Polycotylus
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Polycotylus is a genus of plesiosaur within the family Polycotylidae. The type species is P. latippinis and was named by American paleontologist Edward Drinker Cope in 1869. Eleven other species have
Polycotylus with fetus LACM
Photograph of a paddle of P. latipinnis (1903)
Life restoration of an individual giving birth
Polycotylus with foetus
Dolichorhynchops
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Dolichorhynchops is an extinct genus of polycotylid plesiosaur from the Late Cretaceous of North America, containing the species D. osborni and D. herschelensis, with two previous species having been
Polycotylus
…in the womb, plesiosaurs sacrificed fetal bone strength for accelerated growth rates. Histological analysis and comparisons with another plesiosaur, Dolichorhynchops, showed that some plesiosaur infants were up to forty percent the length of the mother when born, and that infant plesiosaurs may have had some compromised…
Plesiosaurus
Mounted skeleton of the holotype of D. osborni (from Williston, 1903), in the University of Kansas Museum of Natural History
Skeleton in Canadian Fossil Discovery Centre
D. osborni in Vienna