A new species of arboreal viper (Serpentes: Viperidae: Atheris) from Cameroon, Africa

11 Pages·1999·5 MB·

by  Lawson

PROCEEDINGS OF THE BIOLOGICAL SOCIETY OF WASHINGTON
112(4):793-803. 1999.
A new species of arboreal viper (Serpentes: Viperidae: Athens) from
Cameroon, Africa
Dwight Lawson
P.
Department of Biology, The University of Texas at Arlington,
Arlington, Texas 76019-0498, U.S.A.
—
Abstract. A distinctive new species of the arboreal viper genus Athens (A.
broadleyi) is described from Cameroon, Africa. The new taxon inhabits moist
evergreen and semideciduous transition forest in southern Cameroon, Congo,
Central African Republic and Gabon. The new species previously has been
confused with the widespread A. squamigera, but is distinguished from this
species and other congeners by a combination of scale characteristics and a
unique color pattern.
In a recent review, Broadley (1998) com- ing a meter stick. Other standard measure-
mm
mented on an unusual color morph of Ath- ments were taken to the nearest 0.1 us-
ens squamigera from southern Cameroon. ing dial calipers held under a dissecting mi-
&
Perret Mertens (1957) had previously croscope. Features of scalation were ex-
mentioned the same population of Athens amined by holding preserved specimens
from Moloundou in the extreme southeast under a dissecting microscope. Scale ter-
of the country, and suggested that addition- minology generally follows Klauber
al material was needed to ascertain this (1956). Suprarostrals and interorbitals are
population's taxonomic status. Both of used in keeping with Broadley (1998) for
these descriptions agree with a series of other members of the genus. Interrictal
Athens I obtained during a herpetological counts refer to scales across the back of the
survey of the proposed Lac Lobeke pro- head between the posterior supralabials.
tected area of extreme southeastern Came- Anterior body dorsal scale row counts were
roon. Comparison of this material with mu- made approximately one head-length pos-
seum specimens from Cameroon, Demo- terior to the head. Posterior body dorsal
cratic Republic of the Congo, Central Af- scale row counts were made approximately
rican Republic (CAR), topotypic A. one head-length anterior to the vent. Color
anisolepis Mocquard (1887) and the holo- descriptions in preservative and life are
type ofA. squamigera (Hallowell, 1856) re- based on a published standard (Smithe
veals that the southern, inland Cameroon 1975). Institutional abbreviations refer to
population is distinct from all other Atheris Academy of Natural Sciences of Philadel-
species. phia (ANSP), American Museum of Natu-
ral History (AMNH), University of Texas
Methods at Arlington Live Collection (DPL), Uni-
versity of Texas at Arlington Collection of
Specimens of the new Atheris were fixed Vertebrates (UTA). A list of specimens ex-
in 3.7% formalin within 24 hr of collection. amined is given in the Appendix.
Specimens were transferred into 70% eth-
anol within two months after preservation. Systematic Account
Snout-vent length (SVL) and tail length During the summer of 1994 I made her-
mm
(TL) were measured to the nearest us- petological collections at various proposed
794 PROCEEDINGS OF THE BIOLOGICAL SOCIETY OF WASHINGTON
Fig. L (A) Dorsal and, (B) left lateral aspect ofAthens broadleyi holotype, UTA R-37801, head length 29.0
nun.
and existing protected areas throughout Atheris squamigera—ssp. Perret, 1961:137
Cameroon. Specimens of Atheris taken at Atheris squamigera. Broadley, 1998: fig. 8
Lac Lobeke confirm long-standing impres- —
sions that this population is distinct. I pro- Holotype. University of Texas at Ar-
pose that this new snake be known as lington Collection of Vertebrates (UTA) R-
37801, mature female collected vicinity Li-
Atheris broadleyi, new species pondji village. East Province, Cameroon
Figs. 1-2 and 5 (A) — (2°23'05"N, 15°25'41"E), 1 Jun 1994 by D.
Atheris squamigera squamigera. Perret & P. Lawson (original field number DPL
Mertens, 1957:597 3608).
VOLUME NUMBER
112, 4 795
Fig. 2. Athens broadleyi, adult male from the type-locality, ca. 525 mm SVL, DPL 3646. Photo by D. P.
