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Colic modification in iguanine lizards
Abstract
All lizard species of the subfamily Iguaninae except Amblyrynchus cristatus possess from one to eleven transverse valves in the proximal colon. Valves are of two kinds: circular (sometimes with a sphincter valve) or semilunar. Circular valves (if present) always occur proximally to semilunar valves. Intraspecific variation in the number and type of valves is small, but increase with modal number of valves. No significant ontogenetic change in number of valves could be demonstrated. Colic valves in iguanine lizards apparently evolved as simple infoldings of the medical colic wall.
Comparisons are made with colic modifications occurring in other lizard families. Herbivorous species of the Scincidae, Agamidae, and Iguanidae are the only lizards known to exhibit colic partitioning, suggesting that the evolution of these structures is intimately related to the evolution of herbivory in these lizards. The potential taxonomic and phylogenetic importance of lizard colon anatomy is discussed.
... Herbivorous lizards may impact plant reproduction by, for example, pollinating flowers, dispersing seeds, and enhancing seed germination. Iverson (1985) addressed the role of herbivorous lizards in seed dispersal by removing seeds from feces of the endangered Rock Iguanas, Cyclura carinata and C. rileyi, and comparing germination rates to those of noningested seeds. Germination rates did not increase, but seeds were not harmed by ingestion. ...
... In this study, we examined the roles played in seed dispersal and germination by two species of endangered iguanas, Cyclura cornuta and C. ricordii, in the Parque Nacional Isla Cabritos, Dominican Republic. Using the protocol of Iverson (1985), we tested the null hypothesis that germination rates of seeds ingested and defecated by iguanas would not differ significantly from those of noningested seeds. ...
... Although both species of iguanas are common in the area, we did not observe the iguanas defecating and could not assign the samples to species. However, the digestive systems of both species are similar (Iverson, 1980), so effects on seeds are not likely to differ. The seeds in the scats were identified as Ziziphus rignoni, the fallen fruits of which are commonly consumed by iguanas (S. ...
... Scale terminology follows Smith (1946), skin fold terminology follows Frost (1992), and skeletal terminology follows de Queiroz (1987~) and Oelrich (1956). Characters from the literature (Bailey, 1928;Barbour and Noble, 1916;de Queiroz, 1987a,b;Dumkril, 1856;Etheridge and de Queiroz, 1988;Iverson, 1980;Lazell, 1973;Norell and de Queiroz, 1991;Schwartz and Carey, 1977;Stejneger, 1891;Zug, 1971) were reevaluated when specimens were available. Character state polarity was determined by the outgroup method (Maddison et al., 1984;Watrous and Wheeler, 1981). ...
... 65. Colic wall (de Queiroz, 1987a;Iverson, 1980): (0) forms one or more transverse valves; (1)forms numerous irregular transverse folds. The anatomy of the colon was originally studied by Iverson (1980) and later used by de Queiroz ( 1 9 8 7~) as a systematic character. ...
... 65. Colic wall (de Queiroz, 1987a;Iverson, 1980): (0) forms one or more transverse valves; (1)forms numerous irregular transverse folds. The anatomy of the colon was originally studied by Iverson (1980) and later used by de Queiroz ( 1 9 8 7~) as a systematic character. Iverson surveved all ieuanid " species, except Brachylophus vitiensis, Cyclura collei, C. pinguis, C. rileyi, Dipsosaums catalinensis, Iguana delicatissima, Sauromalus ater. ...
A systematic study of the chuckwallas (genus Sauromalus) is presented which combines a traditional monographic revision with a modern phylogenetic analysis. Included are a reassessment of alpha taxonoiny and geographic variation, a hypothesis of evolutionary relationships, a reevaluation o f the relationships of Sauromalus to other iguanid genera, and an examination of trends in morphology, biogeography, and natural history within Sauromalus in light ofthe recovered phylogeny.
... Most herbivorous reptiles, for example, share a suite of characteristics that are considered to facilitate the procurement, digestion, and assimilation of plants. Among these characteristics, conventional wisdom once held that herbivory was restricted to reptiles with large body sizes that lived in warm climates (Pough, 1973;Wilson and Lee, 1974;Iverson, 1980Iverson, , 1982Van Devender, 1982;Zimmerman and Tracy, 1989;Cooper and Vitt, 2002;Vitt, 2004). From an ecophysiological perspective, these ''rules'' of herbivory (sensu Espinoza et al., 2004) make good sense. ...
... Additionally, foraging for plants is considered to be less energetically demanding than chasing small arthropods (Pough, 1973). Large body cavities can also accommodate the long and voluminous guts needed to digest plant tissues (Iverson, 1980(Iverson, , 1982. Second, warm climates provide opportunities to achieve the high body temperatures that are apparently needed to digest plants (Zimmerman and Tracy, 1989;Schall and Dearing, 1994;Espinoza et al., 2004;Vitt et al., 2005). ...
... More generally, how do small-bodied lizards, with their small guts, assimilate sufficient energy and nutrients from plant tissues? For example, aside from having short guts on an absolute scale, herbivorous liolaemids lack the semilunar valves or colic septae that have been reported for larger herbivorous lizards (Iverson, 1980(Iverson, , 1982O'Grady et al., 2005). Also, it is not known whether herbivorous liolaemids, like other herbivorous lizards (Nagy, 1977;McBee and McBee, 1982;Troyer, 1991;Foley et al., 1992;Bjorndal, 1997), harbor the hindgut microsymbionts (primarily bacteria and protozoa) that are responsible for fermenting plant tissues (e.g., hemicellulose, cellulose) into volatile fatty acids that are absorbed by their host's gut. ...
Herbivory is generally thought to be restricted to reptiles with large body sizes that live in warm climates. We show that Liolaemus poecilochromus is primarily herbivorous (>80% plants in diet) even as juveniles, making them the smallest herbivorous reptile known. We detected relatively few differences in diet between the sexes, despite male-biased sexual dimorphism in head and body size. Adults consumed more mites and flowers than juveniles, and we detected a weak ontogenetic shift from omnivory to herbivory that is attributable to the lower volumetric consumption of plants by juvenile males. We discuss the abiotic and biotic conditions that likely selected for herbivory in this and other small-bodied, high-elevation Liolaemus. Herbivoría en general se cree que se limita a los reptiles con cuerpos grandes que viven en climas cálidos. Mostramos que Liolaemus poecilochromus es principalmente herbívora (>80% de plantas en la dieta) incluso los juveniles, convirtiéndolo por esto en el reptil herbívoro más pequeño conocido. Asimismo, detectamos pocas diferencias en la dieta entre los sexos, a pesar del dimorfismo sexual a favor de los machos en el tamaño de la cabeza y el cuerpo. Los adultos consumen más ácaros y flores que los juveniles, por otro lado se detectó un cambio ontogenético débil de omnivoria a herbivoría en los machos juveniles, debido a su bajo consumo de plantas. Discutimos las condiciones abióticas y bióticas que probablemente favorecieron la herbivoría en este y otros Liolaemus de cuerpo pequeño y alta elevación.
... Indeed, large body size does not only confer an advantage through the lower massspecific metabolic requirements but also provides for a large abdomen and thus gut volume and surface area. Moreover, the hindgut is often subdivided into compartments by means of caecal valves providing a fermenting chamber which has been suggested to allow for a more efficient digestion of the plant matter by endosymbionts (Iverson, 1980). Although the consumption of plant matter has evolved many times independently in lizards (Cooper & Vitt, 2002), omnivorous lizards have generally been considered to be relatively unspecialized opportunistic generalists. ...
... Although the consumption of plant matter has evolved many times independently in lizards (Cooper & Vitt, 2002), omnivorous lizards have generally been considered to be relatively unspecialized opportunistic generalists. However, more recent studies have indicated distinct adaptations of the jaw and digestive system in these omnivores involving the evolution of specialized teeth, high bite forces and the development of caecal valves (Iverson, 1980;Espinoza et al., 2004;Herrel, Vanhooydonck & Van Damme, 2004a;Herrel et al., 2008). ...
... Moreover, many of these large herbivores possess specialized teeth (e.g. Hotton, 1955;Robinson, 1976) and hindguts that function as fermenting chambers characterized by the presence of caecal valves (Iverson, 1980;Troyer, 1984;Foley et al., 1992;Herrel et al., 1999a). ...
The evolution of large body size has often been considered a key trait allowing the evolution of herbivory in lizards. Although many omnivorous lizards appear unspecialized, they typically show high bite forces, allowing them to reduce tough and fibrous plant matter. In contrast, true herbivores often show a suite of morphological and physiological specializations, allowing them to efficiently process and assimilate plant material. Moreover, many specialized herbivores have a large body size, thus likely relaxing constraints on bite-force generation given that bite force increases with increasing body mass. In this study, we test whether large herbivorous lizards of the genus Uromastyx have relatively lower bite forces for their body size compared with a medium-sized congener. No differences in bite force or head dimensions were observed between the two species or between both sexes in our sample. Moreover, bite force scaled with positive allometry relative to jaw length, suggesting that larger animals have disproportionately large bite forces. This suggests that even in the largest species, constraints on bite-force generation are still strong, possibly due to the demands imposed on the jaw system by the mechanical properties of the diet.
