Most detailed field guides, when describing lizard species, will discuss details of scalation.  This method is used to distinguish lizards at species and genus level from one another.  Unfortunately this can be bewildering for the layman as the names of the scales tend to be Latinised, much as doctors and surgeons tend to use the Latin names for muscles or bones.  Talk of species being distinguished by the occipital being absent or the 4th or 5th supralabial touching the eye is probably as much help to the ordinary nature enthusiast as the original Latin descriptions made in the eighteenth century.

What follows is therefore an attempt to introduce the reader to how we identify lizards in layman's terms.  You can't get away from using scalation details, but hopefully this article will throw some light on the subject and remove the mystery and panic.

General identification details
It may sound obvious, but before you even think about scales, there are some more obvious characteristics to look for.  The first is the shape or overall appearance of the lizard.  A chameleon can never be mistaken for any other type of lizard simply because of its overall appearance: the coiled tail, the rather flattened body, the eyes and the limbs with their fused toes.  Skinks likewise are often easy to recognise, certainly in Europe, because of their smooth and shiny appearance.  A reptile without legs but with eyelids is a legless lizard, either one of the anguid lizards or a legless skink.  A lizard with a softer-looking skin and lacking eyelids is usually a gecko, at least in Spain, especially if found clinging apparently effortlessly to a vertical surface or ceiling.

Colour may also help, if only in eliminating possible alternatives.  Most European lizards are a shade of brown or green.  All Lacerta and Timon species are green, often very bright especially in breeding season, while the smaller Podarcis may be green and brown and other small lacertids may be brown.  It is important to note that some species may be quite variable in colour from individual to individual, so coloration is not always a reliable guide unless taken in conjunction with other factors.

Size is somewhat subjective, but the largest lizards in Europe are the Lacerta and Timon species, or the legless Scheltopusik (not found in Iberia).  Small lizards tend to be other lacertids or else skinks.  Checking the proportions of the tail to the rest of the body is also a good way of distinguishing lacertids from other lizards: in lacertids the tail tends to be rather longer than the body, often up to twice its length.  

Habitat and geographical location may also be a guide.  Field guides will normally show the range of a species, so by process of elimination you may be able to arrive at a conclusion.  For example in Spain the range of a fair number of species stops short of the Pyrenees.  Habitat can also help to eliminate some possibilities.  For example, if you see a lizard in a tree it is most likely not a skink since the European skinks at any rate tend to be ground dwellers, while a small lizard found in sand near or on the shore has a fair chance of being an Acanthodactylus.

Scales
Scalation details on European lizards are primarily used to tell different lacertids apart from one another, since lacertids are both the most common European lizards and those in whom the scales are clearly defined and (in my opinion anyway) easiest to tell apart.

There are several main areas to be considered  dorsal (essentially the back, from head to the join with the tail), ventral (the belly), the head or cephalic scales, and the tail or caudate scales.

Dorsal area
The scales on the back may be in regular rows (in which case the number of longitudinal and transverse rows can help identify the lizard) or very irregular in their arrangement, and may be  flat or else overlapping one another (imbricate).   In addition the individual scales may be smooth or with one or more keels, usually at the rear edge.  Some lizards have a number of larger scales among the otherwise small scales, while others have highly modified scales along the middle of the back (and sometimes head and neck) that are raised to form crests, although in Spain this really only applies to the chameleon.  Geckos have a rather different dorsal arrangement: most of their scales are very small, giving the impression of a smooth skin, but with rows of intermittent larger, conical scales called tubercles.  Spanish skinks have very smooth and shiny interlocking dorsal scales that appear to be welded together, so tightly do they sit next to one another.

This is tricky to describe if only because of the number of different scales.  However, it is not as hard as one might expect.  We will start with the easiest parts and work through the whole area.

