Middle Ordovician linguliformean microbrachiopods from western Argentina: new data and biogeographic implications

2021 ◽  
pp. 1-13
Author(s):  
Fernando J. Lavié ◽  
Ana I. Mestre ◽  
Marcelo G. Carrera
Keyword(s):  
San Juan ◽  
Middle Ordovician ◽  
Low Diversity

Abstract New linguliform microbrachiopods from the Middle Ordovician are described and illustrated. This fauna was recovered from the uppermost beds of the San Juan Formation in two sections of the Central Precordillera (Argentina), which are accurately dated to the Lenodus pseudoplanus Zone (middle Darriwilian). The fauna consists of the obolid Luthieria diminuta n. gen. n. sp., and the acrotretids Eoconulus tucunucoensis n. sp., Conotreta andina Lavié, Serra, and Feltes, Scaphelasma zharykensis Popov, and Numericoma rowelli Holmer et al. This low-diversity lingulate association displays close similarities with coeval faunas that inhabited the Laurentia, Baltica, and Kazakhstanian regions, in agreement with evidence from other linguliform and rhynchonelliform brachiopods. UUID: http//zoobank.org/fe9acbb0-6654-4462-ba4d-ea2386ae79f6

scholarly journals SPONGE SPICULE ASSEMBLAGES FROM THE MIDDLE ORDOVICIAN OF PONÓN TREHUÉ, SOUTHERN MENDOZA, ARGENTINA

2021 ◽  
Vol 15 (1) ◽  
pp. 37
Author(s):  
Matilde Sylvia Beresi ◽  
Susana Emma Heredia
Keyword(s):  
Carbonate Platform ◽  
San Juan ◽  
Sponge Spicule ◽  
Middle Ordovician ◽  
Low Diversity ◽  
Carbonate Sequence ◽  
Shallow Carbonate Platform

Sponge spicule assemblages are described fom residues of conodont samples from Ordovician strata in the Sierra Pintada, southern Mendoza Province, Argentina. Spicules have been recovered from the Arenigian allochthonous megaconglomerates and from autochthonous limestones and carbonates sandstones of the Ponón Trehue Formation. This formation is a elastic-carbonate sequence representing olistostromic and turbidite facies. Conodonts in this formation are Llandeillan in age. The spicules are calcified and moderately preserved. The material shows a low diversity. Poriferan taxa found in this formation include heteractinid spicules as well as hexactinellid hexactines and non-lithistid demospongiid triaene and oxeas with some doubt. Associations of exclusively heteractinid spicules are restricted to allochthonous blocks of the shallow carbonate platform of the San Juan Formation (Arenig). In the outer platform and slope, autochthonous calcarenites and dark limestones contain hexactine spicules. These spicules evidence the existence of sponges in the Ordovician of the Ponón Trehue area, as a part of the Precordillera terrane. 

scholarly journals Conodont biostratigraphy and global correlation of the middle Darriwilian-lower Sandbian (Ordovician) Las Aguaditas Formation, Precordillera of San Juan, Argentina

2016 ◽  
Vol 43 (1) ◽  
pp. 60 ◽  
Author(s):  
Nicolás A. Feltes ◽  
Guillermo L. Albanesi ◽  
Stig M. Bergström
Keyword(s):  
North American ◽  
Recovery Phase ◽  
San Juan ◽  
Conodont Biostratigraphy ◽  
Middle Ordovician ◽  
Study Section ◽  
The North ◽  
Global Correlation ◽  
Low Diversity ◽  
Argentine Precordillera

Middle Darriwilian to lower Sandbian conodonts were recorded from the Las Aguaditas Formation at its type section in the Argentine Precordillera. A total of 9,974 conodont specimens were recovered from 46 carbonate samples, which represent 68 species of 38 genera. A biostratigraphic study verified a middle Darriwilian age for the interval spanning the contact between the San Juan and the Las Aguaditas formations. The following zones are determined in the study section: the Lenodus variabilis Zone, with the Periodon gladysae and Paroistodus horridus subzones following the Precordilleran scheme; the L. variabilis, Yangtzeplacognathus crassus, and the Eoplacognathus pseudoplanus zones with the Microzarkodina hagetiana and M. ozarkodella subzones, and the Pygodus anserinus Zone, according to the Scandinavian scheme; the Periodon macrodentatus Zone, with the Histiodella sinuosa, H. holodentata and H. cf. holodentata subzones, and the P. zgierzensis Zone with the H. kristinae Subzone that correlates the North American scheme. A stratigraphic gap was recognized between the lower and middle members of the Las Aguaditas Formation. It comprises the Eoplacognathus suecicus and Pygodus serra zones, and the lower subzone of the Pygodus anserinus Zone. The variation of conodont diversity through the study section conforms to shallowing and deepening patterns, which accompanies the changes of the provenance lithology. Three conodont assemblages were quantitatively recognized: a) Diverse conodont association, b) Low diversity conodont association and c) Recovery phase association. We propose to use the North American biozonal scheme of conodonts for the Central Precordillera because of the affinity of documented index taxa, which provides a more accurate intercontinental correlation for the global Middle Ordovician Series.

