenomic approach to elucidate the evolutionary biogeography of syngnatharians. We built upon a recently published phylogenomic study that examined ultraconserved elements by adding 62 species (total 169 species) and one family (Draconettidae), to cover ca. 25% of the species diversity and all 10 families in the group. We inferred a set of time-calibrated trees and conducted ancestral range estimations. We also examined the sensitivity of these analyses to phylogenetic uncertainty (estimated from multiple genomic subsets), area delimitation, and biogeographic models that include or exclude the jump-dispersal parameter ($j)$. Of the three factors examined, we found that the $j$ parameter has the strongest effect in ancestral range estimates, followed by number of areas defined, and tree topology and divergence times. After accounting for these uncertainties, our results reveal that syngnatharians originated in the ancient Tethys Sea ca. 87 Ma (84-94 Ma; Late Cretaceous) and subsequently occupied the Indo-Pacific. Throughout syngnatharian history, multiple independent lineages colonized the eastern Pacific (6-8 times) and the Atlantic (6-14 times) from their center of origin, with most events taking place following an east-to-west route prior to the closure of the Tethys Seaway ca. 12-18 Ma. Ultimately, our study highlights the importance of accounting for different factors generating uncertainty in macroevolutionary and biogeographic inferences.[Historical biogeography; jump-dispersal parameter; macroevolutionary uncertainty; marine fishes; syngnathiformes; ultraconserved elements].

High Encephalization in a Fossil Rorqual Illuminates Baleen Whale Brain Evolution.

Baleen whales are considered underencephalized mammals due to their reduced brain size with respect to their body size (encephalization quotient [EQ] << 1). Despite their low EQ, mysticetes exhibit complex behavioral patterns in terms of motor abilities, vocal repertoire, and cultural learning. Very scarce information is available about the morphological evolution of the brain in this group; this makes it difficult to investigate the historical changes in brain shape and size in order to relate the origin of the complex mysticete behavioral repertoire to the evolution of specific neural substrates. Here, the first description of the virtual endocast of a fossil balaenopterid species, Marzanoptera tersillae from the Italian Pliocene, reveals an EQ of around 3, which is exceptional for baleen whales. The endocast showed a morphologically different organization of the brain in this fossil whale as the cerebral hemispheres are anteroposteriorly shortened, the cerebellum lacks the posteromedial expansion of the cerebellar hemispheres, and the cerebellar vermis is unusually reduced. The comparative reductions of the cerebral and cerebellar hemispheres suggest that the motor behavior of M. tersillae probably was less sophisticated than that exhibited by the extant rorqual and humpback species. The presence of an EQ value in this fossil species that is around 10 times higher than that of extant mysticetes opens new questions about brain evolution and provides new, invaluable information about the evolutionary path of morphological and size change in the brain of baleen whales.

Non-reef environments impact the diversification of extant jacks, remoras and allies (Carangoidei, Percomorpha).

Various factors may impact the processes of diversification of a clade. In the marine realm, it has been shown that coral reef environments have promoted diversification in various fish groups. With the exception of requiem sharks, all the groups showing a higher level of diversity in reefs than in non-reef habitats have diets based predominantly on plankton, algae or benthic invertebrates. Here we explore the pattern of diversification of carangoid fishes, a clade that includes numerous piscivorous species (e.g. trevallies, jacks and dolphinfishes), using time-calibrated phylogenies as well as ecological and morphological data from both extant and fossil species. The study of carangoid morphospace suggests that reef environments played a role in their early radiation during the Eocene. However, contrary to the hypothesis of a reef-association-promoting effect, we show that habitat shifts to non-reef environments have increased the rates of morphological diversification (i.e. size and body shape) in extant carangoids. Piscivory did not have a major impact on the tempo of diversification of this group. Through the ecological radiation of carangoid fishes, we demonstrate that non-reef environments may sustain and promote processes of diversification of different marine fish groups, at least those including a large proportion of piscivorous species.

