Gallinuloides wyomingensis Eastman, 1900

Mayr, Gerald & Weidig, Ilka, 2004, The Early Eocene bird Gallinuloides wyomingensis - a stem group representative of Galliformes, Acta Palaeontologica Polonica 49 (2), pp. 211-217 : 213-214

Gallinuloides wyomingensis Eastman, 1900

Figs. 1–6 .

Referred specimen: WDC CGR−012 (complete articulated skeleton on a slab).

Locality and horizon: Green River Formation, Upper Fossil Butte Member of Fossil Lake (18−inch−layer), Kemmerer, Wyoming, USA, Early Eocene; see Grande (1980) for a detailed description of the locality.

Measurements (in mm, measurements of the holotype in brackets): Humerus: ~47 (right) [46.7 (left), 47.3 (right)]. Ulna: ~48.4 (left), ~49 (right) [49.1 (left)]. Carpometacarpus: 25.5 (left), ~27.1(right) [26.2 (left)]. Femur: 39.7 (right) [41.0 (left)]. Tibiotarsus: 56.4 (left), 56.0 (right) [57.4 (left), 56.7 (right)]. Tarsometatarsus: 34.2 (left), 34.0 (right) [34.5 (left), 33.9 (right)]

Characters bearing on the phylogenetic position of Gallinuloides

(1) The skull has a well−developed os ectethmoidale ( Fig. 3 ) which is reduced in extant Cracidae and Phasianidae (see also Cracraft 1968). The presence of a well developed os ectethmoidale almost certainly is plesiomorphic within galliform birds.

(2) The skull has poorly developed processi postorbitales ( Fig. 3 ) and lacks ossified aponeuroses zygomaticae, which are a characteristic derived feature of all extant Galliformes (see Zusi and Livezey 2000).

(3) The coracoid bears a cup−like, concave facies articularis scapularis ( Fig. 4 ) which also occurs in Paraortygoides (Mayr 2000) and the Paleogene Quercymegapodiidae and Paraortygidae (Mourer−Chauviré 1992, 2000; Alvarenga 1995), but is absent in all crown group Galliformes in which the facies articularis scapularis is flat or slightly convex ( Fig. 5C 1). A cup−like facies articularis scapularis is present in the Anseriformes , the sister taxon of Galliformes , as well as in Mesozoic non−neornithine birds and thus unquestionably primitive within Neornithes (Mourer−Chauviré 1992; Mayr 2000; Clarke 2002). bone is pointed only in the Megapodiidae but blunt in the extant Cracidae and Phasianidae . The scapula of anseriform birds also is very long, and thus the long scapula of Gallinuloides is probably plesiomorphic for galliform birds.

(5) As in Paraortygoides , the furcula has very robust scapi claviculae that are much weaker in crown group Galliformes . Anseriform birds also have robust scapi claviculae and the weak scapi claviculae of extant galliform birds are derived relative to the condition seen in Gallinuloides and probably due to the large crop of galliform birds (Stegmann 1964).

(6) The apex carinae of the sternum protrudes much farther cranially than in extant Cracidae and Phasianidae . The apex carinae is shifted caudally in extant Cracidae and Phasianidae , which is a derived feature probably correlated with the large crop of these birds (Stegmann 1964).

(7) The carpometacarpus ( Fig. 6 ) is very elongate and the spatium intermetacarpale is narrow as in Megapodiidae , Anseriformes ( Fig. 5A 2), and basal non−neornithine birds (e.g., Clarke 2002). The morphology of the carpometacarpus of Gallinuloides strongly differs from the proportionally shorter and wider carpometacarpus of extant Cracidae and Phasianidae ( Fig. 5C 2) and certainly reflects the primitive condition in galliform birds. The narrow intermetacarpal space of Gallinuloides is clearly visible in the holotype (Mayr 2000: 54), which makes it hard to understand why Dyke (2003: 10) considered the carpometacarpus of Gallinuloides to be wide.

(8) As in Paraortygoides and extant Megapodiidae , the trochleae metatarsorum are splayed, whereas they are situated more closely together in extant Cracidae and Phasianidae .

(9) There are no ossified tendons along the leg and wing bones. In Paraortygoides there is only a single ossified tendon along the plantar surface of the tarsometatarsus (which, owing to preservation is not visible in the Gallinuloides specimens). In extant Cracidae and Phasianidae , the tendons along the wing and leg bones usually are heavily ossified, which unquestionably is a derived condition within neornithine birds.

Figures

Fig. 1. Gallinuloides wyomingensis, holotype and hitherto only known specimen (MCZ 342221). Scale bar 20 mm.

Fig. 2. Gallinuloides wyomingensis, newly identified specimen from the Green River Formation (WDC CGR−012). Scale bar 20 mm.

Fig. 3. Gallinuloides wyomingensis, skull (WDC CGR−012). Scale bar 20 mm.

Fig. 4. Gallinuloides wyomingensis furcula and coracoids (WDC CGR−012). The arrow at the left coracoid indicates the cup−like cotyla scapularis which distinguishes Gallinuloides from crown group Galliformes.Scale bar 20 mm.

Fig. 5. Left coracoid (A1, B1, C1) and carpometacarpus (A2, B2, C2) of anseriform and galliform birds in comparison. A. Anas crecca (Anatidae, Anseriformes; SMF 851). B. Gallinuloides wyomingensis (Gallinuloididae, stem group Galliformes; WDC CGR−012). C. Lophortyx gambelii (Phasianidae, crown group Galliformes; SMF 1604). The arrows indicate the facies articularis scapularis of the coracoid which is shallow in crown group Galliformes. Scale bars 5 mm.

Fig. 6. Gallinuloides wyomingensis, left wing (WDC CGR−012). Note the slender, “anseriform” carpometacarpus. Scale bar 20 mm.