Lambert O.,Institute Royal Des Science Naturelles Of Belgique |
Bianucci G.,University of Pisa |
Post K.,Natuurhistorisch Museum Rotterdam
Journal of Mammalogy | Year: 2010
New well-preserved fossils from Peru reveal details of the dentition and morphology of the mandible and rostrum in 2 late middle to early late Miocene beaked whales (Cetacea, Odontoceti, Ziphiidae). Apical mandibular tusks are present in both Nazcacetus urbinai and Messapicetus sp. In the former the tusks are associated with a strong reduction of the postapical dentition, whereas in Messapicetus sp. a complete series of functional upper and lower teeth is retained. The larger sample of Messapicetus sp. from a single locality and age reveals intraspecific variation in size and shape of the tusks and surrounding structures. In addition, the rostrum of Messapicetus displays thickened premaxillae, dorsally closing the mesorostral groove. By comparison with modern beaked whales, most of them highly sexually dimorphic at the level of the tusks and rostrum, we propose that the tusks of Messapicetus were used in intraspecific fights between adult males. Strengthening of the rostrum through the dorsal closure of its transverse section would have reduced the risk of fractures when facing impacts. © 2010 American Society of Mammalogists.
Mayhew D.F.,Natuurhistorisch Museum Rotterdam
Quaternary International | Year: 2013
Early Pleistocene arvicolid faunas from the Norwich Crag Formation of the UK contain species found across Eurasia, indicating that this was then a single faunal province. Several examples of arvicolid evidence for intercontinental connections are discussed, with reference particularly to new material from the locality Easton Wood, Suffolk, UK. This includes teeth referred to Mimomys glendae sp.nov., apparently closely related to Siberian and North American species. The locality also provides the earliest UK occurrences of Lemmus kowalskii and Mimomys tigliensis, a wide ranging and biostratigraphically important species. The immigration of M. tigliensis to West Europe took place in arvicolid zone MNR2 at a time apparently close to its appearance in Russian faunas. The faunas from Easton Wood and the Netherlands support the current arvicolid Early Pleistocene biozonation of South East Europe suggesting that it is applicable to at least the northern part of West Europe. The age of the Norwich Crag deposits at Easton Wood is estimated according to this scheme at between 2.25 and 2.35 Ma, indicating that palaeomagnetic inferences previously used to support a younger age require review. © 2011 Elsevier Ltd and INQUA.
Bianucci G.,University of Pisa |
Collareta A.,University of Pisa |
Post K.,Natuurhistorisch Museum Rotterdam |
Varola A.,University of Pisa |
Lambert O.,CNRS Institute of Earth Sciences
Rivista Italiana di Paleontologia e Stratigrafia | Year: 2016
A new partial fossil skeleton of Messapicetus longirostris (Cetacea: Odontoceti: Ziphiidae) collected in Cisterna quarry (Lecce) from Tortonian (upper Miocene) sediments of the "Pietra leccese" is described. It comprises the fragmentary skull (including most of the rostrum), parts of the mandibles, five teeth, the fragmentary right scapula, and one vertebral centrum. This new record, here referred to a juvenile individual, expands our knowledge about the skeletal anatomy of M. longirostris; this species was until now only known by the holotype, an almost complete skull from the same Cisterna quarry. Moreover, the new specimen confirms the distinction between M. longirostris and M. gregarius (late Miocene, Pisco Formation, Peru) based on several osteological characters (e.g., the presence of a distinct maxillary tubercle and prominential notch in the latter species). New dating of layers in Cerro Colorado, the type locality of M. gregarius, suggests that M. longirostris and M. gregarius were contemporaneous sisterspecies with an antitropical distribution (a biogeographical pattern currently shown by two extant ziphiid genera). Unlike extant ziphiids, feeding predominantly on squid and benthopelagic fish in deep waters, the stem ziphiid M. gregarius was recently proposed to have been a raptorial piscivore who may have fed mainly on schools of epipelagic fish. Similarities at the level of the morphology and proportions of the oral apparatus suggest that the two species of Messapicetus may have occupied roughly identical ecological and trophic niches, a hypothesis supported by the characterization of the Pietra leccese environment as neritic.
Foote A.D.,Copenhagen University |
Newton J.,NERC Life science Mass Spectrometry Facility |
Avila-Arcos M.C.,Copenhagen University |
Kampmann M.-L.,Copenhagen University |
And 6 more authors.
Proceedings of the Royal Society B: Biological Sciences | Year: 2013
Niche variation owing to individual differences in ecology has been hypothesized to be an early stage of sympatric speciation. Yet to date, no study has tracked niche width over more than a few generations. In this study, we show the presence of isotopic niche variation over millennial timescales and investigate the evolutionary outcomes. Isotopic ratios were measured from tissue samples of sympatric killer whale Orcinus orca lineages from the North Sea, spanning over 10 000 years. Isotopic ratios spanned a range similar to the difference in isotopic values of two known prey items, herring Clupea harengus and harbour seal Phoca vitulina. Two proxies of the stage of speciation, lineage sorting of mitogenomes and genotypic clustering, were both weak to intermediate indicating that speciation has made little progress. Thus, our study confirms that even with the necessary ecological conditions, i.e. among-individual variation in ecology, it is difficult for sympatric speciation to progress in the face of gene flow. In contrast to some theoretical models, our empirical results suggest that sympatric speciation driven by among-individual differences in ecological niche is a slow process and may not reach completion. We argue that sympatric speciation is constrained in this system owing to the plastic nature of the behavioural traits under selection when hunting either mammals or fish. © 2013 The Author(s) Published by the Royal Society. All rights reserved.
Sayali D.S.,Abasaheb Garware College |
Ghate H.V.,Modern College |
Van Vondel Bernhard J.,Natuurhistorisch Museum Rotterdam
Zootaxa | Year: 2016
In an ongoing survey of aquatic beetles, the crawling water beetles Haliplus (Liaphlus) arrowi Guignot, 1936 and Haliplus (Liaphlus) angustifrons Régimbart, 1892 were found only from four (three localities for H. arrowi and one locality for H. angustifrons) out of 85 localities sampled in and around the Western Ghats of Maharashtra. Digital images and scanning electron micrographs of diagnostic characters are provided for the first time for both the species. Intraspecific and interspecific variation in the elytral maculation of H. arrowi and H. angustifrons is illustrated. Copyright © 2016 Magnolia Press.