Die systematische Stellung von Angustiphyllum cuneiforme n. gen. n. sp., einer eigenartigen Tetrakoralle aus dem Mitteldevon Nordspaniens

The newly found tetracoralAngustiphyllum cuneiforme n. gen. n. sp. from theGosseletia-Sandstein (Couvinium) of Candás/Prov. Oviedo (Northern Spain) is described and designed an ancestor of the so called “cuneate corals”Homalophyllum Simpson, 1900,Xenocyathellus Bassler, 1937 andHomalophyllites Easton, 1944 from the Devonian and Mississippian of North-America. Because of their undoubtful genetic relations the whole group of cuneate corals is joined to the subfamily Homalophyllidae n. subfam. within the family ZaphrentoididaeSchindewolf, 1938. Evidently the evolution developed in a progressive orthogenetic manner from the new genesAngustiphyllum (Middle Devonian) toXenocyathellus (higher Middle Devonian) andHomalophyllites (Mississippian), whileHomalophyllum (Middle Devonian) separated from this line in a early stage and thenceforth had its own evolution.     

The burrowing of Nereis diversicolor O.F. Müller,together with some observations on Arenicola marina (L.) (Annelida: Polychaeta)

The mechanism of burrowing in Nereis diversicolor O.F. Müller is described. Proboscis eversion in order to make a hole in the substratum is accompanied by a coelomic pressure pulse of 1.2–7.5 kPa, compared with a value of ≈0.3 kPa during ambulatory activity. Forward movement of the tail in the later stages of burial is by longitudinal contraction, usually accompanied by a pulse of about 2 kPa. The septa appear to act as effective hydrostatic pressure barriers during burrowing.In the flange-proboscis sequences of Arenicola marina (L.) the coelomic pressure in the trunk during erection of the flanges is generally slightly higher than that in the head, while the reverse applies during the low-volume proboscis eversion. Major progression of the anterior usually occurs during the first flange-proboscis sequence of each cycle and that of the posterior early in the dilation sequence. External pressure recordings of irrigation-defaecation cycles are given.Nereis uses a similar method of burrowing to that of the free-moving Nephtys but the coelomic pulses of the former are lower, as in the rate of burial (about 0.02 cm s^?1) which is similar to that of Arenicola. Closure of the septa of Nereis during burial suggests that its burrowing mechanism is not as versatile as that of Nephtys.     

Morphological study on the Devonian zosterophyll Serrulacaulis Hueber and Banks: New materials and emendation

The generic diagnosis of the Mid–Late Devonian zosterophyll Serrulacaulis Hueber and Banks is emended based on morphological study on specimens from New York State (USA), Belgium and Venezuela, and new materials of S. spineus n. sp. from the Middle Devonian Hujiersite Formation of Xinjiang, Northwest China. The new species S. spineus has bilateral obdeltoid emergences and sparsely arranged spines on the axis surface, alternately arranged, reniform sporangia with unequal valves. A variety of the axial emergence appearances of Serrulacaulis is noted, which further indicates easily recognizable features of the genus.     

Three-dimensional morphology and palaeobiology of the trace fossil Dactyloidites jordii nov. isp. from the Carboniferous of England

The diverse ichnological assemblage from the outcrops near Howick (Northumberland, United Kingdom) is exceptionally well-preserved. Among these Carboniferous ichnotaxa is a new ichnospecies of Dactyloidites. Specimens were collected and processed using high-resolution serial grinding and photography to produce an accurate and precise three-dimensional model of these new burrows in full colour. The model produced in association with petrographic thin sections and field observations is used as the basis for comparison between Dactyloidites jordii nov. isp. and other ichnospecies of Dactyloidites. The current taxonomic status of the ichnogenus is examined and reviewed. D. jordii nov. isp. is a broadly bisymmetrical, stellate to palmate burrow composed of numerous long, narrow rays that exhibit three orders of branching arranged into tiered galleries radiating from a central shaft. The trace maker is suggested to be a vermiform organism with an adaptive burrowing strategy that facilitates alteration of its burrow construction to accommodate suboptimal sediment conditions. The adaptive nature of trace-making organisms and the inherent anisotropy of many burrowed media highlight the need for ichnologists to provide a type series rather than a single holotype, in order to capture the inherent range of common burrow morphologies.     

