The Impact of Molecular Methods on the Systematics of Angiosperms

A comparison is made between the systematics of selected orders and families based on morphology and other “classical” characters on the one hand, and the results of molecular methods on the other hand. It can be shown that taxa defined by a broad array of characters from morphology, anatomy, embryology and phytochemistry usually are confirmed by molecular results. On the other hand a family like the Saxifragaceae s.l. delimited solely on the basis of floral morphology has been shown to be grossly polyphyletic. Some quite surprising results of the molecular analyses usually agree with some embryological or phytochemical characters, and sometimes even with characters of vegetative morphology and anatomy. As a special case “unequal ancient splits” are discussed, where one clade contains few genera and species usually retaining many primitive characters, and the other shows great diversity and contains the more advanced members.     

Phylogeny of pholcid spiders (Araneae: Pholcidae): combined analysis using morphology and molecules

The spider family Pholcidae comprises a large number of mainly tropical, web-weaving spiders, and is among the most diverse and dominant spider groups in the world. The phylogeny of this family has so far been investigated exclusively using morphological data. Here, we present the first molecular data for the family analyzed in a phylogenetic context. Four different gene regions (12S rRNA, 16S rRNA, cytochrome c oxidase subunit I, 28S rRNA) and 45 morphological characters were scored for 31 pholcid and three outgroup taxa. The data were analyzed both for individual genes, combined molecular data, and molecular plus morphological data, using parsimony, maximum likelihood, and Bayesian methods. Some of the phylogenetic hypotheses obtained previously using morphology alone were also supported by our results, like the monophyly of pholcines and of the New World clade. On the other hand, some of the previous hypotheses could be discarded with some confidence (monophyly of holocnemines, the position of Priscula), and still others need further investigation (the position of holocnemines, ninetines, and Metagonia). The data obtained provide an excellent basis for future investigations of phylogenetic patterns both within the family and among spider families.     

EVOLUTIONARY ORIGIN OF THE CYCLORRHAPHA (DIPTERA): TEST OF ALTERNATIVE MORPHOLOGICAL HYPOTHESES

Abstract— The higher flies, infraorder Cyclorrhapha [=Muscomorpha (McAlpine, 1989)], have undergone enormous radiation since the Cretaceous (∼100 Myr). Rapid morphological evolution in cyclorrhaphans has made their phylogenetic placement with respect to more primitive clades a long-standing problem in dipteran systematics. Of the two most plausible hypotheses, one treats the Cyclorrhapha as sister group to the orthorrhaphous superfamily Empidoidea [=Empidiformia (Hennig, 1948), Orthogenya (Brauer, 1883)], while the other places them within the empidoids. The debate over cyclorrhaphan origin has heretofore focused on homology interpretations for a few character systems, particularly the male genitalia. We provide the first attempt to assemble and quantify all of the available morphological evidence. By cladistic analysis of these data under alternative codings of genitalic features reflecting opposing homology theories, and then excluding these features altogether, we sought to judge which genitalic theory is better supported by the evidence as a whole, and how much the debate matters to resolving cyclorrhaphan origins. Using the analog of a factorial design, we also measured the effect of alternative transformation series in several other controversial characters, of outgroup choice and of successive weighting. Under all manipulations, including both genitalic codings, the Cyclorrhapha originate within the Empidoidea, near the family Atelestidae. However, trees in which the Empidoidea are constrained to be monophyletic are only 1-6 steps longer (out of ∼150), a fit not significantly worse under a permutation test for monophyly. Adult morphological data may not suffice to settle either the placement of Cyclorrhapha or the debate over genitalic homology. Moreover, the issue of genitalic homology does not appear critical to that of cyclorrhaphan origin.     

