Paired fin skeletons and relationships of the fossil group Porolepiformes (Osteichthyes: Sardcopterygii)

The endoskeletal girdles, anocleithrum and paired fin supports of the porolepiform fish Glyptolepis (Osteichthyes: Sarcopterygii: Porolepiformes) are figured and described. The pectoral fin skeleton is known from the proximal part only and the pelvic fin skeleton is fragmentary, but the scapulocoracoid, anocleithrum and pelvic girdle can be reconstructed in their entirety. The anocleithrum is entirely subdermal. The pectoral fin skeleton in shown to be biserial, with a large number of axial mesomeres, whereas the pelvic fin contains fewer mesomeres and is strongly asymmetrical with very few postaxial radials. The scapulocoracoid is essentially similar to a reconstruction figured by Jarvik (1980), but has a more elongate glenoid; this has functional implications. The pelvic girdle consists of two separate halves as in Eusthenopteron, but differs from that genus in lacking dorsolateral rami. A brief survey of the evidence of paired fin structure in other porolepiform genera is carried out to establish whether the structures seen in Glyptolepis are likely to be representative for the Porolepiformes. A study of the morphology and muscle attachments of the paired fin skeletons indicates that the pattern of fin movement was significantly different from that in Neoceratodus. The fin supports and girdles of Glyptolepis are compared with those of other sarcopterygian groups as well as with actinopterygians, placoderms and sharks, in order to establish evolutionary polarities. Glyptolepis is shown to display a number of derived characters. The information gained from the comparison is used to construct a maximum parsimony cladogram, which places coelacanths as the sister group of porolepiforms + lungfishes, with the rhizodonts + tetrapods and osteolepiforms as successive sister groups of this clade. Characters of uncertain polarity are considered in the light of this cladogram. A comparison with recently published cladograms shows that none are completely compatible with the results from this study.     

The oldest sarcopterygian fish

The study of basal sarcopterygians is crucial to an understanding of the relationships and interrelationships of sarcopterygians, including their relationship to tetrapods. The new material from Qujing, Yunnan, southwestern China, represents the oldest known sarcopterygian fish and extends the record of sarcopterygians to the Late Silurian, or about 410 Ma. The new form is close to Youngolepis and Powichthys at the base of the Crossopterygii. Similarities among the lower jaws of onychodonts, porolepiforms, Youngolepis, Powichthys and the new form support a position of onychodonts within the Crossopterygii. Four characters in the character matrix of Cloutier & Ahlberg (1996, in Stiassny et al: Interrelationships of Fishes , Academic Press) are reviewed, and sarcopterygian interrelationships are studied on the basis of their data with minor modifications. The new scheme of sarcopterygian interrelationships differs markedly from Cloutier & Ahlberg's scheme. Neither actinistians nor onychodonts are situated at the base of Sarcopterygii, but within the Crossopterygii. Youngolepis and Powichthys are at the base of the Crossopterygii, instead of being the sister group of dipnoans plus Diabolepis.     

The median‐fin skeleton of the Eastern Atlantic and Mediterranean clingfishes Lepadogaster lepadogaster (Bonnaterre) and Gouania wildenowi (Risso) (Teleostei: Gobiesocidae)

Previous research on the osteology of the Gobiesocidae focused mostly on the neurocranium and the thoracic sucking disc (formed by the paired‐fin girdles). Little attention has been paid to the skeleton of the median fins. The dorsal‐ and anal‐fin skeleton of Lepadogaster lepadogaster and other gobiesocids (excluding Alabes, which lacks these fins) are characterized by the absence of spines, branched fin‐rays, and middle radials. In gobiesocids, the distal radials never ossify and consist of elastic hyaline‐cell cartilage. Gouania wildenowi is unique among gobiesocids in having further reductions of the dorsal‐ and anal‐fin skeleton, including a notable decrease in the size of the proximal‐middle radials in an anterior–posterior direction. Unlike L. lepadogaster, which exhibits a one‐to‐one relationship between the dorsal‐ and anal‐fin rays and proximal‐middle radials, G. wildenowi has a higher number of proximal‐middle radials than distal radial cartilages and fin rays in the dorsal and anal fins. In G. wildenowi, the dorsal‐ and anal‐fin rays do not articulate with the distal tip of the proximal‐middle radials but are instead positioned between proximal‐middle radials, which is unusual for teleosts. Previously unrecognized dorsal and ventral pads of elastic hyaline‐cell cartilage are also present in the caudal skeleton of L. lepadogaster, G. wildenowi, and all other gobiesocids examined. J. Morphol., 2010. © 2009 Wiley‐Liss, Inc.     

