An intermittent mode of formation for the trace fossil Cruziana as a serial repetition of Rusophycus: the case of Cruziana tenella (Linnarsson )

Cruziana is one of the most recognizable trace fossils ascribed to arthropods. It ranges throughout the Phanerozoic and encompasses a diverse set of morphologies. The distinct features of Cruziana have incited fierce debate regarding its mode of formation. Here, we discuss critical aspects of trace fossil formation, namely epibenthic versus endobenthic origin and the ethology of the producer. Cruziana has largely been interpreted as a continuous ploughing trace fossil. It has been suggested, however, that at least some Cruziana could be structures resulting from the concatenation of Rusophycus‐type elements, although this claim remains unexplored. Cruziana tenella from the lower Cambrian of south‐central Sweden illustrates this intermittent mode of formation with a series of Rusophycus eutendorfensis leading into vertically undulating Cruziana that, at end stages of development, reflect a relatively equal depth distribution throughout the trace fossil and a great number of intergrading morphologies. In this study, a morphological evaluation of the intergrading morphologies of Cruziana tenella and Rusophycus eutendorfensis and a short morphometric analysis of the elements comprising Cruziana tenella suggests that at least in some cases Cruziana could be formed in intervals, as the serial overlap of distinct shallow Rusophycus could produce an apparently continuous cruzianaeform morphology. A comparison with possible evidence of intermittent formation on Cruziana semiplicata is made to illustrate the possibility of extending this mode of formation to larger Cruziana. An argument for the rise in the early Cambrian of a primitively intermittent mode of formation is made on the basis of energy efficiency.     

Deep Endichnial Cruziana from the Lower-Middle Ordovician of Spain — A Unique Trace Fossil Record of Trilobitomorph Deep Burrowing Behavior

Full reliefs of Cruziana furcifera from the Lower-Middle Ordovician quartzite sandstone beds (Pochico Formation, southern Spain) points to deep, infaunal burrowing of trilobites. Some specimens show an unusual vertical extension with a wider lower part and a narrower upper part in cross section. They are referred to trilobites, which burrowed deeply in the sediment and were oriented obliquely head down and tail up. Deep burrowing seems to be common for other members of the Cruziana rugosa group, foremost C. rugosa and C. furcifera, less for C. goldfussi. The deep burrowing recorded in the discussed trace fossils can be referred to the earliest common infaunalization caused by trilobites and other arthropods during the Ordovician, probably in a response to a food competition on the sea floor, which promoted a behavioral plasticity within the same taxon or closely related taxa of trilobites.     

Ichnology and sedimentology of a tide‐influenced delta in the Ordovician from the northeastern Alborz range of Iran (Kopet Dagh region)

The Middle–Late Ordovician Ghelli Formation in the Kopet Dagh region northeastern Alborz range of Iran is composed of siliciclastic rocks deposited in a variety of turbidite to marginal marine environments (deep marine clastic fan and related environments and prodelta, distal delta front, proximal delta front and distributary channels). The ichnology of the middle member of the Ghelli Formation is here reported. Combined sedimentological and ichnological analysis allows recognition of a tide‐influenced deltaic succession in the middle member of the Ghelli Formation consisting of three main facies associations: lower distributary channels, delta front and prodelta facies. Twenty‐two ichnogenera have been identified in this marginal marine succession: Arenicolites, Arthrophycus, Bergaueria, Chondrites, Conichnus, Cruziana, Cylindrichnus, Didymaulichnus, Diplichnites, Diplocraterion, Helminthopsis, Gyrochorte, Lockeia, Macaronichnus, Monomorphichnus, Palaeophycus, Planolites, Rosselia, Rusophcus, Skolithos, Teichichnus and ?Scolicia. Their distribution is clearly linked with lithofacies and depositional palaeoenvironments. The ichnological analysis reveals that the trace fossil suites developed in these environments indicate low diversity and low to moderate abundance of burrows, poor development of tiering and sporadic distribution. Low ichnodiversity and low bioturbation intensities with higher bioturbation clusters consist of facies‐crossing ichnogenera, and the impoverishment of suspension‐feeding trophic types indicates ‘stressed’, non‐archetypal expression of the Cruziana ichnofacies. The periodic higher intensities of bioturbation due to variations in hydrodynamic regimes of tidal currents reflect the archetypal of the Cruziana ichnofacies (and rare Skolithos ichnofacies).     

