<oological Journal of the Linnean Society (1989), 95: 335-362. With 4 figures
The status of Pliocercus and Urotheca
(Serpentes:Colubridae), with a review of
included species of coral snake mimics
JAY M. SAVAGE* AND BRIAN I. CROTHER
Department o f Biology, UniversiQ of Miami, P.O. Box 249118, Coral Gables,
Florida 33124, U.S.A.
Receiued January 1988, accepted for publication May 1988
The generic name Urotheca Bibron, 1843 is revived for a group of Neotropical colubrid snakes
diagnosed by a long, thickened but fragile tail and the presenre of a specialized naked pocket on the
asulcate surface of the hcmipenial capitulum. Urotheca includes those species previously placed in the
lateristriga group o f the genus Rhadinaea and the coral snake mimics usually referred to the genus
Pliocercus. The many names based upon the coral snake mimics are shown to represent two speries at
most: Urotheca elapozdes, a bicolour (red and black) or tricolour (red, yellow and black) banded or
ringed form found in Mexico and northern Central America and U. euryzona, which is usually bicolour
(red, yellow or white and black) and ranges from Nicaragua to western Ecuador. Coloration in
IJ. elapoides resembles closely that of sympatric species of venomous coral snakes. Local variation in
coloration and a geographic trend in the colour of the light rings (usually red in the north, white to
the south) in U. euyzona parallcls similar colour variation in the sympatric venomous coral snake
Micrurus mipartitus. These patterns of variation add strong support to the idea that the two species are
mimics of the highly venomous coral snakes. Urotheca, including the non-mimetic species U. decipiens,
U.fuluiceps, U.guentheri, U. lateristrifa, U . multilineata and U.pachyura, shares the characteristic of a very
long and disproportionately thickened and fragilr tail with the coral snake mimics of the distantly
related genus Scaphiodontophis. Members of both gencra have a very high proportion (about 500/,,)of
the tails broken indicating a probable predator escape device. Breakage is intercentral, with a
calcified cap developing over the tip of the distal surface of the new terminal vertebra unlike the
situation in many lizards where there is an intracentral fracture septum and the tail is regrnerated.
KEY WORDS:- ~Serpentes- Colubridae
~
Pliocercus
1JroLheca
~
mimicry
-
systematics - caudal
autotomy.
CONTENTS
Introduction . . . . . . . . . . . . . . . . .
The systematic status of Pliocercus and Urotheca . . . . . . . . .
Genus Urotheca Bibron, 1843 .
. . . . . . . . . . .
The coral snake mimics
. . . . . . . . . . . . . .
Variation in Costa Kican ‘Pliocercus’
. . . . . . . . . . .
Scutellation . . . . . . . . . . . . . . . .
Coloration
. . . . . . . . . . . . . . . .
Discussion of variation and the status of nominal forms . . . . . .
Material examined
. . . . . . . . . . . . . .
Relationships of Urotheca euryzona to upper Central American and Mexican forms .
Mimicry and tail autotomy
. . . . . . . . . . . . .
Acknowlrdgements
. . . . . . . . . . . . . . .
Rererencrs
. . . . . . . . . . . . . . . . .
336
336
34 1
343
346
347
347
348
350
352
357
359
360
*Author to whom correspondence should be addrrsscd.
+
102+4082/89/040335 28 SOS.OO/O
335
0 1989 The Linnean
Society of London
336
J. M. SAVAGE AND B. I. CROI'HER
INTRODUCTION
The members of the nominal genus Pliocercus are a group of small to moderate
sized (to 770 mm in total length), usually ringed (sometimes blotched or banded)
snakes that most often have some or all of the light rings bright red in colour. They
are further distinctive in having extremely long and disproportionally thick tails
(mean tail length=42% of total length) that are very fragile (Liner, 1960;
Wilson, 1968) and whose breakage probably acts as a predator escape device. In
addition, these snakes are members of a guild that are mimics of the venomous
coral snakes (Dunn, 1954; Wickler, 1968; Greene & McDiarmid, 1981).
Populations within the genus, as currently recognized, may be bicolour (black
and a light colour, usually red or white) or tricolour (black, yellow and red), and
are usually ringed (hut sometimes banded) with black.
The present study was initiated by the need to clarify the status oflower Central
American coral snake mimics referred to the genus, as background for a
comprehensive work on the herpetology of Costa Rica. Taylor (1951, 1954)
recognized three species of the genus: Pliocercus diniidialus Cope, 1865 and two new
taxa P. annellalus Taylor, 1951 and P. arubricus Taylor, 1954 in Costa Rica.
Although Dunn & Bailey (1939) considered P. dimidiatus to be a race of
P. euryzonus Cope, 1862, a form originally described from Colombia, Taylor
regarded all four taxa as distinct species. Each of these names is based upon
bicolour, ringed snakes.
Early in their work on the herpetofauna of Costa Rica, N. J. Scott, Jr.
convinced Savage that only a single species of Pliocercus occurred in Costa Rica
and that it was conspecific with the South American bicolour form, P. euryzonus.
Although Scott (1969) listed only the latter name in his review of Costa Rican
snake distribution (by implication synonomizing the other nominal taxa), no
cvidence has been published to justify that conclusion. Nevertheless, Savage
(1973, 1976, 1980)) Greerie & McDiarmid (1981),Wilson & Meyer (1982, 1985),
Scott, Savage & Robinson (1983) and Savage & Villa (1986) have followed this
view.
The original purpose of this paper was to reconsider Scott's ideas in the light of
recently collected material and to relate our analysis of the Costa Rican situation
to a broader geographical context. However, as the study proceeded it became
clear that the snakes referred to Pliocercus by all subsequent authors following
Dunn & Bailey (1939) and Dunn (1944),were questionably distinct, generically,
from some members of the genus Rhadinaea (sensu Myers, 1974). Consequently, it
became necessary to include a review of the generic status of Pliocercus as part of
the study. Because the results of that review require several significant
nomenclatural changes, a discussion of the relationships of the taxa usually placrd
in Pliocercus (Peters & Orejas-Miranda, 1970; Ptrez-Higareda & Smith, 1986)
with Rhadinaea is presented prior to the analysis of individual and geographic
variation.
THE SYSTEMATIC STATUS OF PLIOCERCUS AND UHO'THECA
The genus Pliocercus was described by Cope (1860) for the simultaneously
proposed P. elapoides, (a tricolour red, yellow and black species with a triad of
black rings bordering each red ring) from near Jalapa, Veracruz, Mexico.
CORAL SNAKE MIMICS
337
Subsequent 19th century workers attributed a number of additional bicolour and
tricolour taxa to the genus (see detailed listing of names in the following section of
this paper). However, Boulenger ( 1894) placed the several coral snake mimics
previously referred to Pliocercus together with several other species into the genus
Urotheca Bibron in de la Sagra, 1843 (monotype: Calamaria dumerilii Bibron in d e la
Sagra, 1840). Although the type of Urotheca is a brown snake, with a poorly
defined longitudinal, light stripe on the neck, most authors utilized that generic
name for the coral snake mimics during the next four and a half decades.
Primarily because of the great confusion surrounding the provenance (listed as
Cuba) and identity of the type species--but also influenced by the unclear and
complicated circumstances involving the publication and publication dates of
de la Sagra’s works (see Myers, 1974)-Dunn & Bailey (1939) and Dunn (1944)
applied the name Pliocercus to the coral snake mimics. This course has been
followed by all subsequent workers.
The name Urotheca has had a tortured history in the interim as discussed in
detail by Myers (1974). I t was left in limbo initially because the type species had
not been rediscovered (Dunn, 1944). It was then suggested as a senior synonym
for Rhadinaea Cope, 1863 (orthotype: Taeniophis vermiculaticeps Cope, 1860) by
Dunn ( 1957). Then it was used as a senior synonym for Rhadinaea by Roze ( 1959,
1964, 1966). Finally, Myers (1974) threatened it with extinction through action of
the International Commission on Zoological Nomenclature upon his re-discovery
of the type species, 1Jrotheca dumerilii, and the realization that it belonged in
Rhadinaea as he then conceived of that genus. This species proved to be native to
Colombia not Cuba and belongs to a very distinctive subdivision of Rhadinaea
(sensu lato), the R. lateristriga group (seven or eight species), readily distinguished
from other groups within that genus in details of dentition, hemipenes,
scutellation and caudal morphology. Since the name Urotheca has priority over
Rhadinaea for nomenclatural purposes, Myers’ re-discovery of the type species of
the former and his conclusion that it was congeneric with the latter could have led
to wholesale name changes. Consequently he continued to use the wellestablished name Rhadinaea in his monograph. He never actually applied to the
Commission for suppression of Urotheca because he subsequently decided to
resurrect Urotheca for the R. lateristriga group pending further study of the
hemipenis of U. dumerilii (Myers, personal communication).
During the course of our research on Pliocercus we gradually became aware of
the similarities between these coral snake mimics and the less gaudily coloured
members of the Rhadinaea lateristriga group. The principle clue suggesting the need
to evaluate possible relationships among these snakes was the unusual and striking
resemblance in caudal morphology. As pointed out by Myers ( 1974),snakes of the
R. lateristriga group differ from other members of the genus in having an extremely
long tail (36-47y0 of total length in adults) that is disproportionately thick for
most of its length. Most snakes referred to Rhadinaea by Myers have moderate to
long tails (<350,/, of total length, in adults). Some members of the R. decorata
group have extremely long tails (35-48% of total length) but the tails are slender
and tapering as in most other long tailed colubrid snakes in these species as well as
in shorter-tailed representatives of the genus (Myers, 1974, fig. 5). Myers also
noted the high frequency of broken or missing tails in the R. lateristriga stock
(about 54% in his samples) and pointed out that even when most of the tail has
been lost by a n individual snake, it can be assignable readily to the group because
J . M . SAVAGE AND B. I. CRO'I'HER
338
of the conspicuously thickened tail. The morphology of the tail in Pliocercus is
similar to that of members of the R. lateristriga group: extremely long (35-46O/;, of
total length), distinctly thickened and very frequently broken (48"/, in our
samples and those reported in the literature).
