Caihong: the iridescent Jurassic troodontid

The preservation in situ is spectacular,
(Figs. 1, 2), but probably pales in comparison to the in vivo appearance of early Late Jurassic Caihong juju (PMoL-B00175 (Paleontological Museum of Liaoning, 161 mya), a new troodontid theropod dinosaur, which includes iridescent feathers.

Figure 1. Skull of Caihong from Hu et al. 2018.

Figure 1. Skull of Caihong from Hu et al. 2018. Arrow points to bony lacrimal crest/protuberance. At a screen resolution of 72 dpi this image of a 6cm long skull is about twice life size.

Caihong differs from other theropods

  1. Accessory fenestra posteroventral to promaxillary fenestra
  2. Lacrimal with prominent dorsolaterally oriented crests
  3. Robust dentary with anterior tip dorsoventrally deeper than its midsection
  4. Short ilium (<50% of the femoral length, compared to considerably >50% in other theropods).

Furthermore,
Caihong shows the earliest asymmetrical feathers and proportionally long forearms in the theropod fossil record. But the coracoids remained short discs. So it was not flapping those long feathered arms. It had extensively feathered toes. (Remember, chicken leg scales are former feathers and otherwise birds are naked beneath their feathers.)

About that unique lacrimal crest…
Note that the parietal has taphonomically moved anterior to the frontal. That’s odd, but it sets up another possibility for that elliptical crest bone. Look how it would precisely fit into the space created by the posterior parietal in dorsal view (Fig. 1). More precise, higher resolution data might provide some insight into this possibility.

Figure 2. Caihong overall in situ. This taxon nests better with Buitraptor, not Xiaotingia.

Figure 2. Caihong overall in situ. This taxon nests better with Buitraptor, not Xiaotingia.

Hu et al. nested Caihong
as a basal deinonyychosaur with the coeval Xiaotingia outside of the Troodontidae, but inside of the clade that includes two Solnhofen birds (only Archaeopteryx and Wellnhoferia). Microraptor, Dromaeosaurus and Rahonavis and others. The cladogram nests long-snouted Buitreraptor with Rahonavis and Unenlagia in an unresolved sister clade to the Xiaotingia/Caihong clade. Only a few nodes had Bootstrap scores higher than 50 and the nodes proximal to Caihong are not among them.

By contrast
the large reptile tree (LRT, 1153 taxa) nests long-snouted Caihong with even longer-snouted Buitreraptor in the troodontid clade that includes Anchiornis and Aurornis, basal to more derived troodontids and ‘Later’ Jurassic Solnhofen birds. Rahonavis and Microraptor nest with therizinosaurs and ornitholestids respectively.

Figure 1. Buitreraptor skull with bones and missing bones colorized.

Figure 3. Buitreraptor skull with bones and missing bones colorized. This skull is over 3x the size of Caihong.

Aurornis (Fig. 4) was basal, Caihong was transitional and Buitreraptor was derived in this clade of small troodontids with increasingly longer rostra.

Figure 1. Eosinopteryx and kin, including Xiaotingia, Aurornis and Archaeopteryx (Thermopolis).

Figure 4. Eosinopteryx and kin, including Xiaotingia, Aurornis and Archaeopteryx (Thermopolis).

Caihong may share these ‘unique’ traits
which are damaged in Buitreraptor. 

  1. Accessory fenestra posteroventral to promaxillary fenestra
  2. Lacrimal with prominent dorsolaterally oriented crests
  3. Robust dentary with anterior tip dorsoventrally deeper than its midsection
  4. Short ilium (<50% of the femoral length, compared to considerably >50% in other theropods).

References
Hu et al. (9 co-authors) 2018. A bony-crested Jurassic dinosaur with evidence of iridescent plumage highlights complexity in early par avian evolution. Nature.com/Nature Communications, 12 pp.  DOI: 10.1038/s41467-017-02515-y

Advertisements

The 11th Archaeopteryx: closer to Sapeornis

Figure 1. The 11th specimen attributed to Archaeopteryx in situ. See figure 2 for a reconstruction. This specimen remains in private hands without a museum number.

