Search

Ghost lineages have always challenged the understanding of organism evolution. They participate in misinterpretations in phylogenetic, clade dating, biogeographic, and paleoecologic studies. They directly result from fossilization biases and organism biology. The Cylindrotomidae are a perfect example of an unexplained ghost lineage during the Mesozoic, as its sister family Tipulidae is already well diversified during the Cretaceous, while the oldest Cylindrotomidae are Paleogene representatives of the extant genus Cylindrotoma and of the enigmatic fossil genus Cyttaromyia. Here we clarify the phylogenetic position of Cyttaromyia in the stem group of the whole family, suggesting that the crown group of the Cylindrotomidae began to diversify during the Cenozoic, unlike their sister group Tipulidae. We make a comparative analysis of all species in Cyttaromyia, together with the descriptions of the two new species, C. gelhausi sp. nov. and C. freiwaldi sp. nov., and the revision of C. obdurescens. The cylindrotomid biogeography seems to be incongruent with the phylogenetic analysis, the apparently most derived subfamily Stibadocerinae having apparently a ‘Gondwanan’ distribution, with some genera only known from Australia or Chile, while the most inclusive Cylindrotominae are Holarctic.

8-bit TIFF image stack of microCT scans through the premaxilla of Omorhamphus (YPM 13106; Lower Gray Bull Fm, Eocene, Big Horn Basin, Wyoming). Scan taken at University of Texas High-Resolution X-ray CT Facility by Matthew Colbert. Scan parameters: NSI scanner. Feinfocus source, high power, 200 kV, 0.14 mA, 1 aluminum filter, Perkin Elmer detector, 0.25 pF gain, 1 fps (999.911 ms integration time), no binning, no flip, source to object 218.58 mm, source to detector 1316.527 mm, continuous CT scan, no frames averaged, 0 skip frames, 3600 projections, 6 gain calibrations, 5 mm calibration phantom, data range [-10, 100] (grayscale range adjusted from NSI defaults), beam-hardening correction = 0.3. Voxel size = 0.0302 mm. Total slices = 1813., {"references":["Louchart A, Bhullar B-A, Riamon S and Field DJ (2021) The True Identity of Putative Tooth Alveoli in a Cenozoic Crown Bird, the Gastornithid Omorhamphus. Front. Earth Sci. 9:661699. doi: 10.3389/feart.2021.661699"]}

Understanding the biogeographical and diversification processes explaining current diversity patterns of subcosmopolitan-distributed groups is challenging. We aimed at disentangling the historical biogeography of the subcosmopolitan liverwort genus Lejeunea with estimation of ancestral areas of origin and testing if sexual system and palaeotemperature variations can be factors of diversification. We assembled a dense taxon sampling for 120 species sampled throughout the geographical distribution of the genus. Lejeunea diverged from its sister group after the Paleocene-Eocene boundary (52.2 Ma, 95% credibility intervals 50.1–54.2 Ma), and the initial diversification of the crown group occurred in the early to middle Eocene (44.5 Ma, 95% credibility intervals 38.5–50.8 Ma). The DEC model indicated that (1) Lejeunea likely originated in an area composed of the Neotropics and the Nearctic, (2) dispersals through terrestrial land bridges in the late Oligocene and Miocene allowed Lejeunea to colonize the Old World, (3) the Boreotropical forest covering the northern regions until the late Eocene did not facilitate Lejeunea dispersals, and (4) a single long-distance dispersal event was inferred between the Neotropics and Africa. Biogeographical and diversification analyses show the Miocene was an important period when Lejeunea diversified globally. We found slight support for higher diversification rates of species with both male and female reproductive organs on the same individual (monoicy), and a moderate positive influence of palaeotemperatures on diversification. Our study shows that an ancient origin associated with a dispersal history facilitated by terrestrial land bridges and not long-distance dispersals are likely to explain the subcosmopolitan distribution of Lejeunea. By enhancing the diversification rates, monoicy likely favoured the colonisations of new areas, especially in the Miocene that was a key epoch shaping the worldwide distribution.

