The most primitive osteichthyan braincase?

Most living vertebrates, from teleosts to tetrapods, are osteichthyans (bony fishes), but the origin of this major group is poorly understood. The actinopterygians (ray-finned bony fishes) are the most successful living vertebrates in terms of diversity. They appear in the fossil record in the Late Silurian but are poorly known before the Late Devonian. Here we report the discovery of the oldest and most primitive actinopterygian-like osteichthyan braincase known, from 400-million-year-old limestone in southeastern Australia. This specimen displays previously unknown primitive conditions, in particular, an opening for a cartilaginous eyestalk. It provides an important and unique counterpart to the similarly aged and recently described Psarolepis from China and Vietnam. The contrasting features of these specimens, and the unusual anatomy of the new specimen in particular, provide new insights into anatomical conditions close to the evolutionary radiation of all modern osteichthyan groups.     

浙江鮈亚科鱼类咽骨咽齿的研究

本文记述了近数年来所采集到的和参阅馆藏的大量标本,经整理后,鮈亚科鱼类计有9属22种。今对其咽骨咽齿的形态作了比较研究。研究结果表明,根据咽骨的形态可归纳为两种类型;根据咽齿的形态可分为三种类型。     

A primitive sarcopterygian fish with an eyestalk

The discovery of two Early Devonian osteichthyan (bony fish) fossils has challenged established ideas about the origin of osteichthyans and their divergence into actinopterygians (teleosts and their relatives) and sarcopterygians (tetrapods, coelacanths, lungfishes and related groups). Psarolepis from China and an unnamed braincase from Australia combine derived sarcopterygian and actinopterygian characters with primitive features previously restricted to non-osteichthyans, suggesting that early osteichthyan evolution may have involved substantial parallellism between sarcopterygians and actinopterygians. But interpretation of these fossils has been hampered by poor phylogenetic resolution. Here we describe a basal sarcopterygian fish, Achoania gen, et sp. nov., that fills the morphological gap between Psarolepis and higher sarcoptergyians. We also report the presence of eyestalk attachments in both Achoania and Psarolepis, showing that this supposedly non-osteichthyan feature occurs in basal sarcopterygians as well as the actinoptergyian-like Australian braincase.     

The oldest articulated chondrichthyan from the Early Devonian period

Chondrichthyans (including living sharks, skates, rays and chimaeras) have a fossil record of scales and dermal denticles perhaps dating back to the Late Ordovician period, about 455 million years ago. Their fossil tooth record extends to the earliest Devonian period, almost 418 million years ago, whereas the oldest known articulated shark remains date from the Early Devonian period, about 394 million years ago. Here we report the discovery of an articulated shark that is almost 409 million years old from the Early Devonian (early Emsian) period of New Brunswick, Canada. The specimen, identified as Doliodus problematicus (Woodward), sheds light on the earliest chondrichthyans and their interrelationships with basal jawed vertebrates. This species has been truly problematic. Previously known only from isolated teeth, it has been identified as an acanthodian and a chondrichthyan. This specimen is the oldest shark showing the tooth families in situ, and preserves one of the oldest chondrichthyan braincases. More notably, it shows the presence of paired pectoral fin-spines, previously unknown in cartilaginous fishes.     

浙江鲤科鱼类咽骨咽齿的研究Ⅱ

本文报导浙江(鱼旁)(鱼皮)亚科鱼类咽骨咽齿的研究结果,根据其形态特点可区分为4种类型。     

浙江鲤科鱼类咽骨咽齿的研究Ⅱ

本文报导浙江(鱼旁)(鱼皮)亚科鱼类咽骨咽齿的研究结果,根据其形态特点可区分为4种类型。     

河南鲤科鱼类咽骨咽齿的比较研究(三)

<正> 本文记述了鳑鲏亚科Acheilognathinae鱼类3属6种,现分述如下:鳑鲏亚科:咽齿一列,齿式0·0·5/5·0·0,齿侧扁,两侧对称,咽齿背侧面光滑或具锯齿,先端钩状,咀嚼面狭长,形状各异,微凸、微凹或略平。前角向外突出,后角不明显。鳑鲏亚科各属种检索表A_1咽齿侧面无锯齿B_1前无齿突凹窝面宽约为其突宽的1/2。     

