Feeding Burrows Research Articles

Insights into Population Status and Habitat Patches of Conservation Concern for the Endangered Indian Pangolin (Manis crassicaudata) in Nowshera District, Northwestern Pakistan.

The Indian pangolin (Manis crassicaudata) stands out among the four surviving species of Asian pangolins, being the sole species present in Pakistan and listed as endangered owing to trafficking and illicit commerce. In the present study, we explored the population status of the Indian pangolin and the existing suitable habitats in Nowshera district, Pakistan. We employed the line transect method to confirm the species presence and subsequent population estimation. In a survey effort of 156 km2, a total of 56 signs of Indian pangolin were recorded within the research area. Amongst the 56 signs, 46 were burrows (living burrows (53.57%) and feeding burrows (28.57%)). Digging was observed nine (16.07%) times, along with one direct sighting (1.7%). Our results revealed a population estimate of only 29 pangolins in the Nowshera district, with a population density of 0.013 individuals/km2. Later, MaxEnt was applied to the species' presence points, along with climatic and topographical variables. The MaxEnt model accuracy was good (AUC = 0.811). Of the total area studied, 210 km2 (12.01%) were highly suitable and 238 km2 (13.61%) were moderately suitable habitat for the Indian pangolin. To safeguard the fragile population and habitat of the Indian pangolin, we highly suggest strengthening watch and ward and law enforcement in the study area. By adopting a comprehensive approach that addresses both the direct threats to Indian pangolins and the underlying factors driving their decline, we can effectively protect this endangered species and ensure the preservation of its essential habitats for robust conservation.

Scarabaeolus carniphilus: a necrophagous dung beetle (Coleoptera: Scarabaeinae) buries and feeds on a dead snake

A rare sighting of two male carrion specialist dung beetles, Scarabaeolus carniphilus Deschodt & Davis, 2015, burying a freshly dead Herald snake (Crotaphopeltis hotamboeia (Laurenti, 1768)) is documented from its discovery in the field and subsequent reburial under laboratory conditions. The species studied is a member of the telecoprid (dung roller) Scarabaeini, but behaved here like a paracoprid; it deliberately cut into and removed flesh from the dead snake; these pieces were then taken into a feeding burrow; later a pheromone release stance was taken up near an established burrow; and under laboratory conditions the snake was completely buried. These observations, mostly novel for this species and its genus are clearly documented via photographs and an online time lapse video taken every hour for 24-hours during the snake’s-(re)burial. This note introduces relevant aspects of dung beetle natural history and new biological information for Scarabaeolus and particularly for Sc. carniphilus. It records and interprets a carrion specialist Scarabaeini dung beetle burying and feeding on fresh carrion; highlights natural history findings (pheromone release) previously not considered for the evolution of the Scarabaeini; and aims to stimulate behavioural research into this interesting and under studied genus Scarabaeolus.

NOT ENTIRELY ICHTHYOSAUR: A MYSTERIOUS LAMNIFORM AND ICHTHYOPTERYGIAN-FALL ASSOCIATION FROM THE ABYSSAL UPPER CRETACEOUS OF THE NORTHERN APENNINES (ITALY)

ABSTRACT Axial remains of a large ichthyosaur and a medium-sized anacoracid shark from the deep-water sediments of the Cenomanian of the Northern Apennines (Northern Italy) are described in detail. The specimens were found closely associated (less than 0.3 m apart), and offer an invaluable window into the taphonomy and dead-fall stages of pelagic vertebrates in a Mesozoic abyssal plain. The anacoracid shark remains, initially misinterpreted as an ichthyosaur, consist of eight articulated vertebrae embedded in a block of dark arenaceous matrix, and represent the first occurrence of an articulated shark from the Northern Apennines. The ichthyosaur remains consist of seven discoidal vertebrae and several unidentified fragments. Due to the absence of diagnostic skeletal elements, both specimens are assigned only at higher taxonomic levels. The two fossils, which come from the same outcrop and possibly from the same stratigraphic horizon, share a common taphonomic history, in terms of both their preservation and diagenesis. Mineralogy of the matrices of both is dominated by manganese micro-nodules, consistent with the deposition of polymetallic nodules in bathyal-abyssal settings. Biostratinomic processes that impacted the two specimens also provide insight on the development of Mesozoic marine vertebrate-falls in the deep-sea. Localized pyrite framboids inside the bone spongiosa are possible evidence of the sulfophilic stage (microbially mediated sulfur mobilization during lipid decay) in the ichthyosaur fall. Burrows assigned to Taenidium on the surface of the shark block, interpreted as worm-like feeding burrows or arthropod locomotion and feeding trails, might represent evidence of the enrichment opportunistic stage. Although intriguing, we have no evidence to support the hypothesis that this peculiar association of two pelagic predators is due to ecological interaction between the two animals.

