Hyobranchial Skeleton Research Articles

Skeletal description of Pelophylax caralitanus (Anura: Ranidae): Comparison with other ranids.

A description of the skeletal development of ranids is scarce despite being well known in the family Ranidae. Herein, the description of several species of two genera representing the family Ranidae from Turkey is studied wherein the larval and adult cranial skeletons of Pelophylax caralitanus are described and compared with that of the water frog (Pelophylax bedriagae) and mountain frog (Rana macrocnemis). The data are based on cleared and double-stained specimens of 20 Gosner developmental Stages (26-46). The first element to ossify in P. caralitanus is the parasphenoid (Stage 30), followed by the exoccipitals (Stage 34) and prootics (Stage 35). The metamorphic climax commences at Stage 42 during which several modifications to the chondrocranium will unfold. In addition, ranids demonstrate remarkable differences between the water (Pelophylax sp.) and mountain (Rana sp.) frog species: (a) the ventromedial bridge between the corpora of the suprarostral cartilage in the larval upper jaw, (b) the number of processes of the central corpus in the hyobranchial skeleton, and (c) the differences in the ossification time and sequence between Pelophylax sp. and Rana sp. A detailed description of the larval osteological features of P. caralitanus conforms to the current phylogenetic position and provides a model for comparison with other ranids.

Cranial skeletogenesis of one of the largest amphibians, Andrias japonicus, provides insight into ontogenetic adaptations for feeding in salamanders

Abstract Skeletal development in salamanders is greatly influenced by their complex life history. Although the relationship between skull development and life history has been investigated in a variety of salamander species, few studies have compared skull development among lineages. Here, we describe the cranial skeletogenesis of the Japanese giant salamander, Andrias japonicus (family Cryptobranchidae), for the first time. To conduct interspecific comparisons, we also describe the cranial skeletogenesis of Hynobius nebulosus (Hynobiidae), Pleurodeles waltl (Salamandridae) and Ambystoma mexicanum (Ambystomatidae). Our comparative analyses reveal interspecific differences in cranial skeletogenesis, particularly in the timing of the onset of ossification, the direction of ossification (e.g. from anterior to posterior) and the ossification pattern of the hyobranchial skeleton. The early onset of jaw ossification, posterior extension of the maxilla and posterolateral inclination of the squamosal in An. japonicus might be adaptations that allow An. japonicus to gulp feed, primarily using the suction force generated by opening the mouth wide, while also supplementing that force by depressing the hyobranchial skeleton. Multivariate regression of skull shape on log10-transformed centroid size revealed that the unique skull shape of adult and subadult An. japonicus forms through hypermorphosis.

Comparative analysis of the chondrocranium and hyobranchial skeleton of bromeliad arboreal frog larvae of the genus Phyllodytes Wagler, 1830 (Anura, Hylidae).

The genus Phyllodytes comprises 15 species, ten of them having their tadpole external morphology described in the literature. However, there are few descriptive studies on chondrocranium and hyobranchial skeleton. In this work, we describe the chondrocranium and hyobranchial skeleton of Phyllodytes larvae and discuss shared features and interspecific variation. Our findings suggest that the skeletal morphology is mostly conserved in the genus, with common features including a single suprarostral cartilage, short infrarostral cartilages, and overall short trabecular horns. Main intrageneric variations include the arrangement of the ascending process, the presence of larval otic process, and the configuration of the crista parotica. These variations are not correlated with the phylogenetic structure of the genus. Some distinctive aspects of P. praeceptor and P. gyrinaethes are also described in tadpoles of Osteopilus ocellatus, and could be related to oophagous habits in these tadpoles.

