Neanis

Weidig, Ilka, 2010, New Birds from the Lower Eocene Green River Formation, North America, Records of the Australian Museum 62 (1), pp. 29-44 : 40-43

“ Neanis ” kistneri ( Feduccia, 1973)

Holotype. UWGM 3196 , nearly complete articulated skeleton.

Referred specimen. USNM 336268, nearly complete articulated skeleton lacking the left foot ( Fig. 12 ).

In its overall appearance and sitze, the referred specimen corresponds well with the holotype. The specimens share a large bicipital crest of the humerus, a carpometacarpus with straight ossa metacarpalia of identical length and a short synostosis metacarpalis distalis, and a zygodactyl foot with a strong third toe.

Dimensions. See Tables 7 and 8.

Description. The original description is based on the holotype only, given here are additional characters discernible on the referred specimen.

The exact shape of the skull is difficult to determine, because it is somewhat crushed. In accordance with Galbula , the os frontale is flat and a fossa temporalis is present. A small, slender piece of bone might represent the broken processus postorbitalis. If this identification is correct, the processus postorbitalis would have a length comparable to Galbula . The beak is nearly straight and slender, and shorter than that of Galbulidae . In the mandible, a fenestra caudalis mandibulae is visible.

The coracoid closely resembles that of Primobucco mcgrewi . The processus acrocoracoideus is large and slightly hooked, the processus procoracoideus is also large. In its shape, the processus lateralis resembles closely Atelornis . The facies articularis sterni is large like that of Galbulae and of Coraciiformes s.s. On the cranial side of the sternal end of the coracoid, a fossa is visible. A comparable fossa is present in Brachypteraciidae and some Bucconidae ( Bucco , Chelidoptera , Monasa , and rather flat in Malacoptila striata ). The furcula is rounded V-shaped, an apophysis furculae is not present.

The humerus resembles closely that of Primobucco mcgrewi . The head of the humerus is situated dorsally of the shaft due to the large crista bicipitalis. The crista deltopectoralis is short. The humerus shaft is slightly sigmoidal. The distal end is only poorly preserved and thus does not allow any detailed observations. The ulna is the longest limb element. In contrast to Galbulae, papillae remigiales are not present. The carpometacarpus is moderately long and slender. The ossa metacarpalia are parallel and have the same length. In contrast hereto, the os metacarpale minus is considerably longer than the os metacarpale majus within modern Galbulae. The processus extensorius is slightly turned proximad. The synostosis metacarpalis distalis is short.

Discussion. “ Neanis ” kistneri ( Feduccia, 1973) was first described as Primobucco kistneri , a member of the Bucconidae ( Feduccia, 1973) . Together with three more genera, Feduccia & Martin (1976) then referred the species to the Primobucconidae , and transferred Primobucco kistneri to the genus Neanis . Houde & Olson (1989) regarded the Primobucconidae as a paraphyletic taxon and later referred several genera, which were originally placed into the Primobucconidae by Feduccia & Martin (1976), to the Sandcoleidae . Houde & Olson (1989) regard “ Neanis ” kistneri as “true member(s) of the Galbulae, as evidenced by the structure of the sehnenhalter of the tarsometatarsus” (Houde & Olson, 1989: 2031).

The holotype of “ Neanis ” kistneri clearly exhibits a truly zygodactyl foot with the fourth toe turned backwards and thus differs from the type species of the Primobucconidae , Primobucco mcgrewi , which is clearly anisodactyl and belongs to the Coraciiformes s.s. (Mayr et al., 2004).

The new specimen is better preserved than the holotype, however, only the dorsal side of the right tarsometatarsus is preserved. Thus, additional information on the sehnenhalter cannot be obtained. Nevertheless, “ Neanis ” kistneri exhibits further characters which it shares with the Galbulae as the shape of the skull, especially of the os frontale, the presence of a fossa temporalis, a large facies articularis of the coracoid and the head of the humerus turned medially. Due to these similarities and the presence of a zygodactyl foot with sehnenhalter, I concur with Houde & Olson (1989) that “ Neanis ” kistneri is indeed related to the Galbulae.

Conclusions

An extensive study of the Green River bird specimens revealed both new species such as the Zygodactylidae , as well as new specimens of already described species. The description of the majority of the bird species from the Green River Formation is based on single specimens. Most of these specimens are fairly complete, but severely crushed and thus reveal only limited information on their taxonomic affinities. Further specimens show important new features that allow new insight into the osteology of these species. For Messelornis nearctica , the new specimens show an amount of variation similar to the Messel species Messelornis cristata , and the description of Messelornis nearctica is revised in several characters. In the case of Gallinuloides wyomingensis , the additional data gained from the new specimen allows the recognition of its systematic position as a stem-group representative of the Galliformes (Mayr & Weidig, 2004) . The systematic affinities of “ Neanis ” kistneri proposed by Houde & Olson (1989) are supported based on the new specimen.

The Green River Formation consists of deposits of three lakes which all yielded numerous fossils. The lakes range in age from the Upper Paleocene to the Middle Eocene ( Grande, 1980). Most of the fossil birds were found in the Lower Eocene deposits of Fossil Lake. They are thus slightly older than the well-known avifauna from Messel ( Germany). Many of the bird taxa known from Messel are now also reported from Green River and vice versa (e.g., Mayr, 2000; Mayr et al., 2004; Weidig, 2006). With over 340 described specimens, Messelornis cristata is by far the most abundant bird from Messel ( Hesse, 1990). Until this study, Messelornis nearctica from Green River was only known from single specimen. The new specimens reported herein show that the Messelornithidae are among the most abundant species in Green River besides the Presbyornithidae (Feduccia & McGrew, 1975) . In contrast hereto, with one respectively two known specimens, early galliforms seem to be rare in both sites. This might be due to different life habits, the early galliforms probably spent considerably less time close to the lakes than Messelornis . Messel is especially well known for its abundance of small arboreal birds such as Zygodactylidae , Messelirrisoridae or Gracilitarsidae ( Mayr, 1998) . With Eozygodactylus americanus and the un-named species, the first representatives of Zygodactylidae are now known from the New World. With a total of six specimens in two species, the Zygodactylidae are one of the more abundant avian taxa from the Green River Formation. They are also rather abundant in Messel with twelve specimens in four species ( Mayr, 1998; Mayr & Zelenkov 2009). So far, early Galbulae are unknown from Messel or any other contemporaneous site in Europe and might be restricted to the New World.

ACKNOWLEDGMENTS. I would like to thank the following people for enabling my investigation of the specimens in their collections: M. Cassiliano (UWGM), L. Claessens (MCZ), K. Cloward (NAMAL), M. Florence (USNM), P. Larson (BHI), W. Munk (SMNK), S. Olson (USNM), S. Plodowski (SMF), B. Pohl (WDC), S. Rietschel (SMNK), W. Simpson (FMNH). The study is part of a project supported by the Deutsche Forschungsgemeinschaft (DFG-MA 2328/2–1), which also funded my participation in the SAPE meeting (DFG-KON-1410–WE 4573/1–1). The manuscript strongly benefited from the very helpful comments of Trevor Worthy and Gareth Dyke as well as those of Gerald Mayr on earlier versions.

Figures

Figure 12. “Neanis” kistneri, USNM 336268, scale bar 20 mm.