Greatest Length Of Skull Research Articles

Identification of species of the genus Sylvaemus of northeastern Ukraine by metric characters

The reliable identification of representatives of the genus Sylvaemus is compli-cated by the huge coincidence of external and metrical characters, as well as by the fact that in most of their range, mice are in conditions of sympatry or even syntopy Moreover, identification is complicated by opposite clinal variability in size and geographic variability in fur colouration. The species are also similar in karyotypes, so their reliable identification is usually possible only based on biochemical or molecular analysis. The craniological collection of small mam-mals of O. V. Zorya and collection specimens of the Museum of Nature of V. N. Karazin Kharkiv National University were studied. In total, 436 speci-mens of three species of the genus Sylvaemus were analysed: Sylvaemus ura-lensis, Sylvaemus sylvaticus, and Sylvaemus tauricus. Analysed were 14 odon-tometric and 23 craniological characters. Among the metric characters, three odontometrical—width of first upper molar (WM1), length of second lower molar (LM2), length of lower molar row (LM123)—and seven craniometrical characters—length of first upper molar (LM1), length of foramen incisivum (LFI), length of upper molar row (LUM), width of choana (WCH), height of skull including bulla tympanica (HBCB), length of lower molar row (LLM), length of mandible (LM)—made the greatest contribution to the differentiation of mice of the genus Sylvaemus. Width of first upper molar (WM1), length of first lower molar (LM1), length of second lower molar (LM2), length of brain-case (LBC), least interorbital constriction (LIOC), width of braincase (WBC), distance between incisor and M3 (LIM3), length of upper molar row (LUM), condylobasal length of skull (CBL), palatal length (LPP), greatest length of skull (GLS), and length of lower molar row (LLM) are the least variable metric char-acters. Scatterplots linking LLM/CBL, LUM/CBL, and LUM/GLS appeared to be the most suitable for differentiating the specimens, with minimal overlap of species in the morphospace. In north-eastern Ukraine, the best distribution of mice of the genus Sylvaemus was obtained as a result of the analysis based on both odontometrical and craniological characters, when the correctness of the classification was 100%.

Türkiye’nin Kuzeybatısından Plecotus auritus (Linnaeus, 1758)’a Ait Yeni Bir Yayılış Kaydı ve Bazı Biyoekolojik Özellikleri (Chiroptera: Vespertilionidae)

Species of the genus Plecotus, which have distinctive morphology with their long ears, are common in the Palearctic region. Its distribution area in Türkiye is seen as fragmented. In the present study, a new distribution record for Plecotus auritus (Linnaeus, 1758) from Bolu province is given. External characteristics, fur coloration, skull morphology, morphometric measurements, and some ecological characteristics of the specimen were also recorded. The greatest length of skull, condylobasal length, zygomatic breadth, skull height, and largest diameter of tympanic bulla values were measured as high when compared to the data of Plecotus auritus from Türkiye and Central Europe. It is noted that the species' diet includes Galleria mellonella from the order Lepidoptera. Additionally, call length (ms) (1.4- 4.9 mean= 3.4), max. frequency (kHz) (28.8-62.4 mean= 39.9), min. frequency (kHz) (16.8-36.4 mean= 24.3), and peak frequency (kHz) (22.8-35.6 mean= 28.7) acoustic parameters of Plecotus auritus were determined.

Foraging strategies, craniodental traits, and interaction in the bite force of Neotropical frugivorous bats (Phyllostomidae: Stenodermatinae).