Same but different: aquatic prey capture in paedomorphic and metamorphic Alpine newts

Paedomorphosis describes the retention of larval characters in adult stages and is widespread amongst salamanders. Salamandrid newts exhibit facultative paedomorphosis, where paedomorphic and metamorphic adult forms coexist in the same population. Previous studies have shown that prey capture kinematics do not differ between paedomorphic and metamorphosed ambystomatid salamanders, despite diverging morphology and prey capture performance. It remained unclear, however, whether the stereotypy of prey capture kinematics across morphotypes is restricted to ambystomatids, or can be found in other salamander groups too. Here, we performed biplanar high-speed-recordings of the prey capture behavior in paedomorphic and metamorphic salamandrid newts and only found minor kinematic differences across morphotypes, suggesting that stereotypy across morphotypes is a more general feature within salamanders. We then compared anatomy of skull and hyobranchial skeleton, along with the physiological cross sectional area (PCSA) of the rectus cervicis muscle, the main muscle empowering suction feeding. Besides the overall morphological differences of the feeding apparatus, the PCSA of the rectus cervicis also differs significantly between morphotypes, being twice as large in paedomorphs. Accordingly, paedomorphs can exert more powerful suction strikes, which in turn may be one of the key factors why paedomorphs are more efficient in capturing elusive prey compared to metamorphs.

Biotoxicity of diclofenac on two larval amphibians: Assessment of development, growth, cardiac function and rhythm, behavior and antioxidant system

The non-steroidal anti-inflammatory drug diclofenac (DCF) threatens the health of aquatic animals and ecosystems. In the present study, different biological endpoints (mortality, development and growth, abnormalities, cardiotoxicity, neurotoxicity and antioxidant system) were used to characterize the acute and chronic effects of DCF (at concentrations ranging between 125 and 4000 μg L−1) on two amphibian species from Argentina (Trachycephalus typhonius and Physalaemus albonotatus). Results showed that the larval developmental, growth rates, and body condition of DCF-exposed individuals of both species were significantly reduced. DCF-exposed individuals also showed several morphological abnormalities, including significantly altered body axis, chondrocranium and hyobranchial skeleton, and organ and visceral abnormalities including cardiac hypoplasia, malrotated guts, asymmetrically inverted guts, and cholecystitis. DCF also had a significant effect on the swimming performance of both species: at low concentrations (125 and 250 μg L−1), swimming distance, velocity and global activity decreased, whereas, at high concentrations (1000 and 2000 μg L−1), these behavioral responses increased. Regarding cardiac function and rhythm, at DCF concentrations higher than 1000 μg L−1, the heart frequency and ventricular systole interval of both species were significantly reduced. Regarding the antioxidant system, the activity of acetylcholinesterase indicated that DCF is neurotoxic and thus related to the changes in behavioral performance. The DCF concentrations studied produced a biochemical imbalance between radical oxygen species production and antioxidant systems. The sensitivities to sublethal and chronic DCF exposure in both anuran species were similar, thus indicating the inherent complexity involved in understanding the biotoxic effects of DCF.

Unexpectedly high diversity in a small basin: A taxonomic revision of Eurycheilichthys (Siluriformes: Loricariidae), with descriptions of seven new species

ABSTRACT A taxonomic revision of Eurycheilichthys is provided, and seven new species are described in addition to the two previously known species in this genus: E. pantherinus from the upper rio Uruguay, and E. limulus from the upper rio Jacuí. The genus is diagnosed based on the uniquely derived presence of seven branched pectoral-fin rays, and on the possession of reduced filamentous gill rakers in the oral surface of the hyobranchial skeleton, and presence of a distinct fleshy flap along the posterodorsal margin of the pectoral-fin spine in adult males. The seven new species are described from tributaries to the rio Taquari basin, itself a tributary to the rio Jacuí in Rio Grande do Sul State, southern Brazil. The new species are diagnosed based on color variation, abdominal plate morphology, lip size, parieto-supraoccipital shape, the number of dermal plates, the number of teeth, and body proportions. The high diversity and degree of species endemism in a limited area are discussed and compared to other fish groups. Genetic sequences (GenSeq) of mitochondrial and nuclear DNA, distribution maps, an identification key, and illustrations are presented for all species.

The Tadpole and Karyotype ofRhinellaachavali(Anura: Bufonidae)

Abstract We describe the external morphology, buccal cavity, chondrocranium, hyobranchial skeleton, and musculature of the tadpole of Rhinella achavali (Achaval's Toad), along with its karyotype. Tadpoles were found in a small, permanent stream and were showing schooling behavior. The characterization of the proposed species groups within Rhinella cannot be currently improved using external larval morphology, as it seems to be much conserved within this genus. Buccal cavity morphology confirms the distinctiveness of the Rhinella veraguensis (Veragua Toad) group with respect to other known Rhinella. Musculoskeletal character states are similar among bufonids, although within this family the basal genus Melanophryniscus shows some distinctive states. The karyotype is composed of 22 bi-armed chromosomes, with secondary constrictions in pair 7, as found in the other species in the Rhinella marina (Marine Toad) group.

