Allen E. Greer

Limb Reduction in the Lizard Genus Lerista. 1. Variation in the Number of Phalanges and Presacral Vertebrae

The sandswimming, Australian scincid lizard genus Lerista is the best example of limb reduction in tetrapods in that it comprises an extensive and finely graded morphocline within a group of 51 closely related species. This paper analyzes variation in the number of phalanges and presacral vertebrae within populations and among species. Within populations, phalangeal number varies little and variation is usually symmetrical within individuals. The number of presacral vertebrae is sexually dimorphic, with females averaging 0.4-2.0 more than males. Among species there is a strong, curvilinear, inverse relationship between the number of phalanges and the number of presacral vertebrae. The interspecific morphoclines of phalangeal complements based on the total number of phalanges show that digits in both the manus and pes are lost in the order 1 > 5 > 2 > 3 > 4. Such morphoclines are perfectly linear except at one point in the pes where the series branches to accommodate two mutually exclusive configurations. If these morphoclines represent phylogenetic reductions and if phylogenetic reductions are hypothesized to be globally arrested stages of a basic developmental pattern, then one of these pes configurations must constitute an exception to this generalization. At least one other observed configuration is also likely to be outside a basic, global ontogenetic sequence for the genus.

Limb Reduction in the Scincid Lizard Genus Lerista. 2. Variation in the Bone Complements of the Front and Rear Limbs and the Number of Postsacral Vertebrae

Morphoclines for the front and rear limb bone configurations in the sand-swimming lizard genus Lerista trace only a very narrow pathway through morphological space. The morphoclines are generally finely-graded and linear, except for one mutually exclusive pair of osteological configurations in the manus and one in the pes. These alternative states plus the occurrence of adult configurations not seen in the development of generally primitive tetrapods suggest that limb reduction in Lerista is not simply the global truncation of a primitive developmental sequence. A circumstantial argument is made for the functional significance of at least some of the observed morphology: the condition of near or complete absence of the front limb in conjunction with the retention of two toes on the rear limb is common in Lerista and two other skink lineages inhabiting fine, loosely-consolidated sand. The various configurations in the Lerista morphoclines are disproportionately represented by species; this may reflect speciation opportunities in various habitats. Numbers of postsacral vertebrae are not sexually dimorphic. Coefficients of variation of postsacral vertebrae exceed those for presacral vertebrae, reflecting inversely the relative functional importance of the two parts of the vertebral column. In interspecific comparisons, the number of phalanges in the pes is positively correlated with the number of phalanges in the manus and negatively correlated with the numbers of presacral and postsacral vertebrae. Functionally, this reflects the supplementary relationship between the modalities of limbed locomotion (phalanges) and the com- plementary relationship between the modalities of limbed and trunk locomotion (vertebrae). Among tetrapods lizards are renowned for the many lineages that have undergone limb reduction independently, and among lizards,

Observations on Limb Reduction in the Scincid Lizard Genus Chalcides

The relationships between several mensural and morphological variables are examined in the limb-reduced lineage of scincid lizards, Chalcides. There is a close linear relationship between the relative length of the body and the relative length of the head, the number of phalanges in the manus and in the pes, the relative length of the front and of the rear limb, and the relative length of the body and the number of presacral vertebrae. There is apparently only a loose association between snout-vent length and the number of presacral vertebrae and the number of pre- and postsacral vertebrae. There is a strongly inflected relationship between the number of phalanges and the relative length of the limb, the total number of phalanges, and both the number of presacral vertebrae and the relative length of the body, and the number of sternal + mesosternal ribs and both the relative length of the front limb and the number of parasternal chevrons. The inflected relationships may indicate a shift in emphasis from limbed locomotion to trunk locomotion (lateral undulation). However this supposition can only be tested when more is known of the ecology and behavior of the genus.

