New Lu–Hf and Pb–Pb age constraints on the earliest animal fossils

Barfod, Gry H.; Albarède, Francis; Knoll, Andrew H.; Xiao, Shuhai; Télouk, Philippe; Frei, Robert; Baker, Joel A.

doi:10.1016/s0012-821x(02)00687-8

Cited by 224 publications

(80 citation statements)

References 31 publications

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“…We constrained the divergence between red algae and (green algae ϩ land plants) to a maximum of 3500 My, the age of the first known fossils (20,21). Within the red algae, we constrained the deepest divergence to the age of the oldest known red algal fossil, Bangiomorpha pubescens (1174 -1222 My) (22) and that between Gracilaria tenuistipitata and Palmaria palmata to the age of the Doushantuo Florideophyte fossils (595-603 My) (23,24). Within the green plant lineage, we used the following constraints: the first appearance of spore tetrads indicating the emergence of land plants (432-476 My) (25), the oldest known seeds indicating the emergence of seed plants (355-370 My) (26), several fossils indicating the divergence between angiosperms and gymnosperms (290 -320 My) (27), the earliest known fossil Nymphaeales indicating their divergence from eudicots (115 My minimum) (28), and the Early Cretaceous palynological diversification of angiosperms indicating the divergence of monocots and eudicots (90 -130 My) (29).…”

Section: Methodsmentioning

confidence: 99%

Triassic origin and early radiation of multicellular volvocine algae

Herron

Hackett

Aylward

et al. 2009

Proc. Natl. Acad. Sci. U.S.A.

234

303

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Evolutionary transitions in individuality (ETIs) underlie the watershed events in the history of life on Earth, including the origins of cells, eukaryotes, plants, animals, and fungi. Each of these events constitutes an increase in the level of complexity, as groups of individuals become individuals in their own right. Among the best-studied ETIs is the origin of multicellularity in the green alga Volvox, a model system for the evolution of multicellularity and cellular differentiation. Since its divergence from unicellular ancestors, Volvox has evolved into a highly integrated multicellular organism with cellular specialization, a complex developmental program, and a high degree of coordination among cells. Remarkably, all of these changes were previously thought to have occurred in the last 50 -75 million years. Here we estimate divergence times using a multigene data set with multiple fossil calibrations and use these estimates to infer the times of developmental changes relevant to the evolution of multicellularity. Our results show that Volvox diverged from unicellular ancestors at least 200 million years ago. Two key innovations resulting from an early cycle of cooperation, conflict and conflict mediation led to a rapid integration and radiation of multicellular forms in this group. This is the only ETI for which a detailed timeline has been established, but multilevel selection theory predicts that similar changes must have occurred during other ETIs.evolution ͉ multicellularity ͉ multilevel selection ͉ transitions in individuality ͉ Volvox T he history of life on Earth has involved a number of evolutionary transitions in individuality (ETIs), in which groups of once-autonomous individuals became new individuals. Through the transfer of fitness from the individuals making up the group to the group itself, a new entity was formed with a single fitness and a single evolutionary fate. In this way, groups of interacting molecular replicators became single-celled organisms, prokaryotic cells became a primitive eukaryote, groups of single-celled organisms became multicellular organisms, and groups of multicellular organisms became social individuals (as in the social insects). In many cases such transitions have opened up entire new adaptive landscapes leading to vast radiations as completely new ways of being alive became available (e.g., cellular life, eukaryotes, plants, and animals). Understanding how and why groups of individuals become new kinds of individuals is a major challenge in explaining the history of life.The transition from unicellular to multicellular life is the paradigm case of the integration of lower-level individuals (cells) into a new higher-level individual-the multicellular organism. This transition has occurred dozens of times independently, for example in the red algae, brown algae, land plants, animals, and fungi (reviewed in ref. 1). Among the best-studied ETIs is the origin of multicellularity in the green alga Volvox and its relatives (the volvocine algae), which have been develop...