External morphology, chondrocranium, hyobranchial skeleton, and external and internal oral features of <i>Rhinoderma rufum</i> (Anura, Rhinodermatidae)

The species of Rhinoderma Duméril & Bibron are endemic to the temperate forests of South America in southern Chile and Argentina (Formas et al. 1975). Both have specialized reproductive modes, Rhinoderma darwinii Duméril & Bibron undergoes complete embryonic and larval development in the mouth of the male: newly metamorphosed frogs are expelled into the terrestrial environment (Jorquera et al. 1972). In contrast, embryos of R. rufum (Philippi) do not remain in the male's mouth, but instead are expelled into the water as larvae (Jorquera et al. 1974). Jorquera et al. (1972, 1974) described the normal development of both species. The chondrocranial morphology and visceral skeleton of R. darwinii was described by Lavilla (1987) and its internal oral features by Wassersug & Heyer (1988). The table of normal development of R. rufum (Jorquera et al. 1974) emphasized the duration of each stage of development: however, some features currently used for comparative purposes in tadpole morphological studies were not included or described only briefly. In this work, I include a detailed description of the morphology, particularly of the mouthparts, of the tadpoles of R. rufum, and describe the chondrocranium, hyobranchial skeleton, and the internal features of the oral cavity in this species. In addition, I compare the morphology of the mouth, chondrocranium, and hyobranchial skeleton of the congeneric tadpoles, considering different modes of feeding (endotrophic in R. darwinii versus exotrophic in R. rufum). Last, I present some thoughts about the evolution of larvae of Rhinoderma.

DO LARVAL TRAITS RE-EVOLVE? EVIDENCE FROM THE EMBRYOGENESIS OF A DIRECT-DEVELOPING SALAMANDER, PLETHODON CINEREUS

Recent molecular phylogenies suggest the surprising reacquisition of posthatching metamorphosis within an otherwise direct-developing clade of lungless salamanders (family Plethodontidae). Metamorphosis was long regarded as plesiomorphic for plethodontids, yet the genus Desmognathus, which primarily includes metamorphosing species, is now nested within a much larger clade of direct-developing species. The extent to which the putative reacquisition of metamorphosis in Desmognathus represents a true evolutionary reversal is contingent upon the extent to which both larva-specific features and metamorphosis were actually lost during the evolution of direct development. In this study we analyze development of the hyobranchial skeleton, which is dramatically remodeled during salamander metamorphosis, in the direct-developing red-backed salamander, Plethodon cinereus. We find dramatic remodeling of the hyobranchial skeleton during embryogenesis in P. cinereus and the transient appearance of larva-specific cartilages. Hyobranchial development in this direct-developing plethodontid is highly similar to that in metamorphosing plethodontids (e.g., Desmognathus). The proposed reacquisition of hyobranchial metamorphosis within Desmognathus does not represent the "re-evolution" of a lost phenotype, but instead the elaboration of an existing developmental sequence.

Comparative skull osteology of Karsenia koreana (Amphibia, Caudata, Plethodontidae)

