https://orcid.org/0000-0003-1740-8670
![Sample our Environment & Agriculture journals, sign in here to start your access, latest two full volumes FREE to you for 14 days]({"type":"image" , "src" : "/sda/5934/TOC-Subject-Sample-2021-Environment-Agriculture.jpg"})
Abstract
The aetiocetids are a well-known extinct taxon of Oligocene toothed mysticetes in the North Pacific. They display a high degree of diversity contrasting with that of other tooth-bearing mysticetes such as mammalodontids, llanocetids and Coronodon spp. The disparate developmental patterns (heterochrony) and origin of the first kelp forests in the North Pacific during the Eocene–Oligocene transition might explain such diversity. Aetiocetidae have been the focus of debate regarding the origin of baleen and filter-feeding in Mysticeti. The current interpretation of aetiocetid feeding strategies is based on the presence of teeth, unfused mandibular symphysis and lateral palatal foramina. However, our understating of their feeding apparatus function is limited, leaving associated structures like the zygomatic arch unnoticed. The present study describes a new fossil of a small-sized mysticete (∼3 m long), Kaaucetus thesaurus gen. et sp. nov., which belongs to Aetiocetidae. The protruded squamosal prominence and distinctive zygomatic process present in this new fossil highlight disparity in feeding morphology amongst aetiocetids. Moreover, the zygomatic arch complex and masticatory muscle system reconstruction are crucial to interpreting the likely capability of mastication (shearing motion) in aetiocetids and other toothed mysticetes. Lastly, the record of several aetiocetid genera in Mexico extends the geographical range of the group into the subtropical region.
Acknowledgements
The author thanks the reviewers, R. W. Bossenecker and C.-H. Tsai, and the editors for their assistance and comments that helped improve this manuscript. Also, I extend gratitude to E. H. Nava-Sanchez for his support; the SIP 20131259 and 20211371 (CICIMAR-IPN) projects helped develop the present study. I am thankful for the help and comments of J. Velez-Juarbe and G. Aguirre-Fernández during manuscript preparation. I am extending my appreciation to J. Velez-Juarbe for support and access to the specimen F. goedertorum and the LACM collection. I thank the collectors of the specimen. I thank G. Gonzalez-Barba for allowing access to the MU_EcSj1/29/141 fossil. My gratitude goes to P. W. Dobson for the English text review. I am genuinely grateful to many people who helped in different ways. Part of this study was carried out during AEHC’s MSc thesis at the Centro Interdisciplinario de Ciencias Marinas – Instituto Politécnico Nacional (CICIMAR-IPN), supported by the Consejo Nacional de Ciencia y Tecnología (CONACYT), scholarship 290143 (2012-2014). CONACYT/Becas Mexico, Doctoral Fellowship, grant number 513362/290143 (2017-2021) and the Beca Tesis-IPN program supported AEHC's project.
Supplemental material
Supplemental material for this article can be accessed at: https://doi.org/10.1080/14772019.2022.2100725
Associate Editor: Adrian Lister