A fossil clupeomorph fish from the Albian of the Northwest Territories of Canada, with notes on cladistic relationships of clupeomorphs

A primitive clupeomorph, Erichalcis arcta gen. et sp. nov. is described from the Albian of Northwest Territories, Canada. Erichalcis is uniquely specialized among clupeomorphs in the presence of enlarged lateral line scales and in the structure of the caudal skeleton. Erichalcis is classified as Clupeiformes incertae sedis. The two recognized suborders, Clupeoidei and Denticipitoidei are examined with respect to primitive and derived character states. It is concluded that the clupeoids and denticipitoids are divergently specialized in details of the union between the supraorbital and infraorbital sensory canals and the recessus lateralis. It is further suggested that the reduction in size and the posterior shift of the dermosphenotic in clupeoids is correlated with an upper division of the levator arcus palatini muscle and an antero-dorsal process on the hyomandibular. Cladistic relationships of some Cretaceous clupeomorphs are proposed and it is suggested that Diplomystus brevissimus Cope not be included in the Clupeoidei.     

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.     

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.     

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.     

鲿科八种鱼类同工酶和骨骼特征分析及系统演化的探讨(鲇形目:鲿科)

本文对鲿科Bagridae共4属8种鱼类进行了骨骼系统的研究,并对8种鱼的同工酶谱型进行了分析比较。应用分支系统学原理初步推导出鲿后两者之间。演化趋势表现为身体渐扁,逐渐平展,口渐阔,尾鳍从圆形到叉状进化。对鲿科8种鱼的鳍、肌肉、肝脏、肾脏、心脏、眼的晶状体和脑等7种组织4种同工酶（LDHMDHESADH）的谱型分析表明,8种鱼之间的亲缘关系与形态学特征分析结果相吻合,说明了生化分类和经典分类的一致性。     

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.     

A fossil osteoglossoid fish from Tanzania (E. Africa)

A new genus and species ( Singida jacksonoides ) and a new family (Singididae) of osteoglossoid fishes are described from the lacustrine deposits in Tanzania which have already yielded the primitive clupeomorph Palaeodenticeps. Singida differs from all Osteoglossomorpha in being toothless. Although it shows some affinity with the living Asiatic genus Scleropages , it also exhibits certain characters, particularly in the caudal skeleton, which are usually associated with the recent and fossil Hiodontoidei of North America. Singida shows little affinity with either of the living African genera of Osteoglossoidei. The age of the Singida deposits is unknown, but the fish fauna suggests a Palaeogene (? Oligocene) age.     

Retracted: Evolution and development of the homocercal caudal fin in teleosts

The vertebrate caudal skeleton is one of the most innovative structures in vertebrate evolution and has been regarded as an excellent model for functional morphology, a discipline that relates a structure to its function. Teleosts have an internally‐asymmetrical caudal fin, called the homocercal caudal fin, formed by the upward bending of the caudal‐most portion of the body axis, the ural region. This homocercal type of the caudal fin ensures powerful and complex locomotion and is thought to be one of the most important evolutionary innovations for teleosts during adaptive radiation in an aquatic environment. In this review, we summarize the past and present research of fish caudal skeletons, especially focusing on the homocercal caudal fin seen in teleosts. A series of studies with a medaka spontaneous mutant have provided important insight into the evolution and development of the homocercal caudal skeleton. By comparing developmental processes in various vertebrates, we propose a scenario for acquisition and morphogenesis of the homocercal caudal skeleton during vertebrate evolution.     