Lawson.
—VTA
Paratypes. R-37798-37800 and nation of characters: lateral scales without
44911-21, 10 adult and 4 juvenile females serrated keel; supralabials in contact with
from the type-locality, collected between suboculars (not separated by one or more
May and December 1994, UTA R-44957, scale rows); 14-18 interrictals; interorbitals
an adult female collected in the vicinity keeled; rostral 3.5 to 4 times broader than
Mbanjani village, East Province, Cameroon high; scales in loreal region smooth or with
km
(ca. 5 road south of the type-locality), only slight keel or knob; a dark postocular
7 Sep 1997, and ANSP 20334, an adult stripe persisting in adults; maximum total
mm
male from Nola, Central African Republic length of 765 or more; and a dark tail
(3°32'22"N, 16°02'51"E), collected 27 Oct tip in adult females.
1934 by J. A. G. Rehn of the G. Vanderbilt Specifically, Atheris broadleyi appears to
Africa Expedition. — be most similar to A. squamigera, but dif-
Definition and diagnosis. A species of fers consistently by the combination of: a
Atheris distinguished from all other mem- distinctive and consistent dorsal color pat-
bers of the genus by the following combi- tern of citrine to greenish olive; checked
796 PROCEEDINGS OF THE BIOLOGICAL SOCIETY OF WASHINGTON
black, white and sky blue venter, and a dark above medial suprarostral but not separat-
postocular stripe; more oculars (mode of 15 ing two innermost intemasals; interrictals
versus modes of 12-14, see Table 1); and, 17; interorbitals 6, strongly keeled, those
mm
greater length of 765 or more (versus not contacting oculars enlarged and irregu-
mm
650 maximum for Cameroon A. sqiia- larly shaped; oculars 15/13, supra- and
migerd). Additionally, A. broadleyi usually postoculars keeled, terminating in blunt
has more ventrals (mean of 162 ± 3.3 ver- knobs, suboculars and ventralmost preocu-
sus 157 ± 3.6) and fewer subcaudals (mean lar dorsoventrally compressed, knobbed but
of 51 ± 4.9 versus 52 ± 3.2), and more not keeled, two dorsalmost preoculars fee-
infralabials (mode of 11 versus 10) than A. bly knobbed, enlarged, extending anteriorly
squamigera. into loreal region; oculars separated from
Athens broadleyi lacks serrated keels on nasals by 6/5 smooth or feebly knobbed
its lateral scales differentiating it from an scales loosely arranged in three rows of 1/
East African group comprised of A. cera- 1, 1/2, 4/2; supralabials 11/10, 3-5 contact-
tophora, A. desaixi, A. katagensis, A. nit- ing suboculars; infralabials 11/11, 5-10 on
schei, and A. rungweensis with pronounced each side feebly keeled, anteriormost in
serrations on the lateral scales. Elongate su- contact at the midline, separating mental
praocular scales forming a horn-like projec- from 5 pairs of chin shields; mental 2.3
tion over the eye further distinguishAthens times wider than deep; gulars strongly
ceratophora. Similarly, Athens broadleyi keeled; ventrals 159; subcaudals 50, entire;
lacks lanceolate or acuminate dorsal scales anal entire; dorsal scales about twice as
and fused lateral scale rows, differentiating long as wide, becoming shorter posteriorly,
it from the distinctive East African A. his- in 19-21-16 rows; keel on dorsals increas-
pida and A. acuminata. Athens broadleyi is ing in height from base, decUning rapidly
distinguished from A. chlorechis by having at apex, ending in sHght knob; paraventrals
fewer interrictals (14-18 versus 23 or larger than other dorsals, keeled, angled
more) and fewer mid-body dorsal scale slightly ventrally.
rows (17-23 versus 25-36). In addition to Measurements (mm); SVL 550; tail
differences in color pattern, Athens broad- length 110; eye diameter 5.1; head length
leyi is distinguished from A. anisolepis by 29; head width 21.2; distance from anterior
having completely keeled interorbitals margin of eye to nares 4.7 mm, to tip of
(smooth in A. anisolepis), supralabials in snout 6.8 mm.
