Pliosauridae was formally named by
Harry G. Seeley in 1874. 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". The family Brachauchenidae has been proposed to include pliosauroids which have very short necks and may include
Brachauchenius and
Kronosaurus. However, modern
cladistic analyses found that this group is actually a
subfamily of pliosaurids, and possibly even the "crown group" of Pliosauridae. 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". It includes the short necked and large headed taxa that typify the family. The following
cladogram follows an analysis by Benson & Druckenmiller (2014). }} == References ==