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REDESCRIPTION OF PHALOTRIS NIGRILATUS FERRAREZZI, 1993
(SERPENTES: COLUBRIDAE: XENODONTINAE)
, AND NORMAN SCOTT
Museo Nacional de Historia Natural del Paraguay, Sucursal 1, Ciudad Universitaria, San Lorenzo, Paraguay
a Vertebrados, Facultad de Ciencias, Igua
4225, CP 11400, Montevideo and Departamento de
a, Museo Nacional de Historia Natural y Antropologı
a, Juan C. Go
mez 1436, Montevideo, Uruguay
Research Associate, Smithsonian Institution, P.O. Box 307, Creston, CA 93432, USA
BSTRACT: Phalotris nigrilatus Ferrarezzi, 1993 is a poorly known species described from a single
specimen from Paraguay. Two new specimens make possible a more detailed description of the species,
including a description of the hemipenis, and support the validity of the species. Hemipenial morphology
provides another character that further supports the inclusion of the species in the nasutus group. We
describe variation within the species, probable sexual dimorphism, and the known distribution. It will be
necessary to do further work in Paraguay to establish the conservation status of this apparently rare and
Key words: Colubridae; Elapomorphini; Distribution; Hemipenis; Paraguay; Phalotris nigrilatus;
THE COLUBRID snake genus Phalotris Cope,
1862 is composed of three species groups
(Ferrarezzi, 1993): the nasutus group includes
five species (Lema, 2002a,b), the tricolor
group includes four species (Leynaud et al.,
2005), and the bilineatus group includes three
species (Puorto and Ferrarezzi, 1993). The
genus was revalidated by Ferrarezzi (1993)
who defined it as a monophyletic group near
Apostolepis. With Elapomorphus, these gen-
era form the subfamily Elapomorphinae
(Ferrarezzi, 1994; Hofstadler-Deiques and
Lema, 2005). Species of the genus are found
mainly in open areas from central Brazil and
southern Bolivia to Patagonia in Argentina
(Ferrarezzi, 1993); the species are semi-
fossorial, and in some cases their biology is
Although differences among groups are
seen in external anatomy (e.g., cephalic
scutelation, shape of the body and head,
etc.), morphological characters of the hemi-
penis also show important differences. The
tricolor group has a hemipenis that is slightly
or deeply bilobed with few developed spines,
and a sulcus spermaticus bifurcated in the
proximal region (Ferrarezzi, 1993). In con-
trast, the hemipenis of members of the
bilineatus group has a single, slender hemi-
penis, with apical bifurcation in the sulcus
spermaticus (Ferrarezzi, 1993). The anatomy
of members of this hemipenis in the nasutus
complex is known for P. nasutus and P.
lativittatus (Ferrarezzi, 1993). The hemipenes
of members of this group are deeply bilobed,
calyculate and semicapitate, with enlarged
lateral spines, and with the sulcus spermaticus
bifurcated proximally (Ferrarezzi, 1993;
Lema, 2002b; Zaher, 1999).
Phalotris nigrilatus Ferrarezzi, 1993 be-
longs to the nasutus group, which also
includes P. nasutus (Gomes, 1915), P. con-
color Ferrarezzi 1993, P. lativittatus Ferrar-
ezzi 1993, and P. labiomaculatus Lema
2002b. These species have a pointed snout,
prominent rostral scales, and fusion of the
second and third temporals as synapomor-
Phalotris nigrilatus is known only from the
holotype from Carumbe
, San Pedro, Para-
guay. The specimen (FML 0709) was collect-
ed in 1973 by Rodolfo Golbach, and the first
reference to it was made by Laurent (1974) as
Elapomorphus nasutus. Elapomorphus nasu-
tus (now P. nasutus) was restricted to Brazil
(Peters and Orejas-Miranda, 1970); with the
Golbach record, the geographic distribution
was extended ca. 810 km. No other species of
the nasutus group or additional P. nigrilatus
specimens are known from Paraguay. Ferrar-
ezzi (1993) noted several differences between
the types of P. nigrilatus and P. nasutus in
CORRESPONDENCE: e-mail, firstname.lastname@example.org
Herpetologica, 63(4), 2007, 552–559
2007 by The Herpetologists’ League, Inc.
