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1.
A new heterotrophic sand‐dwelling dinoflagellate, Ankistrodinium armigerum K. Watanabe, Miyoshi, Kubo, Murray et Horiguchi sp. nov., is described from Ishikari Beach, Hokkaido, Japan and Port Botany, NSW, Australia. The dinoflagellate is laterally compressed, possessing a short triangular epicone and a large sac‐like hypocone. It possesses a right‐handed cingulum and a deeply‐incised sulcus. The sulcus descends towards the posterior of the cell where it becomes much deeper and wider, resulting in a bilobed ventral side to the hypocone, with a greater excavation of the left lobe than the right. In addition, the right lobe of the hypocone is shorter than the left lobe, which allows a partial view of the left sulcal wall when the cell is viewed from its right side. The sulcus ascends in the epicone to form an apical groove. The apical groove is linear but terminates in an ellipsoid fashion and its extremity approaches, but does not form a closed loop with the apical end of the linear portion. The dinoflagellate possesses two distinct size classes of trichocysts. The large trichocysts are located in the posterior part of the cell, while small trichocysts are distributed throughout the cell. The dinoflagellate shares morphological characteristics with the heterotrophic sand‐dwelling dinoflagellate, Ankistrodinium semilunatum, the type species of the genus. These include a laterally compressed cell, a right‐handed cingulum, a deeply‐incised sulcus and the same basic structure to the apical groove. Molecular phylogenetic analyses based on small and large subunits of rDNA showed that in both trees, A. semilunatum and A. armigerum formed a robust clade, suggesting that these two species are closely related. Because no organism with the characteristics of this species exists and because this species is closely related to A. semilunatum, we concluded that this species should be described as a second species of the genus Ankistrodinium.  相似文献   

2.
Ten isolated snake vertebrae from Landana and Sassa-Zao, Cabinda Exclave, Angola, present a “primitive” grade morphology with a weak lateral compression and do not belong to Palaeophis aff. typhaeus as originally referred to. They well belong to a single taxon and are here attributed to Palaeophis africanus for which the intracolumnar variation is described and illustrated. This species is Lutetian (middle Eocene) in age and originates from a marine coastal environment confirming again the aquatic capabilities of palaeophiid snakes. It represents the third largest species of Palaeophis with P. colossaeus and P. maghrebianus to which it is closely related in our tentative phylogenetic analysis, indicating that these three taxa could belong to an African clade. This study also contributes to the debate on the existence of primitive and advanced grades among palaeophiid snakes. Palaeophis presents laterally compressed anterior trunk vertebrae that could have been often erroneously considered as representing advanced grade species and potential parataxonomy.  相似文献   

3.
The temnospondyl Sclerocephalus from the Permo‐Carboniferous of Germany is one of the most completely preserved and most abundant Palaeozoic tetrapods. Here, we review the complete osteology of the genus, based on a range of fully grown specimens housed in public collections. Among the four valid species, Sclerocephalus haeuseri and Sclerocephalus nobilis reached an adult size of well beyond 1 m in length, and had robust postcranial skeletons. In the skull, the exoccipital and sphenethmoid bones were ossified, completing the well‐known ossification sequence in S. haeuseri. Large adults had an elongate trunk and a laterally compressed tail, and some individuals also retained lateral line sulci: features that taken together suggest an aquatic life. The coracoid, pubis, carpals, tarsals, and the bony tail are fully ossified in the largest specimens. The genus Sclerocephalus forms a weakly supported clade nesting firmly at the base of the Stereospondylomorpha, and the close resemblance between Sclerocephalus, Onchiodon, and Eryops is found to be partially based on shared derived states, but is mostly based on symplesiomorphies. Cladistic analysis of 54 characters and 18 taxa finds more support for the Eryopoidea hypothesis (Eryopidae + Stereospondylomorpha) than for the Euskelia hypothesis (Eryopidae + Zatracheidae + Dissorophoidea). This indicates that the large temnospondyls of the Permian and Mesozoic probably formed a natural group, and that the terrestrial adaptations of Eryops and the dissorophoids probably evolved by convergence.  相似文献   

4.

