scholarly journals QUANTITATIVELY COMPARING MORPHOLOGICAL TRENDS TO ENVIRONMENT IN THE FOSSIL RECORD (CINCINNATIAN SERIES; UPPER ORDOVICIAN)

Evolution ◽  
2007 ◽  
Vol 61 (6) ◽  
pp. 1455-1465 ◽  
Author(s):  
Andrew J. Webber ◽  
Brenda R. Hunda
Keyword(s):  
Fossil Record ◽  
Upper Ordovician ◽  
Cincinnatian Series

Postembryonic development of Dalmanitina, and the evolution of facial suture fusion in Phacopina

Paleobiology ◽  
2018 ◽  
Vol 44 (4) ◽  
pp. 638-659
Author(s):  
Harriet B. Drage ◽  
Lukáš Laibl ◽  
Petr Budil
Keyword(s):  
Fossil Record ◽  
Postembryonic Development ◽  
Large Sample Size ◽  
Upper Ordovician ◽  
Geological Time ◽  
Fusion Event ◽  
Large Sample ◽  
Prague Basin ◽  
Suture Fusion ◽  
Insight Into

AbstractA large sample of postembryonic specimens of Dalmanitina proaeva elfrida and D. socialis from the Upper Ordovician (Sandbian to Katian) Prague Basin allows for the first reasonably complete ontogenetic sequence of Dalmanitoidea (Phacopina). The material provides an abundance of morphological information, including well-preserved marginal spines in protaspides and meraspides, and hypostome external surfaces throughout. The development of D. proaeva elfrida is unusual due to variability in timing of the first trunk articulation. This broadens our developmental understanding of Phacopina, a diverse group of phacopid trilobites, and also allows us to study the evolution of their specializations in exoskeletal molting behavior. Adult phacopines, unlike most other trilobites, had fused facial sutures. This means that rather than molting through the sutural gape mode, characterized by opening of the facial sutures and separation of the librigenae, they disarticulated the entire cephalon in Salter’s mode of molting. For other phacopine clades (Phacopoidea) the transition to Salter’s mode occurs during the meraspid period or at the onset of holaspis, and its developmental timing is intraspecifically fixed. However, owing to the large sample size, we can see that facial suture fusion likely occurred later in Dalmanitina, usually during the holaspid period, and was intraspecifically variable with holaspides of varying sizes showing unfused sutures. Further, D. proaeva elfrida specimens showed an initial librigenal–rostral plate fusion event, where the librigenae began as separate entities but appear fused with the rostral plate as one structure (the “lower cephalic unit”) from M1, and are discarded as such during molting. Dalmanitoidea is considered to represent the first phacopine divergence, occurring earliest in the fossil record. This material therefore provides insight into how linked morphologies and behaviors evolved, potentially suggesting the timing of facial suture fusion in Phacopina moved earlier during development and became more intraspecifically fixed over geological time.

scholarly journals Paleoecology of Cyclocrinites darwini (Miller) - a cyclocrinitid alga from the Cincinnatian series (Upper Ordovician)

1992 ◽  
Vol 6 ◽  
pp. 177-177
Author(s):  
Peter B. Lask
Keyword(s):  
Structural Similarity ◽  
High Energy ◽  
Energy Conditions ◽  
Upper Ordovician ◽  
Third Order ◽  
Coral Rubble ◽  
Lake Formation ◽  
Lateral Branches ◽  
Key Largo ◽  
Cincinnatian Series

Cyclocrinitids are considered to be calcareous green algae closely related to, or members of, the dasycladacean algae. Cyclocrinitids are characterized by a globular thallus 1-5 cm in diameter consisting of whorls of calcified meromes borne from a tubular or spherical central axis. The species Cyclocrinites darwini is distinguished from other cyclocrinitids by the presence of lateral branches arranged in a stellate pattern at the distal end of each merome.C. darwini is restricted to strata of the Cincinnatian Series. Specimens are commonly found in shale-filled channels cutting through nodular, irregularly-bedded limestones within the Mt. Auburn Formation and the lower Sunset Member of the Arnheim Formation. Numerous specimens are also known from the Bellevue Member of the Grant Lake Formation at Maysville, Kentucky. Each of these units has been interpreted to be the top of separate shoaling-upward, third-order cycles. These facies are abundantly fossiliferous, often consisting of broken, abraded, and reworked material.The modern dasyclad Neomeris is cited for its structural similarity to the cyclocrinitids and ecological parallels have been postulated as well. Neomeris and a similar dasyclad Batophora, thrive while attached to pieces of coral rubble at depths of less than 3 m in the high-energy conditions associated with a reef crest environment at Key Largo, Florida.It is likely that C. darwini lived under similar conditions, attached to rubble in shoaling areas. Preservation only occurred in instances when thalli were broken off from their holdfasts and swept into ripple troughs or downslope channels cutting across the shoals. It has been suggested that the presence of cyclocrinitids is indicative of relatively quiet environments below wave base. For Cyclocrinites darwini, the opposite would appear to be the case.

