Xenoposeidon proneneukos was a rebbachisaurid sauropod dinosaur that roamed the Earth about 140 million years ago. It belonged to the Early Cretaceous of England and is represented by a single partial dorsal vertebra with features quite unlike other sauropods. Members of the clade Sauropoda were saurischian or lizard-hipped dinosaurs characterized by long tails, very long necks, four thick legs, and a head relatively smaller than the body. The group had some of the largest animals to have ever roamed the Earth, including notable dinosaur genera such as the Brontosaurus, Apatosaurus, Diplodocus, and Brachiosaurus.
However, the sauropod dinosaur genus Xenoposeidon has a bit of a backstory. In the 1890s, Phillip James Rufford, a fossil collector, discovered a partial dorsal vertebra close to Hastings in East Sussex, England. Richard Lydekker initially described the vertebra specimen and placed it in the genus Cetiosaurus until it was eventually christened Pelorosaurus conybeari. The specimen remained in the British Natural History Museum in London, England, for about 100 years until paleontologist Mike Taylor decided to probe into the unusualness of the vertebra specimen. He partnered up with Darren Naish and, in 2007, published a description of the vertebra. Since then, the vertebra has been considered the holotype of the new sauropod dinosaur genus Xenoposeidon.
Read on to know more about these sauropod dinosaurs of the Early Cretaceous Period!
Xenoposeidon is pronounced 'ZEE-no-puh-SYE-d'n'. The full scientific name of the dinosaur is Xenoposeidon proneneukos, where the specific epithet means forward sloping and is pronounced 'pro-nen-YOO-koss'. The reason behind this naming is that the upper part of the single bone on which this dinosaur is based slopes forward.
Xenoposeidon was a rebbachisaurid sauropod dinosaur of the clade Sauropoda. Although it is distinct from all other sauropods, Xenoposeidon shares a common feature with the rebbachisaurid diplodocoid Rebbachisaurus garasbae from the mid-Cretaceous of Morocco. The said feature is the M-shaped laminae arrangement on the lateral face of the neural arch. Hence, it is part of Rebbachisauridae, a family of sauropod dinosaurs. Xenoposeidon is the oldest known member of Rebbachisauridae and is important for understanding the palaeobiology and evolution of the group. Moreover, Xenoposeidon proneneukos is represented by the single dorsal vertebra NHMUK PV R2095, preserved at the Natural History Museum in London, England.
The Xenoposeidon dinosaur roamed the Earth about 140 million years ago in the Berriasian and Valanginian stages of the Early Cretaceous of England.
Although the exact timeline of the Xenoposeidon's extinction has not been described in the literature, it can be estimated that they became extinct at the end of the Early Cretaceous Period, about 140 mya.
The Xenoposeidon is from the Ashdown Formation of the Wealden Supergroup of southern England. The Ashdown Formation dates back to the Lower Cretaceous Period and is within the Berriasian–Valanginian stages. It is the oldest and lowermost part of the Hastings Beds and typically comprises siltstones, sandstones, and mudstones. The most likely location of the partial posterior portion of the vertebra discovered in the 1890s was Ecclesbourne Glen near Hastings, East Sussex, England.
No detail is available regarding the Xenoposeidon's habitat. However, it is quite obvious that the Xenoposeidon was a terrestrial animal. From the topographical features of the Ashdown Formation, where the single bone fossil of the dinosaur was found, it can be said that the Xenoposeidons occupied a rocky terrain.
No data is available as to whether the Xenoposeidons lived alone or in groups. However, some studies on fossils have suggested that sauropods could have been gregarious animals and formed herds. The period during which the Xenoposeidons roamed the Earth was also marked by the presence of other dinosaurs such as the Rebbachiasaurus and Archaeoceratops.
The individual lifespan of a Xenoposidon is not available. The group as a whole is believed to have lived throughout the entire stretch of the Lower Cretaceous Period from 145-100.5 Ma.
Due to a lack of data, details of the reproductive features of the Xenoposeidon are not available. The only confirmed fact is that they were oviparous and laid eggs.
