Three-dimensional anatomy of the early Eocene Whitephippus (Teleostei, Lampriformes) documents parallel conquests of the pelagic environment by multiple teleost lineages

ABSTRACT

The early Eocene fossil assemblage of the London Clay (Southeastern England) is a key window to the early Paleogene diversification of teleost fishes in the open ocean. Despite their three-dimensional preservation that offers unique insight into skeletal anatomy, the London Clay fossils are still poorly described for the most part. †Whitephippus tamensis is a fossil teleost from this assemblage, known by several well-preserved specimens. Based on a complete description of the known material, including previously hidden structures (braincase, hyoid, and branchial arches) revealed through 3D microtomography, we reinterpret †Whitephippus as an early member of the teleost group Lampriformes. More specifically, the anatomy of †Whitephippus indicates that it is likely a member of the so-called ‘pelagic clade’ including modern opahs and oarfishes. This redescription of †Whitephippus provides the earliest definitive evidence of lampriforms conquering the pelagic environment, alongside numerous other teleost lineages.

ACKNOWLEDGMENTS

We thank S. Walsh (NMS), E. Bernard and Z. Johanson (NHMUK) for providing access to the fossil material, and R. Arrindell (AMNH), P. Pruvost and Z. Gabsi (MNHN), and R. Singer (UMMZ) for providing access to extant comparative material. D. Delbarre (University of Oxford) and N. Bonde (University of Copenhagen) are thanked for their insightful discussions on the fossil specimens. We thank C. Abraczinskas (University of Michigan Museum of Paleontology) for assistance in scanning line drawings.

Associate editor Jürgen Kriwet and two anonymous reviewers contributed to improve an earlier version of the manuscript. This study includes data produced in the CTEES facility at University of Michigan, supported by the Department of Earth and Environmental Sciences and the College of Literature, Science, and the Arts. Some of these data were collected as a part of a Leverhulme Research Project Grant (RPG-2012-658 to MF). This research was supported by the University of Michigan Rackham Graduate School (Rackham Merit Fellowship to JVA), and the Alexander von Humboldt Foundation (Alexander von Humboldt-Stiftung to DD).

DISCLOSURE STATEMENT

No potential conflict of interest was reported by the author(s).

DATA AVAILABILITY

The tomograms and surface files of segmented elements are available on MorphoSource (www.morphosource.org/projects/000561545).

AUTHOR CONTRIBUTIONS

DD and MF designed the project; DD, JVA, and MF wrote the manuscript; DD, JVA, HTB, and SG produced the data; JVA prepared the figures; all authors approved the final version of the manuscript. DD and JVA contributed equally to this work.

SUPPLEMENTARY FILES

Supplementary File_1.pdf: Three-dimensional anatomy of the early Eocene Whitephippus (Teleostei, Lampriformes) documents parallel conquests of the pelagic environment by multiple teleost lineages.