Registered users receive a variety of benefits including the ability to customize email alerts, create favorite journals list, and save searches.
Please note that a BioOne web account does not automatically grant access to full-text content. An institutional or society member subscription is required to view non-Open Access content.
Contact firstname.lastname@example.org with any questions.
A macrofloral assemblage dominated by elements of the Euramerican dryland biome is described from the Brazil Formation in Clay County, Indiana (Illinois Basin). Fossils were recovered from a thin heterolithic unit between a shallow-marine bed and the paleosol beneath the Minshall Coal, a Middle Pennsylvanian succession deposited near the Atokan-Desmoinesian and Bolsovian-Asturian boundaries. Sedimentological indicators imply accumulation under a seasonal climate, including interbedded siltstone and sandstone deposited during flashfloods, intraclasts eroded from local sources, and charcoal produced by wildfires. The macrofloral assemblage is consistent with a dryland setting, being dominated by large, coriaceous gymnosperm leaves with mesic to xeric traits, including Cordaites spp. indet., Lesleya sp. indet., and Taeniopteris sp. cf. T. multinervia. Sphenopsids and ferns typical of the wetland biome are rare. In contrast, the microfloral assemblage is dominated by fern spores, with lesser lycopsid spores and cordaitalean pollen. The succession indicates that the dryland biome predominated during late regression, prior to the onset of perhumid conditions that resulted in peat accumulation at late lowstand. However, the abundance of palynomorphs from wetland vegetation implies gradual fragmentation of the prevailing dryland flora and replacement by the wetland biome in the transition to glacial maximum. The taphonomic and paleobiogeographic context confirms that floras adapted to seasonal moisture deficit periodically dispersed into tropical lowlands, rather than being transported from ‘extrabasinal’ or ‘upland’ environments. The precocious occurrence of Taeniopteris, more typical of Late Pennsylvanian and Permian floras, may be the earliest record of the fossil-genus, and exemplifies the association of derived plant taxa with dryland habitats. The predominance of broad-leaved gymnosperms with mesic to xeric characters suggests that dryland communities contained more slow-growing and long-lived plants than contemporaneous wetland floras.
The ca. 780–740 Ma Chuar Group, Grand Canyon, Arizona, provides an exceptional record of life during the diversification of crown-group eukaryotes, just prior to the first Cryogenian glaciation. We document in detail the assemblage of organic-walled microfossils preserved in fine-grained siliciclastics throughout the unit. In contrast with earlier studies, we primarily used SEM to document fossil morphologies, augmented by transmitted light microscopy, FIB-SEM, and TEM. This resulted in the discovery of new species and the recognition of broad-ranging, intraspecific biological and taphonomic variation in other species. Twenty-two species and five unnamed morphotypes are described, including three new species: Kaibabia gemmulella, Microlepidopalla mira, and Volleyballia dehlerae; two new combinations: Galerosphaera walcottii and Lanulatisphaera laufeldii; and 17 previously described forms. The possible colonial green alga Palaeastrum dyptocranumButterfield in Butterfield, Knoll, and Swett, 1994 and the index fossil Cerebrosphaera globosa (Ogurtsova and Sergeev, 1989) Sergeev and Schopf, 2010 (= C. buickii Butter-field, 1994) are described for the first time from Chuar rocks. Lanulatisphaera laufeldii, a locally abundant and globally widespread species characterized by submicrometer filamentous processes that form a reticulate network, may be a useful marker for the time interval just before the appearance of vase-shaped microfossils (VSMs) ca. 740 Ma.
Organic-walled microfossil assemblages decline in diversity upsection, coincident with the appearance of VSMs and intermittent euxinia within the basin. Whether this pattern is due to preservational bias related to greater water depth or the higher TOC of upper Chuar rocks or instead reflects biotic turnover related to the spread of euxinic water masses in the basin is unknown.
