173 research outputs found
Silicon Photonic Devices for Sensing, Switching, Polarization and Mode Control
No full textThis thesis starts with an investigation of the local oxidation of silicon (LOCOS) technique to fabricate submicron-size photonic waveguides. Next, the thesis shifts the focus theme from fabrication technology to device designs. The first class of silicon devices that was investigated in this thesis is microring resonator (MRR)-based devices, two of which are targeted for label-free evanescent field sensing. The last MRR-based device proposed is an all-optical switch using a ring-assisted Mach-Zehnder interferometer (RAMZI), which is the essential building block for on-chip silicon photonic circuits. The second class of silicon photonic devices investigated in this thesis is subwavelength grating (SWG) structures for polarization management. The SWG structure features the unique engineering capability of the waveguide effective index. The third class of silicon photonic devices investigated in this thesis is taper-based devices. The taper-based devices are first applied in polarization management. One design is a polarization rotator (PR) using a tapered amorphous silicon layer, which can effectively reduce the insertion loss; while the second design is a PSR based on a taper-etched directional coupler (DC). The thesis also presented a two-mode (de)multiplexer using a simple taper-etched DC, where the fabrication tolerance was greatly improved by the tapered design. All the devices mentioned above were thoroughly examined through numerical simulations. A selective set of devices were fabricated experimentally. For example, the LOCOS wire waveguides were fabricated at the Carleton University MicroFabrication Facility; the MMI coupled slotted MRRs and the TE-pass polarizer based on SWG waveguides have been fabricated using deep ultraviolet (DUV) lithography by the OpSIS and IMEC foundry services through the CMC Microsystems
Representations of Lie Algebras of Vector Fields on Algebraic Varieties and Supervarieties
No full textThis thesis is devoted to a study of the structure and representation theory of some infinite-dimensional Lie algebras and Lie superalgebras. The first family studied is the Lie algebras of vector fields on smooth affine algebraic varieties. After an exposition of the structure of such Lie algebras, we consider representations that admit a compatible action of the coordinate ring of the algebraic variety and are finitely generated as modules over this commutative algebra. We prove that these representations can be associated with a vector bundle that admits a compatible action of the tangent sheaf. We also prove that the action of the tangent sheaf is given by a differential operator. These results allow us to solve a conjecture made in the first papers of this theory. The second family considered is a supergeometry version of the previous. After an investigation of the smoothness of algebraic supervarieties, we prove that the global sections of the tangent sheaf of a smooth integral affine supervariety form a simple Lie superalgebra. Subsequently, we consider representations of this Lie superalgebra that admit a compatible action of global sections of the structure sheaf of the affine supervariety. Analogously to the non-super case, we show that the associated sheaf of modules admits a compatible action of the tangent sheaf when it is coherent. We also prove that this action is defined by a differential operator. Lastly, we study the weight modules with finite multiplicities over the map superalgebra associated with a basic Lie superalgebra. We prove that these representations are either cuspidal or parabolically induced from a cuspidal bounded module over a subalgebra of the map superalgebra. We also show that cuspidal bounded modules are evaluation modules
Dynamic Environmental Change at the Cusp of the Great Oxidation Event: The Gowganda-Lorrain Formation Transition, Cobalt Basin, Ontario and Quebec
No full textThe Huronian Supergroup, an early Paleoproterozoic (ca. 2.45-2.22 Ga) sedimentary succession preserved in Ontario and Quebec, catalogues evidence for the Great Oxidation Event (i.e., the initial rise of oxygen in the atmosphere) through the preservation of redox sensitive minerals in terrestrial deposits: (1) detrital pyrite and uraninite in older strata (evidence of an anoxic atmosphere), and (2) Earth’s earliest red, hematitic, sandstone in younger strata (indicative of a shift to an oxidizing atmosphere). This dissertation comprises three studies from the Cobalt Basin, a northern sub-basin of the greater Huron basin. The first two studies develop depositional models of the northern and easternmost portions of the Cobalt Basin providing details on the glacial to post-glacial paleoenvironments that preserve Earth’s earliest red sandstones. Stratigraphic measurements and correlations reveal that strata are preserved within paleovalleys, interpreted to have developed from glacial excavation as evidenced by basal subglacial deposits. Above these subglacial deposits, strata show a single progradational succession, which captures a transition from glaciomarine to warm and humid fluvial braidplain environments. At the flanks of the paleovalleys, alluvial and/or colluvial deposits occur indicating that terrestrial sedimentation was triggered by enhanced weathering in an unvegetated warm and humid setting due to topographic variations. The successions occur at proximal limits of a passive margin and indicate that progradation was influenced by relative sea-level fall linked to glacio-isostatic uplift. The third study investigates the petrogenesis of reddened sandstone of the aforementioned braidplain deposits. Petrography reveals single-grain rims of pigmentary hematite dust on detrital quartz that are encased by quartz overgrowth cement. This encapsulates evidence that reddening is a syn-sedimentary or early diagenetic feature, formed from widespread oxidizing meteoric waters in a terrestrial setting under an oxygenated atmosphere, prior to burial and lithification of the fluvial deposits. Reddening likely happened close to 2.31 Ga, providing an approximate age for the initiation of oxidative weathering in a terrestrial setting, triggering key feedbacks in nutrient cycling that possibly thrusted Earth’s atmosphere into a stable oxidizing state
Evaluating Time-Dependent Changes in Food Seeking Following Periods of Forced Abstinence and Associated Changes in the Nucleus Accumbens
