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Brief communication Population variation in human maxillary premolar accessory ridges (MxPAR).

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AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY 141:319–324 (2010)
Brief Communication: Population Variation in Human
Maxillary Premolar Accessory Ridges (MxPAR)
Scott E. Burnett,1* Diane E. Hawkey,2 and Christy G. Turner II2
1
2
Comparative Cultures Collegium, Eckerd College, St. Petersburg, FL 33711
School of Human Evolution and Social Change, Arizona State University, Tempe, AZ 85287-2402
KEY WORDS
dental morphology; dental anthropology; nonmetric traits
ABSTRACT
The purpose of this brief communication
is to report the results of an analysis of maxillary premolar accessory ridges (MxPAR), a common but understudied accessory ridge that may occur both mesial and
distal to the central ridge of the buccal cusp of upper
premolars. We developed a new five-grade scoring plaque
to better categorize MxPAR variation. Subsequently, we
conducted a population analysis of MxPAR frequency in
749 dental casts of South African Indian, American Chinese, Alaskan Eskimo, Tohono O’odham (Papago), Akimel O’odham (Pima), Solomon Islander, South African
Bantu, and both American and South African Whites.
Northeast Asian and Asian-derived populations exhib-
ited the highest MxPAR frequencies while Indo-European samples (South African Indians, American and
South African Whites) exhibited relatively low frequencies. The Solomon Islanders and South African Bantu
samples exhibited intermediate frequencies. Our analysis indicates that statistically significant differences in
MxPAR frequency exist between major geographic populations. As a result, the MxPAR plaque has now been
added to the Arizona State University Dental Anthropology System, an important contribution as maxillary
premolar traits are underrepresented in analyses of dental morphology. Am J Phys Anthropol 141:319–324,
2010. V 2009 Wiley-Liss, Inc.
While a number of maxillary premolar variants are
known including the Uto-Aztecan premolar (disto-sagittal ridge), tricuspid premolars, and odontomes, these
traits are all relatively rare and occur at frequencies of
less than 5% in most samples (Scott and Turner, 1997).
Accordingly, their utility in population comparisons may
be limited and such morphological crown variants of
maxillary premolars are rarely included in studies of
human dental morphology. However, premolar accessory
ridges, illustrated in Scott and Turner (1997) are a relatively common crown trait, yet infrequently studied.
Premolar accessory ridges are elevated crests on the
occlusal surface that may be found both mesial and distal to the central ridge of the paracone of maxillary premolars and/or the protoconid of mandibular premolars
(Scott and Turner, 1997). The trait may be present on
both first and second premolars with four occlusal loci
for each dental arcade [mesial first premolar (MP1), distal first premolar (DP1), mesial second premolar (MP2),
distal second premolar (DP2)]. This study solely concerns
maxillary premolar accessory ridges, known as MxPAR
(Burnett, 1998). Maxillary premolar accessory ridges
(see Fig. 1) originate high on the paracone and run down
into the premolar sulcus, largely parallel to the buccallingual axis of the tooth. The orientation and origination
of MxPAR distinguishes them from marginal ridge
extensions, relatively rare ridges that extend obliquely
from the mesial or distal marginal ridge to the sulcus.
Although maxillary premolar accessory ridges
were seemingly first noted in the late 19th century (Zuckerkandl, 1891), they have received little detailed study in
the past three decades. Most of our prior understanding
of MxPAR is derived from four analyses, three of which
are theses or dissertations (Wasser, 1953; Morris, 1965;
Scott, 1973) and not extensively published. As a result,
MxPAR is not widely known though it is occasionally
noted in dental analyses (e.g., Lukacs and Hemphill,
1992). Nonetheless, some important conclusions about the
genetic basis, bilateral symmetry, sexual dimorphism,
trait independence, and population variation of MxPAR
were generated during these early studies.