general body color pattern. In addition, both
forms are widely allopatric. Nevertheless,
Ferrarezzi (1993) found no definite autopo-
morphies to support the specific separation of
the two taxa, treating them as a metaspecies;
he pointed out the necessity of obtaining
more material to understand the systematics
of the nasutus group. He had only one
specimen, and we know nothing of differences
between sexes in the species. Because the
holotype is a female, hemipenial morphology
In 2005, we located two specimens cata-
logued as P. nasutus from Paraguay in the
Natural History Museum in Montevideo
(MNHN). A detailed review of this material
showed them to be specimens of P. nigrilatus.
In this work, we redescribe the holotype of P.
nigrilatus, include a description of the hemi-
penis from the new material, and comment on
variation in the species. The known geo-
graphic distribution of this Paraguayan en-
demic is expanded.
ATERIALS AND METHODS
The new material was fixed and stored in
10% formalin. The holotype in the Fundacio
Miguel Lillo collection (FML) was examined
in Argentina. Ventral scales were counted
following Dowling (1951) and compared with
Peters (1964) because of the difference
between the data given by Laurent (1974;
197 ventrals) and Ferrarezzi (1993; 202
ventrals). Subcaudal counts included neither
the pair contacting the vent nor the terminal
spine of the tail. All symmetric characters are
presented as left/right. Coloration is based on
preserved specimen because scientists have
not examined live specimens. Snout–vent
length (SVL) and tail length (TL) were
measured in the preserved specimens using
a cord and then measured with a ruler. Other
standard measurements were taken using
a slide-caliper (0.01 mm). To minimize error
in the measurements, data are given to
a precision of 0.1 mm. External morphology
was observed under a stereoscope. For
descriptions of hemipenes, we largely follow
the terminology of Dowling and Savage (1960)
and Zaher (1999). To see the morphology of
the hemipenes, we dissected the organs of
MNHN 00089. The right hemipenis was
dissected in situ, and the left was separated
from the body. Both were inflated with agar.
We took the following measurements in
mm: head length (HL), from the jaw articu-
lation to the tip of the snout; snout–vent
length (SVL), from the tip of the snout to the
anal opening; tail length (TL), from the anal
opening to the tip of the tail; total length
(TTL), from the tip of the snout to the tip of
the tail. Additional measurements were: head
width (HEW), where the head is largest; neck
width (NEW), neck immediately behind the
head; mid-body width (MBW), at the region
halfway between the neck and the vent; tail
base width (TBW), at the level of the vent;
and eye diameter (ED).
We took the following measurements of the
cephalic scales: (1) Rostral (RO): (a) on the
midline, from the prefrontal to the lip margin;
(b) from the left rostral margin on the lip to
the right rostral margin on the lip. (2)
Internasals (IN): (a) from the prefrontal/
rostral suture to the nasal/prefrontal suture;
(b) from the prefrontal/rostral suture to nasal/
rostral suture. (3) Prefrontal (PF): (a) from the
loreal/nasal suture on the left to the loreal/
nasal suture on the right; (b) from the rostral
to the middle of the suture with the frontal.