The recent discovery of a plethodontid salamander, Karsenia koreana, in Korea challenged our understanding of the biogeographic history of the family Plethodontidae, by far the largest family of salamanders, which otherwise is distributed in the New World with a few European species. Molecular studies suggest that Karsenia forms a clade with Hydromantes (sensu lato), which includes among its species the only other Old World plethodontids. We studied the skull of K. koreana and compared it with that of other plethodontid genera, especially members of the subfamily Plethodontinae, which it resembles most closely in general anatomy. The anatomy of its skull corresponds to the most generalized and apparently ancestral condition for plethodontids. No clearly autapomorphic states were detected, and no synapomorphies can be found that would link it to other genera. The Karsenia skull is cylindrical and well ossified, giving an impression of strength. In contrast, the skull of Hydromantes is highly derived; the skull is flattened and the bones are weakly ossified and articulated. Hydromantes and Karsenia share no unique anatomical features; differences between them are especially evident in the hyobranchial skeleton, which is generalized in Karsenia but highly modified in Hydromantes, which is well known for its highly projectile tongue. Plethodon and Plethodon-like species, including Karsenia and to a lesser degree Ensatina, represent the more generalized and apparently ancestral plethodontid morphology. Specialized morphologies have evolved along only a few morphological axes within the Plethodontidae, resulting in a pattern of rampant homoplasy. Our analysis of the anatomy of the new Asiatic lineage illuminates some potential mechanisms underlying adaptive morphological evolution within the Plethodontidae.

The plagiosaurid temnospondylPlagiosuchus pustuliferus(Amphibia: Temnospondyli) from the Middle Triassic of Germany: anatomy and functional morphology of the skull

The cranial anatomy of the plagiosaurid temnospondyl Plagiosuchus pustuliferus, from the Middle Triassic of Germany, is described in detail on the basis of a newly discovered skull and mandibular material. The highly derived skull is characterized by huge orbitotemporal fenestrae, a reduction of the circumorbital bones – the prefrontal, postfrontal and (probably) postorbital are lost – and the expansion of the jugal to occupy most of the lateral skull margin. Ventrally the extremely long subtemporal vacuities correlate with the elongate adductor fossa of the mandible. The dentition is feebly developed on both skull and mandible. Ossified ?ceratobranchials and ‘branchial denticles’ indicate the presence of open gills clefts in life. The remarkably divergent cranial morphology of P. pustuliferus highlights the extraordinary cranial diversity within the Plagiosauridae, probably unsurpassed within the Temnospondyli. Specific structural aspects of the skull – including an extremely short marginal tooth row, feeble dentition and an elongated chamber for adductor musculature – together with evidence for a hyobranchial skeleton, suggests that P. pustuliferus utilized directed suction feeding for prey capture. © 2009 The Linnean Society of London, Zoological Journal of the Linnean Society, 2009, 155, 348–373.

The Rheophilous Tadpole Of Telmatobius Atahualpai Wiens, 1993 (Anura: Ceratophryidae)

The external morphology, oral cavity, chondrocranium and hyobranchial skeleton of Telmatobius atahualpai larvae are described. These tadpoles present an oral disc modified into a sucker apparatus and were originally assigned to Hyloscirtus. In order to justify its taxonomic position in Telmatobius, we compare its morphology with Hyloscirtus armatus, H. phyllognathus, Telmatobius truebae, and published data on larvae of other Hyloscirtus and Telmatobius. Tadpoles of T. atahualpai and other Telmatobius differ from the examined species of Hyloscirtus in having a transangular oral disc, inner wall of spiracle present as a slight ridge, two pairs of infralabial projections, smooth prenarial arena, one papilla between postnarial papillae and median ridge, buccal roof arena defined by papillae which converge posteriorly, cornua trabeculae neither expanded anteriorly nor fused medi- ally, syndesmotic articulation between suprarrostral and cornua trabeculae, maximum width of chondrocranium only at the level of the arcus subocularis, fenestrae parietales open, tip of the processus posterior hyalis does not underlie the anterolateral part of the hypobranchial plate, processus posterior hyalis and hypobranchial plate attached only by a ligament, and commissura proxima- lis III absent. The tadpole of T. atahualpai is different from other reophilous Telmatobius larvae in having a oral disc completely bordered by marginal papillae and a labial tooth row formula of 3/7(1). T. atahualpai larvae seem to represent the most specialized Telmatobius tadpole known so far.

