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[dinosaur] Messelopython, new snake from Eocene of Germany, oldest python + acrodont teeth



Ben Creisler
bcreisler@gmail.com

Some new squamate-related papers:

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Messelopython freyi gen. et sp. nov.

Hussam Zaher and Krister T. Smith (2020)
Pythons in the Eocene of Europe reveal a much older divergence of the group in sympatry with boas.
Biology Letters 16(12): 20200735
doi: https://doi.org/10.1098/rsbl.2020.0735
https://royalsocietypublishing.org/doi/10.1098/rsbl.2020.0735


Extant large constrictors, pythons and boas, have a wholly allopatric distribution that has been interpreted largely in terms of vicariance in Gondwana. Here, we describe a stem pythonid based on complete skeletons from the early-middle Eocene of Messel, Germany. The new species is close in age to the divergence of Pythonidae from North American Loxocemus and corroborates a Laurasian origin and dispersal of pythons. Remarkably, it existed in sympatry with the stem boid Eoconstrictor. These occurrences demonstrate that neither dispersal limitation nor strong competitive interactions were decisive in structuring biogeographic patterns early in the history of large, hyper-macrostomatan constrictors and exemplify the synergy between phylogenomic and palaeontological approaches in reconstructing past distributions.

News:

World's earliest python identified from 47 million-year-old fossil remains

https://phys.org/news/2020-12-world-earliest-python-million-year-old-fossil.html


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Free pdf:

M. KavkovÃ, M. ÅulcovÃ, J. DumkovÃ, O. ZahradnÃÄek, J. Kaiser, A. S. Tucker, T. Zikmund & M. Buchtovà (2020)
Coordinated labio-lingual asymmetries in dental and bone development create a symmetrical acrodont dentition.
Scientific Reports 10, Article number: 22040
doi: https://doi.org/10.1038/s41598-020-78939-2
https://www.nature.com/articles/s41598-020-78939-2

Organs throughout the body develop both asymmetrically and symmetrically. Here, we assess how symmetrical teeth in reptiles can be created from asymmetrical tooth germs. Teeth of lepidosaurian reptiles are mostly anchored to the jaw bones by pleurodont ankylosis, where the tooth is held in place on the labial side only. Pleurodont teeth are characterized by significantly asymmetrical development of the labial and lingual sides of the cervical loop, which later leads to uneven deposition of hard tissue. On the other hand, acrodont teeth found in lizards of the Acrodonta clade (i.e. agamas, chameleons) are symmetrically ankylosed to the jaw bone. Here, we have focused on the formation of the symmetrical acrodont dentition of the veiled chameleon (Chamaeleo calyptratus). Intriguingly, our results revealed distinct asymmetries in morphology of the labial and lingual sides of the cervical loop during early developmental stages, both at the gross and ultrastructural level, with specific patterns of cell proliferation and stem cell marker _expression_. Asymmetrical _expression_ of ST14 was also observed, with a positive domain on the lingual side of the cervical loop overlapping with the SOX2 domain. In contrast, micro-CT analysis of hard tissues revealed that deposition of dentin and enamel was largely symmetrical at the mineralization stage, highlighting the difference between cervical loop morphology during early development and differentiation of odontoblasts throughout later odontogenesis. In conclusion, the early asymmetrical development of the enamel organ seems to be a plesiomorphic character for all squamate reptiles, while symmetrical and precisely orchestrated deposition of hard tissue during tooth formation in acrodont dentitions probably represents a novelty in the Acrodonta clade.

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