 Occasionally
the term living fossil will be encountered, which is referring
to a living species (or clade) of organism that is the same or
descended from its counterpart in the fossil
record. While what is or is not a living fossil is rather
subjective, the attribute is most often (and perhaps more validly)
ascribed to an organism that has survived with apparent
little change over a long span of geological history.
Some so called “living fossils” are organisms that
were once only known from fossils before modern, extant living
counterparts were discovered. Notable examples of these are the
Coelacanth, a fish once thought to have gone extinct with the
dinosaurs at the end-Cretaceous extinction, and dawn redwood,
or Metasequoia, a conifer in the Pinophyta family Cupressaceae
that is today native to the Sichuan-Hubei region of China. Darwin
used the term living fossil when he stated: "And it is in
fresh water that we find seven genera of Ganoid fishes, remnants
of a once preponderant order: and in fresh water we find some
of the most anomalous forms now known in the world, as the Ornithorhynchus
and Lepidosiren, which, like fossils, connect to a certain extent
orders now widely separated in the natural scale. These anomalous
forms may almost be called living fossils; they have endured to
the present day, from having inhabited a confined area, and from
having thus been exposed to less severe competition." Some
fossils of what have sometimes been considered living fossils
are shown below.
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Metasequoia
Cone
(Dawn Redwood)
Eocene
Tranquille Shale, British Columbia, Canada |
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