No full textIncubation of craving is a phenomenon whereby responding for cues associated with reward (food and drugs) increases over extended periods of abstinence. Evaluating the mechanisms of food craving has implications in understanding how consumption of foods high in certain macronutrients (fat, sugar) may contribute to continued cravings and subsequent weight gain. The primary goals of this thesis were to examine if forced abstinence from different food rewards resulted in a continued/or delayed craving response by utilizing different behavioral designs (contingent vs non-contingent) and examining associated changes in nucleus accumbens (NAc) immediate early genes, dendritic spine density, and AMPA receptor protein expression. Food self-administration (operant conditioning), classical conditioning, and conditioned place preference (CPP) were utilize for the investigation of incubation of food craving. Abstinence from self-administration of purified pellets was the only food group to display an incubation of craving response. Self-administration of chocolate flavored pellet, sucrose, or chocolate sucrose pellets did not result in an incubation response but did result in consistent responding at all abstinence periods which was associated with elevated dendritic spine density for chocolate flavored pellets. The type of behavioral design affected association FosB labelling as rats that underwent classical conditioning displayed significantly lower FosB in the NAc compared to operant trained rats and food restricted controls. CPP for chocolate flavored pellets or milk chocolate chips showed that the type of food reward can affect the possibility of a place preference response, milk chocolate did not produce CPP. The CPP model was unable to produce an incubation of craving response which may have resulted from the rewarding properties of the food choice and number of training sessions. Exposure to rewarding cues rapidly increased GluR1 expression, but this was not specifically associated with an incubation of craving response, thus the functional significance has yet to be elucidated. The present thesis has highlighted that foods of different macronutrient composition and/or flavors and the use of different behavioral designs can affect the potential for an incubation of craving response and associated NAc changes
Learnings from collaborative monitoring of remote wildlife populations: factors affecting changes in number and distribution of nesting Hudson Bay eiders ducks in the Belcher Islands
No full textAnthropogenic pressures are causing a global decline in biodiversity that, in turn, impacts the human communities depending on it. In the conservation effort, efficient management requires up-to-date and accurate information about the population dynamics, habitat requirements, and distribution of organisms. There is an increasing appreciation of the benefits of coproduction and the combination of multiple knowledge systems to increase our understanding of the rapidly changing ecosystems. In this thesis, I used data from a long-term collaborative monitoring program involving Inuit and federal government researchers to study the factors affecting changes in population size and nesting distribution of a harvested sea duck in south-eastern Hudson Bay, the common eider (Somateria mollissima). I also highlight practical challenges and propose solutions related to cultural and institutional barriers that impede the delivery of respectful approaches and best practices in collaborative research programs involving large and regulated institutions and remote Indigenous communities
Catalysed Hydrothermal Carbonization of Woody Biomass and Recycling of Process Liquid
No full textThe research introduces catalysed hydrothermal carbonization (CHTC) as a treatment method for woody biomass to produce solid hydrochar as well as value-added compounds (VACs). The hydrochar had higher heating values (HHV) of 28.3 MJ/kg and H/C and O/C ratios similar to coal, when using the liquid:biomass (L:B) ratio of 12:1 for the process. Densified CHTC hydrochar pellets were 97% durable, and hydrophobic when compared with wood pellets and torrefied wood pellets. CHTC has the potential to produce VACs such as glycolic acid, formic acid, acetic acid, levulinic acid, 5-hydroxymethylfurfural, and furfural, from the process liquid effluent. Recycling the process liquid at L:B of 5:1 increased the concentration of the VACs and energy yield of the hydrochar. The production yields of the VACs were dependent upon the L:B ratios, they increased parallel with L:B ratios
Hylomyscus heinrichorum Carleton, Banasiak & Stanley, 2015, new species
No full text<i>Hylomyscus heinrichorum</i>, new species <p>(Figs. 5–7; Table 6)</p> <p> <i>Hylomyscus carillus</i>, Hill & Carter, 1941: 97 (part, faunal report); Crawford-Cabral, 1998: 79 (part, faunal report).</p> <p> <i>Praomys carillus</i>, Crawford-Cabral, 1986: 163 (part, name combination, zoogeography).</p> <p> <i>Hylomyscus denniae</i>, Musser & Carleton, 1993: 599, 2005: 1336 (part, systematic checklists, referenced as isolated population of indeterminate status).— Dieterlen, 2013: 435 (part, faunal report, distribution).</p> <p> <i>H</i> [<i>lomyscus</i>]. cf. <i>anselli</i> group, Carleton & Stanley, 2005: 629 (taxonomic revision, definition of the <i>H</i>. <i>anselli</i> species group and its contents).</p> <p> <b>Holotype.</b> FMNH 83796, an adult male prepared as skin and skull, captured 7 October 1954 (skin tag reads “ 7 X 1954 ”) by Gerd H. Heinrich; the field number is recorded on the skin tag as 8778 and as GH 8778 on the now loose skull tag. Machine-printed on back of the tag is “Angolan Zoological Expedition, 1954.” Written in black pen in the collector’s script are the external measurements (“T.L.: 245, Tail: 145, H.F.: 22, Ear: 19”) and habitat (“Evergreen wood. – High mountain region”); the testes were noted as scrotal in position. See Table 6 for cranial measurements of the holotype. The skin is well prepared, in fine condition, and the skull is intact, in good condition with minor damage confined to the left orbital wall.</p> <p> <b>Type locality.</b> Angola, Provincia Huambo, Mount Moco, ca. 12°27.712ʹS, 15°10.600ʹE (per the U.S. National Geospatial-Intelligence Agency).</p> <p>The locality as recorded on the skin tag reads only “ Angola, Mount Moco.” Heinrich collected at two localities on Mt Moco, as evidenced by locality modifiers recorded in the field catalog and by an annotated, X-marked field map accessioned with that catalog (both documents maintained in the FMNH Mammal Division). One X-marked site is centered near the peak of Mt Moco, and a second X is located nearby to the southeast. Specimens obtained at the latter place were labeled “foot” and collected 14–20 Sep 1954. Heinrch then relocated to a higher elevation and settled in a “high mountain region,” presumably corresponding to the former X, where he remained for over three weeks, 22 Sep–16 Oct 1954. The type specimen and referred specimens from Mt Moco all originated from the high mountain locality.</p> <p> <b>Paratypes.</b> All material here assigned to <i>H</i>. <i>heinrichorum</i> originates from two localities in Angola, Provincia Huambo. These include 14 additional specimens from Mt Moco (FMNH 83793–83795, 83797–83799, 83801– 83807, 83895), collected from 5–10 Oct 1954 by G. Heinrich; and 10 specimens from Mount Soque, 42 km WSW Luimbale (FMNH 83783–83792), collected 24–28 Aug 1954 by G. Heinrich.