A review of short-necked plesiosaurs from the Cretaceous of the Western Interior, North America

New plesiosaur records from the Lower Cretaceous of the Neuquén Basin, west-central Argentina, with an updated picture of occurrences and facies relationships

“…125;Berezin, 2011;Kear and Barret, 2011;Benson and Druckenmiller, 2014) and the possibly Early Cretaceous Opallionectes (Kear, 2006a). This feature is also recorded for the latest Jurassic Svalbard cryptocleidoids Spitrasaurus Knutsen, Druckenmiller and Hurum, 2012a and Djupedalia Knutsen, Druckenmiller and Hurum, 2012b, polycotylids (Carpenter, 1996) and some pliosaurids such as Brachauchenius lucasi (Ketchum and Benson, 2010, Ch. 125).…”

On the cranial anatomy of the polycotylid plesiosaurs, including new material ofPolycotylus latipinnis, Cope, from Alabama

“…The morphology of this taxon is very similar to that of Dolichorhynchops, and this description will therefore highlight areas of difference with that taxon and complementary material, rather than comprehensively redescribing the entire skull. A cranial reconstruction of Trinacromerum can be found in Carpenter (1996). Trinacromerum is also larger in terms of raw body size, and the skull is proportionally longer (Trinacromerum = 1.54 X Dolichorhynchops; data from O'Keefe, 2002), although the proportions of the skull are similar.…”

“…County, Kansas (Carpenter, 1996) Polycotylus also has several derived features in the appendicular skeleton. The ischia are very long, longer relatively than in any other plesiosaur, although the other polycotylids (and pliosauromorphs in general) also have relatively long ischia (Carpenter, 1996;O'Keefe, 2002).…”

“…As is the case in all plesiosaurs, the opisthotic is restricted to the paraoccipital process and a small flange fused to the ventro-dorsal aspect of the exoccipital (O'Keefe, in press). Williston illustrates the supraoccipital as bifid; however, this condition has not withstood closer examination (Carpenter, 1996(Carpenter, , 1997, and the supraoccipital in Dolichorhynchops is unpaired and deep antero-posteriorly. This condition is closely similar to that observed in elasmosaurs (Carpenter, 1997).…”

“…Skull Roof-The skull roof of Dolichorhynchops is depicted in Figure 3 (MCZ 1064), and reconstructed in Figure 4. Parts of the reconstruction and various anatomical details from the postorbital bar and jaw suspensorium are taken from the holotype skull, KUVP 1300 (figured by Carpenter, 1996, andWilliston, 1903). The external naris is retracted to a position near the anterior margin of the orbit; the orbit is large and contains a prominent sclerotic ring in KUVP 1300 (not depicted in the reconstruction).…”