Bats in the family Phyllostomidae exhibit great diversity in skull size and morphology that reflects the degree of resource division and ecological overlap in the group. In particular, the subfamily Stenodermatinae has high morphological diversification associated with cranial and mandibular traits that are associated with the ability to consume the full range of available fruits (soft and hard).We analyzed craniodental traits and their relationship to the bite force in 343 specimens distributed in seven species of stenodermatine bats with two foraging strategies: nomadic and sedentary frugivory. We evaluated 19 traits related to feeding and bite force in live animals by correcting bite force with body size.We used a generalized linear model (GLM) and post hoc tests to determine possible relationships and differences between cranial traits, species, and sex. We also used Blomberg's K to measure the phylogenetic signal and phylogenetic generalized least‐squares (PGLS) to ensure the phylogenetic independence of the traits.We found that smaller nomadic species, A. anderseni and A. phaeotis , have a similar bite force to the large species A. planirostris and A. lituratus; furthermore, P. helleri registered a bite force similar to that of the sedentary bat, S. giannae. Our study determined that all the features of the mandible and most of the traits of the skull have a low phylogenetic signal. Through the PGLS, we found that the diet and several cranial features (mandibular toothrow length, dentary length, braincase breadth, mastoid breadth, greatest length of skull, condylo‐incisive length, and condylo‐canine length) determined bite force performance among Stenodermatiane.Our results reinforce that skull size is a determining factor in the bite force, but also emphasize the importance of its relationships with morphology, ecology, and phylogeny of the species, which gives us a better understanding of the evolutionary adaptions of this highly diverse Neotropical bat group.

Functional Traits of Bats Associated with the Use of Wetlands in Colombian Tropical Dry Forests

Bats have a major functional role in wetlands; understanding how functional traits of bats depend on environmental characteristics can facilitate management of ecosystems and their services. In this study, we investigated how bat functional diversity has been affected by different anthropogenic impacts in wetlands of the Trans-Andean tropical dry forest of Colombia. Specifically, we analyzed how different functional traits responded to changing environmental conditions and land use and land cover patterns. We sampled six wetlands during the dry periods of the hydrological cycle from 2014 to 2018 and modeled the functional diversity as a function of environmental variables. To understand the association of bat community structure with environmental variables and biotic factors, we combined the RLQ analysis and the fourth-corner approach to relate environmental characteristics and species traits. The percentages of water surface area and pasture land were found to be associated with the general traits of bats when analyzed using the relative abundance of species. In addition, changes in functional diversity appeared to be driven mainly by larger species (e.g., Phyllostomus hastatus, Artibeus lituratus), whose presence was primarily associated with heterogeneous areas. The fourth-corner analysis revealed that the greatest length of skull is the trait that best describes the presence of bats in landscapes of pastures, water bodies, and high abundance of the shrubs Vismia sp. and Cecropia sp. These results suggest that combinations of specific features are important drivers of variation in functional diversity between wetlands. Considering the high vulnerability of Colombian wetlands, our findings provide fundamental information for the development of strategies for monitoring wetland biodiversity. The results can help identify priority conservation sites and improve environmental decision making.

Nueva especie de Lonchorhina (Chiroptera: Phyllostomidae) de Chiribiquete, Guayana colombiana

Sword-nose bats genus Lonchorhina are characterized by the most developed telic structures among representatives of the Neotropical family Phyllostomidae, including the longest noseleaf, ear pinna, and tragi in respect to their body sizes. Species in the genus Lonchorhina are usually rare in mist-netting inventories, and most of the currently recognized species are represented in museum collections by few specimens from a limited number of localities, preventing a better appreciation of its diversity. The last comprehensive study on the taxonomy of the genus was conducted almost four decades ago based upon a limited number of specimens that did not include all currently recognized species. In this work we evaluate the phenetic a nities and taxonomic placement of divergent Lonchorhina specimens recovered from the Colombian Guayana, through the analysis of both discrete and morphometric skull characters. Our analyses included 105 Lonchorhina specimens, representing the ve currently recognized species, from a substantial portion of the distribution of the genus. As a result of our evaluation, we introduce a new species of sword-nose bat, representing the phyllostomid species with the largest known noseleaf and tragus (noseleaf >41.5 mm, tragus >22.3 mm). The newly introduce taxon is part of the large skull Lonchorhina (Greatest Skull Length, GSL >21.5 mm) and it is closely related in its morphology to L. ma- rinkellei and L. inusitata from which it is easy to tell apart by its unique morphology, overall larger size (GSL media=27.31; StDev=0.5) and more massive dentition. The holotype of Lonchorhina sp. nov. was collected at an inselberg formation, adjacent to Rio Mesay, Puerto Abeja in the Southwestern portion of the National Natural Park Chiribiquete, in the Colombian department of Caqueta, at 340 masl. The National Park Chiribiquete, corresponds to one of the most unexplored areas in the country, enclosing the oldest and largest series of Amazon pictograms (20.000 years bc) registered on the outcrops of the numerous tepuis, in which images of bats are of particular cultural importance, the new species is a tribute to the Karijona people who inhabited the area of Chiribiquete.