</p> <p>Heinrich’s Mount Soque (also as Serra Ussoque) is a ridge-shaped inselberg (12°17.450ʹS, 15°08. 633ʹE), located approximately 20 km NNW Mt Moco and 20 km WSW Luimbale, its peak elevation ca. 2165 m. We presume that Heinrich’s locality modifier, “ 42 km WSW Luimbale,” was a by-road calculation.</p> <p> <b>Diagnosis.</b> A species of the <i>Hylomyscus anselli</i> group characterized by larger size (ONL ≈ 26.0– 27.5 mm; CLM ≈ 4.1–4.3 mm) compared with examples of <i>H</i>. <i>arcimontensis</i> and <i>H</i>. <i>kerbispeterhansi</i> (ONL ≈ 24.5–26.5 mm; CLM ≈ 3.5–4.0 mm), as reflected in most craniodental dimensions recorded (Table 6). Compared with examples of <i>H</i>. <i>anselli</i>, size comparable, but bony palate notably shorter with absolutely and proportionally longer incisive foramina (LIF ≈ 75–80% of LD) that penetrate between the anterior roots of the first molars; molars slightly more robust and zygomatic plate broader; head-and-body and tail average shorter in length, and rostral dimensions (LR, LD) average smaller.</p> <p> <b>Distribution.</b> Restricted to high mountainous region of westcentral Angola as so far known (Fig. 4).</p> <p> <b>Description and comparisons.</b> <i>Hylomyscus heinrichorum</i> can be associated with the other species so far recognized in the <i>H</i>. <i>anselli</i> group (<i>H</i>. <i>anselli</i>, <i>H</i>. <i>arcimontensis</i>, <i>H</i>. <i>kerbispeterhansi</i>) based on certain qualitative traits. Foremost among these are the lack of pectoral mammae; the large expanse of the subsquamosal fenestrum, which together with the postglenoid foramen defines a slender and long hamular process (see Carleton & Stanley, 2005: Fig. 6); and its relatively shorter incisive foramina (namely, shorter in comparison with members of the <i>H</i>. <i>denniae</i> group). The number of mammary glands in <i>H</i>. <i>heinrichorum</i> —six, distributed as one post-axial pair and two inguinal pairs—was verified on several prepared round skins (FMNH 83793, 83795, 83802–83804), all females that were apparently in late-term pregnancy or lactating.</p> <p> Although we excluded external variables in our multivariate analyses, mean differences were highly significant for TOTL, TL, and HBL in one-way ANOVAs that compared our tabulated samples of <i>H</i>. <i>heinrichorum</i> and <i>H</i>. <i>anselli</i> (F values = 13.8–14.4, P <0.001, df 1, 35), but not for HFL (F = 0.02, P = 0.884, df 1, 35). The sample of <i>H</i>. <i>heinrichorum</i> averaged smaller than that of <i>H</i>. <i>anselli</i> for all three significantly different skin variables (Table 6). Our samples of the two species were obtained by different collectors, and such external variables are notoriously variable depending upon investigator habit and field experience. Even so, the disparity in means seems suitably large to convey real taxonomic differences.</p> <p> The pelage of <i>H</i>. <i>heinrichorum</i> resembles that observed in other members of the <i>H</i>. <i>anselli</i> group, being soft and fine in texture, short and closely adpressed to the body. The most notable pelage contrast of the Angolan form involves dorsal pelage color. Individual dorsal hairs can be characterized as medium plumbeous gray tipped with bright buff; the overall effect, however, is not so dark and somber a brown as in examples of <i>H</i>. <i>anselli</i> and <i>H</i>. <i>arcimontensis</i> (Fig. 5), but rather an even toned, dull yellowish brown (buckthorn brown), light to moderate in saturation. Guard hairs are brown with hyaline tips, only a little longer than the dorsal fur except over the rump. There is little tendency toward darker over the middle dorsum or conspicuously brighter flanks as is common in the other two species; color is generally evenly graded in expression over the entire dorsum, from the middle back to the flanks. A few individuals of <i>H</i>. <i>heinrichorum</i> exhibit brighter ochraceous-tipped hairs along the upper leg and shoulder and side of the head; nevertheless, the dorsal pelage color is predominantly even toned in appearance. Dorsal-ventral pelage contrast is well marked but not accentuated by a brighter lateral line. In all three species, the ventral hairs are basally gray and tipped with white, imparting a grayish-white effect. The three can be crudely sorted as bright gray (<i>H</i>. <i>arcimontensis</i>), medium gray (<i>H</i>. <i>heinrichorum</i>), and dark gray (<i>H</i>. <i>anselli</i>), with much variation and overlap among them. The tail of <i>H</i>. <i>heinrichorum</i>, as in other members of the <i>H</i>. <i>anselli</i> group, is notably longer than the head and body (TL ≈ 142–146% of HBL), its color dusky-brown and wholly dark around the circumference; caudal scales are finely textured and hairs short, imparting a naked appearance over most of its length, the fine caudal hairs becoming macroscopically visible toward the tip. The hind foot is short and narrow, as per the genus, with digit 5 nearly as long as digits 2–4; the naked plantar surface bears six well-formed, cushiony pads. Pale brown hairs of the limb usually continue onto the ankle and proximal metatarsum, forming a dusky medial metatarsal streak in some individuals, replaced by white hairs over the distal metatarsum and phalanges; glistening white ungual tufts are present. Pinnae are pale brown to dark tan in the Angolan species, compared with darker, more blackish brown ears in the other two.</p> <p> As a gestalt observation, the skull of <i>H</i>. <i>heinrichorum</i> is approximately equal to or only slightly smaller than <i>H</i>. <i>anselli</i>, albeit heavier in build, but both are substantially larger than <i>H</i>. <i>arcimontensis</i> (Figs. 6, 7). Thus, standard external measurements and those we recorded for the skull and molar rows easily serve to distinguish examples of <i>H</i>. <i>heinrichorum</i> from those of the smaller <i>H</i>. <i>arcimontensis</i> and <i>H</i>. <i>kerbispeterhansi</i> (Table 6); size routinely emerged as the preeminent factor accounting for their separation in multivariate space (Figs. 1, 3). Mensural differences between <i>H</i>. <i>heinrichorum</i> and <i>H</i>. <i>anselli</i>, on the other hand, are not readily grasped when eyeballing series of skulls, yet specimens of each did conform to distinct morphometric footprints based on the cranial measurements we obtained (see Figs. 1, 2 C). However, fewer variables contributed to their discrimination, rendering their cranial separation correspondingly more difficult, based on subtle distinctions. Configuration of the hard palate relative to the length of the incisive foramina offers particularly important contrasts, those variables (BBP, HPL, LIF) loading strongly on that principal component which captured their