Anhinga cf. pannonica Lambrecht, 1916

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 : 5-6

Anhinga cf. pannonica Lambrecht, 1916

MATERIAL: KNM BN 1968, proximal end of a right humerus ( fig. 2 ).

LOCALITY AND AGE: Ngorora Formation, Middle Miocene of Ngorora, western Kenya. The age of these deposits has been estimated to be 12–10.5 mya; their sedimentology confirms a semi-aquatic environment corroborat- ed by the presence of fish, crocodile, and hippo remains within the formation ( Bishop et al., 1971; Pickford, 1981).

DISCUSSION: As many as four species of anhingas (one each from the Americas, Africa, Asia, and Australia) are currently extant (depending on authors; Howard and Moore, 1984; Monroe and Sibley, 1993). However, because these taxa exhibit little morphological variation other than size, there has been much disagreement (especially in older literature) as to how many species should actually be considered valid. Some workers have suggest- ed that anatomical differences represent nothing more than a pattern of geographical variation and treat these birds within a single species, Anhinga anhinga spp., while others accept two— A. anhinga in the Americas and A. melanogaster in the Old World (see Howard and Moore, 1984). This latter arrangement may be more acceptable on purely anatomical grounds— Harrison (1978) noted a difference in the hypotarsal structure between the Old and New World forms that might justify their specific separation.

The fossil record of the Anhingidae is intermittent ( Noriega and Alvarenga, 2002). The earliest apparent example of these birds, Protoplotus beauforti Lambrecht (1930) , was described from a crushed skeleton found in Eocene deposits on the Island of Sumatra, but it is not until the Upper Miocene that the family becomes abundant in the fossil record, especially in South America ( Olson, 1985a; Noriega and Alvarenga, 2002). By this time, however, anhinga osteology is largely indistinguishable from that of the recent genus, thus providing few clues as to the evolution of this group of birds. Outside of South America, in the Old World, three Neogene species are recognised: Anhinga pannonica , from the Upper Miocene of Hungary ( Lambrecht, 1916); Anhinga grandis , from the Upper Pliocene of North America ( Martin and Mengel, 1975); and Anhinga hadarensis from the Upper Pliocene of Ethiopia and early Pleistocene of Tanzania (Brodkorb and Mourer-Chauvire´, 1982). Of these records, the Hungarian species may have been wideranging— Rich (1972) attributed a cervical vertebrae and the proximal portion of a humerus from the Upper Miocene of Tunisia to A. pannonica , and Harrison and Walker (1982) added another fragmentary humerus and the distal portion of a tarsometatarsus from the Upper Miocene of Pakistan to this fossil taxon. As an aside, and to complete our discussion of the African fossil record of these birds, it should be noted that the Quaternary species Anhinga nana Newton and Gadow (1893) described first from Mauritius and later from Madagascar ( Andrews, 1897) was re-identified by Olson (1975) as a cormorant.

Although it is incomplete, KNM BN 1968 closely resembles the known anatomy of both the late Paleogene Anhinga pannonica and the extant A. melanogaster (which survives in Kenya today; Monroe and Sibley, 1993) ( fig. 2 ). Referral to the former species, however, is supported on the basis of the size and age of this element—its placement within the other African fossil taxon, A. haddarensis , is excluded because this species is much stouter and stockier in its limb proportions than any of its kin (Brodkorb and Mourer-Chauvire´, 1982). Even though KNM BN 1968 very closely resembles A. pannonica in details of its preserved morphology ( fig. 2 ), we make this referral tentatively because of a small comparative sample size of A. melanogaster and because of the incompleteness of this fossil. Nonetheless, the new specimen is somewhat larger than all available extant examples of this genus (1.5–3 mm in most dimensions); in this respect KNM BN 1968 may corroborate the arguments of Rich (1972) and Harrison and Walker (1982) regarding material already assigned to A. pannonica .

MEASUREMENTS: KNM BN 1968, length across tuberculum dorsale to tuberculum ventrale— 20 mm; maximum width of caput— 23 mm; cranial extent of crista bicipitalis— 22 mm; shaft width and distal termination of crista bicipitalis— 13 mm.

CICONIIFORMES BRISSON, 1760

PHOENICOPTERIDAE BRISSON, 1760

Leakeyornis aethiopicus ( Harrison and Walker, 1976) Rich and Walker, 1983

MATERIAL: Holotype, BMNH A 4382 , basal portion of rostrum . Paratypes, BMNH A 4383 , proximal end of right tarsometatarsus ; BMNH A 4384 , distal portion of lower jaw ; BMNH A 4385 , distal end of left humerus ; BMNH A 4386 , distal end of right humerus ; BMNH A 4387 , distal end of left humerus ; BMNH A 4388 , proximal end of humerus ; BMNH A 4389-4392 proximal ends of tarsometatarsi ; BMNH A 4393-4394 , distal ends of tarsometatarsi ; BMNH A 4395 , distal end of right femur ; BMNH A 4396-4398 , distal ends of tibiotarsi ( fig. 1 ). All collected and presented to the BMNH by L.S.B. Leakey .

LOCALITY AND AGE: Lower Miocene, Rusinga Island (locality RS 12), Lake Victoria, Kenya (for locality map and detailed information, see van Couvering and Miller, 1969). This is the oldest of the three sites yielding bird material to be described in this paper; sediments at this locality have been dated to 18–16 mya ( van Couvering and Miller, 1969) and again have been interpreted as indicative of floodplain conditions with extensive bodies of standing water ( Andrews et al., 1981).

DISCUSSION: Measurements and interpretation of these specimens were presented by Harrison and Walker (1976) and Rich and Walker (1983).

CICONIIFORMES GARROD, 1874

ARDEIDAE VIGORS, 1825

Figures

Fig. 2. New records of Miocene Kenyan waterbirds. Ciconia minor, incomplete proximal right humerus (KNM RU 3075) in cranial (A) and caudal (B) views; Ciconia sp., distal right humerus (KNH RU 3914) in cranial (C), caudal (D), and proximal (E) views; Ciconia minor, distal left tarsometatarsus (KNM RU 3898) in dorsal (F) and plantar (G) views; Anhinga cf. pannonica, proximal end of right humerus (KNM BN 1968) in cranial (H) and caudal (I) views. Not to scale, see text for measurements.

Fig. 1. Fossil material referred to the Lower Miocene Kenyan flamingo Leakyornis aethiopicus (see Harrison and Walker, 1976). Not to scale. BMNH A 4382 (holotype)—portion of rostrum in dorsal view (A); BMNH A 4383—proximal end of right tarsometatarsus in plantar view (B); BMNH A 4384—distal portion of lower jaw in ventral view (C); BMNH A 4385—distal end of left humerus in cranial (D) and caudal (E) views; BMNH A 4386—distal end of right humerus in cranial (F) and caudal (G) views; BMNH A 4387—distal end of left humerus in cranial (H) and caudal (I) views; BMNH A 4388—proximal end of left humerus in (J) caudal and cranial (K) views; BMNH A 4389—proximal end of tarsometatarsus in plantar (L) and dorsal (M) views; BMNH A 4390—proximal end of tarsometatarsus in dorsal (N) and plantar (O) views; BMNH A 4391—proximal end of tarsometatarsus in plantar (P) and dorsal (Q) views.