Lonchodraco (?) microdon (Seeley, 1870) Rodrigues & Kellner, 2013

Rodrigues, Taissa & Kellner, Alexander Wilhelm Armin, 2013, Taxonomic review of the Ornithocheirus complex (Pterosauria) from the Cretaceous of England, ZooKeys 308, pp. 1-112 : 20-21

Lonchodraco (?) microdon (Seeley, 1870) comb. n. Fig. 6

"Ptenodactylus" microdon Seeley: Seeley 1869: p. xvi [disclaimed]

Ornithocheirus microdon Seeley: Seeley 1870: p. 116, pl. XII, fig. 6-7

Lonchodectes microdon (Seeley): Hooley 1914: p. 535

Ornithocheirus microdon Seeley: Wellnhofer 1978: p. 58

Lonchodectes microdon (Seeley): Unwin 2001: p. 211, table 1

Ornithocheirus oweni Seeley: Seeley 1870: p. 115

Lonchodectes oweni (Seeley): Hooley 1914: p. 535

Lonchodectes microdon (Seeley): Unwin 2001: p. 195, fig. 11C-D, table 1 [synonymy]

Holotype.

CAMSM B54486, anterior portion of the rostrum ( Fig. 6A-F ).

Type locality.

Cambridge, Cambridgeshire, England.

Type horizon.

Cambridge Greensand (Cenomanian; fossils Albian in age).

Referred specimen.

CAMSM B 54439 ( Fig. 6G-L ) (also from the Cambridge Greensand).

Diagnosis.

Lonchodraconid pterosaur with the following combination of characters that distinguishes it from other members of the clade (autapomorphies are marked with an asterisk): premaxillary crest absent; dorsal margin of the premaxillae rounded; deep palatal ridge*; palate between the elevation of the alveolar margins and the palatal ridge concave; spacing between alveoli larger than their diameters*; approximately 4.5 alveoli per 3 cm of jaw margin.

Description.

Lonchodraco(?) microdon was described by Seeley (1870) on the basis of CAMSM B54486, a fragmentary upper jaw with a prominent palatal ridge. Seeley (1870) noted the presence of a concavity on the palate between the elevation of the alveolar margins and the palatal ridge, that the palatal ridge becomes more prominent than the alveolar borders posteriorly, and that the alveolar margins are compressed and rounded. Seeley (1870) also noted a small tip of jaw “associated” with the specimen, but this possibly does not represent the same individual. CAMSM B54486 was recently sampled for histological analysis (M. Riley, pers. comm.). The transverse section of the area that was cut is wider than high, whereas the opposite end is higher than wide, suggesting that the sampled area was located near the anterior end of the snout.

Ornithocheirus oweni was described in the same work ( Seeley 1870) on the basis of CAMSM B 54439 ( Fig. 6G-L ), also an upper jaw. This species is quite similar to Lonchodraco(?) microdon . Both holotypes share a rostrum with parallel alveolar margins, absence of a premaxillary crest, rounded dorsal margin of the premaxillae and maxillae, deep palatal ridge and the concave palate between the alveolar margins and the palatal ridge. Seeley (1870) pointed out that Ornithocheirus oweni differs from Lonchodraco(?) microdon in that its jaw margins are not round but flattened, by the presence of rough interspaces between the alveoli, teeth (alveoli?) circular instead of oval, and the dorsal margin of the premaxillae and maxillae rounded instead of having a sharp keel. However, examination of CAMSM B 54439 established that the alveolar margins are poorly preserved so that the number, shape, and spacing of the alveoli cannot be seen. Furthermore, Lonchodraco(?) microdon has a rounded dorsal margin of the rostrum, as can be observed in anterior and posterior transverse sections of the holotype. As both species share the same morphological features and come from the same deposit they are here considered conspecific.

Remarks.

Unwin (2001) synonymized Ornithocheirus oweni with Lonchodraco(?) microdon and, acting as the First Reviser ( ICZN’s article 24.2.2), gave Lonchodraco(?) microdon priority.

Lonchodraco(?) microdon has small (approximately 3 mm diameter) and evenly spaced alveoli as in Lonchodraco giganteus and Lonchodraco machaerorhynchus . However, it is distinct from Lonchodraco giganteus , lacking a premaxillary crest, having spacing between the alveoli larger than their diameters, and with parallel alveolar margins. These features constrast with those of the type species of the genus. Lonchodraco(?) microdon shares with Lonchodraco machaerorhynchus the parallel alveolar margins and the same alveolar density (4.5 alveoli per 3 cm of jaw margin), but they differ in the spacing between the alveoli, larger in the first. Due to these differences, it is possible that Lonchodraco(?) microdon actually represents a distinct genus. However, in the absence of further evidence, we refrain from naming a new genus and assign the species tentatively to Lonchodraco .

Figures

Figure 6. Lonchodraco (?) microdon comb. n. A-F holotype CAMSM B 54486 (Albian, Cambridge Greensand), anterior fragment of the rostrum A ventral view B respective line drawing C anterior view D respective line drawing E posterior view F respective line drawing. In B dashed lines indicate the portion lost since the original description G-L referred specimen CAMSM B 54439 (Albian, Cambridge Greensand), anterior fragment of the rostrum G ventral view H respective line drawing I anterior view J respective line drawing K posterior view L respective line drawing. Abbreviation: prid - palatal ridge. Arrows indicate alveoli or teeth. Scale bar = 10 mm.