FFluvioviridavidae

The Fluvioviridavidae include two species, Fluvioviridavis platyrhamphus Mayr and Daniels, 2001 from the Green River Formation (Fig. 12.3) and Eurofluvioviridavis robustipes Mayr, 2005 from Messel. The holotype of F platyrhamphus was figured

Fig. 12.1 Hypothesis on the phylogenetic relationships between Paleogene and extant representatives of the "Caprimulgiformes" and Apodiformes. Selected apomorphies of the nodes: 1 long leg (crus longum) of ulnar carpal bone greatly elongated; 2 palatine with strongly protruding caudola-teral angle, 18 or fewer presacral vertebrae (except in Protocypselomorphus); 3 palatine with a distinct rostral process (except in Nyctibiidae), orbital process of quadrate strongly reduced; 4 splenius capitis muscle with cruciform origin, coracoid with foramen for supracoracoideus nerve; 5 humerus abbreviated and stocky; 6 internal index process of proximal phalanx of major wing digit greatly elongated; 7 sternal manubrium reduced, sternal articulation facets for coracoid saddle-shaped or slightly convex, ratio length of humerus to width of shaft in midsection less than 7.0, cnemial crests of tibiotarsus reduced; 8 ventral supracondylar tubercle of humerus elongated and narrow, distal end of radius with marked tubercle on ventral side of shaft, opposite to carpal tubercle of ulna, tar-sometatarsus with deep sulcus on dorsal surface proximal to distal vascular foramen, outermost primaries greatly elongated, measuring at least 2.5 times the length of the longest secondaries, salivary glands greatly enlarged; 9 dorsal supracondylar process of humerus greatly enlarged (also in Trochilidae and Aegialornithidae); 10 ventral cotyla of ulna with weakly pronounced ventroproximal edge, olecranon elongated and narrow, deep fossa on the caudal surface of proximal end of ulna (unknown for Parargornis); 11 humerus head with marked distal protrusion; 12 beak greatly elongated and narrow (unknown for Argornis and Jungornis); 13 palatines extremely widened, cone-like bony protrusion at caudal margin of foramen for optic nerve, mandible with intraramal joint and unusually small proximal end; 14 tarsometatarsus greatly abbreviated, tibiotarsus without ossified supratendinal bridge; 15 temporal fossae well developed, tibiotarsus and tarsometatarsus of about equal length, tarsometatarsus extremely abbreviated. (After Mayr 2002b, 2003c, 2005f)

by Olson (1985, p. 126), who subsequently erroneously assigned it to the oilbird Prefica nivea Olson, 1987 (Olson 1987; Mayr and Daniels 2001; see Sect. 12.2). Undescribed Fluvioviridavis-like birds also occur in the London Clay of Walton-on-the-Naze (Mayr and Daniels 2001). An incomplete skeleton from the Green

Mayr Fossil Bird

Nyctibiidae Aegothelidae A pod id ae

Fig. 12.2 Comparison of skulls of extant "caprimulgiform" and apodiform birds (ventral view). a Oilbird, Steatornis caripensis (Steatornithidae); b Tawny Frogmouth, Podargus strigoides (Podargidae); c Common Nighthawk, Chordeiles minor (Caprimulgidae); d Common Potoo, Nyctibius griseus (Nyctibiidae); e Australian Owlet-nightjar, Aegotheles cristatus (Aegothelidae); f common swift, Apus apus (Apodidae). Not to scale. cdl caudolateral angle of palatine bone, ros rostral process of palatine bone

Nyctibiidae Aegothelidae A pod id ae

Fig. 12.2 Comparison of skulls of extant "caprimulgiform" and apodiform birds (ventral view). a Oilbird, Steatornis caripensis (Steatornithidae); b Tawny Frogmouth, Podargus strigoides (Podargidae); c Common Nighthawk, Chordeiles minor (Caprimulgidae); d Common Potoo, Nyctibius griseus (Nyctibiidae); e Australian Owlet-nightjar, Aegotheles cristatus (Aegothelidae); f common swift, Apus apus (Apodidae). Not to scale. cdl caudolateral angle of palatine bone, ros rostral process of palatine bone

River Formation which was figured by Davis and Briggs (1998, Fig. 3C) may also belong to this group of birds.

