Conciliterga is an extinct order of artiopod arthropods, exclusively known from the

Middle Cambrian Middle or The Middle may refer to: * Centre (geometry), the point equally distant from the outer limits. Places * Middle (sheading), a subdivision of the Isle of Man * Middle Bay (disambiguation) * Middle Brook (disambiguation) * Middle Creek (di ...

. They are placed within the clade

Trilobitomorpha Artiopoda is a clade of extinct arthropods that includes trilobites and their close relatives. It was erected by Hou and Bergström in 1997 to encompass a wide diversity of arthropods that would traditionally have been assigned to the Trilobitomor ...

, which contains the

trilobites Trilobites (; meaning "three-lobed entities") are extinct marine arthropods that form the class Trilobita. One of the earliest groups of arthropods to appear in the fossil record, trilobites were among the most successful of all early animals, ...

and their closest relatives. Conciliterga is united by their partially or wholly fused

tergite A ''tergum'' (Latin for "the back"; : ''terga'', associated adjective tergal) is the Anatomical terms of location#Dorsal and ventral, dorsal ('upper') portion of an arthropod segment other than the head. The Anatomical terms of location#Anterior ...

s, 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 ''Helmetia'' is an extinct genus of arthropod from the middle Cambrian (Wuliuan). Fossils of the type species ''Helmetia expansa'' have been found in the Burgess Shale of Canada. It is characterized by a pair of spines in front of its head. It is ...

'', '' Rhombicalvaria'' and '' Kuamaia''), 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''. 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, suggesting the ''Tegopelte''-like clade is especially derived. '' Kwanyinaspiss inclusion within Conciliterga is unclear, as while many studies place it near

Aglaspidida Aglaspidida is an extinct order of marine arthropods known from fossils spanning the Middle Cambrian to the Upper Ordovician. Initially considered chelicerates, modern anatomical comparisons demonstrate that the aglaspidids cannot be accommodated ...

, a 2010 study found it as a stem-concilitergan instead. However a 2022 study instead recovered it as the closest relative to

trilobite Trilobites (; meaning "three-lobed entities") are extinction, extinct marine arthropods that form the class (biology), class Trilobita. One of the earliest groups of arthropods to appear in the fossil record, trilobites were among the most succ ...

s. Members of Conciliterga are known from only a few locations around the world, mainly the

Maotianshan Shales The Maotianshan Shales () are a series of Early Cambrian sedimentary deposits in the Chiungchussu Formation or Heilinpu Formation, famous for their '' Konservat Lagerstätten'', deposits known for the exceptional preservation of fossilized orga ...

and

Burgess Shale The Burgess Shale is a fossil-bearing deposit exposed in the Canadian Rockies of British Columbia, Canada. It is famous for the exceptional preservation of the soft parts of its fossils. At old (middle Cambrian), it is one of the earliest fos ...

. Another paper published by Losso et al. 2025, which re-analyzed ''Helmetia'', erected two new families within the conciliterga, the Helmetiidae and the Tegopeltidae. Losso et al. 2025 also resolved the taxonomic relationships of '' Arthroaspis'', an artiopod from the

Sirius Passet Sirius Passet is a Cambrian Lagerstätte in Peary Land, Greenland. The Sirius Passet Lagerstätte was named after the Slædepatruljen Sirius, Sirius sledge patrol that operates in North Greenland. It comprises six places in Nansen Land, on the eas ...

locality in northern

Greenland Greenland is an autonomous territory in the Danish Realm, Kingdom of Denmark. It is by far the largest geographically of three constituent parts of the kingdom; the other two are metropolitan Denmark and the Faroe Islands. Citizens of Greenlan ...

, placing it as an early diverging taxon within the conciliterga. Cladogram after Losso et al. 2025:

References

{{Artiopoda Artiopoda Miaolingian extinctions Fossil taxa described in 1997 Cambrian arthropods