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Sagebrush voles of the monotypic genus

Lemmiscus are an endemic North American

lineage of arvicoline rodents with a modern

distribution that encompasses much of the

Basin and Range, Columbia Plateau, Wyoming

Basin, and northern Great Plains provinces

(Hall 1981). Fossil specimens of Lemmiscus

curtatus are widely reported from Late Pleis-

tocene and Holocene sites (FAUNMAP Work-

ing Group 1994, Bell and Mead 1998, Barnosky

and Bell 2003, Bell and Jass 2004). Fossil

localities span much of the modern geographic

range and include extralimital records just

beyond the margin of the present species

range (e.g., Burns 1991, Jass et al. 2002). The

vast majority of these fossils share a basic den-

tal morphology with the extant populations,

with a lower first molar (m1) characterized by

a posterior loop, 5 or occasionally 6 closed tri-

angles, and a simple anterior cap (Fig. 1). The

first and second triangles of the m1 of L. cur-

tatus are of approximately equal size, readily

distinguishing these molars from those of

species of Microtus, which have a smaller sec-

ond triangle and are often found in close geo-

graphic association with L. curtatus in both

Western North American Naturalist 79(2), © 2019, pp. 219–232

Dental variation in a collection of Lemmiscus curtatus

from the northern plains of southern Saskatchewan:

implications for morphological evolution

CHRISTOPHER J. BELL1,3, CHRISTOPHER N. JASS2,3, AND ROBERT W. BURROUGHS4,5,*

1Jackson School of Geosciences, The University of Texas at Austin, Austin, TX 78712

2Royal Alberta Museum, Edmonton, Alberta T5J 0G2, Canada

3Jackson Museum of Earth History, The University of Texas at Austin, Austin, TX 78712

4Committee on Evolutionary Biology, The University of Chicago, Chicago, IL 60637

5Integrative Research Center, Field Museum of Natural History, Chicago, IL 60605

ABSTRACT.—We provide the first documentation of morphological variation in the lower first molar (m1) of Lemmiscus

curtatus from southern Canada. A total of 370 specimens were obtained from owl pellets taken from 4 localities in southern

Saskatchewan. The 4 most common morphotypes are, in order of descending relative abundance, molars with 5 closed

triangles and a well-developed but widely open sixth triangle, molars with 5 closed triangles and a sixth triangle that is

pinched at the confluence of the anterior cap, molars with 5 closed triangles and incipient closure of the sixth triangle

from the anterior cap, and specimens with 6 closed triangles. As is true of other modern populations of L. curtatus, the

samples from Saskatchewan include no morphotypes with only 4 closed triangles. This collection is notable for the rela-

tively high proportion of specimens with pinched, incipient, or full closure of a sixth triangle on the m1, and it also

highlights the complex dynamics of dental evolution in arvicoline rodents.

RESUMEN.—Documentamos por primera vez la variación morfológica del primer molar inferior (m1) de Lemmiscus

curtatus procedente del sur de Canadá. Un total de 370 ejemplares fueron obtenidos de egagrópilas de búho proce-

dentes de cuatro localidades del sur de Saskatchewan. Los cuatro morfotipos más comunes en las muestras son, en

orden descendente de abundancia relativa, molares con cinco triángulos cerrados y un sexto triangulo bien desarrollado,

pero ampliamente abierto, molares con cinco triángulos cerrados y un sexto triangulo que presenta una constricción

a medida que se acerca a la confluencia con la porción anterior del diente, molares con cinco triángulos cerrados y un

sexto triangulo incipientemente cerrado, y molares con seis triángulos cerrados. Al igual que otras poblaciones actuales

de L. curtatus, las muestras de Saskatchewan no incluyen morfotipos que solamente tienen cuatro triángulos cerrados.

Esta colección de molares destaca por la proporción relativamente alta de ejemplares m1 que presentan un sexto triangulo

constreñido, incipientemente cerrado y cerrado y denota la dinámica compleja de la evolución dental en los roedores

arvicolinos.

*Corresponding author: rburroughs@uchicago.edu

219

RWB orcid.org/0000-0003-4384-3430

present-day and paleontological contexts. Older

fossil occurrences of Lemmiscus include many

specimens with an m1 morphology not encoun-

tered in the extant biota; these specimens have

only 4 closed triangles, with a well-developed

fifth triangle that is confluent with the anterior

cap (Fig. 1A). These older fossil records are from

San Antonio Mountain (SAM) Cave, New Mex-

ico (Rogers et al. 2000); Porcupine Cave, Col-

orado (Bell et al. 2004); Cathedral Cave, Nevada

(Jass and Bell 2011); and the Kennewick Road

Cut in Washington (Rensberger et al. 1984,

Rensberger and Barnosky 1993). The oldest of

these occurrences are from SAM Cave, with an

estimated age of approximately 840,000 years

(Rogers et al. 2000), and the lower stratigraphic

levels of the Pit sequence of Porcupine Cave,

Colorado, with an estimated age range between

800,000 and one million years old (Bell and

Barnosky 2000, Barnosky and Bell 2004). The

youngest of the older sites where 4-triangle

morphotypes are common is Cathedral Cave,

with a maximum age between 146.02 +

–2.584

and 153.7 +

–6.4 ka (Jass and Bell 2011).

220 WESTERN NORTH AMERICAN NATURALIST (2019), VOL. 79 NO. 2, PAGES 219–232

Fig. 1. Extinct (A) and extant (B–G) morphotypes of the m1 of Lemmiscus curtatus.A, L. curtatus with “typical”

4-closed-triangle morphotype (SNK-CNJ8); B, L. curtatus with 5 closed triangles (P17.13.39); C, L. curtatus with 5 closed

triangles (P17.13.103); D, L. curtatus with 5 closed triangles and a T6 that is pinched from the anterior cap (P17.13.183);

E, L. curtatus with 5 closed triangles and a T6 that exhibits incipient closure from the anterior cap (P17.13.136); F, L. cur-

tatus with 6 closed triangles (P17.13.210); G, L. curtatus with 4 closed triangles and confluent T5/T6 that together

exhibit incipient closure from the anterior cap (P17.13.370). T = Triangle. Scale bar = 1 mm. SNK-CNJ8 is a temporary

laboratory number assigned by CNJ. The specimen is presented here to illustrate Lemmiscus with 4 closed triangles.

