First fossil representative of the salamander crown-group from a Gondwanan continent:Pleurodeles cf. waltl from the Quaternary of Morocco

2011 ◽  
Vol 32 (2) ◽  
pp. 245-252 ◽  
Author(s):  
Emmanuelle Stoetzel ◽  
Salvador Bailon ◽  
Jean-Claude Rage
Keyword(s):  
Crown Group ◽  
Anthropogenic Dispersal

AbstractNo 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.

scholarly journals The evolution of scarab beetles tracks the sequential rise of angiosperms and mammals

2014 ◽  
Vol 281 (1791) ◽  
pp. 20141470 ◽  
Author(s):  
Dirk Ahrens ◽  
Julia Schwarzer ◽  
Alfried P. Vogler
Keyword(s):  
Dna Markers ◽  
Time Lag ◽  
Dung Beetle ◽  
Crown Group ◽  
Evolutionary Mechanisms ◽  
Fossil Calibration ◽  
Multiple Origins ◽  
Pollen Feeding ◽  
Evolutionary Success ◽  
Terrestrial Biodiversity

Extant terrestrial biodiversity arguably is driven by the evolutionary success of angiosperm plants, but the evolutionary mechanisms and timescales of angiosperm-dependent radiations remain poorly understood. The Scarabaeoidea is a diverse lineage of predominantly plant- and dung-feeding beetles. Here, we present a phylogenetic analysis of Scarabaeoidea based on four DNA markers for a taxonomically comprehensive set of specimens and link it to recently described fossil evidence. The phylogeny strongly supports multiple origins of coprophagy, phytophagy and anthophagy. The ingroup-based fossil calibration of the tree widely confirmed a Jurassic origin of the Scarabaeoidea crown group. The crown groups of phytophagous lineages began to radiate first (Pleurostict scarabs: 108 Ma; Glaphyridae between 101 Ma), followed by the later diversification of coprophagous lineages (crown-group age Scarabaeinae: 76 Ma; Aphodiinae: 50 Ma). Pollen feeding arose even later, at maximally 62 Ma in the oldest anthophagous lineage. The clear time lag between the origins of herbivores and coprophages suggests an evolutionary path driven by the angiosperms that first favoured the herbivore fauna (mammals and insects) followed by the secondary radiation of the dung feeders. This finding makes it less likely that extant dung beetle lineages initially fed on dinosaur excrements, as often hypothesized.

Size At Maturity and Sex Ratio of Arcitalitrus Dorrieni (Hunt, 1925) (Amphipoda, Talitridae) At Two Sites in County Galway, Ireland

Crustaceana ◽  
1997 ◽  
Vol 70 (6) ◽  
pp. 676-693
Author(s):  
Thomas Bolger ◽  
Rory P. O'Hanlon
Keyword(s):  
Sex Ratio ◽  
Northern Hemisphere ◽  
General Pattern ◽  
Breeding Period ◽  
Amphipod Species ◽  
Size At Maturity ◽  
Anthropogenic Dispersal ◽  
Deciduous Woodland

AbstractAnthropogenic dispersal has led to the introduction of several terrestrial amphipod species to the northern hemisphere. One such species, Arcitalitrus dorrieni (Hunt, 1925), a native of Australasia, is now found in several woodland sites in Ireland and Britain. Aspects of the biology of A. dorrieni were investigated in County Galway over a period of two years and compared between a "typical" mixed deciduous woodland habitat and a more "atypical" coniferous woodland habitat. At both sites, statistically significant differences were found between summer (Aug.-Sep.) size at maturity and winter (Jan.-Apr.) size at maturity, i.e., females were mature at smaller sizes in summer than in winter. Between-site comparisons of August-September data for both years showed that females were mature at a significantly smaller size at the mixed deciduous woodland site. A sex ratio biased in favour of females was recorded on all but one sampling date at each site, though on some dates this bias was not significant. The change in cohort sex ratio at both sites was quite distinct and exhibited the same general pattern. During the recruitment of each cohort, the ratio was biased towards males. As the cohort increased in length, however, the ratio changed to a bias in favour of females, so that by the time a particular cohort entered its breeding period the following year, it was biased firmly in favour of females. Possible reasons for the observed patterns are discussed.

