Perspectives in coral reef hydrodynamics

Knowledge of skeletogenesis in scleractinian corals is central to reconstructing past ocean and climate histories, assessing and counteracting future climate and ocean acidification impacts upon coral reefs, and determining the taxonomy and evolutionary path of the Scleractinia. To better understand skeletogenesis and mineralogy in extant scleractinian corals, we have investigated the nature of the initial calcium carbonate skeleton deposited by newly settling coral recruits. Settling Acropora millepora larvae were sampled daily for 10 days from initial attachment, and the carbonate mineralogy of their newly deposited skeletons was investigated. Bulk analyses using Raman and infrared spectroscopic methods revealed that the skeletons were predominantly comprised of aragonite, with no evidence of calcite or an amorphous precursor phase, although presence of the latter cannot be discounted. Sensitive selected area electron diffraction analyses of sub-micron areas of skeletal regions further consolidated these data. These findings help to address the uncertainty surrounding reported differences in carbonate mineralogy between larval and adult extant coral skeletons by indicating that skeletons of new coral recruits share the same aragonitic mineralogy as those of their mature counterparts. In this respect, we can expect that skeletogenesis in both larval and mature growth stages of scleractinian corals will be similarly affected by ocean acidification and predicted environmental changes.     

Skeletal formation in the modern but ultraconservative chaetetid spongeSpirastrella (Acanthochaetetes) wellsi (demospongiae,porifera)

Summary The modern hadromerid coralline spongeSpirastrella (Acanthochaetetes) wellsi exhibits a unique secondary high-Mg calcite (>19 mol % MgCO₃) basal skeleton. The basal skeleton is constructed of bundles of elongated crystals more or less tangentially orientated. The initial formation of these crystals is controlled by soluble highly acidic aspartic and glutamic-rich (40%) macromolecules. The skeletal mineralization occurs in four different loci: in the top of the calicles, at the tabulae, on collagenous anchor fibres, and within closed spaces between the tabulae. The clicle walls are formed on the uppermost top of the basal skeleton as a continuous process. Based on long term stainings with Ca²⁺-chelating fluorochroms (calcein, chlorotetracyclines) the growth rate of this sponge is extremely low with ca. 50–100μm/a. The skeletal formation takes places outside the sponge, within a narrow zone (300–500 nm) between the basopinacoderm and the mature basal skeleton. The sponge produces thread-like folded templates (‘spaghetti fibres’) of 0,5–2 μm size, the shape controlling insoluble organic matrix. These templates become mineralized in a first step as MgCO₃, then are stretched. A soluble organic matrix is also secreted, and remains are included inside the mineralized skeleton. This organic matrix consists of in a complex mixture containing small very acidic proteins (5, 13, 31 KD; 40% Asp and Glu and therefore most probably Ca²⁺-binding) and high molecular weight glycoproteins among several other organic compounds. The mature crystals are high-Mg calcites. During calcification large cells with large reserve granules (LCG) are always present in a tight connection with the basopinacoderm. These cells form also the collagenous anchor fibres. Primary tabulae are formed by a non-collagenous organic sheet. Calcification happens only when LCG cells are enriched on the organic sheet. Randomly oriented high-Mg calcite crystals are growing on the collagenous anchor fibres. The same type of the mineralization is observed within the spaces of the tabulae. This particular case of mineralization is controlled by decaying sponge tissue (ammonification). The δ¹³C values are in equilibrium with the ambient sea water and vary between +3.2 and +2.8 ‰. The mode of mineralization of the basal skeleton can be described as biologically induced resp. matrix mediated.     

Sobralispongia densespiculata, a new coralline sponge from the Upper Jurassic of Portugal

From the Kimmeridgian (Upper Jurassic) of Portugal, the coralline sponge Sobralispongia densespiculata nov. gen. and nov. sp. is described. Main characteristics are a crustose habit, a primary spicule skeleton of very densely packed styles and subtylostyles arranged in a plumose architecture, microscleres of possibly aster-type, and a microgranular to fibrous secondary calcareous skeleton. The primary mineralogy of the calcareous skeleton was probably high-Mg calcitic. An assignment to the demosponge Order Axinellida is proposed.     