Detecting the Spatial Variability of Seagrass Meadows and Their Consequences on Associated Macrofauna Benthic Activity Using Novel Drone Technology

Seagrass meadows are undergoing significant decline locally and globally from human and climatic impacts. Seagrass decline also impacts seagrass-dependent macrofauna benthic activity, interrupts their vital linkage with adjacent habitats, and creates broader degradation through the ecosystem. Seagrass variability (gain and loss) is a driver of marine species diversity. Still, our understanding of macrofauna benthic activity distribution and their response to seagrass variability from remotely sensed drone imagery is limited. Hence, it is critical to develop fine-scale seasonal change detection techniques appropriate to the scale of variability that will apply to dynamic marine environments. Therefore, this research tested the performance of the VIS and VIS+NIR sensors from proximal low altitude remotely piloted aircraft system (RPAS) to detect fine-scale seasonal seagrass variability using spectral indices and a supervised machine learning classification technique. Furthermore, this research also attempted to identify and quantify macrofauna benthic activity from their feeding burrows and their response to seagrass variability. The results from VIS (visible spectrum) and VIS+NIR (visible and near-infrared spectrum) sensors produced a 90–98% classification accuracy. This accuracy established that the spectral indices were fundamental in this study to identify and classify seagrass density. The other important finding revealed that seagrass-associated macrofauna benthic activity showed increased or decreased abundance and distribution with seasonal seagrass variability from drone high spatial resolution orthomosaics. These results are important for seagrass conservation because managers can quickly detect fine-scale seasonal changes and take mitigation actions before the decline of this keystone species affects the entire ecosystem. Moreover, proximal low-altitude, remotely sensed time-series seasonal data provided valuable contributions for documenting spatial ecological seasonal change in this dynamic marine environment.

Distribution of Chinese pangolin (Manis pentadactyla) in Nagarjun forest of Shivapuri Nagarjun National Park, Nepal

The Chinese pangolin (Manis pentadactyla) is one of the world’s critically endangered species, and its distribution is little known in Nepal. This study aimed at understanding the distribution of Chinese pangolin in Nagarjun forest of Shivapuri-Nagarjun National Park, Nepal from September 2017 to May 2018. A total of 15 infrared cameras were used, these were installed randomly in the forest. Only three cameras at three different locations were able to capture photographs of Chinese pangolin. Altogether, three events, comprising 21 still photos of pangolin, their sign and other mammal species in the area were recorded. In addition, 94 pangolin burrows were noticed in the study area. The distribution of Chinese pangolin is influenced by the food, tree canopy and aspect of the area. Majority of the active burrows were found near to feeding burrows where ants and termite’s nest were found abundantly. In addition to Chinese pangolin, the study was able to capture twelve mammalian species including masked palm civet (Paguma larvata) and yellow-throated marten (Martes flavigula). These two species were often seen to enter or try to enter the active burrows of pangolins. The results suggest that Nagarjun Forest serves an important role in mammal conservation with high mammalian biodiversity.

Late Miocene deep-sea trace fossil associations in the Vera Basin, Almería, Southeastern Spain

The Vera Basin in southeastern Spain was a small, tectonically active depocenter throughout the Miocene. In the early Messinian, approximately 7.2 to 6.0 million years ago, the basin received hemipelagic marl deposits that were punctuated by turbidite events. Soles of thin, turbidite sand beds preserve an abundance of pre-depositional graphoglyptid (agrichnial) burrows that represent diverse deep-sea ichnocoenoses, including Paleodictyon, Urohelminthoida and Helminthorhaphe. Post-depositional feeding burrows, including Ophiomorpha (created by crustaceans) and Scolicia (created by echinoids) occur sparsely in some turbidite beds, but they are far out-numbered by the pre-depositional agrichnial burrows. This diverse trace fossil association occurred in a small, short-lived, coastal basin that apparently never got more than a few hundred meters deep. As the basin opened up and flooded in the Late Miocene, the sea floor was colonized rapidly by benthic organisms of uncertain biological affinity, who created a wide variety of anastomosing and meandering tunnels, in which a nourishing food supply (probably bacteria or fungi) apparently grew on mucus-lined walls

Habitat preference and den characterization of Indian Pangolin (Manis crassicaudata) in a tropical lowland forested landscape of southwest Sri Lanka.

