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It’s high time you were told about Psammodromus

The views expressed are those of the author and are not necessarily those of Scientific American.


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Spanish psammodromus (Psammodromus hispanicus), image by Benny Trapp, licensed under licensed under Creative Commons Attribution 3.0 Unported license.

Once again, I have squamate guilt. For a while now I’ve been planning to discuss the lacertid lizard fauna of Europe (or, the European Field Guide Region, or Western Palaearctic, or whatever). European people tend to think of our lacertids as small, boring brown things (bar the few big green species). That might be true but, even so, there are loads of neat species here that have fascinating evolutionary interactions, exhibit surprising and often mostly overlooked behaviour and ecological specialisations, and possess anatomical details that might be surprising if you don’t know lizards in details (like tridentate teeth and a paedomorphic skull shape). I don’t have time for the sort of grand, over-arching review that I’d like to produce (sigh) so I’ll try and deal with them in piecemeal fashion. Today: Psammodromus!

Large psammodromus: note the streamlined appearance, large, keeled and overlapping scales, characteristic longitudinal striping and very long tail. Image by Jack ma, licensed under Creative Commons Attribution-Share Alike 3.0 Unported, 2.5 Generic, 2.0 Generic and 1.0 Generic license.

Psammodromus is a strictly terrestrial lacertid that frequents flat, typically stony or sandy areas and hillsides in Spain, Portugal and northern Africa (there are also small populations in France, Italy, and elsewhere).

Between 6 and 12 Psammodromus species are recognised depending on which source you consult, but the only ones ever discussed in books are the Large psammodromus Psammodromus algirus [adjacent image by Jack ma] and Spanish psammodromus or sand racer P. hispanicus. The former reaches 27 cm in total (though SVL is only 7 cm) and hence is not small for a European lacertid. Males have bright blue, dark-edge shoulder spots and red or orange throats and cheeks during the breeding season.

Small, widely spaced, dense, bushy plants that are frequently twiggy or spiny (so-called garigue-type vegetation) form the dominant flora in the areas inhabited by these lizards (Arnold 1987). Perhaps because selection pressures have improved their ability to frequently take refuge in such dense, spiny vegetation, Psammodromus lizards have a streamlined head and large, overlapping cephalic scales. Indeed, Arnold (2004) noted that Psammodromus possesses several features – including a reduced collar and enlarged, overlapping, keeled dorsal and lateral body scales – indicating that it belongs to a ‘dense vegetation’ ecomorph that has evolved several times within Lacertidae. Psammodromus shares its habitat with Lacerta and Acanthodactylus species but they are often larger and take bigger prey (Arnold 1987). The colubrid snake Coronella girondica is a documented predator of Psammodromus (Pérez-Mellado et al. 1997).

Another Large psammodromus: note blue shoulder spots. Image by Wolfgang Wüster.

>Massively< simplified lacertid phylogeny, showing early divergence into Gallotiinae and Lacertinae. Acanthodactylus by Richard Hing, Gallotia by Petermann, Psammodromus by Wolfgang Wüster.

Where does Psammodromus fit within the lacertid radiation? Molecular analyses recover it as the sister-taxon to the large Gallotia lizards (Fu 2000, Carranza et al. 2004), in which case it’s outside of Lacertinae and belongs to Gallotiinae. Psammodromus and Gallotia also share detailed anatomical features (including hemipenial characters) and both reportedly make squeaking noises (Arnold 1989) that have even been described as “shrill whistles” (Laňka & Vít 1986).

Several authors have argued that some of the more recently evolved lacertine lacertid clades (Podarcis being the ultimate example) have replaced or displaced the members of older lacertid lineages across Europe, pushing these older lineages into refugia or causing their wholesale extinction. As a member of Gallotiinae, Psammodromus has been hypothesised to be one of these older lineages: you might argue that its current range (southwestern Europe and northwestern Africa) indicates restriction to the peripheries (Carranza et al. 2004). Was it previously more widespread prior to the diversification and spread of Podarcis and other new-fangled lacertines?

Today, Psammodromus species are threatened by habitat loss – sadly, they are proving harder and harder to find…

So much more to say about European lacertids… until next time! For previous Tet Zoo articles on lacertids, see…

Refs – -

Arnold, E. N. 1987. Resource partition among lacertid lizards in southern Europe. Journal of Zoology 1, 739-782.

- . 1989. Towards a phylogeny and biogeography of the Lacertidae: relationships within an Old-World family of lizards derived from morphology. Bulletin of British Museum of Natural History (Zoology) 55, 209-257

- . 2004. Overview of morphological evolution and radiation in the Lacertidae. In Pérez-Mellado, V., Riera, N. & Perera, A. (eds) The Biology of Lacertid Lizards. Evolutionary and Ecological Perspectives. Institut Menorquí d’Estudis. Recerca 8, 11-36.

