Thursday, May 29, 2014

McPhee et al. (2014) paper on Antetonitrus, part 2: is Thotobolosaurus a relative of Antetonitrus?

In part 1 of my review of the McPhee et al. (2014) paper on the osteology of the basal sauropod Antetonitrus, I discussed the definition of Sauropodiformes and Sauropoda within in the context of the analysis by McPhee et al. (2014) regarding Antetonitrus. However, one overlooked aspect of the paper that didn't make anyone notice it was the discussion of the possible affinity of the Maphutseng sauropodomorph (aka "Thotobolosaurus") with Antetonitrus on page 157 of the paper.

The Maphutseng sauropodomorph, like the Proctor Lake hypsilophodont and the Dalton Wells quarry iguanodont, has been occasionally mentioned in the literature but has been only briefly described. It was first reported by Ellenberger and Ellenberger (1956) based on sauropodomorph remains pertaining to a minimum of six individuals collected from from the Late Triassic lower Elliot Formation of Maphutseng, Lesotho in the 1950s. The Maphutseng taxon was discussed by Charig et al. (1965), Ellenberger (1970), and Ellenberger & Ginsburg (1966), who noted its affinities with sauropods relative to other "prosauropods"; Ellenberger (1970) coined the nomen nudum "Thotobolosaurus mabeatae" for the Maphutseng sauropodomorph in his discussion of the fossil record of southern Africa for the Triassic-early Jurassic interval, but never described it in detail. Gauffre (1993) preliminarily re-assessed the Maphutseng sauropodomorph and tentatively referred it to the nomen dubium Euskelosaurus browni, but he later (1996) changed his mind about the attribution of this taxon and described it as a distinct sauropodomorph under the nomen ex dissertationae "Kholumolumosaurus ellenbergerorum".

CO 1069-209-59

The remains of "Thotobolosaurus"/"Kholumolumosaurus" being excavated in Maphutseng, Lesotho.

Note: Since this post was published, it has become clear (Peyre de Fabregues and Allain 2016) that Antetonitrus is not from the lower Elliot Formation as previously thought, but instead from the upper Elliot Formation, meaning that the Maphutseng sauropodomorph is clearly not congeneric with Antetonitrus

Charig, A.J., Attridge, J.& Crompton, A.W. 1965.On the origin of the sauropods and the classification of the Saurischia. Proceedings of the Linnean Society 176: 197–221.

Ellenberger, F., and Ellenberger, P. 1956. Le gisement de Dinosauriens de Maphutseng (Basutoland, Afrique du Sud) [The Maphutseng dinosaur locality (Basutoland, South Africa)]. Comptes Rendus de la Société géologique de France 1956:99-101.

F. Ellenberger and L. Ginsburg. 1966. Le gisement de Dinosauriens triasiques de Maphutseng (Basutoland) et l'origine des Sauropodes [The Triassic dinosaur locality of Maphutseng (Basutoland) and the origin of sauropods]. Comptes Rendus de l'Académie des Sciences à Paris, Série D 262:444-447.

Ellenberger, P.. 1970. Les niveaux paléontologiques de première apparition des mammifères primoridaux en Afrique du Sud et leur ichnologie. Establissement de zones stratigraphiques detaillees dans le Stormberg du Lesotho (Afrique du Sud) (Trias Supérieur à Jurassique) [The paleontological levels of the first appearance of primordial mammals in southern Africa and their ichnology. Establishment of detailed stratigraphic zones in the Stormberg of Lesotho (southern Africa) (Upper Triassic to Jurassic). In: S. H. Haughton (ed.), Second Symposium on Gondwana Stratigraphy and Paleontology, International Union of Geological Sciences. Council for Scientific and Industrial Research, Pretoria 343-370.

F.-X. Gauffre. 1993. Biochronostratigraphy of the lower Elliot Formation (southern Africa) and preliminary results on the Maphutseng dinosaur (Saurischia: Prosauropoda) from the same formation of Lesotho. In S. G. Lucas and M. Morales (eds.), The Nonmarine Triassic. New Mexico Museum of Natural History and Science Bulletin 3:147-149.

Gauffre, F. -X., 1996. Phylogenie des dinosaures prosauropodes et etude d’un prosauropode du Trias superieur d’Afrique australe. PhD thesis. Museum National d’Histoire Naturelle, Paris. 156 pp.

Peyre de Fabrègues, C., and Allain, R., 2016. New material and revision of Melanorosaurus thabanensis, a basal sauropodomorph from the Upper Triassic of Lesotho. PeerJ 4: e1639. doi:10.7717/peerj.1639.


Wednesday, May 7, 2014

McPhee et al. (2014) paper on Antetonitrus, part 1: definition of Sauropodiformes

In a paper describing the anatomy of the primitive Triassic sauropod Antetonitrus ingenipes, McPhee et al. (2014) define the clade Sauropodiformes as including all sauropodomorphs more closely related to Sauropoda than to Massospondylus or Plateosaurus, and they slightly retreat from the original systematic placement of Antetonitrus in Sauropoda by treating it as a sauropodiform close to, if not, part of Sauropoda. However, while McPhee et al. summarize the importance of Antetonitrus in highlighting the transition from the sturdy massospondylids and plateosaurids to the bulky and massive sauropods, the use of the definition of Sauropoda sensu Salgado et al. (1997) by the authors should be taken with a grain of salt.

With respect to the cladistic analysis of Sauropod by McPhee et al. (2014), exclusion of Antetonitrus and Lessemsaurus from Sauropoda would render the sauropod clade Gravisauria Allain and Aquesbi, 2008 synonymous with the definition of Sauropoda sensu Salgado et al. (1997). However, Otero and Pol (2013) treat Antetonitrus, Blikanasaurus, and Lessemsaurus as sauropods under the definition of Sauropoda articulated by Allain and Aquesbi (2008), so it makes sense to retain the sauropod classification of Antetonitrus to avoid creating tiresome phylogenetic clade names in future cladistic analyses of basal sauropods because the Early Jurassic sauropodiform Aardonyx is more primitive than the only other non-sauropod sauropodiform clade from southern Africa, Melanorosauridae.

Irrespective of definition of Sauropoda offered by either McPhee et al. (2014) or Allain and Aquesbi (2008), I have decided to straddle the fence and treat Antetonitrus as a true sauropod just for the sake of phylogenetic accuracy and robustness.   

Allain, R. and Aquesbi, N., 2008. Anatomy and phylogenetic relationships of Tazoudasaurus naimi (Dinosauria, Sauropoda) from the late Early Jurassic of Morocco. Geodiversitas 30(2): 345-424.

McPhee, B. W., Yates, A. M., Choiniere, J. N. and Abdala, F., 2014. The complete anatomy and phylogenetic relationships of Antetonitrus ingenipes (Sauropodiformes, Dinosauria): implications for the origins of Sauropoda. Zoological Journal of the Linnean Society, 171: 151–205. doi: 10.1111/zoj.12127

Otero, A.; Pol, D., 2013. Postcranial anatomy and phylogenetic relationships ofMussaurus patagonicus (Dinosauria, Sauropodomorpha). Journal of Vertebrate Paleontology 33 (5): 1138-1168. doi:10.1080/02724634.2013.769444. edit