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.
Supplemental data explanation
Supplemental_Data_File_1_BYU_20808
Ceratodus kirklandi n. sp., BYU 20808 (holotype), right pterygopalatine plate. Specimen from BYU locality 1667, Grand County, Utah; Yellow Cat Member, Cedar Mountain Formation, Lower Cretaceous (Valanginian).
Supplemental_Data_File_2_BYU_20809
Ceratodus kirklandi n. sp., BYU 20809, left prearticular plate. Specimen from BYU locality 1667, Grand County, Utah; Yellow Cat Member, Cedar Mountain Formation, Lower Cretaceous (Valanginian).
Supplemental_Data_File_3_NCSM_30253
Ceratodus molossus n. sp., NCSM 30253 (holotype), right pterygopalatine plate; locality near Emery, Emery County, Utah, Mussentuchit Member, Cedar Mountain Formation, Upper Cretaceous (Cenomanian).
Supplemental_Data_File_4_MNAV_10649
Ceratodus molossus n. sp., MNA.V.10649, right prearticular plate; MNA locality 1067, Garfield County, Utah, Naturita Formation, Upper Cretaceous (Cenomanian).
Supplemental_Data_File_5_UMNH_16774
Ceratodus molossus n. sp., UMNH 16774 (cast), right pterygopalatine plate; locality near Escalante, Garfield County, Utah, Naturita Formation, (Cenomanian).
Supplemental_Data_File_6_OMNH_34765
Ceratodus nirumbee n. sp., OMNH 34765 (holotype), right prearticular plate; OMNH locality V1061, Carbon County, Montana, Cloverly Formation, Lower Cretaceous (Albian).
Supplemental_Data_File_7_BYU_20814
Ceratodus kempae, n. sp., BYU 20814 (holotype), right pterygopalatine plate; BYU locality 1783, Grand County, Utah; Yellow Cat Member, Cedar Mountain Formation, Lower Cretaceous (Valanginian).
Supplemental_Data_File_8_OMNH_60408
Ceratodus frazieri, OMNH 60408, right prearticular plate; OMNH locality 1075, Big Horn County, Montana; Cloverly Formation, Lower Cretaceous (Albian).
Supplemental_Data_File_9_OMNH_66043
Ceratodus gustasoni, OMNH 66043, left prearticular plate; OMNH locality V808, Garfield County, Utah; Naturita Formation, Upper Cretaceous (Cenomanian).