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Chinchilla rats (family Abrocomidae) are hystricomorph rodents primarily inhabiting the central Andes in South America with 8 species in the genus Abrocoma and 2 in Cuscomys. The systematics of this family—relying only on morphological differences—has faced several controversies, particularly in arid-adapted species of Abrocoma (the A. cinerea species complex, or ACC). By using partial DNA sequences of 1 mitochondrial (Cytochrome b) and 2 nuclear genes (GHR and RAG1), we: (i) inferred phylogenetic relationships between 5 species of Abrocoma and 1 of Cuscomys ; (ii) performed molecular species-delimitation analyses in 4 species of the ACC (A. cinerea , A. famatina , A. schistacea , and A. uspallata); and (iii) estimated divergence times using stratigraphic ages of extinct taxa. Our phylogenetic analyses recovered 3 main clades: A. bennettii (basal); C. ashaninka ; and the ACC. Striking differences in habitat use, morphology, and genetics suggest that each of these main clades might represent a distinct genus. In species-delimitation analyses in the ACC, only 2 species were recognized, and we thus suggest the synonymy of A. famatina with A. cinerea and of A. uspallata with A. schistacea. The origin of extant abrocomids was estimated at the late Miocene (~5.6 million years ago, Ma) with the subsequent origin of arboreal species during the early Pliocene (~4.3 Ma) and the ACC during the late Pliocene (~3.3 Ma). We hypothesize that topographic uplift of the central Andes and associated climatic and ecological changes were the main drivers of diversification in this family. [ABSTRACT FROM AUTHOR]

The assemblage of small mammals from a site near Yeniköy (Anatolia) is described. The assemblage was collected by screen-washing a sample from a locality in the Selimye Formation (Sivas basin). The site has a magneto-stratigraphic calibrated age of 29 Ma (younger part of the early Oligocene). The murids dominate in this relatively small collection with Eucricetodon and Pseudocricetodon. In addition, a dipodid, an unidentified erinaceide and the new baluchimyin hystricognath genus and species Zorania milosi nov. gen. et nov. sp. are present. The study of Eucricetodon, Pseudocricetodon and Zorania nov. sp. includes an analysis of incisor enamel microstructure. The incisor microstructure of Eucricetodon shows that there are several parallel long-living lineages within the genus. The Anatolia-Balkans biogeography of the late Eocene-Oligocene is reviewed. Its rodent assemblages are characterised by dominance of murids and presence of taxa that are known from low-latitude Asia. The Paleogene Anatolia-Balkans biogeographic province, is therefore rather different from those of western European and the Indian subcontinent. [ABSTRACT FROM AUTHOR]

Spontaneous embryonic death is a conserved reproductive event in Eutherians. The macro and microscopic characteristics of this type of death are similar between the different taxa. However, in the hystricomorphic rodent plains viscacha (Lagostomus maximus) is exceptional in terms of massiveness (80% embryonic resorption). In this species, of the 10–12 implantation sites (IS) (half in each uterine horn), only the caudal embryos will survive, resorbing the cranial and intermediate IS. We hypothesize that uterine structural variations in L. maximus restrict growth and promote embryo death, with the consequent loss of placental homeostasis in the cranial and middle IS. In this study, different studies (ultrasonography, macroscopy and microscopy) were carried out to analyze different aspects of the intermediate gestation of L. maximus (46 days postcoitus). Ultrasonographic studies revealed that the cranial and middle IS (IS-1, IS-2, and IS-3) had no recognizable embryonic and placental structures as compared to the caudal implantation sites (IS-4). Macroscopically, the areas corresponding to the embryos in the cranial and middle IS were occupied by a necrotic black semi-fluid mass. Moreover, the placenta in these IS was undifferentiated. However, in the caudal IS both the embryo and its placenta were distinguishable. Using histological and immunohistochemical techniques, it was observed that the placentas of IS-1, IS-2 and IS-3 were disorganized and showed hemorrhage, inflammatory infiltration containing neutrophils, macrophages, mast cells and foreign body giant cells, apoptotic trophoblast, and a layer of collagen fibers and fibroblasts that circumscribed each of these IS. In contrast, the placenta of the caudal IS showed an organized maternal-embryonic interface. The characteristics observed in IS in resorption of viscachas in intermediate gestation show that, regardless of gestation time, embryonic death has a similar macro and microscopic morphological pattern among eutherians with invasive placentation. However, the massiveness and sectorization of embryonic death in the plains viscacha make the species a unique model for the study of this reproductive event. [Display omitted] • Embryonic resorption in implantation sites (IS) in L. maximus follows a similar pattern as observed in other species. • The necrosis of the embryos in IS under resorption would indicate its sensitivity to the uterine vascular heterogeneity. • The embryo resorption would give rise to a sterile inflammatory response. • The embryonic death of L. maximus is exceptional among eutherians since it occurs massively (80%) and sectorized. [ABSTRACT FROM AUTHOR]