scholarly journals A diverse assemblage of Permian echinoids (Echinodermata, Echinoidea) and implications for character evolution in early crown group echinoids

2017 ◽  
Vol 91 (4) ◽  
pp. 767-780 ◽  
Author(s):  
Jeffrey R. Thompson ◽  
Elizabeth Petsios ◽  
David J. Bottjer
Keyword(s):  
New Taxa ◽  
Character Evolution ◽  
Morphological Characterization ◽  
Crown Group ◽  
West Texas ◽  
Stem Group

AbstractThe Permian is regarded as one of the most crucial intervals during echinoid evolution because crown group echinoids are first widely known from the Permian. New faunas provide important information regarding the diversity of echinoids during this significant interval as well as the morphological characterization of the earliest crown group and latest stem group echinoids. A new fauna from the Capitanian Lamar Member of the Bell Canyon Formation in the Guadalupe Mountains of West Texas comprises at least three new taxa, includingEotiaris guadalupensisThompson n. sp. an indeterminate archaeocidarid, andPronechinus? sp. All specimens represented are silicified and known from disarticulated or semiarticulated interambulacral and ambulacral plates and spines. This assemblage is one of the most diverse echinoid assemblages known from the Permian and, as such, informs the paleoecological setting in which the earliest crown group echinoids lived. This new fauna indicates that crown group echinoids occupied the same environments as stem group echinoids of the Archaeocidaridae and Proterocidaridae. Furthermore, the echinoids described herein begin to elucidate the order of character transitions that likely took place between stem group and crown group echinoids. At least one of the morphological innovations once thought to be characteristic of early crown group echinoids, crenulate tubercles, was in fact widespread in a number of stem group taxa from the Permian as well. Crenulate tubercles are reported from two taxa, and putative cidaroid style U-shaped teeth are present in the fauna. The presence of crenulate tubercles in the archaeocidarid indicates that crenulate tubercles were present in stem group echinoids, and thus the evolution of this character likely preceded the evolution of many of the synapomorphies that define the echinoid crown group.

scholarly journals Questioning hagfish affinities of the enigmatic Devonian vertebrate Palaeospondylus

2017 ◽  
Vol 4 (7) ◽  
pp. 170214 ◽  
Author(s):  
Zerina Johanson ◽  
Moya Smith ◽  
Sophie Sanchez ◽  
Tim Senden ◽  
Kate Trinajstic ◽  
...  
Keyword(s):  
Semicircular Canals ◽  
Crown Group ◽  
Vertebral Centra ◽  
Stem Group ◽  
Tomographic Data

Palaeospondylus gunni Traquair, 1890 is an enigmatic Devonian vertebrate whose taxonomic affinities have been debated since it was first described. Most recently, Palaeospondylus has been identified as a stem-group hagfish (Myxinoidea). However, one character questioning this assignment is the presence of three semicircular canals in the otic region of the cartilaginous skull, a feature of jawed vertebrates. Additionally, new tomographic data reveal that the following characters of crown-group gnathostomes (chondrichthyans + osteichthyans) are present in Palaeospondylus : a longer telencephalic region of the braincase, separation of otic and occipital regions by the otico-occipital fissure, and vertebral centra. As well, a precerebral fontanelle and postorbital articulation of the palatoquadrate are characteristic of certain chondrichthyans. Similarities in the structure of the postorbital process to taxa such as Pucapampella , and possible presence of the ventral cranial fissure, both support a resolution of Pa. gunni as a stem chondrichthyan. The internally mineralized cartilaginous skeleton in Palaeospondylus may represent a stage in the loss of bone characteristic of the Chondrichthyes.

scholarly journals Crown Group Lejeuneaceae and Pleurocarpous Mosses in Early Eocene (Ypresian) Indian Amber

PLoS ONE ◽  
2016 ◽  
Vol 11 (5) ◽  
pp. e0156301 ◽  
Author(s):  
Jochen Heinrichs ◽  
Armin Scheben ◽  
Julia Bechteler ◽  
Gaik Ee Lee ◽  
Alfons Schäfer-Verwimp ◽  
...  
Keyword(s):  
Early Eocene ◽  
Crown Group ◽  
Pleurocarpous Mosses

scholarly journals The impact of allometry on vomer shape and its implications for the taxonomy and cranial kinesis of crown-group birds