Carranza, S., Arnold, E. N. & Amat, F. 2004. DNA phylogeny of Lacerta (Iberolacerta) and other lacertine lizards (Reptilia: Lacertidae): did competition cause long-term mountain restriction? Systematics and Biodiversity 2, 57-77.

Fu, J. 2000. Toward the phylogeny of the family Lacertidae – why 4708 base pairs of mtDNA sequences cannot draw the picture. Biological Journal of Linnean Society 71, 203-217.

Laňka, V. & Vít, Z. 1986. Amphibians and Reptiles. Hamlyn, Twickenham.

Pérez-Mellado, V., Corti, C. & Cascio, P. L. 1997. Tail autotomy and extinction in Mediterranean lizards. A preliminary study of continental and insular populations. Journal of Zoology 243, 533-541.

Darren Naish About the Author: Darren Naish is a science writer, technical editor and palaeozoologist (affiliated with the University of Southampton, UK). He mostly works on Cretaceous dinosaurs and pterosaurs but has an avid interest in all things tetrapod. His publications can be downloaded at darrennaish.wordpress.com. He has been blogging at Tetrapod Zoology since 2006. Check out the Tet Zoo podcast at tetzoo.com!

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The views expressed are those of the author and are not necessarily those of Scientific American.





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  1. 1. Heteromeles 11:04 am 07/31/2013

    Yeah, habitat loss. I heard second hand about a “reforestation” project to replace mattoral in Spain where in most of their sites, they didn’t have to put any rabbit-proofing around the seedlings they were planting. There weren’t any rabbits.

    For someone used to California chaparral (which has a lot of rabbits and lizards, thankfully), this was kind of a shock. Habitat loss is really bad when there aren’t any rabbits left.

    As for the Psammodromus, they certainly look similar to the chaparral lizards around here, sort of halfway between the fence lizards and the alligator lizards.

    Link to this
  2. 2. Chabier G. 9:50 am 08/1/2013

    Psammodromus is one of my favourite reptile taxa. Psammodromus hispanicus is restricted, in the Ebro Valley at least, to the most open and arid zones, with scattered short shrubs covering less than 50% of the soil. This pseudosteppes have suffered a lot by enormous irrigation projects and European subventions to fallow lands (farmers, instead of leaving arable lands as fallows, break up and plough zones that, otherwise, would never have been cultivated, in order to get the fallow subvention, without loosing arable surface, Mediterranean cheats !). Then, this little lizard has a real problem of habitat loss.
    Psammodromus algirus (and P. jeannae, if this species is accepted), is far more adaptable, it prefers denser habitats, from more covered scrub to evergreen oak forest, and it thrives well in the banks surrounding crop fields, even in the intensely cultivated Ebro “huerta”.
    Psammodromus algirus is very agile, it can be seen jumping from one bush branch to another, or even bounding among rushes (Juncus).
    Podarcis lizards, where occur in simpatry with Psammodromus, live in human buildings and rocky soils and cliffs, Psammodromus lizars (and Achantodactylus) occupy bush covered or steppe lands, with earthy substrate.
    About Gallotia, has this genus ever been confined to he Canary Islands?, I read somewhere that Gallotia “comes” from Psammodromus that colonized the Islands, if it were the case, Psammodromus would be paraphyletic.
    Heteromeles: Spanish conservationists have a common subject of hatred, Spanish “reforestation” politics. I’ve seen how forestry workers cut and put in shredding machines Juniperus, Holm Oaks and other autochthonous understory, that were regrowing in an bleeding out of place Aleppo Pine plantation. Many good Mediterranean shrub areas, habitat for the Iberian Lynx, have been cut off, ploughed, and “reforestated” with pines, good fuel for summer burnings.

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  3. 3. Hai~Ren 10:24 am 08/1/2013

    Just being curious here: do reptiles that live in habitats with lots of spiny plants show any indications of being better armoured? I’ve always had the impression that the scales of some lizards (especially agamids, lacertids, and some skinks) make them less prone to injury from being pricked and otherwise injured while navigating plants adorned with spines and thorns.

    Compare this to say, many so-called house geckos, which have such thin skin that they come across as being very likely to get snagged and impaled.

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  4. 4. Heteromeles 10:32 am 08/1/2013

    Oh, and by the way, what were those croc skulls in http://blogs.scientificamerican.com/tetrapod-zoology/2013/05/16/skulls-for-talking-about/ ?

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  5. 5. naishd 5:00 am 08/2/2013

    Hi everyone, thanks for great and informative comments. I’ve heard real horror stories about the state of play as goes arid-land health and lacertid populations across Africa, Europe and Asia. There are even cases where people have gone looking for lacertids on African steppes and other such places (places where the lizards were abundant and easy to find within recent decades) and failed to find… any.

