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We describe a new species of Stenocercus from an interandean valley of the upper Rio Huallaga on the Amazonian slope of central Peru (Region Huanuco), at an elevation of 1700–1900 m. The new species differs from other Stenocercus , except S. boettgeri , S. haenschi, S. humeralis, and S. varius , by the combination of the following characters: presence of granular scales on the posterior surface of the thighs, enlarged vertebrals, three caudal whorls per autotomic segment, a medially complete antegular fold, non-spinose caudals, and by males lacking a black transverse band on the ventral surface of the neck. However, the new Stenocercus differs from these, with the exception of S. humeralis , by having more scales around the midbody (104–107, =105.66) than S. boettgeri (79–104, Mean= 88.61), S. haenschi (57–64, Mean=60.50), and S. varius (74–88, Mean=82.35); and from S. humeralis by having the scales in the frontonasal region nearly equal in size to the scales in the occipitoparietal region, while in S. humeralis the scales on the frontonasal region are twice or three times longer than the scales on the occipitoparietal region.

We describe a new species of Stenocercus from the montane forest of the right margin of the Marañón river in the northern portion of the Central Andes in northern Peru (Amazonas and La Libertad departments), at elevations ranging from 2300 to 3035 m. Stenocercus omari sp. nov. differs from other Stenocercus species, with the exception of S. amydrorhytus, S. chrysopygus, S. cupreus, S. johaberfellneri, S. latebrosus, S. melanopygus, S. modestus, S. ornatissimus, S. orientalis, and S. stigmosus, by having granular scales on the posterior surfaces of thighs, a conspicuous antehumeral fold and by lacking a vertebral crest. However, Stenocercus omari sp. nov. is easily distinguished from the aforementioned species, except S. orientalis, by the presence of prominently keeled dorsal head scales. The new species differs from S. orientalis by lacking a prominent oblique neck fold and by having a distinct deep postfemoral mite pocket.

We evaluated the influence of environmental temperature and phenotype on thermoregulation by Sceloporus palaciosi, a diurnal iguanid lizard from high elevations in central Mexico. Range of body temperature was 13–36°C with a mean of 27.82 ± 5.31°C. Active lizards had a higher body temperature than inactive ones. After removal of state of activity from analysis, sexes did not differ in body temperature. Body temperature was significantly correlated with temperature of air and substrate in both active and inactive lizards.

The reptile Iguana iguana exhibits four states of vigilance: active wakefulness (AW), quiet wakefulness (QW), quiet sleep (QS) and active sleep (AS). Cerebral activity decreases in amplitude and frequency when passing from wakefulness to QS. Both parameters show a slight increase during AS. Heart rate is at a maximum during AW (43.8+/-7.9 beats/min), decreases to a minimum in QS (25.3+/-3.2 beats/min) and increases in AS (36.1+/-5.7 beats/min). Tonical and phasical muscular activity is present in wakefulness, decreases or disappears in QS and reappears in AS. Single or conjugate ocular movements are observed during wakefulness, then disappear in QS and abruptly reappear in AS. Although these reptiles are polyphasic, their sleep shows a tendency to concentrate between 20:00 and 8:00 h. Quiet sleep occupies the greater percentage of the total sleep time. Active sleep episodes are of very short duration, showing an average of 21.5+/-4.9 (mean+/-SD). Compensatory increment of sleep following its total deprivation was significant only for QS. Reaction to stimuli decreased significantly when passing from wakefulness to sleep. It is suggested that the lizard I. iguana displays two sleep phases behaviorally and somatovegetatively similar to slow wave sleep and paradoxical sleep in birds and mammals.

