The composition of the caudal skeleton of teleosts (Actinopterygil: Osteichthyes)

The diural caudal skeleton of teleostean actinopterygians develops phylogeneticaily and ontogenetically from a polyural skeleton. The reduction of the polyural anlage to four, three, two or fewer centra in the adult caudal skeleton takes different pathways in different genera (e.g. compare Elops and Albula) and groups of teleosts. As a result, ural centra are not homologous throughout the teleosts. By numbering the ural centra in a homocercal tail in polyural fashion, one can demonstrate these and the following differences. The ventral elements (hypurals) always occur in sequential series, whereas the dorsal elements (epurals and uroneurals) may alter like the ural centra. The number of epurals, five or four in fossil primitive teleosts, is reduced in other primitive and advanced teleosts, but the same epurals are not always lost. The number of uroneurals, seven in fossil teleosts, is reduced in living teleosts, but it has not been demonstrated that the first uroneural is always derived from the neural arch of the same ural centrum. The landmark in the homocercal tail is the preural centrum I which can be identified by (1) bifurcation of the caudal artery and vein in its ventral element, the parhypural, (2) its position directly caudal to the preural centrum (PU2) which supports the lowermost principal caudal ray with its haemal spine, (3) carrying the third hypaxial element ventral to the course of arteria and vena pinnalis, and (4) by carrying the first haemal spine (parhypural) below the dorsal end of the ventral cartilage plate. The study of the development of the vertebral column reveals that teleosts have different patterns of centrum formation. A vertebral centrum is a complete or partial ring of mineralized, cartilaginous or bony material surrounding at least the lateral sides of the notochord. A vertebral centrum may be formed by arcocentrum alone, or arcocentral arcualia and chordacentrum, or arco-, chorda- and autocentrum, or arcocentral arcualia and autocentrum. This preliminary research demonstrates that a detailed ontogenetic interpretation of the vertebral centra and of the caudal skeleton of different teleosts may be useful tools for further interpretations of teleostean interrelationships.     

Histochemical study of jaw muscle fibers in the American alligator (Alligator mississippiensis)

The ontogenetic development of caudal vertebrae and associated skeletal elements of salmonids provides information about sequence of ossification and origin of bones that can be considered as a model for other teleosts. The ossification of elements forming the caudal skeleton follows the same sequence, independent of size and age at first appearance. Dermal bones like principal caudal rays ossify earlier than chondral bones; among dermal bones, the middle principal caudal rays ossify before the ventral and dorsal ones. Among chondral bones, the ventral hypural 1 and parhypural ossify first, followed by hypural 2 and by the ventral spine of preural centrum 2. The ossification of the dorsal chondral elements starts later than that of ventral ones. Three elements participate in the formation of a caudal vertebra: paired basidorsal and basiventral arcocentra, chordacentrum, and autocentrum; appearance of cartilaginous arcocentra precedes that of the mineralized basiventral chordacentrum, and that of the perichordal ossification of the autocentrum. Each ural centrum is mainly formed by arcocentral and chordacentrum. The autocentrum is irregularly present or absent. Some ural centra are formed only by a chordacentrum. This pattern of vertebral formation characterizes basal teleosts and primitive extant teleosts such as elopomorphs, osteoglossomorphs, and salmonids. The diural caudal skeleton is redefined as having two independent ural chordacentra plus their arcocentra, or two ural chordacentra plus their autocentra and arococentra, or only two ural chordacentra. A polyural caudal skeleton is identified by more than two ural centra, variably formed as given for the diural condition. The two ural centra of primitive teleosts may result from early fusion of ural centra 1 and 2 and of ural centra 3 and 4, or 3, 4, and 5 (e.g., elopomorphs), respectively. The two centra may corespond to ural centrum 2 and 4 only (e.g., salmonids). Additionally, ural centra 1 and 3 may be lost during the evolution of teleosts. Additional ural centra form late in ontogeny in advanced salmonids, resulting in a secondary polyural caudal skeleton. The hypural, which is a haemal spine of a ural centrum, results by growth and ossification of a single basiventral ural arococentrum and its haemal spine. The proximal part of the hypural always includes part of the ventral ural arcocentrum. The uroneural is a modification of a ural neural arch, which is demonstrated by a cartilaginous precursor. The stegural of salmonids and esocids originates from only one paired cartilaginous dorsal arcocentrum that grows anteriorly by a perichondral basal ossification and an anterodorsal membranous ossification. The true epurals of teleosts are detached neural spines of preural and ural neural arches as shown by developmental series; they are homologous to the neural spines of anterior vertebrae. Free epurals without any indication of connection with the dorsal arococentra are considered herein as an advanced state of the epural. Caudal distal radials originate from the cartilaginous distal portion of neural and haemal spines of preural and ural (epurals and hypurals) vertebrae. Therefore, they result from distal growth of the cartilaginous spines and hypurals. Cartilaginous plates that support rays are the result of modifications of the plates of connective tissue at the posterior end of hypurals (e.g., between hypurals 2 and 3 in salmonids) and first preural haemal spines, or from the distal growth of cartilaginous spines (e.g., epural plates in Thymallus). Among salmonids, conditions of the caudal skeleton such as the progressive loss of cartilaginous portions of the arcocentra, the progressive fusion between the perichondral ossification of arcocentra and autocentra, the broadening of the neural spines, the enlargement and interdigitation of the stegural, and other features provide evidence that Prosopium and Thymallus are the most primitive, and that Oncorhynchus and Salmo are the most advanced salmonids respectively. This interpretation supports the current hypothesis of phylogenetic relationships of salmonids. © 1992 Wiley-Liss, Inc.     

