Carpathiavis meniliticus gen. et sp. nov.
A partial skeleton of a new small avian species is reported from marine sediments of the Rupelian locality Jamna Dolna 2 in southeast Poland. Carpathiavis meniliticus gen. et sp. nov. is characterized by an unusual furcula morphology with stout shafts (scapi clavicularum) and a long, rodshaped furcular apophysis. With regard to furcula shape and the proportions of the wing bones, the new species shows a resemblance to the taxon Eocuculus, which occurs in the late Eocene of North America and the early Oligocene of France. However, there are some distinct differences to Eocuculus, and in overall morphology C. meniliticus is also similar to the late Paleocene/early Eocene taxon Songzia, which is a putative representative of the Ralloidea (rails and allies). Even though a wellfounded phylogenetic assignment of the new species is impeded by the poor preservation of the skeleton, Carpathiavis clearly represents a distinctive new taxon that has not previously been reported from the Rupelian of Europe. In its skeletal morphology, the new taxon differs from all extant avian clades and substantiates previous evidence that in the early Oligocene morphologically distinctive representatives of extinct clades lived alongside essentially moderntype representatives of extant avian groups.
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PaweÅ Mackiewicz, Adam Dawid UrantÃwka, Aleksandra Kroczak & Dorota Mackiewicz (2019)
Resolving phylogenetic relationships within Passeriformes based on mitochondrial genes and inferring the evolution of their mitogenomes in terms of duplications.
Genome Biology and Evolution: evz209
doi:
https://doi.org/10.1093/gbe/evz209https://academic.oup.com/gbe/article/doi/10.1093/gbe/evz209/5580497/Mitochondrial genes are placed on one molecule, which implies that they should carry consistent phylogenetic information. Following this advantage, we present a well-supported phylogeny based on mitochondrial genomes from almost 300 representatives of Passeriformes, the most numerous and differentiated Aves order. The analyses resolved the phylogenetic position of paraphyletic Basal and Transitional Oscines. Passerida occurred divided into two groups, one containing Paroidea and Sylvioidea, while the other, Passeroidea and Muscicapoidea. Analyses of mitogenomes showed four types of rearrangements including a duplicated control region (CR) with adjacent genes. Mapping the presence and absence of duplications onto the phylogenetic tree revealed that the duplication was the ancestral state for passerines and was maintained in early diverged lineages. Next, the duplication could be lost and occurred independently at least four times according to the most parsimonious scenario. In some lineages, two CR copies have been inherited from an ancient duplication and highly diverged, while in others, the second copy became similar to the first one due to concerted evolution. The second CR copies accumulated over twice as many substitutions as the first ones. However, the second CRs were not completely eliminated and were retained for a long time, which suggests that both regions can fulfil an important role in mitogenomes. Phylogenetic analyses based on CR sequences subjected to the complex evolution can produce tree topologies inconsistent with real evolutionary relationships between species. Passerines with two CRs showed a higher metabolic rate in relation to their body mass.
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SQUAMATES
We report the first example of ossified pelvic vestiges in an anomalepidid snake, Liotyplophs beui, and provide a review of the diversity of limb and pelvic elements within Serpentes. We trace the evolution, homology and reduction of the pelvic elements and hindlimbs from the oldest known snakes through to living forms. Evolutionary analysis of the pelvic and limb data shows that the most recent common ancestor of all living snakes (Serpentes) most probably retained all three pelvic elements and rudimentary hindlimbs (femoral spurs). Subsequently, there have been multiple losses of ossified pelvic and hindlimb elements and regaining of ossified pelvic elements. Reduction of the pelvis has followed different routes in the two primary groups of living snakes (scolecophidians and alethinophidians). The single remaining rod-like element in some scolecophidians is the ischium, whereas the single remaining rod-like element in many basal alethinophidians is the pubis. Notably, many basal alethinophidians share a distinctive configuration of cloacal spur (claw), femur and a sizeable pubis, which is likely to be related functionally to the widespread use of the hindlimbs in mating and courtship, rather than the usual representation of the bones as non-functional vestiges.