separation in multivariate space (Fig. 2 C, Table 4). As practical anatomical landmarks when viewing skulls, these loadings translate as absolutely shorter incisive foramina (LIF ca. 69–73% of LD) whose posterior end falls just short of or about level with the anterior border of the M1 anterior root in <i>H</i>. <i>anselli</i>, versus longer incisive foramina (LIF ca. 75–80% of LD) that extend beyond the anterior roots about to the rim of the first lamina of M 1 in <i>H</i>. <i>heinrichorum</i>. Therefore, the incisive foramina in <i>H</i>. <i>heinrichorum</i> are proportionately the longest within the <i>H</i>. <i>anselli</i> group, albeit not so “long” as members of the <i>H</i>. <i>denniae</i> group. The absolutely longer bony palate documented in <i>H</i>. <i>anselli</i>, compared with a shorter palate in <i>H</i>. <i>heinrichorum</i>, is a reciprocal geometric corollary of the different foraminal lengths (Table 6). The shape of the incisive foramina, however, is similar in both: broader over the anterior portion, narrowing slightly over the posterior half. The dorsal notch formed between the upper zygomatic plate and rostrum appears slightly deeper and wider in specimens of <i>H</i>. <i>heinrichorum</i> compared with crania of <i>H</i>. <i>anselli</i> and <i>H</i>. <i>arcimontensis</i> (Fig. 6), a visual impression consistent with the actually broader zygomatic plate recorded in the former (Table 6) and the important contribution of this variable (BZP) to between-group discrimination (Table 4). The interorbital region of <i>H</i>. <i>heinrichorum</i> conforms to that described for the <i>H</i>. <i>anselli</i> group: relatively narrow and amphoral in shape over its anterior portion, with post-orbital shelving weakly expressed in full and old adults, its edges lacking supraorbital ridging or beading. When examining series of skulls arrayed side-by-side (Figs. 6, 7), examples of <i>H</i>. <i>anselli</i> exhibit the longest, more attenuate rostrum, those of <i>H</i>. <i>arcimontensis</i> the shortest and most truncate, and those of <i>H</i>. <i>heinrichorum</i> appear intermediate in rostral length and shape. These macroscopic impressions find some statistical precision in the sample statistics (Table 6), variable loadings of the ordinations performed (Tables 1, 2, 5), and/or one-way ANOVAs (Table 4).</p> <p> Specimens of <i>H</i>. <i>heinrichorum</i> dentally resemble those of <i>H</i>. <i>anselli</i> and <i>H</i>. <i>arcimontensis</i> in the slight curvature of the upper incisors (nearly orthodont or weakly opisthodont), molar proportions, and cusp development. Pigmentation of the enamel face of the upper incisors in <i>H</i>. <i>heinrichorum</i> is a more saturated, medium orange compared with pale yellow-orange in <i>H</i>. <i>anselli</i> and <i>H</i>. <i>arcimontensis</i>; the tone is drab in all three.</p> <p> <b>Ecological notes.</b> Other species of the <i>Hylomyscus anselli</i> group are known to be closely associated with Afromontane forest, typically found within an elevational belt of 1000–2500 m (Carleton & Stanley, 2005; Carleton <i>et al.</i>, 2006; Demos <i>et al</i>., 2014b). The habitat information recorded on the skin tag of all <i>Hylomyscus</i> specimens collected at Mt Moco—“Evergreen wood. – High mountain region”—fits this ecological and topographical setting. Also, a photograph, taken by some member of Heinrich’s field team and labeled only Mt Moco, captures a substantial stand of closed-canopy, high forest in the vicinity of a campsite that we believe to represent Heinrich’s “High mountain” collecting locality (Fig. 8).</p> <p> Mills <i>et al.</i> (2011) documented the condition of Afromontane forest on Mt Moco as part of their ongoing studies of the endangered Swierstra’s Francolin (<i>Francolinus swierstrai</i> Roberts), a partridge-like bird endemic to Angola. High forest persists as small patches, the largest about 25 hectares, restricted to narrow ravines and steep valleys in the remotest parts of the mountain; these isolated fragments are distributed over an elevation of 2000 to 2400 m, a range that falls within the 1400 mm annual rainfall isohyet. Characteristic genera include the Gondwanan conifer <i>Podocarpus</i> along with other evergreen, flowering trees and shrubs (species of <i>Apodytes</i>, <i>Ficus</i>, <i>Halleria</i>, <i>Ilex</i>, <i>Olea</i>, <i>Pittosporum</i>, <i>Polyscias</i>, and <i>Syzygium</i> — Huntley & Matos, 1994; Mills <i>et al.</i>, 2011). Canopy height tends to be irregular, conforming to the steep slopes and rugged valleys that retain forest coverage. Montane grasslands, both natural and anthropogenic, and Miombo woodlands, dominated by <i>Brachystegia</i>, <i>Isoberlinia</i>, and <i>Julbernardia</i>, sprawl in between the high-forest patches; the latter woodlands, a relatively mesic savanna association (Zambezian Woodland Biotic Zone), cover most of the mountain. Presumably, tracts of Afromontane forest were more extensive when Heinrich visited Mt Moco in 1954.</p> <p> Most skin tags of <i>H</i>. <i>heinrichorum</i> from Mt Soque indicate their capture “Along mountain brook through tall grass. – Below mt. top.” Whether remnant Afromontane forest existed in proximity to Heinrich’s trap line is indeterminate from this scant description. When Mills canvassed Mt Soque for Swierstra’s Francolin in 2005, he (Mills <i>et al.</i>, 2011: 6) recorded that Afromontane forest no longer existed, but a few pairs of the endangered francolin were discovered in “dense herbaceous and shrubby growth in gullies and around the mountain summit [peak at 2165 m].”</p> <p> Other rodents collected with <i>Hylomyscus heinrichorum</i> over the same range of dates at both Mt Soque (24–28 Aug 1954) and Mt Moco (5–10 Oct 1954) include <i>Funisciurus congicus</i> Kuhl, <i>Graphiurus murinus</i> Desmarest, <i>Dendromus nyikae</i> Wroughton, <i>Grammomys dolichurus</i> Smuts, <i>Lophuromys angolensis</i> Verheyen, Dierckx, & Huselmans, <i>Myomyscus angolensis</i> Bocage, <i>Oenomys hypoxanthus</i> Pucheran, and <i>Pelomys campanae</i> Huet. Examples of <i>Aethomys namaquensis</i> A. Smith, <i>Graphiurus rupicola</i> Thomas & Hinton, <i>Mus triton</i> Thomas, <i>Otomys cuanzensis</i> Hill & Carter, and <i>Cryptomys mechowi</i> Peters were captured in sympatry with <i>H</i>. <i>heinrichorum</i> only at Mt Soque, but not Mt Moco; specimens of <i>Mus minutoides</i> Smith, <i>Cryptomys hottentotus</i> Lesson, and <i>Thryonomys gregorianus</i> Thomas were also obtained at Mt Moco, but not at Mt Soque. Certain species in some of these genera have been documented in moist forest at high elevations (e.g., <i>Graphiurus</i>, <i>Dendromus</i>, <i>Grammomys</i>, <i>Lophuromys</i> — Stanley <i>et al.</i>, 1998); still more of them are commonly associated with non-forest habitatsgrasslands, open woodlands, marshes and riverine vegetation, thickets and forest edges—environments that are also represented on Mt Moco and were around Heinrich’s campsite at the time of their survey (Fig. 8).