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The abundant shells and hardgrounds in the Cincinnatian Group (Upper Ordovician, Katian) of the upper midwestern United States were commonly encrusted and bored by a variety of organisms. Numerous studies of these sclerobiont communities have provided valuable data for models of ecological succession, symbiosis, space and food resource competition, and taphonomy. An underlying assumption of this work is that most of the skeletal encrusters have remained in place, firmly attached to their hard substrates. This is especially the case with the most common encrusters, thick trepostome bryozoan and cystoporate skeletons, on their most common substrates, flat strophomenide brachiopods. We present evidence here, though, that these bryozoans were often dislodged from their brachiopod hosts, leaving no evidence of their attachment other than horizontal borings in semi-relief from organisms that excavated tunnels (Trypanites and Palaeosabella) at the interface of the brachiopod shell and attaching bryozoan. Similar borings are found on the bases of dislodged bryozoans and in bryoimmured mollusc external moulds. These borings along the bryozoan attachment surfaces caution us that there are significant numbers of missing skeletal encrusters on these hard substrates. [ABSTRACT FROM AUTHOR]

The ichnological study of the Djebel Bouarif Cenomanian deposits (Northern Aurès Range, Algeria) revealed relatively abundant and diverse sclerobiont communities that are preserved in corals, bivalves and gastropods. Fossil traces are dominated by exceptionally preserved Gastrochaenolites, often with tracemakers (bivalves), which are preserved in situ, Entobia, and Maeandropolydora. Other borings are rare and are represented by a single specimen of Rogerella, Nihilichnus, and Spirolites. Among sclerozoans, encrusting juvenile oysters and non-oyster bivalves (Pseudolimea? granulata) are the most abundant groups. Other epibionts, such as gastropods and polychaetes (Glomerula serpentina), are less common; dwarf gastropods were located on a single oyster Costagyra olisiponensis, whereas Glomerula specimens were clustered on the lower and upper surfaces of coral Aspidiscus cristatus. Gastrochaenolites with original tracemakers and all the epibionts studied herein have not been described from the Djebel Bouarif Cenomanian deposits to date. The rare occurrences of Spirolites and Nihilichnus are reported from Algeria for the first time. [ABSTRACT FROM AUTHOR]

When scleractinian corals are negatively impacted by warming, other sclerobiont taxa may contribute to the carbonate budget; however, this knowledge remains limited. The cover (%) and calcification rate (mg CaCO3 cm−2 d−1) of sclerobionts were evaluated before, during, and after the El Niño 2015–16 event on different microhabitats using calcification accretion units (CAUs) in a coral reef from Zihuatanejo de Azueta, in the Mexican Pacific (17°39′13.2″N, 101°37′13.3′′W). The CAUs were deployed over six-month periods from 2014 to 2017 (n = 80; 4 surfaces × 5 CAUs × 4 years). Sclerobionts showed a well-defined microhabitat preference; crustose coralline algae (CCA) dominated well-lit surfaces while cryptics were attractive to heterozoan. The cover of sclerobionts was lower in 2017 than in previous years due to the decrease in cover of CCA, bryozoans, and serpulid polychaetes. Sclerobiont coverage was high in microhabitats exposed to water turbulence but protected from siltation. Calcification rate was maximum during warming conditions because barnacles substantially increased their contribution. CCA decreased their calcification rate in 2017, potentially due to the rise of the sea surface temperature (SST) that extended to April 2016, while bryozoans and serpulid polychaetes showed no temporary changes. These results suggest that the sclerobiont assemblages reacted to the rise of SST caused by the El Niño event and that the decrease in the calcification rate of some taxa was compensated by the increase of others. Coral reefs seem to have a limited buffer capacity to endure the El Niño effects on the accretion process made by sclerobionts, although this implies a sensible change in the assemblage structure. [ABSTRACT FROM AUTHOR]