The first analyses addressing the genetic basis of
MxPAR were undertaken by Wasser (1953) and Gilmore
(1968). Both studies included the examination of MxPAR
ridge presence in twin samples to test for a higher concordance rate between monozygotic twins relative to
dizygotic twins, as would be expected in traits with a
genetic component. Wasser (1953) found that trait concordance for both mesial and distal ridges on the first
premolar occurred more frequently in monozygotic twins
than expected by chance. Similar results were obtained
by Gilmore (1968) on both first and second premolars,
though only mesial ridges and both mesial and distal
ridges counted together were found to be significantly
more concordant among monozygotic twins. The lack of
statistically significant results for distal ridges is likely
due to the small sample of twins studied (Gilmore,
C 2009
V
WILEY-LISS, INC.
C
Grant sponsors: Sigma Xi Scientific Research Society; Arizona
Archaeological and Historical Society; ASU School of Human Evolution and Social Change.
*Correspondence to: Dr. Scott E. Burnett, Assistant Professor of
Anthropology, Eckerd College, St. Petersburg, FL 33711.
E-mail: burnetse@eckerd.edu
Received 24 March 2009; accepted 14 October 2009
DOI 10.1002/ajpa.21230
Published online 1 December 2009 in Wiley InterScience
(www.interscience.wiley.com).
320
S.E. BURNETT ET AL.
Fig. 2. MxPAR scoring plaque.
Fig. 1. Mesial and distal maxillary premolar accessory
ridges (MxPAR).
1968). Both researchers concluded that a strong genetic
component is responsible for MxPAR occurrence.
Studies of bilateral symmetry bolster the case for a
genetic basis for maxillary premolar accessory ridges. An
early study of MxPAR presence/absence in the Tohono
O’odham [Papago] by Morris (1965) found high symmetry between left and right premolars for both mesial and
distal ridges. Mesial ridges exhibited symmetry between
antimeres in 78 and 84% of observations at the MP1 and
MP2 loci, respectively. Even higher symmetry frequencies were found for the distal first premolar (91%) and
distal second premolar loci (95%). The high degree of
symmetry found in MxPAR occurrence supports the
underlying genetic control of the trait suggested by the
twin studies described earlier.
Morphological dental traits exhibiting significant sexual dimorphism often necessitate separating males and
females for analysis. As this is a frequent first test
before pooling data, several studies have examined sexual dimorphism in MxPAR. Morris (1965) found significant sexual dimorphism only at the mesial loci of the
first and second premolars, when only bilaterally symmetrical observations in his Tohono O’odham [Papago]
samples were included. Interestingly, males exhibited
lower MxPAR frequencies than females at the mesial
first premolar locus, but significantly higher MxPAR frequencies at the mesial second premolar locus. However,
the sexual dimorphism in Morris’ sample was no longer
present when his data are examined for asymmetrical
observations and observations where only one antimere
was available. Indeed, subsequent research on eight
samples has found no consistent sexual dimorphism in
MxPAR frequency (Gilmore, 1968; Scott, 1973), including
a pilot study conducted as part of this research (Burnett
et al., 1996).
American Journal of Physical Anthropology
Morphological dental traits should occur independently in order to be analyzed together in a multiple trait
analysis without violating statistical assumptions. As
MxPAR may occur at multiple loci on both first and second premolars, any analysis of trait independence should
first address independence between loci. Gilmore (1968)
was the first to assess MxPAR independence through an
analysis of the dental casts of 120 American Whites (60
male, 60 female). MxPAR was not found to be independent between mesial and distal loci on the same premolar,
nor between corresponding loci on adjacent premolars
(Gilmore, 1968). A later, more extensive analysis of trait
independence conducted by Scott (1973) on 31 tooth/trait
combinations in Southwest Native Americans (n 5
1,251) included the four MxPAR loci (Scott, personal
communication). Many of the other ASU Dental Anthropology System traits were also included (e.g., winging,
shoveling, tuberculum dentale, hypocone, Carabelli’s
cusp, deflecting wrinkle, protostylid, lower molar cusp 6,
lower molar cusp 7). Generally speaking, correlation
coefficients were moderately low between MxPAR loci on
the same premolar (MP1-DP1 5 0.204; MP2-DP2 5
0.294), though higher on average than found between
corresponding loci on adjacent premolars (MP1-MP2 5
0.062; DP1-DP2 5 0.244) (Scott, personal communication). Even lower correlation coefficients were found
when the four MxPAR loci were tested against 27 other
tooth/trait combinations. MxPAR at the MP1 locus exhibited correlation coefficients ranging up to 60.190, with
18 intertrait tests (67%) lower than 60.100. Similarly
low correlations were found at the DP1 (up to 60.169;
74% of intertrait tests under 60.100), MP2 (up to
60.131; 89% of intertrait tests under 60.100), and DP2
loci (up to 60.210; 93% of inter-trait tests under 60.100)
(Scott, personal communication). Collectively, we can
conclude that MxPAR exhibits very low correlations with
other morphological traits in the ASU Dental Anthropology System.
