Operculum regeneration following failed predation in the Silurian gastropod Oriostoma

Regeneration of the calcareous rigiclaudent operculum following severe, non‐lethal, predatory attacks is described in two specimens of the characteristic Silurian gastropod Oriostoma from the English Midlands. This is the first record of the regeneration of opercula in Palaeozoic gastropods and of opercula conjoined with shells that have been repaired after significant, failed, durophagous attacks. In one specimen, a series of repaired injuries culminates in a repaired aperture closed by the operculum. In the second specimen, new shell growth has failed to recover the full extent of the original broken whorl, and the new aperture and operculum, though well developed, are smaller than the originals. Both opercula are unusually thin centrally when compared to other, strongly domed, Oriostoma opercula.     

New data on the jaw apparatus of fossil cephalopods

A newly discovered fossil cephalopod jaw apparatus that may belong to Permian representatives of the Endocochlia is described. Permorhynchus dentatus n. gen. n. sp. is established on the basis of this apparatus. The asymmetry of jaws in the Ectocochlia may be connected with the double function of the ventral jaw apparatus, and the well-developed, relatively large frontal plate of the ventral jaw should be regarded as a feature common to all representatives of ectocochlian cephalopods evolved from early Palaeozoic stock. Distinct features seen in the jaw apparatus of Upper Permian endocochlians include the pronounced beak form of both jaws and the presence of oblong wings on the ventral mandible.     

The suspensorium of Ctenopoma acutirostre: A comparative functional analysis with Anabas testudineus

The functional and structural aspects of the suspensorium of Ctenopoma acutirostre have been correlated with those of Anabas testudineus. The different parts of the suspensorium are described, as are the muscles that are functionally connected with the suspensorium. Functions were analyzed by observations on living specimens, and by measurements recorded from the movie films. The role played by various bones and muscles to carry out the functions (the respiration, the gulping, and the feeding) has been explained. The different bones and muscles have been considered as functional units which often are connected to form couplings. During the respiration in Ctenopoma the depression of the lower jaw is conducted by the levator operculiopercular apparatus-mandible coupling. The presence of this coupling is indicated by the presence of dorso-ventral movement of the operculum. A remarkable ventro-dorsal and antero-caudal movement in the urhyal during feeding shows in Ctenopoma the presence of the sternohyoideus-hyoid apparatus-interopercular-mandible coupling, which depresses the lower jaw. In Ctenopoma, the suspensorium takes part in respiration, gulping, and feeding, whereas in Anabas it is only involved in gulping and feeding. To carry out its functions, the suspensorium implies three articulations: palatocranial, craniohyomandibular, and quadratomandibular with the cranium and the lower jaw, respectively. Finally, the suspensorium has been analyzed as a part of the architectonic structure of the entire head by using a diagrammatic model (fig. 13) based on mutual influence, integration, and couplings.     

Jaw growth and replacement in<Emphasis Type="Italic"> Ophryotrocha labronica</Emphasis> (Polychaeta,Dorvilleidae)

Ophryotrocha labronica, as typical for Eunicida, has a complex jaw apparatus consisting of ventral mandibles and dorsal maxillae. Mandibles are not replaced but are retained throughout life. Larval mandibles have adult-sized cutting plates but their proximal shafts lengthen and enlarge as the worm grows. The maxillary apparatus of O. labronica undergoes three moults or replacements. The initial, or larval maxillae, consisting of two paired basal plates and two paired free denticles, develop in the unreleased larvae. They are replaced in the 5-setiger juvenile by the P1-maxillae consisting of falcate forceps and six denticles. The second moult occurs in the 8- to 9-setiger juveniles and results in the P2-maxillae with bidentate forceps and seven denticles, and the third and final moult results in the K-maxillae and seven denticles. The K-maxillae develop in 9- to 12-setiger males and 13- to 15-setiger females and are not replaced but enlarge proximally. Thus the K-forceps can be traced back through the P2-forceps, P1-forceps, to the larval basal plates, indicating the apomorphic state of the K-forceps. Three pulp cavities, separated by darker fusion lines are visible in weakly sclerotised young K-forceps suggesting the fusion of three separate elements. It is concluded that the Ophryotrocha forceps are homologous to the superior and probably inferior basal plates of other dorvilleids. The internal structure of the Ophryotrocha forceps demonstrates that they are not homologous to the labidognath maxilla I as has been suggested.     