</p> <p> At this stage of understanding, <i>Hylomyscus heinrichorum</i> may be reasonably characterized as endemic to Afromontane forest based on the habitat recorded for the Mt Moco series and on the known affinity of its speciesgroup relatives for highland forest. However, without knowing the exact placement of Heinrich’s trap line and traps, its strict ecological reliance upon this biome must remain inferential pending renewed field surveys. Fresh autecological study is obviously in order.</p> <p> <b>Remarks.</b> To our knowledge, specimens of <i>Hylomyscus heinrichorum</i> have not been collected since the 1954 Heinrich expedition. Until new field assessments are conducted, the conservation status of <i>H</i>. <i>heinrichorum</i> is plausibly considered Near Threatened, if not Vulnerable, in view of the continuing decline in extent and quality of Afromontane forest in Angola (Huntley & Matos, 1994; Mills <i>et al</i>., 2011). Unlike the Endangered classification of Swiestra’s Francolin (IUCN Red List, accessed Jul 2014), a comestible, partridge-sized bird subjected to hunting pressure compounded by disappearance of its preferred habitat, populations of a small murid rodent like <i>H</i>. <i>heinrichorum</i> should remain resilient to habitat loss so long as even minimal forest cover, primary or secondary, persists. The recent documentation of substantial tracts of Afromontane forest in the Namba Mts (Mills <i>et al</i>., 2013), situated in southern Cuanza Sul Province about 80 km northwest of Mt Moco, augurs that ample populations of <i>H</i>. <i>heinrichorum</i> still exist.</p> <p> <b>Etymology.</b> Our specific epithet honors both Gerd Hermann Heinrich (1896–1984) and Hildegarde Maria Buruvna (1917–2012), husband and wife (Fig. 9), to belatedly acknowledge their important field work in Africa conducted in the middle 1900s. Notwithstanding the enduring scientific relevance of their bird and mammal collections, these museum expeditions—to Angola (1953–1955, 1957–1958), Tanzania (1961–1963), and South Africa (1963)—unfolded as a means to an end, that end being to afford Heinrich ye
Design and Application of a Novel Optical Methane Flow Sensor to Quantify Methane Vent Sources at Upstream Oil and Gas Sites
No full textThis thesis first describes the development and characterization of an optical methane mass flux sensor, called the VentX, which was designed for use in hazardous locations such as upstream oil and gas facilities for the continuous quantification of methane emissions from point sources. Two configurations were initially described, with directly irradiated photodetectors ultimately favoured over a fully fiber-coupled version. In both configurations a methane volume fraction-dependent velocity measurement error was observed. Following component-by-component investigations of sources of optical interference, a second prototype was then designed and tested that greatly reduced this velocity measurement error, achieving a methane mass flow rate uncertainty of ±0.40 kg/h at 95% confidence and temperature induced measurement drift of <0.015 m/s/K. The VentX was then used to measure casing gas vent rates at eleven Cold Heavy Oil Production with Sand (CHOPS) wells in Saskatchewan, Canada, in conjunction with a larger aerial study of 962 sites using Bridger Photonics’ Gas Mapping LiDAR (GML). The time-resolved VentX measurements demonstrated that the discrete GML measurements could reproduce mean venting rates, despite observed temporal variability. Venting from CHOPS sites in this region was shown to be grossly underreported, with approximately 60% of the measured methane originating from wells that appeared to exceed regulated venting limits. However, preliminary economic analysis suggested that 97% of these emissions could be mitigated using readily available combustor technology with payback periods <2 years when costing methane emissions based on current carbon pricing. Finally, the VentX meter was deployed at eight oil wells in Alberta, Canada to measure unsteady venting from production storage tanks, a second key oil and gas sector source. Variable and intermittent venting was documented at multiple sites, often in conjunction with varying methane fraction. Analysis revealed the limitations of using simple gas-to-oil ratios (GOR) to estimate storage tank venting and specific recommendations were made to improve the accuracy of emission measurement and reporting. Finally, statistical analyses showed that discrete measurements of individual storage tanks using so called snapshot technologies should be treated with caution, while providing guidelines for required sample sizes to accurately measure aggregate mean emission rates in larger-scale surveys
Plastic ingestion, retention, and transport in animals from the eastern Canadian Arctic
No full textPlastic and microplastic pollution has been recognized as a global concern. I aimed to assess the retention and transport of plastic pollution in the Canadian Arctic using two important animals from the Arctic ecosystem: seals and seabirds. First, I examined 142 seal stomachs from four communities in the eastern Canadian Arctic to identify whether seals are accumulating plastics in their stomachs. No evidence of accumulated plastic debris in seal stomachs was found, suggesting that seals in the eastern Canadian Arctic are likely not exposed to plastics during foraging. Second, the faecal precursors of northern fulmars (Fulmarus glacialis) and thick-billed murres (Uria lomvia) were examined to identify if these birds are excreting microplastics in their guano. Anthropogenic particles were found in both species, however, there was no relationship between the microplastic particles in the faecal precursors and plastic debris found in the stomachs of the same birds
Oecomys sydandersoni Carleton & Emmons & Musser 2009, new species
