Order Squamata
Superfamily Xenophidia (Colubroidea Caenophidia)
Family Elapidae (cobras, coral snakes, and
seasnakes etc.)
Elapids and seasnakes are closely related.
Although they have been considered as separate families, they are now
often combined within the family Elapidae.
Subfamily Elapinae
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Appearance and
morphology: Similar to colubrids. Fangs are
permanently erect on the anterior ends of largely immovable
maxillae and fit into grooved slots in the buccal floor when
the mouth is closed (termed the proteroglyphous condition;
McCarthy, 1985). Unlike the venomous colubrids, each fang
contains an enclosed passae extending the length of the
tooth from an opening at the base for entry of the venom to
an opening near the tip. Cranially, they have only a left
carotid artery, edentulous premaxillaries, longitudinally
oriented, shortened maxillaries, with anterior teeth that
are large and tubular, parietal-parasphenoid sutures. The
mandible lacks a coronoid bone, and the dentray bears teeth.
No cranial infrared receptors occur in pits or surface
indentations. Intracostal arteries arise from the dorsal
aorta at intervals of several trunk segments. The left lung
is greatly reduced or absent; a tracheal lung is commonly
present in the marine taxa and absent in terrestrial ones.
Left and right oviducts are well developed. Some species
with viperine appearance have vertical pupils (Acantophis,
"death adders"). Elapids and hydrophiids can be
distinguished by their choanal processes: elapids have them
(except for Dendroaspis), hydrophiids lack them.
Size: up to 6 m total
length (Ophiophagus hannah)
Distribution:
Worldwide in tropical and subtropical regions except for
Europe.
Habitat: Fossorial to
terrestrial (coral snakes), arboreal (mambas),
savanna-scrubs (taipans: Oxyuranus), semifossorial
(Aspidelaps, Calliophis, Micrurus) or surface
foragers (Bungarus, Naja).
Food: Small reptiles
(Coral snakes), birds and mammals (3 species of mambas),
fish (water cobras, Boulengerina), amphibians and
reptiles (Asian elapines).
Behavior:
Predominantly diurnal (coral snakes, notechines) or
nocturnal (African and Asian cobras, Acantophis).
Defensive display of hood in cobras.
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Naja kaouthia (Cobra), © W. Wüster
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All species are venomous!
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Reproduction: Oviparous (coral
snakes: 2-9 eggs; African elapines, Oxyuranus, Demansia), some
ovoviviparous (Hemachatus, Acantophis, Cryptophis, Drysdalia,
Glyphodon, Pseudechis, Tropidechis), few viviparous
(Denisonia). Notechis may carry up to 100 embryos
(usually 20-40).
Relationships: The hydrophiid
subfamilies Hydrophiinae and Laticaudinae might be included in the
family Elapidae, since they are closely related (Zug et al. 2001).
For practical reasons I put them in a separate list (Hydrophiidae).
Examples: Coral snakes
(Americas), cobras (Africa and Asia), mambas (Africa), kraits (Asia),
tiger snakes (Australia)
Subfamily Hydrophiinae (Sea
Snakes)
Appearance: Adapted to marine
life and swimming by having a tail fin and laterally compressed
bodies. Salt glands surrounding the tongue help maintain osmotic
balance in sea water. The palatine bones lack choanal
processes. Laticauda is the least adapted to sea life;
it retains the wide ventral scales typical of terrestrial snakes and
has only a poorly developed tail fin. Ventral scales are much reduced
in Hydrophis and allies. The nostrils of snakes in the
Hydrophis group are dorsally located and can be closed
with valves.
Size: Terrestrial taxa range
from 18 cm snout-vent length (Drysdalia,Ogmodon
vitiensis) to 2.2 m SVL (Oxyuranus).
Distribution: Indian Ocean,
southwest Pacific, Indian ocean. Pelamis also reaches
Central and South America.
Habitat:
Laticauda in shore marine areas and part-time on land
with good terrestrial locomotion. Other species mainly in coastal
marine and estuarine waters. Pelamis also enters the
open sea. Hydrophis semperi and Laticauda
crockeri are restricted to freshwater lakes in the Philippine
and Solomon Islands. They presumably entered the lakes when there was
a connection to the sea. A few surface foragers (e.g.
Tropidechis) occasionally climb low in shrubs or trees.
Notechis ater is semiaquatic, foraging in or near
water
Food: vertebrates, "true"
seasnakes eat mostly fish, often specializing on certain types of
fish.
Reproduction:
Laticauda lays 1-10 eggs on land.
Hydrophis is viviparous with litter sizes from 1 to 30
(but mostly fewer than 10).
Relationships: Many authors
include the Hydrophiidae in the Elapidae
(e.g. Zug 2001). Others elevate the genus Laticauda to a
distinct family, Laticaudidae. The classification
used here considers the Hydrophiidae as a family for practical
reasons. Rasmussen (1997) suggested to subdivide sea snakes into 3
groups: the Laticauda group
(including the genus Laticauda), the
Aipysurus group (including
Aipysurus and Emydocephalus), and the
Hydrophis group (including
all other sea snakes).