(4) Frontals (FR): (a) from the middle of the
suture with the prefrontal to the parietal/
parietal suture; (b) from the left prefrontal/
supraocular suture to the right prefrontal/
supraocular suture. (5) Parietals (PA): (a) from
frontal/supraocular suture to furthest contact
with dorsal body scales (DBS); (b) from suture
frontal/joint of two parietals to suture between
temporals. (6) Preoculars (PRO): (a) from
center of contact with eye to nasal/prefrontal
suture; (b) from prefrontal/supraocular suture
to middle of the supralabial. (7) Upper
Postoculars (UPO): (a) from supraocular/eye
contact to parietal/fifth supralabial contact; (b)
from supraocular/eye contact to contact of
lower postocular/fifth supralabial. (8) Lower
Postoculars (LPO): (a) from eye/upper post-
ocular contact to contact between third/fourth
supralabials; (b) from eye/third supralabial
contact to parietal/ fifth supralabial suture. (9)
Temporals (TE): (a) from parietal/supralabial
suture to most posterior contact with dorsal
body scales (DBS); (b) from supralabial/DBS
contact to parietal/DBS contact. (10) Anterior
December 2007] HERPETOLOGICA 553
Gulars (AG): from suture to first infralabial/
second infralabial furthest posterior on the
midline. (11) Posterior Gulars (PG): from
anterior gular/fourth supralabial contact to
most posterior contact with DBS.
Specimens examined included the follow-
ing: FML 0709 (holotype), Carumbe
tamento San Pedro, Paraguay. July 1973. Col.:
R. Golbach.; MNHN 00089, MNHN 00091,
Colonia Primavera, Alto Paraguay, Paraguay.
November 1957. Col.: Nigel Wolf.
Note that the last two specimens were
collected before the type specimen. In the
time when the collection took place, all sites
north of the Departamento Central (where
the capital, Asuncio
n, is located) were often
called Alto Paraguay. Accordingly, the Alto
Paraguay referred to is a large region, not the
present-day Departamento of the same name.
The locality is in Departamento San Pedro.
Phalotris nigrilatus Ferrarezzi, 1993
Holotype.—FML 0709; type locality: Para-
guay: Departamento San Pedro, Carumbe
1974 Elapomorphus nasutus Laurent, Acta
gica Lilloana 31: 65.
1984 Elapomorphus nasutus (partim) Lema,
Iheringia 64: 72, fig. 12.
1993 Phalotris nigrilatus Ferrarezzi, Mem.
Inst. Butantan, 55: 30.
2002a Phalotris nigrilatus Lema, Acta Biolo-
gica Leopoldensia 24: 213.
P. nigrilatus differs from tricolor and
bilineatus groups by having a prominent
rostral scale and fusion of the second
and third temporals (synapomorphies that it
shares with species of the nasutus group).
Within the nasutus group, P. nigrilatus, P.
concolor and P. labiomaculatus lack the first
temporal, and the parietals contact the fifth
Among the nasutus group, P. nigrilatus is
distinguished from P. concolor and P. labio-
maculatus by the absence of the first temporal
(temporals 1 + 1inP. concolor and P.
labiomaculatus) and from P. nasutus by the
presence of lateral dark bands along the body
and tail and a vertebral stripe. Finally, P.
nigrilatus can be distinguished from P.
lativittatus by the contact between the rostral
and prefrontal scales (separating the inter-
nasals), the loss of the nuchal collar, and
a blackish head and belly with lateral black
spots. The hemipenis of P. nigrilatus has
curved spines; spines of the hemipenes of the
rest of species in nasutus group are almost
straight. The hemipenis of P. nigrilatus can be
differentiated from species of the bilineatus
group by the presence of two distinct lobes
with well developed lateral spines. It can be
distinguished from hemipenes of the tricolor
group by having more developed, curved
spines, and deeper hemipenial lobes.
Redescription of the Holotype
(an Adult Female)
Coloration.—Dorsal, lateral, and ventral
scales of head dark brown, with rostral plate
paler than rest of head. Immediately behind
posterior tips of parietal plates, coloration
becomes paler, turning into a cream-colored
middorsal band, five scales wide. Sides of neck
dark brown. Thin middorsal stripe, formed by
streaks from bases to apices of vertebral
scales. Stripe starts five scales behind parietal
plates, and ends 22 scales before tip of tail.