Ecological and phylogenetic factors determine which sensory modalities organisms use in their day-to-day activities. Among lizards, empirical studies indicate a tight association between foraging strategies and the ability to detect chemical cues from prey. Consequently, ambush insectivores do not detect food chemicals and these differences have a phylogenetic basis, as ambush lizards mainly belong to the Iguania clade. These data contrast, however, with the widespread uses of chemoreception in the Iguania genus Liolaemus, which are mostly insectivorous ambush predators. Moreover, observations from different Liolaemus species suggest a capability to find prey through chemoreception. In order to clarify the abilities of Liolaemus to detect chemical cues from prey, the chemoreceptive behavior of the insectivorous ambush predator, L. lemniscatus, was studied. Lizards were given the choice between areas with and without chemical cues from a food item (mealworms). Results show that test animals stayed for longer, moved more, and did more chemical exploration (tongue flicks) in the area where chemical cues from mealworms were present. Furthermore, in this area, more individuals displayed behaviors that suggest maintenance and defense of the prey patch. Thus, L. lemniscatus is the first insectivorous Iguania reported to be able to detect chemical cues from prey. Although I propose a mechanism for acquiring chemical detection of prey cues in Liolaemus, I also remark that it is necessary to reanalyze both the abilities to detect and use chemical foraging cues in Iguania at large, and the methodologies traditionally used to study these issues.

We resurrect and redescribe Stenocercus torquatus from the Andes of central Peru in departamentos Junin and Pasco at elevations between 800 and 1800 m. This species was erroneously synonymized with Stenocercus crassicaudatus, which occurs allopatrically in the Andes of southeastern Peru, departamento Cusco. In addition to several scale counts, Stenocercus torquatus differs from S. crassicaudatus in having a black antehumeral collar, two black transverse bands anterior to the antehumeral collar, a shorter tail, the ability to change color, and an arboreal life-style.

The appearance of an organism's color pattern is a function of numerous variables, including the background on which the organism is observed. Hence, color patterns that appear similar or conspicuous when taken out of context, may, in reality, appear quite different when viewed in a natural setting. I investigated the relative conspicuousness of chuckwallas, Sauromalus obesus (= ater) among three populations in which males differ in their coloration. The color pattern of male and female chuckwallas was compared to the background color of rocks on which individuals were observed basking or displaying. Data were also collected on predation pressures and the thermal environment to see whether there was any association with conspicuousness. Male tail and body conspicuousness, and female tail conspicuousness, varied among the three populations. In all populations, male tail color was more conspicuous than male body color and, within all populations, males were more conspicuous than females. However, m...

The study of adaptive radiations has played a funda- mental role in understanding mechanisms of evolution. A recent resurgence in the study of adaptive radiations highlights a gap in our knowledge about determining whether a clade constitutes adap- tive diversification. Specifically, no objective criteria exist to judge whether a clade constitutes an adaptive radiation. Most clades, given enough time, will diversify adaptively to some extent; therefore, we argue that the term "adaptive radiation" should be reserved for those clades that are exceptionally diverse in terms of the range of habitats occupied and attendant morphological adaptations. Making such a definition operational, however, requires a comparative analysis of many clades. Only by comparing clades can one distinguish those that are exceptionally diverse (or nondiverse) from those exhibiting a normal degree of adaptive disparity. We propose such a test, fo- cusing on disparity in the ecological morphology of monophyletic groups within the lizard family Iguanidae. We find that two clades, the Polychrotinae and Phrynosomatinae, are exceptionally diverse and that two others, the Crotaphytinae and Oplurinae, are excep- tionally nondiverse. Potential explanations for differences in diversity are discussed, as are caveats and future extensions of our approach.

We experimentally studied the ability of the iguanid lizard Sauromalus ater to discriminate between plant and animal foods and control stimuli using only chemical cues. When chemicals were presented on cotton swabs, the lizards exhibited stronger responses, as indicated by tongue-flicking and biting, to chemical stimuli from romaine lettuce than from crickets and control substances. Responses to plant and animal food did not differ significantly in S. ater, which eats animal prey only occasionally in natural populations. Although there were no significant differences between responses to cricket chemicals and other stimuli for the entire data set, those individuals that ate or attacked crickets tongue-flicked at high rates in response to cricket chemicals. Based on the presence of herbivory and plant chemical discrimination in three iguanid genera, it is likely that plant chemical discrimination is ubiquitous in iguanids. Given the uncertainty of iguanian phylogeny, the evolution of herbivory and response to plant chemicals cannot be traced with confidence. However, it appears very likely that lingually mediated plant chemical discriminations evolved in the common ancestor of Iguanidae or earlier in iguanian history in response to a shift to an herbivorous diet.