Diagnosis (after Kharin & Czeblukov 2006): Skull. Praemaxillare loosely attached to skull, allowing tip of snout to fold down against lower jaw. Maxillare extending forwards beyond the palatinum (subfamily Aipysurinae Kharin, 1984, subfamily Hydrophiinae F. Boie, 1827: genus Kerilia Gray, 1849 or subgenus Microcephalophis Lesson in Bélanger, 1834 of genus Hydrophis Latreille in Sonnini et Latreille, 1803) or not extending forwards the palatinum (other genera). Maxillare and ectopterygoideum meet broadly, forming joint or suture limited movement.
Palatinum can be depressed but can not rotate above horizontal. Mandibular ’s tooth-row (only dentale) extends posterior beyond suture between spleniale and an- gulare. Frontale suboval. Praefrontale in contact with nasale and in contact with postfrontale. Parietale long and narrow which medial crest. Caudal fins supported by elongate neural spines and elongate parapophyses (reinforced in some sea snakes by haemal spines or hypapophyses). Nostril dorsal, shift from lateral position produces changes in scull and nasal capsule. Posterior end of venom gland situated above corner of mouth. Narial vestibule has smooth lining, as in most snakes. Lingual valve formed from ventral edge of rostral scute. Salt secreted by posterior (median) sublingual gland, natrial gland is absent. Hemipenis with spines and papillae but lacking calyces. Ventals small, not more than one-quarter the breadth on the body (except species of Ephalophis M. Smith, 1931 and of Parahydrophis Burger et Natsuno, 1974 genera) or absent (species of Pelamis Daudin, 1804 and junior of Lapemis Gray, 1834 genera). Subcaudals small, unpaired or absent. Ovoviviparous.
Subfamily Laticaudinae
Diagnosis (after Kharin & Czeblukov 2006): Skull. Praemaxillare rigidly attached to skull. Maxillare extending forwards beyond the palatinum. Maxillare and ectopterygoideum meet in end-to-end joint that moves in all planes. Palatinum can rotate above horizontal. Mandibular ’s tooth-row (only dentale) ends anterior to suture between spleniale and angulare. Frontale subquadrangular in outline. Praefrontale not in contact with nasal. Parietale short, broad and flat. Caudal fins of oar-like tail formed by cutaneous folds without bony supports, dorsal and ventral processes of caudal vertebrae are not elongate. Nostril lateral, in normal position for terrestrial snakes. Posterior end of venom gland bent downward behind corner of mouth. Natrial vestibule has either rugae or papillae, acting as valves. Lingual valve formed from oral epithelium posterior to rostral scute. Hemipenis with cup-shaped calyces. Ventrals large, one-third to more than one-half the breadth of the body. Subcaudals large, paired. Oviparous.
List of Genera ("T" denotes inclusion in phylogenetic tree below):
Subfamily Elapinae
Calliophini CASTOE et al. 2006
Hemibungarini CASTOE et al. 2006
Subfamily Hydrophiinae (following Zug et al. 2001)
"T"
indicates genera that are included in tree below):
Kharin (2004) proposed to revive the genus
Polyodontognathus for Hydrophis
caerulescens. Kharin & Czeblukov (2006) also suggested to revive the family Laticaudidae with the genera Laticauda and Pseudolaticauda. We include it here as Laticaudinae.
Subfamily Laticaudinae
Click
on genus to get a list of species. Use
the Search form for more sophisticated searches (HELP on Search).
Phylogeny of elapids
Consensus of phylogenetic results obtained from analyses of the
individual cytochrome b and 16S rRNA data sets and the combined data
set illustrating only strongly supported nodes (after Keogh
1998).
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Conservative summary of phylogenetic relationships
obtained from the combined analyses of the cytochrome b and
16S rRNA data for (A) the oviparous hydrophiines plus
Notechis ater and (B) the viviparous hydrophiines (after
Keogh et al. 1998)
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References:
CASTOE, Todd A.; ERIC N. SMITH, RAFE M. BROWN and CHRISTOPHER L. PARKINSON (2007)
Higher-level phylogeny of Asian and American coralsnakes, their placement within the Elapidae (Squamata), and the systematic affinities of the enigmatic Asian coralsnake Hemibungarus calligaster (Wiegmann, 1834).
Zoological Journal of the Linnean Society 151, 809–831
Harding,K.A. & Welch,K.R.G. (1980)
Venomous Snakes of the World - A Checklist
Pergamon Press, (Oxford)
ISBN 0-08-025495-0
Also published as Supplement to the journal Toxicon 1 (1980)
Golay P. 1985
Checklist and Keys to the Terrestrial Proteroglyphs of the
World.
Geneva: Elapsoidea.
Golay P, Smith HM, Broadley DG, Dixon JR, McCarthy C, Rage JC,
Schatti B, Toriba M. 1993
Endoglyphs and other major venomous snakes of the world. A
checklist.
S. A. Switzerland: Azemiops.
Hutchinson MN. 1990
The generic classification of the Australian terrestrial elapid
snakes.
