148
Journal of Paleontology 91(1):146–161
Table 1. Measurements of Ceratodus tooth plates described in this work. Angles, in degrees, were measured following protocol outlined and illustrated by Kirkland (1987, fig. 1; see Fig. 1 herein). ABC = angle between mesial (line A–B) and lingual (line B–C) borders, C1Cp = angle between lines defined by first (C1) and last (Cp) crests, C2Cp = angle between lines formed by second (C2) and last (Cp) crests, C3Cp = angle between lines formed by third (C3) and last (Cp) crests, Max. L = maximum length is the end of C1 to Cp from the labial margin in mm, Max.W = maximum width is the labial margin to the lingual-mesial margin junction in mm.
Species
C. stewarti C. molossus
C. kirklandi Specimen
C. nirumbee C. kempae
OMNH 69332 NCSM 30253 UMNH 16774 MNA.V.10649 BYU 20808 BYU 20810 BYU 20811 BYU 20807 BYU 20809 BYU 20812 BYU 20813
OMNH 34765 BYU 20814
Plate
Upper Upper Upper Lower Upper Lower Upper Lower Lower Lower Lower Lower Upper
ABC 130
135 136 149 118 121 121 124 121 133 141 121 111
Rockies, Bozeman, Montana; NCSM, North Carolina Museum of Natural Sciences, Raleigh, North Carolina, U.S.A.; NJSM, New Jersey State Museum, Trenton, New Jersey, U.S.A.; OMNH, Sam Noble Oklahoma Museum of Natural History, Norman, Oklahoma, U.S.A.; SDSM, Museum of Geology, South Dakota School of Mines and Technology, Rapid City, South Dakota, U.S.A.; TATE, Tate Museum, Casper, Wyoming, U.S.A.; UCM, University of Colorado Museum, Boulder, Colorado, U.S.A.; UMNH-VP, Vertebrate Paleonto- logy Collection, Utah Museum of Natural History, Salt Lake City, Utah, U.S.A.; UNSM, University of Nebraska State Museum, Lincoln, Nebraska, U.S.A.; USNM, National Museum of Natural History (formerly United States National Museum), Smithsonian Institution, Washington, D.C., U.S.A.; UTA-AAS, University of Texas at Arlington, Arlington Archosaur Site, Arlington, Texas, U.S.A. (numbers cited from Main et al., 2014, specimens are now deposited at the Perot Museum of Science and Nature, Dallas, Texas, U.S.A.); UWM, University of Wyoming Museum, Laramie, Wyoming, U.S.A.; VOF, Valley of Fire State Park, currently curated at the Nevada State Museum and Historical Society, Las Vegas, Nevada, U.S.A; YPM, Yale Peabody Museum, New Haven, Connecticut, U.S.A.
Systematic paleontology Subclass Dipnoi Müller, 1846
Order Ceratodontiformes Berg, 1940 Family Ceratodontidae Gill, 1872 Genus Ceratodus Agassiz, 1838
Type species.—Ceratodus latissimus Agassiz, 1838.
C1Cp 86
69 70 76 82 86 85 92 88 — 92 88 —
C2Cp 55
49 44 47 52 56 56 46 54 52 59 54 45
C3Cp 29
20 19 20 25 28 28 16 22 26 26 22 21
Max. L 9.8
62.8 —
39.1 26.2 26.8 25.3 30
25.7 —
28.3 29.5 —
Ceratodus stewarti Milner and Kirkland, 2006 Figure 2.1, Table 1
2006 Ceratodus stewarti Milner and Kirkland, p. 515, fig. 7B.
Holotype.—Prearticular plate with fused prearticular (UMNH-VP 16037), Early Jurassic, from the Whitmore Point Member, Moenave Formation; 12km east of St. George, Washington County, Utah, U.S.A. (Milner and Kirkland, 2006, fig. 1B).
Emended diagnosis.—Lower tooth plates with four primary
ridges (the fourth ridge being twinned); upper tooth plate has five ridges with the fifth being twinned; both upper and lower tooth plates have relatively tall ridges, with C1Cp angle being slightly acute.
Occurrence.—Lower Jurassic (Hettangian–Sinemurian), south- ern Utah. The newly referred specimen (OMNH 69332) is from OMNH locality V1737, 4 km west of Goblin Valley State Park, Emery County, Utah, U.S.A.; Kayenta Formation (Lower Jurassic, Sinemurian, see Lucas et al., 2005).
Description.—Milner and Kirkland (2006) described C. stewarti based on a single prearticular tooth plate. The prearticular plate of this species is distinct in its possession of a twinned fourth ridge (here defined as a single crest arising from central mound that splits into two crests before reaching the labial margin), such that five functional cutting surfaces are present; a trait not known to occur in any other ceratodontid from the Jurassic. This species is most similar to Potamoceratodus guentheri
Figure 2. Ceratodus from North America. (1) C. stewarti, OMNH 69332, left pterygopalatine plate in occlusal view; OMNH locality V1737, Emery County, Utah, Kayenta Formation, Lower Jurassic (Sinemurian). (2–7) C. molossus n. sp. (2, 3) Occlusal and dorsal views, respectively, of NCSM 30253 (holotype), right pterygopalatine plate; locality near Emery, Emery County, Utah, Mussentuchit Member, Cedar Mountain Formation, Upper Cretaceous (Cenomanian). (4, 5) Occlusal and dorsal views, respectively, of UMNH 16774, right pterygopalatine plate; locality near Escalante, Garfield County, Utah, Naturita Formation, Upper Cretaceous (Cenomanian). (6, 7) Occlusal and inferior views, respectively, of MNA.V.10649, right prearticular plate; MNA locality 1067, Garfield County, Utah, Naturita Formation, Upper Cretaceous (Cenomanian). (8, 9) C. nirumbee n. sp., occlusal and inferior views, respectively, of OMNH 34765 (holotype), right prearticular plate; OMNH locality V1061, Carbon County, Montana, Cloverly Formation, Lower Cretaceous (Albian). (10, 11) C. kempae n. sp., BYU 20814 (holotype), right pterygopalatine plate in occlusal and dorsal views, respectively; pter. = pterygoid; BYU locality 1783, Grand County, Utah; Yellow Cat Member, Cedar Mountain Formation, Lower Cretaceous (Valanginian). (12, 13) C. frazieri, OMNH 60408, right prearticular plate in occlusal and inferior views; OMNH locality 1075, Big Horn County, Montana; Cloverly Formation, Lower Cretaceous (Albian). (14, 15) C. gustasoni, OMNH 66043, left prearticular plate in occlusal and inferior views, respectively; OMNH locality V808, Garfield County, Utah; Naturita Formation, Upper Cretaceous (Cenomanian).
Max.W 4.9
36.9 35.2 23.8 14.1 14.1 14.3 —
11.1 10.4 13.3 14.5 20.3
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