A new species of Mountain Viscacha (Chinchillidae: Lagidium Meyen) from the Ecuadorean Andes

A new species of mountain viscacha, Lagidium ahuacaense, is described based on a specimen and a mitochondrial cytochrome b (cyt b) sequence obtained from a second individual from Cerro El Ahuaca, Loja Province, Ecuador. In several external and craniodental measurements, the new species differed significantly from the three congeneric species (greatest length of skull, basilar, nasal length, palatilar length, length of diastema, least interorbital breadth, breadth of rostrum and skull height). The cyt b sequence of the Ecuadorean viscacha differed by 14 exclusive nucleotide substitutions from all other sequences of Lagidium examined. Kimura 2-parameter (K2P) genetic distances of the Ecuadorean sequence were 8.1–11.0% to L. peruanum, 7.9–9.9% to L. viscacia and 9.7% to L. wolffsohni. The single known population of the newly described species may not comprise more than a few dozen individuals and warrants urgent conservation actions.

Osteological Variation within the Baldwin County, Georgia, Population of Didelphis virginiana

We analyzed intraspecific and sexually dimorphic osteological varia- tion within the Baldwin County, GA, population of Didelphis virginiana (Virginia opossum). Where possible, 20 measurements (11 cranial/mandibular and 9 post- cranial) were obtained from each of 59 road-killed adult opossums (47 males, 12 females). Although range overlaps exist between the sexes for all measurements, males are significantly larger (P ≤ 0.05) for the following characteristics: greatest length of skull, condylobasal length, basal length, postpalatal length, nasal length, bicanine width, zygomatic breadth, length of mandible, scapula length, humerus length, radius length, femur length, and fibula length. Males exhibit significantly less (P ≤ 0.05) variation in mandibular tooth row length and significantly greater (P ≤ 0.05) variation in scapula length and fibula length. Intraspecific variation ranges from 14-54% for cranial/mandibular and 29-73% for postcranial measure- ments. Sexual dimorphism is most pronounced in cranial/mandibular dimensions. Comparisons with multi-state samples indicate that the continent-wide population of the Virginia opossum is very similar in terms of osteological dimension. The combination of low variation index and nonsignificant difference between the sexes in mandibular tooth row length suggests that this measure may be useful for distinguishing fossil opossum species.

Mistaken view of taxonomic validity undermines conservation of an evolutionarily distinct mouse: a response to Ramey et al. (2005)

1 Department of Biology, University of Washington, Seattle, WA, USA 2 Department of Fisheries and Wildlife Sciences, Virginia Polytechnic Institute and State University, Blacksburg, VA, USA 3 Department of Biology, Valdosta State University, Valdosta, GA, USA 4 New Mexico Museum of Natural History, Albuquerque, NM, USA 5 Department of Environmental, Population, and Organismic Biology, University of Colorado, Boulder, CO, USA 6 School of Molecular and Life Sciences, University of Limpopo, Sovenga, South Africa