The palaeoecology of the primitive, limbed snake Pachyrhachis is reevaluated. Previously considered to have been preserved in a shallow bay with a nearby freshwater source, it is here demonstrated to have inhabited an inter‐reef basin. Evidence for this comes from the position of the nearest palaeoshoreline (450 km away), the finely laminated carbonate mudstones, and the absence of bioturba‐tion, alluvium, and unequivocally terrestrial or freshwater taxa. Marine adaptations of Pachyrhachis include the laterally compressed body and heavily ossified (pachyostotic) vertebrae and ribs. Hydrodynamic considerations indicate that it was a slow swimmer, and thus an ambush rather than pursuit predator. Morphology of the anterior vertebrae suggests that the strike muscles were well‐developed. The narrow head and neck might have been adaptations to reduce water resistance during rapid lunges, and/or to forage in burrows or tight crevices.  相似文献   

5.
《Journal of morphology》2017,278(11):1577-1585
Body elongation in vertebrates can be achieved by lengthening of the vertebrae or by an increase in their number. In salamanders, longer bodies are mostly associated with greater numbers of vertebrae in the trunk or tail region. However, studies on the relative contribution of the length of single vertebra to body elongation are lacking. In this study, we focus on evolutionary and ontogenetic changes in differentiation of the trunk vertebrae and the relative contribution of individual vertebrae to trunk lengthening in Triturus newts, a monophyletic group of salamanders that shows remarkable disparity in body shape. We compared juveniles and adults of the most elongated T. dobrogicus , which has 17 trunk vertebrae, with juveniles and adults of two closely related species (T. ivanbureschi and T. anatolicus belonging to the T. karelinii species complex) representing a stout and robust morphotype with thirteen trunk vertebrae. We show that trunk vertebrae are uniform in size at the juvenile stage of both analyzed morphotypes. In adults, the trunk vertebrae of the elongated T. dobrogicus are largely uniform, while in those of T. anatolicus , the first two vertebrae differ from the remaining trunk vertebrae. There was no difference in the relative contribution of individual vertebrae to body lengthening between species or stages. We conclude that body elongation in Triturus newts is achieved by increasing the number of vertebrae but not their length.  相似文献   

6.
Abstract Scanning electron microscopical studies revealed four distinct morphological larva-types (not instars) of Priapulus caudatus whose lorica-length measured 82–860 μm. The smallest of the larvae are round to oval, have 20 longitudinal ridges, a series of transverse ridges, and have two pairs of laterally situated tubuli near the posterior limits. The second larva-type is dorsoventrally compressed, has a single dorsal and single unsculptured ventral plate each with a prominent midridge near the anterior limits, three infolded lateral plates with a pair of tubuli near the posterior limits. The third and fourth larva-types remain dorsoventrally flattened; the third larva-type has less pronounced sculpturing than the fourth larva-type and is smaller; two pairs of tubuli are situated as in the previous stage. The number and arrangement of scalids on the introvert and pharyngeal teeth differ according to each of the four larva-types and are described. The ultrastructure of all organ systems is described. All scalids are sensilla equipped with ciliated receptor cells. The cuticle is similar to the cuticle in the adult and differs fundamentally from the cuticle of larval Halicryptus. The trunk is richly supplied with sensory structures. Trunk tubuli contain secretory cells. Posteriorly, a gland complex was found which presumably is the precursor of the equivalent gland in postlarvae and adults. The implications of the first larva-type's structural similarity to the larva of Tubiluchus are discussed.  相似文献   

7.
Acanthocephaloides irregularis n. sp. (Arhythmacanthidae) is described from four species of marine fishes in the Gulf of Odessa and Sukhyi Lyman, Ukrainan Black Sea waters, making it the tenth species of the genus. The hosts are the combtooth blenny Parablennius zvonimiri (Kolombatovic) (Blenniidae), the mushroom goby Ponticola eurycephalus (Kessler) (Gobiidae), the tubenose goby Proterorhinus marmoratus (Pallas) (Gobiidae) and the black-striped pipefish Syngnathus abaster Risso (Syngnathidae). The new species is most similar to its closest relative, Acanthocephaloides propinquus (Dujardin, 1845), in proboscis shape and armature (12 longitudinal rows of 5 hooks) and the shape of the trunk, reproductive system and lemnisci, but differs in having randomly distributed trunk spines. These trunk spines are organised in circular rings of individual spines separated by aspinose zones. The new species is also unique in having an anterior trunk collar, a very large triangular cephalic ganglion, nucleated pouches at the posterior end of the proboscis receptacle, and hooks and spines with roots bearing anterior manubria. Valid and invalid species of Acanthocephaloides Meyer, 1932 are listed and a key to all ten species is included.  相似文献   

