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Therizinosauridae

Maleev, 1954 Type genus Therizinosaurus

Its genera lived 100.5–66.0 million years ago Late Cretaceous
Late Cretaceous stages

Therizinosauridae is a family of large, derived therizinosaur dinosaurs known mainly from the Late Cretaceous of Asia and North America, though footprints and isolated remains suggest the group ranged across much of the Laurasian supercontinent, reaching Europe and Africa. As of 2025 it comprises roughly nine well-supported genera, among them Segnosaurus, Erlikosaurus, Nothronychus, and the giant Therizinosaurus, whose elongated hand claws reached about a meter long, the largest of any known land animal. Despite their theropod ancestry these were herbivores that converged on a body plan resembling that of ground sloths: a wide, rounded belly carried on a broad pelvis, stout four-toed feet with a weight-bearing first digit, a long neck, and a small skull tipped with a keratinous beak and leaf-shaped teeth unlike those of other theropods. Their pelvis was unusually opisthopubic, with the pubis directed backward as in birds and ornithischians, and a nearly avian inner ear gave them acute hearing and balance. They nested in colonies, laying clutches of eggs, and are widely regarded as the theropods most specialized for plant eating.

Under dispute

Which genera Therizinosauridae holds depends on its definition. Zanno and colleagues (2009) define it as the least inclusive clade containing Nothronychus, Segnosaurus, Erlikosaurus and Therizinosaurus, a definition Zanno (2010) and Liao and colleagues (2026) follow; under it Erliansaurus, Neimongosaurus and Enigmosaurus fall outside the family. Kobayashi and colleagues (2022) redefine it as the most inclusive clade containing Therizinosaurus but not Alxasaurus, citing the poor resolution among derived therizinosaurs; that definition draws all three in, and Kobayashi and colleagues (2025) follow it. Analyses that leave the derived therizinosaurs unresolved place some or all of these genera inside even the narrower clade (Pu and colleagues, 2013; Sues and Averianov, 2016).

Diagnosis

  1. Enormously elongated manual unguals, especially on digit I
  2. Wide, barrel-shaped torso accommodating an enlarged herbivorous gut
  3. Small skull with an edentulous premaxilla and leaf-shaped cheek teeth
  4. Opisthopubic (posteriorly directed) pubis
  5. Broad, functionally tetradactyl pes with a weight-bearing first digit

Genera placed directly in Therizinosauridae

  • Duonychus Kobayashi et al., 2025 Cenomanian–Santonian (100.5–83.6 Ma)Mongolia
  • Erlikosaurus Barsbold & Perle, 1980 Turonian–Santonian (93.9–83.6 Ma)Mongolia
  • Nanshiungosaurus Dong, 1979 Campanian–Maastrichtian (83.6–66.0 Ma)China
  • Nothronychus Kirkland & Wolfe, 2001 Turonian (93.9–89.8 Ma)United States
  • Paralitherizinosaurus Kobayashi et al., 2022 Campanian (83.6–72.2 Ma)Japan
  • Segnosaurus Perle, 1979 Cenomanian–Turonian (100.5–89.8 Ma)Mongolia
  • Therizinosaurus Maleev, 1954 Maastrichtian (72.2–66.0 Ma)Mongolia

References

  1. Maleev, E. A. (1954). Noviy cherepachoobrazhniy yashcher v Mongolii [New tortoise-like saurian from Mongolia]. Priroda 1954(3): 106-108. maleev1954a
  2. Zanno, L. E. (2010). A taxonomic and phylogenetic re-evaluation of Therizinosauria (Dinosauria: Maniraptora). Journal of Systematic Palaeontology 8(4): 503-543. doi:10.1080/14772019.2010.488045

    Restated the definition of Zanno and colleagues (2009).

    zanno2010a
  3. Kobayashi, Y.; Takasaki, R.; Fiorillo, A. R.; Chinzorig, T.; Hikida, Y. (2022). New therizinosaurid dinosaur from the marine Osoushinai Formation (Upper Cretaceous, Japan) provides insight for function and evolution of therizinosaur claws. Scientific Reports 12(1). Springer Science and Business Media LLC. doi:10.1038/s41598-022-11063-5

    Proposed a stem-based definition, the most inclusive clade containing Therizinosaurus but not Alxasaurus.

    kobayashi2022a
  4. Zanno, L. E.; Gillette, D. D.; Albright, L. B.; Titus, A. L. (2009). A new North American therizinosaurid and the role of herbivory in 'predatory' dinosaur evolution. Proceedings of the Royal Society B: Biological Sciences 276(1672): 3505-3511. The Royal Society. doi:10.1098/rspb.2009.1029

    Gave the node-based definition of Therizinosauridae, with Nothronychus as an internal specifier.

    zanno2009a
  5. Kobayashi, Y.; Zelenitsky, D. K.; Fiorillo, A. R.; Chinzorig, T. (2025). Didactyl therizinosaur with a preserved keratinous claw from the Late Cretaceous of Mongolia. iScience 28(4). Elsevier BV. doi:10.1016/j.isci.2025.112141

    Followed the stem-based definition of Kobayashi and colleagues (2022).

    kobayashi2025a
  6. Liao, C. C.; Freimuth, W. J.; Zanno, L. E.; Xu, X. (2026). A new therizinosaur from the Early Cretaceous Jehol Biota and ecomorphological patterns among early therizinosaurians. Journal of Systematic Palaeontology 24(2): 2710287. Informa UK Limited. doi:10.1080/14772019.2026.2710287

    Followed the definition of Zanno (2010).

    liao2026a
  7. Pu, H.; Kobayashi, Y.; Lü, J.; Xu, L.; Wu, Y.; Chang, H.; Zhang, J.; Jia, S. (2013). An Unusual Basal Therizinosaur Dinosaur with an Ornithischian Dental Arrangement from Northeastern China. PLoS ONE 8(5): e63423. Public Library of Science (PLoS). doi:10.1371/journal.pone.0063423

    Recovered the derived therizinosaurs, with the intermediate genera, as one unresolved Therizinosauridae.

    pu2013a
  8. Sues, H. D.; Averianov, A. (2016). Therizinosauroidea (Dinosauria: Theropoda) from the Upper Cretaceous of Uzbekistan. Cretaceous Research 59: 155-178. doi:10.1016/j.cretres.2015.11.003

    Recovered the derived therizinosaurs, with the intermediate genera, as one unresolved Therizinosauridae.

    sues2016a