Muzzle size, paranasal swelling size and body mass in Mandrillus leucophaeus

The drill (Mandrillus leucophaeus), a forest-living Old World monkey, is highly sexually dimorphic, with males exhibiting extreme secondary sexual characteristics, including growth of paranasal swellings on the muzzle. In this study, the size of the secondary bone that forms the paranasal swellings on the muzzles of drills was assessed in relation to body mass proxies. The relationship between the overall size of the muzzle and surrogate measures of body mass was also examined. In female drills, muzzle breadth was positively correlated with two proxies of overall body mass, greatest skull length and upper M1 area. However, there was no such correlation in males. Paranasal swellings in males also appeared to have no significant relationship to body mass proxies. This suggests that secondary bone growth on the muzzles of male drills is independent of overall body size. Furthermore, this secondary bone appears to be vermiculate, probably developing rapidly and in an irregular manner, with no correlation in the sizes of paranasal swelling height and breadth. However, various paranasal swelling dimensions were related to the size of the muzzle. It is suggested that the growth of the paranasal swellings and possibly the muzzle could be influenced by androgen production and reflect testes size and sperm motility. The size and appearance of the paranasal swellings may thus be an indicator of reproductive quality both to potential mates and male competitors. Further work is required to investigate the importance of the paranasal swellings as secondary sexual characteristics in Mandrillus and the relationship between body size and secondary sexual characteristics. Attention should also be paid to the mechanisms and trajectories of facial growth in Mandrillus.

Using Morphologic Characters to Identify Peromyscus in Sympatry

To assess the usefulness of morphologic characters in identifying deer mice (Peromyscus maniculatus), white-footed mice (P. leucopus) and cotton mice (P. gossypinus) in sympatry, cranial and external measurements were recorded for two groups of these rodents. Each group contained individuals of the three species. One assemblage represented known individuals (species identifications verified using electrophoretic techniques) and the other unknowns (species identification not verified; test group). With the known group, we developed a system of identification based on selected morphologic features. These features were used to determine the identification of individuals in the test group. Following identification, individuals identified in the test group were confirmed using electrophoretic procedures. Two characters (greatest length of skull and length of hindfoot) separated 100% and 91% of P. gossypinus in the known group and 94.6% and 98% in the test group, respectively. A single external metric (tail length/total length) correctly classified 95% of P. maniculatus in both the known and test groups. A suite of four cranial (greatest length of skull, length of nasal, post-palatal length and length of diastema) and one external character (length of tail) correctly classified all of the individuals in the initial group and 90%, 91% and 100% of P. maniculatus, P. leucopus and P. gossypinus, respectively, in the test group. We concluded that morphologic characters can be used to accurately detect species of Peromyscus in sympatry.

A New Chocoan Species of Lonchophylla (Chiroptera: Phyllostomidae)

Lonchophylla is a diverse genus of glossophagines characterized by large, forwardly projecting inner upper incisors and the absence of zygomatic arches. Seven species are currently recognized, including the large-bodied (greatest length of skull >24.5 mm) robusta, handleyi, hesperia, and bokermanni and the small-bodied (greatest length of skull <24.5 mm) thomasi, dekeyseri, and mordax. Lonchophylla species range throughout the Neotropics and include endemics in Amazonia, the Cerrado, and the arid regions of coastal Peru and Ecuador. In this paper I describe a new large-bodied species, Lonchophylla chocoana, from the subtropical rainforests of the Chocó in southwestern Colombia and northwestern Ecuador. I also document the diagnostic external, craniodental, and mitochondrial characters of the new species and summarize morphological characteristics for the new species and its sympatric congeners.

