Xiphactinus audax, skull Ankylosaurus are ocean dwelling creatures that

are ocean dwelling creatures that live their lives attached to the sea floor

They are considered trace fossils because they contain no fossil material

and was inhabited by a rich fauna of marine life such as this crab

the calyx (or head) which contains the mouth parts and internal organs

Xiphactinus audax, skull Ankylosaurus are ocean dwelling creatures thatXiphactinus audax (from Latin and Greek for "audacious sword ray") was a large, 15 to 20 foot long predatory bony fish that lived in the Niobraran Sea, in what is now North America, during the Late Cretaceous. When alive, the beast would have resembled a gargantuan, fanged tarpon. Skeletal remains of Xiphactinus have come from Kansas, Alabama, and Georgia. Despite being preyed on by sharks and mosasaurs, X. audax was, nonetheless, a voracious predator