... Approximately 11% of extant lizards are omnivores (i.e., animals that consume greater than 10% plants), with a minimum of 32 independent evolutionary origins of this dietary strategy (Cooper and Vitt, 2002). In contrast, herbivory is a comparatively rare development and is present in no extant crocodylians and roughly 2% of extant lepidosaurs, although these numbers may increase with additional research because detailed dietary information is lacking for a large number of extant squamate species (Pough, 1973;Iverson, 1980;Jaksic and Schwenk, 1983;Zimmerman and Tracy, 1989;King, 1996;Cooper and Vitt, 2002;Espinoza et al., 2004). This paucity of herbivorous taxa has led to the suggestion that functional constraints restricting the development of herbivory exist in lepidosaurs (Sokol, 1967;Pough, 1973), although most of these studies ignore evidence for lepidosaur herbivory in the fossil record (King, 1996;Nydam, 1999;Nydam and Cifelli, 2005;Jones, 2009). ...
... Tetrapod tooth morphology is generally thought to correspond to diet (e.g., Hotton, 1955;Presch, 1974;Evans et al., 2007), but there has been relatively little research conducted on the osteological specializations related to lepidosaur diet (but see Hotton, 1955;Throckmorton, 1976;Montanucci, 1989;Schwenk, 2000;Cooper and Vitt, 2002;Metzger and Herrel, 2005;Jones, 2008;Daza et al., 2009;Jones, 2009;Curtis et al., 2011;Jones et al., 2012). Most existing research has focused on body size or specializations of the internal organs (Pough, 1973;Iverson, 1980;Troyer, 1984a,b;Herrel et al., 2004;Herrel et al., 2008;Vervust et al., 2010). The few studies that have focused on dentition suggest that tooth morphology correlates with diet in living lepidosaurs, but this idea has been tested infrequently and mostly qualitatively in scattered clades (Hotton, 1955;Montanucci, 1968;Robinson, 1976;Throckmorton, 1976;Sumida and Murphy, 1987;Mateo and Lopez-Jurado, 1992;Barrett, 2000;Herrel et al., 2004;Vervust et al., 2010). ...
Living saurian reptiles exhibit a wide range of diets, from carnivores to strict herbivores. Previous research suggests that the tooth shape in some lizard clades correlates with diet, but this has not been tested using quantitative methods. I investigated the relationship between phenotypic tooth complexity and diet in living reptiles by examining the entire dentary tooth row in over 80 specimens comprising all major dentigerous saurian clades. I quantified dental complexity using orientation patch count rotated (OPCR), which discriminates diet in living and extinct mammals, where OPCR-values increase with the proportion of dietary plant matter. OPCR was calculated from high-resolution CT-scans, and I standardized OPCR-values by the total number of teeth to account for differences in tooth count across taxa. In contrast with extant mammals, there appears to be greater overlap in tooth complexity values across dietary groups because multicusped teeth characterize herbivores, omnivores, and insectivores, and because herbivorous skinks have relatively simple teeth. In particular, insectivorous lizards have dental complexities that are very similar to omnivores. Regardless, OPCR-values for animals that consume significant amounts of plant material are higher than those of carnivores, with herbivores having the highest average dental complexity. These results suggest reptilian tooth complexity is related to diet, similar to extinct and extant mammals, although phylogenetic history also plays a measurable role in dental complexity. This has implications for extinct amniotes that display a dramatic range of tooth morphologies, many with no modern analogs, which inhibits detailed dietary reconstructions. These data demonstrate that OPCR, when combined with additional morphological data, has the potential to be used to reconstruct the diet of extinct amniotes. J. Morphol., 2017.
... The diet of lizards can also be a factor in shaping the morphologies and performance of lizards. For example, herbivory has evolved independently a number of times in lizards (Cooper & Vitt, 2002; Espinoza et al., 2004), and work on the dental and soft tissue specialization structures (Hotton, 1955; Iverson, 1980 Iverson, , 1982 Mateo & López-Jurado, 1992 Dearing 1993; Barrett 2000) as well as the feeding apparatus of some herbivorous species (Throckmorton 1976; Herrel et al. 1998a Herrel et al. ,b, 1999a,b) have shown that herbivorous species possess many morphological specializations (Iverson, 1980Iverson, , 1982 Greene, 1982; Troyer 1984) that allow them to specialise on a diet of vegetation (Harlow et al., 1976; Troyer, 1987). Convergence in the functional aspects of herbivores have been investigated (Throckmorton, 1976; Herrel, 1998b; Stayton, 2006), and much of the convergence in morphology (i.e. ...
... The diet of lizards can also be a factor in shaping the morphologies and performance of lizards. For example, herbivory has evolved independently a number of times in lizards (Cooper & Vitt, 2002; Espinoza et al., 2004), and work on the dental and soft tissue specialization structures (Hotton, 1955; Iverson, 1980 Iverson, , 1982 Mateo & López-Jurado, 1992 Dearing 1993; Barrett 2000) as well as the feeding apparatus of some herbivorous species (Throckmorton 1976; Herrel et al. 1998a Herrel et al. ,b, 1999a,b) have shown that herbivorous species possess many morphological specializations (Iverson, 1980Iverson, , 1982 Greene, 1982; Troyer 1984) that allow them to specialise on a diet of vegetation (Harlow et al., 1976; Troyer, 1987). Convergence in the functional aspects of herbivores have been investigated (Throckmorton, 1976; Herrel, 1998b; Stayton, 2006), and much of the convergence in morphology (i.e. ...
Lizards utilize many different niches across a large variety of habitats. As a result of selective pressures exerted by the particular environments, many lizards in similar habitats have been shown to exhibit convergent morphologies. Classic examples of morphological convergence in similar habitats include the African cichlid fish and the anole lizards in the Antilles, but these are far from the only examples documented. Selection, however, has been thought to act first upon the performance of a species, which leads to a morphology optimal for a particular performance capacity. In lizards, there are numerous studies documenting the convergence in functional capacities within particular environments, but relatively few that have investigated the link between environment, functional capacity and morphology. The few studies that have been conducted investigating this link have shown that particular environments exert selective pressures for a particular performance capacity and the morphology that allows for optimal performance within that environment evolved thereafter. Such convergent evolution has been shown to be irrespective of genetic relationships between the lizards studied, and in some instances have led to misclassifications of species. Here, we review the literature that investigates the functional capacities of lizards, in relation to their morphologies, and the link between their phenotypes and the environment.
... The fact that recent lizards did not succeed in radiating into the herbivorous niche has been a much debated topic in the past (SzARS?, 1962;OSTROM, 1963;SOKOL, 1967;POUGH, 1973;IVERSON, 1980IVERSON, , 1982. The absence of such a radiation is rather unexpected as there are some substantial advantages to a herbivorous life-style. ...
... Still, adaptations of the dental structures have been demonstrated for a number of herbivorous iguanid (HOTTON, 1955;MONTANUCCI, 1968) and agamid (COOPER et al., 1970;COOPER & POOLE, 1973;ROBINSON, 1976;THROCK-MORTON, 1979) lizards. Additionally it turns out that a large number of "true" herbivores have a partitioned colon with large numbers of commensal micro-organisms and nematodes (IVERSON, 1980;TROYER, 1984;BJORNDAL et al., 1990;FOLEY et al., 1992). A partitioned colon slows down the food passage (TROYER, 1984;KARASOV et al., 1986) and provides a fermenting chamber, thus increasing the digestive efficiency. ...
A model of static bite force during the power phase is used to investigate the relationship between the feeding ecology (herbivorous vs. animalivorous) and biomechanics of the jaw system in four species of lizards. For the analysis the bite model of Herrel et al. (1998) is used. The model calculates both the bite and joint forces and the moments at the quadratosquamosal joint for a range of orientations of food reaction forces. No relative jaw movements during the power phase of biting are observed (based on cineradiography) in any of the examined species, thus excluding grinding mechanisms as an adaptation to a herbivorous diet. However, trends in magnitude and orientation of the joint forces and required and remaining moments at the quadratosquamosal joint are similar in species with similar food preferences. Herbivorous lizards bite harder and show lower joint forces for a given bite force than non-herbivorous species do. It is argued that this difference might be a more general characteristic of herbivorous lizards and that a high bite force has an adaptive value for these species. Whereas, in lizards, dental grinding mechanisms are presumably not a prerequisite for a herbivorous diet, adaptations of the digestive apparatus and the development of a relatively high bite force probably are. Additionally it is argued that the shift of the insertion site of the temporal ligament can be considered as a preadaptation for herbivory in lizards. A hypothetical transformation series of the bauplann of the skull departing from a basic lepidosaurian stock and leading to the skull system in extant herbivorous lizards is proposed.
... They have specialized blade-like teeth for shearing plant food (Hotton, 1955; Montanucci, 1968) or massive teeth for crushing (Throckmorton, 1976). Their colons are enlarged (Henke, 1975; Iverson, 1980) and contain intestinal ¯ora that digest cellulose and intestinal structures , that presumably slow the passage of food, are present in some herbivorous lizards (Iverson, 1982; McBee & McBee, 1982). They are present in those species that rely heavily on leaves as food, such as iguanids and Hydrosaurus pustulosus (Taylor, 1922; Iverson, 1982). ...
... Comparative studies of the functional morphology of ingestion in relation to degree of omnivory might also be revealing. The intestines of folivores are enlarged, their colons containing valves not found in other lizards (Henke, 1975; Iverson, 1980). Iverson (1982) found no colic valves in omnivores, which may be a speci®c adaptation for folivory. ...
Animal diets crucially affect fitness, yet many aspects of their ultimate
determinants are unknown. The distribution and extent of herbivory in lizards, its evolutionary
history, and ecological factors that may favour it are discussed. Most lizards are exclusively or
primarily carnivorous, yet many species eat some plants and a few are almost exclusively herbivorous.