Early radiation of echinoderms

1997 ◽  
Vol 3 ◽  
pp. 205-224 ◽  
Author(s):  
James Sprinkle ◽  
Thomas E. Guensburg
Keyword(s):  
Mass Extinction ◽  
Fossil Record ◽  
Early Paleozoic ◽  
Soft Substrate ◽  
Middle Cambrian ◽  
Middle Ordovician ◽  
Late Cambrian ◽  
Low Diversity ◽  
Early Radiation ◽  
Ways Of Life

Echinoderms underwent a major two-part radiation that produced all of the major groups found in the fossil record between the Early Cambrian and the Middle Ordovician. A small initial radiation in the Early and Middle Cambrian produced about nine classes containing low-diversity members of the Cambrian Evolutionary Fauna. These were characterized by primitive morphology, simple ambulacral feeding structures, and the early development of a multiplated stalk or stem for attachment to skeletal fragments on a soft substrate. Several groups became extinct at the end of the Middle Cambrian, leaving the Late Cambrian as a gap of very low diversity in the fossil record of echinoderms with only four classes preserved and very few occurrences of complete specimens, mostly associated with early hardgrounds. The survivors from this interval re-expanded in the Early Ordovician and were joined by many newly evolved groups to produce a much larger radiation of more advanced, diverse, and successful echinoderms representing the Paleozoic Evolutionary Fauna on both hard and soft substrates. At least 17 classes were present by the Middle Ordovician, the all-time high point for echinoderm class diversity, and nearly all of the major ways-of-life (except for deep infaunal burrowing) had been developed. With the rise to dominance of crinoids, many less successful or archaic groups did not survive the Middle Ordovician, and echinoderm class diversity dropped further because of the mass extinction at the end of the Ordovician. This weeding-out process of other less-successful echinoderm groups continued throughout the rest of the Paleozoic, and only five classes of echinoderms have survived to the Recent from this early Paleozoic radiation.

Subspeciation within a punctuated equilibrium evolutionary event: Phylogenetic history of the Lower-Middle Ordovician Paroistodus originalis—P. horridus complex (Conodonta)

2000 ◽  
Vol 74 (3) ◽  
pp. 492-502
Author(s):  
Guillermo L. Albanesi ◽  
Christopher R. Barnes
Keyword(s):  
Carbonate Platform ◽  
Black Shales ◽  
San Juan ◽  
Carbonate Production ◽  
Middle Ordovician ◽  
Lower Member ◽  
Speciation Event ◽  
Restricted Environment ◽  
Evolutionary Event ◽  
Middle Member

A microevolutionary event involving the conodont Paroistodus lineage is documented in the Gualcamayo Formation (Middle Ordovician), Argentine Precordillera. A detailed sampling of limestones throughout the upper part of the San Juan Formation and the lower member of the Gualcamayo Formation yielded over 14,000 well-preserved conodont elements. Paroistodus originalis (Sergeeva, 1963) was recorded through the upper 230 m of the San Juan Formation and the lower member (10 m thick) of the Gualcamayo Formation. The derived species Paroistodus horridus (Barnes and Poplawski, 1973) was recorded throughout the middle member of the Gualcamayo Formation (65 m thick). The intermediate linking forms between both species are identified as two new taxa: Paroistodus horridus primus Albanesi, 1998b, and P. h. secundus Albanesi, 1998b. They were recorded in the uppermost 70 cm of the lower member. Apparently, the speciation event occurred under stressed environmental conditions with the drowning of the carbonate platform, i.e., the San Juan Formation, and the beginning of a deeper and restricted environment represented by the Gualcamayo black shales. The demise of the carbonate production was caused by a sea level rise and a significant influx of volcanic ashes. The punctuated speciation event occurred within an allopatric setting while the Precordillera occupied an isolated (Iapetus) oceanic position in its overall drift from Laurentia to Gondwana.