The caudal skeleton of ostariophysan fishes (Teleostei): Intraspecific variation in trichomycteridae (Siluriformes)

The different elements of the caudal skeleton of the South American catfish genera Nematogenys (Nematogenyinae) and Trichomycterus, Hatcheria, and Bullockia (Pygidiinae) (Siluriformes, Trichomycteridae) show Ontogenetic transformation of the second ural centrum in Trichomycteridae separates the subfamilies Nematogenyinae and Pygidiinae. In the former, the second ural centrum is aligned with the first ural centrum in early stages of ontogeny; it is not fused with the bases of hypurals 3 and 4 in any stage of development. In the Pygidiinae, in contrast, the second ural centrum is connected with the base of hypural 3 from an early stage of development on. One of the most noteworthy features of the Pygidiinae is the epural, a polymorphic element with three or four morphotypes that are species specific. The primitive catfish Nematogenys shows intraspecific variation in the ural centra, segmentation of procurrent caudal rays, and principal caudal ray formulae. Species of Trichomycterus, Hatcheria, and Bullockia are characterized by great intraspecific variability that involves ural centra, the epural, hypurapophyses, and the neural arches of the compound centrum. There is intraspecific variation in the fusion of the hypurals in some species of Trichomycterus. Intraspecific variation of the caudal skeleton of fishes of the family Trichomycteridae involves the presence and frequency of different morphotypes of the epural, neural arch of the compound centrum, fusion of hypurals, and principal caudal ray formulae. Ontogenetic changes of the first and second ural centra, hypurapophyses (with the exception of Nematogenys), and segmentation of procurrent caudal rays (in Nematogenys) are involved also.     

Ontogeny,variation, and homology in Salvelinus alpinus caudal skeleton (Teleostei: Salmonidae)

The ontogeny of the caudal skeleton in the Arctic charr, Salvelinus alpinus was examined using an extensive series of cleared and stained specimens. We demonstrate the presence of skeletal components never reported previously within the Salmonidae. In contrast to the generalized condition for salmonids, seven hypurals (instead of six), and four uroneurals (instead of three) have been found in some specimens. Variation in the number and condition of epurals is documented. New hypotheses are proposed concerning (1) relationships among centra and their associated elements, (2) phylogenetic distribution of caudal characters within the Salmonidae, and (3) homology of caudal components. Using the published phylogenetic hypotheses, we provide evidence, that a seventh hypural and a fourth uroneural are taxic atavism in salmonids. The development of the salmonid homocercal fin is discussed in the light of a polyural scheme based on evidences of a one‐to‐one relationship among ural centra and their associated elements. J. Morphol., 2010. © 2009 Wiley‐Liss, Inc.     

