Even though Ankylosaurus magniventris has been known for over 100 years, its iconic body shape isn’t what was first and subsequently depicted (because there is only one species of Ankylosaurus, I won’t be adding the species name for the rest of the article). There are no complete Ankylosaurus specimens; just bits and pieces of the body are known. So, this article I’ll be taking information from other genera to help explain what Ankylosaurus looked like. This is what paleontologists do until a more complete specimen is found. I’ll hold off on what the armor looked like for the last part of the article.
The body of Ankylosaurus is usually depicted as having a short neck, body, and tail. This is incorrect. For the most part, a complete ankylosaur vertebral column is either unknown or, more properly, not yet described, and so an accurate count of the entire vertebral column is difficult to determine. There are a few nearly complete specimens known from Asia and North America that still need to be described. For the most part they had a neck with 7 or 8 vertebrae (not including atlas/axis) about 9 to 13 “free” dorsal vertebrae, with the last 3 to 6 that form the presacral rod (the vertebrae that attach to the sacrum and forming the synsacrum), which has ribs “attaching” to the anteriorly long iliac blade. The pelvis had 3 to 6 fused sacral vertebrae and possibly up to 40 caudal vertebrae. The body was wide and barrel shaped in cross section (Figure 1). The front of the pelvis was wider than the back part. The first section of the tail had what is termed “free vertebrae,” with the last section having elongate prezygapophyses and postzygapophyses, which stiffened the tail, allowing for the very tip of the tail to have a tail club.
As per typical of dinosaurs and archosaurs in general, the manus, or hand, had five fingers, and only the first three fingers had claws, and the last two did not. The metatarsals were held vertically with a half-moon shape, similar to that seen in sauropods. The unguals, or claws, were wide and flat, which was good for digging (Figure 2). The pes, or foot, had three to four toes, depending on the genus.
And now, the armor: Without having a mummified specimen, the exact placement of ankylosaur armor is pure speculation. I’ve been studying ankylosaur armor for decades. In 2000, I had an article published where I put forth a list of names for different armored regions on the body of ankylosaurs (which I also published in an earlier PT article, no. 45, 2000-2001) (Figure 3). The regions are skull, cervical (neck), pectoral (shoulder region), thoracic (dorsal), pelvic (pelvis), and caudal (tail). I also suggested different rows of armor (which I alluded to in the last article), the majority of which are paired. The dorsalmost is the medial and then the primary, secondary, and finally the tertiary.
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