Cinclosomatidae Mathews, 1922

Nguyen, Jacqueline, Archer, Michael & Hand, Suzanne, 2018, Quail-thrush birds from the Miocene of northern Australia, Acta Palaeontologica Polonica 63 (3), pp. 493-502 : 494-495

Family Cinclosomatidae Mathews, 1922 Genus Cinclosoma Vigors and Horsfield, 1827

Type species: Cinclosoma punctatum ( Shaw, 1794) ; region of Port Jackson , New South Wales, Australia; Recent .

Remarks. —The fossils are referred to Cinclosoma because they possess the following combination of features. Carpometacarpus: ventral portion of trochlea carpalis does not protrude far caudally beyond proximo-caudal edge of os metacarpale minus; fovea lig. ventralis large and deep; proc. cranialis located at level with opening situated proximally of proc. intermetacarpalis; depression on caudo-ventral surface of trochlea carpalis and os metacarpale minus deep; sulcus tendinosus wide and shallow; proc. dentiformis long and situated distal to the proximo-distal midpoint of os metacarpale majus, based on proportions of proximal end and os metacarpale majus. Tibiotarsus: stout, shaft immediately proximal to the distal end is medio-laterally wide (compared with, e.g., Psophodes ); tuberositas retinaculi extensori medialis well developed and separated from its lateral counterpart by a distance of less than length of former; tuberositas retinaculi extensori lateralis prominent, situated on lateral part of pons supratendineus and extends proximally; bony ridges for attachment of retinaculum m. fibularis extend proximally to about level with tuberositas retinaculi extensori medialis; pons supratendineus length about equal to width; condyli lateralis et medialis about equal in proximal and distal extent; impressio lig. intercondylaris very shallow.

Passerines are osteologically very similar to each other, which can make it challenging to diagnose subclades based on skeletal features. However, species of Cinclosoma can be diagnosed by the following apomorphy: on the carpometacarpus, the proc. cranialis is situated distally of the fovea carpalis caudalis, to about level with the opening located proximally of the proc. intermetacarpalis. In species of Ptilorrhoa and Menura , the proc. cranialis is located distally of the fovea carpalis caudalis but proximally of the opening. In acanthisittids, the proc. cranialis is far distally and is situated at approximately the level of the proc. intermetacarpalis.

The fossils differ from species of Ptilorrhoa by exhibiting the following traits. Carpometacarpus: ventral portion of trochlea carpalis more rounded and does not protrude as far beyond proximo-caudal edge of os metacarpale minus; viewed cranially, proc. extensorius more bulbous and expanded ventrally; fovea carpalis caudalis deeper; viewed dorsally, opening located proximally of proc. intermetacarpalis widely open; proc. dentiformis situated further distally relative to midpoint of os metacarpale majus. Tibiotarsus: tuberositas retinaculi extensori medialis more prominent; bony ridges for retinaculum m. fibularis slightly longer and distally terminate at about level with pons supratendineus, rather than proximally of the pons; condylus medialis less inflected medially; condylus medialis about equal, rather than greater than, in distal extent to condylus lateralis.

Because species of Cinclosoma and Ptilorrhoa are sometimes included in Psophodidae ( Gill and Donsker 2018) , we have also included here comparisons of the fossils with species of Psophodes . The fossils are distinguished from species of Psophodes in several features. Carpometacarpus: ventral portion of trochlea carpalis only slightly protrudes beyond proximo-caudal edge of os metacarpale minus; proc. cranialis situated further distally; proximal end of sulcus tendinosus is further distally located on os metacarpale majus, rather than distally adjacent of proc. alularis; proc. dentiformis relatively larger and not located at midpoint of os metacarpale majus but further distally; opening situated proximally of proc. intermetacarpalis widely open, rather than a narrow slit; carpometacarpus less curved dorso-ventrally. Tibiotarsus: distal end narrower relative to width of shaft; tuberositates retinaculorum extensorium relatively longer; tuberositas retinaculi extensori lateralis more prominent and occupies the lateral part of pons supratendineus, rather than only the proximo-lateral part of the pons; bony ridges for retinaculum m. fibularis relatively longer; impressio lig. intercondylaris much shallower; distal profile between condyles shallower. Specimens of Androphobus viridis were not available for study, but can be distinguished from C. elachum sp. nov. in its smaller size ( Boles 2007).