The “earliest tabulate corals” are not tabulates

Geology ◽  
2020 ◽  
Author(s):  
Robert J. Elias ◽  
Dong-Jin Lee ◽  
Brian R. Pratt
Keyword(s):  
Evolutionary History ◽  
Late Ordovician ◽  
Time Span ◽  
Cambrian Explosion ◽  
Middle Ordovician ◽  
Early Ordovician ◽  
Calcareous Alga ◽  
History Of ◽  
Geological Factors ◽  
Tabulate Corals

Putative tabulate-like corals dating to the Cambrian Explosion are not true tabulates. Early Ordovician fossils identified as Lichenaria and previously accepted as the earliest tabulate corals actually belong to Amsassia, which may be a calcareous alga. The earliest definite tabulates appeared in the latest Middle Ordovician as part of the Great Ordovician Biodiversification Event, prior to the earliest confirmed occurrence of tabulate species that do belong to Lichenaria in the Late Ordovician. With Cambrian (Epoch 2) tabulate-like fossils being separated from the appearance of true tabulates by a time span of ~50 m.y., a direct phylogenetic connection is unlikely. Thus, the prevailing understanding of the origin and evolutionary history of tabulate corals needs to be reconsidered. The appearance of both major groups of Paleozoic corals, tabulates and rugosans, at the same time on separate paleocontinents must be taken into account in determining biological and geological factors involved in the Great Ordovician Biodiversification Event.

Amsassia (calcareous alga) from the Lower Ordovician (Tremadocian) of western Newfoundland, and the biologic affinity and geologic history of the genus

2021 ◽  
pp. 1-18
Author(s):  
Dong-Jin Lee ◽  
Robert J. Elias ◽  
Brian R. Pratt
Keyword(s):  
South China ◽  
Geologic History ◽  
Shallow Marine ◽  
Middle Ordovician ◽  
Calcareous Alga ◽  
Tarim Block ◽  
Lower Ordovician ◽  
History Of ◽  
Argentine Precordillera ◽  
Extinct Group

Abstract Modular coral-like fossils from Lower Ordovician (Tremadocian) thrombolitic mounds in the St. George Group of western Newfoundland were initially identified as Lichenaria and thought to include the earliest tabulate corals. They are here assigned to Amsassia terranovensis n. sp. and Amsassia? sp. A from the Watts Bight Formation, and A. diversa n. sp. and Amsassia? sp. B from the overlying Boat Harbour Formation. Amsassia terranovensis n. sp. and A. argentina from the Argentine Precordillera are the earliest representatives of the genus. Amsassia is considered to be a calcareous alga, possibly representing an extinct group of green algae. The genus originated and began to disperse in the Tremadocian, during the onset of the Great Ordovician Biodiversification Event, on the southern margin of Laurentia and the Cuyania Terrane. It inhabited small, shallow-marine reefal mounds constructed in association with microbes. The paleogeographic range of Amsassia expanded in the Middle Ordovician (Darriwilian) to include the Sino-Korean Block, as well as Laurentia, and its environmental range expanded to include non-reefal, open- and restricted-marine settings. Amsassia attained its greatest diversity and paleogeographic extent in the Late Ordovician (Sandbian–Katian), during the culmination of the Great Ordovician Biodiversification Event. Its range included the South China Block, Tarim Block, Kazakhstan, and Siberia, as well as the Sino-Korean Block and Laurentia, and its affinity for small microbial mounds continued during that time. In the latest Ordovician (Hirnantian), the diversity of Amsassia was reduced, its distribution was restricted to non-reefal environments in South China, and it finally disappeared during the end-Ordovician mass extinction. UUID: http://zoobank.org/ef0abb69-10a6-46de-8c78-d6ec7de185fe

Ontogeny in the fossil record: diversification of body plans and the evolution of “aberrant” symmetry in Paleozoic echinoderms

Paleobiology ◽  
2007 ◽  
Vol 33 (1) ◽  
pp. 149-163 ◽  
Author(s):  
Colin D. Sumrall ◽  
Gregory A. Wray
Keyword(s):  
Great Reduction ◽  
Fossil Record ◽  
Evolutionary History ◽  
Total Loss ◽  
Cambrian Explosion ◽  
Growth Stages ◽  
Ecological Constraints ◽  
Fivefold Symmetry ◽  
Primary Body ◽  
History Of

