Redescription of Dapedium pholidotum (Agassiz, 1832) (Actinopterygii, Neopterygii) from the Lower Jurassic Posidonia Shale, with comments on the phylogenetic position of Dapedium Leach, 1822.

Dapedium pholidotum(Agassiz, 1832) (Actinopterygii, Neopterygii) is redescribed based on new material from the Posidonia Shale (Early Jurassic: Early Toarcian) of Germany. Dapediiformes ord. nov. is introduced forDapediumLeach, 1822 and other deep-bodied Mesozoic neopterygians. The species diagnosis ofD. pholidotumis amended. Comparison withD. stollorumThies & Hauff, 2011 andD. caelatumQuenstedt, 1858, also from the Lower Jurassic Posidonia Shale, shows thatD. pholidotumis unique in having: (1) a length/height ratio of the operculum ofc. 0.73, whereas inD. stollorumandD. caelatumthis value reaches onlyc. 0.58; (2) a length/width ratio of the gular plate ofc. 1.6, whereas inD. stollorumandD. caelatumthis value is 1.3; (3) 27 or more caudal fin lepidotrichia, whereas inD. stollorumandD. caelatumthere are 24 and 25 lepidotrichia, respectively; (4) at least 26 dorsal fin lepidotrichia, whereasD. stollorumandD. caelatumpossess only 24 dorsal fin lepidotrichia each; and (5) a length/height ratio of the flank scales immediately behind the operculum of 0.37, whereas inD. stollorumandD. caelatumthis ratio ranges around 0.31 and 0.5, respectively. A cladistic analysis based on modification of a previously published taxon–character matrix shows thatDapediumis the sister group of the ginglymodian fishes [Semionotiformes + Lepisosteiformes]. The generic diagnosis ofDapediumLeach, 1822 is amended. [ABSTRACT FROM AUTHOR]