    Lest anyone says “oh, there are lots of lizards in [insert specific locality], they’re doing fine”, lizard decline is increasingly recognised as a serious global problem. Lots of articles about it online now, see…

    NEW STUDY FINDS WIDESPREAD EXTINCTION OF LIZARD POPULATIONS DUE TO CLIMATE CHANGE
    One by one – lizards are going extinct according to climate change study
    Mass Lizard Extinctions Looming; Global Warming Blamed
    Climate Change Causing Lizards to ‘Wink Out of Existence’

    Darren

    Link to this
  6. 6. naishd 6:26 am 08/2/2013

    In other news… Chabier G (comment # 2): I haven’t seen it hypothesied that Psammodromus might be paraphyletic with respect to Gallotia – the two are shown as sister-taxa in the cladograms I’ve seen. Interesting idea though. I’ll say much more about Gallotia at a later date!

    As for those skulls (comment # 4): I haven’t forgotten, I’m waiting to hear back from someone…

    Darren

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  7. 7. Tayo Bethel 11:27 pm 08/2/2013

    Lizards going extinct?That sounds kinda horrible… first the frogs, now the lizards—who’s next?

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  8. 8. naishd 6:03 am 08/3/2013

    You’ve heard the depressing stories about bats, snakes, and coral reefs, I assume?

    Darren

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  9. 9. Heteromeles 10:11 am 08/3/2013

    How about north-east American forests? With too many deer, there are large stretches where there are no seedlings to replace the adult trees. For example, in much of Wisconsin, yew is more common in people’s yards than it is in the forests.

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  10. 10. Chabier G. 5:13 pm 08/3/2013

    I think species like Podarcis muralis or Zootoca vivipara have some chances to survive in this scenario, giving their enormous range, extending across many degrees of latitude. But the most lizard species in Europe are relictic taxa like the six Iberolacerta, or Algyroides, all of them limited to very small and specific mountain habitats, or endemic from tiny islands like Podarcis lilfordi, Podarcis atrata, and many other Mediterranean lizards. It’s easy to understand that an increase of maximal temperatures of several degrees will be a disaster for these animals.
    But there are some lizards that look like doing well with climatic change, the nocturnal ones, at least one gecko, Tarentola mauritanica. This species has spread its area to altitudes where never before lived. Until some 10 years ago, T. mauretanica was absent in the mountains of Aragón, at least in villages like the one I’m from, at 850 m over sea level. About 10 years ago, the people that make the reptile census in our territory noticed the presence of this gecko in the mountain villages. Since then, these high populations have thriven, their numbers increased. It means nocturnal temperatures are now higher than several years ago. In the lowlands of the Ebro Valley Tarentola mauritanica is really numerous, to say the least, in the towns around Zaragoza one can count an average of 3-5 individuals per street lamp, and there are a lot of street lamps, I’ve counted 12 geckos under some of them. Old people say they never have seen such an abundance of these lizards (well, yeah, I don’t trust a lot in this kind of field research, eyewitness based, but it’s my own impression, too). The mystery, however, is the apparent disappearance of Hemidactylus turcicus, once the most abundant gecko in Zaragoza and surrounding areas, it seems to coincide with the boom of T. mauritanica, but due to the lack of accurate census in the past years we can only speculate.

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  11. 11. Tayo Bethel 4:10 am 08/4/2013

    @Chabier G.
    Niceto hear something nice … sounds like the two gecko species are in competition.

    Dr.Naish:

    I’ve heard most of them—all depressing. Hard not to entertain the notion that within the next century Homo sapiens will have degraded to biosphere to such a degree that we ourselves might face extinction …. drastic, I know, but scary too. Right now the current government is thinking aboutdoing offshore drillin the Bahamas–and all the general public can think of is the quick money that supposedly would come from such a project.

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  12. 12. BrianL 5:37 am 08/4/2013

    Now I do wonder: Shouldn’t warmer temperatures be a positive thing for reptiles in general? I’m not saying that the possible extinction of so many species of them should be ignored, but wouldn’t the possible extension of the reptilian distribution into more northerly and southerly climes in itself be a good thing?

    I’d even wonder if (re-)introducing various reptiles into areas they might well survive in now but might have difficulty reaching by themselves because of man-made obstacles should be attempted. This could perhaps increase their chances for survival as a species. So basically, I wonder, should we be actively using the possibilities that a generally warmer climate provides us with regarding reptiles?

    This subject also touches on exotics, of course. I fear that much of reptile (and amphibian) exotic introduction goes unnoticed or is at the very least poorly documented. What escaped, released or accidentally imported exotic reptiles are going to do in warming temperate zones in the near future is an interesting thought. I do suspect that, at least in western Europe, density of aforementioned roads and people is going to be a problem for most in spreading. Species that can do well in river systems might have an easier time though. Turtles, I’m looking at you.

