1926a Heurnia ventromaculata Jong, Zoologische
Anzeiger, 67:302-3. Type locality: Pionierbivak, Mamberano River, North New
Guinea. Holotype: ZMA 11066. Collector W. C. van Heurn.
Etymology
The name ventromaculata refers to the ventral
spots described by the collector when the specimen was freshly caught.
Distribution
H.
ventromaculata is known only from the type locality.
Size
The type specimen, a male, has a total length of 702 mm, with a 148 mm
tail. The tail/SVL ratio is 26.7%.
External Morphology
This snake is known
only from the type specimen (ZMA 11066). The head is distinct from the neck and
depressed, the body is cylindrical; the eyes are dorsolateral, and slightly
larger than expected for a homalopsid. This account is based upon my scale
count numbers and they disagree slightly with Gyi’s (1970) counts for several
characters.
On the head the
rostral is pentagonal and broader than tall, it is visible from above. The
nasals are divided and are separated by an internasal. The nares are located
toward the inner edges of the nasals. The prefrontal is fused with the loreal
on the right side. On the left side the prefrontal and loreal are separate. The
loreal is twice as long as tall. The prefrontals are tuberculate, while some
other scales also have tubercles; the prefrontal tubercles are better
developed. The frontal is elongated and about equal in length to the parietals.
The parietals are entire. The loreal is in contact with upper labials 2 - 4.
The supraocular is elongated and single; the preocular is single and about two
times taller than wide; the postoculars number two on each side. The dorsal and
ventral scales are about equal in area. There are no subocular scales, although
the ventral postocular undercuts the orbit. The temporal formula is 1 + 2 + 3
on both sides, the primary temporal is exceptionally large. The third row is
difficult to distinguish from the occipitals. There are enlarged scales
following each of the parietals but separated from the temporals by smaller scales.
The upper labials 8/9; the largest are 5/6. The fifth one enters the orbit on
the right; the fourth one enters the orbit on the left. The eighth upper labial
on the right is divided; none are divided on the left.
On the chin the lower
labials numbers 14, the seventh is the largest and the second is the smallest;
1-3 contact the first chin shield. There are three pairs of enlarged chin
shields, the second and third pairs are separated by pairs of smaller scales.
The anterior pair of chin shields is only slightly larger than the second pair,
and the third pair is shorter that the first two pairs, but broader. Gulars
number seven.
On the body the dorsal
scale rows number 29 on the neck, 27 at mid-body, and 21 at posterior body. The dorsal scales are lanceolate in all rows.
The ventral scales number 163 and they are narrow. The anterior ventral scales
are less than twice the height of a nearby dorsal, and at mid-body and posterior
body the ventrals are a little more than twice the height of a nearby dorsal
scale.
On the tail the
divided subcaudal scales number 56. The scales on the dorsum of the tail are
similar to those near the vent. At the base of the tail the width is 84% of the
height in the one specimen.
Color and pattern. The
first 4 dorsal scale rows have light pigment, there is no pattern on the other
rows, presumably it was uniform in color, but the specimen also appears faded.
The venter is mottled. Jong (1926a) had notes from the collector, W. C. von
Heurn, who described the color in life as a uniform gray-black or mud color on
the sides and dorsum with a lighter venter with gray-black spots that extend
onto the chin and labials.
Natural History
While nothing is known
about the details of H. ventromaculata
life history, the area that it lives in has been studied by ecologists because
of a project to dam the Mamberamo River for a hydroelectric plant to power a
large industrial complex. The Mamberamo
River is about 650 km in length and drains a region of steep, rainforest
covered mountains, with a catchment that it is 76,000 km2. The river
carries a heavy sediment load. The Mamberamo River basin has a rich
biodiversity; and its estuary has large areas of freshwater swamps and
extensive areas of mangrove. Thus, there may be other homalopsids and aquatic
herpetofauna to be found in the area (Muchtar and Ilahude, 2001; Richards and
Suryadi, 2002).