Dear colleagues We are pleased to announce some new publications on early mysticetes.
1, Tsai, CH, Goedert, JL, and Boessenecker, RW. 2024. The oldest mysticete in the Northern Hemisphere. Current Biology 34, 1-7. Abstract Extant baleen whales (Mysticeti) uniquely use keratinous baleen for filter-feeding and lack dentition, but the fossil record clearly shows that “toothed” baleen whales first appeared in the Late Eocene. Globally, only two Eocene mysticetes have been found, and both are from the Southern Hemisphere: *Mystacodon selenensis* from Peru, 36.4 mega-annum (Ma) ago and *Llanocetus denticrenatus* from Antarctica, 34.2 Ma ago. Based on a partial skull from the lower part of the Lincoln Creek Formation in Washington State, USA, we describe the Northern Hemisphere’s geochronologically earliest mysticete, *Fucaia humilis* sp. nov. Geology, biostratigraphy, and magnetostratigraphy places Fucaia humilis sp. nov. in the latest Eocene (ca. 34.5 Ma ago, near the Eocene/Oligocene transition at 33.9 Ma ago), approximately coeval with the oldest record of fossil kelps, also in the northeastern Pacific. This observation leads to our hypothesis that the origin and development of a relatively stable, nutrient-rich kelp ecosystem in the latest Eocene may have fostered the radiation of small-sized toothed mysticetes (Family Aetiocetidae) in the North Pacific basin, a stark contrast to the larger Llanocetidae (whether *Mystacodon* belongs to llanocetids or another independent clade remains unresolved) with the latest Eocene onset of the Antarctic Circumpolar Current in the Southern Hemisphere. Our discovery suggests that disparate mechanisms and ecological scenarios may have nurtured contrasting early mysticete evolutionary histories in the Northern and Southern hemispheres. Open-access: https://www.sciencedirect.com/science/article/pii/S0960982224003087 2, Tsai, CH, Kimura T, and Hasegawa, Y. 2024. Coexistence of Oligocene toothed and baleen-assisted mysticetes in the northwestern Pacific. Fossil Record 27, 95-100. Abstract Oligocene mysticetes display an unparalleled diversity and morphological disparity in the evolutionary history of Mysticeti. However, their paleoecological aspects, such as the patterns of coexistence of different morphotypes, remain poorly explored. Here we describe an aetiocetid (toothed mysticete) from the Jinnobaru Formation (lower upper Oligocene, about 28 million years ago) of Umashima Island, Kitakyushu, Japan. Our description of a toothed mysticete from the Oligocene of Umashima exemplifies the coexistence of toothed and baleen-assisted mysticetes in the northwestern Pacific. Hopefully, new finds of Oligocene mysticetes will lead to a well-sampled dataset for analyzing this and other related paleoecological traits to understand the demise of “archaic” Oligocene mysticetes and the subsequent rise of the modern-looking baleen-bearing whales in Miocene times. Open-access: https://fr.pensoft.net/article/111567/ 3, Hernández-Cisneros, AE, Schwennicke, T, Rochín-Bañaga, H, and Tsai, CH. 2023. *Echericetus novellus* n. gen. n. sp. (Cetacea, Mysticeti, Eomysticetidae), an Oligocene baleen whale from Baja California Sur, Mexico. Journal of Paleontology 97, 1309-1328. Abstract Among the several evolutionary lineages of the baleen whales (Mysticeti), the eomysticetids are an ancient successful family that retain possibly nonfunctional teeth and functional baleen, a transitional stage between toothed and baleen-assisted filter-feeding mysticetes. The patchy fossil record leaves gaps in eomysticetid paleobiology interpretations, but their diversity and widespread geographical distribution can be a relevant proxy to understanding the evolution of crown Mysticeti. Here we describe a new baleen whale, *Echericetus novellus* n. gen. n. sp., from the Oligocene of Mexico (slightly older than 27.95 million years ago). This new taxon has morphological features that show its affinity to Eomysticetidae, such as the intertemporal region longer than wide, the elongate and oval temporal fossa, and a well-developed and lobate coronoid process of the mandible. Similarly, our cladistic analyses confirm the inclusion of *Echericetus* in the Eomysticetidae. *Echericetus* reinforces our notion of the eomysticetid diversity and disparity. Geographically, the existence of *Echericetus* from Mexico also indicates that eomysticetid inhabited subtropical regions in the Northern Hemisphere. Last, our discovery of a new eomysticetid from the Oligocene of Mexico provides new insights into the distribution patterns and habitat use of Eomysticetidae, essential to further explain the demise of this transitional lineage between toothed and baleen-bearing whales. Open-access: https://www.cambridge.org/core/journals/journal-of-paleontology/article/echericetus-novellus-n-gen-n-sp-cetacea-mysticeti-eomysticetidae-an-oligocene-baleen-whale-from-baja-california-sur-mexico/8A2836F00C3862A4D792378F85759DD4 Alternatively, please feel free to email me for pdf copies or further discussion: whalet...@ntu.edu.tw or crani...@gmail.com Cheers, Tsai 蔡政修（Cheng-Hsiu Tsai さい まさのぶ) PhD Associate Professor R508, Lab of evolution and diversity of fossil vertebrates（古脊椎動物演化及多樣性實驗室） Department of Life Science & Institute of Ecology and Evolutionary Biology （生命科學系＆生態學與演化生物學研究所） National Taiwan University（台灣大學） No. 1, Sec. 4, Roosevelt Rd., Taipei, 106-17, Taiwan（台灣 106-17 台北市羅斯福路 4 段 1 號） Email: whalet...@ntu.edu.tw; crani...@gmail.com; Tel: 886 - 2 - 3366 - 2448 Twitter: TSAI_NTU508 <https://twitter.com/TSAI_NTU508>; FB: 蔡政修 CH Tsai <https://www.facebook.com/NTUWhaleTsai>; Google Scholar: TSAI, Cheng-Hsiu <https://scholar.google.com/citations?user=AeNkkhAAAAAJ&hl=en>; and Paleo fund-raising <https://giving.ntu.edu.tw/backend/FastDonation.html?DonateNo=28&DonateIOTxt=臺灣大學生命科學系古脊椎動物演化及多樣性實驗室&fbclid=IwAR31Q8p1NFMM7FJGBnlunMjFR7t462rLTyoFuhTGvHU45kMntad4fwa8ANE>
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