Four-triangle morphotypes from radioiso-

topically dated Late Pleistocene deposits were

first reported from Snake Creek Burial Cave,

Nevada (Bell and Mead 1998), and subse-

quently from Pleistocene and early Holocene

sediments in Kokoweef Cave and Antelope

Cave, California (Bell and Jass 2004). The

absence of 4-triangle morphotypes in the

extant populations suggests that the “extinc-

tion” of the morphotype occurred within the

last 9000 years. The long fossil record of the

species presents an intriguing perspective on

dental evolution, suggesting a polymorphic

condition of mixed 4- and 5-triangle morpho-

types within early populations that then per-

sisted for over 800,000 years (Barnosky and

Bell 2003), with the 4-triangle morphotype

disappearing prior to the sampling of modern

populations. The pattern is complemented by

what appears to be increasing relative abun-

dance of 6-triangle morphotypes from the

Late Pleistocene through the modern (Rens-

berger et al. 1984, Barnosky and Bell 2003,

Bell and Jass 2004). The possibility that cli-

matic change, particularly warming, may be

at least partly responsible for initiating evolu-

tionary change in this dental pattern was

explored by Barnosky and Bell (2003).

Detailed and meticulously documented pat-

terns of variation from within extant popula-

tions are essential if we are to explore and

understand fully the driving mechanisms that

shaped tooth morphology across the spatio -

temporal distribution of L. curtatus. Detailed

data on dental variation are essential for docu-

menting the morphological “space” occupied

by various populations and for facilitating the

reliable identification and taxonomic treat-

ment of fossil specimens. This is especially

true for monotypic extant lineages like Lem-

miscus that have a rich fossil record and dis-

play shifting morphological characteristics

through time.

The northernmost extant populations of

L. curtatus extend into southern Alberta and

Saskatchewan (Hall 1981; Fig. 2), and we

recently obtained a reasonably large sample of

teeth and jaws of L. curtatus from owl pellets

collected in southern Saskatchewan, which is

near the extreme northeastern distribution of

the species. Patterns of dental morphology are

not well documented for these populations;

only 3 specimens from southern Canada (MVZ

54471–54473) were included as part of the

most robust previous analysis of dental varia-

tion in Lemmiscus (Barnosky and Bell 2003).

Here, we document the morphological pattern

of the m1s from that sample. We also discuss

the significance of the collection for our under -

standing of the spatial distribution of morpho-

types at higher latitudes, and for broadening

the contextual fabric through which hypothe-

ses of dental evolution are shaped.

METHODS

We examined 370 m1s extracted from owl

pellets collected from 4 localities in south-

western Saskatchewan (Fig. 2, Table 1). The

pellets from all localities were derived from

roosts of Great-horned Owls (Bubo virgini-

anus) in association with abandoned buildings,

and in one instance an owl was present at the

roost (T. Schowalter personal communication

2017). The pellet assemblages from each local-

ity are likely time-averaged to some degree,

but given that pellets will break down even in

protected environments (e.g., an abandoned

building), we infer that the pellets represent a

modern assemblage, reflective of populations

of L. curtatus occurring near the localities

today. All specimens reported here are housed

in the Quaternary Palaeontology collection at

the Royal Alberta Museum in Edmonton under

specimen numbers P17.13.1–P17.13.370.

We examined all lower first molars under

binocular microscope and scored each as

belonging to 1 of 5 morphotypes. The morpho-

types correspond to those used by Barnosky

and Bell (2003) and allowed us to capture data

relevant for exploring transitional morphologi-

cal conditions between morphotypes with 5

and 6 closed triangles. A triangle was consid-

ered open if the dentine field between it and

the next anterior triangle was more than 3

enamel-band widths across. We scored a speci-

men as having a “pinched” condition if the

dentine field between triangles was more than

2, but less than 3 enamel-band widths across.

We scored a specimen as having “incipient

closure” if the dentine field was between 1 and

2 enamel-band widths across. A triangle was

scored as closed if the dentine field was less

than 1 enamel-band width across. The 4 most

common morphotypes are 5T (= 5 closed

triangles), 5T with T6 pinched (= a specimen

with 5 closed triangles and a pinched con -

dition between the sixth triangle and the

BELL ET AL.♦TOOTH MORPHOLOGY OF LEMMISCUS FROM SASKATCHEWAN 221

dentine field of the anterior cap), 5T with

incipient closure of T6 (= 5 closed triangles,

with incipient closure between the sixth trian-

gle and the anterior cap), and 6T (= 6 closed

triangles). A fifth morphotpye was represented

by a single unique specimen (P17.13.370)

described below. All morphotypes are illus-

trated and labeled in Fig. 1. We compiled

summary statistics for the morphotypes from

each locality, based on both number of identi-

fied specimens (NISP) and minimum number

of individuals (MNI). Calculations of relative

abundance based on MNI assume that the

lower dentition retains the same tooth mor-

phology in both sides of the jaw. If the m1s of

an individual had distinct morphologies (i.e., if

there was left-right asymmetry), our calcula-

tion of MNI presented below may overesti-

mate the number of individuals represented in

the sample and may be impacting our calcula-

tions of relative abundance based on MNI. A

complete list of specimen numbers and mor-

photype scores is provided in Appendix 1.

Previous work (e.g., Burroughs et al. 2015)

quantifying shape variation as a reflection of

ontogeny did not identify significant occlusal

pattern shifts in L. curtatus that are a result of

ontogenetic wear. Furthermore, comparisons

of males and females by author RWB indicate

that no substantial sexual dimorphism occurs

within the species. As a result, we conclude

222 WESTERN NORTH AMERICAN NATURALIST (2019), VOL. 79 NO. 2, PAGES 219–232

Fig. 2. Map of collecting localities in context of the fossil and extant distributions of L emmiscus curtatus. Shaded area

shows an approximation of the extant distribution of L. curtatus in North America (following Hall 1981). Dashed ellipse

shows an approximation of the fossil distribution of L. curtatus across the Quaternary. Inset: Collecting localities for owl

pellet remains of L. curtatus reported here. Numbers correspond to localities as described in the text and in Table 1

(e.g., 1 = Locality 1).