Additional study revealed that no characteristic, aside from coloration, will
separate Pliocercus from Rhadinaea (sensu Myers). Dunn's decision to recognize
Pliocercus was based solely upon this criterion. Myers (1974: 233) also regarded the
genus as distinctive based on coloration alone, but related to Rhadinaea. For this
reason we decided to undertake further comparisons between Pliocercus and the
R. lateristriga group.
Putative diagnostic features for the latter stock, aside from tail morphology, as
listed by Myers (1974) include: I , a distinct diastema followed by two fangs, last
fang on maxilla offset laterally; 11, hemipenes single, unicapitate with a distal
naked pocket present on the asulcate side of the capitulum; asulcate folds of
uneverted organ usually two; 3, dorsal scales 17-1 7-1 7; 4, a subpreocular usually
present; 5, temporals usually 1 1; 6, supralabials usually eight; 7, body uniform
brown or black or usually with one or two light stripes; head usually paler than
body or pale ocelli on head and/or neck. Comparisons of these features to those
found in Pliocercus indicated a strong concordance between the two groups as
discussed below.
The maxillary dentition in Pliocercus is composed of a series of 18-19 strongly
recurved, subequal teeth separated by a diastema from two enlarged, posterior
fangs (18-19+2). The last fang is offset laterally. Members of the Rhadinaea
lateristriga group have fewer anterior maxillary teeth ( 1 1--17), a distinct diastema,
and two enlarged posterior fangs, with the last fang offset. The range of variation
in the number of maxillary teeth in individual species of the R. lateristriga group is
two to four, with three species (R.decipiens, R. dumerilii and R. multilineata) having a
maximum of 17 2.
The hemipenis of Pliocercus has not been described in detail previously; the
following account follows the sequence used by Myers (1974) in his revision of
Rhadinaea and is based on a single specimen (CRE 8468). The everted hemipenis
of P. euryzonus (Fig. 1 ) is slightly bilobed (following Branch, 1986) and extends to
the level of subcaudal seven, T h e retractor muscle is undivided. The capitulum
comprises a little over one third of the organ on the sulcate side. T h e sulcus
spermaticus bifurcates just inside the base of the capitulum and is centrolineal
(Myers & Campbell, 1981), but with short widely divergent branches. 'I'he
capitulum is calyculate; the calyces are ornamented with spinules on the asulcate
side and the periphery of the capitulum and are ornamented with papillae on the
sulcate side. The free edge of the capitulum is interrupted twice by fleshy ridges
connecting the stalk to the capitulum. T h e ridges are covered with spines and
between these ridges a deep, conspicuous pocket is present. The pocket is
separated from the stalk by two proximal transverse rows of small spines. The free
edges form a conspicuous overhang on the lateral sides of the capitulum. The
sulcate surface is differentiated; spinules are present basally giving way to 18 small
to moderate sized recurved spines, including a single row of small spines at the
perimeter of the capitulum. The asulcate side possesses two basal hooks
surrounded by scattered tiny spinules that extend halfway up the stalk (the noncapitate portion of the organ). Three pairs of hooks are arranged in two vertical
rows that run from below each of the two fleshy ridges to about halfway down the
+
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CORAL S N A K E MIMICS
I cm
Figure I . Right hernipenis, asulcate surface, of Iholheca euyzona (CRE 8468); the two capitular ridges
are shown as spinous areas lying laterad and distad tcr the distinctive naked pocket.
stalk, and increase in size distally to basally. T h e basal-most pair are the largest
hooks. Overall, the stalk possesses 45 spines above the basal half.
The hemipenes of the Rhadinaea lateristriga group as described and figured by
Myers (1974) are single, capitate and have a bifurcate sulcus with short branches.
The organ is usually short and stout and is five to seven subcaudals in length when
everted (except in R. decipiens and R. pachyura where the organ is nine subcaudals
in length) and has an undivided retractor muscle. T h e capitulum makes up onefifth to one-haif of the length of the organ on the sulcate side, with R. decipiens
having the shortest and R.fulviceps and R. guentheri the longest capitula. T h e sulcus
forks just inside the capitulum, except in R. lateristriga where the fork is halfway up
the capitulum; the sulcus branches on the everted organ but never reaches the tip.
The capitulum is always calyculate with papillate micro-ornamentation on the
sulcate side and spinulate micro-ornamentation on the asulcate side and the
340
J. M. SAVAGE AND B. I . CROTHER
periphery of the capitulum. T h e stalk is always connected to the capitulum on the
asulcate side by two fleshy ridges (which may or may not be adorned with small
spines) that border a conspicuous, deep pocket. Myers (1974) was uncertain as to
the presence of the pocket or fusions on the uneverted hemipenis of R. dumerilii.
Small to moderate sized spines are present above the basal half of the stalk and
range in number from 22-85. A nude area bordered by two rows of two or three
spines each is present on the asulcate side, just basal to the pocket. This region is
not obvious in R. decipiens. The most basal of these spines are typically the largest
on the organ. T h e basal half of the organ is unadorned except for minute spinules
and in R. guentheri and R. lateristriga a single basal hook is present.
It is evident from the above descriptions that Pliocercus euryzonus and Rhadinaea
lateristriga hemipenes are similar in virtually all characters. Pliocercus only differs
from the R. lateristriga group in having the hemipenis slightly bilobed as opposed
to single. Rhadinaea decipiens and R. pachyura have grooved capitula that suggest
bilobation. The most striking feature shared between Pliocercus and the
R. lateristriga group is the presence of two fusions on the asulcate side that connect
the stalk and capitulum and the conspicuous pocket that is formed between the
fusions. The asulcate pocket appears to be a strong synapomorphy (based on
outgroup comparisons to other xenodontines including the other species groups of
Rhadinaea) that unites Pliocercus and the R. lateristriga species group.
Rhadinaea brevirostris, a form with a moderately long ( 1 7 to 25% of total length)
and slenderly tapering tail, also has a conspicuous naked pocket formed by an
enlarged calyx on the asulcate surface of the capitulum. R. brevirostris and its close
allies (which lack the pocket) were regarded as a very distinctive lineage within
Rhadinaea by Myers ( 1974). This conclusion was confirmed by Cadle ( 1984) based
upon molecular evidence, who pointed out the close relationship between the
R. brevirostris group and South American ‘xenodontines’ as opposed to Central
American ‘xenodontines’ including other groups within Rhadinaea (sensu Myers,
1974). Consequently we regard the similarity in R. brevirostris, as compared with
Pliocercus and members of the R. lateristriga group in this one hemipenial feature as
convergent .
In details of scutellation Pliocercus and the Rhadinaea lateristriga stock agree in
having 17-17-17 dorsal scale rows, usually a subpreocular (almost always present
in Pliocercus), the temporals usually 1 1 and the supralabials usually eight.
As a result of our review and comparisions, we are unable to distinguish
between Pliocercus as presently understood and members of the Rhadinaea
lateristriga group, except through differences in coloration and a slight difference
in numbers of maxillary teeth. In addition we are struck by the fact that the two
groups share unique derived character complexes in hemipenial and caudal
morphology. Because of these findings we conclude that the two stocks form a
single monophyletic lineage and consequently their placement into separate
genera is unwarranted. This relationship has not been unnoted by previous
investigators because Boulenger ( 1894) included two R. lateristriga group spccies
(dumerilii and laterislriga) in Urolherca along with all taxa previously placed in
Pliocercus. Myers (1974: 233 and fig. 5 1) was the first to indicate that Pliocercus was
derived from a R. lateristriga group ancestor and to point out the congruence of tail
morphology and hemipenial structure between Pliocercus and the R. laleristriga
group.
I t is with some reluctance that we now address the results ofour conclusion that
+
CORAL SNAKE MIMICS
341
the Rhadinaea lateristriga group and Pliocercus are congeneric and the
complementary one that the genus Rhadinaea as presently constituted is
paraphyletic. The reluctance derives in part from the recognition that other
workers are aware of the composite nature o f the genus (i.e. Cadle, 1984, on
relationships of the R. brevirostris group; current on-going research on the
partitioning ofRhadinaea by C. W. Myers). Thus three alternatives are open to us:
I , retain the status quo and recognize Rhadinaea and Pliocercus as presently
constituted; 2, place Pliocercus as a junior subjective synonym within the large nonmonophyletic assemblage o f species now referred to Rhadinaea; 3, recognize the
R. lateristriga group and Pliocercus as a monophyletic group constituting a separate
genus for which the earliest available name is Urotheca.
Each of these alternatives has disadvantages. T h e first would perpetuate the
name Pliocercus in the literature until such time as a detailed phylogenetic analysis
of Rhadinaea (sensu lato) were to be completed; it would ignore the relationship
established in the present paper. The second would change the names of some
taxa now placed in Pliocercus and Rhadinaea, with the certainty that these names
will undergo another change when Rhadinaea is partitioned. T h e third would
change a number of names from Pliocercus and Rhadinaea to Urotheca, prior to
thorough revision o f other monophyletic groups within Rhadinaea and might prove
to be premature in the light of later findings; there remains an outside possibility
that the type species o f Urotheca may prove to be distinct from other members of
the R. laterislriga group.
Alternative 1 is the most conservative course, the least informative, and the
most contrary to the evidence we have presented and to our systematic
philosophy. Alternative 2 will promote the greatest instability by requiring name
changes for the coral snake mimics now and again later in this century.