We describe a new species of Enyalioides from mid-elevation rainforests in southeastern Ecuador. This represents the fifth species of Enyalioides known to occur east of the Andes in South America; the other four species are E. cofanorum, E. laticeps, E. microlepis and E. praestabilis. Among other characters, the new species can be distinguished from other Enyalioides bydistinct caudal whorls, fewer than 32 longitudinal rows of dorsals at midbody, and bright orange to red gular scales bordered with black in adult males. Morphological similarity suggests that the new species, which we call E. rubrigularis, is closely related to E. praestabilis.

Males of many iguanid lizard species defend territories against conspecific males. We investigated whether territoriality in male sagebrush lizards (Sceloporus graciosus) was associated with defense of mates. Studies on the sagebrush lizard in western Colorado, USA, included mark-recapture census and removal of adult females from the territories of resident males. Adults and juveniles were clearly distinguished by body size. Resident males did not abandon their territories following the removal of adult females. Resident males did not expand the size of their territories following the loss of adult females. Males were not defending juvenile females because most male territories did not include juvenile females. Sagebrush lizards are long lived, and territory defense probably ensures several mating opportunities. We postulate that loss of a mate in one season may be less important than the long-term benefits of territory maintenance and repeated reproduction.

We examined correlates (sex, size, age) of variation in maximal burst speed (racetrack) and in stamina (time until exhaustion at 0.5 km · h⁻¹) in two populations of the iguanid lizard Sceloporus merriami in Big Bend National Park, Texas. Because these populations were known demographically and were studied in several years, we were able to examine the effects of adult age on performance, the between-year repeatability of individual performance, and environmental correlates of yearly variation in performance. Variation in locomotor capacities was striking. Males were faster than females, and lizards from the Grapevine Hills were faster than those from Boquillas (lower elevation). However, sex and population did not affect stamina. Young adults (1-yr-olds) were slightly faster but had slightly less stamina than did older adults (2-3-yr-olds). Adult size (mass, snout-vent length, hind limb length) had little effect on performance. Average performance varied significantly among years, but stamina varied more ...

We describe a new species of Stenocercus from the interandean valley of Rio Chotano on the Amazonian slope of the northern portion of the Cordillera Occidental of Peru (Cajamarca Region), at elevations of between 1997 and 2318 m. Stenocercus arndti sp. nov. differs from other Stenocercus, except from S. bolivarensis, S. carrioni, S. chlorostictus, S. crassicaudatus, S. empetrus, S. eunetopsis, S. simonsii, and S. torquatus, in having granular scales on the posterior surface of the thighs, two caudal whorls per autotomic segment, mucronate caudal scales, and distinct longitudinal row of enlarged vertebral scales. However, Stenocercus arndti sp. nov. is easily distinguished from these species in having a bold black transversal band at midbody that extends ventrolaterally in adult males.

Interspecific spatial overlap profiles are constructed for several pairs of iguanid lizard species. The profiles depict the proportion of activity points within the territories and home ranges of target lizards that are shared with individuals of other lizard species. Results show that within populations some individuals may incur little or no spatial overlap from other lizard species, whereas others have high spatial overlap. These patterns of overlap may be sustained through entire seasons of lizard activity. Profile shapes included distributions that were unimodal and strongly skewed, bimodal, and uniform with roughly equivalent proportions of low, intermediate, and high overlaps. Spatial overlap profiles are idiosyncratic, neither characterizing a particular pair of lizard species, nor typifying a specific habitat type. The observations provide insight into the results of experimental studies that show weak or undetectable effects of competition at the population level, but may include asymmetric effects targeted at specific individuals. In addition, because spatial overlap profiles for a pair of species are variable, interactions cannot be characterized by the results of an experimental manipulation conducted in just one habitat.

