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. 2012;7(11):e49911.
doi: 10.1371/journal.pone.0049911. Epub 2012 Nov 27.

The giant cretaceous Coelacanth (Actinistia, Sarcopterygii) Megalocoelacanthus dobiei Schwimmer, Stewart & Williams, 1994, and its bearing on Latimerioidei interrelationships

Hugo Dutel  1 , John G Maisey, David R Schwimmer, Philippe Janvier, Marc Herbin, Gaël Clément
Affiliations

The giant cretaceous Coelacanth (Actinistia, Sarcopterygii) Megalocoelacanthus dobiei Schwimmer, Stewart & Williams, 1994, and its bearing on Latimerioidei interrelationships

Hugo Dutel et al. PLoS One. 2012.

Abstract

We present a redescription of Megalocoelacanthus dobiei, a giant fossil coelacanth from Upper Cretaceous strata of North America. Megalocoelacanthus has been previously described on the basis of composite material that consisted of isolated elements. Consequently, many aspects of its anatomy have remained unknown as well as its phylogenetic relationships with other coelacanths. Previous studies have suggested that Megalocoelacanthus is closer to Latimeria and Macropoma than to Mawsonia. However, this assumption was based only on the overall similarity of few anatomical features, rather than on a phylogenetic character analysis. A new, and outstandingly preserved specimen from the Niobrara Formation in Kansas allows the detailed description of the skull of Megalocoelacanthus and elucidation of its phylogenetic relationships with other coelacanths. Although strongly flattened, the skull and jaws are well preserved and show many derived features that are shared with Latimeriidae such as Latimeria, Macropoma and Libys. Notably, the parietonasal shield is narrow and flanked by very large, continuous vacuities forming the supraorbital sensory line canal. Such an unusual morphology is also known in Libys. Some other features of Megalocoelacanthus, such as its large size and the absence of teeth are shared with the mawsoniid genera Mawsonia and Axelrodichthys. Our cladistic analysis supports the sister-group relationship of Megalocoelacanthus and Libys within Latimeriidae. This topology suggests that toothless, large-sized coelacanths evolved independently in both Latimeriidae and Mawsoniidae during the Mesozoic. Based on previous topologies and on ours, we then review the high-level taxonomy of Latimerioidei and propose new systematic phylogenetic definitions.

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Conflict of interest statement

Competing Interests: The authors have declared that no competing interests exist.