Arthropod Trace Fossils of the Upper Lower Cambrian Gog Group,Southern Rocky Mountains of Canada

The upper lower Cambrian Gog Group in the southern Rocky Mountains of Canada displays a high diversity and abundance of arthropod traces. Four ichnogenera, Cruziana, Diplichnites, Monomorphichnus, Rusophycus, and “Indeterminate Arthropod Scratches” are discussed, with a total of 17 different ichnospecies, as follows: Cruziana billingsi Fillion and Pickerill, 1990, Cruziana irregularis Fenton and Fenton, 1937, Cruziana jenningsi Fenton and Fenton, 1937, Cruziana navicella Fenton and Fenton, 1937, Cruziana omanica Seilacher, 1970, Cruziana pectinata Seilacher, 1994, Cruziana penicillata Gibb, Chatterton, and Pemberton, 2009, Cruziana plicata Crimes, Legg, Marcos, and Arboleya, 1977, Cruziana tenella Linnarsson, 1871, Diplichnites twelvetreesi (Chapman, 1928), Monomorphichnus bilinearis Crimes, 1970b, Monomorphichnus lineatus Crimes, Legg, Marcos, and Arboleya, 1977, Rusophycus eutendorfensis (Linck, 1942 Linck, O. 1942. Die spur Isopodichnus. Senckenbergiana, 25: 232–255. [Google Scholar]), and Rusophycus unilobus (Seilacher, 1970 Seilacher, A. 1970. Cruziana stratigraphy of “non-fossiliferous” Palaeozoic sandstones. In Crimes, T. P. and Harper, J. C. (eds.), Trace Fossils. Seel House Press, Liverpool, 447–476. [Google Scholar]). Three new ichnospecies, i.e., Cruziana caputinclinata isp. nov., Rusophycus subnotous isp. nov., and Diplichnites obliquus isp. nov., are proposed, described, and illustrated. The ichnofauna collected from three localities (Lake O'Hara, Mount Babel, and Redoubt Mountain) are predominantly Cruziana. Evidence of nutrient-rich substrates containing microbially induced sedimentary structures and the ichnospecies present confirm that the trace fossil bearing strata are part of the Cruziana ichnofacies and were deposited in a fully marine basin between fair weather wave base and storm wave base.     

Controls on trace fossil diversity in an Early Cambrian epeiric sea: new perspectives from northwest Scotland

The Lower Cambrian Eriboll Formation of northwest Scotland is renowned for the high density, low diversity trace fossils (Skolithos ichnofacies) found in its upper Pipe Rock Member. Ichnofabric analysis of the member indicates that relatively small examples of Skolithos terminating at the same foreset boundary were formed during a brief colonization window after a single depositional event, that particularly long Skolithos specimens are equilibrichnia, and that palimpsests of Skolithos represent the marginal, slightly deeper water fringes of the Pipe Rock Member depositional environment. Nearest neighbour analysis, however, suggests that such palimpsests were uncommon. A much more diverse trace fossil assemblage is present in the overlying Fucoid Member (An t‐Sròn Formation), comprising Cruziana barbata, Dactylophycus, Didymaulichnus, Halopoa imbricata, ?Margaritichnus, Monocraterion, Monomorphichnus, Palaeophycus striatus, P. tubularis, ?Phycodes, Planolites montanus, ?Polarichnus, Rusophycus ramellensis, ?Psammichnites, Skolithos and various unidentified traces, and represents the Cruziana ichnofacies. Above the Fucoid Member, the Salterella Grit Member ichnofauna is more impoverished, yielding only Cruziana, Monocraterion, Rusophycus, Skolithos and ?Spirophyton. The ichnological variations between the Pipe Rock, Fucoid and Salterella Grit members are interpreted as being driven by changes in sea level. The low trace fossil diversity in the Pipe Rock Member indicates opportunistic colonization of laterally extensive, shoreface sediments deposited by regular influxes of terrigenous material, which were overlain by more distal, ichnologically diverse sediments (Fucoid Member) as sea level rose. A minor regression then caused an increase in terrigenous sediment input, producing an impoverished, proximal Cruziana ichnofacies (Salterella Grit Member).     