Anatomy of anuran tadpoles from lentic water bodies: systematic relevance and correlation with feeding habits

I studied anatomy, gut content, and the relationship among these traits in a set of anuran tadpoles. Larval stages (mainly Gosner stages 31–36) of nineteen species from various lentic environments were selected. Morphological characters from the skeleton, musculature, oral apparatus and buccopharyngeal cavity were recorded, and a gut content analysis was performed, with emphasis on food size distribution. Ordination techniques were applied in order to find patterns of similarity in morphology and gut content. Canonical ordination methods were used to investigate the relationship among gut content, morphology, and phylogeny in the species considered. The results show that several skeletal, muscular, and buccal characters are relatively maintained within genera. Other features, which have appeared independently in different lineages, reflect convergence phenomena in some cases related to ecological aspects. The configuration of the hyobranchial skeleton, the development of the buccal floor depressor and levator muscles, and mouth gape width correlate with prey size. In some species, morphology is clearly related with feeding. Tadpoles that ingest large food particles relative to their body length present morphological traits attributable to macrophagy. Taxonomically unrelated tadpoles of Dendropsophus nanus, D. microcephalus and Ceratophrys cranwelli possess hyobranchial skeletons with robust, rostrocaudally long ceratohyals and reduced branchial baskets with short ceratobranchials devoid of lateral projections and spicules. Lepidobatrachus llanensis tadpoles have laterally extended ceratohyals which, along with the lateral extension of the jaws, result in a very wide oral apparatus and an ample buccopharyngeal cavity that allows the tadpole to ingest large and whole prey; the branchial basket, although its ceratobranchials lack lateral projections and spicules, is slightly reduced in area. The four species mentioned have a noticeable development of the buccal floor depressor muscles, and buccal cavities with scarce filtering and entrapping structures. In Elachistocleis bicolor, Dermatonotus muelleri, Chiasmocleis panamensis, and Xenopus laevis tadpoles, the branchial basket occupies >70% of the total hyobranchial skeleton area, and the hypobranchial plates are highly reduced; the buccal floor levator muscles are well-developed, with an increased site of attachment on the ventral expansion of the lateral process of the ceratohyal; the scarcity of the filtering structures in the buccopharyngeal cavity are balanced with the great development of the branchial filters and secretory zones; all these features relate to a diet based on small particles not significantly different from those of most other species; however, experimental studies show that species with similar hyobranchial apparatus and muscles are the most efficient when retaining minute particles. Finally, a large group of species present generalized morphological characters, such as a branchial basket occupying about 50% of the total hyobranchial apparatus, intermediate values of mouth gape width and buccal floor levator / depressor muscles ratio, and abundant filtering structures in the buccopharyngeal cavity; these species feed frequently on food particles between 1–30% of the tadpole body length; however, in some of the species, macrophagous diets are also reported in the literature, indicating that this morphology is flexible in more ample prey size ranges.

Cranial ontogeny in Philautus silus (Anura: Ranidae: Rhacophorinae) reveals few similarities with other direct‐developing anurans

Direct development has evolved in rhacophorine frogs independently from other anuran lineages, thereby offering an opportunity to assess features associated with this derived life history. Using a developmental series of the direct-developing Philautus silus (Ranidae: Rhacophorinae) from Sri Lanka, we examine features of cranial morphology that are part of a suite of adaptations that facilitate feeding in free-living tadpoles, but have been changed or lost in other direct-developing lineages. Larval-specific upper jaw cartilages, which are absent from many non-rhacophorine direct-developing species (such as Eleutherodactylus coqui), develop in embryos of P. silus. Similarly, lower jaw cartilages initially assume a larval morphology, which is subsequently remodeled into the adult jaw configuration before hatching. However, the cartilaginous jaw suspension and hyobranchial skeleton never assume a typical larval morphology. The palatoquadrate, which suspends the lower jaw, lacks the posterior connections to the braincase found in many metamorphosing species. Unlike in metamorphosing species, bone formation in P. silus begins before hatching. However, the sequence of bone formation resembles that of metamorphosing anurans more than that of other direct developers. In particular, P. silus does not exhibit precocious ossification of the lower jaw, which is characteristic of some frogs and caecilians that lack a free-living tadpole. These data reveal some similarities between Philautus and other direct-developing anurans. However, the departure of Philautus embryos from the generalized tadpole skeletal morphology is less pronounced than that observed in other direct-developing taxa.