The Indian pangolin (Manis crassicaudata) is under threat due to hunting for local consumption and illegal trafficking of scales and meat. The dearth of scientific studies on the ecology of the M. crassicaudata has impaired accurate assessments of its conservation needs. This study investigated the habitat preference and burrow characteristics of M. crassicaudata in a tropical lowland rainforest in southwest Sri Lanka. A total of 75 burrows (54 feeding burrows and 21 resting burrows) of M. crassicaudata in four different habitat types i.e. secondary forest, Pine-dominated forest, rubber cultivations and tea-dominated home gardens bordering forest were observed using fixed-width transects in order to characterize resting and feeding burrows of this species. The highest density of resting burrows was recorded from the secondary forest (4ha-1), followed by rubber cultivations (2.5ha-1) while no resting burrows were recorded in the Pine-dominated forest and the tea-dominated home gardens bordering forest. Feeding burrows were more abundant in the Pine-dominated forest (5.7ha-1). The burrow depth, burrow opening height, and width were significantly larger in resting burrows compared to feeding burrows. Resting burrows were located at higher elevations (75-100m) with moderately high slopes (450−600), dense canopy cover (>75%) and away from human habitation. Feeding burrows showed a greater variability in terms of associated environmental features. The study further revealed that Indian pangolins exclusively prefer habitats with rocks and boulders under which they dig resting burrows while the location of feeding burrows largely overlaps with the distribution of prey species. The resting burrow design consisted of a bending tunnel that initially slopes downward and then gradually inclines at an angle between 20 and 300, leading to the resting chamber. Our study highlights the importance of conserving fragmented secondary natural forests in changing landscapes of the southwest lowlands of Sri Lanka as these habitats appear to be critical to sustaining populations of M. crassicaudata.

Silicificaciones selectivas en <em>Thalassinoides</em> y otras estructuras biogénicas asociadas a calizas de plataforma marina y <em>hardground</em> (Albiense inferior, Sonabia, Cantabria)

El presente trabajo estudia los diferentes tipos de sílex que aparecen en la Formación Calizas de Oriñón (Aptiense superior-Albiense inferior), en un zona concreta de la costa oriental de Cantabria (Liendo-Castro Urdiales), debido a su gran abundancia y espectacularidad. Las rocas que los incluyen son principalmente biocalcarenitas (wackestones/packstones de pellets, fragmentos de equinodermos, ostreidos, foraminíferos y espículas calcáreas o silíceas calcificadas), siendo el ambiente de depósito marino de plataforma abierta, y existiendo un hardground regional, donde las silicificaciones son diferentes. La fuente de la sílice proviene de la calcitización o disolución de las espículas de esponjas silíceas. 
 Se determina que la gran mayoría de sílex (mosaicos de cuarzo micro-microcriptalino y calcedonita principalmente), se forman por la silicificación selectiva de estructuras biogénicas, siendo las galerías de Thalassinoidespreferentemente silicificadas, debido a que en su relleno existe mayor proporción de materia orgánica y mayor porosidad y permeabilidad. En las calizas que soportan el hardground además de las silicificaciones selectivas sobre fósiles (rostros de belemnites, ostreidos y equínidos), la sílice se acumula de forma importante en huellas de alimentación y rellenos de perforaciones, dando lugar a su vez a costras sobre bioturbaciones y perforaciones que a pesar de su importancia no han podido ser clasificadas. 
 La silicificación de todas las estructuras biogénicas, originó inicialmente fases opalinas y tuvo lugar durante la diagénesis temprana cuando la oxidación de la materia orgánica estaba todavía activa, conservándose en los Thalassinoides silicificados formas (filamentos y cocoides) que podrían ser consideradas microbianas. La transformación ópalo-cuarzo fue temprana, preservándose dichas formas. 
 En las galerías silicificadas de Thalassinoides los procesos diagenéticos son diferentes a los de los sedimentos carbonáticos marinos que las incluyen, y al resto de estructuras biogénicas silicificadas, existiendo en estas galerías neoformación de dolomita y calcita, en un microambiente cerrado donde las condiciones cambian de oxidantes a reductoras.

