Thinking about herpetological field
work in Thailand brings back a lot of memories. One of the most vivid is arriving
at small village on the Gulf of Thailand side of the peninsula and being
greeted by two local men with burlap bags filled with snakes, they had more than 50 snakes in the genus Cerberus.
When we asked them how they collected them, they explained they gathered them
from the mud flat by scooting around on a board and picking them up. We then inquired how long it took to collect the snakes, and they replied, “about half an hour.”
The evidence now suggests that
snakes in the genus Cerberus may be
the most abundant aquatic snakes on the planet. They have an unusual coastal
distribution that extends from the vicinity of Mumbai, India to Paula,
Micronesia a distance equal to about 20% of the Earth’s circumference.
The scientific community first
became aware of the snakes now placed in the genus Cerberus through a
drawing by Patrick Russell in his 1796, two volume, An Account of Indian
Serpents, collected on the Coast of Coromandel. Russell applied the local
Telugu name to the snake, the bockadam. Cerberus has a long and
debris-filled nomenclatural history. This is highlighted by the fact that 16
species of Cerberus have been described since 1799, with at least 44
combinations of names applied to species within the genus. Gyi’s (1970) review
of the homalopsids recognized three species, one of which had two subspecies.
Cogger et al. (1983) placed Homalopsis australis Gray in the
synonymy of Hydrus rynchops Schneider and reduced the number of
recognized species to two.
Alfaro et al. (2004) analyzed 2338 mtDNA bp
from 21 localities and recovered five clades of Cerberus: a South Asia
clade (India and Myanmar), a Greater Sunda Island-Sulawesi clade, a Thai-Malay
Peninsula, Gulf of Thailand clade, a Philippine clade that included C.
microlepis, and an Australopapuan clade, that is quite divergent (0.06 – 0.12)
from the Asian clades (the Asian clades are 0.02–0.06 divergent from each
other).
In an examination of 22 homalopsid
species using three mitochondrial and one nuclear genes, Alfaro et al.
(2008) recovered Cerberus as monophyletic. Using Markov Chain Constant
Rates (MCCR) to test the times of divergence Cerberus appears to have separated
from its sister the puff-faced water snakes of the genus Homalopsis about
14 MYA, while the Asian Cerberus clade diverged from the Australopapuan clade
about 3 MYA.
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Top to bottom: C. australis, C. dunsoni, C. microlepis, C. rynchops (photo by A. Lobo),
C. schneiderii.
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Murphy, Voris, and Karns (2012) have
now reviewed the nomenclature of the genus and define species based upon
morphology and previously published molecular evidence. Three species
have been recognized by recent workers, this paper recognizes five species: a
South Asian C. rynchops (Schneider 1799); the Southeast Asian-Philippine C.
schneiderii (Schlegel 1837); the freshwater Philippine endemic C.
microlepis Boulenger 1896; the Australopapuan C. australis (Gray
1842); and C. dunsoni a new species
from Micronesia. They also select a lectotype for Homalopsis schneiderii Schlegel
based upon a figure published in 1837 and restrict the type locality for this species
to Timor. They also discuss the evidence for a population of Cerberus
australis in Indonesia, west of Weber’s Line.
Citation
Murphy, JC, Voris, HK, Karns, DR. 2012. The dog-faced water snakes, a revision of the genus Cerberus Cuvier,(Squamata, Serpentes, Homalopsidae), with the description of a new species. Zootaxa 3484: 1–34.