No full textOecomys sydandersoni, new species Figures 4, 5; tables 4, 6 Oecomys concolor (part): Musser and Carleton, 1993: 716; Anderson (1997: 389). * 5 P # 0.05; ** 5 P # 0.01; *** 5 P # 0.001. HOLOTYPE: Museo de Historia Natural Noel Kempff Mercado number 2679, an adult male prepared as round skin and skull; collected 30 July 1997 by Louise H. Emmons (original field number LHE 1415). External data recorded on the skin tag include: TOTL, 242 mm; TL, 124 mm; HFL, 23 mm; EL, 17 mm; WT, 45 g (see table 4 for craniodental measurements of the type). The animal was noted as having scrotal testes (11 X 7 mm) and was captured ‘‘in pampa brush on vines.’’ TYPE LOCALITY: Bolivia, Departamento de Santa Cruz, Provincia Velasco, El Refugio Huanchaca, 210 m; 14 ° 46 9 01 0 S /61 ° 02 9 02 0 W (field coordinates as given by the collector; GPS, map datum WGS84). On older maps, the locality now known as El Refugio Huanchaca appears only as Huanchaca, a biological station with a few buildings and an airstrip on private property but now partly within the park. The present owners of the estancia renamed it El Refugio, the place name that appears on specimen labels, but in 2004, they appended Huanchaca to their former designation of El Refugio. ‘‘El Refugio,’’ ‘‘Huanchaca,’’ and the combined form ‘‘El Refugio Huanchaca,’’ as applied in eastern Santa Cruz, are one and the same locality. DIAGNOSIS: A species of Oecomys (Sigmodontinae: Oryzomyini) characterized by a combination of medium size (HBL < 115– 135 mm, HFL < 23–25 mm, ONL < 29– 31 mm), relatively short tail (TL < 125– 140 mm), absolutely and relatively very wide incisive foramina, smaller molars (CLM < 4.4–4.7), presence of alisphenoid struts, and a derived carotid circulatory pattern (skull lacking squamosal-alisphenoid groove, sphenofrontal foramen, and posterolateral groove on the parapterygoid plate; posterior opening to the alisphenoid canal compressed; stapedial foramen absent; groove dorsally crossing the parapterygoid plate present). REFERRED SPECIMENS: BOLIVIA: Beni, Río Iténez, ca. 4 km above Costa Marques, 12 ° 29 9 S / 64 ° 15 9 W (AMNH 210023); Río Iténez, bank opposite Costa Marques, 12 ° 29 9 S / 64 ° 17 9 W (AMNH 209987); Bahía de los Casara, 20 km W Larangiera, Río Iténez, 13 ° 13 9 S / 62 ° 21 9 W (AMNH 210012). Santa Cruz, El Refugio, 210 m, 14 ° 46 9 01 0 S / 61 ° 02 9 02 0 W (USNM 588189, 588190; MNK- LHE 1412); 3 km NE El Refugio, Pampa, 14 ° 44 9 35 0 S /61 ° 01 9 20 0 W (MNK 3763, 3765, 3766, 3772, 3776–3778, 3782, 3788; USNM 584554–584663. DISTRIBUTION: Extreme eastern Bolivia (fig. 6). DESCRIPTION: Size of O. sydandersoni medium for the genus (e.g., larger than O. bicolor or O. auyantepui, smaller than O. mamorae or O. roberti —see fig. 4 and tables 4, 6 herein; and table 28 in Voss et al. 2001). Fur texture soft and fine; pelage moderately short, hairs about 5–7 mm long over the middle rump. Dorsal pelage ochraceous brown to pale tawny, finely intermixed with black over the middle dorsum and generally bright in tone; more grayish showing on head and flanks. General appearance of ventral pelage a pale to medium gray; hairs of chin, throat, and around inguinum entirely white to base in most specimens; hairs over chest and abdomen gray basally with long white tips. Dorsalventral pelage transition moderately defined, without ochraceous lateral line. Eyelids black but no eye-ring per se. Pinnae dark brown to brownish gray, thinly covered with short, ochraceous hairs. Upper surfaces of metatarsals and phalanges covered with whitish to pale ochraceous hairs, general appearance of hind foot a dirty white. Hind-foot conformation typical of the genus—relatively short and broad; bright white ungual tufts developed on digits II–V; digit V nearly as long as digits II– IV; plantar surface smooth with six large, closely positioned pads, the thenar and hypothenar well developed. Tail slightly longer than head and body; color medium to dark brown all around, slightly paler underneath at the base; caudal hairs short, scarcely visible to the unaided eye and not obscuring fine scale pattern; rudimentary pencil expressed at tip of tail. * 5 P # 0.05; ** 5 P # 0.01; *** 5 P # 0.001 Skull ruggedly built for its size, with short rostrum and relatively broad interorbit. Supraorbital shelves present, converging forward such that the least interorbital width is projected relatively anteriad between the orbits; free ledge over orbit heavy, approaching an incipient bead; low temporal ridging continues across the lateral parietals in older individuals. Zygomatic arches noticeably expanded at rear and strongly tapered rostrally; dorsal notch of zygomatic plate well defined, plate relatively broad. Posterolateral wall of braincase consistently perforated by small subsquamosal fenestra, shape slitlike or narrowly ovoid, about one-half the area of the postglenoid foramen; tegmen tympani reduced, touching the ventrolateral squamosal in some specimens but not overlapping it. Alisphenoid struts typically present, delineating a discrete foramen ovale accessorius and masticatory-buccinator foramen. Incisive foramina medium long but very broad, posteriorly terminating just anterior to the anterior root of the M1s; foramina widest toward the rear, posterior ends obtuse (blunt) and anterior ends acute, in some specimens the transition from wide to narrow abrupt. Hard palate basically flat, the palatal gutters shallow and barely evident to the naked eye; palate extends slightly beyond posterior margin of M3s; posterior palatine foramen exits about the middle of M2. Posterolateral-palatal pits well expressed, usually as one large pit with interior perforations plus one or two supernumerary foramina emerging immediately anterior. Mesopterygoid fossa broad and wide, its anterior margin bluntly U-shaped, lacking medial spine or blunt protrusion; roof of mesopterygoid fossa entirely osseous, not perforated by sphenopalatine vacuities. Ectotympanic bulla small, revealing much of the medial periotic, which contributes (as viewed ventrally) to the rear border of the carotid canal. Upper incisors opisthodont, enamel colored dull yellow-orange to a moderately saturated orange. Molars brachyodont and cuspidate as per the genus, uppers with three roots and lowers with two. M1 with well-formed anteroloph and M1–2 with mesoloph. Anterocone broad, anterolingual and anterolabial conules joined medially, not cleft by anteromedian fold; conules distinct in juveniles and young adults, but definition lost with wear. Mesolophid consistently present on m1–2; ectolophid variably developed, absent in some individuals. In one-way ANOVAs, none of the 18 craniodental variables demonstrated significant secondary sexual dimorphism (14 ³, 11 ♀; F 5 0.025 –3.391; P 5 0.975 –0.054). MORPHOLOGICAL COMPARISONS: Specimens of O. sydandersoni can be separated from most species of Oecomys based solely on the osseous character-state differences associated with the complete versus derived carotid arterial patterns (see above descriptions under Results). Other features must be consulted for discrimination from O. concolor and O. mamorae, the other species so far known to possess a derived carotid plan. We encountered slight variation in the expression of the derived carotid pattern among the entire series examined of these three species. In some individuals of O. mamorae (UMMZ 125456, 133793; UCONN 19187–19189) and O. sydandersoni (USNM 584554, 584558), but none of O. concolor, a vestige of a squamosal-alisphenoid groove can be detected on the inner wall of the braincase, but no sphenofrontal foramen is present; in these cases, the stapedial foramen persists as a minute pinhole, a tiny aperture in comparison with the full foramen observed in those Oecomys with a complete carotid circulatory pattern. Notwithstanding these individual exceptions, a large majority of specimens of O. mamorae and O. sydandersoni