Stripe is discontinuous on tail. Sides of body
dark brown (almost black), from midpoint of
fifth dorsal scale row down to contact with
ventral scales. Belly bottom color yellowish
cream with dark brown spots in tips of ventral
scales, formed by continuation of lateral dark
bands of body sides. Dots form a spotted line
along ventral tips. Free edges of ventral scales
not pigmented. Tail coloration with same
pattern as rest of body. Ventral region of tail
cream with lateral incursion of dark dorsal
color, like midbody. Tip of tail yellowish.
Pholidosis.—Muzzle prominent with rostral
scale projecting. Rostral scale touching pre-
frontal, separating internasals. Internasals
subtriangular. Prefrontal wider than frontal
scale. Frontal in contact with supraoculars on
both sides. Frontal and supraoculars reach
parietals. Parietals almost twice as long as
wide. Nasals long, with nostrils in the anterior
tip of the scale. Nasal in contact with
preocular. Preoculars subpentagonal, little
bigger than eye width. Two postoculars.
554 HERPETOLOGICA [Vol. 63, No. 4
Upper postocular smaller than eye, and lower
postocular smaller than upper. Six suprala-
bials, with second to fourth contacting orbit.
Fourth supralabial in contact with lower
postocular. Fifth supralabial bigger than the
others, touching parietal and temporal. Left
temporals 0 + 1 + 2; and right 0 + 1 + 4.
Anterior temporal long and narrow, lying
between last supralabial and parietal. Seven
infralabials on each side, first to fourth
contacting chinshield scales. Third infralabial
contacting first as well as second chinshield.
Holotype with anterior gulars diverging
anteriorly and contacting first infralabials.
Posterior gulars in anterior contact, with
lateral projections contacting fourth infrala-
bials. Second chinshield on right side divided
into two scales. Dorsal scales rows with
reduction one head length behind the head
(17-15-15) without apical pits. Using Peters’
(1964) method, starting with the first ventral
scale wider than long, there are 205 ventral
scales. However, starting with the first ventral
scale that contacts the first dorsal row
(Dowling, 1951), the count is 203. Subcaudals
consist of 27 pairs. Anal plate divided.
Measurements (mm).—HL: 15.7; SVL: 692;
TL: 59; TTL: 751. HL/TTL 5 0.021; TL/TTL
5 0.078. HEW: 10.1; NEW: 8.6; MBW: 11.6;
TBW: 8.0; ED: 1.2. Table 1 shows measure-
ments of cephalic scales.
Variation (Based on Two Males: MNHN 00089
(Fig. 1) and MNHN 00091)
Coloration in preservative.—Head brown
on top and sides. Left side of head of MNHN
00089 blackish brown (including third
through sixth supralabials, and temporal).
Supralabials and rostral scales of MNHN
00091 spotted with dark gray. Ventral region
of head dark brown, with mental, infralabials,
and chinshields profusely spotted with dark
gray. Dorsal color pattern with wide, pale pink
middorsal stripe, six scales wide at mid body
in MNHN 00089 and 00091. A fine, dark
brown vertebral line, formed by elongate
spots on tips of vertebral scales. Vertebral
line starting at the level of the first ventral
scale, finishing at the level of the vent
(MNHN 00089) or starting at level of second
ventral scale and extending a short distance
behind vent (MNHN 00091). Sides of body
uniform blackish brown, from first to fourth
(MNHN 00091) or fifth (MNHN 00089)
dorsal scale row. Ventral ground color light
cream; blackish brown color of body sides
continuing as spots on lateral tips of ventral
scales. Spots small on the anterior ventrals and
larger at mid body. Spots less noticeable in
MNHN 00091. Tail with color pattern similar
to rest of body. Vertebral stripe of MNHN
00089 replaced on tail by line of dots that
reach tip. Tips of light cream subcaudals
spotted like ventral scales. Ventral spots only
on lateral tips of subcaudals in MNHN 00091
but also small spots in centers of subcaudal
scales in MNHN 00091. Terminal 1/3 of
apical spine white.
