Old Earth Ministries Online Dinosaur Curriculum

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Lesson 50 - Nodosauridae

Nodosauridae is a family of ankylosaurian dinosaurs, from the Cretaceous Period of what are now North America, Asia, Australia, Antarctica and Europe.

Diagnostic characteristics for the Nodosauridae include the following: supraorbital boss rounded protuberance, occipital condyle derived from only the basioccipital and ornamentation present on the premaxilla. There is a fourth ambiguous character: the acromion is a knob-like process. All nodosaurids, like other ankylosaurs, may be described as medium-sized to large, heavily built quadrupedal herbivorous dinosaurs, possessing small denticulate teeth and parasagittal rows of osteoderms (a type of armour) on the dorsolateral surfaces of the body.

The clade Nodosauridae was first defined by Paul Sereno in 1998 as "all ankylosaurs closer to Panoplosaurus than to Ankylosaurus," a definition followed by Vickaryous, Maryanska, and Weishampel in 2004. Vickaryous et al. considered two genera of nodosaurids to be of uncertain placement (incertae sedis): Struthiosaurus and Animantarx, and considered the most primitive member of the Nodosauridae to be Cedarpelta.

This lesson will examine two genus of Nodosauridae, Edmontonia and Sauropelta.





Nodosauridae - Edmontonia

Edmontonia in Royal Tyrrell Museum of Palaeontology  (Picture Source)


Edmontonia was an armoured dinosaur, a part of the nodosaur family from the Late
Mounted skeleton of Edmontonia  (Picture Source
 Cretaceous Period (76.5 to 65.5 Ma). It is named after the Edmonton Formation (now the Horseshoe Canyon Formation), the unit of rock it was found in.  Edmontonia was bulky and tank-like at roughly 6.6 m (22 ft) long and 2 m (6 ft) high. It had small, ridged bony plates on its back and head and many sharp spikes along its back and tail. The four largest spikes jutted out from the shoulders on each side, two of which were split into subspines in some specimens. Its skull had a pear-like shape when viewed from above. (Compare 26 feet long and 8 feet high for the M1 Abrams army tank.)

The large spikes were probably used between males in contests of strength to defend territory or gain mates. The spikes would also have been useful for intimidating predators or rival males, protection, or for self-defense. To protect itself from predators, an Edmontonia might have crouched down on the ground to minimize the possibility of attack to its defenseless underbelly.

Rings in the petrified wood of trees contemporary with Edmontonia show evidence of strong seasonal changes in precipitation and temperature; this may hold an explanation for why so many specimens have been found with their armor plating and spikes in the same position they were in life. The Edmontonia could have died due to drought, dried up, and then rapidly became covered in sediment when the rainy season began.


Sauropelta (meaning 'lizard shield') is a genus of nodosaurid dinosaur that existed in the Early Cretaceous Period of North America. One species (S. edwardsorum) has been named although others may have existed. Anatomically, Sauropelta is one of the most well-understood nodosaurids, with fossilized remains recovered in the U.S. states of Wyoming, Montana, and possibly Utah. It is also the earliest known genus of nodosaurid; most of its remains are found in the Cloverly Formation, which dates to about 115 to 110 Ma (million years ago).

It was a medium-sized nodosaurid, measuring about 5 meters (16.5 ft) long. Sauropelta
Sauropelta scale
  (Picture Source
 had a distinctively long tail which made up about half of its body length. Although its body was smaller than a modern black rhinoceros, Sauropelta was about the same mass, weighing in at about 1,500 kilograms (3,300 lb). The extra weight was largely due to its extensive bony body armor, including the characteristically large spines projecting from its neck.

Sauropelta was a heavily-built quadrupedal herbivore with a body length of approximately
Artist impression of Sauropelta, by John Conway (Picture Source
 5 meters (16.5 ft). The skull was triangular when viewed from above, with the rear end wider than the tapering snout.  Unlike some other nodosaurids, the roof of the skull was characteristically flat, not domed. The tail of Sauropelta was characteristically long and made up nearly half of the body length. One skeleton preserved forty caudal (tail) vertebrae, although some were missing, suggesting that the true number of caudal vertebrae may have exceeded fifty. Ossified tendons stiffened the tail along its length. Like other ankylosaurs, Sauropelta had a wide body, with a very broad pelvis and ribcage. The forelimbs were shorter than the hindlimbs, which resulted in an arched back, with the highest point over the hips. Its feet, limbs, shoulders, and pelvis were all very stoutly constructed and reinforced to support a great deal of weight.

Discovery and naming

In the early 1930s, famed dinosaur hunter and paleontologist Barnum Brown collected the holotype specimen of Sauropelta (AMNH 3032, a partial skeleton) from the Cloverly Formation in Big Horn County, Montana. The locality is inside the Crow Indian Reservation. Brown also discovered two other specimens (AMNH 3035 and 3036). The latter is one of the best-preserved nodosaurid skeletons known to science, includes a large amount of in situ armor, and is on display in the American Museum of Natural History in New York City. Expeditions in the 1960s led by the equally renowned John Ostrom of Yale University's Peabody Museum of Natural History recovered additional incomplete specimens from the Cloverly. In 1970, Ostrom coined the genus Sauropelta to include remains discovered by both expeditions. Derived from the Greek σαυρος/sauros ('lizard') and πελτε/pelte ('shield'), this name is a reference to its bony armor. Although Ostrom originally named the species S. edwardsi, nomenclaturist George Olshevsky corrected the spelling to S. edwardsorum in 1991 to conform to Latin grammar rules.


Sauropelta is the earliest known nodosaurid genus. All specimens of S. edwardsorum were recovered from the middle section of the Cloverly Formation in Wyoming and Montana, which dates to the late Aptian through early Albian stages of the Early Cretaceous, or about 115 to 110 Ma (million years ago). Sauropelta lived in wide floodplains around rivers that drained into the shallow inland sea to the north and east, carrying sediment eroded from the low mountains to the west. Periodic flooding of these rivers covered the surrounding plains with new muddy sediments, creating the Cloverly Formation and burying the remains of many animals, some of which would be fossilized. At the end of Cloverly times, the shallow sea would expand to cover the entire region and would eventually split North America completely in half, forming the Western Interior Seaway. Abundant fossil remains of coniferous trees suggest that these plains were covered in forests. Grasses would not evolve until later in the Cretaceous, so Sauropelta and other Early Cretaceous dinosaurian herbivores browsed from a variety of conifers and cycads. Nodosaurids like Sauropelta had narrow snouts, an adaptation seen today in animals that are selective browsers as opposed to the wide muzzles of grazers.

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