Daphoenositta, De Vis, 1897

Nguyen, Jacqueline M. T., 2016, Australo-Papuan treecreepers (Passeriformes: Climacteridae) and a new species of sittella (Neosittidae: Daphoenositta) from the Miocene of Australia, Palaeontologia Electronica 11 (1), pp. 1-13 : 3-4

Genus DAPHOENOSITTA De Vis, 1897

Type Species. Daphoenositta miranda De Vis, 1897

Taxonomic Remarks. The fossil tibiotarsus QM F57897 ( Figure 1.1, 1.3, 1.5 ) is referred to Passeriformes because it possesses the following suite of features: distal end not inflected but in line with long axis of shaft; lateral and medial sides of shaft not confluent with nor extend beyond outer edges of condyli lateralis et medialis, respectively; condyles protrude far cranially and are parallel to each other and to long axis of shaft; distal end of canalis extensorius is aligned with centre of incisura intercondylaris; pons supratendineus is perpendicular or at a slight angle (disto-medially or disto-laterally) to long axis of shaft; tuberositates retinaculorum extensorium well defined; two distinct bony ridges that serve as points of attachment for retinaculum m. fibularis, situated laterally of tuberositas retinaculi extensoris lateralis; trochlea cartilaginis tibialis shallow; and cristae trochleae well developed and about equal in caudal extent.

QM F57897 is referred to Daphoenositta , of the monogeneric Neosittidae (sittellas), by the following character states: (1) distal margin of pons supratendineus located proximally of condylus medialis by a distance about equal to a third of condyle length; (2) lateral and medial bony ridges for attachment of retinaculum m. fibularis long and low; (3) bony ridges for retinaculum m. fibularis are about distally level with tuberositas retinaculi extensoris lateralis; (4) tuberositates retinaculorum extensorium are elongate; (5) tuberositas retinaculi extensoris lateralis is situated on proximo-lateral part of or proximally adjacent to pons supratendineus; (6) tuberositas retinaculi extensoris medialis elevated; (7) tuberositas retinaculi extensoris medialis proximally separated from its lateral companion by a distance about equal to or greater than length of former; (8) condylus lateralis is circular-shaped in lateral aspect; (9) condyles about equal in width; (10) condyles proximo-distally long and deep relative to width of distal end; and (11) width of pons supratendineus about equal to its length.

The fossil tibiotarsus differs from the corresponding bone of all other Australian passerine families except Climacteridae in having a pons supratendineus situated far proximally of the condyles ( Figure 1.1 ). This feature is characteristic of Neosittidae , Climacteridae and other unrelated scansorial passerines examined, including Margarornis and Pseudocolaptes ( Furnariidae sensu lato), Lepidocolaptes ( Dendrocolaptidae ), Certhia ( Certhiidae ), Sitta ( Sittidae ) and Mniotilta ( Parulidae ). A proximally-located supratendinal bridge is also present in the extinct acanthisittid Dendroscansor decurvirostris , a probable tree-trunk forager ( Millener and Worthy, 1991). In non-scansorial passerines, the distal margin of the pons supratendineus is approximately level with the proximal edge of the condylus medialis (e.g., Acanthizidae , Pachycephalidae , Corvidae , Petroicidae ).

Owing to convergence in foraging behaviour, the tibiotarsus of Daphoenositta resembles those of other, unrelated, scansorial passerines, but it can be distinguished from these taxa by several features. For example, the relative distance between the distal margin of the pons supratendineus and the proximal edge of the condylus medialis differs among scansorial taxa. In Daphoenositta and Mniotilta , the pons supratendineus is located proximally of the condylus medialis by a distance about equal to one-third of the length of this condyle (character state 1 above). In Margarornis , Lepidocolaptes , and Certhia , this distance is approximately equal to half the length of the condylus medialis, and in Cormobates , Climacteris , and Sitta it is greater than half the condyle length. In Pseudocolaptes and Dendroscansor , however, the distance between the pons supratendineus and the condyles is less than one-third of the length of the condylus medialis. Daphoenositta is further distinguished from all other scansorial passerines examined except for Dendroscansor and Mniotilta by character state 2. It differs from Cormobates and Climacteris (except Cl. erythrops and Cl. affinis ) in having 3, and differs from all climacterids in 8 and 10. In addition Daphoenositta differs from Sitta in having 3, 5, and 7, Certhia in having 3–5 and 7–10, Lepidocolaptes in the presence of 4 and 7–10, Margarornis by 3, 4, and 8, Pseudocolaptes by 3 and 4, Mniotilta in having 11, and Dendroscansor in having 5 and 6.

Figures

FIGURE 1. Distal left tibiotarsi of Daphoenositta trevorworthyi sp. nov. QM F57897 (1, 3, 5) compared with that of Da. chrysoptera AM.O.64965 (2, 4, 6). 1-2, cranial aspect; 3-4, caudal aspect; 5-6, lateral aspect. Abbreviations: cl, condylus lateralis; cm, condylus medialis; em, epicondylus medialis; lrf, lateral bony ridge of retinaculum m. fibularis; mrf, medial bony ridge of retinaculum m. fibularis; ps, pons supratendineus; rct, ridge on trochlea cartilaginis tibialis; trel, tuberositas retinaculi extensoris lateralis; trem, tuberositas retinaculi extensoris medialis. Arrows indicate scratch marks. Scale bar equals 2 mm.