Tuzoia

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Extinct genus of arthropod

title: "Tuzoia" type: doc version: 1 created: 2026-02-28 author: "Wikipedia contributors" status: active scope: public tags: ["burgess-shale-fossils", "wheeler-shale", "cambrian-genus-extinctions", "hymenocarina", "fossil-taxa-described-in-1912", "taxa-named-by-charles-doolittle-walcott"] description: "Extinct genus of arthropod" topic_path: "general/burgess-shale-fossils" source: "https://en.wikipedia.org/wiki/Tuzoia" license: "CC BY-SA 4.0" wikipedia_page_id: 0 wikipedia_revision_id: 0

::summary Extinct genus of arthropod ::

| fossil_range = | image = USNM 80478 Tuzoia.jpg | image_caption = Carapace of Tuzoia retifera | image2 = Tuzoia life restoration.jpg | image2_caption = Life restoration | taxon = Tuzoia | authority = Walcott, 1912 | type_species = Tuzoia retifera | type_species_authority = Walcott, 1912 | subdivision_ranks = Species | subdivision = See text

Tuzoia (from Mount Tuzo, a mountain in the Canadian Rockies) is an extinct genus of large bivalved arthropod known from Early to Middle Cambrian marine environments from what is now North America, Australia, China, Europe and Siberia. The large, domed carapace reached lengths of 180 mm, making them amongst the largest known Cambrian arthropods.

Description

::figure[src="https://upload.wikimedia.org/wikipedia/commons/e/eb/Tuzoia_diagram.jpg" caption="Diagrammatic reconstruction"] ::

The largest carapaces of Tuzoia are known to reach 18 cm in length, suggesting a total body length of approximately 23 cm. Along the sides of the carapace a spiked ridge is present, and the edges and midline of the carapace are also spiked in many species. These spines likely functioned to aid stability while swimming. The carapaces are marked with a reticulate (net-like) pattern, which was likely to increase the structural integrity of the valves while remaining lightweight. The head had a anterior/ocular sclerite at the top, a single pair of large stalked eyes, and a pair of segmented antennae. The head also bore pairs of cephalic appendages, which have curved setae. The first two limb pairs, dubbed the "cephalothoracic legs" have 7 podomeres (segments), with spinose endites (structures that project downwards from the limbs), with the legs ending in a terminal claw. The basipods (basalmost segments of the limbs closest to the body) are greatly elongated, and bears 5 to 6 endites, which become spinose at their ends. It is unclear whether exopods (the upper branch of a two branched (biramous) limb) are present on these limbs. There are likely 10 pairs of trunk legs excluding the cephalothoracic legs. These had seven podomeres, the first with a spinose endite, with the limb ending in a terminal claw, and a similarly elongated basipod, which had a spine proximal to that of the first podomere. These limbs likely had paddle-shaped exopods. The body terminates with a large tail fan.

Ecology

Tuzoia was likely an actively swimming organism. It had historically been considered a pelagic organism, due to their wide distribution. However, the soft tissues described in 2022 suggest an alternative interpretation as an animal that swam close to the seafloor (nektobenthic) as a predator or a scavenger. Tuzoia was likely capable of walking along the seafloor with the carpace flexing outwards to allow the legs to contact the substrate.

Taxonomy

They were formerly considered to be the only members of the family Tuzoiidae until 2022, when a new genus Duplapex was described from the Cambrian of China, which differs from Tuzoia by having a flat carapace. Their phylogenetic position was long uncertain due to the lack of soft tissue remains, a close relationship with Isoxys was proposed based on similarities of their carapaces. However soft tissues described in 2022 suggest instead that Tuzoia was a member of Mandibulata, as the earliest diverging member of a paraphyletic Hymenocarina, and that similarities to isoxyids may be due to retained plesiomorphies.

