Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
6148
pubmed:dateCreated
1988-1-12
pubmed:abstractText
There are very few high-resolution studies of the fossil record from which to assess the relative frequency of gradualistic and punctuated evolution. Here I report some of the first detailed evidence of phyletic gradualism in benthic macroinvertebrates, based on a study of approximately 15,000 trilobites from central Wales. Over a period of about three million years, as many as eight lineages underwent a net increase in the number of pygidial ribs, a species-diagnostic character. The end members of most lineages have previously been assigned to different species and, in one case, to different genera. In view of intermediate morphologies and temporary trend reversals, however, practical taxonomic subdivision of each lineage proved impossible. The apparent success of earlier Linnean nomenclature (with its implications of discrete species) could easily have been misinterpreted as evidence of punctuation and stasis, and it is probable that detection of many other gradualistic patterns has been hindered by ready application of binominal taxonomy to fossils.
pubmed:commentsCorrections
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:status
MEDLINE
pubmed:issn
0028-0836
pubmed:author
pubmed:issnType
Print
pubmed:volume
330
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
561-3
pubmed:dateRevised
2010-11-18
pubmed:meshHeading
pubmed:articleTitle
Parallel gradualistic evolution of Ordovician trilobites.
pubmed:affiliation
Department of Geology, Trinity College, Dublin, Ireland.
pubmed:publicationType
Journal Article