Echinoderms have long been characterized by the presence of ambulacra that exhibit pentaradiate symmetry and define five primary body axes. In reality, truly pentaradial ambulacral symmetry is a condition derived only once in the evolutionary history of echinoderms and is restricted to eleutherozoans, the clade that contains most living echinoderm species. In contrast, early echinoderms have a bilaterally symmetrical 2-1-2 arrangement, with three ambulacra radiating from the mouth. Branching of the two side ambulacra during ontogeny produces the five adult rays. During the Cambrian Explosion and Ordovician Radiation, some 30 clades of echinoderms evolved, many of which have aberrant ambulacral systems with one to four rays. Unfortunately, no underlying model has emerged that explains ambulacral homologies among disparate forms. Here we show that most Paleozoic echinoderms are characterized by uniquely identifiable ambulacra that develop in three distinct postlarval stages. Nearly all “aberrant” echinoderm morphologies can be explained by the paedomorphic ambulacra reduction (PAR) model through the loss of some combination of these growth stages during ontogeny. Superficially similar patterns of ambulacral reduction in distantly related clades have resulted from the parallel loss of homologous ambulacra during ontogeny. Pseudo-fivefold symmetry seen in Blastoidea and the true fivefold symmetry seen in Eleutherozoa result from great reduction and total loss, respectively, of the 2–1–2 symmetry early in ontogeny. These ambulacral variations suggest that both developmental and ecological constraints affect the evolution of novel echinoderm body plans.

South America’s earliest (Ordovician, Floian) crinoids

2015 ◽  
Vol 89 (4) ◽  
pp. 622-630 ◽  
Author(s):  
Thomas E. Guensburg ◽  
Beatriz G. Waisfeld
Keyword(s):  
Late Ordovician ◽  
Middle Ordovician ◽  
Early Ordovician ◽  
Northwest Argentina ◽  
Anal Sac

AbstractTwo new Early Ordovician crinoids have been discovered in Gondwanan rocks of northwest Argentina.Ramseyocrinus argentinusn. sp., among the most complete for the genus, aids in reconstructing key morphology.Ramseyocrinusis unorthodox with just four radials forming the entire cup, these articulating to five arms above and a tetrameric stem below. Evidence is presented radials comprise A, B, D, and E ray elements (C absent) with B and D radials adjoining to form a compound facet for the C arm. Thus the cup entirely lacks posterior plating; an elongate anal sac projects from the CD tegmen region alongside the C arm. Cup synapomorphies closely linkRamseyocrinusand the Middle OrdovicianTetragonocrinus; inclusion of this clade within disparids is tenuous.Quechuacrinus ticsan. gen. and sp., increases the paleogeographic range of reteocrinid camerates, previously documented only from Laurentia. This taxon expresses synapomorphies characterizing the Late OrdovicianReteocrinus, demonstrating the antiquity of this morphotype.

scholarly journals Enduring evolutionary embellishment of cloudinids in the Cambrian

2021 ◽  
Vol 8 (12) ◽  
Author(s):  
Tae-Yoon S. Park ◽  
Jikhan Jung ◽  
Mirinae Lee ◽  
Sangmin Lee ◽  
Yong Yi Zhen ◽  
...  
Keyword(s):  
Asexual Reproduction ◽  
Fossil Record ◽  
Evolutionary History ◽  
Structural Complexity ◽  
Cambrian Explosion ◽  
Animal Group ◽  
Reproduction Mode ◽  
First Case ◽  
History Of ◽  
Mode Tracking

The Ediacaran–Cambrian transition and the following Cambrian Explosion are among the most fundamental events in the evolutionary history of animals. Understanding these events is enhanced when phylogenetic linkages can be established among animal fossils across this interval and their trait evolution monitored. Doing this is challenging because the fossil record of animal lineages that span this transition is sparse, preserved morphologies generally simple and lifestyles in the Ediacaran and Cambrian commonly quite different. Here, we identify derived characters linking some members of an enigmatic animal group, the cloudinids, which first appeared in the Late Ediacaran, to animals with cnidarian affinity from the Cambrian Series 2 and the Miaolingian. Accordingly, we present the first case of an animal lineage represented in the Ediacaran that endured and diversified successfully throughout the Cambrian Explosion by embellishing its overall robustness and structural complexity. Among other features, dichotomous branching, present in some early cloudinids, compares closely with a cnidarian asexual reproduction mode. Tracking this morphological change from Late Ediacaran to the Miaolingian provides a unique glimpse into how a primeval animal group responded during the Cambrian Explosion.