Conichnus Männil 1966, not conichnus Myannil 1966

Vertically curved, unbranched, strongly lined burrows are prominent features of muddy outer‐shelf/offshore deposits of Cretaceous to Pleistocene age. Such burrows are usually called Terebellina, but use of this ichnogenus should be avoided for two reasons: 1) the type species of Terebellina is a large agglutinated foraminiferid referable to Bathysiphon, not a trace fossil; and 2) most trace fossils identified with Terebellina are either examples of Palaeophycus (in cases where burrows are essentially horizontal and occur individually) or Schaubcylindrichnus (where burrows are oblique to stratification and occur in aggregations or loose clusters). The replacement name S. freyi is proposed for this latter category of burrow.

These light‐colored, grain‐lined burrows are conspicuous structures in the dark‐colored, outer‐shelf mudrocks of the lower Pleistocene Rio Dell Formation. The burrows are part of a typical “distal Cruziana ichnofacies”; association of structures, including Teichichnus, Planolites, Palaeophycus, and Chondrites, occurring in thoroughly bioturbated background sediments. Schaubcylindrichnus freyi in the Rio Dell is interpreted as the dwelling structure of a gregarious, endobenthic organism, comparable to the lined burrows produced by the deposit‐feeding polychaete Clymenella.     

Devonian Trace Fossils of the Horlick Formation,Ohio Range,Antarctica: Systematic Description and Palaeoenvironmental Interpretation

The clastic Horlick Formation contains an ichnofauna of 28 ichnotaxa dominated by burrowers. These are a mixture of simple vertical forms (Skolithos linearis, S. magnus, Bergaueria cf. langi, Rosselia socialis, Monocraterion isp.), U or arc-like forms (Diplocraterion parallelum, Arenicolites types A and B, Catenarichnus antarcticus, C. isp., aff. Lanicoidichna isp.), and complex, vertical spiral structures (Asterosoma isp., Spirophyton isp.). Horizontal burrows include Ancorichnus cf. capronus, Palaeophycus tubularis, and Psammichnites devonicus isp. nov. Surface traces comprise Haplotichnus isp., Cruziana problematica, C. rhenana, Rusophycus aff. carbonarius, R. isp., Protovirgularia rugosa, Lockeia ornata and cubichnia indet., while trackways include Diplichnites gouldi, D. isp., Maculichna? isp. and large imprints. The Horlick Formation (maximum 56 m) records an early Devonian transgression onto a deeply weathered land area that lay in the direction of Marie Byrd Land, spreading from the South Africa sector of Gondwana. Analysis of the trace fossils confirms their formation in near-shore to intertidal environments, with some ichnotaxa living close to the marine/fluvial boundary (e.g., Spirophyton, aff. Lanicoidichna, Cruziana problematica, Rusophycus aff. carbonarius, Maculichna?). The ichnofauna probably comprised a variety of marine suspension and deposit-feeding worms, shallow burrowing molluscs (bivalves and possibly bellerophontids) and several different types of arthropods, including trilobites.     

Spatial distribution and habitat preference of the endangered tarantula, Brachypelma klaasi (Araneae: Theraphosidae) in Mexico

Brachypelma, a genus of nine endangered tarantula species in Mexico, is the only group of spiders included in Appendix II of CITES, owing to habitat degradation and illegal trafficking. However, while the majority of the nine species of Brachypelma are thought to be threatened, little is known of their ecology and distribution. Brachypelma klaasi is the rarest species, occurring in a few isolated populations on the Pacific coast of Mexico. We present an analysis of population distribution and micro-habitat requirements of B. klaasi over different spatial scales within the biological reserve at Chamela, Jalisco as part of a wider ecological study of the endangered Brachypelma group. Burrows and dispersing spiders were confined to a southern area of the reserve covering approximately 0.5 km². Within this area, burrows were not aggregated at lower spatial scales (2⁴–2¹⁶ m²), unlike other related species. Also, there was no evidence that intra-specific interactions (either positive or negative interactions) influenced the distribution of burrows. Distribution of burrows at low spatial scales was related to low afternoon temperatures and high humidity in mid-summer. These abiotic factors may influence the survival and development of eggs and spiderlings, and appear to be more important in governing the distribution of B. klaasi than are food resources or intra-specific interactions. We discuss how these findings may facilitate the re-introduction of captive-bred individuals of B. klaasi and other Brachypelma species.     