Anolis roquet, the only iguanid lizard on the Lesser Antillean island of Martinique, exhibits

We examined the role of tongue extrusions for the detection of chemicals in the iguanid lizard Sceloporus jarrovi , prior to the breeding season. Most extrusions resulted in the tongue touching the substrate and are referred to as tongue-touches. A total of 2819 tongue-touches were observed for four age/sex classes of lizards. We could not demonstrate that the tongue is involved in the detection of a natural predator, the Arizona kingsnake ( Lampropeltis pyromelana ), and it was clear that it was not used to find food. It did, however, seem to be involved in the exploration of temporally and spatially unfamiliar areas. The possibility that the tongue is involved in the detection of conspecifics is discussed for this study, as well as for complementary studies. Possible marking attempts in the form of chin wipes, pelvic rubs, and defaecations were examined. The latter two possibilities were not important at this time of year. Chin wiping may result in the depositing of chemical markers, although no external chin glands were found and the possibility is still uncertain.

A population of Sceloporus virgatus, an iguanid lizard, was studied to determine the adult patterns of activity and inactivity. Activity was primarily a function of the sex and age of the individual, as well as reproductive condition. Activity was highest during the breeding season when males were active daily (97% of the days) and females were active 76% of the days. Males were also active longer and moved greater distances than females. Males lost mass during this high activity period. During the nonbreeding season, females were active more days than males. Activity levels were not substantially different for females during the breeding and nonbreeding season. Male activity decreased dramatically during the nonbreeding season and activity differed depending on the age of the lizard. Year—old males were nearly twice as active as older males (57% compared to 29% of the days). Activity was so low in these large, older males that territory maintenance was probably no longer functional. This low activity sug...

Relationships between male social behaviour and female reproductive coloration in the iguanid lizard Holbrookia propinqua were examined by introduction of tethered non-resident lizards into the territories of adult males. Introduced lizards were plainly coloured females, females having bright reproductive coloration, adult males, plain females painted to resemble brightly coloured females, bright females painted to mimic plain females, and males painted with the bright yellow and orange secondary sexual coloration of females. Resident males courted all unpainted females, despite being aggressively rejected by the brightly coloured ones. They also courted all but two females in each of the painted groups. All unaltered non-resident males were challenged, attacked or subjected to other aggressive behaviour by residents, but all non-resident males painted to resemble bright females were courted. This differential treatment is highly significant. It clearly demonstrates that the bright female pigmentation functions in sex recognition, identifying a female to males. Other stimuli, especially pheromonal and behavioural cues, may contribute to sex recognition. Because sex recognition alone seems insufficient to account for the evolution of bright female coloration in H. propinqua and several other iguanids, several proposed additional functions are discussed.

A single population of the iguanid lizard, Sceloporus grammicus, was found to have fission polymorphisms in three of four metacentric macrochromosome pairs. This variation resulted in eight different karyotypes in a sample of 24 lizards. Of these 24 lizards, 7 were single heterozygotes, 11 were double heterozygotes, and 1 was a triple heterozygote. Meiotic analyses of males heterozygous for different combinations of fissions indicated completely normal disjunction and production of chromosomally balanced gametes. The polymorphisms in this population did not appear to deviate strongly from Hardy-Weinberg equilibrium. There was no evidence of selection against chromosomal heterozygotes in this population.

Summary The seasonality of the reproductive cycles of adults of the Iguanid lizard, Anolis sagrei, was studied. Twenty-three samples totalling 449 females and 142 males, were collected at Belize City, Belize, Central America. Large males are always reproductively active. Egg production, as measured by frequency of females with enlarging ovarian eggs and/or with an oviducal egg(s), was generally highest in the wet season (May through August). Earlier experimental work had implicated moisture as a cue involved in the regulation of female reproductive activity. Statistical analyses (particularly stepwise multiple regression) of the data reported here indicated that temperature, not rain, was the best predictor of reproductive activity. A hypothesis was suggested that the cue regulating a cycle may not be that factor best predicting the cycle, per se, but a factor which is important in reducing mortality of some critical stage in egg development after oviposition.

Subcutaneous Silastic capsules which continuously released melatonin at low rates (10 μg/day) either (i) lengthened the period of the freerunning activity rhythm in two iguanid lizard species (Sceloporus occidentalis andS. olivaceus) exposed to either continuous illumination or continuous darkness or (ii) induced arrhythmicity inS. olivaceus exposed to continuous illumination. These results and previous observations that two melatonin synthesizing sites in lizards, the pineal organ and lateral eyes, are involved in circadian rhythmicity suggest that melatonin may be a chemical messenger between the pineal or eyes and other elements of the circadian system.