Interrelationships among primate higher taxa

One of the most controversial issues in primate palaeontology concerns the phylogenetic position of the extinct primate infraorder Adapiformes. During the Eocene, this group of primates of modern aspect possessed a holarctic distribution, and may have been present in the poorly known Palaeogene of Africa. Mainly on the basis of craniodental morphology, at least four hypotheses have been proposed concerning the phylogenetic interrelationships among adapiforms and other primate higher taxa: (1) that adapiforms are ancestral to both lemuriforms (including Lorisoidea) and anthropoids; (2) that adapiforms cannot be shown to possess a special phylogenetic relationship with either lemuriforms or anthropoids; (3) that adapiforms are the sister taxon of lemuriforms; and (4) that Adapiformes is not a natural, monophyletic group, but rather consists of nested clades within the radiation of lemuriforms. Here, we describe features of the ankle and wrist joints of several adapiform taxa that provide an independent test of the preceding hypotheses. These traits suggest that lemuriforms are monophyletic with respect to known adapiforms, but that adapiforms nevertheless are their stem lineage (sensu Ax).     

Sequences of cytochrome b gene for primitive cyprinid fishes in East Asia and their phylogenetic concerning

1140 bp of cytochrome b gene were amplified and sequenced from 14 species of primitive cyprinid fishes in East Asia. Aligned with other ten cytochrome b gene sequences of cyprinid fish from Europe and North America retrieved from Gene bank, we obtained a matrix of 24 DNA sequences. A cladogram was generated by the method of Maximum likelihood for the primitive cyprinid fishes. The result indicated that subfamily Leuciscinae and Danioninae do not form a monophyletic group. In the subfamily Danioninae, Opsariichthys biden and Zacco platypus are very primitive and form a natural group and located at the root. But the genera in subfamily Danioninae are included in different groups and have not direct relationship. Among them, Aphyocypris chinensis and Yaoshanicus arcus form a monophyletic group. Tanichthys albonubes and Gobiocypris rarus have a close relation to Gobioninae. The genus Danio is far from other genera in Danioninae. In our cladogram, the genera in Leuciscinae were divided into two groups that have no direct relationship. The genera in Leuciscinae distributed in Europe, Sibera and North America, including Leuciscus, Rutilus, Phoxinus, N. crysole, Opsopoeodus emilae, form a monophyletic group. And the Leuciscinae in southern China including Ctenopharyngodon idettus, Mylopharyngodon piceus, Squalibarbus and Ochetobius elongatus have a common origination.     

The potential of vertebrate microfossils for marine to non-marine correlation in the Late Jurassic

Fish (cartilaginous: elasmobranch and bony: osteichthyan actinopterygian) and reptile (crocodile) microfossils comprising scales and teeth have been examined from a series of limestone samples in the Upper Jurassic of France and Germany to gauge the possibilities of using them for correlation between fully marine and hypo-or hyper-saline (non-marine) deposits.     

Sonic hedgehog function in chondrichthyan fins and the evolution of appendage patterning

The genetic mechanisms regulating tetrapod limb development are well characterized, but how they were assembled during evolution and their function in basal vertebrates is poorly understood. Initial studies report that chondrichthyans, the most primitive extant vertebrates with paired appendages, differ from ray-finned fish and tetrapods in having Sonic hedgehog (Shh)-independent patterning of the appendage skeleton. Here we demonstrate that chondrichthyans share patterns of appendage Shh expression, Shh appendage-specific regulatory DNA, and Shh function with ray-finned fish and tetrapods. These studies demonstrate that some aspects of Shh function are deeply conserved in vertebrate phylogeny, but also highlight how the evolution of Shh regulation may underlie major morphological changes during appendage evolution.     

Cambrian origins and affinities of an enigmatic fossil group of arthropods

Euthycarcinoids are one of the most enigmatic arthropod groups, having been assigned to nearly all major clades of Arthropoda. Recent work has endorsed closest relationships with crustaceans or a myriapod-hexapod assemblage, a basal position in the Euarthropoda, or a placement in the Hexapoda or hexapod stem group. Euthycarcinoids are known from 13 species ranging in age from Late Ordovician or Early Silurian to Middle Triassic, all in freshwater or brackish water environments. Here we describe a euthycarcinoid from marine strata in Argentina dating from the latest Cambrian period, extending the group's record back as much as 50 million years. Despite its antiquity and marine occurrence, the Cambrian species demonstrates that morphological details were conserved in the transition to fresh water. Trackways in the same unit as the euthycarcinoid strengthen arguments that similar traces of subaerial origin from Cambro-Ordovician rocks were made by euthycarcinoids. Large mandibles in euthycarcinoids are confirmed by the Cambrian species. A morphology-based phylogeny resolves euthycarcinoids as stem-group Mandibulata, sister to the Myriapoda and Crustacea plus Hexapoda.     