Two new species of Ulota (Orthotrichaceae,Bryopsida) with multicellular spores,from the Hengduan Mountains,Southwestern China

Abstract

Two new species, Ulota yunnanensis and Ulota gigantospora, are described from Yunnan and Sichuan Provinces, China. Both have multicellular spores, a relatively uncommon character in the genus. Differences between the species include growth form and habit, leaf areolation, capsule shape, peristome structure and ornamentation, operculum shape and colour, as well as vaginula and calyptra hairiness. These characters and those discriminating the new species from other ones with similar spore type are discussed and illustrated.     

Über den Kieferapparat der Lytoceratacea (Ammonoidea)

The jaw apparati of Paleozoic and Triassic ammonoids are simìlar in shape to parrots’ beaks; they possess sharp cutting-edges and consist of chitinous material. Together with the similar jaw apparati of recent Coleoids, they constitute the Normal-Type of cephalopod jaws. The jaw apparati of the Jurassic-Cretaceous ammonites possess wide, shovel-like lower jaws without cutting-edges. They consist either of an undivided chitinous plate (Anaptychus) or of this and two additional calcitic plates (Aptychi) on its outer flanks. Jaw apparati of this type are here called Aptychus-Type jaws. New finds in the Upper Cretaceous of Japan suggest the existence of a third type of jaw apparatus which is here called the Rhynchaptychus-Type. Jaws of this type are mainly characterized by possession of calcitic rostra on the tips of the jaws. They seem to be restricted to members of the order Lytoceratacea (excluding the Heteromorphs).     

Fine morphology of the jaw apparatus of Puncturella noachina (Fissurellidae,Vetigastropoda)

Jaws of various kinds occur in virtually all groups of Mollusca, except for Polyplacophora and Bivalvia. Molluscan jaws are formed by the buccal epithelium and either constitute a single plate, a paired formation or a serial structure. Buccal ectodermal structures in gastropods are rather different. They can be nonrenewable or having final growth, like the hooks in Clione (Gastropoda, Gymnosomata). In this case, they are formed by a single cell. Conversely, they can be renewable during the entire life span and in this case they are formed by a set of cells, like the formation of the radula. The fine structure of the jaws was studied in the gastropod Puncturella noachina. The jaw is situated in the buccal cavity and consists of paired elongated cuticular plates. On the anterior edge of each cuticular plate there are numerous longitudinally oriented rodlets disposed over the entire jaw surface and immersed into a cuticular matrix. The jaw can be divided into four zones situated successively toward the anterior edge: 1) the posterior area: the zone of formation of the thick cuticle covering the entire jaw and forming the electron‐dense outer layer of the jaw plate; 2) the zone of rodlet formation; 3) the zone of rodlet arrangement; and 4) the anterior zone: the free scraping edge of the plate, or the erosion zone. In the general pattern of jaw formation, Puncturella noachina resembles Testudinalia tessulata (Patellogastropoda) studied previously. The basis of the jaw is a cuticular plate formed by the activity of the strongly developed microvillar apparatus of the gnathoepithelium. However, the mechanism of renewal of the jaw anterior part in P. noachina is much more complex as its scraping edge consists not just of a thick cuticular matrix rather than of a system of denticles being the projecting endings of rodlets. J. Morphol. 275:775–787, 2014. © 2014 Wiley Periodicals, Inc.     

Key innovations in Mesozoic ammonoids: the multicuspidate radula and the calcified aptychus

A nearly complete radula with seven elements per row preserved inside of an isolated, bivalved, calcitic lower jaw (= aptychus) of the Late Jurassic ammonite Aspidoceras is described from the Fossillagerstätte Painten (Bavaria, southern Germany). It is the largest known ammonite radula and the first record for the Perisphinctoidea. The multicuspidate tooth elements (ctenodont type of radula) present short cusps. Owing to significant morphological differences between known aptychophoran ammonoid radulae, their possible function is discussed, partly in comparison with modern cephalopod and gastropod radulae. Analogies between the evolution of the pharyngeal jaws of cichlid fishes and the ammonoid buccal apparatus raise the possibility that the evolution of a multicuspidate radula allowed for a functional decoupling of the aptychophoran ammonoid jaw. The radula, therefore, represents a key innovation which allowed for the evolution of the calcified lower jaws in Jurassic and Cretaceous aptychophoran ammonites. Possible triggers for this morphological change during the early Toarcian are discussed. Finally, we hypothesize potential adaptations of ammonoids to different feeding niches based on radular tooth morphologies.     