In laboratory experiments, we determined the effects of body temperature and the quantity of food consumed on the probability of feeding, the passage time of food, and the digestive coefficient in the iguanid lizard Uta stansburiana. Between body temperatures of 20 and 36 C, the probability of eating increased curvilinearly with body temperature but was inversely related to the quantity of food offered. For lizards fed an unrestricted ration, the average consumption rate increased from 0 to 50 mg g⁻¹ day⁻¹ between body temperatures of 20 and 28 C and remained constant between 28 and 36 C. The passage time of food decreased curvilinearly as body temperature increased. For lizards fed an unrestricted daily ration, the mean passage time ranged from 4.6 days at 22 C to 1.2 days at 32 C. For lizards fed a restricted ration, the mean passage time ranged from 9.2 days at 22 C to 1.8 days at 32 C. Body temperature and feeding regime each had a small but significant effect on the digestive coefficient. In the rest...

Throughout the year Sceloporus jarrovi is capable of significant supercooling of the deep-body temperature below the freezing point of its tissues. For S. jarrovi there was no seasonal acclimatization of the supercooling limit (SL). In fact, during the more severe winter of this study the ability to supercool decreased significantly from the levels measured during the summer and second, more moderate winter. There was a significant and positive linear regression of SL on freezing point (FP), and this relationship has a higher elevation than that reported for reptiles as a whole. There appears to be an optimum constant acclimation temperature for maximum supercooling (i.e., about 25 C). Below this level the ability to supercool decreases. Although constant low-temperature exposure decreased supercooling ability, there was no such effect following daily cycled-temperature exposure (-2 C to 30 C). There was a significant lowering by dehydration of the SL and FP at constant temperatures from 15 to 25 C. At 25...

Sceloporus jarrovi *exhibits intraspecific differences in temporal and micro- habitat resource usage. During the summer months of 1974 and 1975, most adult activity occurred in the early morning while most juvenile activity occurred near noon. Lizards were active an average of only 2.5 days/wk. Because the animals were active on different days and at various times of the day, defended territories sometimes overlapped spatially. Terri- toriality of S. jarrovi is closely tied to the maintenance of an adequate food supply; a temporal distribution of territories may increase feeding efficiency. Perch site differences were also noted.

This study was designed to determine how food abundance affects territory size for the insectivorous lizard Sceloporus jarrovi. Observations and experiments were per- formed in the field in southeastern Arizona during 1971 and 1972 summers. Territories were defined as defended areas, and the convex polygon method was used to determine territorial boundaries. Preliminary studies showed that all adult and most juvenile lizards defended territories against lizards of the same species, size, and sex. Sex and body size influenced territory size. Within size classes, territories of 8 8 averaged more than twice territory size of Y Y. Lizards in the larger size class had territories more than twice those of smaller animals. Natural food abundance, determined with adhesive-coated Masonite? boards, was inversely correlated with territory size. Summer territories compressed significantly when food was added even though natural food supplies seemed adequate. Territories returned to initial sizes with the removal of additional food. Experiments involving the locations of concentrated food sources within the territory pro- vided some evidence for the hypothesis that ease of food obtainment may be an important factor in determining summer territorial size and location.

In the territorial iguanid lizard Holbrookia propinqua territory-holding males were found to court nonresident females more intensely than coresident females. Resident males also attempted to force copulation more frequently with nonresident females. These results indicate that males can operationally distinguish resident from nonresident females and suggest that males may recognize individual females. The selective forces underlying differential responses to resident and nonresident females presumably are related to differences in expected mating opportunities.

Black (Ctenosaura pectinata) and green (Iguana iguana) iguanid lizards were implanted with chronic electrodes in forebrain, orbital cavities and nuchal muscles; electrodes were also

The seasonal food habits of Anolis limifrons, an iguanid lizard, were studied by examining the stomachs of 512 individuals collected on Barro Colorado Island, Panama Canal Zone, during three periods. Frequency and length of prey and length of predators were determined. Frequency distributions of different size classes of potential prey were obtained from leaf litter and low vegetation samples. The lizards selected larger size classes of potential prey. All size classes of predators captured the smaller size classes of prey, but the larger prey were taken by larger predators. More female than male lizards had food in their stomachs. There was no wet season—dry season difference in frequency of food found in the stomachs.

