First cranial endocasts of early Miocene sirenians (Dugongidae) from the West Indies

ABSTRACT

We report and describe the first sirenian endocranial casts from the West Indies based on three specimens collected from two quarries of the upper Oligocene–lower Miocene Colón Formation, in the province of Matanzas, western Cuba. We assign them to Dugongidae incertae sedis, based on a phylogenetic analysis of fossil and extant sirenians. Thus, these new specimens provide a unique opportunity to describe the endocranial neuroanatomy of this family. The endocasts are suggestive of dugongids with limited vision and olfaction, based on the diminished olfactory and optic nerves. Additionally, we provide a geological reinterpretation of the Colón Formation and its paleoecological setting. Altogether, these data provide further insight into the diversity and evolution of sirenians, especially Caribbean dugongs.

RESUMEN

Se describen los primeros moldes endocraniales de sirénido hasta ahora reportados de las Antillas. Los tres especímenes que reportamos provienen de dos canteras con afloramientos de la Formación Colón, en la provincia de Matanzas, Cuba. Esta formación se considera de edad Oligoceno tardío a Mioceno temprano, pero nosotros asignamos los moldes al Mioceno temprano. Conjuntamente, proveemos una lista de caracteres y un análisis filogenético que puede ayudar aclarar su posición sistemática. Por falta de material comparativo, los moldes endocranianos no se pudieron atribuir a una especie, y por ende los asignamos a la familia Dugongidae incertae sedis, por su posición en el árbol filogenético. Estos especímenes permiten un acercamiento a la historia, diversidad y evolución de los sirénidos, y en especial de los dugongídos en el neógeno caribeño.

ACKNOWLEDGMENTS

We thank A. Tejedor for the revision of an earlier manuscript. E. Robinson, F. Maurrasse, L. S. Collins, and J. Alvarez Licourt for their guidance, generally stratigraphy and microfossils, particularly foraminifera, and use of their paleolaboratories. We also thank O. Jiménez and D. Domning for suggestions and guidance, E. Abreu, O. Gil, and R. Figueroa for discussing their observations on fossil occurrence at the quarries, the quarry workers who discovered the fossils discussed here, M. Voss for answering questions regarding specimen SMF-M3921, and E. Przybyszewski for his help with the phylogenetic analysis. We also thank J. Vélez-Juarbe, an anonymous referee, and the handling editor O. Lambert.