Eastmanosteus
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Name:
Eastmanosteus
(Eastman's bone).
Phonetic: East-man-oh-stee-us.
Named By: Obruchev - 1964.
Synonyms: Dinichthys pustulosus
Classification: Chordata, Palcodermi,
Arthrodira, Dinichthyoidea, Dinichthyidae.
Species: E. pustulosus
(type), E.
calliapsis, E. licharevi, E. lundarensis, E. magnificus,
E. pustulosus, E. yunnanensis.
Diet: Carnivore/Piscivore.
Size: Up to 3 meters long.
Known locations: Worldwide, including Australia
- Gogo Formation, Canada, China, Iran, Poland, Russia,
USA.
Time period: Eifelian through to the Famennian of
the Devonian.
Fossil representation: Many known specimens of the
bony exoskeleton, some traces of soft tissue including circulatory
structures (blood vessels), muscle fibres, and nerve tissue.
Eastmanosteus
was originally known as Dinichthys
pustulosus until it was realised to
be a separate genus in its own right. In these circumstances the
species name is retained and added to the new genus to become the type
species for the new genus. Hence Dinichthys pustulosus
became
Eastmanosteus pustulosus, the genus name being
derived from the man
who named the earlier Dinichthys species.
Eastmanosteus
was morphologically similar to its larger cousin Dunkleosteus,
although because Eastmanosteus was much smaller,
it probably had a
different ecological niche. Also the smaller size of Eastmanosteus
meant that it could operate in environments where the large bulk of
giants like Dunkleosteus would have been
problematic.
Fossils
of Eastmanosteus calliapsis from the Australian
Gogo Formation have
been very interesting in that they reveal the presence of soft tissues
such as muscles and blood vessels. This is an important discovery as
usually only the bony plates are preserved. Although reconstructing
the entire inner workings of Eastmanosteus and by
extension placoderms
is still difficult from these remains, they do offer an intriguing
glimpse at the living animal. This preservation may in part be due to
the fact that E. calliapsis is estimated to be
about half the upper
size estimate of the genus (1.5 meters long for the species as
opposed to three meters long for the maximum genus size). It also
represents some of the earliest preserved soft tissue known, since
the Devonian period stretches back over three-hundred and sixty million
years ago. The Australian Gogo Formation itself is estimated to be
from the Frasnian stage of the Devonian, making the soft tissue
remains of Eastmanosteus over three-hundred and
seventy-five million
years old.
Further reading
- Branch Agnatha. In D. V. Obruchev (ed.) - Fundamentals of
Paleontology. Vol. XI. Agnatha, Pisces. Izdatel'stvo "Nauka” Moscow
36-167 - D. V. Obruchev - 1964.
- A new species of eastmanosteid arthrodire (Pisces: Placodermi) from
Gogo, Western Australia. - Zoological Journal of the Linnean Society
Volume 90 Issue 1, Pages 1 – 64. - K. Dennis-Bryan - 1986.
- Eastmanosteus lundarensis sp. nov. from the
Middle Devonian Elm Point
and Winnipegosis Formations of Manitoba - Journal of Vertebrate
Paleontology - vol 16 issue 4 - Gavin F. Hankea, Kenneth W. Stewarta
& George E. Lammers - 1996.
- Exceptional preservation of nerve and muscle tissues in Late Devonian
placoderm fish and their evolutionary implications. - Biology Letters 3
(2): 197–200 - Kate Trinajstic, Carina Marshall, John Long &
Kat Bifield - 2007.
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