Pristiguana brasiliensis, new genus and species, from the Upper Cretaceous Baurú Formation of Brazil, is the oldest fossil referable to the living lizard family Iguanidae. It resembles living primitive South American iguanids in some features, but also shows similarity to members of the related family Teiidae. Iguanid fossils do not appear in North America until the early Eocene, probably by waif dispersal from South America during the late Paleocene or early Eocene. A southern continental (Gondwanan) origin of iguanids is more plausible than the northern one often suggested.

1. 1. Mean O 2 consumption of controls at 35°C was 329 μ1/g per hr. 2. 2. Mean rate of heart beat/min of controls at 15,20,25,30 and 35°C was 43, 65,96,140 and 185 respectively. 3. 3. Mean ventilatory rate/min of controls at 15,20,25,30 and 35°C was 25,27, 31,35 and 37 respectively. 4. 4. Values of O 2 consumption, rate of heart beat and ventilatory rate determined for controls, sham-parietalectomized and parietalectomized individuals did not differ significantly ( P > 0·05) between treatments or between day 0 and day 30 within a treatment.

1. 1. Implants of progesterone were made in the brain, pituitary and subcutaneous locations in lizards (Sceloporus cyanogenys) during the phase of ovarian growth. 2. 2. Implants located in the hypothalamus were very effective in preventing futher ovarian development, an action that mimicked that of hypophysectomy. 3. 3. Implants in other regions of the brain, in the pituitary or subcutaneous locations were ineffective in preventing ovarian growth and subsequent ovulation. 4. 4. Plasma progesterone titers were not increased by progesterone implants.

Black (Ctenosaura pectinata) and green (Iguana iguana) iguanid lizards were implanted with chronic electrodes in forebrain, orbital cavities and nuchal muscles; electrodes were also

The neurosecretory system of the desert iguanid Dipsosaurus dorsalis consist of paired paraventricular and supraoptic nuclei from which four separate neurosecretory tracts arise and coalesce to form a common tract that runs through the median eminence region, where it comes into intimate contact with capillaries of the portal system, to the pars nervosa. Herring bodies were observed in both the median eminence and in the pars nervosa. In addition paired tracts from the paraventricular nuclei pass directly to the pars nervosa via a dorsal route without entering the median eminence. The paraventricular and supraoptic nuclei are connected at their anterior and posterior margins by bridges of neurosecretory cells. The numbers of neurosecretory cells, the dimensions of the hypothalamic centers and of individual cell nuclei were counted and measured. Round and oval cell nuclei were identified in both supraoptic and paraventricular areas, the former predominating in the paraventricular nuclei and the latter in the supraoptic nuclei.

Eutrombicula yunkeri is described as new from specimens collected from the Blackish Nightjar, Caprimulgus nigrescens , and an iguanid lizard, Tropidurus torquatus , taken in Surinam.

Fallisia effusa gen.nov., sp.nov. (Haemosporidiidea: Garniidae) is described in the teiid lizard, Neusticurus bicarinatus, from Pará State, north Brazil. Schizogony and gametogony both take place within thrombocytes and white cells of the peripheral blood. There is no development in the red blood cells, by which character the organism is differentiated from Garnia, the other known genus within the family. Another species, Fallisia modesta gen.nov., sp.nov., is described in the iguanid lizard, Tropidurus torquatus hispidus, also from Pará, Brazil. It is distinguished from F. effusa by its development principally in the lymphocytes, as opposed to the thrombocytes. There are other, striking morphological differences between the two species. It is recommended that great care is needed in the interpretation of so-called ‘exo-erythrocytic stages’ of saurian plasmodia, which may well really belong to members of the Garniidae, in mixed infections.