scholarly journals Extraordinary fossils reveal the nature of Cambrian life: a commentary on Whittington (1975) ‘The enigmatic animal Opabinia regalis , Middle Cambrian, Burgess Shale, British Columbia’

2015 ◽  
Vol 370 (1666) ◽  
pp. 20140313 ◽  
Author(s):  
Derek E. G. Briggs
Keyword(s):  
British Columbia ◽  
Royal Society ◽  
Early Evolution ◽  
Cambrian Explosion ◽  
Burgess Shale ◽  
Critical Interval ◽  
Middle Cambrian ◽  
Early Ordovician ◽  
History Of ◽  
350Th Anniversary

Harry Whittington's 1975 monograph on Opabinia was the first to highlight how some of the Burgess Shale animals differ markedly from those that populate today's oceans. Categorized by Stephen J. Gould as a ‘weird wonder’ ( Wonderful life , 1989) Opabinia , together with other unusual Burgess Shale fossils, stimulated ongoing debates about the early evolution of the major animal groups and the nature of the Cambrian explosion. The subsequent discovery of a number of other exceptionally preserved fossil faunas of Cambrian and early Ordovician age has significantly augmented the information available on this critical interval in the history of life. Although Opabinia initially defied assignment to any group of modern animals, it is now interpreted as lying below anomalocaridids on the stem leading to the living arthropods. This commentary was written to celebrate the 350th anniversary of the journal Philosophical Transactions of the Royal Society .

Early Palaeozoic metamorphic history of the Midland Valley, Southern Uplands–Longford-Down massif and the Lake District, British Isles

1984 ◽  
Vol 75 (2) ◽  
pp. 245-258 ◽  
Author(s):  
G. J. H. Oliver ◽  
J. L. Smellie ◽  
L. J. Thomas ◽  
D. M. Casey ◽  
A. E. S. Kemp ◽  
...  
Keyword(s):  
Accretionary Prism ◽  
Late Ordovician ◽  
Ocean Floor ◽  
Lower Grade ◽  
Lake District ◽  
Reflectance Measurement ◽  
Early Ordovician ◽  
Metamorphic History ◽  
History Of ◽  
Early Palaeozoic

ABSTRACTA model for the early Palaeozoic metamorphic history of the Midland Valley and adjacent areas to the S in Scotland, England and Ireland is based on the results of new field mapping, thin section petrography, electron probe microanalysis, X-ray diffractometry, conodont and palynomorph colouration and graptolite reflectance measurement.The oldest metamorphic rocks of the Midland Valley of Scotland, excluding xenoliths in post-Silurian lavas, are possibly the blueschist occurrences in the melange unit of the Ballantrae complex. These may be tectonised remnants of (?)pre-Arenig ocean-floor subducted during closure of the Iapetus Ocean. In the early Ordovician, the melange terrane was dynamothermally metamorphosed during obduction of newly-formed ocean crust. The obduction process piled up a thick sequence of various ocean-floor types such that burial metamorphism in parts reached pumpellyite-actinolite facies; elsewhere prehnite-pumpellyite and zeolite facies was attained.Whilst the Midland Valley acted as an inter- or fore-arc basin during the Late Ordovician and Silurian and experienced burial metamorphism, an accretionary prism was formed to the S. Accretion, tectonic burial and metamorphism of ocean-floor and trench sediment was continuous in the Southern Uplands and the Longford-Down massif of Ireland through Late Ordovician to Late Silurian times. Rocks at the present-day surface vary from zeolite facies to prehnitepumpellyite facies. Silurian trench-slope basin sediments can be recognised in part by their lower grade of burial metamorphism. Greenschist facies rocks of the prism probably lie close to the surface.The Lake District island-arc terrane of Northern England has an early Ordovician history of burial metamorphism up to prehnite-pumpellyite facies. The Late Ordovician and Silurian metamorphic history is one of sedimentary burial complicated by tectonism and intrusion of granite plutons to a relatively high level. The Iapetus suture is marked by a weak contrast in metamorphic grade.

