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Abstract We describe an exceptionally well-preserved vampyropod,Syllipsimopodi bidenigen. et sp. nov., from the Carboniferous (Mississippian) Bear Gulch Lagerstätte of Montana, USA. The specimen possesses a gladius and ten robust arms bearing biserial rows of suckers; it is the only known vampyropod to retain the ancestral ten-arm condition.Syllipsimopodiis the oldest definitive vampyropod and crown coleoid, pushing back the fossil record of this group by ~81.9 million years, corroborating molecular clock estimates. Using a Bayesian tip-dated phylogeny of fossil neocoleoid cephalopods, we demonstrate thatSyllipsimopodiis the earliest-diverging known vampyropod. This strongly challenges the common hypothesis that vampyropods descended from a Triassic phragmoteuthid belemnoid. As early as the Mississippian, vampyropods were evidently characterized by the loss of the chambered phragmocone and primordial rostrum—traits retained in belemnoids and many extant decabrachians. A pair of arms may have been elongated, which when combined with the long gladius and terminal fins, indicates that the morphology of the earliest vampyropods superficially resembled extant squids. 

‘Heteromorph ammonoids’ encompass all ammonoid species whose shapes do not conform to a closely coiled planispiral shell. The term is useful as a broad description for such ammonoids. However, as a concept, ‘heteromorph ammonoids’ no longer has any scientific value or explanatory power. Although such ammonoids have traditionally been considered aberrant forms, they represent instead an integral part of the evolutionary history of the Ammonoidea. ‘Heteromorph ammonoids’, as a whole, are a poly- phyletic group, consisting of a heterogeneous mixture of taxa without any phylogenetic, morphological or ecological coherence. Their treatment as a single entity risks conflating convergences and phylogenetic affinities. It also vastly oversimplifies the stunning array of morphologies and ecological niches occupied by these animals. Investigation into the uncoiling (and recoiling) of ammonoids is a legitimate and worthwhile enterprise, especially in view of the realization that this phenomenon occurred several times in the history of the Ammonoidea. However, few insights can be gained by treating ‘heteromorph ammonoids’ as a single entity. Studies of such ammonoids should focus on monophyletic groups within a well‐constrained phylogenetic and stratigraphical framework to yield meaningful results.