Here we find two male Scalloped Oxen, battling for a female's attention. Once the fight commences, they will retract their heads inside their armored shells, allowing the neck to act as a battering ram. It is an impressive display, even if you're not a female Scalloped Oxen. Concept art by Kate Pfeilschiefter.
Here is Pfeilschiefter's full description for this illustration, titled "Territorial Dispute":
The Scalloped Oxen are large reptilian omnivores distantly related to tortoises. They thrive in a variety of warm climates, surviving in lean times via fatty stores beneath their flexible external carapaces. They travel in herds with a social structure similar to that of wild horse bands, the lead males of these herds attempt to add females to their ranks through showy displays and by battering rivals with their armored necks.
"Territorial Dispute" is featured with the artist's permission and was spotted on r/ImaginaryBeasts.