A NEW SPECIES OF THE SPHENODONTIAN REPTILE CLEVOSAURUS FROM THE LOWER JURASSIC OF SOUTH WALES

Abstract:  Small reptiles from the Early Jurassic Pant 4 fissure fill in Glamorgan, South Wales (St. Bride's Island, Pant Quarry), were formerly provisionally attributed to three species of sphenodontian lepidosaurs. A re-analysis, aided by new material, has found this herpeto-fauna to consist almost exclusively of a single new species, Clevosaurus convallis sp. nov . , with only one specimen referable to Sphenodontia incertae sedis . Clevosaurus is known from the Upper Triassic and Lower Jurassic in various parts of the world, but C. convallis represents the first occurrence of the genus in the Jurassic of Britain. The material is fragmentary but includes numerous premaxillae, maxillae, dentaries and palatines, and the new species is distinguished by the unique combination of six large additional dentary teeth and a very short nasal process of the premaxilla, along with the diagnostic Clevosaurus features.     

贵州上三叠统一新的海龙(爬行纲:双孔亚纲)

根据头骨和下颌建立了海龙一新属新种——短吻贫齿龙(Miodentosaurus brevis gen.et sp.nov.)。其正型标本是采自贵州三叠纪法郎组的一具骨架(台中自然科学博物馆标本编号NMNS-004727/F003960)。虽然头后骨胳还没有修理,但是几近完好的头骨和下颌显示出许多与众不同的特征,足以确定该标本代表了一新的海龙属种。短吻贫齿龙是个体较大的海龙,其全长超过4 m,头骨背部最长约为33 cm。吻直且极短是其最显著的特征之一。其他主要特征有:前颌骨沿前背中央有一隆嵴;上颌仅前颌骨有6枚圆锥形齿,无上颌骨齿;上颌骨沿前腹侧缘有一沟槽;下颌齿骨齿都集中在前端且至多不超过6枚。依据上述这些特征很易把短吻贫齿龙与其他已知海龙相区别。短吻贫齿龙头骨顶面松果孔大且很前位,头骨腭面的锄骨和翼骨均无齿,它的颈较长(至少可以辨认出13个颈椎)。这些特征显示短吻贫齿龙可能与包括中国安顺龙属(Anshunsaurus)在内的Askeptosauroidea超科有相近的系统关系。     

AN INTEGRATIVE APPROACH TO DISTINGUISHING THE LATE PERMIAN DICYNODONT SPECIES OUDENODON BAINII AND TROPIDOSTOMA MICROTREMA (THERAPSIDA: ANOMODONTIA)

Abstract:  The dicynodonts Oudenodon bainii and Tropidostoma microtrema are remarkably similar in most aspects of their morphology. The most obvious distinguishing feature is the presence of tusks and/or postcanine teeth in T. microtrema and their absence in O. bainii . However, some specimens of T. microtrema lack tusks or postcanine teeth. This variability raises the possibility that O. bainii and T. microtrema are not distinct species, but rather endpoints on a morphological continuum. Resolution of this uncertainty is necessary because both species play important roles in Upper Permian terrestrial biostratigraphy. Here we address this issue using several types of data. Our results show that the bone histology of T. microtrema is comparable with that of O. bainii, emphasizing their similarity. However, a geometric morphometric analysis of snout shape and a traditional morphometric analysis of skull dimensions can reliably differentiate tuskless specimens from those with tusks and/or postcanine teeth. We examine several scenarios (e.g. anagenesis, sexual dimorphism) that could explain the observed distinction, but multiple lines of evidence, including stratigraphic range data, suggest that the two morphotypes are regarded best as distinct species. Because O. bainii specimens have been collected at Tropidostoma Assemblage Zone localities in the Karoo Basin of South Africa, the first appearance of O. bainii can no longer be used to define the base of the Cistecephalus Assemblage Zone and Oudenodon -based correlations with other basins should be made with caution.     

Description of two new sympatric species of the genus Hisonotus Eigenmann and Eigenmann, 1889, from upper Rio Tapajós, Mato Grosso state, Brazil (Pisces: Ostariophysi: Loricariidae).

Two new species of the genus Hisonotus are described from the upper Rio Tapajós basin, Mato Grosso State, Brazil. They are small species, growing up to about 30.0 mm SL, having the scapular bridge wide and totally exposed or having a small median pair of arrector fossae, and the abdomen completely covered with large plates in adult specimens (about 23.0 mm SL). They are distinguished from their congeners by the following combination of characters: Hisonotus chromodontus has 20-40 reddish-brown tipped premaxillary teeth, and 15-38 on the dentary bones; 2324 plates on the longitudinal series; a prominent large dark brown lateral stripe extending from the tip of the snout to the caudal blotch; transversal dark brown bars very inconspicuous or absent. Hisonotus luteofrenatus has a moderate number (12-28) of hyaline or slightly yellow-tipped premaxillary teeth, and 9-26 on the dentary bones; 25-26 plates on the longitudinal series; a characteristic yellow line extending from the anterior part of each orbit, over the inferior nostril, both converging to the tip of the snout.     