Orthogonikleithrus leichi n. gen., n. sp. (pisces: teleostei) from the late jurassic of Germany

Orthogonikleithrus leichi n. gen and n. sp. from the Late Jurassic of Zandt, W-Germany resemblesLeptolepides in the supra- and infraorbital sensory canals and in the length of the anterior process of the maxilla, andAscalabos in the massive aspect of the premaxilla. The caudal skeleton has some similarities with that ofLeptolepides (e. g. the broadening of the neural and haemal spines of the last caudal vertebrae, length of uroneurals 1 and 2), but also with that ofAnaethalion (in the neural arches above preural centrum 1 and ural centra). According to this combination of features, the fish remains as Elopocephala incertae sedis.     

Vertebral column and associated elements in dipnoans and comparison with other fishes: development and homology.

A vertebral column consisting of a persistent notochord and ossified arcocentra is the primitive condition for Gnathostomata; it still persists in primitive actinopterygians and sarcopterygians. Advanced actinopterygians and sarcopterygians develop numerous types of centra that include, among others, the presence of holocentrum, chordacentrum, and autocentrum. The chordacentrum, a mineralization or calcification of the fibrous sheath of the notochord, is only found in actinopterygians, whereas an autocentrum is a synapomorphy of teleosts above Leptolepis coryphaenoides. The chordacentrum, formed by migration of cartilaginous cells from the arches into the fibrous sheath of the notochord and usually covered by a thin calcification, is a unique feature of chondrichthyans. The actinopterygian chordacentrum and the chondrichthyan chordacentrum are not homologous. The postcaudal cartilaginous centrum is only known in postcaudal vertebrae of living dipnoans. The holocentrum is present in certain fossil dipnoans and actinopterygians, where it has been independently acquired. It is formed by proliferation of cartilage cells around the elastica externa of the notochord. These cells later ossify, forming a compact centrum. A vertebral column formed by a persistent notochord without vertebral centra is the primitive pattern for all vertebrates. The formation of centra, which is not homologous among vertebrate groups, is acquired independently in some lineages of placoderms, most advanced actinopterygians, and some dipnoans and rhipidistians. Several series of structures are associated with the vertebral column such as the supraneurals, interhaemals, radials, and ribs. In living dipnoans median neural spine, "supraneural," and dorsal radial result from growth and distal differentiation of one median cartilage into two or three median bones during ontogeny. The median neural spine articulates with the neural arch and fuses with it in the caudal vertebrae early in ontogeny. Two bones differentiate in the anterior abdominal vertebrae, i.e., the proximal neural spine and the distal "supraneural." Three bones differentiate in front of the dorsal fin, i.e., the proximal neural spine, the middle "supraneural", and the distal radial; the same pattern is observed in front of the anal fin (the proximal haemal spine, the middle interhaemal, and the distal radial). Considering that the three dorsal (and also the three ventral) bones originate from growth of only one cartilage, they cannot be serial homologs of the neural spines, or "supraneural." They are linear homologs of the median neural cartilage in living dipnoans. The development of these elements differs within osteichthyans from sarcopterygians to actinopterygians, in which the neural spine originates as a continuation of the basidorsal arcualia and in which the supraneural and radial originate from independent cartilages that appear at different times during early ontogeny. The ribs of living dipnoans are unique in that they are not articulated with parapophyses, like in primitive fossil dipnoans, but a remnant of the ventral arcuale surrounded by a small arcocentrum remains at its base. A true caudal fin is absent in living dipnoans. The postcaudal cartilages extend to the caudal tip of the body separating dorsal and ventral rays (or the camptotrichia). Actinotrichia are present in young dipnoans. They are also known in extant actinistians and actinopterygians. They probably represent the primitive state for teleostomes. In contrast, the camptotrichia are unique for extant dipnoans (and probably Carboniferous and younger dipnoans). Lepidotrichia apparently developed many times among osteichthyans.     