Figure 1. The 11th specimen attributed to Archaeopteryx in situ. See figure 2 for a reconstruction. This specimen remains in private hands without a museum number. Note all the soft tissue feathers preserved here.

Archaeopteryx number 11
(Figs. 1, 2) has no museum number and is in private hands, but Foth et al. 2014 published a description in Nature. These authors unfortunately considered this specimen just another Archaeopteryx, but one well supplied with feather impressions. In the large reptile tree (LRT, subset Fig. 3) this Solnhofen bird nests at the base of the node that produced two specimens of Sapeornis, a clade convergent with Euronithes in having a pygostyle.  The 11th specimen is complete and articulated, but lacks a large part of the cranium.

Figure 2. Most of the complete Solnhofen birds, including Archaeopteryx and the eleventh specimen to scale.

Figure 2. Most of the complete Solnhofen birds, including Archaeopteryx and the eleventh specimen to scale.

Foth et al. 2014 do not mention
the lack of a sternum. Sapeornis likewise lacks a sternum even though more primitive taxa have one.

Figure 4. The eleventh Archaeopteryx nests with Sapeornis.

Figure 4. The eleventh Archaeopteryx nests with Sapeornis.

At first glance
this appears to be an ordinary Archaeopteryx. However, when you put the dividers on the bones you find that it differs in subtle ways from the holotype and is more similar to Sapeornis and its sisters. As I mentioned yesterday, it would be a good thing for all early bird workers to start considering the Solnhofen birds individual genera, not a single genus. It’s just a lazy habit we have to overcome.

References
Foth C, Tischlinger H and Rauhut OWM 2014. New specimen of Archaeopteryx provides insights into the evolution.of pennaceous feathers. Nature 511:79–83.DOI: 10.1038/nature13467

Ostromia: The Haarlem specimen of Archaeopteryx

Updated January 17, 2018 with a new tracing and nesting of Ostromia as a sister to Eosinopteryx in the proximal outgroup clade to the birds. 

A recent paper
by Foth and Rauhut 2017 reexamined the incomplete Haarlem specimen on plate and counter plate (TM 6928, 6929, Figs. 1–3) originally attributed to a pterosaur (Pterodactylus crassipes, von Meyer 1857) and later to Archaeopteryx crassipes (Ostrom 1970). The co-authors renamed the specimen Ostromia crassipes and nested it with Anchiornis (Fig. 2), a larger troodontid with a short coracoid outside of the bird clade in the large reptile tree (LRT).

Figure 1. The Haarlem specimen of Archaeopteryx now named Ostromia crassipes.

Figure 1. The Haarlem specimen of Archaeopteryx now named Ostromia crassipes.

Foth and Rauhut 2017
considered Anchiornis“the possibly oldest and most basal clade of avialan, here named Anchiornithidae.” And they considered Ostromia the first and only anchiornithid outside of the Tiaojushan Formation of China.

Figure 1. Anchiornis, the pre-bird troodontid, to scale with Ostromia, the Solnhofen bird, the Haarlem specimen.

Figure 1. Anchiornis, the pre-bird troodontid, to scale with Ostromia, the Solnhofen pre-bird, the Haarlem specimen.

The authors employed a previously published phylogenetic analysis
from Foth et al. 2014. which looked at the privately owned 11th specimen of Archaeopteryx. Unfortunately their cladogram lumped all Archaeopteryx specimens (Fig. 3) together. So we’re dealing with a possible taxonomic chimaera and a certain taxon exclusion.

Figure 3. Several Solnhofen birds, including Archaeopteryx, compared to Ostromia to scale.

Figure 3. Several Solnhofen birds, including Archaeopteryx, compared to Ostromia to scale.

The variety shown by the Solnhofen birds
(Fig. 3) should invite phylogenetic analysis (Fig. 4). But Foth et al. (2014, 2017) did not respond to the invitation. If they had done so, perhaps they would have replicated the results of the LRT in nesting Ostromia with other coeval Archaeopteryx specimens. Their Ostromia nests here with Eosinopteryx, not with Anchiornis.

In size, strata and morphology
Ostromia nests rather closely to the other Solnhofen birds in the LRT, but in the proximal outgroup, along with Eosinopteryx and Xiaotingia.