Based on a literature survey of diets of over 450 lizard species, the distribution and degree of
omnivory and herbivory are described. Some plants occur in the diets of slightly over half of lizard
species, and plants formed 10% or more of the dietary volume of 12.1% of species, and 90% or more of
the diet of 0.8% of species. The greatest percentage of omnivorous species (> 10% plant diet),
over 30% in each, and highest mean percentage plant matter in the diet are in Iguanidae,
Corytophanidae, Gerrhosauridae, Agamidae, Xantusiidae, and Tropiduridae. Numerous other omnivores
occur in Lacertidae and Scincidae and fewer in several additional families. Herbivorous lizards
(> 90% plant volume) tend to be folivorous and to possess adaptations for processing leaves,
including specialized dentition for cutting or reducing leaves, elongated intestines, colic valves
that slow passage of food, and intestinal flora that digest cellulose. Omnivorous lizards lacking
such specializations may eat some leaves, but consume much more fruit, flowers, and seeds, plant
parts that are easy to digest, likely to be very abundant seasonally, and may be highly nutritious.
Some lizards eat nectar and pollen; even sap is eaten by at least one gecko. Ontogenetic increase in
plant consumption and decrease in prey consumption is known, but its generality has been
controversial. Such ontogeny has been demonstrated in three iguanid species, a skink, a lacertid,
two tropidurids, a phrynosomatid, and two corytophanids, but it does not occur in some other species. The
importance of specific foods may vary with age. Omnivory and/or herbivory have originated in many lizard
families, with at least nine origins in Iguania and 23 in Scleroglossa. Origins have been rare in Gekkonoidea
and Anguimorpha and common in Scincomorpha, especially in Lacertidae and Scincidae. Losses of omnivory have
been much less frequent than gains. Only a few origins can account for all the herbivory in lizards.
Concentrated changes tests show that there is a significant association in Lacertidae, Lacertiformes,
Lacertoidea, Scincidae, and Scleroglossa between insularity and omnivory. Insular lizards may broaden
their diets to compensate for limited availability of prey. Addition of other factors that reduce availability
of prey, i.e. extreme aridity and cave-dwelling, to insularity, strengthened the relationship to omnivory
in Lacertidae and Lacertoidea. We were unable to demonstrate a role of aridity independent of insularity, but
present anecdotal evidence suggests that it may promote evolution of plant consumption. Large body size in
lizards has long been associated with herbivory, and more recently, with omnivory in lacertid lizards. Using
a conventional regression approach in which each species is considered to supply an independent data point,
this relationship was confirmed for all lizards. Although larger species have diets with more plants, plant
consumption accounts for only 9% of the variation in body length, which is not surprising given that other
factors such as predation, competition, and sexual selection affect body size. The frequency of transitions
body size associated with transitions to omnivory or carnivory was also examined. In Iguania, Scleroglossa,
and all lizards, transitions supporting the hypothesis that omnivory favours increase in body size were significantly
more frequent than non-supporting transitions. This suggests that substantial plant consumption favours
evolution of larger size, probably because of the energetic considerations first presented by Pough (1973).
Because actively foraging lizards move widely through the habitat to locate prey and tongue-flick to locate
prey by chemical cues, we hypothesized that they may be more likely to evolve omnivory than ambush foragers,
which wait motionless for prey and do not tongue-flick to locate or identify prey. The basis of this prediction is that
the wider seaching of active foragers predisposes them to contact with a greater variety and quantity of plants
and that chemosensory tongue-flicking used by omnivores to identify plant food might be easier to evolve in active
foragers that already use pre-chemical discrimination. The prediction is supported by a significantly greater
per species frequency of origins of omnivory by active foragers than by ambushers. A scenario for the progressive
evolution of omnivory and herbivory from ancestrally carnivorous lizards is discussed.
... We were not able to determine experimentally the assimilation efficiency of iguanas feeding on Batis. However, it is likely to be lower than for algae, both because marine iguanas have a gut morphology specialized (simplified) for feeding on algae (Iverson 1980(Iverson , 1982, and because we frequently observed undigested fragments of Batis in the feces of individuals feeding within the Batis patch, suggesting some digestive difficulty. ...
... The hindgut of marine iguanas is apparently specialized for processing the simplified cell structure of the filamentous red and green algae common in the cold waters of the Galápagos Islands ( Wikelski et al. 1993). They completely lack the 8-12 septa found in the hindgut of all other iguanid species, which probably function to slow down food passage (Iverson 1980(Iverson , 1982. Indeed, we frequently observed undigested pieces of Batis in the feces of iguanas on Seymour. ...
Foraging theory predicts that dietary niche breadth should expand as resource availability decreases. However, Galápagos marine
iguanas often die during algae shortages (El Niños) although land plants abound where they rest and reproduce. On Seymour
Norte island, a subpopulation of iguanas exhibited unique foraging behavior: they consistently included the succulent beach
plant B. maritima in their diet. We investigated the consequences of land-plant feeding for body size and survival. Batis-eaters supplemented their algae diet both before and after intertidal zone foraging, and more Batis was eaten during tides unfavorable for intertidal zone foraging (dawn and dusk). Larger, energy-constrained iguanas fed more
on land than did smaller animals. Compared to intertidal zone algae, Batis was 39% lower in caloric content (1.6 vs. 2.6 kcal g–1 dry mass), 56% lower in protein (8.3 vs. 18.9% dry mass) and 57% lower in nitrogen (1.3 vs. 3.0% dry mass). In spite of its
lower nutrient value, iguanas that supplemented their diet with this plant were able to attain nearly twice the body size
of other iguanas on the island. Age estimates indicate that many Batis-eaters survived repeated El Niño episodes during which animals of their relative size-class experienced high mortality on
other islands. The larger animals were, however, completely dependent upon this supplementary source of food to maintain condition,
and all perished in the 1997–1998 El Niño when high tides inundated and killed Batis on Seymour Norte Island. We hypothesize that Batis feeding developed as a local foraging tradition, and that dietary conservatism and strong foraging site fidelity explain
why the inclusion of land plants in the diet has been observed in only a single population. Ultimately, a unique algae-adapted
hindgut morphology and physiology may limit a switch from marine to terrestrial diet.
... Iguanines have at least some caudal vertebrae with 2 pairs of bony projections (Etheridge 1967) as well as folds in the colon and hind marginal teeth with laterally compressed crowns often with many cusps (Etheridge 1964;Iverson 1980Iverson , 1982. Ctenosaura refers to a comb-like structure of enlarged scales on the dorsal crest, and members are distinguished by a series of enlarged whorls of spiny scales on the tail ( Fig. 1; Bailey 1928, de Quieroz 1987a. ...
Ctenosaura similis (Black Spiny-tailed Iguana) is native to Mexico and Central America, where it is a wide-ranging habitat-generalist that is well adapted to human-altered environments. Black Spiny-tailed Iguana is considered one of the larger, heavier iguanid species, identified by its coloration and a series of enlarged whorls of spiny scales on the tail. Despite harvest rates for human consumption and the pet trade, Black Spiny-tailed Iguana is currently considered a species of least concern in their native range. There have been several introductions outside of their native range, many of which have become established due to their generalist nature. In Florida, Black Spiny-tailed Iguana was first introduced in 1979 and has been reported in 24 counties. Early removal efforts of other introduced iguanids such as Ctenosaura pectinata (Mexican Spiny-tailed Iguana) and Iguana iguana (Green Iguana) could serve as case studies to develop and implement eradication and management plans for this species. We provide a comprehensive summary of natural history findings on Black Spiny-tailed Iguana, including management methods and potential ecological impacts as an invasive species in the southeastern United States.
... These include the switch to partial herbivory by Coachella Fringe-toed Lizards (Uma inornata) in times of abundant flowers (Durtsche 1992). Iverson (1980Iverson ( , 1982 examined the gut structure of iguanines and determined that Dipsosaurus is the least specialized for digestion of plant material. The high preferred body temperature of the Desert Iguana may facilitate digestion by this relatively small iguanine herbivore (Mautz and Nagy 1987). ...
... Iguanas are limited in the amount of forage they can ingest and process in a given time period. For example, the presence of colic folds in largely herbivorous iguanas is thought to increase absorptive surface area, provide microhabitats for microbes that aid in the breakdown and fermentation of plant material, and slow the movement of food for increased digestive action (Iverson 1980;Mackie et al. 2004). Therefore, the near doubling of the nitrogen content we measured in plants on Allen Cay (Fig. 4) would, thus, translate into greater growth potential for the iguanas on Allen Cay as they likely absorb more nutrients per unit time than their conspecifics on islands with lower nutrient quality plants and supports our hypothesis that high nutrient density is driving large body size in these iguanas. ...
We utilized natural experiment opportunities presented by differential conditions (presence/absence of seabirds and invasive species) on cays in the Bahamas to study whether interisland variations in food resources contributed to gigantism in Allen Cays Rock Iguanas (Cyclura cychlura inornata). We analyzed the stable carbon (δ¹³C) and nitrogen (δ¹⁵N) isotope values from iguana tissues and resources from each island food web to test the predictions that (1) food webs on islands with seabirds exhibit the influence of marine subsidies from seabird guano, whereas those from non-seabird islands do not, and (2) size differences in iguanas among cays were due to either (a) supplemental food availability from mice and/or seabird carcasses killed by barn owls (Tyto alba) and/or (b) access to more nutrient-rich vegetation fertilized by seabird guano. Food web components from the seabird island (Allen Cay) had 5–9‰ higher δ¹⁵N values than those on the other cays and Allen Cay plants contained nearly two times more nitrogen. Bayesian stable isotope mixing models indicated that C3 plants dominated iguana diets on all islands and showed no evidence for consumption of mice or shearwaters. The iguanas on Allen Cay were ~ 2 times longer (48.3 ± 11.6 cm) and ~ 6 times heavier (5499 ± 2847 g) than iguanas on other cays and this was likely from marine-derived subsidies from seabird guano which caused an increase in nitrogen concentration in the plants and a resultant increase in the δ¹⁵N values across the entire food web relative to non-seabird islands.
