Several subdivisions within the group are recognised including Jianfengiidae (including
Fortiforceps,
Jianfengia,
Sklerolibyon and possibly
Parapeytoia) which are known from the Early Cambrian of China, as well as the Cheiromorpha (containing at least
Yohoia,
Haikoucaris, and Leanchoiliidae), known with certainty from the Early-Mid Cambrian of North America, China and Australia, which is distinguished from Jianfengiidae by having a fewer number of body segments (20+ in Jianfengiidae, as compared to typically only 11 to 13 in Cheiromorpha). The
monophyly of Megacheira is uncertain, with some studies recovering the group as
paraphyletic.
Parapeytoia from the Cambrian of China which was formerly misinterpreted as a
radiodont was later suggested to be a member of this group. Possible megacheirans include
Enalikter described from the
Silurian of the
United Kingdom, and
Bundenbachiellus from the Early
Devonian of
Germany; due to their possession of great appendage-like cephalic appendages. However, their relationship to megacheirans has been questioned, due to the uncertain
homology of their appendages.
Kootenichela has been suggested to be a
chimera of various arthropod taxa. The Late Cambrian
Orsten taxon
Oelandocaris typically considered to be a crustacean relative, has also been suggested in some studies to be a megacheiran.
List of genera • †
Tanglangia • †
Oelandocaris? • †Jianfengiidae •
Sklerolibyon •
Jianfengia •
Parapeytoia? •
Fortiforceps • †Kootenichelidae? •
Kootenichela? •
Worthenella? •
Pseudoiulia? • †Cheiromorpha •
Yohoia •
Haikoucaris • Leanchoiliida •
Enaliktidae? •
Enalikter? •
Bundenbachiellus? • Leanchoiliidae •
Actaeus •
Alalcomenaeus •
Leanchoilia •
Oestokerkus •
Yawunik •
Kanoshoia •
Lomankus Relationship to other arthropods Megacheirans are either suggested to be stem-group
chelicerates (the group containing
arachnids,
sea spiders and
horseshoe crabs, among other extinct groups) or stem-group arthropods outside the split between Chelicerata and the other major group of living arthropods,
Mandibulata (which includes
crustaceans,
insects,
centipedes and
millipedes, among others). alongside neuroanatomy and the presence of a reduced
labrum resembling those of modern chelicerates. The proponents of this hypothesis argue that chelicerae and the great appendages are homologous structures. Other studies suggest that the megacheirans are stem-group arthropods based on the argument that the great appendages are homologous to the frontal appendages of stem-group arthropods like
Isoxys and
radiodonts. This identity is disputed, with other authors suggesting that the frontal appendages of radiodonts are homologous to the labrum of modern arthropods. Cladogram of Arthropoda after Aria et al. 2020, showing megacheirans (as indicated by the orange bar) as a paraphyletic stem group to modern arthropods:supplemental material }}}}}}}}}} }}}}}}}} }} }}}}}} }} }}}}}}}}}}}}}}}}}}|style=font-size:85%}}Placement of megacheirans (represented by orange bar) as a paraphyletic assemblage at the base of total-group Chelicerata, after Lerosey-Aubril and Ortega-Hernández (2026): }} }} }}}}}}}}}}}}}}}}}}}}}}}}}}|style=font-size:85%}} ==References==