Among the extant crocodylians are two species with long, narrow snouts: Gavialis gangeticus,the Indian gharial and Tomistoma schlegelii, the "false" gharial. These enigmatic species are considered by the IUCN red list as critically endangered and vulnerable, respectively. However, despite this, knowledge of their evolutionary history is lacking. Extensive debate has surrounded the gharials for over four decades and remains unsolved today: the so-called gharial problem. Whereas molecular studies consistently indicate that these two species are sister taxa, morphological studies of both living and fossil taxa find that they belong to distantly related lineages. Moreover, molecular clock estimates indicate a shallow divergence time of 18-31 million years ago. This entirely contradicts the rich fossil record of gharials: in contrast to the modern gharials, these fossil taxa comprise a huge diversity and suggest that tomistomines and gavialines have diverged from each other at least 70 million years ago, prior to the K/Pg mass extinction. European museums, and especially the Royal Belgian Institute of Natural Sciences, Brussels, comprise rich collections containing many of the oldest fossil gavialoids, crucial to solving the gharial problem. Nevertheless, few modern morphological studies have been performed on these specimens, and their stratigraphic age is often poorly constrained. Therefore, in a new project we will use a multidisciplinary approach to study these specimens, combining morphological study and biostratigraphic analyses using dinoflagellate cysts. Moreover, we will revise the classical methods used by paleontologists to study fossil crocodylians, devising a new phylogenetic framework that makes use of both morphological, molecular, and biostratigraphic data. Here, we will present some of the first preliminary results of this project.
Located in
Library
/
RBINS Staff Publications 2023
Here we review the fossil record of European mesonychids, which are known only through the genera Dissacus and Pachyaena from Thanetian and Ypresian localities (from MP6 to MP10 reference-levels). We describe two new species, Dissacus rougierae, sp. nov., and Dissacus raslanloubatieri, sp. nov., respectively from Palette (Ypresian, ≈MP7) and from La Borie (Ypresian, ≈MP8 + 9). We also describe new specimens of D. europaeus from Berru (Thanetian, ≈MP6). The evolution of the geographic distribution of the European mesonychids is characterized by three phases: (1) the mesonychid Dissacus appeared in Europe during the Thanetian (≈ 57–58 Mya), probably due to dispersal from North America; D. europaeus survived the PETM event (≈ 56 Mya) and possibly experienced a dwarfism; (2) the large mesonychid Pachyaena migrated into Europe shortly after the Paleocene-Eocene boundary (≈ 55 Mya), but it was restricted to northwestern Europe, while Dissacus is recorded at this time only in southwestern Europe (Palette); and (3) Pachyaena rapidly disappeared from European environments, while Dissacus subsequently dispersed into northwestern Europe (≈ 54–52 Mya). We performed phylogenetic analyses in order to identify the relationships of the new species among mesonychids. It seems that the mesonychids went through two radiative events: the first during the Paleocene, the second mostly during the early Eocene. The first one corresponds to the diversification of Dissacus, while the latter resulted in the appearance of the most specialized mesonychids, such as Pachyaena and Mesonyx.
Located in
Library
/
RBINS Staff Publications 2017
Belgium represents a key region for studying the Middle to Upper Palaeolithic transition (MUPT) in North-West Europe. This area sits at the crossroads between Palaeolithic cultural facies with influences from eastern, western and southern Europe intermingling during the Late Middle Palaeolithic and the MUPT. Until recently, a temporal gap believed to be around 4ka (ca 42-38 ky calBP) existed between the Late Mousterian and the earliest dated Aurignacian settlements in the region [1, 2]. The dates obtained on Neanderthal remains from Spy fell into this gap, making them the latest Neanderthals in the region [3]. Including the dates from Spy, a gap of two millennia remained between the dates on Neanderthals and the beginning of the Aurignacian. Based on this chronological evidence, the transition from Neanderthals to Anatomically Modern Humans (AMH) in this region was believed to have been without contact between species. AMH would have settled in an area Neanderthals abandoned long before. As part of the PalaeoChron project, we have redated the Neanderthal specimens from Spy (tooth, maxilla and scapula), Engis 2 (skull and tooth) and Fond-de-Forêt (femur), using the compound specific radiocarbon dating method in place at the Oxford Radiocarbon Accelerator Unit. This method is based on the extraction of the amino acid hydroxyproline that occurs in mammalian collagen using preparative liquid chromatography. This method is more efficient than others in eliminating modern carbon contamination such as conservation materials. In this presentation, we report the new radiocarbon dates obtained on the Belgian Neanderthal specimens. These results show how much impact sample preparation can have on the AMS measurement when specimens have been heavily preserved with conservation materials, which is often the case for human remains. These results also now place the Belgian Neanderthal remains from Spy, Engis and Fond-de-Forêt in their proper chronometric context and allow us to refine our understanding of the disappearance of Neanderthals in north-western Europe and integrate this with other evidence for the human occupation of this region during the Palaeolithic.
Located in
Library
/
RBINS Staff Publications 2019