scholarly journals Late Ordovician Palynomorphs

1985 ◽  
Vol 4 (1) ◽  
pp. 11-26 ◽  
Author(s):  
S. G. Molyneux ◽  
F. Paris
Keyword(s):  
New Species ◽  
North America ◽  
Late Ordovician ◽  
Middle Ordovician ◽  
Early Ordovician ◽  
Core Samples ◽  
Type Section ◽  
A New Species

Abstract. ACRITARCHSOrdovician acritarchs have been recorded in five core samples collected between 2520 ft. and 3000 ft. in Well E1-81, and ten cutting samples taken between 12150 ft. and 13240 ft. in Well J1-81A. All the assemblages recovered are of Late Ordovician age; no Early Ordovician or Middle Ordovician assemblages have been identified.Investigations have so far concentrated on the acritarch assemblages from Well El-81. The highest three Ordovician samples from depths of 2520 to 2550 ft., 2552 to 2557 ft., and 2562 to 2567 ft., yielded similar assemblages which include Veryhachium irroratum, V. cf. lairdii, V. oklahomense?, V. subglobosum, V. trispinosum, Villosacapsula setosapellicula and a new species, Striatotheca sp. A. Navifusa similis? is represented by one specimen in the sample from 2552 to 2557 ft. Another specimen from the same sample is tentatively referred to Aremoricanium syringosagis. Specimens of Baltisphaeridium, Peteinosphaeridium, Leiofusa and Eupoikilofusa occur throughout the interval 2520 to 2567 ft. but are rare. Commonly occurring species include V. irroratum and V. setosapellicula. V. irroratum has been recorded from the Middle Ordovician of North America (Loeblich & Tappan, 1969) and the Caradoc of England (Turner, 1984) but Cramer & Diez (1979) maintain that it has its acme in the Ashgill. V. setosapellicula is common in the Sylvan Shale of Oklahoma (Loeblich, 1970) which is generally understood to be of Ashgill age, but is rare in the Eden Shale (Caradoc) of Indiana (Colbath, 1979) and in the type section of the Caradoc Series in Shropshire, England (Turner, 1984). . . .

An Examination of Life History and Behavioral Evolution Across the Ediacaran–Cambrian Transition

2014 ◽  
Vol 88 (2) ◽  
pp. 205-206
Author(s):  
James D. Schiffbauer ◽  
Shuhai Xiao
Keyword(s):  
Evolutionary History ◽  
Charles Darwin ◽  
Good Reason ◽  
Cambrian Explosion ◽  
Gradual Transition ◽  
Sixth Edition ◽  
History Of ◽  
Satisfactory Answer ◽  
Life On Earth ◽  
Cambrian System

With the 1859 publication of On the Origin of Species, Charles Darwin posed contention against his synthesis on the history of life. His dilemma specifically regarded that the geologically sudden appearance of complex shelly invertebrates at the Cambrian Explosion followed an incomprehensible absence of a long-standing gradual transition to such forms. Indeed, as quoted from Chapter 10 of the sixth edition, “To the question why we do not find rich fossiliferous deposits belonging to these assumed earliest periods prior to the Cambrian system, I can give no satisfactory answer… the difficulty of assigning any good reason for the absence of vast piles of strata rich in fossils beneath the Cambrian system is very great… The case at present must remain inexplicable; and may be truly urged as a valid argument against the views here entertained” (p. 286–288). In the 155 years since this assertion, paleontologists focusing on the strata of the Ediacaran–Cambrian transition have uncovered a rich evolutionary history prior to the radiation of animals, but our resulting discoveries have neither been without debate nor unraveled the intricacies suggested by Darwin's dilemma. While we are continuing to learn from both geological and paleontological records, the organisms, their expanding ecosystem intricacy, and the increasing complexity of their behaviors during the Ediacaran and Cambrian periods are yet not well understood. With rapidly growing data and ideas, this transition in evolutionary history has become one of the intellectually richest periods in our record of life on Earth.

