The Sultan Formation is a Middle and Upper Devonian inner shelf carbonate sequence in southern Nevada containing four stromatoporoid-dominated biofacies. Reported herein is a study of the Ironside Dolomite and Valentine Limestone Members exposed at Mountain Springs, Nevada. Eight lithofacies are distinguished and interpreted as a transgressive sequence, with deposition ranging from the supratidal zone to just below wave base. Each of the biofacies is unique and confined to a specific depositional environment as interpreted from the lithofacies reconstructions. The purpose of the study was to gain a better understanding of the range of ecologic conditions—physical, chemical, and biological—to which these stromatoporoids were adapted.

Based on the research, it is concluded that stromatoporoids flourished in a variety of nonreef habitats which ranged from highly stressful peritidal environments where only stromatoporoids were accommodated to less stressful offshore habitats where other organisms may have been in direct competition. Although habitat generalists are usually poor competitors, these stromatoporoids appear to have been an exception. Their ability to colonize a variety of substrata, their broad tolerances to chemical conditions and circulation patterns, and their emphasis on high rates of lateral growth have permitted them to simultaneously occupy unstable tidal channel embayments and more benign offshore habitats.

The Treptoceras duseri shale unit within the Waynesville Formation of Late Ordovician (early Richmondian) age in southwest Ohio and the equivalent Trilobite shale unit in the same formation exposed in adjacent portions of Indiana represent an Ordovician shallow marine mud-bottom epeiric sea facies. These fine-grained elastics contain a moderately diverse mollusk-trilobite assemblage dominated by vagrant epifaunal detritus-feeding calymenid and asaphid trilobites, large endobyssate and infaunal filter-feeding pelecypods, and nektonic nautiloids. Articulate brachiopods, ectoprocts, and pelmatozoan echinoderms form only minor elements of this fauna.

This mollusk-trilobite assemblage was common in Late Ordovician shallow marine clastic environments where mobility was an asset and there was an abundance of oxygen and food resources. Such assemblages are characteristic of the Lorraine Fauna of Late Ordovician (Edenian to Richmondian) age that occurs from the Ohio Valley north and east into New York, Ontario, Quebec, and Ireland. These early Paleozoic mud-bottom assemblages were considerably modified by the Late Ordovician extinction event and were replaced in the Silurian and Devonian by distinctly different assemblages dominated by large epifaunal strophomenid and spiriferid brachiopods, crinoids, and phacopid trilobites.

Early Cambrian Leptomitus zitteli Walcott, 1886, is a tubular, double-walled, demo-sponge from the Parker Slate of Vermont and is one of the few intact sponges of that age known. It occurs with skeletal fragments of ?Protospongia hicksi Hinde, 1887. Hazelia walcotti (Resser and Howell, 1938) is a thin-walled, tubular sponge with crudely clustered oxeas in a thatched skeleton. It is known from the Kinzers Formation of Pennsylvania. Early occurrences of Leptomitus and Hazelia indicate that at least these two lineages had diverged by the latter part of the Early Cambrian. The impression described as Leptomitus minor by Resser and Howell (1938) lacks spicules and is not a sponge.

Detailed morphological study of well-preserved specimens of Bukryaster hayi (Bukry) Prins and Sissingh by means of light and scanning electron microscopes reveals that the arms of the star-shaped nannofossil are pierced by pronounced perforations, reminiscent of those of the Tertiary genus Pemma Klumpp. Those and other features differentiate the taxon from Rucinolithus hayii Stover (1966) and help delimit the stratigraphic range of this important Campanian nannofossil.

