Linda Trueb

A new frog family (Anura: Terrarana) from South America and an expanded direct-developing clade revealed by molecular phylogeny

Three frogs of a new species found in cloud forests on two nearby mountains in Guyana were included in a molecular phylogeny of 17 nuclear and mitochondrial genes (10,739 aligned sites) that revealed that their closest relative is Terrarana (Brachycephalidae, Craugastoridae, Eleutherodactylidae, and Strabomantidae) and their next-closest relative is Hemiphractidae (marsupial frogs). We place these frogs in a new family, genus, and species which is strongly supported as the basal clade within Terrarana: Ceuthomantidae n. fam., Ceuthomantis smaragdinus n. gen, n. sp. Morphological evidence supports the placement of two other species from the Guiana Highlands, Pristimantis aracamuni (BarrioAmoros & Molina) and P. cavernibardus (Myers & Donnelly), in the new family and genus. This close phylogenetic relationship of terraranans and marsupial frogs, nearly all of which have direct development, supports an hypothesis that direct development evolved early in the evolution of this huge clade (~1000 species), for which we propose the unranked taxonomic epithet Orthobatrachia.

Phylogenetic relationships of glassfrogs (Centrolenidae) based on mitochondrial and nuclear genes

Glassfrogs (family Centrolenidae) represent an exceptionally diverse group among Neotropical anurans, but their evolutionary relationships never have been assessed from a molecular perspective. Mitochondrial and nuclear markers were used to develop a novel hypothesis of centrolenid phylogeny. Ingroup sampling included 100 terminals, with 78 (53%) of the named species in the family, representing most of the phenotypic diversity described for the group. Thirty-five species representing taxa traditionally associated with glassfrogs were used as outgroups. Gene sampling consisted of complete or partial sequences of three mitochondrial (12S, 16S, ND1) and three nuclear markers (c-myc exon 2, RAG1, POMC) for a total of approximately 4362bp. Phylogenies were estimated using maximum parsimony, maximum likelihood, and Bayesian analyses for individual genes and combined datasets. The separate analysis of mitochondrial and nuclear datasets allowed us to clarify the relationships within glassfrogs; also, we corroborate the sister-group relationship between Allophryne ruthveni and glassfrogs. The new phylogeny differs significantly from all previous morphology-based hypotheses of relationships, and shows that hypotheses based on few traits are likely to misrepresent evolutionary history. Traits previously hypothesized as unambiguous synapomorphies are shown to be homoplastic, and all genera in the current taxonomy (Centrolene, Cochranella, Hyalinobatrachium, Nymphargus) are found to be poly- or paraphyletic. The new topology implies a South American origin of glassfrogs and reveals allopatric speciation as the most important speciation mechanism. The phylogeny profoundly affects the traditional interpretations of glassfrog taxonomy, character evolution, and biogeography-topics that now require more extensive evaluation in future studies.

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

Osteology, skeletal development, and chondrocranial structure of Hamptophryne boliviana (Anura: Microhylidae)

Hamptophryne boliviana is a medium‐sized microhylid frog inhabiting the forest‐floor leaf litter of South American rainforests. Larvae of this species typically are found near the bottom of small ponds and water‐filled depressions in the forest. On the basis of cleared‐and‐stained specimens, the larval chondrocranium is described, as well as the development of the skeleton and its condition in adults. Contrary to previous reports, adult Hamptophryne boliviana possess neopalatine (= palatine) bones. The vomer is divided into anterior and posterior parts; the degree of development of the posterior vomers varies among individuals and bilaterally within individuals. In its osteological development, Hamptophryne differs from most other anurans studied in that the vomer, and bones of the suspensorium and mandible, appear postmetamorphically. Similarly, the ischium, pubis, carpals, and tarsals do not appear until metamorphosis is completed. The chondrocranium possesses paired suprarostral cartilages—elements that have been reported to be absent in microhylid larvae. Furthermore, the chondrocranium differs from those described for other microhylid taxa by the possession of 1) a subpalatoquadrate bar that is described herein and 2) a greatly expanded, fenestrate sheet of cartilage associated with the larval otic process and otic capsule.

