that its teeth were self-sharpening because they "[wore] against each other as the animal fed." Scientists consider these teeth to be advanced compared to other early sauropodomorphs, as they share features with the sauropods. However, scientists do not consider Yunnanosaurus to be especially close to the sauropods in phylogeny because the remaining portions of the animals body are distinctly "prosauropod" in design. This critical difference implies that the similarity in dentition between Yunnanosaurus and sauropods might be an example of convergent evolution. Classification The type species, Y. huangi, was named by C. C. Young in 1942, who erected the family Yunnanosauridae to contain it, though the family currently comprises only this genus and sometimes Jingshanosaurus. The specific name honours Huang Chiching ("T.K. Huang"), the director of the National Geological Survey of China. Young also named a second species, Y. robustus, in 1951, but this has since been included in the type species. The confusion in classification arose due to that the earliest specimens of Y. huangi were of juvenile individuals while the Y. robustus specimens represented fully grown adults. However, Sekiya et al. (2013) described a juvenile of Y. robustus and were able to differentiate it from Y. huangi. Yunnanosaurus had been assigned to several taxa over the years, including Thecodontosauridae and Plateosauridae, but a more recent phylogenetic analysis conducted by Novas et al. (2011) shows that this genus is part of the taxon Massopoda in a clade with Anchisaurus and Jingshanosaurus. Apaldetti et al. (2011) also found that Yunnanosaurus belonged in Massopoda, but found that this genus was more primitive than both Jingshanosaurus and Anchisaurus. Distinguishing anatomical features A diagnosis is a statement of the anatomical features of an organism (or group) that collectively distinguish it from all other organisms. Some, but not all, of the features in a diagnosis are also autapomorphies. An autapomorphy is a distinctive anatomical feature that is unique to a given organism. Y. huangi According to Barrett et al. (2007), the skull of Y. huangi can be distinguished from other sauropodomorphs based on the following characteristics: a small external naris a robust expanded nasal process of the premaxilla a downward projection from the rear of the maxillary ascending process no nutritive foramina on the lateral surface of maxilla a shallow circular depression on the lateral surface of the ventral lacrimal process a midline boss near the front of the frontals a prominent midline boss