湖北淅川盆地上白垩统蜥脚类幼年个体新材料

描述湖北郧县淅川盆地晚白垩世地层中产出的蜥脚类恐龙化石。标本不关联保存于马家村组中段灰绿色含钙泥质粉砂岩中,材料包括牙齿、脊椎和肢骨化石等。从愈合特征（如分离的椎体和椎弓）分析,这些化石至少由2个未成年个体组成。这些化石体现出的特征组合,如股骨近端外侧突出,近端外缘向内侧倾斜,荐前椎气腔构造发育,以及牙齿呈细长的棒状,表明湖北郧县马家村组地层发现的蜥脚类可归入巨龙形类中的多孔椎龙类或者更进步的类群。新材料的发现对于进一步了解中国乃至东亚地区白垩纪晚期的蜥脚类恐龙分布和演化具有一定的意义。     

第四纪响蜥(Tinosaurus)化石的首次发现

在陕西洛南张坪洞穴的第四系中采得一些响蜥类(Tinosaurus)化石,有保存相当完好的上下齿骨和齿列,这是响蜥在第四纪的首次报道,使该属化石的地史分布从早第三纪延伸到第四纪。新材料下颌骨较粗壮,但个体很小,有齿间沟,同时兼具亚洲种及北美种的某些特征,因此建立一新种Tinosaurus luonanensis sp．nov．。     

水丰水库的池沼公鱼生物学

本文报道了1942年横断鸭绿江而成的水丰水库的池沼公鱼生物学,内容包括性状变异、年龄和生长、食性、繁殖、群体结构、群体消长变化及渔业利用。水丰水库的池沼公鱼一龄体长(到尾叉的体长,后同)74毫米,体重3克;二龄体长99毫米,体重6.5克。体长体重关系式:logW=2.5306logL-1.7590。主要以浮游动物为食,但不同栖息地点食物组成有明显差异。一龄即达性成熟;性比为1♀:1.24♂;个体繁殖力905—19051粒,平均4330粒;个体繁殖力Y(百粒鱼卵)与体长L(厘米)的相关方程式为Y=58.4860L-402.7606;群体增殖速度(Vp)等于1494;4至5月在水库岸边产卵,卵粘性,水温10—15℃,约经12天孵出仔鱼。群体由1—3龄3个龄组组成,1321尾标本的平均年龄为1.15;65.1—80毫米体长组的个体为主要渔获对象,占整个渔获的65.5%。池沼公鱼是目前水丰水库第一位的经济鱼类,1982年鱼产量120万斤,占总鱼产的57.8%。       

Dlx5 and Dlx6 expression in the anterior neural fold is essential for patterning the dorsal nasal capsule

Morphogenesis of the vertebrate facial skeleton depends upon inductive interactions between cephalic neural crest cells (CNCCs) and cephalic epithelia. The nasal capsule is a CNCC-derived cartilaginous structure comprising a ventral midline bar (mesethmoid) overlaid by a dorsal capsule (ectethmoid). Although Shh signalling from the anterior-most region of the endoderm (EZ-I) patterns the mesethmoid, the cues involved in ectethmoid induction are still undefined. Here, we show that ectethmoid formation depends upon Dlx5 and Dlx6 expression in a restricted ectodermal territory of the anterior neural folds, which we name NF-ZA. In both chick and mouse neurulas, Dlx5 and Dlx6 expression is mostly restricted to NF-ZA. Simultaneous Dlx5 and Dlx6 inactivation in the mouse precludes ectethmoid formation, while the mesethmoid is still present. Consistently, siRNA-mediated downregulation of Dlx5 and Dlx6 in the cephalic region of the early avian neurula specifically prevents ectethmoid formation, whereas other CNCC-derived structures, including the mesethmoid, are not affected. Similarly, NF-ZA surgical removal in chick neurulas averts ectethmoid development, whereas grafting a supernumerary NF-ZA results in an ectopic ectethmoid. Simultaneous ablation or grafting of both NF-ZA and EZ-I result, respectively, in the absence or duplication of both dorsal and ventral nasal capsule components. The present work shows that early ectodermal and endodermal signals instruct different contingents of CNCCs to form the ectethmoid and the mesethmoid, which then assemble to form a complete nasal capsule.     

