An istiodactylid pterosaur from the Upper Cretaceous

An istiodactylid pterosaur from the UpperCretaceous Nanaimo Group, Hornby Island, BritishColumbia, Canada

Victoria M. Arbour and Philip J. Currie

Abstract: An unusual jaw found in a calcite nodule from Collishaw Point, Hornby Island, British Columbia (off the eastcoast of Vancouver Island) represents the first definitive pterosaur found in British Columbia, and the first istiodactylidfrom Canada. The nodule was derived from the Northumberland Formation (Nanaimo Group), a fossiliferous formationknown for producing numerous plants, invertebrates, sharks, and mosasaurs. The pterosaur is represented by the anteriorportion of the rostrum, including the anterior edge of the nasoantorbital fenestra, and numerous small, triangular teeth lack-ing denticles. These teeth are similar in overall morphology to the teeth of istiodactylids, but are smaller, more numerous,more tightly packed, and have proportionately smaller crowns. Although fragmentary, this specimen is diagnostic and rep-resents a new genus of istiodactylid pterosaur. Its presence in the upper Campanian Northumberland Formation makes thisthe latest occurring istiodactylid and extends the stratigraphic and geographic range of this enigmatic group of pterosaurs.

Resume : Une mandibule inhabituelle trouvee dans un nodule de calcite provenant de Collishaw Point, sur l’ıle Hornby,en Colombie-Britannique (cote est de l’ıle de Vancouver) represente le premier exemple definitif de pterosaure de cetteprovince et le premier istiodactylide du Canada. Le nodule est derive de la Formation de Northumberland (Groupe de Na-naimo), une formation fossilifere connue pour ses nombreux fossiles de plantes, d’invertebres, de requins et de mosasaures.Le pterosaure est represente par la partie anterieure du rostre, dont la bordure anterieure de la fenetre nasoantorbitale, etde nombreuses petites dents triangulaires exemptes de denticules. Ces dents presentent une morphologie globale semblablea celle des dents d’istiodactylides, bien qu’elles soient plus petites, plus nombreuses et de disposition plus compacte, etque leurs couronnes soient proportionnellement plus petites. Bien que fragmentaire, ce specimen est diagnostique et repre-sente un nouveau genre de pterosaures istiodactylides. Sa presence dans la Formation de Northumberland du Campaniensuperieur en fait le plus recent des istiodactylides et repousse les limites des distributions stratigraphique et geographiquede cet enigmatique groupe de pterosaures.

Introduction

VIPM 1513 (Vancouver Island Palaeontological Mu-seum), a calcite nodule containing a fragmentary jaw froman istiodactylid pterosaur, was surface collected from Col-lishaw Point, Hornby Island, British Columbia (Fig. 1),where the upper Campanian Northumberland Formation ofthe Nanaimo Group crops out (Katnick and Mustard 2003).The Northumberland Formation is composed primarily ofdark grey silty mudstones with thin-bedded sandstone turbi-dites, which Katnick and Mustard (2003) interpret as a deep-water environment at the edges of a submarine fan. This for-mation is notable for its high concentration of fossiliferouscarbonate nodules, and Collishaw Point is one of the mostfossiliferous localities, having produced numerous inverte-brates, teleosts, sharks, mosasaurs, plants (Ludvigsen andBeard 1997), and most recently, ornithurine and enantiorni-thine birds (Morrison et al. 2005). Although pterosaur fossils

have been recovered from Alberta (Godfrey and Currie2005), VIPM 1513 represents the first record of a pterosaurfrom British Columbia, and the first pterosaur cranial mate-rial in Canada. Although fragmentary, the preserved remainsare distinct from all other known istiodactylid pterosaurs andare herein assigned to a new genus and species.