Despite significant advances in invertebrate phylogenomics over the past decade, the higher-level phylogeny of Pycnogonida (sea spiders) remains elusive. Due to the inaccessibility of some small-bodied lineages, few phylogenetic studies have sampled all sea spider families. Previous efforts based on a handful of genes have yielded unstable tree topologies. Here, we inferred the relationships of 89 sea spider species using targeted capture of the mitochondrial genome, 56 conserved exons, 101 ultraconserved elements, and 3 nuclear ribosomal genes. We inferred molecular divergence times by integrating morphological data for fossil species to calibrate 15 nodes in the arthropod tree of life. This integration of data classes resolved the basal topology of sea spiders with high support. The enigmatic family Austrodecidae was resolved as the sister group to the remaining Pycnogonida and the small-bodied family Rhynchothoracidae as the sister group of the robust-bodied family Pycnogonidae. Molecular divergence time estimation recovered a basal divergence of crown group sea spiders in the Ordovician. Comparison of diversification dynamics with other marine invertebrate taxa that originated in the Paleozoic suggests that sea spiders and some crustacean groups exhibit resilience to mass extinction episodes, relative to mollusk and echinoderm lineages. Deutsche Forschungsgemeinschaft BR5039/3-1 National Science Foundation ANT-0551969, ANT-0440577 Ministerio de Economía y Competitividad POL2006-06399/CGL, CTM2012-39350- C02-01 Antarctic Science AA3010 National Science Foundation IOS-1552610

The attine ants are a monophyletic lineage that switched to fungus farming ca. 55–60 MYA. They have become a model for the study of complex symbioses after additional fungal and bacterial symbionts were discovered, but their abdominal endosymbiotic bacteria remain largely unknown. Here, we present a comparative microbiome analysis of endosymbiotic bacteria spanning the entire phylogenetic tree. We show that, across 17 representative sympatric species from eight genera sampled in Panama, abdominal microbiomes are dominated by Mollicutes, α‐ and γ‐Proteobacteria, and Actinobacteria. Bacterial abundances increase from basal to crown branches in the phylogeny reflecting a shift towards putative specialized and abundant abdominal microbiota after the ants domesticated gongylidia‐bearing cultivars, but before the origin of industrial‐scale farming based on leaf‐cutting herbivory. This transition coincided with the ancestral single colonization event of Central/North America ca. 20 MYA, documented in a recent phylogenomic study showing that almost the entire crown group of the higher attine ants, including the leaf‐cutting ants, evolved there and not in South America. Several bacterial species are located in gut tissues or abdominal organs of the evolutionarily derived, but not the basal attine ants. The composition of abdominal microbiomes appears to be affected by the presence/absence of defensive antibiotic‐producing actinobacterial biofilms on the worker ants' cuticle, but the significance of this association remains unclear. The patterns of diversity, abundance and sensitivity of the abdominal microbiomes that we obtained explore novel territory in the comparative analysis of attine fungus farming symbioses and raise new questions for further in‐depth research., see also the Perspective by Pringle

21 pages; International audience; We describe Superstesaster promissor gen. et sp. nov., a starfish from the Smithian (Early Triassic) of Utah (USA) that fills a major gap in the fossil record of the Asteroidea. The post-Palaeozoic crown group Asteroidea are distinct from any of the diverse Palaeozoic forms. However, current understanding of the Palaeozoic–Mesozoic transition is blurred by a large gap in the fossil record between the Early Permian and the Middle Triassic. Building on the newly described taxon, a phylogenetic analysis investigates the relationships between Palaeozoic and Mesozoic Asteroidea. Including 30 species and 70 morphological characters, it is the most comprehensive phylogeny produced for fossil starfishes so far. Relationships among Palaeozoic forms remain poorly resolved, but their position in the tree is grossly consistent with stratigraphy. The tree topology implies the appearance of a wide range of morphologies during the Ordovician, a bottleneck during the end-Devonian events, and a second diversification during the Carboniferous, before a diversity decline at the end of the Permian. Superstesaster promissor nests above Palaeozoic taxa and appears as the sister group to the post-Palaeozoic Asteroidea. It represents the first record of a member of the stem group in the Mesozoic, and it likely reflects the ancestral morphology of the crown group. S. promissor shares with the crown group typical ambulacral and adambulacral plate shape and articulation. Phylogenetic relationships within the crown group remain poorly resolved, although three clades are consistent with molecular and morphological phylogenies available for extant forms: Valvatacea (Comptoniaster, Pentasteria, Advenaster, Noviaster), Forcipulatacea (Germanasterias, Argoviaster) and Velatida (Tropidaster, Protremaster). A Triassic and Jurassic radiation of the crown group is confirmed. Most Triassic and Jurassic forms do not share all synapomorphies with extant clades and usually represent separate clades or stem members of modern clades rather than true members of modern families.