Alternative 3 may risk additional name changes (although we believe not) but
results in a relatively radical re-alignment of taxa and is not based upon an
extensive analysis of all Rhadinaea lineages or several sets of potentially significant
characteristics (e.g. osteology). Nevertheless, it is informative, it has fewer
potential unfortunate and/or real results than the other two, and we have adopted
this alternative as the best one to follow under the circumstances.
Genus Urotheca Bibron, 1843
1843. Urotheca Bibron
1860. Pliocercus Cope (monotype: Pliocercus elapoides Cope, 1860).
1860. Elapochrus W. Peters (monotype: Elapochrus deppei W. Peters, 1860).
1863. Cosmiosophis Jan (monotype: Liophis lricinctus Jan, 1863).
Type species
Calamaria dumerilii Bibron, 1840, by monotypy
Dejinilion
Small to moderate-sized (to 795 mm in total length), terrestrial, ‘xenodontine’
snakes, with long tails ( > 3 5 0 / , of total length in adults), that are
disproportionately thick and very fragile. Basic complement of colubrid head
shields, most bearing minute scale organs (tubercles). Head barely distinct from
neck, body cylindrical. Pupil of eye round. Nasal variable, often divided; a loreal;
J. M. SAVAGE AND B. I. CKO’I‘HER
342
one or two preoculars and frequently a subpreocular; one or two postoculars;
temporals 1 1 or 1 2; two pairs of elongate chin shields. Dorsal scales smooth,
except for the occasional presence of supraanal keels in males of one species
(U.guentheri), in 17-17-17 rows; no apical scale pits; anal plate divided;
subcaudals divided. Maxillary teeth 13- 19 followed after a distinct diastema by
two enlarged, usually ungrooved fangs (grooved in some individuals of
U . guentheri); teeth anterior to diastema subequal; ultimate fang offset laterally;
mandibular teeth subequal; no hypapophyses on posterior vertebrae. Hemipenes
single or slightly bilobed symmetrical, with a bifurcate sulcus spermaticus; organ
unicapitate, with the capitulum calyculate and the calyces with papillate microornamentation on the sulcate surface and spinulate micro-ornamentation on the
asulcate side; the stalk of the organ connected to the capitulum by two fleshy
ridges on the asculate surface that border a distinct naked pocket within the
capitulum; central sector of hemipenes covered by large spines and hooks, basal
portion by small spinules. Dorsal coloration is variable: uniform; marked with
conspicuous white and sometimes dark lateral stripes; or with a bicolour, tricolour
or tricolour triad coral snake mimic pattern, usually involving black and red or
white or black red and yellow rings around the body.
+
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Diagnosis
The peculiar morphology of the fragile, thickened, long tail ( > 35% of the total
length in adults) and the hemipenes will immediately distinguish Urotheca from all
its colubrid cognates, including what appear to be its closest relatives, the genera
Coniophanes, Rhadinaea (exclusive of the R. brevirostris group, Cadle, 1984) and
Trimetopon. ‘The first two genera have slender, tapering tails that are not easily
broken. In Trimetopon the tail is relatively stout but only moderately long
(22-33% of total length). All of these genera lack the distal asulcate pocket on the
hemipenes that is diagnostic of Urotheca. In addition all Coniophanes have distinctly
grooved fangs and a posterior scale reduction (no grooves or weakly grooved fangs
in some individuals of one species and no scale reduction in Urotheca).
Among New World colubrids two other genera have relatively long, thickened
tails that appear to be extremely fragile as indicated by a high proportion of
specimens with broken or incomplete tails. Enulius is a group of three small (to
5.50 mm in total length), fossorial or semi-fossorial species with the body and tail
uniform in colour. Tail length is 30-42% of total length in adult Enulius and
around SO”/;, of the tails have been broken or lost. This genus is only distantly
allied to Urotheca (placed in different tribes by Jenner, 1981) and is trenchantly
different from i t in the following diagnostic features (contrasting character states
for Urotheca in parentheses): maxillary teeth 3-5 + 2 ungrooved fangs ( 13-1 9 2,
usually ungrooved fangs); hemipenes non-capitate, covered with minute, uniform
spines (capitate, large and small spines basally, capitulum calyculate); one or two
apical scale pits (no scale pits).
The second genus, Scaphiodontophis, appears to have a similar tail morphology
and further resembles some Urotheca in having a coral snake colour pattern,
although the pattern may be restricted to the tail and/or the anterior part of the
body. The two genera differ fundamentally from one another as seen in this list of
features diagnostic for Scaphiodontophis (contrasting characteristics for Urotheca are
included in parentheses): 39-59 subequal, hinged maxillary teeth (13-19 2,
non-hinged), no fangs (two fangs), hypapophyses on posterior vertebrae (absent)
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CORAL SNAKE MIMICS
343
and asymmetric, single non-capitate hemipenes, with a simple sulcus spermaticus
(symmetric, single or slightly bilobed, capitate organ, with bifurcate sulcus).
Coloration will readily separate ~caphiodontophisfrom the superficially similarly
coloured Urotheca. Scaphiodontophis always have tricolour, banded coral snake
patterns although the banding may be restricted to the anterior portion of the
body. In the area of sympatry with those U. elapoides that are tricolour banded,
Scaphiodontophis have a pattern oftricolour dyads (two black bands separated from
one another by a yellow or white band for each red band), rather than tricolour
monads (one black band for each red area, with red and black areas separated by
yellow).
A number of other genera of New World colubrid snakes include species with
stout or long to very long tails. None however, exhibits these two features
simultaneously, the tails being either stout and short (e.g. most Tantilla) or long
and tapering (e.g. Nothopsis and Sibon).
Included species
Urotheca decipiens (Gunther), Urotheca dumerilii (Bibron), Urotheca elapoides
(Cope), Urotheca euryxona (Cope), Urotheca fuluiceps (Cope), Urotheca guentheri
(Dunn), Urotheca lateristriga (Berthold), Urotheca multilineata (W. Peters), and
Urotheca pachyura (Cope).
Distribution
From Tamaulipas and Oaxaca, Mexico, south through northern and western
Colombia to western Ecuador and northern Venezuela.
Remarks
The dates of publication of the Spanish and/or French editions of the text and
atlas of Ram6n de la Sagra’s great work in 12 folio volumes on the HistorinJisica,
politica y natural de la Isla de Cuba are uncertain (Smith & Grant, 1958; Myers,
1974). We follow Smith & Grant (1958) and Schwartz & Thomas (1975) in
dating the name Urotheca as 1843 and the atlas containing the original description
of Calamaria dumerilii as 1840.
T H E CORAL SNAKE MIMICS
Cope (1860) originally proposed the name Pliocercus elapoides for a tricolour
(red, yellow and black) species and the same species was given new names by
W. Peters (1860) and Jan (1863) in short order. Salvin (1861) proposed the name
P. aequalis for a bicoloured snake from Baja Verapaz, Guatemala, having broad
alternating red and black rings. Cope (1862) described a third member of this
stock as P. euryxonus from the Truando region, Departamento Choc6, Colombia.
The latter species is a bicolour (black and white), ringed form with very narrow
white rings. Shortly thereafter, Jan (1863) described the same species as LiophiJ
splendens. Another bicoloured taxon, P. dimidiatus, was added to the genus by Cope
( 1865) on the basis of an example with moderately broad red rings from ‘Arriba’,
Costa Rica. As noted above, for most of the remainder of the 19th century and the
early 20th century these snakes were placed in the genus Urotheca Bibron but
Dunn & Bailey (1939) and Dunn (1944) exhumed the name Pliocercus for these
forms, a practice followed by all subsequent workers.
344
J. M. SAVAGE AND B. I . CRO'rHER
In the interim a substantial number ofadditional names has been proposed for
representatives of this genus. As a convenience for the subsequent discussion all
available species group names for Pliocercus are listed below along with an
indication of the colour pattern of each type specimen. T h e following
abbreviations are used to indicate coloration in this list and throughout the
remainder of this paper: BI = Bicolour (black and light); BIs = small black spots;
BIS = large black spots; BIB = banded; BIR = ringed; T = tricolour (black, red
and yellow or white); TZ=black rings, light interspaces suffused with red or
yellow dorsally; T M = tricolour monads, one black ring for each red ring; red and
black rings separated from one another by yellow rings; TT = tricolour triads,
three black rings for each red ring; red rings contact secondary black rings which
are separated from the primary black ring by a yellow ring; Tt = tricolour triad,
with outer two black rings weakly developed. The letter b indicates that the black
areas form bands (e.g. T M b ) not rings.
T h e following style of notation indicates variation: T M / T t b = two different
patterns on same individual; T M , T T = two different patterns in individuals of the
same population.
In order to discuss geographic variation throughout this paper without the use
of an overly ponderous set of adjectives hicolour refers to snakes having alternating
black, red and yellow transverse bands or rings across the body. Bicolour snakes
have alternating black and red or yellow or white bands or rings (BIB, BIR).
Individuals with the dorsal area of the light rings suffused with red or yellow ('1Z)
are also included when we speak of bicolour populations or of geographic
variation to distinguish them from tricolour banded and/or ringed ones. Since the
TZ state is known currently only in Urotheca from Costa Rica, although we suspect
it occurs in Nicaragua and western Panama as well, this terminology should cause
no difficulty.
In most examples of the genus many scales in the dorsal and or lateral areas of
the red rings are tipped with black. In some bicolour forms the black forms a more
or less evident narrow, secondary black band between the primary black rings.
The tricolour triad condition apparently arises from the tricolour monad pattern
by the expansion of the black pigment over the entire (originally red) scale row
that borders the outer margin of the yellow rings to form very narrow secondary
black rings (see Smith & Landy, 1965: pl. 1). The black pigmentation then
increases to include several scale rows to form well-developed secondary black
rings (see Greene & McDiarmid, 1981: fig. 1E).