Middle Ordovician (Darriwilian) linguliform and craniiform brachiopods from the Precordillera (Cuyania Terrane) of west-central Argentina

2016 ◽  
Vol 90 (6) ◽  
pp. 1068-1080 ◽  
Author(s):  
Fernando J. Lavié ◽  
Juan L. Benedetto
Keyword(s):  
Conical Shell ◽  
San Juan ◽  
Middle Ordovician ◽  
Central Argentina ◽  
West Central ◽  
First Time

AbstractMiddle Ordovician lingulacean, trematid, and craniid brachiopods are described and illustrated for the first time from the uppermost part of San Juan Formation limestones of the Precordillera Basin, west-central Argentina. Sampled beds fall within theAhtiella argentinabrachiopod Zone, which, according to associated conodonts, is of early-mid Darriwilian age. The fauna consists of the linguloideansGlossella cuyanican. sp. andLingulasma? sp., the discinoideanTrematissp., the siphonotretidChilcatreta tubulatan. gen. n. sp., and a conical shell that is referred provisionally to the order Craniida. The linguliforms from the Cuyania (Precordillera) terrane, although still poorly known, display close similarities to those inhabiting low-to-intermediate latitude palaeocontinents, particularly Laurentia and Baltica, in accordance with evidence from rhynchonelliform brachiopods.

Untangling a Darriwilian (Middle Ordovician) palaeoecological event in Baltoscandia: conodont faunal changes across the ‘Täljsten’ interval

2009 ◽  
Vol 100 (04) ◽  
pp. 353-370 ◽  
Author(s):  
Johanna I. S. Mellgren ◽  
Mats E. Eriksson
Keyword(s):  
High Resolution ◽  
Close Correlation ◽  
Environmental Indicators ◽  
Lower Half ◽  
Thick Section ◽  
Zone Boundary ◽  
Middle Ordovician ◽  
Abundance Patterns ◽  
Low Diversity

ABSTRACTConodont faunal dynamics and high-resolution biostratigraphy in the lithologically and faunally anomalous ‘Täljsten’ succession, which spans the DarriwilianLenodus variabilis–Yangtzeplacognathus crassusZone boundary, were investigated in a 2·5 m-thick section on Mt Kinnekulle that includes an interval yielding fossil meteorites and extraterrestrial chromite. The previous interpretation that this interval reflects a regression is consistent with the occurrence and abundance patterns of some conodont taxa. The disappearance of e.g.,Periodon, suggests that the regression began prior to the deposition of the grey ‘Täljsten’. The transition from red to grey limestone coincides with a conspicuous faunal re-arrangement. The lower half of the ‘Täljsten’ reflects a gradual shallowing favourable for some taxa, such asLenodus, and the immigration ofMicrozarkodinacf.ozarkodellaandHistiodella holodentata. In the middle of the ‘Täljsten’ interval, coinciding with the appearance of abundant cystoids, conditions became less hospitable for conodonts, resulting in a low diversity and low abundance fauna, which occurs to the top of the interval. The overlying red limestone, apparently deposited during a deepening event, marks a return to pre-‘Täljsten’ conditions with a re-organised fauna. The close correlation between the lithologic shifts and conodont faunal changes demonstrates the usefulness of conodonts as environmental indicators.

Middle Ordovician (Whiterockian) trilobites from the Sunblood Formation, District of Mackenzie, Canada

1991 ◽  
Vol 65 (5) ◽  
pp. 801-824 ◽  
Author(s):  
James V. Tremblay ◽  
Stephen R. Westrop
Keyword(s):  
New Species ◽  
North America ◽  
The South ◽  
Middle Ordovician ◽  
Low Diversity ◽  
Shallow Subtidal ◽  
Three New Species

In the South Nahanni River area of the District of Mackenzie, the Middle Ordovician Sunblood Formation comprises mainly limestones and dolostones of intertidal and shallow-subtidal origin, as indicated by the presence of desiccation polygons, fenestral fabric, and oncolites. Faunas of well-preserved, silicified trilobites from a low-diversity, nearshore, Bathyurus-dominated biofacies are compositionally distinct from faunas in correlative strata around North America that represent different shelf to upperslope biofacies. A temporal biostratigraphy applicable to nearshore biofacies through much of the Whiterockian Series consists of five zones, in ascending order: Bathyurus mackenziensis, B. sunbloodensis, B. margareti, B. nevadensis, and B. granulosus. Twenty-six species are assigned to 18 genera, of which Ludvigsenella is new. Three new species of Bathyurus are B. mackenziensis, B. sunbloodensis, and B. margareti.

Integrated chitinozoan, conodont, and graptolite biostratigraphy from the upper part of the Cape Cormorant Formation (Middle Ordovician), western Newfoundland

2001 ◽  
Vol 38 (3) ◽  
pp. 387-409 ◽  
Author(s):  
Roberto Albani ◽  
Gabriella Bagnoli ◽  
Jörg Maletz ◽  
Svend Stouge
Keyword(s):  
Early Stage ◽  
Foreland Basin ◽  
Black Shales ◽  
Head Group ◽  
Middle Ordovician ◽  
Head Groups ◽  
Taconic Orogeny ◽  
Low Diversity ◽  
Conodont Fauna ◽  
Abundance And Diversity