... Cellulose and other plant foods are digested in the anterior colon. The proximal colon contains two transverse valves: a circular valve and a semilunar valve ( Iverson, 1980). Cellulose from plant foods is digested by gut commensal flora. ...
There are no standard guidelines for the treatment of cryptosporidiosis in reptiles. The aim of this study was to evaluate the efficacy of two cryptosporidiosis therapies in captive green iguanas. Eight green iguanas aged 2–6 years, including 6 (1 ♂ and 5 ♀) animals with chronic diarrhea, received treatment for cryptosporidiosis. The presence of Cryptosporidium sp. oocysts was determined in 8 iguanas (100%), Isospora sp. oocysts were detected in 3 animals (37.5%), and Oxyuridae eggs were observed in 5 iguanas (62.5%). The animals were divided into two therapeutic groups (A and B). Group A iguanas were administered halofuginone (Halocur, 0,50 mg/ml Intervet Productions S.A., France) at a dose of 110 mg/kg body weight (BW) every 7 days for 5 weeks. Group B animals were administered sulfadiazine and trimethoprim (Norodine Vet Oral Paste sulfadiazine 288,3 mg/g, trimethoprim 58 mg/g, ScanVet Animal Health A/S, Denmark) at 75 mg/kg BW per os every 5 days for 5 weeks and spiramycin and metronidazole (Stomorgyl, spiramycin 1500000 IU, metronidazole 250 mg, Merial, France) at 200 mg/kg BW every 5 days for 5 weeks. Both groups received hyperimmune bovine colostrum and subcutaneous fluids. Before treatment, the average number of Cryptosporidium sp. oocysts in 1 g of feces was determined at 1.71 * 105 (±313,262.44) in group A and 1.56 * 105 (±262,908.53) in group B; the average number of Isospora sp. oocysts was determined at 3.53 * 103 (±1747.38), and the average number of Oxyuridae eggs was determined at 810 (±496.74). Blood tests were performed once before treatment. The results of blood morphology and biochemistry tests before treatment revealed leukocytosis with a significant increase in heterophile and monocyte counts in all animals. Dehydration, elevated hematocrit values and low levels of Na+, Ca2+, PO4− and Cl− ions were observed in 6 iguanas. Two iguanas died during treatment. The gross necropsy revealed acute inflammation of gastric and duodenal mucosa, mucosal ecchymoses in the gastrointestinal tract, hepatomegaly and liver congestion, cholecystitis, enlarged kidneys and renal edema and congestion, cystitis, and an absence of fat bodies. Parasites were not detected in any developmental form after 40 days of therapy and during an monthly 18-month follow-up period. Effective treatment of cryptosporidiosis in reptiles minimizes the adverse consequences of disease, improves the animals’ well-being and decreases euthanasia rates.
... aun cuando esta constituye una especie abundante y está distribuida en todo el cayo. Según Iverson (1980) C. carinata y C. cornuta solamente consumen los frutos de esta planta y evitan otras partes con mayor concentración de alcaloides lo que refleja una selección de recursos alimentarios. ...
Cyclura nubila nubila is an endemic subspecies of Cuba and it has been listed as Vulnerable in the IUCN Red List. The present investigation was developed in November 2013 and February 2014 in Caguamas and Palomo cays, respectively. Thirty-seven fecal pellets were collected through fixed transects on sandy coast vegetation and subsequently moistened with water and alcohol to separate and identify diet‘s components. Nine species of plants in Caguamas and four in Palomo were identified as part of iguana‘s diet. The most frecuent plant species were Conocarpus erectus, Setaria parviflora and Thalassia testudinum in Palomo and Cochorus hirsutus in Caguamas. In Palomo 45% of fecal pellets contained corporal parts of dragonflies and 5% parts of crabs. The consumption of animal matter is due to the low floristic diversity of Palomo cay. The iguana‘s diet in Caguamas included more plant components mainly fruits. This study contributes to increase knowledge of trophic ecology and management of the species in the archipelago of Jardines de la Reina.
... aun cuando esta constituye una especie abundante y está distribuida en todo el cayo. Según Iverson (1980) C. carinata y C. cornuta solamente consumen los frutos de esta planta y evitan otras partes con mayor concentración de alcaloides lo que refleja una selección de recursos alimentarios. ...
Cyclura nubila nubila is an endemic subspecies of Cuba and it has been listed as Vulnerable in the IUCN Red List. The present investigation was developed in November 2013 and February 2014 in Caguamas and Palomo cays, respectively. Thirty-seven fecal pellets were collected through fixed transects on sandy coast vegetation and subsequently moistened with water and alcohol to separate and identify diet's components. Nine species of plants in Caguamas and four in Palomo were identified as part of iguana's diet. The most frecuent plant species were Conocarpus erectus, Setaria parviflora and Thalassia testudinum in Palomo and Cochorus hirsutus in Caguamas. In Palomo 45% of fecal pellets contained corporal parts of dragonflies and 5% parts of crabs. The consumption of animal matter is due to the low floristic diversity of Palomo cay. The iguana's diet in Caguamas included more plant components mainly fruits. This study contributes to increase knowledge of trophic ecology and management of the species in the archipelago of Jardines de la Reina.
... Obstructed animals may present with depression, anorexia and/or vomiting (Anderson, 1992;Wellehan and Gunkel, 2004). For an adequate interpretation of imaging knowledge about the gastrointestinum anatomy of the green iguana is required (Iverson, 1980;Smith et al., 2001). Diagnostic imaging like x-ray, ultra-sound, computed tomography (CT) and endoscopy should be combined to reliably diagnose the localization of the foreign body (Hernandez-Divers, 2001;Schumacher and Toal, 2001;Banzato, 2013). ...
Introduction:
This case report includes different diagnostic imaging methods for localization of textile foreign bodies in reptiles and shows the limitations and advantages of these methods. A six-year-old, male, green iguana was presented to our clinic after ingesting a sock 5 days earlier. Ultrasound, contrast x-ray, computed tomography and endoscopy were used to locate the foreign body before surgery. Attempts to remove the sock endoscopically failed. The sock was surgically removed via celiotomy and enterotomy.
... The difference between T. scripta and these species may be related to differences in their gastrointestinal tracts. Iguanas possess either spiral valves or transverse folds in the large intestine, which slow the passage of digesta and increase the surface area for absorption (Iverson 1980). Red-bellied turtles lack such valves, but the fermentation chamber in this turtle has expanded to include the small as well as large intestine ). ...
... The broadness of this part of the rib cage (see Brown 1908, fig. 12) suggests a large hindgut fermentation digestive system analogous to that seen in herbivorous lizards (Iverson 1980); in such lizards the colon diameter is greatly enlarged and partitioned internally into chambers for the microflora (Iverson 1982;McBee and McBee 1982;King 1996). ...
The armor-plated dinosaur Ankylosaurus magniventris is redescribed based on specimens from the Hell Creek Formation of northeastern Montana, USA., Lance Formation of Wyoming, USA., and from the Scollard Formation of south-central Alberta, Canada. Except for brief descriptions, most of these specimens have not been described in detail. Ankylosaurus is one of the largest known ankylosaurids, having an estimated length of up to 6.25 m (20.5 ft). It is characterized by a long, low skull having very prominent cranial horns that project laterally or dorsolaterally. The body armor includes a large half-ring that sat across the base of the neck and shoulders and a large, low tail club.
... The majority of studies linking phenotypic specialization with herbivory in lizards have generally focused on digestive anatomy and physiology. Various strategies for potentially increasing nutrient uptake from plants appear to be utilized, including deliberate ingestion of sand and small rocks (Sylber, 1988), presence of cellulolytic bacteria and intestinal nematodes (Dubuis et al ., 1971;Sokol, 1971;Nagy, 1977) and partitioning and enlargement of the colon and caecum (Iverson, 1980Iverson, , 1982Herrel, Vanhooydonck & Van Damme, 2004). It has also been noted that some herbivorous lizards (e.g. ...
Although the relationship between dietary and phenotypic specialization has been well documented for many ver-tebrate groups, it has been stated that few such general trends can be established for lizards. This is often thought to be due to the lack of dietary specialization in many lizards. For example, many species that are reported to be insectivorous may also consume a variety of plant materials, and the reverse is often true as well. In this study, we investigate whether a correlation exists between general cranial form and dietary niche in lizards. Additionally, we test previously proposed hypotheses suggesting that herbivorous lizards should be larger bodied than lizards with other diets. Our data indicate that lizards specializing in food items imposing different mechanical demands on the feeding system show clear patterns of morphological specialization in their cranial morphology. True herbivores (diet of fibrous and tough foliage) are clearly distinguished from omnivorous and carnivorous lizards by having taller skulls and shorter snouts, likely related to the need for high bite forces. This allows herbivores to mechanically reduce relatively less digestible foliage. Carnivores have relatively longer snouts and retroarticular processes, which may result in more efficient capture and processing of elusive prey. When analysed in an explicit phylogenetic con-text, only snout length and skull mass remained significantly different between dietary groups. The small number of differences in the phylogenetic analyses is likely the result of shared evolutionary history and the relative paucity of independent origins of herbivory and omnivory in our sample. Analyses of the relationship between diet and body size show that on average herbivores have a larger body size than carnivores, with omnivores intermediate between the two other dietary groups.