Spatial competition among clonal organisms in extant and selected paleozoic reef communities

Summary Occurrences of densely packed benthic organisms in extant reefs are of two types: 1) live-live interactions, where two living organisms interact, and 2) live-dead associations, where only one is alive and uses the other as a substrate. The latter are common in reef deposits due to biostratinomic feedback, i.e. dense skeletal accumulations provide hard substrates for clonal recruitment, thus facilitating greater frequency of live-dead encounters than in lower biomass level-bottom communities dominated by solitary organisms. Differentiating between these two types in ancient reefs is difficult, often impossible. Most live-live interactions among clones in extant reef communities involve competition for space. Clonal spatial competition is divisible into four types: 1) direct-aggressive: encrusting overgrowth; 2) indirect-passive: depriving neighbors of resources, chiefly sunlight, by growth above them; 3) stand-off: avoidance of competition by organisms adopting positions that avoid or minimize direct polyp/zooid contact; and 4) overwhelming: one clone/ species volumetrically or numerically overwhelms the other, meeting minimal resistance. Despite class-order level differences in taxa, our results indicate that extant analogs, based on the arrangement and distortion of skeletons, are valuable for recognizing live-live interactions in Silurian and Carboniferous reefs and interpreting the types of spatial competition represented. Comparison of overhead (plan) views of live-live coral competition in Polynesian reefs with vertical sections of Silurian and Carboniferous sponge-dominated reefs and biostromes suggests that direct-aggressive competition is more common among extant than among Paleozoic reef-builders. Stand-offs showing clone margin distortion and overwhelming with minor skeletal distortion are most common in our fossil examples and probably relate to the dominance of these reefs by sponges. Success by extant sponges in spatial competition is largely due to allelochemical deterrence which may explain the predominance of stand-off and overwhelming confrontations in fossil sponges rather than tentacle-mesentery based direct aggression among extant corals and bryozoans.     

Fifty million years of herbivory on coral reefs: fossils,fish and functional innovations

The evolution of ecological processes on coral reefs was examined based on Eocene fossil fishes from Monte Bolca, Italy and extant species from the Great Barrier Reef, Australia. Using ecologically relevant morphological metrics, we investigated the evolution of herbivory in surgeonfishes (Acanthuridae) and rabbitfishes (Siganidae). Eocene and Recent surgeonfishes showed remarkable similarities, with grazers, browsers and even specialized, long-snouted forms having Eocene analogues. These long-snouted Eocene species were probably pair-forming, crevice-feeding forms like their Recent counterparts. Although Eocene surgeonfishes likely played a critical role as herbivores during the origins of modern coral reefs, they lacked the novel morphologies seen in modern Acanthurus and Siganus (including eyes positioned high above their low-set mouths). Today, these forms dominate coral reefs in both abundance and species richness and are associated with feeding on shallow, exposed algal turfs. The radiation of these new forms, and their expansion into new habitats in the Oligocene–Miocene, reflects the second phase in the development of fish herbivory on coral reefs that is closely associated with the exploitation of highly productive short algal turfs.     

New spicular skeletons in Turbellaria,and the occurrence of spicules in marine meiofauna1

With Florianella, Bertiliella and Acanthiella, three new genera of Turbellaria are described, one from deep mud bottoms off Norway, and two from sandy bottoms off the south-eastern United States. Whereas the new family Bertiliellidae (within Turbellaria-Eukalyptorhynchia) is established for the two former genera, the latter is of uncertain systematic position, combining features of Archoophora and Prolecithophora-Combinata. All three genera are characterized by a spicular skeleton located in the basement membrane. In the Bertiliellidae the spicules are calcareous (aragonite). A survey of other spiculiferous Turbellaria and meiofauna in general suggests that spicular skeletons, instead of being a special adaptation to the interstitial environment, play a role in body support and tissue economy, and are, in some cases (Turbellaria and Mollusca), possibly relics indicating phylogenetic relationship.     