I encourage bird workers
to not lump the Solnhofen birds together as a single taxonomic unit, but to split them into individual specimens. There’s a treasure to be found there. Each one deserves to be its own species, if not its own genus.

References
Foth C and Rauhut OWM 2017. Re-evaluation of the Haarlem Archaeopteryx and the radiation of maniraptoran theropod dinosaurs. BMC Evolutionary Biology 17:236
Foth C, Tischlinger H, Rauhut OWM 2014. New specimen of Archaeopteryx provides insights into the evolution of pennaceous feathers. Nature 511:79–82.
Ostrom JH 1970. Archaeopteryx: notice of a “new” specimen. Science. 1970;170:537_538.
Von Meyer H 1861. Archaeopteryx lithographica und Pterodactylus. N Jb Min Geognosie Geol Petrefaktenkd. 1861:678–679.

TM = Teylers Museum in Haarlem, the Netherlands

The origin of hummingbirds

Hummingbirds are the tiniest of living birds.
They are famous for hovering with wings beating so rapidly they essentially blur from view. Today hummingbirds live only in the New World.

Prum et al. 2015
based on DNA, nested hummingbirds with swifts and these nested with the nocturnal nightjars. That is the traditional nesting.

In the LRT 2015
based on morphology, hummingbirds nest with the extinct Eocypselus (Fig. 4, 50 mya) and the sea gull, Chroicocephalus (Figs. 1, 3; extant). Mayr 2004 reported on an Old World hummingbird, Eurotrochilus inexpectatus (Fig. 4; 30 mya), from the early Oligocene.

Elsewhere on the cladogram,
swifts nest with owls in the large reptile tree (LRT, 1129 taxa).

Figure 1. A sea gull hovering. Many birds can do this for short periods, but sea gulls are phylogenetic sisters to hummingbirds, so this is where it all began for hummers.

Figure 1. A sea gull hovering. Many birds can do this for short periods, but sea gulls are phylogenetic sisters to hummingbirds, so this is where it all began for hummers.

To be fair,
swifts also hover. And here is a sample of that on YouTube. https://www.youtube.com/watch?v=9u8YuBGQWb0
It should be noted that swifts do not feed while hovering. They speed through the air snatching insects in flight. On the other hand, gulls do hover, and here is another image of that (Fig. 2). Gulls appear to hover only in a breeze, which is often present at shorelines. Thus gulls represent the awkward origin of hummingbird hovering, which improved with faster wingbeats. a deeper sternum and a smaller size.

Figure 2. The smallest gull, Hydrocoloeus_minutus, hovering while feeding.

Figure 2. The smallest gull, Hydrocoloeus_minutus, hovering while feeding.

Fossils tell us
that hummingbird-sized specimens, like Eocypselus (Figs. 3, 4), lived 50 mya and probably originated much earlier. One-sixth the size of the small gull, Hydrocoloeus (Figs. 2, 3), Eocypselus had a relatively short, small beak and shorter legs, though still longer than the wings.

Figure 2. Chroicocephalus, the smaller Hydrocoloeus, the much smaller Eocypselus and the ruby-throated hummingbird, Archilochus to scale.

Figure 3. Chroicocephalus, the smaller Hydrocoloeus (the smallest living gull), the much smaller Eocypselus and the ruby-throated hummingbird, Archilochus to scale.

Of course, small size is key to hummingbird evolution.
At this point, I’m not aware of any gulls smaller than Hydrocoloeus, whether extant or in the fossil record. I would like to see a skeleton of Hydrocoloeus to see if it had a larger sternum relative to the 1.25x larger Chroicocephalus. I also wonder if it has a faster wingbeat when hovering based on its smaller size.

Figure 3. Eocypselus from 50 mya, Eurotrochilus, from 30 mya and Archilochus, the extant ruby-throated hummingbird to scale.

Figure 4. Eocypselus from 50 mya, Eurotrochilus, from 30 mya and Archilochus, the extant ruby-throated hummingbird to scale.

The fossil Eutrochilus
(Fig. 4, Mayr 2004) bridges the time gap between Eocypselus and extant hummingbirds and would appear to be a complete and fully realized hummingbird itself, living some 30 mya, while originating much earlier. Eocypselus (Fig. was not much different in size or morphology.

