CRANIAL INFRASPECIFIC DIFFERENTIATION IN PROECHIMYS-IHERINGI THOMAS (RODENTIA, ECHIMYIDAE)

Proechimys iheringi Thomas is an echimyid rodent occurring in eastern Brazil from the states of Bahia to Sao Paulo. MOOJEN (1948) recognized six subspecies of P. iheringi primarily on the basis of clinal variation in the number of cheekteeth counterfolds. In this study we analyzed infraspecific differentiation in 13 morphometric cranial characters in three populations assignable to three subspecies of P. iheringi. Cranial dimensions vary clinally increasing from north to south and morphometric differentiation is correlated with geographic distance. The congruence between the clinal variation in cheekteeth counterfolds and cranial traits indicates that the trinomial nomenclature should not be applied to P. iheringi.561344

AN ANALYSIS OF MORPHOLOGICAL DISCRIMINATION BETWEEN PROECHIMYS-DIMIDIATUS AND PROECHIMYS-IHERINGI (RODENTIA, ECHIMYIDAE)

Four species were recognized by MOOJEN (1948) for the subgenus Trinomys, genus Proechimys: P. setosus, P. albispinus, P dimidiatus, and P iheringi. The latter two species are very similar and difficult to distinguish on a morphological basis. Proechimys dimidiatus is a monotypic species restricted in distribution to the state of Rio de Janeiro, whereas six subspecies have been described for P iheringi. Of the six subspecies recognized for P iheringi, P. i. bonafidei and P i. iheringi occur in the state of Rio de Janeiro, and thus can be confused with P dimidiatus. We examined qualitative aspects of the cranium in P dimidiatus, P i. bonafidei, and P i. iheringi to assess the usefulness of these structures to characterize and separate these taxa. Bacular morphology was investigated in P dimidiatus and P. i. iheringi. We also employed standard multivariate morphometric procedures to determine whether the three taxa can be discriminated by quantitative cranial characters. The structure of the incisive foramen, including the shape of the vomerine sheath and the pos-orbital process of zygoma were shown to be important characters to separate P dimidiatus, P. i. bonafidei, and P. i. iheringi. Proechimys dimidiatus and P. i. iheringi also differ in bacular morphology. Discriminant function analysis of 18 cranial metric traits correctly allocated all individuals of P. dimidiatus, P. i. bonafidei, and P i. iheringi to their predicted groups, in spite of substantial variation in cranial dimensions within and among the three taxa.2284179518920

CRANIOMETRIC VARIATION AND SUBSPECIFIC DIFFERENTIATION IN THRICHOMYS APEREOIDES IN NORTHEASTERN BRAZIL (RODENTIA, ECHIMYIDAE)

Thrichomys apereoides is an echimyid rodent which ranges in distribution from northeastern and central Brazil into Paraguay. Five subspecies are recognized, although each form is not well characterized and diagnosis is based primarily in pelage color variation. In this study we employed procedures from multivariate statistics to assess the systematic status of subspecies described from northeastern Brazil. The results of the craniometric analysis cannot be reconciled with the subspecies currently recognized for northeastern Brazil. Populations assigned to T. a. laurentius and T. a. inermis form a continuum of variation in cranial size, although they differ in cranial shape from a population from the locality of Bodoco in the state of Pernambuco. The implications of these findings for the systematics of T. apereoides are discussed.60317618

PROECHIMYS ALBISPINUS MINOR, A NEW SUBSPECIES FROM THE STATE OF BAHIA, NORTHEASTERN BRAZIL (RODENTIA, ECHIMYIDAE)

Described a new subspecies, Proechimys albispinus minor, based on specimens from the highlands locality of Morro do Chapeu in the state of Bahia, in northeastern Brazil. The new subspecies can be distinguished by a smaller body and cranial size, finer pelage, absence of an ochraceous subapical zone in the aristiform hairs in the middorsal region, and ochraceous-orange subapical region in the setiform hairs in the middorsal region and outer thighs.60423724

SYSTEMATIC IMPLICATIONS OF CRANIOMETRIC VARIATION IN PROECHIMYS-IHERINGI THOMAS (RODENTIA, ECHIMYIDAE)