In addition to a marked rise in marine biodiversity, the Ordovician witnessed the most profound increase in the complexity of marine ecosystems in the history of the earth, including the expansion of tiering and enhanced biotic interactions. In order to understand these changes, it is important to study palaeoecological relationships among organisms at the commencement of the Great Ordovician Biodiversification Event (GOBE). Here, we describe sclerobionts associated with one of the earliest bryozoans in the fossil record, the oldest known trepostome, Orbiramus from the Fenhsiang Formation (late Tremadocian) of Hubei Province, China. These sclerobionts are diverse and include borings (e.g. Trypanites and Sanctum), bioclaustrations of vermiform organisms, and syn‐vivo fouling by the putative black coral Sinopathes and other bryozoans. Diverse sclerobiotic associations and intricate palaeoecological relationships had already been established between bryozoans and other metazoans by the Tremadocian, showing the early onset of the 'hard substrate revolution' during the GOBE. [ABSTRACT FROM AUTHOR]

The exposed calcareous rocky area of the Abu Qir Headland, east of Alexandria, Egypt which range from coarse grains, through pebbles, cobbles, and boulders to rocky platforms, was significantly colonized by sclerobionts (epibionts and endobionts). The epibiont species diversity was comparatively higher than that of endobionts. Epibiont communities included bryozoans (the anascan-grade cheilostome Biflustra savartii), serpulid (Hydroides elegans, Spirobranchus cf. tetraceros, Vermiliopsis striaticeps and Protula or Apomatus) and spirorbid (Spirorbis) wormtubes, and balanoid barnacles (Amphibalanus amphitrite, Balanus trigonus, and Perforatus perforatus). The cheilostome bryozoan colonies, which developed extensive sheets, proliferated on the study rocky shore either encrusting the bioeroded basement directly, or encrusting other epilithic taxa, particularly balanoid barnacles and serpulid worms. Encrusters displayed a remarkable marginal competitive interaction (overgrowth and stand-off) for space on the study rocky shore. On the other hand, endobionts were not well represented on the studied rocky shore exposure. It was possible to identify three ichnotaxa: Gastrochaenolites, Maeandropolydora, and Finichnus. The findings documented represent a significant contribution to our knowledge of sclerobionts composition, sequence of their colonization and/or bioerosion, and their mutual relationships on the intertidal rocky shore of the Abu Qir Headland. [ABSTRACT FROM AUTHOR]

Here we describe the composition and distribution of sclerobionts on the late Eocene bivalve Carolia placunoides and provide information about its paleoecology. More than 250 shells were collected from the Temple Member of the Qasr El-Sagha Formation exposed in El-Fayum Province. Nine ichnogenera have been recorded including Gastrochaenolites , Maeandropolydora , Caulostrepsis , Entobia , Centrichnus , Belichnus , Anellusichnus, Oichnus and Trypanites. The dense population of borings made by boring bivalves, Gastrochaenolites , is the most remarkable. Encrusters include serpulid worms (Spirobranchus cf. luxata), balanoid barnacles, and oysters. Shells of juvenile Carolia were the most dominant encrusters. Sclerobionts occurred on left and right valves; they apparently favoured the interior surfaces on both valves but they preferred no special sites. The Carolia placunoides shell concentration is interpreted as para-autochthonous assemblage. [ABSTRACT FROM AUTHOR]

Attached epilithic foraminifera constitute an important but overlooked component of the benthic foraminiferal assemblage in the Pleistocene sediment of the central Arctic Ocean. We report 12 types of epilithic foraminifera that have colonised lithic and biogenic grains found in glacial sediments, including representatives of the genera Rhizammina, Hemisphaerammina, Ammopemphix, Diffusilina, Subreophax, Placopsilina, Placopsilinella, Hormosinelloides and Tholosina, accompanied by mat-like and ribbon-like forms of uncertain taxonomic affinity. The attached agglutinated forms appear to be colonisers, adapted to extremely oligotrophic conditions. [ABSTRACT FROM AUTHOR]