Old World vs. New World
So, based on Eutrochilus, hummingbirds used to be in Europe. Now they are restricted to the New World. Why? There is a long list of hummingbird eaters online here. Something killed European hummingbirds in the Old World… maybe microbes?

Vultures had a similar split.
Today we have New World vultures (like Coragyps, derived from petrels) and Old World vultures (like Torgos, derived from falcons) in the LRT. The odd exception to this hemispherical split is the dodo, Raphus, and its kin, all New World flightless vultures isolated on islands in the Old World. Then there’s a report of an Old World vulture in Miocene Nebraska (Zhang et al. 2012). Really, what’s to stop them? And what killed Old World vultures in the New World? So again, there’s another mystery in need of a good explanation.

References
Mayr G 2004. Old World fossil record of modern-type hummingbirds. Science 304:861–864,
Ksepka DT, Clarke JA, Nesbitt SJ, Kulp FB and Grande L. 2013. Fossil evidence of wing shape in a stem relative of swifts and hummingbirds (Aves, Pan-Apodiformes). Proceedings of the Royal Society B: Biological Sciences 280 (1761): 20130580. doi:10.1098/rspb.2013.0580. Supplementary materials here.
McGuire JA et al. (7 coauthors) 2014. Molecular Phylogenetics and the Diversification of Hummingbirds. Current Biology, 2014; DOI: 10.1016/j.cub.2014.03.016
Zhang Z, Feduccia A and James HF 2012. A Late Miocene Accipitrid (Aves: Accipitriformes) from Nebraska and Its Implications for the Divergence of Old World Vultures. PLoS ONE7(11): e48842. https://doi.org/10.1371/journal.pone.0048842

https://wordpress.com/post/pterosaurheresies.wordpress.com/10805
https://www.livescience.com/44593-first-hummingbird-evolutionary-tree.html

Extant bird phylogeny: basal divisions

Using the same 231 characters from
the large reptile tree (LRT, 1085 taxa) the subset of extant birds and their allies also came out fully resolved (Fig. 1).

Figure 1. 5-frame GIF of a subset of the LRT focused on extant birds and their closest relatives. Though incomplete, patterns are emerging.

Figure 1. 5-frame GIF of a subset of the LRT focused on extant birds and their closest relatives. Though incomplete, patterns are emerging. Please note: Aepyornis now nests with Struthio. 

Prum et al. 2015 used DNA
to determine the phylogeny of Neoaves (nearly all living bird species). They reported this “remains the greatest unresolved challenge in dinosaur systematics”, but that was before the recent alignment of Ornithischia and Theropoda by Baron et al. 2017.

I have to admit
as usual, before I started adding more extant birds to the LRT, I knew nothing about them. Their generic names were new to me. You might remember the LRT started with just a chicken (Gallus) and an ostrich (Struthio). Now there are 42 birds with 143 outgroup taxa.

Birds are tough.
Often they fuse skull bones. That may be why other workers find protrusions and bumps to base their traits on. Some of the best data for many taxa come from decades old drawings and photos from skull sellers. I made many mistakes along the way, now minimized. The cladogram was my mentor here, telling me with autapomorphies where to look for mistakes.

Matching all prior workers,
tinamous and ratites were recovered as basalmost taxa. In the Prum et al. DNA study, chickens, crakes, screamers and ducks branch off first. In the LRT, which includes extinct taxa, the predators and toothed birds split off first. Distinct from the Prum et al. study, in the LRT long-legged walking birds are basal to many clades. Even the basalmost toothed bird, Yanornis, from the Early Cretaceous, is a long-legged walking bird, also capable of flying. And yes, this puts the origin of the clade of extant birds back to just after the Jurassic. Jurapteryx, from the Late Jurassic, is not far off.

Herons come next,
followed by all other birds with the corn crake (Crex) the hammerkop (Scopus) and the limp kin (Aramus) at the base. Adding taxa allows me to amend an earlier nesting of the elephant bird (Aepyornis) with ducks. Now Struthio and Aepyornis nest together.

In the Prum et al. study
swifts + hummingbirds split off after chickens + ducks.