沟鲹骨骼系统的研究——兼与鲹科某些种类比较

对沟鲹骨骼系统的特征进行了观察,并比较其与蓝圆鲹、美长吻鲹、游鳍叶鲹及镰鳍裸胸鲹等4种鲹科鱼类的差别,结果表明,它们脑颅上的上筛骨、侧筛骨、犁骨、额骨、眶下骨、蝶耳骨、翼耳骨和上耳骨等,咽颅上的前上颌骨、腭骨、舌颌骨、尾舌骨、鳃盖骨和上枕骨等;肩带上的主后颞骨、后颞骨、上匙骨、后匙骨等均有明显的差异,其中某些特征可能是...     

Evolutionary biology: lamprey Hox genes and the origin of jaws

The development of jaws was a critical event in vertebrate evolution because it ushered in a transition to a predatory lifestyle, but how this innovation came about has been a mystery. In the embryos of jawed vertebrates (gnathostomes), the jaw cartilage develops from the mandibular arch, where none of the Hox genes is expressed; if these are expressed ectopically, however, jaw development is inhibited. Here I show that in the lamprey, a primitively jawless (agnathan) fish that is a sister group to the gnathostomes, a Hox gene is expressed in the mandibular arch of developing embryos. This finding, together with outgroup comparisons, suggests that loss of Hox expression from the mandibular arch of gnathostomes may have facilitated the evolution of jaws.     

Mitochondrial d-loop sequence variation and phylogeny of gobiobotine fishes

The mitochondrial DNA control region is amplified and sequenced from 8 genera and 10 species of gobiobotine fishes. The phylogenetic tree of Gobiobotinae and some representative species of other Cyprinid subfamilies obtained by the method of neighborhood joining, maximum likelihood and maximum parsimony with Danio rerio as an outgroup indicates that Gobiobotinae fishes are a monophyletic group which is close to Gobioninae subfamily. Gobiobotinae should be included into subfamily Gobioninae in terms of phylogenetic analysis. The research result supports that Gobiobotinae can be divided into genus Xenophysogobio and Gobiobotia. Xenophysogobio is the most primitive genera in the subfamily.     

Phylogenetic studies of Chinese labeonine fishes (Teleostei:Cyprinidae) based on the mitochondrial 16S rRNA gene

The mitochondrial 16S ribosomal RNA gene is sequenced from 24 ingroups taxa, including 18 species from Labeoninae grouped in 13 genera. Phylogenetic analyses are subjected to neighbor joining, maximum parsimony, maximum likelihood and Bayesian analyses. Phylogenetic analysis indicates that Labeoninae is basically a monophyletic assemblage and can be divided into 2 major clades: one comprising the genera Cirrhinus, Crossocheilus and Garra; and the other consisting of the genera Labeo, Sinilabeo, Osteochilus, Pseudoorossocheilus, Parasinilabeo, Ptychidio, Semilabeo, Pseudogyricheilus, Rectori and Discogobio. According to our present analysis,the features such as the presence of the adhesive disc on the chin and the pharyngeal teeth in 2 rows used in the traditional taxonomy of Labeoninae provide scarce information for phylogeny of labeonine fishes.     

Whales originated from aquatic artiodactyls in the Eocene epoch of India

Although the first ten million years of whale evolution are documented by a remarkable series of fossil skeletons, the link to the ancestor of cetaceans has been missing. It was known that whales are related to even-toed ungulates (artiodactyls), but until now no artiodactyls were morphologically close to early whales. Here we show that the Eocene south Asian raoellid artiodactyls are the sister group to whales. The raoellid Indohyus is similar to whales, and unlike other artiodactyls, in the structure of its ears and premolars, in the density of its limb bones and in the stable-oxygen-isotope composition of its teeth. We also show that a major dietary change occurred during the transition from artiodactyls to whales and that raoellids were aquatic waders. This indicates that aquatic life in this lineage occurred before the origin of the order Cetacea.     

广东北江鲃亚科鱼类咽骨咽齿的比较研究

<正> 北江水系鲃亚科鱼类的研究已有报导,本文就其咽骨咽齿的形态作比较研究,现分述如下:鲃亚科:咽骨长宽度变异颇大,骨长为骨宽的2.0～6.0倍,体长为骨长的10.0～23.0倍。前肢与后肢约等长或前肢略短于后肢。前角圆钝,后角不显。咽齿2～3列,左右对称,内列5齿,中列2～4齿,外列2齿,内列第1齿一般较小,各齿光滑无锯齿,咀嚼面较宽。