The scale right on the front of the snout on the upper jaw is the rostral. Behind the rostral, running along the upper lips of the lizard's jaw, are the supralabials. There are usually 4-5 of these on each side.  They normally stop short of the eye.  Directly between the eye and the upper edge of the jaw is the subocular.
On each side of the jaw, behind the rostral but above the supralabials, are, respectively, the supranasal and the postnasal.  The nostril is usually situated between or in one of these scales.  Backwards from the postnasal and above the supralabials are usually 1-2 loreals.

Looking down on the top of the lizard's head, behind the rostral and between the supranasals is located the internasal.  Sometimes the internasal divides the supranasals, sometimes it sits behind them and they meet in the middle.  The internasal is followed by a prefrontal on each side.  A third scale may sit between the two prefrontals.  Behind the prefrontals, roughly between the eyes, is a large scale, the frontal.  On either side of the frontal is a pair or more of supraoculars (2-4 is the norm for lacertid lizards) sitting above the eye socket.  Below the supraoculars are 1-2 rows of supraciliaries,  smallish scales above the eye, while granules are very small scales between the large supraoculars and the smaller supraciliaries.  The term granules is also used for very small scales elsewhere on a lizard's body.

Continuing backwards from the frontal there is a pair of frontoparietals that usually meet not only the frontal but one or more supraoculars on each side.  Behind each frontoparietal is a parietal, and there may be an interparietal between the parietals.  Behind the interparietal will be an occipital scale in most Spanish lacertids (Acanthodactylus erythurus, the Fringe-Fingered Lizard, is the exception).  The parietals and occipital (if present) are the last of the large distinctive scales on the top of the head.  Each parietal has 1-3 or so supratemporals, medium-sized narrow scales, along its outer border.  On each side of the head, further back from the eye, are two largish scales surrounded by smaller ones, the maseterica which is closer to the eye and the tympanic scale which is close to the front edge of the ear.

On the underneath of the head, ie the lower jaw, the single large scale at the front is the mental.  The scales running backwards from the mental and forming the lower lip are the sublabials or infralabials.  On the underneath of the jaw behind the mental and touching the sublabials on either side are pairs of large scales called submaxillaries.  These are paired at the front of the jaw but as they proceed backwards are separated by smaller scales.  One of the main things to look for when looking at the underneath of a lizard's jaw is how many of the submaxillaries touch each other before being separated this way. 

The so-called collar is a row of scales where the head joins the neck.  The collar may be smooth, or the scales may be imbricate (overlapping), or it may be absent or poorly defined.

Ventral area
The scales on the belly are often arranged in regular rows, and the number of rows counted lengthwise and crosswise can be a guide to the species.  Also look on the underside of the rear limbs for a group of scales that appear to stand out in rows, sometimes meeting in the area of the cloaca (anus) where the tail meets the body.  These are the femoral pores which are absent in some species but present in others, often only in the male of the species.  Femoral pores are an important key to identifying a lizard.

Tail area
Scales on a lizard's tail are usually arranged in regular whorls but may be irregular.  If the scales are keeled and/or imbricate, this also helps in identification.

The above system is most usually used in connection with identifying lacertid, or true, lizards, in Spain.  Lizards of other families are more easily identified, or at least distinguished from lacertids, due to a combination of shape, size and location (see the section on General Identification Details).  

Other areas to note
On the head, look at the relative size of the ear (assuming it is visible, which is not always the case  another possible distinguishing characteristic!).  There may also be a small number of scales protruding from the rear edge of the ear (so-called lobes).  Also look at the eye, and in particular the colour of the iris and whether the pupil is round or slit-like.  These head details may in fact be easier to note than the scalation.

On the rear limbs, see if one toe is much longer than the others.  If so it will usually be the fourth toe, but not always.  Admittedly this can be difficult to tell if the lizard is running off at full speed!  In the laboratory experts count various aspects beneath the fourth toe of the rear limb, but this is not really practical for most of us.

In summary
The above guide is as much a guide to the conventions and terms used in describing lizards as a guide to their identification in Spain.  It can thus be used anywhere in the world, especially those countries where a multitude of different lizards can cause confusion.

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