Prior studies have also found significant frequency differences between samples. However, it is difficult to
derive firm conclusions about geographic patterning in
MxPAR occurrence as mostly Native American and IndoEuropean-derived samples were analyzed (Morris, 1965;
Gilmore, 1968; Scott, 1973). Wasser (1953) studied additional samples representing American Black, Chinese,
Mexican, and Yaqui-Mexican populations, though only
the first premolar was examined and trait frequencies
were calculated using the tooth count method instead of
the individual count method used by the remaining studies. Nonetheless, irrespective of loci, prior research suggests MxPAR occurrence is highest in Africans, followed
MAXILLARY PREMOLAR ACCESSORY RIDGES (MXPAR)
321
TABLE 1. Description of MxPAR plaque grades
Grade
Description
0
T
Absent. No detectable ridge formation.
Truncated ridge. Ridge does not extend continuously from the buccal
ridge to the medial sulcus. Truncated ridges should be scored to size
using the following grades and are not differentiated from nontruncated ridges in analysis.a
Trace. A continuous ridge is barely discernable, but seen under strong light.
Small. A thin continuous ridge, yet easily palpable.
Medium. A continuous ridge with moderate thickness.
Pronounced. A large, thick, continuous ridge that dominates the locus.
1
2
3
4
a
See the work by Burnett (1998) for further discussion of truncated ridges.
by Native Americans, Chinese, and Indo-European samples in descending order. It is worthwhile to note that
MxPAR have also been noted in both australopithecines
(Robinson, 1956) and Neanderthals (Bailey, 2002), indicating further potential for research on fossil hominins.
Most researchers who have analyzed MxPAR have
considered only ridge presence or absence (Wasser, 1953;
Morris, 1965; Gilmore, 1968). While providing useful information, these studies do not account for the wide
range of variation seen in maxillary premolar accessory
ridges. The first attempt at further distinguishing
MxPAR variation was early work by Scott (1973), who
divided ridges into small and large categories and scored
ridges for both mesial and distal loci together for each
tooth. For the present study we developed a more
detailed five-grade scoring system that better reflects
MxPAR variation than scoring systems with fewer
grades. The purpose of this brief communication is to
introduce a new scoring plaque (see Fig. 2) in the Arizona State University Dental Anthropology System, and
to illustrate some of the geographic variation in MxPAR
frequency. This is an important contribution as maxillary premolar traits are underrepresented in most studies of dental morphology.
MATERIALS AND METHODS
MxPAR data were collected using a reference plaque
(see Fig. 2) with a five-grade rank scale (Table 1) after
prior ranking systems developed by the primary author
(SEB) did not appear to adequately capture MxPAR variation. The plaque was developed to aid in the analysis of
both mesial and distal accessory ridges on both first and
second maxillary premolars with a single reference plaque. Specimens represented on the plaque were chosen
to depict increasing MxPAR size. A strong raking light
and 103 hand lens were used for better illuminating
subtle variations in MxPAR morphology during data collection, as generally recommended for other crown traits
(Scott, 2008).
