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Patterns of growth and variation of the appendicular skeleton were examined in Thorius, a speciose genus of minute terrestrial plethodontid salamanders from southern Mexico. Observations were based primarily on ontogenetic series of each of five species that collectively span the range of adult body size in the genus; samples of adults of each of seven additional species provided supplemental estimates of the full range of variation of limb skeletal morphology. Limbs are generally reduced, i.e., pedomorphic, in both overall size and development, and they are characterized by a pattern of extreme variation in the composition of the limb skeleton, especially mesopodial elements, both within and between species. Fifteen different combinations of fused carpal or tarsal elements are variably present in the genus, producing at least 18 different overall carpal or tarsal arrangements, many of which occur in no other plethodontid genus. As many as four carpal or tarsal arrangements were observed in single population samples of each of several; five tarsal arrangements were observed in one population of T. minutissimus. Left-right asymmetry of mesopodial arrangement in a given specimen is also common. In contrast, several unique, nonpedomorphic features of the limb skeleton, including ossification of the typically cartilaginous adult mesopodial elements and ontogenetic increase in the degree of ossification of long bones, are characteristic of all species and distinguish Thorius from most related genera. They form part of a mechanism of determinate skeletal growth that restricts skeletal growth after sexual maturity. Interspecific differences in the timing of the processes of appendicular skeletal maturation relative to body size are well correlated with interspecific differences in mean adult size and size at sexual maturity, suggesting that shifts in the timing of skeletal maturation provide a mechanism of achieving adult size differentiation among species. Processes of skeletal maturation that confer determinate skeletal growth in Thorius are analogous to those typical of most amniotes - both groups exhibit ontogenetic reduction and eventual disappearance of the complex of stratified layers of proliferating and maturing cartilage in long bone epiphyses - but, unlike most amniotes, Thorius lacks secondary ossification centers. Thus, the presence of secondary ossification centers cannot be used as a criterion for establishing determinate skeletal growth in all vertebrates.

Miniaturization of body size is often accompanied by peculiarities in morphology that can have functional consequences. We examined the feeding behavior and morphology of the miniaturized plethodontid salamander Thorius, one of the smallest vertebrates, to determine if its performance and biomechanics differ from those of its larger relatives. High-speed imaging and dynamics analysis of feeding at a range of temperatures show that tongue projection in Thorius macdougalli is ballistic and achieves accelerations of up to 600 G with low thermal sensitivity, indicating that tongue projection is powered by an elastic-recoil mechanism. Preceding ballistic projection is an unusual preparatory phase of tongue protrusion, which, like tongue retraction, shows lower performance and higher thermal sensitivity that are indicative of movement being powered directly by muscle shortening. The variability of tongue-projection kinematics and dynamics is comparable to larger ballistic-tongued plethodontids and reveals that Thorius is capable of modulating its tongue movements in response to prey distance. Morphological examination revealed that T. macdougalli possesses a reduced number of myofibers in the tongue muscles, a large projector muscle mass relative to tongue mass, and an unusual folding of the tongue skeleton, compared with larger relatives. Nonetheless, T. macdougalli retains the elaborated collagen aponeuroses in the projector muscle that store elastic energy and a tongue skeleton that is free of direct myofiber insertion, two features that appear to be essential for ballistic tongue projection in salamanders.

A new minute salamander of the genus Thorius is described from the western highlands of the Mexican state of Guerrero. Previously, three congeners were known from the central portion of the state. The fourth species we herein describe occurs in the western portion of the Sierra Madre del Sur of Guerrero and is allopatric from nearest congeners by about 80 km. The new species is distinguished from Guerreran congeners by a combination of body size, external morphology, and dentition.

Ability, equity, and culture: Sustaining inclusive urban education reform, edited by Kozleski and Thorius (2014), is a remarkable compilation of work, written by a diverse ensemble of educators, researchers, practitioners, and advocates. A thought-provoking book that looks critically at urban education reform, the authors challenge readers to have a broader understanding of what the term inclusivity entails. The editors present the work of 17 authors who were all part of the National Institute for Urban School Improvement (NIUSI). These authors shed light on various aspects of systemic urban reform in policy, pedagogy, and practice. Issues discussed ranged from the micro to the macro change initiatives to classroom environments and district culture, as well as successful models of student-centered programs around the country. Using data from 12 years of research conducted under the sponsorship of NIUSI, the contributors paint a hopeful, if daunting, a portrait of what equitable, inclusive, and culturally responsive education should and could look like. Ultimately, the contributors of this book believe that sustainable, scalable, successful systemic educational reform is attainable, provided that all stakeholders are committed to cultural responsivity and inclusivity for all students. In order to achieve this goal, the authors posit that reform needs to combat discrimination based on socially constructed notions of difference, such as gender, race, ethnicity, ability, class, and sexual orientation.

