Orthoconic cephalopods and associated fauna from the late Ordovician Soom Shale Lagersta¨tte, South Africa

ABSTRACT. Orthoconic cephalopods from the Soom Shale Member (Ashgill) are exceptionally preserved and are colonized by lingulate brachiopods and cornulitids. Other fossils commonly associated with orthocones include myodocopid ostracodes and chitinozoans. Size distribution analysis of the brachiopods on one orthocone indicates that it was colonized in vivo. Four orthocone radulae are preserved extending the record of these structures 50 My back to the late Ordovician. Orthocone radula configuration is more similar to that of ammonoids and coleoids than to that of nautiloids.     

Ammoniten mit Kieferapparat und Radula aus Lias-Geschieben

Jaws and radula have been found in two adult microconch specimens of the Liassic ammonite speciesEleganticeras elegantulum (Young & Bird, 1828) from glacial drift boulders near Hamburg. They are more similar to those of recent dibranchiates than ofNautilus, the radula having seven longitudinal rows of teeth instead of thirteen in recentNautilus. Since bothOwens classification of the cephalopods into Dibranchiata and Tetrabranchiata according to the number of gills (which cannot be observed in fossil cephalopods) andSchwarz’ division into Ecto- and Endocochlia according to the (assumed) relative position of body and shell are rather unfortunate, the radula is suggested as a sound basis of classification. It is acceptable to paleo- as well as to neozoologists. As yet, the known evidence is sufficient for a twofold division only: Class Cephalopoda Subclass Lateradulata: Nautiloidea Subclass Angusteradulata: Ammonoidea Coleoidea     

First record of a complete arm crown of the Early Jurassic coleoid Loligosepia (Cephalopoda)

The higher rank systematics of coleoid cephalopods are primarily based on the total number of arms. Completely preserved arm crows are, therefore, the most important character complex by which fossil representatives can be assigned to higher taxa. Whereas belemnoids—similar to modern Decabrachia—are well-known to have ten hooklet-bearing arms, recent studies have shown that Middle-Late Jurassic and Late Cretaceous gladius-bearing coleoids belong to the Vamyropoda, owing to having only eight hooklet-free arms. The arm number of Early Jurassic gladius-bearing coleoids was unclear for a long time. This paper, however, reports the first unequivocally complete arm crown from the Early Jurassic (Toarcian). It consists of eight strongly phosphatised arms of equal shape. Affinity with decabrachiate coleoids is therefore unlikely. The mantle sack of the specimen, which was identified as Loligosepia aalensis (Schübler in Zieten, 1832), has, furthermore, an unusual arrangement of numerous angular pieces. The irregular scattering of the mantle fragments was most probably caused by a scavenger. Finally, hooklets in the food residues in the posterior mantle indicate that Loligosepia preyed upon belemnites.     

New insights into the buccal apparatus of the Goniatitina: palaeobiological and phylogenetic implications

Exceptionally well‐preserved radulae and lower jaws found both inside the body chamber of Cravenoceras fayettevillae (Mississippian) and in isolated nodules (Mississippian and Pennsylvanian) were analysed using CT scan and synchrotron propagation phase‐contrast tomography. This approach reveals new anatomical details allowing us to investigate wear, preservation and muscle insertion in the buccal mass of the Goniatitina. For comparison, Recent cephalopod radulae were also investigated. The radula in the Goniatitina consists of nine elements per row, and its morphology is conservative in the group. The shape of the teeth is similar to that in some Recent coleoids. The lower jaw is morphologically closer to that of Recent Nautilus, consisting of a wide outer lamella and a reduced inner lamella. The morphology of the inner lamella reflects the outer lamella in smaller dimensions and does not protrude posteroventrally. The space between the inner and outer lamellae allows for muscle insertion. Our morphological data indicate that a mosaic of characters is present in the buccal mass of Goniatitina with some parts of the buccal mass being more primitive than others. This implies that different parts of the buccal mass may have followed different evolutionary histories.     

A new cephalopod with soft parts from the Upper Carboniferous Francis Creek Shale of Illinois, USA

A ten armed fossil from the Pennsylvanian Francis Creek Shale and belonging to the famous Mazon Creek biota is described as a cephalopod. Apart from a superficial resemblance to the coleoids, there is little basis for an assessment of the animal's affinities. A mineralized Bask shaped structure preserved in calcite and seen in both part and counterpart in fragmentary form may represent the fossilized remains of an internal organ such as the stomach or ink sac A small, dark circular spot positioned anterior to the appendages could be the animal's eye although mere is no internal structure visible. The extremely rare occurrence of Palaeozoic cephalopods with soft parts has so far been Ended to the Francis Creek Shale and the Devonian Hunsrückschiefer of Germany. The Mazon Creek biota includes many fossils which show a remarkable standard of soft part preservation which in some cases includes the fossilization of eye spots and stomach traces. Previously deserted Mazon Creek cephalopods have included the tentacular impression of a squid complete with arm hooks, and the radulae and shells of both coleoids and nautiloids. The specimen described here is the first from the Palaeozoic to show any hint of organ preservation.     

