I have heard several authors and seen several reconstructions that have portrayed some ornithischians, particularly heterodontosaurids and basal ceratopsians, as omnivorous. I was wondering, is there any positive evidence in support of this hypothesis? That is, beyond "well its possible that they could have been omnivorous based on their anatomy and the fact that a lot of living herbivorous animals have been documented occasionally eating meat" and more along the lines that "this evidence suggests these animals were most likely including some amount of animal matter in their diet". The only evidence I have been able to find so far is Farke's mention of how heterodontosaurid canines do not vary with sex or sexual maturity.
You can make it your own research project - like Zanno & Makovicky, when they collected (a) morphological evidence and (b) direct evidence (like bite marks, stomach contents, coprolites) for herbivory in theropods and came to a phylogenetically-informed hypothesis:
https://www.researchgate.net/publication/49697724_Herbivorous_ecomorphology_and_specialization_patterns_in_theropod_dinosaur_evolution
Of course your approach (demonstrating omnivory in ornithischians) would be vice versa to what they did.
There are further possible data sources, such as (c) tooth wear patterns (macrowear to microwear) which might be diet-specific or (d) stable isotope geochemistry (e.g. 15N is known to become enriched from lower to higher trophic levels, but their might not be much N preserved in case of dinosaur fossils).
Article Herbivorous ecomorphology and specialization patterns in the...
Please read the recent post by Ashu Kosla in researchgate
Ostracods, plant tissues, and other inclusions in coprolites from the Late
Cretaceous Lameta Formation at Pisdura, India: Taphonomical and
palaeoecological implications. Palaeogeography, Palaeoclimatology, Palaeoecology 418 (2015) 90–100
Look at the micro structure of the teeth will tell the real true story.
moreover, consider size and mrtabolic rate to hipotesize on omnivory... several authors relate the small size in ornithischian dinosaurs as an indirect evidence of omnivory, together with anatomically plesiomorphic dentition. This kind of conclusions is arribed in Heterodontosaurids (See Sereno 2012) such as Heterodontosaurus (Norman et al., 2011), Fruitadens (Butler et al., 2010, 2012), Manidens (Becerra et al., 2013, 2016) and you can also look for this kind of reference in papers of feeding behavior in oprnithischia of Norman and Weishampel. I don´t remember if this kind of feeding is mentioned in Eocursor, Lesothosaurus, and stormbergia, but you can search the papers by your oun.
Cheers!
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