Fish fingers: digit homologues in sarcopterygian fish fins

A defining feature of tetrapod evolutionary origins is the transition from fish fins to tetrapod limbs. A major change during this transition is the appearance of the autopod (hands, feet), which comprises two distinct regions, the wrist/ankle and the digits. When the autopod first appeared in Late Devonian fossil tetrapods, it was incomplete: digits evolved before the full complement of wrist/ankle bones. Early tetrapod wrists/ankles, including those with a full complement of bones, also show a sharp pattern discontinuity between proximal elements and distal elements. This suggests the presence of a discontinuity in the proximal-distal sequence of development. Such a discontinuity occurs in living urodeles, where digits form before completion of the wrist/ankle, implying developmental independence of the digits from wrist/ankle elements. We have observed comparable independent development of pectoral fin radials in the lungfish Neoceratodus (Osteichthyes: Sarcopterygii), relative to homologues of the tetrapod limb and proximal wrist elements in the main fin axis. Moreover, in the Neoceratodus fin, expression of Hoxd13 closely matches late expression patterns observed in the tetrapod autopod. This evidence suggests that Neoceratodus fin radials and tetrapod digits may be patterned by shared mechanisms distinct from those patterning the proximal fin/limb elements, and in that sense are homologous. The presence of independently developing radials in the distal part of the pectoral (and pelvic) fin may be a general feature of the Sarcopterygii.     

Ontogenetic evidence supporting a relationship between <Emphasis Type="Italic">Brotulotaenia</Emphasis> and <Emphasis Type="Italic">Lamprogrammus</Emphasis> (Ophidiiformes: Ophidiidae) based on the morphology of exterilium and rubaniform larvae

Analysis of the Dana collection of larval fishes yielded 36 exterilium larvae and 17 rubaniform larvae, referable to the Ophidiidae. Both larval types reach large sizes before transformation and are characterized by an exterilium gut, although it is less strongly expressed in rubaniform larvae. Both have early-forming, elongate, descending processes of the coracoid that serve to support the trailing intestines. Both have a greatly reduced pelvic girdle attached to a stalklike cartilaginous structure, resulting in a pelvic fin origin well posterior to the cleithral symphysis, a position that is without precedent in the family Ophidiidae. Both of these larval types also strongly display an anterior to posterior developmental sequence, lose the pelvic fin rays at transformation, and have extraordinarily elongate proximal radials supporting their dorsal and anal fins and modified proximal radials supporting the anterior dorsal fin rays. After examination of these larvae and reference to 5 previously described exterilium larvae and 1 previously described rubaniform larva, we conclude that they belong to Lamprogrammus (three species) and Brotulotaenia (four species), respectively. The most recent classification of the Ophidiidae places Brotulotaenia in the monotypic subfamily Brotulotaeniinae, and Lamprogrammus in the subfamily Neobythitinae along with 37 other genera. The latter subfamily is an unwieldy assemblage for which monophyly has never been established. Ontogenetic evidence suggests a closer relationship between Brotulotaenia and Lamprogrammus, and the most economical reorganization of the ophidiids would involve incorporating the latter genus into the Brotulotaeniinae.     