A New Family Of Coleoids From The Lower Jurassic Of Osteno, Northern Italy

The discovery of well preserved and almost complete fossil coleoid cephalopods near Osteno in northern Italy has allowed the original study of a single specimen by Pinna (1972) to be enhanced. The unusual structure of the ten arms, showing a clear differentiation in the shape of the arm hooks (long and thin on six arms and short and stocky on the other four), is a distinctive character which is not present in any Jurassic family of coleoids known to date. We distinguish two new genera: Ostenoteuthis, with the species O. siroi sp. nov., and Uncinoteuthis, with the species U. cuvieri sp. nov. The new family Ostenoteuthidae (Order uncertain) is erected for them. The systematic position of this family within the fossil coleoids is discussed.     

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.     

Systematics and distribution of the New Zealand onychoteuthid fauna (Cephalopoda: Oegopsida), including a new species, Notonykia nesisi sp. nov.

Onychoteuthid squids are among the most common cephalopods found in New Zealand waters, and comprise a major portion of the regional diets of teuthophagous marine mammals. Although several recent publications have addressed aspects of various species’ biology and reproduction, the systematics of the group remains poorly understood. Herein the ontogenetic and adult morphologies of regionally occurring known species of the genera Moroteuthis, Onychoteuthis, and Notonykia are redescribed, and Notonykia nesisi sp. nov. is described for the first time. Ontogenetic and sexually dimorphic variation in characters and character states associated with body proportions, and beak, radula, tentacular hook, palatine tooth and gladius morphologies are also described and compared between local onychoteuthid taxa for the first time.     

The radula of the Late Cretaceous scaphitid ammonite Rhaeboceras halli (Meek and Hayden, 1856)

Abstract: Radular teeth occur between the jaws in two specimens of the Late Cretaceous scaphitid ammonite Rhaeboceras halli (Meek and Hayden, 1856) from the Western Interior of the United States. The detailed morphology of the teeth has been revealed by propagation phase contrast X‐ray synchrotron microtomography. Each row of the radula of R. halli consists of a total of seven teeth (a central rachidian, two pairs of lateral and one pair of marginal teeth), as in other known ammonoid radulae, although the central tooth could not be confirmed in the specimens examined. The lateral teeth are multicuspid and robust, and the marginal teeth are long (4.6 mm) and slender. In overall morphology, the heterodont and ctenoglossan radula of R. halli is similar that of Jurassic and Cretaceous ammonites with the same aptychus‐type lower jaw, that is, the Aptychophora. This discovery reveals the range of variation in radular morphology, which could be related to ecological or phylogenetic factors. It also invalidates the hypothesis that the hook‐like structures in R. halli previously described are radular elements.     

The Staining of Radulae

A review of the various methods of staining and mounting radulae is given. Normally the radula should be extracted with 0.5 to 1% sodium hydroxide solution, and the associated tissues removed before staining. Two staining methods are recommended for facilitating the interpretation of radulae. Newly formed teeth and the bases of older ones are well stained by saturated aqueous chlorazol black E (up to 10 minutes). A more uniformly stained specimen) in which the cusps of all but the young teeth are alone stained, may be obtained by using the “oxidation-dahlia technic”. The radula is oxidized in N/10 potassium permanganate solution until black and subsequently decolorized in saturated aqueous oxalic acid. It is then stained in 0.1% aqueous dahlia (Hofmann's violet), the staining time varying from 10 to 30 minutes, according to the material. It is then dehydrated and passed through xylene and clove oil into Canada balsam. Other mountants may be employed but glycerin jelly is only recommended for the rapid examination of unstained radulae. Several other staining methods are mentioned, and general precautions to be observed while mounting are discussed.     

