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Altispinax: The Mysterious Meat-Eater of Early Cretaceous England

Introduction

There are many dinosaur species which have been identified based upon very scant remains, and this article concerns one of them: a meat-eating dinosaur named Altispinax dunkeri. If you’ve never heard of this animal before, you’re not alone. It’s not exactly a name that readily springs to mind when one thinks of dinosaurs. After all, Altispinax is only known from three vertebrae that were found back in the 1850s, and nothing else has been found since then which can be positively attributed to this animal. Other isolated fossils have been found here and there, but there’s really no way to tell if all of these isolated bones, teeth, and claws all belong to the same creature. Broadly, we are reasonably sure that it was a meat-eating dinosaur, but aside from that, there’s not much else to go on.

Discovery and Description

In 1855, a British lawyer and amateur fossil hunter named Samuel H. Beckles (April 12, 1814 – September 4, 1890) was prospecting for fossils in southeastern England. Not far from the site of the Hastings battlefield, he discovered a series of three vertebrae with unusually tall dorsal spines, measuring about 14 inches (35 centimeters) from the top of the centrum disk to the top of the spine (1).

The holotype specimen of Altispinax (collections ID code: BMNH R1828, or maybe it’s NHMUK R1828). Image from “Dinosaurs of Great Britain and the role of the Geological Society of London in their discovery: basal Dinosauria and Saurischia” by Darren Naish and David M. Martill (2007). Journal of the Geological Society, volume 164. Page 503, Figure #7 (Pages 493-510).
https://darrennaish.files.wordpress.com/2013/01/naish-martill-2007-gsl-british-dinosaurs-pt-i-saurischia.pdf.

The following year in 1856, the famous British paleontologist Sir Richard Owen wrote a description of this fossil in which he ascribed it to the genus Megalosaurus, which had been classified about thirty years earlier. The description of the fossil reads as follows:

“Three anterior dorsal vertebrae: p, parapophysis, or lower transverse process: t, accessory tubercle contributing some attachment to the head of the rib: d, diapophyses, or upper transverse process, fractured, which gave attachment to the tubercle of the rib: b, oblique buttress extending from the parapophysis to the diapophysis, and contributing to the support of the neural platform : z, the prozygapophysis, z’, the zygapophysis, forming the ends of the neural platform and articulating the neural arches of the vertebrae with each other, ns, the neural spine of the foremost of these vertebras, ns’, the neural spine of the second vertebra; it expands at its extremity, overhangs the anterior shorter spine, and developes a strong bony plate from its back part which fixes it to n”, the similarly developed and modified spine of the third vertebra. The extraordinary size and strength of the spines of these anterior dorsal vertebrae, indicate the great force with which the head and jaws of the Megalosaurus must have been used” (2).

This is a drawing (yes, that’s a drawing, not a photograph) of the vertebrae, made by Joseph Dinkel which accompanies Owen’s article. Public domain image, Wikimedia Commons.
https://commons.wikimedia.org/wiki/File:Becklespinax.jpg.

The fossil vertebrae were found in the rocks of the “Wealden Supergroup”. This is a multi-layer series of geological formations consisting largely of sandstones and mudstones which are spread throughout much of southeastern England and date to the early Cretaceous Period. This geological super-formation is divided into several sub-units called “groups”, and each of these groups are divided further into “formations”. These include the “Hastings Beds Group” (dated from the Berriasian to Valanginian Stages of the early Cretaceous Period), the “Weald Clay Group” (Hauterivian and Barremian, possibly extending into the Aptian), and the “Wealden Group” (Barremian to Aptian) (3).

The vertebrae fossils were found in the rock layers of the “Hastings Beds Group”. Specifically, the fossils were found in the Wadhurst Clay Formation of East Sussex. This formation dates to the Valanginian Stage of the early Cretaceous Period, and even more specifically to the early to middle Valanginian. This would place the vertebrae’s date range at about 138-135 million years ago. During this same time, iconic early Cretaceous dinosaurs such as Iguanodon and Baryonyx had not yet evolved. Instead, Altispinax shared its habitat with the armored ankylosaur Hylaeosaurus, the sauropods Pelorosaurus and Xenoposeidon, and the small ornithopods Valdosaurus and Echinodon. Isolated fossils of Iguanodon-like animals have also been found here, as well as fossils of frogs, crocodiles, and small mammals. Since no other large carnivorous dinosaurs are known from this place and time, Altispinax might have been the top predator within its environment (4).

