Results of the Search for Strange Quark Matter and Q-balls with the SLIM Experiment

The SLIM experiment at the Chacaltaya high altitude laboratory was sensitive to nuclearites and Q-balls, which could be present in the cosmic radiation as possible Dark Matter components. It was sensitive also to strangelets, i.e. small lumps of Strange Quark Matter predicted at such altitudes by various phenomenological models. The analysis of 427 m^2 of Nuclear Track Detectors exposed for 4.22 years showed no candidate event. New upper limits on the flux of downgoing nuclearites and Q-balls at the 90% C.L. were established. The null result also restricts models for strangelets propagation through the Earth atmosphere.Comment: 14 pages, 11 EPS figure

Revision of the fossil rodent <i>Acaremys</i> Ameghino, 1887 (Hystricognathi, Octodontoidea, Acaremyidae) from the Miocene of Patagonia (Argentina) and the description of a new acaremyid

<div><p>Within South American rodents, the Acaremyidae is an independent fossil lineage of octodontoids represented in the late Oligocene–middle Miocene of Patagonia. <i>Acaremys</i> is represented by six species recorded in the early Miocene, which have not been re-studied since their original description. Morphological and phylogenetic analyses suggest that <i>Acaremys</i> is paraphyletic. Three species are valid, <i>Acaremys</i><i>murinus</i>, <i>Acaremys</i><i>major</i>, and <i>Acaremys</i><i>messor</i>. <i>Acaremys</i><i>karaikensis</i> is a junior synonym of <i>Acaremys</i><i>murinus</i>. ‘<i>Acaremys</i>’ <i>tricarinatus</i> is excluded from the genus being closely related to <i>Sciamys</i>. The new species, <i>Pseudoacaremys kramarzi</i>, is closely related to ‘<i>Acaremys</i>’ <i>tricarinatus</i> and <i>Sciamys</i>. ‘<i>Acaremys</i>’ <i>preminutus</i> is excluded from the family being closely related to the early Miocene <i>Protacaremys prior</i>, or living octodontoids. The phylogenetic analysis demonstrated that Acaremyidae includes <i>Platypittamys</i>, <i>Galileomys</i>, <i>Acaremys</i>, <i>Pseudoacaremys</i> and <i>Sciamys</i>. The new acaremyid increases the diversity of extinct octodontoids and added a new evolutionary lineage within Acaremyidae. The evolutionary history of the superfamily suggests that the hypsodonty and the consequently occlusal simplification evolved twice within Octodontoidea: in Acaremyidae and in Octodontidae. In addition, the cladistic analysis confirmed that most character ambiguities are due to missing data, and hence, it is essential to find better remains to elucidate the relationships among acaremyids.</p></div

Late Miocene capybaras from Argentina: Skull anatomy, taxonomy, evolution, and biochronology

Fossil capybaras are morphologically extremely varied, but previous studies have disagreed on whether this diversity reflects intraspecific variation or the existence of multiple species. Here, we review the capybaras from the classic Argentinian Late Miocene localities of Paraná River cliffs (“conglomerado osífero” of the Ituzaingó Formation, Entre Ríos), and Chillhué and Guatraché shallow lakes (Cerro Azul Formation, La Pampa), and perform a morphometric analysis of their upper cheek teeth and the posterior portion of the rostrum. Our results confirm that all of the specimens from the “conglomerado osífero” belong to the single species Cardiatherium paranense. In addition, we refer a specimen from Tupungato (Río de los Pozos Formation, Mendoza) to C. paranense, thus expanding its geographical range. The material from La Pampa represents a different taxon, and is here preliminary referred to Cardiatherium aff. orientalis. Our systematic interpretation of Late Miocene capybaras suggests that the early radiation of this group was not as explosive as previously thought, and was likely constrained by the early acquisition of large size, increasing complexity of the cheek teeth, and probably semi-aquatic habits

Late Miocene potamarchine rodents from southwestern Amazonia, Brazil - with description of new taxa

The fossil rodents from the southwestern Amazonia of Brazil have been studied since the first half of the 20th century. Several caviomorph rodents were reported for the Neogene of this region, mainly neoepiblemids and dinomyids. Until recently, the record of dinomyids in the Solimões Formation (Late Miocene) was predominantly based on a few isolated teeth, which made it difficult to make more accurate taxonomic identifications due to the scarcity of diagnostic characters. Here, new remains, more complete than those previously reported, of potamarchine dinomyids from the Neogene of Brazil are described. A new species of Potamarchus and a new genus and species of a Potamarchinae are erected. In addition, new material of Potamarchus murinus and Potamarchus sp. is identified. These data suggest a higher diversity of dinomyids in in the western Amazonia than previously supposed