When two equals three: developmental osteology and homology of the caudal skeleton in carangid fishes (Perciformes: Carangidae)

Ontogeny often provides the most compelling evidence for primary homology in evolutionary developmental studies and is critical to interpreting complex structures in a phylogenetic context. As an example of this, we document the ontogenetic development of the caudal skeleton of Caranx crysos by examining a series of cleared and stained larval and postlarval specimens. By studying ontogeny, we are able to more accurately identify some elements of the adult caudal skeleton than is possible when studying the adult stage alone. The presence of two epurals has been used as a synapomorphy of Caranginae (homoplastically present in the scomberoidine genera Scomberoides and Oligoplites). Here we find that three epurals (ep) are present in larvae and small postlarval juveniles (i.e.,<25 mm standard length [SL]) of C. crysos and other carangines, but ep2 never ossifies and does not develop beyond its initial presence. Ep2 was last observed in a 33.6 mm SL specimen as a small nodule of very lightly stained cartilage cells and eventually disappears completely. Therefore, the two epurals present in the adult are ep1 and ep3. In other carangines examined (e.g., Selene, Selar), the rudimentary ep2 ossifies and appears to fuse to the proximal tip of ep1. In these taxa, therefore, the two epurals of the adult appear to be ep1+2 and ep3. We found no indication of three epurals at any stage in the development of Oligoplites (developmental material of Scomberoides was unavailable). We discuss the osteology of the caudal skeleton of carangoid fishes generally and emphasize the power and importance of ontogeny in the identification of primary homology.     

Some remarks on the axial skeleton in Protopterus (Pisces, Dipnoi)

Based on a comparative morphological study of the axial skeleton in a broader range of "primitive bony fishes" a reevaluation of some characteristic traits of the vertebral column in the African lungfish has been done. The axial skeleton of living dipnoans has to be regarded as reduced from a more complex phylogenetic state and may be neotenic in some respect. The formation of perichordal bony autocentra could be confirmed, at least in one specimen. The well-known invasion of mesenchymal cells into the fibrous sheet of the notochord is interpreted as a rudimentary chordacentric "vertebralization". Also included is an analysis of the peculiar urostyle of lungfishes, its regeneration capacity and its bearing upon the principles of vertebra-formation.     

Functional morphology of the caudal region of certain clupeiform and perciform fishes with reference to the taxonomy

The caudal anatomy (caudal skeleton, musculature, vascularization, innervation, and urohypophysis) and swimming behavior of three clupeiform and three perciform fishes: Elops hawaiensis (Cupeiformes: Elopidae), Oncorhynchus nerka (Cupeiformes: Salmonidae), Chanos chanos (Clupeiformes: Chanidae), Kuhlia sandvicensis (Perciformes: Kuhlidae), Apogon menesemus (Perciformes: Apogonidae), and Gnathanodon speciousus (Perciformes: Carangidae), were studdied. The taxonomic significance of caudal structures was determined and evaluated by detailed examination of differences in caudal anatomy. An interpretation of functional significance of these differences was attempted by relating them to observed differences in swimming behavior. The swimming behavior was studied by the observation of swimming activities of fish while resting or cruising and while feeding in the aquarium, and by an analysis of each frame of an 8 mm movie film of swimming activities. There are certain consistent and basic differences between all three species of the order Clupeiformes and all three species of the order Perciformes in respect to caudal structures. Although certain caudal structures show overlapping in number and/or complexity of arrangement, they seem to indicate more complex structural organization in Clupeiformes than Perciformes. The differences confirm the conclusion of others that the order Clupeiformes is more “primitive” than the order Perciformes. With respect to caudal structures of the three clupeiform species studied, E. hawaiensis is the most “primitive” and, of the three perciform species studied, K. sandvicensis is the most “primitive.” Caudal structural variations from one species to another are related to the mode of adaptation to swimming as well as to the evolutionary status of the species.     

