The first articulated skull roof and braincase of Melvius chauliodous (Amiidae, Vidalamiinae) from the Upper Cretaceous Kirtland Formation, San Juan Basin, New MexicoCitation for this article: Sullivan, R. M., Jasinski, S. E., & Williamson, T. E. (2023) The first articulated skull roof and braincase of Melvius chauliodous (Amiidae, Vidalamiinae) from the Upper Cretaceous Kirtland Formation, San Juan Basin, New Mexico. Journal of Vertebrate Paleontology . https://doi.org…

Abstract

ABSTRACTA new, exceptionally well-preserved articulated skull roof and braincase of Melvius chauliodous, from the Kirtland Formation of New Mexico, reveals new features that provide detailed osteological information for Melvius, thus allowing for a reassessment of characters that defines the genus, its two recognized species M. chauliodous and M. thomasi, and its phylogenetic relationships within Vidalamiinae. The new features include the presence of dermopterotic rays (‘ribs’) and parietal ray bundles, previously unknown for both species of Melvius. The presence of elongated dermopterotic rays, a feature previously considered to be distinctive for the genus Calamopleurus, and tribe Calamopleurini, is now documented in Melvius, but these rays differ in their point of origination at the posteromedial corners of both dermopterotics. Bundles of short fan-shaped rays emanating from below the posterolateral corners of the parietals are also documented in both species of Melvius. Melvius was previously placed in the tribe Vidalamiini (Subfamily Vidalamiinae), but because it shares some unique features with members of the tribe Calamopleurini and the genus Calamopleurus, its placement within Vidalamiini, and the recognition of these two distinct clades (tribes) within Vidalamiinae, are not supported in our phylogenetic analysis. Previous characters distinguishing Melvius species, particularly differences in postinfraorbital ornamentation between M. chauliodous and M. thomasi, are considered dubious. However, other features may serve to determine interspecific variation or differences. For the present, we retain both species until more definitive material of M. thomasi is described. ACKNOWLEDGMENTSForemost, RMS thanks J. Petersen (discoverer) and T. Knopick who helped collect the specimen, and who have been invaluable field assistants to RMS in collecting fossil vertebrates from the San Juan Basin for over a decade. We are especially grateful to P. Holroyd (UCMP) for providing photos of UCMP 131707 and UCMP 129681 that were crucial in identifying this latter element. Thanks are also extended to M. Sims (KU Biodiversity Institute and Natural History Museum) for verifying the locality information of the KUVP specimens mentioned within and for providing us with high resolution photos of KUVP 88378 that helped in interpreting and reconfirming the identity of this element. Special thanks to T. Tokaryk and M. Gilbert for additional information regarding Canadian occurrences of Melvius. RMS thanks D. Fowler (Dickinson Museum Center and Badlands Dinosaur Museum) for discussions regarding phylogenetic analyses and paleogeography as they pertain to this study. N. Volden (NMMNH) aided in securing information regarding the fossil amiid specimens previously housed in the collections of the University of New Mexico and we thank her for her help. L. Rinehart prepared the ventral side of NMMNH P-88899 and RMS prepared the dorsal side of the specimen. RMS thanks P. Reser for making recommendations regarding the preparation of the dorsal side of the skull which is greatly appreciated. We are most grateful to L. Cavin (Muséum d’histoire Naturelle, Geneva) for his insightful comments and additional correspondence regarding fossil amiid fishes and for reviewing our paper. We also thank P. L. Godoy and an anonymous reviewer who greatly improved an earlier version of this manuscript. We thank JVP editors T. Argyriou and J. Harris for their guidance in the publication of our manuscript. Lastly, we thank P. Gensler Bureau of Land Management (BLM) for his continued support in our research in the San Juan Basin of New Mexico and for issuing the necessary permits needed to conduct our fieldwork. Both newly referred specimens (NMMNH P-88899 and P-88901) were collected under BLM Paleontological Resources Use Permit No. NM 14-09S (renewal) issued to S. Lucas, T. Williamson, and G. Morgan.AUTHOR CONTRIBUTIONSRMS and SEJ conceived and executed the project, drafted the manuscript, scored the characters, and edited the manuscript. SEJ ran the analyses. RMS, SEJ and TEW analyzed the data and reviewed this version.SUPPLEMENTARY FILESSupplementary Data 1: document including Figs. S1, S2, Tables S1–S4, Character list, Data matrix, Discussion of Grande and Bemis (Citation1998) phylogenetic results, and supplemental references.Supplementary Data 2: NEXUS file.Supplementary Data 3: TNT file.Supplementary Data 4: Most parsimonious trees file.