Ewa Roniewicz

TOWARDS A NEW SYNTHESIS OF EVOLUTIONARY RELATIONSHIPS AND CLASSIFICATION OF SCLERACTINIA

Abstract The focus of this paper is to provide an overview of historical and modern accounts of scleractinian evolutionary relationships and classification. Scleractinian evolutionary relationships proposed in the 19th and the beginning of the 20th centuries were based mainly on skeletal data. More in-depth observations of the coral skeleton showed that the gross-morphology could be highly confusing. Profound differences in microstructural and microarchitectural characters of e.g., Mesozoic microsolenine, pachythecaliine, stylophylline, stylinine, and rhipidogyrine corals compared with nominotypic representatives of higher-rank units in which they were classified suggest their separate (?subordinal) taxonomic status. Recent application of molecular techniques resulted in hypotheses of evolutionary relationships that differed from traditional ones. The emergence of new and promising research methods such as high-resolution morphometrics, analysis of biochemical skeletal data, and refined microstructural observations may still increase resolution of the “skeletal” approach. Achieving a more reliable and comprehensive scheme of evolutionary relationships and classification framework for the Scleractinia will require close cooperation between coral biologists, ecologists, geologists, geochemists, and paleontologists.

An early Hettangian coral reef in southern France: Implications for the end-Triassic reef crisis

Abstract The oldest known Jurassic coral reef is exposed in the Ardèche region of southern France. This reef site, consisting of at least three reefal bodies, is of early Hettangian age and thus immediately postdates the end-Triassic mass extinction, which is well known for its catastrophic effect on reef building. Bulk carbonate carbon isotopes of the limestones below the reef are likely to record environmental perturbations subsequent to the mass extinction. The main reef is surprisingly well developed (20 m in thickness, 200 m in lateral extent) and composed of at least four genera and six species of corals—not only holdover genera from the Triassic, but also one newly evolved genus (Phacelophyllia), contributed to reef construction. Just like their latest Triassic counterparts, the reef is dominated by phaceloid corals with a considerable contribution of microbialite. The reef predates similarly well developed structures by almost ten million years. The shelf setting of the reef renders it unlikely that refuges around oceanic islands are needed to explain survival of corals across the end-Triassic mass extinction.

Middle Triassic cnidarians from the New Pass Range, central Nevada

We describe three scleractinian corals and one species of hydrozoan from the New Pass Range, central Nevada, which together constitute the oldest Triassic cnidarian assemblage from North America. They occur in carbonate rocks tentatively correlated with the Augusta Mountain Formation, Star Peak Group. At generic and higher levels, these cnidarians seem representative of early Mesozoic Tethyan faunas and carbonate lithofacies, but they indicate some endemism. Although the original aragonitic skeletons and microstructure are destroyed by recrystallization, the corals still yield important details allowing their correct taxonomic assignment. They contain the minitrabecular cerioid coral, Ceriostella variabilis new genus and species, the thick-trabecular, thamnasteroid coral Mesomorpha newpassensis new species, and an undeterminable cuifastreid coral tentatively assigned to Cuifastraea. The discovery of Mesomorpha marks the first occurrence of this genus outside the Jurassic and Cretaceous seas. Also discovered is a remarkably corallike hydrozoan, Cassianastraea reussi (Laube), already known from the Carnian stage of the western Tethys. This is the first occurrence of this species outside the western Tethys.

Late Triassic (Carnian) corals from Timor-Leste (East Timor): their identity, setting, and biogeography

Four scleractinian coral taxa are described from limestones within a sandstone-shale séquence correlated with the Late Triassic Babulu Formation, Manatuto township, on the northern coast of Timor-Leste (East Timor). The coral fauna consists of three phaceloid taxa, Paravolzeia tìmorìca gen. et sp. nov., Craspedophyll ramosa sp. nov., Margarosmilia confluens (Münster), and a generically indeterminate solitary taxon attributed to the family Margarophylliidae. Ali four corals are related at various taxonomie levels to Carnian faunas from the Dolomites of northern Italy. Previously, only Norian coral faunas were known from the Triassic of Timor. The fauna exhibits both similarities to and differences from Carnian faunas of the Dolomites and helps confirm palaeogeographic affinities with the western Tethys, although during Late Triassic time Timor lay in the distant southeastern portai of the Tethys. Despite isolation from the western Tethys, the presence of two species foundalso in the Dolomites indicates that larvai dispersai occurred between the two areas.