17种陆生贝类齿舌的扫描电镜观察及 分类学意义探讨

采用扫描电镜观察了3目10科12属17种陆生贝类的齿舌形态.结果 显示,17种陆生贝类齿舌的中央齿均为1列,侧齿12～218列不等,缘齿0～204列不等.中央齿依齿片上小齿数目分为单齿型、三齿型和多齿型;侧齿与缘齿的形态多样,侧齿齿片上小齿数1～6枚不等,缘齿齿片上小齿数1～10枚不等.结合以往报道的38种陆生贝类齿舌...     

Radula formation in two species of Conoidea (Gastropoda)

The radula is the basic feeding structure in gastropod molluscs and exhibits great morphological diversity that reflects the exceptional anatomical and ecological diversity occurring in these animals. This uniquely molluscan structure is formed in the blind end of the radular sac by specialized cells (membranoblasts and odontoblasts). Secretion type, and the number and shape of the odontoblasts that form each tooth characterize the mode of radula formation. These characteristics vary in different groups of gastropods. Elucidation of this diversity is key to identifying the main patterns of radula formation in Gastropoda. Of particular interest would be a phylogenetically closely related group that is characterized by high variability of the radula. One such group is the large monophyletic superfamily Conoidea, the radula of which is highly variable and may consist of the radular membrane with five teeth per row, or the radular membrane with only two or three teeth per row, or even just two harpoon-like teeth per row without a radular membrane. We studied the radulae of two species of Conoidea (Clavus maestratii Kilburn, Fedosov & Kantor, 2014 [Drilliidae] and, Lophiotoma acuta (Perry, 1811) [Turridae]) using light and electron microscopy. Based on these data and previous studies, we identify the general patterns of the radula formation for all Conoidea: the dorsolateral position of two groups of odontoblasts, uniform size, and shape of odontoblasts, folding of the radula in the radular sac regardless of the radula configuration. The morphology of the subradular epithelium is most likely adaptive to the radula type.     

Indirect evidence for ecophenotypic plasticity in radular dentition of Littoraria species (Gastropoda: Littorinidae)

In examination of radulae from all but one of the 36 speciesof the littorinid genus Littoraria we found extraordinary intraspecificvariation in those occurring on a range of substrates. Radulaefrom rock showed a less well developed `hood' on the rachidiantooth, a strikingly enlarged major cusp on each of the fivecentral teeth, fewer cusps on the outer marginal teeth and theradular ribbon was longer, when compared with radulae of conspecificsfrom plant substrates. The radulae of species found exclusivelyon rock differed in similar ways from those restricted to plantsubstrates (mangroves, driftwood and saltmarsh). We suggestthat this may be an example of phenotypic plasticity of radularform, induced by substrate and/or diet, as recently shown experimentallyin another littorinid genus. The mechanism of inducible plasticitydeserves further study. Ecotypic variation in the radula maybe widespread in littorinids, and radular characters shouldtherefore be used with caution in studies of taxonomy, phylogenyand adaptation. (Received 20 July 1998; accepted 10 November 1998)     

TRANSFER EXPERIMENT SUGGESTS ENVIRONMENTAL EFFECTS ON THE RADULA OF LITTORARIA FLAVA (GASTROPODA: LITTORINIDAE)

Phenotypic variation in radulae has been studied in severallittorinid species because of this organ's intrinsic relationshipwith diet and, consequently, with the environment. In this work,we compared the radulae of the Brazilian species Littorariaflava found in mangroves and on rocky shores. Individuals ofL. flava showed marked differences in the shape of the cuspsamong samples from rocky shore and mangrove. In a transfer experiment,the shape of the radula changed within 40 days. A differentresponse was observed in individuals transferred to mangrove,where two different phenotypes were found, suggesting eitherintrapopulational variation in the responses to change of environmentalconditions, or that some snails showed a slow reaction to theenvironmental changes. The alterations could be attributed toecophenotypic plasticity. Analysis of variance showed that thelength of the radula in L. flava was strongly influenced bythe substrate (F_6,22=17.13, P<0.000), but apparently notby the transfer experiment. (Received 3 May 2005; accepted 18 July 2005)     

Two new species of the genus <Emphasis Type="Italic">Leptochiton</Emphasis> (Mollusca,Polyplacophora) from north-western Pacific

Two new species of the genus Leptochiton, L. сommandorensis sp. nov. and L. incubatus sp. nov. from north-western Pacific are described. Leptochiton сommandorensis differs from the congeners in having radial rows of granules in the lateral areas of intermediate valves, unicuspid dental cap on major lateral teeth of the radula, and dorsal scales with two ribs. Leptochiton incubatus differs from the congeners in having one aesthete pore in each granule, a shallow depression between the central and lateral areas of intermediate valves and between the antemucronal and postmucronal areas of the tail valve, and unicuspid head of major lateral teeth of radula. This species is brooding.     