Although relationships between intestinal morphology between trophic groups in reptiles are widely assumed and represent a cornerstone of ecomorphological narratives, few comparative approaches actually tested this hypothesis on a larger scale. We collected data on lengths of intestinal sections of 205 reptile species for which either body mass (BM), snout-vent-length (SVL) or carapax length (CL) was recorded, transforming SVL or CL into BM if the latter was not given, and analyzed scaling patterns with BM and SVL, accounting for phylogeny, comparing three trophic guilds (faunivores, omnivores, herbivores), and comparing with a mammal dataset. Length-BM relationships in reptiles were stronger for the small than the large intestine, suggesting that for the latter, additional factors might be relevant. Adding trophic level did not consistently improve model fit; only when controlling for phylogeny, models indicated a longer large intestine in herbivores, due to a corresponding pattern in lizards. Trophic level effects were highly susceptible to sample sizes, and not considered strong. Models that linked BM to intestine length had better support than models using SVL, due to the deviating body shape of snakes. At comparable BM, reptiles had shorter intestines than mammals. While the latter finding corresponds to findings of lower tissue masses for the digestive tract and other organs in reptiles as well as our understanding of differences in energetic requirements between the classes, they raise the hitherto unanswered question what it is that reptiles of similar BM have more than mammals. A lesser effect of trophic level on intestine lengths in reptiles compared to mammals may stem from lesser selective pressures on differentiation between trophic guilds, related to the generally lower food intake and different movement patterns of reptiles, which may not similarly escalate evolutionary arms races tuned to optimal agility as between mammalian predators and prey.
The evolution of body size was reconstructed in chuckwallas (genus Sauromalus), large herbivorous lizards of southwest North America, using a phylogeny derived from sequence variation in the mitochondrial cytochrome b gene. The body mass of two endemic island species (S. hispidus and S. varius) is typically fivefold larger than mainland species. We tested the hypothesis that large body size has evolved on these islands in response to local ecological conditions against the alternative hypothesis that large size is simply retained from large iguanine ancestors. The most parsimonious tree topology depicts the insular gigantic Sauromalus as monophyletic, having diverged from a common ancestor on the Baja California peninsula after the radiation of smaller bodied clades. In a robustness analysis of this topology, we found general support for this tree over alternative topologies representing minimum evolution hypotheses that imply large body size is retained from large iguanine ancestors. The most parsimonious reconstruction of body size evolution implies a change from large to small size after the Sauromalus ancestor diverged from Iguana, and one reversal back to large size within Sauromalus. The large size increase in the gigantic clade contrasts with evolutionary stasis of small body size (for an iguanine) in mainland populations. The gigantic species show 3-4% total sequence divergence from S. obesus populations on the nearby Baja California peninsula, and mainland populations of S. obesus obesus show similar levels of divergence from each other. An analysis of character transitions and comparative behavior implicates predation, and its relaxation on isolated islands, as a strong selective force in Sauromalus. Patterns of genetic differentiation in Sauromalus and biogeographic implications are discussed.
As ectotherms, amphibians and reptiles do not have to support the metabolic expense of endothermy and are characterized by low rates of energy flow and high efficiencies of biomass conversion, relative to birds and mammals (Pough 1983). The low energy requirements of amphibians and reptiles have important ramifications for digestive processing and, in herbivorous species, for the level of energy that must be generated by fermentations in the gastrointestinal tract.
Introduction, Active foraging and sit-and-wait predation are often considered as two very disparate foraging strategies (Huey and Pianka, 1981). As implied by the name, active foragers actively search for food and, in the process, will cover large distances. Typical sit-and-wait predators on the other hand will wait motionless for prey to pass by, at which they will dart with a sudden burst of movement. These animals are often cryptically colored and do not move around for prolonged periods of time (see Table 7.1). Herbivores, however, need to forage actively for food, but have radiated extensively within a group of lizards seemingly predisposed to a sit-and-wait strategy. Differences in foraging mode in lizards seem to be roughly associated with a deep split within the lizard phylogeny: the transition from “fleshy-tongued” Iguania to the “scaly-tongued” Scleroglossa. It has been suggested that this split is tightly associated with evolution of the use of the tongue for chemoreceptive purposes either at the level of the scleroglossans (Schwenk, 1993, 2000; Cooper, 1994) or independently in each of the scleroglossan radiations (Reilly and McBrayer, this volume, Chapter 10). The development of a tongue that allowed animals to detect and assess sedentary prey is thought to have allowed lizards to search extensive areas for prey that would otherwise remain undetected. As a consequence, active foragers tend to consume unpredictably distributed and clumped prey (e.g. termites). Sit-and-wait predators, on the other hand, tend to eat more active and larger prey (Pough et al., 2001). é Cambridge University Press 2007.
Bacterial Biogeochemistry, Third Edition focuses on bacterial metabolism and its relevance to the environment, including the decomposition of soil, food chains, nitrogen fixation, assimilation and reduction of carbon nitrogen and sulfur, and microbial symbiosis. The scope of the new edition has broadened to provide a historical perspective, and covers in greater depth topics such as bioenergetic processes, characteristics of microbial communities, spatial heterogeneity, transport mechanisms, microbial biofilms, extreme environments and evolution of biogeochemical cycles. Provides up-to-date coverage with an enlarged scope, a new historical perspective, and coverage in greater depth of topics of special interest Covers interactions between microbial processes, atmospheric composition and the earth's greenhouse properties Completely rewritten to incorporate all the advances and discoveries of the last 20 years such as applications in the exploration for ore deposits and oil and in remediation of environmental pollution.
A new lizard genus and species, Ornatocephalus metzleri, is described from the World Heritage Messel Pit Fossil Site (Middle Eocene: basal Lutetian, Geiseltalium). It is placed within the Scincoidea (Scincidae, Cordyliformes + Paramacellodidae) but no attribution to a distinct family can be made. Its phylogenetic position is problematic as it probably represents the descendant of a stem group taxon of the Scincoidea or a "link" between Scincidae and Cordyliformes. Extensive phylogenetic analyses using numerical taxonomy have been undertaken. Unaltered and modified matrices from different authors are analysed in order to generate a variety of phylogenetic hypotheses. These are discussed with the results of comparative anatomy, the latter having a higher impact on the final classification. Generic characters of the new taxon are as follows: The dorsal aspect of the skull is covered with a characteristic osteodermal pattern, the jugal has a huge posterior process, the retroarticular process and teeth show a typical scincoid morphology. Six well preserved specimens can safely be attributed to the new species which is not yet known from any other fossil site. The very long prehensile tail of Ornatocephalus metzleri, its curved claws, limb proportions and missing body osteoderms strongly suggest an arboreal mode of life. The long tail could secure support by grabbing branches, but probably was too fragile to hold the entire body weight. The locomotion and microhabitat exploitation of Ornatocephalus metzleri can best be compared to the arboreal emerald monitors Varanus prasinus and Varanus beccarii with their long tails and strongly curved claws. In three of the fossil specimens intestinal contents are still preserved. They contain plant remains and a few fragments of insect cuticula. Due to its cover of osteoderms, the skull was largely akinetic, suggesting Ornatocephalus metzleri not to be an effective and agile predator, but a rather large herbivore and occasional insectivore, which was probably capable of strenuous biting. The presence of Ornatocephalus metzleri in the Lower Middle Eocene of Messel neither supports nor contradicts the current opinions of Scincoid Paleobiogeography.
Like living herbivorous lizards, chelonians, birds, and mammals, plant-eating dinosaurs, probably relied on a symbiotic gut microflora, housed in a hindgut fermentation chamber, to break down plant cell wall constituents. Large herbivorous dinosaurs probably fed on plants whose allelochemical defenses were geared more toward reducing digestibility than attacking the herbivore's metabolism directly, obviating the need for a foregut fermentation chamber and permitting these large herbivores to take advantage of the energetic benefits of hindgut fermentation for digestion of low-quality fodder. Differences in dentitions among the groups of herbivorous dinosaurs may correlate with differences in standard metabolic rate, activity level, body size, or food quality, or combinations of these factors, but the relative importance of each is difficult to assess. Because the mass of the fermentation contents was probably large in big herbivorous dinosaurs, the heat of fermentation may have been a significant source of thermoregulatory heat for these reptiles. -from Author
The disappearance of nonavian dinosaurs is only a small part of a greater class of extinctions known as “mass extinctions.” Mass extinctions are global events characterized by unusually high rates of extinction. The five episodes of mass extinctions in Earth history are the Permo-Triassic extinction, the Late Ordovician extinction, the Late Devonian extinction, the Triassic-Jurassic extinction, and the Cretaceous-Tertiary (K/T) extinction. This chapter focuses on patterns of geologic and biotic changes that occurred during the Cretaceous-Tertiary (K/T) extinction. It also highlights the similarities and differences in interpretations of geologic and fossil records. It concludes with two scenarios explaining the differing views about dinosaur extinction.