First occurrence of the Ichnogenus Selenichnites from the Middle Jurassic Strata of the Skoura Syncline (Middle Atlas, Morocco); Palaeoecological and palaeoenvironmental context

Mesozoic strata of North Africa yield the first occurrence of the ichnogenus Selenichnites. The trace fossils occur on the top surface of a sandy carbonate deposit in the axis of a Middle Atlas syncline (Skoura Syncline, NE Morocco). The ichnofossil-bearing horizon belongs to the Late Bajocian–Early Bathonian Ich Timellaline/Bou Akrabene Formation. The trace fossils are crescent-shaped and the best preserved exhibits a posterior central axial impression (possible telson tail impression). They are interpreted as feeding burrows (fodinichnia) or hiding depressions of Xiphosurids or Limulids (horseshoe crabs) on a sandy carbonate substrate beneath a veneer of muddy deposits. The sedimentological character suggests a relatively protected shallow water subtidal palaeoenvironment preceding the Bathonian regression of the Atlas domain. This discovery provides the first evidence of xiphosurans or xiphosuran-like organisms inhabiting the southern shores of the Tethys in the Middle Jurassic.

Trace fossils from the Eocene Lillebælt Clay Formation, Røsnæs, Denmark

A cliff exposure of the Eocene Lillebaelt Clay Formation, on the Rosnaes peninsula of Zealand, Denmark, has yielded a diverse trace-fossil assemblage. The trace fossils are described formally for the first time and assigned to Phymatoderma melvillensis , unnamed clusters of small burrows, Ophiomorpha nodosa , Spongeliomorpha isp., Dreginozoum beckumensis , Bichordites isp., Chondrites isp., Atollites zitteli ? and ? Rhizocorallium isp. The preservation of the trace fossils is strongly related to early diagenetic enhancement. The trace-fossil assemblage is dominated by a combination of dwelling and feeding burrows. The bioturbation took place in very clean clay of a shelf setting far offshore. The trace-fossil assemblage is indicative of the distal Cruziana ichnofacies.

Lithofacies and ichnology of the Late Maastrichtian–Danian Nsukka Formation in the Okigwe area, Anambra Basin, Southeastern Nigeria

Sedimentological and ichnological studies of the Late Maastrichtian to Danian Nsukka Formation in the Okigwe area of the Anambra Basin, Southeastern Nigeria were carried out to ascertain the lithofacies and to reconstruct the depositional environment. The lithofacies include concretionary black shale (F1), heterolithic facies (F2), bioturbated mudstone (F3), bioturbated sandstone (F4), ripple-bedded sandstone (F5), cross-bedded sandstone (F6), parallel-bedded sandstone (F7), bioturbated black shale (F8), and bioturbated shelly sandstone (F9). Some of the beds are significantly bioturbated with bioturbation index (BI) ranging from 3 to 5. Five lithofacies associations were distinguished and interpreted as follows: lithofacies association I represents offshore to lower shoreface transition sediments; lithofacies association II is middle to lower shoreface; lithofacies III comprises upper shoreface to foreshore and lagoon/bay sediments; lithofacies association IV is of upper shoreface origin; and lithofacies association V is proximal offshore. The shallow marine setting was dominated by currents, waves and occasional storm. The trace fossil assemblage comprises Ophiomorpha nodosa and Skolithos linearis representing the Skolithos ichnofacies and Thalassinoides suevicus, Teichichnus rectus, Paleophycus herberti and Planolites montanus representing the Cruziana ichnofacies. The six trace fossils described in this study are equally distributed into two ethological categories, domichnia (dwelling burrows) and fodinichnia (feeding burrows). The distribution of the two ethological categories in the sediments within the shallow marine environment was controlled by the energy of the environment, amount of organic detritus, degree of oxygenation and salinity.

