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, 7 (3), e33170

New Insights Into the Skull of Istiodactylus Latidens (Ornithocheiroidea, Pterodactyloidea)

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New Insights Into the Skull of Istiodactylus Latidens (Ornithocheiroidea, Pterodactyloidea)

Mark P Witton. PLoS One.

Abstract

The skull of the Cretaceous pterosaur Istiodactylus latidens, a historically important species best known for its broad muzzle of interlocking, lancet-shaped teeth, is almost completely known from the broken remains of several individuals, but the length of its jaws remains elusive. Estimates of I. latidens jaw length have been exclusively based on the incomplete skull of NHMUK R3877 and, perhaps erroneously, reconstructed by assuming continuation of its broken skull pieces as preserved in situ. Here, an overlooked jaw fragment of NHMUK R3877 is redescribed and used to revise the skull reconstruction of I. latidens. The new reconstruction suggests a much shorter skull than previously supposed, along with a relatively tall orbital region and proportionally slender maxilla, a feature documented in the early 20(th) century but ignored by all skull reconstructions of this species. These features indicate that the skull of I. latidens is particularly distinctive amongst istiodactylids and suggests greater disparity between I. latidens and I. sinensis than previously appreciated. A cladistic analysis of istiodactylid pterosaurs incorporating new predicted I. latidens skull metrics suggests Istiodactylidae is constrained to five species (Liaoxipterus brachyognathus, Lonchengpterus zhoai, Nurhachius ignaciobritoi, Istiodactylus latidens and Istiodactylus sinensis) defined by their distinctive dentition, but excludes the putative istiodactylids Haopterus gracilis and Hongshanopterus lacustris. Istiodactylus latidens, I. sinensis and Li. brachyognathus form an unresolved clade of derived istiodactylids, and the similarity of comparable remains of I. sinensis and Li. brachyognathus suggest further work into their taxonomy and classification is required. The new skull model of I. latidens agrees with the scavenging habits proposed for these pterosaurs, with much of their cranial anatomy converging on that of habitually scavenging birds.

Conflict of interest statement

Competing Interests: The author has declared that no competing interests exist.

Figures

Figure 1
Figure 1. Skull reconstructions of Istiodactylus latidens based on NHMUK R3877.
Reconstructions of this skull have changed somewhat over time, though each diagram was suggested to represent a skull 560 mm in total length. (A) Hooley (B) Arthaber (C) Wellnhofer (D) Fastnacht . All drawings modified from sources except (B) which has been redrawn and somewhat simplified.
Figure 2
Figure 2. Right maxillary bar and tomial portion of right dentary of NHMUK R3977 (Istiodactylus latidens), the ‘missing’ jaw pieces.
(A) lateral view (B) medial view. Scale bar represents 50 mm.
Figure 3
Figure 3. Right lateral view of the skull and mandible of NHMUK R3877 (Istiodactylus latidens).
(A) fossil material assembled with a complete jaw length (B) new skull reconstruction. Scale bar represents 50 mm.
Figure 4
Figure 4. Evidence of crushing and displacement in the rostrum of NHMUK R3877.
(A) Right lateral view (B) dorsal. Arrow 1 denotes displacement of the posterior region of the premaxilla from the anterior rostrum; arrow 2 indicates dorsally upturned region of the dorsal facia; dotted line shows continuation of the dorsal margin denoted by arrow 2 beyond its posterior broken surface. Scale bar represents 50 mm.
Figure 5
Figure 5. Comparisons of istiodactylid skull material, scaled to the same jaw length.
(A) Istiodactylus latidens (NHMUK R3877) (B) Istiodactylus sinensis (NGMC 99-07-11) (C) Nurhachius ignaciobritoi (IVPP V-13288). Note the reclined, elongate orbital regions of I. latidens and P. sinensis compared to that of N. ignaciobritoi, and the characteristically tall, slender-boned construction of this region in I. latidens. (B) after Andres and Ji (C) after Wang et al. .
Figure 6
Figure 6. Topology of strict consensus and 50 percent majority rule consensus trees of istiodactylid interrelationships.
Numbers beneath branches indicate bootstrap support. (A) Ornithocheiroidea (B) Istiodactylidae.
Figure 7
Figure 7. Life restoration of a group of Istiodactylus latidens dining on a stegosaur carcass in a shallow, Lower Cretaceous riverbed.

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