A conodont, thelodont and acanthodian fauna from the Lower Přídolí (Silurian) of the Much Wenlock area, Shropshire

Conodonts, thelodonts and acanthodians have previously been collected from the P?ídolí of Shropshire (Welsh Borderland) from bone beds such as the Ludlow Bone Bed. In general, specimens collected from these types of deposit are very abraded and make taxonomic studies difficult. This contribution describes well preserved thelodont microelements from two samples from the Downton Castle Sandstone Formation (P?ídolí, Silurian) of the Much Wenlock area of Shropshire. Head scales, a wide variety of transitional scales, and pore scales of the lateral line sensory canals of the thelodont Paralogania ludlowiensis (Gross) are described for the first time. A new acanthodian Nostolepis linleyensis sp. nov. and elements from the apparatus of the conodont Ozarkodina?hemensis sp. nov. are documented from the same samples. The thelodonts in both samples are typical of upper Ludlow–P?ídolí faunas from across the Welsh Borderland, and are also present in smaller numbers in the Ludlow Series of Gotland, Sweden, Saaremaa Island, Estonia, and in Latvia and Lithuania. The conodont O? hemensis sp. nov. is restricted to the Much Wenlock area of Shropshire. The co-occurrence of well preserved elements of conodonts and thelodonts suggests that they were deposited fairly rapidly with little or no re-working and that a restricted marine environment prevailed in the early P?ídolí in the Much Wenlock area of Shropshire.     

Kinematic analysis of jaw protrusion in orectolobiform sharks: A new mechanism for jaw protrusion in elasmobranchs

Jaw protrusion is an important component of prey capture in fishes, although the mechanics of protrusion have thus far been studied largely in teleosts. Elasmobranchs are also able to protrude their jaws (Tricas and McCosker [1984] Proc. Cal. Acad. Sci. 43: 221–238; Tricas [1985] Mem. S. Calif. Acad. Sci. 8:81–91.; Frazzetta and Prange [1987] Copeia 4:979–993). Several related features of the feeding apparatus contribute to jaw protrusion in sharks. Labial cartilages form an extendible series attached dorsally to the anterolateral face of the palatoquadrate and ventrally to the anteroventral surface of Meckel's cartilage. The labial cartilage chain swings anterolaterally as the lower jaw is depressed, thrusting the labial margins forward to form a circular oral opening and displacing the jaw apparatus towards the food; this pattern is analogous to halecomorph and primitive actinopterygian fishes in which the maxilla swings forward (Lauder [1979] J. Zool. Lond. 187:543–578). The palatoquadrate and Meckel's cartilage also project anteriorly and represent the major contribution to protrusion. These movements occur simultaneously with enlargement of the oral cavity to generate suction. The wobbegong sharks (Orectolobidae) are specialized for jaw protrusion. The spotted wobbegong protrudes its jaw by 33% of its chondrocranial length using two different mechanical systems. In the first mechanism of jaw protrusion, the intermandibularis and interhyoideus muscles medially compress the lower jaw and hyomandibulae. Compression of the lower jaw results in a more acute symphyseal angle so that the anteroposterior alignment of the lower jaw increases due to the rotation of each lower jaw towards a saggital orientation. Distal compression of the hyomandibulae at their attachments to the jaws swings the jaws forward. The second mechanism involves rotation of the ceratohyal around a posterior process of the lower jaw, pushing the hyomandibulae anteroventrally, thereby pushing the jaw articulation ventrally and anteriorly to protrude the jaws. © 1994 Wiley-Liss, Inc.     

Eurytholia plates (Problematica) from the late Silurian of the Austrian Carnic Alps

A small fauna of phosphatic plates of the enigmatic organism Eurytholia bohemica [Ferretti A., Serpagli E., ?torch P., 2006. Problematic phosphatic plates from the Silurian-Early Devonian of Bohemia, Czech Republic. Journal of Paleontology 80 1026–1031.], is described for the first time from upper Silurian beds of Austria. Other known Silurian occurrences of this taxon were restricted to Bohemian localities even if the genus had been previously reported from several Ordovician outcrops. The extension of E. bohemica from the microcontinent of Perunica to that of Carnica suggests that Eurytholia was not an uncommon constituent of Silurian fauna, at least at intermediate latitudes in the southern hemisphere.     

Reduction index of the upper M2 in marmosets

Marmosets have reduced second molars of which size and shape are varied in different species. Mesiodistal and buccolingual diameter of the first and second upper molars in 16 species were measured, and molar area (molar rectangle) and M2 reduction index were calculated by the equation,R=(M2 area/M1 area) × 100. This index ranged from 36.1 inSaguinus oedipus geoffroyi to 70.6 which was the largest found inCebuella pygmaea. Species ofSaguinus showed relatively wide variation as well as a consistantly smaller index. The index forCallithrix registered around 60 andLeontopithecus rosalia was positioned within this genus. There was no relationship between this index and body size of each form. The sizes of the first molar and second molar may not significantly correlate either with body size across species, becauseLeontopithecus rosalia had exceptionally large molars for its body size and contrarily genusSaguinus had relatively small molars. When the shape of the mandible was expressed as length/width ratio, the reduction index significantly correlate with this ratio in genusSaguinus andCallithrix, indicating that longer jaw in shape had relatively large M2. The reduction indices of two possible subspecies,S. oedipus geoffroyi andS. o. oedipus, were 36.1 and 47.3, respectively. This difference suggested that there was a difference in diet or function of jaw apparatus beyond subspecies level.     