Patesia n. gen., a new Late Devonian stem xiphosurid genus

Xiphosura, the so-called horseshoe crabs, are a group of extant marine chelicerates that have a fossil record extending back to the Lower Ordovician. Their temporal range, coupled with a supposed record of bradytelic evolution has made them a focus of palaeontological consideration for over two centuries. As such, there are an array of taxa erected during the 20^th century that have remained unexamined in light of new material and revised phylogenetic theories. Stem xiphosurids in particular require further research to uncover the diversity and disparity of non-crown group horseshoe crabs. To align with the recent increase in mid to late Paleozoic horseshoe crab research, we reconsider the stem xiphosurids “Kasibelinurus” randalli and “Bellinurus” alleganyensis from the Late Devonian of Pennsylvania and New York State. We conclude that they are synonyms and belong in neither Kasibelinurus nor Bellinurus, and the new genus, Patesia, is erected to accommodate them. Reconsidering stem xiphosurids highlights that particularly in the Late Devonian there was a high disparity of form. One such stem xiphosurid may represent the morphological stock that gave rise to the Carboniferous taxa and the first xiphosurid radiation.     

Serrulacaulis furcatus gen. sp. nov., a New zosterophyll from the lower upper devonian of New York state

A new zosterophyll is described from the lower Upper Devonian of New York. Serrulacaulis furcatus is characterized by two rows of emergences which are opposite in arrangement and attached on opposite margins of the axis. They are deltoid in side view and are contiguous vertically, giving the stem a scalloped or saw-toothed appearance. Epidermis over much of the plant consists of elongate cells and interspersed isodiametric cells. The vascular strand consists of spirally thickened tracheids. Rhizomes are densely covered by rhizoids that are more numerous on small papillae and at the apex of tooth-like emergences. Aerial axes terminate in circinate apices. Some axes bear short-stalked, reniform sporangia arranged alternately in two rows on one side of the axis only. The dehiscence zone is a thickened rim over the distal, convex margin of the sporangium. Dehiscence is basipetal, producing two equal valves. Spores are smooth to slightly granulate, circular to subtriangular, with a trilete mark that extends $\text{1}\text{3}$–$\text{1}\text{2}$ the radius and is surrounded by a darkened triangular area. Sawdonia ornata, described earlier from the same quarry, and now Serrulacaulis, are the two genera of zosterophylls proven to occur in Late Devonian time. The world-wide distribution of zosterophylls and the fact that the group is a natural one are reviewed.     

Evidences of habitat displacement between two common soft-bottom SW Atlantic intertidal crabs

The intertidal burrowing crab Chasmagnathus granulatus Dana is the dominant species in soft sediments and vegetated intertidal areas along the SW Atlantic estuaries (southern Brazil 28°S to the northern Argentinean Patagonia 41°S) where it produces dense and extensive burrowing beds. The mud crab Cyrtograpsus angulatus Dana coexists with Ch. granulatus in this area, but it also inhabits areas to the south (northern and central Argentinean Patagonia). A survey covering both areas showed that C. angulatus rarely live in burrows when coexisting with Ch. granulatus, but form large burrowing beds when not coexisting with Ch. granulatus. When both species coexisted, burrowing beds of C. angulatus are restricted to sandy-muddy areas. Only rarely are burrows of C. angulatus found within Ch. granulatus beds. However, when Ch. granulatus were experimentally excluded within their burrowing beds, new settlers of C. angulatus made burrows and maintained them until they reached large size. Paired (inside and outside Ch. granulatus burrowing bed) sampling during high tide using beach nets showed that C. angulatus rarely venture inside the Ch. granulatus crab beds. Other field experiments showed that adults Ch. granulatus always displace C. angulatus from burrows. Furthermore, in several sites located south of the limit of distribution of Ch. granulatus at the Patagonian coast, soft bare intertidals are dominated by burrowing beds of C. angulatus mixed with the congener C. altimanus Dana. Together, these evidences suggest that the mud crab C. angulatus is displaced from soft bottom areas by the burrowing crab Ch. granulatus. It is an example of competitive exclusion through aggressive interference in soft-bottom habitats when the shared resource is the access to sediment surface, a two-dimensional well-defined resource.     

