Conciliterga

Conciliterga Temporal range: Cambrian Stage 3–Wuliuan PreꞒ Ꞓ O S D C P T J K Pg N
Diagrammatic reconstruction of Tegopelte
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Arthropoda
(unranked):	†Artiopoda
Subphylum:	†Trilobitomorpha
Subclass:	†Conciliterga Hou & Bergström, 1997[1]
Type species
†Helmetia expansa Walcott, 1918
Genera
†Tegopelte †Helmetia †Saperion †Skioldia †Rhombicalvaria †Haifengella †Kuamaia †Kwanyinaspis?

Conciliterga is an extinct order of artiopod arthropods, exclusively known from the Middle Cambrian. They are placed within the clade Trilobitomorpha, which contains the trilobites and their closest relatives.[2]

Holotype of Helmetia expansa

Conciliterga is united by their partially or wholly fused tergites, which gives rise to their name (Conciliterga is composed of the Latin words concilio ("to unite") and tergum ("back")). Most members of this clade are elliptical in body shape, with 6-9 thoracic tergites, a head shield and a large tail shield in the members with incomplete tergite fusion. These members, which formerly comprised the order Helmetiida (which currently only contains Helmetia, Rhombicalvaria and Kuamaia),[3] also have various other characteristics like a lack of axial region, rostral and pararostral plates on the head, and compound eyes near the rostral plate. In addition, they have essentially uniform biramous limbs running down the body with coarse endopods, alongside a pair of antennae. A second clade is also observed, containing Tegopelte, Saperion and Skioldia.[3] This clade is characterised by wholly fused tergites (although Skioldia still shows traces of their outlines, and so is likely more basal), alongside more ventral eyes. Haifengella, while appearing very helmetiid-like, has been recovered as the basalmost concilitergan,[4] suggesting the Tegopelte-like clade is especially derived. Kwanyinaspis's inclusion within Conciliterga is unclear, as while many studies place it near Aglaspidida, a 2010 study found it as a stem-concilitergan instead.[3] However a 2022 study instead recovered it as the closest relative to trilobites.[4] Members of Conciliterga are known from only a few locations around the world, mainly the Maotianshan Shales and Burgess Shale.

References

1. Xianguang, Hou; Bergström, Jan (22 December 1997). "Arthropods of the Lower Cambrian Chengjiang fauna, southwest China". Fossils and Strata. 45: 1–117. doi:10.18261/8200376931-1997-01.
2. Du, Kun‐sheng; Ortega‐Hernández, Javier; Yang, Jie; Zhang, Xi‐guang (June 2019). "A soft‐bodied euarthropod from the early Cambrian Xiaoshiba Lagerstätte of China supports a new clade of basal artiopodans with dorsal ecdysial sutures". Cladistics. 35 (3): 269–281. doi:10.1111/cla.12344. ISSN 0748-3007.
3. Paterson, John R.; Edgecombe, Gregory D.; GarcíA‐Bellido, Diego C.; Jago, James B.; Gehling, James G. (March 2010). "Nektaspid arthropods from the Lower Cambrian Emu Bay Shale Lagerstätte, South Australia, with a reassessment of lamellipedian relationships". Palaeontology. 53 (2): 377–402. doi:10.1111/j.1475-4983.2010.00932.x.
4. Jiao, De-Guang; Du, Kun-Sheng; Zhang, Xi-Guang; Yang, Jie; Eggink, Daniel (May 2022). "A new small soft-bodied non-trilobite artiopod from the Cambrian Stage 4 Guanshan Biota". Geological Magazine. 159 (5): 730–734. doi:10.1017/S0016756821001254.