Paleobiological studies of early metazoan evolution are critically dependent on the accurate stratigraphic subdivision and correlation of uppermost Proterozoic and Lower Cambrian sequences. Planktonic microfossils evolved rapidly during this period and are widely distributed and abundant in Vendian and Lower Cambrian rocks; therefore, they provide what is potentially one of the best means of correlating successions of this age. In Ny Friesland, Spitsbergen, tillite-bearing detrital rocks of the uppermost Proterozoic Polarisbreen Group are overlain without apparent unconformity by the Tokammane Formation, a tripartite lithologic sequence consisting of quartzarenites (Blårevbreen Member) overlain by dark shales with subordinate sandstone (Topiggane Member) and dolomites (Ditlovtoppen Member). Salterella, hyoliths, and other invertebrate remains occur in the upper part of the Tokammane succession; trace fossils are found in the Tokammane quartzarenites and shales, as well as in the uppermost few meters of the Polarisbreen sequence. Planktonic microfossils occur throughout the succession. They indicate that the Polarisbreen Group is Vendian in age and that a hiatus corresponding in time to the latest Vendian and (perhaps) earliest Cambrian coincides with the Polarisbreen/Tokammane boundary. Lower Topiggane shale samples contain acritarchs comparable to those found in the sub-Holmia Lontova Beds of Eastern Europe. Upper Topiggane samples contain diverse acritarch assemblages that indicate a late Holmia or Protolenus age, suggesting the presence of a second hiatus within the Tokammane Formation. Planktonic microfossils allow biostratigraphic correlation with other sequences both within (East Greenland) and between (East European Platform) paleocontinents. Like those from other areas, diversity trends exhibited by late Proterozoic and Early Cambrian acritarchs from Spitsbergen indicate a major Vendian episode of extinction followed by Early Cambrian rediversification of planktonic microfossils.

The wall of Michelinia meekana Girty is composed predominantly of lamellae that are approximately parallel to the median dark line, confirming its placement in the genus Michelinia s.s. The presence of a Praemichelinia-type microstructure in some parts of the wall is a recurrence of primitive architecture that suggests derivation of Michelinia from Praemichelinia.

A large collection of Silurian halysitids, mainly from the Limestone Point, La Vieille, and Petit Rocher Formations of northern New Brunswick, includes nine species distributed among Catenipora Lamarck, Halysites Fischer von Waldheim, and Cystihalysites Tchernyshev. One species, Cystihalysites belledunensis, is new, and, of the others, half are previously unknown in the Chaleur Bay region and half have been described before from this area.

All species are defined using both qualitative and quantitative data. Statistical analysis of serial sections of a corallum of Cystihalysites belledunensis suggests that any random section of a halysitid will yield quantitative data representative of that colony.

Preliminary analysis of the relationships between species distributions and stratigraphy and sedimentary associations suggests strong facies-control on the distribution of the four most abundant species. Both Catenipora simplex (Lambe) and Catenipora micropora (Whitfield) occur mostly in outer shelf facies. Cystihalysites belledunensis n. sp. and Cystihalysites encrustans (Buehler) never occur together, the former being found in predominantly high-energy inner shelf facies and the latter in the outer shelf facies.

The hermatypic scleractinian cryptic coral biota living under mobile rubble in the reef flat and back reef zones of a Fijian fringing reef was surveyed in detail in August of 1984; only 138 days later the reef was struck by the first of two sequential hurricanes (57 days apart). The same sample areas were re-studied in August 1985, thereby providing the first detailed census of pre- and post-hurricane cryptic reef coral populations, and allowing an assessment of hurricane impact on these populations.

The 61 cryptic species (60 corals and Millepora) show 88 percent commonality with the intertidal and shallow subtidal reef surface coral population (68 species), and therefore are a good representation of the surface biota.

A major effect of the hurricanes was a reduction of almost 50 percent in the number of boulders sheltering cryptic coral. However, among boulders that retained coral through the storms, there was only a 5 percent reduction in the mean number of corals per boulder, signifying that damage to the surviving population was minor. The composition of the surviving cryptic coral population is essentially unchanged from its pre-hurricane state (there are differences in absolute abundances), and the relative importance of the species does not show marked change in most cases. Coral morphologies show little change in their absolute and relative percent abundances after the hurricanes. In contrast to what is normally seen in reef surface habitats, therefore, coral colony form did not appear to be an important determinant in survivability for those living under boulders; primary selection by the storms seems to have been on boulder form rather than cryptic coral form.

Cryptic sub-rubble coral populations may function as a preserve for elements of the pre-hurricane reef surface community. For example, delicately-branching forms that are commonly devastated in reef surface habitats during hurricanes may, in some cases, be preserved in great numbers under boulders or in other cryptic habitats. This provides a “recruitment pool” that can greatly accelerate their recovery and re-establishment on the post-hurricane reef surface, and dampen the potentially severe community dislocations arising from intense competition for space in “instantaneous” new reef substrate.