Copyright of Therya is the property of Asociacion Mexicana de Mastozoologia, A. C. and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This investigation seeks to discriminate variations in anatomic landmarks of regional nerve block/surgical importance in skulls of two phylogenetically related laboratory species; the Old-world porcupines (H. cristata) and Cane rat (T. swinderianus), and comparedfrontal sinus shape outline architecture in mid-sagittal section for both. Using Generalized Procrustes Analysis, the study utilized thirty-seven and forty-eight skull samples of each respectively. for landmarks assessments in right lateral, ventral and right lateral hemi-mandibular views, and Elliptical Fourier analyses for frontal sinus contours. Extremely significant (P ≤ 0.0001) interspecies landmark size variations were observed with Mahalanobis distance of 1.89, 2.03 and 2.06 for the evaluated positions respectively, mean centroid size ranged from 3200 mm in H. cristata to 1400 in T. swinderianus. Shape regression model suggested similar allometric pattern except in mandibles (λ Wilks 0.96, F 44.55) but (λ Wilks 0.88, F 127.9) between species. EFA descriptors demonstrated. amplitude associated attenuations in harmonic values (factor about 1/8 to 1/22,000) with angular orientation in major axes values reduced by not more than ¼ after size normalization. PC1 & 2 contributed 81.19%, 6.29% but 100% in within and between species analysis. Stepwise harmonic increments outline reconstructions demonstrated disparities up to the 6th harmonics with marginally lower variance value in cane rats (1.37) than in porcupines (1.68). The results conclude that skull shape and size disparities observed suggest despite similar phylogeny both are diverse and does not compare in structural and frontal sinus outline shapes.

The plains viscacha is a hystricognathi rodent with special reproductive characteristics. Despite poly‐ovulation of 800 oocytes, it generates a high embryonic mortality since from 10 to 12 implantations only one or two offspring are born. The present work analyses the morphological, morphometrical, histochemical and lectinhistochemical characteristics of the uterus and uterine cervix of pregnant and non‐pregnant viscacha. Anatomically, the uterus has two horns each one continued with a short cervix devoid of glands. The structure of the uterus is like that of other species; however, the proportion and size of its glands varies according to the physiological state. In viscacha, there is no uterine body and cervices cannot be differentiated externally. The formation of two sack bottoms is determined by the presence of a middle raphe in the cranial portion of the vagina. The so‐described anatomy is different from that described in other hystricognathi such as guinea pig and coypu. The cervix presents two microscopically differentiable regions: the endocervix and the ectocervix lined by epithelia with different characteristics. The general characteristics of the uterus of L. maximus do not show specific differences with those of other mammals that might explain its peculiar gestation. [ABSTRACT FROM AUTHOR]

The origin and early evolution of South American rodents are ongoing subjects of debate. The caviomorphs of the Peruvian localities of Santa Rosa and Contamana are the oldest South American rodents so far known. The Santa Rosa rodents are abundant and diverse, but dating was based on biostratigraphy (?Eocene), whereas in various Contamana sites radiometric dates, vertebrate biochronology and palynostratigraphy suggest an age of 41.6–40.94 Ma (late middle Eocene). Previous faunal comparisons between the localities have identified few shared taxa. Here we studied new and previously described rodent fossils from Santa Rosa and analysed their biochronological and biogeographical implications. We recognize five new taxa and three genera for Santa Rosa, four of them previously known only from the Eocene Contamana region. Thus, the Santa Rosa and the late middle Eocene Contamana assemblages appear to be chronologically closer than previously thought. An ?Eocene age for Santa Rosa is substantiated by other mammals reported from Santa Rosa. With 11 named genera and 15 species, the Santa Rosa rodents represent the most species‐rich South American Palaeogene rodent assemblage known. The Eocene radiation in the Neotropics that gave rise to this diversity was not associated with an immediate geographical dispersion to higher latitudes, perhaps because different biogeographical barriers or factors of competition delayed their dispersal. Evidence suggests that replacement, rather than a persistence of conservative long‐lasting lineages, was the dominant process among Palaeogene tropical caviomorph rodents. [ABSTRACT FROM AUTHOR]

