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

2015; Taylor & Francis; Volume: 14; Issue: 4 Linguagem: Inglês

10.1080/14772019.2015.1043361

1478-0941

Detlev Thies, Jens Waschkewitz,

Evolution and Paleontology Studies

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 for Dapedium Leach, 1822 and other deep-bodied Mesozoic neopterygians. The species diagnosis of D. pholidotum is amended. Comparison with D. stollorum Thies & Hauff, 2011 Thies, D. & Hauff, R. B. 2011. A new species of Dapedium Leach, 1822 (Actinopterygii, Neopterygii, Semionotiformes) from the Early Jurassic of South Germany. Palaeodiversity, 4, 185–221. [Google Scholar] and D. caelatum Quenstedt, 1858, also from the Lower Jurassic Posidonia Shale, shows that D. pholidotum is unique in having: (1) a length/height ratio of the operculum of c. 0.73, whereas in D. stollorum and D. caelatum this value reaches only c. 0.58; (2) a length/width ratio of the gular plate of c. 1.6, whereas in D. stollorum and D. caelatum this value is 1.3; (3) 27 or more caudal fin lepidotrichia, whereas in D. stollorum and D. caelatum there are 24 and 25 lepidotrichia, respectively; (4) at least 26 dorsal fin lepidotrichia, whereas D. stollorum and D. caelatum possess only 24 dorsal fin lepidotrichia each; and (5) a length/height ratio of the flank scales immediately behind the operculum of 0.37, whereas in D. stollorum and D. caelatum this ratio ranges around 0.31 and 0.5, respectively. A cladistic analysis based on modification of a previously published taxon–character matrix shows that Dapedium is the sister group of the ginglymodian fishes [Semionotiformes + Lepisosteiformes]. The generic diagnosis of Dapedium Leach, 1822 is amended.