Systematics of Sylvilagus Gray, 1867 (Lagomorpha: Leporidae) from Southwestern North America

A multivariate morphological analysis of 26 cranial, mandibular, and dental characters was carried out on five taxa of cottontails: Sylvilagus floridanus chapmani (J. A. Allen, 1899), S.f. cognatus (Nelson, 1907), S. f. holzneri (Mearns, 1896), S. f. robustus (Bailey, 1905), and S. nuttallii pinetis (J. A. Allen, 1894). Discrete characters of upper P2 and P3 and lower p3 were examined in the above taxa, S. n. grangerii (J. A. Allen, 1895), and S. a. audubonii in the context of cladistic analyses. In the latter series of analyses, particular attention was paid to inter- and intrapopulational variation in the S. f. floridanus (J. A. Allen, 1890) and robustus taxa and in S. audubonii (Baird, 1857). I describe dental variation among holotypes and topotypes of these three taxa. My principal objective was to assess whether or not S. robustus was a subspecies of S. floridanus . An analysis of variance indicated that robustus differed from other taxa in six characters (greatest length of skull, condylobasal length, breadth of rostrum, interbasioccipital length, width of tympanic bullae, and mastoid breadth). Principal component analysis indicated ontogenetic differences between robustus and remaining taxa. Neighbor joining analysis in every case correctly classified each specimen examined to its predetermined taxon. Besides a large difference in size, several discrete differences in cranial and dental morphology separated S. robustus from the parapatric S. f. chapmani and from the nominal subspecies, S. f. floridanus ;, characters based on premolar enamel pattern in particular differentiated between S. f. floridanus and robustus . In phylogenetic analyses of 24 dental characters, S. cognatus , S. robustus , and S. holzneri were successive sister taxa to an unresolved clade consisting of two paraphyletic S. nuttallii “subspecies” and two subspecies of S. floridanus (sensu stricto). I propose that Sylvilagus robustus is a species distinct from S. floridanus and its subspecies, some of which probably also constitute distinct species. These results help clarify biogeographic problems inherent in the genus Sylvilagus under the current taxonomic framework.

Habitat factors affecting the geographic size variation of Japanese moles.

Japanese moles of the genus Mogera show remarkable geographic variation in body size. In order to determine which habitat factors affect them, 260 specimens of Mogera imaizumii were collected from 27 localities, 280 specimens of M. wogura were collected from 23 localities, and 41 specimens of M. tokudae were obtained from two localities. The relationships between size, geographic location and seven habitat factors consisting of habitat (rice field) area, soil hardness, and five meteorological components, were analyzed. All three species showed a positive correlation between greatest skull length and habitat area. Populations of M. imaizumii from areas with heavy snow were significantly smaller than those from areas with little or no snow and this variation was also explained by the negative correlation with total annual precipitation. In addition, the size of M. imaizumii varied positively with the variation in annual mean temperature. In the correlation between skull size of M. wogura and habitat area, there was a significant difference in the Y-intersept between the populations from central Honshu and those from southern Honshu, Shikoku and Kyushu. This variation was well explained by the negative correlation between skull size and mean minimum temperature. This variation, however, was not constant across all populations examined, because M. wogura were smaller in narrow valleys, even where mean minimum temperatures were low.

Geographic Variation of Sexual Dimorphism in the Raccoon Procyon lotor

-Geographic variation of sexual dimorphism for 22 cranial characters was investigated in raccoons (Procyon lotor) from 87 localities. Geographic variation in the degree of sexual dimorphism occurred only for canine width and the degree of sexual dimorphism in canine width was significantly less for raccoons from W of the Continental Divide than those from E of the Continental Divide. The lack of geographic variation in sexual dimorphism of greatest length of skull indicates that sexual dimorphism in body size of raccoons also does not vary geographically (skull length is highly correlated with body size). Thus, it appears that selection pressures responsible for sexual dimorphism in raccoons are acting uniformly throughout much of the range of the species. Geographic variation in the degree of sexual dimorphism for canine width may be the result of geographic variation in the intensity of intrasexual selection (i.e., variation in the intensity of male-male competition for mates during the breeding season). If so, the apparent lack of geographic variation in sexual size dimorphism of raccoons may indicate that male body size is not under the same kinds of selection pressures (e.g., intrasexual selection) as canine size.