Evolving between land and water: key questions on the emergence and history of the Hippopotamidae (Hippopotamoidea,Cetancodonta, Cetartiodactyla)

The fossil record of the Hippopotamidae can shed light on three major issues in mammalian evolution. First, as the Hippopotamidae are the extant sister group of Cetacea, gaining a better understanding of the origin of the Hippopotamidae and of their Paleogene ancestors will be instrumental in clarifying phylogenetic relationships within Cetartiodactyla. Unfortunately, the data relevant to hippopotamid origins have generally been ignored in phylogenetic analyses of cetartiodactyls. In order to obtain better resolution, future analyses should consider hypotheses of hippopotamid Paleogene relationships. Notably, an emergence of the Hippopotamidae from within anthracotheriids has received growing support, leading to reconciliation between genetic and morphological evidence for the clade Cetancodonta (Hippopotamidae + Cetacea). Secondly, full account needs to be taken of the Hippopotamidae when studying the impact of environmental change on faunal evolution. This group of semi‐aquatic large herbivores has a clear and distinct ecological role and a diverse and abundant fossil record, particularly in the African Neogene. We examine three major phases of hippopotamid evolution, namely the sudden appearance of hippopotamines in the late Miocene (the “Hippopotamine Event”), the subsequent rampant endemism in African basins, and the Pleistocene expansion of Hippopotamus. Each may have been influenced by multiple factors, including: late Miocene grass expansion, African hydrographical network disruption, and a unique set of adaptations that allowed Hippopotamus to respond efficiently to early Pleistocene environmental change. Thirdly, the fossil record of the Hippopotamidae documents the independent emergence of adaptive character complexes in relation to semiaquatic habits and in response to insular isolation. The semiaquatic specializations of fossil hippopotamids are particularly useful in interpreting the functional morphology and ecology of other, extinct groups of large semiaquatic herbivores. Hippopotamids can also serve as models to elucidate the evolutionary dynamics of island mammals.     

Comparative studies of vegetative anatomy in the Theaeeae of Sri Lanka

Anatomical characters of the mature leaf blade, petiole, young stem and wood were examined in order to substantiate taxonomic boundaries between genera and species of Theaeeae in Sri Lanka. Two species of Temstroemia , one of Adinandra , four of Eurya and two of Gordonia were studied.
The presence of sclereids in most organs of the plant was found to be a common character within the family. However, three distinct types of sclereid are reported. Two basic types of stomata, anomocytic and gordoniaceous, are recognized. The origin of phellogen in the young stems is pericyclic in Gordonia and subepidermal in the other three genera. The species within these genera also appear to have several distinctive characters of their own. Important wood characters have been tabulated in order to illustrate the primitive and advanced characters. Gordonia , especially, exhibits anatomical features which are quite different from those of Temstroemia, Adinandra send Eurya.     

The phylogenetic position of the Clitellata and the Echiura - on the problematic assessment of absent characters*

Absent characters (negative characters) are difficult to assess and their correct interpretation as symplesiomorphies, synapomorphies or convergencies (homoplasies) is one of the greatest challenges in phylogenetic systematics. Different phylogenetic assessments often result in contradictory phylogenetic hypotheses, in which the direction of evolutionary changes is diametrically opposed. Especially in deciding between primary (plesiomorphic) and secondary (apomorphic) absence, false conclusions may be reached if only the outgroup comparison and the principle of parsimony are employed without attempting any biological evaluation or interpretation of characters. For example, in the higher‐level systematization of the Annelida and related taxa different assessments of absent characters have led to conflicting hypotheses about the phylogenetic relationships and the ground pattern of the annelid stem species. Varying phylogenetic interpretations regarding the absence of the chemosensory nuchal organs in the clitellates and their presence in polychaetes initiated a controversy that produced two alternative phylogenetic hypotheses: (1) the Clitellata are highly derived Annelida related to a subtaxon within the, in this case, paraphyletic ‘Polychaeta’ or (2) the Clitellata are comparatively primitive Annelida representing the sister group of a monophyletic taxon Polychaeta. In the former, the absence of nuchal organs in the Clitellata is regarded as a secondary character, in the latter as primary. As most Clitellata are either limnetic or terrestrial, we must ask which characters are plesiomorphies, taken from their marine stem species without changes. In addition to a thorough investigation and evaluation of clitellate characters, a promising approach to these questions is to look for such characters in limnetic and terrestrial annelids clearly not belonging to the Clitellata. A similar problem applies to the evaluation of the position of the Echiura, which lack both segmentation and nuchal organs. Evidence is presented that in both taxa these absent characters represent derived, apomorphic character states. The consequences for their phylogenetic position and the questionable monophyly of the Polychaeta are discussed. The conclusion drawn from morphological character assessments is in accordance with recently published hypotheses based on molecular data.     