Biogenic Sedimentary Structures of the Yellow River Delta in China and Their Composition and Distribution Characters

The biogenic sedimentary structures (i.e., the morphology and trace makers of burrows, tracks, trails and traces made by extant organisms) and their composition and distribution characters in different micro environments and sub environments of the Yellow River delta in China are described. Three ichnocoenosis can be recognized: (1) Steinichnus-like ichnocoenosis, includes F, Y-shaped traces, birds' footprints on bedding plane, and Y, U-shaped burrows in intrastratal bedding, produced by Coleoptera (Heteroceridae), Orthoptera (Gryllotalpidae) and birds. It is majorly found at the delta plain point bar deposits, denoting the fresh water-related terrestrial environments. (2) Steinichnus-Psilonichnus-like ichnocoenosis, consitsis of Steinichnus-like traces on the bedding plane and Psilonichnus-like burrow which a vertical, irregularly J-, Y-, or U-shaped burrows, some of them with bulbous basal cells burrows in the intrastratal bedding, created by Coleoptera (Heteroceridae), Orthoptera (Gryllotalpidae) and crabs. It is observed in the delta plain abandoned distributary channels, and the delta front tidal creek and subaquous distributary channels, indicating the brackish water environment. (3) Palaeophycus-like ichnocoenosis, includes the round entrance burrows or with craters-shaped loop-protrusionsand and the parallel forked trails on the bedding plane, and the U, J or vertical shaped feeding burrows are in the intrastratal bedding, majorly produced by the clam (bivalve molluscs), gastropods and Nereis. It is present in the subaqueous interdistributary bay, reflecting the intertidal related environment.

The déjà vu effect: Recurrent patterns in exploitation of ecospace, establishment of the mixed layer, and distribution of matgrounds

Although the notion of recurrent trace-fossil assemblages through geologic time as a result of similar sets of environmental conditions has a long history in ichnology, the idea that recurrent ichnofaunas may have occurred in connection with macroevolutionary events has not yet been put forward. We refer to this phenomenon as “the Deja vu effect,” and suggest that understanding its signifi cance may shed light on how organisms colonize underutilized or empty ecospace, the establishment of the mixed layer, and the temporal and spatial distribution of matgrounds. These recurrent trace-fossil assemblages record the activity of the epifauna and a very shallow tier infauna, in the absence of mid- to deep-tier trace fossils and mottled textures. They typically consist of grazing trails, very shallow feeding burrows, and arthropod trackways. Shallow-tier burrows and trails with well-developed scratch marks may be present. These ichnofaunas suggest that the initial exploitation of underutilized or empty ecospace is linked to a set of recurrent behavioral strategies to obtain food from matgrounds and fi rmgrounds in the absence of a well-developed mixed layer. Preservation of these behaviors in the form of trace fossils is mediated by a set of taphonomic conditions. These taphonomic windows occur during the initial colonization of empty or underutilized ecospace, such as the Ediacaran-Cambrian transition or the subsequent colonization of the land, but also after the end-Permian mass extinction, which may have had a negative impact on the mixed layer in marine environments, producing a return to the ecologic conditions of the early Paleozoic.

TAPHONOMIC ASPECTS OF THE MIOCENE ICHNOFOSSIL-LAGERSTÄTTE FROM CALCARENITE TURBIDITIC BEDS IN THE VERGHERETO MARLS (NORTHERN APENNINES, ITALY)

Five, 3-8 cm-thick calcarenitic turbiditic beds belonging to overbank deposits in the marginal sector of Marnoso-arenacea Basin, close to the intrabasinal high of Verghereto (Romagna, Northern Apennines, Upper Miocene), exhibit a well preserved ichnofossil-lagerstatte. The lagerstatte is composed by 43 ichnotaxa: 31 of them are preserved as casts at the sole of turbidites (background hypichnia) (group a), while 12 of them occur at the top (post-turbidite epichnia) and within (endichnia) (group b). The ichnodensity reaches its maximum at the top of the turbiditic beds. Background hypichnia (group a) is represented by graphoglyptids and non-graphoglyptid resting traces (background ichnofauna), with three-dimensional networks and shafts, meander systems, radiate, plug-shaped or stellatae structures forming clusters and unbranched systems of strings. Many taphonomic features suggest a fluting induced by bottom currents; graphoglyptids should have colonised the substrate after the action of these currents being not destroyed or fluted. All hypichnial structures are perfectly preserved by the turbidite casting and in this phase also endichnial burrows could develop. Post-turbidite epichnia (group b) concern vagile feeding burrows that developed horizontal patterns in a post-turbiditic regime, during the suspension phase of fine material; they were probably produced by organisms transported by suspension flows. Here, the very high ichnodensity suggests a competition among burrowers under stable currents with occurrence of vagile opportunistic organisms immediately followed by others that produced radiate spreite structures. SHORT NOTE