Speciation and demographic history of the Cortez bonefish, Albula sp. A (Albuliformes: Albulidae), in the Gulf of California inferred from mitochondrial DNA

Nucleotide sequence data from a segment of the mitochondrial cytochrome b (Cyt b ) gene were used to infer demographic history and examine conditions that may have led to speciation in the Cortez bonefish ( Albula sp. A) in the Gulf of California, Mexico, a currently undescribed species of bonefish in the Albula vulpes complex. Analysis of molecular variance in 39 individuals collected from three localities along the eastern gulf coast, over c. 850 km, revealed a lack of population structure among localities (overall Φ _ST=−0·015), with 100% of the genetic variation distributed within populations. Analysis of combined sequences from these individuals using neutrality tests and the mismatch distribution provided evidence of a population expansion dating to the Pleistocene. The population expansion was supported by maximum likelihood estimates of changes in long-term female effective population size ( N _ef). A molecular clock estimate of divergence, provisionally calibrated for the Cyt b gene in Albula , indicates that Albula sp. A and its sister species in the eastern Pacific, Albula esuncula , diverged from a common ancestor c. 5·0–8·8 million years ago. This date is about the time the Baja California peninsula separated from mainland Mexico during the formation of the Gulf of California. Oceanographic and ecological changes associated with the opening of the gulf likely provided conditions favourable for adaptive radiation and reproductive isolation, ultimately resulting in the allopatric formation of two separate lineages. The co-occurrence of Albula sp. A and A. esuncula found today in the coastal Pacific waters of northern Mexico is most probably the result of secondary contact after speciation.     

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。     

Functional morphology of the caudal skeleton in teleostean fishes

The basic function of the caudal skeleton in teleostean fishes is to support the caudal fin, but its parts contribute to this function in somewhat different ways. The main axis for this support is the upturned terminal end of the vertebral column, which ends at the base of the uppermost principal rays. The uroneural struts just ahead of this axis provide support for it. The parts of the caudal skeleton behind and below this upturned axis, the hypurals and parhypural, not only support the caudal rays but also provide a means for differential movements between the upper and lower parts of the fin base. This basic caudal skeleton varies with the position of the fish in the sequence of teleosten evolution, the way in which the fish uses its caudal fin, and to some extent with the shape of the fin.     

四十五种叶蝉的染色体研究（同翅目：叶蝉总科）

研究观察了45种中国雄性叶蝉的减数分裂,其中44种的核型为首次报道,染色体数目变化在2n=12～26之间,性别决定均为XO型。从叶蝉总科的组型图来看,该科染色体数目变化在2n=8～28之间,峰值为2n=18(16+XO),另外几种类型2n=16,20,22也有较高的出现频率。科内染色体数目的进化不具有明显的方向性,2n=22(20+XO)是该科的原始核型,易位导致的不均等互换可能是染色体数目进化的主要机制。从精子发生来看叶蝉总科与角蝉总科的关系较为密切,两者的共同特点是：①精母细胞体积较大,显著不同于沫蝉和蝉科;②减数分裂行为及精子变态过程相似;③染色体数目较少,染色体体积较大;④减数分裂前期具有典型的花束期,没有弥散期,因而不同于蜡蝉。但是由于叶蝉总科的染色体变异范围明显大于角蝉总科,而角蝉总科的核型相对较为保守,从核型上来说角蝉总科是比叶蝉总科较为原始的类群。     

一种雷氏放射孢子虫的鉴定及其特征描述

放射孢子虫(Actinosporean)是黏体动物在其中间宿主水生无脊椎动物体内的一个生活阶段。研究鉴定并描述了一种雷氏放射孢子虫的形态和分子特征。该放射孢子虫的主要形态结构是: 由三个极囊、内含孢原质的孢子体和三个尾突组成, 无孢柄。极囊位于孢子体顶端, 呈梨形, 长5.2 μm, 宽2.9 μm; 孢子体侧面观呈长椭圆形, 长16.4 μm, 宽9.5 μm; 三个尾突基本等长, 呈锚状, 平均长度102.6 μm, 宽9.54 μm, 尾突末端轻微的上翘。每个尾突远侧端表面有许多形状不规则的棘状小刺。18S rDNA序列比对表明, 该雷氏放射孢子虫与国外已报道的Myxobolus cultus 18S rDNA序列一致性最高, 达98.41%, 由此推测该雷氏放射孢子虫可能为M. cultus的对应放射孢子虫阶段。研究丰富了国内放射孢子虫的基础研究。