First multilocus and densely sampled timetree of trevallies, pompanos and allies (Carangoidei, Percomorpha) suggests a Cretaceous origin and Eocene radiation of a major clade of piscivores.

Carangoid fishes (trevallies, pompanos, jacks, dolphinfishes, cobias and remoras) include about 159 species of marine fishes found in tropical and temperate waters worldwide (Froese and Pauly, 2014). Many carangoids are powerful swimmers and active piscivores in and around coral-reef ecosystems. Some carangoid lineages, such as dolphinfishes, have evolved a pelagic lifestyle, while remoras spend their adult life attached to cetaceans, sharks, manta rays and large teleosts, feeding off skin parasites or leftovers from their host's meals. In spite of their taxonomic diversity, ecological dominance, economic importance to humans, and a rich fossil record dating to the Paleogene, relatively little is currently known about the tempo of evolution of this group. Here we present the results of the first time calibration study of carangoid fishes. Using a fossil-calibrated molecular timetree that includes 133 species of carangoids (∼85% of extant species), we show that this group originated in the Late Cretaceous and that several major lineages were already present before the K-Pg extinction. All major clades were in existence by the end of the Eocene, even though significant diversification has continued to occur throughout the history of this group.

First joint record of Mesopithecus and cf. Macaca in the Miocene of Europe.

Cercopithecid fossil remains from the post-evaporitic Messinian (5.40-5.33 Ma, MN13, latest Turolian, latest Miocene) locality of Moncucco Torinese (Tertiary Piedmont Basin, NW Italy) are described. A talus is assigned to the fossil colobine Mesopithecus pentelicus, while a proximal fragment of ulna and a male lower canine are attributed to cf. Me. pentelicus. An isolated I(2) and M3 are assigned to the papionin cf. Macaca sp., and two cercopithecid phalanges are left unassigned even to the subfamily level. The record of Mesopithecus at Moncucco Torinese agrees well with the previously-known range of this species in Italy and elsewhere in Europe, whereas that of cf. Macaca constitutes only the second occurrence of macaques in the Miocene of Eurasia. Although the co-occurrence of these two genera in a single locality had been previously reported in the Pliocene, this is the first instance in which macaques are associated with the Late Miocene M. pentelicus instead of Mesopithecus monspessulanus. The record of cf. Macaca and Mesopithecus-and especially the latter's talar morphology, similar to that of extant arboreal colobines-fits well with paleoenvironmental reconstructions of Moncucco Torinese based on the associated fauna, which indicate a humid and densely-forested environment, probably with more open and drier habitats nearby. From a paleobiogeographic viewpoint, the record of Macaca at Moncucco Torinese, together with the previously reported occurrence at Almenara-Casablanca M (Spain), supports the contention that macaques dispersed from Africa into Europe during the latest Miocene (ca. 5.9-5.3 Ma) at the same time as the sea level drop associated with the Messinian Salinity Crisis.

The tympanoperiotic complex of the blue whale, Balaenoptera musculus.

The tympanoperiotic complex of a blue whale Balaenoptera musculus is described and compared to the homologous structures in the other extant and fossil baleen whale species. The periotic and the tympanic bulla represent informative anatomical regions in both functional and phylogenetic studies and for this reason a micro-CT scan of the bones was performed in order to better characterize their external aspect and to reconstruct the inner structures. In particular, the cochlea, the semicircular canals and associated portions of the periotic are reconstructed so that these structures may be used in phylogenetic analyses. We observed that the blue whale periotic is characterized by the presence of a strong dorsal protrusion which is posteriorly bordered by a previously undescribed morphological character that we name the posterotransverse fossa. The peculiar shape of the anterior process and the en echelon organization of the posterior foramina of the pars cochlearis are also described and compared. From a phylogenetic perspective, the blue whale is confirmed to be closely related to the fin whale, Balaenoptera physalus, but it is suggested, based on ear bone characters only, that it diverged before the other balaenopterid species in the phylogeny of Balaenopteridae. This placement supports a series of morphological observations suggesting that the extant blue whale was an early-diverging member of Balaenoptera. Our results help to decipher the evolutionary origin of the blue whale, the largest living animal, by allowing new and more detailed morphological analyses of the balaenopterid fossil record.

