Ghost lineage

Phylogeny of ichthyosaurs. While thick horizontal lines signify the existence of a fossil record for the respective time and taxa, thin lines represent ghost lineages.

A ghost lineage is a phylogenetic lineage that is inferred to exist but has no fossil record.[1]

Name

In 1992, an article stated: These additional entities are taxa [groups] that are predicted to occur by the internal branching structure of phylogenetic trees....I refer to these as ghost lineages because they are invisible to the fossil record.[1] The author elaborated on its meaning in further articles.[2][3]

Examples

A selection of gaps within the fossil record of animals having hard body parts. Other notable examples are Chronoperates and Protanguilla

When looking back at extinct organisms, there are some groups of organisms (or lineages) that have gaps in their fossil records. These organisms or species may be closely related to one another, but there are no traces in the fossil records or sediment beds that might shed some light on their origins. A classic example is the coelacanth, a type of fish related to the lungfishes and to primitive tetrapods. It seems that coelacanths have also been around for the past 80 million years, but have failed to leave us any fossils to look at. The reason for this is their environment, which is deep water near volcanic islands; therefore, these sediments are hard to get to, giving these coelacanths an 80 million year gap or ghost lineage.[4] Another ghost lineage was that of the averostran theropods, a ghost lineage now reduced considerably thanks to the discovery of Tachiraptor.[5]

Duration and diversification

It is possible that the gaps in one organism's evolution can help us identify events in the fossil record. This can be done by calculating an actual ghost lineage's duration through intervals of time. It shows how the ghost lineage duration will go down as diversity goes up, helping to better understand when and maybe why the gaps happened.[6]

See also

Refer also: Ghost population

References

  1. 1 2 Norell, Mark A (1992). Novacek, M.J. and Wheeler, Q.D., eds. Taxic Origin and Temporal Diversity: The Effect of Phylogeny, in Extinction and Phylogeny. Columbia University Press, New York. pp. 89–118.
  2. ↑ Norell, Mark A (1992). "The Fossil Record and Evolution: Comparing Cladistic and Paleontologic Evidence for Vertebrate History". 255. Science: 1690–1693. doi:10.1126/science.255.5052.1690.
  3. ↑ http://earth.geology.yale.edu/~ajs/1993/11.1993.15Norell.pdf
  4. ↑ http://www.ucmp.berkeley.edu/taxa/verts/archosaurs/ghost_lineages.php
  5. ↑ Langer, Max C.; Rincón, Ascanio D.; Ramezani, Jahandar; Solórzano, Andrés; Rauhut, Oliver W.M. (8 October 2014). "New dinosaur (Theropoda, stem-Averostra) from the earliest Jurassic of the La Quinta formation, Venezuelan Andes". Royal Society Open Science. Royal Society. doi:10.1098/rsos.140184. Retrieved 17 October 2014.
  6. ↑ http://rsbl.royalsocietypublishing.org/content/3/2/201.full


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