As a further aid in using the list of described taxa, a reference to the colour
plates ofdorsal patterns provided by Greene & McDiarmid (1981) is given where
appropriate. Documented synonymy is also indicated.
Pliocercus elapoides Cope, 1860 (syntypes: ANSP 38 10-38 13; near Jalapa,
Veracruz, Mexico). TT. Greene & McDiarmid (1981: fig. 1E).
Elapacharus deppei W. Peters, 1860 (holotype: ZMB; Mexico). TT. = elapoides.
Pliocercus aequalis Salvin, 1861 (holotype: BM 1946.1.1.4; San Ger6nimo and the
mountains of Verapaz, Baja Verapaz, Guatemala). BIR. Greene & McDiarmid
(1981: fig. 1F).
Pliocercus euryzanus Cope, 1862 (holotype: USNM 4303, now lost; Truand6 regibn,
Chocb, Colombia). BIR.
Liophis splendens Jan, 1863 (holotype: MSNM; BogotS, Cundinamarca,
Colombia). BIR. = euryzonus (Boulenger, 1894).
CORAL SNAKE MIMICS
345
Liophis tricinctus Jan, 1863 (syntypes: NHMW, MSNM, ZMUC; Mexico).
TT. = elapoides.
Pliocercus dimidiatus Cope, 1865 (holotype: USNM 6363; ‘Arriba’, Costa Rica).
BIR. Greene & McDiarmid (1981: fig. 1D).
?Pliocercus .sargii Fischer, 1881 (holotype: SMNS 2012; Cobhn, Alta Verapaz,
Guatemala). BIR. = aegualis.
Pliocercus salvinii Muller, 1878 (holotype: NHMB 1495; Verapaz, Guatemala).
TM/TMB.
I,. (iophis) elapoides var. diastemus Bocourt, 1886 (syntypes: MNHP 88-132-133;
Plateau of Guatemala). T M , TT.
Pliocercus bicolor H. M. Smith, 1941 (holotype: USNM 25203; Tuxpan, Veracruz,
Mexico). BIR.
Pliocercus elapoides laticollaris H. M. Smith, 1941 (holotype: USNM 110767;
Tenosique, Tabasco, Mexico). TMb/Ttb (most black rings on body reduced to
bands) =saluinii (Stuart, 1963).
Pliocercus elapoides semicinctus K. Schmidt, 1941 (holotype: FMNH 7247 1; Double
Falls, Stann Creek, Belize). Ttb (many or all black rings reduced to bands)
=salvinii (placed as synonym of laticollaris by Peters & Orejas-Miranda, 1970).
Pliocercus andrewsi H. M. Smith, 1942 (holotype: FMNH 36323; Libre Unibn,
Yucatin, Mexico). TM. Greene & McDiarmid (1981: fig. 1C).
Pliocercus elapoides schmidti H. M. Smith, 1942 (holotype: MCZ 26843; Chichkn
ItzA, Yucathn, Mexico). Tt.
Pliocercus elapoides celatus H. M. Smith, 1943 (holotype: MVZ 24689; Ciudad
Tamaulipas, Mexico). Tt/TM.
Pliocercus annellatus Taylor, 1951 (holotype: K U 25370; Morehouse Finca,
Cartago, Costa Rica). BIR.
Pliocercus elapoides salvadorensis Mertens, 1952 (holotype: SMF 42301; Finca San
JosC, Santa Tecla, La Libertad, El Salvador). TM.
Pliocercus arubricus Taylor, 1954 (holotype: KU 3 1943; Isla Bonita, Heredia, Costa
Rica). TBs.
Pliocercus andrewsi paciJicus H. M. Smith & Chrapliwy, 1957 (holotype:
UIMNH 40832; Pacific slopes of Finca Custepeque, Chiapas, Mexico). Tt
(dorsally), T M (ventrally).
Pliocercus elupaides hobartsmithi Liner, 1960 (holotype: T U 17600; El Salto Falls,
San Luis Potosi, Mexico). TM. Greene & McDiarmid ( 1981: fig. 1A).
Pliocercus elapoides occidentalis H. M. Smith & Landy, 1965 (holotype:
UIMNH 61401; La Concepcibn, near Putla, Oaxaca, Mexico). T M (suggestion
of TT posteriorly).
Two other interesting variants have been described but not named. One of
these (Smith & Langebartel, 1950) is from the Sierra Madre ofOaxaca and has a
tricolour triad pattern but the black rings are connected by black down the
middorsal line. Another (Greene, 1969; Greene & McDiarmid, 1981: fig. 1B;
Ptrez-Higareda & Smith, 1986) from the Los Tuxtlas area of Veracruz, Mexico,
has the body nearly uniform red with a black nuchal band and a black band
across the anal plate that extends dorsally on each side for several scale rows but is
not complete across the supraanal region. Some or most of the scales are tipped
with black to form small spots (BIs). A hatchling from a female coloured as
described above (Greene, 1969) was bicolour with 14 black bands and two black
rings (BIB/BIR).
346
J . M . SAVAGE A N D B. I . CKOTHEK
As may he seen in the above listing and the sections below, the use of the name
Pliocercus for the coral snake mimics placed by us in the genus Urotheca is deeply
entrenched. This has caused some stylistic awkwardness in discussing variation
and the status of these taxa in the following paragraphs through repeated
reference to or citation ofPliocercus. Consequently, insofar as possible we have used
only specific names in the present and following sections to avoid confusion, while
recognizing that all snakes under discussion belong to the genus Urotheca. We have
also retained the spelling of specific names as published in a cited paper for the
same reason.
Peters & Orejas-Miranda (1970) recognized seven species in the genus
Pliocercu,r, two tricoloured forms ( P . nndrewsi and P. elapoides) and five hicoloured
taxa (P. annellatus, P. arubricus, P. bicolor, P. dimidiatus and P. euryzonus). These
authors state that the euryzonus has a wide range in Amazonia, but we can find 110
specimens or documentation that any member of this stock occurs east of the
Andes in South America. H. M. & R . B. Smith (1976) listed two tricolour
(P. andrewsi and P. elapoides) and a single bicolour species, P. euryzonus (including
bicolour) for Mexico. By implication they also recognized P. dimidiatus, but make
no mention of the two bicolour species described by Taylor from Costa Rica. Scott
(1969) listed only a single species, P. euryzonus, from Costa Rica, making
P. annellatus, P. arubricus and P. dimidiatus synonyms of P. euryzonus without
detailing evidence for this conclusion. Wilson & Dugas ( 1972) tentatively
accepted Scott’s arrangement when recording Y . euryzonus from Honduras.
Greene & McDiarmid (1981) suggested that a maximum of two taxa are
represented in the myriad forms recognized by Peters & Orejas-Miranda (1970)
and H . M. & R. B. Smith (1976): 1 , a southern bicolour species that ranged from
Honduras to South America and 2, a northern species containing all tricolour
examples in the genus as well as bicolour populations from Guatemala and
Mexico. The oldest available names for these forms are Pliocercus euryzonus for the
southern species and P. elapoides for the northern one.
Wilson & Meyer (1982, 1985) similarly accepted the concept that no more than
two taxa are concerned: 1, a hicolour species ranging from Veracruz, Mexico, into
South America ( P .euryzonus) and 2, a tricolour species of Mexico and upper
Central America (P. elnpoides). They notably differed from Peters & Ore.jasMiranda (1970) in regarding all bicolour examples as conspecific. Because of thc
extensive variation in the six specimens from Honduras, Wilson & Myer
questioned the validity of the described subspecies of elapoides.
Recently, Ptrez-Higareda & Smith (1986) proposed that two bicolour species
should be recognized, Pliocercus bicolor of Veracruz and adjacent Puebla, Mexico,
and P. aequalis ranging from Guatemala to South America. By implication these
authors continued to recognize two tricolour specics P. andrewsi and P. e1apoide.r.
VARIATION IN CYXT.4 KICAN ‘PLIOCERCUS’
Six forms of bicolour Pliocercus were recogniLed by Peters & Orejas-Miranda
(1970) and H . M. & R. B. Smith (1976). One of these ( P . bicolor) was thought to
be restricted to eastern Mexico, but the others were distributed from northeastern Honduras to western Ecuador. Characteristics utilized in the original
devcriptions and/or by subsequent authors to distinguish among these nominal
t d u include: scutcllation (head shields, dorsal scale rows and segmental counts)
CORAL SNAKE MIMICS
347
and coloration (colour and extent of light rings; form of light head bar; number
and extent of black body and tail rings). The following paragraphs summarize the
variation in available material (N = 33; 12 males; 14 females; six juveniles and one
unsexed adult) from Costa Rica.
Scutellation
The enlarged upper head shields uniformly show the basic colubrid
complement of a rostra], paired internasals, a prefrontal, paired supraoculars, a
frontal and paired parietals. The nasal is completely divided, a more or less
trapezoidal loreal is excluded from the orbit by one to four preoculars with the
commonest conditions 3-3 ( N = 14), 2-3 ( N = 8 ) and 2-2 ( N = 7); 1-2, 1-1 and
4-3 each with N = 1 also occur. Postoculars are usually 2-2 ( N = 2 9 ) , less often
2-3 ( N = 2) or 3-3 ( N = 1 ) . Temporals are usually 1 1, rarely 1 2 ( N = 4 out of
64 sides). Supralabials are usually 8-8 ( N = 2 3 ) , sometimes 8-9 ( N = 7 ) or 9-9
( N = 2), with labials four and five usually bordering the orbit (when eight labials
present) or five and six (when nine are present). Infralabials are 9 to 1 1 , with
10-10 ( N = 1 7 ) and 9-9 ( N = 9 ) the commonest conditions, rarer are 10--11
( N = 4 ) , 9-10 (2); five to seven infralabials meet the chin shields on each side, with
6-6 present in 24 examples.
