Known from a single tiny leg preserved in Myanmar amber
Elektorornis chenguangi (Fig. 1; Xing et al. 2019; Late Cretaceous, 99 mya; HPG-15-2) has a remarkably long pedal digit 3.
The authors considered Elektornis
a member of the clade Enantiornithes based on the following traits:
- distal condyles of the tibiotarsus contacting medially
- J-shaped metatarsal I
- metatarsal IV mediolaterally reduced relative to metatarsals III and IV
- metatarsal IV trochlea reduced to a single condyle,
None of the above traditional traits
are scored in the large reptile tree (LRT, 1870+ taxa), where, nevertheless, all traditional enantiornithines nest together in a single clade using other tested traits.
The LRT was unable to resolve the nesting of Elektornis
based on so few character traits. Three trees were recovered. Elektornis nested with a different taxon in each tree (Fig. 1). None have the iconic long pedal digit 3. Only the enantiornithine chick, STM 34-1 (Fig. 1), that nests close to Chiappeavis has similarly long penultimate phalanges (a trait not tested by the LRT). Neither of these taxa are listed in the analysis by Xing et al. 2019.
The PILs (parallel interphalangeal lines)
that can be traced in Elektornis show an interesting pattern (Fig. 1). The lateral and medial line sets are continuous, showing how phalanges probably flexed and extended in sets. By contrast the transverse line sets are all interrupted by intervening bones. In other taxa that show an interrupted PILs pattern the manus or pes is stiffened, not as flexibile or extensible. Perhaps this confirms earlier interpretations that hypothesize the use of elongate pedal digit 3 as a bark probe, seeking insects in the manner of manual digit 3 in the aroboreal placental aye-aye (Daubentonia).
Xing, L et al. (6 co-authors) 2019. A New enantiornithine bird with unusual pedal proportions found in amber. Current Biology. 29 (14): 2396–2401.