Molecular systematics,historical ecology,and phylogeography of Halimeda (Bryopsidales)

Halimeda (Bryopsidales), a genus of calcified, segmented green seaweeds, abounds in reefs and lagoons throughout the tropics. To investigate phylogenetic, phylogeographic, and historic ecological relationships of the genus, the nuclear rDNA including the SSU and both ITS regions were sequenced. A maximum likelihood tree revealed the following: (1) there were anatomical and morphological synapomorphies for five well-supported lineages; (2) the last common ancestor of one lineage invaded sandy substrata; those of two other lineages established in wave-affected habitats, whereas the cenancestor of the remaining two lineages occupied sheltered rocky slopes. Yet, several species adapted to new habitats subsequently, resulting in several cases of convergence; (3) all lineages separated into Atlantic and Indo-Pacific daughters, likely resulting from the rise of the Panamanian Isthmus. Each daughter pair gave rise to additional convergent species in similar habitats in different oceans; (4) Halimeda opuntia, the only monophyletic pantropical species detected so far, dispersed from the Indo-Pacific into the Atlantic well after the closure event; (5) minor SSU-sequence differences across species and phylogeographic patterns of vicariance indicated a relatively recent diversification of the extant diversity. Cretaceous and Early Tertiary fossil look-alikes of modern species must then have resulted from iterative convergence.     

Of teeth and trees: A fossil tip‐dating approach to infer divergence times of extinct and extant squaliform sharks

Fossil tip‐dating allows for the inclusion of morphological data in divergence time estimates based on both extant and extinct taxa. Neoselachii have a cartilaginous skeleton, which is less prone to fossilization compared to skeletons of Osteichthyans. Therefore, the majority of the neoselachian fossil record is comprised of single teeth, which fossilize more easily. Neoselachian teeth can be found in large numbers as they are continuously replaced. Tooth morphologies are of major importance on multiple taxonomic levels for identification of shark and ray taxa. Here, we review dental morphological characters of squalomorph sharks and test these for their phylogenetic signal. Subsequently, we combine DNA sequence data (concatenated exon sequences) with dental morphological characters from 85 fossil and extant taxa to simultaneously infer the phylogeny and re‐estimate divergence times using information of 61 fossil tip‐dates as well as eight node age calibrations of squalomorph sharks. Our findings show that the phylogenetic placement of fossil taxa is mostly in accordance with their previous taxonomic allocation. An exception is the phylogenetic placement of the extinct genus ?Protospinax , which remains unclear. We conclude that the high number of fossil taxa as well as the comprehensive DNA sequence data for extant taxa may compensate for the limited number of morphological characters identifiable on teeth, serving as a backbone for reliably estimating the phylogeny of both extinct and extant taxa. In general, tip‐dating mostly estimates older node ages compared to previous studies based on calibrated molecular clocks.     

Discovery of a “Living Dinosaur”: Globally unique modern hexactinellid sponge reefs off British Columbia, Canada

Summary Globally unique hexactinellid sponge reefs occur on the continental shelf off British Columbia, Canada. They cover about 425 km² of seafloor on the continental shelf off British Columbia (Canada) in water depths between 165 and 240 metres and occur on a low-angle deep shelf, iceberg scoured seafloor, characterized by very low sedimentation rates and very stable environmental conditions. The sponge bioherms are up to 19 metres high with steep flanks, whereas the biostromes are 2–10 metres thick and many kilometres wide. They all consist of dense populations of only seven hexactinellid species. Three of them, all hexactinosan species (Aphrocallistes vastus, Heterochone calyx, Farrea occa) are the main frambuilders, composing a true rigid framework of sponge skeletons encased in a organic rich matrix of modern clay baffled by the sponges. Growth rates of hexactinosan sponges range in the order of 0–7 centimetres per year. The base of the oldest sponge reefs date from approximately 9000 years b.p. Different invertebrate and fish faunas occupy the reefs than occur on adjacent seafloor areas and some species appear to use the sponge reef complex structures as refugia where they can hide. Sidescan sonar data and direct observation by manned submersible clearly show that large areas of sponge reefs have been heavily damaged by seafloor trawling in the past decade. These unique extant siliceous sponge reefs can be used as a modern analogue for a better understanding and interpretation of fossil siliceous sponge reefs, known from many ages and many locations world wide.     

First reported occurrence of wewokellid sponges (Calcarea, Heteractinida) from the Permian of central Iran

The new calcisponges Regispongia fluegeli n. sp., and Iranospongia circulara n. gen. n. sp., are described from central Iran. These are the first heteractinid sponges reported from the Permian of the region. These wewokellid sponges are large, irregularly cylindrical forms with a distinct axial spongocoel. The calcareous spicular skeletons of both taxa have been overgrown and are recrystallized. However, the preserved skeleton of Regispongia fluegeli does include large polyactines in the main endosomal layer and small octactines and possibly other polyactine spicules in both the relatively massive dermal layer and the distinct, delicately spiculed, gastral layer. Iranospongia is characterized by a discontinuous ring of vertical exhalant canals interior to the dense dermal layer, and by an interior skeleton net that includes common coarse vertical fibers. Individual spicules in Iranospongia are commonly obscured, but locally some remnants of possible polyactines occur in outer parts of the skeleton.     