The small size and apparent external morphological similarity of the minute salamanders of the genus Thorius have long hindered evolutionary studies of the group. We estimate gene and species trees within the genus using mitochondrial and nuclear DNA from nearly all named and many candidate species and find three main clades. We use this phylogenetic hypothesis to examine patterns of morphological evolution and species coexistence across central and southern Mexico and to test alternative hypotheses of lineage divergence with and without ecomor- phological divergence. Sympatric species differ in body size more than expected after accounting for phylogenetic relationship, and morphological traits show no significant phylogenetic signal. Sympatric species tend to differ in a combination of body size, presence or absence of maxillary teeth, and relative limb or tail length, even when they are close relatives. Sister species of Thorius tend to occupy climatically similar environments, which suggests that divergence across climatic gradients does not drive species formation in the genus. Rather than being an example of cryptic species formation, Thorius more closely resembles an adaptive radiation, with ecomorphological divergence that is bounded by organism-level constraints. © 2013 The Linnean Society of London, Biological Journal of the Linnean Society, 2013, 109, 622-643. ADDITIONAL KEYWORDS: biogeography - diversification - morphology - phylogeny - species formation - systematics.

We describe three new species of minute salamanders, genus Thorius, from the Sierra Madre del Sur of Oaxaca, Mexico. Until now only a single species, T. minutissimus, has been reported from this region, although molecular data have long shown extensive genetic differentiation among geographically disjunct populations. Adult Thorius pinicola sp. nov., T. longicaudus sp. nov., and T. tlaxiacus sp. nov. are larger than T. minutissimus and possess elliptical rather than oval nostrils; T. pinicola and T. longicaudus also have longer tails. All three new species occur west of the range of T. minutissimus, which has the easternmost distribution of any member of the genus. The new species are distinguished from each other and from other named Thorius in Oaxaca by a combination of adult body size, external morphology and osteology, and by protein characters (allozymes) and differences in DNA sequences. In addition, we redescribe T. minutissimus and a related species, T. narisovalis, to further clarify the taxonomic status of Oaxacan populations and to facilitate future studies of the remaining genetically differentiated Thorius that cannot be satisfactorily assigned to any named species. Populations of all five species considered here appear to have declined dramatically over the last one or two decades and live specimens are difficult to find in nature. Thorius may be the most endangered genus of amphibians in the world. All species may go extinct before the end of this century.

Despite several recent studies, the phylogeny of plethodontid salamanders is not yet fully resolved and the phylogenetic positions of several key genera, especially Aneides, Hemidactylium, Hydromantes and Karsenia, are contentious. Here we present a combined dataset of complete mitochondrial genomes and three nuclear loci for 20 species (16 genera) of plethodontids, representing all major clades in the family. The combined dataset without mitochondrial third codon positions provides a fully resolved, statistically well-supported tree. In this topology two major clades are recovered. A northern clade includes Aneides, Desmognathus, Ensatina, Hydromantes, Karsenia, Phaeognathus and Plethodon, with Plethodon being the sister taxon to the rest of the clade. Hydromantes and Karsenia are sister taxa, and Aneides is recovered as the sister taxon to Ensatina. Desmognathus + Phaeognathus form the sister taxon to Aneides + Ensatina. An eastern/southern clade comprises two subclades. One subclade, the spelerpines (Eurycea, Gyrinophilus, Pseudotriton, Stereochilus, Urspelerpes) is the sister taxon to a subclade comprising Hemidactylium, Batrachoseps and the tropical plethodontids (represented by Bolitoglossa, Nototriton and Thorius). In this topology Hemidactylium is well-supported as the sister taxon to Batrachoseps. Only when mitochondrial third codon positions are included using maximum likelihood analysis is Hemidactylium recovered as the sister taxon to Batrachoseps + tropical genera. Hypothesis testing of alternative topologies supports these conclusions. On the basis of these results we propose a conservative taxonomy for Plethodontidae.

