Type Crania of the Devonian Placoderm Macropetalichthys from North America: Resolving Key Nomenclatural and Stratigraphic Conundrums

ABSTRACTAn abundant, diverse, and moderately well-preserved assemblage of organic-walled microphytoplankton is reported from two exposures of the Middle Devonian (Givetian) Gravel Point Formation at Little Traverse Bay, Michigan. The palynoflora consists of 13 prasinophyte and 19 acritarch species, together with some scolecodonts and chitinozoans. This is the first microphytoplankton assemblage to be described from the Middle Devonian of Michigan, and is clearly Givetian in age. It is closely comparable with, albeit less diverse than, Middle Devonian acritarch/prasinophyte assemblages reported from elsewhere in North America. Based on the diversity and abundance of the acritarch and prasinophyte taxa, along with evidence from marine faunas, the Gravel Point sediments accumulated in a normal, low-energy, offshore environment, with periodic regressions indicated by stromatoporoid–coral bioherms. Four of the acritarch species are restricted to the Middle Devonian of North America; the other specific components are typically, but not exclusively, Middle Devonian in age. Although some species are restricted to North America, others are cosmopolitan in distribution.

North American members of the genusPlateumarisThomson, 1859, are revised; 17 species are recognized and 23 taxonomic changes are made in their classification.Plateumarisballi andP.schaefferiare described as new species. Names elevated from subspecies to species rank areP.robusta(Schaeffer) andP.frosti(Schaeffer);P.aurifera(LeConte) is revalidated, removed from junior synonymy withP.wallisi(Schaeffer);Donacia idolaHatch is considered a junior subjective synonym ofP.dubia(Schaeffer);D.pyritosaLeConte is considered a junior subjective synonym ofP.pusilla(Say); an altered species concept is transferred toP.flavipes(Kirby), withD.wallisiSchaeffer as a new junior subjective synonym, andP.flavipesof authors is correctly namedP.shoemakeri(Schaeffer);D.longicollisSchaeffer andD.vermiculataSchaeffer are considered new junior subjective synonyms ofP.neomexicana(Schaeffer);D.flavipennisMannerheim is considered a junior subjective synonym ofP.germari(Mannerheim);D.rufaSay (notD.rufaof authors) is transferred toPlateumarisfromDonacia, with an altered species concept applied to it, andD.affinisKirby,D.sulcicollisLacordaire,D.chalceaLacordaire,D.kirbyiLacordaire, andD.jucundaLeConte are considered new junior subjective synonyms ofP.rufa(Say). The taxon previously consideredD.nitidaGermar (sensu Schaeffer) is redescribed asP.schaefferi;P.nitida(Germar) is a valid, different species, withD.emarginataKirby,D.juncinaCouper, andD.pacificaSchaeffer considered new junior subjective synonyms ofP.nitida. Neotypes are designated forDonacia pusillaSay,Donacia rufaSay,Donacia metallicaAhrens andDonacia nanaMelsheimer; lectotypes are designated for all other names, where necessary.Among Palaearctic taxa,Plateumaris morimotoiKimoto andP.hirashimaiKimoto are considered new junior subjective synonyms ofP.weiseiDuvivier, andP.sachalinensisMedvedev,P.orientalisShavrov andDonacia mongolicaSemenov are considered probable junior subjective synonyms ofP.weisei;P.sulcifronsWeise andP.affinis(Kunze) and its synonyms are considered new junior subjective synonyms ofP.rustica(Kunze);P.caucasicaZaitsev is considered a probable junior subjective synonym ofP.roscidaWeise;P.discolor(Panzer) (and its synonyms) andP.lacordairii(Perris) are considered junior subjective synonyms ofP.sericea(L.); newP.obsoletaJacobson andP.sociaChen are considered probable junior subjective synonyms ofP.sericea.Based on phylogenetic analysis, five species groups are recognized, theP.braccatagroup (two species),P.rufagroup (five species),P.pusillagroup (eight species),P.shoemakerigroup (four species), andP.nitidagroup (seven species). The current subgeneric classification ofPlateumarisis rejected. Characters hitherto used for subgenera ofPlateumarisare shown to be either plesiomorphic or widely distributed among unrelated taxa; the relatively minor structural differences do not merit use of a subgeneric classification.JuliusinaReitter is a junior objective synonym ofPlateumarisThomson.Based on fossil and chorological data, the geographic history of donaciines in general and ofPlateumarisin particular is deduced to be so old as to obscure correlations of more recent phylogenetic divergences with specific geologic events. The geographic history of even the most highly derived donaciine groups extends well into the Cretaceous. Therefore, explanations are speculative beyond the generality that donaciines have a long geologic history.

