Quirks in the cladistic analysis of Lourinhasaurus by Mocho et al. (2014)

It's been barely a year since the second of the three Jurassic Portuguese sauropods, the brachiosaurid titanosauriform Lusotitan ataialensis, was put in a cladistic context by Mannion et. al. (2013) ten years after it was recognized as generically distinct from Brachiosaurus and Giraffatitan. Now, Mocho et. al. (2014) have published a paper re-assessing the cladistic position of the third described Portuguese sauropod, Lourinhasaurus alenquerensis, following in the footsteps of Mannion et. al. (2012, 2013) in putting all of Portugal's sauropod taxa in a phylogenetic context. While it's good that Mocho et al. update the osteology of this genus given that the uncertain placement of some macronarian and non-neosauropod taxa previously assigned to Camarasauridae, I happened to notice a few aspects of the phylogenetic analysis of Lourinhasaurus that seem inconsistent with current state-of-the-art knowledge of eusauropod systematics. Therefore, I have had the opportunity to carefully scrutinize the results of the Lourinhasaurus cladistic analyses by Mocho et al. (2014).

For starters, Lourinhasaurus was originally named as a new Apatosaurus species, A. alenquerensis, by Lapparent and Zbyszewski (1957) and later referred to Camarasaurus by McIntosh (1990a), although McIntosh (1990b) did not rule out the possibility of alenquerensis constituting its own genus due to its higher humerus to femur length ratio. Dantas et. al. (1998) removed alenquerensis from Camarasaurus  based on comparisons with known specimens of Camarasaurus and assigned it to a new genus, which they named Lourinhasaurus, while designating a partial postcranial skeleton from Moinho do Carmo among the syntype series as the lectotype for L. alenquerensis. Because the original description of this taxon had a rather inadequate diagnosis, Upchurch et. al. (2004) found it to be in an unstable position in Eusauropoda, raising the question about the precise placement of Lourinhasaurus among derived eusauropods, including neosauropods. 

Cladistic analyses of Lourinhasaurus by Mocho et al. (2014) using the Wilson (2002) matrix (top) and Upchurch et al. (2004) data matrix (bottom). Note that the Lourinhasaurus phylogeny using the Upchurch et al. (2004) matrix is partly flawed because it did not incorporate data from the cladistic analysis of Curry Roger and Forster (2001).  

When comparing the cladistic analyses of Lourinhasaurus by Mocho et. al. (2014) using the Wilson (2002) and Upchurch et al. (2004) data matrices, it's interesting that while both phylogenies recover a monophyletic Camarasauridae formed by Camarasaurus, Lourinhasaurus, and Tehuelchesaurus, the phylogeny based on the Upchurch et al. (2004) data matrix places Nemegtosaurus and Quaesitosaurus

as diplodocoids rather than titanosaurs and Haplocanthosaurus as a basal macronarian rather than a diplodocoid, while failing to support a monophyletic Euhelopodidae sensu D'Emic (2012). However, this is likely due to the failure of Mocho et. al. (2014) to incorporate characters from the cladistic analyses of D'Emic (2012) and Whitlock (2011) but also the redescription of  Nemegtosaurus and  Quaesitosaurus by Wilson (2005) into the data matrix of Upchurch et al. (2004). Indeed, the cladistic analysis of Titanosauria by Upchurch et al. (2004) did not incorporate characters from the data matrix by Curry Rogers and Forster (2001), although those authors did mention that cladistic results from the latter paper If Camarasauridae sensu Mocho et. al. (2014) holds up in future cladistic analyses concerning the interrelationships of non-titanosauriform macronarians, then Lourinhasaurus would be closely related to Camarasaurus as stated by McIntosh (1990). However, putative camarasaurids such as Dashanpusaurus from the Middle Jurassic of Sichuan, eastern China were not included by Mocho et. al. (2014), so it's unclear whether Camarasauridae had a cosmopolitan distribution in the Middle to Late Jurassic.

References:

Curry Rogers, K., and Forster, C.A., 2001. The last of the dinosaur titans: a new sauropod from Madagascar. Nature 412: 530–534.

D'Emic, M.D., 2012. The early evolution of titanosauriform sauropod dinosaurs. Zoological Journal of the Linnean Society 166 (3): 624–671.

Dantas, P., Sanz, J. L., Marques da Silva, C., Ortega, F., dos Santos V.F., and Cachão, M. 1998. Lourinhasaurus n. gen. Novo dinossáurio saurópode do Jurássico superior (Kimmeridgiano superior-Tithoniano inferior) de Portugal. Comunicações do Instituto Geológico e Mineiro 84 (1A): 91-94.

Lapparent, A.F. de and Zbyszewski, G., 1957. Les dinosauriens de Portugal. Mém. Serv. géol. Port. 2: 1-63.

Mannion, P. D., Upchurch P., Mateus O., Barnes R. N., and Jones M. E. H., 2012. New information on the anatomy and systematic position of Dinheirosaurus lourinhanensis (Sauropoda: Diplodocoidea) from the Late Jurassic of Portugal, with a review of European diplodocoids. Journal of Systematic Palaeontology 10(3), 521–551.

Mannion, P. D., Upchurch P., Barnes R. N., and Mateus O., 2013. Osteology of the Late Jurassic Portuguese sauropod dinosaur Lusotitan atalaiensis (Macronaria) and the evolutionary history of basal titanosauriforms. Zoological Journal of the Linnean Society 168: 98–206.