TABLE 1. Summary of geographic locations and associ-

ated sample size (n) for the m1s of Lemmiscus curtatus.

Locality Latitude Longitude n

1 49.20370 −107.82745 221

2 49.08703 −108.69135 34

3 49.18177 −109.28230 35

4 49.19337 −108.13618 79

that neither ontogeny nor sexual dimorphism

are contributing significantly to patterns of vari-

ation in this or other samples of L. curtatus.

RESULTS

Table 2 and Fig. 3 provide summary

descriptive statistics of the morphotypes pre-

served in the sample (n= 369). One specimen

that we report here (P17.13.370) was excluded

from the summary statistics because it repre-

sents a unique morphotype, having 4 closed

triangles and confluent T5/T6 that exhibits

incipient closure from the anterior cap (Fig.

1G). This morphology was noted in low num-

bers (n= 8) in the fossil assemblage at

Kokoweef Cave (Bell and Jass 2004), and find-

ing it in the modern biota was unexpected.

Although treated as a 4-triangle form previ-

ously (Bell and Jass 2004), the morphology is

not comparable to most fossil specimens

described as having a 4-triangle morphotype

because the T6 is strongly developed and

nearly closed from the anterior cap. In the

sense of previous evolutionary hypotheses,

under which 4-triangle forms give way to

modern populations characterized by 5 or 6

closed triangles, we now consider these speci-

mens to be anomalous morphologies of those

5- or 6-triangle forms. Therefore, no 4-triangle

forms comparable to previously described fos-

sil populations are present in our sample, as

would be predicted given our understanding

of the distribution of that morphology through

time (Bell and Jass 2004). Five-triangle forms

are the most common morphotype, followed

by intermediate forms (i.e., 5-triangles with

either a pinched T6 or a T6 with incipient clo-

sure from the cap). Six-triangle forms are less

abundant but occur in each of the 4 sampled

localities, with a relative abundance between

approximately 6% and 10%.

DISCUSSION

The recovery of a large sample of m1s

exhibiting considerable variation in morphol-

ogy is reflective of the morphological variation

occurring in extant populations of L. curtatus

in portions of southwestern Saskatchewan.

Remains from owl pellets are good proxies for

understanding the richness and diversity of

local environments (e.g., Barnosky 1994, Terry

2008, 2010, Heisler et al. 2013, 2016), and we

infer that the variation observed in our sam-

ples represents a proxy for the distribution of

morphotypes within populations of L. curtatus

in southern Saskatchewan. The remains come

from sheltered environments in or near aban-

doned buildings, indicating that they were

BELL ET AL.♦TOOTH MORPHOLOGY OF LEMMISCUS FROM SASKATCHEWAN 223

TABLE 2. Summary descriptive statistics for tooth morphotypes of Lemmiscus curtatus from Saskatchewan, Canada.

Morphology Right (n) Left (n) NISP R.A. (NISP) MNI R.A. (MNI)

Locality 1

5T 54 51 105 47.5 54 47.4

5T, T6 pinched 32 33 65 29.4 33 28.9

5T, T6 incipient closure 18 16 34 15.4 18 15.8

6T 8 9 17 7.7 9 7.9

TOTAL 112 109 221 100 114 100

Locality 2

5T 7 5 12 35.3 7 35

5T, T6 pinched 7 6 13 38.2 7 35

5T, T6 incipient closure 4 3 7 20.6 4 20

6T 0 2 2 5.9 2 10

TOTAL 18 16 34 100 20 100

Locality 3

5T 10 15 25 71.4 15 65.2

5T, T6 pinched 4 1 5 14.3 4 17.4

5T, T6 incipient closure 2 1 3 8.6 2 8.7

6T 0 2 2 5.7 2 8.7

TOTAL 16 19 35 100 23 100

Locality 4

5T 21 22 43 54.4 22 52.4

5T, T6 pinched 14 10 24 30.4 14 33.3

5T, T6 incipient closure 3 3 6 7.6 3 7.1

6T 3 3 6 7.6 3 7.1

TOTAL 41 38 79 100 42 99.9

deposited within a relatively recent timeframe.

Owl pellets are subject to breakdown from a

number of weathering processes (e.g., tram-

pling, decay, and insect activity; Andrews

1990), but in the absence of mechanical break-

down we infer that the remains are not signifi-

cantly time-averaged, certainly not to the

degree that a fossil deposit would be.

One of the more striking features of the

collection of molars from Saskatchewan is

the high proportion of specimens with some

degree of expression of a sixth triangle. Previ-

ous evaluation of a large sample of modern

L. curtatus from across the present-day distri-

bution indicated that approximately 75% of

individuals had a 5-triangle morphotype, with

the remaining 25% showing some expression

of the sixth triangle (Barnosky and Bell 2003).

In our samples, percentages of specimens

with some expression of a sixth triangle (i.e.,

specimens with a sixth triangle that exhibits

pinching, incipient closure, or complete clo-

sure) were 52.5% (Locality 1), 64.7% (Locality

2), 28.6% (Locality 3), and 55.6% (Locality 4).

Therefore, these collections represent popula-

tions with surprisingly complex molars.

Our data do not directly address the

hypothesis that warming temperatures may

have triggered an evolutionary response toward

increased molar complexity in L. curtatus dur-

ing the middle Pleistocene (Barnosky and Bell

2003). However, our data are especially intrigu-

ing because the collections were taken near

the northeastern periphery of the geographic

range for the species, are at relatively high lati-

tude, and are from relatively cold climatic

conditions. We find it interesting that such

complexity characterizes populations living at

relatively cooler latitudes than populations

that are characterized by 5-triangle morpho-

types farther to the south (Barnosky and Bell

2003). This suggests that although warming

might have initiated genetic or developmental

mechanisms leading to increased complexity,

warmer temperatures may be insufficient to

explain the spatial distribution of populations

with high relative abundance of complex mor-

photypes in the extant biota. We now know

that populations in northern Nevada (Bell and

Jass 2004) and southern Saskatchewan (this

paper) show such complexity. Evaluation of

additional samples is necessary to determine

the full measure of populations that are char-

acterized by more complex m1s (i.e., relatively

high abundance of morphotypes with some

expression of a sixth triangle). Other popula-

tions from across the range of the species are

not presently reported well enough to permit

detailed reconstruction of relative abundance

of various morphotypes (raw data were not

reported by Barnosky and Bell 2003).