PHYLOGENETIC RELATIONSHIPS IN SEED PLANTS

Abstract— The phylogenetic relationships of nineteen extant and fossil seed plants are considered. Analysis of 31 characters produced ten topologically similar and equally parsimonious cladograms. A strict consensus tree derived from these cladograms places Lyginopteris as the sister taxon to the other seed plants included. Within this clade all the taxa considered, except medullosans and cycads, form a single monophyletic group defined by the presence of flattened seeds and saccate pollen ("platy-sperms"). Relationships between medullosans, cycads, and "platysperms" were not resolved, but within the "platysperm" clade conifers and cordaites ( Cordaixylon, Mesoxylon ) + Ginkgo form a monophyletic group ("coniferophytes"). The "higher platysperms" (glossopterids, Caytonia , corystosperms, Bennettitales, Pentoxylon , Gnetales, and angiosperms) are also monophyletic, but their relationship to "coniferophytes," peltasperms, and Callistophyton is unresolved. Pentoxylon is placed as sister taxon to the Bennettitales, and together they form the sister group to a clade in which Gnetales and angiosperm are sister taxa. The Bennettitales + Pentoxylon + Gnetales + angiosperms ("anthophytes") form a monophyletic sister group to the corystosperms. This analysis is compared with current classifications of seed plants. It does not support a close relationship between Bennettitales and cycads, it provides no evidence for seed plant polyphyly, and it strongly suggests that the current concept of seed ferns has little value in a phylogenetic context.     

The dorsal fin engine of the seahorse (Hippocampus sp.)

The muscles, fin ray joints, and supporting structures underlying the dorsal fin are described for two seahorse species: Hippocampus zosterae and Hippocampus erectus. A fan-shaped array of cartilaginous bones, the pterigiophores, form the internal supporting structure of the dorsal fin. Each pterigiophore is composed of a proximal radial that extends from a vertebra to the dorsal side of the animal, where it fuses to a middle radial. The middle radials fuse with each other to form a dorsal ridge upon which sit the spheroidal distal radials. Each distal radial articulates with a fin ray on its dorsal side and is attached to the dorsal ridge on its ventral side by a material that has been histologically identified as elastic cartilage. Together these connections form a two-axis joint that permits elevation, depression, and inclination of the ray. Each fin ray is actuated by two bilateral pairs of muscles, an anterior pair of inclinators, and a posterior pair of depressors. The anteriormost fin ray is actuated by three bilateral pair of muscles, the inclinators, the depressors, and a pair of elevator muscles that are positioned anterior to the inclinators. Preliminary examinations of the ray joints of the pectoral and anal fins of adult H. zostera and the pectoral fins of newborn H. erectus revealed structures similar to that seen in the dorsal fins. To further explore the structure and function of the dorsal fin gross dissections and simple functional tests were performed on H. erectus and H. barbouri and behavioral observations were made of all three species plus Hippocampus kuda.     

Description of Careproctus guillemi n. sp. (Pisces: Scorpaeniformes) from Weddell Sea

Careproctus guillemi differs from the other Careproctus species in the following combination of characters: pectoral fin rays 22 (11 + 4+7); pectoral girdle with three round radials (1 + 0+ 1 + 1); mouth oblique and maxillary extending beyond posterior edge of eye. Relationships between C. guillemi and C. longipectoralis are provided. The endochondral pectoral girdle of C. longipectoralis is described for the first time.     

