Massopoda

Reconstruction of Massospondylus carinatus, copyright Saberrex.

Belongs within: Sauropodomorpha.
Contains: Sauropoda.

The anchisaurs: near-lizards or near-sauropods?
Published 15 October 2012
Reconstruction of Anchisaurus polyzelus by Brian Franczak.

The ‘prosauropods’ are one group of dinosaurs that seemingly don’t get no respect. While most other groups have their swarms of enthusiasts, there are relatively few inclined to shout their enthusiasm for non-sauropod sauropodomorphs from the roof-tops. Pop culture has a tendency to gloss them over: in the 1990s TV series Walking with Dinosaurs, for instance, their appearance was limited to a brief cameo at the end of the first episode. Despite this, they are perhaps the most ‘dinosaur-y’ of all dinosaurs, if comparisons with generic ‘dinosaur’ depictions are to be made.

The name ‘Anchisauria’ was introduced by Galton & Upchurch (2004) for the most exclusive clade uniting the genera Anchisaurus and Melanorosaurus. Galton & Upchurch were working under the framework that prosauropods formed a monophyletic sister group to the sauropods, but subsequent phylogenetic analyses have placed sauropods close to Melanorosaurus and hence within Anchisauria (Yates 2010; Yates et al. 2010; Pol et al. 2011). The name ‘Anchisauria’ can be translated as ‘near lizards’, but they are more properly near sauropods. Still, because this is to be a prosauropod-centred post, I will ignore the sauropods from this point on unless they insist on pushing their way in (presumably not a difficult task for a sauropod).

Reconstruction of Aardonyx celestae by Julius Csotonyi.

The two anchoring genera remain the most consistent non-sauropod members of the clade. The South American Riojasaurus, placed within Melanorosauridae by Galton & Upchurch (2004), has subsequently been placed outside Anchisauria. The Argentinian Lessemsaurus was also treated by those authors as a melanorosaurid, but may be a basal sauropod proper, while the status of the English Camelotia needs more work (Pol et al. 2011 were unable to resolve its position between Anchisauria and its close relatives). The Chinese Yunnanosaurus was placed within Anchisauria by Yates (2010), but other analyses have disagreed. Two recent genera, Aardonyx Yates et al. 2010 and Leonerasaurus Pol et al. 2011 are currently regarded as anchisaurians.

Mounted skeleton of Leonerasaurus taquetrensis, from here. Note that a large part of this skeleton is evidently reconstructed, as the described skeleton is much more fragmentary.

Anchisaurus polyzelus, from the early Jurassic of Connecticut, reached about four metres in length and is represented by the remains of a number of individuals. Some of these have been described as separate species such as Ammosaurus major and Yaleosaurus colurus, but Yates (2010) regarded them as representing a single species. This makes the ‘2.5 m’ estimate of length given for this species by Galton & Upchurch (2004) too small, as based on a potential juvenile. Nevertheless, it was evidently such a good number that the fossil record apparently decided not to let it pass: the Argentinian anchisaur Leonerasaurus taquetrensis is about that size. The South African Aardonyx celestae was about twice the size of Anchisaurus.

Reconstruction of Melanorosaurus readi, by Steveoc 86. Note that the four species illustrated in this post have been placed in order of increasing proximity to Sauropoda, as resolved by Pol et al. (2011).

Melanorosaurus readi was quite a bit larger, close to eight metres, and phylogenetic analyses have accordingly placed it as the closest relative to sauropods. Interestingly, M. readi was nevertheless quite a bit earlier than the other non-sauropod anchisaurs, being late Triassic rather than early Jurassic, and the smaller anchisaurs evidently survived the evolution of their larger cousins by some time. As well as its larger size, M. readi resembled sauropods in being an obligate quadruped. The other anchisaurs retained their plesiomorphic bipedality; the forelimbs of Aardonyx indicate that it was probably unable to adopt a comfortably quadrupedal stance (being unable to pronate its hands to a great degree, it would have had to rest them on their sides if it tried to do so). Pol et al. (2011) placed Leonerasaurus closer to the sauropods and Melanorosaurus than either Anchisaurus or Aardonyx, but the distal part of its forelimbs are unfortunately unknown.