Lemmiscus curtatus was included in only

a single phylogenetic analysis of arvicolines

(Robovský et al. 2008). The resultant phylo-

genetic hypothesis was based on karyotype,

behavioral characters, and morphological char-

acters, and those results tentatively placed

L. curtatus near the base of Arvicolini, although

this hypothesis should be considered tenuous

(Robovský et al. 2008). If this phylogenetic

placement holds, the importance of under-

standing the evolutionary patterns within L.

curtatus becomes critical for allowing compar-

isons to the more speciose clade of Microtus.

As suggested by our data set and by previously

published records (e.g., Barnosky and Bell

2003), morphological patterns of various popu-

lations in the extant biota present a complex

224 WESTERN NORTH AMERICAN NATURALIST (2019), VOL. 79 NO. 2, PAGES 219–232

Fig. 3. Relative abundance (percentage of NISP) of morphotypes per collection locality.

mosaic across the landscape, with some popula-

tions having characteristically high abundance

of 6-triangle morphotypes. With such patterns

now at least preliminarily documented, it is

possible to begin to investigate the mechanistic

underpinnings that produce these patterns.

The driver(s) of the variation documented here

are unknown; possible explanations include

selection, genetic drift, or other phenomena

such as epigenetic polymorphism.

Teasing apart the evolutionary mechanisms

(e.g., selection and drift) underlying the mor-

phological variation in L. curtatus will require

further documentation of detailed population-

level data on dental morphology. Previous

quantitative approaches to examining varia-

tion of North American voles were applied to

the separation of species within morphological

space (e.g., Wallace 2006, McGuire 2011).

Quantitative intraspecific morphological com-

parisons exist for some taxa (e.g., Barnosky

1993, Piras et al. 2008, Ledevin et al. 2010),

and similar analyses may clarify our observa-

tions and help to contextualize our data across

the history of Lemmiscus. Quantification of

tooth variation across the spatio-temporal dis-

tribution of L. curtatus is outside the scope

of this paper but is ongoing (e.g., Burroughs

2016, 2017).

Acquisition of molecular-based phylogeo-

graphic sampling and full documentation of

quantitative genetic sampling for all popula-

tions of L. curtatus across its spatiotemporal

distribution are likely now attainable. Previ-

ously, it was impossible to collect molecular

information from fossil specimens of Lemmis-

cus, but advances in extraction and sequenc-

ing of ancient DNA now make this plausible.

Collectively, our observations highlight a poten-

tial path for developing a deeper understand-

ing of the evolutionary history of L. curtatus.

Tools that may assist in explaining how pat-

terns of dental variation are expressed devel-

opmentally are now in early stages of develop -

ment (e.g., Renvoisé et al. 2017) and promise

further insights in this field in coming years.

Our evaluation of morphological variation

in the m1 of L. curtatus from Saskatchewan

indicates a mosaic of morphotypes, with both

6-triangle morphologies and morphologies

approaching a 6-triangle state being more

abundant than noted elsewhere in modern

populations (e.g., Barnosky and Bell 2003).

Documentation of patterns of variation in

populations of L. curtatus begins to provide

the data necessary for elucidation of dental

evolution in the group. The rich fossil record

of L. curtatus and the changing expressions of

dental morphotypes through time and across

space make this a particularly interesting group

for explorations of this kind. The fact that

Lemmiscus is monotypic, and appears to have

been monotypic for its entire documented his-

tory, emphasizes that establishment of the

relationship between morphological patterns

and taxonomic boundaries remains a particu-

larly challenging problem. The data presented

here, combined with data derived from prior

studies, suggest that populations of L. curtatus

have strong differences in the propensity to

express variation in the m1, and that the varia-

tion that is expressed differs from place to

place. When considered in its entirety, the

North American fossil record of L. curtatus

expresses more dental variation than is ex -

pressed by other voles in the Pleistocene and

extant biotas, with the exception of Microtus

pennsylvanicus (Weddle and Choate 1983,

Davis 1987, Barnosky 1990, 1993) and Micro-

tus chrotorrhinus (Martin 1973). Meaningful

geographic patterns in expressed variation are

documented for M. pennsylvanicus (e.g., Wed-

dle and Choate 1983, Davis 1987), and are now

at least suggested for L. curtatus. Although we

have some understanding of how developmen-

tal biases create the structure underlying this

morphological variation, further work will be

required to determine why the variation in

our sample and in other populations of L. cur-

tatus is shaped the way that it is.

ACKNOWLEDGMENTS

Tim Schowalter collected, processed, and

sorted the owl pellets. Christina Barrón-Ortiz

translated the abstract. Conversations with

Corey Scobie and Christina Barrón-Ortiz led

to crucial references in the literature. Aman-

dah VanMerlin assisted with the production of

the map in Fig. 2.

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BELL ET AL.♦TOOTH MORPHOLOGY OF LEMMISCUS FROM SASKATCHEWAN 227

APPENDIX 1. Specimens of Lemmiscus curtatus examined for this study. Locality 1 = P17.13.1–P17.13.221; Locality 2 =

P17.13.222–P17.13.255; Locality 3 = P17.13.256–P17.13.290; Locality 4 = P17.13.291–P17.13.370.