International audience; The Paleoproterozoic (2.5-1.6 Ga) Era is a decisive time in Earth and life history. The paleobiological record (microfossils, stromatolites, biomarkers and isotopes) illustrates the biosphere evolution during a time of transitional oceanic and atmosphere chemistries. Benthic microfossil assemblages are recorded in a variety of oxygenated, sulfidic, and ferruginous environments representative of the spatial heterogeneities and temporal variations characteristic of this Era. The microfossil assemblages include iron-metabolizing and/or iron-tolerant prokaryotes, sulfur-metabolizing prokaryotes, cyanobacteria, other undetermined prokaryotes, and eukaryotes. The undetermined microfossils represent a majority of the assemblages and thus raise a challenge to determine the nature and role of microorganisms in these changing environments. Despite the early evolution of the eukaryotic cellular toolkit, early eukaryotic crown group diversification may have been restrained in the Paleoproterozoic by ocean chemistry conditions, but it increased during the late Mesoproterozoic-early Neoproterozoic despite the continuation of similar conditions through the (miscalled) "boring billion", then amplified significantly (but perhaps within lower taxonomic levels), with the demise of euxinic conditions and increase in ecological complexity. The emerging picture is one of a changing and more complex biosphere in which the three domains of life, Archaea, Bacteria and Eukarya, were diversifying in various ecological niches marked by the diversification of identified microfossils, stromatolites, increasing abundance of preserved biomarkers, and appearance of macroscopic problematic fossils or trace fossils.

Background The dentitions of extinct organisms can provide pivotal information regarding their phylogenetic position, as well as paleobiology, diet, development, and growth. Extant birds are edentulous (toothless), but their closest relatives among stem birds, the Cretaceous Hesperornithiformes and Ichthyornithiformes, retained teeth. Despite their significant phylogenetic position immediately outside the avian crown group, the dentitions of these taxa have never been studied in detail. To obtain new insight into the biology of these ‘last’ toothed birds, we use cutting-edge visualisation techniques to describe their dentitions at unprecedented levels of detail, in particular propagation phase contrast x-ray synchrotron microtomography at high-resolution. Results Among other characteristics of tooth shape, growth, attachment, implantation, replacement, and dental tissue microstructures, revealed by these analyses, we find that tooth morphology and ornamentation differ greatly between the Hesperornithiformes and Ichthyornithiformes. We also highlight the first Old World, and youngest record of the major Mesozoic clade Ichthyornithiformes. Both taxa exhibit extremely thin and simple enamel. The extension rate of Hesperornis tooth dentine appears relatively high compared to non-avian dinosaurs. Root attachment is found for the first time to be fully thecodont via gomphosis in both taxa, but in Hesperornis secondary evolution led to teeth implantation in a groove, at least locally without a periodontal ligament. Dental replacement is shown to be lingual via a resorption pit in the root, in both taxa. Conclusions Our results allow comparison with other archosaurs and also mammals, with implications regarding dental character evolution across amniotes. Some dental features of the ‘last’ toothed birds can be interpreted as functional adaptations related to diet and mode of predation, while others appear to be products of their peculiar phylogenetic heritage. The autapomorphic Hesperornis groove might have favoured firmer root attachment. These observations highlight complexity in the evolutionary history of tooth reduction in the avian lineage and also clarify alleged avian dental characteristics in the frame of a long-standing debate on bird origins. Finally, new hypotheses emerge that will possibly be tested by further analyses of avian teeth, for instance regarding dental replacement rates, or simplification and thinning of enamel throughout the course of early avian evolution. Electronic supplementary material The online version of this article (doi:10.1186/s12862-016-0753-6) contains supplementary material, which is available to authorized users.

Among the fossils of hitherto unknown mammals that Darwin collected in South America between 1832 and 1833 during the Beagle expedition [1] were examples of the large, heavily armored herbivores later known as glyptodonts. Ever since, glyptodonts have fascinated evolutionary biologists because of their remarkable skeletal adaptations and seemingly isolated phylogenetic position even within their natural group, the cingulate xenarthrans (armadillos and their allies [2]). In possessing a carapace comprised of fused osteoderms, the glyptodonts were clearly related to other cingulates, but their precise phylogenetic position as suggested by morphology remains unresolved [3,4]. To provide a molecular perspective on this issue, we designed sequence-capture baits using in silico reconstructed ancestral sequences and successfully assembled the complete mitochondrial genome of Doedicurus sp., one of the largest glyptodonts. Our phylogenetic reconstructions establish that glyptodonts are in fact deeply nested within the armadillo crown-group, representing a distinct subfamily (Glyptodontinae) within family Chlamyphoridae [5]. Molecular dating suggests that glyptodonts diverged no earlier than around 35 million years ago, in good agreement with their fossil record. Our results highlight the derived nature of the glyptodont morphotype, one aspect of which is a spectacular increase in body size until their extinction at the end of the last ice age., Facultad de Ciencias Naturales y Museo