Evolutionary innovation accelerates morphological diversification in pufferfishes and their relatives.

Evolutionary innovations have played an important role in shaping the diversity of life on Earth. However, how these innovations arise and their downstream effects on patterns of morphological diversification remain poorly understood. Here, we examine the impact of evolutionary innovation on trait diversification in tetraodontiform fishes (pufferfishes, boxfishes, ocean sunfishes, and allies). This order provides an ideal model system for studying morphological diversification owing to their range of habitats and divergent morphologies, including the fusion of the teeth into a beak in several families. Using three-dimensional geometric morphometric data for 176 extant and fossil species, we examine the effect of skull integration and novel habitat association on the evolution of innovation. Strong integration may be a requirement for rapid trait evolution and facilitating the evolution of innovative structures, like the tetraodontiform beak. Our results show that the beak arose in the presence of highly conserved patterns of integration across the skull, suggesting that integration did not limit the range of available phenotypes to tetraodontiforms. Furthermore, we find that beaks have allowed tetraodontiforms to diversify into novel ecological niches, irrespective of habitat. Our results suggest that general rules pertaining to evolutionary innovation may be more nuanced than previously thought.

A multi-locus timetree of surgeonfishes (Acanthuridae, Percomorpha), with revised family taxonomy.

We present the most comprehensive time-calibrated, species-level hypothesis of the timing of Acanthuridae (surgeonfishes and allies) evolution based on 76% of the extant diversity and nine genes. We recover two major acanthurid clades, Nasinae and Acanthurinae, and infer a much more recent Nasinae crown age (17 Ma) compared to a previous dating study for Naso. The Acanthurinae represent an older group that originated ~42 Ma, with most diversification occurring since the Early Miocene (beginning ~21 Ma). Our results strongly support a paraphyletic Acanthurus and Ctenochaetus, with multiple analyses recovering a clade grouping Ctenochaetus, A. nubilus and A. pyroferus. Contrary to previous studies, we also provide strong evidence that thick-walled, gizzard-like stomachs evolved only once within Acanthurus and that this morphology has a common origin in Acanthurus and Ctenochaetus. Based on our molecular analyses, in conjunction with the large body of morphological evidence, we recommend dissolving the genus Ctenochaetus into the genus Acanthurus.

A multi-locus molecular timescale for the origin and diversification of eels (Order: Anguilliformes).

Anguilliformes are an ecologically diverse group of predominantly marine fishes whose members are easily recognized by their extremely elongate bodies, and universal lack of pelvic fins. Recent studies based on mitochondrial loci, including full mitogenomes, have called into question the monophyly of both the Anguilliformes, which appear to be paraphyletic without the inclusion of the Saccopharyngiformes (gulper eels and allies), as well as other more commonly known eel families (e.g., Congridae, Serrivomeridae). However, no study to date has investigated anguilliform interrelationships using nuclear loci. Here we present a new phylogenetic hypothesis for the Anguilliformes based on five markers (the nuclear loci Early Growth Hormone 3, Myosin Heavy Polypeptide 6 and Recombinase Activating Gene 1, as well as the mitochondrial genes Cytochrome b and Cytochrome Oxidase I). Our sampling spans 148 species and includes 19 of the 20 extant families of anguilliforms and saccopharyngiforms. Maximum likelihood analysis reveals that saccopharyngiform eels are deeply nested within the anguilliforms, and supports the non-monophyly of Congridae and Nettastomatidae, as well as that of Derichthyidae and Chlopsidae. Our analyses suggest that Protanguilla may be the sister group of the Synaphobranchidae, though the recent hypothesis that this species is the sister group to all other anguilliforms cannot be rejected. The molecular phylogeny, time-calibrated using a Bayesian relaxed clock approach and seven fossil calibration points, reveals a Late Cretaceous origin of this expanded anguilliform clade (stem age ~116 Ma, crown age ~99 Ma). Most major (family level) lineages originated between the end of the Cretaceous and Early Eocene, suggesting that anguilliform radiation may have been facilitated by the recovery of marine ecosystems following the KP extinction.