F. platyrhamphus was a small, presumably insectivorous bird with a wide beak, long wings, and short feet. The coracoid has a cup-like articulation facet for the scapula and a foramen for the supracoracoideus nerve, and both the alular and major wing digits bear ungual phalanges. The caudal margin of the sternum exhibits two pairs of shallow incisions. The long hallux reaches nearly the length of the tarsometatarsus. Eurofluvioviridavis is distinguished from Fluvioviridavis by its much stronger feet, and certainly occupied an ecological niche different from that of its North American relative (Mayr 2005e).

Fig. 12.3 Skeleton of Fluvioviridavisplatyrhamphus Mayr and Daniels, 2001 (Fluvioviridavidae) from the early Eocene Green River Formation (holotype, Staatliches Museum für Naturkunde Karlsruhe, Germany, SMNK-PAL.2368a). (Photo by Sven Tränkner)

Assignment of fluvioviridavids to a clade including the Steatornithidae, Podargidae, and Cypselomorphae is tentative and is mainly based on overall similarity, including the presence of a wide beak and short legs. Likewise, classification of Eurofluvioviridavis into the Fluvioviridavidae is not strongly based. As noted previously (Mayr 2005e), the short and stout tarsometatarsus of Eurofluvioviridavis resembles that of the Eocene Quercypsittidae (Sect. 16.3.2) in the shape of the large trochlea for the second toe and the presence of a wing-like flange on the trochlea for the fourth toe. However, judging from the morphology of the large accessory trochlea, quercypsittids appear to have been fully zygodactyl (i.e., the fourth toe was permanently retroverted), whereas Eurofluvioviridavis, as evidenced by the position of the feet of the holotype skeleton, was at best facultatively zygodactyl or semizygodactyl (i.e., the fourth toe either was spread laterally or could be turned forward and backward).

Fluvioviridavis resembles Palaeopsittacus georgei from the London Clay of Walton-on-the-Naze, which was described as a parrot by Harrison (1982b). The type specimen consists of a nearly complete coracoid and several fragmentary bones (Fig. 12.4). Mayr and Daniels (1998) described additional specimens of P. georgei from the type locality Walton-on-the-Naze, and Mayr (2003b) tentatively referred a postcranial skeleton from Messel to this species (Fig. 12.4). Assignment of P. georgei to the Psittaciformes is disproved by these new specimens, which show that the species lacks a zygodactyl foot. Although the new fossils substantially contribute to a better understanding of the skeletal morphology of P. georgei,

Fig. 12.4 a Postcranial skeleton of Palaeopsittacus cf. georgei Harrison, 1982 from the middle Eocene of Messel (Staatliches Museum für Naturkunde Karlsruhe, Germany, SMNK-PAL.3834a); b-f holotype of P. georgei from the early Eocene London Clay of Walton-on-the-Naze (Natural History Museum, London, UK, BMNH A 5163). b Incomplete left scapula; c incomplete right coracoid; d proximal right ulna; e distal right tibiotarsus; f proximal right tarsometatarsus. snf foramen for supracoracoideus nerve. (Photos by Sven Tränkner)

Fig. 12.4 a Postcranial skeleton of Palaeopsittacus cf. georgei Harrison, 1982 from the middle Eocene of Messel (Staatliches Museum für Naturkunde Karlsruhe, Germany, SMNK-PAL.3834a); b-f holotype of P. georgei from the early Eocene London Clay of Walton-on-the-Naze (Natural History Museum, London, UK, BMNH A 5163). b Incomplete left scapula; c incomplete right coracoid; d proximal right ulna; e distal right tibiotarsus; f proximal right tarsometatarsus. snf foramen for supracoracoideus nerve. (Photos by Sven Tränkner)

its phylogenetic affinities remain uncertain. As in Fluvioviridavis, the coracoid of Palaeopsittacus exhibits a foramen for the supracoracoideus nerve.

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