Evolution of Pipoid Frogs: Morphology and Phylogenetic Relationships of Pseudhymenochirus

The phylogenetic relationships of the poorly known African pipid frog Pseudhymenochirus merlini were studied using phylogenetic analysis of comparative morphology. Forty-nine characters from fourteen species were surveyed from integumentary structures, osteology (especially of the cranium and pectoral girdle), and larvae. The resultant cladogram is well corroborated; only six of the characters exhibited homoplasy. Pseudhymenochirus is not merely a primitive Hymenochirus, nor is it an inter- mediate between Xenopus and Hymenochirus. It is the sister-group to Hymenochirus (boettgeri and curtipes) and possesses several derived features not found in other pipids. Pseudhymenochirus and Hy- menochirus together (the hymenochirines) are the sister-group to Pipa; the three genera are included in the subfamily Pipinae. Several of the unique features in hymenochirines may be related to the small size of these animals.

Leptodactylid Frogs of the Genus Telmatobius in Ecuador with the Description of a New Species

Three species of Telmatobius occur above 2,450 m in the Ecuadorian Andes. Telmatobius niger (including T. cinereus, new synonym) is the most widespread, whereas T. vellardi and T. cirrhacelis, new species, have restricted distributions in the cordilleras of southern Ecuador. Included in the species accounts are redescriptions of the holotypes of T. niger and T. veUardi, descriptions of the larvae of these species, and a discussion of morphological variation in T. niger. On the bases of observations reported here, certain emendations to the definition of the genus Telmatobius are suggested.

THE EARLIEST KNOWN PIPOID FROG FROM SOUTH AMERICA: A NEW GENUS FROM THE MIDDLE CRETACEOUS OF ARGENTINA

Abstract Vertebrate remains from the Late Albian–Early Cenomanian Candeleros Formation of northwestern Patagonia include those of a pipoid frog, which is described herein. The fossils consist of partially articulated and disarticulated elements, some of them badly broken, that are mostly exposed in ventral aspect. The description is based on one incomplete skeleton that presumably belongs to a single individual; this specimen possesses a combination of character states not present in other known non-palaeobatrachid pipimorph taxa and is identified here as a new genus and species, Avitabatrachus uliana. The species is moderately small (estimated snout-vent length ca. 35 mm) and shares with Pipidae conch-like squamosals, deeply excavated prootics to form channels for the Eustachian tubes, articulations for the lower jaws at the anterolateral corners of otic capsules, and fused sacrum and urostyle. Avitabatrachus possesses at least eight presacral vertebrae, the first two of which are fused, with flat, opisthocoelous centra. Unique features of this taxon are the presence of parasagittal flanges along the posterior halves of the otic capsules and the wide transverse processes of the posterior presacral vertebrae, which are only slightly anteriorly directed. Preliminary comparisons with other fossil pipoid taxa in the context of recent parsimony analyses suggest that it is the sister taxon of Pipidae. However, this phylogenetic placement of the new taxon should be corroborated in a future rigorous analysis that should include some putative stem pipid taxa that currently are being restudied.

The cranial osteology and hyolaryngeal apparatus of Rhinophrynus dorsalis (Anura: Rhinophrynidae) with comparisons to recent pipid frogs

The cranial osteology (including the hyolaryngeal apparatus) of Rhinophrynus dorsalis (Anura: Rhinophrynidae) is described from whole skeletons and serial cross sections. Some unique features of the extensively ossified skull include the enlarged and protracted olfactory region, for which the nasals form part of the septum nasi; the relatively short maxillaries and broad premaxillaries, and the immense quadratojugal; the extreme forward position of the quadrate; the lack of a firm articulation of the pterygoid and quadrate with the neurocranium and crista parotica; the quadrate lacking the distinct processes typical of other frogs; a single foramen for Nn. II–VII; a large, distinct operculum; and a bipartite hyale.

Morphology and Development of the Skull in the Frog Hyla septentrionalis

The skull of Hyla septentrionalis is solidly roofed and partly fused with the skin of the head. The roofing bones (nasals, frontoparietals, and ethmoid), and the maxillary flanges are involved in integumentary coossification. Co-ossified skin is characterized by bone deposition continuous between, and in, the dense connective tissue of the dermal layer of the skin, which effectively obliterates the lower dermal layer and unites the epidermis and superficial dermis with the underlying bone. The ethmoid is usually considered to be completely endochondral in origin; in order to explain its involvement with integumentary-cranial co-ossification, a dual origin from two ossification centers, one endochondral and the other intermembranous, is suggested. Development of the skull of Hyla septentrionalis resembles that of other hylids. Integumentarycranial co-ossification is not evident until all the cranial bones are well formed. Some variation in the extent of cranial development is correlated with sex and age.