Sonic hedgehog signalling from foregut endoderm patterns the avian nasal capsule

Morphogenesis of the facial skeleton depends on inductive interactions between cephalic neural crest cells and cephalic epithelia, including the foregut endoderm. We show that Shh expression in the most rostral zone of the endoderm, endoderm zone I (EZ-I), is necessary to induce the formation of the ventral component of the avian nasal capsule: the mesethmoid cartilage. Surgical removal of EZ-I specifically prevented mesethmoid formation, whereas grafting a supernumerary EZ-I resulted in an ectopic mesethmoid. EZ-I ablation was rescued by Shh-loaded beads, whereas inhibition of Shh signalling suppressed mesethmoid formation. This interaction between the endoderm and cephalic neural crest cells was reproduced in vitro, as evidenced by Gli1 induction. Our work bolsters the hypothesis that early endodermal regionalisation provides the blueprint for facial morphogenesis and that its disruption might cause foetal craniofacial defects, including those of the nasal region.     

Swimming performance of juvenile white sturgeon (Acipenser transmontanus): training and the probability of entrainment due to dredging

White sturgeon, Acipenser transmontanus (Richardson), are at risk of entrainment from dredging, with young-of-the-year fish at greatest risk. To evaluate this entrainment risk, swimming performance trials were conducted in a laboratory swim tunnel with hatchery-reared juvenile white sturgeon with varying experience levels including: naïve (only tested once), tested (re-tested after being kept in no flow) and trained (re-tested after kept in flow for nearly three weeks). Individuals of various sizes (80–100 mm TL) and all experience levels were strongly rheotactic (> 80%), but endurance was highly variable among fish. Small juveniles [< 82 mm total length (TL)] had lower escape speeds (< 40 cm s⁻¹) than medium (82–92 mm TL) and large (> 93 mm TL) naïve fish (42–45 cm s⁻¹), all of which had lower escape speeds than trained fish (72 cm s⁻¹). Behavior was also highly variable among fish. Overall, benthic station-holding behaviors were least frequent in small fish, intermediate in medium and large fish, and most frequent in trained large fish. Probability of entrainment of juvenile white sturgeon can be reduced by maintaining dredge head flow fields at less than 45 cm s⁻¹ for wild-spawned fish or by rearing hatchery fish to > 93 mm TL and exposing the fish to moderate flow velocities (10–12 cm s⁻¹) prior to their release.     

长吻和南方大口鲶胃肠道消化能力的研究

通过对长吻（Ｌｅｉｏｃａｓｉｓｌｏｎｇｉｒｏｓｔｒｉｓ）、南方大口鲶（Ｓｉｌｕｒｕｓｍｅｒｉｄｉｏｎａｌｉｓ）胃、肠道所作大体解剖观察对比、粘膜扫描电镜观察、蛋白酶和淀粉酶活力测定等的研究结果表明,南方大口鲶的胃壁和胃粘膜皱褶非常发达,其伸缩能力远强于长吻。但长吻的胃、肠粘膜的分泌功能较南方大口鲶强,其蛋白酶和淀粉酶活力强于相近体重的南方大口鲶。南方大口鲶的发达的胃壁作用可能在于有较强的伸张能力以便一次性地食贮较多或较大个体食物,并在胃内进行初步消化。总体评价,长吻一次性的摄食能力不如南方大口鲶,但对同种食物的消化能力强于相近或相同体重的南方大口鲶。南方大口鲶胃、肠道消化生理特点适于一次捕食较大个体食物,具间歇性摄食的消化生理特点。而长吻则适于以较高摄食频率和对食物较强的消化利用率以适应营养的需要。     

Long-term impact of an invertebrate predator, Heterocope septentrionalis, on an arctic pond zooplankton community

1. A long-term field experiment to determine what forces structure and maintain the large-bodied zooplankton assemblages in ponds which lack visual predators was undertaken at the Toolik Lake Research Station in arctic Alaska. Predatory copepods, Heterocope septentrionalis, were introduced to a pond that lacked both fish and invertebrate predators, but contained small- to medium-sized zooplankton, Bosmina longirostris , Daphnia pulex , and Diaptomus pribilofensis. A second pond, which also lacked any predators but had a population of B. longirostris , but no other abundant species, served as a reference population for B. longirostris.
2. The introduction of H. septentrionalis caused the extinction of D. pulex within 1 year and drove B. longirostris to extremely low densities within 4 years. The population of B. longirostris in the reference pond fluctuated throughout the study period, but remained above five individuals per litre. This experiment demonstrates that H. septentrionalis , under natural conditions, made a numerical response to abundant prey and had the capacity to eliminate or reduce vulnerable prey populations of small- to medium-sized zooplankton.     