display the typical derived condition as described under Results. Such occasional atavistic reminders of the ancestral character state are to be expected in view of the evolutionary polarity established for carotid arterial patterns in muroid rodents (Bugge, 1970; Carleton, 1980; Voss, 1988; Weksler, 2006). As currently documented, a wide geographic gap separates the ranges of O. sydandersoni, in eastern Bolivia, and O. concolor, in southern Venezuela and northwestern Brazil (fig. 6). Examples of O. sydandersoni and O. mamorae, however, have been collected in close proximity in eastern Bolivia (fig. 6), and their identification may pose greater difficulty. Individuals of O. sydandersoni are smaller than those of O. concolor and O. mamorae, a contrast readily appreciated from variable loadings derived for the first principal component (fig. 2; table 2) or simple inspection of univariate means (table 4). Length of tail is absolutely and relatively shorter in specimens of O. sydandersoni (TL < 106% of HBL) compared with those of O. concolor (TL < 118% of HBL) and O. mamorae (TL < 113% of HBL). The dorsal pelage of O. sydandersoni is only slightly longer (5–7 mm), as measured on the rump, than that possessed by the shortfurred O. concolor (4–5 mm); dorsal pelage of O. mamorae is the longest of the three (7– 9 mm). Oecomys sydandersoni and O. concolor resemble one another in dorsal pelage coloration, albeit somewhat darker in tone in O. concolor. More grayish hues are evident over the head and flanks of O. sydandersoni, compared with a dominant fulvous-brown color in O. concolor. The dorsal pelage of O. mamorae shows the most gray, ranging from gray to grayish buff, and a buffy to bright ochraceous lateral strip demarcates the upper- and underparts in most specimens. The ventrum of O. sydandersoni appears gray, in contrast to dull white, from the chin to inguinum, as observed in most specimens of O. concolor and O. mamorae; some individuals of the latter two exhibit encroachment of basal gray hairs over the middle abdomen. The dorsal-ventral pelage contrast thus tends to be more sharply marked in O. concolor and O. mamorae. Besides cranial size (table 4), subtle but consistent differences in shape provide other reliable means to distinguish the three species (fig. 4). The condition of the supraorbital shelf and interorbital region is similar in O. sydandersoni and O. concolor, and both differ in the same ways from O. mamorae. In the latter species, the interorbit is narrower, and the free edge of the shelf is thinner, less prominent, and confined to the rear of the orbit. Hence, the least interorbital constriction of O. mamorae occurs about the middle of orbits (more amphoral), whereas the more prominent shelves in O. sydandersoni and O. concolor extend farther forward such that the least interorbital width appears more anteriad (more cuneate). The zygomatic plate is broadest in specimens of O. mamorae (table 4), and its dorsal notch appears more deeply excised compared with O. sydandersoni and O. concolor. Posterior termination of the incisive foramina is approximately the same in all three species, reaching the level of the anterior root of the first molars, but their typical shape differs notably among them: anterior and posterior ends acute in O. concolor, gently curving along the lateral edges and widest near their middle; foramina also widest at the middle in O. mamorae, but outward bowing less pronounced, the foramina appearing more nearly parallel sided and narrower; the foramina in O. sydandersoni are noticeably widest toward the rear, the posterior ends obtuse (blunt) and anterior ends acute. The bony palate noticeably projects beyond the posteri- or margins of the M3s in examples of O. sydandersoni and O. concolor, as in most oryzomyines, but the rear termination of the hard palate in O. mamorae is more or less even with the caudal margin of the M3s. Perhaps in correlation with their longer palates, the posterolateral palatal pits are well developed in the former two—typically as one large pit with interior perforations plus one or two supernumerary foramina emerging immediately anterior—whereas pit construction in O. mamorae is simpler, usually consisting of a single opening. Most of these size and shape contrasts figure prominently in the phenetic patterns derived from the various multivariate analyses and are reflected in the signs and strengths of variable loadings (figs. 2, 3; tables 2, 3; see Results). The occurrence of the alisphenoid strut, the slim bony column that delineates foramina at the base of the alisphenoid, varies within and among species of oryzomyines (Carleton and Musser, 1989; Voss and Carleton, 1993; Musser et al., 1998), including those of Oecomys (Weksler, 2006). Among the three species with a derived carotid pattern, we observed an alisphenoid strut in most specimens of O. concolor and O. sydandersoni but rarely in those of O. mamorae (table 5). In some individuals, the strut exists as a slender thread (which we counted as present) or is found on only one side of the skull. Used in conjunction with other measurements and qualitative traits, the presence/absence of the alisphenoid strut is useful for identifying specimens of O. mamorae and O. sydandersoni where their ranges approach one another. Three other species of Oecomys — O. bicolor, O. roberti, and O. trinitatis —have been documented to date in the Parque Nacional Noel Kempff Mercado (Emmons et al., 2006), albeit not in syntopy with O. sydandersoni (see below). The three can be easily differentiated from the new species by a combination of size and qualitative features of the skin and skull. Foremost, they all possess a complete carotid circulatory plan, in contrast to the derived pattern exhibited by specimens of O. sydandersoni. Oecomys bicolor is a diminutive species compared with O. sydandersoni and averages appreciably smaller in every external and cranial dimension quantified (table 6). The dorsal pelage of O. bicolor is shorter and closely cropped, 3–4 mm long at rump (pelage longer in O. sydandersoni, 5–7 mm), and its ventral pelage is uniformly bright white (mostly gray in O. sydandersoni). Furthermore, O. bicolor possesses a relatively shorter tail, only about as long as the head and body (longer, absolutely and relative to the head and body in O. sydandersoni), and the caudal hairs are longer, forming a more distinct terminal pencil (pencil indistinct in O. sydandersoni). Specimens of O. sydandersoni approach those of O. roberti and O. trinitatis in size but average smaller in most dimensions (table 6). Noteworthy are the longer, broader rostra in examples of O. roberti and O. trinitatis (truncate in O. sydandersoni), heavier supraorbital shelf with a distinct bead (incipient bead in O. sydandersoni), and longer bony palate that extends forward beyond the M1s (shorter palate terminates approximately equal with the