The Upper Chesterian Pitkin Formation of the Ozark Dome region contains a large and diverse, yet highly endemic, coral fauna consisting of 10 genera of rugose corals and three of tabulate corals. Coral distribution within the formation is affected by stratigraphic, paleoecologic, and possibly paleogeographic controls. Although it is impossible at this time to fully evaluate the importance of stratigraphic controls on the coral distribution, the occurrence of two types of carbonate bioherms within the formation provides substantial paleoecologic control on the distribution of certain corals. Despite the high endemism and facies restriction, the coral fauna has proven to be biostratigraphically sensitive, correlating with middle and upper Chesterian coral zones in the Western Interior Province of North America. Among the Pitkin corals herein described are the new genera: Lesliella n. gen. (L. amplexa n. sp., type species) and Parvaxon n. gen. (P. minutum n. sp., type species). Other newly described species are: Amplexizaphrentis browni n. sp., Barytichisma clubinei n. sp., B. ozarkana n. sp., and Leonardophyllum arkansanum n. sp., which represents the first reported occurrence of the genus in strata below the Pennsylvanian boundary.

Collections of four Ordovician bryozoan species from habitats of differing levels of taxonomic diversity were examined in order to assess the effect of environmental conditions on intraspecific and interspecific morphologic patterns. Up to 20 morphometric characteristics were measured for each species from populations in both high-diversity and low-diversity settings. Character means and the levels of character variability differ between populations in different diversity zones. Across species, mean character values differ significantly in 41 percent of the total comparisons, permitting intraspecific and interspecific multivariate discrimination of populations from the two diversity zones.

The partitioning of clonal morphologic variability into within-colony (nonheritable) and among-colony (potentially heritable) components reveals that habitat conditions favoring high diversities appear to promote a greater proportion of potentially heritable genetic variation both within- and among-species than do low-diversity settings wherein a larger percentage of variation is ecophenotypic, or nonheritable, plasticity. Although the actual percentages vary from species to species, this pattern is obtained for representatives of four different trepostome bryozoan families and therefore is robust. Variability of this sort, if unrecognized, could lead to taxonomic oversplitting along ecologic gradients. These local, facultative adjustments to environmental conditions may be indicative of processes involved in the reactions of populations to selective pressures.

Analyses such as this, coupled with examinations of character covariances, may permit the recognition not only of environmentally-induced morphologic plasticity and the proportions of potentially heritable and nonheritable variability, but also provide evidence for intraspecific changes in the rates and timing of developmental events (i.e., across-population or facultative heterochrony).

A large collection of Silurian Syringoporidae, mainly from the Limestone Point and La Vieille formations of northern New Brunswick, includes one new species and three species previously described from this area. Syringopora lambei n. sp. is distinguished from the superficially similar S. bifurcata Lonsdale by its larger corallites with much broader axial tubes and less frequent corallite contacts. Similar problems which have existed in the past in the distinction of S. compacta Billings and S. reteformis Billings can be resolved, as shown in this study, on the basis of the larger, geniculate and densely-packed corallites of S. reteformis. All four species are defined using more quantitative data than has previously been applied to syringoporid taxonomy. A new lectotype for S. compacta is proposed. Recognition of epibionts on a corallum of S. bifurcata as virtually identical to the “epithecal scales” used to distinguish Syringoalcyon Termier and Termier from Syringopora Goldfuss argues strongly against the continued recognition of the former as a separate genus. Preliminary analysis of syringoporid distributions in relation to stratigraphy and sedimentary associations suggests strong facies and paleoenvironmental control on these distributions. For this reason and because of their long stratigraphic ranges, no well-defined biozonal scheme can be proposed at this time.

The Oñate Formation of Middle Devonian (Givetian) age is exposed in the Mud Springs Mountains of New Mexico, where it is represented by an unusually shaly and extremely fossiliferous facies. Tabulophyllum traversensis (Winchell) found here is the only rugose coral species known thus far from Middle Devonian rocks of New Mexico and is of special interest as evidence of migration between the area of the Oñate occurrence and those in the Cedar Valley Limestone in Iowa and the Traverse Group of Michigan. The occurrence is also of interest because of the association of the Oñate coral with the receptaculitid Sphaerospongia sp. cf. S. tessellata (also known from Canada, Australia, and New York). The corals apparently utilized receptaculitids as a solid substrate for post-larval growth and developed an extremely broad flat base, fixed to the upper surface of Sphaerospongia.