Fossil rodents from the Río Santa Cruz (RSC) classic localities (Santa Cruz Formation, Early–Middle Miocene) are known by the works of F. Ameghino and W.B. Scott since the end of the 19th and beginning of the 20th centuries. These caviomorph rodents have not been comprehensively reviewed since then. In this contribution, we studied new fossil specimens from the cliffs of the RSC (Province of Santa Cruz, Argentina) collected with accurate stratigraphic and geographic data during fieldtrips in 2013 and 2014. An increase in the caviomorph taxonomic richness is observed, based upon our taxonomic study of caviomorphs previously recorded in the RSC. Also, these fieldworks recovered for the first time several taxa previously found in other Santacrucian and even older Patagonian localities (Colhuehuapian, Early Miocene). As a general evolutionary pattern, we note an increase of derived euhypsodont taxa (Prolagostomus, Pliolagostomus, Schistomys, and Eocardia) in Segundas Barrancas Blancas (16.47–15.3 Ma). In addition, a taxonomic replacement of Phanomys by Schistomys is noted between Barrancas Blancas (17.21–16.3 Ma) and Segundas Barrancas Blancas, as well as a notably increase in the abundance of the large Perimys onustus in the latter locality. The present study provides a revision of the caviomorph systematics, and intends to be the starting point to understand the diversity (in all its aspects) and the evolution of this group during the Santacrucian, a major event in the South American mammalian history.

The genus Galea Meyen, 1833 includes at least five species of terrestrial, diurnal and herbivorous cavies that occupy grasslands and rocky scrub areas at both high and low elevations in South America. According to the available molecular and morphological data, Galea comes Thomas, 1919 is restricted to highland areas above 2000 m in southern Bolivia and northwestern Argentina. Its distributional range as well as its morphological distinctiveness from other closely related species (Galea leucoblephara and Galea musteloides) is poorly documented. Using both qualitative and quantitative morphological traits, we provided an emended diagnosis for G. comes. In addition, we added six new locality records to its known distribution. [ABSTRACT FROM AUTHOR]

The genus Myoprocta Thomas, 1903 includes two living species of medium-sized caviomorph rodents of the family Dasyproctidae, the red acouchi, Myoprocta acouchy (Erxleben 1777), and the green acouchi, Myoprocta pratti Pocock 1913. Whereas some recent revisionary work has considered both species to be allopatrically distributed, other reports suggest that both taxa co-occur in eastern Colombia. In this contribution, I revaluate some qualitative and quantitative skull traits within Myoprocta to clarify its taxonomy and distribution. Multivariate analyses of quantitative skull characters support the distinction between M. acouchy and M. pratti, contradicting the findings of some previous authors. Based on these results and the examination of ~100 skins, I concur with the hypothesis that the two species are allopatrically distributed. [ABSTRACT FROM AUTHOR]

Contents: This study reports the histochemistry and the distribution of glycoconjugates (GCs) in the zona pellucida (ZP) of preantral, secondary, tertiary, polyovulatory and atretic follicles of ovaries from non‐pregnant (NPr) and pregnant (Pr) females of Lagostomus maximus. GCs were studied using histochemical and lectin histochemical methods. The viscacha ZP was positive to all the histochemical techniques. In addition, it was observed that the intensity of staining of the ZP was constant in the different follicular stages between both female groups. The lectin histochemical study revealed that ZP was positive for certain lectins (WGA, RCA‐I and CON‐A) and that the labelling did not vary between the different follicular stages, but between the two groups of females. By using both histochemical techniques, it was established that the GCs present in the ZP label the complexity of the area. These results allow us to increase our knowledge on the biology of the viscacha's ovary, particularly contributing to the study of polyovulation. [ABSTRACT FROM AUTHOR]

Chinchilla chinchilla (Lichtenstein, 1830), a hystricomorph rodent of the family Chinchillidae, is a highland species that inhabits the Andean foothills of northern Chile and southern Bolivia, specifically the Antofagasta and Atacama regions in Chile and Potosí in Bolivia, at elevations of 3,500-5,000 m. It has a silky-soft pelage of extremely dense and long fur, the color of which is bluish, pearl, or brownish gray on the dorsum. The furry tail is covered with coarse hairs on the dorsal surface. C. chinchilla is distinguished from Lagidium and Lagotomus by its small size and differs from C. lanigera in its smaller rounded ears and a shorter tail. Although new populations were found recently, this species is considered "Critically Endangered" requiring continued protection by law and further research of its genetics and ecology. [ABSTRACT FROM AUTHOR]

