Hook-nosed lance vipers

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Hook-nosed lance vipers
Porthidium nasutum

Porthidium nasutum

Systematics
without rank: Toxicofera
Subordination : Snakes (serpentes)
Superfamily : Adder-like and viper-like (Colubroidea)
Family : Vipers (Viperidae)
Subfamily : Pit vipers (Crotalinae)
Genre : Hook-nosed lance vipers
Scientific name
Porthidium
Cope , 1871

The hook-nosed lance vipers or inverted lance vipers ( Porthidium ) are a genus of snakes from the subfamily of pit vipers . The genus occurs with nine species in Central America and northern South America. All species are forest inhabitants, most of them inhabit areas with a pronounced dry season, but some species the tropical rainforest . Hook-nosed lance vipers are poisonous, but most species are said to be toxic to humans. For one species ( P. nasutum ) there are contradicting data and reports of deaths. The German name refers to the elongated tip of the snout of most species.

features

anatomy

Hook-nosed lance snakes are small to medium-sized, relatively slender to relatively powerful snakes. The head is large, broad and clearly set off from the neck. The snout is pointed and the canthus is sharp. Depending on the species, the tip of the snout is barely, moderately or strongly elongated. The tail is not suitable for grasping. The species have total lengths of 55 to over 75 cm.

Scaling

The rostral is usually higher than it is wide. The top of the head is covered with small, mostly keeled scales. There are 2–8 intersupraoculars . The number of supralabials is 8 to 11, the number of infralabials 8 to 14. The number of ventral scales ( ventral shields ) varies between 123 and 174, the number of mostly undivided subcaudalia between 23 and 44 and the number of dorsal rows of scales in the middle of the body between 21 and 27.

coloring

The basic color of the top is usually brown or gray, but can also be reddish brown or yellowish brown. On the back, the animals show two rows of alternating or opposite, large, more or less angular, dark spots that are separated by a narrow, light strip in the middle of the back. On the flanks there are one or more rows of smaller and diffuse spots below. The sides of the head are mostly unmarked, but some species show a dark postocular stripe that extends from the back of the eye to behind the corner of the snout.

distribution and habitat

Hook-nosed lance vipers are common in Central America and northern South America. The distribution area extends from southeast Mexico to the south to the mid-west of Ecuador . The areas of six of the nine species are each very small. Hook-nosed lanceolers are forest inhabitants, most of them inhabit areas with a pronounced dry season, but some species the tropical rainforest . Most species occur predominantly at altitudes below 1000 m.

Porthidium dunni

Systematics

The number of species and subspecies has been controversial for a long time, Campbell & Lamar only recognize 9 species:

A molecular genetic investigation including 7 of the 9 species has confirmed the monophyly of the genus Porthidium to this extent for the time being, but the species P. nasutum has turned out to be paraphyletic .

Lifestyle, Diet and Reproduction

Almost all species of the genus are predominantly nocturnal, more rarely diurnal and exclusively living on the ground. The food spectrum includes small vertebrates and invertebrates . The main food is apparently lizards , amphibians and small mammals and rarely birds are captured less frequently . Small mammals are mainly eaten by large individuals. All species are viviparous, young animals are mostly born in the rainy season. Between 3 and 36 young per litter are proven.

Poison

Hook-nosed lance vipers, like all pit vipers, are poisonous, the poisonous effect on humans is described as weak for most species. There are contradicting data for one species ( P. nasutum ), some authors describe the effects of a bite as minor, while other authors describe severe pain and necrosis up to death after a bite .

swell

Individual evidence

  1. ↑ Todd A. Castoe, Mahmood M. Sasa, Christopher L. Parkinson: Modeling nucleotide evolution at the mesoscale: The phylogeny of the Neotropical pitvipers of the Porthidium group (Viperidae: Crotalinae). Molecular Phylogenetics and Evolution, Volume 37, Issue 5, 2005: pp. 881-898
  2. ^ Jonathan A. Campbell, William W. Lamar: The Venomous Reptiles of the Western Hemisphere. Comstock; Ithaca, London; 2004: p. 470

literature

  • David A. Warrell: Snakebites in Central and South America: Epidemiology, Clinical Features, and Clinical Management . In: Jonathan A. Campbell, William W. Lamar: The Venomous Reptiles of the Western Hemisphere. Comstock; Ithaca, London. 2004. ISBN 0-8014-4141-2 : pp. 709-761.
  • Jonathan A. Campbell, William W. Lamar: The Venomous Reptiles of the Western Hemisphere. Comstock; Ithaca, London; 2004 ISBN 0-8014-4141-2

Web links

Commons : Hook-nosed Lance-Vipers ( Porthidium )  - Collection of images, videos and audio files