anterior border of the M1s in O. sydandersoni). The expansive bony palate in these two species inversely correlates with their shorter incisive foramina, which end anterior to the level of the front root of the M1s. Their incisive foramina are also shaped differently, lacking the posterior widening and blunt ends characteristic of O. sydandersoni. The distinctive dorsal pelage of O. trinitatis — deep (8–10 mm), palpably luxuriant, and lustrous—at once separates it from examples of O. sydandersoni, as well as those of O. bicolor and O. roberti. Moreover, the ventrum of O. trinitatis is darker gray, the hairs often tipped with buff, its caudal hairs are longer, and, as in O. bicolor, the tail possesses a more noticeable terminal pencil compared with O. sydandersoni. The degree of caudal hairiness and pencil development are comparable in O. sydandersoni and O. roberti, but the tail of the latter is longer and its dorsal pelage is shorter (3–5 mm in contrast to 5–7 mm in O. sydandersoni). ECOLOGICAL NOTES: At the type locality of El Refugio Huanchaca, Emmons and associates captured 22 of 23 individuals of O. sydandersoni in open savanna characterized by a mosaic of long grasses and smaller clumps of woody vegetation (fig. 7). The grassland is deeply flooded by standing water (ca. 0.5 m) for 1–4 months during the wet season (December–March), and the woody vegetation grows on elevated mounds or hummocks originally formed around termite nests within the grassland. Because cattle no longer graze within the park and the wet grasslands tend to suppress fires, the woody vegetation on these hummocks is dense and well developed, with tall trees in the center and many woody vines. Examples of O. sydandersoni were uniformly collected within the large forested hummocks in snap traps or Sherman live traps placed above ground, up to 2.5 m high on vines, trunks, or branches within arm’s reach. A single individual was captured in closed riverine forest, taken at 1.5 m height on a vine in a shrub along the river’s edge. Most O. sydandersoni were captured in 1998, when 21 individuals were obtained in the woody hummocks during 1430 trap-nights of collecting effort, along with the forest species Hylaeamys acritus (13), Proechimys longicaudatus (16), and Marmosa murina (1). Four other oryzomyine species (Cerradomys maracajuensis, Holochilus sciureus, Oligoryzomys microtis, Pseudoryzomys simplex) and one akodont (Necromys lenguarum) were captured in the surrounding grassland matrix. We find it noteworthy that O. sydandersoni was the only arboreal cricetid rodent caught in these woodland islands, that it was the most abundant rodent in that habitat, and that its occurrence was nearly confined to that patchy habitat. Emmons and Bolivian colleagues have tallied over 30,000 trap-nights of survey in nearby habitats, including over 11,000 trapnights in contiguous semideciduous forests, and captured only a single O. sydandersoni. They have failed to secure the species in dryground savanna woodland that lacks dense tree clumps (Cerrado proper), or in sporadically flooded ‘‘termite’’ savannas that contain many small shrubs and only small wooded hummocks (, 10 m across). Three other species of Oecomys — O. bicolor, O. roberti, and O. trinitatus —were obtained in the adjacent, continuous-canopied, semideciduous forests. These observations portray O. sydandersoni as a fairly narrow habitat specialist with a geographically restricted distribution. Such characteristics would perhaps account for its heretofore escape from the eyes of taxonomists and present rarity in collections. As its distribution is so far known, O. sydandersoni joins other species with limited geographic ranges that have been recently documented from extreme eastern Bolivia, in the Parque Nacional Noel Kempff Mercado or its vicinity. These include the forest oryzomyine Hylaeamys acritus (Emmons and Patton, 2005), the akodonts Juscelinomys huanchacae and J. guaporensis (Emmons, 1999), and the rare marsupial Cryptonanus unduaviensis (Voss et al., 2005), which has been collected in the grassland matrix that surrounds the woodland patches inhabited by O. sydandersoni (Emmons et al., 2006). Whether the restricted ranges apparent for this group of species reflect a common historical response to the interplay of ecological change and biogeographic events in eastern Bolivia invites further research (Emmons et al., 2006). REMARKS: The condition of the basal carotid arterial circulation in O. sydandersoni, O. concolor, and O. mamorae offers a morphological synapomorphy that suggests their closer relationship relative to other species of Oecomys. Such a provisional kinship hypothesis is encouraged by independent and combined analyses of IRBP sequences and morphological traits among oryzomyines (Weksler, 2003, 2006), in which the sistergroup pairing of O. concolor and O. mamorae was consistently and strongly supported among the five exemplars of Oecomys studied (other species included O. bicolor, O. catherinae, and O. trinitatis). The molecular voucher that Weksler called O. mamorae (MVZ 155005 from Peru, Amazonas, Río Cenepa), however, proves to be an example of O. roberti (identified by GGM and reconfirmed by J.L. Patton), a species with a complete carotid circulatory pattern (table 1). Confidence in the sister-group relationship of O. concolor and O. mamorae is thus eroded based on Weksler’s data. Our foremost purpose in documenting the carotid pattern displayed by all Oecomys type specimens (table 1) was to constrain the differential diagnosis of the new species from Bolivia with respect to the most morphologically similar species currently recognized (Musser and Carleton 2005). In addition to possession of the same carotid circulatory plan, the resemblance of O. concolor and O. sydandersoni is striking, as conveyed by the earlier tentative identification of the few known Bolivian specimens as O. concolor (Musser and Carleton, 1993). The fine series later obtained by Emmons allowed morphological and morphometric confirmation of the two as valid species and appreciation of their approximately equivalent level of differentiation from O. mamorae (fig. 3), the third species of Oecomys known to possess the apomorphic carotid condition. Whether the derived carotid arterial pattern constitutes a synapomorpy of these three species or evolved independently will require further molecular and morphological studies based on broader taxon sampling within the genus and among other oryzomyines. ETYMOLOGY: The first three examples of O. sydandersoni were collected by Sydney Anderson (fig. 8) and members of his field team in 1964 and 1965, along the Río Iténez in eastern Bolivia. As a fresh-faced assistant curator in 1963, he had revived the earlier natural history explorations in Bolivia undertaken for the American Museum of Natural History, notably those of Anthon
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