Thesis (Ph. D.)--University of Texas at Austin, 1999. / Vita. Includes bibliographical references (leaves 202-215). Available also in a digital version from Dissertation Abstracts.

"A thesis submitted to the Graduate Faculty of Georgia Southern University in partial fulfillment of the requirements for the degree Master of Science." Title from PDF of title page (Georgia Southern University, viewed on May 6, 2010). Dana Nayduch, major professor; Lance McBrayer, Oscar Pung, committee members. Electronic version approved: December 2009. Includes bibliographical references (p. 26-30).

Understanding why organisms possess certain combinations of life-history traits is important to our understanding of how natural selection operates. Combinations of life-history traits evolve in response to the costs of current reproduction to both survival and future reproduction. Reproductive costs have been broadly categorised into two types: 1) survival costs, and 2) potential fecundity costs. As a means of predicting and explaining variation in reproductive investment in lizards and snakes, Shine and Schwarzkopf (1992) attempted to determine the relative importance of the two kinds of costs to individual lifetime fitness (the SS model). They concluded that most lizard species are unlikely to make trade-offs between current and future reproduction (fecundity costs). In this study of a temperate-zone lizard, Elgaria coerulea, I have three main objectives: 1) to provide the first natural history data for a Canadian population of this species, 2) to describe life-history traits for this population, and 3) to formally test the predictions of the SS model and discuss its potential predictive power. Individual Elgaria coerulea occupy relatively small areas, thus minimising costs associated with a long-distance migration. In addition to having limited movement, Elgaria coerulea rely on hiding as one of their main anti-predator strategies, although there is sex-dependent variation in their retreat-site selection. Emergence patterns of male Elgaria coerulea did not change over their reproductive cycle. In contrast, the probability of capturing an adult female in the open steadily increased over the summer. These results suggest that the benefits of emerging from cover outweigh the costa in females, but not males. Annual survival rate of adult females was 44% and juvenile survival rate was 22%. The survival rate of adult males likely fell in between these values, but I was not able to estimate it directly because of small sample sizes. I infer from the female’s relatively high survival rate that the necessity for gravid females to spend more time in the open during gestation does not translate simply to increased mortality. Gravid females have reduced sprint speed and sprint speed was inversely related to the burden of the clutch. Therefore, gravid females presumably could reduce their predation risk by remaining closer to cover than males or juveniles. However, this is not the case; all northern alligator lizards remained close to cover. Thus, the lack of shift in anti-predator behaviour of gravid females may be a result of all Elgaria coerulea relying on crypsis rather than sprinting as an anti-predator defence. I did detect a difference in body coloration. Gravid females had more black pigmentation than males or juveniles. The black pigmentation may help females blend in with their background better than males, thereby reducing predation risk, or help increase their body temperature at a quicker rate. Another important anti-predator strategy in Elgaria coerulea is tail autotomy, and once again I measured variation in this trait between males and females. Gravid females never lose small parts of their tails, perhaps giving them extra time to escape from a predator. Furthermore, recent tail loss was not seen in gravid females during late gestation. By contrast, males were equally likely to autotomise at any time of the year. Females may be less likely than males to lose their tails because of the potential reproductive gain by females with intact tails. Females with intact tails had a higher probability of being reproductive and females with longer tails had larger newborn. Finally, I show that some Elgaria coerulea trade current reproduction for growth. Examination of reproductive costs in Elgaria coerulea revealed problems with incorporating cold-climate reptile species into the SS model. Because cold-climate species spend significant time in hibernation each year they have relatively short interclutch intervals. For these species the SS model predicts that trade-offs between current and future reproduction are more likely. The likelihood of fecundity costs also increases, even that concurrent growth and reproduction may be more prevalent than previously believed, as is evident in Elgaria coerulea. Both of these factors need to be incorporated into the SS model is increase our ability to make predictions about the evolution of reproductive effort in cold-climate species. / Graduate

There has long been a need for a comparative study of the osteological and myological structures of the reptilian family Teiidaeo This present study is organized to increase our understanding of the anatomical features of the head and thorax regions of two members of distinct phylogenetic branches of the family Teiidaeo The two genera discussed are Cnemidophorus and Ameiva.

Blainville (1835) wrote the first description of a sand lizard and named it Callisaurus draconoides. Since his time various authors have published articles concerning sand lizards. Girard (1851) described Holbrookia maculata, Trochel (1852) described Cophosaurus texanus, and that same year Baird and Girard synonymized Cophosaurus with Holbrookia providing the name Holbrookia texana, which has stood for over 100 years. Subsequently, Baird (1858) described Uma notata.

