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 The Chondrichthyes first appear in the fossil record about 400 myn years ago and saw a great radiation in the Late Devonian around the time of the Placoderm extinction. The early fossils indicate their structure has changed little through to the extant forms. The Carboniferous saw the first holocephalans (Chimeras and Rabbit fish) and the rays appear in the fossil record during the Jurassic.

 This class is best characterised by their prismatic, calcified cartilage lining the endoskeleton. Recent chondrichthyans show sexual dimorphism of their pelvic metapterygium (into mating organs) although this seems not to be present in some of the earlier forms such as cladoselache (which may now be considered to be in a sister group to the Chondrichthyes)

 What are considered to be the first shark scales appear in the early Silurian but are not associated with teeth or jaws. This has lead to the theory that they evolved from Thelodonts, whose scales are very similar. The phylogeny of chondrichthyes seems complex and is still actively debated. There are 2 subclasses; Elasmobranchii and Holocephali and it is in the former (superorder Cladoselachemorpha, order; Symmoriida) that the bizarre stethacanthid sharks are placed. Living from the Late Devonian through to the Permian, they carried a bony brush like structure adorning the main dorsal fin of the males. The recently renamed Stethacanthus (Akmonistion zangerli) became celebrated as one of the best ever Palaeozoic sharks found, following its discovery by Stan Woods in the Carboniferous, Bearsden site of Scotland .


Stethacanthus now renamed Akmonistion zangerli by Coates & Sequeira


Stethacanthus in my collection

Example 1 (Head, anvil and brush)

sharkfinished.jpg (35733 bytes)        Head and Anvil                            tt-anvil.jpg (68153 bytes)      Detail of anvil (inverted)

Example 2 (Slightly disarticulated head, anvil and brush)

shark1.jpg (60140 bytes)   sharkhead.jpg (115881 bytes)   sharkhead2.jpg (126413 bytes)

Example 3 (Disarticulated jaw elements plus anvil and brush)



Other Carboniferous Bearsden material in my collection



    hh-stethspine.jpg (104056 bytes)   p-babysteth.jpg (86741 bytes)

    p-shsp2.jpg (64461 bytes)  hh-falc.jpg (85762 bytes)

   p-shsp1.jpg (89794 bytes)  

   p-sharkspine.jpg (60104 bytes)   Other spines


Bear Gulch sharks

  BGF571A8.jpg (192471 bytes)   BGF571A2.jpg (235994 bytes)


gg-habshark.jpg (47128 bytes)   Heteropetalus elongatulus, L.Carboniferous, Bear Gulch, US

gg-heteropet.jpg (52864 bytes)   Harpagofututor volsellorhinus L.Carboniferous, Bear Gulch, US

008.jpg (219918 bytes)