Abstract:
A new genus and species of boxfish (Ostraciidae) is described on the basis of five specimens from the Menilitic Formation of the Lower Rupelian part of the middle Oligocene (ca. 35 MYA) of Moravia, Czechoslovakia. A sixth but incomplete specimen is recorded from the Menilitic Formation of southern Poland. The fossil record of the family previously was based only on Eolactoria sorbinii from the lower Eocene of Monte Bolca, Italy, and on isolated carapace scale plates also dating back to the Eocene. The new genus differs most significantly from all other Recent and fossil ostraciids in the greater posterior extension of the carapace onto the caudal peduncle; the lesser number of anteroposteriorly compressed centra of the vertebrae of the caudal peduncle; the greater length of the caudal fin in relatively small specimens; and perhaps by having a reduced number of caudal rays (nine rather than 10).
The new species is a typical member of the in-shore benthic Ostraciidae, but the other fishes with which it is associated in the Menilitic Formation are nearly all more off-shore mesopelagic species of Myctophidae and Gonostomatidae. To account for this, we propose that the new species represents the oceanic, pelagic, pre-settlement stage of this genus, as in the Recent Lactoria, some species of which, especially L. diaphana, remain pelagic to sizes of over 100 mm SL and can be sexually mature while pelagic before settling into their conclusive benthic state.
