Hylaeosaurus ‭(‬forest lizard‭)

Short Info

Hylaeosaurus ‭(‬forest lizard‭)

Phonetic : Hy-lay-e-o-sore-us.

Named By : Gideon Mantell‭ ‬-‭ ‬1833

Diet : Herbivore

Size : Estimated 3 – 7 meters long

Type of Dinosaur : Armoured Dinosaur

Type Species : H.‭ ‬armatus‭ (‬type‭)‬

Found in : England.‭ ‬Furhter remains from Europe have been attributed to the genus,‭ ‬but many of these are now considered to be from other genera.

When it Lived : Early Cretaceous, 150-135 million years ago

Hylaeosaurus (/haI.li:oU?s/ hyy-LEE/o-SOR@s; Greek pronunciation: hylaios/ulaios ‘belonging to forest’ and sauros/sauros ‘lizard”) was a herbivorous ankylosaurian dinosaur. It lived around 136 million years ago in the late Valanginian phase of the early Cretaceous Period of England.


Hylaeosaurus armatusSven Sachs, Jahn J. Hornung, CC BY 2.5, via Wikimedia Commons


Gideon Mantell discovered Hylaeosaurus in 1832. It was one of three dinosaurs Richard Owen used to base the Dinosauria in 1842. Although four species were included in the genus of Hylaeosaurus, only Hylaeosaurus Armatus is currently considered valid. Hylaeosaurus’ anatomy and only a few remains have been discovered. Although it was thought to have been a basal Nodosaurid according to a recent Cladistic Analysis, it was actually a basal Ankylosaurid.

Hylaeosaurus measured approximately five metres in length. It was an armoured dinosaur with at least three long spines along its shoulder.

West Sussex was the first place where Hylaeosaurus fossils have been found. Gideon Mantell, a fossil collector, wrote to Benjamin Silliman on 20 July 1832 that several boulders that had been blown up in Tilgate Forest were containing the bones of a saurian. The fifty pieces were assembled by a local fossil dealer. He described them as “great consarns of bites, boanes” Mantell, despite doubts regarding the value of the fragments purchased them and soon discovered that they could be combined into one skeleton. It was partially articulated. Mantell was thrilled with his find, as previous Megalosaurus and Iguanodon specimens had only contained single bone elements. In fact, the discovery was the complete non-avian dinosaur skull ever found. Although he was strongly inclined to identify the find as belonging the latter genus of dinosaurs, William Clift, curator of the Royal College of Surgeons of England Museum, and John Edward Gray began to question the authenticity of his description. Clift was the first person to notice that the plates and spikes could have been part of a body armor, which was attached to the back or sides the rump. Mantell created a new generic name in November 1832: Hylaeosaurus. It comes from the Greek word ulaios (hylaios), which means “of the wood”. Mantell initially claimed that Hylaeosaurus was a “forest lizard”, in reference to the Tilgate Forest where it was first discovered. Later, he claimed it to mean “Wealden Lizard”, which is another word for forest. This was in reference the Wealden Group (an early Cretaceous geological formation where the dinosaur was first discovered).

Mantell submitted the piece to London’s Geological Society on 30 November. He returned to London shortly thereafter and, on 5/12/12, he reported on the discovery to great acclaim at a Society meeting. He was also told that the paper he had prepared was three times too long. Charles Lyell, Mantell’s friend, advised him to rewrite the paper and publish an entire book about his fossil finds. He also dedicated a chapter to Hylaeosaurus. Mantell completed the volume in three weeks using notes from earlier years. Henry De la Beche advised him on 17 December that because of the new nomenclature, only the person who gave a complete species name would be recognized as the author. Hylaeosaurus needed a unique name to add. On 19 December, Mantell chose the Latin word armatus to refer to the spikes or armour plates. Mantell stated that “there is every reason to believe that its back was equipped with a formidable row spines that form a dermal fringe or that its tail had the same appendage.” His The Geology of the South-East of England, published May 1833, validly named the type species Hylaeosaurus Armatus. Mantell published a photo of his discovery in The Geology of the South-East of England. Another drawing was included in the fourth edition of The Wonders of Geology in 1840.

Hylaeosaurus was the least well-known of the three animals Sir Richard Owen used to define Dinosauria in 1842. The other two genera were Megalosaurus, Iguanodon, and Megalosaurus. Hylaeosaurus has not been given much attention despite its inclusion in the life-sized models of Benjamin Waterhouse Hawkins, which were placed in Crystal Palace Park. It also did not function as a wastebasket taxon. Owen, in 1840, proposed a new hypothesis regarding the spikes. Noting that they were asymmetrical, he incorrectly believed they were belly-ribs or gastralia.

Gideon Mantell recovered the original specimen from Tilgate Forest. The Natural History Museum of London acquired it in 1838. It is listed under the inventory number NHMUK3775 (previously BMNH R3775). It was discovered in the Tunbridge Wells Sand Formation, a layer that dates back to the Valanginian era. The Tunbridge Wells Sand Formation is approximately 137 million years old. This holotype, which is the most valuable specimen, is made up of the front end a skeleton without the forelimbs. However, only the stones on the block’s face can be easily analyzed. It measures approximately 135 x 75 cm. The holotype includes the back of the skull, possibly lower jaws, ten verbrae, both the scapulae and several spikes or armour plates. Viewed from the bottom, the skeleton can be seen. The museum started to remove the bones using both mechanical and chemical methods in the early 20th century. The blocks fell apart because of the way the acids were able to dissolve the glue and the gypsum used to repair the fossils. In 2020, Mark Graham published the limited information he had gleaned from his preparations since 2003. He also published a revised description.

Hylaeosaurus Armatus was the name given to several finds made on the British mainland. Paul Barrett and Susannah Maidment in 2011 concluded that the holotype could be ascertained to be the same species because of the presence Polacanthus within the same layers.

Hylaeosaurus has been mentioned as an additional remains, from the Isle of Wight (the Ardennes of), France, Buckeberg Formations, Germany, Spain, and Romania. Polacanthus may be the true owner of the remains found in France. Other references are also dubious. In 2013, however, two possible remains were found in Germany: a spike (specimen DLM 537) and the lower end a humerus (specimen GPMM A3D.3). These were referred to as Hylaeosaurus sp.

Source: Wikipedia