Memoirs of the Queensland Museum 28: 397&endash;405.
Keogh JS, Smith SA. 1996
Taxonomy and natural history of the Australian bandy-bandy snakes
(Elapidae: Vermicella) with the description of two new
species.
Journal of Zoology (London) 240: 677&endash;701.
Keogh,J.S. 1998
Molecular phylogeny of elapid snakes and a consideration of their
biogeographic history.
Biological Journal of the Linnean Society 63: 177&endash;203
Keogh, J. Scott; Richard Shine and Steve Donnellan 1998
Phylogenetic Relationships of Terrestrial Australo-Papuan Elapid
Snakes (Subfamily Hydrophiinae) Based on Cytochrome b and 16S rRNA
Sequences.
Mol. Phylogenet. Evol. 10 (1): 67&endash;81
Kharin-V-E (1984)
A review of sea snakes of the group Hydrophis sensu lato
(Serpentes, Hydrophiidae). 3. The genus Leioselasma [in
Russian].
ZOOLOGICHESKII ZHURNAL 63 (10): 1535-1546
Kharin-V-E 1984
Revision of sea snakes of subfamily Laticaudinae Cope, 1879 sensu
lato (Serpentes, Hydrophiidae).
TRUDY ZOOLOGICHESKOGO INSTITUTA 124: 128-139
Kharin, V.E. 2004
On the taxonomic status of the sea snake Hydrophis caerulescens (Shaw, 1802) (Serpentes: Hydrophiidae). [Polyodontognathus]
Biologiya Morya (Vladivostok) 30 (3): 227-229
Kharin, V. E. (2005)
A check-list of sea snakes (Serpentes: Laticaudidae, Hydrophiidae) of the World Ocean [in Russian].
Izv. TINRO 140: 71-89
Kharin, Vladimir E. and Vladimir P. Czeblukov (2006)
A New Revision of Sea Kraits of Family Laticaudidae Cope, 1879 (Serpentes: Colubroidea).
Russian Journal of Herpetology 13 (3): 227-241
Knight A, Mindell DP. 1994
On the phylogenetic relationships of Colubrinae, Elapidae, and
Viperidae and the evolution of front-fanged venom systems in
snakes.
Copeia 1994: 1&endash;9.
Keogh,J.S. 1998
Molecular phylogeny of elapid snakes and a consideration of their
biogeographic history.
Biological Journal of the Linnean Society 63: 177&endash;203
McCarthy CJ. 1985
Monophyly of the elapid snakes (Serpentes: Reptilia). An
assessment of the evidence.
Zoological Journal of the Linnean Society 83: 79&endash;93.
McCarthy CJ. 1986
Relationships of the laticaudine sea snakes (Serpentes: Elapidae:
Laticaudinae).
Bulletin of the British Museum of Natural History (Zoology) 50:
127&endash;161.
McDowell, S. B. (1969)
Notes on the Australian sea-snake Ephalophis greyi M. Smith
(Serpentes: Elapidae: Hydrophiinae) and the origin and classification
of sea-snakes.
J Linn. Soc. Zool. 48: 333-349
McDowell, S. B. (1972)
The genera of sea-snakes of the Hydrophis group (Serpentes:
Elapidae).
Trans. Zoo]. Soc. Lond 32: 189-247
Rasmussen,A.R. (1997)
Systematics of sea snakes: a critical review
In: Thorpe,R.S., Wüster,W. & Malhotra,A. (eds.)
Venomous snakes - ecology, evolution and snakebite,
Clarendon Press (Oxford)/Symp. zool. Soc. Lond. 70: 15-30
Slowinski, Joseph B.; Boundy, Jeff & Lawson,R. 2001
The phylogenetic relationships of Asian coral snakes (Elapidae:
Calliophis and Maticora) based on morphological and molecular
characters.
Herpetologica 57 (2): 233-245
Slowinski JB. 1989
The interrelationships of Laticaudine sea snakes based on the
amino acid sequences of short-chain neurotoxins.
Copeia 1989: 783&endash;788.
Slowinski JB. 1994
A phylogenetic analysis of Bungarus (Elapidae) based on
morphological characters.
Journal of Herpetology 28: 440&endash;446.
Slowinski JB. 1995
A phylogenetic analysis of the New World coral snakes (Elapidae:
Leptomicrurus, Micruroides, and Micrurus) based on allozyme and
morphological characters.
Journal of Herpetology 29: 325&endash;338.
Slowinski JB, Knight A, Rooney AP. 1997
Inferring species trees from gene trees: A phylogenetic analysis
of the Elapidae (Serpentes) based on the amino acid sequences of
venom proteins.
Molecular Phylogenetics and Evolution 8: 349&endash;362.
Spawls, S. & W. Branch (1995)
The Dangerous Snakes of Africa
Blandford, London
Zug,G.R.; Vitt, L.J. & Caldwell, J.P. (2001)
Herpetology,
2nd ed.
Academic Press San Diego, London, [...]XIV + 630 pp.
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Created: 21 Jan 1996 / Last changed or updated: 1 Jan 2008