The scarcity of fossil remains of the Xenoposeidon leaves very little scope to speculate the features of the entire animal. As illustrated by Taylor and Naish, the Xenoposeidon was an elephant-sized dinosaur with a tail, a long neck, and a small head. Considering it was a sauropod, this physical description is quite acceptable.
The single vertebra NHMUK PV R2095 of the Xenoposeidon held at the Natural History Museum, London, England, consists of the base of a tall neural arch and the centrum. It lacks the upper portion of the neural arch and the anterior face of the centrum. The centrum's concave posterior face suggests that the anterior faces of the vertebrae from this section of the Xenoposeidon's spine were convex to fit in with the shape. Furthermore, the specimen bone makes it clear that the neural canal was circular and small at its posterior opening but teardrop-shaped and large anteriorly. The neural arch's base spans the length of the centrum and joins the latter's posterior face. The lateral face of the arch has broad areas of featureless bone with an anterior lean of 35 degrees. Like other sauropods, their teeth would have been highly evolved to suit a herbivorous diet. It is not known how many teeth the Xenoposeidons had.
Due to the lack of fossil remains, there is no estimation of the total number of bones the Xenoposeidon had. The little that is known about its overall build is based on comparisons with other sauropods, such as the diplodocids and brachiosaurids.
No data is available regarding the communication behavior of the Xenoposeidons.
The lack of fossil remains make it impossible to give an estimate of how big a Xenoposeidon was. If it had a build like a diplodocid, a Xenoposeidon would have been about 66 ft (20 m) long. On the contrary, a body form like a brachiosaurid would make the Xenoposeidon about 49 ft (15 m) long. From another perspective, a Xenoposeidon would approximately be as large as a fully-grown African elephant.
No information is available regarding how fast Xenoposeidons move. Given their massive size, it may be assumed that they were not very swift-footed either. It was a quadrupedal dinosaur that walked on all fours.
If the Xenoposeidon resembled the Brachiosaurus, it would weigh approximately 16,755 lb (7,600 kg). On the other hand, if the Xenoposeidon was built like the lighter and longer Diplodocus, it would weigh about 6,173 lb (2,800 kg).
Male and female dinosaurs, in general, had no distinct names.
A baby dinosaur is usually referred to as a hatchling or juvenile.
The only information about the Xenoposeidon's diet is that it was a herbivore.
There is no concrete data to confirm whether the Xenoposeidons were aggressive or not. Considering they were herbivores, an educated might assume that they were not as violent and aggressive as predatory carnivores.
After Xenoposeidon proneneukos, the next oldest member of the family Rebbachisauridae is Histriasaurus.
Michael P. Taylor, the paleontologist who described Xenoposeidon, is a computer programmer. Besides naming the Xenoposeidon in 2007 with Darren Naish, Tyler is co-credited with naming two other dinosaur genera - Haestasaurus in 2015 with Phil Mannion and Paul Upchurch and Brontomerus in 2011 with Richard Cifelli and Matt J. Wedel.
O.C. Marsh coined the term Sauropoda in 1878. Its Ancient Greek meaning is lizard foot. Most sauropod fossil finds are rare, with specimens usually lacking limbs, tail tips, or heads. Most species have been described based on disarticulated and isolated bones.
The name Xenoposeidon has two parts. The first part, Xenos, is Greek for strange, and the latter part, 'poseidon', is perhaps a reference to Poseidon, the god of the sea, earthquakes, storms, and horses in ancient Greek religion and mythology.
The single bone fossil of the Xenoposeidon does not shed any light on the prehistoric animal's overall size. The only educated guess is that it could have been the size of either the sauropod Diplodocus or Brachiosaurus.
Here at Kidadl, we have carefully created lots of interesting family-friendly dinosaur facts for everyone to discover! For more relatable content, check out these Xenotarsosaurus facts, or Yinlong facts for kids.
You can even occupy yourself at home by coloring in one of our free printable Letter A Dinosaurs coloring pages.
The main image is by Mike Taylor.