Pliosaurus portentificus

Pliosaurus portentificus Noé, Smith & Walton, 2004

Holotype: CAMSM J.46380, anterior portion of a mandible.
Stratum typicum: Kimmeridge Clay, within Aulacostephanus mutabilis to Aulacostephanus eudoxus ammonite zones, lower Kimmeridgian, Upper Jurassic.
Locus typicus: Ely, Cambridgeshire, United Kingdom.
Diagnosis: Pliosaurian plesiosaur with elongate mandibular symphysis extending to the rear of the eight tooth pair; functional alveoli pair two to six are enlarged; splenials extend approximately half the length of the ventral surface of the mandibular symphysis (from Knutsen 2012, modified after Noé et al. 2004).
Current status: Nomen dubium.
Comments: Pliosaurus portentificus was established by Noè et al. (2004) based upon the symphyseal portion of a mandible with remnants of both post-symphyseal mandibular rami. Noè et al. (2004) observed that the specimen’s small size and incomplete interdentary suture fusion suggest an immature individual, though likely from a small species comparable in size to Liopleurodon macromerus (now Pliosaurus macromerus, see Knutsen, 2012). They also found that the downturned tip of the dentary suggests the anterior end of the cranial rostrum was likewise slightly downturned. Noè et al. (2004) distinguished Pliosaurus portentificus from other species of Pliosaurus by the presence of eight dentary teeth per side adjacent to the symphysis. This would represent an intermediate stage between the smaller number of 5–6 teeth in Pliosaurus macromerus and the higher number of 9–11 teeth per side found in Pliosaurus brachydeirus and Pliosaurus brachyspondylus. Knutsen (2012) listed Pliosaurus portentificus among the taxa of questionable validity, pointing out that the interpretation of tooth positions in Noè et al. (2004) was largely based on information from Tarlo (1959, 1960) which cannot be confirmed. Following a new interpretation by Knutsen (2012), the number of teeth adjacent to the symphysis in Pliosaurus portentificus is close to that of Pliosaurus brachyspondylus and Pliosaurus brachydeirus. Pliosaurus portentificus is thus likely a young individual of one of the other Pliosaurus species known from the same stratigraphic level and should be considered Pliosaurus sp.. Benson et al. (2013) likewise concluded that the taxon is a nomen dubium referable to Pliosaurus indet..