Generic characteristics of _Tantilla_ are as follows: size small, body
slender, head not noticeably distinct from body; preoculars one;
postoculars one or two; nasals two; loreal absent; smooth dorsal scales
in 15 rows; anal plate usually divided but sometimes single; subcaudals
paired; usually two enlarged, posterior, grooved fangs on the maxilla
separated by a small diastema from the other maxillary teeth (Baird and
Girard, 1853:131; Cope, 1900:1110; Dunn, 1928:24; Blanchard, 1938:369;
Schmidt and Davis, 1941:268; Wright and Wright, 1957:722; Conant,
1958:180). Of these characteristics, only the following were invariable
in our sample: size small, body slender, head not noticeably distinct
from body; postoculars one or two; smooth dorsal scales; posterior
grooved fangs on maxilla. The dorsal scales, anal, and subcaudals were
"correct" 92 per cent of the time; the preoculars and nasals were
"correct" 97 per cent of the time.
[Illustration: FIG. 5. Ventral view of right maxilla of _T. gracilis_
(KU 83484), x 39. Actual length of bone is 2.44 mm. A. Detail of bone.
B. Outline sketch of bone to illustrate characteristics examined.
Lateral flange (PLF) forms an obtuse angle (ADC) with main axis of bone
(AB); a reference line (2), perpendicular to the main axis of the bone,
is used to locate the tooth-socket directly opposite the tip of the
suborbital process (SOP); the anterior and posterior edges of the
suborbital process are not parallel at any point (reference lines 1 and
3).]
_Tantilla_ reportedly has two nasals (Baird and Girard, 1853:131; Cope,
1900:1110; Wright and Wright, 1957:722). _Tantilla gracilis_ usually has
a single nasal that is divided below the naris; variation in this
characteristic is discussed above.
In addition to the generic characteristics, specific characteristics for
_T. gracilis_ are as follows: supralabials 5-8 (usually 6); supralabials
3 and 4 entering orbit; infralabials 5-7 (usually 6); temporals 1 + 1;
ventrals 115-138 in females, 106-132 in males; subcaudals 33-53 in
females, 40-57 in males; tail length 13-27 per cent total length in
females, 15-30 per cent in males (Baird and Girard, 1853:132; Cope,
1900:1111-12; Force, 1935:653-54; Taylor, 1936:337-38; Blanchard,
1938:371-72; Kirn, Burger, and Smith, 1949:240-49). Excepting the number
of temporals and the supralabials entering the orbit, the
characteristics of the specimens in our sample are within the ranges of
variation mentioned above. Of the 10 maxillary characteristics studied,
no variation was observed in number of fangs or angle of lateral flange.
Because our data have some bearing on the problem of geographic
variation in _T. gracilis_ and the recognition of subspecies, we comment
briefly on the status of subspecies in _T. gracilis_. Kirn, Burger and
Smith (1949) proposed the recognition of two subspecies of _Tantilla
gracilis_ (_T. g. gracilis_ Baird and Girard and _T. g. hallowelli_
Cope). These subspecies were diagnosed on the basis of differences in
ventrals, subcaudals, and the ratio of tail length to total length;
sexual dimorphism in each characteristic was considered. We do not
recognize these subspecies for the reasons given below.
The data of Kirn _et al._ (1949) appear to be presented inaccurately in
part. Both of us independently recalculated the mean given for each
characteristic for each subspecies, using the data in figures 2-4 of
Kirn _et al._ (1949:242, 244-245). Of their 12 means presented (table 1,
p. 247) only two agree with our recalculated means, although the means
calculated by each of us independently are in complete agreement (Table
5). Also, we independently calculated the percentages of specimens of
each "subspecies" that are included in the ranges of variation given in
their diagnoses (Table 5); again, our independent calculations are in
complete agreement. In our opinion the differences between the
populations for the characteristics analyzed do not warrant recognition
of subspecies (Fig. 6).
TABLE 5. Means of "Diagnostic" Characteristics of T. g. gracilis Baird
and Girard and T. g. hallowelli Cope.
