Dinheirosaurus

ML 414 was first uncovered in 1987 by Mr. Carlos Anunciação. He was associated with the Museu da Lourinhã, and after the excavations which lasted from the time of discovery until 1992,[2] the specimen was then moved into the museum, and catalogued under the number 414.[3] Dantas et al. preliminarily announced ML 414 as soon as the excavations were complete. To remove the fossils from the surrounding rock, a bulldozer and tilt hammer were needed. The fossils were situated at the top of a coastal cliff, and once removed, were shipped to Lourinhã in two blocks with the help of a crane. A year before being described as a new taxon, Dantas et al. assigned ML 414 to Lourinhasaurus alenquerensis, previously grouped under Apatosaurus. José Bonaparte and Octávio Mateus studied the material of Lourinhasaurus, concluding one specimen, under the name ML 414, to be more closely related to diplodocids of the Morrison Formation, and thus warranting a new binomial name. This new species was described as Dinheirosaurus lourinhanensis, with a full meaning of "Porto Dinheiro lizard from Lourinhã".[2][3]

Dinheirosaurus material included vertebrae, ribs, partial pelvis, and gastroliths. The vertebrae were certainly from the cervical and dorsal regions, and are articulated. The two cervicals are not greatly preserved, although the twelve dorsals are articulated and in good condition. Other vertebral material includes seven centra that are fragmentary and a few neural arches, which are unattached. 12 dorsal ribs are preserved, as well as some appendicular elements.[2] David Weishampel et al. did not recognize all the material as belonging to Dinheirosaurus, and only found 9 dorsals in the holotype, while also misinterpreting the pubis as a limb fragment. They also incorrectly stated that it was found in the Camadas de Alcobaça Formation.[4] Another pair of vertebrae, under collection number ML 418, was originally assigned to Dinheirosaurus by Bonaparte and Mateus, but is now considered to be a distinct new unnamed genus of diplodocid.[3][5]

Size comparison

Dinheirosaurus was an average sized diplodocid, and had an elongated neck and tail.[4] The main features of the genus are based on its vertebral anatomy, and multiple vertebrae from across the spine have been found.[2] In total, Dinheirosaurus would have had an approximate length of 20–25 metres (66–82 ft) and weighed 8.8 metric tons (9.7 short tons).[6][7][8]

The animal is not known well from non-vertebral material, currently only consisting of partial ribs and a fragment of a pelvis. One of the ribs attached to the cervicals, and is quite fragmentary. It is elongated, although that might be a feature of distortion. Also undescribed by Bonaparte & Mateus are a set of thoracic ribs. Two ribs are from the left side of the animal. They are T-shaped in cross section, and display plesiomorphic features, although their incomplete state makes their identification uncertain. Multiple right ribs are preserved, including both the shafts and heads. They are similar to the left ribs, which also show that they lack pneumtization.[3] Other appendicular (non-vertebral) material includes a very incomplete and fragmentary shaft of the pubis, and over one hundred gastroliths. The pubis displays practically no anatomical features, and the gastroliths were not described in detail by Mannion et al. in 2012.[3]

Dinheirosaurus is not extremely well known, and as a consequence, its phylogenetic position is not certain. In 2012 during a redescription of the taxon by Philip Mannion et al., it was recovered, in both cladograms, to be sister species to Supersaurus vivianae and together forming the most basal diplodocines. A 2012 cladogram, published by Mannion et al. and using a modified matrix of Whitlock (2011) found that Dinheirosaurus was more primitive than Torneria and more derived than Apatosaurus.[3] However, a cladogram from 2014 found that their group was supported, but in fact more primitive than Apatosaurus, and therefore outside Diplodocinae.[9] In 2015, Dinheirosaurus lourinhanensis was considered a species of Supersaurus in a new combination S. lourinhanensis; their results are shown below.[1] However, to either confirm or refute this hypothesis, several remains of the holotype need to be prepared.[10]

Previously, Dinheirosaurus was classified within a Diplodocidae excluding Apatosaurus, for the differences anatomically are quite great. Bonaparte & Mateus found that a few features present suggested that Dinheirosaurus was more derived than Diplodocus, but plesiomorphic features also present conclude that they branched separately and Dinheirosaurus is not the descendant of Diplodocus.[2] A 2004 study by Upchurch et al. found that Dinheirosaurus was an intermediate diplodocoid, along with Cetiosauriscus, Amphicoelias, and Losillasaurus.[4]

As a diplodocid, it is probable that Dinheirosaurus possessed a whip-tail. If it did, it has been speculated that its tail could have been used like a bullwhip, with supersonic speed[11] or, more recently, as a tactile organ to keep in touch with other members of a group.[12] Being related to both Apatosaurus and Diplodocus, Dinheirosaurus probably possessed a squared snout. This means that it was probably a non-selective ground-feeding sauropod.[13]

Dinheirosaurus was one of many dinosaurs to have lived in the Lourinhã Formation during the Late Jurassic.[2] Many theropods, sauropods, and especially ornithischians are also from the Lourinhã Formation, which contains a similar fauna to the North American Morrison Formation.[4] Many theropods are known including an unnamed genus of abelisaurid;[15] the allosaurid Allosaurus europaeus; the ceratosaurid Ceratosaurus dentisculatus;[16] the coelurosaurians Aviatyrannis jurassica,[17] and cf. Richardoestesia; an intermediate theropod;[15] and the megalosaurid Torvosaurus gurneyi.[17] Sauropods are less common, with only an intermediate diplodocid as well as Dinheirosaurus;[3] the camarasaurid Lourinhasaurus alenquerensis; the turiasaur Zby atlanticus;[18] and the brachiosaurid Lusotitan known.[19] Ornithischians are well represented, with identified remains persisting to Trimucrodon cuneatus;[20] Alocodon kuehnei;[21] the stegosaurians Dacentrurus armatus, Miragaia longicollum,[22] and Stegosaurus ungulatus;[23] the ankylosaurid Dracopelta zbyszewskii;[24] the ornithopods Draconyx loureiroi,[25] Camptosaurus sp.,[18] Phyllodon henkelli,[21] and cf. Dryosaurus sp.[26]

• Dinheirosaurus