Distribution of Maximum Snout-Vent Length among Species of Scincid Lizards

-The distribution of maximum snout-vent length for 1206 of the approximately 1227 described species of scincid lizards ranges from 23-490 mm, has a mode of 55 mm, a median of 69 mm, a mean of 82 mm, and is strongly right skewed. At both the small and large ends of the distribution, there are noticeable lineage effects, that is, a few lineages contribute a large proportion of the species. Perhaps surprisingly given the surface-volume relationships of small animals, many of the smallest species occur in arid or seasonally arid habitats. Egg size may be the limiting factor in the evolution of small adult size. The larger species tend to be burrowers (litter and sand swimmers), have diets different from the usual (for scincids) arthropods, occur on small oceanic islands (absence of predators?), or are live-bearing. Species of skinks that have gone extinct in the last 200 years have been relatively larger than species that have survived. The overall shape of the size distributions for scincids and gekkonids, the only other major group for which there are comparable data, are surprisingly similar, suggesting a common cause such as tracking evolutionarily the same size spectrum of arthropod prey. al of Herpet logy, Vol. 35, No. 3, pp. 383-395, 2001 right 2 01 Society for the Study of Amphibi s and R ptiles ibution of Maximum Snout-Vent Length among Species of Size is a key feature in the biology of most animals because of its relationship to a wide variety of ecological and physiological attributes (Peters, 1983; Calder, 1984; Schmidt-Nielsen, 1984; Harvey and Pagel, 1991). But what determines size? One approach to this question is to examine the distribution pattern of some measure of size both within and among lineages. Here I present the distribution curve for one aspect of size, maximum snout-vent length, for the largest family of lizards, the skinks; make some observations about its shape and some attributes of the species at its extremes (where correlating factors are likely to be most pronounced), and compare it with the only other large group of lizards for which there are similar data, the geckos. There are approximately 1227 described species of living and recently extinct (since Euroe is a key feature in the biology of most i als because of its relationship to a wide vai ty of ecol gical nd physiological attributes pean expansion) scincid lizards (pers. obs.). These species comprise approximately 31.7% of all lizard species (based on a total of 3865 species, Bauer, 1992). Skinks are also one of the most diverse lizard groups, in part, because of their repeated reduction of limbs and their consequent extension into subsurface microhabitats. Data on size for 1206 species of skinks (98.3% of all skink species) form the basis of this analysis. MATERIALS AND METHODS Maximum snout-vent length (SVL and henceforth, size), measured to the nearest whole millimeter, was the variable chosen to estimate species size. There were two reasons for choosing this variable. First, it is easy to determine, especially from the literature, and, hence, it can be broadly surveyed. Second, it is indicative of the 383 This content downloaded from 157.55.39.35 on Wed, 31 Aug 2016 04:37:28 UTC All use subject to http://about.jstor.org/terms

Intrapopulational and Interspecific Variation in Digital Limb Bones and Presacral Vertebrae of the Genus Hemiergis (Lacertilia, Scincidae)

The configuration of the phalanges and the number of presacral vertebrae vary within and among seven populations representing the five species of Hemiergis. Phalangeal variation within popu- lations is rare, being restricted to three of the seven populations sampled. Phalangeal variation among populations suggests a pattern of generally simultaneous reduction of phalanges in the manus and pes. This pattern is in contrast to that observed in Lerista, another genus of fossorial Australian skinks, in which the phalanges of the manus are reduced to a progressively greater degree than are the phalanges of the pes as limbs are reduced. All populations show sexual dimorphism in numbers of presacral vertebrae, females having more presacrals than males. The most parsimonious transformation series among modal

Hyperphalangy in Squamates: Insight on the Reacquisition of Primitive Character States in Limb-Reduced Lineages

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The Loss of the External Ear Opening in Scincid Lizards

Abstract Scincid lizards have probably lost the external ear opening at least 17 times. Based on features of the middle ear, especially the orientation and attachment of the extracolumella and columella, five basic types of ear loss are recognized. These five types are strongly associated with major lineages. Ear loss seems to be associated with both small size and fossorial habits.

From Sphenomorphus to Lipinia: Generic Reassignment of Two Poorly Known New Guinea Skinks

Abstract Lygosoma nototaenia Boulenger, 1914, and Lygosoma albodorsale Vogt, 1932, previously placed in the genus Sphenomorphus, are redescribed from the three known specimens of each (including two new specimens of the latter species) and transferred to the genus Lipinia. The phenotypically similar genus Scincella is distinguished from Lipinia by an apomorphic feature of the secondary temporal scales. A novel phalangeal condition, shortening of the third phalanx of the fourth toe, is identified in Lipinia cheesmanae and Lipinia longiceps.

A new character within the taxonomically difficult Sphenomorphus group of lygosomine skinks, with a description of a new species from New Guinea

Abstract The postsupraocular, a small oblique scale just posterior to the supraoculars and medial to the pretemporal scales, is a derived character within the taxonomically difficult Sphenomorphus group of lygosomine skinks. This character occurs in 22 of the approximately 125 described species of Sphenomorphus currently recognized. The species with this distinctive character occur in the southern Philippine Islands, New Guinea, and the Solomon Islands and are called, informally, the Sphenomorphus maindroni group. A new species in the group is described from New Guinea, where most of the species occur. A key to the species with the distinctive character is provided.

Aspects of the morphology and reproductive biology of the Australian Earless Dragon Lizard Tympanocryptis tetraporophora

In the small Australian dragon (agamid) lizard Tympanocryptis tetraporophora mean snout-vent length (SVL) does not differ significantly between the sexes within the species as a whole. However, in a large sample from Sturt National Park, in northwestern New South Wales, males are larger than females both in snout-vent length and in mass. Large specimens are notably lacking from collections made during the coolest time of year.The number of premaxillary teeth is not correlated with head size. However, the number of acrodont teeth on the maxilla and dentary increases with head size.The modal number of presacral vertebrae is 23. There is no sexual dimorphism in either the number of postsacral vertebrae or the number of postsacral vertebrae with transverse processes. Hyperphalangy occurs in 3.2% of specimens. Gross variation in the sacral vertebrae occurs in 5.3% of specimens.For allometric analysis, two samples were considered: specimens from Stud National Park and all other specimens. Head length and hind l...