8.
To explore the relationship between morphological change and species diversification, we reconstructed the evolutionary changes in skull size, skull shape, and body elongation in a monophyletic group of eight species that make up salamander genus Triturus. Their well‐studied phylogenetic relationships and the marked difference in ecological preferences among five species groups makes this genus an excellent model system for the study of morphological evolution. The study involved three‐dimensional imagery of the skull and the number of trunk vertebrae, in material that represents the morphological, spatial, and molecular diversity of the genus. Morphological change largely followed the pattern of descent. The reconstruction of ancestral skull shape indicated that morphological change was mostly confined to two episodes, corresponding to the ancestral lineage that all crested newts have in common and the Triturus dobrogicus lineage. When corrected for common descent, evolution of skull shape was correlated to change in skull size. Also, skull size and shape, as well as body shape, as inferred from the number of trunk vertebrae, were correlated, indicating a marked impact of species' ecological preferences on morphological evolution, accompanied by a series of niche shifts, with the most pronounced one in the T. dobrogicus lineage. The presence of phylogenetic signal and correlated evolutionary changes in skull and body shape suggested complex interplay of niche shifts, natural selection, and constraints by a common developmental system. © 2014 The Linnean Society of London, Biological Journal of the Linnean Society, 2014, 113 , 243–255.  相似文献   

9.
A new species of the genus Cirrhimuraena (Anguilliformes: Ophichthidae), Cirrhimuraena indica sp. nov., is described based on eight specimens collected from the Paradip (Odisha) and Petuaghat harbours (West Bengal) along the Bay of Bengal. The species is distinct in having the upper jaw fringed with 16–17 cirri before posterior nostril and 4–5 in between the anterior and posterior nostrils on the side; dorsal fin originates above the level of gill opening, predorsal length is 9.3–10.9 in total length; the head is relatively large, the length is 9.3–9.8 in total length; no infraorbital pores are observed between the nostrils; teeth are numerous, small, conical and in bands on each jaw; pores are present before the gill opening 10–11 and before anus 47–48; pectoral-fin length is 2.4–2.8 in head length; predorsal vertebrae are 8–10, pre-anal vertebrae 43–47 and total vertebrae 164–169. In the maximum likelihood tree analysis for COI gene, the new species belongs to the same clade as the other congener of Cirrhimuraena chinensis and is separated from the species morphologically and genetically.  相似文献   

10.
Pleuroxus smirnovi sp. nov. (Cladocera: Chydoridae) is found in a temporary freshwater body near Lake Zor‐Kul, the Pamirs (territory of Tajikistan). This large, brownish chydorine, with especially high body compressed laterally and supplied with a sharp dorsal keel, “untypical” of the genus Pleuroxus, at the same time, has the number of setae in filter plates of gnathobases II–V typical of this genus, namely 8‐8‐6‐4. My finding of P. smirnovi sp. nov. is a new evidence of an incomplete faunistic coverage and an imperfect state of today's systematics of the subfamily Chydorinae, because this new species has a set of characters apparently intermediate between the genera Pleuroxus Baird, 1843, Plurispina Frey, 1991 and Planicirculus Frey, 1991. Previously, large, compressed, and keeled chydorines were regarded as exclusively Australian, agreeing with ideas on a high endemism of the Australian cladoceran fauna. But after my finding of P. smirnovi sp. nov. we can speak only on “a predominantly Australian” distribution of such forms. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

