Passeriformes ( Linnaeus, 1758 )

Nguyen, Jacqueline M. T., Hand, Suzanne J. & Archer, Michael, 2016, The Late Cenozoic Passerine Avifauna from Rackham’s Roost Site, Riversleigh, Australia, Records of the Australian Museum 68 (5), pp. 201-230 : 203

Order Passeriformes ( Linnaeus, 1758) Family Maluridae Swainson, 1831

Genus et species indet.

Fig. 1A

Material. QM F30361, distal left tibiotarsus.

Measurements (mm). Preserved length 5.2, distal width ca 1.6, depth of condylus lateralis ca 1.6, depth of condylus medialis ca 1.7.

Description and comparisons. QM F30361 ( Fig. 1A ) is a distal tibiotarsus with the cristae trochlea and the bony ridges for attachment of the retinaculum m. fibularis broken off. This fossil is referred to Maluridae because it possesses the following combination of features. The distal part of the shaft is craniocaudally compressed and its cranial surface is planar. The sulcus extensorius is very shallow and is displaced laterally of the medio-lateral midpoint of the shaft. The tuberositas retinaculi extensoris lateralis is situated on the proximo-lateral part of the pons supratendineus. The proximal edge of the condylus medialis is about level with the distal margin of the pons supratendineus. The condylus lateralis is greater in proximal extent than the condylus medialis. In cranial aspect, the condylus lateralis is slightly wider than its medial counterpart.

QM F30361 is smaller in size than the tibiotarsi of extant malurids studied. The fossil differs from species of Malurus and Clytomyias insignis in that the sulcus extensorius is situated further laterally, and the tuberositas retinaculi extensoris lateralis does not project beyond the proximal margin of the pons supratendineus. It differs from Amytornis because the length of the pons supratendineus is approximately equal to, not less than, its width and the condylus lateralis is greater in distal extent than the condylus medialis, rather than being equal in distal extent. QM F30361 is further distinguished from Amytornis and from Stipiturus malachurus ( Fig. 1B ) by the distal shaft being slightly narrower relative to the width of the distal end. The fragmentary nature of the fossil precludes its referral to a lower taxonomic level, pending recovery of more complete material.

Remarks. Fairywrens, emu-wrens and grasswrens ( Maluridae ) are small, sprightly passerines that are primarily found in Australia but also live in New Guinea. Most species have characteristically long, cocked tails and are poor fliers, and forage on or close to the ground. They occur in sparse to dense low vegetation in a variety of habitats. In Australia, fairywrens ( Malurus ) are found in nearly every habitat, including rainforest, eucalypt woodland, grassland, coastal heath, shrubland in semi-arid and arid areas, and suburban parks and gardens. Emu-wrens ( Stipiturus ) occur in wet to dry heaths and spinifex ( Triodia ) grass in woodland. Grasswrens ( Amytornis ) inhabit spinifex-covered rocky outcrops and hillsides, desert dunes and dry flood plains in arid and semi-arid areas ( Schodde, 1982; Higgins et al., 2001; Rowley & Russell, 2007). Today, the Purple-crowned ( M. coronatus ), Red-backed ( M. melanocephalus ) and Variegated ( M. lamberti ) Fairywrens and the Carpentarian Grasswren A. dorotheae are found in the Riversleigh region.

Material referred to Malurus sp. has been recorded from the late Pleistocene Cloggs Cave and Holocene Mabel Cave in eastern Victoria, and the late Pleistocene Devil’s Lair and Holocene Skull Cave in Western Australia ( Baird, 1986, 1991a,b). Specimens identified as Stipiturus malachurus have been found in Cloggs Cave and the late Pleistocene Seton Rock Shelter in South Australia ( Baird, 1986, 1991a). Remains of Amytornis were also reported from the latter site and from late Quaternary cave deposits in the Flinders Ranges and in the Nullarbor Plains region ( Baird, 1986, 1990, 1991a).

Figures

Figure 1. Distal left tibiotarsi of(A) fossil malurid gen.et sp. indet. QM F30361 and (B) Stipiturus malachurusAM O.68207 in cranial aspect. Some characteristic features of Maluridae shown: 1, sulcus extensorius very shallow and displacedlaterally of the medio-lateral midpoint of the shaft; 2, tuberositas retinaculi extensori lateralis situated on proximo-lateral part ofpons supratendineus; 3, condylus lateralis greater in width and in proximal extent than condylus medialis. Scale bar = 2 mm.