Runx2 is essential for larval hyobranchial cartilage formation in Xenopus laevis

The vertebrate transcription factor protein Runx2 is regarded as a "master regulator" of bone formation due to the dramatic loss of the osseous skeleton in the mouse homozygous knockout. However, Runx2 mRNA also is expressed in the pre-hypertrophic cartilaginous skeleton of the mouse and chicken, where its developmental function is largely unknown. Several tiers of Runx2 regulation exist in the mouse, any of which may account for its seeming biological inactivity during early stages of skeletogenesis. Unlike mouse and chicken, zebrafish require Runx2 function in early cartilage differentiation. The present study reveals that the earlier functional role of Runx2 in cartilage differentiation is shared between zebrafish and Xenopus. A combination of morpholino oligonucleotide injections and neural crest transplants indicate that Runx2 is involved in differentiation of the cartilaginous hyobranchial skeleton in the frog, Xenopus laevis. Additionally, in situ hybridizations show runx2 mRNA expression in mesenchymal precursors of the cartilaginous skull, which reveals the earliest pre-patterning of these cartilages described to date. The early distribution of runx2 resolves the homology of the larval suprarostral plate, which is one of the oldest controversies of anuran skull development. Together these data reveal a shift in Runx2 function protein during vertebrate evolution towards its exclusive roles in cartilage hypertrophy and bone differentiation within the amniote lineage.

Morphological characterization of Leptodactylus elenae tadpoles (Anura: Leptodactylidae: L. fuscus group), from central Paraguay

In this paper we characterize the morphology of Leptodactylus elenae tadpoles (L. fuscus group) from central Paraguay, considering external morphology, oral disc, buccopharyngeal cavity, skeleton and musculature (N = 17; Gosner Stage 36–37; Central, Paraguay). Specimens were fixed with 10% formaline and were prepared according to a classic staining protocol. These larvae show external traits similar to those of other taxa within the group, such as an ovoid and depressed body, left spiracle, ventromedial vent tube, and marginal papillae interrupted in a wide rostral gap. Distinctive features are the rounded snout, the distally wide and rounded tail, the labial tooth formula 2(2)/3(1), lateral constrictions absent, and the large internal marginal papillae, intercalated every two or four small external marginal papillae. Inside the buccopharyngeal cavity, traits shared with related species are the prenarial ridge, the transversal nares, two pairs of infralabial papillae, the medial ones joined at their bases, four lingual papillae, and dorsal and ventral vela with secretory epithelium. Skeletal configuration is constant within the genus, with common character states such as the quadripartite suprarostral cartilage, quadratoorbital commissure and larval crista parotica present, larval otic process absent, ceratobranchials fused to the hypobranchial plates, anterior branchial process, and basihyal absent. Leptodactylus elenae and other L. fuscus group species resemble taxa from the L. pentadactylus group, due to the configuration of the branchial process, the articular process of the palatoquadrate, the suspensorium, and the trabecular horns; this can be observed in the chondrocranium and hyobranchial skeleton morphospaces for 22 species of the genus. Finally, muscular features are also maintained at intra-genus level, with common traits such as m. mandibulolabialis superior absent, mm. diaphragmatopraecordialis, interhyoideus posterior and hyoangularis medialis present, m. subarcualis rectus I with 3 slips, and m. subarcualis rectus II–IV inserted on ceratobranchial III. Further analyses on intraspecific variation and descriptions of related larvae are needed to improve the knowledge about this diverse genus.

Hyobranchial skeleton and hypobranchial muscles of rhipidistians

The hyobranchial skeleton of the porolepiform rhipidistian Laccognathus panderi Gross is described. The double composition of the ceratohyal in crossopterygians is proposed. The urohyal of porolepiforms, like that of Latimeria, consists of cartilaginous axial and membranous peripheral portions. The differences between porolepiforms and osteolepiforms in the structure of the hyobranchial skeleton, particularly, in the shape of the urohyal are attributable to different arrangements of the hypobranchial muscles. Porolepiforms and coelacanths have retained the coracomandibularis muscle inherited from early gnathostomes, whereas the same muscle of osteolepiforms was transformed into the geniohyoideus muscle. This transformation is accounted for by functional changes in the hyobranchial apparatus.