Apes and Tricksters: The Evolution and Diversification of Humans’ Closest Relatives

The evolutionary history of humans comprises an important but small branch on the larger tree of ape evolution. Today’s hominoids—gibbons, orangutans, gorillas, chimpanzees, and humans—are a meager representation of the ape diversity that characterized the Old World from 23–5 million years ago. In this paper, I briefly review this evolutionary history focusing on features important for understanding modern ape and human origins. As the full complexity of ape evolution is beyond this review, I characterize major geographic, temporal, and phylogenetic groups using a few flagship taxa. Improving our knowledge of hominoid evolution both complicates and clarifies studies of human origins. On one hand, features thought to be unique to the human lineage find parallels in some fossil ape species, reducing their usefulness for identifying fossil humans. On the other hand, the Miocene record of fossil apes provides an important source for generating hypotheses about the ancestral human condition; this is particularly true given the dearth of fossils representing our closest living relatives: chimpanzees and gorillas.     

Tarsals of the extinct insectivoran family Nyctitheriidae (Mammalia): evidence for archontan relationships

Astragali and calcanea from the English late Eocene, attributed to the extinct 'insectivoran' family Nyctitheriidae, are described for the first time. They contrast with those of the strict sense insectivorans, the Lipotyphla, in which order nyctitheres have usually been placed, and compare more closely with those of Scandentia (tree shrews) and the extinct Plesiadapiformes. Functional analysis demonstrates that inversion of the foot was possible between the astragalus and calcaneum of nyctitheres, allowing them to be interpreted as having had a tree-dwelling, probably scansorial, mode of life. These tarsal bones are compared with those of other placental mammals. Cladistic analysis of tarsal characters places nyctitheres as sister group to the Plesiadapiformes within the superorder Archonta, excluding Chiroptera (bats). An independent analysis of dental characters places them as sister group to the rest of the Archonta, but still excluding bats. Combining the dental and tarsal characters places nyctitheres as sister group to Plesiadapiformes and all modern groups of archontans except bats. A new osteological synapomorphy is proposed for the Archonta, which is thus considered to comprise Chiroptera, Deccanolestes , Nyctitheriidae, Plesiadapiformes, Dermoptera (including Mixodectidae), Scandentia and Primates. Insectivorans s.l . have long been at the centre of arguments on placental origins, although lipotyphlans are usually regarded as a monophyletic group, rather than paraphyletic stem placentals. Reidentification of an extinct lipotyphlan family as having archontan relationships raises the possibility of advances in other areas of insectivoran phylogeny when more postcranial elements become known. The early Oligocene extinction of nyctitheres may be causally related to the rise of insectivorous microchiropteran bats, which, because of their flying ability, would have been able to forage more widely.     