The evolutionary origin of the durophagous pelagic stingray ecomorph.

Studies of the origin of evolutionary novelties (novel traits, feeding modes, behaviours, ecological niches, etc.) have considered a number of taxa experimenting with new body plans, allowing them to occupy new habitats and exploit new trophic resources. In the marine realm, colonization of pelagic environments by marine fishes occurred recurrently through time. Stingrays (Myliobatiformes) are a diverse clade of batoid fishes commonly known to possess venomous tail stings. Current hypotheses suggest that stingrays experimented with a transition from a benthic to a pelagic/benthopelagic habitat coupled with a transition from a non-durophagous diet to extreme durophagy. However, there is no study detailing macroevolutionary patterns to understand how and when habitat shift and feeding specialization arose along their evolutionary history. A new exquisitely preserved fossil stingray from the Eocene Konservat-Lagerstätte of Bolca (Italy) exhibits a unique mosaic of plesiomorphic features of the rajobenthic ecomorph, and derived traits of aquilopelagic taxa, that helps to clarify the evolutionary origin of durophagy and pelagic lifestyle in stingrays. A scenario of early evolution of the aquilopelagic ecomorph is proposed based on new data, and the possible adaptive meaning of the observed evolutionary changes is discussed. The body plan of †Dasyomyliobatis thomyorkei gen. et sp. nov. is intermediate between the rajobenthic and more derived aquilopelagic stingrays, supporting its stem phylogenetic position and the hypothesis that the aquilopelagic body plan arose in association with the evolution of durophagy and pelagic lifestyle from a benthic, soft-prey feeder ancestor.

Population dynamics with a mixed type of sexual and asexual reproduction in a fluctuating environment.

BACKGROUND: Carassius gibelio, a cyprinid fish from Eurasia, has the ability to reproduce both sexually and asexually. This fish is also known as an invasive species which colonized almost all continental Europe, most likely originating from Asia and Eastern Europe. Populations of both sexually and asexually reproducing individuals exist in sympatry. In this study we try to elucidate the advantages of such a mixed type of reproduction. We investigate the dynamics of two sympatric populations with sexual and asexual reproduction in a periodically fluctuating environment. We define an individual-based computational model in which genotypes are represented by L loci, and the environment is composed of L resources for which the two populations compete. RESULTS: Our model demonstrates advantageous population dynamics where the optimal percentage of asexual reproduction depends on selection strength, on the number of selected loci and on the timescale of environmental fluctuations. We show that the sexual reproduction is necessary for "generating" fit genotypes, while the asexual reproduction is suitable for "amplifying" them. The simulations show that the optimal percentage of asexual reproduction increases with the length of the environment stability period and decrease with the strength of the selection and the number of loci. CONCLUSIONS: In this paper we addressed the advantages of a mixed type of sexual and asexual reproduction in a changing environment and explored the idea that a species that is able to adapt itself to environmental fluctuation can easily colonize a new habitat. Our results could provide a possible explanation for the rapid and efficient invasion of species with a variable ratio of sexual and asexual reproduction such as Carassius gibelio.

A long-bodied centriscoid fish from the basal Eocene of Kabardino-Balkaria, northern Caucasus, Russia.