Discussion

Altispinax is not a well-known dinosaur, but even though it is not a major star in dinosaur paleontology circles and it is not a creature well-known to the general public, largely due to the fact that the only evidence for it comes from a single fragmentary specimen found nearly 170 years ago, Altispinax has received a surprisingly high amount of academic attention. Every now and then, professional paleontologists dabble in Altispinax speculation, analyzing these three vertebrae for the umpteenth time and pondering where exactly it fits in the theropod family tree.

Unsurprisingly, because these finds are 170 years old and are known only from fragmentary remains, Altispinax’s position in the dinosaur family tree has been regularly shuffled around because nobody, it seems, can make up their minds about what sort of animal it was. When it was first discovered, Sir Richard Owen believed that these spines belonged to Megalosaurus bucklandi, one of the first dinosaurs to be discovered and named. During the 19th and 20th Centuries, the name “Megalosaurus” was considered a “wastebasket taxon” – any remains of a meat-eating dinosaur which could not be positively identified were classified as Megalosaurus. As a result, this genus name acquired a long list of species names. Indeed, early reconstructions of Megalosaurus incorporated these three tall-spined vertebrae into its anatomy. For example, the British sculptor Benjamin Waterhouse Hawkins created a statue of Megalosaurus for Crystal Palace Park in which it possessed a bison-like hump over its shoulders.

Middle 19th Century reconstruction of Megalosaurus by Benjamin Waterhouse Hawkins, on display in Crystal Palace Park. Note the prominent bison-like hump over the shoulder. Photo by C. G. P. Gray (2007). Creative Commons Attribution 3.0 Unported license.
https://commons.wikimedia.org/wiki/File:London_-Crystal_Palace-_Victorian_Dinosaurs_1.jpg
.

When Megalosaurus’ appearance was further refined during the late 1800s into a definitely dinosaurian appearance, but in an incorrect upright pose as championed by people such as Joseph Leidy and Louis Dollo, this reconstruction again showed Megalosaurus with tall neural spines, forming a low ridge running down the middle of its back.

Late 19th Century reconstruction of Megalosaurus by Christian Von Meyer, in which the animal is portrayed with tall neural spines on its dorsal and sacral vertebrae. Illustration from Extinct Monsters, 5th Edition, by Reverend Henry N. Hutchinson. London: Chapman and Hall, 1897. Page 78. https://archive.org/details/extinctmonsters00hutciala.

In 1923, the famed German paleontologist Friedrich Von Huene took a look at the three spines from southern England, as well as a single tooth that was discovered in Germany which had been given the name Megalosaurus dunkeri. Von Huene lumped these fossils together in the belief that they both came from the same species, and determined that they did not, in fact, come from Megalosaurus. So he gave these spines and the solitary tooth a new name – Altispinax dunkeri, “Dunker’s high-spined ruler” (5).

Later researchers justifiably felt that Von Huene had jumped the gun by assuming that the tooth from Germany and the vertebrae from England belonged to the same species. Furthermore, new species had been discovered since then. In the late 1940s in the United States, another large theropod was discovered with a prominent ridge running down its back which looked remarkably similar to the three vertebrae found in England. In 1950, the American dinosaur was named Acrocanthosaurus atokensis, and other paleontologists began to wonder if the mysterious vertebrae found in England came from a similar animal. In the 1980s, paleontologist and paleo-artist Gregory Paul felt that the three vertebrae represented a European version of Acrocanthosaurus, so he gave it a provisional name of “Acrocanthosaurus altispinax”, though he wasn’t absolutely certain if he was correct. In 1991, George Olshevsky stated that these three spines did not belong to Acrocanthosaurus, but belonged to a new genus, and so it was named Becklespinax altispinax, named in honor of Samuel Beckles who had discovered the vertebrae in 1855 (6).

Skeleton of Acrocanthosaurus on display at the North Carolina Museum of Natural Sciences. Photo by Famille Wielosz-Caron (August 4, 2007). Creative Commons Attribution 2.0 Generic license.

Illustration of Becklespinax made by the paleo-artist James Robins in the magazine Dinosaurs!, issue #46, page 1084. Durham: Atlas Editions Partworks, Inc., 1994.

The name Becklespinax remained in place for the next twenty-five years until 2016 when it was challenged by Michael Maisch. He said that since Friedrich Von Huene recognized this animal as a distinct species back in 1923, this pre-dated George Olshevsky’s recognition of this animal as a distinct species in 1991. Therefore, the name Altispinax held priority over the more recent name Becklespinax, and therefore the name Becklespinax should be discarded. So in 2016, the old name of Altispinax dunkeri was resurrected (7).

