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

@article{Smith2014HallucigeniasOC,
  title={Hallucigenia’s onychophoran-like claws and the case for Tactopoda},
  author={Martin R. Smith and Javier Ortega-Hern{\'a}ndez},
  journal={Nature},
  year={2014},
  volume={514},
  pages={363-366}
}
The Palaeozoic form-taxon Lobopodia encompasses a diverse range of soft-bodied ‘legged worms’ known from exceptional fossil deposits. Although lobopodians occupy a deep phylogenetic position within Panarthropoda, a shortage of derived characters obscures their evolutionary relationships with extant phyla (Onychophora, Tardigrada and Euarthropoda). Here we describe a complex feature in the terminal claws of the mid-Cambrian lobopodian Hallucigenia sparsa—their construction from a stack of… Expand

Figures and Topics from this paper

Hallucigenia’s head and the pharyngeal armature of early ecdysozoans
TLDR
Phylogenetic results indicate that equivalent structures characterized the ancestral panarthropod and, seemingly, the ancestral ecdysozoan, demonstrating the deep homology of panaranthropod and cycloneuralian mouthparts, and providing an anatomical synapomorphy for the ecdy sozoan supergroup. Expand
A superarmored lobopodian from the Cambrian of China and early disparity in the evolution of Onychophora
TLDR
Luolishaniids display the highest degree of limb specialization among Paleozoic lobopodians, constitute more than one-third of the overall morphological disparity of stem group Onychophora, and are substantially more disparate than crown group representatives. Expand
Palaeontology: Hallucigenia's head
TLDR
Data is presented on newly examined 508-million-year-old fossils of Hallucigenia sparsa that at last reveal the head in some detail and provides concrete evidence of structures that might have existed in the last common ancestor of the Ecdysozoa. Expand
A Cambrian fossil from the Chengjiang fauna sharing characters with gilled lobopodians and radiodontans
Background: Lobopodians are worm-like animals with simple legs. Probably representing a grade of organization, rather than an explicit clade, some lobopodians are thought to have given rise to bothExpand
Homology of Head Sclerites in Burgess Shale Euarthropods
The Cambrian fossil record of euarthropods (extant arachnids, myriapods, crustaceans, hexapods) has played a major role in understanding the origins of these successful animals and indicates thatExpand
Origin and evolution of the panarthropod head - A palaeobiological and developmental perspective.
TLDR
The proposed model aims to clarify contentious issues on the evolution of the panarthropod head, and lays the foundation from which to further address this complex subject in the future. Expand
A three-dimensionally preserved lobopodian from the Herefordshire (Silurian) Lagerstätte, UK
TLDR
Thanahita distos joins only seven other known three-dimensionally preserved lobopodian or onychophoran (velvet worm) fossil specimens and is the first lobopODian to be formally described from the Silurian. Expand
Onychophoran-like myoanatomy of the Cambrian gilled lobopodian Pambdelurion whittingtoni
TLDR
It is shown that Pambdelurion's myoanatomy conforms closely to that of extant onychophorans, with unsegmented dorsal, ventral and longitudinal muscle groups in the trunk, and extrinsic and intrinsic muscles controlling the legs. Expand
A Cambrian unarmoured lobopodian, †Lenisambulatrix humboldti gen. et sp. nov., compared with new material of †Diania cactiformis
TLDR
The study augments the morphological diversity of Cambrian lobopodians and presents two evolutionary extremes of cuticular ornamentation: one represented by the Humboldt lobopODian, which was most likely entirely “naked”, the other epitomized by †D. Expand
Onychophoran-like musculature in a phosphatized Cambrian lobopodian
TLDR
This first report of Palaeozoic onychophoranMusculature establishes peripheral musculature as a characteristic of the ancestral panarthropod, but documents an unexpected muscular configuration in a new early Cambrian (Stage 3) lobopodian. Expand
...
1
2
3
4
5
...

References

SHOWING 1-10 OF 44 REFERENCES
Cambrian lobopodians and extant onychophorans provide new insights into early cephalization in Panarthropoda
TLDR
New material of the early Cambrian lobopodian Onychodictyon ferox from southern China is described, which reveals hitherto unknown head structures, including a proboscis with a terminal mouth, an anterior arcuate sclerite, a pair of ocellus-like eyes and branched, antenniform appendages associated with this ocular segment. Expand
CAMBRIAN LOBOPODIANS-ANCESTORS OF EXTANT ONYCHOPHORANS?
TLDR
It is suggested that the lobopodians, phylum Lobopodia, are arranged in two classes, the extinct Xenusia for marine forms, and the Onychophora for terrestrial forms. Expand
The morphology of Opabinia regalis and the reconstruction of the arthropod stem‐group
TLDR
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. Expand
An armoured Cambrian lobopodian from China with arthropod-like appendages
TLDR
D. cactiformis is described as an ‘armoured’ lobopodian from the Chengjiang fossil Lagerstätte (Cambrian Stage 3), Yunnan, southwestern China, remarkable for possessing robust and probably sclerotized appendages, with what appear to be articulated elements. Expand
Morphology and affinities of Eridostracina: Palaeozoic ostracods with moult retention
TLDR
The morphology of the eridostracine Cryptophyllus socialis from the Upper Devonian of Russia is reconstructed using the process of exfoliation of successive exuviae, and it is suggested that the main function of these structures was the strengthening of the connection between the accumulated valves. Expand
Moulting in the lobopodian Onychodictyon from the lower Cambrian of Greenland
A number of lobopodian taxa from the Cambrian display pairs of sclerotized plates symmetrically positioned along the dorsum of the animal, predominantly above the walking appendages. Most genera wereExpand
Beyond the Burgess Shale: Cambrian microfossils track the rise and fall of hallucigeniid lobopodians
TLDR
Hallucigeniids are revealed as an important and widespread component of disparate Cambrian communities from late in the Terreneuvian (Cambrian Stage 2) through the ‘middle’ Cambrian (Series 3); their apparent decline in the latest Cambrian may be partly taphonomic. Expand
A palaeontological solution to the arthropod head problem
TLDR
It is shown that a group of previously problematic Cambrian arthropods from the Burgess Shale and Chengjiang faunas form a clade close to crown-group euarthropods, the group containing myriapods, chelicerates, insects and crustaceans, and two pre-oral appendages. Expand
The morphology and phylogenetic position of the Cambrian lobopodian Diania cactiformis
TLDR
New observations on D. cactiformis are made using newly collected material, rejecting the evidence for sclerotized, segmented and articulated appendages; instead the appendages compare more closely to lobopods. Expand
Tardigrades as ‘Stem-Group Arthropods’: The Evidence from the Cambrian Fauna
TLDR
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. Expand
...
1
2
3
4
5
...