Nine population samples composed of the dental casts
from 749 individuals were included in this study. Samples were chosen to represent major world populations
including: Africans (South African Bantu), Asians
(American Chinese), Asiatic Indians (South African
Indians), Europeans (American White, South African
White), Melanesians (Solomon Islanders), and Native
Americans (Alaskan Eskimo, Tohono O’odham [Papago],
Akimel O’odham [Pima]). All sample observations were
made entirely by the primary author (SEB), except the
South African White, South African Indian, and Akimel
O’odham (Pima) samples, which were scored in total or
in part by the second author (DEH). The above samples
are all curated in the Laboratory of Dental Anthropology, School of Human Evolution and Social Change at
Arizona State University. On the basis of other morphological and genetic data we predict that the IndoEuropean samples (American Whites, South African
Whites, and South African Indians) and the Northeast
Asian/Asian-derived samples (Native American, American Chinese) should exhibit similar frequencies within
each group. As noted previously, prior research on
population variation indicates that the Northeast Asian
and Asian-derived samples will exhibit higher MxPAR
frequencies than the Indo-European samples (Wasser,
1953; Scott, 1973).
The ideal breakpoint and locus for analysis was determined through an examination of the predicted differences between the Northeast Asian/Asian-derived and
Indo-European samples. A breakpoint refers to a trait
definition aimed at delimiting quasi-continuous trait
expression into a presence–absence dichotomy. In some
cases, the use of a higher plaque grade to distinguish
between trait presence and absence may allow better
differentiation between samples with similar trait frequencies but different size ridges. To minimize the confounding effect of random variation at each possible
breakpoint-locus combination, the optimal trait breakpoint and locus were determined independently. Each
breakpoint was then examined for consistent sample differences across all four loci (MP1, DP1, MP2, DP2) in
light of the predicted sample relationships. Similarly, the
most productive locus was identified by examination of
significant sample differences consistent with our predictions across all possible breakpoint combinations. This
analysis is further detailed by Burnett (1998).
The individual count method was employed for analysis (Scott and Turner, 1997). Individuals with only one
scorable antimere for a given locus were included in the
sample to maximize the number of possible observations.
The higher MxPAR grade was employed for individuals
exhibiting trait asymmetry between antimeres at a given
locus. This method assumes that maximal trait expression is most representative of genetic potential with
environmental factors inhibiting trait expression on the
antimere (Scott and Turner, 1997). Accessory ridges are
occasionally truncated and do not reach the premolar
sulcus and this often appears to be related to other morphological variants, such as accessory cusplets, triangular ridge bifurcation, or marginal ridge extensions
(Burnett, 1998). An example of a truncated ridge is provided on the plaque (T), however, as truncation appears
to be the result of independent morphological variants,
we recommend that truncated ridges be scored to the
appropriate size grade (1–4) and only the ridge size
grade used in analysis.
American Journal of Physical Anthropology
322
S.E. BURNETT ET AL.
