Elpistostege and the origin of the vertebrate hand

@article{Cloutier2020ElpistostegeAT,
  title={Elpistostege and the origin of the vertebrate hand},
  author={Richard Cloutier and Alice M. Clement and Michael S. Y. Lee and Roxanne No{\"e}l and Isabelle B{\'e}chard and Vincent Roy and John A. Long},
  journal={Nature},
  year={2020},
  volume={579},
  pages={549 - 554}
}
The evolution of fishes to tetrapods (four-limbed vertebrates) was one of the most important transformations in vertebrate evolution. Hypotheses of tetrapod origins rely heavily on the anatomy of a few tetrapod-like fish fossils from the Middle and Late Devonian period (393–359 million years ago)1. These taxa—known as elpistostegalians—include Panderichthys2, Elpistostege3,4 and Tiktaalik1,5, none of which has yet revealed the complete skeletal anatomy of the pectoral fin. Here we report a 1.57… 
A new elpistostegalian from the Late Devonian of the Canadian Arctic.
TLDR
A new elpistostegalian from the Late Devonian period of the Canadian Arctic that shows surprising disparity in the group, and shows specializations for swimming that are unlike those known from other sarcopterygians.
Brain Reconstruction Across the Fish-Tetrapod Transition; Insights From Modern Amphibians
TLDR
It is shown that anurans and caecilians appear to have brains that fill their endocasts to a similar degree to that of lungfishes and salamanders, but not coelacanth, and the telencephalon is tightly fitted within the endocast in all four taxa.
Morphology of Palaeospondylus shows affinity to tetrapod ancestors.
Palaeospondylus gunni, from the Middle Devonian period, is one of the most enigmatic fossil vertebrates, and its phylogenetic position has remained unclear since its discovery in Scotland in 1890
The Evolution of the Spiracular Region From Jawless Fishes to Tetrapods
TLDR
The first confirmed example of a complete spiracular gill in any vertebrate is presented, in the galeaspid (jawless stem gnathostome) Shuyu, and comparisons with two other groups of jawless stem Gnathostomes indicate that they also probably possessed full-sized Spiracular gills and that this condition may thus be primitive for the gnathOSTome stem group.
Development of the Pectoral Lobed Fin in the Australian Lungfish Neoceratodus forsteri
TLDR
This study suggests that the acquisition of embryonic mesenchyme at the junction between the axial body wall and the appendicular bud opened the door to the formation of the brachial plexus and the specialization of individual muscles in the lineage that gave rise to tetrapods.
Sarcopterygian fin ontogeny elucidates the origin of hands with digits
TLDR
These developmental patterns indicate that the digit program originated in postaxial fin radials and later expanded anteriorly inside of a preexisting autopod-like domain during the evolution of limbs, which supports the significance of classical models proposing a bending of the tetrapod metapterygial axis.
Mandibular musculature constrains brain–endocast disparity between sarcopterygians
TLDR
The results show that regions of lowest brain–endocast disparity are associated with regions of bony reinforcement directly adjacent to masticatory musculature for the mandible except in Neoceratodus and Latimeria, where there is less reinforcement away from high mandibular muscle mass.
Conserved Mechanisms, Novel Anatomies: The Developmental Basis of Fin Evolution and the Origin of Limbs
TLDR
This review presents historical hypotheses regarding paired fin evolution and limb origins, summarizes key aspects of central appendage patterning mechanisms in model and non-model species, addresses how modern comparative developmental data interface with the authors' understanding of appendage anatomy, and highlights new approaches that promise to provide new insight into these well-traveled questions.
A fresh look at Cladarosymblema narrienense, a tetrapodomorph fish (Sarcopterygii: Megalichthyidae) from the Carboniferous of Australia, illuminated via X-ray tomography
TLDR
The first full, virtual cranial endocast of any tetrapodomorph fish is presented, giving insight into the early neural adaptations in this group, and further work is required to resolve megalichthyid interrelationships.
Sustained high rates of morphological evolution during the rise of tetrapods.
TLDR
It is shown that combining osteological and ichnological calibration data results in major shifts on the time of origin of all major groups of tetrapodomorphs (up to 25 million years) and that low rates of net diversification, not fossilization, explain long ghost lineages in the early tetrapdomorph fossil record.
...
...

References

SHOWING 1-10 OF 55 REFERENCES
The pectoral fin of Panderichthys and the origin of digits
TLDR
A CT scan study of an undisturbed pectoral fin of Panderichthys is presented demonstrating that the plate-like ‘ulnare’ of previous reconstructions is an artefact and that distal radials are in fact present and makes a strong case for fingers not being a novelty of tetrapods but derived from pre-existing distal Radials present in all sarcopterygian fish.
Ancestry of the Tetrapods
DURING the last few decades it has become increasingly clear that theTetrapods were derived from a group of fishes having their closest affinities with the Devonian Crossopterygii and Dipnoi. In
The origin of vertebrate limbs.
  • M. Coates
  • Biology
    Development (Cambridge, England). Supplement
  • 1994
TLDR
A composite framework of several phylogenetic hypotheses is presented incorporating living and fossil taxa, including the first report of an acanthodian metapterygium and a new reconstruction of the axial skeleton and caudal fin of Acanthostega gunnari, indicating further directions for comparative experimental research.
A Devonian tetrapod-like fish and the evolution of the tetrapod body plan
TLDR
The discovery of a well-preserved species of fossil sarcopterygian fish from the Late Devonian of Arctic Canada that represents an intermediate between fish with fins and tetrapods with limbs, and provides unique insights into how and in what order important tetrapod characters arose is reported.
A Devonian tetrapod-like fish reveals substantial parallelism in stem tetrapod evolution
TLDR
A large, lobe-finned fish from the Late Devonian of China disrupts previously accepted stem-tetrapod phylogeny and reveals parallel evolution within the lineage, suggesting that ecological diversity and biogeographical provinciality in the tetrapod stem group have been underestimated.
Tetrapod-like middle ear architecture in a Devonian fish
TLDR
It is shown that the spiracular region is radically transformed from osteolepiforms and represents the earliest stages in the origin of the tetrapod middle ear architecture, suggesting that the middle ear of early tetrapods evolved initially as part of a spiracular breathing apparatus.
Pectoral girdle and fin anatomy of Gogonasus andrewsae long, 1985: Implications for tetrapodomorph limb evolution
TLDR
A phylogenetic analysis indicates a more stemward position for Gogonasus in a weakly supported clade with other “osteolepidid” taxa, compared to other recent studies placing Gog onasus crownward of osteolespidid fishes and the Tristichopteridae, as the sister taxon to the “Elpistosteglia” + Tetrapoda.
The postcranial skeleton of the Devonian tetrapod Tulerpeton curtum Lebedev
TLDR
A cladistic analysis indicates that Tulerpeton is a reptiliomorph stem-group amniote and the earliest known crown-group tetrapod: Acanthostega and Ichthyostega are successively more derived plesion stem- group tetrapods and do not consititute a monophyletic ichthyostegalian radiation.
The pelvic fin and girdle of Panderichthys and the origin of tetrapod locomotion
TLDR
The evolution of tetrapod locomotion appears to have passed through a stage of body-flexion propulsion, in which the pelvic fins played a relatively minor anchoring part, before the emergence of hindlimb-powered propulsion in the interval between Panderichthys and Acanthostega.
Elginerpeton pancheni and the earliest tetrapod clade
TLDR
Elginerpeton, described here on the basis of cranial remains from Scat Craig, is, together with the fragmentary genus Obruchevichthys from the Upper Frasnian of Latvia and Russia, the oldest known stem tetrapod.
...
...