HYDRAULIC BURROWING IN THE BIVALVE MYA ARENARIA LINNAEUS (MYOIDEA) AND ASSOCIATED LIGAMENTAL ADAPTATIONS

The burrowing behaviour of the bivalve Mya arenaria from tidalflats of the Dutch Wadden Sea has been observed and recorded.Compared to other bivalves, M. arenaria is a very slow burrower,its burrowing behaviour being unique among bivalves since itis based essentially on the ejection of water through the pedalgape, with little assistance by the foot, which performs onlyan anchoring function. Water ejection is specially powerfuland individual jets may last several seconds, thus constitutingan effective means of removing sand from below the animal duringdigging. This hydraulic burrowing is more effective in loosesandy than in cohesive muddy substrates. Water ejection is providedby the ability of the bivalve to rock its valves across a dorsoventralaxis. This rocking motion implies special modifications of theligamental area. The ligament is conical in appearance and runsdorso-ventrally between the two chondrophores which are placedin two planes parallel to the cardinal axis. During rockingthe whole ligament acts in torsion and the lamellar layer ofthe ligament opposes closing of the anterior part of the valves.During normal adduction of the valves the ligament acts in bending,the axis of motion being placed internally with respect to thecardinal axis. This leads to approaching of the umbones withcomplete adduction and to resorption of the left umbo. Fromthe adaptive point of view, the slow hydraulic mode of burrowingis sufficient to cope with the slow sedimentation and erosionrates of the tidal flats in which M. arenaria lives. This burrowingmode implies the existence of a tiny foot, which leaves roomfor other organs within the mantle cavity. This, together withanterior divarication of the valves permits a large volume ofwater to be ejected from the mantle cavity, but, in the caseof M. arenaria, also the existence of an enormous stomach, possiblyas an adaptation for food processing. (Received 12 April 1996; accepted 2 October 1996)     

Seasonal thermoregulation in the burrowing parrot (Cyanoliseus patagonus)

Birds exposed to seasonal environments are faced with the problem of maintaining thermogenic homoeostasis. Previous studies have established that birds native to the Holarctic increase their Resting Metabolic Rate at different ambient temperatures (RMR_Ta) and Basal Metabolic Rate (BMR) in winter as an adaptation to cold temperature since winters are more severe, while their non-Holarctic counterparts generally decrease their winter BMR as an energy saving mechanism during unproductive and dry winter months. In this study, we examined seasonal thermoregulation in the burrowing parrot (Cyanoliseus patagonus), a colonial psittacine native to the Patagonian region of Argentina, a region with an unpredictable environment. We found significantly higher mass specific RMR_Ta and BMR in summer than in winter. Both summer and winter BMR of the species fell within the predicted 95% confident interval for a parrot of its size. Body mass was significantly higher in winter than in summer. The burrowing parrot had broad thermo-neutral zones in winter and summer. The circadian rhythm of core body temperature (T_b) of burrowing parrots was not affected by season, showing that this species regulated its T_b irrespective of season. These results suggest that the burrowing parrots' seasonal thermoregulatory responses represent that of energy conservation which is important in an unpredictable environment.     

Brachiopod ecology in mid-Palaezoic sediments near Khenifra,Morocco

The modes of occurrence of a Silurian atrypid and a Devonian rhynchonellid near Khenifra in central Morocco are described. They are both thought to have lived on isolated shoals within muddy basins. A substrate for brachiopod attachment in each case was provided by lime-secreting algae. Most of the Devonian rhynchonellids are preserved in olistostromes, within Carboniferous shales, but some are in situ. The rhynchonellid, which is identified as Eoperegrinella, is thought to have taken over the ecological niche previously occupied by the atrypid, identified as Dubaria, during Devonian times. Descendent rhynchonellids of the same group in the Mesozoic lived in a similar way.     

