name: Sauropelta time: Early Cretaceous locality: North America (Montana) size: 25 ft/7.6 m long
Sauropelta, from the western USA, is the largest known member of the nodosaur family of ankylosaurs, the armored dinosaurs of Cretaceous times. It is estimated to have weighed over 3 US tons/3 tonnes.
Its massive body was encased in a bony armor. This consisted of bands of horn-covered plates with raised keels, which ran transversely over the body from the neck to the end of the long, tapering tail. The plates were embedded in the skin to form a strong, but flexible, covering all over the animal's back. Attacks from the side were deterred by a row of sharp spikes that stuck out sideways from each flank.
This slow-moving herbivore would have needed such protection against the attacks of the carnivorous dinosaurs of the day.
name: Silvisaurus time: Early Cretaceous locality: North America (Kansas) size: 11 ft/3.4 m long
Silvisaurus was covered in the heavy bony armor characteristic of the nodosaurs. Thick plates encased the neck, a more open arrangement of plates lay across the back and tail, and heavy spikes flanked the body.
Silvisaurus is, however, considered to be a primitive member of the family. Most nodosaurs had toothless beaks at the front of their jaws, but Silvisaurus retained teeth in its upper jaw. For this reason, some paleontologists believe that Silvisaurus may be ancestral to some of the later members of its family.
As in most of the nodosaurs and later ankylosaurs, the amount of bone in the skull of Silvisaurus was much reduced, so that it was lightweight and full of cavities and air passages. These could have been used to produce sounds for communicating with other members of the species. Such vocalization was not unknown among dinosaurs; for example, the gregarious duckbills had inflatable nasal sacs or hollow crests on their heads, through which the animals probably produced sounds for social communications among the herd (see pp. 146-153).
name: Nodosaurus time: Late Cretaceous locality: North America (Kansas and Wyoming) size: 18 ft/5.5 m long Nodosaurus is the typical nodosaur, and has given its name to the whole family (see also p. 157). Its body armor was arranged from neck to tail in transverse bands. These consisted of narrow, rectangular plates that covered the ribs, alternating with broad plates that occupied the spaces in between. Hundreds of bony bosses or nodes studded the broad plates, hence the animal's name — Nodosaurus, meaning "node lizard."
The skull of Nodosaurus was small, long and narrow, with weak teeth — typical features of the family. The shoulders and hips were powerfully developed to carry the great weight of the body armor, as were the strong, stout legs with their broad, hoofed feet. The bones of the hips were so modified as weight-bearing structures that they no longer resembled the typical ornithis-chian, or "bird-hipped," pattern (see pp. 92-93).
An unusual find in Kansas consisted of the skeletons of several nodosaurs, all lying on their backs. They were found in marine sediments of Late Cretaceous age. This could represent a small herd of animals that were overcome at the same time, and were washed down to the sea; alternatively, these individuals could have come together after death by chance.
In either case, as they were swept along in the river, the decaying organs would have generated gases that bloated the body. This, combined with the weight of the armor on the back, would have made them top-heavy, and so they would have flipped over, and floated downstream on their backs. Eventually, they would have sunk into the mud of the seabed, belly-side up, in which position they were preserved.
name: Struthiosaurus time: Late Cretaceous locality: Europe (Austria, France,
Hungary and Romania) size: 6 ft 6 in/2 m long Struthiosaurus is remarkable since it is the smallest-known member of the nodosaur family — in fact, the smallest of the whole ankylosaur group. This has led paleontologists to speculate that it may have lived and evolved on islands. Many large types of animal tend to develop dwarf species when confined to such isolated habitats — an adaptation to the limited food resources found there. In Tertiary times, for example, species of dwarf elephant and hippopotamus evolved on the islands of the Mediterranean. A modern example is provided by the ponies of the Shetland Islands off northern Scotland.
In Late Cretaceous times, some 80 million years ago, most of modern Europe was covered by shallow seas. Dry land was only present in the form of name: Panoplosaurus time: Late Cretaceous locality: North America (Alberta,
Montana, South Dakota and
Texas) size: 15 ft/4.4 m long The latest of the nodosaurs, and the last known, Panoplosaurus was a medium-sized animal in comparison to some of its relatives. But it was massively built, and encased in a heavy body armor. It could have weighed as much as 4 US tons/3.6 tonnes.
The armor consisted of broad, square plates with keels, arranged in wide bands across the neck and shoulders. The rest of the back was covered in smaller, bony studs. Massive spikes, angled to the side and front, guarded each flank, especially on the shoulders.
Even Panoplosaurus' head was protected with thick, bony plates, so solidly fused to the underlying skull bones that their boundaries cannot be seen. But inside, this solid, bony box was full of cavities and air passages, with a bony palate separating the nasal system from the mouth. This would have enabled the animal to eat and breathe at the same time. The snout was narrow, which could suggest that Panoplosaurus rooted about among the ground vegetation to find the plants that it preferred.
sauropelta euoplocephalus silvisaurus talarurus
islands. Perhaps groups of Struthiosaurus got marooned on various of these islands, and gradually evolved a smaller species, maybe several species on different islands, in the same way as the fauna of today's Galapagos Islands is thought to have developed.
Despite this theory of isolated development, Struthiosaurus retained its protective body armor. A variety of armor covered its back. There were plates around the neck; small bony studs covered the back and tail; and a fringe of spikes guarded each flank.
sauropelta euoplocephalus silvisaurus talarurus
panoplosaurus ankylosaurüs saichania panoplosaurus ankylosaurüs
It is likely that Panoplosaitrus actively defended itself against attack, unlike many of its relatives that would probably have squatted down on the ground and relied on their armor plating to protect them. Panoplosaurus could have charged, directing one of its spiked shoulders toward the attacker. Its forelegs were strongly built, and especially well endowed with muscles in the elbow area. This suggests that the animal was quite maneuverable, and could move its forequarters nimbly in reaction to its enemy's tactics. A charging rhinoceros is the most apt, modern equivalent.
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