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[dinosaur] Stillatuberoolithus, new theropod egg from Utah + synapsid spine + more



Ben Creisler
bcreisler@gmail.com

New papers:

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Free pdf:

Stillatuberoolithus storrsi oogen. et oosp. nov.

Sara E. Oser, Karen Chin, Joseph J. W. Sertich, David J. Varricchio, Seung Choi & Jeffrey Rifkin (2021)
Tiny, ornamented eggs and eggshell from the Upper Cretaceous of Utah represent a new ootaxon with theropod affinities.
Scientific Reports 11, Article number: 10021
doi: Âhttps://doi.org/10.1038/s41598-021-89472-1
https://www.nature.com/articles/s41598-021-89472-1



A new Cretaceous ootaxon (eggshell type) from the Kaiparowits Formation of Grand Staircase-Escalante National Monument is among a growing number of very small eggs described from the Mesozoic. Analyses of two partial eggs (~â17.7 mm in diameter) and 29 eggshell fragments reveal that this new ootaxon exhibits nodose ornamentation with distinctive branching pore canals that open atop the nodes. Its two-layered microstructure consists of a mammillary layer and a continuous layer with rugged grain boundaries between calcite grains. Although the exact identity of the egg producer is unknown, the eggshell microstructure and small size is consistent with a small-bodied avian or non-avian theropod. The specific combination of small egg size, branching pores, two-layered microstructure, and dispersituberculate ornamentation preserved in this new ootaxon is unique among theropod eggs. This underscores that both eggshell and skeletal fossils of Cretaceous theropods can display a mosaic of transitional morphological and behavioural features characteristic of both avian and non-avian taxa. As such, this new ootaxon increases the diversity of Cretaceous eggs and informs our understanding of the evolution of theropod eggshell microstructure and morphology.


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Vera Weisbecker (2021)
Evolution: Bend it like basal synapsids
Current Biology 31(9): 9R437âR439
DOI: https://doi.org/10.1016/j.cub.2021.03.017
https://www.cell.com/current-biology/fulltext/S0960-9822(21)00356-0
https://www.sciencedirect.com/science/article/abs/pii/S0960982221003560


Mammals can amplify their strides through unique up-and-down spinal movements. This ability was long considered to have evolved from lizard-like ancestors with spines moving sideways. A new study now suggests that, instead, it derived from an extinct, previously unknown spinal form.

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Spencer G. Lucas (2021)
Carboniferous tetrapod biostratigraphy, biochronology and evolutionary events.
Geological Society, London, Special Publications 512 The Carboniferous Timescale (advance online publication)
doi: https://doi.org/10.1144/SP512-2021-5
https://sp.lyellcollection.org/content/early/2021/04/30/SP512-2021-5


Tetrapod (amphibian and amniote) fossils of Carboniferous age are known almost exclusively from the southern part of a paleoequatorial Euramerican province. The stratigraphic distribution of Carboniferous tetrapod fossils is used to identify five land-vertebrate faunachrons: (1) Hortonbluffian (Givetian-early Visean), the time between the FAD of tetrapods to the beginning of the Doran; (2) Doran (late Visean-early Bashkirian), the time between the FAD of the baphetid Loxomma and the beginning of the Nyranyan; (3) Nyranyan (late Bashkirian-Moscovian), the time between the FAD of the eureptile Hylonomus and the beginning of the Cobrean; (4) Cobrean (Kasimovian-late Gzhelian), the time between the FAD of the eupelycosaur Ianthasaurus and the beginning of the Coyotean; and (5) Coyotean (late Gzhelian-early Permian), the time between the FAD of the eupelycosaur Sphenacodon and the beginning of the Seymouran. This biochronology provides insight into some important evolutionary events in Carboniferous tetrapod evolution.

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