Palaeospondylus gunni
Chondrichthyes, Palaeosponyliformes, Palaeospondylidae
Geological
Time: Middle Devonian (385 Million Years Old)
Size (25.4
mm = 1 inch): Fish fossil is 30 mm in length on a 44 mm by 33 mm matrix
Fossil Site:
Achanarras Slate Quarry, Caithness, Scotland
Fossil Code:
AW44
Price: $135.00
The
small fossil fish here has been the cause of controversy
since it was first discovered in 1890 by two cousins named
Gunn. It comes primarily from this single location, with
a few found at two nearby locations as well. Not only is
it minute in size, but it has structures unlike that found
on most other fish. It possesses a strange basket-like apparatus
on its snout, a well-developed cartilaginous vertebral column
(hence the generic name), but no apparent fins. A prominent
feature of the head of every specimen is a pair of unusual
rods termed the occipital lamellae. These are identical with
the cranial ribs found on lungfish. The only lungfish so
far known from these deposits is the 30 centimeter long Dipterus
valenciennsi, for which the smallest examples are about 60
millimeters in length. If the rostral apparatus of Palaeospondylus
is interpreted as a larval attachment organ, then it may
well be the larva of Dipterus. Recent studies seem to confirm
Palaeospondylus to be a lungfish, but why is it so different
in appearance from Dipterus? The current thinking is that
it underwent a sharp metamorphosis, rather than a gradual
transition from juvenile to adult. Some researchers prefer
to attribute the anterior attachment organ with those of
lampreys, arguing for Palaeospondylus as a parasite. Whichever
the case: oldest known fossil vertebrate larva or oldest
known vertebrate parasite, Palaespondylus gunni is a unique
example of the early lives of fish on this planet.
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