Dorsal scale rows are uniformly in 17-17-17 rows. Taylor (1954) recorded a
formula of 2 1 to 19, 17- 17 for the holotype of Pliocercus arubricus. Taylor’s counts
apparently were made far anterior on the neck of this example (i.e. less than one
head length posterior to head) and these higher counts may be obtained on the
anteriormost scale rows in other examples having 17 rows one head length
posterior to the head (the standard place to count these scales). Ptrez-Higareda &
Smith (1986) reached a similar conclusion. Segmental counts are: ventrals in
males ( N = 12) 131-139, X = 134.2; in females ( N = 13) 131-142, X = 136.1; in total
sample (N = 32) 124-1 42, X = 134.4; subcaudals in males ( N = 8) 90- 122,
X= 111.8; in females ( N = 6 ) 93-120, X = 1 1 1.2; in total sample ( N = 18) 90-122,
X= 113.2. There seems to be no sexual dimorphism in segmental counts in
correlation with the absence of sexual dimorphism in tail lengths in this sample.
Tail length as a percentage of total length in adults is: in males ( N = 4 ) 38.5-45.8,
X=42.8; in females ( N = 4 ) 39.8-42.8, X=41.7.
+
+
CoLo ra tion
All Costa Rican examples are ringed with black markings separated by lighter
areas (white, yellow or red ). In some of these snakes the light areas are bright red
to form a series of red rings that alternate with the black ones (BIR). This is the
coloration attributed to all known non-tricolour ‘Pliocercus’ reported in the
literature from elsewhere in Latin America. It is also the coloration reported for
the types of the nominal taxa P.euryzonus, P. dimidiatus, P. aequalis, P. bicolor, and
P. annellatus. In these snakes the throat and the light areas on the anterior onequarter to one-third of the venter are often yellow, grading into bright red on the
posterior part of the body and underside of the tail. However, there is substantial
variation in the coloration (in life) of the Costa Rican members of the genus. In
many specimens the red coloration extends only part way down the sides and the
first several scale rows (and the ventral areas) are yellow or white. I n others the
348
J . M . SAVAGE AND B. I. CKUI’HEK
red is restricted to the mid-dorsal region and the lateral and ventral areas are
yellow or white. Still others have the dorsal portion of the light areas yellow and
the more lateral areas white. All of these are tricolour snakes but only the black
forms rings (‘TZ).Finally, some examples are ringed in black and white. There is
no apparent geographic consistency in the degree to which the red is developed in
the Costa Rican material. After a short time in preservative the red coloration is
lost and regardless of the coloration in life all of these snakes then appear to have a
bicolour pattern of black and light rings.
In most examples of the genus many of the dorsal scales in the light areas are
tipped with black, T h e amount and extent laterally to which black tipping occurs
is variable and exhibits no geographic trend in lower Central America. Elsewhere
in the range of non-tricolour ‘Pliocercus’ dark tipping is also usually present and
shows similar variability, although examples from Guatemala and Honduras tend
to have the black concentrated to form narrow secondary bands between the
black rings.
Geographic differences in the width of the light dorsal areas or rings have been
noted by previous authors. These light areas are narrow and measure 3 scale row
in longitudinal extent ( =width) in South American and eastern Panamanian
samples of Pliocercus euryzonus. Examples of this stock from the remainder of
Central America and Mexico have substantially wider light areas ( 1 6 scale rows
wide, Smith, 1941). In the Costa Rican series the light dorsal areas ( N = 2 8 ) are
1-3t scale rows wide with the following distribution ( N in parenthcses): 1 ( l ) , l &
(11, 13 (101, 2 (111, 3 (11, 3 t (2).
I n most members of this stock there is a distinct light head bar across the back of
the head involving the parietal plates. The bar is usually red in life, but may be
yellow or orange. I t is usually about the same width as the light body areas or
slightly narrower. T h e light head bar is barely indicated, broken on the midline or
very narrow in South American and eastern Panamanian examples. North of
Costa Rica the head band may be the equivalent of 1 --3 scale rows in width. In the
Costa Rican series (N = 26) the head bar is well-developed and usually covers the
central one-half to two-thirds of the parietal shields. Its width varies between 4-2+
dorsal scales as follows ( N in parentheses): ( 3 ) , 1 ( 7 ) , l + (12), 2 (2), 24 (2).
The number of black rings on the body and tail also has been used as a
systematic character by previous authors. I n Costa Rican examples, body rings
( N = 3 2 ) are 1 3 5 2 2 4 ( X = 17.6), tail rings ( N = 2 1 ) 4i-131 (X=9.0). It should be
noted that the first (nuchal) black figure is incomplete across the throat (i.e. it is a
band not a ring) in all forms. I t however, has been counted by previous authors
and us as one of the black body rings.
Discuxrion of variation and the status of nominal forms
Taylor (1951, 1954) and Peters & Orejas-Miranda (1970) placed Costa Rican
‘Pliocercus’ under three names: P. annellatus, P. arubricus and P. dimidiatus. The
salient features of the holotypes of these taxa (all from Costa Rica) are given
below including features emphasized by their describers as differentiating them
from other forms. P . nnnellatus: dorsal scale rows 17-17-1 7; two preoculars; eight
supralabials, with four and five bordering orbit; ventrals 137; subcaudals 73
body completely ringed with red posteriorly, red rings 2 24 scale rows wide; head
bar broad, two scale rows wide, red; black body rings 2 2 t (tail incomplete).
+;
CORAL SNAKE M I M I C S
349
P. arubricus: dorsal scale rows 21 to 19 -1 7- 17; two preoculars; eight
supralabials, four and five bordering orbit; ventrals 139, subcaudals 1 12; upper
portions of light dorsal areas ‘light lavender’, sides and venter white; light areas
3--3) scale rows wide; head bar broad, cream in colour; black body and tail rings
18++8$.
P. [eur_y<onus]dimidiatus: dorsal scale rows 17-1 7-1 7; three preoculars; nine
supralabials, five and six bordering orbit; ventrals 127, subcaudals 120; body
ringed with red and black; red rings 33 scale rows wide; head bar broad, two scale
rows wide, red; black body and tail rings 14 8.
The earliest of these names is Pliocercus dimidiatus Cope, 1865. Prior to Taylor
(1951) the name was applied to examples from Nicaragua, Costa Rica and
western and central Panama. Taylor (1951) described annellatus, which was
differentiated from P. dimidiatus (features in parentheses) by having two
preoculars ( 3 ) , eight supralabials, with four and five bordering the orbit (nine,
with five and six bordering the orbit), 22$ black body rings (14). All of the
presumed diagnostic features of these putative species are represented in our
sample and intermediate states for each are also present: two preoculars on one
side of the head, three on the other is a common variant; eight supralabials (with
four and five bordering the orbit on one side), nine on the other (with five and six
bordering the orbit) are common conditions; and body ring numbers from 13* to
224 are represented for each whole and half interval between these two extremes.
We therefore conclude that the types of P.dimidiatusand P. annellatusare conspecific.
When Taylor (1954) described Pliocercus arubricus he did so primarily on the
basis of coloration. He believed that P. dimidiatus, P. annellalus and the extralimital
P. eur_yZonuswere red and black ringed snakes. The single specimen of P. arubricus
was diagnosed as lacking red in its coloration but having the lighter bands ‘light
lavender’ dorsally, and the sides and venter white. Otherwise, as pointed out by
Taylor it resembles the type of P. annellatus to a surprising degree. We suspect that
Taylor’s description of the coloration for this snake was recorded after it had been
in preservative for a short time and the initially red or pink dorsal light suffusion
had faded somewhat. Except for the stated colour difference this example agrees
closely with other Costa Rican specimens of the group that have the red colour
restricted to the upper area of the otherwise white or yellow interspaces ( T Z ) . If
this snake actually had lavender instead of red on the dorsum in life, we would still
rcgard it as only an extreme variant in the substantial range of reddish hues found
in living representatives of the genus.
Although Peters & Orejas Miranda ( 1970) characterized Pliocercus nrubriciis as
distinct because of the high number of dorsal scale rows (21-19) across the neck
reported by Taylor (1954), we have shown earlier in the present paper that this
feature is based on counts made far forward on the neck (instead of one head
length posterior to the head) and can be duplicated in other individuals of the
genus. Consequently, because neither the coloration nor scale row counts seem in
themselves significant enough to override the many other resemblances between
the holotype ofP. arubricus and other Costa Rican examples, we conclude that it is
conspecific with them. This means that only a single species of this group is
represented by material from the Republic (Fig. 2 ) . O u r conclusion was
anticipated by Scott (1969), who was followed by Savage & Vial (1974), Greene
& McDiarmid ( 1981 ) and Wilson & Meyer ( 1982, 1985) without fully detailing
the evidence. Pkrez-Higareda & Smith (1986) reached a similar conclusion.
+
350
J . M .SAVAGE AND B. I . CRO'I'HER
The question still remains as to the correct name for the single Costa Rican
species. The first name to be based on a Costa Rican example was Pliocercus
dimidiatus and was applied for many years to material from Nicaragua and central
and western Panama as well. Dunn & Bailey (1939) regarded P. dimidiatus as the
northern race of the South American form, P. euryzonus, because some Panama
examples are intermediate between the two nominal species. According to Dunn's
unpublished notes typical P. euryzonus differed from northern matcrial in pattern,
with the head bar absent and the light rings only scale row wide. Peters &
Orejas-Miranda (1970) also utilized the latter feature to separate a northern
(dimidiatus) and southern (euryzonus) subspecies.