Copyright of Revista Mexicana de Biodiversidad is the property of Universidad Nacional Autonoma de Mexico, Instituto de Biologia and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Wild cavies from the taxonCavia aperea–Cavia porcellusare known for their extensive use of acoustic signals for communication including a courtship call that is a rarity in Mammalia. The genusCaviaincludes an insular species (Cavia intermedia) derived from a continental “asocial”Cavia magna. We hypothesized that the courtship call and all the other 12 acoustic signals previously described forC. aperea–C. porcelluswere synapomorphies of the genus and took the opportunity of recording the critically endangeredC. intermedia. Four field trips lasting 10 days were conducted in 2008 and 2009. After collecting and analysing nearly 350 sound files of 38 individuals, we found all the 12 calls of wild and domestic cavies previously described, including the courtship call, and a new call, a peep. Despite the presence of the peep, our description ofC. intermediaacoustic repertoire showed the evolutionary stability of the acoustic repertoire of this rodent genus of 6 species, even after domestication ofC. porcellusand 8000 years under insular selective forces inC. intermedia. We present a discussion about the communicative function ofCaviacalls in a comparative context and its repertoire size in accordance with the complexity level of sociality of this caviomorph rodent. [ABSTRACT FROM PUBLISHER]

Copyright of Therya is the property of Asociacion Mexicana de Mastozoologia, A. C. and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The aim of the present study was to characterize the epididymal sperm of Spix's yellow-toothed cavy ( Galea spixii) through two different recovery methods. Nine sexually mature males were euthanized and the complexes, testes-epididymis, were dissected. For each animal, one epididymis was processed by flotation method and the other was processed by retrograde flushing method, both using a TES-based buffered media. After recovery, we evaluated the sperm for motility, vigour, viability, functional membrane integrity and morphology. Morphometric data from the different sperm regions were evaluated by using an appropriate software. After recovery, both methods provide similar values for all the sperm parameters, aiming the recovery of more than 300 × 106 sperm, presenting >50% motile sperm, with normal morphology and functional membrane. The total sperm length in this sperm was 48.87 ± 0.1, and the sperm head presented 9.4%, on average. A notable characteristic was the prominent acrosome found in the G. spixii sperm. In conclusion, we demonstrate that either flotation or retrograde flushing methods are suitable for the recovery of sperm from cauda epididymis of Spix's yellow-toothed cavies. [ABSTRACT FROM AUTHOR]

Hystricognathi represent a monophyletic taxon within Rodentia. Since phylogenetically analyzed morphological systems are essential for revealing evolutionary processes, this study identifies evolutionary character transformations on the stem lineage of Hystricognathi as derived from the author's own work and the literature. Data so far indicate that evolutionary transformations in the rostral head region, the loss of tactile ability in the outer nasal skin and the mobile arrangement of the associated cartilage, were allied with a switch from omnivorous to herbivorous and fiber-rich nutrition. Additional character transformations in the skull assist in digesting such food. Structures associated with reproduction and placentation show a remarkable pro portion of derived character conditions: the chorioallantoic placenta has a ring-shaped organization and growth structure which optimizes the capacity for passive diffusion, a subplacenta occurred as a specialized region responsible for placental invasion and the inverted yolk sac facilitates substance exchange with the main placenta. Finally, precocial newborns evolved as a derived condition within Rodentia. All things considered, a mode of reproduction is indicated, which does not demand excessive additional energy intake by the mother and is in accordance with her low energetic diet. Hystricognathi possess major character transformations that represent prerequisites for their successful radiation at the time when more open ecosystems and grasslands evolved during Earth history. The analysis resulted in the reconstruction of a life-near picture of the hystricognath stem species pattern with high explanatory power in terms of changes in space and time and their interdependence with biodiversity.