Just as its name has been altered over the years, Altispinax’s phylogeny has also changed. In 1856, Sir Richard Owen classified this animal as a megalosaur. Then, following the discovery of Acrocanthosaurus in the late 1940s, it was believed to be an allosaur (later, Acrocanthosaurus was re-classified as a carcharodontosaurid). In 1991, George Olshevsky classified Altispinax once again as a megalosaur, specifically in the family Eustreptospondylidae. By the late 1990s, it was re-classified again as being more closely-related to a Middle Jurassic allosaur from China called Sinraptor, and was therefore placed in the allosauroidean family Metriacanthosauridae, which includes Metriacanthosaurus, Sinraptor, and Yangchuanosaurus. These species measured 20-25 feet long (which was the same size estimate commonly seen for Altispinax), had curvaceous skulls, and unusually tiny hands with stubby fingers and claws. Allosaurus, with its gigantic hands and meat hook claws, was a rough-and-tumble attacking predator (numerous injuries on fossils prove this), but its cousin Sinraptor did not have such well-developed hands. In 2003, Darren Naish classified this creature as belonging to the more evolutionarily-advanced super-family Allosauroidea, but didn’t hazard placing it into a specific allosaur family (8). In a 2007 article, Darren Naish wrote “Several other tetanurans exhibit a similar pattern of neural arch laminae to Becklespinax, including Condorraptor, Piatnitzkysaurus and Sinraptor, and Sinraptor in particular exhibits a superficially similar morphology: this could mean that Becklespinax is a sinraptorid, but there are no uniquely shared characters that might demonstrate this. For now, pending further discoveries, Becklespinax remains an indeterminate tetanuran of unknown affinities. Its combination of characters, and uniquely expanded neural spines tips, mean that it is a valid, diagnosable taxon” (9).

Skeleton of Sinraptor. Photo by Ian Armstrong (April 17, 2005). Creative Commons Attribution-Share Alike 2.0 Generic license.

Some people wondered if Altispinax might have been a spinosaur or perhaps a carcharodontosaur, since species from both groups have been found in Europe, and especially considering that carcharodontosaurs like Acrocanthosaurus and spinosaurs like Suchomimus and Ichthyovenator were known to have tall neural spines on its vertebrae forming a dorsal ridge. In a 2007 article, back when the animal was still referred to as Becklespinax, Darren Naish wrote “there are no shared derived characters that might unite Becklespinax with either spinosaurids or carcharodontosaurids, and these suggestions can’t be supported”(10). But not long after this was written, Concavenator was discovered in Spain, and old questions were resurrected regarding Altispinax’s position on the theropod family tree. It was determined that Concavenator was a carcharodontosaurid, and there were several noticeable similarities between this animal and Altispinax. Now, many people are once again changing Altispinax’s phylogeny, saying that, yes, it is a carcharodontosaur, but as to whether or not it is, it’s anybody’s guess at this point. Darren Naish re-classified Altispinax as a carcharodontosaurid in 2011, and the science website Palaeos also classifies Altispinax (identified on the web-page as Becklespinax) as a member of the family Carcharodontosauridae (11).

Skeleton of Concavenator, a 20 foot carcharodontosaurid from Spain. Photograph by Santiago Torralba (August 22, 2008). Creative Commons Attribution 2.0 Generic license.

Reconstructed skeleton of Concavenator. (May 1, 2019). Creative Commons Attribution-Share Alike 4.0 International license.

Reconstruction

Well, time to reconstruct what the whole animal may have looked like. It is not yet clear if Altispinax was more closely related to Sinraptor or to Concavenator. Although both of these animals had different features to the structure of their skull, outwardly they would have looked very similar to each other. Both groups of animals also had short arms with small hands, and would have had an allosaur-ish body structure. One wonders if the carcharodontosaurids evolved directly from the metriacanthosaurids like Sinraptor, but this is just a guess on my part.

