Ana M. BÃEZ (2021)
Barremian anurans of the Iberian Peninsula: new insights into their taxonomic diversity.
in FOLIE A., BUFFETAUT E., BARDET N., HOUSSAYE A., GHEERBRANT E. & LAURIN M. (eds), Palaeobiology and palaeobiogeography of amphibians and reptiles: An homage to Jean-Claude Rage.
Comptes Rendus Palevol 20(6): 75-90.
The Barremian continental successions of the Iberian Peninsula have yielded numerous remains of anurans. Some of these finds consist of fragmentary bones whereas others furnish more complete evidence on the skeletal morphology and proportions of the represented taxa. Notwithstanding the foregoing, most of these records have been ascribed either to the relatively basal extant costatan clade or to the poorly known extinct genus Eodiscoglossus Villalta, 1954 based on insufficient data. Recent revisions of some of these materials have demonstrated the presence of traits presumably plesiomorphic and unknown in extant costatans, thereby casting doubts on their phylogenetic placements. Herein two specimens from the upper Barremian Las Hoyas Konservat-lagerstÃtte are thoroughly described and compared, providing evidence of additional anuran taxa in this site. One of these specimens, initially reported as cf. Eodiscoglossus, is referred to Wealdenbatrachus Fey, 1988, a genus already described in the coeval fossil site of UÃa. Another specimen consisting of a partial postcranial skeleton is documented by a latex-rubber cast and a photograph; it represents a new taxon whose phylogenetic position remains uncertain due to the incompleteness of the available evidence. Comments on a third specimen that might belong to another taxon are included, although its detailed description awaits its full preparation. The overview of the Barremian taxa currently recognized from Iberia reveals the co-occurrence of taxa of different sizes, body proportions, and lifestyles, suggesting some ecological partitioning in consonance with the heterogeneous habitats represented in the yielding fossil sites.
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Cecilia Mariana Krmpotic, FabiÃn Nishida, Fernando Carlos Galliari, MarÃa Teresa Pombo, Francisco AcuÃa, Claudio Gustavo Barbeito & Alfredo Armando Carlini (2021)
The Dorsal Integument of the Southern Long-Nosed Armadillo Dasypus hybridus (Cingulata, Xenarthra), and a Possible Neural Crest Origin of the Osteoderms. Discussing Evolutive Consequences for Amniota.
Journal of Mammalian Evolution (advance online publication)
doi:
https://doi.org/10.1007/s10914-021-09538-9https://link.springer.com/article/10.1007/s10914-021-09538-9
Osteoderms are present in most tetrapod lineages with considerable lineage-specific variation. It has been hypothesized that osteoderms are a case of "deep homology" in craniates, but the embryonic origin of osteoderms -and other related postcranial exoskeletal elements- is still under debate. Most authors support its mesodermal origin, while others suggest that osteoderms are derived from neural crest scleroblastic cells in sauropsids. The armadillos (Xenarthra, Cingulata) are the only living mammals and the only extant synapsids with osteoderms. Here, we aim to identify skeletogenic neural crest cells in the dorsal skin of armadillos in order to assess if osteoderms have a neuroectodermal origin in mammals, similar to what is observed in sauropsids. For this purpose, skin samples from fetuses and newborn specimens of Dasypus hybridus were processed and the embryological development of osteoderms was characterized using different immunohistochemical markers (HNK-1, PDGFR Î, S-100, and C5). For the first time, we report cell populations that were reactive to skeletogenic neural crest markers, indicating an ectomesenchymal origin of the mammalian osteoderms. Our results demonstrate similar molecular _expression_ for mammals as in sauropsids and, therefore, this strongly suggests that osteoderms in both groups would have a homologous embryonic origin.
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Shai Meiri, Gopal Murali, Anna Zimin, Lior Shak, Yuval Itescu, Gabriel Caetano & Uri Roll (2021)
Different solutions lead to similar life history traits across the great divides of the amniote tree of life.
