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Exceptionally preserved plant parenchyma in the digestive tract indicates a herbivorous diet in the Middle Eocene bird Strigogyps sapea (Ameghinornithidae)

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Abstract

The holotype skeleton of the avian species Strigogyps sapea from the Middle Eocene of Messel preserves remains of the digestive tract that have not been studied so far. The crop content of the specimen includes numerous densely packed, tiny spherules containing large cavities. These peculiar structures match well with previously described fossil plant parenchyma cells with starch grain moulds. We hypothesize that the spherule layer represents plant parenchyma ingested by the bird, and that the spherules themselves are casts of cytoplasm with storage organelles. Our study provides a further example of exceptional soft tissue preservation in Messel vertebrates and shows that Strigogyps was at least facultatively herbivorous. A herbivorous diet of Strigogyps is also indicated by the fact that the crop content includes seed remains, and it constitutes further evidence against previously hypothesized close affinities between the taxon and the carnivorous Phorusrhacidae.

Kurzfassung

Das Skelett des Holotyps von Strigogyps sapea, einer Vogelart aus dem mittleren Eozän von Messel, enthält Reste des Verdauungstraktes, welche bisher nicht untersucht wurden. Insbesondere weist der Kropfinhalt des Fossils zahlreiche, dicht gepackte kleine Kügelchen auf, welche große Hohlräume enthalten. Diese eigenartigen Strukturen stimmen gut mit früher beschriebenen Abdrücken von fossilen, Stärkekörnern enthaltenden Pflanzenparenchymzellen überein. Wir nehmen an, dass die Körnchenschicht des Strigogyps-Fossils Pflanzenparenchym repräsentiert, welches durch den Vogel aufgenommen wurde, und dass die Körnchen selbst Abgüsse von Cytoplasma mit Speicherorganellen sind. Unsere Studie liefert ein weiteres Beispiel außergewöhnlicher Weichteilerhaltung bei Wirbeltieren aus Messel und zeigt, dass Strigogyps zumindest fakultativ pflanzenfressend war. Eine herbivore Ernährungsweise von Strigogyps wird auch durch die Tatsache gestützt, dass der Kropfinhalt Samen enthält und stellt einen weiteren Beleg dar, der gegen eine nähere Verwandtschaft zwischen diesem Taxon und den carnivoren Phorusrhacidae spricht.

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Acknowledgments

We are indebted to H.-J. Gregor, who first directed our attention to the spherules in the Strigogyps fossil. We further thank S. Schaal and E. Brahm for making the specimen available for study, and S. Tränkner for taking the photographs for Fig. 1. We are most grateful to H. Wilkinson for permission to reproduce figures of Eocene starch grain moulds, drawing our attention to the article by Wang et al. (2010), and for comments on the possible identity of the spherules in the Messel bird. We further acknowledge reviews of the manuscript by S. Baszio and H. Alvarenga.

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Mayr, G., Richter, G. Exceptionally preserved plant parenchyma in the digestive tract indicates a herbivorous diet in the Middle Eocene bird Strigogyps sapea (Ameghinornithidae). Paläontol Z 85, 303–307 (2011). https://doi.org/10.1007/s12542-010-0094-5

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  • DOI: https://doi.org/10.1007/s12542-010-0094-5

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