Hallucigenia’s head and the pharyngeal armature of early ecdysozoans

@article{Smith2015HallucigeniasHA,
  title={Hallucigenia’s head and the pharyngeal armature of early ecdysozoans},
  author={Martin R. Smith and Jean‐Bernard Caron},
  journal={Nature},
  year={2015},
  volume={523},
  pages={75-78}
}
The molecularly defined clade Ecdysozoa comprises the panarthropods (Euarthropoda, Onychophora and Tardigrada) and the cycloneuralian worms (Nematoda, Nematomorpha, Priapulida, Loricifera and Kinorhyncha). These disparate phyla are united by their means of moulting, but otherwise share few morphological characters—none of which has a meaningful fossilization potential. As such, the early evolutionary history of the group as a whole is largely uncharted. Here we redescribe the 508-million-year… 
Palaeontology: Hallucigenia's head
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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.
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TLDR
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Discussion on ‘Tabelliscolex (Cricocosmiidae: Palaeoscolecidomorpha) from the early Cambrian Chengjiang Biota and the evolution of seriation in Ecdysozoa’ by Shi et al. 2021 (JGS, jgs2021-060)
Exceptionally preserved fossils are key to reconstructing the origin of the modern animal body plans in the Cambrian radiation. The Panarthropod phyla Euarthropoda, Onychophora and Tardigrada have
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References

SHOWING 1-10 OF 49 REFERENCES
Hallucigenia’s onychophoran-like claws and the case for Tactopoda
TLDR
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 and phylogenetic significance of Kerygmachela kierkegaardi Budd (Buen Formation, Lower Cambrian, N Greenland)
TLDR
It can be demonstrated from the reconstruction of theArthropod stem-group that full arthropod segmentation has a different derivation from that of the annelids, and this suggests that the ‘Articulata’ of Cuvier should be dismantled, and the arthropods considered to be a group of protostomes which are phylogenetically distinct from the classic spiralians.
Onychophoran cephalic nerves and their bearing on our understanding of head segmentation and stem-group evolution of Arthropoda.
TLDR
The model allows the onychophoran cephalic nervous system to be interpreted as a modified circumoral nerve ring, similar to that seen in the nematodes and other cycloneuralians, which is regarded as supporting the Ecdysozoa model of arthropod relationships.
Maotianshan-Shale nemathelminths — Morphology, biology, and the phylogeny of Nemathelminthes
TLDR
It is argued that the loricate Cambrian taxa (the fourth set) are derivatives of the stem lineage of the Loricifera, which implies that minute size, slight bilateralisation, a specific piercing apparatus developed along the evolutionary path of these animals toward life in the interstitial, characterise the crown group.
Pikaia gracilens Walcott, a stem‐group chordate from the Middle Cambrian of British Columbia
TLDR
The Middle Cambrian Pikaia gracilens (Walcott) has an iconic position as a Cambrian chordate, but until now no detailed description has been available and its relationships to both extant and extinct chordates and other deuterostomes are explored.
The brain of Echiniscus viridissimus Peterfi, 1956 (Heterotardigrada): a key to understanding the phylogenetic position of tardigrades and the evolution of the arthropod head
TLDR
The analysis suggests that the brain is derived from nervous elements of four segments with the fourth segment having contributed paired dorsal ganglia and their connecting vertical tracts to the first trunk ganglia of the ventral chain.
New Palaeoscolecidan Worms from the Lower Cambrian: Sirius Passet, Latham Shale and Kinzers Shale
TLDR
These finds from Greenland provide further evidence that palaeoscolecidans possessed a complex anterior introvert directly comparable to a number of priapulid-like taxa from other Burgess Shale-type assemblages.
Nectocaridid ecology, diversity, and affinity: early origin of a cephalopod-like body plan
TLDR
The morphology of the tentacles and fins are revised, and mouthparts and phosphatized gills are described for the first time, and a mathematical analysis supports the presence of the earliest known camera-type eyes, and fluid mechanical considerations suggest that the funnel is optimized for efficient jet propulsion in a low Reynolds number flow regime.
New observations of the lobopod-like worm Facivermis from the early cambrian Chengjiang Lagerstätte
TLDR
The affinities of Facivermis are regarded here as being close to the lobopods, in addition, the lobe-like appendages of FacIVERmis are very crucial to exploring the origin of the appendage of lobopod and arthropods.
New early Cambrian animal and onychophoran affinities of enigmatic metazoans
TLDR
A new 'armoured lobopod' from the Chengjiang fauna is described and shows close affinity with the enigmatic Microdictyon, and soft-part anatomy suggests that the group has affinities with the Burgess Shale 'lobopod', Aysheaia.
...
1
2
3
4
5
...