The feeding habits of adult Sauromalus hispidus and adult Sauromalus varius were studied on four islands in the midriff region of the Gulf of California, Mexico. Diets were determined by examining a total of 1875 fecal pellets from four islands during the summer, fall and spring of 1979-1980. Results of a point frame technique demonstrated that the diet of S. varius consisted of 22 plant species and 12 plant families whereas that of S. hispidus was made up of 35 plant species and 20 plant families. Chuckwallas ate a strictly vegetarian diet, preferring shrubs over forbs, cacti, and grasses or leaves over flowers, fruits, seeds, and stems. No plant parts from halophytic species were found in the pellets. Plant trophic diversity in the diet was highest on Isla San Esteban and lowest on Isla Mejia. Examination of the fecal pellets also revealed that they contained gravel and sand. Some gravel and sand were ingested by the lizards on all 25 of the study sites. The consistency with which gravel was found in the fecal pellets from all sites and every season, suggests that these lizards had intentionally ingested this material as a part of their food regime. No correlation was found between the plant frequencies at the sites and the plant frequencies in the pellets. Neither species of giant chuckwalla appears to seek out plants based on the plant's relative abundance.
The evolution of body size was reconstructed in chuckwallas (genus Sauromalus), large herbivorous lizards of southwest North America, using a phylogeny derived from sequence variation in the mitochondrial cytochrome b gene. The body mass of two endemic island species (S. hispidus and S. varius) is typically fivefold larger than mainland species. We tested the hypothesis that large body size has evolved on these islands in response to local ecological conditions against the alternative hypothesis that large size is simply retained from large iguanine ancestors. The most parsimonious tree topology depicts the insular gigantic Sauromalus as monophyletic, having diverged from a common ancestor on the Baja California peninsula after the radiation of smaller bodied clades. In a robustness analysis of this topology, we found general support for this tree over alternative topologies representing minimum evolution hypotheses that imply large body size is retained from large iguanine ancestors. The most parsimonious reconstruction of body size evolution implies a change from large to small size after the Sauromalus ancestor diverged from Iguana, and one reversal back to large size within Sauromalus. The large size increase in the gigantic clade contrasts with evolutionary stasis of small body size (for an iguanine) in mainland populations. The gigantic species show 3-4% total sequence divergence from S. obesus populations on the nearby Baja California peninsula, and mainland populations of S. obesus obesus show similar levels of divergence from each other. An analysis of character transitions and comparative behavior implicates predation, and its relaxation on isolated islands, as a strong selective force in Sauromalus. Patterns of genetic differentiation in Sauromalus and biogeographic implications are discussed.
The positive contrast gastrointestinal study is a common non-invasive diagnostic technique that does not require anesthesia and enables good visualization of the digestive tract. Radiographic anatomy and reference intervals for gastrointestinal contrast transit time in inland bearded dragons (Pogona vitticeps) were established using seven animals administered 15 ml/kg of a 35% w/v suspension of barium by esophageal gavage. Dorso-ventral and lateral radiographic views were performed at 0, 15, 30 min, 1, 2, 4, 6, 8, 12 h, and then every 12 h up to 96 h after barium administration. Gastric emptying was complete at a median time of 10 h (range 4–24 h). Median jejunum and small intestinal emptying times were 1 h (range 30 min–2 h) and 29 h (range 24–48 h), respectively. Median transit time for cecum was 10 h (range 8–12 h). Median time for contrast to reach the colon was 31 h (range 12–72 h) after administration. Results were compared to those obtained in other reptilian species. This technique appeared safe in fasted bearded dragons and would be clinically applicable in other lizard species.
Dinuclear gold(i) dithio- and diselenophosph(in)ate complexes were prepared to serve as precursors for subsequent oxidative addition (OA) chemistry following reaction with mild oxidant iodine, I2. The new OA products circumvented the formation of the expected dinuclear Au(ii) complexes, but instead formed novel chelating mononuclear square-planar gold(iii) products of the type [AuI2{E2PR2}] (R = (CH2)2Ph; E = S, ; E = Se, ) and [AuI2{Se2P(OR)2}] (R = Et, ; (i)Pr, ) directly. We further demonstrate that this process is chemically reversible as all the Au(iii) complexes undergo chemical reductive elimination to the starting dinuclear Au(i) complexes in the presence of SnI2 as determined by (119)Sn and (31)P NMR. The complexes () were all prepared from the reaction between I2 and the corresponding dinuclear gold(i) precursor material. All new complexes were characterized by (1)H, (31)P, (77)Se (for E = Se) NMR, infrared spectroscopy, elemental analysis and single crystal X-ray diffraction.
Evidence of communal nesting and site fidelity in hadrosaurian dinosaurs from the Late Cretaceous Two Medicine Formation of Montana indicates a close parallel with herbivorous iguanine lizards. Raised nests prevented egg drowning, while communal habits and site fidelity facilitated fecal ingestion by young, which infected them with a microflora appropriate for herbivory.
Absorption of small water-soluble nutrients in vertebrate intestines occurs both by specific, mediated transport and by non-specific, passive, paracellular transport. Although it is apparent that paracellular absorption represents a significant route for nutrient absorption in many birds and mammals, especially small, flying species, its importance in ectothermic vertebrates has not previously been explored. Therefore, we measured fractional absorption (ƒ) and absorption rate of three paracellular probes (arabinose, l-rhamnose, cellobiose) and of 3-O-methyl d-glucose (absorbed by both mediated and paracellular pathways) by the large herbivorous lizard, Uromastyx aegyptia, to explore the relative importance of paracellular and mediated transport in an ectothermic, terrestrial vertebrate. Fractional absorption of 3-O-methyl d-glucose was high (ƒ = 0.73±0.04) and similar to other vertebrates; ƒ of the paracellular probes was relatively low (arabinose ƒ = 0.31±0.03, l-rhamnose ƒ = 0.19±0.02, and cellobiose ƒ = 0.14±0.02), and decreased with molecular mass, a pattern consistent with other vertebrates. Paracellular absorption accounted for approximately 24% of total 3-O-methyl d-glucose uptake, indicating low reliance on this pathway for these herbivorous lizards, a pattern similar to that found in other terrestrial vertebrates, and different from small flying endotherms (both birds and bats).
The historical biogeography of the lizard clade Iguanidae is complicated. In addition to difficulties within the New World, where most of the more than 900 living species are found, two extant iguanid clades, Brachylophus and Oplurinae, occur well outside it. Moreover, there is a small set of Eocene species in Europe, most notably those placed in the genus Geiseltaliellus. To examine the relevance of Geiseltaliellus to iguanid biogeography, I redescribe several well-preserved specimens (nearly complete skeletons with epidermal scales) from the middle Eocene lake deposits of Messel, Germany. These specimens were previously referred to the type species, G. longicaudus, but comparison with the type material reveals differences that warrant specific distinction. Messel Geiseltaliellus resembles extant Basiliscus in squamation and parietal growth. Phylogenetic analysis of morphological data using Bayesian and parsimony methods suggests the following about the evolution of pleurodont iguanians: (1) Iguanidae is monophyletic, its members united by unique features of the snout; (2) Iguanidae is divided into two major clades, one consisting of Polychrotinae* + Corytophaninae, Iguaninae + Hoplocercinae and Crotaphytinae (Clade A), the other of Phrynosomatinae, Tropidurinae* and Oplurinae (Clade B); (3) Polychrotinae* and Corytophaninae are sister taxa; and (4) Geiseltaliellus is on the stem of Corytophaninae. The presence of Geiseltaliellus in Europe during the warm, humid Eocene suggests dispersal from North America and a more northerly distribution of the corytophanine stem than the crown. Geiseltaliellus represents a separate invasion by Iguanidae of the Old World and an evolutionary dead end. On the basis of its fossil record and modern distribution, Clade A is interpreted as ancestrally North American. Persistent conflict of morphological with molecular genetic data on iguanid relationships remains to be resolved.
Herbivorous animals that digest plant structural tissues almost invariably depend on the fermentative activity of symbiotic populations of microbes, housed in the digestive tract, to degrade plant fiber. The evolution of microbial fermentation systems entails an intricate coevolution among microbe species, as well as between microbes and herbivores. Beyond some level of biochemical specialization, fermentative microflora cannot survive outside of the host's body, and can only be transferred among herbivores by close contact. Yet in order actually to coevolve with the herbivore species, the microbe populations must be transmitted from one generation of herbivore to the next. In order to evolve the most effective system for utilizing plant materials for food, i.e. dependence on a microbial fermentation system, herbivores must concurrently evolve behavioral adaptations that ensure contact between generations. The evolution of social systems in a variety of animals, from termites to dinosaurs, may be originally associated with their herbivorous habits.
1.1. Nutrient absorption efficiencies of Cnemidophorus sexlinealus fed domestic crickets (Acheta dornest ica) were calculated by extracting proteins, carbohydrates and lipids from food and feces.2.2. Lipids were absorbed at 88.5% efficiency, soluble carbohydrates at 84.2% and soluble protein at 83.1%.3.3. The average energy absorbed from each cricket (kcal/prey) was 0.30 for protein, 0.208 for lipid and 0.012 for carbohydrate.4.5. Including non-available energy, such as that contained in structural carbohydrates and proteins as measured by bomb calorimetry, in estimating prey profitability overestimates the value of prey. Hence, calculations of available nutrients produce more accurate estimates of prey value.
The green iguana, Iguana iguana, is herbivorous throughout life, and depends on a microbial fermentation system in the hindgut to degrade plant fiber. Because the metabolic rates of lizards are proportional to body mass raised to the 0.80 power, hatchling iguanas have 2X, and juveniles 1.4X, greater relative energy requirements (kJxg body mass-1xday-1) than full-grown adults. Growing animals also need a higher protein intake, for contruction of body tissues, than do mature animals. This study investigated how growing iguanas achieve a relatively greater nutrient intake than adults. Hatchling and juvenile iguanas do not have higher relative capacities of the digestive tract than mature iguanas, nor do they digest plant materials more effectively. Instead, growing iguanas select diets higher in digestible protein, and digest the same food 1.3X to 2X more rapidly, than adults. Young iguanas may accomplish their shorter food transit times by maintaining higher body temperatures.