The Oligo-Miocene flamingo Harrisonavis croizeti represents an intermediate form between the highly specialized extant flamingo cranial morphology and the more generalized ancestral phoenicopteriform one, characterized by the extinct taxon Palaelodus. However, the original description of H. croizeti lacked detail and the lectotypic skull was lost; thus, it is not known how the ancestral phoenicopterid cranial morphology differed from that of recent forms. Here, we describe new cranial material from Oligo-Miocene deposits of France, including a mostly complete skull with an articulated upper bill, a disarticulated upper bill, and pieces of lower bill. We assign this material to H. croizeti and compare it to all previously reported fossil flamingo cranial material as well as to all six living species. We also use 3D computed tomographic data to reconstruct the skull of H. croizeti in three dimensions. The skull and bill of H. croizeti are similar to those of living species, although they display less specialized filter feeding traits, including a straighter bill with less surface area for filtration lamellae and points of articulation with the lower bill which are less developed. The less specialized form of H. croizeti suggests the extant Phoenicopterus retains a skull morphology more similar to the ancestral condition of crown group flamingos, and the extant Phoenicoparrus form is more derived.

International audience; The study of bone growth rate and metabolic rate evolution in archosaurs (crocodiles, dinosaurs including birds, and pterosaurs) and close outgroups has become a subject of major interest among paleontologists in recent years. In this paper, we estimate the bone growth rate of Euparkeria using a new statistical inference model for the humerus. We modified the taxonomic range of extant species used in previous studies, on which we performed quantitative measurements of histological features and bone growth rates. Bone growth rate values estimated for Euparkeria are crucial in understanding the ancestral condition for archosaurs because this taxon is considered the closest relative to the archosaur crown group. We obtained an instantaneous growth rate of 6.12 μm/day, suggesting that Euparkeria shared with other non-archosaurian archosauromorphs (Prolacerta, Proterosuchus, and Erythrosuchus) a condition of high growth rate compatible with endothermy. This derived state may have been inherited by some Triassic crurotarsans, as suggested by the high instantaneous bone growth rate (14.52 μm/day) estimated in this study for Postosuchus. Jurassic crurotarsans may have lost endothermy during the transition from terrestrial habitats and active predation to aquatic habitats and sit-and-wait predation behaviors, so that Cretaceous crocodiles may be secondarily ectothermic, as suggested by δ18O values. In conclusion, we provide new evidence for the hypothesis of an ancestral endothermic state for the last common ancestor of archosaurs, and show that non-archosaurian archosauromorphs and Triassic crurotarsans may have been characterized by a thermometabolism more similar to that of dinosaurs than to that of lepidosaurs and turtles.

No fossil belonging to the Caudata crown-group has been hitherto described from a former Gondwanan continent. We report the first known extinct member of the caudate crown-clade from Africa, i.e. a Gondwanan territory. It belongs to the Recent genus Pleurodeles (Salamandridae) and is referred to as Pleurodeles cf. waltl. The fossils come from the Pleistocene of Morocco. They show that Pleurodeles (likely P. waltl) has been present in Africa for at least two million years and that anthropogenic dispersal is not the cause of its presence in this continent.

Although the phylogeny of the filmy fern family (Hymenophyllaceae) is rapidly coming into focus, much remains to be uncovered concerning the evolutionary history of this clade. In this study, we use two data sets (108‐taxon rbcL + rps4, 204‐taxon rbcL) and fossil constraints to examine the diversification of filmy ferns and the evolution of their ecology within a temporal context. Our penalized likelihood analyses (with both data sets) indicate that the initial divergences within the Hymenophyllaceae (resulting in extant lineages) and those within one of the two major clades (trichomanoids) occurred in the early to middle Mesozoic. There was a considerable delay in the crown group diversification of the other major clade (hymenophylloids), which began to diversify only in the Cretaceous. Maximum likelihood and Bayesian character state reconstructions across the broadly sampled single‐gene (rbcL) phylogeny do not allow us to unequivocally infer the ancestral habit for the family or for its two major clades...

The earliest pterygote (winged insect), dated from the Lower Carboniferous (Namurian A/E1, circa 324 millions years ago) is described from the Upper Silesian Basin in the Czech Republic. On the basis of its wing venation, it is attributed to the Archaeorthoptera Bethoux and Nel, 2002, crown group of the “Orthoptera”. Besides Apterygota (Collembola and Archaeognatha) known from the Lower Devonian, extremely rare pterygote insects are known from Lower Carboniferous deposits when they first appeared. The present discovery supports the hypothesis of the presence of the ancestor lineage of the orthopteroid in the Lower Carboniferous ecosystems.