| Named By: | Edward Drinker Cope in 1869 |
| Time Period: | Late Cretaceous, 84-81 Ma |
| Location: | Potentially cosmopolitan distribution with fossils located in North America, South America, Eurasia, Australia. Most fossils located within the USA in what was once the Western Interior Seaway |
| Size: | 4.3 meters long |
| Diet: | Carnivore |
| Fossil(s): | Remains of multiple individuals, some of them revealing impressions of soft tissues |
| Classification: | | Chordata | Reptilia | Squamata | Mosasauridae | Plioplatecarpinae | Plioplatecarpini | |
| Also known as: | | Holcodus coryphaeus | Holcodus ictericus | Holcodus mudgei | Holosaurus | Lestosaurus coryphaeus | Lestosaurus felix | Lestosaurus gracilis | Lestosaurus ictericus | Lestosaurus latifrons | Lestosaurus simus | Liodon ictericus | Liodon mudgei | Platecarpus anguliferus | Platecarpus coryphaeus | Platecarpus felix | Platecarpus gracilis | Platecarpus ictericus | Platecarpus latifrons | Platecarpus mudgei | Platecarpus simus | Platecarpus tectulus | Sironectes | |
Platecarpus ("flat wrist") is an extinct genus of aquatic lizards belonging to the mosasaur family, living around 84-81 million years ago during the middle Santonian to early Campanian, of the Late Cretaceous period. Fossils have been found in the United States and a possible specimen in Belgium and Africa. A well-preserved specimen of Platecarpus shows that it fed on moderate-sized fish, and it has been hypothesized to have fed on squid, and ammonites as well. Like other mosasaurs, it was initially thought to have swum in an eel-like fashion, although another study suggests that it swam more like modern sharks. An exceptionally well-preserved specimen of P. tympaniticus known as LACM 128319 shows skin impressions, pigments around the nostrils, bronchial tubes, and the presence of a high-profile tail fluke, showing that it and other mosasaurs did not necessarily have an eel-like swimming method, but were more powerful, fast swimmers. It is held in the Natural History Museum of Los Angeles County.