Trophic polymorphism in a riverine fish: morphological, dietary, and genetic analysis of mountain whitefish

Trophic polymorphisms are a prominent form of phenotypic diversification in many animal taxa. Northern temperate lakes have become model systems for the investigation of sympatric speciation due to trophic polymorphisms. Many examples of niche-based phenotypic variation occur in temperate lakes, whereas northern rivers offer few such examples. To further investigate the conditions under which trophic polymorphisms are likely to evolve, the present study examined phenotypic variation related to snout size and shape in the mountain whitefish (Salmonidae: Prosopium williamsoni ), which has been hypothesized to exhibit a rare example of reproductively isolated trophic morphs in a northern river-dwelling fish species. Variation in snout size and shape increased greatly with body size and, although this variation was continuously distributed, individuals in the largest size class tended to lie at phenotypic extremes. At one extreme were individuals with a large bulbous snout and a sloping forehead ('pinocchio'), and at the other were individuals that lack the bulbous snout and have a concave forehead ('normal'). The pinocchio trait may result from a stage-specific developmental switch that occurs late in ontogeny. Consistent differences were found with respect to diet between individuals with extreme snout morphologies, but no evidence was found for assortative mating within populations at seven microsatellite loci. The explosive mating system of this species may be responsible for this lack of assortative mating. The present study highlights the influence of ecological factors in shaping phenotypic and behavioural diversification due to trophic morphology.  © 2007 The Linnean Society of London, Biological Journal of the Linnean Society , 2007, 92 , 253–267.     

Variation in the Late Triassic Canjilon quarry (Upper Chinle Group, New Mexico) phytosaur skulls: a case for sexual dimorphism

The Canjilon quarry, located in north-central New Mexico near Ghost Ranch, contains a death assemblage of phytosaurs located stratigraphically high within the Petrified Forest Formation of the Chinle Group (Revueltian = early-mid Norian). The site has yielded numerous fossils ofPseudopalatus-grade phytosaurs, including at least 10 skulls collected from the locality byCharles Camp in 1928 and 1933 and another collected more recently byAlex Downs, curator of paleontology at Ghost Ranch. A re-examination of these skulls reveals two morphotypes that differ only in the relative lengths and relative robustness of their premaxillae. In these two morphotypes, the premaxillae define the shape and length of the rostral crest, the dimensions of which are independent of skull size. In one morphotype, the premaxillae are long, thin bones that lead to an abrupt, volcano-like narial crest. In the second morphotype, the premaxillae are of approximately the same length, but expand dorsoventrally halfway along their lengths, creating a longer and more robust crest. The most probable explanation of these two variants in rostral crest morphology in a Single, catastrophic death assemblage is thatPseudopalatus-grade phytosaurs are sexually dimorphic. Thus, the larger, more robust crest of the first morphotype is probably a display feature, most likely of the male animal. The more gracile snout änderest characterize the female morph. In the sample of phytosaurs examined, there are three individuals of the more robust (male) morphotype, five individuals of the gracile (female) morphotype, and three individuals (2 adult, 1 juvenile) that cannot be assigned to either morphotype because the skulls are too damaged to make an aecurate assessment. This is the first clear evidence of sexual dimorphism in phytosaurs, and has important implications for phytosaur species-level taxonomy, as well as for understanding aspects of their paleobiology (e.g., population dynamics).     

Trigonognathus kabeyai,a new genus and species of the squalid sharks from Japan

Two specimens of the peculiar squalid shark,Trigonognathus kabeyai gen. et sp. nov., were collected from the coastal waters of Wakayama and Tokushima, Japan, by bottom trawl at depths of 330 and 360 meters. Shape of teeth similar in both jaws; slender, unicuspid, canine-like, without any cusplets or serrations, with weak thin fold on both lingual and labial sides in anterior teeth on both jaws; tooth at symphysis of each jaw longest. Interspace between teeth very wide. Both jaws triangular in shape. Most of dermal denticles on body and head roughly rhombic, swollen very much near central part, with about 10–40 facets on the dorsal surface of its crown. Preoral snout length very short. Many small organs considered to be photophores present mainly on ventral surfaces of head and body.     

长吻(鱼危)幼鱼发育的研究

长吻(鱼危)的幼鱼发育共分为仔鱼前期、仔鱼期和稚鱼期三个阶段。本文记述的是幼鱼发育各阶段外部形态的变化和内部器官的建成以及不同时期出现的集群、摄食、避光等生物学特性。对提高鱼苗成活率,培育出优质健壮的苗种有指导意义。       

Pelagic larvae of Ventrifossa garmani (Gadiformes: Macrouridae) from Suruga Bay and offshore waters of Japan

Three pelagic larvae [5.1–5.9 mm in head length (80+ to 101+ mm in total length)] of a macrourid fish, Ventrifossa garmani, from Suruga Bay and offshore waters of central Japan are described. The specimens were characterized by a remarkably elongate caudal region (caudal region length >15.6 times head length), the longest known to date among macrourid larvae and juveniles. Other characteristics included a short snout, first dorsal and pelvic fin rays not elongated, external melanophores on most of the body and posteriorly on the anal fin membrane, and six or seven rectangular clusters of internal melanophores laterally on the anterior caudal region.