TABLE 2. MxPAR scores for each sample by locus and grade
Locus
Sample
Tohono O’odham [Papago] (N 5 94)
Alaskan Eskimo (N 5 50)
Akimel O’odham [Pima] (N 5 100)
American Chinese (N 5 52)
Solomon Islanders (N 5 56)
South African Bantu (N 5 100)
American White (N 5 98)
South African Indian (N 5 99)
South African White (N 5 100)
Grade
n
n
n
n
n
n
n
n
n
5
5
5
5
5
5
5
5
5
Mesial P1
Distal P1
Mesial P2
Distal P2
0
1
2
3
4
0
1
2
3
4
0
1
2
3
4
0
1
2
3
4
30
16
55
22
28
64
65
80
82
18
7
11
7
9
23
18
11
7
17
12
11
9
6
6
5
2
3
2
2
7
5
6
1
3
0
1
8
9
5
6
4
0
1
0
1
7
10
24
14
14
39
46
50
50
10
9
16
3
10
35
15
19
22
34
10
20
11
15
15
20
22
12
12
5
21
13
8
5
6
2
6
23
13
12
7
4
5
4
1
4
17
4
12
13
15
25
42
37
31
4
1
3
2
3
13
5
10
5
43
11
28
11
19
35
25
18
23
19
25
41
18
15
18
15
18
27
7
6
9
7
2
3
3
8
9
3
1
2
7
14
21
27
19
22
4
1
6
4
5
11
2
8
6
41
17
21
17
14
43
23
22
15
30
15
43
13
12
12
27
30
15
16
13
21
7
7
9
11
14
26
Interobserver concordance was analyzed by comparison of scores obtained by two of us (SEB, DEH) on a
sample of 40 individuals chosen at random from casts in
four samples (Akimel O’odham [Pima], Bantu, South
African Indian, and American White) of the ASU dental
anthropology collections. Two types of concordance were
analyzed: plaque grade concordance and scorability concordance. Plaque grade concordance measures the ability
of different researchers to score a trait using the same
or similar grades on the scoring plaque. Scorability concordance measures the ability to consistently determine
whether a tooth should be analyzed or not. Reasons for
not analyzing a tooth include wear, cast flaws, caries,
and tooth damage. Scorability concordance is measured
by dividing the number of observations scored by both
analysts by the number of total observations possible.
Intraobserver concordance was similarly assessed using
50 Bantu casts by one of us (SEB) with a 6-month interval between examination sessions. Truncated ridges
were not scored to a specific grade during the interobserver comparison of grade concordance, but were
included in the remaining intraobserver concordance
assessment.
RESULTS AND DISCUSSION
Inter- and intraobserver concordance
Concordance of MxPAR scoring for plaque grade was
high in both inter- and intraobserver comparisons. Interobserver concordance scores were high with 95.8% (185/
193) of observations within one plaque grade. Similar
scores were found in the intraobserver analysis, where
97.0% (256/264) of observations were concordant within
one grade. Scoring differences of only one grade are
thought to result from actual trait expression being intermediate to grades and not due to plaque or examiner
error (Nichol, 1990). The high levels of concordance
found for MxPAR are slightly higher than the average
found by Nichol and Turner (1986) for traits in the current Arizona State University Dental Anthropology System, suggesting that the new plaque can be used reliably
for within and between-observer scoring.
A scorability concordance of 82.2% (263/320) occurred
between observers. Intraobserver scorability resulted in
a concordance of 79.6% (210/264) in deciding whether
the tooth could be scored or not. The difficulty in deciding whether a tooth can be scored for MxPAR is largely
attributable to the effect of occlusal wear.
American Journal of Physical Anthropology
Scoring
Though sample differences were identified regardless
of the presence/absence breakpoint employed, a breakpoint at Grade 2 resulted in the most consistent statistically significant differences (p \ 0.05) between Northeast
Asian/Asian-derived samples and the non-Asian samples
(American Whites, South African Whites, Asiatic Indians, South African Bantu). For optimal results, ridges
typified by plaque Grades 2–4 may be considered present
while Grades 0–1 reflect trait absence. But, dichotomizing occurrence even on the basis of 0/1–4 (breakpoint of
1) still provides powerful geographic differentiation. The
same statistically significant population differences were
found most consistently at the distal locus on the first
premolar (DP1), suggesting that DP1 should be considered the key locus, though other loci may also be fruitful
for analysis (see Burnett, 1998).
