What’s with the metacarpal of “Brachiosaurus” nougaredi?

After the recent description of Zby atlanticus (Mateus et al., 2014), I’ve decided to start analyzing the material of “Brachiosaurus” nougaredi (Lapparent, 1960). The species is definitely distinct from Brachiosaurus altithorax. However, the most distinctive material of “B”. nougaredi, a gigantic sacrum that is surprisingly narrow, has been lost for a while now, so only the photographs of Lapparent can be used to compare. The sacrum is approximately 130 cm long, but that is with only four of the vertebrae preserved. With all five, the sacrum would be upwards of 165 cm long, a gigantic size that would make an individual with the proportions of Sauroposeidon easily 40 meters long. Yet even though it was considered a brachiosaurid, which I think are some of the best sauropods, and is one of the largest dinosaurs ever, barely anyone has heard of it, and apart from the publications by Mannion et al. and Lapparent, only Nima has ever mentioned it that I can find. It is really time the sacrum was redescribed.

The sacrum, however, is not what I’m writing about here. Lapparent also assigned three metacarpals, a phalanx, and a tibia that were collected, and a radius, ulna and carpal that were left because they were “too fragmentary to collect”, although nowadays, any potentially unique fossils are and/or should be collected. The third metacarpal is currently the only material of “Brachiosaurus” nougaredi that can be located. Mannion et al. redescribed the metacarpal, finding it to be an indeterminate titanosauriform. I am not certain that this is the best placement, although they cannot be blamed for not knowing about recently named taxa. The turiasaur Zby has been named this year for a forelimb, and this can be directly compared to the third metacarpal of “B.” nougaredi. This is where it gets interesting.

Third metacarpal of "Brachiosaurus" nougaredi. From Mannion et al., 2013

Third metacarpal of “Brachiosaurus” nougaredi. From Mannion et al., 2013.

Third metacarpal of Zby atlanticus. From Mateus et al., 2014

Third metacarpal of Zby atlanticus. From Mateus et al., 2014.

Third metacarpal of Angolatitan adamastor. From Mateus et al., 2011

Third metacarpal of Angolatitan adamastor. From Mateus et al., 2011.

Manus of Morosaurus sp.

Manus of Morosaurus sp. From Osborn, 1904.

Third metacarpal of Sauroposeidon proteles. From Rose, 2007

Third metacarpal of Sauroposeidon proteles. From Rose, 2007.

Although it is more short and robust, the metacarpal of Zby has quite a resemblance to that of “B.” nougaredi. Both share a ridge along the proximal end, a more-or-less even metacarpal shaft, a distal end that is similar in morphology, and a proximal bulge that is proportionately small. The Sauroposeidon metacarpal is not very complete, but still shows a small proximal bulge (assuming that the known fragment is the proximal end). Other than Zby, the most resemblance to the “Brachiosaurus” nougaredi metacarpal is that of Angolatitan, recovered as a primitive somphospondylian by Mannion et al.. This has strange implications for the placement of the metacarpal of “B.” nougaredi. It might end up that the metacarpal is not of “B.” nougaredi, but in fact from a turiasaur. This would mean that Turiasauria is not an explicate european group, and that it also known from Africa.

Even though I keep thinking that the metacarpal is simply just a case of convergent evolution, I’m not convinced that it is the truth. The distal and proximal ends seem to be rugose, but I think that they are in fact actually partially eroded, meaning that it won’t be easy to find the truth. The features of this metacarpal imply that either “Brachiosaurus” nougaredi is a turiasaur, turiasaurs might be more derived than thought previously, Angolatitan and “Brachiosaurus”  nougaredi are not as derived as some analyses find them, or features of both groups were aquired indepentantly.

References:

Mannion, P.D.; Upchurch P.; Barnes R.N.; & Mateus O. (2013). “Osteology of the Late Jurassic Portuguese sauropod dinosaur Lusotitan atalaiensis (Macronaria) and the evolutionary history of basal titanosauriformes“. Zoological Journal of the Linnean Society 168: 98–206. doi10.1111/zoj.12029

Mateus, O.; Jacobs, L.L.; Schulp, A.S.; Polcyn, M.J.; Tavares, T.S.; Neto, A.B.; Morais, M.L.; Antunes, M.T. (2011). “Angolatitan adamastor, a new sauropod dinosaur and the first record from Angola“. Anais da Academia Brasileira de Ciências 83 (1): 221–233. doi10.1590/S0001-37652011000100012ISSN 0001-3765

de Lapparent, A.F. (1960). “Les dinosauriens du “continental intercalaire” du Sahara central“. Mémoires de la Société Géologic de France, Nouvelle Série 88A 39(1-6): 1–57

Mateus, O. V.; Mannion, P. D.; Upchurch, P. (2014). “Zby atlanticus, a new turiasaurian sauropod (Dinosauria, Eusauropoda) from the Late Jurassic of Portugal”. Journal of Vertebrate Paleontology 34(3): 618–634. doi10.1080/02724634.2013.822875

Rose, P.J. (2007). “A new titanosauriform sauropod (Dinosauria: Saurischia) from the Early Cretaceous of central Texas and its phylogenetic relationships“. Palaeontologia Electronica 10(2)

Osborn, H.F.  (1904). “Manus, sacrum and caudals of Sauropoda”. Bulletin of the American Museum of Natural History 20: 181–190

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About ijreid

I am an amateur palaeontologist thats hobbies include studying extinct amniotes, specifically dinosaurs, birds, and mammals. Occasionally, I focus my time on detailed and accurate illustrations of dinosaurs, and I have completed drawings of Dysalotosaurus, Micropachycephalosaurus, Zhuchengtyrannus, Troodon, Eotyrannus, Europelta, and Achillobator. I do not believe in copyrights, and think that the world would be better if everything was open access.
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2 Responses to What’s with the metacarpal of “Brachiosaurus” nougaredi?

  1. Nima says:

    ….Or the metacarpal may have nothing to do with “Brachiosaurus” nougaredi. There’s nothing to indicate the forelimb material was found in association with the sacrum, the metacarpal is clearly from a much smaller animal, and for all we know they could have been found miles apart.

    Based on the shape of the sacrum (so far as we can tell from the horrible photos) “Brachiosaurus” nougaredi is probably either a brachiosaur or a basal somphospondyl like Paluxysaurus. If a turiasaur-looking metacarpal were found in the general area, that may only indicate that a turiasaur was there too, but was mistakenly referred to “B”. nougaredi. However some titanosauriform metacarpals are similarly robust, so there’s no guarantee it was a turiasaur either. This reminds me of the Hudiesaurus controversy, where they found a huge vertebra and then a forelimb from a much smaller sauropod far away, and referred it to the same animal despite no overlapping material or comparison to other species from the region.

    This is what happens when you don’t collect all the material you find…

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    • ijreid says:

      Quite true. I guess in this case I’m using “B.” nougaredi referring to the metacarpal individual, Mannion never specifically stated that it should be lectotype, but as the only currently located material it does hold contention. (The material itself is really too bad to base a taxon on it)

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