Specimen number Side Element Morphotype

P17.13.1 Left Dentary, i1–m2 5T

P17.13.2 Left Dentary, i1–m2 5T

P17.13.3 Left Dentary, i1–m2 5T

P17.13.4 Left Dentary, i1–m2 5T

P17.13.5 Left Dentary, i1–m2 5T

P17.13.6 Left Dentary, i1–m2 5T

P17.13.7 Left Dentary, i1–m2 5T

P17.13.8 Left Dentary, i1–m2 5T

P17.13.9 Left Dentary, i1–m2 5T

P17.13.10 Left Dentary, i1–m2 5T

P17.13.11 Left Dentary, i1–m2 5T

P17.13.12 Left Dentary, i1–m2 5T

P17.13.13 Left Dentary, i1–m2 5T

P17.13.14 Left Dentary, i1–m2 5T

P17.13.15 Left Dentary, i1–m2 5T

P17.13.16 Left Dentary, i1–m2 5T

P17.13.17 Left Dentary, i1–m2 5T

P17.13.18 Left Dentary, i1–m2 5T

P17.13.19 Left Dentary, i1–m2 5T

P17.13.20 Right Dentary, i1–m2 5T

P17.13.21 Right Dentary, i1–m2 5T

P17.13.22 Right Dentary, i1–m2 5T

P17.13.23 Right Dentary, i1–m2 5T

P17.13.24 Right Dentary, i1–m2 5T

P17.13.25 Right Dentary, i1–m2 5T

P17.13.26 Right Dentary, i1–m2 5T

P17.13.27 Right Dentary, i1–m2 5T

P17.13.28 Right Dentary, i1–m2 5T

P17.13.29 Right Dentary, i1–m2 5T

P17.13.30 Right Dentary, i1–m2 5T

P17.13.31 Right Dentary, i1–m2 5T

P17.13.32 Right Dentary, i1–m2 5T

P17.13.33 Right Dentary, i1–m2 5T

P17.13.34 Right Dentary, i1–m2 5T

P17.13.35 Right Dentary, i1–m2 5T

P17.13.36 Right Dentary, i1–m2 5T

P17.13.37 Right Dentary, i1–m2 5T

P17.13.38 Left Dentary, i1–m3 5T

P17.13.39 Left Dentary, i1–m3 5T

P17.13.40 Left Dentary, i1–m3 5T

P17.13.41 Left Dentary, i1–m3 5T

P17.13.42 Left Dentary, i1–m3 5T

P17.13.43 Left Dentary, i1–m3 5T

P17.13.44 Left Dentary, i1–m3 5T

P17.13.45 Left Dentary, i1–m3 5T

P17.13.46 Left Dentary, i1–m3 5T

P17.13.47 Left Dentary, i1–m3 5T

P17.13.48 Left Dentary, i1–m3 5T

228 WESTERN NORTH AMERICAN NATURALIST (2019), VOL. 79 NO. 2, PAGES 219–232

APPENDIX 1. Continued.

Specimen number Side Element Morphotype

P17.13.49 Left Dentary, i1–m3 5T

P17.13.50 Left Dentary, i1–m3 5T

P17.13.51 Left Dentary, i1–m3 5T

P17.13.52 Left Dentary, i1–m3 5T

P17.13.53 Left Dentary, i1–m3 5T

P17.13.54 Left Dentary, i1–m3 5T

P17.13.55 Left Dentary, i1–m3 5T

P17.13.56 Left Dentary, i1–m3 5T

P17.13.57 Left Dentary, i1–m3 5T

P17.13.58 Left Dentary, i1–m3 5T

P17.13.59 Left Dentary, i1–m3 5T

P17.13.60 Left Dentary, i1–m3 5T

P17.13.61 Left Dentary, i1–m3 5T

P17.13.62 Left Dentary, i1–m3 5T

P17.13.63 Right Dentary, i1–m3 5T

P17.13.64 Right Dentary, i1–m3 5T

P17.13.65 Right Dentary, i1–m3 5T

P17.13.66 Right Dentary, i1–m3 5T

P17.13.67 Right Dentary, i1–m3 5T

P17.13.68 Right Dentary, i1–m3 5T

P17.13.69 Right Dentary, i1–m3 5T

P17.13.70 Right Dentary, i1–m3 5T

P17.13.71 Right Dentary, i1–m3 5T

P17.13.72 Right Dentary, i1–m3 5T

P17.13.73 Right Dentary, i1–m3 5T

P17.13.74 Right Dentary, i1–m3 5T

P17.13.75 Right Dentary, i1–m3 5T

P17.13.76 Right Dentary, i1–m3 5T

P17.13.77 Right Dentary, i1–m3 5T

P17.13.78 Right Dentary, i1–m3 5T

P17.13.79 Right Dentary, i1–m3 5T

P17.13.80 Right Dentary, i1–m3 5T

P17.13.81 Right Dentary, i1–m3 5T

P17.13.82 Right Dentary, i1–m3 5T

P17.13.83 Right Dentary, i1–m3 5T

P17.13.84 Right Dentary, i1–m3 5T

P17.13.85 Right Dentary, i1–m3 5T

P17.13.86 Right Dentary, i1–m3 5T

P17.13.87 Right Dentary, i1–m3 5T

P17.13.88 Right Dentary, i1–m3 5T

P17.13.89 Right Dentary, i1–m3 5T

P17.13.90 Right Dentary, i1, m1 5T

P17.13.91 Left Dentary, i1, m1, m3 5T

P17.13.92 Left Dentary, i1, m1, m3 5T

P17.13.93 Right Dentary, i1, m1, m3 5T

P17.13.94 Right Dentary, i1, m1, m3 5T

P17.13.95 Left Dentary, m1, m2 5T

P17.13.96 Right Dentary, m1, m2 5T

P17.13.97 Left m1 5T

P17.13.98 Left m1 5T

P17.13.99 Right m1 5T

P17.13.100 Right m1 5T

P17.13.101 Right m1 5T

P17.13.102 Left Partial Dentary, i1–m2 5T

P17.13.103 Right Partial Dentary, i1–m2 5T

P17.13.104 Left Partial Dentary, i1, m1 5T

P17.13.105 Right Dentary, i1, m1 5T, Microtus-like cap

morphology

P17.13.106 Left Dentary, i1–m2 5T, T6 incipient closure

P17.13.107 Left Dentary, i1–m2 5T, T6 incipient closure

P17.13.108 Right Dentary, i1–m2 5T, T6 incipient closure

P17.13.109 Right Dentary, i1–m2 5T, T6 incipient closure

P17.13.110 Right Dentary, i1–m2 5T, T6 incipient closure

P17.13.111 Right Dentary, i1–m2 5T, T6 incipient closure

P17.13.112 Right Dentary, i1–m2 5T, T6 incipient closure

BELL ET AL.♦TOOTH MORPHOLOGY OF LEMMISCUS FROM SASKATCHEWAN 229

APPENDIX 1. Continued.