The genus Cyphaspis Burmeister, 1843, is first known from the northern Laurentian Sheinwoodian. By the late Homerian, the genus had appeared in England and Baltica, and from the Ludlow through the Lower and Middle Devonian it had an essentially cosmopolitan distribution. The Mississippian Dixiphopyge Brezinski, 1988, may represent a relict distribution of Cyphaspis, and if so should be considered a junior subjective synonym. Cyphaspis is considered the sister taxon of Otarion Zenker, 1833. The oldest, Sheinwoodian, species of either genus are very similar, but the clades evolved to the point of gross morphological disparity in the Devonian.New species from the Wenlock and probably Ludlow of northwestern Canada are Cyphaspis lowei, C. munii, C. buchbergeri, and C. mactavishi. New ontogenetic material of the Zlichovian C. dabrowni (Chatterton, 1971) further demonstrates the pervasiveness of the basic juvenile morphology of the tribe Otarionini.

Because of the absence of invertebrate faunas, previous correlations of Lower and Middle Devonian nonmarine sedimentary rocks in the western United States have resulted in various age assignments. Although vertebrate fossils are present in these strata, they have not been widely used for biostratigraphic correlation in North America. Recent work indicates that, despite problems of endemism of these faunas during the Early Devonian, vertebrate fossils do provide a tentative basis for correlation. The lower part of the Grassy Flat Member of the Water Canyon Formation and the Beartooth Butte Formation at Beartooth Butte are shown to be Emsian in age, whereas the Beartooth Butte Formation in the Bighorn Mountains is late Lochkovian to early Pragian. An endemic fauna restricted to the Sevy Dolomite and Lippincott Member of the Lost Burro Formation is also considered to be Emsian. The Middle Devonian fauna has a more cosmopolitan distribution; similar assemblages at disparate localities in North America provide a framework for the use of the fauna in placing age constraints on stratigraphic units. For the first time pteraspidids are unequivocally identified from Middle Devonian strata. Together with a characteristic fauna of arthrodires and antiarchs, they are used to correlate the Yahatinda Formation of Alberta with the Spring Mountain channel of the Lemhi Range, Idaho, and the upper part of the Grassy Flat Member of the Water Canyon Formation, all of which can now be dated as late Givetian. Elliott, D. K., and Johnson, H. G., 1997, Use of vertebrates to solve biostratigraphic problems: Examples from the Lower and Middle Devonian of western North America, in Klapper, G., Murphy, M. A., and Talent, J. A., eds., Paleozoic Sequence Stratigraphy, Biostratigraphy, and Biogeography: Studies in Honor of J. Granville (“Jess”) Johnson: Boulder, Colorado, Geological Society of America Special Paper 321.

The lingulid brachiopod species Bicarinatina kongakutensis n. sp. is recorded here from the Middle Devonian (Eifelian) Ulungarat unit in Arctic Alaska. A restudy of the type species, Bicarinatina bicarinata (Kutorga) from the Middle Devonian (Eifelian) of Eastern Europe, suggests close affinities to the Ordovician genus Pseudolingula and gives good reason to assign Bicarinatina to the family Pseudolingulidae. There are no important points of difference in the morphologies of Bicarinatina and the Early Carboniferous lingulid genus Liralingua and, thus, both genera have been synonymized.