A comparative ontogenetic study of the tetraodontiform caudal complex

Konstantinidis P. and Johnson, G. D. 2012. A comparative ontogenetic study of the tetraodontiform caudal complex. —Acta Zoologica (Stockholm) 93 : 98–114. Interpretation of the caudal complex of adult Tetraodontiformes has proven problematic because of the consolidation of the component elements. Here, we show that an ontogenetic approach offers considerable elucidation of the homology of the caudal complex, resulting in a new understanding of the grundplan of these fishes. The reductions of structures of the caudal complex are interpreted in a phylogenetic context. The caudal skeleton of larval triacanthodids resembles that of many adult percomorphs; however, during subsequent development epural 3 disappears, while epural 2 is reduced so that it can hardly be distinguished from the uroneural remnants. Juvenile triacanthids have an epural 2 that is lost in ontogeny, and the cartilaginous parhypural becomes integrated into the large hypural plate. In ostraciids and diodontids, the parhypural is absent throughout development. The hypural plates of adult balistids, monacanthids and tetraodontids have a conspicuous diastema between the dorsal and ventral portions. However, in early stages of the former two, the dorsal and ventral portions are continuous in cartilage proximally and remain fused in the adults. In tetraodontids, the two hypurals are separate from their initial appearance in cartilage and never fuse, raising the question of homology of the individual hypurals among the different families.     

The ontogenic development of the vertebrae in some gekkonoid lizards

The ontogeny of amphicoelous vertebrae was studied in Ptyodactylus hasselquistii and Hemidactylus turcicus, and that of procoelous vertebrae, in Sphaerodactylus argus. The embryos were assigned arbitrary stages, drawn to scale, and mostly studied in serial sections. Resegmentation occurs as in all amniotes. A sclerocoel divides each sclerotome into an anterior “presclerotomite” and a denser posterior “postsclerotomite.” Tissue surrounding the intersegmental boundary forms the centrum, which is intersegmental. Tissue around the sclerocoel builds the intervertebral structures, which are midsegmental. In the trunk and neck, postsclerotomites form neural arches, and presclerotomites build zygapophyses. The adult centrum consists of the perichordal primary centrum, plus neural arch bases (= secondary centrum). Between the latter and the arch proper, a neurocentral suture persists until obliterated in maturity. A dorso-ventral central canal persists on either side of the primary centrum, between the latter and the secondary centrum. The notochord becomes true cartilage midvertebrally in all vertebrae, and elastic cartilage intervertebrally in the posterior caudal region. Elsewhere its characteristic tissue persists. Intervertebrally, cervical hypapophyses, caudal chevrons and chevron-bases in the trunk are preformed early in cartilage. Directly ossifying median intercentra are added later in all regions. The first cervical presclerotomite is absent: the hypapophysis (= corpus) of the atlas consists exclusively of postsclerotomitic tissue, there is no proatlas, and the odontoid lacks the apical half-centrum present in other lepidosaurians. In the autotomous caudal region presclerotomites are as prominent as postsclerotomites. Both build neural arches, the two arches of each vertebra remaining distinct and ossifying separately, so that the intersegmental autotomy split persists between them. The last sclerotome is complete, its postsclerotomite forming a half centrum which ossifies. In Sphaerodactylus, while the vertebrae ossify, each intervertebral ring becomes concave anteriorly, convex posteriorly; it remains as a cushion between the condyle and a facet formed by differential growth of the centra. Thus these procoelous centra resemble the amphicoelous centra of Ptyodactylus and Hemidactylus, rather than the procoelus centra of other squamates. The vertebral column of Gekkonoidea closely resembles in its development and microscopical structure that of Sphenodon.     

