- Common names: moccasins, copperheads, cantils.
is a genus
of venomous pitvipers
found in North America
from the United States
south to northern Costa Rica
. The name is derived from the Greek
, meaning "hook" and odon
, which means "tooth", and is likely a reference to the fangs. Three species are currently recognized, all of them polytypic
and closely related.
Members of this genus have a number of features in common. All species have a relatively broad head with short fangs. A loreal scale
is present, except in A. piscivorus
. There are usually nine large symmetrical platelike scales on the crown of the head, but in all species these are often irregularly fragmented or have sutures, especially in A. bilineatus
. All have a sharply defined canthus rostralis
and a vertically elliptical pupil. There are 6-10 (usually 8) supralabial scales
and 8-13 (usually 10-11) sublabials
. The dorsal scales
are mostly keeled and at midbody number 21-25 (usually 23), while A. piscivorus
has 23-27 (usually 25). There are 127-157 ventral scales
and 36-71 subcaudals
. Of the latter, some may be divided. The anal scale
is single. All have a color pattern of 10-20 dark crossbands on a lighter ground color, although sometimes the crossbands are staggered as half bands on either side of the body.
The phylogeny of the three species has long been controversial. Studies based on morphological (Gloyd & Conant, 1990) and venom characteristics (Jones, 1976) support the idea that A. bilineatus and A. contortrix are more closely related. However, an analysis of mitochondrial DNA was conducted by Knight et al. (1992), as well as more recent molecular studies (Parkinson et al., 1997, 1999) have concluded that A. bilineatus and A. piscivorus are sister taxa, with A. contortrix being a sister species to them both.
Found in North America
from the northeastern and central USA
southward through peninsular Florida
and southwestern Texas
. In Central America
on the Atlantic versant from Tamaulipas
and Nuevo León
southward to the Yucatan Peninsula
. Along the Pacific coastal plane and lower foothills from Sonora
south through Guatemala, El Salvador
to northwestern Costa Rica
All are semiaquatic to terrestrial and are often found near sources of water. However, A. contortrix
and A. bilineatus
are also found in dry habitats, often far from permanent streams or ponds.
The members of this genus are all ovoviviparous
It is assumed that the venom of all three species is not unlike that of A. contortrix
, which contains thrombinlike enzymes that act upon the coagulant activity of the blood. A study of electrophoretic
patterns of proteins in venoms among and within populations of A. contortrix
and A. piscivorus
showed that substantial variation exists (Jones, 1976), and there is no reason to believe that these differences do not correspond with variations in toxicity.
*) Not including the nominate subspecies.
||Mexico and Central America. On the Atlantic side it is found in Mexico in Tamaulipas, Nuevo León, possibly northern Veracruz and Chiapas (in the Middle Grijalva Valley). On the Yucatan Peninsula it occurs in Campeche, Yucatán, Quintana Roo and northern Belize. On the Pacific side it is found from southern Sonora in Mexico south through Guatemala, El Salvador, Honduras and Nicaragua to southwestern Costa Rica. On the Pacific side the distribution is almost continuous, while on the Atlantic side it is disjunct.
||The United States (Texas, Oklahoma, Kansas, Missouri, Arkansas, Louisiana, Mississippi, Alabama, Georgia, Florida, South Carolina, North Carolina, Tennessee, Kentucky, Virginia, West Virginia, Illinois, Indiana, Ohio, Iowa, Pennsylvania, Maryland, New Jersey, Delaware, New York, Connecticut, Massachusetts), Mexico (Chihuahua, Coahuila). |
||The eastern United States from extreme southeastern Virginia, south through peninsular Florida and west to Arkansas, southeastern Kansas, eastern and southern Oklahoma and eastern and central Texas. A few records exist from along the Rio Grande River in Texas, but these are thought to represent isolated populations that possibly no longer exist. |
'') Type species
This genus was previously much larger and also included the following genera:
- Daudin FM. 1801-1803. Histoire naturelle, générale et particulière des reptiles: ouvrage faisant suit à l'histoire naturelle générale et particulière, composée par Leclerc de Buffon; et rédigée par C.S. Sonnini, miembre de plusieurs sociétés savantes. 8 vols. F. Dufart, Paris (for a discussion of the publication date, see F. Harper, 1940, Amer. Midl. Nat. 23: 693).
- Fischer JG. 1813. Zoognosia tabulis synopticus illustrata, in usum praelectionum Academiae Imperialis medico-chirurgicae Mosquensis edita. 3d ed. vol. 1, pt. 3 (Reptiles, Poissons): 57-117. Nicolai Sergeidis Vsevolozsky, Moscow.
- Fitzinger LJ. 1826. Neue Classification der Reptilien nach ihren natürlichen Verwandtschaften: nebst einer Verwandtschafts-Tafel und einem Verzeichnisse der Reptilien-Sammlung des K. K. Zoologischen Museums zu Wien. J.G. Heubner, Vienna. 66 pp.
- Jones JM. 1976. Variation of venom proteins in Agkistrodon snakes from North America. Copeia 1976(3): 558-562.
- Knight A, Densmore III LD, Real ED. 1992. Molecular systematics of the Agkistrodon complex, p. 49-70 In Campbell JA, Brodie Jr. ED. 1992. Biology of the Pitvipers. Texas: Selva. 467 pp. 17 plates. ISBN 0-9630537-0-1.
- Link HF. 1807. Beschreibung der naturalien-sammlung der Universität zu Rostock. Zweite abtheilung, pp. 51-100. Gebruckt bei Adlers Erben, Rostock.
- Palisot de Beauvois AMFJ. 1799. Memoir on Amphibia. Serpentes. Transactions of the American Philosophical Society 4: 362-381.
- Parkinson CL. 1999. Molecular systematics and biogeographical history of pitvipers as determined by mitochondrial ribosomal DNA sequences. Copeia 1999(3): 576-586.
- Parkinson CL, Moody SM, Ahlquist JE. 1997. Phylogenetic relationships of the "Agkistrodon complex" based on mitochondrial DNS data. P. 63-78 In Thorpe RS, Wüster W, Malhotra A. 1997. Venomous snakes: ecology, evolution and snakebite. Clarendon Press, Oxford.
- Sonnini CS, Latreille PA. 1801. Histoire naturelle des reptiles, avec figures dissinees dápres nature. 4 Vols. Paris (for a discussion of the publication date, see F. Harper, 1940, Amer. Midl. Nat. 23: 692-723).
- Troost G. 1836. On a new genus of serpents, and two new species of the genus Heterodon, inhabiting Tennessee. Ann. Lyc. Nat. Hist., New York, 3: 174-190.
- Wagler JG. 1830. Natürliches System der Amphibien, mit vorangehender Classification der Säugthiere und Vögel. Ein Beitrag zur vergleichenden Zoologie. J.G. Cotta, München. 354 pp.