Figures

Figure 1
Figure 1. Geological context of Megalocoelacanthus dobiei Schwimmer, Stewart & Williams, 1994.
Left, white star indicates the geographic location of the locality of AMNH FF 20267 in the Niobrara chalk of Lane County Kansas, USA (modified from http://www.kgs.ku.edu/General/Geology/County/klm/lane.html). Right, stratigraphic correlation chart between the principal stratigraphic units from North America (taken from [1]). The Niobrara Formation in Lane County, Kansas, is correlated with the Blufftown, Mooreville, and Eutaw Formations in Alabama and Georgia, where the first occurrences of Megalocoelacanthus were reported.
Figure 2
Figure 2. Megalocoelacanthus dobiei Schwimmer, Stewart & Williams, 1994, AMNH FF 20267 from lower Campanian of the Niobrara Formation.
Ethmosphenoid portion of the skull in right lateral view. Abbreviations: ant.com.so.s.c, anterior commissure of supraorbital sensory line canal; ant.pr, antotic process; a.w.Par, ascending wing of parasphenoid; Bsph, basisphenoid; bucc.can, buccal canal; gr.j.v, groove for jugular vein; L.e, lateral ethmoid; L.r, lateral rostral; Na, nasal; Pa.a, anterior parietal; Pa.p, posterior parietal; Par, parasphenoid; pi, pillar; pr.con, processus connectens; sph.c, sphenoid condyle; So, supraorbital series; so.s.c, supraorbital sensory line canal; v.l.fo, ventrolateral fossa; ?v.pr.Pa, ventral (descending) process of the parietal. Scale bar  = 10 cm.
Figure 3
Figure 3. Megalocoelacanthus dobiei Schwimmer, Stewart & Williams, 1994, AMNH FF 20267 from lower Campanian of the Niobrara Formation.
Ethmosphenoid portion of the skull in left lateral view. Abbreviations: ant.pr, antotic process; a.w.Par, ascending wing of parasphenoid; Bsph, basisphenoid; bucc.can, buccal canal; f.v.nas-b.can, foramen for ventral branch of naso-basal canal; gr.j.v, groove for jugular vein; io.s.c, infraorbital sensory line canal; L.e, lateral ethmoid; L.r, lateral rostral; Na, nasal; nos.a, anterior nostril; nos.p, posterior nostril; Pa.p, posterior parietal; Par, parasphenoid; pi, pillar; pr.con, processus connectens; sph.c, sphenoid condyle; So, supraorbital series; so.s.c, supraorbital sensory line canal; v.l.fo, ventrolateral fossa; v.pr.L.r, ventral (descending) process of the lateral rostral; ?v.pr.Pa, ventral (descending) process of the parietal. Scale bar  = 10 cm.
Figure 4
Figure 4. Megalocoelacanthus dobiei Schwimmer, Stewart & Williams, 1994, AMNH FF 20267 from lower Campanian of the Niobrara Formation. Isolated snout.
A, right anterolateral view; B, posterior view. Abbreviations: ant.ros, anterior opening for the rostral organ; c.nos.a, canal for the anterior nostril; d.l.Pmx, dorsal lamina of the premaxilla; f.a.n.c, anterior foramen of the nasal capsule; L.r, lateral rostral; m.p.s.c, median pore for the sensory line canal; n.c, nasal capsule; nos.a, anterior nostril; Pmx, premaxilla. Scale bar  = 1 cm.
Figure 5
Figure 5. Megalocoelacanthus dobiei Schwimmer, Stewart & Williams, 1994, AMNH FF 20267 from lower Campanian of the Niobrara Formation.
Otoccipital portion of the skull in right lateral view. Abbreviations: Ext.l, lateral extrascapular; ?f.o.a, foramen for the orbitonasal artery; ot.s.c, otic sensory line canal; ot.s.c.m, medial branch of the otic sensory line canal; ot.sh, otic shelf; pi, pilar; Pp, postparietal; Pro, prootic; Stt, supratemporal; Stt.com, supratemporal commissure; v.pr.Stt, ventral (descending) process of the supratemporal. Scale bar  = 10 cm.
Figure 6
Figure 6. Megalocoelacanthus dobiei Schwimmer, Stewart & Williams, 1994, AMNH FF 20267 from lower Campanian of the Niobrara Formation.
Otoccipital portion of the skull in right medial view. Abbreviations: Ext.l, lateral extrascapular; ot.sh, otic shelf; Pp, postparietal; Pro, prootic; Stt, supratemporal; v.pr.Pp, ventral (descending) process of the postparietal; v.pr.Stt, ventral (descending) process of the supratemporal. Scale bar  = 10 cm.
Figure 7
Figure 7. Megalocoelacanthus dobiei Schwimmer, Stewart & Williams, 1994, AMNH FF 20267 from lower Campanian of the Niobrara Formation.
Otoccipital portion of the skull in left lateral view. Abbreviations: Ext.l, lateral extrascapular; ot.s.c, otic sensory line canal; ot.s.c.m, medial branch of the otic sensory line canal; ot.sh, otic shelf; pi, pillar; Pp, postparietal; Pp.a.d, anterior depression of the postparietal; Pro, prootic; Stt, supratemporal; Stt.com, supratemporal commissure; v.pr.Stt, ventral (descending) process of the supratemporal. Scale bar  = 10 cm.
Figure 8
Figure 8. Megalocoelacanthus dobiei Schwimmer, Stewart & Williams, 1994, AMNH FF 20267 from lower Campanian of the Niobrara Formation.
Otoccipital portion of the skull in left medial view. Abbreviations: Ext.l, lateral extrascapular; ot.sh, otic shelf; Pp, postparietal; Pro, prootic; v.pr.Pp, ventral (descending) process of the postparietal. Scale bar  = 10 cm.
Figure 9
Figure 9. Megalocoelacanthus dobiei Schwimmer, Stewart & Williams, 1994, holotype specimen CCK 88-2-1 from lower Campanian of the Blufftown Formation.
Isolated basisphenoid. A, right lateral view; B, posterior view; C, anterior view; D, dorsal view. Abbreviations: ant.pr, antotic process; d.s, dorsum sellae; gr.j.v, groove for jugular vein; n.p, notochordal pit; o.v.pr.Pa, overlapping surface for descending process of parietal; pit.fos?, pituitary fossa; pr.con, processus connectens; sph.c, sphenoid condyle; spt.fos?, suprapterygoid fossa. Scale bar  = 5 cm.
Figure 10
Figure 10. Megalocoelacanthus dobiei Schwimmer, Stewart & Williams, 1994, AMNH FF 20267 from lower Campanian of the Niobrara Formation.
A, anterior catazygal. B, posterior catazygal.
Figure 11
Figure 11. Megalocoelacanthus dobiei Schwimmer, Stewart & Williams, 1994, AMNH FF 20267 from lower Campanian of the Niobrara Formation.
Palate bones. A, right palatoquadrate in lateral (top) and medial (bottom) views. B, parasphenoid in ventral view. C, right (top) and left (bottom) autopalatines in lateral (left) and medial (right) views. Abbreviations: art.ant.pr, surface for articulation with the antotic process; Bsph, basisphenoid; Mpt, metapterygoid; n.p, notochordal pit; Par, parasphenoid; pr.con, processus connectens; Pt, pterygoid; Q, quadrate; t.Par, toothed area of parasphenoid; v.sw.Pt, ventral swelling of pterygoid. Scale bar  = 5 cm.
