Pachycostasaurus
| Pachycostasaurus Temporal range: Middle Jurassic | |
|---|---|
| Holotype fossil, Peterborough Museum | |
| Scientific classification | |
| Domain: | Eukaryota | 
| Kingdom: | Animalia | 
| Phylum: | Chordata | 
| Class: | Reptilia | 
| Superorder: | †Sauropterygia | 
| Order: | †Plesiosauria | 
| Family: | †Pliosauridae | 
| Genus: | †Pachycostasaurus Cruickshank et al., 1996 | 
| Species: | †P. dawni | 
| 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.