Direct evidence of carnivory in the early-diverging Alvarezsaurian Bannykus
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GRAPHICAL ABSTRACT
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PUBLIC SUMMARY
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Direct evidence of carnivory in Bannykus wulatensis is presented through analyzing its intestinal contents.
Bone fragments suggests an efficient chemical digestion of Bannykus wulatensis.
The evolution of manual digits and diets may have been decoupled in alvarezsaurians.
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ABSTRACT
A dietary shift from carnivory to insectivory has been proposed to explain the morphological evolution of alvarezsaurians, particularly the adaptive manual digital reduction and body size miniaturization. However, based solely on morphological shifts, this hypothesis lacks direct dietary evidence to support either carnivory or insectivory. Here, we present the first dietary evidence for alvarezsaurians, derived from the intestinal contents of the Early Cretaceous Bannykus wulatensis. Our analysis revealed significantly higher levels of calcium and phosphorus in the intestinal contents compared to the surrounding sandstone. Scanning electron microscopy identified hard tissue debris and possible soft tissues surrounded by phosphatized bacteria and tightly packed hollow microspheres, suggesting that the intestinal contents were strongly pseudomorphed by phosphatized microbes during fossilization. Raman spectroscopy showed characteristic peaks indicative of bone-derived material, consistent with the hard tissue debris in the intestinal contents. Our results suggest that Bannykus had a carnivorous diet with strong chemical digestion, which likely compensated for its delicate cranial structures and small teeth. These results imply that if a dietary shift to insectivory occurred, it likely took place later in alvarezsaurian evolution, probably coinciding with a reduction in body size.-
Keywords:
- Bannykus wulatensis /
- intestinal content /
- insectivory /
- carnivory /
- coprolite /
- diet /
- Raman spectrum
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REFERENCES
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Wang S., Ding N., Ma W., et al. (2025). Direct evidence of carnivory in the early-diverging Alvarezsaurian Bannykus. The Innovation Geoscience 3:100143. https://doi.org/10.59717/j.xinn-geo.2025.100143
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Wang S., Ding N., Ma W., et al. (2025). Direct evidence of carnivory in the early-diverging Alvarezsaurian Bannykus. The Innovation Geoscience 3:100143. https://doi.org/10.59717/j.xinn-geo.2025.100143
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Figure 1.
Silhouette and photographs of Bannykus wulatensis holotype (IVPP V25026) showing the yellowish conglomerate enclosed by the partial gastralia ribcage
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Figure 2.
EDS results for the yellowish conglomerate enclosed by the partial gastralia ribcage
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Figure 3.
Ground sections and EMP results highlighting the differences in microstructures, chemical components, and roundness of the minerals cemented in the host sandstone and conglomerate samples
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Figure 4.
SEM images showing the phosphatized hollow microspheres (A-C), apatite crystals (D-F), and phosphatized microbes (G), illustrating the heterogeneous nature of the conglomerate (H-I)
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Figure 5.
SEM images showing the phosphatized soft tissues (A-I) and debris of hard tissues (J-L) within the intestinal contents
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Figure 6.
Raman spectrum results illustrating feature peaks indicative of bony substrates of the intestinal content
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Figure 7.
Time-calibrated simplified phylogeny showing the interrelationships of alvarezsaurians, along with the accompanying decreases in body size and the reduction of manual digits (not to scale)
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