| Pachycostasaurus Temporal range: Middle Jurassic
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|---|---|
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| Holotype fossil, Peterborough Museum | |
Scientific classification 
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| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Reptilia |
| Superorder: | †Sauropterygia |
| Order: | †Plesiosauria |
| Family: | †Pliosauridae |
| Genus: | †Pachycostasaurus Cruickshank et al., 1996 |
| Species: | †P. dawni
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| Binomial name | |
| †Pachycostasaurus dawni Cruickshank et al., 1996
| |
Pachycostasaurus (meaning 'thick-ribbed lizard') is an extinct Pliosauroid from the Oxford Clay formation of Peterborough, England.