薄鳞鱼类化石的新发现及其地层意义

本文记述了薄鳞鱼类(leptolepids)一新属新种——罗家峡隆德鱼(Longdeichthys luojiaxiaensis gen.et sp.nov.)。它和广泛分布于我国北方的另一原始真骨鱼类狼鳍鱼(Lycoptera)共生。因而,为研究真骨鱼类的演化和确定我国北方中生代含鱼岩系的时代及地层对比上,提供了新的资料。     

Anatomical and Histological Investigations on the Caudal Skeleton of Apteronotus leptorhynchus (Apteronotidae,Gymnotoidei)

The caudal skeleton of Apteronotus leptorhynchus was studied at various stages from hatching to the adult stage using anatomical and histological techniques. The caudal skeleton that supports the lepidotrichia is reduced to a rhomboid caudal plate (caudal cartilage) that extends the vertebral axis. This cartilage appears for the first time in 8 day old fish, postero-ventral to the notochord. During its growth, perichondral and endochondral ossification occurs, beginning at the anterior end of the cartilage. Comparison with the anatomy and ontogeny of the typical caudal skeleton of teleosts allows us to interpret the caudal cartilage of A. leptorhynchus as an hypuro-opisthural component that is homologous to the cartilage that occurs at the tip of the axial skeleton in Eigenmannia virescens.     

A new genus and two new species of gobiid fishes (Perciformes) from the Chagos Archipelago,Central Indian Ocean

Synopsis A recent (1979) expedition to the Chagos Archipelago resulted in the collection of about 40 new taxa of fishes. A new genus,Trimmatom, and two new species,T. nanus andT. offucius, are described here. The new genus is characterized by having all pelvic-fin rays simple (unbranched), a scaleless body, no head pores, a wide gill opening extending anteroventrally to below the eye, and hypurals 1 and 2 fused to the complex formed by the fusion of the ural centrum and hypurals 3 and 4.T. nanuss andT. offucius are differentiated on the basis of fin ray counts and colour pattern.T. nanus is the smallest vertebrate yet to be described. Mature females with ovaries full of eggs are 8–10 mm in standard length.     

隆德鱼的新材料及其系统关系的初步分析——辽宁西部晚中生代地层和鱼群研究之一

依据辽宁西部三个地点的新材料和宁夏、内蒙古的标本,对罗家峡隆德鱼(Longdeichthys luojiaxiaensis Liu,1982)的形态特征作了补充描述和修订,并初步分析讨论了“薄鳞鱼类”的研究现状以及隆德鱼的系统关系。认为隆德鱼可能已是鲱头鱼派(Clupeocephala)的成员,与德国和法国基末里期的Leptolepides sprattiformis(Blainville)最为相近。     

圆尾鱼属(■Cyclurus,Amiidae,Pisces)在中国的首次发现(英文)

记述了弓鳍鱼亚科一新种:Cyclurus orientalis(东方圆尾鱼),标本采集于中国湖南省湘乡市下湾铺早始新世至中始新世下湾铺组。化石因具有以下特征而被归入弓鳍鱼亚科(Ami-inae):尾前椎为双椎型;除第一尾椎和第一尾下骨外,其余尾椎和尾下骨均一对一愈合;无膜质尾骨;背鳍长。因其第一冠状骨上的牙齿顶端圆钝,而被归入Cyclurus属。本新种与Cy-clurus属中其他种的区别在于:背鳍鳍条较少;身体短而高;脊椎和椎体较少。在始新世淡水鱼类的跨太平洋分布达到鼎盛时,由于弓鳍鱼亚科并非仅分布于太平洋两岸的类群,因此不能作为跨太平洋分布的指示类群。弓鳍鱼亚科在北半球的分布范围更广,与某些其他淡水鱼类群例如狗鱼科(Esocidae)和骨舌鱼科(Osteoglossidae)相似,这种现象只能用有别于形成跨太平洋分布的地质背景来解释。     

Senegalese sole bone tissue originated from chondral ossification is more sensitive than dermal bone to high vitamin A content in enriched Artemia

