Designed by Paul Smith 2006. This website is copyrighted by law.
Material contained herewith may not be used without the prior written permission of FAUNA Paraguay.
Photographs on this web-site were taken by Paul Smith, Hemme Batjes, Regis Nossent,
Alberto Esquivel, Arne Lesterhuis, José Luis Cartes, Rebecca Zarza and Hugo del Castillo and are used with their permission.
SUBORDER SERPENTES - SNAKES
No groups of reptiles inspires such diverse emotions of fear, admiration, disgust and respect as the Suborder Serpentes - the Snakes. A distinctive group of legless reptiles, they are also highly successful and occur on all global continents except Antarctica. The Paraguayan snakes are classified into two Infraorders (Scolecophidia and Alethinophidia) which are made up of seven distinct families. Snakes dominate the Paraguayan reptile fauna, with almost two-thirds of the species recorded in the country belonging to this suborder.
Snakes have an extremely elongate body with more than 120 presacral vertebrae. Vertebrae are procoelous. They lack temporal arches and there is usually no postorbital bar. The quadrate is movable but attached to the cranium. The lachrymal, squamosal and epipterygoid bones are all absent. Maxillae, palatines and pterygoids are all movable. Mandibles are united at the symphysis with ligaments. Anterior portion of the brain case is completely ossified. The parietal foramen and interorbital septum are absent. Eyes lack sclerotic ossicles. The eyelids are fused closed, forming a transparent brille in most. The eyes lack foveae and retinal cells lack oil droplets. Unique duplex cones are present on the retina in addition to rods. The ophthalmic division of the trigeminal nerve is largely intercranial. Exoccipitals meet dorsally to the foramen magnum. Jacobson´s Organ is highly-developed, enclosed in a capsule between the septomaxilla and vomer. Growth is indeterminate due to loss of epiphyses. Hind limbs and pelvic girdle are reduced, and in most cases absent. Tail is not autotomous.
INFRAORDER SCOLECOPHIDIA - BLIND SNAKES
Three Paraguayan families represent this order - the Anomalepididae, Leptotyphlopidae and Typhlopidae. These species are small, slender and cylindrical with a worm-like body. Ventral and dorsal scales are similar and shiny, with little difference in size. Scolecophidians have paired carotid arteries and intercostal arteries in almost every body segment. There is an optic foramen in the frontal bone and a coronoid bone in the lower jaw. No neural spines are present on the vertebrae, and hypapophyses are reduce don absent on both the anterior and posterior vertebrae. Vestigial pelvic elements are present internally but there are no external limbs. Liver is multi-lobed and an enlarged rectal caecum is present. Only the right oviduct is present in the female and there is no vestige of the left. Eye has a simple retina with only cones present, generally the external eye is reduced and covered with a head scale. The tail is short, terminating in a spine.
INFRAORDER ALETHINOPHIDIA - TRUE SNAKES
The remaining four families of snakes in Paraguay - the Boidae, Colubridae, Elapidae and Viperidae - all belong to the Microrder Macrostomata, where they are separated into two Gigafamilies Booidea (including only the Boidae) and Caenophidia (for the other families). Members of this infraorder have duplex retinas with rods and duplex cones. The brille (spectacle) is present, but the eyes are not covered with scales. Neural spines are well-developed on the vertebrae. Females have paired oviducts.
REFERENCES
Fouquette MJ (unpublished) - Synopsis of Recent Reptiles to Genus - Arizona University
Whitfield P Ed.1984 - Longman Illustrated Animal Encyclopedia - Guild Publishing, London.