Natural cultch type influences habitat preference and predation,but not survival,in reef‐associated species

A shared origin with fresh and dredged cultch and availability via mining have made fossil cultch a commonly used reef restoration substrate. However, important differences in shape and size between whole‐shell cultch and fossil cultch may impact the complexity of reefs constructed from these materials. To determine if these differences may impact the development of restored reefs, we quantified the interstitial space each cultch type provides and constructed reef mesocosms to measure (1) the immediate effects of exposure to each cultch type on mortality of blue crab (Callinectes sapidus) and pink shrimp (Farfantepenaeus duorarum); (2) the tendency of crab, shrimp, and Florida crown conch (Melongena corona) to be found on habitats composed of each substrate type and their position within each in split‐substrate mesocosms; and (3) the influence of cultch type on predation of Eastern oysters (Crassostrea virginica) by crabs and conch. Aggregation of fossil cultch contains more shells and provides less interstitial space than an equivalent volume of whole‐shell cultch. Although immediate mortality following deployment was low and did not differ among cultch types, we found that all species were more likely to be found on fresh cultch over fossil cultch in choice experiments and used each habitat type differently. Cultch type also impacted the size of oysters consumed by crabs in short‐term feeding trials. The structure and traits of habitats created by various materials should be added to the growing list of issues considered when natural communities are to be restored in oyster reefs and other environments.     

Ultrastructure of the atrioventricular valve and ventricular endo- and myocardium of the tigerfish,Hydrocynus forskahlii

Osteology of four extant species of Bregmacerotidae, Bregmaceros houdei, B. bathymaster, B. japonicus, and B. macclellandi, is described for the first time. The osteological analysis enables the recognition of two groups: (1) B. houdei and B. bathymaster, and (2) B. japonicus and B. macclellandi. Considerable differences in the structure of skull, and pectoral and pelvic girdles among the species indicate the existence of at least two phyletic lines within the genus. Knowledge of the skeleton may be of great importance for the taxonomy of fossil and extant species of Bregmaceros.     

Sponge borehole size as a relative measure of bioerosion and paleoproductivity

Bioerosion intensity has been proposed as a measure of paleoproductivity in fossil reefs, but it is difficult to measure directly because fossil corals are often incomplete and because it is difticult to infer the length of time a given coral was exposed to bioeroding organisms. Both nutrient availability and taphonomic factors can affect bioerosion intensity as measured in dead corals. Here, we examine these two effects separately using data from previous studies on bioerosion in modern and fossil corals. Size of individual sponge borings accurately reflects total bioerosion in modern massive and branching corals on the Great Barrier Reef. Total bioerosion in both massive and branching corals decreases outward across the continental shelf, paralleling trends in nutrient availability. Size of individual Cliothosa hancocki borings decreases across the shelf in branching Acropora but not in massive Porites. Fossil sponge borings Entobia convoluta and Uniglobites glomerata in massive corals from Oligocene and Miocene reefs in Puerto Rico are smallest in Oligocene shelf-edge reefs, intermediate in Oligocene patch reefs, and largest in Miocene patch reefs. Both facies-related influence, represented by Oligocene shelf-edge reefs vs. Oligocene patch reefs, and nutrient-related influence, represented by Oligocene vs. Miocene patch reefs, were reflected in the size of sponge boreholes. Size of sponge borings also varies among species of host corals, apparently in relation to skeletal architecture. Borehole size is inversely correlated with skeletal density as measured by the relative proportion of skeleton and pore space in transverse thin section. There is a weak positive correlation between borehole size and corallite diameter. These findings contradict reported positive correlations between total bioerosion and bulk density in modern corals. Borehole size appears accurately to reflect intensity of total internal bioerosion in fossil corals. Facies-controlled taphonomic overprints and influence of skeletal differences between coral species limit the use of sponge borehole size to a rough indicator of paleoproductivity in fossil coral reef environments.     

