Sulidae Reichenbach, 1849

Mayr, Gerald, 2002, A skull of a new pelecaniform bird from the Middle Eocene of Messel, Germany, Acta Palaeontologica Polonica 47 (3), pp. 507-512 : 508

Family? Sulidae Reichenbach, 1849

Remarks.—The specimen described herein is assigned to the suborder Steganopodes of the Pelecaniformes (sensu Cracraft 1985) because of the following characters: (1) beak long, with tip of upper beak hooked; (2) narial openings strongly reduced; (3) dorsal surface of mandibular rami medio−laterally very wide, with a plane dorsal surface; (4) pars symphysialis of mandible very short; (5) presence of distinct fossae temporales.

At least characters (1), (2) and (3) unquestionably are derived within neognathous birds. The hooked rostrum is primitively absent in the extant Phaethontidae and Paleogene Prophaethontidae (see Harrison and Walker 1976a) and justifies assignment of the Messel pelecaniform to the suborder Steganopodes sensu Cracraft (1985) , i.e., a clade comprising Fregatidae , Pelecanidae , Sulidae , Phalacrocoracidae , and Anhingidae . Characters (3) and (4), as well as the fairly long pterygoids distinguish it from ciconiiform birds (storks, herons and allies), of which especially the Scopidae (hamerkop) have a superficially similar bill shape (see below).

Tentative assignment to the Sulidae is based on the following characters: (1) upper beak and mandibular rami deep and (2) bearing numerous impressions of vessels; (3) presence of a deeply excavated recessus tympanicus dorsalis ( Fig. 1 , “upper tympanic recess” of Cracraft 1985: 836). I consider these three characters to be derived within neognathous birds, and within the Pelecaniformes their combination only occurs in the Sulidae . However, since characters (1) and (2) are widespread among other neognathous birds, and character (3) is also found in Fregatidae and Phaethontidae , classification of the Messel pelecaniform into the Sulidae is tentative.

Figures

Fig. 1. Masillastega rectirostris gen. et sp. nov., holotype (Universität Bonn, Institut für Paläontologie; collection number 140b). A. Coated with ammonium chloride to enhance contrast, note the impressions of vessels on the beak; scale bar equals 10 mm. B. Interpretative drawing; the hatched area marks the recessus tympanicus dorsalis, the asterisks indicate the wide, plane dorsal surface of the left mandibular ramus. C. X−ray photograph.