New Insights on theAristonectes parvidens(Plesiosauria, Elasmosauridae) Holotype: News on an Old Specimen

The cranial anatomy and relationships of Cardiocorax mukulu (Plesiosauria: Elasmosauridae) from Bentiaba, Angola

“…Each premaxilla of MGUAN PA278 has a lateral tooth count of five, as indicated by the number of premaxillary alveoli ( Fig 6 ). The lateral tooth count in MGUAN PA278 is the same as Styxosaurus snowii [ 42 ], Libonectes morgani [ 61 ], Tuarangisaurus keyesi Wiffen and Moisley, 1986 [ 62 , 63 ], Lagenanectes richterae Sachs, Hornung, and Kear, 2017 [ 11 ], Leivanectes bernandoi Páramo-Fonseca, O’Gorman, Gasparini, Padilla, and Parra Ruge, 2019 [ 20 ], and Callawayasaurus colombiensis [ 10 ], but differs from Thalassomedon haningtoni [ 13 ] (4 premaxillary teeth), Elasmosaurus platyurus Cope, 1868 [ 64 , 65 ] (6 premaxillary alveoli), Eromangasaurus australis Sachs, 2005 [ 15 , 17 , 21 ] (3–4 premaxillary alveoli), and the aristonectines Kaiwhekea katiki Cruickshank and Fordyce, 2002 [ 53 , 66 ] (7 premaxillary alveoli), Morturneria seymourensis Chatterjee and Smalls, 1989 [ 67 , 68 ] (8–9 premaxillary teeth) and Aristonectes parvidens Cabrera, 1941 [ 53 , 69 , 70 ] (~13 premaxillary alveoli). Premaxillary alveoli become sequentially larger posteriorly.…”

“…Seventeen alveoli are discernable in the maxilla. A count of 17 maxillary alveoli in MGUAN PA278 is distinguishable from the high maxillary alveoli counts of aristonectine elasmosaurids (more than 50 maxillary teeth in Aristonectes parvidens and 36 in Kaiwhekea katiki ) [ 70 ], Styxosaurus snowii (at least 15 maxillary teeth) ( S1 Fig ), Libonectes morgani (13–14 maxillary teeth) [ 61 ], Tuarangisaurus keyesi (15 maxillary alveoli) [ 63 ], and Nakonanectes bradti (14 maxillary teeth) [ 41 ]. The upper tooth row on the right side of the skull terminates at approximately the midpoint of the supratemporal fenestra.…”

“…In ventral view, the vomer does not have a ventral ridge, as in Libonectes morgani (D1-8213) [ 71 ]. The vomer extends posteriorly beyond the internal naris and is not separated medially by the pterygoids ( Fig 6 ), as in Lagenanectes richterae [ 11 ], and the aristonectines Morturneria seymourensis [ 67 , 68 ] and Aristonectes parvidens [ 70 ].…”

“…There are at least 20 alveoli present in the dentary, like Futabasaurus suzukii (20 alveoli) [ 78 ], and possibly Tuarangisaurus keyesi (20–21 alveoli) [ 63 ]. This is contrasted with 18–19 dentary alveoli in Libonectes morgani [ 61 ], at least 18 in Thalassomedon haningtoni ( S2 Fig ), 16–18 in Styxosaurus snowii [ 42 ] ( S3 Fig ), 18–19 in Nakonanectes bradti [ 41 ], 17–18 in Terminonatator ponteixensis [ 40 ], 42–44 in Kaiwhekea katiki [ 66 ], approximately 50 or more in Aristonectes quiriquinensis [ 76 ], and 63–65 in Aristonectes parvidens [ 70 ]. The dentary alveoli of MGUAN PA278 are slightly ellipsoidal in shape, with compression along the labio-lingual axis.…”

“…This notch delineates the ventral margin of a fenestra that separates the neural arches. This fenestra is present in multiple elasmosaurid taxa, including Elasmosaurus platyurus [ 65 ], Libonectes morgani [ 92 ], Nakonanectes bradti [ 41 ], Tuarangisaurus keyesi [ 63 ], Vegasaurus molyi O’Gorman, Salgado, Olivero, and Marenssi, 2015 [ 93 ], and Aristonectes parvidens [ 70 , 94 ]. The lateral surface of the atlas-axis complex does not present a bulge at the interface between the atlas and axis centrum, unlike Styxosaurus snowii , but is rather flat and smooth [ 42 ].…”