Common names: Wall's hump-nosed viper.

Hypnale walli is a venomous

Venomous snake

"Poisonous snake" redirects here. For true poisonous snakes, see Rhabdophis.Venomous snakes are snakes which have venom glands and specialized teeth for the injection of venom...

 pitviper

Crotalinae

The Crotalinae, commonly known as "pit vipers" or crotaline snakes, are a subfamily of venomous vipers found in Asia and the Americas. They are distinguished by the presence of a heat-sensing pit organ located between the eye and the nostril on either side of the head...

 species

Species

In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...

 found in Sri Lanka

Sri Lanka

Sri Lanka, officially the Democratic Socialist Republic of Sri Lanka is a country off the southern coast of the Indian subcontinent. Known until 1972 as Ceylon , Sri Lanka is an island surrounded by the Indian Ocean, the Gulf of Mannar and the Palk Strait, and lies in the vicinity of India and the...

. The smallest member member of its genus, it is distinguished by having a strongly upturned nose and lower scale counts. No subspecies

Subspecies

Subspecies in biological classification, is either a taxonomic rank subordinate to species, ora taxonomic unit in that rank . A subspecies cannot be recognized in isolation: a species will either be recognized as having no subspecies at all or two or more, never just one...

 are currently recognized.

Description

The smallest member of the genus Hypnale

Hypnale

Hypnale is a genus of venomous pitvipers found in Sri Lanka and southwestern India. Three monotypic species are currently recognized . All members have a more or less upturned snouts that produce a hump-nosed effect.-Description:...

, the only male with a complete tail measured 30.5 cm in length with a tail of 4.3 cm (14% of total length), while the largest female was 28.3 cm in total length with a tail of 3.5 cm. The body is stoutly built.

This species is distinguished from H. hypnale

Hypnale hypnale

Hypnale hypnale is a venomous pitviper species found in India and Sri Lanka. No subspecies are currently recognized.-Description: Grows to an average of 30-45 cm in length. The Armed Forces Pest Management Board states 0.4-0.6 m in length....

 by a snout that has a strongly upturned tip. This is due to an extended rostral scale, which is immediately followed by a raised wartlike hump covered 10 minute scales. Also, the hemipenes

Hemipenis

A hemipenis is one of a pair of intromittent organs of male squamates .Hemipenes are usually held inverted, within the body, and are everted for reproduction via erectile tissue, much like that in the human penis. Only one is used at a time, and some evidence indicates males alternate use between...

 have clearly visible spines. It is distinguished from H. nepa

Hypnale nepa

Hypnale nepa is a venomous pitviper species found in Sri Lanka. Relatively small, they are distinguished by a strongly upturned snout. No subspecies are currently recognized.-Description:...

 by its lower scale counts.

The scalation includes 17 rows of dorsal scales

Dorsal scales

In snakes, the dorsal scales are the longitudinal series of plates that encircle the body, but do not include the ventral scales.When counting dorsal scales, numbers are often given for three points along the body, for example 19:21:17...

 at midbody that that usually lack keels

Keeled scales

Keeled scales refer to reptile scales that, rather than being smooth, have a ridge down the center that may or may not extend to the tip of the scale, making them rough to the touch...

, 7 supralabial scales

Supralabial scales

In reptiles, the supralabial scales, also called upper-labials, are those scales that border the mouth opening along the upper jaw. They do not include the median scale . The term labial originates from Labium , which refers to any lip-like structure...

, 120-126 ventral scales

Ventral scales

In snakes, the ventral scales are the enlarged and transversely elongated scales that extend down the underside of the body from the neck to the anal scale. When counting them, the first is the anteriormost ventral scale that contacts the paraventral row of dorsal scales on either side...

 and 28-33 subcaudal scales

Subcaudal scales

In snakes, the subcaudal scales are the enlarged plates on the underside of the tail. These scales may be either single or divided and are preceded by the anal scale....

.

Regarding the color pattern, Gloyd and Conant (1990) examined a number of preserved specimens, mentioning that some were so faded as to render the pattern almost invisible. One of these, however, had a faint narrow stripe down the center of its back. In general, the color pattern is described as consisting of a series of 18-24 dorsolateral small subtriangular brown blotches, pointing upwards. These are slightly darker than the ground color, except for the upper edges that may be considerably darker. A pair of dark brown blotches are present on the side of the head, along with a pair of dark stripes carving backward on the sides of the neck. The ventral surface is strongly flecked and dappled with graying brown.

Geographic range

Found in Sri Lanka

Sri Lanka

Sri Lanka, officially the Democratic Socialist Republic of Sri Lanka is a country off the southern coast of the Indian subcontinent. Known until 1972 as Ceylon , Sri Lanka is an island surrounded by the Indian Ocean, the Gulf of Mannar and the Palk Strait, and lies in the vicinity of India and the...

. The type locality given is "Kanneliya Forest, Udugama Southern Province, Ceylon [Sri Lanka], elevation approximately 1,000 ft."

Taxonomy

According to Gloyd and Conant (1990), the taxonomic status of this species is unclear. Although described here as a species, it may eventually be classified as a subspecies of H. nepa

Hypnale nepa

Hypnale nepa is a venomous pitviper species found in Sri Lanka. Relatively small, they are distinguished by a strongly upturned snout. No subspecies are currently recognized.-Description:...

, or even as the minimum extreme for H. nepa with regard to its low ventral

Ventral scales

In snakes, the ventral scales are the enlarged and transversely elongated scales that extend down the underside of the body from the neck to the anal scale. When counting them, the first is the anteriormost ventral scale that contacts the paraventral row of dorsal scales on either side...

 and subcaudal

Subcaudal scales

In snakes, the subcaudal scales are the enlarged plates on the underside of the tail. These scales may be either single or divided and are preceded by the anal scale....

scale counts, as well as its relatively short tail.