Trans-Pacific graptolite faunal relations: the biostratigraphic position of the base of the Cincinnatian Series (Upper Ordovician) in the standard Australian graptolite zone succession

1990 ◽  
Vol 64 (6) ◽  
pp. 992-997 ◽  
Author(s):  
Stig M. Bergström ◽  
Charles E. Mitchell
Keyword(s):  
New York ◽  
Close Correlation ◽  
Late Ordovician ◽  
Upper Ordovician ◽  
Important Species ◽  
Type Area ◽  
Cincinnatian Series ◽  
Early Late ◽  
Drill Cores

Recent studies of drill-cores and outcrops have resulted in the discovery of previously unknown, taxonomically diverse, graptolite faunas in the late Middle (Mohawkian) and early Late Ordovician (Cincinnatian) strata in the Cincinnati region, the type area of the Cincinnatian Series. These faunas contain several zonal indices and other biostratigraphically important species that are used for close correlation with the standard graptolite zone succession in New York and Quebec. The new data show that the base of the Cincinnatian Series in its type area is near the middle of the Climacograptus (Diplacanthograptus) spiniferus Zone. Significantly, about a dozen Cincinnati region graptolite species are shared with apparently coeval strata in the standard Australian graptolite zone succession in Victoria, and this key faunal evidence indicates that the base of the typical Cincinnatian corresponds to a level near the middle of the Climacograptus (Climacograptus) baragwanathi Zone (Ea2) of the Eastonian Stage. This represents a considerable revision of some recently published correlations of the basal Cincinnatian in terms of the Australian graptolite zone succession.

scholarly journals Discriminating signal from noise in the fossil record of early vertebrates reveals cryptic evolutionary history

2015 ◽  
Vol 282 (1800) ◽  
pp. 20142245 ◽  
Author(s):  
Robert S. Sansom ◽  
Emma Randle ◽  
Philip C. J. Donoghue
Keyword(s):  
Fossil Record ◽  
Evolutionary History ◽  
Biological Factors ◽  
Sea Level Changes ◽  
Upper Ordovician ◽  
Recovery Potential ◽  
Random Models ◽  
Rock Record ◽  
Early Vertebrates ◽  
Fossil Records

The fossil record of early vertebrates has been influential in elucidating the evolutionary assembly of the gnathostome bodyplan. Understanding of the timing and tempo of vertebrate innovations remains, however, mired in a literal reading of the fossil record. Early jawless vertebrates (ostracoderms) exhibit restriction to shallow-water environments. The distribution of their stratigraphic occurrences therefore reflects not only flux in diversity, but also secular variation in facies representation of the rock record. Using stratigraphic, phylogenetic and palaeoenvironmental data, we assessed the veracity of the fossil records of the jawless relatives of jawed vertebrates (Osteostraci, Galeaspida, Thelodonti, Heterostraci). Non-random models of fossil recovery potential using Palaeozoic sea-level changes were used to calculate confidence intervals of clade origins. These intervals extend the timescale for possible origins into the Upper Ordovician; these estimates ameliorate the long ghost lineages inferred for Osteostraci, Galeaspida and Heterostraci, given their known stratigraphic occurrences and stem–gnathostome phylogeny. Diversity changes through the Silurian and Devonian were found to lie within the expected limits predicted from estimates of fossil record quality indicating that it is geological, rather than biological factors, that are responsible for shifts in diversity. Environmental restriction also appears to belie ostracoderm extinction and demise rather than competition with jawed vertebrates.

Upper Ordovician conodonts, brachiopods, and chronostratigraphy of the Whittaker Formation, southwestern District of Mackenzie, N.W.T., Canada

1989 ◽  
Vol 26 (1) ◽  
pp. 74-87 ◽  
Author(s):  
Charles E. Mitchell ◽  
Walter C. Sweet
Keyword(s):  
United States ◽  
Common Ancestor ◽  
Red River ◽  
The Arctic ◽  
Upper Ordovician ◽  
Standard Section ◽  
The Common ◽  
Cincinnatian Series

Ten samples from a 160 m section through the lower Whittaker Formation yielded Red River Province conodonts as well as a shelly macrofossil assemblage representing the "Arctic Ordovician fauna." Both the microfossils and macrofossils have strong affinities with taxa represented in strata of Cincinnatian age in the western Midcontinent Province of North America.Conodont-based graphic correlation of section W-1 with a Composite Standard Section developed for midcontinental United States indicates that the lower Whittaker Formation on the east flank of the Redstone Arch represents nearly the entire Cincinnatian Series. Trilobites of the Ceraurus mackenziensis Zone occur in strata correlative with the upper Edenian and those of the Whittakerites planatus Zone first appear at or just below the projected base of the Maysvillian Stage. The age of the Ceraurinella necra Zone is still uncertain but is likely to be early Edenian.Thaerodonta recedens (Sardeson) and other elements of the Bighornia – Thaerodonta fauna also debut in uppermost Edenian or lowermost Maysvillian strata. The morphology of Sowerbyella redstonensis n.sp. and Thaerodonta recedens from the lower Whittaker Formation indicates that the common ancestor of early Thaerodonta species may have arisen during latest Edenian time. The first appearance of Thaerodonta may constitute a useful biostratigraphic datum throughout the Red River Province. The strongly Thaerodonta-like species, Sowerbyella redstonensis n.sp., is described from silicified material of mid-Edenian age.

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