Name: Gillicus
Phonetic: Gill-ee-cuss.
Named By: Edward Drinker Cope‭ ‬-‭ ‬1875.
Classification: Chordata,‭ ‬Actinopterygii,‭ ‬Osteoglossomorpha,‭ ‬Ichthyodectiformes,‭ ‬Ichthyodectidae,‭ ‬Ichthyodectinae.
Species: G.‭ ‬arcuatus.
Type: Carnivore.
Size: 2‭ ‬meters long.
Known locations: USA.
Time period: Coniacian through to the Maastrichtian of the Cretaceous.
Fossil representation: Numerous specimens.

       Gillicus was related to another Cretaceous bony fish, ‭‬Xiphactinus,‭ ‬and with it shared a streamlined body with a strongly upturned mouth.‭ ‬These characteristic features have led both fish to be compared to the modern day Tarpon,‭ ‬although neither of them are actually related to it.
       Gillicus had several small sharp teeth in its mouth and is thought to have used them filter zoo plankton.‭ ‬It is also thought by some to have eaten smaller fish by sucking them into its mouth with a vacuum when the jaws suddenly opened.‭ ‬Gillicus however was towards the bottom of the food chain,‭ ‬even being preyed upon by its larger relative Xiphactinus.‭ ‬A well-known specimen shows an entire Gillicus inside the belly of the Xiphactinus,‭ ‬although it may have ended up killing the larger predator though internal injury caused by its thrashing about inside.‭ ‬Gillicus would have also been prey to the sharks and mosasuars that were also active at the time and location.

Further reading
- On the occurrence of Gillicus arcuatus (Cope, 1875) (Pisces, Ichthyodectiformes) in Mexico. - Boletin de la Sociedad Geologica Mexicana vol 61, issue 2. - Jesús Alvarado-Ortega & Héctor Porras- Múzquiz - 2009.


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