Specimen number Side Element Morphotype

P17.13.113 Right Dentary, i1–m2 5T, T6 incipient closure

P17.13.114 Left Dentary, i1–m3 5T, T6 incipient closure

P17.13.115 Left Dentary, i1–m3 5T, T6 incipient closure

P17.13.116 Left Dentary, i1–m3 5T, T6 incipient closure

P17.13.117 Left Dentary, i1–m3 5T, T6 incipient closure

P17.13.118 Left Dentary, i1–m3 5T, T6 incipient closure

P17.13.119 Left Dentary, i1–m3 5T, T6 incipient closure

P17.13.120 Left Dentary, i1–m3 5T, T6 incipient closure

P17.13.121 Left Dentary, i1–m3 5T, T6 incipient closure

P17.13.122 Left Dentary, i1–m3 5T, T6 incipient closure

P17.13.123 Left Dentary, i1–m3 5T, T6 incipient closure

P17.13.124 Left Dentary, i1–m3 5T, T6 incipient closure

P17.13.125 Right Dentary, i1–m3 5T, T6 incipient closure

P17.13.126 Right Dentary, i1–m3 5T, T6 incipient closure

P17.13.127 Right Dentary, i1–m3 5T, T6 incipient closure

P17.13.128 Right Dentary, i1–m3 5T, T6 incipient closure

P17.13.129 Right Dentary, i1–m3 5T, T6 incipient closure

P17.13.130 Right Dentary, i1–m3 5T, T6 incipient closure

P17.13.131 Right Dentary, i1–m3 5T, T6 incipient closure

P17.13.132 Right Dentary, i1–m3 5T, T6 incipient closure

P17.13.133 Right Dentary, i1–m3 5T, T6 incipient closure

P17.13.134 Right Dentary, i1–m3 5T, T6 incipient closure

P17.13.135 Right Dentary, i1, m1, m3 5T, T6 incipient closure

P17.13.136 Left Dentary, m1–m3 5T, T6 incipient closure

P17.13.137 Left Dentary, m1–m3 5T, T6 incipient closure

P17.13.138 Left m1 5T, T6 incipient closure

P17.13.139 Right m1 5T, T6 incipient closure

P17.13.140 Left Dentary, i1–m2 5T, T6 pinched

P17.13.141 Left Dentary, i1–m2 5T, T6 pinched

P17.13.142 Left Dentary, i1–m2 5T, T6 pinched

P17.13.143 Left Dentary, i1–m2 5T, T6 pinched

P17.13.144 Left Dentary, i1–m2 5T, T6 pinched

P17.13.145 Left Dentary, i1–m2 5T, T6 pinched

P17.13.146 Left Dentary, i1–m2 5T, T6 pinched

P17.13.147 Left Dentary, i1–m2 5T, T6 pinched

P17.13.148 Left Dentary, i1–m2 5T, T6 pinched

P17.13.149 Left Dentary, i1–m2 5T, T6 pinched

P17.13.150 Left Dentary, i1–m2 5T, T6 pinched

P17.13.151 Left Dentary, i1–m2 5T, T6 pinched

P17.13.152 Right Dentary, i1–m2 5T, T6 pinched

P17.13.153 Right Dentary, i1–m2 5T, T6 pinched

P17.13.154 Right Dentary, i1–m2 5T, T6 pinched

P17.13.155 Right Dentary, i1–m2 5T, T6 pinched

P17.13.156 Right Dentary, i1–m2 5T, T6 pinched

P17.13.157 Right Dentary, i1–m2 5T, T6 pinched

P17.13.158 Right Dentary, i1–m2 5T, T6 pinched

P17.13.159 Right Dentary, i1–m2 5T, T6 pinched

P17.13.160 Right Dentary, i1–m2 5T, T6 pinched

P17.13.161 Right Dentary, i1–m2 5T, T6 pinched

P17.13.162 Right Dentary, i1–m2 5T, T6 pinched

P17.13.163 Left Dentary, i1–m3 5T, T6 pinched

P17.13.164 Left Dentary, i1–m3 5T, T6 pinched

P17.13.165 Left Dentary, i1–m3 5T, T6 pinched

P17.13.166 Left Dentary, i1–m3 5T, T6 pinched

P17.13.167 Left Dentary, i1–m3 5T, T6 pinched

P17.13.168 Left Dentary, i1–m3 5T, T6 pinched

P17.13.169 Left Dentary, i1–m3 5T, T6 pinched

P17.13.170 Left Dentary, i1–m3 5T, T6 pinched

P17.13.171 Left Dentary, i1–m3 5T, T6 pinched

P17.13.172 Left Dentary, i1–m3 5T, T6 pinched

P17.13.173 Left Dentary, i1–m3 5T, T6 pinched

P17.13.174 Left Dentary, i1–m3 5T, T6 pinched

P17.13.175 Left Dentary, i1–m3 5T, T6 pinched

P17.13.176 Left Dentary, i1–m3 5T, T6 pinched

P17.13.177 Left Dentary, i1–m3 5T, T6 pinched

230 WESTERN NORTH AMERICAN NATURALIST (2019), VOL. 79 NO. 2, PAGES 219–232

APPENDIX 1. Continued.

