Do phytoliths in sinopterid pterosaur bellies mean they were herbivores?

Others seem to think so.
“This is a once-in-a-hundred-years discovery,” says David Martill, a paleontologist at the University of Portsmouth who was not involved in the research. He adds that the new evidence is a “smoking gun” for pterosaur herbivory, showing definitively that the fierce-looking winged creatures were not always carnivorous.”

Martill says the evidence made him a convert. “I, for one, thought that the fine beak tip of tapejarids was most likely used for picking small water fleas from shallow water or for eating insects.”

“Direct evidence is fundamental to settling this kind of debate,” says R. Pêgas at the University of São Paulo, who was not involved in the study. “This closes the debate and confirms that pterosaurs had more dietary diversity than previously thought.”

Figure 1. Sinopterus atavismus specimen with stomach contents. ” data-image-caption=”

Figure 1. Sinopterus atavismus specimen with stomach contents.

” data-medium-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/07/sinopterus.stomach.plants588.jpg?w=223″ data-large-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/07/sinopterus.stomach.plants588.jpg?w=584″ class=”size-full wp-image-93637″ src=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/07/sinopterus.stomach.plants588.jpg” alt=”Figure 1. Sinopterus atavismus specimen with stomach contents.” width=”584″ height=”787″ srcset=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/07/sinopterus.stomach.plants588.jpg?w=584&h=787 584w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/07/sinopterus.stomach.plants588.jpg?w=111&h=150 111w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/07/sinopterus.stomach.plants588.jpg?w=223&h=300 223w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/07/sinopterus.stomach.plants588.jpg 588w” sizes=”(max-width: 584px) 100vw, 584px” />

Figure 1. Sinopterus atavismus specimen with stomach contents. This is a great specimen!

Details
“At the top of the pterosaur’s stomach (Fig 1), the imaging revealed numerous large quartz crystals. Quartz is often found within gastroliths, a type of mineralized stomach stone that many modern animals such as birds and lizards store in their gizzards or stomachs to help crush hard foods such as plants.”

Sounds like the upper chamber was a gizzard. In birds that’s the usually the second chamber. The first chamber in birds is usually the acid bath.

A google search revealed, “unlike most birds, pelicans and other sea fowl, have 3 stomachs, the proventriculus, the gizzard, and a third, which filters bones.“

“Lower in the stomach, Jiang and Zhang’s team discovered hundreds of phytoliths, small mineral deposits that build up between growing plant cells.”

“Pinning phytoliths to specific plants can be difficult, but those found within the pterosaur appear to come mostly from woody plants, with a few from flowering plants or conifers. “

Okay. Let’s think about this. If a pelican needs 4 pounds of fish each day, which part of the woody plant morphology is Sinopterus eating in similar bulk?

What is a phytolith?
“Rigid, microscopic mineral deposits found in some plant tissues, often persisting after the decay of the plant. The plants which exhibit them take up dissolved silica from the groundwater, whereupon it is deposited within different intracellular and extracellular structures of the plant.”

“Silicon is important as a nutrient for phytoplankton (diatom, radiolarian, silicoflagellates and sponges) and for the phytolith production by terrestrial vegetation.”

I knew nothing about phytoliths until now. As you can tell, I still know very little, but from the above terrestrial vegetation usually produces phytoliths. Afterwards, in the course of fire, monsoon, etc, these microscopic elements can enter the marine realm where the silicon can be useful in phytoplankton production.

Figure 3. Sinopterus atavismus skull restored (gray areas). ” data-image-caption=”

Figure 3. Sinopterus atavismus skull restored (gray areas).

” data-medium-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2020/11/sinopterus_atavismus-skulldgs588.jpg?w=300″ data-large-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2020/11/sinopterus_atavismus-skulldgs588.jpg?w=584″ class=”size-full wp-image-50910″ src=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2020/11/sinopterus_atavismus-skulldgs588.jpg” alt=”Figure 3. Sinopterus atavismus skull restored (gray areas).” width=”584″ height=”509″ srcset=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2020/11/sinopterus_atavismus-skulldgs588.jpg?w=584&h=509 584w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2020/11/sinopterus_atavismus-skulldgs588.jpg?w=150&h=131 150w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2020/11/sinopterus_atavismus-skulldgs588.jpg?w=300&h=261 300w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2020/11/sinopterus_atavismus-skulldgs588.jpg 588w” sizes=”(max-width: 584px) 100vw, 584px” />

Figure 2 Sinopterus atavismus skull restored (gray areas), flipped from the original. See figure 1.

Curious…
So were woody plants the diet and sustenance of this pterosaur? Or did pond scum with an accumulation of wind-born phytoliths (perhaps after a fire or storm) wash in along with the little fish the pterosaur usually ate in quantity (going back to the standard model)?

After all, pterosaurs with a similar rostrum, like Pteranodon, ate little fish from the Niobrara Sea, according to fossil evidence.

Did that phytolith accumulation kill this sinopterid (blocking normal digestion)?
That hypothesis is based on the batch of phytoliths (Fig 1) lacking in other sinopterids.

Did sinopterids regularly regurgitate accumulated phytoliths and this one died just a little too soon? Or was it poisoned or otherwise killed by the phytolith accumulation?

Is woody herbivory a pterosaur diet with that sinopterid rostral morphology?

Just wondering…

PS
This reminds me of the ‘fighting’ fishes and pterosaurs from the Solnhofen that likely died without conflict due to anoxia – not fighting.

References
Jiang S et al (5 co-authors) 2025. First occurrence of phytoliths in pterosaurs—evidence for herbivory. Science Bulletin. .doi:10.1016/j.scib.2025.06.040
Thilakanayaka V et al 2021. Contribution of terrestrially derived phytolith as a marine silicon sink. Online here.
Wang Y et al 1998. Application of phytolith study in marine geology in China. Online here.
Wu Y et al 2018. Dinosaur-associated Poaceae epidermis and phytoliths from the Early Cretacous of China. National Science Review, 5, 721-727.

Publicity
Pterosaur died with belly full of plants—a fossil first: Science online