PHYLOGENETIC RELATIONSHIPS AMONG EXTANT BRACHIOPODS

Abstract— The monophyletic status of the Brachiopoda and phylogenetic relationships within the phylum have long been contentious issues for brachiopod systematists. The relationship of brachiopods to other lophophore-bearing taxa is also uncertain; results from recent morphological and molecular studies are in conflict. To test current hypotheses of relationship, a phylogenetic analysis was completed (using PAUP 3.1.1) with 112 morphological and embryological characters that vary among extant representatives of seven brachiopod superfamilies, using bryozoans, phoronids, pterobranchs and sipunculids as outgroups. In the range of analyses performed, brachiopod monophyly is well supported, particularly by characters of soft anatomy. Arguments concerning single or multiple origins of a bivalved shell are not relevant to recognizing brachiopods as a clade. Articulate monophyly is very strongly supported, but inarticulate monophyly receives relatively weak support. Unlike previous studies, the nature of uncertainties about the clade status of Inarticulata are detailed explicitly here, making them easier to test in the future. Calcareous inarticulates appear to share derived characters with the other inarticulates, while sharing many primitive characters with other calcareous brachiopods (the articulates). Experimental manipulation of the data matrix reveals potential sources of bias in previous hypotheses of brachiopod phylogeny. Although not tested explicitly, lophophorate monophyly is very tentatively supported. Molecular systematic studies of a diverse group of brachiopods and other lophophorates will be particularly welcome in providing a test of the conclusions presented here.     

On the phylogeny of the Arminidae (Gastropoda, Opisthobranchia, Nudibranchia) with considerations of biogeography

In the past, the different genera of the family Arminidae have been diagnosed (mostly) on the basis of plesiomorphic characters and therefore their monophyly is questionable. The Arminidae are characterized by the autapomorphies 'possession of marginal sacs' and 'rhinophores with longitudinal lamellae'. The genus Heterodoris is excluded from the family. Two possible hypotheses about the phylogenetic relationships within the Arminidae are presented.
The Arminidae probably originated in the western Pacific, near Japan and have distributed in a westerly direction. The most primitive species ( Dermatobranchus ) are restricted mainly to the western Pacific region while the more derived species ( Armina ) have a world-wide distribution.     

Life on the fly: phylogenetics and evolution of the helicopter damselflies (Odonata,Pseudostigmatidae)

Ingley, S.J., Bybee, S.M., Tennessen, K.J., Whiting, M.F. & Branham, M.A. (2012). Life on the fly: phylogenetics and evolution of the helicopter damselflies (Odonata, Pseudostigmatidae). —Zoologica Scripta, 41, 637–650. Helicopter damselflies (Odonata: Pseudostigmatidae) form a relatively small, yet highly specialized group of odonates, including the largest extant odonate (wingspan of ～190 mm). Pseudostigmatids are found throughout Central and South America, with the exception of one species that is found exclusively in East Africa. Pseudostigmatids oviposit exclusively in phytotelmata and forage on orb‐weaver spiders, which they pluck from webs. Pseudostigmatids also exhibit unique forms of both broad and narrow wings. Although the ecology of these behaviours and morphological features have been studied, their phylogenetic origins and evolutionary history are unknown. Here, we examine the origins of pseudostigmatid wing forms, oviposition in phytotelmata and spider feeding within a modern phylogenetic context, testing for single origins of each character. Phylogenetic analyses are based on 59 morphological characters and ～5 kb of sequence data. Our findings include a well‐supported monophyletic Pseudostigmatidae and Coryphagrion grandis as sister to the Neotropical genera. The genus Mecistogaster is paraphyletic, with Pseudostigma nested within the clade. The genus Microstigma is supported as monophyletic and forms a sister group relationship to the clade of Megaloprepus and Anomisma. The sister group relationship to Pseudostigmatidae is less clear. On the basis of this phylogenetic analysis, we propose three new tribes (Coryphagrionini, Microstigmatini and Mecistogastrini). As Pseudostigmatidae is monophyletic, the behaviour of gleaning spiders from webs appears to derive from a single origin. There are two origins of broad wings within Pseudostigmatidae. Oviposition in phytotelmata most certainly evolved multiple times within Coenagrionoidea. These findings provide new insights into pseudostigmatid evolution that can be used to generate hypotheses regarding behaviour and morphological adaptation in this unique and threatened group of damselflies.     

