Nycticorax cf. nycticorax Linnaeus, 1758

Dyke, Gareth J. & Walker, Cyril A., 2008, New Records of Fossil ‘ Waterbirds’ from the Miocene of Kenya, American Museum Novitates 3610 (1), pp. 1-12 : 6-7

Nycticorax cf. nycticorax Linnaeus, 1758

MATERIAL: KNM MB 562, right coracoid lacking ventral portion of sternal end ( fig. 3 ).

LOCALITY AND AGE: Maboko Island, Lake Victoria, western Kenya. The age of these deposits has been estimated to be 16.5– 14.5 mya; sediments at Maboko are somewhat older than those exposed at Ngorora and have been inferred to represent a floodplain environment ( Andrews et al., 1981).

DISCUSSION: Although the Night Heron ( Nycticorax ) appears to represent a distinct taxon that may have separated early from the other herons ( Ardeidae ), there is presently little fossil evidence for this. Rasmussen et al. (1987) described a tarsometatarsus from the Jabal Qatrani Formation (Oligocene) in Fayum Province, Egypt, which they considered virtually indistinguishable from the recent Blackcrowned Night Heron ( Nycticorax nycticorax ), currently present throughout Africa, southern Europe, and Asia ( Monroe and Sibley, 1993). This appears to be the earliest Paleogene record of the genus known to date ( Olson, 1985a; Rasmussen et al., 1987).

The coracoid from Maboko Island (KNM MB 562) is typical of Nycticorax in that it has a projecting processus acrocoracoideus and a ventrally developed facies articularis clavicularis ( fig. 3 ). The shape of the concavity of the surface between the processus acrocoracoideus and the facies articularis humeralis in this specimen distinguishes it from the neotropical Yellow-crowned Night Heron (Nyctinyassa violacea); this concave area also resembles extant specimens of Nycticorax nycticorax ( fig. 3 ). Although the dimensions of KNM MB 562 are smaller than comparative material of both these two extant genera (perhaps suggesting specific status for this specimen), we follow Rasmussen et al. (1987) in tentatively referring this fossil to the extant N. nycticorax .

MEASUREMENTS: KNM MB 562, preserved length to dorsal lip of facies articularis sternalis— 41 mm; maximum medial width of head— 9 mm; dorsal thickness of head— 4 mm; lateral width to processus procoracoideus— 7 mm; dorsal thickness at midshaft— 4 mm.

CICONIIDAE GRAY, 1840

Figures

Fig. 3. New records of Miocene Kenyan waterbirds. Indeterminate cranial end of right coracoid referred to Threskiornithidae (KNM MB 563) in ventral (A), dorsal (B), and medial (C) views; Nycticorax cf. nycticorax, incomplete right coracoid (KNH MB 562) in medial (D), dorsal (E), and ventral (F) views. Not to scale, see text for measurements.