Vancouver Island and the surrounding islands (includingHornby Island) represent an amalgamation of terranesknown as the Insular Superterrane. Two competing hypothe-ses for the palaeolatitude of the Insular Superterrane duringthe Cretaceous are (1) that the Insular Superterrane was lo-cated north of the Franciscan–Sierran plate boundary in Cal-ifornia during much of the Cretaceous, and (2) the ‘‘BajaBritish Columbia’’ hypothesis, which suggests that thesuperterrane was located at least 2400 km south of itspresent-day location, at approximately the modern-day loca-tion of Baja California (Ward et al. 1997). The Northumber-land Formation may have been deposited 1600–3500 kmsouth of its present location (Ward et al. 1997; Krijgsmanand Tauxe 2006; Miller et al. 2006), and as such, it maypreserve a very different vertebrate fauna from that of thewell-known coeval faunas of Alberta.

Systematic palaeontologyPterosauria Kaup, 1834Pterodactyloidea Plieninger, 1901Ornithocheiroidea Seeley, 1891 (sensu Unwin, 2003)

Received 10 June 2010. Accepted 22 September 2010. Publishedon the NRC Research Press Web site at cjes.nrc.ca on22 December 2010.

Paper handled by Associate Editor H.-D. Sues.

V.M. Arbour1 and P.J. Currie. Department of BiologicalSciences, University of Alberta, Edmonton, AB T6G 2E9,Canada.

1Corresponding author (e-mail: [email protected]).

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Can. J. Earth Sci. 48: 63–69 (2011) doi:10.1139/E10-083 Published by NRC Research Press

Istiodactylidae Howse, Milner, & Martill, 2001

Gwawinapterus gen. nov

ETYMOLOGY: 6Gwa’wina Kwakwala for raven, and from pteron(Greek) for winged. Kwakwala is spoken by the Kwakwa-ka’wakw people of Vancouver Island.DIAGNOSIS: As for type and only species.

Gwawinapterus beardi gen. et sp. nov

ETYMOLOGY: After Graham Beard, who discovered the speci-men, and for his contributions to the study of palaeontologyon Vancouver Island.HOLOTYPE: VIPM 1513a and VIPM 1513b, part and counter-part of a single nodule.TYPE LOCALITY: Upper Campanian Northumberland Formation,Nanaimo Group, from Collishaw Point, Hornby Island, Brit-ish Columbia.DIAGNOSIS: An istiodactylid pterosaur differing from all otherknown istiodactylids in having more than 25 teeth on thepremaxilla–maxilla, and in having the tooth root more thantwice the height of the crown.

DescriptionThe specimen (Fig. 2) is embedded in a hard nodule and

has been split in half. Most edges of the bone are broken,except for the dorsal and anterior edges. The bone surfaceis preserved on much of the central portion of the specimen,as the true surface on one side and an imprint in the sur-rounding matrix on the other (Fig. 3). The remainder of thebone is broken in cross-section, showing the alveoli for theteeth, the tooth roots, and replacement teeth.

The anterior edge of the bone is rounded and dorsoven-trally deep (95 mm). The bone bifurcates posteriorly, with

the dorsal portion and the ventral, tooth-bearing portiononly 21 mm in height. This bone most likely represents partof the premaxilla (and possibly part of the maxilla), with thefenestra nested within the bifurcation representing the na-soantorbital fenestra. The length of the premaxilla–maxillaanterior to the nasoantorbital fenestra is 65 mm.

Alveoli for at least 26 teeth are preserved on each side ofthe nodule, although five alveoli in the middle of the seriesare more difficult to discern because of breakage. Teeth maybe present anterior to the first identifiable alveolus, but thebone is partially broken and obscured by infilled matrix, sothis is difficult to verify. Eleven or 12 of these alveoli arepresent below the nasoantorbital fenestra. The teeth are sin-gle-rooted and have triangular, labiolingually compressedcrowns (Fig. 4). Some are broken and visible in sagittal sec-tion. Tooth crowns are approximately 4 mm tall, and thetooth height including the root is 14–16 mm. The crownheight to mesiodistal width ratio is approximately 1.45. Thelabiolingual width of the teeth cannot be measured. Theteeth are straight and show no posterior or lingual curvature.No denticles are present. The tooth crowns are so closelyspaced that most are touching each other along the edges.