Several studies have evaluated the effects of dietary vitamin A (VA) on the incidence of skeletal deformities during early ontogeny of fish, but little is known about its effects on bones depending on their process of ossification (dermal or chondral). We examined the incidence of skeletal deformities along development (30 and 48 dph) by double staining technique, in dermal (haemal and caudal vertebral bodies) and chondral (neural and haemal spines, epural, parahypural and hypurals) bones in Senegal sole post metamorphosed larvae fed with different dietary VA levels (37 000, 44 666, 82 666 and 203 000 UI total VA kg^?1 DW) during Artemia feeding phase (6–37 dph, at 18°C). Results obtained in this study showed that dietary VA disrupted the skeletogenesis in Senegalese sole post metamorphosed larvae by increasing the incidence of skeletal deformities in the axial skeleton and caudal fin complex, which were dependent on both bone morphogenesis and ossification processes. Fish fed with the highest dietary VA content showed the highest incidence of skeletal deformities and its value increased along ontogeny. However, when we compared the incidence of deformities in skeletal structures considering their ossification process, most skeletal structures derived from chondral ossification showed a significant higher increase in deformity incidences in fish fed an excess of VA (44 666, 82 666 and 203 000 UI kg^?1 DW), however within chondral bones, hypurals deformity incidence only increased in sole larvae fed Artemia highest VA content. In contrast, this dietary dose‐response effect was only noted in dermal bones from fish fed the highest dose of VA (203 000 UI kg^?1 DW). In addition, the incidence of deformities in chondral bones increased even when the dietary imbalance of VA was corrected, whereas dermal bones were not affected at later ages. These results indicated that depending on the ossification process from which different skeletal structures are derived, bones might be differentially affected by high dietary VA content. Those directly originated from the connective tissue with a preliminary cartilage stage were more sensitive to dietary VA excess than those formed by intramembranous ossification.     

Leis' conundrum: homology of the clavus of the ocean sunfishes. 1. Ontogeny of the median fins and axial skeleton of Monotrete leiurus (Teleostei, Tetraodontiformes, Tetraodontidae)

We describe the ontogeny of the axial skeleton and median fins of the Southeast Asian freshwater puffer Monotrete leiurus, based on a reared developmental series. Most elements of the axial skeleton in M. leiurus arise in membrane bone. Only the base of the anterior three neural arches, the base of the hemal arches of the third preural centrum, the neural and hemal arches and spines of the second preural centrum, the parhypural, the two hypural plates, and the single epural are preformed in cartilage. In contrast to most teleosts, the proximal-middle radials of the dorsal and anal fins are upright and symmetrical and their distal tips coalesce during development to form a deep band of cartilage, from which the spherical distal radials are spatially separated.     

Early development of fin-supports ani fin-rays in the milkfishChanos chanos

Development of fin-supports and fin-rays was observed in larval and juvenileChanos chanos, Chondrification of the caudal complex started at 4.70 mm SL. Ossification of the caudal elements started at 7.80 mm SL and was nearly completed at about 30 mm SL. Cartilaginous fusion of caudal elements, which occurs in hypurals of higher teleostean fishes but is not seen in lower teleosts, was observed between the neural arch of the preural centrum 1 and that of the ural centrum 1 via a small cartilage bridging the distal tips of the two arches. Caudal finrays began to develop at 6.60 mm SL, and an adult complement of principal rays was attained at 7.35 mm SL. Dorsal and anal pterygiophore elements were first evident at 6.70 mm and 6.65 mm SL, respectively. All proximal radiais were formed at 8.15 mm SL in both fins. Formation of dorsal and anal fin-rays started simultaneously at 8.60 mm SL, and adult fin-ray complements were attained at 10,00 mm and 10.70 mm SL, respectively. In the pectoral fin, the cleithrum, coraco-scapular cartilage and blade-like cartilage (fin plate) had already been formed at 4.65 mm SL. The mesocoracoid was observed to originate from the coraco-scapular cartilage and become detached from it in the course of ossification. Pectoral fin-ray formation started at 13.80 mm SL and was completed in number of rays at 20.00 mm SL. In the pelvic fin, the basipterygium was first evident at 13.00 mm SL. Pelvic fin-rays appeared at 13.80 mm SL and attained their adult count at 17.15 mm SL.     

