The world’s oldest fossil seal record

Cajus Diedrich

doi:10.4236/ns.2011.311117

Abstract

A femur fragment with an Early Lutetian (early Middle Eocene) age is the world’s oldest fossil record from a seal, and, is described as Praephoca bendullensis nov. gen. nov. spec. This find pushes back the earliest evolution of seals into the Paleocene epoch. The femur has plesiomorphic terrestrial mammal characteristics but has a morphology that is already closer to that of Miocene and present day seals. The Eocene seal femur was found at Fürstenau-Dalum in north-west Germany, in a conglomerate rich in shark teeth that was deposited in a coastal delta environment to the north-west of the central European Rhenish Massif mainland, in the southern pre-North Sea Basin. This discovery has led to a revision of the theory that phocids originated along the coastline of the North American continent. Instead they can now be interpreted to have originated in the tropical Eocene climate of central Europe. Although the fossil records of pinnipeds in Europe during the Eocene, Oligocene and Miocene are extremely sparse, they appear to have inhabited the pre- North Sea basin, within the influence of temperate and arctic upwellings. The distribution of abundant teeth from white and megatooth sharks of two different lineages appears to correlate with that of the seals, which the sharks most probably hunted; providing supporting evidence that the phocids were already adapted as shallow marine coastal inhabitants by this time.

Highlights

The oldest seals on planet Earth were thought to have appeared about 28 m.y. ago during the North American Oligocene [1], but more recent reports claim to have found an even younger (Miocene) “missing link” between terrestrial mammals and the basal pinnipeds in the Arctic [2]
A newly discovered seal femur from a recently excavated site at Fürstenau-Dalum in north-west Germany (Figures 1(a) and (b)) [5] and a review of other rare European remains of Oligocene age from the pre-North Sea basin have combined to suggest a different scenario from that proposed by previous authors, who have suggested a basal pinniped evolution starting in, or along the coastline of, the North American landmass [4]
Other seal femora [10] have been studied with respect to their measurements [11], including bone material in the University of Alaska Museum (UAM), Oligocene remains housed in the Dobergmuseum, Bünde (DMB) in Germany, Miocene material from the Oertijdmuseum de Groene Poort, Boxtel (MAB) in the Netherlands, and modern seal remains from the southern North Sea Basin at the Seehundstation, Friedrichskoog (SFI) in Germany

Summary

INTRODUCTION

The oldest seals on planet Earth were thought to have appeared about 28 m.y. ago during the North American Oligocene [1], but more recent reports claim to have found an even younger (Miocene) “missing link” between terrestrial mammals and the basal pinnipeds in the Arctic [2]. Neither the palaebiogeography nor the suggested (but unproven) Eocene age for the beginning of the evolution of evolution of earless seals (phocids) [3,4,6,7] can be supported by the evidence from this new fossil seal site in Germany This vertebrate-rich site has been the subject of interdisciplinary studies; it contains mainly shark remains and a variety of marine mammals [5]. Central Europe experienced a tropical climate during the Middle Eocene and many terrestrial mammal groups were already well developed at this time These are, to date, mainly known from the German fluvial and freshwater lake sites at Messel and Geiseltal (Figure 1(a)) [8], from which no seal ancestors have been recorded, nor have any early phocids been reported from other Eocene marine vertebrate fossil localities of the European pre-North Sea basin in France, Belgium, or England (Figure 1(a))

MATERIALS AND METHODS

THE WORLD’S EARLIEST PHOCID FOSSIL

The Evolutionary Beginnings of the Earliest Phocids

Palaeobiogeography and Habitat of Early Seals

Findings

THE PHOCID PREDATORS