Cephalomyopsis hypselodontus is a member of the family Cephalomyidae, originally described based on some isolated remains from the Colhuehuapian locality of Bryn Gwyn (Chubut Province, Argentina). Some specimens from the Deseadan localities of Cabeza Blanca (Chubut Province, Argentina) and Lacayani (La Paz Department, Bolivia), first described as Cephalomyidae morphotype 2 and 3, were later included in the genus. Also, a specimen found in Arroyo Avalos (Corrientes Province, Argentina) was included in the genus, but a taxonomic revision at the species level was never conducted. In this contribution, I revise all the specimens included in the genus, as well as new specimens found in Bryn Gwyn. The new specimens include the most juvenile teeth known so far and the first complete upper tooth row known for the genus. As a result, I define a single species for the genus and discuss the implication of this new systematic proposal. The species has a wide geographical distribution and a long biochron, the longest among cephalomyids. Finally, I discuss the dissimilarities between different localities in Argentina and Bolivia and the implications in the evolutionary history of Cephalomyidae and Chinchilloidea. • Genus Cephalomyopsis only has one species. • The species has a wide geographical distribution and a long biochron, the longest among cephalomyids. • The new specimens include the most juvenile teeth known so far and the first complete upper tooth row known for the genus. • In the Deseadan SALMA chinchilloids were widely distributed across South America. • This taxonomic decision supports the decline propose for the Cephalomyidae during the Colhuehuapian SALMA. (in another bullet point) This also support the presence of Chinchilliodea incertae sedis outside Patagonia during the Late Oligocene–Early Miocene. [ABSTRACT FROM AUTHOR]

The objective of this study focused on the comparative morphological and histochemical analysis of the duodenum of fetuses, juveniles and adult coypu ( Myocastor coypus bonariensis ), the major socioeconomic wildlife resource of Argentina. Histological and histochemical procedures for in situ characterization of glycoconjugates (GCs) were used. This study evidenced that fetal mucins differ histochemically in many respects from their adult counterparts. Only in fetuses from 90 days-post coitus (dpc) glycogen-rich sites were observed throughout the duodenal epithelium. The goblet cells appeared from 105 dpc and their secretory content varied considerably after birth. Duodenal glands presented scanty neutral and sulphated GCs in the 30-day juveniles; in adults the proportion of these GCs increased, and carboxylated and sialylated GCs were also observed. The results obtained in this work may be used in future studies to evaluate the effects of diet and intestinal pathologies in the glycosylation pattern of GCs. Also, knowledge of the normal glycoprofile of the duodenum of M. coypus bonariensis during its ontogenetic development may constitute a basis for the study of this organ in other Hystricognathi rodents. [ABSTRACT FROM AUTHOR]

A total of 30 animals of the genus Dasyprocta were cytogenetically studied. They belong to the following species: D. prymnolopha (N=20), D. leporina (N=6), D. fuliginosa (N=1) and Dasyprocta sp. (N=3) (Dasyproctidae, Hystricognathi). Cell suspensions were obtained by peripheral blood culture, besides bone marrow and spleen cells, from D. prymnolopha and D. leporina. The diploid number was 64/65 for all samples. The karyotypes showed similarity, and chromosomal polymorphism was not detected by Giemsa conventional staining and G banding. The constitutive heterochromatin distribution at the pericentromeric region of all the chromosomes was similar in all species. D. prymnolopha, D. leporina and Dasyprocta sp. presented variation in the heterochromatical block size at one of the homologues of the A18 pair. D. fuliginosa presented the heterochromatin uniformly distributed in all chromosomes. There was not variation in the NORs pattern in the species studied.Foram estudados citogeneticamente um total de 30 animais das espécies D. prymnolopha (N=20), D. leporina (N=6), D. fuliginosa (N=1) e Dasyprocta sp. (N=3) (Dasyproctidae, Histricognathi). As preparações cromossômicas foram obtidas do cultivo de sangue periférico, além de medula óssea e baço em D. prymnolopha e D. leporina. O número diplóide foi de 64/65 em todos os exemplares. O cariótipo mostrou similaridade, não sendo detectado, através de coloração convencional de giemsa e de banda G, polimorfismo cromossômico em qualquer uma das espécies estudadas. A distribuição da heterocromatina constitutiva na região pericentromérica de todos os cromossomos foi similar nas quatro espécies. D. prymnolopha, D. leporina e Dasyprocta sp. apresentaram variação no tamanho do bloco heterocromático em um dos homólogos do par A18. D. fuliginosa apresentou a heterocromatina uniformemente distribuída em todos os cromossomos. Não houve variação no padrão das RONs entre as esp��cies estudadas.

The goal of this perspective is to propose a concerted effort for the study of the diversity of South American rodents to transition into the genomic era. We first review progress made in the last few decades in our understanding of the age, geographical origins, phylogenetic relationships and diversity of caviomorph and sigmodontine rodents, two major components of the South American fauna. Then, we examine their current representation in genomic/transcriptomic databases, and outline a research program to obtain a set of genomes and transcriptomes that represent major groups within each of these two lineages. We propose standards for voucher specimens and associated data and explore the role of museums and research collections in this endeavor. We envision a concerted international effort to guide and accelerate progress in the field.