CHARACTER DIAGNOSIS, FOSSILS AND THE ORIGIN OF TETRAPODS

I. The traditional view of the origin of tetrapod vertebrates is that they are descendants of fossil osteolepiform fish, of which Eusthenopteron is best known. In recent years both that conclusion and the methodology by which it has been reached have been challenged by practitioners of cladistic analysis. Particularly a recent review by Rosen et al. (1981) claims that Dipnoi (lungfish) are the sister-group of the Tetrapoda, that Osteolepiformes is a non-taxon and that Eusthenopteron is more distant from tetrapods than are Dipnoi, coelacanths and probably the fossil Porolepiformes. We attempt to refute all these concludions by use of the same cladistic technique. 2. We accept that all the above-mentioned groups, together with some less well-known taxa, can be united as Sarcopterygii by means of shared derived (apomorph) characters. We also agree that Porolepiformes and Actinistia (coelacanths) can be characterized as valid taxa. The primitive and enigmatic fossil fish Powichthys is accepted as representing the plesiomorph sister-group of true porolepiforms. 3. Only two apomorph features, the course of the jaw adductor muscles and the position of incurrent and excurrent nostrils, appear to unite all the fish, living and fossil, currently regarded as Dipnoi. The characteristic tooth plates and the presence of petrodentine both exclude important primitive fossil forms. 4. Contrary to the opinion of Rosen et al., Osteolepiformes can be characterized — by the arrangement of bones forming the cheek plate, the presence of basal scutes to the fins and by the unjointed radials of the median fins. However, if these are true autapomorphies they exclude any osteolepiform from direct tetrapod ancestry. 5. Tetrapoda is a monophyletic group characterized by ten or more autapomorphies, including the bones of the cheek plate, a stapes and fenestra ovalis, and a series of characters of the appendicular skeleton. 6. Tetrapods have a true choana (internal nostril). We accept that the posterior (excurrent) nostril of Dipnoi is the homologue of the tetrapod choana. However, we assert that the posterior nostril of all bony fish is the homologue of the choana. This assertion would be refuted if any fish showed separate posterior nostril and choana. We reject the claim that this ‘three nostril condition’ occurred in porolepiforms and osteolepiforms. The evidence for a choana in porolepiforms is inadequate. Osteolepiforms had a true choana, characterized as in tetrapods by its relationship to the bones of the palate, but no third nostril. Dipnoans are not choanate. 7. Following cladistic practice, the relationship of the extant taxa is established first. Dipnoi are thus shown to be the living sister-group of tetrapods, but only on ‘soft anatomy’ characters unavailable in fossils. Coelacanths are the living sister-group of the taxon so formed. 8. The relationship of the fossil taxa to the extant sarcopterygians is then considered. The synapomorphy scheme proposed by Rosen et al. is discussed at length. Virtually all the characters they use to exclude close relationship of Eusthenopteron (and hence all osteolepiforms) to tetrapods, in favour of coelacanths and dipnoans, are invalid. 9. A series of synapomorphies uniting osteolepiforms and tetrapods is proposed, including a true choana (hence the taxon Choanata), the histology of the teeth, and a number of characters of the humerus. The recently discovered fossil Youngolepis, which lacks a choana, represents the sister-group of the Choanata, and is not uniquely close to Powichthys. The latter, as a porolepiform (s.l.) is a member of the sister-group to Choanata plus Youngolepis. 10. Our cladistic analysis suggests that all the extinct taxa considered are more closely related to tetrapods than are the Dipnoi. Moreover fossil evidence suggests that Dipnoi, considered as an extant taxon, may not even be the living sister-group of Tetrapoda. Early fossil dipnoans appear to have been marine fish without specific adaptations for air breathing. If so the apparent synapomorphies of Dipnoi and Tetrapoda may be homoplastic — the insistence on grouping extant taxa first would then have yielded an invalid inference.     

Pectoral fin and girdle development in the basal actinopterygians Polyodon spathula and Acipenser transmontanus

The pectoral fins of Acipenseriformes possess endoskeletons with elements homologous to both the fin radials of teleosts and the limb bones of tetrapods. Here we present a study of pectoral fin development in the North American paddlefish, Polyodon spathula, and the white sturgeon, Acipenser transmontanus, which reveals that aspects of both teleost and tetrapod endoskeletal patterning mechanisms are present in Acipenseriformes. Those elements considered homologous to teleost radials, the propterygium and the mesopterygial radials, form via subdivision of an initially chondrogenic plate of mesenchymal cells called the endoskeletal disc. In Acipenseriformes, elements homologous to the sarcopterygian metapterygium develop separately from the endoskeletal disc as an outgrowth of the endoskeletal shoulder girdle that extends into the posterior margin of the finbud. As in tetrapods, the elongating metapterygium and the metapterygial radials form in a proximal to distal order as discrete condensations from initially nonchondrogenic mesenchyme. Patterns of variation seen in the Acipenseriform fin also correlate with putative homology: all variants from the "normal" fin bauplan involved the metapterygium and the metapterygial radials alone. The primary factor distinguishing Polyodon and Acipenser fin development from each other is the composition of the endoskeletal extracellular matrix. Proteoglycans (visualized with Alcian Blue) and Type II collagen (visualized by immunohistochemistry) are secreted in different places within the mesenchymal anlage of the fin elements and girdle and at different developmental times. Acipenseriform pectoral fins differ from the fins of teleosts in the relative contribution of the endoskeleton and dermal rays. The fins of Polyodon and Acipenser possess elaborate endoskeletons overlapped along their distal margins by dermal lepidotrichia. In contrast, teleost fins generally possess relatively small endoskeletal radials that articulate with the dermal fin skeleton terminally, with little or no proximodistal overlap.     