In his letter (1), Gamfeldt asks questions concerning broader aspects of our study (2). In response, salamander biomass has been substantially reduced. In the upper cloud forest habitat at El Rincon, San Marcos, Guatemala, 3 formerly abundant salamander species and a 4th relatively rare species were not found. Although 3 other species were found as often or slightly more so than in the past, the overall salamander density at El Rincon is much lower compared to previous decades. These 7 species constitute the entire salamander community at this site, and no species were found on our recent surveys that were not present in the 1970s. The total salamander biomass at the site is only a fraction of what it once was; vastly fewer amphibians and reptiles (specifically salamander-eating snakes) were encountered than in the past. Similarly, forest habitat with formerly dense populations of Pseudoeurycea and Thorius on Cerro San Felipe, Oaxaca, Mexico, now contain no Pseudoeurycea (based on our surveys) and very few Thorius compared with previous decades, although suitable habitat remains. All salamander species have declined at this site, with no compensation from any other salamander species.

7TH INTERNATIONAL CONGRESS ON VERTEBRATE MORPHOLOGY MEETINGBOCA RATON, FLORIDA-- From 27 July to 1 August, animals with a backbone drew the attention of morphologists, evolutionary biologists, and other researchers. A new analysis of the family tree of the Thorius genus of salamanders reported at the meeting suggests that a few species have reacquired traits that their earliest ancestors had lost.

Five new species of diminutive salamanders of the endemic Mexican genus Thorius (Plethodontidae) are described from the Sierra de Juirez in northern Oaxaca. The species are diagnosed by adult body size, external proportions, dentition, osteology and coloration. The three species that have been studied using protein electrophoresis are genetically unique; all differ from T. macdougalli, the only species of the genus previously known from these mountains. Each of the six species studied has distinct geographic and elevational ranges, and there is a complex pattern of geographic overlap and replacement. As many as three species co-occur locally at elevations up to 2955 m on Cerro Pelon, and each species is sympatric with at least one other. One species descends to approximately 800 m, which is the lowest known elevational record for the genus. The new taxa include the full size range of the genus, with two large and three small species.

Relative size and arrangement of the brain and paired sense organs are examined in three species of Thorius, a genus of minute, terrestrial salamanders that are among the smallest extant tailed tetrapods. Analogous measurements of representative species of three related genera of larger tropical (Pseudoeurycea, Chiropterotriton) and temperate (Plethodon) salamanders are used to identify changes in gross morphology of the brain and sense organs that have accompanied the evolution of decreased head size in Thorius and their relation to associated changes in skull morphology. In adult Thorius, relative size (area measured in frontal plane, and length) of the eyes, otic capsules, and brain each is greater than in adults of all of the larger genera; relative size of the nasal capsules is unchanged or slightly smaller. Interspecific scaling phenomena–negative allometry of otic capsule, eye and brain size, isometry or slight positive allometry of nasal capsule size, all with respect to skull length–also are characteristic of intraspecific (ontogenetic) comparisons in both T. narisovalis and Pseudoeurycea goebeli. Predominance of the brain and eyes in Thorius results in greater contact and overlap among these structures and the nasal capsules in the anterior portion of the head. This is associated with anterior displacement of both the eyes and nasal capsules, which now protrude anterior to the skull proper; a change in eye shape; and medial deformation of anterior braincase walls. Posteriorly, predominance of the otic capsules has effected a reorientation of the jaw suspensorium to a fully vertical position that is correlated with the novel presence of a posteriorly directed squamosal process and shift in origin of the quadropectoralis muscle. Many of these changes in cranical morphology may be explained simply as results of mechanical (physical) interactions among the skeletal, nervous, and sensory components during head development at reduced size. This provides further evidence of the role of nervous, sensory, and other “soft” tissues in cranial skeletal morphogenesis, and reinforces the need to consider these tissues in analyses of skull evolution.

Salamanders of the genus Thorius (Plethodontidae) are among the smallest tetrapods. Hypotheses of limb skeletal evolution in these vertebrates were evaluated on the basis of estimates of natural variation, comparisons of skeletal homology, and analysis of molecular phylogeny. Nine carpal arrangements occur in Thorius, more than in all twelve related genera of typically larger salamanders; six of these arrangements are unique. They represent a trend toward a decrease in the number of separate cartilages that is independent of locomotor and ecological specialization. Miniaturization may be an important source of morphological novelty, distinct from local adaptation, in vertebrates.

