Housekeeping in the bird subset of the LRT, plus Cnemiornis enters

Updated May 23, 2021 and May 29, 2021
with an updated cladogram (Fig. 4).

One new taxon,
the giant flightless goose, Cnemiornis (Figs. 1, 2), and an old taxon with a new nesting, the Cretaceous enigma bird, Asteriornis (Field et al. 2020, Fig. 3), were recovered after a four-day binge review of theropods and birds in the large reptile tree (LRT 1861+ taxa; subset Fig. 4). Other changes are reviewed below. Low scores in your phylogenetic analysis = trouble.

You might remember,
we looked at Asteriornis, the so-called ‘super chicken, a year ago here (now updated).

Figure 3. The extinct and flightless Cnemiornis (at right) compared to the extant and volant Cereopsis, the New Zealand goose.
Figure 1. The extinct and flightless Cnemiornis (at right) compared to the extant and volant Cereopsis, the New Zealand goose.
Figure 2. Cnemiornis skull in three views. Compare to latest Cretaceous Asteriornis in figure 3.
Figure 2. Cnemiornis skull in three views. Compare to latest Cretaceous Asteriornis in figure 3. Not sure what the red bone is below the fused prefrontal/lacrimal.

Cnemiornis calcitrans
(Owen 1866; recently extinct; 1 m tall) is the New Zealand goose, a very large and flightless goose with reduced forelimbs, reduced sternum and not much webbing between the toes. The neck is longer than in Anser and pedal digit 1 is absent. So is the radius (Fig. 1). Compare the skull of Cnemiornis (Fig. 2) to that of the Cretaceous bird, Asteriornis (Fig 3).

Figure 3. Latest Cretaceous Asteriornis nests with highly derived flightless geese in the LRT, not with chickens. The maxilla, prefrontal + lacrimal and postfrontal + postorbital are newly identified here based on comparative anatomy with Cnemiornis (Fig. 2). So is the new posterior border of the nasals, no longer conjoined.

Asteriornis maastrichtensis
(Field et al. 2020; latest Cretaceous, 66 mya; NHMM 2013 008) was originally considered basal to chickens and geese, but here nests as a sister to the giant filghtless goose, Cnemiornis, a highly derived, rather than basal, bird. The authors reported, “The fossil represents one of the only well-supported crown birds from the Mesozoic era.” Note the fused lacrimal + prefrontal, the robust postfrontal + postorbital that together separate the orbit from the antorbital fenestra and temporal fenestrae. Now these two openings almost connect with one another as in Cnemiornis, a rare trait in other birds and tetrapods in general.

Contra the conclusion of Field et al. 2020,
the presence of highly derived Asteriornis in latest Cretaceous strata indicates that all taxa that phylogenetically precede it had Cretaceous roots. At present this is only confirmed by the presence of 80-million-year-old Patagopteryx, an ostrich ancestor. Other Cretaceous crown birds will surely follow.

Figure 4. Subset of the LRT focusing on theropods and birds. Colors indicate the appearance of long legs vs short legs and aquatic vs terrestrial niches.

Other changes to the theropod subset of the LRT include:

  1. Megapodes (Megapodius) moves one node closer to ratites (Rhea).
  2. Torgos, the Old World vulture now nests with Buteo, the common buzzard. New World vultures still nest with pigeons, as before.
  3. The long-legged shorebird, Oedicnemus, moves one node over from crows to nest with Charadrius, the plover. Rhynchochetos, the flightless kagu, joins them.
  4. Two small terrestrial pigeons, Columba and Caloenas + New World vultures, now branch off from water-loving plovers, and this clade is basal to water-loving shoebill storks, pelicans, frigates and petrels. I guess it’s time to start looking for a water-loving pigeon with long legs in the Cretaceous.
  5. The frigate bird (Fregata) now nests between the shoebill (Balaeniceps) and the pelican (Pelecanus).
  6. The long-beaked hamerkop (Scopus) moves one node over. It is now basal to long-beaked barbets, toucans (Pteroglossus) and hornbills on one node and on the other node, the long-beaked ibis (Threskiornis) and spoonbill giving rise to the short-beaked ducks and geese. Given that Cretaceous Asterornis now nests with geese, it’s time to start looking for hamerkops earlier in the Cretaceous.

Of course, none of the above hypothetical interrelationships
match genomic testing, which readers should be discouraged from ever using in deep time studies. Why? Because they lead to false positives. Using traits, as in the LRT, let’s you see, trait-by-trait how taxa slowly evolved via microevolution. With the present housekeeping based on new taxa and fresh looks at old taxa, the evolution from one taxa to another looks better. Not perfect. Never perfect. Just better.

Sharp-eyed readers will note
the deletion of all Bootstrap/Jackknife scores in the LRT and its subsets from now on. A kind reader noted such scores are impossible given the size of the LRT, overlooking the note that all such scores are based on smaller overlapping subsets due to limitations in computing power. That excuse is no longer needed with the deletion of all Bootstrap/ Jackknife scores from public view. The reader was right. Such scores are not appropriate for the LRT because they misinform. I will continue to use Bootstrap scores in my studies because they indicate strong and weak nodes in fully resolved subsets of the LRT. PAUP usually needs three extra steps to get scores over 50. Scores under 50, despite being fully resolved, usually means some sort of problem in my experience. Just getting a fully resolved subset is only the first step. Behind the scenes it won’t be the only step.

Field DJ, Benito J, Chen A, Jagt JWM and Ksepka DT 2020. Late Cretaceous neornithine from Europe illuminates the origins of crown birds. Nature 579:397–401.
Owen R 1866. XI. On Dinornis (Part X.): containing a Description of part of the Skeleton of a flightless Bird indicative of a New Genus and Species (Cnemiornis calcitrans, Ow.) Journal of Zoology 1866 The Zoological Society of London.
Padian K 2020. Poultry through time. Nature online

4 thoughts on “Housekeeping in the bird subset of the LRT, plus Cnemiornis enters

  1. The thing that you show in green is not the maxilla, it is part of the premaxilla, the maxilla is the anterior part of the thing you show in blue as the jugal. I would recommend obtaining a chicken skull and disarticulating it at the sutures to show to yourself which bones these are. Short of that, there are many anatomical references out there since birds have some of the best studied skulls of any animal (again, thanks to the aforementioned chicken).

    • I followed the authors originally (March 2020) on that matter and found it to be wrong last weekend. Take a closer look at the images and those of the new sister taxon, Cnemiornis, both overall and in detail. You will see the suture. Geese are far from chickens phylogenetically so the skull of one does not provide great data for the other.

      • Geese have the same configuration, you can disarticulate their skulls in the exact same way, with the same regions disarticulating. There are no sutures where you show them, only solid bone. I’m referring to chickens because the references for them are more numerous and their skulls are easier to obtain, but you can do the same with a goose.

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