December 21st

Box #21 in our count down is Holophagus…

Days 1-5 of the count down.
Days 6-10 in the count down
Days 11-15 of the count down
Days 16-20 of the count down
Days 21-25 of the count down
Holophagus, a Jurassic coelocanth

Holophagus: the “Whole Eater”

Holophagus swam in the late Jurassic seas surrounding Europe. The fossils from the Lias clay and Solnhofen limestone both preserve beautiful specimens, but an excerpt from On Some New Fossil Fish From the Lias of Lyme Regis best describes the reasoning behind the unusual name.

“A coelocanth fish, remarkable in its resemblance, especially in the contour of the head, to the Cretaceous genus Macropoma, and for substantiating Prof. Huxley’s demonstration of the persistence of type presented by this family, which ranged from the Coal-measures to the Chalk.” Sir Philip de M. Grey Egerton Bart, 1868

Coelocanths are quite well known for their relatively recent reappearance, and are often considered “living fossils” for how similar they are to their extinct relatives. They are quite adaptable, and even Holophagus itself survived the Jurassic extinction events and thrived into the early Cretaceous Period. La Huerguina Formation in Spain preserves many beautiful fossils with fur and feathers, and fish like Holophagus complete with scales and delicate fins.

Coelocanths today are only known to live in deep, cold oceans, and prefer volcanic islands with networks of caves. They are slow swimmers, and prefer to simply drift on the current by the ocean floor until they come across something tasty, like a fish, squid, or crab. It’s difficult to say if Holocanthus used the same strategy, because some are found in areas ranging from shallow seas to deep lagoons, and the Cretaceous species lived in an area known for brackish water and freshwater swamps.

A slow, ambush feeding strategy works well for all these habitats. Many fish in lagoons and coral reefs hunt in the same way, and are often have the same bright colors and patterns as the rocks and coral they hide in. In the swap, snapping turtles and several fish also use cryptic coloring, lying in wait until unobservant prey swim just a little too close…then snap! The mouth opens wide and water flows into gaping jaws. The unwary victim gets sucked into the predator’s mouth in an instant.

2 thoughts on “December 21st

  1. Never knew this existed, I’m glad I learned about it. We should definitely specify prehistoric coelacanths more often, the only truly memorable ones to me are Mawsonia and Macropoma from the Cretaceous.
    Today, I will discuss Opisthotriton, a salamander from the late Cretaceous to the Paleocene of North America. It was part of a now extinct lineage of salamanders with long bodies that survive the K-Pg extinction event. The family itself is something that I’d like to refer to as “almost living fossils” because they survived the aforementioned extinction event but became extinct nonetheless. Aside from that there isn’t much else in regards to information on Ophistotriton.

    Like

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