The Paleocene-Eocene transition is of crucial interest for interpreting the Cenozoic evolutionary radiation of vertebrates. A substantial increase of the number of vertebrate families occurred between the Late Paleocene and Early Eocene, with the appearance of most of the representatives of extant lineages. Basal Eocene marine fish diversity is currently poorly known, exclusively restricted to two assemblages from Denmark and Turkmenistan, respectively. Exceptionally well-preserved articulated skeletal remains of fishes have recently been discovered from a basal Eocene sapropelitic layer exposed along the Kheu River in the Republic of Kabardino-Balkaria, northern Caucasus, Russia. Here, we report on Gerpegezhus paviai gen. et sp. nov., a new peculiar syngnathoid fish from this new Ciscaucasian locality. The morphological structure of the single available specimen suggests that it is the first long-bodied member of the superfamily Centriscoidea, representing the sole member of the new family Gerpegezhidae, which forms a sister pair with the extant family Centriscidae.

Nine exceptional radiations plus high turnover explain species diversity in jawed vertebrates.

The uneven distribution of species richness is a fundamental and unexplained pattern of vertebrate biodiversity. Although species richness in groups like mammals, birds, or teleost fishes is often attributed to accelerated cladogenesis, we lack a quantitative conceptual framework for identifying and comparing the exceptional changes of tempo in vertebrate evolutionary history. We develop MEDUSA, a stepwise approach based upon the Akaike information criterion for detecting multiple shifts in birth and death rates on an incompletely resolved phylogeny. We apply MEDUSA incompletely to a diversity tree summarizing both evolutionary relationships and species richness of 44 major clades of jawed vertebrates. We identify 9 major changes in the tempo of gnathostome diversification; the most significant of these lies at the base of a clade that includes most of the coral-reef associated fishes as well as cichlids and perches. Rate increases also underlie several well recognized tetrapod radiations, including most modern birds, lizards and snakes, ostariophysan fishes, and most eutherian mammals. In addition, we find that large sections of the vertebrate tree exhibit nearly equal rates of origination and extinction, providing some of the first evidence from molecular data for the importance of faunal turnover in shaping biodiversity. Together, these results reveal living vertebrate biodiversity to be the product of volatile turnover punctuated by 6 accelerations responsible for >85% of all species as well as 3 slowdowns that have produced "living fossils." In addition, by revealing the timing of the exceptional pulses of vertebrate diversification as well as the clades that experience them, our diversity tree provides a framework for evaluating particular causal hypotheses of vertebrate radiations.

Skin patterning and internal anatomy in a fossil moonfish from the Eocene Bolca Lagerstätte illuminate the ecology of ancient reef fish communities.

Colour patterning in extant animals can be used as a reliable indicator of their biology and, in extant fish, can inform on feeding strategy. Fossil fish with preserved colour patterns may thus illuminate the evolution of fish behaviour and community structure, but are understudied. Here we report preserved melanin-based integumentary colour patterning and internal anatomy of the fossil moonfish Mene rhombea (Menidae) from the Bolca Lagerstätte (Eocene (Ypresian), north-east Italy). The melanosome-based longitudinal stripes of M. rhombea differ from the dorsal rows of black spots in its extant relative M. maculata, suggesting that the ecology of moonfish has changed during the Cenozoic. Extant moonfish are coastal schooling fish that feed on benthic invertebrates, but the longitudinal stripes and stomach contents with fish remains in M. rhombea suggest unstructured open marine ecologies and a piscivorous diet. The localized distribution of extant moonfish species in the Indo-Pacific Ocean may reflect, at least in part, tectonically-driven reorganization of global oceanographic patterns during the Cenozoic. It is likely that shifts in habitat and colour patterning genes promoted colour pattern evolution in the menid lineage.

Biogeographic history of Palearctic caudates revealed by a critical appraisal of their fossil record quality and spatio-temporal distribution.