Specimen number Side Element Morphotype

P17.13.178 Left Dentary, i1–m3 5T, T6 pinched

P17.13.179 Right Dentary, i1–m3 5T, T6 pinched

P17.13.180 Right Dentary, i1–m3 5T, T6 pinched

P17.13.181 Right Dentary, i1–m3 5T, T6 pinched

P17.13.182 Right Dentary, i1–m3 5T, T6 pinched

P17.13.183 Right Dentary, i1–m3 5T, T6 pinched

P17.13.184 Right Dentary, i1–m3 5T, T6 pinched

P17.13.185 Right Dentary, i1–m3 5T, T6 pinched

P17.13.186 Right Dentary, i1–m3 5T, T6 pinched

P17.13.187 Right Dentary, i1–m3 5T, T6 pinched

P17.13.188 Right Dentary, i1–m3 5T, T6 pinched

P17.13.189 Right Dentary, i1–m3 5T, T6 pinched

P17.13.190 Right Dentary, i1–m3 5T, T6 pinched

P17.13.191 Right Dentary, i1–m3 5T, T6 pinched

P17.13.192 Right Dentary, i1–m3 5T, T6 pinched

P17.13.193 Right Dentary, i1–m3 5T, T6 pinched

P17.13.194 Right Dentary, i1–m3 5T, T6 pinched

P17.13.195 Right Dentary, i1–m3 5T, T6 pinched

P17.13.196 Right Dentary, i1, m1 5T, T6 pinched

P17.13.197 Right Dentary, i1, m1, m3 5T, T6 pinched

P17.13.198 Right Dentary, m1, m2 5T, T6 pinched

P17.13.199 Left m1 5T, T6 pinched

P17.13.200 Left m1 5T, T6 pinched

P17.13.201 Left m1 5T, T6 pinched

P17.13.202 Left m1 5T, T6 pinched

P17.13.203 Left m1 5T, T6 pinched

P17.13.204 Right Dentary, m1 5T, T6 pinched

P17.13.205 Left Dentary, i1–m2 6T

P17.13.206 Left Dentary, i1–m2 6T

P17.13.207 Right Dentary, i1–m2 6T

P17.13.208 Right Dentary, i1–m2 6T

P17.13.209 Left Dentary, i1–m3 6T

P17.13.210 Left Dentary, i1–m3 6T

P17.13.211 Left Dentary, i1–m3 6T

P17.13.212 Left Dentary, i1–m3 6T

P17.13.213 Left Dentary, i1–m3 6T

P17.13.214 Right Dentary, i1–m3 6T

P17.13.215 Right Dentary, i1–m3 6T

P17.13.216 Right Dentary, i1–m3 6T

P17.13.217 Right Dentary, i1–m3 6T

P17.13.218 Left m1 6T

P17.13.219 Right m1 6T

P17.13.220 Right Partial Dentary, m1 6T

P17.13.221 Left Dentary, i1–m3 6T, T4/T5 confluent

P17.13.222 Left Dentary, i1–m2 5T

P17.13.223 Left Dentary, i1–m2 5T

P17.13.224 Left Dentary, i1–m3 5T

P17.13.225 Left Dentary, i1–m3 5T

P17.13.226 Left Dentary, i1–m3 5T

P17.13.227 Right Dentary, i1–m2 5T

P17.13.228 Right Dentary, i1–m2 5T

P17.13.229 Right Dentary, i1–m2 5T

P17.13.230 Right Dentary, i1–m2 5T

P17.13.231 Right Dentary, i1–m3 5T

P17.13.232 Right Dentary, i1–m3 5T

P17.13.233 Right Dentary, i1–m3 5T

P17.13.234 Left Dentary, i1–m2 5T, T6 incipient closure

P17.13.235 Left Dentary, i1–m3 5T, T6 incipient closure

P17.13.236 Left Dentary, m1, m2 5T, T6 incipient closure

P17.13.237 Right Dentary, i1–m2 5T, T6 incipient closure

P17.13.238 Right Dentary, i1–m2 5T, T6 incipient closure

P17.13.239 Right Dentary, i1–m3 5T, T6 incipient closure

P17.13.240 Right Dentary, i1–m3 5T, T6 incipient closure

P17.13.241 Left Dentary, i1–m2 5T, T6 pinched

P17.13.242 Left Dentary, i1–m3 5T, T6 pinched

BELL ET AL.♦TOOTH MORPHOLOGY OF LEMMISCUS FROM SASKATCHEWAN 231

APPENDIX 1. Continued

Specimen number Side Element Morphotype

P17.13.243 Left Dentary, i1–m3 5T, T6 pinched

P17.13.244 Left Dentary, i1–m3 5T, T6 pinched

P17.13.245 Left Dentary, i1, m1 5T, T6 pinched

P17.13.246 Left Dentary, m1, m2 5T, T6 pinched

P17.13.247 Right Dentary, i1–m2 5T, T6 pinched

P17.13.248 Right Dentary, i1–m2 5T, T6 pinched

P17.13.249 Right Dentary, i1–m3 5T, T6 pinched

P17.13.250 Right Dentary, i1–m3 5T, T6 pinched

P17.13.251 Right Dentary, i1–m3 5T, T6 pinched

P17.13.252 Right Dentary, i1–m3 5T, T6 pinched

P17.13.253 Right Dentary, i1–m3 5T, T6 pinched

P17.13.254 Left Dentary, i1–m3 6T

P17.13.255 Left Dentary, i1–m3 6T

P17.13.256 Left Dentary, i1–m2 5T

P17.13.257 Left Dentary, i1–m2 5T

P17.13.258 Left Dentary, i1–m2 5T

P17.13.259 Left Dentary, i1–m2 5T

P17.13.260 Left Dentary, i1–m2 5T

P17.13.261 Left Dentary, i1–m2 5T

P17.13.262 Left Dentary, i1–m3 5T

P17.13.263 Left Dentary, i1–m3 5T

P17.13.264 Left Dentary, i1–m3 5T

P17.13.265 Left Dentary, i1–m3 5T

P17.13.266 Left Dentary, m1 5T

P17.13.267 Left Dentary, m1, m2 5T

P17.13.268 Left Dentary, m1, m2 5T

P17.13.269 Left m1 5T

P17.13.270 Left m1 5T

P17.13.271 Right Dentary, i1–m2 5T

P17.13.272 Right Dentary, i1–m2 5T

P17.13.273 Right Dentary, i1–m3 5T

