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Reptile
The reptiles are a group of vertebrate animals. All reptiles are tetrapods, they are all amniotes (animals whose embryos are surrounded by an amniotic membrane). Today they are represented with four orders:
Reptiles are found on all continents except for Antarctica, although their main distribution comprises the tropics and subtropics. Reptiles don't have a constant body temperature. They are only able to a limited extent to actively regulate their body temperature, which is largely dependent on the environmental temperature. Most reptile species are carnivorous and oviparous (egg-laying). Some species are ovoviviparous, and a few species are truly viviparous.
However, note the below described taxonomy issues; mammals and birds are all descendants of reptiles.
Classification of reptiles
Reptiles classically included all the amniotes except birds and mammals. Thus reptiles were defined as the set of animals that includes crocodiles, alligators, tuataras, lizards, snakes, and turtles, grouped together as the class Reptilia. This is still the usual definition of the term.
However, in recent years many taxonomists have begun to insist that taxa should be monophyletic, that is, groups should include all descendants of a particular form. The reptiles as defined above would be paraphyletic, since they exclude both birds and mammals, although these also developed from the original reptile. Colin Tudge writes:
- Mammals are a clade, and therefore the cladists are happy to acknowledge the traditional taxon Mammalia; and birds, too, are a clade, universally ascribed to the formal taxon Aves. Mammalia and Aves are, in fact, subclades within the grand clade of the Amniota. But the traditional class reptila is not a clade. It is just a section of the clade Amniota: the section that is left after the Mammalia and Aves have been hived off. It cannot be defined by synamorphies, as is the proper way. It is instead defined by a combination of the features it has and the features it lacks: reptiles are the amniotes that lack fur or feathers. At best, the cladists suggest, we could say that the traditional Reptila are 'non-avian, non-mammalian amniotes'. (Tudge, p.85)
Some cladists thus redefine Reptilia as a monophyletic group, including both the classic reptiles as well as the birds and perhaps the mammals (depending on ideas about their relationships). Others abandon it as a formal taxon altogether, dividing it into several different classes. However, other biologists believe that the common characters of the standard four orders are more important than the exact relationships, or feel that redefining the Reptilia to include birds and mammals would be a confusing break with tradition. A number of biologists have adopted a compromise system, marking paraphyletic groups with an asterisk, e.g. class Reptilia*. Colin Tudge notes other uses of this compromise system:
- By the same token, the traditional clas Amphibia becomes Amphibia*, because some ancient amphibian or other gave rise to all the amniotes; and the phylum Crustecea becomes Crustacea*, because it may have given rise to the insects and myriapods (centipedes and millipedes.) if we believe, as some (but not all) zoologists do, that myripaods gave rise to insects, then they should be called Myriapoda*....by this convention Reptilla without an asterisk is synonmous with Amniota, and incliudes birds and mammals, where as Reptila* means non-avian, non-mammalian amniotes. (Tudge, p.85)
Evolution of the reptiles
Several thousand fossil species showing a clear smooth transition from the ancestors of reptiles to present-day reptiles exist.
The first true "reptile" or Amnitoes are categoized as Anapsids, having a solid skull with holes only for nose, eyes, spinal cord, etc. Turtles are believed by some to be surviving Anapsids, as they also share this skull structure, but this point has become contentious lately, with some arguing that turtles reverted to this primitive state in order to improve their armor. Both sides have strong evidence, and the conflict has yet to be resolved.
Shortly after the first reptiles, two branches split off. One group, the synapsida, had a pair of holes in their skull behind the eyes, which was used to both lighten the skull and to increase the space for jaw muscles. The other group, Diapsida, possesed the same holes, along with a second pair located higher on the skull. The Synapsida eventually evolved into mammals, while Diapsida split yet again into two lineages, the lepidosaurs (which contian modern snakes, lizards and tuataras, as well as (debatably) the extinct sea reptiles of the mesozoic) and the archosaurs (modernly represented by only crocodiles and birds, but containing pterosaurs and dinosaurs).
See also
External links
references
The Variety of Life Colin Tudge, Oxford University Press, 2000
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The Herpetological Conservation Trust
A UK registered charity dedicated to the conservation of Reptiles & Amphibians.
http://www.hcontrst.f9.co.uk/
Partners in Amphibian and Reptile Conservation
Working to conserve amphibians and reptiles by promoting research, sound habitat management, and educating the public.
http://www.parcplace.org/
Guyana Marine Turtle Conservation Society
Information on marine turtles and the societies objectives and current projects.
http://www.gmtcs.org.gy
California Tiger Salamander Conservation
Understanding how populations are affected by urbanization is an important issue in amphibian conservation planning. Ambystoma californiense have been studied by the Center for Conservation Biology at Stanford University since 1993 in order to assess threats to the population in a highly modified landscape.
http://www.stanford.edu/group/CCB/Biodiv/CTS.html
Crocodile Specialist Group
Dedicated to conserving alligators, caimans, crocodiles and gharials and returning them to former abundance. The site contains CSG programs, newsletters, an action plan for crocodilian conservation, and a Photo Gallery.