Species

After Vannier et al., 2007, and subsequent literature:

Phylogeny of Hymenocarina after Izquierdo-López and Caron (2024){{clade|{{clade |label1=Hymenocarina |1={{clade |1={{clade |1={{clade |1=Tuzoia [[File:Tuzoia_life_restoration.jpg|70px]] |2=Perspicaris[[File:Perspicaris.png|70px]]}} |2={{clade |1=Pectocaris [[File:Pectocaris_inopinata.png|70px]] |label2=Protocarididae |2={{clade |1=Loricicaris[[File:Loricicaris.png|70px]] |2={{clade |1=Tokummia [[File:Tokummia.png|70px]] |2=Branchiocaris [[File:Branchiocaris.png|70px]] |2={{clade |1={{clade |1={{clade |1=Plenocaris [[File:Plenocaris.png|70px]] |2={{clade |1=Ercaicunia [[File:Ercaicunia_multinodosa_pennetta.png|70px]] |2= Clypecaris[[File:Clypecaris_serrata.png|70px]]}}}} |2={{clade |1=Pauloterminus [[File:Pauloterminus_2.png|70px]] |2={{clade |1=Canadaspis [[File:Canadaspis_perfecta.png|70px]] |2={{clade |1=Waptia [[File:20211025_Waptia_fieldensis.png|70px]] |2=Chuandianella [[File:Chuandianella_life_reconstruction.jpg|70px]] |3={{clade |1=Vermontcaris |label2=Odaraiidae |2={{clade |1=Odaraia [[File:Odaraia.png|70px]] |2={{clade |1=Jugatacaris [[File:Jugatacaris.png|70px]] |2={{clade |1={{clade |1=Fibulacaris [[File:Fibulacaris_nereidis.jpg|70px]] |2=Pakucaris [[File:Pakucaris.png|70px]] |2={{clade |1=Balhuticaris [[File:Balhuticaris.png|70px]] |2=Nereocaris [[File:Nereocaris.png|70px]]

References

References

  1. (2007). "''Tuzoia'': morphology and lifestyle of a large bivalved arthropod of the Cambrian seas". [[Journal of Paleontology]].
  2. Julien Kimmig & Brian R. Pratt. (2015). "Soft-bodied biota from the middle Cambrian (Drumian) Rockslide Formation, Mackenzie Mountains, northwestern Canada". [[Journal of Paleontology]].
  3. (December 2022). "The problematic Cambrian arthropod Tuzoia and the origin of mandibulates revisited". Royal Society Open Science.
  4. (January 2022). "A new bivalved arthropod from the Cambrian (Stage 3) Qingjiang biota expands the palaeogeographical distribution and increases the diversity of Tuzoiidae". Journal of the Geological Society.
  5. Zhao, J. (2015).''The Revision of Tuzoia and Longquania from Early Cambrian Guanshan Biota of Eastern Yunnan, China''. Published Master Degree thesis. China: Northwest University, 56. [in Chinese with English abstract].
  6. (November 2019). "The bivalved arthropod Tuzoia from the Balang Formation (Cambrian Stage 4) of Guizhou, China, and new observations on comparative species". Papers in Palaeontology.
  7. Chen, W. Y., Zhao, Y. L., Yang, X. L., and Wen, R. Q. (2017). Tuzoia Walcott, 1912 from the Cambrian 'Tsinghsutung Formation' of Guzihou, China. ''Acta Palaeontologica Sinica'' 56, 301–311. [in Chinese with English abstract].
  8. (27 August 2025). "Cambrian (Stage 4-Drumian) non-trilobite arthropods from the Murero biota (Spain)". Journal of the Geological Society.
  9. (October 2016). "The first report of the bivalved arthropod Tuzoia from the Skryje–Týřovice Basin (Barrandian area, Czech Republic)". Annales de Paléontologie.
  10. Ivantsov, A. I., Zhuravlev, A. I., Krasilov, V. A., Leguta, A. V., Melnikova, L. M., Urbanek, A., et al. (2005). ''Unique Sinsk Localities of Early Cambrian Organisms (Siberia Platform)''. Moscow: Nauka. Rossiyskaya Akademia Nauk, 143. [in Russian].
  11. (2022). "New Data on the Bivalved Arthropod Tuzoia From the Cambrian (Series 2, Stage 4) Guanshan Biota in Kunming, Yunnan, Southwest China". Frontiers in Earth Science.
  12. (24 July 2024). "The Cambrian ''Odaraia alata'' and the colonization of nektonic suspension-feeding niches by early mandibulates". Proceedings of the Royal Society B.

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