Dental Ontogeny in Pliocene and Early Pleistocene Hominins

Until recently, our understanding of the evolution of human growth and development derived from studies of fossil juveniles that employed extant populations for both age determination and comparison. This circular approach has led to considerable debate about the human-like and ape-like affinities of fossil hominins. Teeth are invaluable for understanding maturation as age at death can be directly assessed from dental microstructure, and dental development has been shown to correlate with life history across primates broadly. We employ non-destructive synchrotron imaging to characterize incremental development, molar emergence, and age at death in more than 20 Australopithecus anamensis, Australopithecus africanus, Paranthropus robustus and South African early Homo juveniles. Long-period line periodicities range from at least 6–12 days (possibly 5–13 days), and do not support the hypothesis that australopiths have lower mean values than extant or fossil Homo. Crown formation times of australopith and early Homo postcanine teeth fall below or at the low end of extant human values; Paranthropus robustus dentitions have the shortest formation times. Pliocene and early Pleistocene hominins show remarkable variation, and previous reports of age at death that employ a narrow range of estimated long-period line periodicities, cuspal enamel thicknesses, or initiation ages are likely to be in error. New chronological ages for SK 62 and StW 151 are several months younger than previous histological estimates, while Sts 24 is more than one year older. Extant human standards overestimate age at death in hominins predating Homo sapiens, and should not be applied to other fossil taxa. We urge caution when inferring life history as aspects of dental development in Pliocene and early Pleistocene fossils are distinct from modern humans and African apes, and recent work has challenged the predictive power of primate-wide associations between hominoid first molar emergence and certain life history variables.     

Rediscovery of the Tagragra Tracksite (Maastrichtian,Agadir, Morocco): Agadirichnus elegans Ambroggi and Lapparent 1954 is Pterosaurian Ichnotaxon

ABSTRACT

Discovered in 1954 by Ambroggi and Lapparent, the Tagragra tracksite (Maastrichtian, Agadir, Morocco) yielded tracks of theropod dinosaurs, birds and enigmatic forms tentatively attributed to Lacertilia under the name Agadirichnus elegans. The original specimens are today considered to be lost, and the status of A. elegans has been questioned, even though these footprints can retrospectively be referred to pterodactyloid pterosaur tracks. In order to discuss the status of these foot prints, the historical site has been actively sought and recently rediscovered by one of us (MdD). New material confirms the presence of pterodactyloid footprints, with two morphotypes, in two different facies, respectively associated with bird and theropod tracks. Morphotype I is tentatively conferred to Pteraichnus Stokes 1957 Stokes, W. L. 1957. Pterodactyl tracks from the Morrison Formation. Journal of Palaeontology, 31:952–4.[Web of Science ®] , [Google Scholar], which extends the stratigraphical distribution of this ichnotaxon to the Maastrichtian. Morphotype II corresponds to the original ichnospecies A. elegans Ambroggi and Lapparent 1954 Ambroggi, R., and A. F. de Lapparent 1954. Les empreintes de pas fossiles du Maestrichtien d'Agadir. Notes du Service Géologique du Maroc, 10:43–6. [Google Scholar], which is here reassessed as a valid ichnotaxon, with the designation of a neotype. Thus, A. elegans Ambroggi and Lapparent 1954 Ambroggi, R., and A. F. de Lapparent 1954. Les empreintes de pas fossiles du Maestrichtien d'Agadir. Notes du Service Géologique du Maroc, 10:43–6. [Google Scholar] is historically the first pterosaurian ichnotaxon ever described.     

Succession des peuplements d’échinides du Crétacé inférieur dans le Haut Atlas atlantique (Maroc) ; révision systématique et intérêt stratigraphique

The rich echinoid fauna from the Lower Cretaceous of the Agadir, Haha and Essaouira basins has been revised taxonomically, based on new and abundant collections. Forty-seven species have been identified, of which 20 are reported for the first time from this region and a further three represent new species left in open nomenclature. Their stratigraphic ranges have been determined accurately by reference to the regional ammonite zonation. However, it is also possible to use a local biostratigraphical scheme based on the echinoid succession, where ammonites are rare. The Toxasteridae, which are very abundant and underwent rapid evolution, are the most useful biostratigraphically. The genus Toxaster appears in the Lower Berriasian and continues until the Gargasian passing through the following succession: T. africanus, T. granosus, T. kiliani, T. lorioli, T. obtusus, T. exilis, T. retusus, T. maurus, T. peroni, T. collegnoi. The presence of Eoholaster, Macraster, Douvillaster, Palhemiaster, Heteraster and Pygopyrina is signaled for the first time in the Atlantic High Atlas region.     

Study of the Optical and Thermoplasmonics Properties of Gold Nanoparticle Embedded in Al2O3 Matrix

Plasmonics - In this paper, the optical and thermoplasmonics properties of nanocomposites consisting of spherical gold nanoparticles (AuNPs) integrated in $${Al}_{2}{O}_{3}$$ matrix are determined...