Data from: New Cretaceous lungfishes (Dipnoi, Ceratodontidae) from western North America

Ceratodontid lungfishes are generally rare, poorly represented elements of North America’s Mesozoic ecosystems, with previously known maximum diversity in the Late Jurassic. Herein we describe four new species of the form genus Ceratodus, from the Cretaceous of the Western Interior, considerably expanding fossil representation of post-Triassic dipnoans in North America. To model taxonomic and morphologic diversity, we adopt a four-fold system of phenetically based species groups, named for exemplars from the Morrison Formation. Ceratodus kirklandi n. sp. (Potamoceratodus guentheri group) and C. kempae n. sp. (C. frazieri group) represent a hitherto unsampled time interval, the Valanginian. Ceratodus nirumbee n. sp. and C. molossus n. sp. extend the temporal ranges of the C. fossanovum and C. robustus groups upward to the Albian and Cenomanian, respectively. These new occurrences show that ceratodontids maintained their highest diversity from the Late Jurassic through the mid-Cretaceous (Albian–Cenomanian), an interval of ~60 Myr. The existing record suggests that some of the later (mid-Cretaceous) ceratodontids may have been tolerant of salt water; to date, there is no evidence that they aestivated. Only a few occurrences are known from horizons younger than Cenomanian. Demise of ceratodontids appears to be part of a broader pattern of turnover that occurred at the Cenomanian-Turonian boundary in North America.

角齿鱼科肺鱼（Ceratodontid lungfishes）通常为北美中生代生态系统中较为罕见、化石记录匮乏的类群，此前已知其最高多样性出现于晚侏罗世。本文记述了产自北美西部内陆白垩纪地层的4个角齿鱼属（Ceratodus）新种，极大扩充了北美三叠纪后肺鱼类（dipnoans）的化石记录。为构建分类学与形态多样性模型，我们采用基于表型特征的四分类物种群体系，该体系以莫里逊组（Morrison Formation）的代表类群命名。基尔兰角齿鱼（Ceratodus kirklandi n. sp.，隶属于冈瑟河角齿鱼群（Potamoceratodus guentheri group））与肯普角齿鱼（C. kempae n. sp.，隶属于弗雷泽角齿鱼群（C. frazieri group））代表了此前尚未被采样的凡蓝今期（Valanginian）地层。尼伦比角齿鱼（Ceratodus nirumbee n. sp.）与墨洛瑟角齿鱼（Ceratodus molossus n. sp.）分别将福萨诺瓦姆角齿鱼群（C. fossanovum group）与粗壮角齿鱼群（C. robustus group）的生存时代上限延伸至阿尔布期（Albian）与森诺曼期（Cenomanian）。这些新发现表明，角齿鱼科肺鱼的多样性峰值时段从晚侏罗世一直延续至白垩纪中期（阿尔布期-森诺曼期），时长约60百万年（~60 Myr）。现有记录显示，部分白垩纪中期的角齿鱼科类群可能已适应咸水环境；截至目前，尚无证据表明它们存在夏眠行为。仅在少量晚于森诺曼期的地层中发现过角齿鱼科肺鱼的化石记录。角齿鱼科肺鱼的灭绝似乎与北美地区森诺曼期-土仑期界线（Cenomanian-Turonian boundary）处发生的大范围生物更替事件密切相关。