Development of the paired fins in the paddlefish, Polyodon spathula

In Polyodon spathula, the pectoral fin radials, with the exception of the metapterygium, are derived from the decomposition of a single continuous cartilage fin plate that is continuous with the scapulocoracoid. This cartilage sheet develops two interior splits to form three precursor pieces, and these decompose in a predictable way to generate the propterygium and radials. The metapterygium is an extension of the scapulocoracoid that segments off of it during early development. To our knowledge, this has not been reported for acipenserids or other basal actinopterygians. In teleosts, the proximal radials also develop from the "break up" of an initially continuous paddle-like sheet of cartilage along the posterior edge of the scapulocoracoid, and in Polypterus and sharks a similar pattern holds. Thus, the pattern observed in Polyodon may represent the basal developmental condition for the gnathostome pectoral fin. The process underlying development of the superficially similar cartilages of the pelvic and pectoral fins is different. In the pectoral fin, the metapterygium is segmented off of the scapulocoracoid and other radials form from the decomposition of the cartilage plate. In contrast, individual rod-like basipterygial elements form in a close one-to-one correspondence with the middle radials of the pelvic fin, but later fuse to form an anterior element that is branched in appearance. To evaluate further claims of similarity among the pectoral and pelvic fin elements of various fishes, the course of the development of these structures must be observed. The pectoral fin and girdle in Polyodon ossifies in a different sequence than that proposed as ancestral (and highly conserved) for actinopterygians: the supracleithrum ossifies significantly before the cleithrum. The later ossification of the cleithrum in Polyodon may be related to the primary use of the caudal fin vs. the pectoral fins in their locomotion.     

Relationships of the temperate Australasian labrid fish tribe Odacini (Perciformes; Teleostei)

The labrid tribe Odacini comprises four genera and 12 species of fishes that inhabit shallow kelp forest and seagrass areas in temperate waters of Australia and New Zealand. Odacines are morphologically disparate, but share synapomorphies in fin structure and fusion of teeth into a beak-like oral jaw. A phylogenetic analysis of odacines was conducted to investigate their relationships to other labrid fishes, the relationships of species within the tribe, and the evolution of herbivory within the group. Fragments from two mitochondrial genes, 12S rDNA and 16S rDNA, and two nuclear genes, Tmo4C4 and RAG2, were sequenced for seven odacine species (representing all four genera), eight species representing the other major labrid lineages, and three outgroup species. Maximum likelihood and maximum parsimony analyses on the resulting 2338 bp of DNA sequence produced nearly identical topologies differing only in the placement of a clade containing the cheiline Cheilinus fasciatus and the scarine Cryptotomus roseus. The remaining clades received strong bootstrap support under maximum parsimony, and all clades in the maximum likelihood analysis received high bootstrap proportions and high posterior probabilities. The hypsigenyine labrid Choerodon anchorago formed the sister group to the odacines. Within the odacines, Odax cyanoallix+Odax pullus formed the sister to the remaining odacines, with Odax acroptilus, Odax cyanomelas, and Siphonognathus argyrophanes forming successively closer sister groups to the clade Haletta semifasciatus+Neoodax balteatus. Either herbivory evolved twice in the odacines, or herbivory evolved once with two reversions to carnivory. The latter hypothesis appears more likely in the light of odacine feeding biology.     

