Haestasaurus

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Haestasaurus
Temporal range:
Ma
↓
Left humerus of the type specimen
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Clade: Dinosauria
Clade: Saurischia
Clade: †Sauropodomorpha
Clade: †Sauropoda
Clade: †Neosauropoda
Clade: †Macronaria
Genus: †Haestasaurus
Upchurch, Mannion, & Taylor, 2015
Species:
†H. becklesii
Binomial name
†Haestasaurus becklesii
(Mantell, 1852)

Haestasaurus is a

sauropod dinosaur, belonging to the Macronaria, that during the Early Cretaceous lived in the area of present-day England. The only species is Haestasaurus becklesii.[1]

Description

Restoration
Skin impression

As a sauropod, Haestasaurus would have been a large quadrupedal long-necked dinosaur. Little information is available about the specifics of its build because only a forelimb is known of the animal.

An indication of the size of Haestasaurus is given by the length of the forelimb elements. The humerus is 599 millimetres long, the ulna 421 millimetres and the radius, situated next to the ulna in the lower arm, has a length of 404 millimetres.[1]

A 2015 study found several unique anatomical traits (

autapomorphies) distinguishing Haestasaurus from related species. The inner front corner of the humerus is protruding, forming a processus entepicondylaris anterior. Between the front condyles of the lower humerus two small vertical ridges are present. The upper surface of the radius has, measured from front to rear, its largest width along the outer rim, which edge is nearly straight instead of strongly convex. The lower front of the radius is lightly concave between outer and inner ridges. A unique combination is present of a robust ulna, its upper surface having a width equalling more than 40% of the shaft length, with a slender radius having an upper width of less than 30% of total length.[1]

A rock associated with the forelimb, NHMUK R1868, was the first specimen known preserving parts of the sauropod skin. These probably are not impressions as the visible surface of the scales is convex, but natural casts. An area of 215 by 195 millimetres has been preserved. It shows non-overlapping hexagonal scales with a diameter of between ten and twenty-five millimetres. The scales gradually decrease in size, perhaps towards the elbow, to provide it greater flexibility. The scales strongly resemble skin impressions of later sauropod finds.

Reginald Walter Hooley in 1917,[3] but had incorrectly been identified as representing the underside of the epidermis
.

History of discovery and naming

In 1852, the collector

Samuel Husband Beckles obtained a block of Wealden Sandstone that had become visible at low tide off the coast of East Sussex near Hastings. The precise location is today unknown. It proved to contain a large forelimb which was studied by Gideon Mantell. The same year, Mantell in a lecture named the find as a second species of Pelorosaurus: Pelorosaurus becklesii, the specific name honouring Beckles.[4]

Left ulna

Pelorosaurus becklesii at first received little attention, perhaps also because the fossils remained in the private collection of Beckles; they were acquired by the

Camarasaurinae within the Brachiosauridae.[10] In 1990, John Stanton McIntosh confirmed that the species was not co-generic with Pelorosaurus conybeari.[11]

In 2015, Paul Upchurch, Philip D. Mannion and

Life Science Identifier which in this case is 9D2E9827-D6D5-444A-A01C-69CAE4FFCA22.[1] Haestasaurus was one of eighteen dinosaur taxa from 2015 to be described in open access or free-to-read journals.[12]

Left radius

The

metacarpal was referred to P. becklesii, specimen NHMUK R1869, but its large size precludes its belonging to the holotype.[1]

Relationships

By the end of the twentieth century, most researchers agreed that P. becklesii was a member of the

cladistic analyses to establish the exact position of Haestasaurus in the evolutionary tree. Due to the limited material available however, it proved impossible to obtain a single solution to this problem. Two major alternatives presented themselves. One possibility was that Haestasaurus was indeed a, basal, member of the Titanosauria. Alternatively, Haestasaurus was a basal member of the larger clade of the Macronaria, a close relative of Camarasaurus, Janenschia or Tehuelchesaurus. The authors favoured the last possibility because the traits pointing to a membership of the Titanosauria, such as a robust humerus and a robust ulna, could easily have been developed in a process of convergent evolution, as adaptations for weight-bearing. Haestasaurus would then represent a rare late-surviving basal macronarian.[1]

References

  1. ^
    doi:10.1371/journal.pone.0125819
  2. PMID 35145214
    .
  3. ^ Hooley, R.W. 1917. "On the integument of Iguanodon bernissartensis Boulenger, and of Morosaurus becklesii Mantell". Geological Magazine 6: 148–150
  4. ^ Mantell G.A., 1852, "On the structure of the Iguanodon and on the fauna and flora of the Wealden Formation", Notice: Proceedings of the Royal Institute of Great Britain. 1852 1: 141–146
  5. ^ Lydekker R., 1888, "Note on a new Wealden Iguanodont and other Dinosaurs", Quarterly Journal of the Geological Society 44: 46–61
  6. ^ Marsh O.C., 1889, "Comparison of the principal forms of the Dinosauria of Europe and America", American Journal of Science (series 3), 37: 323–330
  7. ^ Nicholson H.A. & Lydekker R., 1889, Manual of Palaeontology Volume 2. Edinburgh and London: Blackwood
  8. ^ Lydekker R., 1890, "On remains of small sauropodous dinosaurs from the Wealden", Quarterly Journal of the Geological Society of London, 46: 182–184
  9. ^ Lydekker R., 1893, "On a sauropodous dinosaurian vertebra from the Wealden of Hastings", Quarterly Journal of the Geological Society 49: 276–280
  10. ^ Von Huene, F., 1932, Die fossile Reptil-Ordnung Saurischia, ihre Entwicklung und Geschichte, Monographien zur Geologie und Palaeontologie 1(4), Leipzig: Gebrueder Borntraeger pp. 361
  11. ^ McIntosh J.S., 1990, "Sauropoda". In: Weishampel D.B., Dodson P., Osmólska H., (editors), The Dinosauria. First Edition, Berkeley: University California Press, pp. 345–401
  12. ^ "The Open Access Dinosaurs of 2015". PLOS Paleo.
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