Palaeospondylus gunni
Chondrichthyes, Palaeosponyliformes, Palaeospondylidae
Geological
Time: Middle Devonian (385 Million Years Old)
Size (25.4
mm = 1 inch): 16 mm in length on a 25 mm by 24 mm matrix
Fossil Site:
Achanarras Slate Quarry, Caithness, Scotland
Fossil Code:
AW08
Price: $150.00
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. This is a detailed example from material
collected in the 1970s.
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