Biology:Habeliida

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

External video

Animated 3D model of Habelia moving its gnathobases

Animated turntable rotation of 3D model of Habelia

Diagrammatic reconstruction of Habelia. Key g=gnathobase en=endopod, ex=exopod cx = head exopod e1-5 = head endopods

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), with 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).

Ecology

Restoration of Wisangocaris feeding on trilobites, as inferred from stomach contents

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.

Taxonomy

It is divided into two families, Habeliidae (monotypic, containing only Habelia), and Sanctacarididae (containing Sanctacaris, Utahcaris and Wisangocaris) Messorocaris has been suggested to be part of the order in some studies, but this is uncertain. They are suggested to be stem-group chelicerates, though they lack the chelicerae present in true chelicerates. They may be the ancestral group from which modern chelicerates emerged:

Cladogram after O’Flynn et al, 2023:

Total group Arthropoda

"Gilled lobopodians" (Pambdelurion, Kerygmachela)100px       Opabinia 100px       Radiodonta (e.g Anomalocaris) 100 px   Deuteropoda     Kylinxia 100px     Fengzhengia 100px           Kiisortoqia 100px     Bushizheia 100px         Megacheira 100 px       Habeliida 100px       Mollisonia 100px     Chelicerata (horseshoe crabs, sea spiders, arachnids, etc) 100px               "Great appendage bivalved forms" (Occacaris, Forfexicaris)     Isoxyida 100 px         Artiopoda (including Trilobita) 100 px   Mandibulata   Fuxianhuiida 100 px       Myriapoda (millipedes, centipedes, etc) 100px       Hymenocarina 100px     Pancrustacea (crustaceans, insects, etc)

Cladogram after Lerosey-Aubril and Ortega-Hernández (2026):

Pan‑Chelicerata     †Jianfengia 100px     †Sklerolibyon 100px   Megacheira       †Fortiforceps 100px     †Yohoia 100px       †Haikoucaris 100px     †Leanchoiliidae 100px         †Mollisoniida 100px       †Wisangocaris 100px Habeliida     †Habelia 100px       †Sanctacaris 100px     †Utahcaris     chelicerae present   †Megachelicerax 100px       †Offacolus 100px         †Setapedites 100px     †Dibasterium 100px         †Weinbergina 100px       †Venustulus 100px       Pycnogonida (sea spiders) 100px       Xiphosura (horseshoe crabs) 100px       Arachnida 100px     †Eurypterida (sea scorpions) 70px

References

Wikidata ☰ Q124047958 entry