Ornithocheirus simus (Owen, 1861)

Rodrigues, Taissa & Kellner, Alexander Wilhelm Armin, 2013, Taxonomic review of the Ornithocheirus complex (Pterosauria) from the Cretaceous of England, ZooKeys 308, pp. 1-112 : 10-13

Ornithocheirus simus (Owen, 1861) Figs 1 -3

Pterodactylus simus Owen: Owen 1861: p. 2, pl. I, fig. 1-5

Ornithocheirus simus (Owen): Seeley 1869: p. xvi

Ornithocheirus simus (Owen): Seeley 1870: p. 127

Criorhynchus simus (Owen): Owen 1874: p. 7

Ornithochirus [sic](?) simus (Owen): Lydekker 1888: p. 16

Criorhynchus simus (Owen): Hooley 1914: p. 536

Criorhynchus simus (Owen): Arthaber 1922: p. 18, fig. 7a, b

Criorhynchus simus (Owen): Kuhn 1967: 38

Criorhynchus simus (Owen): Wellnhofer 1978: p. 60, fig. 8, 29

Ornithocheirus simus (Owen): Unwin 2001: p. 194, table 1

Ornithocheirus platyrhinus Seeley: Seeley 1869: p. xvii [disclaimed]

Ornithocheirus platyrhinus Seeley: Seeley 1870: p. 128

Criorhynchus platyrhinus (Seeley): Hooley 1914: p. 536

Criorhynchus simus (Owen): Wellnhofer 1978: p. 60 [synonymy]

Ornithocheirus simus (Owen): Unwin 2001: fig. 7, table 1 [synonymy]

Holotype.

CAMSM B54428, anterior portion of the rostrum ( Fig. 1A-D ).

Type locality.

Cambridge, Cambridgeshire, England.

Type horizon.

Cambridge Greensand (Cenomanian; fossils Albian in age).

Referred specimens.

CAMSM B54552 ( Fig. 1E-H ), CAMSM B54429 ( Fig. 2A-D ), CAMSM B54677 ( Fig. 2E-H ), MANCH L.10832 ( Fig. 3A-D ), and NHMUK PV 35412 ( Fig. 3E-H ) (all from the Cambridge Greensand).

Diagnosis.

Pterodactyloid pterosaur with the following combination of characters that distinguishes it from other members of the clade (autapomorphies are marked with an asterisk): tall rostrum*; first pair of premaxillary teeth directed ventrally*; first pair of upper alveoli slightly displaced posteriorly from the anterior margin of the premaxilla*; ventral margin of the palate straight; rostrum not expanded anteriorly.

Description.

Ornithocheirus simus was first described on the basis of a fragmentary anterior portion the premaxillae and maxillae (CAMSM B54428), which remains the best preserved specimen undoubtly referable to this species. This fragment has, in lateral view, a rounded profile, and all preserved tooth sockets are oriented ventrally. Owen (1861) described the specimen in detail and noted its very large size, that its first pair of alveoli were directed downwards, and that the anterior margin of the rostrum is tall above the first pair of alveoli. Owen (1861) thus separated it from Pterodactylus sedgwickii [= Camposipterus(?) sedgwickii , see below], in which the first pair of alveoli opens on the anterior margin of the rostrum, facing somewhat forwards, and the anterior margin of the rostrum was not as tall. Owen (1861) also noted that the anterior depression present in the holotype of Ornithocheirus simus was not as marked in another specimen referable to this species. Personal observations of several rostra referable to Ornithocheirus simus (for example, CAMSM B54429, B54552, and B54677, MANCH L.10832, and NHMUK PV 35412) suggest that this depression could have been produced by postmortem abrasion and should be avoided as a character (contra Fastnacht 2001).

Ornithocheirus simus lacks an anterior expansion of the rostrum. As noticed by Owen (1861), there is matrix adhered on the right side of the specimen, which can give the false impression that the palate is broader at the fourth pair of alveoli. Another interesting feature noted by Owen (1861) is the separation between the alveoli of the first pair, equivalent to the largest diameter of the alveolus, and that the bone between these two alveoli projects below from the level of the palate, but not forming an elongated structure. Owen (1861) observed that no median ridge is preserved.

In the original description and illustration, CAMSM B54428 had a tooth preserved in the first left alveolus ( Owen 1861: table I, figures 1 to 5). Unwin (2001) suggested that the tooth was possibly glued in this position. During examination of the holotype in 2007, it was observed that the tooth was not preserved with the holotype anymore and could not be found.