2020 ◽  
Author(s):  
Olivia Plateau ◽  
Christian Foth
Keyword(s):  
Anterior Part ◽  
Correct Identification ◽  
Temporal Region ◽  
Shape Variation ◽  
Crown Group ◽  
Multivariate Statistical ◽  
Morphological Differences ◽  
Cranial Kinesis ◽  
The Impact ◽  
Shape Data

AbstractCrown birds are subdivided into two main groups, Palaeognathae and Neognathae, that can be distinguished, among others, by the organization of the bones in their pterygoid-palatine complex (PPC). Shape variation to the vomer, which is the most anterior part of the PPC, was recently analysed by Hu et al. (2019) with help of geometric morphometrics to discover morphological differences between palaeognath and neognath birds. Based on this study, the vomer was identified as sufficient to distinguish the two main groups (and even more inclusive neognath groups) and their cranial kinetic system. As there are notable size differences between the skulls of palaeognaths and neognaths, we here investigate the impact of allometry on vomeral shape and its implication for taxonomic classification by re-analysing the data of the previous study. Different types of multivariate statistical analyses reveal that taxonomic identification based on vomeral shape is strongly impaired by allometry, as the error of correct identification is high when shape data is corrected for size. This finding is evident by a great overlap between palaeognath and neognath subclades in morphospace. The correct identification is further influenced by the convergent presence of a flattened vomeral morphotype in multiple neognath subclades. As the evolution of cranial kinesis has been linked to vomeral shape in the original study, the existing correlation between shape and size of the vomer across different bird groups found in the present study questions this conclusion. In fact, cranial kinesis in crown birds results from the loss of the jugal-postorbital bar in the temporal region and ectopterygoid in the PPC and the combination of a mobilized quadrate-zygomatic arch complex and a flexible PPC. Therefore, we can conclude that the vomer itself is not a suitable proxy for exploring the evolution of cranial kinesis in crown birds and their ancestors.

scholarly journals Insights into the evolution of oxygenic photosynthesis from a phylogenetically novel, low-light cyanobacterium

2018 ◽  
Author(s):  
Christen L. Grettenberger ◽  
Dawn Y. Sumner ◽  
Kate Wall ◽  
C. Titus Brown ◽  
Jonathan Eisen ◽  
...  
Keyword(s):  
Atmospheric Oxygen ◽  
Evolutionary Model ◽  
Reaction Centers ◽  
Oxygenic Photosynthesis ◽  
Oxygen Production ◽  
Crown Group ◽  
Low Light ◽  
Extrinsic Proteins ◽  
Structural Parts ◽  
Life On Earth

AbstractAtmospheric oxygen level rose dramatically around 2.4 billion years ago due to oxygenic photosynthesis by the Cyanobacteria. The oxidation of surface environments permanently changed the future of life on Earth, yet the evolutionary processes leading to oxygen production are poorly constrained. Partial records of these evolutionary steps are preserved in the genomes of organisms phylogenetically placed between non-photosynthetic Melainabacteria, crown-group Cyanobacteria, and Gloeobacter, representing the earliest-branching Cyanobacteria capable of oxygenic photosynthesis. Here, we describe nearly complete, metagenome assembled genomes of an uncultured organism phylogenetically placed between the Melainabacteria and crown-group Cyanobacteria, for which we propose the name Candidatus Aurora vandensis {au.rora Latin noun dawn and vand.ensis, originating from Vanda}.The metagenome assembled genome of A. vandensis contains homologs of most genes necessary for oxygenic photosynthesis including key reaction center proteins. Many extrinsic proteins associated with the photosystems in other species are, however, missing or poorly conserved. The assembled genome also lacks homologs of genes associated with the pigments phycocyanoerethrin, phycoeretherin and several structural parts of the phycobilisome. Based on the content of the genome, we propose an evolutionary model for increasing efficiency of oxygenic photosynthesis through the evolution of extrinsic proteins to stabilize photosystem II and I reaction centers and improve photon capture. This model suggests that the evolution of oxygenic photosynthesis may have significantly preceded oxidation of Earth’s atmosphere due to low net oxygen production by early Cyanobacteria.

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