Dunn and all previous workers favoured the idea that bicolour, ringed 1Jrotheca
(or Pliocercus) had the light rings red in colour in life. As we have shown above this
is not uniformly the case in Costa Rica since some examples have yellow or white
rings. Recently C. W. Myers pointed out to us that members of this stock from
eastern Panama and Colombia are black and white ringed snakes, without any
red coloration in life, while those from central Panama have red rings. In
correlation with the narrow white rings, the number of black body and tail rings
are somewhat greater (18f24+, 12+-18+, respectively) in southern examples
than in the Costa Rican series, with the number generally decreasing from south
t o north. Ventral (1 18-136, X = 125.7) and subcaudal (97-1 19, X= 113) counts
show no differences.
For these reasons and the fact that there seems to be a clinal change in pattern
and coloration from northern Colombia through eastern to central Panama, we
concur with the conclusion of Dunn & Bailey ( 1 939) that only a single species of'
this group is represented in lower Central America. Material from eastern
Nicaragua falls within the range of variation described for Costa Rican samples as
well: black rings (body: 13+--19f, X = 16.8; tail 81 101, X=9.1); ventrals 129 -140
(?= 133.9), subcaudals 104..119 ( X = 1 1 1.8).
Scott ( 1969) (followed by Savage & Vial ( 1974), Greene & McDiarmid ( 1981 )
and Wilson & Meyer (1982, 1985) and Pkrez-Higareda & Smith (1986)) reached
a similar conclusion without fully documenting its basis. The earliest available
name for this form is Pliocercus euryzonus Cope, 1862, which must now be cal!ed
Urotheca euryzona (Cope). We eschew the use of trinomials in this species, since the
variation in pattern and colour shows a clinal change from south to north and for
the reasons outlined by Savage & Heyer (1969). Consequently the nominal taxa
P. annellatus, P. arubricus and P. dimidiatus are placed in the synonymy of
1J. euryzona.
As an aside it is interesting to note a rather frequent variation found in the
white rings of Urotheca euryzona from eastern Panama and South America and not
noted for northern samples. I n some examples one to five rings are broken b y
black to form incomplete rings. In others a ring may be asymmetric and
developed only as a light bar on one side. A rare variant has the light ring
bifurcated to form a Y-shaped figure on one side.
+
Material examined
Urotheca euryzona (Cope, 1862) Figs 2 3.
COSTA RICA: Alajuela: Venado (CRE 3655-56); Isla Bonita ( K U 31943); Bijagua
( U C R 8528); Carlago: El Silencio de Sitio Mata; La Suiza (CRE 233); 6.4 km
CORAL SNAKE MIMICS
351
Figurr 2. Distribution ofcoral snakt. mimics o f t h c grnus Urothm in Costa Rira
S. Catie (KU 25730); Turrialba (KU 30993, KU 35510, KU 3551 1 ) ; probably
Turrialba (CRE 862, CRE 2780); San Ramon de Tres Rios (UCR 651 2).
Guanacaste: El Silencio de Tilaran (CRE 6232, CRE 6327); Heredia: La Selva
(CRE 68, CRE3664, CRE 3756, USC 303, UCR 3365, CRE 8468, CRE 4526);
1.5 km N. Puerto Viejo (KU63863); Rio Frio (UCR3347, UCR5739,
FSM 30482, FSM 30851); Limdn: 9 14 km E. Siquirres on road to Turrialba; El
Tigre (CRE 290); Los Diamantes (UMMZ 117590); Tortuguero (FSM 31 784,
FSM 15672), 2.5 km S. (AMNH 89168); vicinity of San Clemente (CRE 8550);
Penhurst (UCR 2440); Finca Cobal (UCR 3378); c. 3 km S. Siquirres on road to
Turrialba (UCR 5718); Comadre (UCR 651 1, UCR 6995); Barra del Colorado
(AMNH 12675); Puntarenas: Eladios, 10 km E. Monteverde (UCR 8502).
NICARAGUA: Rio Sun j k a n : San Juan Del Norte (USNM 15634-6, USNM 25333,
USNM 24698); Rio San Juan (USNM 19566 -7). PANAMA: Darie'n: mouth Rio
Canclon (KU 124195); Tararcuna Camp (KU 75735); Tupisa, Rio Chucunaque
(AMNH 36178); El Real (USNM 140672); Bocas del Toro: Almirante
(KU 80237); Sun Blas: Atlantic side DariCn (USNM 32495); Armilla, Quebrada
Venado (USMN 150135 36); Cocle': El Valle de Anton (AMNH 76013).
COLOMBIA: Chocd: Andagoya (USNM 124251); Rio San Juan (USNM 154498);
Serrania de Baudo, N. slope Alto del Buey (AMNH 119803); Valle de Cauca:
between Cali and Buenaventura, Represa del Rio Anchicaya (USNM 267250);
Antioquia: Medellin (AMNH 35549, AMNH 3555 1); Huila: Neiva, upper Rio
Magdalena (AMNH 20390-9 1 ); ECUADOR: Cotopaxi: Corazbn (USNM 2 1 1062
63); Pichincha: Gualea (USNM 21 1064); below Pacto (USNM 21 1065); Santo
Doming0 de 10s Colorados (?) (USNM 2 1 1066).
352
J. M. SAVAGE AND B. I. CKOI’HER
Figure 3. Distribution of CJrulheca euyzona basrd on material examined a nd authenticatrd literature
I-ecurds. Rerausc ofthe map srale and the number ofrecords ~ I I FCosta Rica the dots on that portion of
thc map represent several localitics. A detailed map of the distribution of this species in Costa Rica is
provided in Fig. 2.
RELATIONSHIPS OF UROTHECA E U R Y ~ O N A‘1.0
UPPER CENTRAL AMERICAN AND MEXICAN F O R M S
Samples of coral snake mimics belonging in Urotheca from north of Nicaragua
include an astonishing array of variation in colour pattern. Bicolour snakes of the
genus from Veracruz, Mexico, include ringed, spotted or banded individuals
(Smith, 1941; Greene, 1969; PCrez-Higareda & Smith, 1986), while those from
Atlantic lowland Guatemala (Stuart, 1948; Duellman, 1963) and Honduras
(Wilson & Dugas, 1972) are ringed. ‘I‘ricolour Urotheca range from Tamaulipas
and Oaxaca, Mexico, south to Honduras and El Salvador, and usually have
complete black rings around the body. O n e population (ranging along the
Atlantic slope from Tabasco, Mexico, through Guatemala to Belize) has most of
the dark markings incomplete across the venter to consist of dorsal black bands
(Schmidt, 1941; Smith, 1941; Stuart, 1948). Coloration is extremely variable
within the ringed tricolour sample with some specimens at the extremes having
tricolour monads (Smith, 1943; Greene & McDiarmid, 198 1 ) or well-developed
tricolour triads (Greene & McDiarmid, 1981). Others have every stage of
intermediary between these conditions: tricolour monads anteriorly and black
spots separating the yellow rings from the red rings mid-dorsally on the posterior
portion of the body (Smith & Landy, 1965); tricolour monads anteriorly, weakly
developed secondary black rings in tricolour triads posteriorly (Smith, 1942);
tricolour monads anteriorly and tricolour triads posteriorly (Smith, 1941);
CORAL SNAKE MIMICS
353
tricolour triads but secondary black markings not crossing venter (Smith &
Chrapliwy, 1957).
Peters & Orejas-Miranda (1970) recognized four species in the region: 1,
Pliocercus bicolor of Veracruz, Mexico (BIR); 2, P. euryzonus of eastern Guatemala
(BIR); 3, P. andrewsi of Yucatan and southwestern Oaxaca, Mexico (TT) and 4,
P. elapoides of Mexico, Guatemala, Belize and El Salvador ( T M , T M and TT, TT;
some with black bands, some with black bands and rings, most with black rings).
H . M . & R . B . Smith (1976) adopted the same arrangement, which is not
surprising since the Peters & Orejas-Miranda treatment is essentially based on
H. M. Smith’s several published papers on these coral snake mimics (see
References at end of this paper).
Greene & McDiarmid (1981) suggested that the variation in coloration shown
in Mexican and upper Central American samples bridged the gaps among
bicolour, tricolour monad and tricolour triad specimens as well as among spotted,
banded or ringed examples. Consequently they recognized only a single species
(Pliocercus elapoides), as occurring north of Honduras. They also implied that this
taxon might prove to be conspecific with the southern form (euryzonus). Wilson &
Meyer (1982, 1985), in contrast, although also recognizing only two species in the
genus, restricted the name P. elapoides to tricolour examples and applied the name
P. euryzonus to all bicolour specimens. T h e nominal tricolour species according to
this scheme ranges from El Salvador and Honduras northward and the bicolour
form occurs from Veracruz, Mexico to South America.
The essential difference between these two classifications is Greene &
McDiarmid’s ( 198 1) emphasis on the conspecificity of bicolour and tricolour
specimens from Mexico, Guatemala and Belize and Wilson & Meyer’s (1982,
1985) utilization of colour pattern (BI versus T) as a basis for species recognition.
The northern record for black ringed, non-tricolour snakes placed in Urotheca
euvzona earlier in the present paper is separated by a distance of approximately
305 km from the nearest locality for a northern bicolour snake (from Tela, northwestern Honduras to the Bonanza area of north-eastern Nicaragua). T h e
northern bicolour samples represent three apparently allopatric populations
(distances between populations in parenthesis): Guatemala-Honduras (250 km),
Los Tuxtlas, Veracruz, Mexico ( 1 75 km) and northern Veracruz and adjacent
Puebla, Mexico.
Greene & McDiarmid (1981) and Wilson & Meyer (1982, 1985) apparently
concurred in regarding the single, bicolour Honduras example ( M C Z 229 1 1 ) as a
Pliocercus euryxonus; Greene & McDiarmid because its pattern was similar to that of
lower Central American examples (black rings wider than the light rings), Wilson
& Myer because it was bicolour. The last two authors were probably influenced in
their decision by the occurrence of tricolour snakes in Honduras. The nearest
record for tricolour examples of this stock ( M C Z 22052, 26870; Progreso,
Departmento de Yoro) is about 41 km south-west of the locality (Tela,
Departamento de Atlantida) for the bicolour specimen.
