Making sense of ‘lower’ and ‘upper’ stem‐group Euarthropoda, with comments on the strict use of the name Arthropoda von Siebold, 1848

  title={Making sense of ‘lower’ and ‘upper’ stem‐group Euarthropoda, with comments on the strict use of the name Arthropoda von Siebold, 1848},
  author={Javier Ortega‐Hern{\'a}ndez},
  journal={Biological Reviews},
The ever-increasing number of studies that address the origin and evolution of Euarthropoda - whose extant representatives include chelicerates, myriapods, crustaceans and hexapods - are gradually reaching a consensus with regard to the overall phylogenetic relationships of some of the earliest representatives of this phylum. [] Key Result Here, I review the convoluted terminology associated with the classification of stem-group Euarthropoda, and propose a synapomorphy-based distinction that allows 'lower…

Revision of the mollisoniid chelicerate(?) Thelxiope, with a new species from the middle Cambrian Wheeler Formation of Utah

The recent re-interpretation of the Lower Palaeozoic euarthropod group Mollisonia as belonging to Chelicerata has triggered a renewed interest for the poorly known family Mollisoniidae. In this

A new aglaspidid euarthropod with a six-segmented trunk from the Lower Ordovician Fezouata Konservat-Lagerstätte, Morocco

The presence of a pair of postventral plates, widely attached to each other and located under the posterior-most trunk tergite and the base of the tailspine, indicates a phylogenetic relationship with the enigmatic group Aglaspidida.

New opabiniid diversifies the weirdest wonders of the euarthropod stem group

Once considered ‘weird wonders’ of the Cambrian, the emblematic Burgess Shale animals Anomalocaris and Opabinia are now recognized as lower stem-group euarthropods and have provided crucial data for

New multipodomerous appendages of stem-group euarthropods from the Cambrian (Stage 4) Guanshan Konservat-Lagerstätte

Two new euarthropods from the Cambrian Stage 4 Guanshan Biota of South China are reported, with Lihuacaris ferox appendages resembling the frontal appendages of radiodonts, as well as the post-oral endopods of chengjiangocaridid fuxianhuids and other deuteropods with well-documented raptorial/predatory habits.

New opabiniid diversifies the weirdest wonders of the euarthropod lower stem group

The phylogenetic evidence expands opabiniids to multiple Cambrian Stages spanning approximately five million years and underscores the power of treespace visualization for resolving imperfectly preserved fossils and expanding the known diversity and spatiotemporal ranges within the euarthropod lower stem group.

The functional head of the Cambrian radiodontan (stem-group Euarthropoda) Amplectobelua symbrachiata

This study is the first description of appendicular structures other than the frontal appendages in the functional head region of radiodontans, revealing novel feeding structures in the morphological transition from the lower- to the upper- stem-group of Euarthropoda.

Reviewing the bases for a nomenclatural uniformization of the highest taxonomic levels in arthropods

This paper defends the rightful use of Arthropoda and Euarthropoda as key terms in organizing the major branches of the arthropod evolutionary tree and emend EuArthropoda based on the most recent findings in this field.

Ordovician opabiniid-like animals and the role of the proboscis in euarthropod head evolution

Phylogenetic analysis suggests that two specimens of opabiniid-like euarthropods with anterior proboscis from the Middle Ordovician Castle Bank Biota, Wales, UK may be sister to radiodonts and deuteropods, substantially extending the geographic and temporal range of Opabiniidae.

Ancestral morphology of Ecdysozoa constrained by an early Cambrian stem group ecdysozoan

This study suggests acquisition of pharyngeal armature, and therefore a change in feeding strategy, may have characterised the origin and radiation of crown group ecdysozoans from Acosmia -like ancestors.



Specialized appendages in fuxianhuiids and the head organization of early euarthropods

The presence of a pair of specialized post-antennal appendages (SPAs) in the fuxianhuiid head, which attach at either side of the posteriorly directed mouth, behind the hypostome, indicates that antenniform deutocerebral appendages with many podomeres are a plesiomorphic feature of the ancestral euarthropod head.

The “evolution” of Anomalocaris and its classification in the arthropod class Dinocarida (nov.) and order Radiodonta (nov.)

  • D. Collins
  • Environmental Science
    Journal of Paleontology
  • 1996
The remarkable “evolution” of the reconstructions of Anomalocaris, the extraordinary predator from the 515 million year old Middle Cambrian Burgess Shale of British Columbia, reflects the dramatic

Tardigrades as ‘Stem-Group Arthropods’: The Evidence from the Cambrian Fauna

  • G. Budd
  • Geography, Environmental Science
  • 2001
Fossils from the Cambrian period suggest how both the ‘body plans’ of extant phyla were assembled, and also how various ‘minor’ phyla relate to the larger groupings of today such as the arthropods and annelids.

Cambrian Derivatives of the Early Arthropod Stem Lineage, Pentastomids, Tardigrades and Lobopodians An ‘Orsten’ Perspective

‘Orsten’-type preservation is the phosphatisation of cuticular surfaces without any further deformation and has yielded completely three-dimensional fossils, mainly arthropods at scale of 100 μm—2 mm, implying that the ancestry of Arthropoda lies even further back well in the Pre-Cambrian.


The headures of several important taxa, Fuxianhuia, Canadaspis, Odaraia, Chengjiangocaris and Branchiocaris are redescribed, revealing the essential similarity between them, including an anterior sclerite that appears to be a widespread feature of basal arthropods.

Hallucigenia’s onychophoran-like claws and the case for Tactopoda

The results indicate a sister-group relationship between Tardigrada and Euarthropoda, adding palaeontological support to the neurological and musculoskeletal evidence uniting these disparate clades.

The morphology of Opabinia regalis and the reconstruction of the arthropod stem‐group

It is concluded that these three taxa probably form a paraphyletic grouping at the base of the arthropods, and retention of lobopod-like characters within the group provides important documentation of the lobopOD-arthropod transition.

Stem group arthropods from the Lower Cambrian Sirius Passet fauna of North Greenland

  • G. Budd
  • Geography, Environmental Science
  • 1998
Discussion of fossil evidence for the origin and early evolution of the arthropods has been dominated for many years by the evidence from the Middle Cambrian Burgess Shale from British Columbia

The morphology, mode of life, and affinities of Canadaspis perfecta (Crustacea: Phyllocarida), Middle Cambrian, Burgess Shale, British Columbia

The evidence suggests that C. perfecta fed on coarse particles, possibly with the aid of currents set up by the biramous appendages, as the earliest well-preserved crustacean.