Permian sclerobionts of brachiopods present in outcrops of clayey or silty limestones of the Paso Hondo Formation, in southern Mexico, include representatives of the enigmatic group Hederelloidea. This group, with uncertain affinities, has in the past generally been considered to be related to the Phylum Bryozoa but which, given its prismatic ultrastructure and larger size, is currently considered as an independent group of lophophorates. As with most sclerobiont faunas, the fossil record of hederelloids is abundant from the Silurian to Devonian, but they are very scarce in the Upper Paleozoic where they are restricted to subtropical paleolatitudes of moderate depth, calcareous shale or clay limestone facies. In particular, the genus Hederella has only been reported from the Carboniferous of North America and the United Kingdom and from the Permian (Sakmarian) of Siberia. The presence of hederelloids in the Paso Hondo Formation, which crops out in the State of Chiapas, on the border of Mexico and Guatemala, constitutes the first record of this group for Mexico, the youngest at a global level, and extends the temporal distribution of the Order Hederelloidea to the Roadian. The hederelloids present in the Paso Hondo Formation are attached to shells of rhynchonellid and athyridid brachiopods and associated with other sclerobionts, such as bryozoans of the orders Trepostomata and Cystoporata. [ABSTRACT FROM AUTHOR]

Organisms of unknown biological affinity are widespread in Paleozoic ecosystems and play key ecological roles. Recognition of these roles relies on consistent identification and sound taxonomy, yet many microproblematica lack complex morphological features that could be the basis for qualitative taxonomic diagnoses. Allonema is an incertae sedis calcareous sclerobiont widespread in Paleozoic carbonates. At least seven species of Allonema have been proposed, but their diagnoses based on size ranges overlap. In this work, dimensions of 590 individuals from the Silurian of Estonia and Sweden have been measured. Regression analysis of the dimensions revealed two groups, overlapping in size ranges, but differing significantly in proportions. These groups could be matched with previously described A. botellus and A. moniliforme, but both showed a wider range of sizes than previously reported. Another previously described species, A. minimum, fell within the range of dimensions of A. moniliforme and is proposed to be its junior synonym. Differences in proportions revealed in the study do not seem to be dependent on sedimentary environment or local growth conditions such as competition for space, and thus may represent consistent interspecific variability. Although the affinity of Allonema remains unknown, this quantitative approach to its taxonomy reduces unnecessary species in the genus. The success of this approach may encourage its application to other microproblematica populating the fossil record. [ABSTRACT FROM AUTHOR]

The living Tridacna maxima shell provides an example of a good substrate for many colonizing marine organisms (sclerobionts). Many factors affect the colonization choices of these organisms, such as morphology and size of the host shell, water depth (related to light penetration), suspended particulate load, and turbidity, among others. In addition to these factors, contamination plays an important role in the colonization choice along the coast of the Red Sea in Egypt. In the present study, 25 specimens of T. maxima shells of different sizes were collected at different depths from eight sites along the Egyptian Red Sea coast. There are two types of contamination at these sites. The first type results from anthropogenic activities, such as tourism, fishing, landfilling, shipping, renewal of ship operations, shipyards, dredging, and petroleum production; this type is represented by the El-Esh area, Hurghada Harbor, Safaga Harbor, and Quseir Harbor. The second type results from the natural inputs from wadis and is represented by the El-Esh area, Quseir Harbour, and Wadi El-Gemal, while the Abu Galawa Lagoon, the Abu Ghusun, and the Hamata Reefs represent uncontaminated areas (control areas). The present study documents the colonization phenomena on T. maxima shells at all of the study sites. These phenomena differed from one another in the abundance and diversity of sclerobionts, and unexpectedly, the contaminated areas recorded the highest abundance and diversity of colonizing organisms. [ABSTRACT FROM AUTHOR]

