Sunday, 6 December 2009
British Wildlife: V
Valdosaurus canaliculatus (Galton, 1975)
Dryosauridae; Ornithischia; Sauropsida; Chordata
The dryosaurids are a family of basal iguanodontians (the clade of ornithopod - bird-foot - dinosaurs including such iconic beasts as Parasaurolophus, Camptosaurus and Iguanodon). Within the family, the type genus - Dryosaurus, from Jurassic North America - is probably most well-known. There are at least two, but probably three, other genera though: Callovosaurus of Jurassic England; Valdosaurus of Cretaceous England; and Elrhazosaurus of Cretaceous Niger. The latter genus was until very recently considered an additional species of Valdosaurus, V. nigeriensis. A recent paper by Peter Galton (2009) erects the new genus for that species.
Valdosaurus canaliculatus, currently the only species in the genus, is known from parts of southern England (notably West Sussex and the Isle of Wight), as well as Romania. The generic name means "Wealden lizard", after The Weald, the part of southeast England known for its unique geology. Although only incomplete skeletons are known, enough can be inferred about the animal's body shape from more-or-less complete skeletons of its cousin Dryosaurus.
Vipera berus (Linnaeus, 1758)
Viperidae; Squamata; Sauropsida; Chordata
The adder is one of three snakes native to Great Britain (there are, of course, none at all in Ireland: if you believe the legend, St. Patrick, patron saint of the island, drove all serpents out; if you believe in cold, hard evidence, Ireland was isolated from Great Britain and mainland Europe during glaciated periods when the snakes could have migrated back from the Continent). It is, however, the only venomous snake. Despite about a hundred adder bites inflicted upon humans each year, very few have ever been fatal (about twelve in the entire 20th century), and most of these would have been people with weakened immune systems, i.e. old or very young.
Preserved female adder
Oxford Museum of Natural History
Adders are also the only British snake to be sexually dimorphic. Males, as illustrated in the artwork, are silvery-grey with a black zigzag along the back. Females are browner overall, with a less contrasting zigzag. Famously, you can also get black adders. Apart from Great Britain, adders can also be found across Eurasia right away across to Far Eastern Russia. They also range very far north, up to the Arctic Circle.
Arvicola amphibius (Linnaeus, 1758)
Cricetidae; Rodentia; Mammalia; Chordata
The water vole is a familiar rodent to many people: those who were brought up reading or watching the many TV adaptations of Kenneth Grahame's Wind in the Willows will know this animal as Ratty. Of course, the water vole is not a rat, but a plump, relatively short-tailed muroid rodent in an altogether different family, being closely related to other voles, lemmings and hamsters. You may double take at the scientific name: isn't it supposed to be Arvicola terrestris? Well, Carl Linnaeus, the father of taxonomy as we know it, described two species of water vole, a terrestrial one (A. terrestris), and an amphibious one (A. amphibius). In his tome Systema Naturae (10th ed.), which in which most of the animal species he had ever seen were described, the name A. amphibius appears on an earlier page than A. terrestris. This gives A. amphibius priority. This was only realised recently, and however much we might prefer A. terrestris, it is the other name which will stick. Unless enough people appeal to the ICZN for a reversion of the name back to A. terrestris. Anyhoo, the current name makes more sense; it's as much as a terrestrial mammal as I am an arboreal one.
Stuffed water vole
Bristol City Museum
Water voles aren't completely aquatic of course, they are amphibious, nesting underground. They spend little time out in the open, except when feeding. The water vole in Britain has been threatened by numerous things, including draining of waterways, but most notably the introduction of the American mink (Neovison vison), a predator which specifically targets the vole as its main source of prey. Water voles are on the increase in the UK, due in part to increased conservation efforts, although mink still remain a threat.
Do not confuse this species with what is known as the water vole in North America: the species found there is Microtus richardsoni (possibly, but probably not, actually in Arvicola).
Galton, P. M. (2009) Notes on Neocomian (Late Cretaceous) ornithopod dinosaurs from England - Hypsilophodon, Valdosaurus, "Camptosaurus", "Iguanodon" - and referred specimens from Romania and elsewhere. In: Revue de Paléobiologie 28(1):211-73. PDF here.
Next week, W: an Essex sylviid, a sickle-shaped moth and a Scottish reptiliomorph.