=============================================================================
| _T. g. gracilis_ | _T. g. hallowelli_
-----------------+-----------------------------+-----------------------------
| | |Per cent | | |Per cent
CHARACTERISTICS | | Mean |specimens | | Mean |specimens
| Mean | (Kirn, |of Kirn, | Mean | (Kirn, |of Kirn,
|(Kirn, |_et al._)|_et al._ | (Kirn, |_et al._)|_et al._
|_et al._|recalcu- |included |_et al._ |recalcu- |included
| 1949) | lated |their |in 1949) | lated |in their
| | by us |diagnosis | | by us |diagnosis
-----------------+--------+---------+----------+---------+---------+---------
Ventrals--females|125.67 | 125.71 | 69.4 | 130.07 | 130.07 | 79.6
Ventrals--males |115.97 | 116.61 | 70.0 | 121.22 | 120.87 | 69.7
| | | | | |
Caudals--females | 40.99 | 40.82 | 62.8 | 46.79 | 43.82 | 77.4
Caudals--males | 47.75 | 48.29 | 78.3 | 51.67 | 50.29 | 51.0
| | | | | |
Tail L./total L. | | | | | |
females | .1976| .1976| 69.0 | .2084| .2076| 74.2
Tail L./total L. | | | | | |
males | .2336| .2362| 56.1 | .2477| .2423| 79.6
-----------------------------------------------------------------------------
The data presented by Kirn _et al._ do not demonstrate intergradation
between two populations. Moreover, the diagnostic ranges of the number
of subcaudals in males of _hallowelli_ and the ratio of tail length to
total length in males of _gracilis_ do not include the recalculated
means for those characteristics. Furthermore, the means for the
following characteristics are dangerously close to being excluded from
their respective "diagnostic" ranges: in _hallowelli_, the number of
ventrals in males; in _gracilis_, the number of subcaudals in females,
and the ratio of tail length to total length in females. It is
incongruous that Kirn _et al._ state (p. 243) that "the coefficient of
geographic divergence is .6 per degree latitude" for ventrals, and on
the same page they state that "The average number of ventrals gradually
increases toward the north in _Tantilla gracilis_ except in southern
Oklahoma and central Arkansas (the area of intergradation between _T. g.
gracilis_ and _T. g. hallowelli_) where the change seems to be more
abrupt." The data presented in Kirn _et al._ (1949) do not demonstrate
an abrupt change.
The present sample of _T. gracilis_ from Kansas is clearly within the
geographic range of _T. g. hallowelli_ as mapped by Kirn _et al._
(1949:241). However, for the sample from Kansas, the mean number of
subcaudals of males is well within the diagnostic range for _T. g.
gracilis_ (Table 6), the mean number of subcaudals of females is closer
to the mean of _gracilis_ than it is to the mean of _hallowelli_ (Table
5), and the mean of the ratio of tail length to total length of both
sexes is within or very close to the diagnostic range for _gracilis_
(Table 6).
[Illustration: FIG. 6. Frequency polygons presenting ratios of tail
length to total length for males of _T. g. gracilis_ and _T. g.
hallowelli_ from Kirn, _et al._ (1949). The dotted vertical lines
represent the means given by Kirn, _et al._ (1949) for _gracilis_ (left)
and _hallowelli_ (right); the solid vertical lines represent the
recalculated means for _gracilis_ and _hallowelli_, respectively, using
the data of Kirn, _et al._ The hatched bars represent the range included
by Kirn, _et al._ (1949) in their diagnoses of _gracilis_ (left) and
_hallowelli_ (right).]
TABLE 6. Comparison of the Means of Some Characteristics of the Sample
of _Tantilla gracilis_ from Kansas (Our Data) with Some of the
Diagnostic Characteristics (Kirn _et al._, 1949:240) of _Tantilla
gracilis gracilis_.
============================================================
|Diagnostic range for | Mean of the sample
CHARACTERISTIC | _T. g. gracilis_ |("_T. g. hallowelli_")
| | from Kansas
---------------+---------------------+----------------------
No. of | |
subcaudals | 40-50 | 48.4 (N = 109)
males | |
| |
Tail L./ | |
Total L. | .160-.200 | .20 (N = 79)
females | |
| |
Tail L./ | |
Total L. | .200-.235 | .23 (N = 109)
males | |
---------------+---------------------+----------------------
Smith and Sanders (1952:218) pointed out an error in the range of
subcaudals in female _T. g. gracilis_ as stated in table 1 (p. 247) of
Kirn _et al._ We add some additional corrections that should be made on
the same page. In table two, column two ("Sex"), the words "male" and
"female" are reversed for each characteristic. Also, in table two,
column four ("Means from data of Force"), the means for caudals should
be corrected from 33.61 to 43.61 in females and from 39.99 to 50.32 in
males, as based on our recalculations from Force's data; we did not
recalculate the means of Force's data for the other characteristics.
The discussion above demonstrates that the number of subcaudals and the
ratio of tail length to total length are weak characteristics for
diagnosing _T. g. gracilis_ and _T. g. hallowelli_. The only remaining
diagnostic characteristic given by Kirn _et al._ (1949) is the number of
ventrals. Nevertheless, a step-cline in the number of ventrals, if one
exists, is yet to be demonstrated. Therefore, we completely agree with
Dowling (1957:32), who stated that "... the overlap in each character is
so great that any subspecific differences appear to be as yet undefined.
It is here suggested that _T. gracilis_ be retained as binomial...."