记比耶鱼(Birgeria)在中国的首次发现

记述了采自云南罗平晚三叠世法郎组竹杆坡段的比耶鱼一新种──刘氏比耶鱼（Ｂｉｒｇｅｒｉａ ｌｉｕｉ ｓｐ． ｎｏｖ．）,这是比耶鱼化石在中国的首次发现。刘氏比耶鱼与产自瑞士圣乔治山中三叠世边境沥青层的史氏比耶鱼最为相近,两者仅在尾柄长高之比、尾鳍长短与上下叶外缘交角、背鳍和臀鳍辐状支鳍骨的数目、臀鳍辐状骨骨板的大小、以及侧线管骨化与否等特征上略有差异。比耶鱼与软骨硬鳞鱼超目的鲟形目最为接近,两者共有一系列特征,如除尾上叶外体侧裸露,副蝶骨末端伸达头后,鳃盖骨退化;但比耶鱼同时也具有不少的特有特征,代表了软骨硬鳞鱼超目的另一类群──比耶鱼目（Ｂｉｒｇｅｒｉｉｆｏｒｍｅｓ　ｏｒｄ． ｎｏｖ．）。刘氏比耶鱼的发现进一步表明华南扬子区中、晚三叠世鱼类化石与特提斯西部的鱼群具有密切的动物地理关系。     

Differentiation of chondrocytes and scleroblasts during dorsal fin skeletogenesis in flounder larvae

In teleosts, the embryonic fin fold consists of a peridermis, an underlying epidermis and a small number of mesenchymal cells. Beginning from such a simple structure, the fin skeletons, including the proximal and distal radials and lepidotrichia (finrays), develop in the dorsal fin fold at the larval stage. Their process of skeletogenesis and embryonic origin are unclear. Using flounder larvae, we report the differentiation process for chondrocytes and scleroblasts prior to fin skeletogenesis and the effects of retinoic acid (RA) on it. In early larvae, the mesenchymal cells grow between the epidermis and spinal cord to form a line of periodical condensations, which are proximal radial primordia, to produce chondrocytes. The prescleroblasts, which ossify the proximal radial cartilages, differentiate in the mesenchymal cells remaining between the cartilages. Then, mesenchymal condensations occur between the distal ends of the proximal radials, forming distal radial primordia, to produce chondrocytes. Simultaneously, condensations occur between the distal radial primordia and peridermis, which are lepidotrichia primordia, to produce prescleroblasts. Exogenous RA specifically inhibits the mesenchymal condensation prior to the proximal radial formation together with the down-regulation of sonic hedgehog (shh) and patched (pta) expression, resulting in the loss of proximal radials. Thus, it was indicated that differentiation of the precursor cells of radials and lepidotrichia begins in the proximal part of the fin fold and that the initial mesenchymal condensation prior to the proximal radial formation is highly susceptible to the effects of RA. Lepidotrichia formation does not occur where proximal radials are absent, indicating that lepidotrichia differentiation requires interaction with the radial cartilages. To examine the suggestion that neural crest cells contribute to the medial fin skeletons, we localized the HNK-1 positive cells in flounder embryos and slug and msxb-positive cells in pufferfish, Fugu rubripes, embryos. That the positive cells commonly arrive at the proximal part of the fin fold does not contradict the suggestion, but their final destiny as radial chondrocytes or lepidotrichia scleroblasts, should be further investigated.     

Description of two new species of Santelmoa (Teleostei, Zoarcidae) from the Southern Ocean

Detailed examination of eelpouts in collected material from the Gerlache Strait and the Bellingshausen Sea, during the Spanish Antarctic Expeditions Bentart 03 and Bentart 06, and from the Bransfield Strait, during the Danish Galathea 3 Expedition, at depths between 1,056 and 1,837?m, revealed two undescribed species of Santelmoa Matallanas 2010. Herein, Santelmoa fusca sp. nov. and Santelmoa antarctica sp. nov. are described on the basis of twelve specimens. Santelmoa fusca can be separated from all other Santelmoa species by the following characters: mouth terminal; two posterior nasal pores; lateral line double; two irregular rows of palatine teeth; dorsal fin rays 109–113; anal fin rays 88–94; vertebrae 27–29?+?87–91?=?114–118; two pyloric caeca well developed; scales reduced to tail; pelvic fins and vomerine teeth present. Santelmoa antarctica can be separated from all other Santelmoa species by the following characters: mouth subterminal; two posterior nasal pores; suborbital pores seven (6?+?1); lateral line double; single row of palatine teeth; supraoccipital dividing the posterior end of frontals; central radials notched; dorsal fin rays 109–112; anal fin rays 89–93; vertebrae 27?+?89–92?=?116–119; two pyloric caeca well developed; scales, ventral fins and vomerine teeth present. Santelmoa fusca and S. antarctica can readily be separated from each other by squamation (reduced to tail vs. on the tail and on the posterior part of body); suborbital pore pattern (6?+?0 vs. 6?+?1), as well as several morphometric characters. The relationships of the two new species with congeners are discussed.     