Systematics of Massopoda
Massopoda [Anchisauria]BM21
    |  i. s.: IngentiaBM21
    |--Sarahsaurus aurifontanalisBM21
    `--+--+--XingxiulongBM21
       |  `--+--LeonerasaurusBM21
       |     |--Mussaurus Bonaparte & Vince 1979BM21, GU04
       |     |    `--M. patagonicus Bonaparte & Vince 1979GU04
       |     |--AnchisauridaeGU04
       |     |    |--Clepsysaurus pennsylvanicus Lea 1851M96
       |     |    |--Ammosaurus Marsh 1891GU04
       |     |    |    `--A. major (Marsh 1889) [=Anchisaurus major; incl. An. solus Marsh 1892]GU04
       |     |    `--Anchisaurus Marsh 1885BM21, GU04 (see below for synonymy)
       |     |         `--*A. polyzelus (Hitchcock 1865)Y03 (see below for synonymy)
       |     `--+--SefapanosaurusBM21
       |        |--MeroktenosBM21
       |        |--Aardonyx celestaeBM21, BNB17
       |        `--+--SauropodaBM21
       |           `--MelanorosauridaeGU04
       |                |--Melanorosaurus Haughton 1924BM21, GU04
       |                |    |--M. readi Haughton 1924GU04
       |                |    `--M. thabanensis Gauffre 1993GU04
       |                `--+--Camelotia Galton 1985GU04
       |                   |    `--C. borealis Galton 1985GU04
       |                   `--Lessemsaurus Bonaparte 1999GU04
       |                        `--L. sauropoides Bonaparte 1999GU04
       `--+--+--Yunnanosaurus Young 1942BM21, GU04 [Yunnanosauridae]
          |  |    `--Y. huangi Young 1942 [incl. Y. robustus Young 1951]GU04
          |  `--+--SeitaadBM21
          |     `--Jingshanosaurus Zhang & Yang 1995BM21, GU04
          |          `--J. xinwaensis Zhang & Yang 1995GU04
          `--+--+--+--Leyesaurus marayensisNS15, BNB17
             |  |  `--Adeopapposaurus mognaiNS15, P10
             |  `--Massospondylus Owen 1854BM21, GU04 [Massospondylidae]
             |       |--M. browni Seeley 1895 (n. d.)GU04
             |       |--M. carinatus Owen 1854GU04 [=Plateosaurus carinatusP10]
             |       |--M. harriesi Broom 1911 (n. d.)GU04
             |       |--M. hislopi Lydekker 1890 (n. d.)GU04
             |       |--M. kaalaeBM21
             |       `--M. schwarzi Haughton 1924 (n. d.)GU04
             `--+--GlacialisaurusBM21
                |--Coloradisaurus Lambert 1983BM21, GU04 [incl. Coloradia Bonaparte 1978GU04]
                |    `--C. brevis (Bonaparte 1978)GU04 [=*Coloradia brevisB78]
                `--+--Lufengosaurus Young 1941BM21, GU04
                   |    |--L. changhduensisD07
                   |    `--L. huenei Young 1941GU04 (see below for synonymy)
                   `--GyposaurusGU04
                        |--G. capensis Broom 1911 (n. d.)GU04
                        `--G. sinensis Young 1941GU04 [=Anchisaurus capensisN85]

Anchisaurus Marsh 1885BM21, GU04 [=Amphisaurus Marsh 1882 (preoc.)GU04, Megadactylus Hitchcock 1865 (preoc.)GU04, Yaleosaurus Huene 1932GU04]

*Anchisaurus polyzelus (Hitchcock 1865)Y03 [=Megadactylus polyzelusGU04; incl. A. colurus Marsh 1891GU04, Yaleosaurus colurusN85]

Lufengosaurus huenei Young 1941GU04 [=Massospondylus hueneiP10, Plateosaurus hueneiP10; incl. L. magnus Young 1947GU04]

*Type species of generic name indicated

References

[BNB17] Baron, M. G., D. B. Norman & P. M. Barrett. 2017. A new hypothesis of dinosaur relationships and early dinosaur evolution. Nature 543: 501–506.

[BM21] Beccari, V., O. Mateus, O. Wings, J. Milàn & L. B. Clemmensen. 2021. Issi saaneq gen. et sp. nov.—a new sauropodomorph dinosaur from the Late Triassic (Norian) of Jameson Land, central east Greenland. Diversity 13: 561.

[B78] Bonaparte, J. F. 1978. Coloradia brevis n. g. et n. sp. (Saurischia, Prosauropoda), dinosaurio Plateosauridae de la Formacion Los Colorados, Triasico superior de La Rioja, Argentina. Ameghiniana 15 (3–4): 327–332.

[D07] Dixon, D. 2007. The Complete Illustrated Encyclopedia of Dinosaurs & Prehistoric Creatures. Hermes House: London.

[GU04] Galton, P. M., & P. Upchurch. 2004. Prosauropoda. In: Weishampel, D. B., P. Dodson & H. Osmólska (eds) The Dinosauria 2nd ed. pp. 232–258. University of California Press: Berkeley.

[M96] Marsh, O. C. 1896. The Dinosaurs of North America: Washington.

[N85] Norman, D. 1985. The Illustrated Encyclopedia of Dinosaurs. Salamander Books: London.

[NS15] Novas, F. E., L. Salgado, M. Suárez, F. L. Agnolin, M. D. Ezcurra, N. R. Chimento, R. de la Cruz, M. P. Isasi, A. O. Vargas & D. Rubilar-Rogers. 2015. An enigmatic plant-eating theropod from the Late Jurassic period of Chile. Nature 522: 331–334.

[P10] Paul, G. S. 2010. Dinosaurs: A Field Guide. A & C Black.

Pol, D., A. Garrido & I. A. Cerda. 2011. A new sauropodomorph dinosaur from the Early Jurassic of Patagonia and the origin and evolution of the sauropod-type sacrum. PLoS One 6 (1): e14572.

[Y03] Yates, A. M. 2003. A new species of the primitive dinosaur Thecodontosaurus (Saurischia: Sauropodomorpha) and its implications for the systematics of early dinosaurs. Journal of Systematic Palaeontology 1: 1–42.

Yates, A. M. 2010. A revision of the problematic sauropodomorph dinosaurs from Manchester, Connecticut and the status of Anchisaurus Marsh. Palaeontology 53 (4): 739–752.

Yates, A. M., M. F. Bonnan, J. Neveling, A. Chinsamy & M. G. Blackbeard. 2010. A new transitional sauropodomorph dinosaur from the Early Jurassic of South Africa and the evolution of sauropod feeding and quadrupedalism. Proceedings of the Royal Society of London Series B—Biological Sciences 277: 787–794.

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