Nongeographic Morphologic Variation in the Mexican Vole (Microtus mexicanus)

Nongeographic Morphologic Variation in the Mexican Vole (Microtus mexicanus)

Tonatia evotis and Tonatia silvicola

Forearm more than 45; greatest length of skull more than 24. Limbs, ears and noseleaf without wart-like granulations 3 3 (2) Size large, forearm more than 55. Ears less than 32. Postorbital constriction more than 5. Faint pale stripe on top of head T. bidens Size variable, if forearm more than 50, then ears more than 32. Postorbital constriction less than 5. No pale stripe on top of head 4 4 (3) Underparts pure white except chin and sides of venter. Present only in South America T. carrikeri Underparts dusky to pale. If there is any white, it is only a small gular patch. From southern Mexico to northern Argentina 5 5 (4) Maxillary toothrow 9.5 or more; pale patches at bases of ears. Underparts paler, frequently with a white gular patch T. silvicola Maxillary toothrow 9.2 or less. No pale patches at bases of ears. Underparts dusky, contrasting only slightly with dorsum T. evotis

Additional Records of Bauerus dubiaquercus (Chiroptera: Vespertilionidae) in Mexico

Bauerus dubiaquercus Van Gelder, 1959) was supposed to be distributed in a disjunct pattern several parts of Middle America Van Gelder, 1959; Engstrom and Wilson, 1981; Medellin et al., 1986; Engstrom et al., 1987). Some specimens we have collected substantiate the more or less continuous occurrence of B. dubiaquercus in this part of the Continent. Three adult males MZFC No.991, 992, 993) were collected in Omiltemi 2,300 m), 36 km W Chilpancingo, Guerrero, oil 18 March and 13 April 1985. These specimens were captured in mist-nets that were placed over a narrow stream in it pine-dominated cloud forest at Arroyo Agua Fria. These males appeared to be reproductively ictive with testes 5.1 mm March), 5.0 mm March), and 4.8 mm April) in length. Body and skull measurements mm) are, respectively: total length, 106.0, 110.0, 104.0; length of tail, 49.0, 43.0, 46.0; length of forearm dry including carpals), 48.6, 50.6, 50.5; greatest length of skull, 19.8, 20.5, 20.5; zygomatic breadth, 12.2, 12.9, 12.8; postorbitary constriction, 4.1, 4.0, 4.1; length of maxillary toothrow, 6.6, 7.0, 6.8; breadth of braincase, 8.3, 8.2, 8.3; weight, 14.0, 20.0, 13.0 g. An adult lactating female CIQR0 No.170) was captured inside a Mayan house, 30 km S Felipe Carrillo Puerto 30 in), Quintana Roo on 28 June 1986. No embryos were observed during necropsy. Body and skull measurements mm) are: total lenght of body, 120.0; length of tail, 51.0; length of forearm dry including carpals), 52.1; greatest length of skull, 21.2; zygomatic breadth;, 13.3; postorbital constriction, 4.0; length of maxillary toothrow, 7.2; breadth of braincase, 8.4; weight, 16.0 g. These localities represent the first records for the states of Guerrero and Quintana Roo. The Guerrero record on the Pacific versant is about 670 km southeast of the record in Jalisco Engstrom and Wilson, 1981), and it extends upwards the known elevational range 850 m. The peninsular record from Quinta Roo extends the known distribution of this bat in the Caribbean lowlands northward approximately 285 kin NNE of the closest locality Augustine, Mountain Pine Ridge) in Belize McCarthy, in press) and extends downwards the known elevational range Engstrom et al., 1987) 370 m. The specimens were deposited in the Museo de Zoologia, Facultad de Ciencias, UniversidadnacionalAutonoma de Mexico and the mammal collection of Centro de Investigaciones de Quintana Roo. We followed Engstrom and Wilson 1981) and Martin and Schmidly 1982) for the generic ranking of Bauerus. T. McCarthy and D. Wilson reviewed an earlier draft and offered valuable information. F. Tuz and F. Romero assisted in the field.

