Pliosauridae Temporal range: Late Triassic - Late Cretaceous, 228–89.3 Ma PreꞒ Ꞓ O S D C P T J K Pg N
Cast of Attenborosaurus conybeari (NHMUK R1339), Natural History Museum
Liopleurodon ferox mounted skeleton, Museum of Paleontology, Tübingen
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Class:	Reptilia
Superorder:	†Sauropterygia
Order:	†Plesiosauria
Suborder:	†Pliosauroidea
Family:	†Pliosauridae Seeley, 1874
Subgroups
†Anguanax †Arminisaurus †Attenborosaurus †Hauffiosaurus †Marmornectes †Monquirasaurus †Pachycostasaurus †Rhaeticosaurus †Thalassiodracon †Thalassophonea Benson & Druckenmiller, 2013 †Gallardosaurus †Ischyrodon †Liopleurodon †Megalneusaurus †Simolestes †Peloneustes †Pliosaurus †Brachaucheninae Williston, 1925 †Acostasaurus †Brachauchenius †Kronosaurus †Lorrainosaurus †Luskhan †Makhaira †Megacephalosaurus †Polyptychodon †Sachicasaurus †Stenorhynchosaurus

Pliosauridae is a family of plesiosaurian marine reptiles from the Latest Triassic to the early Late Cretaceous (Rhaetian to Turonian stages) of Australia, Europe, North America and South America. The family is more inclusive than the archetypal short-necked large headed species that are placed in the subclade Thalassophonea, with basal forms resembling other plesiosaurs with long necks. They became extinct during the early Late Cretaceous and were subsequently replaced by the mosasaurs. It was formally named by Harry G. Seeley in 1874.^[1]

Pliosauridae is a stem-based taxon defined in 2010 (and in earlier studies in a similar manner) as "all taxa more closely related to Pliosaurus brachydeirus than to Leptocleidus superstes, Polycotylus latipinnis or Meyerasaurus victor".^[1] The family Brachauchenidae has been proposed to include pliosauroids which have very short necks and may include Brachauchenius and Kronosaurus.^[2] However, modern cladistic analyses found that this group is actually a subfamily of pliosaurids,^[3] and possibly even the "crown group" of Pliosauridae.^[4]

Within Pliosauridae, there is a more derived clade called Thalassophonea. Thalassophonea was erected by Roger Benson and Patrick Druckenmiller in 2013. The name is derived from Greek thalassa (θάλασσα), "sea", and phoneus (φονεύς), "murderer". It is a stem-based taxon defined as "all taxa more closely related to Pliosaurus brachydeirus than to Marmornectes candrewi".^[5] It includes the short necked and large headed taxa that typify the family.^[6][7] The largest representatives reached 10–11 metres (33–36 ft), in length, with around a quarter of this length being the head. Thalassophonean pliosaurs represented the largest marine predators during their existence, spanning more than 80 million years.^[6]

The following cladogram follows an analysis by Benson & Druckenmiller (2014).^[5]

• Media related to Pliosauridae at Wikimedia Commons