Anne M. Maglia

OSTEOLOGY AND SKELETAL DEVELOPMENT OF DISCOGLOSSUS SARDUS (ANURA : DISCOGLOSSIDAE)

Although frogs in the archaeobatrachian family Discoglossidae are reasonably well known, descriptions of their larval skeletons and osteogenesis are almost nonexistent. Skeletogenesis, chondrocranial development, and the adult skeleton of Discoglossus sardus are described on the basis of cleared and stained, dry, and radiographed specimens. In D. sardus, the first elements to ossify are the parasphenoid, frontoparietals, exoccipitals, neural arches, ischium, long bones, and dermal elements of the pectoral girdle (Gosner Stage 36). Major reconstruction of the chondrocranium begins at the onset of metamorphosis (Stage 41), contemporaneous with the ossification of the premaxillae, maxillae, vomers, and septomaxillae. Several cranial (e.g., pterygoid, mentomeckelian, sphenethmoid) and postcranial (e.g., carpals, hyoid) elements do not commence ossification until after metamorphosis (Stage 46). Discoglossids are characterized by the presence of a facial foramen in the lateral wall of the chondrocranium, a rod‐like epipubis developing from two primordia, and the lack of a neopalatine bone. Adult male Discoglossus possess an enlarged, crested metacarpal II and a broad prepollical element. This detailed description serves as a model to compare the development of other discoglossid frogs and provides detailed descriptions of several enigmatic structures. J. Morphol. 233:267–286, 1997.

Comparative Development of Anurans: Using Phylogeny to Understand Ontogeny1

Abstract Hypotheses of relationships are critical to describing and understanding patterns of evolution within groups of organisms. But rarely has a comparative, historical approach been employed to study developmental change, particularly among anurans. A recent resurgence of interest in collecting basic ontogenetic information provides us with the opportunity to compare ontogenetic trajectories in a phylogenetic framework. Larval skeletons and osteological development were examined for 22 taxa and compared to two hypotheses of relationships—that of Cannatella, and one proposed herein based on 41 morphological characters from larvae and 62 from adults. Larval characters were mapped on the alternate cladograms using the ACCTRAN optimization criterion. Several larval features are highly conserved among some anurans, suggesting that there is some level of canalization of morphology early in ontogeny. In contrast, a number of morphologies vary among groups, supporting the fact that there have been major evolutionary modifications to anuran larval morphologies early in ontogeny and in the early evolutionary history of anurans.

Ontogeny of the bizarre: an osteological description of Pipa pipa (Anura: Pipidae), with an account of skeletal development in the species

ABSTRACT

AN ANATOMICAL ONTOLOGY FOR AMPHIBIANS

Herein, we describe our ongoing efforts to develop a robust ontology for amphibian anatomy that accommodates the diversity of anatomical structures present in the group. We discuss the design and implementation of the project, current resolutions to issues we have encountered, and future enhancements to the ontology. We also comment on future efforts to integrate other data sets via this amphibian anatomical ontology.

Skeletal morphogenesis of the vertebral column of the miniature hylid frog Acris crepitans, with comments on anomalies.

Although the vertebral columns of anurans have received much study in the last 150 years, few detailed descriptions exist of the skeletal morphogenesis of this anatomical unit. Herein, the ontogeny of the vertebral skeleton of the hylid frog Acris crepitans is described based on cleared and double‐stained specimens, radiographs, and 3D reconstructions generated from synchrotron microCT scans. The adult axial formula is 1‐7‐1‐1, and the vertebral centra are epichordal and procoelous. The neural arches are nonimbricate, and there is a medial articulation between the laminae of Presacrals I and II. Free ribs are absent. The sacral diapophyses are uniform in width or slightly expanded distally. The urostyle is slender, round in cross section, and about equal in length to the presacral region. Presacral vertebrae are the first to form, developing in a cephalic‐to‐caudal sequence. However, development and growth are decoupled and growth is fastest initially in the posterior presacrals and sacrum. In addition, there is a time lag between the formation of the presacral/sacral region and the postsacral region. More than 8.5% of the specimens examined have vertebral anomalies, and about 50% display small variants from the typical vertebral column morphology. However, these malformations do not seem to have been so severe as to have affected survival. J. Morphol., 2009.

Developmental Evolution of the Anuran Sacro-Urostylic Complex

ABSTRACT. The sacro-urostylic region of anurans, which consists of a single sacral vertebra and a rodlike urostyle, is one of the most unusual specializations of the group and seems to have appeared concomitant with their origin and the move toward saltation. The ontogeny of the sacro-urostylic region follows two different pathways. In some taxa, the anterior end of the hypochord (ventral, unsegmented structure of the urostyle) never exceeds to the level of the anterior end of Postsacral Vertebra 1, whereas in others it extends anteriorly to the level of the sacrum. Thus, as the hypochord migrates dorsally during metamorphosis, it either fuses to the overlying Postsacral 1 or to the sacrum. In the first developmental mode, the adult morphology consists of an articulating sacrum and urostyle, as in the jumping frogs Acris crepitans and Discoglossus sardus. In the second developmental mode, the adult morphology results in a fused sacrum and urostyle, which is characteristic of the hopping-burrowing Spea multiplicata and the aquatic Xenopus laevis. The articulation between the sacrum and urostyle constitutes the best joint for saltatorial locomotion, whereas the loss of mobility between these two elements seems to increase stability for digging and swimming. Further rigidity in the sacro-urostylic complex is achieved by fusion of additional vertebrae to the sacrum and urostyle to form a synsacrum, as in the aquatic Hymenochirus curtipes, and may represent an adaptive trait for maintaining the body straight during swimming.

Identifying character non-independence in phylogenetic data using data mining techniques

Undiscovered relationships in a data set may confound analyses, particularly those that assume data independence. Such problems occur when characters used for phylogenetic analyses are not independent of one another. Although a data mining technique known as rule induction from coverings has earlier been shown to be a promising approach for identifying such non-independence, its inherent computational complexity has limited its application for large phylogenetic data sets. Herein we present a parallelized implementation of the rule induction from coverings strategy which overcomes some of these limitations. We also discuss two heuristics that have been applied to the algorithm to further improve its efficiency.

Identifying Character Non-independence in Phylogenetic Data Using Parallelized Rule Induction from Coverings

Undiscovered relationships in a data set may confound analyses, particularly those that assume data independence. Such problems occur when characters used for phylogenetic analyses are not independent of one another. Although a data mining technique known as rule induction from coverings has earlier been shown to be a promising approach for identifying such non-independence, its inherent computational complexity has limited its application for large phylogenetic data sets. Herein we present a parallelized implementation of the rule induction from coverings strategy which overcomes some of these limitations. We also discuss two heuristics that have been applied to the algorithm to further improve its efficiency.