A new genus of Early Devonian plants with novel strobilar structures and vegetative appendages from the Posongchong Formation of Yunnan,China

A new plant, Dibracophyton acrovatum gen. et sp. nov., is described from the Lower Devonian (Pragian) Posongchong Formation of Wenshan District, southeastern Yunnan, China. The plant has creeping axes from which arise vegetative and fertile axes. The vegetative axes helically bear lateral dichotomous appendages with curved or round tips. The fertile axes possess terminal strobili with numerous fertile units arranged in irregular helices. Each fertile unit consists of a stalked long-elliptical sporangium, with dehiscence into two equal valves, and two discrete long-ovate bracts covering sporangium from above–below directions. A new genus and species is thus established based on these characters and is temporarily regarded as incertae sedis of Tracheophyta, although it perhaps closes to the barinophytes in affinity. Detailed comparisons with other plants having a similar architecture, i.e., sporangia closely associated with modified vegetative structures, are made. The discovery of D. acrovatum further enriches the composition of the Posongchong flora and demonstrates great morphological disparity of the Early Devonian vascular plants.     

Fluctuations in a late devonian-early Mississippian phytoplankton flora of Ohio,U.S.A

Fossil diversity and abundance fluctuations of Late Devonian (Famennian)—Early Mississippian (Tournaisian) phytoplankton assemblages were determined in a stratigraphic sequence of samples in Barberton test core 3, from northeast Ohio. Both diversity and abundance were relatively high during deposition of the lower Chagrin Shale (Upper Devonian) and both decreased during deposition of the upper Chagrin Shale. The overlying Cleveland Shale (Upper Devonian) is characterized by sharply increased abundance with a corresponding (although less marked) increase in diversity; in contrast, both abundance and diversity were at relatively low levels during deposition of the Lower Mississippian Bedford Shale, the uppermost unit of the sequence. These trends agree with the phytoplankton periodicity model presented by Tappan, which indicates large-scale extinction at the end of the Devonian.Many of the acritarch and prasinophycean algal taxa have restricted stratigraphic occurrences within the section studied, making them useful for local and perhaps worldwide correlation. The stratigraphically restricted taxa provide a basis for the proposal of five biostratigraphic zones within the Upper Famennian (Upper Devonian) and a portion of the Lower Mississippian. In ascending order occur: the Gorgonisphaeridium ohioense Assemblage Zone, the Acriora petala Assemblage Zone, the Muraticavea enteichia Range Zone, the Cymatiosphaera labyrinthica Range Zone, and the Navifusa drosera Assemblage Zone.     

Gladioscutum lauriei n.gen. n.sp. (Archaeocopida) from the Middle Cambrian of the Georgina Basin,central Australia

A small crustacean with extremely long anterodorsal spines occurs in the Middle Cambrian of the western part of the Georgina Basin. It is assigned to the new genusGladioscutum (type speciesG. lauriei n. sp.), and is described from a sample collected from the Arthur Creek Formation, in the Huckitta area of the Northern Territory. The carapaces, preserved as flattened, outspread valves on the surface of finely laminated, dark grey micritic limestone, are comparable with those of Archaeocopida and Archaeostraca. On the basis of gross carapace morphology, an archaeocopid relationship is preferred.     

Lectin Binding to Radopholus citrophilus and R. similis Proteins

Lectin-binding glycoproteins in seven populations of two burrowing nematode sibling species were probed with five different biotinylated lectins on Western blots, and differences were correlated with nematode ability to parasitize citrus and to overcome citrus rootstock resistance. Banding patterns of molecular weight standards were fit best by an exponential decay function, and a predictive equation was used to estimate molecular weights (r² = 0.999). A band (131 kDa) that labeled with the lectin Concanavalin A (Con A) occurred in extracts from cuticles and egg shells of populations of Radopholus citrophilus that parasitize citrus. Wheat germ agglutin labeled a band (58 kDa) in aqueous homogenates of populations that reproduce in roots of citrus rootstock normally resistant to burrowing nematodes. The two sibling species R. citrophilus and R. similis were distinguished by a high molecular weight Con A-labeled band (608 kDa) from cuticle and egg shells. Probing blots with the lectin Limulus polyphemus agglutinin indicated that each population contained a band (12-16 kDa) specifically inhibited by the addition of 25 mM neuraminic acid, suggesting that glycoproteins with sialic acid moieties are present in burrowing nematodes.     