Estimates of Precambrian eukaryotic diversity and disparity indicate broad trends of increase in the Mesoproterozoic Era, leading to a peak and then rapid decline by ca. 750 Ma. The organic-walled microfossil assemblage presented here is representative of that mid-Neoproterozoic height of eukaryotic species richness. Organic-rich shales and siltstones of the mid-Neoproterozoic upper Alinya Formation, eastern Officer Basin, Australia, preserve an abundant and diverse assemblage of organic-walled microfossils deposited in a low-latitude, shallow marine setting. Use of scanning electron microscopy (SEM) revealed an unexpected level of morphological detail not visible in transmitted light microscopy. This led to the recognition of new species as well as establishment of degradational sequences, which aid in fossil recognition. In total, 26 taxa are described here; these include 21 previously named forms, four newly described species (Caelatimurus foveolatus, Culcitulisphaera revelata, Karenagare alinyaensis, and Morgensternia officerensis), and one new combination (Vidalopalla verrucata).
Systematic revision of the Late Ordovician brachiopod genera EochonetesReed, 1917 and ThaerodontaWang, 1949 was conducted utilizing specimen-based morphometric and species-level phylogenetic analyses. Previous studies had recognized Thaerodonta and Eochonetes as either distinct taxonomic entities or synonyms. New multivariate and phylogenetic analyses confirm the synonymy of Thaerodonta with Eochonetes and provide a framework to assess evolutionary and ecological patterns within the clade. Multivariate analyses were employed to delineate species in morphospace and provided information on potential species relationships. Phylogenetic analysis was used to produce an evolutionary framework for taxonomic revision and identify character evolution within the clade. Most species previously assigned to Thaerodonta are transferred to Eochonetes, and three others are excluded from Eochonetes and provisionally referred to other sowerbyellid genera. Three new species (Eochonetes maearum new species, E. voldemortus new species, E. minerva new species) are described, one species (Leptaena saxeaSardeson, 1892) is synonymized with E. recedensSardeson, 1892, and one subspecies (Thaerodonta mucronata scabraHowe, 1965) is rejected. This study demonstrates that a combination of complementary approaches and data types has the potential to advance interpretations beyond analyses confined to single analytical tools. Specifically, multivariate analyses provide constraints on species boundaries, whereas species-level phylogenetic analyses provide frameworks to examine morphological, ecological, and biogeographic evolution within a clade.
Coleoid specimens from the Jurassic of northern Chile are included in two different species of Trachyteuthis, i.e., T. covacevichiFuchs and Schultze, 2008 and T. chilensis n. sp., and in a new genus and a new species, Pseudoteudopsis perezi n. gen. n. sp. The specimens described and figured are from two different areas in northern Chile. Those referred to Pseudoteudopsis perezi n. gen. n. sp. came from a locality north of Calama and are associated with ammonites indicating the lower Callovian uppermost bodenbenderi to lowermost proximum zones (≈ gracilis Standard Zone) of the Andean ammonite zonation. Those described as T. covacevichi and T. chilensis n. sp. came from the Cordillera de Domeyko, northeast of Taltal, and are associated with ammonites indicating the middle Oxfordian transversarium Zone.
The middle part of the Santa Rosita Formation (Tremadocian) is well exposed in the Iruya area, northwestern Argentina. At the Pantipampa and Rodeo Colorado localities, it is composed of shale and sandstone representing a wave-dominated shelf with influence of storm activity. Twenty-two trilobite species are described from these localities. Low-diversity assemblages from the lower part of the succession (Kainella meridionalis Kobayashi, Asaphellus catamarcensis Kobayashi, Leptoplastides marianus [Hoek]) are diagnostic of the early Tremadocian Kainella meridionalis Zone. Trilobites from the middle part of the sequence are much more diverse. Kainella teiichii Vaccari and Waisfeld, Gymnagnostus kobayashii n. sp., Conophrys sp. indet., Asaphellus clarksoni n. sp., A. stenorhachis (Harrington), A. isabelae Meroi Arcerito, Waisfeld and Balseiro, Ogygiocaris? iruyensis n. sp., Niobe (Niobella) inflecta (Harrington and Leanza) n. comb., Metayuepingia riccardii n. sp., Pseudokainella keideli Harrington, Apatokephalus rugosus n. sp., Onychopyge acenolazai n. sp., O. gonzalezae n. sp., Nileus cingolanii n. sp., N. erici n. sp., Leptoplastides marianus, Parabolinella sp. indet., Hapalopleura sp. indet., and Ceratopygidae gen. et sp. indet., occur at different levels of the Kainella teiichii Zone. This biostratigraphic unit includes the oldest records of Nileus Dalman and Ogygiocaris? Angelin; Metayuepingia Liu, Niobe (Niobella) Reed, and Onychopyge Harrington are here first reported from the Tremadocian of southwest Gondwana. Finally, the uppermost part of the succession is characterized by the absence of the genus Kainella Walcott and the occurrence of Bienvillia tetragonalis (Harrington), Asaphellus stenorhachis, Pseudokainella keideli and Leptoplastides sp. indet., which are indicative of the middle Tremadocian Bienvillia tetragonalis Zone. The trilobites described in this paper provide a basis for the refinement of correlations with other Lower Ordovician sections of the Cordillera Oriental. The genera recognized have their closest affinities with faunas from Scandinavia, Great Britain, and China.