Abrocoma schistacea Thomas, 1921 is an abrocomid rodent commonly known as the Sierra del Tontal chinchilla rat. This medium-sized chinchilla rat is a rock specialist that inhabits the pre-Andean foothills of southern San Juan Province (Argentina) within an elevation range of 1,100-2,900 m. Its saxicolous specializations include padded feet with leathery tubercles on the pads. Incisors are large and orthodont; molariform teeth appear broad. A. schistacea is a creosotebush dietary specialist that can be distinguished from other chinchilla rats by living in groups of 3-4 individuals. This species is categorized as of low conservation concern in Argentina but is currently listed as "Data Deficient" by the International Union for Conservation of Nature and Natural Resources. [ABSTRACT FROM AUTHOR]

We report the discovery of a new early Oligocene vertebrate fauna from the vicinity of Zallah Oasis in the Sirt Basin of central Libya. The Zallah Incision local fauna has been recovered from the base of a fluvial channel within a rock unit that has been mapped as “Continental and Transitional Marine Deposits.” This rock unit has produced fossil vertebrates sporadically since the 1960s, but the Zallah Incision local fauna is the most diverse assemblage of fossil mammals currently known from this unit. In addition to lower vertebrates, the fauna includes an indeterminate sirenian, the anthracothere Bothriogenys , a new species of the hyracoid genus Thyrohyrax , new species of the hystricognathous rodent genera Metaphiomys and Neophiomys , Metaphiomys schaubi , and a new species of the parapithecid primate genus Apidium . The Zallah Incision local fauna from Libya appears to be close in age to Fayum quarries V and G in the Jebel Qatrani Formation of Egypt and the Taqah locality in the Ashawq Formation of Oman. Considered together, these early Oligocene faunas support a modest level of faunal provincialism across the northern part of Afro-Arabia during the early Oligocene. [ABSTRACT FROM AUTHOR]

Octodontoidea is the most diverse clade of hystricognath rodents, and is richly recorded in South America since at least the Oligocene. A parsimony-based morphological phylogenetic analysis of a wide range of extant and extinct octodontoids recovered three major clades, here recognised as Echimyidae, Octodontidae, and Abrocomidae. Taxa previously assigned to Echimyidae or Octodontoidea incertae sedis are here interpreted for the first time as early representatives of Ctenomyinae (Octodontidae), Octodontinae or Abrocomidae. Based on our results, we estimate the divergence of octodontoid families and subfamilies to have occurred during the Late Oligocene, which is consistent with molecular estimates, but older than previous inferences based on the fossil record. Contrary to previous suggestions, we show the first appearances of modern members of Abrocomidae, Octodontinae and Ctenomyinae to be distinctly decoupled from the origin of these clades, with different stages in the evolutionary history of octodontoids seemingly following distinct phases of palaeoenvironmental change. Depending on the phylogenetic pattern, fossils from the stage of differentiation bear evolutionary information that may not be provided by crown groups, thus highlighting the unique and important contribution of fossils to our understanding of macroevolutionary patterns. [ABSTRACT FROM AUTHOR]

Social groups of capybaras are stable and cohesive. The species' vocal communication is complex and mediates social interaction. The click call is emitted in a variety of contexts by animals from all age groups, but differs among groups; its attributed function is to keep contact among animals. To evaluate the presence of individual characteristics in the click call of capybaras, we recorded the vocalizations emitted spontaneously by six adults kept either solitary or in groups. We selected and measured the acoustic parameters of 300 click call phrases, 50 per individual. The parameters were submitted to a discriminant function analysis that revealed a classification accuracy of 76.8 %. A General Linear Model analysis revealed significant differences among the six individuals, and post hoc results showed that differences between a given pair were different from those of any other pair. The acoustic parameters that most contributed to discriminate the individual calls were click interval duration and click duration, suggesting that temporal parameters are more important than frequency parameters for individuals' discrimination. The findings of individual characteristics in the click calls indicate that these vocalizations can be used as vocal signatures during social interactions. [ABSTRACT FROM AUTHOR]