The ‘biomineralization toolkit’ and the origin of animal skeletons

Biomineralized skeletons are widespread in animals, and their origins can be traced to the latest Ediacaran or early Cambrian fossil record, in virtually all animal groups. The origin of animal skeletons is inextricably linked with the diversification of animal body plans and the dramatic changes in ecology and geosphere–biosphere interactions across the Ediacaran–Cambrian transition. This apparent independent acquisition of skeletons across diverse animal clades has been proposed to have been driven by co‐option of a conserved ancestral genetic toolkit in different lineages at the same time. This ‘biomineralization toolkit’ hypothesis makes predictions of the early evolution of the skeleton, predictions tested herein through a critical review of the evidence from both the fossil record and development of skeletons in extant organisms. Furthermore, the distribution of skeletons is here plotted against a time‐calibrated animal phylogeny, and the nature of the deep ancestors of biomineralizing animals interpolated using ancestral state reconstruction. All these lines of evidence point towards multiple instances of the evolution of biomineralization through the co‐option of an inherited organic skeleton and genetic toolkit followed by the stepwise acquisition of more complex skeletal tissues under tighter biological control. This not only supports the ‘biomineralization toolkit’ hypothesis but also provides a model for describing the evolution of complex biological systems across the Ediacaran–Cambrian transition.     

Relationship between osteology and aquatic locomotion in birds: determining modes of locomotion in extinct Ornithurae

The evolutionary history of aquatic invasion in birds would be incomplete without incorporation of extinct species. We show that aquatic affinities in fossil birds can be inferred by multivariate analysis of skeletal features and locomotion of 245 species of extant birds. Regularized discriminant analyses revealed that measurements of appendicular skeletons successfully separated diving birds from surface swimmers and flyers, while also discriminating among different underwater modes of swimming. The high accuracy of this method allows detection of skeletal characteristics that are indicative of aquatic locomotion and inference of such locomotion in bird species with insufficient behavioural information. Statistical predictions based on the analyses confirm qualitative assessments for both foot‐propelled (Hesperornithiformes) and wing‐propelled (Copepteryx) underwater locomotion in fossil birds. This is the first quantitative inference of underwater modes of swimming in fossil birds, enabling future studies of locomotion in extinct birds and evolutionary transitions among locomotor modes in avian lineage.     

The oldest Gondwanan fossil of Leiinae (Diptera,Mycetophilidae): Phylogenetic and evolutionary implications

A fossil Mycetophilidae from the Aptian Crato Formation—Cretomanota gondwanica gen. nov., sp. nov.—is described, which is the first mycetophilid from the Crato Formation and corresponds to the oldest known fossil leiine and only the second Gondwanan fossil mycetophilid described so far. Cretomanota gondwanica and both species of Alavamanota Blagoderov and Arillo were added as terminals to the data matrix of a general phylogenetic analysis of the Mycetophilidae, and both fit into the Leiinae. Alavamanota is monophyletic, sister to the clade composed by Cretomanota and the extant genus Manota Williston. The biology of the extant members of this fungivorous family corroborates the reconstruction of the Crato palaeoenvironment as including woodlands with humid habitats and microhabitats. The presence of a Cretaceous member of the tribe Manotini at low latitudes in South America reinforces the hypothesis that the clade with all manotines except Leiella Edwards corresponds to a Lower Cretaceous offshoot from a group in southern Gondwana expanding its distribution to more northern areas into the Gondwana and into Laurasia.     

An evolutionary fast‐track to biocalcification

The ability to construct mineralized shells, spicules, spines and skeletons is thought to be a key factor that fuelled the expansion of multicellular animal life during the early Cambrian. The genes and molecular mechanisms that control the process of biomineralization in disparate phyla are gradually being revealed, and it is broadly recognized that an insoluble matrix of proteins, carbohydrates and other organic molecules are required for the initiation, regulation and inhibition of crystal growth. Here, we show that Astrosclera willeyana, a living representative of the now largely extinct stromatoporid sponges (a polyphyletic grade of poriferan bauplan), has apparently bypassed the requirement to evolve many of these mineral‐regulating matrix proteins by using the degraded remains of bacteria to seed CaCO₃ crystal growth. Because stromatoporid sponges formed extensive reefs during the Paelozoic and Mesozoic eras (fulfilling the role that stony corals play in modern coral reefs), and fossil evidence suggests that the same process of bacterial skeleton formation occurred in these stromatoporid ancestors, we infer that some ancient reef ecosystems might have been founded on this microbial–metazoan relationship.     