Pholidosis.—Rostral prominent but not so
evident as in holotype, in contact with pre-
frontal. Preocular long and pentagonal. Both
specimens with one preocular (or loreal), two
postoculars, and temporals 0 + 1 on each side.
MNHN 00089 with six supralabials (second
and third contacting the orbit) on both sides,
but MNHN 00091 with six supralabials on left
and seven (third and fourth contacting the
orbit) on right side. Fifth supralabial in
contact with parietal in MNHN 00089 (as in
the holotype); MNHN 00091 the same on the
left side, and sixth supralabial contacting
parietal on right side. Both specimens with
eight infralabials on each side, with the first
four contacting chinshields. In MNHN 00089,
anterior gulars almost rectangular and without
projections. Anterior gulars in MNHN 0091
TABLE 1.—Measurements of cephalic scales of the speci-
mens analyzed (given in mm). RO: Rostral; IN: Internasal;
PF: Prefrontal; FR: Frontal; PA: Parietal; PRO: Preocular;
UPO: Upper postocular; LPO: Lower postocular; TE:
Temporal; FG: First gular; SG: Second gular. See text for
explanation of measurement methodology.
FML 0709 MNHN 0089 MNHN 0091
RO 2.4 3 3.1 2.4 3 3.8 2.3 3 3.5
IN 2.5 3 1.1 2.5 3 1.4 2.4 3 1.4
PF 5.1 3 3.2 5.5 3 3.2 5.6 3 3.4
FR 3.5 3 3.7 3.9 3 4.7 3.7 3 4.2
PA 7.1 3 3.5 7.4 3 4.5 6.8 3 3.6
PRO 1.4 3 0.9 1.6 3 1.2 1.9 3 1.3
UPO 0.9 3 0.9 1.0 3 0.7 1.0 3 0.7
LPO 0.8 3 1.0 0.8 3 0.9 0.5 3 0.7
TE 5.3 3 2.8 5.2 3 1.7 4.8 3 2.0
FG 4.1 2.9 3.2
SG 4.4 4.3 9.6
December 2007] HERPETOLOGICA 555
deeply separated anteriorly and in broad
contact with first and second infralabials. In
MNHN 00089, posterior gulars divergent and
completely separated except at their most
anterior projection. MNHN 00091 with sec-
ond gulars unusually long and narrow, in
contact through their anterior half, but
curving laterally and becoming widely di-
vergent in their posterior half. Dorsal scale
rows without reduction, with 15-15-15 anteri-
or, middle and posterior rows, respectively.
Following Peters (1964), MNHN 00089 with
184 ventral scales, and MNHN 00091 with
186. Using the system of Dowling (1951),
ventral scale counts 183 and 185, respectively.
Both specimens with anal plate divided.
MNHN 00089 with 35 subcaudals, and
MNHN 00091 with 33. Dorsal body scales
without apical pits.
Measurements (mm).—MNHN 00089: HL:
18.0; SVL: 809; TL: 182; TTL: 991. HL/TTL
5 0.018; TL/TTL 5 0.184. HEW: 11.1; NEW:
9.2; MBW: 11.9; TBW: 7.4; ED: 1.4. Mea-
surements of cephalic scales are shown in
MNHN 00091: HL: 17.3; SVL: 727; TL:
171; TTL: 898. Ratios of head and tail by total
length are 0.019 and 0.190 respectively.
HEW: 9.6; NEW: 8.1; MBW: 9.5; TBW: 6.7;
Sexual dimorphism.—There are no differ-
ences in color pattern between males and the
female, but there are differences in morpho-
logical ratios and scale counts between sexes.
The female has a shorter tail (ratio: 0.078) in
proportion to the body length, while males
have a longer tail (Ratios: 0.184 and 0.190).
The female has 203 ventral scales, while the
males have 183 and 185. Subcaudals are 27 in
the female, and 33 and 35 in the males.