Ontogeny of the skull, lower jaw, and hyobranchial skeleton ofHypogeophis rostratus (Amphibia: Gymnophiona: Caeciliidae) revisited

Few detailed descriptions of the development of the head skeleton in caecilian amphibians are available. One of those is the work of Marcus and students (e.g., Gehwolf [1923] Z Anat Entwick 68:433-454; Marcus [1933] Anat Anz 80:142-146; Marcus et al. [1935] Gegenbaurs Morphol Jb 76:375-420) on the morphology and development of the skull, lower jaw, and hyobranchial skeleton in the Seychellean caeciliids Hypogeophis rostratus and Grandisonia alternans. These workers described a high number of individual ossifications that fuse during ontogeny to form the adult skull. Although later studies have doubted the generality of those observations, the work of Marcus and his students has been hugely influential in subsequent studies of caecilian skull morphology and amphibian evolution. Based on new observations on an ontogenetic series of 32 sectioned and cleared and stained specimens, ranging from the beginning of chondrification to the adult, the development of the skull, lower jaw, and hyobranchial skeleton of H. rostratus are described. The new results are largely incompatible with those of Marcus and students and no evidence for several of the reported ossifications, including supra-, infra-, and basioccipital, epiotic, pleurosphenoid, preethmoid, posterior vomer, prepalatine, quadratojugal, postparietal, second coronoid, supraangular, and complementare, is found. It is argued that most of Marcus et al.'s reports of nonexistent ossifications are based on false phylogenetic preconception, misinterpretation of the observed morphology, and technical error. Data on the ossification sequence of the skull and lower jaw in H. rostratus are provided and briefly compared to published information on Dermophis mexicanus and Gegeneophis ramaswamii.

A complete trematosaurid amphibian from the Middle Triassic of Germany

ABSTRACT Recent finds of small temnospondyls from the Lower Keuper (Ladinian, Middle Triassic) of southern Germany are referred to a new trematosaurid genus and species, Trematolestes hagdorni. It is the first trematosaurid represented by a nearly complete skeleton. Trematolestes is characterized by an unpaired frontal and a minute lacrimal at the orbital rim wedged in between an extensive prefrontal and a wide maxilla. Further characteristic are keeled, laterally compressed palatal tusks, a strong palatine and ectopterygoid dentition, and minute maxillary and posterior dentary teeth. In the visceral skeleton, ceratobranchial parts of the hyobranchial skeleton and an unpaired basibranchial element are ossified. The ribs bear pronounced spine-like uncinate processes throughout the trunk and anterior tail skeleton. The forelimb is minute, with a strongly abbreviated humerus not exceeding the length of the lower arm, rudimentary radius and ulna, and a small, probably four-fingered hand skeleton. Unlike the situation in capitosauroids, the trunk was deep with an elongated recurved ilium and a highly modified sacral rib. The trunk is composed of 22 vertebrae, while the caudal vertebral count is at least 24, but probably exceeded 30. Phylogenetic analysis suggests that Trematolestes is closely related to the Madagascan genus Tertremoides and together they are nested with the rostrum-bearing slender-headed lonchorhynchines.

Morphology and metamorphosis ofEupsophus calcaratustadpoles (anura: Leptodactylidae)

Eupsophus calcaratus, a leptodactyloid frog from the austral Andean forests of Argentina and Chile, has endotrophic, nidicolous tadpoles. We studied a metamorphic series from Stages 31 to 46 of Gosner's developmental table (1960). Other than the scarce pigmentation, proportionately large eyes, and massive developing hindlimbs, the remaining external characters are similar to those of generalized, exotrophic larvae. At the same time, internal morphology does not reveal any character state attributable to the endotrophic-nidicolous way of life; conversely, structures such as the hyobranchial skeleton and the mandibular cartilages are similar to those of exotrophic-macrophagous tadpoles. The metamorphic process is characterized by the delayed development of diverse structures (e.g., ethmoid region, palatoquadrate, and hyobranchial apparatus), and the retention of some larval characters (e.g., parietal fenestrae, overall absence of ossification) with the absence of development of some "juvenile" characters (e.g., adult otic process, several bones) in metamorphosed individuals. These heterochronic processes and truncation of larval development are related to a shorter larval life (when compared to other species of the austral Andean region) and to the small size at metamorphosis.