The oviduct is a very thin organ with a very tortuous appearance. It is divided into three segments: the infundibulum, the ampulla and the isthmus. Particularly, the oviduct of the viscacha lacks the intramural portion described in other species. The mucosa shows longitudinal pleats. The free edge of the infundibulum ends as small fimbriae that are of variable length and do not completely cover the ovary. The proportion of ciliated and secretory epithelial cells varied both in relation to the segments of the oviduct analysed and to the physiological state (anoestrus, follicular phase, early pregnancy and late pregnancy). The glycocalix and the apical region of the superficial epithelial cells are PAS and alcian-blue positive. The muscular layers vary in thickness in different regions. Some lectins such as UEA-1 and DBA showed variations in the binding pattern during the different physiological stages analysed whereas RCA-1and WGA had a very stable pattern. [ABSTRACT FROM AUTHOR]

The general objective of this study focused on the duodenal histological and histochemical analysis of fetuses and adults of plains viscacha ( Lagostomus maximus) from the Buenos Aires province ( Argentina). Histological techniques, histochemical procedures for localizing and characterizing glycoproteins ( GPs) and lectin histochemical techniques for the identification of specific sugar residues were used. The duodenal structure of all age groups here considered was typical of mammals. We identified a proliferation phase and an epithelial morphogenesis in mid-gestational fetuses, an intermediate period of cell differentiation in at-term fetuses and a posterior stage of physiological maturation in adults. According to histochemistry, the diverse GPs elaborated and secreted into the duodenum show a high degree of histochemical complexity related to the multiple functions of mucus in the digestive tract. The GPs in the duodenum of L. maximus and their glycosylation patterns varied according to the animal's age and the developmental state of the organ. [ABSTRACT FROM AUTHOR]

The long-term isolation of South America during most of the Cenozoic produced a highly peculiar terrestrial vertebrate biota, with a wide array of mammal groups, among which caviomorph rodents and platyrrhine primates are Mid-Cenozoic immigrants. In the absence of indisputable pre-Oligocene South American rodents or primates, the mode, timing and biogeography of these extraordinary dispersals remained debated. Here, we describe South America's oldest known rodents, based on a new diverse caviomorph assemblage from the late Middle Eocene (approx. 41 Ma) of Peru, including five small rodents with three stem caviomorphs. Instead of being tied to the Eocene/Oligocene global cooling and drying episode (approx. 34 Ma), as previously considered, the arrival of caviomorphs and their initial radiation in South America probably occurred under much warmer and wetter conditions, around the Mid-Eocene Climatic Optimum. Our phylogenetic results reaffirm the African origin of South American rodents and support a trans-Atlantic dispersal of these mammals during Middle Eocene times. This discovery further extends the gap (approx. 15 Myr) between first appearances of rodents and primates in South America. [ABSTRACT FROM AUTHOR]

The article presents a study that traces the characteristics of evolutionary changes of Hystriocognathi. Records on the study of Hystriocognathi, first identified by the Swedish zoologist Tycho Tullberg in 1899, are included. Description of the morphological systems that covers the lower jaw, maxillare and rostral nasal complex are given in detail. Inner organs did not have sufficient recorded study but data of its reproductive strategy using a K-strategy are available. Part of the analysis of the evolutionary characteristics implies that the rodent was initially omnivorous but converted to herbivorous and fiber-rich food.

The family Caviidae is represented in modern faunas by cavies and maras, whereas the family Hydrochoeridae is represented by capybaras. The evolutionary origin of these families has been related to a diversity of plesiomorphic fossil forms (recorded from the late Oligocene up to the middle Miocene) traditionally grouped in the family 'Eocardiidae'. These fossil forms were included, together with Caviidae and Hydrochoeridae, within the Cavioidea s.s. (sensu stricto), because they share high crowned cheek teeth, double-hearted occlusal surface, short lower incisors, and moderate hystricognathy. Within Cavioidea s.s., caviids and hydrochoerids were interpreted as forming its crown group, because they have unique craniomandibular and dental features. In this contribution, a new taxon of Cavioidea s.s. from the middle Miocene of central Patagonia, Argentina, is described, and its phylogenetic position is determined on the basis of a morphological cladistic analysis in which 'eocardiids' were included. The study permits the understanding of the sequence of appearance of characters that originated the highly divergent morphology of crown-group cavioids. The analysis of the sequence of appearance of the characters that traditionally diagnosed the crown group indicates that these changes did not occur at the same time. On the contrary, many of these features seem to have appeared at different nodes of the evolutionary history of Cavioidea s.s. The remarkably derived morphology of modern cavioids is the result of a stepwise appearance of a mosaic of evolutionary innovations that originated gradually along the history of Cavioidea during the late-middle Miocene. [ABSTRACT FROM AUTHOR]