Journal of Biological Research-Thessaloniki Â28: 3
doi:
https://doi.org/10.1186/s40709-021-00134-9https://link.springer.com/article/10.1186/s40709-021-00134-9Free pdf:
https://link.springer.com/content/pdf/10.1186/s40709-021-00134-9.pdfAmniote vertebrates share a suite of extra-embryonic membranes that distinguish them from anamniotes. Other than that, however, their reproductive characteristics could not be more different. They differ in basic ectothermic vs endothermic physiology, in that two clades evolved powered flight, and one clade evolved a protective shell. In terms of reproductive strategies, some produce eggs and others give birth to live young, at various degrees of development. Crucially, endotherms provide lengthy parental care, including thermal and food provisioningâwhereas ectotherms seldom do. These differences could be expected to manifest themselves in major differences between clades in quantitative reproductive traits. We review the reproductive characteristics, and the distributions of brood sizes, breeding frequencies, offspring sizes and their derivatives (yearly fecundity and biomass production rates) of the four major amniote clades (mammals, birds, turtles and squamates), and several major subclades (birds: Palaeognathae, Galloanserae, Neoaves; mammals: Metatheria and Eutheria). While there are differences between these clades in some of these traits, they generally show similar ranges, distribution shapes and central tendencies across birds, placental mammals and squamates. Marsupials and turtles, however, differ in having smaller offspring, a strategy which subsequently influences other traits.
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The avian eggshell is a natural protective envelope that relies on the phenomenon of biomineralization for its formation. The shell is made of calcium carbonate in the form of calcite, which contains hundreds of proteins that interact with the mineral phase controlling its formation and structural organization, and thus determine the mechanical properties of the mature biomaterial. We describe its mineralogy, structure and the regulatory interactions that integrate the mineral and organic constituents during eggshell biomineralization.
Main Body.
We underline recent evidence for vesicular transfer of amorphous calcium carbonate (ACC), as a new pathway to ensure the active and continuous supply of the ions necessary for shell mineralization. Currently more than 900 proteins and thousands of upregulated transcripts have been identified during chicken eggshell formation. Bioinformatic predictions address their functionality during the biomineralization process. In addition, we describe matrix protein quantification to understand their role during the key spatially- and temporally- regulated events of shell mineralization. Finally, we propose an updated scheme with a global scenario encompassing the mechanisms of avian eggshell mineralization.
Conclusion
With this large dataset at hand, it should now be possible to determine specific motifs, domains or proteins and peptide sequences that perform a critical function during avian eggshell biomineralization. The integration of this insight with genomic data (non-synonymous single nucleotide polymorphisms) and precise phenotyping (shell biomechanical parameters) on pure selected lines will lead to consistently better-quality eggshell characteristics for improved food safety. This information will also address the question of how the evolutionary-optimized chicken eggshell matrix proteins affect and regulate calcium carbonate mineralization as a good example of biomimetic and bio-inspired material design.
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Also:Â
An isolated, articulated, but crushed ossified lung of a mawsoniid coelacanth is reported from uppermost Cretaceous (upper Maastrichtian) of Oued Zem, Morocco. The specimen is the last record of a coelacanth before their pseudo-extinction at the end of the Mesozoic. The specimen is also the first record of a marine coelacanth in the Mesozoic of Morocco and the first occurrence of coelacanths in the phosphate deposits of North Africa. The large size of the lung suggests a fish estimated at between 3.65 m and 5.52 m total body length.
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Enormous ancient fish fossil discovered in search of pterodactyl remains
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Amir Siraj & Abraham Loeb (2021)
Breakup of a long-period comet as the origin of the dinosaur extinction.
Scientific Reports Â11, Article number: 3803
doi:
https://doi.org/10.1038/s41598-021-82320-2https://www.nature.com/articles/s41598-021-82320-2The origin of the Chicxulub impactor, which is attributed as the cause of the K/T mass extinction event, is an unsolved puzzle. The background impact rates of main-belt asteroids and long-period comets have been previously dismissed as being too low to explain the Chicxulub impact event. Here, we show that a fraction of long-period comets are tidally disrupted after passing close to the Sun, each producing a collection of smaller fragments that cross the orbit of Earth. This population could increase the impact rate of long-period comets capable of producing Chicxulub impact events by an order of magnitude. This new rate would be consistent with the age of the Chicxulub impact crater, thereby providing a satisfactory explanation for the origin of the impactor. Our hypothesis explains the composition of the largest confirmed impact crater in Earthâs history as well as the largest one within the last million years. It predicts a larger proportion of impactors with carbonaceous chondritic compositions than would be expected from meteorite falls of main-belt asteroids.
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Harvard's Avi Loeb has a new theory about dinosaur-killing comet Chicxulub
The kind of space rock that wiped T.rex and friends from our planet might be more common than previously thought.
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