An early chondrichthyan and the evolutionary assembly of a shark body plan

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An early chondrichthyan and the evolutionary assembly of a shark body plan. / Coates, Michael; Finarelli, John; Sansom, Ivan; Andreev, Plamen; Criswell, Katherine; Tietjen, Kristen; Rivers, Mark; La Riviere, Patrick.

In: Royal Society of London. Proceedings B. Biological Sciences, Vol. 285, No. 1870, 20172418, 10.01.2018.

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Coates, Michael ; Finarelli, John ; Sansom, Ivan ; Andreev, Plamen ; Criswell, Katherine ; Tietjen, Kristen ; Rivers, Mark ; La Riviere, Patrick. / An early chondrichthyan and the evolutionary assembly of a shark body plan. In: Royal Society of London. Proceedings B. Biological Sciences. 2018 ; Vol. 285, No. 1870.

Bibtex

@article{9e52e40ef40f4e0ca30f11b7baf6ecaa,
title = "An early chondrichthyan and the evolutionary assembly of a shark body plan",
abstract = "Although relationships among the major groups of living gnathostomes are well established, the relatedness of early jawed vertebrates to modern clades is intensely debated. Here, we provide a new description of Gladbachus, a Middle Devonian (Givetian ~385-million-year-old) stem chondrichthyan from Germany, and one of the very few early chondrichthyans in which substantial portions of the endoskeleton are preserved. Tomographic and histological techniques reveal new details of the gill skeleton, hyoid arch and jaws, neurocranium, cartilage, scales and teeth. Despite many features resembling placoderm or osteichthyan conditions, phylogenetic analysis confirms Gladbachus as a stem chondrichthyan and corroborates hypotheses that all acanthodians are stem chondrichthyans. The unfamiliar character combination displayed by Gladbachus, alongside conditions observed in acanthodians, implies that pre-Devonian stem-chondrichthyans are severely under-sampled and strongly supports indications from isolated scales that the gnathostome crown group originated at the latest by the early Silurian (~440 mya). Moreover, phylogenetic results highlight the likely convergent evolution of conventional chondrichthyan conditions among earliest members of this primary gnathostome division, while skeletal morphology points towards the likely suspension feeding habits of Gladbachus, suggesting a functional origin of the gill slit condition characteristic of the vast majority of living and fossil chondrichthyans.",
keywords = "chondrichthyes , gill skeleton , scales , Middle Devonian , gnathostome phylogeny, computed tomography",
author = "Michael Coates and John Finarelli and Ivan Sansom and Plamen Andreev and Katherine Criswell and Kristen Tietjen and Mark Rivers and {La Riviere}, Patrick",
year = "2018",
month = jan,
day = "10",
doi = "10.1098/rspb.2017.2418",
language = "English",
volume = "285",
journal = "Royal Society of London. Proceedings B. Biological Sciences",
issn = "0962-8452",
publisher = "The Royal Society",
number = "1870",

}

RIS

TY - JOUR

T1 - An early chondrichthyan and the evolutionary assembly of a shark body plan

AU - Coates, Michael

AU - Finarelli, John

AU - Sansom, Ivan

AU - Andreev, Plamen

AU - Criswell, Katherine

AU - Tietjen, Kristen

AU - Rivers, Mark

AU - La Riviere, Patrick

PY - 2018/1/10

Y1 - 2018/1/10

N2 - Although relationships among the major groups of living gnathostomes are well established, the relatedness of early jawed vertebrates to modern clades is intensely debated. Here, we provide a new description of Gladbachus, a Middle Devonian (Givetian ~385-million-year-old) stem chondrichthyan from Germany, and one of the very few early chondrichthyans in which substantial portions of the endoskeleton are preserved. Tomographic and histological techniques reveal new details of the gill skeleton, hyoid arch and jaws, neurocranium, cartilage, scales and teeth. Despite many features resembling placoderm or osteichthyan conditions, phylogenetic analysis confirms Gladbachus as a stem chondrichthyan and corroborates hypotheses that all acanthodians are stem chondrichthyans. The unfamiliar character combination displayed by Gladbachus, alongside conditions observed in acanthodians, implies that pre-Devonian stem-chondrichthyans are severely under-sampled and strongly supports indications from isolated scales that the gnathostome crown group originated at the latest by the early Silurian (~440 mya). Moreover, phylogenetic results highlight the likely convergent evolution of conventional chondrichthyan conditions among earliest members of this primary gnathostome division, while skeletal morphology points towards the likely suspension feeding habits of Gladbachus, suggesting a functional origin of the gill slit condition characteristic of the vast majority of living and fossil chondrichthyans.

AB - Although relationships among the major groups of living gnathostomes are well established, the relatedness of early jawed vertebrates to modern clades is intensely debated. Here, we provide a new description of Gladbachus, a Middle Devonian (Givetian ~385-million-year-old) stem chondrichthyan from Germany, and one of the very few early chondrichthyans in which substantial portions of the endoskeleton are preserved. Tomographic and histological techniques reveal new details of the gill skeleton, hyoid arch and jaws, neurocranium, cartilage, scales and teeth. Despite many features resembling placoderm or osteichthyan conditions, phylogenetic analysis confirms Gladbachus as a stem chondrichthyan and corroborates hypotheses that all acanthodians are stem chondrichthyans. The unfamiliar character combination displayed by Gladbachus, alongside conditions observed in acanthodians, implies that pre-Devonian stem-chondrichthyans are severely under-sampled and strongly supports indications from isolated scales that the gnathostome crown group originated at the latest by the early Silurian (~440 mya). Moreover, phylogenetic results highlight the likely convergent evolution of conventional chondrichthyan conditions among earliest members of this primary gnathostome division, while skeletal morphology points towards the likely suspension feeding habits of Gladbachus, suggesting a functional origin of the gill slit condition characteristic of the vast majority of living and fossil chondrichthyans.

KW - chondrichthyes

KW - gill skeleton

KW - scales

KW - Middle Devonian

KW - gnathostome phylogeny

KW - computed tomography

U2 - 10.1098/rspb.2017.2418

DO - 10.1098/rspb.2017.2418

M3 - Article

VL - 285

JO - Royal Society of London. Proceedings B. Biological Sciences

JF - Royal Society of London. Proceedings B. Biological Sciences

SN - 0962-8452

IS - 1870

M1 - 20172418

ER -