Morphology and growth of lepidosirenid lungfish tooth plates (Pisces: Dipnoi)

The structure of the tooth plates of Protopterus and Lepidosiren was investigated to determine the causes and consequences of postlarval shape change. During growth, the basal area of the tooth plates increases, some cusps become more prominent, and shearing surfaces are sharpened. The jaw articulation restricts the range of movements of the lower jaw, and causes the tooth plates to occlude precisely; the resulting wear patterns are regular. The tooth plates are composed of enamel, trabecular dentine, and petrodentine. A petrodentine column forms the core of a tooth plate; it is flanked by trabecular dentine. Microhardness measurements show that trabecular dentine is comparable in hardness to mammalian dentine, whereas the petrodentine is comparable to enamel. The location and differential wear of these tissues produce the prominent cusps and self-sharpened blades of the adult tooth plates.     

Anomalies in the cephalic area of laboratory-reared larvae and juveniles of the common sole,Solea solea: oral jaw apparatus,dermal papillae and pigmentation

Synopsis The post-metamorphic common sole, Solea solea, as well as the other Soleidae and Cynoglossidae, are characterized by oral jaw elements without teeth on the ocular side. A relatively large proportion of late sole larvae and early juveniles, routinely reared in the laboratory, showed dentigerous and shape-modified premaxillae and mandibles on the ocular side. Abnormal jaws were associated with dermal papillae and a lack of pigmentation on parts of the ocular side of the head. These features are probably the result of suppressed epigenetic mechanisms normally active during ontogeny. Insights into the morphological evolution of the soleid jaw apparatus are discussed.     

Functional design and evolution of the pharyngeal jaw apparatus in euteleostean fishes

Functional and structural patterns in the pharyngeal jaw apparatus of euteleostean fishes are described and analysed as a case study of the transformation of a complex biological design. The sequential acquisition of structural novelties in the pharyngeal apparatus is considered in relation to both current hypotheses of euteleostean phylogeny and patterns of pharyngeal jaw function. Several euteleostean clades are corroborated as being monophyletic, and morphologically conservative features of the pharyngeal jaw apparatus are recognized. Functional analysis, using cinematography and electromyography, reveals four distinct patterns of muscle activity during feeding in primitive euteleosts (Esox) and in derived euteleostean fishes(Perca, Micropterus, Ambloplites, Pomoxis). The initial strike, buccal manipulation, pharyngeal manipulation, and the pharyngeal transport of prey into the oesophagus all involve unique muscle activity patterns that must be distinguished in analyses of pharyngeal jaw function. During pharyngeal transport, the upper and lower pharyngeal jaws are simultaneously protracted and retracted by the action of dorsal and ventral musculoskeletal gill arch couplings. The levator externus four and retractor dorsalis muscles, anatomical antagonists, overlap for 70–90°of their activity period. Levatores externi one and two are the main protractors of the upper pharyngeal jaws in the acanthopterygian fishes studied. The major features of pharyngeal jaw movement in primitive euteleosts are retained in many derived clades in spite of a dramatic structural reorganization of the pharyngeal region. Homologous muscles have radically changed their relative activity periods while pharyngeal jaw kinematics have been modified relatively little. Patterns of transformation of activity may thus bear little direct relationship to the sequence of structural modification in the evolution of complex designs. Overall function of a structural system may be maintained, however, through co-ordinated modifications of the timing of muscle activity and anatomical reorientation of the musculoskeletal system. Deeper understanding of the principles underlying the origin and transformation of functional design in vertebrates awaits further information on the acquisition of both structural and functional novelties at successive hierarchical levels within monophyietic clades. This is suggested as a key goal of future research in functional and evolutionary morphology.     