Abstract: The lower Pleistocene Kritika Member of the Rhodes Formation is composed of predominantly siliciclastic deposits that are sometimes intercalated with hardbottoms formed by drowning of former beachrock beds. A wide variety of sclerobionts occur in this environment, very different from the poorest soft‐bottom populations occurring in other levels of the Kritika Member. The most characteristic, abundant and frequently diverse are the encrusting forms: coralline algae, bivalves, serpulid worms, and bryozoans. Numerous other groups of sessile and vagile organisms are associated with these crust‐forming communities. A number of skeletal organisms (sometimes including zooxanthellate coral colonies) formed small carbonate buildups on top of several beachrock beds. Boring organisms also occur. Evidence for a two‐step deepening succession over the previously formed beachrock is provided by palaeontological and sedimentological data. The rapidly cemented sandy‐conglomeratic beds were first colonised by a relatively shallow‐water (around 20m) biocoenosis of mostly encrusting organisms. Another association, with encrusting and erect organisms, was later established in a deeper environment (20–40m). A comparison with Holocene beachrock occurring on the coast of Rhodes was also undertaken. Their submerged part provided habitat for poorer but similar biotas to those occurring in the Kritika Member. The lower Pleistocene beachrock and associated organogenic fossil assemblages indicate repeated drowning episodes during deposition of the Kritika Member and provide help in sequence stratigraphic interpretations of these siliciclastic deposits. Notably, they can be used as indicators of relative sea‐level changes. [Copyright &y& Elsevier]

Reworked concretions have been significant substrates for boring and encrusting organisms through the Phanerozoic. They provide large, relatively stable calcareous surfaces in systems where sedimentation is minimal. Diverse sclerobiont communities have inhabited reworked concretions since the Ordovician, so they have been important contributors to our understanding of the evolution of these ecological systems. Here, we describe reworked concretions from southern Israel where they are critical for interpreting the stratigraphy and paleoenvironment of an Upper Cretaceous sedimentary sequence. These cobble-sized concretions (averaging roughly 1,000 cm) are found at the base of the Menuha Formation (Santonian to lower Campanian, Mount Scopus Group) unconformably above the top of the Zihor Formation (Turonian-Coniacian, Judea Group) exposed in the Ramon region of the Negev Highlands. The concretions are almost entirely composed of micritic limestone, and many are exhumed, cemented burrow-fills apparently from 10-20 m of upper Zihor Formation strata removed by erosion. There are also a few cobbles of dolomitic limestone and rare vertebrate bone. The cobbles are moderately to heavily bored by bivalves (producing Gastrochaenolites) and worms (forming Trypanites), and a few have cemented oysters. They are densely arrayed in a single layer, often touching each other or only a few centimeters apart. The sclerobionts associated with the cobbles, along with their hydrodynamic arrangement, strongly suggest that these cobbles accumulated in very shallow water above normal wave base. Most of them (77%) are encrusted on their top surfaces only, indicating that they were bored in place and not later delivered to a deeper environment by submarine currents. The rest of the Menuha Formation above is a chalk with relatively few macrofossils (primarily shark teeth and oysters) and a few trace fossils ( Planolites and Thalassinoides are the most common). These reworked cobbles show that the initial deposits of the Menuha Formation accumulated in very shallow water. This has important implications for the development of the Syrian Arc structures in this region, especially the Ramon Monocline. [ABSTRACT FROM AUTHOR]

Encrustation by diverse sclerobionts is found on about 4% of upper Famennian cephalopods from the active Kowala Quarry, Holy Cross Mountains, central Poland. These infested cephalopods are represented mostly by clymeniid ammonites, but also include goniatitids and nautiloids. Sclerobionts on cephalopod shells include crinoids (represented by their holdfasts, about 57% of encrusters), moulds of problematic worm tubes (less common, about 28.5%), bryozoans, microconchids, possible cornulitids and organisms of uncertain affinities. All of the sclerobionts likely utilised shells of dead cephalopods as a hard substrate for their settlement. However, most of the infestation appears on internal moulds because the cephalopod aragonite was dissolved during diagenesis. It is possible that some of the sclerobionts encrusted exhumed lithified internal moulds. These isolated cephalopod shells and internal moulds likely served as benthic islands for various encrusters on a Devonian muddy sea-floor. [ABSTRACT FROM AUTHOR]

