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.2018 Jan 10;285(1870):20172418.
doi: 10.1098/rspb.2017.2418.

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

Affiliations

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

Michael I Coates et al. Proc Biol Sci..

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 ofGladbachus, a Middle Devonian (Givetian approx. 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 confirmsGladbachus as a stem chondrichthyan and corroborates hypotheses that all acanthodians are stem chondrichthyans. The unfamiliar character combination displayed byGladbachus, 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 (approx. 440 Ma). 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 ofGladbachus, suggesting a functional origin of the gill slit condition characteristic of the vast majority of living and fossil chondrichthyans.

Keywords: Chondrichthyes; Middle Devonian; gill skeleton; gnathostomes; jaws; scales.

© 2018 The Author(s).

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Conflict of interest statement

The authors declare no competing interests.

Figures

Figure 1.
Figure 1.
Gladbachus adentatus Heidtke & Krätschmer [31]. (a) Rendering of cranial and pectoral girdle remains in dorsal view and (b) ventral view; (c) mandibular tooth; (d) cranial roof scale; (e) branchial denticle; (f) trunk scale. All denticles and scales are rendered semi-transparent from micro-computed tomography scans. bhy, basihyal; chy, ceratohyal; hb, hypobranchial; mc, Meckel's cartilage; na, neural arches; nc, neurocranium; or, orbital ring; pop, postorbital process; pq, palatoquadrate; sco, scapulocoracoid.
Figure 2.
Figure 2.
Gladbachus adentatus Heidtke & Krätschmer [31]. (a) Palatoquadrate; (b) Meckel's cartilage; (c) jaws, hyoid arch and gill arches restored, dorsal view; (d) gills reconstructed ventral view; (e) reconstruction of articulated mandibular arch, left lateral view. adf, adductor fossa; bhy, basihyal; cbr, ceratobranchial; chy, ceratohyal; cop, copula; ebr, epibranchial; end, endolymphatic duct; fm/oc, foramen magnum/occipital cotylus; gl, glenoid; hb, hypobranchial; hy, hyomandibula; mp, mesial process; opr, otic process; pbr, pharyngobranchial; pop, postorbital process; ppr, palatine process; pq, palatoquadrate; q, quadrate condyle, unmineralized site of; ssc, semicircular canal network; ocf, otico-occipital fissure.
Figure 3.
Figure 3.
Phylogenetic placement ofGladbachus adentatus Heidtke & Krätschmer [31]. (a) parts (i) and (ii) join at arrowheads. Strict consensus, complete tree. (b) Strict consensus of chondrichthyan total-group obtained from reduced taxon set; arrowhead joins arrowhead of (a) part (i). Branch colours: black, stem-group gnathostomes; green, Osteichthyes; magenta, acanthodid stem Chondrichthyes; red, non-acanthodid stem Chondrichthyes; purple, Holocephali (crown Chondrichthyes); blue, Elasmobranchii (crown Chondrichthyes). Circles mark nodes with bootstrap support greater than 50% and/or decay values greater than 1; filled circles mark nodes with bootstrap support greater than 75% and/or decay values greater than 3. (c) Phenetic results: PCO 1 (18.1% explained variance) is plotted on the vertical axis and PCO 2 (9.6%) is plotted on the horizontal axis. (d) PCO 1 (vertical) versus PCO 3 on the horizontal axis (8.1%). Details of the PCO analysis are presented in the electronic supplementary material. The four traditionally named groups (placoderms in purple, acanthodians in green, chondrichthyans in blue, osteichthyans in red) cluster in distinct non-overlapping regions on the first three PCO dimensions. Relevant stem chondrichthyan taxa are indicated in each plot.
Figure 4.
Figure 4.
Early chondrichthyan phylogeny: simplified strict consensus of phylogenetic analysis results calibrated against Ordovician–Carboniferous chronostratigraphic chart. Consensus computed from matrix with 86 taxa and 262 characters. Taxon bar colour: black, non-chondrichthyan; magenta, acanthodid stem chondrichthyan; red, non-acanthodid stem chondrichthyan; purple, holocephalan crown chondrichthyan; blue, elasmobranch crown chondrichthyan. Bar length corresponds to earliest occurrence stage duration. Brown bar signifies the total range of chondrichthyan-like scale-based taxon. Timescale (Ma) from Cohenet al. [59]. Complete cladogram shown in figure 3a.
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References

    1. Zangerl R. 1981. Chondrichthyes I. In Handbook of paleoichthyology 3A (ed. Schultze H-P.), 115 p New York, NY: Gustav Fischer Verlag.
    1. Janvier P. 1996. Early vertebrates. Oxford, UK: Oxford: University Press.
    1. Stahl BJ. 1999. Chondrichthyes III. In Holocephali. Handbook of paleoichthyology 4 (ed. Schultze H-P.), 164 p München, Germany: Verlag Dr. Friedrich Pfeil.
    1. Miller RF, Cloutier R, Turner S. 2003. The oldest articulated chondrichthyan from the Early Devonian period. Nature 425, 501–504. (10.1038/nature02001) - DOI - PubMed
    1. Maisey JG, Miller R, Turner S. 2009. The braincase of the chondrichthyan Doliodus from the Lower Devonian Campbellton Formation of New Brunswick, Canada. Acta Zool.-Stockholm Suppl. 90, 109–122. (10.111/j.1463-6395.2008.00330.x) - DOI

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