Proechimys iheringi is an echimyid rodent that ranges in distribution from the state of Bahia to the state of Sao Paulo in southeastern Brazil. The current taxonomic treatment of P. iheringi stems from MOOJEN (1948), and includes a formal subspecific structure and an alternative hypothesis which postulates various levels of differentiation and isolation between geographic populations of R iheringi. According to the formal structure six subspecies are recognized primarily on the basis of increasing number of cheekteeth counterfolds from northern to southern localities, whereas under the alternative hypothesis two forms, P. i. iheringi and P. i. paratus, arc regarded as specifically isolated. We examined variation in cranial morphometric traits in all subspecies recognized by MOOJEN (1948), in addition to P. i. eliasi, a new form recently described from the state of Rio de Janeiro (PESSOA and REIS 1993). Cranial variation as revealed by multivariate analysis is not congruent with the formal subspecific structure but rather supports MOOJEN'S (1948) conjecture that P. i. paratus and P. i. iheringi may be specifically differentiated. The remaining forms currently recognized as P. i. denigratus, P. i. gratiosus, P. i. panema, P. i. bonafidei, and P. i. eliasi may be part of another taxon specifically distinct from P. i. paratus and P. i. iheringi.2324179518120

BACULAR VARIATION IN THE SUBGENUS TRINOMYS, GENUS PROECHIMYS (RODENTIA, ECHIMYIDAE)

Bacular morphology and variation in the four species of spiny rats of the subgenus Trinomys, genus Proechimys is described. Each species can be uniquely diagnosed on the basis of bacular morphology alone. Proechimys dimidiatus and P. iheringi have similar overall bacular morphology, although they differ noticeably from P. setosus and P. albispinus. The latter two species differ markedly in the morphology of the baculum.57210010

GEOGRAPHIC-VARIATION IN PROECHIMYS-DIMIDATUS (GUENTHER) (RODENTIA, ECHIMYIDAE)

Proechimys dimidiatus (Guenther) is an echimyid rodent restricted in distribution to the state of Rio de Janeiro, Brazil. This species was regarded by MOOJEN (1948) to lack geographic variation in pelage, skull, and teeth characters and thus considered monotypic. In the present study, morphometric cranial variation was analyzed in population samples of P. dimidiatus by means of univariate and multivariate procedures. The statistical analyses employed in this paper detected among-locality character variation and population differentiation in P. dimidiatus in spite of the existence of significant within-population variation in skull dimensions. Both univariate and multivariate analyses disclosed no clear geographic trend in cranial character variation in P. dimidiatus. The three populations analyzed were shown to be different in the reduced space of canonical variates, although there seems to be no correlation between morphometric differentiation and geographic distance.2254179538339

MULTIVARIATE MORPHOMETRIC ANALYSIS OF SELECTED PROISOTOMA SPECIES (COLLEMBOLA, ISOTOMIDAE)

Multivariate analyses were applied to seven species of the collembolan genus Proisotoma. Principal components analysis and canonical variates analysis resulted in different patterns of ordination. All species, except for P. tenella form a tight cluster in the principal components analysis, whereas three major clusters were produced by canonical variates analysis. The clusters displayed in the reduced space of canonical variates are concordant, in part, with groupings based on a different set of morphologic characters and may have systematic significance.227416719810

A NEW SUBSPECIES OF PROECHIMYS-IHERINGI THOMAS (RODENTIA, ECHIMYIDAE) FROM THE STATE OF RIO-DE-JANEIRO, BRAZIL

Described a new subspecies of Proechimys iheringi based on specimens collected in the coastal sand plains of the state of Rio de janeiro, southeastern Brazil. This new subspecies can be distinguished by a combination of traits that include an absence of cinnamon ground color in the subapical zone of setiform hairs tail longer than head and body with a whitish brush in the tip, bullae large and well inflated, and by the structure of the septum of the incisive foramen, where the vomer is visible ventrally between the premaxillae and maxillae.58318119

THE CONTRIBUTION OF CRANIAL INDETERMINATE GROWTH TO NON-GEOGRAPHIC VARIATION IN ADULT PROECHIMYS-ALBISPINUS (IS GEOFFROY) (RODENTIA, ECHIMYIDAE)

Analysed the contribution of cranial indeterminate growth in 19 metric characters to intrapopulation variation in Proechimys albispinus (Is. Geoffroy). Individuals were assigned to eight age classes on the basis of tooth eruption and surface wear criteria. The variation in skull characters was partitioned into age and residual components in adult individuals of age classes 6-8. An average of 17.34 percent of the variation in skull traits is due to the age effect in the three combined age classes of adults, and the remaining 82.66 percent accounts for residual variation within age classes. Discriminant function analysis correctly classified 80 percent and 72 percent of individuals to age classes 6 and 7, respectively, whereas all individuals in age class 8 were correctly classified. The implications of these findings for the taxonomy and systematics of the genus Proechimys are discussed.56421922