Phylogenetic analysis of the Pinnotheridae (Crustacea, Brachyura) based on larval morphology, with emphasis on the Dissodactylus species complex

Comparative larval morphology was used to elucidate phylogenetic relationships within the Pinnotheridae and the Dissodactylus species complex. Within the family, seven zoeal and six megalopal characters suggested two equally parsimonious phylogenetic hypotheses for pinnotherid larvae, both with Ostracotheres tridacnae representing the sister group for the Dissodactylus complex. Results indicated that the genus Pinnotheres is a polyphyletic taxon, and that the traditional subfamilial arrangement comprises paraphyletic taxa within the subfamilies Pinnotherinae and Pinnothereliinae. Certain evidence has suggested that Fabia and Juxtafubia should be excluded from the Pinnotherinae and placed into the Pinnothereliinae. Larval and adult morphology suggested that Pinnotheres politus should be included within Tumidotheres. The phylogenetic analysis within the Dissodactylus complex involved one zoeal and 16 megalopal characters. Results suggested a single phylogenetic hypothesis based on larval morphology. Combining adult morphology with larval evidence resulted in two equally parsimonious phylogenetic hypotheses, one of which agreed with a previously suggested hypothesis based only on adult characters.     

水螨群总科阶元系统发育的支序分析 (蜱螨亚纲：水螨群)

对水螨群9总科进行了系统发育分析,支序分析选用了23个形态学特征和3个生物学特征。据分析结果所揭示的9总科间的系统发育关系和姐妹群关系,将水螨群9总科划分为5类：拟水螨类,含冥绒螨总科;始水螨类,含溪螨总科;真水螨类,含古水螨类和新水螨类;古水螨类,含水螨总科、盾水螨总科和皱喙螨总科;新水螨类,含刺触螨总科、腺水螨总科、湿螨总科和雄尾螨总科。类间姐妹群关系为：拟水螨类与始水螨类+真水螨类为姐妹群,始水螨类与真水螨类(古水螨类+新水螨类)为姐妹群,古水螨类与新水螨类为姐妹群。该文还就所提出的水螨群5类9总科的阶元排列建议与已有的观点进行了比较。     

Historical Burden In Systematics And The Interrelationships Of 'Parareptiles'

The interrelationships within the clade comprised of turtles, pareiasaurs, and procolophonid-like taxa are investigated via a cladistic analysis incorporating 56 characters. A single most parsimonious tree was found (80 steps, c. i. = 0·8) in which the successive outgroups to turtles are: pareiasaurs, Sclerosaurus, lanthanosuchids, procolophonoids (=Owenetta, Barasaurus and procolophonids), and nyctiphruretians (= nycteroleterids). Thus, as suggested recently by other workers (Reisz, in Fischman, 1993) turtles are the highly modified survivors of a radiation of poorly-known reptiles commonly called ‘parareptiles’. Pareiasaurs are united with turtles on the basis of twenty unambiguous derived features which are absent in other basal amniotes (=‘primitive reptiles’) and reptiliomorph amphibians: for example, the medially located choana, enlarged foramina palatinum posterius, blunt cultriform process, fully ossified medial wall of the prootic, opisthotic-squamosal suture, lateral flange of exoccipital, loss of ventral cranial fissure, thickened braincase floor, ‘pleurosphenoid’ ossification, reduced presacral count, acromion process, trochanter major, reduced fifth pedal digit, and presence of transverse processes on most caudals. Recent phylogenetic proposals linking turtles with captorhinids, with dicynodonts, and with procolophonoids are evaluated. None of the proposed traits supporting the first two hypotheses is compelling. The procolophonoid hypotheses is supported by only one synapomorphy (the slender stapes). All other synapomorphies proposed in favour of the above groupings either occur in many other primitive amniotes, or are not primitive for turtles, or are not primitive for the proposed chelonian sister-group. Nyctiphruretus and Lanthanosuchids and nycteroleterids, often considered to be seymouriamorph amphibians, are demonstrated unequivocally to be amniotes. The ‘rhipaeosaurs’, currently considered to be pareiasaur relatives, are shown to be a heterogenous assemblage of seymouriamorphs, therapsids and nycteroleterids. The phylogeny proposed here indicates that many of the traits of the earliest known turtle, Proganochelys, previously interpreted as unique specialisations, also occur in pareiasaurs and other near outgroups of turtles, and must instead represent the primitive chelonian condition: for example, the wide parietals and the short quadrate flange of the pterygoid. The sequence of acquisition of chelonian traits is discussed: many features once thought to be diagnostic of turtles actually characterize larger groupings of procolophonomorphs, and must have evolved long before the chelonian shell appeared. These traits include most of the chelonian-pareiasaur synapomorphies listed above, and many others which characterize more inclusive groupings found in this analysis. In putting Proganochelys much closer to the main line of chelonian evolution, in elucidating the sequence of acquisition of chelonian traits, and in reducing greatly the number of differences between turtles and their nearest relatives, this study helps bridge one of the major gaps in the fossil record. The failure of previous cladistic analyses to identify correctly the nearest relatives of turtles is attributed to biased character selection, caused by an over-reliance on cranial characters deemed ‘important’ by earlier workers, and by a tendency to shoehorn ‘parareptile’ taxa into phylogenies derived from analyses restricted to ‘mainstream’ groups such as synapsids, diapsids, turtles, and ‘captorhinomorphs’. Many of the synapomorphies that resolve turtle origins are postcranial, and the three nearest outgroups to turtles are all highly bizarre groups which were dismissed as ‘too specialized’ by early workers and continued to be inadequately assessed even by workers using a cladistic framework.     