INFLUENCE OF BEACH MORPHODYNAMICS ON THE DISTRIBUTIONS OF THE OPHELIID POLYCHAETE EUZONUS SP. AND ITS FEEDING BURROWS ON A SANDY BEACH: PALEOECOLOGICAL AND PALEOENVIRONMENTAL IMPLICATIONS FOR THE TRACE FOSSIL MACARONICHNUS SEGREGATIS

Abstract The aim of this study was to determine the paleoecological and paleoenvironmental significance of the trace fossil Macaronichnus segregatis by examining its extant counterpart, feeding burrows of the opheliid polychaete Euzonus, which was periodically sampled on a wave-dominated sandy beach on the Pacific coast of Japan from June to December 2006. The distributions of Euzonus and its feeding burrows normal to the shoreline ranged from 5 m to 40 m. The vertical thickness distributions ranged from 32 cm to 123 cm (Euzonus) and from 34 cm to 126 cm (burrows). These parameters increase with decreasing beach-face gradient. The midpoints (median levels) of the vertical distributions invariably occurred near the midforeshore (corresponding to high-tide level). Foreshore width and vertical thickness also increase with decreasing beach-face gradient. These findings suggest that changes in the distributions of Euzonus and its burrows in the midforeshore environment vary with beach morphodynamics. The verti...

Paleoecological significance of the trace fossils of Dhosa Oolite Member (Jumara Formation), Jhura dome, Mainland Kachchh, Western India

Dhosa Oolite Member of the Jumara Formation comprises alternating bands of oolitic limestones and shales, exposed in Jhura dome of Mainland Kachchh, Western India. This sequence is highly bioturbated and exhibits a moderate diversity and behaviourally complex assemblage of ichnospecies. The rhythmically bedded sequence shows three different levels of preservation of traces. Epichnial tiering consists of moderately bioturbated oolitic limestone exhibiting horizontal or low-angle protrusive/retrusive biogenic laminae, commonly dominated by feeding structures like Rhizocorallium jenense, R. irregulare, Zoophycos brianteus and Zoophycos isp. The endichnial structures within the oolitic limestone can be separated into two different preservational trace fossil suites. The endichnial shallow suites consist chiefly of deposit feeders like Chondrites intricatus, C. targionii, Planolites beverleyensis, Taenidium cameronensis, Thalassinoides isp., Z. brianteus, Z. cf circinnatus and Zoophycos isp. and few suspension feeder forms like Palaeophycus tubularis; while endichnial deep suites consist of Chondrites intricatus, Skolithos linearis and Zoophycos isp. Hypichnial structures consists abundant, cylindrical, branched, horizontal, large-sized three dimensional feeding burrows of Thalassinoides isp. and somewhat irregular, obtuse angle ramification burrows of Phycodes isp., which are attached to the lower surface of the casting medium. The trace fossil association indicates Cruziana ichnofacies and abundance of Zoophycus species below the fair weather wave base level is largely a preservational artifact. The preservational processes of the trace fossils indicate soft substrate and diversity and their abundance reflects the other palaeoecological parameters of the open shallow marine environments.

Nest and Brood Chamber Structure of Two South American Dung Beetles: Gromphas lacordairei Brullé and Ontherus sulcator (Fabricius) (Coleoptera: Scarabaeidae: Scarabaeinae)

Thirty-three nests of Gromphas lacordairei Brullé and Ontherus sulcator (Fabricius) were studied at Navarro, Buenos Aires, Argentina. Nests examined in the field and micromorphological studies of brood chambers demonstrate for the first time that G. lacordairei shows delayed provisioning, constructs nests with storage burrows, and makes brood masses with a discrete external wall of soil. These characters place G. lacordairei in Pattern II nesting behavior. Ontherus sulcator constructs either brood balls beneath dung pads by direct provisioning or only feeding burrows. The orientation and structure of the egg chamber is different from those of Ontherus mexicanus Harold.