Onshore expansion of benthic communities after the Late Devonian mass extinction

A detailed ichnological analysis of the Upper Devonian–Lower Mississippian Bakken Formation of sub‐surface Saskatchewan and the partially coeval Exshaw Formation of Alberta indicates the presence of an anomalous ichnofacies gradient. The distal Cruziana Ichnofacies, which in rocks of other ages is restricted to lower‐offshore facies, here ranges from this setting to the lower shoreface. No archetypal Cruziana Ichnofacies is present in these deposits. This pattern is interpreted as resulting from the differential effects of the Late Devonian mass extinction in shallow‐water ecosystems. The onshore expansion evidenced by ichnological data is consistent with the pattern displayed by the body‐fossil record, which indicates a re‐invasion of shallow‐water environments by the Palaeozoic evolutionary fauna during the Late Devonian and into the Early Carboniferous. The ichnofauna studied is overwhelmingly dominated by deposit feeders, with suspension feeders being notably absent, further underscoring the importance of trophic type as a selectivity trait during mass extinctions.     

Burrow construction and behavior of tilefish,Lopholatilus chamaeleonticeps,in Hudson Submarine Canyon

Synopsis During 22 daylight submersible dives in August 1979 numerous juvenile and adult tilefish, Lopholatilus chamaeleonticeps, were observed in and around vertical burrows in the clay substrate of portions of Hudson submarine canyon in depths from 110–230 m. The size and shape of the burrows varied considerably with the smallest juveniles occupying simple vertical shafts in the substrate. Larger fish were found in much larger burrows (up to 4–5 m in diameter and at least 2–3 m deep) that were funnel shaped in cross-section with the upper conical portions containing numerous smaller burrows of associated crabs. The range of burrow sizes observed suggests a regular sequence of burrow construction by tilefish and the associated crabs. Both juvenile and adult tilefish swam into the burrows head first and exited tail first. This behavior, which would preclude the possibility of ambushing prey, and evidence of predation by sharks and other tilefish, suggests that the burrow is a refuge from predators.Tilefish burrows appear to serve as a focus for biological activity. Species associated with the burrows included galatheid crabs, Cancer sp., Acanthocarpus alexandri, Homarus americanus, Heliocolenus dactylopterus and Conger oceanicus. Tilefish may play an important role in structuring outer continental shelf communities. They physically shape their environment and probably have significant biological interactions with the species that associate with their burrows.     

Habitat mediates the outcome of a cleaning symbiosis for a facultatively burrowing crayfish

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Territorial Pheromones of Female Red-backed Salamanders

Pheromones provide an important source of communication during social interactions of caudate amphibians. To further examine their use in territorial defense, we performed a laboratory experiment to test the hypothesis that non-courting female red-backed salamanders (Plethodon cinereus) deposit pheromones in or on fecal pellets, as males are known to do during territorial advertisement. Four conditions were tested: (1) a burrow marked with a female's own pellet vs. a burrow marked by a conspecific female's pellet, (2) own vs. unmarked burrows, (3) conspecific vs. unmarked burrows, and (4) paired unmarked burrows as a control. Females nose-tapped (for olfactory cues) their own and conspecific pellets about equally. However, they spent significantly more time in both threat and submissive behavior toward the conspecific pellets and spent significantly more time in their own marked burrows. We infer that female P. cinereus do deposit pheromones in or on fecal pellets and that these pellets may be used to advertise territories. The behavioral responses of females toward pellets of other females were more aggressive than those of males (in a previous study) toward pellets of other males.     