Biogeography of late Silurian and devonian rugose corals

The influence of paleogeography in epicontinental seas: A case study based on Middle Devonian strata from the MacKenzie Basin, Northwest Territories, Canada

Late Silurian to middle Devonian acanthodians of Eastern Australia

Devonian climate and reef evolution: Insights from oxygen isotopes in apatite

Abstract. The known stratigraphic ranges of 66 acritarch species from eight independently dated Middle Devonian sections in North America are plotted. Twenty seven species are restricted to the Middle Devonian in North America, yet only 12 species occur in more than one section. None of these 12 species is, as yet, known to occur outside North America. This apparent endemism is believed to be due partly to the lack of study of contemporaneous assemblages from elsewhere in the world.

Analysis of some five hundred ostracode-bearing samples in two diamond drill cores (GSC DD1 Arkona and GSC DD2 Ipperwash) from Bosanquet Township, Lambton County permits more exact understanding of the stratigraphic distribution of Ostracoda in the Middle Devonian (Givetian) Hamilton Group of southwestern Ontario. This allows more precise age determination and stratigraphic correlation of late Middle Devonian Ostracoda in southern Ontario with Middle Devonian ostracode faunas of the Michigan Basin and borderlands in central North America. The ostracode fauna of the Hamilton Group in these drill cores, contained within the Bell, Rockport Quarry, Arkona, Hungry Hollow, and Widder formations and, in GSC DD2, part of the overlying Ipperwash Formation, comprises some 50 genera represented by almost twice that number of species. These are, with few exceptions, synonymous with ostracode faunas previously reported from elsewhere in the Michigan Basin. The palaeocopid ostracode fauna is dominated by species of the suborders Beyrichicopina and Kloedenellocopina and the podocopid ostracode fauna is represented by species of the suborders Podocopina and Metacopina. There are no leperditicopids. This Hamilton Group ostracode assemblage is of latest Middle Devonian age and may be equated, in part, with similar faunas of the Silica Formation of southeastern Michigan northwestern Ohio, the Traverse Group of the northern part of the lower peninsula of Michigan, and Middle Devonian faunas of western New York State. The Hamilton Group ostracodes from southwestern Ontario appear to have evolved during a period of relatively stable environmental conditions and represent lineages of continuous faunal development.

The Middle Devonian Epoch, ~ 393–383 million years ago, is known for a peak in diversity and highest latitudinal distribution of coral and stromatoporoid reefs. About 388 million years ago, during the late Eifelian and earliest Givetian, climax conditions were interrupted by the polyphased Kačák Episode, a short-lived period of marine dys-/anoxia associated with climate warming that lasted less than 500 kyr. Reconstruction of the seawater temperature contributes to a better understanding of the climate conditions marine biota were exposed to during the event interval. To date, conodont apatite-based paleotemperatures across the Eifelian–Givetian boundary interval have been published from Belarus, France, Germany and North America (10–36° S paleolatitude). Here we provide new δ18Oapatite data from the Carnic Alps (Austria, Italy) and the Prague Synform (Czech Republic). For better approximation of the paleotemperature record across the Kačák Episode, a latitude-dependent correction for Middle Devonian seawater δ18O is applied. Because δ18Oapatite data from shallow marine sections are influenced by regional salinity variations, calculated mean sea surface temperatures (SST) are restricted to more open marine settings (22–34° S paleolatitude). Water temperatures reach ~ 34 °C in the Prague Synform and ~ 33 °C in the Carnic Alps and suggest that SSTs of the southern hemisphere low latitudes were ~ 6 °C higher than previously assumed for this time interval.

