Altispinax

Credit: PaleoGeekSquared on the Wikimedia Commons.

*Altispinax* is an extinct genus of carnosaurian dinosaur that lived in England during the Early Cretaceous.

## History

Likely during the 1850s, Samuel Husbands Beckles found dinosaur bone nodules near Bettle, Sussex; he sent these to Richard Owen, who reports them first in 1856. Joseph Dinkel made a lithograph of the main specimen, which was sent to Owen. It was a series of 3 back vertebrae and extremely tall tail spines, shown in an 1884 edition of an 1855 volume work on British fossil reptiles. This leads to the misconception that the fossils were found closer to 1884. Owen refers these to *Megalosaurus bucklandii*, thinking the vertebrae were of the shoulder. It is assumed he knew of these as far back as 1853, where he directed Benjamin Waterhouse Hawkins to sculp a hump on the Crystal Palace *Megalosaurus* sculpture, which inspired a paleoart meme for other 1800s reconstructions.

These are known known as NHMUK R1828, likely found in a layer of the Hastings Bed Group, Late Valanginian-aged. It is 3 posterior dorsals, with Owen reporting 2 additional series of dorsal centra in the nodules od the 2 right ribs. Olshevsky thought the holotype made the 8th, 9th and 10th dorsal, with later research assuming they are the 10th, 11th and 12th, instead. Richard Lydekker (1888) compared these to *M. dunkeri*. Friedrich von Huene (1923) erected a new genus to house this species, creating *Altispinax*. *A. dunkeri* was first used by Oskar Kuhn (1939). Later researchers, however, consider it a nomen dubium due to the undiagnostic nature of the tooth, and no relationship between the tooth and vertebrae can be verified. Gregory S. Paul (1988) gave it a new name, being *"Acrocanthosaurus" dunkeri*, having to same epithet to emphasize their relationship to the vertebrae. Paul himself was uncertain of his classification. Thus, *Becklespinax* was erected in 1991 because of this by George Olshevsky. Thus, *B. altispinax* was born, with *A. altispinax* and *A. lydekkerhueneorum* becoming junior objective synonyms.

Michael Maisch (2016) analyzed this history, finding von Huene erected *A. dunkeri* off vertebrae and not the *M. dunkeri* tooth. Since they were of different specimens, later scientists were wrong to class them as distinct, Maisch cites the ICZN rules, stating two distinct species share the same name. Since the later names by Paul and Olshevsky are junior objective synonyms, *A. dunkeri* takes priority, and is the correct name for usage.

## Description

Paul (1988) tentatively estimated it weight 1 tonne shorter than *Acrocanthosaurus atokensis*, being 8 meters (26 feet) long. The 3 vertebrae have ~35 centimeter-long neural spines, about as tall as *Ichthyovenator*. They have irregular rugosities at the upper 3rd part. Ralph Molnar finds the two spines closest to the skull are fused. The single closest is ~2/3 the height of the others, and appears to be broken, with the spine behind partly overgrowing the gap. Molnar explains this is due to an injury to a back frill, with the wounds closing from behind. Darren Naish (2003) gives a new interpretation; that this gap is natural, finding the closest were not fused, with the spines of the 11th and 12th jointed at the top. The spines transversely expand above, having a width of ~55 millimeters. Naish notes Owen found large depressions at the neural arch sides, explaining them as a result of pneumatization. This is the first time this is found in a dinosaur. In 2006, it was found that Christain Hermann von Meyer (1837) had already found this, finding it in Saurischia. The discovery of *Concavenator* found the short anterior may be incomplete.

## Classification

Olshevsky assigned it to Eustreptospondylidae. Naish (2003) considered it an allosauroid. Most researchers, however, assign it as Tetnaurae incertae sedis.