As for the sail, that was a bit difficult. For years, paleo-artists depicted sail-backed bipedal dinosaurs, like the old renditions of Spinosaurus, with a sail located on the back between the arms and the legs. But the best position for a theropod’s sail is directly over the hips, not between the front limbs and hind limbs as is often seen. Animals that have their sails positioned between the front legs and back legs are quadrupedal animals, like Dimetrodon, and also what we now know Spinosaurus to be like. In a four-legged animal, the body is held off of the ground in an arch, braced by the four legs, and as such the main body has the structural support necessary to carry a sail over the back. However, in a bipedal animal, the hips form a fulcrum which balances the animal. If a bipedal animal had a sail located in a Dimetrodon-like way, positioned between the arms and legs, it would make the animal front-heavy. Therefore, a sail would be better positioned over the hips. Of course, this discounts the possibility that the animal had an unusually long tail to counter-balance the weight in the front. This is with the assumption that Becklespinax’s sail was short, extending only a small distance along the length of its back. It’s possible that it may have had a skeleton similar to Acrocanthosaurus, which had raised dorsal spines running all along its back, from the base of the skull, and extending down to the tip of the tail. However, this cannot be definitively stated to be the case until more of this animal is discovered.

The drawing that you see below was made with No. 2 pencil.

Altispinax dunkeri. © Jason R. Abdale (May 3, 2021).

Source Citations:

  1. Everything Dinosaur. “Remembering Samuel Husbands Beckles (1814-1890)”, by Mike Walley (August 24, 2014).; I Know Dino podcast. Episode 54 – “Becklespinax” (December 8, 2015).
  2. Richard Owen (1856). “Monograph on the fossil Reptilia of the Wealden Formation. Part IV”. Palaeontographical Society Monographs, volume 10.
  3. Darren Naish, “Pneumaticity, the early years: Wealden Supergroup dinosaurs and the hypothesis of saurian pneumaticity”. In Richard T. J. Moody, E. Buffetaut, Darren Naish, and David M. Martill, eds., Geological Society Special Publication No. 343 – Dinosaurs and Other Extinct Saurians: A Historical Perspective. London: The Geological Society, 2010. Pages 229-230.
  4. David B. Weishampel, ‎Peter Dodson, ‎Halszka Osmólska, eds., The Dinosauria, Second Edition. Berkeley: University of California Press, 2004. Page 73; Darren Naish, “Pneumaticity, the early years: Wealden Supergroup dinosaurs and the hypothesis of saurian pneumaticity”. In Richard T. J. Moody, E. Buffetaut, Darren Naish, and David M. Martill, eds., Geological Society Special Publication No. 343 – Dinosaurs and Other Extinct Saurians: A Historical Perspective. London: The Geological Society, 2010. Page 230; Mindat. “Becklespinax”; British Geological Survey. “Wadhurst Clay Formation”; Oladapo Odunayo Akinlotan (October 2015), The Sedimentolody of the Ashdown Formation and the Wadhurst Clay Formation, Southeast England. PhD Thesis, University of Brighton. Page 1.
  5. Smithsonian Magazine. “B is for Becklespinax”, by Riley Black (October 22, 2012).
  6. Smithsonian Magazine. “B is for Becklespinax”, by Riley Black (October 22, 2012).
  7. Michael W. Maisch (2016), “The nomenclatural status of the carnivorous dinosaur genus Altispinax v. Huene, 1923 (Saurischia, Theropoda) from the Lower Cretaceous of England”. Neues Jahrbuch für Geologie und Paläontologie – Abhandlungen, volume 280, issue 2. Pages 215-219.
  8. George Olshevsky (1991). “A revision of the parainfraclass Archosauria Cope, 1869, excluding the advanced Crocodylia”. Mesozoic Meanderings, volume 2. Pages 22-23 (1-196); Theropod Database. “Carnosauria”; Dinosaur Mailing List. “Re: Becklespinax” (February 18, 1997); Darren Naish (2003), “A definitive allosauroid (Dinosauria; Theropoda) from the Lower Cretaceous of East Sussex”. Proceedings of the Geologists’ Association, volume 114. Pages 319-326; Darren Naish and David M. Martill (2007), “Dinosaurs of Great Britain and the role of the Geological Society of London in their discovery: basal Dinosauria and Saurischia”. Journal of the Geological Society, volume 164. Pages 502-503, Figure #7 (Pages 493-510).
  9. Tetrapod Zoology. “Of Becklespinax and Valdoraptor”, by Darren Naish (October 2, 2007).
  10. Tetrapod Zoology. “Of Becklespinax and Valdoraptor”, by Darren Naish (October 2, 2007).
  11. Theropod Database. “Carnosauria”; Naish, Darren (2011). “Theropod Dinosaurs”. In Batten, ed., English Wealden Fossils. The Palaeontological Association. Pages 526-559; Smithsonian Magazine. “B is for Becklespinax”, by Riley Black (October 22, 2012); Palaeos. “Theropoda: Avetheropoda: Carcharodontosauridae”.

Bibliography: