Panoplosaurus (Completely armoured lizard)
Panoplosaurus (Completely armoured lizard)
Named By : Lawrence M. Lambe - 1919
Diet : Herbivore
Size : Estimated 7 meters long
Type of Dinosaur : Armoured Dinosaur
Type Species : P. mirus (type)
Found in : Canada, Alberta - Dinosaur Park Formation, Saskatchewan - Judith River Formation. USA, Montana - Bearpaw Shale Formation, New Mexico - Ojo Alamo Formation
When it Lived : Late Cretaceous, 79-75 million years ago
Panoplosaurus, a genus that includes armoured dinosaurs from the Late Cretaceous period of Alberta, Canada is known. Only a few specimens of this genus have been found. They are all from the Dinosaur Park Formation’s middle Campanian, which dates back to approximately 75 to 76 millions years ago. Lawrence Lambe named it after its extensive armour. This is the name of a “well-armoured Lizard”, which was first discovered in 1917. Panoplosaurus is sometimes used as a name for material that is not Edmontonia. This complicates its phylogenetic or ecological interpretations. At one time, it was thought to have been found in Alberta, New Mexico, and Texas with specimens from Canada and the United States. Panoplosaurus’ skull and skeleton are very similar to those of its relatives. However, there are some significant differences. For example, Panoplosaurus has a lumpy skull osteoderms and a fused shoulder blade. It also has regular-shaped plates on its neck, as well as a body without prominent spines. It was a quadrupedal creature, approximately 5 m (16 ft), and 1,600 kg (3.500 lb). The skull is short in stature, has a domed top and bony plates covering the cheeks. The top of the neck was covered with circular groups of plates. Both the forelimbs and hindlimbs were approximately the same length. It is possible that the hand only had three fingers. The entire body was covered with plates, osteoderms, and scutes. These included large elements at the skull and neck, small, round bones under the chin, and smaller ossicles to fill in the gaps between larger osteoderms.
Lawrence Lambe, Public domain, via Wikimedia Commons
Panoplosaurus was initially classified as a stegosaur that was related to Ankylosaurus (a similarly-armoured form). Later, the group was divided and ankylosaurs became their own group. It was initially considered to be close to Edmontonia within the Panoplosaurinae subfamily, but it was later moved into a general place in Nodosauridae. Edmontonia was once considered to be the same taxon of Panoplosaurus. This made it the only Campanian nodosaur. However, this was quickly disproved and they are now considered distinct. Panoplosaurus was named after its consistent placement in phylogenetic analyses near Edmontonia and the American taxon Animantarx. It was not related to Struthiosaurus or Nodosaurus but was close enough to them when it was. Panoplosaurus comes from deposits that are slightly older than Edmontonia rugosidens. It lived alongside hadrosaurids such as Lambeosaurus or Corythosaurus as well as ceratopsids such as Centrosaurus as well as small dinosaurs such as Ornithomimus and Dromaeosaurus.
Charles M. Sternberg, a Canadian paleontologist, discovered a complete skull, and a significant amount of the skeleton of an armored dinosaur in Quarry 69 of Canada’s Belly River Group. It was 64 m (210 ft above sea level). The Canadian Museum of Nature accession number CMN2759 identified the specimen as a complete skull. It was found 4.43 km (2.75 miles) south of Red Deer River, Alberta. The Canadian paleontologist Lawrence M. Lambe, of the Geological Society was describing the material. He completed the description of both the skull and the osteoderms before his death in March 1919. The Royal Society of Canada published Lambe’s posthumous work. Sternberg published a supplement description of the vertebrae, limb material and other details that Lambe hadn’t yet reached. Panoplosaurus is a Greek hoplon that means “well-armoured Lizard”.
Although the original name of the holotype discovery beds was Belly River, they now belong to the Dinosaur Park Formation’s upper level. They date back to the late Campanian period, 75-76 million years ago. A number of additional specimens have been referred to this genus since, including the Royal Ontario Museum (ROM 1215) and Royal Tyrrell Museum of Paleontology (83.25.2) from the Dinosaur Park Formation of Alberta and an unnumbered Oklahoma Museum of Natural History(OMNH) scapulocoracoid of the Aguja Formation of Texas. In 1981, a scapula taken from the Naashoibito member in the Kirtland Formation, New Mexico, was called Panoplosaurus. However, it’s not clear if this specimen is the ankylosaurid taxon Nodocephalosaurus. Walter P. Coombs referred 18 other specimens to the genus in 1978. These were based on the assumption Edmontonia was a synonym of Panoplosaurus. Kenneth Carpenter disagreed in a 1990 review of Late Cretaceous nodosaurids. Coombs questioned the 1990 referral of ROM1215 to Panoplosaurus. Roland A. Gangloff referred DPMWA 90-25 from Alaska to Edmontonia in 1995 based upon the anatomy of the absence of diagnostic traits. However, Victoria Arbour, colleagues and others retained ROM1215 in Panoplosaurus’ genus in 2009. This confined the genus to the holotype CMN2759 and specimen AMNH 3072 all of which are from the upper Dinosaur Park Formation. Arbour and Philip J. Currie also restricted Panoplosaurus’ 2016 range to the holotype due to uncertainties around the referrals of different specimens between it and Edmontonia rugosidens or Edmontonia longiceps. All of these specimens are from the Dinosaur Park Formation, and similar deposits.