A new look into the periorbital morphology of Goniopholis (Mesoeucrocodylia: Neosuchia) and related forms

The periorbital morphology of goniopholidids is discussed, exploring the diversity of patterns and the relevance of the data for phylogenetic studies. Revision of material is focused on Goniopholis spp. and aff. Goniopholis spp., from England, Germany, and Belgium, providing a comparative description of their interorbital morphology. Traditional interpretation of the interorbital elements in species of Goniopholis (G. simus, G. baryglyphaeus), where the frontal is interpreted as excluded from the orbit by a prefrontal-postorbital contact in the skull roof, is contested and clarified through the analysis of new specimens, including a morphometric analysis. In Goniopholis, failure to identify the palpebral and its subtle contact with the prefrontal has lead to misinterpretation of elements and structures near the orbit, and the differential preservation/loss of palpebrals explains variability of the orbit in shape and orientation. In all European goniophilidids the frontal reaches the primary orbital border and there is no prefrontal-postorbital contact on the dorsal surface of the skull. Extensive contact of the palpebral with the primary orbital border creates a secondary (functional) orbital border, from which the frontal is excluded in most taxa. The condition is not exclusive of European goniopholidids and is paralleled by protosuchids, peirosaurids, and baurusuchids. At least four main morphological patterns are recognized, revealing a high diversity of European goniopholidids.