DiscussionDuring the Late Cretaceous, teeth lacking denticles could

be found in some non-avian theropods, birds, pterosaurs,crocodilians, mosasaurs, and plesiosaurs. Mosasaurs, plesio-saurs, and crocodilians typically have large, pointed, conicalteeth that are widely spaced from each other. Most smalltheropod teeth have denticles and are recurved (e.g., Larson2008; Sankey 2008). Spinosaurid teeth lack denticles, butthe teeth are conical and have distinct carinae, and are typi-cally much larger than those in VIPM 1513 (Sues et al.2002; Dal Sasso et al. 2005). Paronychodon teeth lack den-

Fig. 1. Map showing the location of VIPM 1513. (A) Map of Canada showing location of Vancouver Island in British Columbia. (B) Mapof Vancouver Island showing location of Hornby Island off the east coast. (C) Map of Hornby Island showing the location of CollishawPoint. Area shaded light grey represents surface exposure of Northumberland Formation. Modified from Katnick and Mustard (2003).

64 Can. J. Earth Sci. Vol. 48, 2011

Published by NRC Research Press

Fig. 2. VIPM 1513 part and counterpart. Anterior is to the right in the top photograph, and to the left in the bottom photograph. Scale bar =10 cm.

Fig. 3. VIPM 1513 part and counterpart interpretive drawings (A and B, respectively), showing distribution of teeth, bone surface, bonecross-section, and bone imprint on the two halves. Scale bar = 10 cm. (C) Generalized istiodactylid skull showing preserved portion ofGwawinapterus.

Arbour and Currie 65


Fig. 4. Tooth morphology of Gwawinapterus beardi. (A) Specimen drawing of the first four preserved teeth in VPIM 1513. The tip of thesecond tooth (from right) is restored. Cross-hatching represents area where the dentine of the root is broken and lost. Boxes A, B, C, and Dcorrespond to the labeled drawing and photos.

Table 1. Comparison of proportions in Istiodactylus sinensis, Nurhachius, and Gwawinapterus.

TaxonHeight of maxilla–premaxilla ventralto nasoantorbital fenestra

Length anterior to na-soantorbital fenestra Height:length ratio

Istiodactylus sinensis 15 85 0.17Nurhachius 8.5 91 0.09Gwawinapterus 21 65 0.32

Note: Measurements are in mm.



ticles but possess longitudinal ridges on the crown (Larson2008). Ichthyornis teeth are laterally compressed and lackserrations, but the root is expanded relative to the crown(Martin and Stewart 1977). Bird teeth are also mesiodistallyconstricted at the base of the crown (Sankey et al. 2002;Currie and Coy 2008; Sankey 2008). The teeth of VIPM1513 do not closely match any known dinosaur, bird, croco-dilian, mosasaur, or plesiosaur teeth.

The teeth of VIPM 1513 are most similar to those of is-tiodactylid pterosaurs, based on the labiolingually com-pressed, triangular shape of the crown, lack of denticles andcarinae, and tapering root. Although contradictory in someaspects of the topology of pterosaur phylogeny, Unwin(2003) and Kellner (2003) each found Istiodactylus latidensto be a member of the Ornithocheiroidea. Lu et al. (2009)also found the Istiodactylidae within the Ornithocheiroidea.

Istiodactylid teeth are often closely spaced (Andres and Ji2006). In particular, VIPM 1513 most closely resembles Is-tiodactylus sinensis in the shape of the maxilla and the spac-ing of the teeth. The rostrum of I. latidens is lower (Howseet al. 2001) than in Gwawinapterus, and the rostrum of Nur-hachius is more sharply tapering (Wang et al. 2005).

Gwawinapterus has more teeth preserved than any otherknown istiodactylid; I. latidens has 12 teeth on each pre-maxilla–maxilla (Howse et al. 2001), as does Longchengpte-

rus (Wang et al. 2006; considered a junior synonym ofNurhachius by Lu et al. 2008). Nurhachius has 14 teeth(Wang et al. 2005), I. sinensis has 15 (Andres and Ji 2006),and Hongshanopterus has 17–19 (Wang et al. 2008). Thereare three teeth below the nasoantorbital fenestra in I. sinen-sis (Andres and Ji 2006), and no teeth below the fenestra inI. latidens (Howse et al. 2001), as compared with 11 inVIPM 1513. Teeth are present along approximately half theskull length in Hongshanopterus (Wang et al. 2008). Liaox-ipterus is preserved with the ventral side of the lower jawsexposed (Lu et al. 2008), so no comments can be madeabout the arrangement of teeth along the maxilla. Lu et al.(2008) observed that I. sinensis had a greater number ofteeth compared with Liaoxipterus and Nurhachius, but isalso larger than these taxa.

The teeth of Nurhachius and I. sinensis have proportion-ately smaller roots, taller crowns, and are spaced morewidely apart compared with Gwawinapterus, although theteeth in Nurhachius and I. sinensis are still closely spacedcompared with many other pterosaur taxa with teeth (Andresand Ji 2006). Wang et al. (2008) considered a reduction inthe number of teeth, and a restriction of the teeth to the an-terior portion of the skull, to be derived traits within the Is-tiodactylidae, and they considered Hongshanopterus (with agreater number of teeth and teeth found more posteriorlythan Istiodactylus and Nurhachius) a more basal member ofthe group.

It is difficult to estimate the total length of the skull or thewingspan of Gwawinapterus. Measurements (Table 1) of theheight of the maxilla–premaxilla ventral to the nasoantorbi-tal fenestra, and the length of the rostrum anterior to the na-soantorbital fenestra suggest VIPM 1513 may have beensimilar in size to I. sinensis, which has a wingspan ofaround 3 m. Measurements of I. sinensis and Nurhachiuswere made using the software program ImageJ and pub-lished photos of these specimens. Gwawinapterus wouldhave had a deeper snout with smaller but more numerousand tightly packed teeth compared with other istiodacytlids(Fig. 5).

Gwawinapterus represents the latest known istiodactylid,as it is from the upper Campanian. Most istiodactylids (Hon-gshanopterus, Istiodactylus, Liaoxipterus, and Nurhachius)are from the Jehol Group of China, which is Aptian in age(Wang and Lu 2001; Wang et al. 2005, 2006, 2008; Andresand Ji 2006; Lu et al. 2008). I. latidens and isolated istio-dactylid teeth from Las Hoyas and Galve, Spain, are Barre-mian in age (Howse et al. 2001; Sanchez-Hernandez et al.2007; Vullo et al. 2009), and isolated istiodactylid teethhave been identified from the Jurassic Morrison Formationin the USA (Bakker 1998). The presence of Gwawinapterusin the Upper Cretaceous of British Columbia extends thestratigraphic range of the Istiodactylidae by almost 40 mil-lion years (Fig. 6). Dyke et al. (2009) considered the mid toLate Cretaceous pterosaur record to be relatively complete;however, the large stratigraphic range extension of the Istio-dactylidae into the Late Cretaceous suggests that the ptero-saur record is far from complete. In addition,Gwawinapterus is the latest occurring toothed pterosaur,which suggests that the mid and Late Cretaceous were notcompletely dominated by edentulous taxa, as suggested byUnwin (2005).

Fig. 5. Gwawinapterus (C) compared with (A) Istiodactylus sinen-sis and (B) Longchengpterus (= Nurhachius). Gwawinapterus has acomparatively deeper rostrum and smaller, more closely packedteeth. Specimens are scaled to the same length from the anterioredge of the nasoantorbital fenestra to the anterior edge of the ros-trum. I. sinensis modified from Andres and Ji (2006), and Long-chengpterus modified from Lu et al. (2008).



AcknowledgementsMany thanks to G. Beard for the opportunity to study this

specimen, and to K. Padian for feedback on early drafts ofthe manuscript. Thanks also to D. Larson and S. Persons foruseful discussions on tooth identification and pterosaur pa-laeobiology. C. Coy prepared VIPM 1513. Funding toVMA is provided by a Natural Sciences and EngineeringResearch Council Alexander Graham Bell Canada GraduateScholarship — Doctoral, an Alberta Ingenuity Studentship,and a University of Alberta China Institute Student TravelGrant. Reviews from H.-D. Sues, D. Unwin, and C. Bennettimproved the manuscript and are gratefully acknowledged.

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An istiodactylid pterosaur from the Upper Cretaceous