The Cape Cormorant Formation of the Table Head Group exposed on the Port au Port Peninsula, western Newfoundland, is composed of dark-brown to black shales with interbeds of thin calcareous silty and sandy distal turbidites. Distinctive carbonate conglomerates and breccias derived from the foundering shelf are occasionally found in the formation. The sediments accumulated in the foreland basin formed during the early stage of the Taconic orogeny. The faunas from the upper part of the Cape Cormorant Formation include graptolites, conodonts, and chitinozoans. The graptolites are well preserved, but are of low diversity and are referred to the Darriwil Pterograptus elegans Zone. Conodonts recorded from the distal turbidites are rare and fragmented. The faunas include taxa that are known from the St. George and Table Head groups. The conodont fauna is tentatively assigned to the Histiodella kristinae Phylozone and to the younger, unzoned interval. The chitinozoans are well preserved and the yield is high. The fauna is assigned to the Cyathochitina jenkinsi Zone and to an undefined interval. The abundance and diversity of the chitinozoan assemblages display a cyclic pattern, which is related to changes of the oceanic watermass in the foreland basin. The new chitinozoan species Belonechitina nevillensis n. sp., Belonechitina uniformipunctata n. sp., and Cyathochitina cormorani n. sp. are described.

scholarly journals Bioestratigrafía y provincialismo de conodontes del tramo medio-superior de la Formación San Juan en el cerro Viejo de Huaco, Precordillera, Argentina

2018 ◽  
Vol 45 (2) ◽  
pp. 274 ◽  
Author(s):  
Matías J. Mango ◽  
Guillermo L. Albanesi
Keyword(s):  
North Atlantic ◽  
Species Level ◽  
San Juan ◽  
Insufficient Information ◽  
Entire Interval ◽  
Middle Ordovician ◽  
The North ◽  
Atlantic Province ◽  
The North Atlantic ◽  
Color Alteration

The present study deals with the conodont biostratigraphy from the middle and upper parts of the San Juan Formation (Lower-Middle Ordovician) exposed at the Los Gatos creek section, west of the cerro Viejo de Huaco, Central Precordillera of San Juan Province. The numerous conodonts recovered, corresponding to 55 species, allow to recognize a series of biozones in the studied section. The biostratigraphic analysis carried out herein allows determining associations of conodonts assignable to the Oepikodus evae, Oepikodus intermedius, Baltoniodus triangularis-Tripodus laevis and Lenodus variabilis zones that correspond to the middle Floian to lower Darriwilian. The Baltoniodus navis and Microzarkodina parva zones were not identified due to insufficient information provided by this stratigraphic section. In general, the levels corresponding to the Baltoniodus triangularis-Tripodus laevis Zone contain more conodonts, than the records of other localities from Precordillera. These specimens are well preserved with a color alteration index (CAI) of 2-2.5, indicating overburden paleotemperatures ranging from 60° and 155° C. The large presence of fragmented conodonts, with recrystallized surfaces and crystal overgrowth, could indicate the effect of distinctive diagenetic fossil processes on the bearer limestone. The analysis of the diversity and abundance of genera and species of conodonts by chronostratigraphic intervals presents a great percentage of cosmopolitan taxa, 18% and 38% in common, at species level, only with the North-American Midcontinent Province (NAMP), and with a small percentage with the North-Atlantic Province (NAP) and the Precordillera, which allows to approximate a greater paleobiogeographic affinity of the conodonts recovered with those of the NAMP than those of the NAP for the entire interval studied. On the other hand, the Precordillera is verified as a province with its own characteristics as identified by several authors.

Initial diversification of macroboring ichnofossils and exploitation of the macroboring niche in the lower Paleozoic

Paleobiology ◽  
1978 ◽  
Vol 4 (2) ◽  
pp. 163-170 ◽  
Author(s):  
David R. Kobluk ◽  
Noel P. James ◽  
S. George Pemberton
Keyword(s):  
Lower Cambrian ◽  
High Stress ◽  
Lower Paleozoic ◽  
Middle Ordovician ◽  
Rapid Speciation ◽  
Low Diversity ◽  
Stress Environment ◽  
Boring Organisms

The traces of macroboring organisms are known throughout the Phanerozoic, with diversification and exploitation of the macroboring niche paralleling variations in the development of skeletal metazoa. The oldest macroboring biota is an abundant yet low diversity fauna in hardgrounds and reefs of Lower Cambrian age. Following the extinction of archaeocyathids at the end of the Lower Cambrian (and thus the demise of skeletal reefs until the Middle Ordovician), boring organisms appear to be restricted to submarine hardgrounds. With the development of skeletal reefs in the Middle Ordovician the macroboring fauna shows a rapid speciation and a dramatic increase in diversity. This same pattern occurs again in the Devonian. This record appears to represent refuge of the fauna in low stress, hardground environments when skeletal reefs were not present and radiation in the high stress environment of the reef when large skeletal metazoa were abundant and diverse.

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