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

ABSTRACT

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.

ACKNOWLEDGMENTS

The authors are indebted to A. C. Milner, L. Steel, H. Ketchum, S. Chapman, and P. Barrett (BMNH), J. Cooper (BMNHB), M. Reich (GZG), S. Kaiser (IPB), E. Sterbaut, A. Folie, and T. Smith (IRSBN), D. Schwarz-Wings (MB), M. Ramalho and J. Sequeira (MG), and B. Battail and V. Bouetel (MNHN) for access to specimens used in this study. Michael J. Benton (BRSUG) kindly revised an early version of the text, and S. W. Salisbury (University of Queensland) and D. Schwarz-Wings (MB) provided detailed critiques of the original manuscript. M.B.A. extends further gratitude to R. Edmonds (Jurassic Coast Heritage Team) and P. Ensom (DORCM) for access to DORCM 12154; D. Schwarz-Wings for the generous exchange of ideas; P. Gill, M. Ruta, and M. Sakamoto (BRSUG) for their critique and advice on the use of morphometric data; R. Schouten (BRSUG) for advice on preparation of DORCM 12154; S. Powell (BRSUG) for valuable directions on macrophotography. J.J.H. acknowledges J. Kimmig for providing especially valuable support and information; and M. Reich and T. Stegemann (GZG) for logistical support with the loan of IPB R359.

Goniopholis DORCM 12154 was recovered with the kind permission of the Swanage Town Council and Natural England, and prepared with financial support from the Jurassic Coast Trust (England). M.B.A. receives a scholarship from Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq Proc. n° 200381/2006–7), Brazil; and also benefited from the following small awards: (a) the Bob Savage Memorial Fund (BRSUG), at the BMNH and MG; (b) Synthesys project FR-TAF-4858, at MNHN; (c) Synthesys project BE-TAF-5357, at RBINS-IRSNB/RMCA/NBG. J.J.H. benefited from grants from Synthesys project GB-TAF-4204, at BMNH. Synthesys (http://www.synthesys.info/) is financed by the European Community Research Infrastructure Action under the FP6 “Structuring the European Research Area Programme.”

Handling editor: Johannes Müller.