Open Paleo

Unaysauridae

Müller et al., 2018 Type genus Unaysaurus

Its genera lived 227.3–205.7 million years ago Late Triassic
Late Triassic stages

Unaysauridae is a clade of early-branching sauropodomorph dinosaurs from the Late Triassic of Gondwana, erected for the Brazilian Unaysaurus and Macrocollum together with the Indian Jaklapallisaurus. These were small to medium-sized, long-necked bipeds recovered as the sister group to the more derived plateosaurs. Members are united chiefly by a strongly expanded front portion of the inner ankle bone and, where the skull is known, by an extra opening in the upper jaw. Which genera belong is unsettled: later work has added the Indian Pradhania and the Zimbabwean Musango and Musankwa while dropping Jaklapallisaurus, and the grouping's validity has been questioned, since several of its defining traits cannot be confirmed across all its members owing to their incomplete and fragmentary remains, and some analyses instead place Unaysaurus and Macrocollum among the plateosaurids.

Under dispute

Unaysauridae (Unaysaurus, Macrocollum, Jaklapallisaurus) is recovered as a valid clade sister to Plateosauria by Müller and colleagues (2018), but its validity is contested: Beccari and colleagues (2021) instead recover Macrocollum and Unaysaurus at the base of Plateosauridae and note that its diagnostic astragalar and promaxillary characters cannot be confirmed across all members owing to missing material. Membership and position are both unsettled. Ezcurra and colleagues (2023) recovered the clade sister to Plateosauridae but with resampling frequencies below 30%, and Barrett and colleagues (2026) recovered it comprising Unaysaurus, Macrocollum, Pradhania, Musango and Musankwa — excluding Jaklapallisaurus — sitting outside Massopoda in their strict consensus but as the earliest-diverging clade within Massopoda in some of their most-parsimonious trees. Wang and colleagues (2025) did not recover the clade at all, splitting Unaysaurus into Plateosauridae alongside Plateosaurus while grouping Macrocollum with Pradhania and Musankwa at the base of Massopoda.

Diagnosis

  1. Astragalus with a cranially expanded medial condyle (about 1.6 times the craniocaudal length of the lateral condyle)
  2. Promaxillary fenestra present (where the skull is known)
  3. Longitudinal ventral sulcus on the proximal and middle caudal centra

Genera placed directly in Unaysauridae

  • Jaklapallisaurus Novas et al., 2010 Norian (227.3–205.7 Ma)Indiaunder dispute
  • Macrocollum Müller et al., 2018 Norian (227.3–205.7 Ma)Brazil
  • Musango Barrett et al., 2026 Norian (227.3–205.7 Ma)Zimbabweunder dispute
  • Unaysaurus Leal et al., 2004 Norian (227.3–205.7 Ma)Brazil

References

  1. Müller, R. T.; Langer, M. C.; Dias-da-Silva, S. (2018). An exceptionally preserved association of complete dinosaur skeletons reveals the oldest long-necked sauropodomorphs. Biology Letters 14(11): 20180633. The Royal Society. doi:10.1098/rsbl.2018.0633

    Erected Unaysauridae.

    müller2018a
  2. Beccari, V.; Mateus, O.; Wings, O.; Milàn, J.; Clemmensen, L. B. (2021). Issi saaneq gen. et sp. nov.-A New Sauropodomorph Dinosaur from the Late Triassic (Norian) of Jameson Land, Central East Greenland. Diversity 13(11). MDPI AG. doi:10.3390/d13110561

    Questioned the validity of Unaysauridae, citing missing data and fragmentary specimens, and tested it in the analysis describing Issi.

    beccari2021a
  3. Ezcurra, M. D.; Müller, R. T.; Novas, F. E.; Chatterjee, S. (2023). Osteology of the sauropodomorph dinosaur Jaklapallisaurus asymmetricus from the Late Triassic of central India. The Anatomical Record. Wiley. doi:10.1002/ar.25359

    Recovered Unaysauridae sister to Plateosauridae at low resampling support.

    ezcurra2023a
  4. Wang, Y. M.; Zhang, Q. N.; Wang, Y. C.; Xu, H.; Chen, J.; Feng, Z.; Xu, X.; Wang, T.; You, H. L. (2025). A new Early Jurassic dinosaur represents the earliest-diverging and oldest sauropodomorph of East Asia. Scientific Reports 15(1). Springer Science and Business Media LLC. doi:10.1038/s41598-025-12185-2

    Did not recover Unaysauridae, placing Unaysaurus with Plateosaurus.

    wang2025a
  5. Jones, B. (2026). The Princeton Encyclopedia of Dinosaurs: Sauropods. Princeton University Press.

    Reviews Unaysauridae, of Unaysaurus, Macrocollum and Jaklapallisaurus, noting its validity has been questioned and its position relative to Plateosauridae varies.

    jones2026b
  6. Barrett, P. M.; Botha, J.; Sciscio, L.; Stuart, B. P.; Lovegrove, J.; Munyikwa, D.; Zondo, M.; Broderick, T. J.; Edwards, S. F.; Mbambo, E.; Chapelle, K. E. J.; Dollman, K. N.; Tolan, S.; Choiniere, J. N. (2026). A new sauropodomorph dinosaur from the Pebbly Arkose Formation (Upper Triassic: Norian) of Kariba, Zimbabwe. Journal of Systematic Palaeontology 24(2): 2678610. Informa UK Limited. doi:10.1080/14772019.2026.2678610

    Expanded Unaysauridae to include Pradhania, Musango and Musankwa while excluding Jaklapallisaurus.

    barrett2026a