The tectonics and depositional history of the Ordovician and Silurian rocks of Notre Dame Bay, Newfoundland

1985 ◽  
Vol 22 (4) ◽  
pp. 607-618 ◽  
Author(s):  
R. J. Arnott ◽  
W. S. McKerrow ◽  
L. R. M. Cocks
Keyword(s):  
Strike Slip ◽  
Late Ordovician ◽  
Island Arc ◽  
The West ◽  
Depositional History ◽  
Middle Ordovician ◽  
The North ◽  
Lower Ordovician ◽  
History Of ◽  
Ophiolitic Rocks

In the Notre Dame Bay region, ophiolitic rocks underlie a thick sequence of Lower Ordovician volcanic-arc rocks to the north of the Lobster Cove – Chanceport Fault. Neither this fault nor the Lukes Arm – Sops Head Fault shows evidence of very large strike-slip movements, as parts of the same arc, together with much arc-derived detritus, straddle both faults. Towards the east, this arc-derived detritus becomes more distal in aspect and passes laterally into the Dunnage Mélange. During the Middle Ordovician Epoch (late Llandeilo and early Caradoc), most areas show a marked decrease in volcanic activity and in the amount of coarse detritus deposited. Coarse turbidites reappear, at different times in different areas, during the Late Ordovician. These are related to several fault-bounded basins and to movements on the Lukes Arm – Sops Head Fault. Many of these faults, particularly in the east, are marked by olistostromes, several of which can be dated by fossils as Late Ordovician and Early Silurian. The whole region, between the Reach Fault on the east and the Baie Verte – Brompton Line on the west, has a stratigraphic unity. If it has been moved by strike slip relative to the Long Range, then any such fault must lie to the west of the Baie Verte – Brompton Line. The interpretation of an Early Ordovician island arc moving above an easterly directed subduction zone is in accord with both the geochemical and palaeontological evidence. The Notre Dame Bay region may have been converted into a transform-dominated margin in the Late Ordovician and Early Silurian in a manner analogous to the oblique slip tectonic regimes of the Californian and New Zealand margins during the Tertiary, with a precursor of the Reach Fault marking the edge of the continent after the Notre Dame island arc had collided with North America.

scholarly journals The appearance and duration of the Jehol Biota: Constraint from SIMS U-Pb zircon dating for the Huajiying Formation in northern China

2020 ◽  
Vol 117 (25) ◽  
pp. 14299-14305 ◽  
Author(s):  
Saihong Yang ◽  
Huaiyu He ◽  
Fan Jin ◽  
Fucheng Zhang ◽  
Yuanbao Wu ◽  
...  
Keyword(s):  
Evolutionary History ◽  
Secondary Ion Mass Spectrometry ◽  
Temporal Distribution ◽  
Northern China ◽  
Time Span ◽  
Hebei Province ◽  
Jehol Biota ◽  
History Of ◽  
Fossil Records ◽  
Secondary Ion

The Lower Cretaceous Huajiying Formation of the Sichakou Basin in northern Hebei Province, northern China contains key vertebrate taxa of the early Jehol Biota, e.g.,Protopteryx fengningensis,Archaeornithura meemannae,Peipiaosteus fengningensis, andEoconfuciusornis zhengi. This formation arguably documents the second-oldest bird-bearing horizon, producing the oldest fossil records of the two major Mesozoic avian groups Enantiornithes and Ornithuromorpha. Hence, precisely determining the depositional ages of the Huajiying Formation would advance our understanding of the evolutionary history of the Jehol Biota. Here we present secondary ion mass spectrometry (SIMS) U-Pb zircon analysis results of eight interbedded tuff/tuffaceous sandstone samples from the Huajiying Formation. Our findings, combined with previous radiometric dates, suggest that the oldest enantiornithine and ornithuromorph birds in the Jehol Biota are ∼129−131 Ma, and that the Jehol Biota most likely first appeared at ∼135 Ma. This expands the biota’s temporal distribution from late Valanginian to middle Aptian with a time span of about 15 My.

Sign in / Sign up

Export Citation Format

Share Document