Aside from the taxonomic and nomenclatural problems surrounding Ornithocheirus simus , its basic structure is controversial. Several authors considered it a long-snouted animal with a robust premaxillary crest (e.g., Wellnhofer 1987, 1991; Fastnacht 2001; Unwin 2001; Veldmeijer 2006), whereas others have suggested that it was actually a short-snouted pterosaur with a tall and massive rostrum (e.g., Hooley 1914; Arthaber 1922; Kuhn 1967; Kellner 1990). References to a reconstruction as a longirostrine pterosaur with a thick premaxillary crest are based on the alleged similarities between Ornithocheirus simus and the more complete holotype of Tropeognathus mesembrinus Wellnhofer, 1987. As the holotype and the several rostra referable to Ornithocheirus simus are fragmentary, it is very difficult to assess which view is correct. Therefore, we refrained from using the presence or absence of a crest in the diagnosis, but several other features (e.g., tall rostrum, position of the first pair of premaxillary teeth) support the distinctiveness of this species among the Cambridge Greensand pterosaur assemblage and in comparison with Tropeognathus mesembrinus (see Taxa from other deposits, below), leading us to propose here that Ornithocheiridae should be restricted to Ornithocheirus simus .

Remarks.

As detailed above, the taxonomic history of the genus Ornithocheirus and of the species Ornithocheirus simus is quite complex. To summarize, CAMSM B54428 was first described by Owen (1861) as Pterodactylus simus . Upon recognition that Ornithocheirus simus differed from the species of Pterodactylus , Seeley (1869, 1870) referred it to Ornithocheirus , whereas Owen (1874) subsequently transferred it to Criorhynchus . Both Ornithocheirus and Criorhynchus are based on the same type species ( Ornithocheirus simus ), and are therefore objective synonyms.

Seeley (1870: 128) named the species Ornithocheirus platyrhinus based on CAMSM B54552, an anterior portion of the rostrum ( Fig. 1E-H ), with the description: "another fragment, with the area very long, is marked Ornithocheirus platyrhinus ". The area to which Seeley (1870) referred is the tall rostrum. Even this a short characterization makes the name available. CAMSM B54552 is quite incomplete but shows features diagnostic of Ornithocheirus simus : tall rostrum; first pair of premaxillary teeth ventral; first pair of upper dental alveoli slightly placed back from the anterior margin of the premaxilla and ventral profile of the palate straight. Due to the fragmentary nature of this material, it cannot be determined if the anterior expansion of the rostrum was also absent or if the other alveoli have the same sizes and spacing as in CAMSM B54428. Both specimens differ slightly in size, CAMSM B54552 being approximately 7.5 cm high anteriorly and CAMSM B54428 is approximately 6.5 cm high. This difference may be due to ontogenetic or individual variation. Hence, we follow Unwin (2001) in considering Ornithocheirus platyrhinus a subjective junior synonym of Ornithocheirus simus .

Figures

Figure 1. Ornithocheirus simus. A-D holotype CAMSM B 54428 (Albian, Cambridge Greensand), anterior part of the rostrum A left lateral view B respective line drawing C ventral view D respective line drawing E-H referred specimen CAMSM B 54552 (Albian, Cambridge Greensand), anterior part of the rostrum E anterior view F respective line drawing G left lateral view H respective line drawing. Abbreviations: m - maxillae, pm - premaxillae. Arrows and numbers indicate alveoli or teeth and their respective position. Scale bar = 10 mm.

Figure 2. Ornithocheirus simus. A-D referred specimen CAMSM 54429 (Albian, Cambridge Greensand), anterior part of the rostrum A right lateral view B respective line drawing C anterior view D respective line drawing E-H referred specimen CAMSM 54677 (Albian, Cambridge Greensand), anterior part of the rostrum E right lateral view F respective line drawing G anterior view H respective line drawing. Abbreviations: m - maxillae, pm - premaxillae. Arrows and numbers indicate alveoli or teeth and their respective position. Scale bar = 10 mm.

Figure 3. Ornithocheirus simus. A-D referred specimen MANCH L 10832 (Albian, Cambridge Greensand), anterior part of the rostrum A left lateral view B respective line drawing C anterior view D respective line drawing E-H referred specimen NHMUK PV 35412 (Albian, Cambridge Greensand), anterior part of the rostrum E right lateral view F respective line drawing G anterior view H respective line drawing. Abbreviations: m - maxillae, pm - premaxillae. Arrows and numbers indicate alveoli or teeth and their respective position. Scale bar = 10 mm. Photos E and G courtesy of The Natural History Museum.