New Eocene Coleoid (Cephalopoda) Diversity from Statolith Remains: Taxonomic Assignation, Fossil Record Analysis, and New Data for Calibrating Molecular Phylogenies.

Pascal Neige,Didier Merle,Hervé Lapierre

doi:10.1371/journal.pone.0154062

Abstract

New coleoid cephalopods are described from statolith remains from the Middle Eocene (Middle Lutetian) of the Paris Basin. Fifteen fossil statoliths are identified and assigned to the Sepiidae (Sepia boletzkyi sp. nov.,? Sepia pira sp. nov.), Loliginidae (Loligo clarkei sp. nov.), and Ommastrephidae (genus indet.) families. The sediments containing these fossils indicate permanent aquatic settings in the infralittoral domain. These sediments range in age from 46 Mya to 43 Mya. Analysis of the fossil record of statoliths (from findings described here, together with a review of previously published data) indicates marked biases in our knowledge. Fossil statoliths are known from as far back as the Early Jurassic (199.3 to 190.8 Mya) but surprisingly, to the best of our knowledge, no record occurs in the Cretaceous. This is a “knowledge bias” and clearly calls for further studies. Finally, we attempt to compare findings described here with fossils previously used to constrain divergence and/or diversification ages of some coleoid subclades in molecular phylogenies. This comparison clearly indicates that the new records detailed here will challenge some estimated divergence times of coleoid cephalopod subclades.

Highlights

Cephalopods are known from the fossil record as far back as the Cambrian, some 530 million years ago [1]
New fossil statoliths described here (Sepia boletzkyi sp. nov.,? Sepioida genus (Sepia) pira sp. nov., Loligo clarkei sp. nov., Ommastrephidae genus indet.) from the Middle Lutetian of the Paris Basin further our knowledge of the coleoid cephalopods clade. They confirm that fossil statoliths are “neglected fossils” and argue in favor of intensifying the search for them, especially in Cretaceous times
We suggest a diversification of the family Ommastrephidae and an emergence of the genus Sepia as early as 46 to 43 Mya

Summary

Introduction

Cephalopods are known from the fossil record as far back as the Cambrian, some 530 million years ago [1]. During the Lutetian, the deposition of a vast carbonate platform with various biofacies [26,30], and the paleogeographic location on the edge of the Atlantic Ocean and northern domains (Fig 3) and close to the Tethys Ocean, provided favorable global conditions for the preservation of a hotspot of paleobiodiversity containing around 3000 species of marine Several great naturalists such as Lamarck, Cuvier, and Brongniart studied the site of “La Falunière” of Thiverval-Grignon which was famed for its remarkable fossil richness. Comparisons with recent species were based in part on literature analysis, but were mostly made with specimens collected by one of us (PN) during the Cephalopod Parasite Workshop at Banyuls-sur-Mer (November 1996) organized by Sigurd von Boletzky (see [22,48] for detailed studies on statoliths and beak morphometry, respectively). Nov is different from the second Lutetian species, Loligo applegatei Clarke and Fitch, 1979, which has a diagnostic sharply pointed lateral dome This new fossil species has statolith sizes from 1.00 to 1.10 mm. The species is known from the Thiverval-Grignon section (see Table 1) from the Middle Lutetian and has an approximate age of 46 to 43 Mya

Discussion

Conclusion