Combining isotopic and ecomorphological data to refine bovid paleodietary reconstruction: a case study from the Makapansgat Limeworks hominin locality

The relationship between environmental change and hominin evolution remains obscure. For the most part, this stems from the difficulty of reconstructing ancient hominin habitats. Bovids are among the most frequently utilized paleoenvironmental indicators, but little is known about the habitat preferences of extinct taxa. It is generally assumed that fossil bovids both ate the same things and occupied the same habitats as their closest extant relatives. We test the first part of this assumption by reconstructing the diets of seven bovids from Makapansgat Limeworks, South Africa. Since diet and habitat are linked, these reconstructions have implications for our understanding of fossil bovid habitat tolerances. Ecomorphological and stable carbon isotope analyses are employed, allowing us to take advantage of the strengths and overcome the weaknesses of both. In most cases, fossil bovids did have similar diets to their extant relatives, and probably occupied similar habitats. Gazella vanhoepeni and Aepyceros sp., however, were almost exclusive browsers, and not mixed feeders like their living counterparts.     

Structure of recent and fossil mysid statoliths (Crustacea,Mysidacea)

Statoliths of 61 Recent species representing all subfamilies of Mysidae were studied with special emphasis on internal structure. In addition 5 samples of fossil statoliths from Miocene deposits were examined. Species of Boreomysinae and Rhopalophthalminae show simple roughly spherical organic statoliths, with setae originating from the sensory cushion and anchored in the statolith with distal branches extending shortly below the surface. All other subfamilies possess mineralized statoliths of greater structural complexity, with differentiation in core and mantle, where each part may consist of up to three layers. Habitus is hemispherical to discoidal. External gross structures are dorsal tegmen, ventral fundus, and the ambitus forming the outer toroidal to semi-toroidal circumference. Setae penetrate the mantle through mineralic canals and insert on the surface of the core. As suggested by congeneric species of Schistomysis, there is no principal structural difference between statoliths mineralized with fluorite compared to vaterite. However, vaterite statoliths tend to be more often of moruloid appearance and are exceptional by showing a central conical hole (the hilum) or a central cavity in certain forms. These structures are typical of fossil calcite statoliths. In vaterite and fluorite statoliths, the mantle shows radially arranged (= spherulitic) crystal aggregates. Such arrangements are badly preserved in fossil calcite statoliths. In large extant statoliths, concentric structures, mainly in the form of superficial striation and/or concentric microstrata, are visible in coexistence with radial aggregates. Stratification is possibly due to stratified deposition of the nonmineralized gland product, while the spherulitic structure is indicative of subsequent radial growth of crystal aggregates. The structure of accessory fluorite statoliths in the statocyst of Mesopodopsis slabberi leads to the hypothesis that mantle material is formed by secretions of the caudal statocyst gland. After demineralization of fluorite, vaterite and calcite statoliths, an organic template remains showing most essential morphological features of the statolith. From this we conclude that the structure of the statolith is (almost) entirely matrix mediated. © 1993 Wiley-Liss, Inc.     

Understanding the murky history of the Coral Triangle: Miocene corals and reef habitats in East Kalimantan (Indonesia)

Studies on ancient coral communities living in marginal conditions, including low light, high turbidity, extreme temperatures, or high nutrients, are important to understand the current structure of reefs and how they could potentially respond to global changes. The main goal of this study was to document the rich and well-preserved fossil coral fauna preserved in Miocene exposures of the Kutai Basin in East Kalimantan, Indonesia. Our collections include almost forty thousand specimens collected from 47 outcrops. Seventy-nine genera and 234 species have been identified. Three different coral assemblages were found corresponding to small patch reefs that developed under the influence of high siliciclastic inputs from the Mahakam Delta. Coral assemblages vary in richness, structure, and composition. Platy coral assemblages were common until the Serravallian (Middle Miocene), while branching coral assemblages became dominant in the Tortonian (Late Miocene). By the late Tortonian massive coral assemblages dominated, similar to modern-style coral framework. Our results suggest that challenging habitats, such as the Miocene turbid habitats of East Kalimantan, might have played an important role during the early diversification of the Coral Triangle by hosting a pool of resilient species more likely to survive the environmental changes that have affected this region since the Cenozoic. Further research that integrates fossil and recent turbid habitats may provide a glimpse into the dynamics and future of coral reefs as “typical” clear-water reefs continue to decline in most regions.