The first sedimentary rocks from Batavia Knoll, on the western edge of the Perth Abyssal Plain, eastern Indian Ocean, have been recovered, yielding an assemblage of invertebrate fossils hitherto undocumented from this part of the world. The fauna consists of 22 species of Mollusca, including new gastropods, a calliotropid Planolateralus acanthanodus n. sp.; a margaritid Igonoia levimargarita n. sp.; a procerithiid Procerithium arenacollicola n. sp.; and aporrhaids Drepanocheilus bataviensis n. sp. and Anchura pelsaerti n. sp. In addition, pleurotomariid, ringiculid, and architectonicid gastropod taxa were recovered. Bivalves are represented by members of the Nuculanidae, Inoceramidae, Pinnidae, Buchiidae, Lucinidae, Veneridae, and Hiatellidae. Scaphopods (Dentaliidae) and ammonites (two taxa, of Desmoceratidae and Hamitidae) are also present. Further recovered were one species of Serpulidae (Polychaeta), two of Trachyleberididae (Ostracoda), and a probable echinoid fragment. The fossil assemblage was dominated by shallow marine suspension-feeding taxa (39% of the suite). Detritivorous and herbivorous taxa comprised 22% and 9%, respectively, with nektic and epifaunal carnivores amounting to 30%. Taphonomic analyses of these fossils and their host sedimentary facies revealed the Batavia Knoll sandstone was deposited in a shallow marine environment during a mass-flow event. Biostratigraphic range data of the preserved macro- and microfossil assemblages imply an age of latest Albian, contemporaneous with the rifting of Batavia Knoll from Greater India during the broader India—Australia—Antarctica breakup in the mid-Cretaceous.
Fieldwork conducted in the Wasatch Formation in and around Fossil Butte has yielded a diverse assemblage of early Eocene vertebrates. Fossil vertebrates are distributed through three discrete stratigraphic intervals within the uppermost 180 m of the main body of the Wasatch Formation underlying the Green River Formation. These assemblages were derived primarily from fluvial overbank mudstone units overprinted with variably well-developed paleosols. The lowest (20 m) and highest (60 m) sections are characterized by less mature and more hydromorphic paleosols, whereas the middle section (100 m) is typified by more mature paleosols and more abundant channel sandstones.
The combined assemblages contain at least 46 species of mammals. Faunal characteristics include high abundances of equid perissodactyls and a relatively high abundance and diversity of notharctines primates, an apparent absence of omomyid primates, relatively high rodent diversity, and relatively diverse and abundant artiodactyls. One new genus (Eoictops new genus) and three new species (Eoictops novaceki new species, Palaeosinopa lacus new species, and ?Notoparamys blochi new species) are included in the Fossil Butte assemblage. Also recorded are late occurrences of two hyopsodontid condylarths and an early occurrence of a rare phenacodontid condylarth. The relatively high abundances of equids and notharctines suggest that vertebrate samples were derived from relatively open paleohabitats that included forested areas along water courses.
All three assemblages contain characteristic Lysitean (Wasatchian biochron Wa-6) elements, but the occurrence of the palaeotheriid perissodactyl Lambdotherium in the uppermost horizon indicates a Lostcabinian (Wa-7) age for at least the top of the Wasatch Formation. The overlying predominantly fish-bearing Fossil Butte Member of the Green River Formation also contains Lambdotherium and is therefore Wa-7 in age as well.
We report the first Tertiary bird fossil from Central America, an ungual phalanx from a large, unknown genus and species of Accipitridae from the early Miocene Centenario Fauna, Panama. This specimen provides another example of a Neogene bird from North and Central America with its possible closest living relatives occurring today in Africa. In contrast, there is no evidence of African affinities among the reptile or mammal fossils from the Centenario Fauna.