This report describes an intestinal obstruction in a green iguana (Iguana iguana). The patient was presented with vomiting and subtle signs of abdominal pain. Radiographs and ultrasound imaging did not reveal any abnormalities. A coeliotomy was performed and a 30-cm piece of absorbent cotton was removed surgically from the large intestine.
A major difference between reptile and mammalian herbivores is that the former do not masticate their food. Actually, food particle size reduction by chewing is usually considered one of the adaptations facilitating the higher metabolic rates of mammals. However, quantitative comparisons of ingesta particle size between the clades have, to our knowledge, not been performed so far. We measured mean fecal particle size (MPS) in 79 captive individuals of 14 reptile herbivore species (tortoises, lizards, and Corucia zebrata) by wet sieving and compared the results with a mammalian dataset. MPS increased with body mass in both clades, but at a significantly higher level in reptiles. Limited evidence in free-ranging and captive individuals of Testudo hermanni indicates that in reptiles, the ability to crop food and food particle size significantly influence fecal particle size. The opportunistic observation of a drastic particle size difference between stomach and intestinal contents corroborates findings that in reptiles, in contrast to terrestrial mammals, significant ingesta particle size reduction does occur in the gastrointestinal tract, most likely owing to microbial action during very long ingesta retention. Whether behavioral adaptations to controlling ingesta particle size, such as deliberate small bite sizes, are adaptive strategies in reptiles remains to be investigated.
"The original publication is available at www.springerlink.com"A central question in behavioral ecology has been why animals live in groups. Previous theories about the evolution of sociality focused on the potential benefits of decreased risk of predation, increased foraging or feeding efficiency, and mutual aid in defending resources and/or rearing offspring. This paper argues that access to mutualistic endosymbiotic microbes is an underappreciated benefit of group living and sets out to reinvigorate Troyer’s hypothesis that the need to obtain cellulolytic microbes from conspecifics influenced the evolution of social behavior in herbivores and to extend it to nonherbivores. This extension is necessary because the benefits of endosymbionts are not limited to nutrition; endosymbionts also help protect their hosts from pathogens. When hosts must obtain endosymbionts from conspecifics, they are forced to interact. Thus, complex forms of sociality may be more likely to evolve when hosts must repeatedly obtain endosymbionts from conspecifics than when endosymbionts can be obtained either directly from the environment, are vertically transmitted, or when repeated inoculations are not necessary. Observations from a variety of taxa are consistent with the ideas that individuals benefit from group living by gaining access to endosymbionts and the complexity of social behavior is associated with the mode of acquisition of endosymbionts. Ways to test this theory include (a) experiments designed to examine the effects of endosymbionts on host fitness and how endosymbionts are obtained and (b) using phylogenetic analyses to examine endosymbiont-host coevolution with the goal of determining the relationship between the mode of endosymbiont acquisition and host sociality.
The processes of filtration and expression of suspensions of biological solids are reviewed in the context of vertebrate digestion. We show that the digesta of the brushtail possum and sheep form a contiguous matrix of particles from which a fluid phase can be expressed by the application of pressure. These findings are examined in respect of their possible contribution to phase separation and the sorting of particles within the gastrointestinal tracts of vertebrates. The morphological adaptations and motility of various digestive compartments are related to the processing of digesta with high solid phase content, in particular the formation and dispersion of the particle matrices. A brief description is given of techniques for evaluating the properties of digesta with high solid phase content.
The herbivorous tortoise Xerobates agassizii contends with large fluctuations in the quality and abundance of desert pastures. Responses to grass (Schismus barbatus), herbage (Sphaeralcea ambigua) and pelleted diets were studied in captive animals. Digestive anatomy was investigated in wild tortoises. Cornified esophageal epithelia and numerous mucus glands along the digestive tract indicated a resistance to abrasive diets. Gastric contents were acidic whereas hindgut digesta were near neutral pH. The colon was the primary site of fermentation with short-chain fatty acids mainly comprised of acetate (69-84%), propionate (10-15%) and n-butyrate (1-12%). Fibre digestion was extensive and equivalent to 22-64% of digestible energy intakes. Large particles of grass (25 mm; Cr-mordants) were excreted as a pulse but retained longer than either fluids (Co-EDTA) or fine particles (2 mm; Yb). Patterns of marker excretion suggested irregular mixing of only the fluid and fine particulate digesta in the stomach and the colon. Mean retention times of Cr-mordants were 14.2-14.8 days on the grass and high-fibre pellets. Intakes of grass were low and accompanied by smaller estimates of digesta fill than for the high-fibre pellets. Digestive capacity was large and estimated at 11-21% of body mass on these diets. The capacious but simple digestive anatomy of the tortoise may provide the greatest flexibility in utilizing a variety of forages in its unreliable habitat.
Herbivory is an uncommon feeding strategy in lizards. Appropriate diet formulations for captive lizards should be based on performance measures, yet few data are available on the effect of plant fiber on food intake, nutrient utilization and growth of captive herbivorous lizards. This study was conducted to determine the effect of three levels of dietary fiber on dry matter intake, nutrient and energy metabolizability and growth rate of the green iguana (Iguana iguana). Twenty-one captive iguanas were fed nutritionally complete diets containing three levels of dietary fiber: 19, 24, and 27% neutral detergent fiber. The iguanas were fed each diet for at least 12 wk, and total excreta were collected for 11.3 +/- 4.0 d (means +/- , range of 7 to 25 d). Diets and excreta were analyzed for dry matter, organic matter, gross energy, neutral detergent fiber, acid detergent fiber, and acid detergent lignin. The study was designed as a Latin square crossover. Across all diets, dry matter intake was proportional to body mass1.0 (BM). Growth rate was greater (P < 0. 05) when iguanas were fed the low and medium fiber diets (2.2 and 2. 4 g/d, respectively) than when fed the high fiber diet (1.4 g/d). However, mean daily dry matter intake of the three diets [7.2 g/(d. kg BM)] was not different. In general, digestibility of fiber fractions and the metabolizability of dietary energy decreased (P < 0.05) as the level of dietary fiber increased. These data suggest that a diet containing less than 27% neutral detergent fiber should be fed if rapid growth is to be sustained during intensive captive production of green iguanas.
In the families Agamidae, Gerrhosauridae, Iguanidae, and Scincidae, species that weigh more than 300 g are almost all herbivores, whereas those weighing less than 50-100 g are carnivores. Juveniles of large herbivorous species tend to be carnivorous until they reach body weights of 50-300 g. Diet is compared to metabolic expenditure in these lizards. Although smaller animals have higher weight-specific metabolic rates, the greater total metabolic rate of larger animals requires a greater caloric intake. Juvenile animals and species of small body size are primarily insectivorous. It is postulated that larger animals of these families are unable to meet caloric demands on a diet of insects, have no practical alternative animal prey, and rely instead on vegetation. The families Anguidae, Chamaeleontidae, Helodermatidae, Teiidae, and Varanidae do not include herbivorous species, although each family has species that weigh more than 300 g. Morphological, ecological, and physiological specializations in these families account for the absence of herbivorous species. For an unspecialized lizard, evolution of large body size both requires and permits an herbivorous diet.
A field study of the ethoecology of the rock iguana, Cyclura pinguis, on Anegada, British Virgin Islands was conducted from 27 March to 5 May 1968. The sympatric Hispaniolan species, C. ricordi and C. cornuta, were observed from 12 to 16 May 1968. The results of these studies and all known ethoecological literature on the genus are discussed. Cyclura pinguis inhabits primarily xeric limestone areas, is heliothermic, and exhibits behavioral thermoregulation. Retreats nearly always consist of natural cavities in the limestone or beneath boulders. C. ricordi and C. cornuta are primarily burrowers. Adult of all three species are principally herbivorous, although some animal matter is taken. Probably all Cyclura juveniles are primarily insectivorous. Parasitism from ticks and nematodes is a common occurrence in Cyclura. Five adult males on the main study plot ranged from 522 to 545 mm (x̅ = 534.60 ± 3.88 mm) in snout-vent length and from 5.95 to 7.17 kg (x̅=6.72 ± 0.21 kg) in body weight; five adult females ranged from 426 to 487 mm (x̅ = 468.00 ± 10.87 mm) in snout- vent length and from 4.31 to 5.13 kg (x̅ = 4.75 ± 0.13 kg) in body weight. The five males occupied home ranges from 116.06 to 985.11 m2 (x̅ = 546.61 ± 160.46 m2) in area; home ranges of the five females measured from 155.47 to 412.31 m2 (x̅ = 276.28 ± 41.62 m2). Extensive unutilized zones existed between home ranges of iguanas of the same sex. Aside from food, available shelter seems to be the most importait factor governing selection of home range locale. Cyclura pinguis exhibited a density of 2.03 iguanas/hectare (0.82/acre), the lowest density figure of any lizard for which data are documented. The sex ratio was equal. Evidence suggests monogamy. Three adult females had 12, 14, and 16 yolked ovarian follicles. Adulthood appears to be attained between 7 and 9 years of age and between 350 and 400 mm snout-vent length. The reproductive cycle in C. pinguis suggests synchronization with the two rainfall maxima in the Virgin Islands. Adult iguanas far outnumbered juveniles (87.5% vs. 12.5%) suggesting decline of the population. This disproportionate age structure seems to be the result of interactions (competition/predation) with domestic livestock. With the resultant loss in fecundity, relatively few adults now exist to continue the population. A conservation program is outlined whereby the population might be restored. This program might be applicable to other decimated Cyclura populations as well.