Cranial skeletal morphology, ontogeny and variation are examined in five species of Thorius, a genus of diminutive plethodontid salamanders that are among the smallest, extant, tailed tetrapods. The skull of adull Thorius is characterized by: (1) limited development or absence of several ossified elements and dentition; (2) increased inter-and intraspecific variability; (3) novel morphological configurations of the braincase and jaw suspensorium. Posthatching cranial mineralization in all species of Thorius is truncated precociously with respect to that typical of larger and more generalized plethodontid genera, such as Pseudoeurycea. These features implicate paedomorphosis as a predominant mechanism responsible for the evolution of decreased size in Thorius from larger plethodontid ancestors. Interspecific differences in cranial morphology are evident; species may be characterized by greater or lesser degrees of truncated development. However, there is no consistent relationship between degree of paedomorphosis and mean adult body size in interspecific comparisons. Adult morphology of several individual elements represent potentially useful taxonomic characters for distinguishing species. Reduction, increased variability, and morphological novelty are common to many lineages of dwarfed taxa. They represent a null hypothesis for examination of the developmental mechanisms and morphological consequences of miniaturization in other groups.

Patterns of genetic relationship and taxonomic identity are examined in Thorius, an enigmatic genus of minute neotropical salamanders that represent the smallest tailed tetrapods. Data comprise an electrophoretic analysis of 16 protein loci in 69 population samples from 55 localities throughout the range of the genus in southern Mexico. Eight of the nine described species are genetically distinct: Nei's D commonly exceeds 0.9. There is no biochemical evidence of more than a single species at Zoquitlan, Pue., type locality of T. schmidti and T. maxillabrochus. Genetic differentiation between disjunct subspecies of T. pennatulus is less than the mean pairwise value between described species, but exceeds that observed between some sympatric species pairs. Seven additional as yet undescribed species are identified, based either on their sympatric occurrence with, or great genetic differentiation from, described species. Most species initially identified by electrophoresis are morphologically distinct. Electrophoretic data fail to resolve the taxonomic affinity of a few remaining populations, although they do provide clearcut and distinguishable hypotheses of relationship that can be tested using other sources, such as morphology. The 15 species constitute three faunal units: Veracruz and eastern Puebla; Sierra de Juarez, Oaxaca; southern and western Oaxaca, and Guerrero. Local endemism is observed within each region, in which sympatry involving two or three species is common. Species frequently demonstrate narrow elevational zonation and distinct habitat and microhabitat preference (e.g., arboreal vs terrestrial). The distribution of four species on Cerro Pelon, Oax., is examined in detail.

HIGH mountains on the southern edge of the Mesa Central in Puebla, Oaxaca, and western Veracruz have isolated mesically adapted species in many groups of the Mexican herpetofauna. This is especially true in the Amphibia where such diverse genera as Pseudoeurycea, Microbatrachylus, and Hyla have one or several "insular" species in the region. Thoriine salamanders are no exception for ten forms occur in humid habitats between the Mesa Central and

Radiographs of series of Thorius pulmonaris, Parvimolge townsendi, Lineatriton lineolus and various other plethodontids were made with a beryllium-window x-ray machine, using the techniques described by Miller (1957). The radiographs were examined for x-ray opaque areas in the hyoid and mesopodials. Opaque hyoid elements were easily detected. Most of the available specimens of Lineatriton and Parvimolge were not preserved in positions convenient for x-ray study of the limbs, and the number of x-ray opaque mesopodials in them could not be determined accurately. The series of Thorius, however, was preserved with the trunk straight and the limbs at right angles to the body, and in these the number of opaque mesopodials could be counted. In order to verify the radiographic determinations of ossified or calcified mesopodials, three of the x-rayed specimens of Thorius pulmonaris were cleared and stained with alizarin red S. One, a large adult female (26.9 mm.), had the maximum number of x-ray opaque mesopodials observed in Thorius; a second female (24.5 mm.) had an intermediate number; a third female (23.4 mm.) was the largest that had no opaque mesopodials. In each of these the number of elements that stained with alizarin agrees with the number that were x-ray opaque. It is felt, therefore, that the use of x-rays to determine the presence or absence of ossifications or calcifications is justified, and that the results obtained are consistent with those that would be ob