A description of the neotype of Liolaemus anomalus Koslowsky is given, with comments about its relationships, geographical variation and ecology. The comparison of new samples of this poorly known tropidurine lizard with the holotype of Phrynosaura werneri Müller suggests their synonymy., Material digitalizado en SEDICI gracias a la colaboración del Dr. Jorge Williams (FCNM-UNLP)., Facultad de Ciencias Naturales y Museo

In the previous paper Sites (1983) described several chromosome polymorphisms within three cytotypes of Sceloporus grammicus. It was concluded that evolution of these chromosomal rearrangements was probably not causally related to speciation. Several of the models discussed yielded specific predictions about population structure that are amenable to empirical testing with an independent data set. This study reports on allozyme variation within and among the same three cytotypes (2n = 32, 2n = 34, and 2n = 36) in the same geographic area as those studied by Sites (1982a) and focuses on three major points of interest: (1) genetic divergence within and among these cytotypes; (2) population subdivision as determined by the distribution of allele frequencies across the population samples; and (3) levels of heterozygosity maintained in each of these cytotypes.

In the course of field research in South America, William E. Duellman and his associates obtained specimens of an undescribed iguanid lizard in the Paso El Choique area in southern Provincia de Mendoza, Argentina. A careful comparison of these lizards with other Argentine iguanids revealed that the new species is a member of the widespread, Andean-Patagonian genus Liolaemus; however, it is easily distinguished by a significant combination of several morphological characters from its congeners. In recognition of the discoverer of this new iguanid, it herewith is named after Dr. William E. Duellman, who has advanced so appreciably field and taxonomic studies on the herpetofauna of South America., Se describe una nueva especie argentina de iguánido tropidurino, Liolaemus duellmani, de las regiones rocosas volcánicas de la Cordillera Andina, en el Sur de la Provincia de Mendoza, Paso El Choique, a 2000-2400 m de altura. La nueva forma, que se diferencia netamente de todas las especies conocidas del género, es larga hasta 170 mm, y se caracteriza por la lepidosis heteronota, las escamas dorsales casi lisas, imbricadas y casi yuxtapuestas, las escamas ventrales mucho más grandes que las dorsales, un número relativamente alto de escamas alrededor del cuerpo (85-90) y una coloración de bandas transversales oscuras, escotadas posteriormente, sobre un fondo grisáceo rojizo, jaspeadas de puntos blancos azulados. La forma que más se le aproxima es Liolaemus ruíbali de los Andes de Uspallata, Mendoza, la que todavía difiere de L. duellmani por ser mucho más pequeña, por tener cola más corta y un número inferior de escamas alrededor del cuerpo, escamas laterales más uniformes y un patrón de coloración muy diferente. Se ponen en evidencia algunas convergencias morfológicas entre la nueva forma y las especies del género Ctenoblepharis., Material digitalizado en SEDICI gracias a la colaboración del Dr. Jorge Williams (FCNM-UNLP)., Facultad de Ciencias Naturales y Museo

Enclosed populations of fence lizards demonstrate a stereotyped and stable social structure. Animals can be categorized by aggressive type allowing for a comparison of normal and altered behavior. The normal patterns of social behavior are reliably abolished by bilateral lesions in the amygdaloid nuclei: nucleus sphericus, nucleus ventromedialis, nucleus of the lateral olfactory tract, posterior hyperstriatum or posterior one third of the dorsal ventricular ridge. The behavioral change seen after ablation reflects a lack of responsiveness to visual social signals. After such lesions lizards no longer assert dominance or respond with appropriate subordinance behavior. These animals also manifest a general decrease in activity, attentiveness and responsiveness. Bilateral lesions in the anterior two thirds of the dorsal ventricular ridge do not reliably change social behavior but do produce the decrease in spontaneous behavior.

The myrmicine ant Crematogaster brevispinosa attacks juveniles and possibly adults of the iguanid lizard, Anolis lineatopus; bitten juveniles usually run away. A juvenile A. lineatopus caged together with 38 C. brevispinosa specimens died within hours due to attacks by these ants. On a study site in Kingston, Jamaica, fewer A. lineatopus were found to inhabit a patch densely occupied by C. brevispinosa than a structurally similar patch where this ant was not present. Similarly, fewer A. lineatopus eggs and anole egg-shells were found in the patch with C. brevispinosa than in that where this species was absent. These findings bear directly on the innate ant avoidance response of juvenile A. lineatopus demonstrated in the laboratory.