Figure 12
Figure 12. Megalocoelacanthus dobiei Schwimmer, Stewart & Williams, 1994, AMNH FF 20267 from lower Campanian of the Niobrara Formation.
Right lower jaw. A, lateral view. B, medial view. Abbreviations: Ang, angular; art.Q, surface for articulation with the quadrate; Co, coronoids; co.pr.Ang, coronoid process of the angular; De, dentary; d.p, enlarged sensory pore within the dentary; f.pop.s.c, opening for the preopercular sensory line canal; f.V.m, foramen for the mandibular ramus of the trigeminal nerve; f.VII.m.ext, foramen for the external mandibular ramus of the facial nerve; f.VII.m.int, foramen for the internal mandibular ramus of the facial nerve; i.add.md, insertion point for the adductor mandibulae muscle; i.art-hy.lig, insertion point for the articular-hyomandibular ligament; i.surf-a.intermd, insertion surface for the anterior ramus of intermandibular muscle; Mm, mentomeckelian; m.s.c, mandibular sensory line canal; Part, prearticular; Rart, retroarticular; ?sop.br, subopercular branch of the preopercular canal; Spl, splenial. Scale bar  = 10 cm.
Figure 13
Figure 13. Megalocoelacanthus dobiei Schwimmer, Stewart & Williams, 1994, AMNH FF 20267 from lower Campanian of the Niobrara Formation.
Left lower jaw. A, lateral view. B, medial view. Abbreviations: Ang, angular; art.Q, surface for articulation with the quadrate; co.pr.Ang, coronoid process of the angular; De, dentary; d.p, enlarged sensory pore within the dentary; f.pop.s.c, opening for the preopercular sensory line canal; f.V.m, foramen for the mandibular ramus of the trigeminal nerve; f.VII.m.ext, foramen for the external mandibular ramus of the facial nerve; gr.VII.m.int, groove for the internal mandibular ramus of the facial nerve; i.add.md, insertion point for the adductor mandibulae muscle; i.art-hy.lig, insertion point for the articular-hyomandibular ligament; i.surf-a.intermd, insertion surface for the anterior ramus of intermandibular muscle; Mm, mentomeckelian; m.s.c, mandibular sensory line canal; Rart, retroarticular; ?sop.br, subopercular branch of the preopercular canal; Spl, splenial. Scale bar  = 10 cm.
Figure 14
Figure 14. Megalocoelacanthus dobiei Schwimmer, Stewart & Williams, 1994, AMNH FF 20267 from lower Campanian of the Niobrara Formation.
A, left principal coronoid in lateral (left) and medial (right) views. B, articulars of the left (top) and right (bottom) lower jaws. Scale bar  = 2 cm. C, gular plates in external (left) and internal (right) views. Abbreviation: i.rd.intermed: insertion ridge for the intermandibular muscle. Scale bar  = 10 cm. Arrows oriented anteriorly.
Figure 15
Figure 15. Megalocoelacanthus dobiei Schwimmer, Stewart & Williams, 1994, AMNH FF 20267 from lower Campanian of the Niobrara Formation.
A, branchial arches; B, symplectic; C, ceratohyal; D, left (top) and right (bottom) operculars in lateral (left) and medial (right) views. Scale bar  = 5 cm.
Figure 16
Figure 16. Megalocoelacanthus dobiei Schwimmer, Stewart & Williams, 1994, AMNH FF 20267 from lower Campanian of the Niobrara Formation.
A, basibranchial and basibranchial tooth plate in dorsal view (top), and ventral view (bottom). B, urohyal in dorsal view (top), and ventral view (bottom). Abbreviations: a.t.p.Bb, anterior tooth plate of the basibranchial; art.Cb1, surface for articulation with the first ceratobranchial; art.Cb2, surface for articulation with the second ceratobranchial; art.Ch, surface for articulation with the ceratohyal; art.Uhy, surface for articulation with the urohyal; Bb, basibranchial; p.t.p.Bb, posterior tooth plate of the basibranchial. Scale bar  = 5 cm.
Figure 17
Figure 17. Megalocoelacanthus dobiei Schwimmer, Stewart & Williams, 1994, holotype specimen CCK 88-2-1 from lower Campanian of the Blufftown Formation.
Close-up view of branchial denticles present on the edge of the gill arches of the holotype specimen. Arrows indicate the denticles embedded in the matrix. Scale bar  = 1 mm.
Figure 18
Figure 18. Megalocoelacanthus dobiei Schwimmer, Stewart & Williams, 1994, AMNH FF 20267 from lower Campanian of the Niobrara Formation.
Shoulder girdle. A, Left cleithrum in lateral (left) and medial (right) views. B, right cleithrum in lateral (left) and medial (right) views. C, clavicle in posterior (top) and anterior (bottom) views. D, right scapulocoracoid in medial (top) and lateral (bottom) views. E, left scapulocoracoid in medial (top) and lateral (bottom) views. Abbreviations: Cl, cleithrum; Ecl, extracleithrum. Scale bar  = 10 cm (A–B), 5 cm (C–E).
Figure 19
Figure 19. Megalocoelacanthus dobiei Schwimmer, Stewart & Williams, 1994.
A, neural spine of the holotype specimen CCK 88-2-1 from lower Campanian of the Blufftown Formation in lateral (left) and anterior (right) views. B, scale of AMNH FF 20267 from lower Campanian of the Niobrara Formation. Scale bar  = 5 cm.
Figure 20
Figure 20. Comparison of the palatoquadrate of two actinistians showing the presence/absence of the ventral swelling of the pterygoid (arrow) coded as character 110.
A, Axelrodichthys, right palatoquadrate in medial view (modified from Maisey 1986). B, Latimeria, left palatoquadrate in medial view (modified from Forey 1998). Scale bar  = 20 mm.
Figure 21
Figure 21. Result of the first phylogenetic analysis based on 39 taxa and 110 characters.
Strict consensus tree of the 584 equally parsimonious trees (length  = 288; consistency index  = 0.4132; retention index  = 0.6938). Branch in grey is supported only by ambiguous synapomorphies.
Figure 22
Figure 22. Result of the second phylogenetic analysis based on 37 taxa and 110 characters.
Strict consensus tree of the 22 shortest trees (length  = 287; consistency index  = 0.4146; retention index  = 0.6929). Nodes are numbered from 1 to 30, and the list of apomorphies for each node and terminal taxon is given in Information S5. Numbers on the left of the node indicate the Bremer decay indices. Bootstrap values are indicated after the Bremer decay indices if superior to 50%.
See this image and copyright information in PMC