Thyroptera discifera (Chiroptera, Thyropteridae) in Bolivia

Journal Article Thyroptera discifera (Chiroptera, Thyropteridae) in Bolivia Get access Marcos P. Torres, Marcos P. Torres Departamento de Ciencias Naturales, Universidad Nacional de Río Cuarto, 5800 Río Cuarto, Círdoba, Argentina Search for other works by this author on: Oxford Academic Google Scholar Tomas Rosas, Tomas Rosas Servicie Nacional de Control de Fiebre Hemorrágica Boliviana, Magdalena, Beni, Bolivia Search for other works by this author on: Oxford Academic Google Scholar Sergio I. Tiranti Sergio I. Tiranti Departamento de Ciencias Naturales, Universidad Nacional de La Pampa, 6300 Santa Rosa, La Pampa, Argentina Search for other works by this author on: Oxford Academic Google Scholar Journal of Mammalogy, Volume 69, Issue 2, 20 May 1988, Pages 434–435, https://doi.org/10.2307/1381410 Published: 20 May 1988 Article history Received: 02 September 1986 Accepted: 27 March 1987 Published: 20 May 1988

Morphologic Variation and Hybridization in Myotis yumanensis sociabilis and Myotis lucifugus carissima

Morphologic variation was examined in 240 Myotis yumanensis sociabilis and 169 Myotis lucifugus carissima from northeastern California and southcentral Oregon to determine whether extreme similarity was due to intraspecific variation or to hybridization. Seven external and eight cranial variables were analyzed using multi-variate discriminant analyses. Intraspecific variation is partially responsible for mensurable overlap, so that forearm length and greatest length of skull do not differentiate large M. y. sociabilis from small M. l. carissima . Pelage color and skull profile also fail to distinguish some individuals. Morphologically intermediate individuals were found in roosts shared by both species. Two multivariate analyses showed condylo-premaxillary length to be the best discriminating character although separation of the two species by this character alone was poor. Limited hybridization is probably occurring in the area from which I obtained specimens. Eleven animals were classified as hybrids based on statistical probabilities. The probable explanation for hybridization is the relatively recent establishment of sympatry between the two species following Pleistocene climatic events. Some morphologic convergence may be the result of a greater degree of ecologie similarity in this area of sympatry. Because intraspecific variation complicates identification of pure parental types as well as hybrids, it is impossible to verify introgression by using statistical methods. The current status of the two species in other parts of their ranges suggests introgression is not occurring. The taxonomic history of M. yumanensis and M. lucifugus is reviewed.

Geographic Variation and Sexual Dimorphism in Ord's Kangaroo Rat, Dipodomys ordii

Geographic variation was assessed in 4,335 male and 3,518 female specimens of Ord's kangaroo rat ( Dipodomys ordii ) from throughout the range of the species. A total of 16 skull measurements was analyzed and, of these, 11 showed significant sexual dimorphism. Greatest skull length, bullar-premaxillary length, and basal length showed the greatest relative differences between sexes. All characters showed significant interlocality variation in both sexes. Relative to the degree of intralocality variability, the third molar width showed the least interlocality variation; the three characters mentioned above plus greatest skull depth and upper diastemal length were the most variable between localities within each sex. Localities were projected onto three principal components based on correlations of characters. Component I (a size factor) showed that for both sexes the large individuals occur east of the western Cordillera, and smaller animals are found to the west in the United States and Mexico. Populations of the eastern and western parts of the range are linked by those that are morphologically intermediate. At least two complexes are formed in the western part of the range. Specimens from Padre and Mustang islands are separated from the others by component II, which has high loadings for greatest skull width, least interorbital width, least supraoccipital width, and greatest interparietal width. The third component has its highest correlation with third molar width, and the southernmost localities are large for this character. Patterns of interlocality heterogeneity are discussed in terms of sympatry with other Dipodomys species.