Xiphactinus

Name: Xiphactinus‭ (‬Sword Ray‭)‬.
Phonetic: Zif-ack-tih-nus.
Named By: Joseph Leidy‭ ‬-‭ ‬1870.
Classification: Chordata,‭ ‬Actinopterygii,‭ ‬Osteoglossomorpha,‭ ‬Ichthyodectiformes,‭ ‬Ichthyodectidae,‭ ‬Ichthyodectinae.
Species: X.‭ ‬audax,‭ ‬X.‭ ‬vetus.
Type: Carnivore.
Size: 4‭ ‬to‭ ‬6‭ ‬meters long.
Known locations: USA,‭ ‬Alabama,‭ ‬Georgia,‭ ‬Kansas.‭ ‬Europe.‭ ‬Australia.‭ ‬Canada.
Time period: Coniacian through to the Maastrichtian of the Cretaceous.
Fossil representation: Many specimens from across the globe.

       The broad range of fossils discovered around the world suggests that the bony fish Xiphactinus had a cosmopolitan distribution.‭ ‬A comparable similar fish with regards to appearance is the modern day Tarpon.‭ ‬Although Tarpon are not related to the ancient Xiphactinus,‭ ‬their streamlined bodies and strongly upturned mouths bear a striking resemblence.
       One important difference between the two fish are the enlarged teeth present in Xiphactinus fossils.‭ ‬If Xiphactinus failed to swallow its prey in one go,‭ ‬the teeth would have dug in preventing its prey from escaping,‭ ‬allowing Xiphactinus to steadily slide its prey into its mouth,‭ ‬one bite at a time.
       The discovery of a two meter Gillicus arcuatus inside the fossil of a Xiphactinus twice its size is proof that it was a formidable predator,‭ ‬although it is thought that the Xiphactinus may have died from internal injury due to the Gillicus struggling inside of it,‭ ‬explaining why the Gillicus was not digested.‭ ‬Xiphactinus was however also preyed upon by other larger predators as evidenced in a fossil of the shark Cretoxyrhina at least one specimen of which has been found with a large Xiphactinus inside of it.‭ ‬Another shark active in the Western Inland Seaway,‭ ‬‬Squalicorax,‭ ‬also exhibits Xiphactinus remains inside of its own.



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