Pkrez-Higareda & Smith (1986) suggested a third arrangement for the bicolour
forms while reporting on recently collected material from the Los Tuxtlas area of
Veracruz, Mexico. They recognized Pliocercus bicolor from northern Puebla,
northern Veracruz and the Los Tuxtlas area as distinct. In addition they referred
Greene’s (1969) specimens and a newly collected one (UNAM-LT 2731) to
P. elapoides. Finally, all other bicolour examples from Guatemala to South
354
J. M.SAVAGE AND B. I . CROI'HER
America were placed in P. aequalis. It should be noted that in this scheme P. bicolor
and P. elapoides are believed to be sympatric. In addition, three of the Los Tuxtlas
P. 'hicolor' differ from the holotype of P. bicolor and agree with the one Los Tuxtlas
P. 'elupoides' in having a considerable number of distinct black markings; most of
the marks form black bands and not rings on the body.
None of these alternatives may be rejected out of hand since no features of
scutellation distinguish any of the named taxa and/or unnamed, uniquely
coloured specimens from one another. Segmental counts that in most snake
species having a broad distributional range exhibit some geographic variation are
suprisingly constant in these IJroLheca, as may be seen from the summary below.
Data for this tabulation of Upper Central American and Mexican samples are
derived primarily from the literature and a n unpublished thesis ( A. K . Smith,
'I'ABLE 1. Summary o f scgmcntal counts
N
su bc a udnla
N
Vr 11trals
~~
1
4
5
7
32
14
2
.l'
I
5
17
3
5
2
2
132
129-134
128-133
129-140
124-14'2
118-136
(X = 130)
0
3
( X = 131.1)
3
(X = 133.9)
(X = 134.4)
( X = 125.7)
18
5
6
89-112
87-112
104-119
90- 122
97-119
103-109 ( X
7
(94- 109)
85 100 ( G
(86-100)
=
122-131 ( X = 128)
124-136 ( 2 = 129.6)
0
4
94-114 (X
=
127-128 (X = 127 5)
0
1
95
123-128 (X = 124.4)
( I 2 1-1
2
29)
128 136
106)
93.9)
105)
( I 1 4 1 15)
( 124-129)
I30
6
(X
3
1
1
(X =
127-131 ( X = 1292)
(123-1 34)
13'3 144 ( X = 136.5)
( I3 1-144)
I
96
1
(X =
98.3)
97)
111.8)
113.2)
113.0)
97
(97 100)
90
(85-93)
1
1
=
I
126-131 (X = 127.8)
10
=
126-128 (X = 227)
(125 128)
I36
1134-136)
4
7
(X
(X
(X
=
130.7)
127
I24
(122-131)
I20
12.5 I36 (X = 130.5)
5
I15
(107 116)
(88 106'
0
0
0
2
102-1 I I (X = 10fi.5)
CORAL SNAKE M I M I C S
355
1969) that reviews variation in tricolour 'Pliocercus'. Unfortunately, although the
latter author provides ranges for these counts by sex, and in some cases means, he
does not indicate sample sizes. We have included his data where pertinent in
parentheses below our summary of published values, to more accurately
document variation (Table 1 ) .
The only hint ofgeographic variation in these counts is in the higher number of
subcaudals on the average ( 2 = 1 13.1j in the southern samples referred earlier in
the prescnt paper to Urotheca euryzona, which ranges from Nicaragua to South
America. It is however important to note that there is a definite sexual
dimorphism in segmental counts in the tricolour populations (ventrals in males
122-134, X = 126.9, in females 123--144, X = 134.5; subcaudals in males 94 116,
X = 107.8, in females 85-109, X=97.5) and in tail length to total length ratios
(37.8-44.9% in males, 35.0-41.070 in females). The number of bicolour
specimens from northern areas is small and insofar as known are females except
for two unsexed juveniles (UTA 3 157-3 158j , so possible sexual dimorphism
cannot be assessed.
Much emphasis has been placed by previous workers on the number of black
rings or bands that cross the body as a means ofdistinguishing nominal taxa in the
genus. Variation in this feature is summarized in Table 2 (in the case of tricolour
triad samples the count refers to the number of primary black rings = number of
triads); the lower set of numbers in parentheses is from A. K. Smith (1969).
The low number of black body rings that was thought by Smith (1942) and
Smith and Chrapliwy ( I 957) to characterize Pliocercus andrewsi seem to represent
one extreme in this variation as pointed out by A. K. Smith (1969). Examples
referred to P. elupoides by Smith (1941, 1942) from nearby localities approach
Yucatan P. andrewsi in the number of black body rings (the holotype, MCZ 26843
and one paratype MCZ 26836 of the name P. schmidti from Chichtn Itza have 12
and 1 1 black rings, respectively). The holotype ( U I M N H 40833) and only known
example of the putative form, P.andrewsz pac$cus, of Pacific slope, eastern
'I'ABLL 2.Nurnbrr of' black rings/baiids
Pattrrn
N
Number or black body
bands, blotches or rings
~
Bicolour
Northrrn Vrracruz
LOSTuxtlas
C u a tc.oi;tl;i-Hond u ras
Nicaragua
Costa Rica
E.Panama-South Amrrica
BIR
BIS/BIB, BIB, BIK
BI R
RIR
BIK, 'IB
BIK
I
6
6
7
32
13
14
2 17
20-27
134-195
134-22;
18p24j
( X = 91
(X = 24.5)
( i = 16.8)
( X = 17.6)
(X = 22.3)
11-16
9-15
(5-16)
9-23
11-18
54 7
9
7 13
8
9 13
10-20
( X = 12.8)
( i = 11.0)
'l'ricolour
Nor~h-castcrnM r x i c o
Eastern Mexico
'l'abasco to Brlize
Yucatin
Yucatan "andrewri"
w Oaxaca
E.Oaxaca t o SLV Cuatrrnala
Cltiapas ' ' a n d w e d '
El Salvador
Honduras
4
26
(X = 16.8)
( i = 13.5)
(X
=
(X
=
6.1)
9.3)
( X = 10.8)
( 2 = 143)
356
J . M. SAVAGE AND B. I . CROTHER
Chiapas, Mexico, has eight black body rings. A black body ring count ofeight to
ten is common in other Pacific slope, Chiapas specimens (Smith, 1942) and one
example (USNM 110772) has seven. Consequently we conclude that the two
nominal forms of P. andrewsi (andrewsi and pacificus) recognized by H. M. & R . €3.
Smith (1976) are conspecific with elapoides. This conclusion was reached
previously by A. K. Smith (1969) and is implicit in Greene & McDiarmid’s
treatment (1981).
The data on coloration thus support the concept advanced by Greene &
McDiarmid (1981) and Wilson & Meyer (1982, 1985) that all tricolour Urotheca
from northern Central America and Mexico are conspecific. The more or less
continuous spectrum of colour patterns from tricolour banded (monads or triads)
through tricolour monad rings, to weakly tricolour triad to well-developed triad
individuals, combined with variants where two different patterns are found on
different individuals in the same sample or two different patterns are seen on a
single individual, further indicates that only one species is involved. Finally the
extreme variation exhibited in coloration and its lack of geographic consistency
precludes the recognition of subspecies in this complex even by those biologists
who, unlike ourselves, ascribe significance to that arbitrary category. T h e earliest
name available for the species is Piiocercus elapoides Cope, 1860, which now should
be known as Urotheca elapoides (Cope).The following names (all based on tricolour
snakes) are regarded as junior synonyms of U. elapoides (listed by specific or
subspecific name for reference to the list of available names at the beginning of this
paper): andrewsi, celatus, deppei, diastemus, hobartsmithi, laticollaris, occidentalis,
pacijicus, saivadorensis, salvinii, schmidti, semicinctus, and tricinctus.
The status of the populations of bicolour Urotheca found in Mexico, Guatemala
and Honduras remains a problem. In pattern they most closely resemble
11. euryzona as diagnosed above but differ in having a lower number of subcaudal
scutes ( N = 6 ; 87-1 12, X = 102.6. N=28; 90-122, X = 112.9 in U. euryzona). In this
regard the northern samples agree more closely with the tricolour species
lJ.elapoides (subcaudals: 85 115, X-99.2) than with the southern form.
The single bicolour individual of this stock from Honduras (MCZ 2291 1; Tela,
Departamento, Atlantida) was apparently considered to be conspecific with
Nicaragua and Costa Rica samples (regarded as IJrotheca euryzona in this paper) by
Greene & McDiarmid (1981). The salient features of the Tela snake (a female)
are 134 ventrals, 25 black rings and the light rings I f to 2 scale rows in width. In
these characteristics, especially in the number of black body rings, this specimen
agrees with bicolour examples from Atlantic versant Guatemala (black body rings
20- 27). The numbers of black body rings in Nicaragua-Costa Rica IJ. euryzona are
13$-22$. For this reason we regard the Tela example as most closely allied to
northern bicolour Urotheca.
Currently available data point to three possible alternative interpretations:
1, northern bicolour examples are conspecific with the tricolour snakes referred to
IJrotheca elapoides (Greene & McDiarmid, 198 1 ); 2, northern bicolour examples
are conspecific with the bicolour species U . euryzona (Wilson & Meyer, 1982,
1985); or 3, all populations belong to a single, variable, wide-ranging species (a
possibility mentioned by Greene & McDiarmid, 1981, in comparing all
populations in this complex), in which case there would be one valid species
( I / . elapoides).