North American and Chinese lower and middle Paleozoic representatives of the hyolith order Orthothecida are here placed in the families Orthothecidae Syssoiev, Novitatidae Syssoiev, Decorithecidae Syssoiev, Chelsonellidae n. fam., ?Isitithecidae Syssoiev, and ?Tchuranithecidae Syssoiev. The Orthothecidae is redefined, and the Decorithecidae is in part synonymized with the Novitatidae.

Re-examination of type specimens of some species formerly included in the order Hyolithida requires placement of these species in the order Orthothecida. The type suite of Hyolithes newsomensis Foerste from the Middle Silurian of Tennessee is divided into two species, and is used as a basis for the new genus Foersteotheca; the species F. merryi is new. Hyolithes richardi Clarke from the Lower Devonian of New York is designated as the type species of the new genus Devoniotheca. Orthotheca cyrene Walcott from the Middle Cambrian of China is now included under Decoritheca. Foersteotheca, Devoniotheca, and Decoritheca are here placed in the redefined family Novitatidae. Hyolithes vanuxemi Walcott is assigned to the new genus Chelsonella in the new family Chelsonellidae. The types of Hyolithes newtoni Walcott from the Upper Cambrian of South Dakota and Hyolithes canalis from the Middle Cambrian of China are both included under Decoritheca with question.

Recognition of orthothecid hyoliths in the Cambrian of North America and China provides a more accurate record of the geographic and stratigraphic distribution of this group. The discovery of Foersteotheca and Devoniotheca constitutes the first known middle Paleozoic orthothecid occurrences from North America. In addition, reports of Tchuranithecidae and Isitithecidae in North America, if authentic, are the first occurrences of these forms in North America. The discovery in North America of hyolith taxa previously known only from the Soviet Union and China raises the possibility of intercontinental correlation using these fossils.

Examination of collections from the Falkland Islands and South Africa shows that Chonetes falklandicus Morris and Sharpe, 1846, is a true Chonetes and is probably conspecific with Chonetes (Pleurochonetes) lauriata Isaacson, 1977, from Bolivia. Notiochonetes skottsbergi (Clarke, 1913) is quite different from C. falklandicus but is often associated with it in Malvinokaffric Realm Lower Devonian deposits.

The septate, lamellose, spiriferacean brachiopod genus Tylothyris North, 1920, is considered to be a delthyridid of the subfamily Tylothyridinae Carter, 1972. Herein, the diagnosis of the Tylothyridinae is emended to include forms with micro-ornament, and with a myophragm or median septum on the floor of the pedicle valve.

For the first time, Tylothyris is formally reported from the Traverse Group rocks of Michigan, Givetian through early Frasnian in age. Two species of the genus occur in the Traverse Group. The first, T. subvaricosa (Hall and Whitfield, 1872), previously described by Stainbrook (1943) from the Cedar Valley Limestone of Iowa, is also known from the Milwaukee Formation of Wisconsin and the Mineola Limestone of Missouri. Tylothyris randalia Stainbrook, 1943, also from the Cedar Valley Limestone, is considered to be synonymous with T. subvaricosa. In the Traverse Group, T. subvaricosa occurs in the Bell Shale, Rockport Quarry Limestone, Ferron Point Formation, Genshaw Formation, Alpena Limestone, Gravel Point Formation, Norway Point Formation, and Potter Farm Formation. The second species, T. rockportensis n. sp., occurs only in the Rockport Quarry Limestone, and appears to be endemic to the Michigan Basin.

Tylothyris is considered to have originated in the Illinois area during the late Eifelian, then to have migrated to the Michigan area by the early Givetian. With the onset of Taghanic Onlap during the late Givetian, the genus dispersed from its Illinois–Michigan area of origin, becoming distributed across much of North America during the Frasnian and Famennian, and becoming essentially cosmopolitan in distribution during the Tournaisian. Tylothyris apparently became extinct by the end of the Visean.