The Middle Devonian (lower–middle Givetian) Hamilton Group of New York State is an iconic unit in North America, which has contributed many key concepts in stratigraphy, sedimentary geology, paleoecology, and evolution. This interval comprises a 100- to 1200-m-thick clastic wedge, shed westward from the Acadian Mountains, with thin but persistent carbonates. Despite the rich and diverse invertebrate fauna that consists of more than 300 species of corals, bryozoans, brachiopods, mollusks, echinoderms, and trilobites, the age of the Hamilton Group is rather poorly constrained in terms of chronostratigraphy owing to the rarity of biostratigraphically useful conodonts and goniatites. The upper part of the Hamilton Group that is the focus of this paper apparently belongs to the Polygnathus timorensis to middle Polygnathus ansatus Conodont chronozones. The middle to upper Hamilton Group in New York State comprises three formations—the Skaneateles, Ludlowville, and Moscow—each defined as an interval delimited with a sharply based fossiliferous limestone-calcareous siltstone; these formations are interpreted as containing condensed transgressive deposits overlain by thicker highstand to falling-stage shales, mudstones/siltstones, and sandstones. The eastern equivalents of these formations are dominated by fine-grained sandstones and siltstones and include two formations: the Panther Mountain Formation, equivalent to the Skaneateles and Ludlowville formations combined, and the Cooperstown Formation, equivalent to the Moscow Formation. In the present paper, we review, revise and update a hierarchical framework of lithostratigraphic subdivisions of these formations, including 24 members (four new), 50 submembers (more than half newly proposed or redefined; 14 informal at this time), and more than 80 named beds, both formal and informal. This refined lithostratigraphy provides an excellent framework for studying high-resolution sequence stratigraphy. As defined herein, members and most submembers represent high-frequency depositional sequences with basal shell-rich carbonates and abrupt flooding surfaces that mark the bases of highstand deposits. Not only are most of the members and submembers traceable across western and central New York, but also to a lesser extent into adjacent regions that include southern Ontario, Ohio, the Michigan Basin, and northeastern Pennsylvania. Nevertheless, much work on correlation remains to be done in eastern New York and central Pennsylvania, where local progradation of siliciclastics and expansion of successions obscures many of the finer scale features.

A series of small road cuts of lower Boyle Formation (Middle Devonian: Givetian) near Waco, Kentucky, has produced numerous specimens of three blastozoan clades, including both “anachronistic” diploporan and rhombiferan “cystoids” and relatively advanced Granatocrinid blastoids. This unusual assemblage occurs within a basal grainstone unit of the Boyle Limestone, apparently recording a local shoal deposit. Diploporans, the most abundant articulated echinoderms, are represented by a new protocrinitid species, Tristomiocystis globosus n. gen. and sp. Glyptocystitoid rhombiferans are represented by isolated thecal plates assignable to Callocystitidae. Three species of blastoids, all previously undescribed, include numerous thecae of the schizoblastid Hydroblastus hendyi n. gen. and sp., the rare nucleocrinid Nucleocrinus bosei n. sp., and an enigmatic troosticrinid radial. The blastoid Nucleocrinus is typical for the age; however, the callocystitid, schizoblastid, and protocrinitid are not. Hydroblastus is the oldest known schizoblastid. Middle and Upper Devonian callocystitids have been previously reported only from Iowa and Michigan USA with unpublished reports from Missouri USA and the Northwest Territories, Canada. This occurrence is thus the first report of a Middle Devonian rhombiferan from the Appalachian foreland basin. Tristomiocystis is the first known protocrinitid in North America and the only protocrinitid younger than Late Ordovician. This occurrence thus represents a range extension of nearly 50 million years for protocrinids. This extraordinary sample of echinoderms in a Middle Devonian limestone from a well-studied area of North America highlights the incompleteness of the known fossil record, at least in fragile organisms such as echinoderms.

Morphology of the leaves of stem compressions originally attributed to Protolepidodendron scharyanum from the Middle Devonian of North Xinjiang, China is reinvestigated. The leaf is three-dimensional, consisting of one central abaxial segment and four lateral adaxial segments, and does not conform to the once bifurcate leaf of Protolepidodendron. Specimens are therefore transferred to Leclercqia cf. L. complexa. This is the first unequivocal report of the genus Leclercqia in China based on complete leaf morphology. The distribution of Leclercqia is discussed, demonstrating a more or less cosmopolitan genus in the Middle Devonian. The Middle Devonian flora of North Xinjiang shows great similarity to that of Venezuela and North America, and almost no relationship with that of Yunnan, South China.