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  13. 13. naishd 7:05 am 08/4/2013

    Thanks for great comments. Heteromeles (comment # 9): on the matter of ecological collapse, over-browsing by deer, forests populated by ‘walking dead’ trees etc., have you seen my review article of Cristina Eisenberg’s The Wolf’s Tooth: Keystone Predators, Trophic Cascades and Biodiversity? The article is here on ver 2.

    On the issue of how the herpetofauna is changing.. yes, there’s widespread evidence for this worldwide. Geckos from Mediterranean and even subtropical habitats are undoubtedly spreading further north and south, escaped pythons, boas and even monitor lizards and snapping turtles are increasingly surviving in the wild in Europe and North America and either breeding or set to breed soon, and non-native anoles, Old World lacertids and colubrids are having impacts on island-dwelling endemics in various locations. Even here in the UK, we have a new, weird assemblage of southern and eastern European lacertids that are now occupying habitat used by the two native species.

    Shouldn’t climatic warming be good for reptiles (as per Brian’s comment # 12)? Theoretically, yes, but the problem is that climatic amelioration isn’t the only thing happening right now – massive environmental degradation is occurring, with reptile-killing pathogens on the rise (here’s a 2010 piece that discusses recent snake population crashes documented in Europe, North America, tropical Africa and elsewhere). In other words, even in a world better suited for reptiles due to warmer climates, conditions overall are becoming far, far worse, not better. Of course, those species well-suited for degraded, low-quality habitats will perhaps do well. But everything else will be gone. One species replacing 500, that sort of thing.

    Darren

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  14. 14. Tayo Bethel 8:16 am 08/4/2013

    Malo malo…

    Bad,bad. I dont even want toimagine what speciesofreptilescould go extinct before they’re even discovered …

    Link to this
  15. 15. David Marjanović 6:01 pm 08/4/2013

    Spanish conservationists have a common subject of hatred, Spanish “reforestation” politics. I’ve seen how [...]

    *rageflail*

    Link to this
  16. 16. Chabier G. 9:29 am 08/5/2013

    Well, to be honest, there are some conservationists among Forestry Engineers, and well done reforestations, but the overall landscape about spanish reforestation can be very sad, Even the language is perverted, the pine plantations are called “bosque” (=forest), the evergreen oak patches trying to recover are “monte alto” (=high bush), or “Matorral” (shrub). Then, when we hear TV news about forest burnings, we can know what’s the most valuable burnt vegetation, often referred as “bush” or “shrub”.

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  17. 17. Chabier G. 6:24 am 08/7/2013

    There is a feature of Gallotia anatomy I´ve remembered now, back to my job. The only Gallotia specimen I’ve disected (whose skeleton I preserve) is a Gallotia atlanticus adult male, found near dead in a ship container and brought to our rescue center. Well, it had a deep and clearly visible round pit in the center of the interparietal scale, which probably shelters a pineal eye. If my interpretation is true, it would be the only lacertid with a conspicuous pineal eye, AFAIK. At least, Iberian Lacertinae and Gallotinae (Psammodromus) I’ve seen don’t have anything but a plain interpatietal scale.

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  18. 18. AlHazen 10:07 pm 08/12/2013

    Totally different, unrelated, bunch of lizards, but… I’m proud of myself for noticing something, and this is a FAIRLY recent lizard post on which to boast.

    Orthodoxy among lepidosaurian taxonomists is that the Gila Monster (& Mexican Beaded Lizard) are closely related to Monitor lizards. I have been taking this on faith, not bothering to look up what shared derived traits(*) unite them. But I ***think*** I may now have noticed one.

    Last week I went to the Zoo in Seattle with grandchildren. Seattle has a Komodo Dragon (at least one): it was exhibiting typical lizard behaviour, though it did turn its head a couple of times to suggest it was live rather than stuffed. But it was sprawled up against the glass at the front of its enclosure, so I could look at its lower back/right hip/tail base from a distance of a foot or so. The scales are BEADLIKE! The (dorsal) body surface is covered by a regular (I think rectangular lattice, though all I can swear I remember is that one axis of the array was crosswise: perpendicular tp the body axis) array of little (3mm diameter?) spheres.

    I had never noticed this before. (The AMNH in New York has a couple of stuffed specimens in their third floor Herp hall, so I COULD have noticed it, but I wasn’t thinking phylogenetically the last time I visited…) So: IS possession of beadlike scales a (soft tissue) synapomorphy of (some superclade of?) the clade comprehending Monsters and Monitors?

    (*) I guess if you stood me up against a wall and demanded that I name one I’d say “something about the details of the intra-mandibular joint”…

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  19. 19. David Marjanović 6:15 am 08/14/2013

    Also, big venom glands in the lower jaw and the lower jaw only.

    Link to this

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