contact with oculars (separated by a scale Color in preservative (ethanol after for-
row in A. anisolepis), and usually fewer su- maUn) has not changed appreciably from
prarostrals. — life: dorsum of head uniformly citrine with
Description of holotype. Rostral flat- oHve-yeUow keels; sides of head spectrum
tened, dorsal margin slightly concave me- yellow extending onto lateral aspect of
dially, 3.5 times broader than high, con- neck; face straw yellow; a diffuse dark
tacting anteriormost supralabials, three un- stripe extending from the ventral posterior
keeled suprarostrals and divided left nasal; margin of the eye caudad to the rictus, in-
medial suprarostral the smallest, 1.3 times corporating the last three supralabials and
wider than high, right and left suprarostrals posterior margin of the eighth, barely ex-
as wide as high; right and left nasals par- tending onto the last three infralabials; dor-
tially divided above the nares, left nasal fur- sum of body citrine anteriorly becoming
ther divided at anteriormost edge forming a greenish olive posteriorly, broken by 29
separate small scale; nares large, covering black-bordered sulphur yellow crossbands,
approximately 30% of nasal, directed lat- crossbands on anterior half of body do not
erally and slightly posteriorly; intemasals 5, meet on midline, becoming indistinct on
strongly keeled, medial scale lying directly neck, posterior 15 crossbands conspicuous.
VOLUME NUMBER
112, 4 797
complete across the dorsum; tail with 9 0.3); ratio right suprarostral width to height
moderately distinct, complete crossbands; 0.65-1.3 (0.91 ± 0.2); suprarostrals 3-7
tail tip black; interstitial skin color varied, [3]; intemasals 3-5 [5]; interorbitals 3-8
corresponds to dorsal color pattern; throat [6]; oculars 12-16 [15]; total scales in lo-
and neck white; venter sky blue, irregularly real region 3-7 (5.3 ± 1.2) [6]; supralabials
suffused with white anteriorly, becoming 9-12 [10]; infralabials 9-12 [11]; ratio of
increasingly darker posteriorly; white mental width to depth 1.3-2.5 (2 ± 0.3);
blotch on lateral portion of every third and/ chin shields 4-7 [5]; interrictals 14-18
or fourth (occasionally second) ventral [17]; ratio eye diameter to head length
scale extending onto paraventral, blotches 0.15-0.24 (0.18 ± 0.02); ratio head length
become more pronounced as venter darkens to SVL 0.05-0.07 (0.06 ± 0.01); ratio head
posteriorly, forming a checkered pattern; width to head length 0.64-0.84 (0.78 ±
ventral color extends onto paraventrals and 0.05); ratio eye-nares to head length 0.13-
occasionally—onto adjacent dorsal scale. 0.16 (0.15 ± 0.01); ratio eye-snout to head
Variation. The 15 paratypes closely re- length 0.21-0.27—(0.24 ± 0.01).
semble the holotype in color, pattern, and Distribution. Atheris broadleyi is
scalation. Posterior portions of the venter in known from southern Cameroon from the
some individuals (including the only male Nyong River just southeast of Yaounde
in the type series) are more uniformly dark (iriri2"E, 3°27'38"N, DPL 5508), south
than that of the holotype, but always have through the Dja Forest Reserve (Broadley
distinct white lateral blotches. Specimens 1998) and east at least as far as the Sangha
from the western extent of the range (see
region of the Central African Republic (Fig.
below) may be less boldly patterned, and
3). This distribution corresponds to a region
are almost uniformly citrine/greenish olive
previously mapped for Cameroon as moist
with barely discernable crossbands and
evergreen and semideciduous forest (tran-
postocular stripe (DPL 5508). Juveniles less
than 300 mm SVL (UTA R-37798, 44913, sition forest) comprised of Baillonella tox-
isperma and Gilbertiodendron dewevrei
44918, 44920) have white tail tips, and (CENADEFOR
1985). This region also fea-
remnants of a pale tail tip are present in two
tures palm swamps and large scrub grass-
subadult specimens (UTA R-44915 and
UTA land clearings associated with seasonal high
44919). R-37799 is the largest of the
mm UTA water tables (D. Thomas, pers. comm.). The
series (768 total length), R-37798
mm distribution of Atheris broadleyi presum-
the smallest (247 total length). One to
ably follows this forest type into northern
three isolated scales are present in the in-
Gabon and Congo.