Regressive astogenese beiNudonychocella n.g.n.sp. und anderen bryozoen aus der tuffkreide von maastricht

Nudonychocella nuda n.g.n.sp. from the Maastrichtian chalk tuff is a cheilostome bryozoan species which shows totally opened “membranimorph” zooecia and avicularia. Its ancestrula, however, displays — likeOnychocella Jullien — semicircular opesiae and normally formed calcified frontal walls (cryptocysts), revealing its lineage from this genus which belongs to the Coilostega. This is suggested to be a matter of regressive astogeny, unknown until now in bryozoology, during which the calcareous cryptocyst, being characteristic for that genus, was totally reduced.Onychocella cyclostoma (Goldf.) andO. koninckiana (v. Hagenow) also show the tendency to reduce their calcareous frontal walls which are still widely normal during the neonastic stage of the colony. InCastanopora bipunctata (GOLDF.), however, the cribrimorph frontal shield may disappear totally. A satisfactory explanation of this phenomenon may be that the neonastic stage characterising the peripheral growing tip of the colony with its incompletely calcified frontal walls of the zooids dominated the whole colony, induced by a stop of the calcification of the cryptocyst, with the exception of the ancestrula, the result of which being a secondary membranimorph stage, characteristic for the Malacostega. The reduction of the calcification does not contradict to Dollo’s rule concerning the irreversibility of the evolution. Consequences arising for taxonomic questions and phylogenetic research are discussed.     

Development of successive cambia and pattern of secondary growth in the stem of the Neotropical liana Rhynchosia phaseoloides (SW.) DC. (Fabaceae)

The occurrence of flattened stems in Rhynchosia phaseoloides (SW.) DC. (Fabaceae) has been known for years, but little interest has been shown toward elucidating its secondary growth. This study aims to (1) understand the pattern of secondary growth and development of vascular elements from the cambium at different stages of stem growth and (2) elucidate the type, size and distribution of cells related to these processes at different regions of the stem. Dilatation growth in main stems and branches of R. phaseoloides is achieved by successive cambia formed in two areas of the actual cortex that are opposed to each other by approximately 180°. Only the first cambial ring is functionally normal and closed-elliptical in outline, supporting the growth of the middle part of the rather flat stem. Later on, this stem becomes oval to oblong in cross-section outline by the activity of successive cambia from which cells produce further xylem, phloem and parenchyma tissues in a somewhat fan-shaped way. As shown in cross section, a flat cable-like structure of several modules results, forming wings relative to the primary central axis tissues. The secondary cambia are formed by dedifferentiation of cortical parenchyma cells, resulting in small clusters of radially arranged meristematic bands of cells. From these meristematic bands, an outward-facing crescent-shaped new band of cambium is originated. The innermost cells of this meristematic band form the parenchymatic tissue that connects the new lateral module to the proximal one. This occurs several times during the whole stem ontogeny.     

Kinematics of swimming in two burrowing anguilliform fishes

Anguilliform or eel-like fishes are typically bottom dwellers, some of which are specialized burrowers. Although specializations for burrowing are predicted to affect the kinematics of swimming, it remains unknown to what extent this is actually the case. Here we examine swimming kinematics and efficiency of two burrowing anguilliform species, Pisodonophis boro and Heteroconger hassi, with different degrees of specialization for burrowing. Our data suggest that differences in the swimming kinematics may indeed be related to the differences in burrowing specialization and style between both species. The resemblance between the swimming kinematics of P. boro and previously published data for Anguilla anguilla and Anguilla rostrata may be linked with the relatively limited burrowing specialization of P. boro and suggests an overall stereotypy in anguilliform forward-swimming patterns. The body of H. hassi, in contrast, is more specialized for tail-first burrowing and backward swimming bears a striking resemblance to the backward burrowing motions observed in this species. These motions differ significantly from backward swimming in Anguilla and in P. boro. The kinematics of forward swimming are, however, comparable across species. Thus, our data suggest that specializations for burrowing may affect swimming kinematics in anguilliform fishes, but also that forward swimming and burrowing are not necessarily incompatible. Future studies comparing the kinematics and mechanics of burrowing in these and other anguilliform fishes are needed to better understand how specializations for burrowing constrain backward swimming in H. hassi.