Becklespinax

Becklespinax Temporal range: Early Cretaceous, 133 Ma PreЄ Є O S D C P T J K Pg N ↓
Holotype (BMNH R1828) illustrated c. 1850s
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Order:	Saurischia
Suborder:	Theropoda
Clade:	Avetheropoda
Clade:	†Carnosauria
Genus:	†Becklespinax Olshevsky, 1991
Species:	†B. altispinax (Paul, 1988) [originally Acrocanthosaurus]
Synonyms
Acrocanthosaurus? altispinax Paul, 1988 (type) Altispinax altispinax (Rauhut, 2003)

Becklespinax is a genus of large predatory theropod dinosaur from the Early Cretaceous of England.

Discovery

Probably during the early 1850s, fossil collector Samuel Husband Beckles discovered some nodules with dinosaur bones in a quarry near Battle, East Sussex. These he sent to palaeontologist Richard Owen, who reported them in 1856.^[1] Owen had a lithography made by Joseph Dinkel of the main specimen, a series of three back vertebrae with very tall spines, whose image was also shown in an 1884 edition of an 1855 volume of his standard work on British fossil reptiles,^[2] leading to the misunderstanding the fossils had been recovered close to 1884. Owen, who referred the specimens to Megalosaurus bucklandii, thought the vertebrae were part of the shoulder region and it has been assumed that he must have already known of the find in 1853 as he directed Benjamin Waterhouse Hawkins to put a hump on the back of the life-sized Megalosaurus sculpture in Crystal Palace Park, which again inspired other restorations from the 19th century.^[3][4]

The humped Megalosaurus in Crystal Palace Park, London.

In 1888 Richard Lydekker associated the vertebrae with material referred to Megalosaurus dunkeri, a Cretaceous form based on a tooth found in Germany.^[5] In 1923 Friedrich von Huene created a separate genus for Megalosaurus dunkeri. He referred the three vertebrae to this genus and based its name, Altispinax (meaning "with high spines") on their appearance. Megalosaurus dunkeri hereby received the new combination name Altispinax dunkeri, a combination actually used for the first time in 1939 by Oskar Kuhn.^[6]

Later it was understood that Altispinax was a nomen dubium because the original tooth was undiagnostic. No relationship could be proven with the vertebrae. These were therefore in 1988 by Gregory Paul named as a new species of Acrocanthosaurus, Acrocanthosaurus? altispinax. The specific name was deliberately made identical to the old generic name, to emphasize that both referred to the vertebrae.^[7] As indicated by the question mark, Paul himself was uncertain about this assignment. In 1991 for this reason a new genus, Becklespinax, was named by George Olshevsky, in honour of the original discoverer, Beckles. The new combination name of the type species Acrocanthosaurus? altispinax thus became Becklespinax altispinax.^[8] The species names Altispinax altispinax^[9][10] and Altispinax lydekkerhueneorum^[11] are its junior objective synonyms, i.e. they refer to the same material but the name Becklespinax altispinax has priority.

The holotype of Becklespinax, BMNH R1828, was probably found in a layer of the Hastings Bed Group dating from the late Valanginian. It consists of a series of three posterior dorsal vertebrae. Owen also reported the presence in the nodules of two right ribs and two additional series of two dorsal vertebral centra each.^[1] Olshevsky thought the holotype represented the eighth, ninth, and tenth dorsal vertebra; later researchers, however, have assumed them to be the tenth, eleventh and twelfth.^[12]

Description

Von Meyer's restoration of Megalosaurus with long neural spines

Paul in 1988 tentatively estimated that A. altispinax weighed one tonne and was shorter than Acrocanthosaurus atokensis, itself by him estimated at the time as eight metres (26 ft) long.^[7]

The three Becklespinax altispinax back vertebrae from Sussex have about thirty-five centimetres high neural spines or processus spinosi, about as relatively tall as those of Ichthyovenator.^[13] These show irregular rugosities on the upper third part. According to Ralph Molnar the two spines closest to the skull are ankylosed or fused. The single closest spine is only about two-thirds the height of the others and looks as it has broken off, while the spine behind partly overgrows the gap. This Molnar explained as a result of injury to a back frill, the wound later closing from behind.^[12] In 2003, Darren Naish gave a different interpretation, suggesting the gap was natural. He denied that the front two vertebrae were ankylosed but observed that the spines of eleventh and twelfth vertebrae were joined at the top. The spines are also transversely expanded above, with a width of about fifty-five millimetres. Naish also pointed out that Owen had noted the large depressions on the neural arch sides and had explained them as a result of pneumatisation, the first time this phenomenon would explicitly have been observed with a dinosaur.^[14][15] In 2006 however, it was reported that in 1837 Christian Erich Hermann von Meyer already had commented on this phenomenon with the Saurischia in general.^[16] The discovery of a back crest incorporating only two high vertebrae in Concavenator, in 2010 provided corroboration that the short anterior Becklespinax spine may be complete.^[17]

Olshevsky originally assigned Becklespinax to the Eustreptospondylidae. In 2003 Naish considered it a member of the Allosauroidea.^[14] Most researchers give a less precise placement as Tetanurae incertae sedis.^[18][19]

References

External links

• Data related to Becklespinax at Wikispecies