Interactions between Zostera capensis, Callianassa kraussi and Upogebia africana: deductions from field surveys in Langebaan Lagoon, South Africa

Callianassid sandprawns and eelgrasses have been postulated to have mutually negative effects on each other. The relationship between Callianassa kraussi and Zostera capensis was investigated in Langebaan Lagoon on the west coast of South Africa by correlative field surveys. Seven facts point to mutually antagonistic interactions between the species: (1) cover of Z. capensis was negatively correlated with density of C. kraussi; (2) Z. capensis was largely confined to the high shore, whereas C. kraussi occurred in unvegetated sandbanks below the eelgrass beds; (3) at sites where Z. capensis was absent, C. kraussi extended farther up the shore than in its presence; (4) C. kraussi reached a larger maximum size in sandbanks than in beds of Z. capensis; (5) immediately below eelgrass beds there was a 'frontier zone' where above-ground Z. capensis was absent but below-ground root-rhizomes appeared to exclude C. kraussi; (6) sediment penetrability was greater in sandbanks than in eelgrass beds; (7) rate of burrowing by C. kraussi was faster in unvegetated sandbanks than in eelgrass beds. Conversely, the density and sizes of the mudprawn Upogebia africana were greater in beds of Z. capensis than in sandflats dominated by C. kraussi. Although this evidence is correlative, it suggests that Z. capensis excludes C. kraussi because it stabilises the sediment and inhibits burrowing, and that C. kraussi prevents establishment of eelgrass beds by destabilising the sediment and suspending material that smothers the eelgrass. In the process, two distinct habitats are created. U. africana may benefit directly from eelgrass because it requires stable sediment for its semi-permanent U-tubes; but also indirectly because Z. capensis excludes C. kraussi, which may disrupt these feeding burrows. At the head of the lagoon where sediments are very fine and compact, U. africana occurs both in and below the eelgrass bed, and coexists with at least low densities of C. kraussi, although Z. capensis and C. kraussi are still negatively correlated.

Triassic trace fossils from lacustrine shoreline deposits of the Passaic formation, douglassville, pennsylvania

Lake‐margin deposits of the Late Triassic Passaic Formation, Douglassville, Pennsylvania, have yielded a moderate variety of trace fossils. The greatest diversity and abundance of trace fossils occurs on the sole of a thin gray claystone overlain and underlain by gray siltstones. Specimens of Cochlichnus anguineus, Helminthoidichnites tenuis, Helminthopsis hieroglyphica, Treptichnus pollardi, and paired trails reflect simple, unspecialized, horizontal grazing as well as feeding traces under very shallow water lacustrine conditions. The lack of commonly associated Scoyenia burrows in these deposits may possibly be related to the degree of maturation of the organic debris available. The traces, as well as a lack of meniscate burrows, compare favorably to the Mermia ichnofacies, except Passaic deposits exhibit evidence of subaerial exposure. This unit most likely records a lacustrine expansion whereby grazing trails were emplaced under fully subaqueous conditions. Subsequent shallowing and desiccation, followed by sediment influx during rainstorms, favored preservation of these traces. In contrast, the Scoyenia ichnofacies consists of feeding burrows of Scoyenia gracilis and Spongeliomorpha milfordensis within reddish brown siltstones and mud‐stones (redbed sequence). The Scoyenia ichnofacies records limited exploitation, by opportunistic infaunal deposit feeders, of lake‐margin nutrients carried in during occasional rainstorms that punctuated otherwise extended periods of aridity.

Deep-sea benthic food content recorded by ichnofabrics; a conceptual model based on observations from Paleogene flysch, Carpathians, Poland

Fluctuations in the input of organic matter into a deep-sea environment can be deciphered from ichnofabrics if the continuous processes of hemipelagic sedimentation and bioturbation are episodically interrupted by turbidite deposition. Below turbidites, the bioturbated zone may be preserved almost intact; the benthic food content in such frozen tiers can be interpreted from the ethology, size, penetration depth, and density of trace fossils. Especially high benthic food content is characterized by (1) dark sediment color, (2) complete bioturbation, (3) high density of burrows produced near-surface in several levels, (4) rarity or absence of graphoglyptids, and (5) deep tiers completely bioturbated by feeding burrows having an open connection to the surface. Oxygen-deficiency can be eliminated as a reason for the black color of the sediment; the size, diversity, and penetration depth of the trace fossils are similar to that of modern and fossil counterparts formed under well-oxygenated settings that are not restricted in benthic food. An increase in sedimentation rate enhances the burial of benthic food and is indicated by the downward extension of the bioturbated zone and by increasing burrow density. Our analysis suggests that several other black shale occurrences may result from increased organic matter input rather than from water-column anoxia due to sluggish circulation. Our model is supported by similarities with other deposits that contain many frozen tiers.