11.
A new benthic phototrophic dinoflagellate is described from sediments of a tropical marine cove at Martinique Island and its micromorphology is studied by means of light and electron microscopy. The cell contains small golden-brown chloroplasts and the oval nucleus is posterior. It is laterally compressed, almost circular in shape when viewed laterally. It consists of a small epitheca tilted toward the right lateral side and a larger hypotheca. In the left view, the cingulum is more anterior and the epitheca is reduced. The cingulum is displaced and left-handed. This organism is peculiar in having no apical pore and its thecal plate arrangement is 2′ 1a 7′′ 5c 3s 5′′′ 1′′′′. The plates are smooth with small groups of pores scattered on their surface. An area with 60–80 densely arranged pores is found near the centre of the 2′′′ plate, on the left lateral side. Morphologically, these features are different from all other laterally compressed benthic genera. In addition, molecular genetic sequences of SSU and partial LSU form a distinct and well-supported clade among dinoflagellates and support the erection of a new genus. However, molecular phylogenies inferred from ribosomal genes failed to confirm any clear relationship with other benthic taxa and affinity with other laterally compressed dinoflagellates has not been demonstrated. Hence, the taxonomic affinity of Madanidinium loirii with a defined order and family is unclear at the moment.  相似文献   

12.
13.
Vertebral body compression is a common problem in commercial farming of Atlantic salmon. Although risk factors, such as vaccination and malnutrition, have been identified, the etiology is largely unknown. Histological studies of Atlantic salmon have shown that in a compressed deformity (platyspondyly) the length of the compact bone is reduced while the notochord start to form atypical chrondrogenic structures. In mammals, similar remodeling activities have been linked to inflammatory processes in the tissue. Hence, we wanted to investigate whether the compressed vertebrae in Atlantic salmon showed presence of local (IL‐1β, TNF‐α1), systemic (IgM) and chronic (MMP‐13, MMP‐9) immune responses (measured with quantitative PCR). Unvaccinated groups of Atlantic salmon that would later develop high or low prevalence of vertebral compression during on‐growth in seawater were sampled at seawater transfer, and 3 and 6 weeks after seawater transfer. In addition, compressed and normal vertebrae from the high deformity prevalence group were sampled 44 weeks after transfer to seawater. MMP‐13 was significantly up‐regulated in the group that developed a high prevalence of deformity, and also significantly up‐regulated in compressed vertebrae, 44 weeks after seawater transfer. In compressed vertebrae, MMP‐13 was equally up‐regulated in the notochord, compact bone and trabecular bone. The results of the present study suggest that MMP‐13 may serve as an early indicator for bone remodeling which may lead to vertebral compression, and that there is a relationship between the development of vertebral compression and increased remodeling activities in farmed Atlantic salmon.  相似文献   

14.
Most myzostomids are ectocommensals of crinoids on which they move freely. Their locomotion is ensured by five pairs of parapodia located laterally below their trunk. Each parapodium in Myzostoma cirriferum is a conical structure that includes a hook-like chaeta, replacement chaetae and an aciculum. Structure and ultrastructure of the myzostomid chaetae are similar to those of polychaetes: they are formed by a chaetoblast, which gives rise to microvilli where chaetal material is assembled on the outer surface. Myzostoma cirriferum walks on its host. It moves the anterior part, the posterior part or the lateral parts forwards but is able to rotate of 180° on itself. Its locomotion entirely depends on parapodial motions and not on trunk movements. Three pairs of muscles are involved in parapodial motions: parapodium flexor and parapodium extensor, aciculum protractor and aciculum retractor, and hook protractor with conjunctor. A functional model is proposed for explaining the global motion of a parapodium in M. cirriferum that may be extended to all ectocommensal myzostomids.  相似文献   

15.
The new species Samariscus leopardus is described from one specimen caught at a depth of 159 m in the Indian Ocean, 11°22′ S, 61°42′ E. The species is easily distinguishable from the remaining species of the genus from a set of the following characteristics: the absence of a lateral line on both sides of the body, a short ventral fin, 42 vertebrae (9 trunk and 33 caudal), 5 rays of pectoral fin, and spotted coloration. Other morphological specific features, including topography of sensory canals of the head, are described.  相似文献   

