Predatorial Borings in Late Precambrian Mineralized Exoskeletons

Bengtson, Stefan; Zhao, Yue

doi:10.1126/science.257.5068.367

Cited by 264 publications

(139 citation statements)

References 10 publications

Supporting

Mentioning

134

Contrasting

Unclassified

Order By: Relevance

“…Clearly, bilaterians became armored in the Ediacaran-Cambrian transition. This finding suggests that the development of hard mouth parts may have been a key innovation to allow for additional expansion of macrophagous predators, giving rise to the first arms race (26). The small shelly taxa diversified over the next 14 Myr, which culminated in the Cambrian explosion of bilaterian diversity; this explosion seems to have occurred over a relatively short 10 Myr (29).…”

Section: Fossil Recordmentioning

confidence: 99%

See 1 more Smart Citation

Evolution of centralized nervous systems: Two schools of evolutionary thought

2012

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

112

View full text Add to dashboard Cite

Understanding the evolution of centralized nervous systems requires an understanding of metazoan phylogenetic interrelationships, their fossil record, the variation in their cephalic neural characters, and the development of these characters. Each of these topics involves comparative approaches, and both cladistic and phenetic methodologies have been applied. Our understanding of metazoan phylogeny has increased greatly with the cladistic analysis of molecular data, and relaxed molecular clocks generally date the origin of bilaterians at 600-700 Mya (during the Ediacaran). Although the taxonomic affinities of the Ediacaran biota remain uncertain, a conservative interpretation suggests that a number of these taxa form clades that are closely related, if not stem clades of bilaterian crown clades. Analysis of brain-body complexity among extant bilaterians indicates that diffuse nerve nets and possibly, ganglionated cephalic neural systems existed in Ediacaran organisms. An outgroup analysis of cephalic neural characters among extant metazoans also indicates that the last common bilaterian ancestor possessed a diffuse nerve plexus and that brains evolved independently at least four times. In contrast, the hypothesis of a tripartite brain, based primarily on phenetic analysis of developmental genetic data, indicates that the brain arose in the last common bilaterian ancestor. Hopefully, this debate will be resolved by cladistic analysis of the genomes of additional taxa and an increased understanding of character identity genetic networks.The fact that some of these building stones are universal does not, of course, mean that the organs to which they contribute are as old as these molecules or their precursors.von Salvini-Plawen and Mayr (1) A ny consideration of the evolution of centralized nervous systems is inextricably linked to an understanding of the phylogeny of living metazoans, their fossil history, the vast range of complexity in their nervous systems, and the development of these nervous systems. For this reason, any attempt to reconstruct the phylogeny of metazoan CNSs must be based on all lines of evidence available. The molecular phylogenetic studies of the last 20 y are particularly important in understanding metazoan interrelationships as well as the time frame in which these animals arose and radiated, and we now have increased insights into the genetics underlying the development of CNSs.First, I will review the fossil history of the earliest putative metazoans, and then, I will discuss different comparative approaches to analyzing both molecular and morphological data: the molecular clock hypothesis, which has yielded a range of possible dates for the origin and divergence of metazoans; developmental genetics and its contribution to our understanding of the patterning of metazoan bodies, particularly patterning of the CNS; and conclusions based on the first outgroup analysis of metazoan central neural characters. Finally, I will review two hypotheses concerning the morphological complexity of the ...

show abstract

Section: Fossil Recordmentioning

confidence: 99%

“…Bilaterian body fossils are absent, but small calcified shells of Cloudina and Namacalathus and the earliest evidence of predation in the form of holes bored into these calcified shells do occur (26).…”

Section: Fossil Recordmentioning

confidence: 99%

Evolution of centralized nervous systems: Two schools of evolutionary thought

2012

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

112

View full text Add to dashboard Cite

show abstract

“…A range of biological phenomena typically associated with animals first appears during the late Ediacaran interval (~580-541 Myr ago (Ma)), including skeletogenesis 4 , reef building 5 and macroscopic predation 6 . Body fossils of late Ediacaran macro-organisms include at least some early animals 3 , but crucially, most plausible claims for metazoans lie within the diploblasts rather than the Bilateria 3 .…”

mentioning

confidence: 99%

Ichnological evidence for meiofaunal bilaterians from the terminal Ediacaran and earliest Cambrian of Brazil

et al. 2017

View full text Add to dashboard Cite

The evolutionary events during the Ediacaran-Cambrian transition (~541 Myr ago) are unparalleled in Earth history. The fossil record suggests that most extant animal phyla appeared in a geologically brief interval, with the oldest unequivocal bilaterian body fossils found in the Early Cambrian. Molecular clocks and biomarkers provide independent estimates for the timing of animal origins, and both suggest a cryptic Neoproterozoic history for Metazoa that extends considerably beyond the Cambrian fossil record. We report an assemblage of ichnofossils from Ediacaran-Cambrian siltstones in Brazil, alongside U-Pb radioisotopic dates that constrain the age of the oldest specimens to 555-542 Myr. X-ray microtomography reveals three-dimensionally preserved traces ranging from 50 to 600 μ m in diameter, indicative of small-bodied, meiofaunal tracemakers. Burrow morphologies suggest they were created by a nematoid-like organism that used undulating locomotion to move through the sediment. This assemblage demonstrates animal-sediment interactions in the latest Ediacaran period, and provides the oldest known fossil evidence for meiofaunal bilaterians. Our discovery highlights meiofaunal ichnofossils as a hitherto unexplored window for tracking animal evolution in deep time, and reveals that both meiofaunal and macrofaunal bilaterians began to explore infaunal niches during the late Ediacaran. NATuRE ECoLoGy & EvoLuTIoN Articles Nature ecology & evolutioNsupport for these suggestions is limited to purported body fossils of sponges 19 and demosponge biomarkers 20 . A considerable gap therefore remains between the fossil record of the late Ediacaran and molecular clock estimates for deep splits in the animal tree, for example the origin of Metazoa and Eumetazoa 3 . Assuming that contemporary molecular clock analyses yield accurate, if imprecise 18 , node ages for animal divergences, a small body size and concomitant limited fossilization potential 21 could reconcile these discordant records of animal evolution (but see ref. 22 ).The small body size of the ancestral bilaterian is supported by recent phylogenomic analyses of deep animal relationships, with acoel flatworms and xenoturbellids (Xenacoelomorpha) being a sister group to all remaining bilaterians (Nephrozoa) 23 , and smallbodied spiralian taxa (the 'Platyzoa') recognized as a paraphyletic grade with respect to macroscopic trochozoans 24 . This suggests that early bilaterians and spiralians were small bodied, possibly meiofaunal, and moved using ciliary gliding.Meiofauna comprises all organisms between 32 and 1,000 μ m in size that inhabit pore-water-rich sediments in freshwater to deepmarine environments 25 . Modern meiofaunal communities include animals, foraminifera and some ciliates, and contribute significantly to sediment bioturbation and bioirrigation 26,27 . The meiofauna can be divided into permanent members (that is, animals with organisms of a small size adapted and restricted to the meiofaunal, interstitial realm) and temporary meiofauna (for example, the ...

show abstract

“…Wood thinks that the skeletons provided protection against newly evolved predators. Some Cloudina fossils from that period even have holes in their sides, which scientists interpret as the marks of attackers that bored into the creatures' shells 6 .…”

Section: Modern Mirrorsmentioning

confidence: 99%