Because MxPAR is located on the occlusal surface it is
therefore subject to tooth wear. Many studies have noted
difficulty in scoring traits due to wear (Morris, 1970;
Nichol and Turner, 1986; Wu and Turner, 1993), including MxPAR (Scott, 1973). A detailed analysis of the effect
of dental wear on MxPAR by the senior author (Burnett,
1998) suggests that the degree of wear influences sample
frequencies so that trait frequency decreases as wear
increases. This occurs even though more teeth were
deemed unscorable as wear increased (i.e., teeth considered to be too worn were not scored). Thus, decline in
MxPAR frequency across increasing wear grades is not
related to trait presence and absence, but likely a result
of violating the assumption that missing data is randomly absent (Little and Rubin, 1987; Little, 1988). Burnett (1998) found that teeth with MxPAR were more
likely to be excluded due to excessive wear than are
teeth without MxPAR. Subsequent research has identified similar wear-related frequency biases in commonly
studied morphological dental traits such as shoveling of
the maxillary central incisor, upper canine distal accessory ridge, and lower molar cusp number (Burnett et al.,
1998). In addition, wear-related biases may be different
between morphological traits or between observers
(Burnett, 1998; Burnett et al., 1998). Because of variation in the location and angle of tooth facets, it is difficult to generalize about the level of wear that impacts
occlusal traits such as MxPAR. Moderate lingual wear
on the paracone may obliterate ridge presence at the
smaller grades while MxPAR may still be palpable near
the premolar sulcus after subjected to a similar degree of
apical wear. Comparisons among samples with appreciable differences in degree of wear (Burnett, 1998), or
other factors that may inhibit the assessment of wear
MAXILLARY PREMOLAR ACCESSORY RIDGES (MXPAR)
323
As a result of our study, the MxPAR plaque has
recently been included in the Arizona State University
Dental Anthropology System (Turner et al., 1991), thus
providing an additional useful trait from an underrepresented tooth class in the system. Researchers who own a
previous version of the Dental Anthropology System
may request a copy of the MxPAR plaque by e-mail
(hawkey@asu.edu). The plaque is available at shipping
cost.
ACKNOWLEDGMENTS
Fig. 3. MxPAR frequencies per sample grouping (breakpoint
5 2).
Special thanks are extended to G. Richard Scott and
Donald H. Morris for their insightful comments and discussions of premolar morphology. The article was
improved through the comments of two anonymous
reviewers. The dental casts used herein were collected
by: H. Bailit and E.F. Harris, Solomon Islanders; J.D.
Cadien, American Chinese; A.A. and T. Dahlberg, Akimel O’odham [Pima]; D.H. Morris, Bantu, Tohono
O’odham [Papago], South African Indians and Whites;
C.G. Turner II, American Whites and Alaskan Eskimo.
LITERATURE CITED
(e.g., cast quality), may ultimately confound sample relationships. Accordingly, caution is urged for scoring
MxPAR with moderate to severe degrees of wear, as is
true of other occlusal variants (Wu and Turner, 1993).
Population variation
Statistically significant differences in MxPAR frequencies suggest the trait is useful in population comparisons. The highest MxPAR frequencies were identified in
Northeast Asian/Asian-derived (American Chinese,
Tohono O’odham [Papago], Akimel O’odham [Pima],
Alaskan Eskimo) samples while lower frequencies were
found in all three Indo-European samples (South African
Indians, American and South African Whites) (Table 2;
Fig. 3). For example, employing the recommended breakpoint of Grade 2 at the DP1 locus, the four Northeast
Asian/Asian-derived samples exhibited frequencies from
57.0 to 80.2%, while three Indo-European samples exhibited much lower frequencies of 23.4–33.0%. The relatively low frequency of MxPAR in Indo-European samples corresponds with the general trend toward dental
simplification in these populations; the relatively high
frequency of MxPAR in Sinodonts (Northeast Asians and
Native Americans) corresponds with the general trait
intensification in these groups (Scott and Turner, 1997;
Hawkey, 2002).
Generally speaking, the Solomon Islander and Bantu
samples exhibited frequencies intermediate to the two
major groups mentioned above, though not at all loci/
breakpoint combinations. Though the results from both
the Northeast Asian/Asian-derived and Indo-European
samples support the pattern seen in prior research on
MxPAR (e.g., Wasser, 1953, Scott, 1973), few data are
available to compare with the South African Bantu and
Solomon Islander samples. Wasser’s (1953) analysis of a
small ‘‘Negroid’’ sample, likely composed of AfricanAmericans, found higher MxPAR frequencies than identified in the South African Bantu sample in our analysis.