http://www.flmnh.ufl.edu/natsci/herpetology/crocs.htm
Sea Turtle Research Unit (SEATRU)
Information on research and conservation and educational activities.
http://www.kustem.edu.my/seatru/
BBC News | Vanishing reptiles prompt concern
Scientists say there is evidence that reptiles are undergoing a decline even more marked than that now affecting amphibians.
http://news.bbc.co.uk/1/hi/sci/tech/871395.stm
Tomistoma Task Force
A nonprofit wildlife conservation initiative for endangered crocodilian Tomistoma schlegelii (False Gharial).
http://www.tomistoma.org/
Vernal Pool Ecosystems
Proceedings from a 1996 Conference on the ecology, conservation, and management of vernal pools. The vernal pools of California's Central Valley support four species of native amphibians.
http://www.cnps.org/vernalpools/contents.htm
Amphibians and Reptiles in the UK
Contains information on reptile and amphibian species native to the UK, and practical tips on how to help conserve them.
http://www.threadnaught.net/~caleb/ukherp.html
Declining Amphibian Populations Task Force
Based at the Open University Ecology and Conservation Research Group and operate under the umbrella of the IUCN Species Survival Commission. The mission of the DAPTF is to determine the nature, extent and causes of declines of amphibians throughout the world, and to promote means by which declines can be halted or reversed.
http://www.open.ac.uk/daptf/
The Horned Lizard Conservation Society
A non-profit organization dedicated to the appreciation, study and conservation of the various species of Horned Lizards.
http://webpages.marshall.edu/~moorej/toads/HLCS_home.html
North American Amphibian Monitoring Program
Part of a global effort to study and conserve amphibians.
http://www.im.nbs.gov/amphibs.html
Triturus
Information on the growth, habitats and conservation of newts of the genus Triturus.
http://www.darkwave.org.uk/~caleb/triturus.html
The Action Plan for Australian Reptiles
Action plans for individual species and information on recovery programmes.
http://www.ea.gov.au/biodiversity/threatened/action/reptiles/index.html
AmphibiaWeb
Allows free access to information on amphibian biology and conservation.
http://elib.cs.berkeley.edu/aw/
The Antiguan Racer Conservation Project
Give information about the racer snake, Alsophis antiguae, its location and the work being undertaken to protect it.
http://www.antiguanracer.org/html/home.htm
Gopher Tortoise Council
Group that works toward the conservation and education about the gopher tortoise (Gopherus polyphemus). General information about the tortoise, conservation and education efforts, and publications are available.
http://www.gophertortoisecouncil.org/
West Indian Iguana Specialist Group
This group works to study and conserve West Indian iguanas (Cyclura and Iguana), which are among the most endangered lizards in the world, and their habitats. It includes data on each species' habitat, current status, estimated population size, threats, conservation activities, and reports.
http://www.scz.org/iguana/
Proyecto CoquÃ
Information on the herpetofauna of Puerto Rico, and the research, education and conservation efforts of Eleutherodactylus spp. in particular. In English and Spanish.
http://www.cnnet.clu.edu/procoqui/
Turtle Conservation Unit
General information about this unit, which is responsible for research on turtle conservation in Malaysia.
http://www.seafdec.org/mfrdmd/mfrdmd002.html
Amphibians of Canada
Amphibians of Canada are examined in the light of conservation, life history, and habitats.
http://collections.ic.gc.ca/amphibians/index.html
Amphibians and Reptiles in Great Lakes Wetlands.
An overview of the threats and conservation of amphibians and reptiles in the Great Lakes Wetlands. It also has information on the value and threats of wetlands in general.
http://www.on.ec.gc.ca/glimr/data/amphib-reptile-factsheet/intro.html
Canadian Amphibian and Reptile Conservation Network
A collection of professionals and amateurs devoted to studying, monitoring and conserving amphibians and reptiles in Canada.
http://eqb-dqe.cciw.ca/partners/carcnet/carcnethome.html
British Chelonia
A charity dedicated to the preservation and conservation of tortoises, turtles, and terrapins worldwide.
http://www.britishchelonia.org/
Amphibian Conservation Alliance
A non-profit organization working to conserve amphibians worldwide through a variety of research, education, and advocacy programs.
http://www.frogs.org/index.asp
Project Golden Frog
Information about the species Atelopus zeteki, threats to its survival and conservation efforts.
http://www.ranadorada.org/goldenfrog.htm
Amphibian Information Website
Searchable databases of literature references, researchers, and web sites dealing with amphibian conservation. The references database contain data only for USA.
http://www.mp2-pwrc.usgs.gov/ampCV/ampdb.cfm
Swiss Amphibian and Reptile Conservation Programme
A task force to promote, implement and coordinate efforts to conserve the native amphibian and reptile fauna, which is protected by law since 1967.
http://www.karch.ch/
British Chelonia Group
A charity dedicated to the welfare of tortoises, terrapins and turtles. Information on aspects of care and husbandry is given, as well as scientific articles.
http://www.britishcheloniagroup.org.uk
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