五味子科的系统发育:核糖体DNA ITS区序列证据

The Schisandraceae is one of the most important taxa for understanding the origin and evolution of primitive angiosperms due to its basal position in the recent cladograms of the angiosperm based both on several gene sequences and on morphological characters, but phylogenetic relationships within the family are still unresolved. The sequences of nrDNA ITS region of 15 species representing four sections of Schisandra Michx., two sections of Kadsura Kaempf. ex Juss. and one outgroup, Illicium fargesii Finet et Gagnep., were used to reconstruct the phylogeny of Schisandraceae. Fourteen most parsimonious trees (Length=259, CI=0.934 and RI=0.889) were obtained from the analysis with I．fargesii as the outgroup. In the consensus tree, the genus Schisandra was found to be divided into three clades. Sect. Pleiostema formed a clade together with sect. Maximowiczia, sect. Sphaerostema was weakly supported to be the sister group of a clade comprising S. bicolor var. tuberculata and Kadsura species. In particular, S. bicolor var. tuberculata, a species of sect. Schisandra, was nested within Kadsura. It seems from this result and the morphological characters that Schisandra might not be a monophyletic group. According to the present molecular phylogeny, both elongated hypocarpium and deciduous habit originated independently at least twice in the Schisandraceae, and therefore, the value of the present morphological characters used in the classification of the family Schisandraceae should be reevaluated.     

The family Lomariopsidaceae (Filicopsida) and its probable ancestors

The family Lomariopsidaceae includes eight genera of tropical ferns– Arthrobotrya, Bolbitis, Egenolfia, Elaphoglossum, Lomagramma, Lomariopsis, Teratophyllum and Thysanosoria. Salient morphological features of the Lomariopsidaceae have been enumerated. Views of various authors postulating evolution of this family from Thelypteroid, Dryopteroid, Polystichoid or Dennstaedtioid stocks are discussed and it is concluded that they do not seem to be the ancestors of the Lomariopsidoid ferns. On the other hand, it appears, on the basis of various characters, that the Tectarioid ferns could possibly be the ancestors of the Lomariopsidaceae.     

