Habeliida is an order of extinct arthropods that existed during the middle Cambrian. They are thought to be some of the oldest members of the chelicerate lineage.
Description
Members of Habeliida are characterized by a numbers of features. These include: bulging head shields, which have notches to accommodate a pair of compound eyes, and triangular extensions outward to the sides. Attached to the head are 5 pairs of segmented, thin upper antennae-like exopods (upper limb branches), along with a reduced first appendage at least in Habelia, followed by 5 pairs of seven-segmented spined endopod (lower branch) grasping appendages, which are attached to basal segments (basipods), that increase in size posteriorly and are gnathobasic, that is modified to have inward-facing spines. Along the body run limbs with paddle-shaped exopods which are fringed by narrow lamellae. The body ends with a telson, which is either elongate and spine like (Habelia) or paddle-shaped (Sanctacarididae).[1]
Ecology
Habeliids were likely predatory, using the upper exopod head appendages as sensory organs, while using the lower spined head endopods to grasp prey. They are thought to have been durophagous, with the robust gnathobases (spined basal sections of limbs) used to shred hard-shelled organisms. Remains of trilobites have been found as stomach contents in Wisangocaris.[1]
Taxonomy
It is divided into two families, Habeliidae (monotypic, containing only Habelia), and Sanctacarididae (containing Sanctacaris, Utahcaris and Wisangocaris)[1] Messorocaris has been suggested to be part of the order in some studies, but this is uncertain.[2] They are suggested to be stem-group chelicerates, though they lack the chelicerae present in true chelicerates.[3] They may be the ancestral group from which modern chelicerates emerged:[4]
Cladogram after O’Flynn et al, 2023:[5]
| Total group Arthropoda |
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Cladogram after Lerosey-Aubril and Ortega-Hernández (2026):[4]
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References
- 1 2 3 Aria, Cédric; Caron, Jean-Bernard (21 Dec 2017). "Mandibulate convergence in an armoured Cambrian stem chelicerate". BMC Evolutionary Biology. 17 (1): 261. Bibcode:2017BMCEE..17..261A. doi:10.1186/s12862-017-1088-7. ISSN 1471-2148. PMC 5738823. PMID 29262772.
- ↑ Lerosey-Aubril, Rudy; Kimmig, Julien; Pates, Stephen; Skabelund, Jacob; Weug, Andries; Ortega-Hernández, Javier (November 2020). Zhang, Xi-Guang (ed.). "New exceptionally preserved panarthropods from the Drumian Wheeler Konservat-Lagerstätte of the House Range of Utah". Papers in Palaeontology. 6 (4): 501–531. Bibcode:2020PPal....6..501L. doi:10.1002/spp2.1307. ISSN 2056-2799.
- ↑ Aria, Cédric (Oct 2022). "The origin and early evolution of arthropods". Biological Reviews. 97 (5): 1786–1809. doi:10.1111/brv.12864. ISSN 1464-7931. PMID 35475316.
- 1 2 Lerosey-Aubril, Rudy; Ortega-Hernández, Javier (2026-04-01). "A chelicera-bearing arthropod reveals the Cambrian origin of chelicerates". Nature: 1–7. doi:10.1038/s41586-026-10284-2. ISSN 1476-4687.
- ↑ O’Flynn, Robert J.; Liu, Yu; Hou, Xianguang; Mai, Huijuan; Yu, Mengxiao; Zhuang, Songling; Williams, Mark; Guo, Jin; Edgecombe, Gregory D. (August 2023). "The early Cambrian Kylinxia zhangi and evolution of the arthropod head". Current Biology. 33 (18): 4006–4013.e2. Bibcode:2023CBio...33E4006O. doi:10.1016/j.cub.2023.08.022. hdl:10141/623137. ISSN 0960-9822. PMID 37643622.