Name: Climatius
Phonetic: Cli-mat-e-us.
Named By: Louis Agassiz‭ ‬-‭ ‬1845.
Synonyms: Ctenacanthus latispinosus, Euthacanthus gracilis, Euthacanthus grandis, Euthacanthus macnicoli, Euthacanthus macnicolli.
Classification: Chordata,‭ ‬Acanthodii,‭ ‬Climatiiformes,‭ ‬Climatiidae.
Species: C.‭ ‬reticulatus‭ (‬type), C. gracilis, C. grandis, C. latispinosus, C. macnicoli, C. scutiger, C. uncinatus.
Diet: Carnivore/Piscivore.
Size: 7.5‭ ‬centimetres long.
Known locations: Europe.‭ ‬North America.
Time period: Early Devonian.
Fossil representation: Many known specimens.

       As a‭ '‬spiny shark‭' ‬Climatius was not a true shark but was still related to them.‭ ‬Climatius was probably an open water hunter of smaller fish,‭ ‬and two clues to indicate this are both the strongly developed caudal fin and the large pectoral fins.‭ ‬As the caudal fin‭ (‬loosely dubbed the tail‭) ‬propelled Climatius forward it would also have the effect of putting the fish into a‭ '‬nosedive‭' ‬towards the bottom.‭ ‬To counter this effect the pectoral fins act like hydrofoils to keep Climatius in a straight line as it swims forward.‭ ‬This may sound like a lot to infer for a fish that is only known from fossils,‭ ‬but this principal actually applies to all fish.
       Climatius was probably a visually orientated predator as indicated by its large forward facing eyes.‭ ‬Once these located potential prey,‭ ‬the powerful tail would be employed to give chase and close the distance.‭ ‬Climatius would then use its small but sharp teeth to seize its prey,‭ ‬although rather surprisingly the teeth were only present in their lower jaw.‭ ‬This may have been so that it was easier to manipulate prey in the mouth so that it could be swallowed.‭ ‬Like in sharks,‭ ‬Climatius replaced its teeth as they became worn.
       Not only did Climatius have the standard complement of strong spines‭ ‬present in the major fins‭ (‬pectoral,‭ ‬pelvic,‭ ‬anal and both dorsal‭)‬,‭ ‬it also had an additional four pairs of spines that ran along the underside.‭ ‬With a combined total of fifteen hard spines Climatius was significantly more protected than the related Acanthodes,‭ ‬and would have been a difficult mouthful for predators.

Further reading
- Distribution of vertebrates in the Silurian of Estonia - E. Mark-Kurik - 1969.


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