McIntosh, J.S. 1990a. Sauropoda. pp. 345-501. In: Weishampel, D.B., Dodson, P., and Osmólska, H. (eds.). The Dinosauria. University of California Press, Berkeley.

McIntosh, J.S., 1990b. Species determination in sauropod dinosaurs with tentative suggestions for their classification. pp. 53-69. In: Carpenter, K., and Currie, P.J. (eds) Dinosaur systematics: approaches and perspectives. Cambridge: Cambridge University Press.

Mocho, P., Royo-Torres, R., and Ortega, F., 2014. Phylogenetic reassessment of Lourinhasaurus alenquerensis, a basal Macronaria (Sauropoda) from the Upper Jurassic of Portugal. Zoological Journal of the Linnean Society 170 (4): 875-916.  DOI: 10.1111/zoj.12113  http://onlinelibrary.wiley.com/doi/10.1111/zoj.12113/abstract

Upchurch, P., Barrett, P.M. and Dodson, P. 2004. Sauropoda. pp. 259-322. In: Weishampel, D.B.; Dodson, P.; & Osmólska, H. (eds.). The Dinosauria, 2nd edition. University of California Press, Berkeley.

Whitlock, J.A., 2011. A phylogenetic analysis of Diplodocoidea (Saurischia: Sauropoda). Zoological Journal of the Linnean Society 161: 872–915.

Wilson, J.A., 2002. Sauropod dinosaur phylogeny: critique and cladistic analysis. Zoological Journal of the Linnean Society 136 (2): 215–275.

Wilson, J.A, 2005. Redescription of the Mongolian sauropod Nemegtosaurus mongoliensis Nowinski (Dinosauria: Saurischia) and comments on Late Cretaceous sauropod diversity. Journal of Systematic Palaeontology 3 (3): 283-318. 10.1017/S1477201905001628.

New Apatosaurus ajax remains from Lakes Quarry, Colorado

An interesting article from Huffington Post:

Apatosaurus Snout Bone, Missing Piece Of Long-Neck Dinosaur, Finally Discovered

A small roadside quarry west of Denver, site of some of the infamous "Bone Wars" of the 19th century, has revealed a new treasure: the snout of the long-necked dinosaur Apatosaurus ajax.

The specimen, nicknamed Kevin, is the first Apatosaurus ajax muzzle ever found, and the discovery is likely to help paleontologists un


derstand how A. ajax is related to other Apatosaurus kin, said Matthew Mossbrucker, the director of the Morrison Natural History Museum in Morrison, Colo., and the paleontologist who first identified the bones.

While a skull of Apatosaurus louisae from Dinosaur National Monument in Utah (CM 11162) has become the basis for most restorations of the head of Apatosaurus, it should be noted the type specimen of Apatosaurus ajax (YPM 1860) includes some cranial remains, as does another A. ajax specimen, YPM 1840 (type of Atlantosaurus immanis). Moreover, a skull of Apatosaurus ajax found in situ with the neck vertebrae (CMC VP 7180) provides more info on the cranial anatomy of this species (Barrett et. al. 2011).

The article then states:

Teeth found in Quarry 5 by Lakes were declared by Marsh in 1884 to belong to Diplodocus lacustris, another long-neck species. But those teeth, now held in Yale's collections, look just like Kevin's. In other words, Diplodocus lacustris didn't exist — instead, Lakes found part of Kevin and missed the rest.

If the type specimen of Diplodocus lacustris is the same individual as the snout found by Matthew Mossbrucker, then YPM 1922 would become the fourth known specimen of Apatosaurus ajax that includes cranial remains. Not a bad idea.

Barrett, P. M., G. W. Storrs, M. T. Young, and L. M. Witmer. 2011. A new skull of Apatosaurus and its taxonomic and palaeobiological implications. Annual Symposium of Vertebrate Palaeontology and Comparative Anatomy, Lyme Regis, UK.

 



Update: The cladistic analysis by Tschopp et al. (2015) fails to recover Atlantosaurus immanis as sister to Apatosaurus ajax to the exclusion of other apatosaurine diplodocids, but it confirms that the braincase labeled YPM 1860 and considered by McIntosh (1995) to be from the same individual as YPM 1840 is apparently from the holotype of A. ajax. Moreover, Tschopp et al. throw cold water on the possibility that the Lakes Quarry 5 apatosaurine premaxilla and maxilla could be from the same individual as Diplodocus lacustris. Until the specimen discussed in the Huffington Post article is described in more detail, YPM 1860 and CMC VP 7180 should be considered the only Apatosaurus ajax specimens that include cranial material.

About the author

Hello all,

My name is Vahe Demirjian and I have been a freelance expert in Mesozoic animals for over 10 years. With universal recognition that birds are not a group separate from reptiles but instead a group of theropod dinosaurs closely aligned with the raptor dinosaurs of Jurassic Park fame, I now tend to view dinosaurs not as terrifying animals but instead one of the surviving groups of Mesozoic animals (just as mammals are merely living derivatives of extinct reptiles like Dimetrodon), having come in a huge variety of shapes, size, habitats, adaptations, et cetera.

I first learned about the names of many extinct dinosaurs when I bought a copy of the book Scholastic Dinosaurs A to Z and my grandpa gave me a copy of David Lambert's book Field Guide to Dinosaurs. The purpose of my blog, however, is to comment on the sauropod dinosaurs, with respect to their taxonomy, biogeography, biology, and discovery. I hope this blog will provide interesting never-before-heard facts about the largest group of extinct dinosaurs that ever lived.