Phenotypic plasticity and nutrition in a phytophagous insect: consequences of colonizing a new host

The European rose-hip fruit fly Rhagoletis alternata (Diptera, Tephritidae) infests hips of Rosa species. This fly includes R. rugosa, an Asian species now cultivated all over Europe, in its host range. Differences in size and biomass of hips between the ancestral host R. canina and the new host translate into better growth, shorter larval development of larvae within hips of R. rugosa and larger body size and fertility of flies which developing in the new host. In turn this causes different interactions with other organisms of the food-web centred on the host plant. The importance of nutrition and phenotypic plasticity is twofold: they generate a considerable part of life-history diversity within a species and reinforce differences in the ecological context of the ancestral and new host.     

Characterization of chemical defenses in ranid tadpoles against a fish predator

Tadpoles of some ranid species appear to possess chemical defenses against fish predators, but the chemicals have not been characterized. Here, we evaluated the vulnerability of three Japanese anuran tadpole species (Glandirana rugosa, Pelophylax nigromaculatus, and Hyla japonica) to a fish (Gnathopogon elongatus elongatus) and analyzed the defensive chemicals extracted from the unpalatable tadpoles. Additionally, we examined the defensive behavior of unpalatable tadpoles in response to fish chemical cues. The fish rejected both G. rugosa (83%) and P. nigromaculatus (48%), but not H. japonica (0%). Many of the rejected tadpoles survived (60–80%). Possible defensive chemicals were extracted by methanol from the skin of G. rugosa, but were not identifiable by gas chromatography–mass spectrometry because of small quantities. The chemicals have high polarity and non-volatility. When exposed to fish chemical cues, P. nigromaculatus decreased activity presumably as a defensive behavior, but G. rugosa did not. We demonstrated the presence of chemical defenses in at least two of these species and revealed that G. rugosa releases more effective or greater amounts of defense chemicals than P. nigromaculatus with respect to this fish predator. The increased efficacy of chemical defenses may correlate with decreasing defensive behavior.     

Effects of the subterranean herbivorous rodent Spalacopus cyanus on herbaceous vegetation in arid coastal Chile

Summary The impact of the subterranean herbivorous rodent Spalacopus cyanus Molina on the herbaceous vegetation was studied by comparing biomass, species richness and species diversity at the end of the growing season in areas with and without burrows in coastal arid Chile. Total biomass was 60% higher in areas with burrows. This difference was mainly due to the large increase of Mesembryanthemum cristallinum L., a succulent prostrate annual herb. Unexpectedly, bulb biomass of geophytes, eaten by Spalacopus, did not differ between areas. However, in areas with burrows bulbs of geophytes were more numerous and smaller. It is possible that burrowing activities facilitate the occurrence of new small bulbs through seed germination. Species composition and diversity did not differ greatly between areas. Burrowing activities by Spalacopus, the life cycle of Mesembryanthemum, and climate seem to be the most important factors determining species abundance and diversity of herbs in this system.This is a contribution of the Program of Arid Zone Studies of Universidad de La Serena     

Hybridization with invasive Rosa rugosa threatens the genetic integrity of native Rosa mollis

Hybridization between invasive and native species often has severe consequences on fitness and survival of the native relative. We investigated the extent of hybridization between the neophyte Rosa rugosa and native R. mollis, an endangered species in Germany. Rosa mollis is found in only one large population in Germany close to the Baltic coast, which has been heavily invaded by R. rugosa for at least 60 years. We analysed all individuals of R. mollis from this mixed population using microsatellite markers and morphological characters and compared these data with those from allopatric populations of R. mollis and R. rugosa. In the mixed population we identified nine plants (45% of the population) as hybrids between R. mollis (seed parent) and R. rugosa (pollen parent) by the presence of microsatellite alleles private for R. rugosa. These individuals were also morphologically intermediate between the parental species. Gene flow from R. mollis into R. rugosa was negligible. We detected a very low genetic diversity and a low number of seeds per hip in the mixed population of R. mollis, pointing to genetic depletion and low fitness. In the light of these results and the difficulties in removing invasive R. rugosa from European coastlines, we discuss possible conservation strategies for this endangered population. © 2012 The Linnean Society of London, Botanical Journal of the Linnean Society, 2012, 170 , 472–484.     

Burrowing owls and burrowing mammals: are ecosystem engineers interchangeable as facilitators?