Cladistic analysis of Neuroptera and their systematic position within Neuropterida (Insecta: Holometabola: Neuropterida: Neuroptera)

A phylogenetic analysis of Neuroptera using thirty‐six predominantly morphological characters of adults and larvae is presented. This is the first computerized cladistic analysis at the ordinal level. It included nineteen species representing seventeen families of Neuroptera, three species representing two families (Sialidae and both subfamilies of Corydalidae) of Megaloptera, two species representing two families of Raphidioptera and as prime outgroup one species of a family of Coleoptera. Ten equally most parsimonious cladograms were found, of which one is selected and presented in detail. The results are discussed in light of recent results from mental phylogenetic cladograms. The suborders Nevrorthi‐ formia, Myrmeleontiformia and Hemerobiiformia received strong support, however Nevrorthiformia formed the adelphotaxon of Myrmeleontiformia + Hemerobiiformia (former sister group of Myrmeleontiformia only). In Myrmeleontiformia, the sister‐group relationships between Psychopsidae + Nemopteridae and Nymphidae + (Myrmeleontidae + Ascalaphidae) are corroborated. In Hemerobiiformia, Ithonidae + Polystoechotidae is confirmed as the sister group of the remaining families. Dilaridae + (Mantispidae + (Rhachiberothidae + Berothidae)), which has already been proposed, is confirmed. Chrysopidae + Osmylidae emerged as the sister group of a clade comprising Hemerobiidae + ((Coniopterygidae + Sisyridae) + (dilarid clade)). Despite the sister‐group relationship of Coniopterygidae + Sisyridae being only weakly supported, the position of Coniopterygidae within the higher Hemerobiiformia is corroborated. At the ordinal level, the analysis provided clear support for the hypothesis that Megaloptera + Neuroptera are sister groups, which upsets the conventional Megaloptera + Raphidioptera hypothesis.     

The systematic position of Meruidae (Coleoptera, Adephaga) and the phylogeny of the smaller aquatic adephagan beetle families

A phylogenetic analysis of Adephaga is presented. It is based on 148 morphological characters of adults and larvae and focussed on a placement of the recently described Meruidae, and the genus‐level phylogeny of the smaller aquatic families Gyrinidae, Haliplidae and Noteridae. We found a sister group relationship between Gyrinidae and the remaining adephagan families, as was found in previous studies using morphology. Haliplidae are either the sister group of Dytiscoidea or the sister group of a clade comprising Geadephaga and the dytiscoid families. Trachypachidae was placed as the sister group of the rhysodid‐carabid clade or of Dytiscoidea. The monophyly of Dytiscoidea including Meru is well supported. Autapomorphies are the extensive metathoracic intercoxal septum, the origin of the metafurca from this structure, the loss of Mm. furcacoxalis anterior and posterior, and possibly the presence of an elongated subcubital setal binding patch. Meruidae was placed as sister group of the Noteridae. Synapomorphies are the absence of the transverse ridge of the metaventrite, the fusion of abdominal segments III and IV, the shape of the strongly asymmetric parameres, and the enlargement of antennomeres 5, 7 and 9. The Meru‐noterid clade is the sister group of the remaining Dytiscoidea. The exact position of Aspidytes within this clade remains ambiguous: it is either the sister group of Amphizoidae or the sister group of a clade comprising this family and Hygrobiidae + Dytiscidae. The sister group relationship between Spanglerogyrinae and Gyrininae was strongly supported. The two included genera of Gyrinini form a clade, and Enhydrini are the sister group of a monophylum comprising the remaining Enhydrini and Orectochilini. A branching pattern (Peltodytes + (Brychius + Haliplus)) within Haliplidae was confirmed. Algophilus, Apteraliplus and the Haliplus‐subgenus Liaphlus form a clade. The generic status of the two former taxa is unjustified. The Phreatodytinae are the sister group of Noterinae, and Notomicrus (+ Speonoterus), Hydrocoptus, and Pronoterus branch off successively within this subfamily. The search for the larvae of Meru and a combined analysis of morphological and molecular data should have high priority. © The Willi Hennig Society 2006.     