NUMERICAL TAXONOMY OF LIMNANTHACEAE

A numerical taxonomic study of the angiosperm family Limnanthaceae is presented. The 21 OTUs include all taxa recognized in a recent monograph of Limnanthes (Mason, 1952), plus Floerkea proserpinacoides, two undescribed Limnanthes species, and two artificial interspecific F₁ Limnanthes hybrids. One species (L. montana) was treated as two OTUs: measurements for one OTU were taken from field collections and for the other, from garden-grown plants. A maximum of 35 characters was used in the numerical analyses. Raw data for each character were given equal weighting by condensation. Coefficients of resemblance were established using the mean character difference (MCD) method. Tryon's clustering technique (called key communality cluster analysis) was used. Three numerical analyses of Limnanthaceae were made: one with all 35 characters (T analysis), one with 18 floral characters (F analysis), and one with 17 pre- or post-anthesis or vegetative characters (V analysis). Relative positions of OTUs in the T and F analyses are substantially different from those in a conventional taxonomic treatment of the family. The V analysis shows many differences from the T and F analyses. In all analyses the two OTUs representing L. montana were closer to other OTUs than to each other. The two hybrid OTUs showed greater resemblance to one parent than to the other and in two analyses one hybrid was not intermediate between the parents. Similarities between the T and F analyses are explained on the basis of the predominance of floral characters in both. The differences between these two analyses on the one hand and the V analysis and phylogenetic arrangement of the family on the other are attributed to parallelisms in the evolution of floral characters associated with iucreasing autogamy in each of the two phyletic lines in the family. Analyses emphasizing floral characters will place evolutionarily remotely related outcrossing OTUs together and unrelated, autogamous OTUs together. Using characters that are mostly unassociated with the breeding system the positions of OTUs in a numerical analysis are similar to their positions in a phylogenetic arrangement. The V analysis agrees best with suggestions concerning phylogenetic affinities among the taxa in the family, and provides a useful context for the generation of further evolutionary hypotheses.     

Ontogenetic evidence for the Paleozoic ancestry of salamanders

The phylogenetic positions of frogs, salamanders, and caecilians have been difficult to establish. Data matrices based primarily on Paleozoic taxa support a monophyletic origin of all Lissamphibia but have resulted in widely divergent hypotheses of the nature of their common ancestor. Analysis that concentrates on the character states of the stem taxa of the extant orders, in contrast, suggests a polyphyletic origin from divergent Paleozoic clades. Comparison of patterns of larval development in Paleozoic and modern amphibians provides a means to test previous phylogenies based primarily on adult characteristics. This proves to be highly informative in the case of the origin of salamanders. Putative ancestors of salamanders are recognized from the Permo-Carboniferous boundary of Germany on the basis of ontogenetic changes observed in fossil remains of larval growth series. The entire developmental sequence from hatching to metamorphosis is revealed in an assemblage of over 600 specimens from a single locality, all belonging to the genus Apateon. Apateon forms the most speciose genus of the neotenic temnospondyl family Branchiosauridae. The sequence of ossification of individual bones and the changing configuration of the skull closely parallel those observed in the development of primitive living salamanders. These fossils provide a model of how derived features of the salamander skull may have evolved in the context of feeding specializations that appeared in early larval stages of members of the Branchiosauridae. Larvae of Apateon share many unique derived characters with salamanders of the families Hynobiidae, Salamandridae, and Ambystomatidae, which have not been recognized in any other group of Paleozoic amphibians.     

The heart and aortic arches of rhinatrematid caecilians (Amphibia: Gymnophiona)

Previous studies have shown there to be considerable inter-specific variation in the cardiovascular anatomy of five of the six families of caecilians. Observations on the previously unstudied Rhinatrematidae reveal this family to be characterized by a number of cardiovascular features that are unique within the Gymnophiona. These include a poorly developed sinus venosus sinistra, a short truncus arteriosus, separate carotid and systemic arches and the right atrium larger than the left. Character analysis indicates that these unique features are primitive within the Gymnophiona and they provide considerable additional support for the hypothesis that the Rhinatrematidae are the sister-group to all other caecilians. This hypothesis appears to be among the best supported hypotheses of relationships within the Gymnophiona. Caecilian cardiovascular variation provides a useful source of evidence for phylogeny reconstruction that should be integrated into phylogenetic studies of the group.