Evolution within the Silurian cephalopod genusInversoceras

Specimens of the Silurian cephalopod genusInversoceras from the Wenlockian Slite Beds of Gotland, Sweden, are more curved and swollen than those from the Ludlowian Hemse Beds of Gotland. The former population is interpreted as a direct ancestor to the latter. The younger form,Inversoceras p. perversum, originally described by Barrande from Bohemia, includes both individuals with a fairly straight shell and with a slightly curved shell. The distinctly curved and swollen form from the Wenlock beds is herein described as a new subspecies,I. p. eoperversum. I. p. falciformis from the Ludlowian of Bohemia is excluded fromI. perversum and. treated as a distinct species. Its relationship to the olderI. p. eoperversum is discussed. This discussion also includesI. dayi from the Niagarian of North America.     

A simple apparatus for measuring hardness of agar and Gelrite plates

A simple apparatus for measuring hardness of Gelrite and agar plates, that can be easily fabricated, is described. It gives reproducible results comparable with those obtained with expensive commercial equipment. It has been successfully used to improve enumeration ofThiobacillus ferrooxidans andT. thiooxidans on solid media plates.     

Anatomy and Ultrastructure of Ventral Pharyngeal Organs and their Phylogenetic Importance in Polychaeta (Annelida). IV. The Pharynx and Jaws of the Dorvilleidae

An anatomical and ultrastructural investigation of the ventral pharyngeal organ, jaws and replacement of jaws was carried out in Ophryotrocha gracilis and Protodorvillea kefersteini (Dorvilleidae). The pharynx exhibits the following features: jaw apparatus present, consisting of paired mandibles and rows of maxillary plates, the latter are fused to form a single piece; cuticular jaws electron-dense, in P. kefersteini with collagen fibres; muscle bulbus solid, composed of muscle cells only; parallel running myofilaments, centrally located mitochondria and nuclei, bulbus epithelium containing the mandibles and gland cells, maxillary plates lying on folds corresponding to a tongue-like organ, connected with mandibles by longitudinal investing muscles; numerous gland cells not united to distinct salivary glands. Development of jaw replacements occurs in epithelial cavities beside the functional maxillae. Shape of maxillary plates is preformed by microvilli carrying cell processes. Maxilloblasts change their shape during the development. Synapomorphic structures occurring in ventral pharyngeal organs of other species outside the Eunicea are not present and even the closely related Dinophilidae exhibit a completely different pharyngeal organ. Therefore, convergent evolution of these organs is the most probable explanation. These findings do not agree with the hypothesis of the homology of the ventral pharyngeal organs in the Polychaeta.     

Evolutionary aspects of cephalic sensory papillae of the Indo‐Pacific species of Eleotris (Teleostei: Eleotridae)

Eleotris species (Teleostei: Eleotridae) are one of the most common fish in Indo‐Pacific estuaries and insular freshwater streams. In these rivers, they are a sit‐and‐wait predator. They have an amphidromous life cycle, that is adults grow, feed and reproduce in rivers, while larvae have a marine dispersal phase. Larvae recruit back to rivers and settle in stream habitats. Primary characters used to determine Eleotris species are the presence and the disposition of cephalic sensory papillae rows on the operculum and under the eyes as well as scale row numbers. The morphology of these cephalic sensory papillae is of particular importance in this predatory genus as it is generally correlated in fish to predation and feeding. In this paper, we have established a molecular phylogeny of the genus based on the 12 mitochondrial protein‐coding genes to discuss the relationship between Indo‐Pacific Eleotris species. There is a well‐supported dichotomy in the molecular phylogeny, and this separation into two main clades is also morphologically visible, as it reveals a difference in the arrangement of cephalic sensory papillae. Indeed, the phylogeny distinguishes the species with the “open” pattern of the operculum sensory papillae and the species with the “closed” one. This phylogeny thus reflects the morphology of the opercular papillae. The evolution of this character is discussed in terms of the adaptation of the Eleotris genus to life in tropical insular river systems.     

Silurian craniide brachiopods from Gotland

Seven craniide brachiopod genera are described from the Silurian (Wenlock–Ludlow) of Gotland, including one new genus and five new species. The new genus and species Thulecrania septicostata is unique among Silurian craniides as it possesses solid spines. The new species Lepidocrania multilamellosa is the first Silurian record of this poorly known Permian genus. The problematic North American Propatella Grubbs, 1939 , was originally described as a gastropod, but the new species Propatella palmaria from Gotland shows that it is a craniide with sutured hollow spines of a type not previously recorded from Silurian craniides. The dorsal valves of the new species Valdiviathyris? bicornis are remarkably similar to those of the type species and represent the first possible Palaeozoic record of this poorly known extant craniide. This first systematic study of craniide brachiopods from the Silurian of Gotland shows that the diversity is relatively high as compared to other known Silurian craniide faunas, but a more thorough comparison is not possible due to the lack of data from most parts of the world. The new data from Gotland support the view that the craniides were not affected by the end‐Ordovician extinction.