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Soft tissue analyses of preserved enantiornithean ovarian follicles (1 Viewer)


Well-known member
Bailleul, A.M., J. O’Connor, Z. Li, Q. Wu, T. Zhao, M.A. Martinez Monleon, M. Wang, and X. Zheng (2020)
Confirmation of ovarian follicles in an enantiornithine (Aves) from the Jehol biota using soft tissue analyses
Communications Biology 3: 399
doi: 10.1038/s42003-020-01131-9

The remains of ovarian follicles reported in nine specimens of basal birds represents one of the most remarkable examples of soft-tissue preservation in the Early Cretaceous Jehol Biota. This discovery was immediately contested and the structures alternatively interpreted as ingested seeds. Fragments of the purported follicles preserved in an enantiornithine (STM10-12) were extracted and subjected to multiple high-resolution analyses. The structures in STM10-12 possess the histological and histochemical characteristics of smooth muscles fibers intertwined together with collagen fibers, resembling the contractile structure in the perifollicular membrane (PFM) of living birds. Fossilized blood vessels, very abundant in extant PFMs, are also preserved. Energy Dispersive Spectroscopy shows the preserved tissues primarily underwent alumino-silicification, with minor mineralization via iron oxides. No evidence of plant tissue was found. These results confirm the original interpretation as follicles within the left ovary, supporting the interpretation that the right ovary was functionally lost early in avian evolution.

Fred Ruhe

Well-known member
Fig. 1 Photograph of an enantiornithine indet, STM10–12. General view of the slab a and close-up on the purported ovarian follicles, all approximately the same size (pink arrows in b). Close-ups on these same structures (pink arrows) in the counterslab c. Two fragments were used for different analytical methods d. The first fragment (orange outline) was prepared using ground sectioning methods. The second fragment (blue outline) was demineralized and processed for paraffin histology. Abbreviations: Frag. fragment, sed sediment.



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Fred Ruhe

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Gerald Mayr, Thomas G. Kaye, Michael Pittman, Evan T. Saitta & Christian Pott, 2020

Reanalysis of putative ovarian follicles suggests that Early Cretaceous birds were feeding not breeding

Scientific Reports volume 10, Article number: 19035

Free pdf: https://www.nature.com/articles/s41598-020-76078-2.pdf


We address the identity of putative ovarian follicles in Early Cretaceous bird fossils from the Jehol Biota (China), whose identification has previously been challenged. For the first time, we present a link to the botanical fossil record, showing that the “follicles” of some enantiornithine fossils resemble plant propagules from the Jehol Biota, which belong to Carpolithes multiseminalis. The botanical affinities of this “form-taxon” are currently unresolved, but we note that C. multiseminalis propagules resemble propagules associated with cone-like organs described as Strobilites taxusoides, which in turn are possibly associated with sterile foliage allocated to Liaoningcladus. Laser-Stimulated Fluorescence imaging furthermore reveals different intensities of fluorescence of “follicles” associated with a skeleton of the confuciusornithid Eoconfuciusornis zhengi, with a non-fluorescent circular micro-pattern indicating carbonaceous (or originally carbonaceous) matter. This is inconsistent with the interpretation of these structures as ovarian follicles. We therefore reaffirm that the “follicles” represent ingested food items, and even though the exact nature of the Eoconfuciusornis stomach contents remains elusive, at least some enantiornithines ingested plant propagules.


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