16.
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.  相似文献   

17.
Summary Thysanote alternans n. sp., a lernaeopodid copepod parasitic on Polynemus sextarius is described and illustrated. A key to 19 species of Thysanote is provided (two unnamed species included). Specific diagnosis within the genus is based on the number and shape of maxillary and posterior trunk processes. The limitations of their value as discriminant characteristics are discussed. Host affiliations of the members of the genus are examined. Distribution of Thysanote is shown to have two centres, one in the Indian Ocean and another, a smaller one, in the Caribbean. The connections between them are tenuous. ac]19810127  相似文献   

18.
Bone pathology in the titanosaur dinosaur Uberabatitan ribeiroi from the Marília Formation (Bauru Group, Late Cretaceous) of Uberaba city (Minas Gerais State, Brazil) is analysed here. They include two fused procoelous mid‐caudal vertebrae (CPPLIP‐1020) and a haemal arch (CPPLIP‐1006) of the middle section of the tail with a healing fracture callus. The analyses of the caudal vertebrae CPPLIP‐1020 of Uberabatitan permit us to recognize the following signs, based on CT scan and external macroscopic observations: (1) ossified longitudinal tendons; (2) likely ossified intervertebral disc, producing fused vertebral bodies; (3) fused right zygapophyseal process with a laterally developed osteophyte affecting this joint; (4) osteophytes and exostoses at different portions of the vertebrae; (5) cloacae, bone erosion and likely internal infection. According to all the processes observed in these caudals, we could not discard at least two possibilities for the diagnosis of the fused vertebrae. It could be the result of a spondyloarthropathy process (considering most of the observed signs) or possibly have been associated with an infection (e.g. discospondylitis/infections spondylitis or septic arthritis). The bone lesion record in Uberabatitan ribeiroi from the Late Cretaceous of Brazil increases the range of study of titanosaur dinosaurs, which although have a large fossil record, have few pathological studies.  相似文献   

19.
One new kinorhynch genus and species and one new species from the genus Zelinkaderes are described from sandy sediment off Fort Pierce, Florida. The new genus and species, Tubulideres seminoli gen. et sp. nov. is characterized by the presence of the first trunk segment consisting of a closed ring, the second segment of a bent tergal plate with a midventral articulation and the following nine segments consisting of a tergal and two sternal plates. Cuspidate spines are not present, but flexible tubules are located on several segments, and in particular concentrated on the ventral side of the second segment. Middorsal spines are present on all trunk segments and are alternatingly offset to a position slightly lateral to the middorsal line. Zelinkaderes brightae nov. sp. is characterized by its spine formula in having middorsal spines on trunk segments 4, 6 and 8–11, lateroventral acicular spines on segment 2, lateral accessory cuspidate spines on segments 2 and 8, ventrolateral cuspidate spines on segments 4–6 and 9, lateroventral acicular spines present on segments 8 and 9, and midterminal, lateral terminal and lateral terminal accessory spines on segment 11. The spine formula of Z. brightae nov. sp. places it in a position in between Z. submersus and a clade consisting of Z. klepali and Z. floridensis. The new findings on Z. brightae nov. sp. have led us to propose an emended diagnosis for the genus.  相似文献   

20.
Iquius nipponicus Jordan 1919 was described on the basis of a single specimen from the Miocene of Iki Island, Nagasaki, Japan, and was tentatively assigned to the family Clupeidae. The holotype consists of the anterior portion of the body (lacking the anal and caudal fins and most of the caudal vertebrae), and is re-examined. The species is re-described based on additional specimens from the type locality. This species possesses an extremely stout third dorsal spine-like fin ray with a smooth posterior edge, an expanded anterior portion of the maxilla covering approximately half of the bone, 13 branched anal fin rays, and 22 abdominal and 16 caudal vertebrae. A phylogenetic study using the character matrix from a previous study suggests that the species forms a clade with xenocyprinins, but it differs from xenocyprinins in the form of the maxilla and the dentary and the numbers of branched anal fin rays and vertebrae. The present study concludes that the genus Iquius does not belong to the family Clupeidae. Iquius is a distinct and valid genus that is closely related to cultrins and xenocyprinins of the family Cyprinidae.  相似文献   

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