Xiphactinus

A long time ago, a huge fish lived in the sea.

It had sharp teeth. This fish liked to eat other fish.

One fish was found with another fish inside its belly. The smaller fish was still whole. This happened because the big fish died right after eating. We find these fish bones in many lands. They are in places like America and Australia. Scientists study these old bones to learn about the past.

Xiphactinus was a large fish that lived in the sea.

Its name means "sword-ray." This fish belonged to a group called Ichthyodectiformes.

It looked like a giant fish with many sharp fangs.

These fish were hunters. They ate other fish to survive. Scientists found many fossils that prove this. One famous fossil shows a "fish-within-a-fish."

A large Xiphactinus had a smaller fish called Gillicus inside its belly. The smaller fish was still whole. The big fish likely died right after swallowing its prey. This may have happened because the prey struggled too much.

We find Xiphactinus bones in many parts of the world. They are in the United States, Canada, and Europe. Fossils also appear in Australia, Venezuela, and Argentina. Young Xiphactinus may have lived in shallow waters. This helped them stay safe and find food. Even as babies, they likely ate other fish. Sharks may have eaten Xiphactinus if they were dead or hurt.

Xiphactinus was a huge predatory fish that lived in the ocean.

Its name comes from Greek and Latin words meaning "sword-ray." This fish belonged to a group called Ichthyodectiformes.

It looked like a very large fish with many sharp fangs. Scientists say it looked a bit like a giant tarpon. These fish lived a long time ago during the Late Cretaceous period. They were important hunters in the ancient seas.

These fish were very hungry hunters.

Scientists have found at least twelve specimens of Xiphactinus audax with food in their stomachs. One famous fossil is called the "Fish-Within-A-Fish." This fossil shows a Xiphactinus that had swallowed a fish called Gillicus arcuatus. The smaller fish was nearly perfectly preserved inside the larger one. The big fish likely died right after eating. This may have happened because the struggling prey ruptured an organ.

People have found Xiphactinus fossils in many different places.

In the 1850s, the first fossil was found in the Niobrara Chalk. Other bones come from the Carlile Shale and Greenhorn Limestone in Kansas. You can find them in many U.S. states like Georgia and New Jersey. Fossils also appear in Canada, Europe, and Australia. They have even been found in Venezuela and Argentina. This shows they lived in many parts of the world.

Young Xiphactinus may have lived in shallow waters near the sea. This might have helped them stay safe from bigger animals. It also gave them plenty of food to eat. Even when they were small, their teeth show they ate fish. As they grew, their diet likely stayed the same. Large sharks like Cretoxyrhina may have eaten Xiphactinus if they were hurt. One fossil even shows a Xiphactinus inside a large shark.

Some people have even tried to name these fossils in strange ways. In 1982, a man named Carl Baugh found a Y-shaped bone in Texas. He called it "Unicerosaurus" and thought it was a horn. He even claimed it belonged to a unicorn. Most scientists did not agree with him. They believed the bone was just a spine from a large fish. In 2010, some leaders in Kansas tried to make the fish a state fossil. They called it the "X-fish," but a different animal was chosen instead.

Xiphactinus was a genus of large predatory marine fish.

Its name comes from Latin and Greek words meaning "sword-ray." These fish were ray-finned fish that lived during the Late Cretaceous period. They existed from the late Albian stage to the late Maastrichtian stage. This was a time when many famous prehistoric animals lived in the oceans. Xiphactinus belonged to an extinct order called Ichthyodectiformes. This group is considered a close relative of modern teleosts, which are the most common type of bony fish today.

Physically, Xiphactinus was a massive and intimidating hunter. It superficially resembled a gargantuan, fanged tarpon. Tarpons are modern fish known for their large size and scales. The skull of Xiphactinus was built for predation.

Its teeth were sharp and designed to catch other marine life. Scientists believe these fish were voracious predators. This means they had a very strong appetite and hunted constantly. Their body structure allowed them to move effectively through the ancient seaways.

Evidence of their hunting habits is preserved in the fossil record. Researchers have collected at least a dozen specimens of the species Xiphactinus audax that still contained undigested or partially digested prey in their stomachs.

One of the most famous discoveries is known as the "Fish-Within-A-Fish" specimen. This fossil was collected by George F. Sternberg. It contains a nearly perfectly preserved long ichthyodectid fish called Gillicus arcuatus inside the larger Xiphactinus. The larger fish likely died shortly after consuming its meal. Scientists suggest the struggling prey may have ruptured an internal organ during the swallowing process.

We can learn about the life cycle of Xiphactinus by looking at different ages. Like many modern tarpons, juvenile Xiphactinus likely spent time in shallow seaway margins. These shallow areas provided protection from larger predators. They also offered rich food resources that might have been harder to find in open marine waters. However, scientists note that a lack of shallow, nearshore deposits in the Western Interior Seaway makes this difficult to confirm. Even as juveniles, these fish were hunters. The teeth of young specimens indicate their diet did not change much as they grew. They were fish-eating predators from a very young age.

Fossils of Xiphactinus have been discovered across many different parts of the world. The first fossil was found in the Niobrara Chalk during the 1850s. Other remains come from the Carlile Shale and Greenhorn Limestone in Kansas. In the United States, fossils appear in Cretaceous formations in Georgia, Alabama, North Carolina, and New Jersey. The genus is also found in Canada, specifically in the Kanguk and Ashville Formations. Beyond North America, specimens have been located in Europe, Australia, Venezuela, and Argentina. This wide distribution shows that Xiphactinus was a successful inhabitant of global oceans.

In the ancient ocean food web, Xiphactinus was both a hunter and potential prey. While they were large predators, they were not at the very top of the chain. Dead or injured Xiphactinus individuals were likely scavenged by large sharks. Two notable genera of sharks from that time were Cretoxyrhina and Squalicorax. There is direct evidence of this relationship in the fossil record. Charles H. Sternberg collected a specimen of a large Cretoxyrhina that contained the remains of a Xiphactinus inside it. This demonstrates how energy moved through the Cretaceous marine ecosystem.

Sometimes, fossils of Xiphactinus have led to scientific misunderstandings or unusual claims. In 1982, Carl Baugh found a Y-shaped fossil in the limestone beds of the Paluxy River in Texas. He informally named it "Unicerosaurus." Baugh claimed the bone was a forehead horn from a new genus of dinosaur. He even suggested it belonged to the unicorn mentioned in religious texts. However, John Armstrong described the fossil in 1987 as a Y-shaped petrified bone. It was likely just a neural spine from a large fish like the Portheus. Most scientists did not take these claims seriously. Later, in 2010, there was an effort in Kansas to make Xiphactinus audax the state fossil. They referred to it as the "X-fish," but the state chose Tylosaurus instead.