Additional research is needed to determine if the discrepancy between these two samples is spurious, or due
to biological variation in African or African-derived populations.
Bailey SE. 2002. Neandertal dental morphology: implications
for modern human origins. Ph.D. dissertation, Department of
Anthropology, Arizona State University, Tempe.
Burnett SE. 1998. Maxillary premolar accessory ridges
(MxPAR): worldwide occurrence and utility in population differentiation. M.A. thesis, Department of Anthropology, Arizona State University, Tempe.
Burnett SE, Hawkey DE, Turner CG II. 1996. Accessory ridges
in maxillary premolars: a preliminary study of their occurrence in four populations. Am J Phys Anthropol Supp 22:76.
Burnett SE, Irish JD, Fong MR. 1998. How much is too much?
Examining the effect of dental wear on studies of dental morphology [abstract]. Am J Phys Anthropol Supp 26:115–116.
Gilmore RW. 1968. Epidemiology and heredity of accessory occlusal ridges on the buccal cusps of human premolar teeth.
Arch Oral Biol 13:1035–1046.
Hawkey DE. 2002. The peopling of South Asia: evidence for
affinities and microevolution of prehistoric populations of
India and Sri Lanka. Spolia Zeylanica Vol. 39, Colombo:
Department of National Museums, Sri Lanka. p 1–300
Little RJA. 1988. A test of missing completely at random for
multivariate data with missing values. J Am Stat Assoc
83:1198–1202.
Little RJA, Rubin DB. 1987. Statistical analysis with missing
data. New York: Wiley.
Lukacs JR, Hemphill BE. 1992. Dental anthropology. In: Human
skeletal remains from Mahadaha: a gangetic mesolithic site.
South Asia Occasional Papers and Theses No. 11. Cornell University. p 157–270.
Morris DH. 1965. The anthropological utility of dental morphology. Ph.D. dissertation, Department of Anthropology, University of Arizona, Tucson.
Morris DH. 1970. On deflecting wrinkles and the Dryopithecus
pattern in human mandibular molars. Am J Phys Anthropol
32:97–104.
Nichol CR. 1990. Dental genetics and biological relationships of
the Pima Indians of Arizona. Ph.D. dissertation, Department
of Anthropology, Arizona State University, Tempe.
Nichol CR, Turner CG II. 1986. Intra- and interobserver concordance in classifying dental morphology. Am J Phys Anthropol 69:299–315.
Robinson JT. 1956. The dentition of the australopithecinae. Pretoria: Transvaal Museum Memoir, Number 9.
Scott GR. 1973. Dental morphology: a genetic study of American
white families and variation in living Southwest Indians.
Ph.D. dissertation, Department of Anthropology, Arizona
State University, Tempe.
American Journal of Physical Anthropology
324
S.E. BURNETT ET AL.
Scott GR. 2008. Dental morphology. In: Katzenberg MA, Saunders
SR, editors. Biological anthropology of the human skeleton, 2nd
ed. New York: Wiley-Liss. p 265–298.
Scott GR, Turner CG II. 1997. The anthropology of modern
human teeth: dental morphology and its variation in
recent human populations. Cambridge: Cambridge University
Press.
Turner CG II, Nichol CR, Scott GR. 1991. Scoring procedures
for key morphological traits of the permanent dentition: the
Arizona State University Dental Anthropology System. In:
American Journal of Physical Anthropology
Kelley MA, Larsen CS, editors. Advances in dental anthropology. New York: Wiley-Liss. p 13–31.
Wasser RC. 1953. Morphological traits of the maxillary first premolar. M.A. thesis, Department of Anthropology, University of
Arizona, Tucson.
Wu L, Turner CG II. 1993. Brief communication: variation in
the frequency and form of the lower permanent molar middle
trigonid crest. Am J Phys Anthropol 91:245–248.
Zuckerkandl E. 1891. Anatomie der Mundhohle mit besonderer
Berucksichtingung der Zahne. Vienna.
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