Overlooked and infamous ancestors to Hesperornis in the LRT

After review and rescoring
with a larger selection of toothed birds, the Late Cretaceous loon-mimic, Hesperornis (Fig. 1), now nests with the STM9-52 specimen (mistakenly referred to Yanornis, Fig. 1). And these nest with the London specimen of Archaeopteryx (FIg. 1). And these nest in the LRT with the infamous Archaeovolans (originally Archaeoraptor, a composite fossil).

So, based on phylogenetic bracketing,
in the large reptile tree (LRT, 2021 taxa) incomplete and infamous Archaeovolans should have had a long slender stiff tail (Fig. 1).

Figure 4. Taxa between Solnhofen birds and extant birds in the LRT. Click to enlarge. Here Iteravis nests as the last common ancestor of paleognath and neognath birds (= crown birds).
Figure 1. Taxa between Solnhofen birds and extant birds in the LRT. Click to enlarge. Here Archaeovolans nests basal to the London specimen of Archaeopteryx and Hesperornis. Other Solnhofen bird specimens (at top) nest closer to one another. This is why it is so important to test all the Solnhofen birds in analyses, something that is never done outside of the LRT.

According to Wikipedia
“Zhou et al. found that the head and upper body actually belong to a specimen of the primitive fossil bird Yanornis. A 2002 study found that the tail belongs to a small winged dromaeosaur, Microraptor, named in 2000. The legs and feet belong to an as yet unknown animal.”

Figure 1. Archaeoraptor from Rowe et al. 2000. Colored areas indicate different sources for matrix and fossils there in.
Figure 2. Archaeoraptor from Rowe et al. 2000. Colored areas indicate different sources for matrix and fossils there in. The feet belong to Yanornis or a close relative. Click here for more backstory.

According to the LRT
the upper body nests two nodes apart from Yanornis (Fig. 1).

That makes me wonder
if the Chinese farmers who found Archaeovolans noticed that that it had a long tail, but not well preserved. So they added a tail and hind limbs from another available specimen. The nesting of Archaeovolans basal to birds with a long tail and apart from Yanornis is an interesting twist to this story of the farmers’ crude understanding of phylogenetic bracketing.

In any case, no one wants a forgery.
Better to have genuine partial fossils than to build a complete chimaera. and have it accepted by pterosaur experts.

Another notable difference in today’s revised LRT::
Enantiornithes is no longer a discreet clade, but a transitional grade between Solnhofen birds and crown birds. Prior to housekeeping enantiornine birds did form a separate clade with the London specimen of Archaeopteryx (Fig. 1) at the base.

Yet another notable difference in today’s revised LRT:
Phylogenetically miniaturized taxa (e.g. Microcursor and Protopteryx) nest between large Solnhofen birds and later Early Cretaceous birds.

Archaeovolans repatriatus
(IVPP V12444, Czerkas and Xu 2002) This Early Cretaceous bird had a controversial beginning as Archaeoraptor liaoningensis). Originally the the long stiff tail and hind limbs came from a different specimen, but phylogenetic bracketing indicates this genus did have a long stiff tail (Fig. 1) Zhou and Zhang (2002) considered the specimen another Yanornis, a taxon with a short pygostyle. Here Archaeovolans nests between enantiornithes and the London specimen of Archaeopteryx leading to Hesperornis (Fig. 1) and on the other branch, Eogranivora + higher birds.

Archaeopteryx lithographica
The London specimen – BMNH 37001, is the holoytype for the genus and species. Here it nests between Archaeovolans (above) and the STM9-52 specimen previously assigned to Yanornis (Fig. 1).

“Needs a new name” taxon
(Zhang & Zhou, 2001, STM9-52, Aptian, Early Cretaceous) was originally considered an ornithurine bird, close to Yanornis. Here this toothed bird with oversized hands, a long neck, and small head nests basal to a toothed bird with no hands: Hesperornis (Fig. 1). The sternum was greatly enlarged laterally and posteriorly, without a keel, as an anchor for powerful flight or swimming muscles, as in penguins. Tiny gastralia here are about to disappear. The sacrum is wide and the elements are not fused. The pubis extends the body posteriorly. Tiny triangular patellas are present, precursors to large patellas on Hesperornis.

Hesperornis regalis
(Marsh 1872a, b c) Late Cretaceous ~90 mya, 1.8m in length, was a toothed, flightless, marine loon-mimic with asymmetrical feet. It swam with powerful hind limb tipped by elongate lateral toes (digit #4), seen to a lesser extend in precursor clade members. This is one more example of flightlessness in the largest of its kind together with reduced wings. The premaxilla was elongated. The pectoral girdle was reduced and the humerus was a vestige. Note the large patella (in blue) extending above the femur. Huge muscles were anchored to the long pelvis. The teeth had bulbous roots and were set in a groove, convergent with mosasaurs like Tylosaurus.

Hesperornis, with no hands,
is a sister to the STM9-52 specimen. with the largest hands among tested taxa. At first glance, that might seem weird, but think of it this way. While Hesperornis swam like a loon, the STM9-52 specimen might have swam like a penguin, by flapping those large hands. Apparently (Fig. 1) this big hand / no hand split had origins prior to the Late Jurassic (based on the London specimen of Archaeopteryx).

As reported earlier,
key to understanding the previously murky origins of hesperornithids is the inclusion of precursor taxa that traditionally did not enter prior analyses. Taxon exclusion continues to be the number one problem in paleontology today. This is just one more example.

This appears to be a novel hypothesis of interrelationships.
If not, please send a citation to I can promote it here.

Czerkas SA and Xu 2002. Feathered Dinosaurs and the Origin of Flight, Czerkas SJ ed., The  Dinosaur Museum Journal 1: vi + 136 pp.
Marsh OC 1872a. Discovery of a remarkable fossil bird. American Journal of Science, Series 3, 3(13): 56-57.
Marsh OC 1872b. Preliminary description of Hesperornis regalis, with notices of four other new species of Cretaceous birds. American Journal of Science 3(17):360-365.
Marsh OC 1872c. Notice of a new and remarkable fossil bird. American Journal of Science, Series 3, 4(22): 344.
Marsh, OC 1880. Odontornithes, a Monograph on the Extinct Toothed Birds of North America. Government Printing Office, Washington DC.
Martin L 1984. A new Hesperornithid and the relationships of the Mesozoic birds. Transactions of the Kansas Academy of Science 87:141-150.
von Meyer H 1861. Archaeopteryx litographica (Vogel-Feder) und Pterodactylus von Solenhofen. Neues Jahrbuch für Mineralogie, Geognosie, Geologie und Petrefakten-Kunde. 1861: 678–679.
Owen R 1863. On the Archaeopteryx von Meyer, with a description of the fossil remains of a long-tailed species from the lithographic stone of Solnhofen. Philosophical Transactions of the Royal Society, London 153: 33-47.
Zhang F and Zhou Z 2001. A Primitive Enantiornithine Bird and the Origin of Feathers. Science 290 (5498): 1955-1959.

wiki/Archaeoraptor scandal

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