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Egg accumulation with 3D embryos provides insight into the life history of a pterosaur

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Science  01 Dec 2017:
Vol. 358, Issue 6367, pp. 1197-1201
DOI: 10.1126/science.aan2329

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  • Comment to: Wang et al. 2017, Egg accumulation with 3D pterosaur embryos

    Wang et al. 2017 [1] present wonderful news about a unique fossil site in which hundreds of pterosaur eggs several times accummulated en masse.

    The authors assumed the eggs were originally laid in nests, whether buried in the sand or on the beach, then later transported. That is because the authors consider pterosaurs to be archosaurs, which is the current majority view. Birds and crocodilians are also archosaurs, and they lay their eggs in nests at an early stage of fertilization.

    By contrast, the minority view follows results recovered in a large and growing, wide-gamut online phylogenetic analysis [2] in which pterosaurs are recovered within a third clade of lepidosaurs between Sphenodontia (= Rhynchocephalia) and Squamata. Distinct from archosaurs, lepidosaurs generally wait to lay their eggs, sometimes until the moment before hatching. The minimal thickness of pliable pterosaur eggshells [1] is also a characteristic of lepidosaurs, especially those that carry their embryos until just before hatching.

    Pterosaur adults were unlikely to die in storms [contra 1] because they were able to sense their approach and fly to safety. A scenario must be envisioned in which several year-classes of flocking pterosaurs, some of them carrying eggs, were not able to fly away.

    Step-by-step alternate scenario

    Flocks of pterosaurs, many of them females carrying eggs, visited the egg accumulation site, which was near a lake [1].

    If the lake ‘...

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    Competing Interests: None declared.