The disjunct geographical range of many lineages of caudates points to a complex evolutionary and biogeographic history that cannot be disentangled by only considering the present-day distribution of salamander biodiversity. Here, we provide a critical reappraisal of the published fossil record of caudates from the Palearctic and quantitatively evaluate the quality of the group's fossil record. Stem-Urodela and Karauridae were widespread in the Palearctic in the Middle Jurassic, suggesting an earlier, unsampled diversification for this group. Cryptobranchidae reached Europe no later than the Oligocene, but this clade was subsequently extirpated from this continent, as well as from western and central Asia. The relatively recent appearance of hynobiids in the fossil record (Early Miocene) is most likely an artefact of a taphonomic bias against the preservation of high-mountain, stream-type environments which early members likely inhabited. Salamandroids first appear in Europe, expanding into Asia by the Miocene. The apparently enigmatic and disjunct distribution of extant caudate lineages is therefore explained by a wider past geographical range, as testified by the fossil record, which was fragmented during the late Cenozoic by a combination of tectonic (i.e. the uplift of the Tibetan Plateau) and climatic drivers, resulting in regional extirpations.

The Phylogeny of Rays and Skates (Chondrichthyes: Elasmobranchii) Based on Morphological Characters Revisited.

Elasmobranchii are relatively well-studied. However, numerous phylogenetic uncertainties about their relationships remain. Here, we revisit the phylogenetic evidence based on a detailed morphological re-evaluation of all the major extant batomorph clades (skates and rays), including several holomorphic fossil taxa from the Palaeozoic, Mesozoic and Cenozoic, and an extensive outgroup sampling, which includes sharks, chimaeras and several other fossil chondrichthyans. The parsimony and maximum-likelihood analyses found more resolved but contrasting topologies, with the Bayesian inference tree neither supporting nor disfavouring any of them. Overall, the analyses result in similar clade compositions and topologies, with the Jurassic batomorphs forming the sister clade to all the other batomorphs, whilst all the Cretaceous batomorphs are nested within the remaining main clades. The disparate arrangements recovered under the different criteria suggest that a detailed study of Jurassic taxa is of utmost importance to present a more consistent topology in the deeper nodes, as issues continue to be present when analysing those clades previously recognized only by molecular analyses (e.g., Rhinopristiformes and Torpediniformes). The consistent placement of fossil taxa within specific groups by the different phylogenetic criteria is promising and indicates that the inclusion of more fossil taxa in the present matrix will likely not cause loss of resolution, therefore suggesting that a strong phylogenetic signal can be recovered from fossil taxa.

Diversity, palaeoecology and palaeoenvironmental significance of the Eocene chondrichthyan assemblages of the Bolca Lagerstätte, Italy.

Over the last few years, the morphology, taxonomy and systematics of the cartilaginous fish taxa of the two main sites of the Bolca Lagerstätte, Italy, (Pesciara and Monte Postale sites) have been extensively discussed in a series of papers, resulting in a complete revision of this neglected component of the Eocene Tethyan ichthyofauna. Here, we provide a comprehensive overview of the diversity, palaeoecology and palaeoenvironmental significance of the two chondrichthyan assemblages of the Pesciara and Monte Postale sites. The assemblages include 14 shark species (Lamniformes and Carcharhiniformes) and batoids (Torpediniformes, Rhinopristiformes, Myliobatiformes, Platyrhinidae and Zanobatidae), as well as a single putative chimaeriform. The Pesciara and Monte Postale sites are characterized by eight chondrichthyan taxa each, but the taxonomic compositions are distinctly different reflecting the dissimilarities in the overall composition of both fish assemblages. Palaeoecological interpretations and habitat preferences of the two chondrichthyan assemblages are consistent with previously hypothesized palaeoenvironmental settings based on sedimentological, palaeontological and geochemical evidence. The chondrichthyan assemblages of the two sites appear to be constituted by ecologically vicariant taxa, with both characterized by a predominance of benthic species with durophagous/cancritrophic feeding modes. Taxonomic composition, habitat preferences and palaeobathymetric analyses support the hypothesis that both assemblages occupied tropical marine shallow waters (likely up to 50 m deep) of the inner portion of the Lessini Shelf. The taxonomic composition of both sites is considerably different from that of any other contemporaneous Tethyan and Boreal chondrichthyan assemblages.