teroculabial region in five of the paratypes,
Atheris broadleyi was the most common
but do not completely separate oculars and
snake in the Lac Lobeke, Cameroon survey,
supralabials. Scales in the loreal region are
smooth in eight specimens and feebly but does not appear in a slightly larger col-
knobbed in seven. lection from the vicinity of Oesso, Congo,
The paratypes exhibit the following var- just across the Sangha River (Kate Jackson,
iation (means and standard deviations in pa- pers. comm.). Atheris broadleyi is abundant
rentheses, modes in brackets, see Table 1): near the type-locality. Local collectors ob-
ventrals 157-169 (162 ± 3.3); subcaudals tained 24 specimens in 48 hours, indicating
45-59 [50]; midbody dorsal scale rows 17- remarkable densities for a snake by Central
23 (20 ± 1.6); anterior body dorsal scale African forest—standards.
rows 16-21 [19]; posterior body dorsal Etymology. The specific epithet is a
scale rows 13-18 [16]; ratio rostral width patronym for Donald G. Broadley in rec-
to height 3.2-5 (3.9 ± 0.5); ratio medial ognition of his considerable contributions to
suprarostral width to height 1-2.2 (1.2 ± the herpetology of Africa in general, and
798 PROCEEDINGS OF THE BIOLOGICAL SOCIETY OF WASHINGTON
T
I
14° 18°
/
('
^^- / Central
^
s
African
Cameroon
Republic
\
Yaounde
\ 24J
\ Nola
'N-.
^-
T " '
I
Lac /
'\ f Lobeke j\ j
..,^^_^
'o*
Equatorial * •0
Guinea
j
; Congo
c4
I
Gabon •>
/^ Lukolela
/
—4 r\ /
Congo
/
Brazzaville^'Kinshasa
Atlantic
/'V\ / Democratic
,.^
Ocean
Republic of
^°
Congo
^ the
8°'
Angola
10 14° 16° 18'
± !
1
I I \
Fig. 3. Localities of Athens broadleyi (triangles), A. squamigera (inverted triangles), and A. anisolepis
(squares) in west Central Africa. Outlined symbols indicate type-localities.
VOLUME 112, NUMBER 4 799
his recent clarifications of the genus Athens green, violet or a mottled combination of
in particular. — yellow and violet. Unlike A. squamigera, A.
Comparisons. Broadley (1998) provid- broadleyi appears to be highly consistent in
ed a key to the species ofAthens by which color pattern.
A. broadleyi is readily diagnosed from all South-central Cameroon is an area of
members of the genus except A. anisolepis possible sympatry between Atheris broad-
and the widely distributed and highly vari- leyi and A. squamigera for which material
able A. squamigera. Athens broadleyi is is available. Specimens from Metet and Bi-
(AMNH
also distinctly allopatric from all but A. tye 5254, 51841-43) have a pro-
squamigera. Although recognized in recent nounced, dark postorbital stripe and several
treatments (e.g., McDairmid et al. 1999, features of scutellation overlapping A.
&
Broadley 1998, Trape Roux-Esteve broadleyi. I have referred the south-central
1995), A. anisolepis is similar to A. squa- Cameroon material to Atheris squamigera
migera and its validity remains uncertain on the basis of dorsal color pattern and scu-
(Broadley 1998). Descriptive statistics and tellation. However, this area Ues at the tran-
differences among A. broadleyi, A. aniso- sition between the coastal moist evergreen
lepis and A. squamigera are summarized in forest ofA. squamigera and the inland tran-
Table 1. For the purpose of comparisons sition forest of A. broadleyi, and may rep-
with the new taxon, information for four resent an integration zone between the taxa
populations of A. squamigera is presented (Fig. 3). Collections from other areas of
separately in Table 1. Atheris squamigera is possible sympatry at the southern limit of
widely distributed in forests from Senegal A. broadleyi are lacking.
