Kentrosaurus (Spike lizard)
Kentrosaurus (Spike lizard)
Named By : Edwin Hennig – 1915
Diet : Herbivore
Size : Estimated 5 meters long
Type of Dinosaur : Armoured Dinosaur
Type Species : K. aethiopicus (type)
Found in : Africa, Tanzania, Tendaguru formation
When it Lived : Late Jurassic, 155-150 million years ago
Kentrosaurus is a genus stegosaurid dinosaur that was discovered in the Late Jurassic of Tanzania. K. aethiopicus is the type species, which was first described and named by Edwin Hennig, a German paleontologist. Although it is often considered a “primitive member” of the Stegosauria family, recent cladistic analyses have shown that it is more derived than other stegosaurs. It is also a close relative to Stegosaurus from North American Morrison Formation within Stegosauridae.
Only the Tendaguru Formation has been able to find fossils of K. Aethiopicus. It dates back to around 152 million years ago. German East Africa expeditions discovered hundreds of bones between 1909-1912. While no complete skeletons have been found, the remains provide a good idea of the animal’s build.
Kentrosaurus was approximately 4.5m (15 ft) long as an adult and weighed around one tonne (1.13 tons). It was able to walk on its hind legs and all fours. It had a small head and a long beak that it used to eat plant material. It had a row of small plates running down its neck, and back. These plates merged to form spikes at the hip and tail. The tail end of the spikes was the longest and was used to defend the animal. A long spike was also found on each shoulder. There are two types of thigh bones, which suggests that one sex is larger and more powerful than the other.
In 1909, the German Tendaguru expedition discovered Kentrosaurus’ first fossils. The expedition leader Werner Janensch recognized them as belonging to a stegosaur on July 24, 1910. Edwin Hennig, a German paleontologist, described them in 1915. Hennig coined the name Kentrosaurus. It is derived from the Greek kentron/kentron meaning “sharp point”/ “prickle”, and sauros/sauros mean “lizard”. Hennig also added the specific name “aethiopicus” to indicate the origin from Africa.
Sebastian Wallroth, Public domain, via Wikimedia Commons
From 1909, Kentrosaurus bones were discovered in four quarries of the Mittlere Saurierschichten. The German Expedition discovered over 1200 bones of Kentrosaurus in four field seasons. Many of these bones were destroyed during World War II. The Museum fur Naturkunde Berlin now houses almost all of the material (roughly 350 specimens) while the Museum of the Institute for Geosciences of the University of Tubingen has a composite mount with approximately 50% of the original bones.
Although there were no complete individuals found, some material, including a tail, hip and several dorsal vertebrae, was found in the association. These are the foundation of the Museum fur Naturkunde Janensch’s mount. Research Casting International remounted the mount in a more comfortable pose after it was taken down during museum renovations in 2006/2007. Other material, including a spine and braincase, were thought to have been lost or damaged during World War II. All the cranial material that was lost was found later in a basement drawer.
Kentrosaurus Aethiopicus is the type and only accepted species of Kentrosaurus. It was first named in 1915 by Hennig. In 1993, fragmentary fossil material from Wyoming was classified as a North American Kentrosaurus species, K. longispinus. It was named Stegosaurus aethiopicus by Charles Gilmore in 1914. This action was rejected by the paleontological communities and S. longispinus was assigned to Alcovasaurus. It differs from Kentrosaurus because of its longer tail spikes and more complex structure of the pelvis, vertebrae, and pelvis.
Hennig didn’t designate a Holotype specimen in the original description. Hennig, however, selected the most complete partial skeleton from Kentrosaurus’ osteology, systematic location and palaeobiology in 1925 in a detailed monograph (see syntype). The material includes a complete series of tail vertebrae, several back vertebrae, a sacrum, five sacral vertebrae, and both ilia. It is part of the Museum fur Naturkunde’s mounted skeleton in Berlin, Germany. Kindope, Tanzania is the type locale, located near Tendaguru hill.
Peter Galton, unaware that Hennig had already described a lectotype as a specimen, selected specimens MB.R.1930, and MB.R.1931 from Hennig’s 1915 descriptions to be ‘holotypes’. Because Hennig’s selection is priority, this definition of a “holotype” is invalid. Heinrich Mallison clarified in 2011 that Hennig had all of the material available to him in 1915. All bones found before 1912, when Hermann Heck completed the last German excavations in Germany, were paralectotypes. MB.R.4800, however, is the correct lectotype.
Kentrosaurus was small stegosaur. The typical dinosaurian body plan included a small head, long neck, long forelimbs, long hindlimbs, and a muscular, horizontal, and muscular tail. The stegosaurid characteristics that were most prominent included the elongation of the head and its flatness, powerful build, pillar-like hindlimbs, erect, pillar-like hindlimbs, and an array plates and spikes running along the animal’s top mid-line. Hennig’s 1925 monograph only revealed one complete tooth. A part of the dentary, the lower tooth-bearing bone in the front, was later discovered. It bears a newly emerging tooth. Some tooth fragments were also recovered from matrix that had stuck to other bones. Although it is smaller than the Stegosaurus deep dentary, it is nearly identical in form. The tooth is similar to a typical stegosaurian one, with a small base and vertical grooves that create five ridges.