Hemipenial Description (Based on
Retractor muscle of hemipenis originating
at level of 29th subcaudal scale. Hemipenis
bilobed and semicapitate (Fig. 2). Capitula
less than one-third of total length, semicaly-
culate, and marked at base by large pockets
and grooves on asulcate and lateral faces.
Central body almost naked, with scattered
spinules; two rows of large spines on each
side, and a series of smaller spines towards
base. Sulcate face with spinulate calyces,
becoming gradually smaller towards base of
lobes. Spermatic groove divided in distal two-
thirds of organ. Each lateral surface of central
FIG. 1—Ventral and dorsal view of the specimen
556 HERPETOLOGICA [Vol. 63, No. 4
body with 8–12 large spines, disposed in two
rows, with rows converging basally. Distal pair
of spines on each side markedly larger and
usually curved distally, remainder of spines
smaller and usually straight. Basal segment
with 3–4 stright spinules on sides and 9
spinules on asulcate face.
Measurements (mm) of everted right hemi-
penis of specimen MNHN 00089: Total
length: 23.9; longer lobe: 5.9; shorter lobe:
5.5; width of lobes: 3.9; width at mid body
hemipenis: 6.70; length of longest spine: 2.7.
Habitat and distribution.—The two known
localities are in Departmento San Pedro,
Paraguay, east of and near to the Paraguay
River (Fig. 3). The holotype is from Estancia
and the other specimen is from
Colonia Primavera, about 56 km to the S of
the type locality.
According to Lema (2002b), the type
locality corresponds to the Paraguayan Chaco
formation. Based on the criteria of ENPAB
(2003), both localities (type locality and
Primavera) are in a transition zone between
Wet Chaco and Alto Parana
Forest. Following Keel et al. (1993), the range
of the species falls in a transition sector
between the Littoral Central Ecoregion and
Selva Central Ecoregion, with natural com-
munities including lagoons, swamps, rivers,
tall and medium forests, grasslands and rock
hills. However, because the distribution of the
species is close to the Paraguay River, the
habitat is moist, with precipitation and mean
temperature values of 1400 mm and 23 C
respectively. At the present time, the area’s
forests are largely replaced by agriculture and
Life history.—Little is known about the life
history of this rare species. Phalotris nigrilatus
has a modified rostral scale and reduced eyes,
which are indicative of fossorial habits. We
have not found information concerning diet.
Conservation.—This species seems to be
endemic to Paraguay. In the restricted distri-
bution of the species, there are no protected
areas. The Secretarı
a del Ambiente in Para-
guay treats this species as ‘‘Endangered’’.
The specimens of the Uruguayan museum
were collected in 1957. The holotype was
collected in 1973, and the species has not
been re-collected in more than 30 yr. More
studies near the type locality are needed to
better understand the status of this rare
species. The littoral regions along the Para-
guay River are extremely modified by human
populations. With accelerating disturbance as
a result of explosive population increases, the
future of this and other species along the
rivers is precarious.
Species of the nasutus group are distributed
in south-central Brazil (P. lativittatus, P.
nasutus, P. labiomaculatus and P. concolor)
and Paraguay (P. nigrilatus). Phalotris lativit-
tatus and P. concolor are typical of the
Cerrado Domain. Phalotris nasutus seems to
be the most versatile species; it typically can
be found in Cerrado Domain, but also occurs
in Amazonia and in the Cerrado-Chaco
FIG. 2—Hemipenis of MNHN 00089 showing sulcate
and asulcate sides.
FIG. 3—Map showing type locality of P. nigrilatus
(triangle) and the position of the two additional specimens
December 2007] HERPETOLOGICA 557
transition zone (Lema, 1999). Phalotris labio-
maculatus is endemic to the Amazonian
Domain (Lema, 2002b). Ferrarezzi (1993)
pointed out that species in the nasutus group
are characteristic of open areas such as
Cerrado. The habitat of P. nigrilatus has more
vegetative components of the Atlantic Forest
or Chaco than Cerrado.