Comparative osteology and phylogenetic systematics of fossil and living bony-tongue fishes (Actinopterygii, Teleostei, Osteoglossomorpha)

Several recent studies using analyses of morphological characters have addressed the interrelationships of Osteoglossomorpha, a group that sometimes is considered the living sister group of all other living teleosts. Many characters used in these studies were found to be poorly defined, to be coded incorrectly or illogically, or to display more variation than was described. The goal of this study is to address these concerns and contribute generally to knowledge of the morphology and systematic relationships of osteoglossomorphs. Analysis of 72 characters (65 informative) scored for 20 genera resulted in two most parsimonious cladograms (171 steps, CI = 0.6433, CI = 0.6139 excluding uninformative characters, HI = 0.3977, HI = 0.3861 excluding uninformative characters; RI = 0.7782; RC = 0.5006). Osteoglossomorpha is supported by both synapomorphies and homoplasies, although its monophyly was not truly tested in this analysis (only a single outgroup, Elops , was included in the analysis). The only difference in the topologies of these cladograms is in the position of ?Lycoptera (recovered as either the sister group of all other osteoglossomorphs sampled or of ?Eohiodon +Hiodon ). ?Ostariostoma is recovered as the sister group of all non‐hiodontiform osteoglossomorphs. Mormyrids are the sister group of notopterids + osteoglossids. This clade has not been found in other recent analyses. Mormyrids and notopterids usually are considered more closely related to each other than to any other group; characters not included here support this relationship and future consideration of these characters must be made. Although almost completely dichotomous, many nodes of the resulting trees lack rigorous support. For example, ?Palaeonotopterus is interpreted as the sister group of all mormyrids sampled, although for this taxon only 22% of characters could be scored. © 2003 The Linnean Society of London. Zoological Journal of the Linnean Society , 2003, 137 , 1?100.     

宁夏狼鳍鱼科一新属

本文记述了狼鳍鱼科一新属,即同心鱼属(Tougxinichthys gen.nov.)化石产自宁夏同心县康家湾;海原县石峡口一带的六盘山群上部。同心鱼(Tongxinichthys)与狼鳍鱼(Lycoptera)很相似。后者被认为是我国华北地区晚侏罗世鱼群的主要成员。而同心鱼的某些特征较为进步。因此,同心鱼的生存时代有延续到早白垩世早期的可能性。同心鱼的发现,增加了狼鳍鱼类的新成员。对狼鳍鱼类的形态解剖,系统演化,及亲缘关系的深入研究,提供了新的资料。     

Vertebral pneumatic structures in the Early Cretaceous sauropod dinosaur Pilmatueia faundezi from northwestern Patagonia,Argentina

One of the diagnostic characters of dicraeosaurid sauropods is a reduction of pneumatization of dorsal and caudal vertebrae relative to their Flagellicaudata sister taxon, Diplodocidae. Here, we analyse pneumatic structures in the dicraeosaurid sauropod Pilmatueia faundezi, compare them to those of diplodocoids and report the first record of camerate chambers in a dicraeosaurid. The pneumatic structures are in a posterior cervical centrum (MLL-Pv-002) and consist of lateral pneumatic fossae on the centrum that communicate internally with large camerae. By contrast, Pilmatueia's dorsal and caudal vertebrae (MLL-Pv-005-016) lack pneumatic fossae on the centra, which is consistent with the previously reported reduced pneumaticity in dicraeosaurids. Nevertheless, the base of the neural arch and possibly the base of the bifid neural spines of a posterior dorsal vertebra (MLL-Pv-005) show pneumatic internal chambers. The pneumatic features of the Pilmatueia cervical centrum and dorsal neural arch we describe indicate that the degree of pneumatization is variable within dicraeosaurids.