Anatomy and relationships of Aipichthys pretiosus and 'Aipichthys' nuchalis (Acanthomorpha: Lampridomorpha), with a review of Late Cretaceous relatives of oarfishes and their allies

作者：Delbarre Daniel J^*; Davesne Donald; Friedman Matt

来源：Journal of Systematic Palaeontology, 2016, 14(7): 545-567.

DOI：10.1080/14772019.2015.1078538

• Aipichthys
• Lampridomorpha
• Lampridiformes
• Acanthomorpha
• Cretaceous

The Cenomanian acanthomorph teleost Aipichthys is best known from two species: Aipichthys minor and Aipichthys velifer. Two poorly studied species of Aipichthys, Aipichthys pretiosus from Slovenia and Aipichthys nuchalis from the English Chalk, have been excluded from all recent studies of the genus. Previous accounts of A. pretiosus - the type species of Aipichthys - are inadequate, while A. nuchalis has been described as too incomplete to interpret. Here we completely redescribe A. pretiosus and utilize computed tomography to reveal previously hidden skeletal anatomy of A. nuchalis. Aipichthys pretiosus has a long sagittal crest, with the supraoccipital, frontal and mesethmoid bones contributing to this structure. Based on this and other features, we find that A. pretiosus belongs to a clade that is more closely related to extant Lampridiformes than all other nominal species of Aipichthys. As A. pretiosus is the type species for the genus, we recommend all other species of the genus should be temporarily referred to as 'Aipichthys'. 'Aipichthys' nuchalis possesses a concave posterior margin and a thickened anterior margin to the supraoccipital crest, and is placed in a polytomy alongside 'A.' minor, 'A.' velifer, 'Aipichthys' oblongus and Freigichthys. Further investigation is needed to determine whether 'Aipichthys' is congeneric with and can be reassigned to Freigichthys, or whether a new generic name is needed for these taxa. We also include two additional taxa in our analysis: Nardovelifer altipinnis, the oldest fossil previously attributed to the lampridiform crown, and Gigapteryx tethyestris, an incertae sedis acanthopterygian. We find that Nardovelifer has a number of primitive characters not found in crown Lampridiformes, and resolve it as a stem lampridiform. We find that Gigapteryx is closely related to Pycnosteroides, together forming the sister clade to all other lampridomorphs. Finally, we examine the diversity of Cretaceous lampridomorphs and discuss their palaeobiogeography and palaeoecology.

• 出版日期2016