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We report on the first detailed study of the atlasâaxis complex in the lizard clade Dibamidae, a family of poorly known fossorial squamates distributed in tropical or subtropical climates. This skeletal bridge is characterized by several features, such as the complete absence of the first intercentrum or the appearance of the first free cervical rib on the axis (usually less developed in Dibamus relative to that in Anelytropsis). Our study shows morphological differences of the atlasâaxis complex in the Mexican blind lizard Anelytropsis relative to those of Asian Dibamus, the only two known extant genera of this clade. With regard to taxonomy and phylogenetic topology of the Dibamidae within Squamata, a huge conflict exists between morphology versus molecules. The morphology of the atlasâaxis complex is therefore compared with several potential sister clades + Sphenodon. Dibamids share several features with limbless Gekkota, Scincoidea, and Amphisbaenia. The complete absence of the first intercentrum is observed in Rhineura floridana and in Ateuchosaurus chinensis as well, and the free rib associated with the synapophyses of the axis is also present in Acontias meleagris. However, some of these features may result from a limbless, burrowing ecology and thus could represent homoplastic characters. In any case, the morphology of the atlasâaxis shows that dibamids share most character states with skinks. Although the atlasâaxis complex forms only an additional source of information, this conclusion is consistent with most morphological rather than molecular tree topologies.
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The "earlyâburst" model of adaptive radiation predicts an early increase in phenotypic disparity concurrent with lineage diversification. Although most studies report a lack of this coupled pattern, the underlying processes are not identified. The continental radiation of Hemidactylus geckos from Peninsular India includes morphologically diverse species that occupy various microhabitats. This radiation began diversifying ~36 Mya with an early increase in lineage diversification. Here, we test the "earlyâburst" hypothesis by investigating the presence of ecomorphs and examining the pattern of morphological diversification in a phylogenetic framework. Two ecomorphs--terrestrial and scansorial species--that vary significantly in body size and toepad size were identified. Unlike the prediction of the "earlyâburst" model, we find that disparity in toepad morphology accumulated more recently ~14 Mya and fit the OrnsteinâUlhenbeck model. Ancestral state reconstruction of the two ecomorphs demonstrates that terrestrial lineages evolved independently at least five times from scansorial ancestors, with the earliest diversification in terrestrial lineages 19â12 Mya. Our study demonstrates a delayed increase in morphological disparity as a result of the evolution of terrestrial ecomorphs. The diversification of terrestrial lineages is concurrent with the establishment of open habitat and grasslands in Peninsular India, suggesting that the appearance of this novel resource led to the adaptive diversification.
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James R. Stewart Â& Daniel G. Blackburn (2019)
A developmental synapomorphy of squamate reptiles.
Evolution and Development (advance online publication)
doi:
https://doi.org/10.1111/ede.12317https://onlinelibrary.wiley.com/doi/10.1111/ede.12317The reptilian clade Squamata is defined primarily by osteological synapomorphies, few of which are entirely unambiguous. Studies of developing squamate eggs have revealed a uniquely specialized feature not known to occur in any other amniotes. This feature--the yolk cleft/isolated yolk mass complex--lines the ventral hemisphere of the egg. During its formation, extraembryonic mesoderm penetrates the yolk and an exocoelom (the yolk cleft [YC]) forms in association with it, cutting off a thin segment of yolk (the "isolated yolk mass" [IYM]) from the main body of the yolk. The YCâIYM complex has been observed and described in more than 65 squamate species in 12 families. In viviparous species, it contributes to the "omphaloplacenta," a type of yolk sac placenta unique to squamates. The only squamates known to lack the IYM are a few highly placentotrophic skinks with minuscule eggs, viviparous species in which it clearly has been lost. Given its absence in mammals, chelonians, crocodylians, and birds, the YCâIYM complex warrants recognition as a developmental synapomorphy of the squamate clade. As in extant viviparous lizards and snakes, the YCâIYM complex presumably contributed to the placenta of extinct viviparous squamates.
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The study of cervical anatomy in the Miocene machairodontine felid Machairodus aphanistus reveals the early stages of evolution of the sabre-toothed adaptations in the homotherin lineage. The cervical vertebrae of M. aphanistus show a surprising mosaic of features, combining a more primitive atlas than its derived relative Homotherium, with a set of elongated, caudal cervical vertebrae that display well-developed transverse processes with complex and strong muscle insertion areas. In spite of its primitive morphology, the atlas of M. aphanistus does show a slight caudal projection of the atlas wings, indicating an emphasis on vertical motions of the cranial portion of the neck and skull. The rest of the cervical vertebrae of M. aphanistus show clear adaptations for strength, flexibility and precise control of neck motions compatible with the canine shear-bite model and comparable to those of Homotherium. Such a powerful and flexible neck could provide additional stability to partly compensate for the risk of canine breakage created by the less specialized adaptations of the skull and cranial cervical vertebrae for the machairodontine bite.
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