Abstract: The genus Ctenomys of subterranean rodents is one of the most diverse of the mammal radiation. In addition to external and skull morphology, studies of Ctenomys alpha taxonomy have relied in an intense manner on chromosomal variation and several populations of this genus have been characterized only by means of cytogenetic techniques. Ctenomys pearsoni is the most karyotypically variable species of the genus (2n=56-70). The goal of this study was to assess the pattern of geographic variation of the skull morphology in several karyomorphs of Ctenomys pearsoni. Our main results indicate that, with the exception of the Solís karyomorph, the remaining are morphologically indistinguishable. These results also agree with previous morphological and population genetics analyses performed in this species. Taken together the available evidence, we support the point of view that not all fixations of chromosomal rearrangement define independent evolutionary units. [Copyright &y& Elsevier]

In this paper, we describe four fossil rodent taxa from two new localities situated in the Idam Unit (‘Bioturbated Unit’) of the Dur At-Talah escarpment in central Libya. These rodents belong to the family Phiomyidae (Hystricognathi) and are distributed amongst three genera ( Phiomys, Protophiomys, and Talahphiomys gen. nov.) that include three new species ( Phiomys hammudai sp. nov., Protophiomys durattalahensis sp. nov., and Talahphiomys libycus sp. nov.). Although some of these new species are morphologically close to certain phiomyids from the latest Eocene and Oligocene of the Jebel el-Qatrani Formation of the Fayum in Egypt, the Idam rodent faunas lack the abundant and somewhat morphologically derived Fayum phiomyids (such as: Metaphiomys, Gaudeamus, Paraphiomys, Phiocricetomys), thereby excluding a similar age for the Dur At-Talah rodent assemblages. More resemblance is shared with the phiomyid ( Protophiomys algeriensis) of the Nementcha locality in Algeria, for which a late middle Eocene age is presently admitted. Protophiomys is a primitive representative of the phiomyid African radiation and it is represented at Dur At-Talah by a slightly more derived species ( Pr. durattalahensis) than that of Nementcha, thereby suggesting a younger age for Dur At-Talah. As a result, the new rodent assemblages suggest a late middle Eocene age for the Idam (‘Bioturbated’) deposits of the Dur At-Talah escarpment. This age hypothesis is substantiated by other mammals (especially Proboscidea), which occur in the same sedimentological unit. Interestingly, the dental pattern of Protophiomys and that of Talahphiomys have somewhat stronger affinities with South Asian hystricognath baluchimyines than with Fayum phiomyids. It is clear that baluchimyines and phiomyids have a common ancestry, and that dispersal occurred between Asia and Africa during the middle of the Palaeogene. However, it is not clear if both groups can be strictly separated in two distinct natural groups inasmuch as some baluchimyines (e.g. Lophibaluchia, Bugtimys, Hodsahibia) appear to be phiomyid-like, and some early members of phiomyids (e.g. Protophiomys, Talahphiomys) are baluchimyine-like. South Asia and North Africa represent two centres of adaptive radiation of early hystricognathous rodents. The strong dental resemblances between early Asian and African forms are perhaps the result of subsequent convergent evolution after an initial dispersal from Asia. Otherwise, the systematics of these rodents has to be entirely revised, or we must consider that their historical biogeography is much more complex. © 2010 The Linnean Society of London, Zoological Journal of the Linnean Society, 2010, 160, 195–213. [ABSTRACT FROM AUTHOR]

A new African species of hystricognathous rodent, Gaudeamus lavocati sp. nov., is described herein from the early Oligocene deposits of Zallah locality (Sirt basin, Central Libya). The dental morphology of this species is very close to that of some earliest South American caviomorphs. It allows a reinterpretation of molar crest homologies among earliest caviomorphs, pentalophodonty being confirmed as the plesiomorphic molar condition in Caviomorpha. This morphological resemblance argues for close affinities between Gaudeamus and earliest South American hystricognaths. Cladistic analysis supports Gaudeamus lavocati sp. nov. as the first known African representative of Caviomorpha, implying that its ancestors were part of the African phiomyid group that crossed the South Atlantic by a direct immigration route. Alternatively, the series of derived dental features of Gaudeamus could also be interpreted as evolutionary synchronous convergences of an African hystricognath lineage towards the specialized pattern of some caviomorphs. However, the high level of similarities concerning teeth morphology and enamel microstructure and the similar age of fossiliferous strata on both continents make this interpretation less probable. The phylogenetic position of this taxon is of considerable importance because it represents an enigmatic component of the phiomorph–caviomorph radiation in Africa and appears as a new clue toward the understanding of caviomorph origins. [ABSTRACT FROM AUTHOR]