Materpiscis
Name:
Materpiscis
(Mother fish).
Phonetic: May-ter-pi-cis.
Named By: J. A. Long, K. Trinajstic, G.
C. Young & T. Senden - 2008.
Classification: Chordata, Gnathostomata,
Placodermi, Ptyctodontida, Ptyctodontidae.
Species: M. attenboroughi
(type).
Diet: Carnivore.
Size: About 28 centimetres long.
Known locations: Australia - Gogo Formation.
Time period: Late Devonian.
Fossil representation: Well preserved pregnant
individual with soft tissue impressions.
The
Gogo Formation of Australia is easily one of the most important areas
in the world concerning the study of Devonian era fish, and of these
the genus Materpiscis is one of the most
significant. The reason for
this is that the holotype specimen of Materpiscis
is a pregnant female
with a single embryo inside. This is conclusive proof that
Materpiscis did not lay eggs that were then
externally fertilised by
males, but instead hatched out and developed young inside of its
body. The holotype even preserves the umbilical cord which would have
allowed oxygenated blood and nutrients to flow into the body of the
developing embryo. The embryo was already a quarter of its expected
adult size, perhaps meaning that it was near to being born when the
mother fish died, but also that it would have been very well
developed, giving the young fish a much better chance of survival
against predators.
This
has confirmed a long standing theory that ptyctodontid placoderms
gave birth to live young given that genera that are known from male and
female specimens display claspers in the males and smooth pelvic fin
bases in females. These features allow the males to grip hold of the
females while they insert sperm inside the female’s body. Males of
fish species without claspers wait for females to lay eggs and then
swim over the top of them depositing sperm over the top. Although
fish are commonly perceived as egg layers, with 97% of known
species doing this, live birth in fish is still well documented even
in modern fish.
Materpiscis
seems to have been a fairly slow swimming fish that spent
much of its time near the bottom. The tail is elongated and developed
so that it did not brush against the bottom even when the
forequarters of the fish were close to touching it. The fore fins are
broad and well developed perhaps indicating that Materpiscis
was
adapted more for stability and manoeuvrability. The teeth of
Materpiscis were adapted into crushing plates,
strongly suggesting
that Materpiscis fed upon tougher shelled animals
that may have been
living on the bottom. Two small protrusions rose up from the tip of
the snout, but their purpose and possible function is still unknown.
Aside
from Materpiscis, a specimen of the genus Austroptyctodus
also
from the Gogo Formation has been found with three juvenile embryos
inside a pregnant female. This indicates that Materpiscis
was not the
only genus capable of bearing live young, and perhaps the practice
was relatively common in some type of placoderm fish.
Materpiscis
means ‘Mother fish’, and is of course a reference to
the live birth displayed in the holotype. The species name
attenboroughi is in honour of the naturalist David Attenborough best
known for presenting numerous productions about life and the planet,
including raising the profile of the Gogo Formation. David
Attenborough has had many animals and plants named in his honour, and
before the type species of Materpiscis was
established, a plesiosaur
genus Attenborosaurus
was named after him in 1993.
Further reading
- Live birth in the Devonian period. - Nature 453 (7195):
650–652. - J. A. Long, K. Trinajstic, G. C. Young
& T. Senden - 2008.
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