References

    1. Schwimmer DR, Stewart JD, Williams GD (1994) Giant fossil coelacanths of the Late Cretaceous in the eastern United States. Geology 22: 503–506.
    1. Carvalho de MSS, Maisey JG (2008) New occurrence of Mawsonia (Sarcopterygii: Actinistia) from the Early Cretaceous of the Sanfranciscana Basin, Minas Gerais, southeastern Brazil. Geological Society, London, Special Publications 295: 109–144.
    1. Cavin L, Forey PL (2004) New mawsoniid coelacanth (Sarcopterygii: Actinistia) remains from the Cretaceous of the Kem Kem beds, Southern Morocco. In: Arratia G, Tintori A, editors. Mesozoic Fishes 3 – Systematics, Paleoenvironments and Biodiversity. München: Verlag Dr. Friedrich Pfeil. 493–506.
    1. Gallo V, Carvalho de MSS, Santos HRS (2010) New occurence of †Mawsoniidae (Sarcopterygii, Actinistia) in the Morro do Chaves Formation, Lower Cretaceous of the Sergipe-Alagoas Basin, Northeastern Brazil. Boletim do Museu Paraense Emilio Goeldi 5: 195–205.
    1. Maisey JG (1986) Coelacanths from the Lower Cretaceous of Brazil. American Museum Novitates 2866: 1–30.

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