Here we present teiid lizard fossils from Gruta do Urso, Aurora do Tocantins, Tocantins State, northern Brazil. We describe a left lower jaw of a "Cnemidophorinae" indet. and a right dentary attributed to Tupinambis sp. These materials share with extant Teiidae a heterodont dentition with subpleurodont tooth implantation, and are assigned to Teiinae and Tupinambinae based on dental characteristics. The paleofaunal assemblage from Gruta do Urso suggests a late Pleistocene/early Holocene age. These records add to our knowledge of the Quaternary fauna of northern Brazil.

Here is provided the first description of Pleistocene lizards recovered from five caves (Baikong, Juyuan, Queque, Sanhe, and Zhiren) in Chongzuo, Zuo River area of Guangxi Zhuang Autonomous Region, southern China. Lizard remains reported here come from faunas that include Gigantopithecus blacki or Homo sapiens dating from the Early to Late Pleistocene with age-range estimates from 2.0Ma to 111ka. The recovery of agamids (Agamidae), skinks (Scincidae), a large species of Gekko, and smaller forms of gekkonids (Gekkonidae) is of interest in that the diversity of lizards for the caves is high given the extremely small sample size from the deposits. The description of cf. Draco reported here is the first indication of the possible occurrence of this genus in the Pleistocene record. Southern China and the adjacent territories in Vietnam and Laos have a diverse lizard fauna today. Cave deposits with established chronologies in the local karst regions such as recovered in Chongzuo, can help record the diversity within the local lizard community through time. Although the fossil lizards reported here appear to represent mammalian prey remains (highly fragmented), caves that contain owl roost pellet deposits might represent a more diverse squamate community with the additional advantage of having specimens that are not as fragmented. Because a Pleistocene-age lizard record does occur in the caves reported here, in all likelihood equivalent deposits should occur in the numerous caves throughout southern China and Southeast Asia.

The reptilian clade Squamata is defined primarily by osteological synapomorphies, few of which are entirely unambiguous. Studies of developing squamate eggs have revealed a uniquely specialized feature not known to occur in any other amniotes. This feature—the yolk cleft/isolated yolk mass complex—lines the ventral hemisphere of the egg. During its formation, extraembryonic mesoderm penetrates the yolk and an exocoelom (the yolk cleft [YC]) forms in association with it, cutting off a thin segment of yolk (the “isolated yolk mass” [IYM]) from the main body of the yolk. The YC–IYM complex has been observed and described in more than 65 squamate species in 12 families. In viviparous species, it contributes to the “omphaloplacenta,” a type of yolk sac placenta unique to squamates. The only squamates known to lack the IYM are a few highly placentotrophic skinks with minuscule eggs, viviparous species in which it clearly has been lost. Given its absence in mammals, chelonians, crocodylians, and birds, the YC–IYM complex warrants recognition as a developmental synapomorphy of the squamate clade. As in extant viviparous lizards and snakes, the YC–IYM complex presumably contributed to the placenta of extinct viviparous squamates.

Natural terrain constantly challenges locomotor stability. Bipedal parasagittal runners rely on proximo-distal control mechanisms and passive mechanical mechanisms to rapidly adjust to changing environments. However, it is not known how sprawled bipedal runners, like the basilisk lizard, adjust to unexpected perturbations. This study examines how basilisks navigate visible drop perturbations to elucidate the control strategies used to maintain stability. We ran four basilisk lizards along a 2.7 m long trackway with an embedded 6-d.o.f. force plate. Control trials were recorded with the force plate mounted flush to the track surface. We lowered the plate to 40% of the lizards’ limb length, relative to the track surface, for perturbation trials. We hypothesized that much like parasagittal runners, basilisks would rely on three distinct compensatory mechanisms to convert the potential energy (PE) change from the drop into fore-aft and vertical kinetic energy (KE) or to increase the total energy of the system (Ecom), as well as a fourth potential mechanism converting PE into medio-lateral KE, as a result of their sprawled limb posture. On average, lizards ran slower (T-ratio30=2.548, p = 0.0162) and with a more vertical limb posture (T-ratio28=-6.119, p < 0.0001) during the drop perturbation. As expected, vertical KE increased in drop surface trials. However, contrary to our hypothesis, the drop perturbation appeared to have little detectable effect on fore-aft and medio-lateral KE. Preliminarily, these results suggest that the sprawled limb posture may afford increased robustness to perturbations such as a sudden drop in surface height, facilitating kinematic compensations independent of significant kinetic changes. / Kinesiology

The anterior myology of Crotaphytus wislizeni and C. collaris is described in detail and a statistical analysis is made of the differences in the relative bone sizes, and the number of eggs per clutch, as well as other taxonomic characters previously applied to these species. The significant differences found with respect to the shape of the skull, that of the body, and the character of the hyoid are correlated with muscular development and habits of the two species. The descriptive material is accompanied by detailed myological and osteological illustrations of C. wislizeni. Comparative notes are made on C. reticulatus which is found to be intermediate between these species with respect to its myology. The results of this study indicate that Gambelia and Crotaphytus are synonymous.