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.
CLASS REPTILIA - REPTILES
Our perception of what makes a reptile has changed considerably in recent years as a result of molecular and genetic studies which show that Reptilia is actually a paraphyletic or polyphyletic grade, unless birds and mammals are incorporated. Amongst the most significant developments is the suggestion that crocodiles are in fact more closely related to birds than other "reptiles", with both being classified in the Infraclass Archosauria, whilst the value of the traditional separation of the reptiles into the Subclasses Anapsida and Diapsida (see below) on the basis of skull morphology has now been seriously questioned. Obviously the repercussions of such wide-ranging taxonomic re-hauling are great, and for the time being most taxonomists choose to "stick with" the traditional arrangements of birds and reptiles remaining in separate classes for convenience whilst further evidence of the true phylogenetic relationships in these groups is gathered. Reptile taxonomy is for this reason in a state of flux and is likely to change drastically in coming years. Here retaining the "traditional" arrangement we give the characteristics that define reptiles as they are popularly understood.
Reptiles are tetrapods (though limbs are secondarily lost in some groups) with the digits ending in claws. The skull has a single occipital condyle and small supratemporal, whilst the parietal and squamosal are in broad contact externally. The tabular may be reduced or absent and where present it is not in contact with the opisthotic. Teeth are non-pediciellate, but their exact form varies between taxa. The first two cervical vertebrae are modified into an atlas and axis. Typically there are two sacral vertebrae and ribs are present on the presacral vertebrae. A sternum is present in most groups and articulates with some ribs (except in turtles and snakes). The heart has two atria and a divided ventricle (or in some cases two ventricles). The skin is non-glandular with epidermal scales, some with dermal plates underlying the skin. Fertilisation is internal with amniote eggs. Eggs are shelled and oviposited on land, though some species are viviparous and give birth to live young.
SUBCLASS ANAPSIDA (turtles, tortoises and terrapins)
Anapsida means "without arch". Anapsids lack a temporal fossa and the temporal region is completely roofed or emarginated. The jugal has an alar process and the ectopterygoid is absent. Humerus lacks a supinator process. Limbs short and robust, present in all species.
SUBCLASS DIAPSIDA (snakes, lizards and crocodiles)
Diapsida means "double arch". Diapsids have an upper temporal fossa in all and a lower temporal fossa in some. A sub-orbital opening is present and the post-orbital region is short. The enlarged premaxillary forms the majority of the snout tip. Lack tabular and parasphenoid teeth. The parietal foramen is small or absent and the quadratojugal is L-shaped. Anterior pleurocentra keeled and prominent transverse processes on the trunk vertebrae. Limbs are long and slender, though they have been secondarily lost by some. Metapodials overlap proximally.
REFERENCES
Fouquette MJ (unpublished) - Synopsis of Recent Reptiles to Genus - Arizona University
Whitfield P Ed.1984 - Longman Illustrated Animal Encyclopedia - Guild Publishing, London.
