Euchambersia mirabilis is unique amongst Permo-Triassic therapsids because it has an external maxillary fossa associated with a ridged canine. This anatomy led to the commonly accepted conclusion that the fossa accommodated a venom gland, which would make Euchambersia the earliest known venomous land vertebrate. Indeed, Euchambersia is considered to be the most robustly supported case of an extinct venomous species and serves as a model for infering envenoming capacity in fossil species. Here, a review of the literature on Euchambersia, with special emphasis on canine morphology, shows that this hypothesis is often based on inaccurate drawings of the canine and, for post-1986 authors, it is even based on the assumption that the canine of Euchambersia is grooved, whereas it is actually only ridged. This does not invalidate the venomous therocephalian hypothesis, but nevertheless emphasizes the critical importance of first hand observations of original material for any type of work in vertebrate paleontology. This review offers an interesting example of how observations and the resulting scientific hypotheses interact, grow, and can reciprocally influence each other.

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