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Section: Methodsmentioning

confidence: 99%

Triassic origin and early radiation of multicellular volvocine algae

Herron

Hackett

Aylward

et al. 2009

Proc. Natl. Acad. Sci. U.S.A.

234

303

View full text Add to dashboard Cite

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“…M any fossil embryos are known from the Weng'an Phosphate Member of the Ediacaran Doushantuo Formation (580-600 Ma) (1)(2)(3). Among these, embryos at an advanced stage of development with complex organization are uncommon (4)(5)(6)(7)(8)(9)(10)(11).…”

mentioning

confidence: 99%

Complex embryos displaying bilaterian characters from Precambrian Doushantuo phosphate deposits, Weng'an, Guizhou, China

Chen

Bottjer

et al. 2009

Proc. Natl. Acad. Sci. U.S.A.

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Three-dimensionally preserved embryos from the Precambrian Ediacaran Doushantuo Formation, Weng'an, Guizhou, southern China, have attracted great attention as the oldest fossil evidence yet found for multicellular animal life on Earth. Many embryos are early cleavage embryos and most of them yield a limited phylogenetic signal. Here we report the discovery of two Doushantuo embryos that are three-dimensionally preserved and complex. Imaging techniques using propagation phase-contrast based synchrotron radiation microtomography (PPC-SR-CT) reveal that the organization of cells demonstrates several bilaterian features, including the formation of anterior-posterior, dorso-ventral, and right-left polarities, and cell differentiation. Unexpectedly, our observations show a noticeable difference in organization patterns between the embryos, suggesting that they represent two distinct taxa. These embryos provide further evidence for the presence of bilaterian animals in the Doushantuo biota. Furthermore, these bilaterians had already diverged into distantly related groups at least 40 million years before the Cambrian radiation, indicating that the last common ancestor of the bilaterians lived much earlier than is usually thought.early animal evolution ͉ early metazoan evolution ͉ nondestructive 3-D reconstruction ͉ precambrian ediacaran embryos ͉ Weng'an biota

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“…At Weng'an the Doushantuo Formation can be about 40 m thick . In some sections, the region just above the Middle Phosophorite unit has been dated at 576 MA and the region just below this unit has been dated at 599 MA (Barford et al 2002;Chen et al 2004); the dating of this part of the formation is poorly constrained. The upper part of the Basal Phosphorite unit terminates some time before the Middle Phosphorite unit and begins after 621 MA.…”

Section: Time Of First Appearance Of Ediacaran Genera and Their Geolomentioning

confidence: 99%

The rise of bilaterians

Freeman

2009

Historical Biology

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Recently Shen et al. have argued that the Ediacaran faunas from Avalon-Charnwood [580 -560 million years ago (MA)], the White Sea-Flinders Range (560-550 MA) and Namibia (550 -543 MA) occupied the same morphospace even though these faunas differed in species composition, ecology, biogeography and age. The traits they used to characterise these faunas could not distinguish between important promorphological features such as radial vs. bilaterian and unitary vs. colonial animals. Their inappropriate assignment of symmetry properties led to the homogenisation of morphospace in these different faunas. Another way to examine shifts in morphospace involves sorting out radial vs. bilaterian and unitary vs. colonial genera in terms of their time of first appearance in the fossil record. While genera with both kinds of symmetry properties and unitary and colonial animals were present during the early Ediacaran, there was a large proportional increase in new bilaterian genera and a decrease in colonial genera beginning between 560-550 MA. The increase in bilaterians may have been associated with the ability to exploit food sources in and on the substrate of shallow water environments.

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New Lu–Hf and Pb–Pb age constraints on the earliest animal fossils

Cited by 224 publications

References 31 publications

Triassic origin and early radiation of multicellular volvocine algae

Triassic origin and early radiation of multicellular volvocine algae

Complex embryos displaying bilaterian characters from Precambrian Doushantuo phosphate deposits, Weng'an, Guizhou, China

The rise of bilaterians

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