to western Kenya (Spawls and Branch In addition to differences in color and
1995). As evidenced by this species de- scalation, Atheris broadleyi differs from
scription and the intraspecific variability of Cameroon A. squamigera in behavior and
A. squamigera (Table 1), previous descrip- reproduction. Both in the field and in cap-
tions of this taxon may have inadvertently tivity, A. broadleyi are more aggressive, ac-
increased the reported variation in many tive and alert than A. squamigera, striking
characters by combining distinct species readily and repeatedly with little provoca-
with A. squamigera. tion (pers. obs.). Neonate Atheris broadleyi
With the exception of occasional speci- (Fig. 5 A) resemble the adults in coloration,
mens which uniformly darken in preserva- but have a pale colored tail tip that disap-
tive over time, color and pattern features of pears as they mature. This is in contrast to
Atheris in preservative closely resemble A. squamigera from western Cameroon that
those in life (pers. obs.). Atheris squami- produce almost uniform charcoal-black off-
gera are most often apple green to turquoise spring with pale green eyes and a pale tail
blue with yellow crossbands above and yel- tip (Fig. 5 B). These neonates attain the ap-
low, green or blue ventrally (Fig. 4, ple green or turquoise blue adult coloration
Schmidt 1923, pers. obs.). Occasional spec- with successive post-natal sheds. The pale
imens of A. squamigera from the Came- tail tip persists in female A. squamigera
roon-Nigeria frontier (UTA R-44963, from western Cameroon, but is lost in
44926, Stuck-Stim 1979, Lawson 1993) males from this population as they mature.
and Congo (AMNH 45940, 51840), and A pair of Atheris broadleyi collected as
specimens ofA. anisolepis (AMNH 1 1898- adults at the type-locality in 1994 and main-
99) are uniform spectrum yellow sparsely tained in captivity in the United States have
flecked with yellow-green spots. Atheris reproduced twice. Courtship and copula-
squamigera from the Congo River above tions were observed between 28 June and
(AMNH
Kinshasa 45940, 45943, 45945, 11 July 1995, and 13 young (one deformed)
51840) may be uniform yellow, turquoise were bom on 10 February 1996. Courtship
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800 PROCEEDINGS OF THE BIOLOGICAL SOCIETY OF WASHINGTON
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VOLUME NUMBER
112, 4 801
mm
Fig. 4. Athens squamigera, adult male from vicinity Nguti, Southwest Province, Cameroon, ca. 375
SVL, DPL 5348. Photo by D. R Lawson.
was observed on 13 July 1996, but no off- or coiled among vine tangles, sitting in ap-
spring were produced that year. Courtship parent ambush along arboreal rodent run-
was observed again on 10 June 1997 and ways (pers. obs.). The few direct observa-
continued for approximately one week. tions of this species in the wild occurred at
Five live and three stillborn young were the forest edge.
produced on 17 February 1998. The male There is a preponderance of females in
was observed courting and trying to copu- samples of both Atheris broadleyi and A.
late approximately one week prior to par- squamigera from Cameroon indicating a
turition. Specimens of A. squamigera from strong collecting bias or skewed sex ratio
western Cameroon maintained under simi- in the populations. Males of both species
lar captive conditions to the A. broadleyi are considerably smaller than females.
above have been observed in courtship in Males and females of A. broadleyi are
September-October and have given birth in much longer and more robust than their A.
April (pers. obs.). Pitman (1974) reported squamigera counterparts (Table 1, Figs. 2
similar timing of reproduction for A. squa- and 4).
migera in Uganda.
Like its congeners, Atheris broadleyi is Acknowledgments
primarily nocturnal (Spawls and Branch
1995, pers. obs.). Specimens have been The manuscript benefitted from the com-
found as they were either active on the ments and assistance of J. A. Campbell and
ground during or following evening rains. R. L. Gutberlet. P. Ustach provided the
802 PROCEEDmGS OF THE BIOLOGICAL SOCIETY OF WASHINGTON
Fig. 5. (A) Neonate Athens broadleyi bom to parents from the type-locality; (B) Neonate A. squamigera
from wild-caught gravid female DPL 5318. Banyang-Mbo Wildlife Sanctuary. Southwest Province, Cameroon.
Photos by J. A. Campbell.