Upper Triassic Corals from Nevada, Western North America, and the Implications for Paleoecology and Paleogeography

Abstract Late Carnian–early Norian corals from the Luning and Osobb formations in west-central Nevada represent an important Late Triassic fauna for understanding the paleoecology and the paleogeography of the eastern Panthalassa region during Late Triassic time. The corals occur in bedded limestone representing biostromes and patch reefs and their composition presages the important global changeover of faunas of the intra-Norian interval. A taxonomic analysis of over 60 specimens reveals a majority of colonial corals ranging from cerioid, astreoid (i.e., cerioid-plocoid lacking walls), meandroid and thamnasterioid types. Surprisingly, remnants of the original aragonite microstructure remain in some specimens, allowing a better comparison with more remote Tethyan corals. In total, 14 genera have been identified from Nevada while two genera remain undetermined. The fauna is composed of species considered typical of both the North American Cordillera and cratonal South America. The following genera and species are new and endemic to the Americas: Khytrastrea silberlingi and K. cuifiamorpha, Flexastrea serialis, Nevadoseris punctata, Areaseris nevadaensis and a new genus Minasteria (with Astrocoenia shastensis Smith, 1927 as type species). Likewise are the new species: Margarogyra silberlingi and Curtoseris dunlapcanyonae. Genera Meandrovolzeia, Margarogyra, Ceriostella, Ampakabastraea, Retiophyllia, Distichomeandra, Curtoseris, Thamnasteria and Astraeomorpha provide important links to the former Tethys province. The revised coral fauna changes previous views of the close taxonomic similarity with the Tethys, instead producing a paleogeographic pattern emphasizing a much greater degree of endemism. This pattern emphasizes the isolation of Nevada from the Tethys and the similarities with some outboard terranes of the Cordillera.

Early Norian (Triassic) Corals from the Northern Calcareous Alps, Austria, and the Intra-Norian Faunal Turnover

The first description of early Norian coral fauna from the Northern Calcareous Alps (Dachstein Plateau and Gosaukamm), Austria, is presented: 31 scleractinian species from 24 genera (including three corals not formally determined), and three hexanthiniarian species belonging to two genera. The stratigraphical position of the main part of the fauna discovered in the South Dachstein Plateau at the Feisterscharte is determined by means of the conodont Epigondolella quadrata (Lacian 1); single finds are from the horizons with Epigondolella triangularis and Norigondolella navicula (Lacian 3), and one close to the horizon with Epigondolella cf. multidentata (Alaunian 1). Rare corals from the Gosaukamm are from the Lacian 1 and Alaunian. Five species are described as new: Retiophyllia vesicularis, Retiophyllia aranea, Margarosmilia adhios, Hydrasmilia laciana; one new genus and species from the family Coryphylliidae, Margarogyra hirsuta; one new genus and species, Thamnasterites astreoides, cannot be assigned to a family. Two hexanthiniarian species, Pachysolenia cylindrica and Pachydendron microthallos, known exclusively from the Tethyan lower Norian, represent stratigraphically valuable species. A regularly porous coral from the family Microsolenidae, Eocomoseris, which up to now has only been known from the Jurassic and Cretaceous, is here identified from the Triassic strata (originally described as Spongiomorpha [Hexastylopsis] ramosa). Predominant taxa show solitary and phaceloid (pseudocolonial) growth forms and an epithecal wall; pennules-bearing corals are common. Carnian genera and genera typical of the Lacian and Lacian—early Alaunian prevail; a hydrozoan genus Cassianastraea has also been encountered as well as a scleractiamorph coral, Furcophyllia septafindens). The faunal composition contrasts with that of well known late Norian—Rhaetian ones, the difference being observed not only at the generic but also at the family level. The post-early Norian change in coral spectrum documents the turnover of the coral fauna preceding that at the Triassic/Jurassic boundary.

TRIASSIC ROOTS OF THE AMPHIASTRAEID SCLERACTINIAN CORALS

Abstract The Early Carnian (Upper Triassic) phaceloid coral originally described by Volz (1896) as Hexastraea fritschi, type species of Quenstedtiphyllia Melnikova, 1975, reproduced asexually by “Taschenknospung” (pocket-budding), a process documented herein for the first time. This type of budding is recognized only in the Amphiastraeidae, a family thus far recorded only from Jurassic-Cretaceous strata. Similar to amphiastraeids, Quenstedtiphyllia fritschi (Volz, 1896) has separate septal calcification centers and a mid-septal zone built of serially arranged trabeculae. The most important discriminating characters of the new amphiastraeid subfamily Quenstedtiphylliinae are one-zonalendotheca and radial symmetry of the corallite in the adult stage (in contrast to two-zonal and bilateral symmetry in the adult stage in Amphiastraeinae). Quenstedtiphyllia fritschi shares several primitive skeletal characters (plesiomorphies) with representatives of Triassic Zardinophyllidae and, possibly, Paleozoic plerophylline rugosans: e.g., thick epithecal wall and strongly bilateral early blastogenetic stages with the earliest corallite having one axial initial septum. To interpret the phylogenetic status of amphiastraeid corals, we performed two analyses using plerophylline rugosans and the solitary scleractinian Protoheterastraea, respectively, as the outgroups. The resulting phylogenetic hypotheses support grouping the Zardinophyllidae with the Amphiastraeidae in the clade Pachythecaliina (synapomorphy: presence of pachytheca). Taschenknospung is considered an autapomorphy for the Amphiastraeidae. This study is the first attempt to analyze the relationships of the Triassic corals cladistically.