P17.13.274 Right Dentary, i1–m3 5T

P17.13.275 Right Dentary, i1–m3 5T

P17.13.276 Right Dentary, i1–m3 5T

P17.13.277 Right Dentary, i1–m3 5T

P17.13.278 Right Dentary, i1, m1, m3 5T

P17.13.279 Right Dentary, m1, m2 5T

P17.13.280 Right Dentary, m1, m2 5T

P17.13.281 Left Dentary, m1–m3 5T, T6 incipient closure

P17.13.282 Right Dentary, i1–m2 5T, T6 incipient closure

P17.13.283 Right Dentary, i1–m3 5T, T6 incipient closure

P17.13.284 Left Dentary, i1–m2 5T, T6 pinched

P17.13.285 Right Dentary, i1–m2 5T, T6 pinched

P17.13.286 Right Dentary, i1–m2 5T, T6 pinched

P17.13.287 Right Dentary, i1–m2 5T, T6 pinched

P17.13.288 Right Dentary, i1–m2 5T, T6 pinched

P17.13.289 Left Dentary, i1–m2 6T

P17.13.290 Left Dentary, i1–m2 6T

P17.13.291 Left Dentary, i1–m2 5T

P17.13.292 Left Dentary, i1–m2 5T

P17.13.293 Left Dentary, i1–m2 5T

P17.13.294 Left Dentary, i1–m2 5T

P17.13.295 Left Dentary, i1–m2 5T

P17.13.296 Left Dentary, i1–m2 5T

P17.13.297 Left Dentary, i1–m2 5T

P17.13.298 Left Dentary, i1–m2 5T

P17.13.299 Left Dentary, i1–m2 5T

P17.13.300 Left Dentary, i1–m3 5T

P17.13.301 Left Dentary, i1–m3 5T

P17.13.302 Left Dentary, i1–m3 5T

P17.13.303 Left Dentary, i1–m3 5T

P17.13.304 Left Dentary, i1–m3 5T

P17.13.305 Left Dentary, i1–m3 5T

P17.13.306 Left Dentary, i1–m3 5T

P17.13.307 Left Dentary, i1–m3 5T

232 WESTERN NORTH AMERICAN NATURALIST (2019), VOL. 79 NO. 2, PAGES 219–232

APPENDIX 1. Continued.

Specimen number Side Element Morphotype

P17.13.308 Left Dentary, i1–m3 5T

P17.13.309 Left Dentary, i1, m1 5T

P17.13.310 Left Dentary, i1, m1 5T

P17.13.311 Left m1 5T

P17.13.312 Left m1 5T

P17.13.313 Right Dentary, i1–m2 5T

P17.13.314 Right Dentary, i1–m2 5T

P17.13.315 Right Dentary, i1–m2 5T

P17.13.316 Right Dentary, i1–m2 5T

P17.13.317 Right Dentary, i1–m2 5T

P17.13.318 Right Dentary, i1–m2 5T

P17.13.319 Right Dentary, i1–m2 5T

P17.13.320 Right Dentary, i1–m2 5T

P17.13.321 Right Dentary, i1–m2 5T

P17.13.322 Right Dentary, i1–m2 5T

P17.13.323 Right Dentary, i1–m2 5T

P17.13.324 Right Dentary, i1–m3 5T

P17.13.325 Right Dentary, i1–m3 5T

P17.13.326 Right Dentary, i1–m3 5T

P17.13.327 Right Dentary, i1–m3 5T

P17.13.328 Right Dentary, i1–m3 5T

P17.13.329 Right Dentary, i1–m3 5T

P17.13.330 Right Dentary, i1–m3 5T

P17.13.331 Right Dentary, m1, m2 5T

P17.13.332 Right Dentary, m1, m2 5T

P17.13.333 Right m1 5T

P17.13.334 Left Dentary, i1–m2 5T, T6 incipient closure

P17.13.335 Left Dentary, i1–m3 5T, T6 incipient closure

P17.13.336 Left m1 5T, T6 incipient closure

P17.13.337 Right Dentary, i1–m3 5T, T6 incipient closure

P17.13.338 Right Dentary, i1–m3 5T, T6 incipient closure

P17.13.339 Right Dentary, i1–m3 5T, T6 incipient closure

P17.13.340 Left Dentary, i1–m2 5T, T6 pinched

P17.13.341 Left Dentary, i1–m2 5T, T6 pinched

P17.13.342 Left Dentary, i1–m2 5T, T6 incipient closure

P17.13.343 Left Dentary, i1–m2 5T, T6 pinched

P17.13.344 Left Dentary, i1–m2 5T, T6 pinched

P17.13.345 Left Dentary, i1–m2 5T, T6 pinched

P17.13.346 Left Dentary, i1–m2 5T, T6 pinched

P17.13.347 Left Dentary, i1–m3 5T, T6 pinched

P17.13.348 Left Dentary, i1–m3 5T, T6 pinched

P17.13.349 Left Dentary, i1–m3 5T, T6 pinched

P17.13.350 Right Dentary, i1–m2 5T, T6 pinched

P17.13.351 Right Dentary, i1–m2 5T, T6 pinched

P17.13.352 Right Dentary, i1–m2 5T, T6 pinched

P17.13.353 Right Dentary, i1–m2 5T, T6 pinched

P17.13.354 Right Dentary, i1–m2 5T, T6 pinched

P17.13.355 Right Dentary, i1–m3 5T, T6 pinched

P17.13.356 Right Dentary, i1–m3 5T, T6 pinched

P17.13.357 Right Dentary, i1–m3 5T

P17.13.358 Right Dentary, i1–m3 5T

P17.13.359 Right Dentary, i1–m3 5T, T6 pinched

P17.13.360 Right Dentary, i1–m3 5T, T6 pinched

P17.13.361 Right Dentary, m1, m2 5T, T6 pinched

P17.13.362 Right Dentary, m1, m2 5T, T6 pinched

P17.13.363 Right m1 5T, T6 pinched

P17.13.364 Left Dentary, i1–m2 6T

P17.13.365 Left Dentary, i1–m3 6T

P17.13.366 Left Dentary, m1, m2 6T

P17.13.367 Right Dentary, i1–m2 6T

P17.13.368 Right Dentary, i1–m2 6T

P17.13.369 Right Dentary, i1–m2 6T

P17.13.370 Right Dentary, i1–m2 4T, T5/T6 confluent,

T6 incipient closure