Terrestrial vertebrates exhibit dynamic, positive interactions that form and dissolve under different circumstances, usually with multiple species as participants. Ecosystem engineers are important facilitators of other species because they cause physical changes in the environment that alter resource availability. Although a species can be associated with more than one partner, facilitators may not be interchangeable if they differ in abundance, behavioral characteristics, or interactions with other factors in ways that condition the outcome of the association. We examined interactions between burrowing owls (Athene cunicularia) and two burrowing mammals, hairy armadillos (Chaetophractus villosus) and plains vizcachas (Lagostomus maximus), and determined whether these ecosystem engineers are interchangeable for owls. We examined reproductive success for owls nesting in these mammal burrows, constructed a logistic regression model to identify habitat characteristics associated with owl nests, and examined the engineering activities of the mammals. Data on reproduction and habitat indicate that armadillos and vizcachas are not interchangeable for owls. Thirty-five percent of the nests in vizcacha burrows produced fledglings; no fledglings were produced from nests outside vizcachas colonies, even though owls nest successfully in armadillo burrows in other parts of Argentina. Vizcachas facilitate burrowing owls by construction of burrows and by producing open understory vegetation through herbivory. In contrast, armadillos do not alter vegetation, and their burrows are suitable for nest sites only when they occur in recently burned areas or areas maintained by anthropogenic disturbance. Our habitat model also suggests that fire plays a key role in maintaining owl populations because fire is the only natural process that reduces shrubs to the level required by owls. Current management practices of eradication of vizcachas and fire suppression in shrublands could have strong negative consequences for burrowing owls.     

A comparative study on the phylogenetic diversity of culturable actinobacteria isolated from five marine sponge species

A cultivation-based approach was employed to compare the culturable actinobacterial diversity associated with five marine sponge species (Craniella australiensis, Halichondria rugosa, Reniochalina sp., Sponge sp., and Stelletta tenuis). The phylogenetic affiliation of the actinobacterial isolates was assessed by 16S rDNA-RFLP analysis. A total of 181 actinobacterial strains were isolated using five different culture media (denoted as M1–M5). The type of medium exhibited significant effects on the number of actinobacteria recovered, with the highest number of isolates on M3 (63 isolates) and the lowest on M1 (12 isolates). The genera isolated were also different, with the recovery of three genera on M2 and M3, and only a single genus on M1. The number of actinobacteria isolated from the five sponge species was significantly different, with a count of 83, 36, 30, 17, and 15 isolates from S. tenuis, H. rugosa, Sponge sp., Reniochalina sp., and C. australiensis, respectively. M3 was the best isolation medium for recovery of actinobacteria from S. tenuis, H. rugosa, and Sponge sp., while no specific medium preference was observed for the recovery of actinobacteria from Reniochalina sp., and C. australiensis. The RFLP fingerprinting of 16S rDNA genes digested with HhaI revealed six different patterns, in which 16 representative 16S rDNAs were fully sequenced. Phylogenetic analysis indicated that 12 strains belong to the group Streptomyces, three strains belong to Pseudonocardia, and one strain belongs to Nocardia. Two strains C14 (from C. australiensis) and N13 (from Sponge sp.) have only 96.26% and 96.27% similarity to earlier published sequences, and are therefore potential candidates for new species. The highest diversity of three actinobacteria genera was obtained from Sponge sp., though the number of isolates was low. Two genera of actinobacteria, Streptomyces, and Pseudonocardia, were isolated from both S. tenuis and C. australiensis. Only the genus of Streptomyces was isolated from H. rugosa and Reniochalina sp. Sponge species have been demonstrated here to vary as sources of culturable actinobacterial diversity, and the methods for sampling such diversity presented may be useful for improved sampling of such diversity.     

The Trace Fossil Paleodictyon within The Cruziana Ichnofacies: First Record from The Devonian in Pennsylvania

Offshore marine deposits of hemipelagic dark-gray shales comprising the Middle Devonian Mahantango Formation have yielded the first evidence of the trace fossil Paleodictyon from Pennsylvania. Paleodictyon occurs in conjunction with a diversity of largely deposit-feeding trace fossils belonging to the Cruziana ichnofacies, and documents another example of a shallower-water occurrence of this ichnofossil in Paleozoic rocks.