Sedimentologic and palaeontological investigation of the Upper Pliocene Slama Formation in the Lower Chelif Basin (NW Algeria) led us to collect important bivalve assemblages for taxonomic and taphonomic purposes. A rather comprehensive inventory list of Upper Pliocene bivalves from northwestern Algeria is now available and consists of 30 species, 17 of which are extinct ones. Four principal taphonomic attributes were analysed: bioerosion, encrustation, fragmentation, and abrasion. Physical and biogenic sedimentary structures are used for palaeoenvironmental interpretations. The taphonomic, sedimentologic and ichnological characteristics of most of the deposits suggests they originated from discontinuous processes of winnowing and bypassing of sediments, probably due to the action of storms in shallow waters, mainly in the shoreface depositional environment. The bivalve assemblage is dominated by disarticulated valves and displays significant taphonomic alteration in the shells. Sclerobionts traces in shells particulary affect the oyster shells. Bioerosion traces are predominately those of clionid sponges (Entobia isp.), polychaetes (Maeandropolydora isp. and Caulostrepsis isp.), bivalves (Gastrochaenolites isp.), and of predatory gastropods (Oichnus isp.). Among the sclerobionts, the identified encrusters were juvenile oyster recruits, barnacles, polychaetes (serpulid tubeworms), bryozoans (Microporella sp. and Acanthodesia sp.), and vermetid gastropods (Petaloconchus intortus). [ABSTRACT FROM AUTHOR]

Middle Devonian (Givetian) rugose corals from the Holy Cross Mountains (Miłoszów), Poland, have been analysed with respect to epibiont colonization patterns. Solitary microconchid tubeworms and colonial bryozoans, hederelloids and ascodictyids numerically dominate on the coral hosts. Moreover, the same taxonomic groups of epibionts dominate both the larger (Heliophyllum, Acanthophyllum , Stringophyllum , Ceratophyllum , Cystiphylloides) and smaller (Thamnophyllum) corallites, indicating the true pattern of epibiosis was achieved. The presence of common bioclaustrated epibionts, constricted and rejuvenated coral calyces, as well as epibionts growing concordantly with the host's growth direction, indicate that at least some corals were colonized during life. The observed low number of overgrowth cases of various epibionts on coral hosts suggests, that competition for hard substrate was negligible, most probably due to abundant coral substrates on muddy sea-bottom of the Givetian sea at Miłoszów. This epibiont community is similar to other known Devonian encrusting communities which likely developed in a more nutrient-rich palaeoenvironments and differs markedly from taxonomically-poor assemblages developing in a more oligotrophic conditions. The presence of Rothpletzella encruster, which is considered to be related to green algae, indicates that the Miłoszów coral community dwelled within the limits of the photic zone. • Middle Devonian (Givetian) epibionts colonizing rugose corals were analysed. • Larger and smaller corals were encrusted by the same epibiont groups. • Microconchids, bryozoans, hederelloids and ascodictyids are dominant groups. • Bioclaustrations and orientation of crinoid holdfasts indicate syn vivo epibiosis. • Encrusting algae Rothpletzella point to photic conditions in the coral habitat. [ABSTRACT FROM AUTHOR]

Silicified fossils collected in ploughed fields at Gavrus (Calvados, France), mainly mollusc shells, are Bajocian in age, and come from the Oolithe ferrugineuse de Bayeux Formation. The entire formation is highly condensed and most fossils are reworked. Their silicification allowed treatment with dilute hydrochloric acid. This treatment brought to light numerous encrusting sclerobionts: Porifera (3 taxa), Bryozoa (n), Polychaeta (9), Brachiopoda (n), Bivalvia (5). The borings and bioerosional traces are described using the "categories of architectural design" as defined by Buatois et al. (2017). Among the 28 ichnotaxa described (corresponding to an ichnodisparity of 14), Planavolites wisshaki isp. nov., Kleithrichnus belemnophilus igen. nov., isp. nov. and Foggara foggara igen. nov., isp. nov. are new. Some Gastrochaenolites dijugus Kelly and Bromley, 1984 borings accommodate the shell of the presumed borer Lithophaga fabella J.-A. Eudes-Deslongchamps, 1838. A group of Nododendrina europaea (Fischer, 1875) on a belemnite rostrum provides a good instance of an ichnogenetic series. Encrusting sclerobionts and macroscopic boring and bioerosional trace-makers are dominantly suspension feeders. The ichnofacies is a peculiar Entobia -ichnofacies, found in deeper, lower-energy environments than the "classical" coastal Entobia -ichnofacies, on deep shell-grounds far from the coast, in the deep euphotic zone. [ABSTRACT FROM AUTHOR]