Leis' conundrum: homology of the clavus of the ocean sunfishes. 2. Ontogeny of the median fins and axial skeleton of Ranzania laevis (Teleostei, Tetraodontiformes, Molidae)

One of the most conspicuous characters of the ocean sunfishes, family Molidae, is the punctuation of the body by a deep, abbreviated, caudal fin-like structure extending vertically between the posterior ends of the dorsal and anal fins, termed the clavus by Fraser Brunner. Homology of the clavus has been a matter of debate since the first studies on molid anatomy in the early 1800s. Two hypotheses have been proposed: 1) It is a highly modified caudal fin; 2) It is formed by highly modified elements of the dorsal and anal fins. To resolve this homology issue, we studied the ontogeny of the molid vertebral column and median fins and compared it to that of a less morphologically derived gymnodont (see Part 1 of this study), a member of the family Tetraodontidae. We show that in molids the chorda never flexes during development, that the claval rays form from the posterior ends of the dorsal and anal fins toward the middle, thus closing the gap inward, and that elements of the molid clavus have an identical development and composition as the proximal-middle and distal radials of the regular dorsal and anal fins. We thus conclude that the molid clavus is unequivocally formed by modified elements of the dorsal and anal fin and that the caudal fin is lost in molids.     

Hemichordates and deuterostome evolution: robust molecular phylogenetic support for a hemichordate + echinoderm clade

SUMMARY Hemichordates were traditionally allied to the chordates, but recent molecular analyses have suggested that hemichordates are a sister group to the echinoderms, a relationship that has important consequences for the interpretation of the evolution of deuterostome body plans. However, the molecular phylogenetic analyses to date have not provided robust support for the hemichordate + echinoderm clade. We use a maximum likelihood framework, including the parametric bootstrap, to reanalyze DNA data from complete mitochondrial genomes and nuclear 18S rRNA. This approach provides the first statistically significant support for the hemichordate + echinoderm clade from molecular data. This grouping implies that the ancestral deuterostome had features that included an adult with a pharynx and a dorsal nerve cord and an indirectly developing dipleurula-like larva.     

Dealing with saturation at the amino acid level: a case study based on anciently duplicated zebrafish genes

The ray-finned fishes (Actinopterygii) seem to have two copies of many tetrapod (Sarcopterygii) genes. The origin of these duplicate fish genes is the subject of some controversy. One explanation for the existence of these extra fish genes could be an increase in the rate of independent gene duplications in fishes. Alternatively, gene duplicates in fish may have been formed in the ancestor of all or most Actinopterygii during a complete genome duplication event. A third possibility is that tetrapods have lost more genes than fish after gene or genome duplication events in the common ancestor of both lineages. These three hypotheses can be tested by phylogenetic reconstruction. Previously, we found that a large number of anciently duplicated genes of zebrafish are sister sequences in evolutionary trees suggesting that they were produced in Actinopterygii after the divergence of Sarcopterygii [Phil. Trans. R. Soc. Lond. B 356 (2001) 119]. On the other hand, several well-supported trees showed one of the two fish genes as the sister sequence to a monophyletic clade that included the second fish gene and genes from frog, chicken, mouse and human. These so-called outgroup topologies suggest that the origin of many fish duplicates predates the divergence of the Sarcopterygii and Actinopterygii and support the hypothesis that tetrapods have lost duplicates that have been retained in fish. Here we show that many of these 'outgroup' tree topologies are erroneous and can be corrected when mutational saturation is taken into account. To this end, a Java-based application has been developed to visualize the amount of saturation in amino acid sequences. The program graphically displays the number of observed frequent and rare amino acid replacements between pairs of sequences against their overall evolutionary distance. Discrimination between frequent and rare amino acid replacements is based on substitution probability matrices (e.g. PAM and BLOSUM). Evolutionary distances between sequences can be computed from the fraction of unsaturated sites only and evolutionary trees inferred by pairwise distance methods. When trees are computed by omitting the saturated fraction of sites, most fish duplicates are sister sequences.