A study conducted in 1998 showed that a correlation exists between the diversification of a species and the duration of its ghost lineage namely that a shorter ghost lineage implies that there will be greater species diversification. The duration between distinct fossils can be measured and used to derive information about the evolutionary history of a species. Another ghost lineage was that of the averostran theropods, a ghost lineage now reduced considerably due to the discovery of Tachiraptor. 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. It seems that coelacanths have also been around for the past 80 million years but have failed to leave any fossils. A classic example is the coelacanth, a type of fish related to the lungfishes and to primitive tetrapods. Fossils can then be mapped onto cladograms and range charts to assess which lineages are missing in the fossil record. Biologists may infer the existence of ghost lineages by examining sequential stratigraphic units in the fossil record. 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. When looking back at extinct organisms, there are some groups of organisms (or lineages) that have gaps in their fossil records. Other notable examples are Chronoperates and Protanguilla. Examples A selection of gaps within the fossil record of animals having hard body parts. A ghost lineage is a one direct connection between the descendant and the ancestor, whereas a ghost taxon has many split descendants. It is important to note that ghost lineages and ghost taxa are not the same. In 1992, an article stated: "These additional entities are taxa 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." Phylogenetic trees constructed based on fossil records and Darwin's Theory of Evolution often give an indication that species with similar phenotypes existed, although its fossil has not been discovered. Examples of Lazarus taxa include the famous coelacanths, as well as the Philippine naked-backed fruit bat. A ghost lineage is any gap in a taxon's fossil record, with or without reappearance, while a Lazarus taxon is a type of ghost lineage wherein a species is believed to have gone extinct due to an absence of it in the fossil record, but then reappears after a period of time. Ghost lineages and Lazarus taxa are related concepts, as both stem from gaps in the fossil record. Ghost lineages assume unseen diversity in the fossil record and serve as predictions for what the fossil record could eventually yield these hypotheses can be tested by unearthing new fossils or running phylogenetic analyses. The process of determining a ghost lineage relies on fossilized evidence before and after the hypothetical existence of the lineage and extrapolating relationships between organisms based on phylogenetic analysis. Thin lines represent ghost lineages.Ī ghost lineage is a hypothesized ancestor in a species lineage that has left no fossil evidence, but can still be inferred to exist or have existed because of gaps in the fossil record or genomic evidence. Thick horizontal lines signify the existence of a fossil record for the respective time and taxa. Phylogenetic lineage that is inferred to exist but has no fossil record Phylogeny of ichthyosaurs.
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