https://deepblue.lib.umich.edu/bitstream/2027.42/137252/1/evo01083.pdf
The skeletons of Sceloporus, Uta, Urosaurus, Sator, Petrosaurus, Uma, Callisaurus, and Holbrookia are described and compared with one another and with other iguanid lizard genera. Intraspecific and intrageneric variation in the region of the sternum and xiphisternum is very great, leaving no osteological basis for recognition of the "urosaurine" and "utiform" generic groups proposed by Savage (1958). Petrosaurus is osteologically the most distinctive genus; it is not more similar to Uta than to other sceloporine genera. Osteological comparisons of Uta and Urosaurus do not provide a strong argument either for or against their recognition as separate genera. Three subgroups are recognized within the sceloporines: (1) Petrosaurus with 4 sternal ribs (3 in the others), (2) Uta, Urosaurus, Sator, and Sceloporus with hook-like processes on the clavicle, and (3) Callisaurus, Holbrookia, and Uma with 2 cervical ribs (3 in the others). Phrynosoma differs from the sceloporines in many characteristics of skeletal and external morphology, and the genus is removed from the sceloporine group where it was placed by Savage (1958). The skeletal characters of the iguanine group of genera proposed by Savage (1958) (Iguana, Ctenosaura, Enyaliosaurus, Cyclura, Dipsosaurus, Sauromalus, Amblyrhynchus, Conolophus, Crotaphytus, and Brachylophus) are described, and Crotaphytus is removed from the group. Comparison of sceloporines with iguanines indicates that they are not closely related. Of the iguanid genera of North and Central America, the most similar to the sceloporines is Crotaphytus. Of the sceloporines, Petrosaurus is most similar to Crotaphytus. The skeletal characters of the West Indian and South American genera Leiocephalus, Hispaniolus, Liolaemus, Stenocercus, Tropidurus, Uranoscodon, Plica, Urocentron, Platynotus, Proctotretus, and Ctenoblepharis are briefly described, and the group name "tropidurine" is applied to them. The sceloporines are osteologically more similar to the tropidurines than to other iguanid genera.
Cellulase activity in the large intestine of chuckwallas was similar to that in a cow's rumen. However, tracer evidence that ash-free dry matter assimilation in the large intestine was small indicates that cellulose digestion is not of major importance in the energy balance of these lizards. Gut pH changes and fractional assimilations of K, Na, Cl, Ca, Mg, Fe, Al, Mn, Sr, B and Cu were similar to those in non-ruminant mammalian herbivores.
Contrary to earlier descriptions, the Galapagos marine iguana is not a particularly fast swimmer, the mean velocity for burst swimming by large adults being only 0.85 m/s. Moreover, this lizard depends on physiological patterns characteristic of terrestrial iguanids in its amphibious existence. Aerobic metabolic scope is relatively restricted and highly dependent upon body temperature. This function reaches a maximum at 35 C, a value characteristic of basking marine iguanas, but substantially higher than the water temperatures at which the most strenuous activities of this species occur. Its abilities to forage in cool waters appear to depend upon substantial anaerobic capacities, which resemble those of terrestrial iguanids. As in these other lizards, anaerobic metabolic scope appears relatively independent of temperature in the marine iguana. Physiological results and a review of the probable events leading to the evolution of the Galagapos marine iguana support a view of this animal as a representative of a terrestrial line that was preadapted for exploiting a unique combination of circumstances.
The antigenic properties of the major hemoglobin component of the Galapgaos iguanas were studied using second-approximation qualitative and quantitative immunochemical techniques. Phylogenetic distances, relative to the Galapagos marine iguana. Amblyrhynchus cristatus, were established on the basis of immunological cross-reactions.
1.1. The serum proteins of three species of Galapagos iguanas, Amblyrhynchus cristatus, Conolophus pallidus and Conolophus subcristatus, and one mainland South American species, Iguana iguana, were studied by means of immunodiffusion and immunoelectrophoresis.2.2. A. cristatus, the Galapagos marine iguana, was found to be immunologically more closely related to the Galapagos terrestrial iguanas C. pallidus and C. subcristatus, than to the mainland species I. iguana.3.3. A. cristatus deme differences were not observed with the techniques employed.
The serum proteins of two genera of Galapagos iguanas were studied by means of immunochemical and electrophoretic methods. The albumin-like fraction of the serum of the Galapagos land iguana, genus Conolophus, demonstrated greater anodal mobility than the albumin of Amblyrhynchus, the Galapagos marine iguana. The marine reptile was shown to possess four antigenic serum components not found in the land reptile. Double-diffusion analysis, using rabbit antiserum to the serum of Amblyrhynchus cristatus (Santa Cruz Island), indicated taht the antigenic profile of the Santa Cruz, Hood, Tower, Albemarle and James Island populations of Amblyrhynchus were identical when the eliciting immunogen is the serum of the Santa Cruz marine iguana.
Early reports of Lampropedia suggested that it occurred in stagnant or muddy waters, rotting vegetation, and liquid manure. More recently, "window-pane sarcinae" have been observed in the rumen contents of sheep and cattle. Now we have found that this organism is a frequent component not only of the gut flora of herbivorous reptiles but also of nematodes inhabiting the guts of some of these reptiles. This, taken together with the other evidence, suggests that Lampropedia may be often associated with other microorganisms in those parts of the vertebrate alimentary tract in which cellulose digestion is occurring.
Uber den Blindarm der Amphibien
- Tiedemann F.
Tiedemann, F. (1817) Uber den Blindarm der Amphibien. Deutsch. Arch. f. d. Physiol. hrsg V. Meckel F. 3:368-373.
On some p i n t s of relation between the morphological structure of the intestine and the diet of reptiles. Bihang. Tillk. Svenska. Vet.-Akad Cellulose digestion and nutrient assimila-tion in Sauromalus obesus, a plant-eating lizard
- E Lonnberg
Lonnberg, E. (1902) On some p i n t s of relation between the morphological structure of the intestine and the diet of reptiles. Bihang. Tillk. Svenska. Vet.-Akad. Handingar Band 28(IV), 8:3-53. N a g, K.A. (1977) Cellulose digestion and nutrient assimila-tion in Sauromalus obesus, a plant-eating lizard. Copeia, 1977(21:355-362.
Systematics and evolu-tion in the West Indian iguanid genus Cyclura. Studies Fauna Curacao and Other Caribbean Islands
- A Schwartz
- W M Carey
Schwartz, A., and W.M. Carey (1977) Systematics and evolu-tion in the West Indian iguanid genus Cyclura. Studies Fauna Curacao and Other Caribbean Islands, 173: 15-97.
Grundzüge des Innenreliefs vom Rumpfdarm der Wirbeltiere
- Jacobshagen E.
Jacobshagen, E. (1937) Grundzuge des Innenreliefs vom Rumpfdarm der Wirbeltiere. Anat. Am., 83:241-261.
Galapagos &anas: Amblyrhynchus and Conkophus serum piocin relationships
- P J Himins
- C S Rand
- J Haynes
Himins, P.J., C.S. Rand, and J. Haynes (1974) Galapagos &anas: Amblyrhynchus and Conkophus serum piocin relationships. J. Exp. Zool., 189:255-259.
On the anatomy and histology of the alimentary tract of the lizard Uromastyx aegyptia [sic] (Forskal)
- M R El-Toubi
- H M Bishai
El-Toubi, M.R., and H.M. Bishai (1959) On the anatomy and histology of the alimentary tract of the lizard Uromastyx aegyptia [sic] (Forskal). Bull. Fac. Sci. Cairo Univ., 34t13-50.
Reptilian arboreal folivores In: The Ecol-ogy of Arboreal Folivores
- Rand
- As
Rand, AS. (1979) Reptilian arboreal folivores. In: The Ecol-ogy of Arboreal Folivores. G.G. Montgomery, ed. Smith-sonian Institution Press, Washington. Romer, AS., and T.S. Parsons (1977) The Vertebrate Body, ed.
Eigentumliche Reliefbildungen der tiefen Wandschichten im Enddarm der Saurier, ihre Entstehung und Bedeutung
- Esch H.
Esch, H. (1936) Eigentumliche Reliefbildungen der tiefen Wandschichten im Enddarm der Saurier, ihre Entstehung und Bedeutung. Anat. Am., 82162-190.
Vergleichende Anatomie der Wirbelthiere mit Berücksichtigung der Wirbellosen
- Gegenbaur
Gegenbaur, C. (1901) Vergleichende Anatomie der Wirbel-thiere mit Beriicksichtigung der Wirbellosen. Wilhelm von Engelmann, Leipzig, Vol. 11, pp. 1-215.
Vergleichend‐morphologische Untersuchungen am Magen‐Darm‐Trakt der Agamidae und Iguanidae (Reptilia:Lacertilia)
- Henke J.
Henke, J. (1975) Vergleichend-morphologische Unter-suchungen a m Magen-Darm-Trakt der Agamidae und Iguanidae (Repti1ia:Lacertilia). Zool. Jb. Anat., 94,505-569.
- Young
On some points of relation between the morphological structure of the intestine and the diet of reptiles
- Lonnberg E.
Evolution of the iguanine lizards (Sauria, Iguanidae) as determined by osteological and myological characters
- Avery D. F.
Systematics and evolution in the West Indian iguanid genus Cyclura
- Schwartz A.