Buccal mass structure of the Cretaceous ammonite Gaudryceras

A rhynchaptychus attributed to the lower jaw of Gaudryceras sp. from the Upper Santonian rocks of Hokkaido, Japan, has an interesting impression well-preserved on the inner surface of the outer lamella. The impression is regarded as the imprints of chitin-secreting cells (beccublast cells), because of similarity in the characteristic arrangement of polygonal pits to those of modern coleoids. Each unit cell impression of G. sp. is, however, about five to ten times larger than in modern coleoids known to us. In modern coleoids and Nautilus a layer of tall beccublast cells is intercalated between the buecal muscles and the outer side of the upper jaw and/or the inner side of the lower jaw. The other sides of the jaws are, in contrast, free from jaw muscles, and are covered directly with a thin connecting tissue. Based on these observations a possible buecal mass structure of G. sp. is restored. The beccublast cell impressions of Gaudryceras and modern coleoids markedly differ from that of modern Nautilus in the absence of numerous micropores. This fact suggests weaker mechanical properties of the jaw muscles in Gaudryceras than in Nautilus , as the branching ends of beccublast cells of the latter are inserted in the micropores to keep a firm attachment of the jaw muscles on the jaw plates.     

红条毛肤石鳖齿舌主侧齿中铁还原酶分布及与生物矿化的关系

以红条毛肤石鳖Acanthochiton rubrolineatus(Lischke)齿舌为材料,通过切片和酶组织化学技术,在光镜和电镜下对齿舌主侧齿的微结构及高铁还原酶的存在进行观察,从微观角度了解齿舌主侧齿齿尖的矿化机理。结果显示,成熟主侧齿由齿尖和齿基组成。齿尖结构由外至内分为三层,最外层为磁铁矿层,前后齿面磁铁矿层的厚度不等,后齿面约50μm,前齿面约5-10μm。向内依次为棕红色的纤铁矿层,厚约10μm,及略显黄色的有机基质层,有机基质层占据着齿尖内部的大部分结构。高分辨透射电镜下显示磁铁矿由条状四氧化三铁颗粒组成,长约2-3μm,宽约100-150nm。齿舌的矿化是一个连续过程,不同部段处于不同的矿化阶段,齿舌囊上皮细胞沿囊腔分布,并形成齿片。未矿化的新生主侧齿齿尖中存在由有机基质构成的网状结构。随矿化的进行,有机基质内出现矿物颗粒。初始矿化的齿尖外表面有一个细胞微突层,微突的另一端为囊上皮细胞,矿物质经由微突层达齿尖并沉积于有机基质中,齿尖随之矿化并成熟。初始矿化齿尖的外围有大量的三价铁化物颗粒,稍成熟的齿尖外围同时还出现二价铁化物。新生或初始矿化主侧齿齿尖外围的囊上皮细胞中有大量球形类似于铁蛋白聚集体的内容物,直径0.6-0.8μm,球体由膜包围。齿舌囊上皮组织中存在三价高铁还原酶,此酶分布于上皮细胞的膜表面,可能与齿尖表面磁铁矿的生成有一定的关系。       

Beaks and radulae of Early Carboniferous goniatites

About one hundred goniatite beaks (jaws) and five radulae from the Late Mississippian (Early Carboniferous) of Arkansas wgere studied with light and scanning electron microscopy (SEM). Four beaks were found within the body chamber of the goniatite Girtyoceras. Owing to the three-dimensional preservation, these oldest known beaks could be studied in detail and compared with those in living coleoids. The beaks are univalved, and the lower one is larger than the upper. Each beak consists of an organic outer and inner lamella; only the rostrum is weakly calcified. In the lower beak the outer and inner lamellae are about the same length, but in the upper beak the outer lamella is considerably shorter than the inner lamella. The goniatite beaks resemble those in living coleoids in the relative length of the outer and inner lamellae in the upper beak, which probably indicates similarity in muscle insertion. Concerning the length of the inner and outer lamellae, the lower beak is similar to that in Vampyroteuthis and the pelagic octopod Tremoctopus. Late Mississippian goniatite beaks dealt with here are similar to those of Carboniferous and Permian goniatites in general morphology, but differ from those of Mesozoic ammonoids. In the latter ammonoids, the lower beak has a long outer lamella and a short inner lamella, whereas both lamellae have about equal length in the goniatites. Goniatite radulae remain stable during ammonoid evolution and demonstrate a more or less distinct similarity with those in living coleoids.