Geography and the subcaudal scute differences (% = 99.2 in northern tricolour
snakes; X = 102.6 in northern bicolour examples; X = 112.9 in the southern series)
CORAL SNAKE MIMICS
357
Figure 4.Distribution of lirotheca elupoides based principally on the literature.
favour alternative 1. Coloration might seem to favour alternative 2, although
there is a range gap of some 300 km across northern Honduras between the
nearest known approach of northern and southern populations lacking tricolour
rings. If alternative 1 is acceptable (tricolour and bicolour ringed snakes are
conspecific) then there is no logical grounds for rejecting alternative 3 except for
the hiatus between the distributions of northern and southern forms and the
complete absence of ringed tricolour snakes in the south. While we strongly
suspect that only a single wide-ranging species (alternative 3) is involved, the
slight differences between northern and southern forms in subcaudal counts and
the absence of records from across northern Honduras recommend a conservative
approach to the situation. For these reasons we regard the coral snake mimics of
the genus Urotheca to be composed of two allopatric species: U. elapoides (Cope) of
Mexico and upper Central America (Fig. 4) and U . euryzona (Cope) of northern
Nicaragua, Isthmian Central America and north-western South America
(Fig. 3 ) . The latter form is marked with black and usually red rings (bicolour) but
is never black, red and yellow ringed. The northern species is usually ringed in
black, red and yellow but sometimes the black is in the form of bands. Two
populations (the nominal taxa U. aequalis of Guatemala, Belize and Honduras and
U. bicolor of northern Veracruz, Mexico) regarded here as synonyms of U. elapoides
are red and black ringed (bicolour). The samples from Los Tuxtlas, Veracruz,
Mexico of bicoloured (red and black) spotted, banded and/or ringed snakes
(Greene, 1969; Pkrez-Higareda & Smith, 1986) also are placed in U. elapoides
under this arrangement. We can find no justification for Pkrez-Higareda &
Smith’s (1986) view that some bicolour Urotheca are referable to U. elapoides and
others to U. bicolor.
MIMICRY AND TAIL AUTOTOMY
Greene & McDiarmid (1981) discussed in some detail the concordance of
colour patterns between various species of the highly venomous coral snakes
358
J . M. SAVAGE AND B. I. CKOI'HER
(Micrurus) and those of sympatric local populations of Urotheca. Examples include
the co-occurrence of the bicolour red and black ringed Micrurus diastema with
bicolour U. elapoides in Atlantic versant Guatemala (Greene & McDiarmid, 1981:
fig. 1 F), tricolour monad M . diastema and U. elapoides on the Yucatin Peninsula
(Fig. 1C) and tricolour triad M . ele'gans with the similarly marked U. elapoides in
central Veracruz, Mexico (Fig. 1E). Bicolour U. euryzona were shown to be
coloured like sympatric red and black ringed M . mipartitus in that account
(Fig. 1D). O n the basis of this and other cases of concordance in coloration
between Micrurus and other sympatric snakes (of the genera Atractus,
Eythrolamprus and Lampropeltis) and the innate avoidance of coral snake patterns
by two relevant predators (S. M. Smith, 1975), Greene & McDiarmid concluded
that some (if not all) of these cases involve Batesian and/or Miillerian mimicry.
O u r analysis of coloration in Urotheca euyzona provides additional evidence of
concordance of coloration between Urotheca and Micrurus in lower Central
America. The bicolour species of venomous coral snake, M . mipartitus, is regarded
usually as ranging from Nicaragua southward to western Ecuador and northern
and western Venezuela, although Roze (1983) suggests that a northern and
southern species may be recognized. Urotheca euryzona is sympatric with
M . mipartitus over much of the same region. As pointed out above, Costa Rican
U. euyzona have the light rings completely red or pink or the rings are white or
yellow with the upper three-quarters to one-quarter red or the dorsal portion of
the ring is yellow or the entire ring is white. This variation closely matches the
situation in Costa Rican M . mipartitus where the light rings are usually entirely red
or pink, or the rings are white to cream with the pink restricted to the upper scale
rows (Savage & Vial, 1974), exactly as in many Costa Rican U . euryzona. In some
of the Costa Rican M . mipartitus the light rings are cream dorsally or are
completely white. The fact that individual variation in a restricted geographic
area is so closely paralleled in a coral snake and a presumed mimic adds further
support to the mimicry hypothesis.
An additional feature of colour variation in Urotheca provides further evidence
of mimicry. As pointed out above U. euyzona from Ecuador, western Colombia
and eastern Panama are white and black ringed snakes. In central Panama the
light rings are usually red as in Costa Rica and Nicaragua. Micrurus mipartitus
from northern South America and eastern Panama are black and white ringed
snakes, with only the head band and light tail rings red in colour. As in
U. euryzona, M . mipartitus from central and western Panama have red rings around
the body indicating a concordant geographic change in coloration for both model
and mimic.
Liner (1960) called attention to the ability of 'Pliocercus' to lose the tail in a
manner reminiscent of lizards having fracture septa in the caudal vertebrae and
tail autotomy. Wilson (1968) described the caudal vertebrae of a Urotheca elupoides
as having a groove across the transverse processes that presumably allowed the
tail to be broken off rather easily if that appendage is grasped by a predator.
Etheridge (1967) however had already pointed out that although the tail of
Pliocercur is extremely fragile, breakage is intervertebral. Examination of all
specimens in our samples of U. decipiens, U. euryzona, U.guentheri and U.pachyura in
which the tail has been broken shortly before capture and/or preservation showed
intercentral breakage. In those snakes with older breaks a calcified cap
apparently develops over the exposed portion of the vertebra but all showed
CORAL SNAKE MIMICS
359
intercentral breakage. Muiioz ( 1987) interpreted the situation differently for he
reported that intracentral fractures were the rule in these taxa and
Scaphiuduntuphis. Muiioz also indicated that the vertebral fractures produced
irregular margins on the remaining vertebral fragment and that there was no
consistent topographic location for the fracture plane. He further showed that the
presumed intracentral fractures had occurred a t different points along the
vertebral axis in different individuals and consequently no consistent fracture
zone associated with any particular feature was indicated.
Fortunately, C. W. Myers very kindly has provided us with information that
clarifies this situation. T h e following statements are based on an unpublished
study of tail breakage in Urutheca and Scaphiudontuphis carried out jointly by Myers
& A. H. Savitzky utilizing x-rays and cleared and stained tail-tips. They observed
that breakage was almost always intervertebral “although they do not part
cleanly and the edges of the two adjacent vertebrae are frequently damaged in the
process”. Myers (personal communication) suggests that these irregular and
damaged vertebral margins are what Muiioz viewed as “intracentral fractures”,
an interpretation with which we agree. Nothing in the available data supports
Wilson’s (1968) idea that there is a functional intravertebral fracture plane in the
vertebrae of these snakes and Myers (personal communication) suggested that the
‘groove’ described by Wilson may be a muscle scar.
As noted above, a very high number of individuals of the genus have
incomplete tails (about 5004). The long and fragile tail probably associated with
tail-thrashing behaviour (Greene, 1973) seems to constitute a predator-avoidance
complex. Since the tail does not regenerate, the elongate tail apparently allows for
several breaks (and escapes) over time with each succeeding loss shortening the
tail. It is doubtful that this system is truly autotomous and these snakes (unlike
many lizards) probably are incapable of spontaneously fracturing the vertebrae in
response to a tactile stimulus, but instead require some slight physical resistance to
separate the tail segments.
A similar condition occurs in Neotropical snakes of the genus Scaphioduntuphis
(Etheridge, 1967; Henderson, 1984) that includes other members of the coral
snake mimic guild. Scaphiuduntuphis differs markedly from Urotheca and its allies in
dentition (Savitzky, 1983) and hemipenes (Jenner, 1981) and they belong in
nominally different subfamilies (Dowling & Duellman, 1978), the Colubrinae
and Xenodontinae, respectively. It is intriguing to note the presence of both
mimicry and tail loss defences against predation in combination in two distantly
related stocks since the specialized tail loss defence also seems to occur in at least
1 1 species (Enulius and Urutheca) lacking coral snake patterns. One can only
imagine what sort of predator and/or predation pressures moulded the
development of these two systems, perhaps simultaneously. Certainly there is a
fruitful avenue for future behavioural ecological study on these unusually
modified snakes.
ACKNOWLEDGEMENTS
We are indebted to the following curators for their cooperation in providing
specimens and data for inclusion in this study (abbreviations for catalogued
specimens in parentheses): William E. Duellman, University of Kansas (KU);
W. Ronald Heyer and Roy W. McDiarmid, National Museum ofNatural History
360
J. M. SAVAGE AND 8. I . CRO’I’HER
(USNM); Douglas C. Robinson, Universidad de Costa Rica ( U C R ) ; Arnold G.
Kluge, University of Michigan ( U M M Z ) .
The following abbreviations (erroneously referred to as acronyms by many
authors) as listed by Leviton et al. (1980) cited in the text indicate the location of
other preserved specimens in collections: ANSP, BM, FMNH, MCZ, MNHP,
MSNM, NHMB, NHMW, SMF, SMNS, U I M N H , ZMB, ZMUC.
In addition we thank F. Gchlbach of Baylor University for making a copy of
A. K. Smith’s unpublished thesis available: Harry W. Greene, University of
California, Berkeley (MVZ) and Norman J. Scott, Jr, U.S. Fish and Wildlife
Service-University of New Mexico, who read early drafts of the manuscript and
suggested many improvements. Special thanks go to Charles W. Myers, American
Museum of Natural History (AMNH), who read and critiqued a draft of this
paper and shared his extensive knowledge ofcolubrid snakes with us. We also wish
to acknowledge the support of the Organization for Tropical Studies (OTS) in
the field phase of this research. The senior author began work on this project while
a John Simon Guggenheim Memorial Fellow (1963-64) and thanks the
Guggenheim Foundation for its aid.
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