When Ferrarezzi (1993) described P. nigri-
latus, he noted that this species has the most
derived characters compared with the other
species in the nasutus group. He wrote: ‘‘O
mulo de material e o auxilio de novos dados
veis para a com-
o das relac¸o
ticas no grupo’’
(Translation: The accumulation of material and
the aid of new comparative data are essential to
understand the systematic relationships of the
group) (Ferrarezzi, 1993:34). Autopomorphies
of P. nigrilatus (contact between rostral and
prefrontal scales, loss of nuchal ring, black
head and belly spotted) are now supported by
two additional specimens.
Laurent (1974) counted 197 ventral scales
in the holotype, but evidently he was mis-
taken. The gulars are some of the most
variable scales (Fig. 4).
P. nigrilatus shows differences in hemipe-
nial morphology from the other species of
nasutus group in which this organ is known.
The hemipenis of P. labiomaculauts was
described by Lema (2002a), and that of P.
nasutus was described by Ferrarezzi (1993)
and Zaher (1999). Ferrarezzi (1993) also gave
a brief description of the hemipenis of P.
lativittatus. The hemipenis in the nasutus
group seems to be asymmetric, semicaliculate,
and semicapitate. In the case of P. labioma-
culatus and P. nigrilatus, the lobes are deeply
bifurcate, while in P. nasutus the hemipenis is
slightly bilobed. A difference between the
hemipenes of P. labiomaculatus and P.
FIG. 4—Shape of gular scales. 1: FML 0709 (Holotype), note the right posterior gular shaped by two scales. 2: MNHN
0089. 3: MNHN 0091. Acronyms of gulars- ar: anterior right; al: anterior left; pr: posterior right; pl: posterior left.
558 HERPETOLOGICA [Vol. 63, No. 4
nigrilatus is that the latter has calyces covering
all the lobes, while in P. labiomaculatus the
calyces are absent in the apex of the lobes.
A synapomorphy among the nasutus group
is the presence of well developed hemipenial
spines on the sides of the organ. The curvature
in the largest hemipenial spines of P. nigrilatus
is not seen in other members of the group and
may be considered an autapomorphy. The
origin of the hemipenial retractor muscle in
MNHN 0089 is very posterior, only six
subcaudals before the tip of the tail.
Finally, P. nigrilatus seems to be the most
evolved species in the group, and P. concolor
retains the most primitive characters (Ferrar-
ezzi, 1993). Both species occupy ranges
peripheral to those of other members of the
P. nasutus group, with P. concolor to the
northeast and P. nigrilatus to the southwest.
Acknowledgments.—We thank G. Scrocchi (Fundacio
Miguel Lillo) for assistance with holotype examination and
comments and revision of this manuscript, A. Toscano
(MNHN, Director) for his help during examination of
specimens of the MNHN, H. Cabral, A. Yanosky and R.
Clay (Guyra Paraguay Foundation) for assistance with
location of Colonia Primavera, and F. Burbrink, G.
Leynaud and another anonymous reviewer for comments
on the manuscript. P. Cacciali also thanks the World
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.Accepted: 21 May 2007
.Associate Editor: Frank Burbrink
Phalotris nigrilatus Ferrarezzi, 1993, es una especie poco
conocida, descrita en base a un u
nico ejemplar procedente
de Paraguay. Dos nuevos especimenes, hacen posible una
n mas detallada de la especie, incluyendo la
n de hemipene y apoyando la validez de la
especie. La morfologı
a del hemipene aporta otro caracter
que apoya la inclusio
n de esta especie en el grupo nasutus.
Describimos la variacio
n dentro de la especie, probable
dimorfismo sexual y distribucio
n conocida. Sera
realizar un trabajo mas intenso en Paraguay con la finalidad
de conocer el estado de conservacio
n de esta aparente-
mente rara y ende
December 2007] HERPETOLOGICA 559