Ankylosauridae

Ankylosauridae is a family of armored dinosaurs that lived long ago. These dinosaurs were part of a larger group called Ankylosauria and were closely related to another group known as Nodosauridae. The oldest members of this family appeared about 122 million years ago, and they disappeared around 66 million years ago during a big event that changed Earth a long time ago.

These dinosaurs mainly ate plants and always walked on all four legs. They had special teeth shaped like leaves and their bodies were covered with tough, bony plates called scutes. What made them really special were their strong defenses, like a rounded head, bony pieces on their skull, armored plates along their bodies, and a big, bony club at the end of their tail they could use to protect themselves.

Ankylosaurids have only been found in the northern part of the world, in places like North America, Europe, and Asia. The very first of these dinosaurs to be discovered was named Ankylosaurus by Peter Kaiser and Barnum Brown in Montana back in 1906. Barnum Brown later gave this group its name, Ankylosauridae, and also named a smaller group within it called Ankylosaurinae in 1908.

Anatomy

Ankylosaurids were strong, heavily armored dinosaurs. They had special bony pieces on their skulls that formed horn-like shapes and rows of thick plates along their bodies that acted like a shield. Unlike their close relatives, they had only two layers of armor around their necks.

The most famous feature of these dinosaurs was their tail club—a large, bony ball at the end of their tails made from special vertebrae and enlarged bone plates. This helped protect them from predators. Scientists discovered a well-preserved ankylosaur named Zuul, named after a monster from Ghostbusters, which showed more details about their body structure.

History of study

In 1906, Barnum Brown and Peter Kaisen found the first ankylosaurid dinosaur, called Ankylosaurus, in Montana. They discovered parts of its skull, teeth, vertebrae, and ribs, along with many bony plates covering its body. At first, some scientists were unsure about this discovery and thought it might belong to another dinosaur group called Stegopelta.

Scientists have wondered if differences in the shape of ankylosaurid tail clubs might be related to the genders of these dinosaurs. This idea suggests that the tail clubs could have been used in behaviors between members of the same species. However, clear evidence showing this has not been found. If one gender had much larger tail clubs, we might find more of those in fossils today.

Phylogeny

In 1978, a scientist named W.P. Coombs, Jr. grouped almost all known armored dinosaurs into two families: Nodosauridae and Ankylosauridae. This was an important study that helped scientists understand these dinosaurs better.

Later, in 1998, another scientist named Paul Sereno defined Ankylosauridae as all ankylosaurs more closely related to Ankylosaurus than to Panoplosaurus. More details were added in 2001 and 2021 to better describe this group of dinosaurs. The basal subfamily Shamosaurinae was defined to include certain ankylosaurs like Gobisaurus and Shamosaurus.

In 2004, a study found that some early ankylosaurids included Gargoyleosaurus, Gastonia, and Minmi, along with others from China, Mongolia, and North America.

In 2012, scientists analyzed many known ankylosaurs and found that Gargoyleosaurus and Gastonia belonged to a different group, while Cedarpelta and Liaoningosaurus were early ankylosaurids.

In 2016, a new study by Arbour and Currie looked at many ankylosaurids, including Gastonia, Cedarpelta, Chuanqilong, and others, but some relationships between certain ankylosaurids were still unclear.

Paleobiology

Ankylosaurids were likely slow-moving animals. Their legs show that they carried their weight mostly on one bone, with the other helping muscles attach. This suggests they moved in a steady, elephant-like way.

They had strong muscles in their back legs and tail. Their tail could swing side to side but not up and down easily, which helped them use their tail club for defense. Their teeth were shaped like leaves, showing they mostly ate plants. Some scientists think a few types might have eaten insects or fish, but this is not certain. There are different ideas about why they had tail clubs, such as for fighting or defending against attackers.

Timeline of genera

The image shows the timeline of different groups within the Ankylosauridae family. It helps us see when these armored dinosaurs lived and how they changed over millions of years. The timeline starts around 122 million years ago and ends with their extinction 66 million years ago.