By contrast,
in the LRT swifts (Eocypselus) and hummingbirds (Archilochus) nest between terns (Thalasseus) and kingfishers (Megaceryle). Nearby, high-energy dippers (Cinclus) nest with other wing swimming birds: murres (Uria) and penguins (Aptenodytes). Cinclus is traditionally considered a passerine, but the sparrow, Passer, does not nest with it in the LRT. Passer nests between chickens and parrots (Ara), all seed eaters.

In the Prum et al. study
seed-eating passerines arise from carnivorous falcons and seriema (Cariama). That does not seem right on the face of it. In the LRT passerines arise from omnivores, like Chauna.

Neotony
juvenile traits found in adult specimens, evidently produced all of our short-legged birds and produced smaller adult birds, found at derived nodes. Juveniles of flamingos and other long-legged taxa have short legs. Of course, some small birds also had large and giant descendants, all at derived nodes.

As in many studies that conflict with the LRT
the lack of appropriate fossil outgroup taxa seems to set their cladograms in other directions. That can happen. DNA studies can never solve this problem.

Apologies for earlier mistakes due to
naive misidentifications and taxon exclusion. Those will be repaired.

Nullius in verba

References
Baron MG, Norman DB, Barrett PM 2017. A new hypothesis of dinosaur relationships and early dinosaur evolution. Nature  543:501–506.
Prum RO et al. (6 coauthors) 2015.
A comprehensive phylogeny of birds (Aves) using targeted next-generation DNA sequencing.

Splitting up the Palaeognathae

Distinct from earlier DNA and morphological studies
members of the Euornithes (extant birds and their closest kin) are undergoing tree topology shifts when they enter the large reptile tree (LRT, 1076 taxa). We’ve seen this before with other reptile and mammal clades.

Today we’ll be talking about
the base of the Euornithes, the ratites and tinamous (= Palaeognathae).

Ratites have no keel on their sternum.
But that keel fails to appear on several flightless birds in several clades. Wikipedia reports, “Flightlessness is a trait that evolved independently multiple times in different ratite lineages. The systematics involved [in the ratites] have been in flux.”

Wikipedia reports,
“There are three extinct groups [of Palaeognathae], the Lithornithiformes (Lithornis + Pseudocrypturus.), the Dinornithiformes (moas) and the Aepyornithiformes (elephant birds), that are undisputed members of Palaeognathae.” 

Disputing those traditional assignments,
in the LRT (Fig. 1):

  1. the moa, DInornis, nests with parrots
  2. the elephant bird, Aepyornis, nests with the ostrich, Struthio.

When I added
the kiwi
Apteryx Fig. 2) and elephant bird (Aepyornis (Fig. 3) to the LRT a monophyletic clade(?) Ratites + tinamous (= Palaeognathae; pink taxa in Fig. 1) was not recovered. The remaining ratites are not a clade, but a grade of basal birds with tinamous, like Rhynchotus, nesting basal to and the proximal outgroup to the clade Neognathae.

And yes, the Solnhofen bird
Jurapteryx recurva (= Eichstätt specimen of Archaeopteryx) is the basalmost member (= last common ancestor) of the Euornithes. That means, someday we’ll be finding palaeognathid ostrich, cassowary and tinamou ancestors in the Early and Late Cretaceous. That has not happened yet (to my knowledge).

Currently filling this Cretaceous gap
are the toothed birds Yanornis, Apsaravis, Ichthyornis and HesperornisThey now nest within the Euornithes (the clade of extant birds). Evidently teeth redeveloped in this clade as they did in Pelagornis, the giant albatross-like bird with bony teeth. Earlier we looked at the reappearance of digit ‘0’ in screamers, so old genes can and do reassert themselves in birds.

Without this clade of toothed Cretaceous birds
there would have been, a long Cretaceous gap in the fossil record of Euornithes. I’m sure this gap will be filled someday with toothless birds. When it is filled phylogenetic bracketing indicates they’re going to look like dippers, like Cinclus, and screamers, like Chauna. As mentioned earlier, this gap is currently not filled, nor even hinted at (Fig. 1).

Figure 2. Jurapteryx, Pseudocrypturus, Apteryx and Proapteryx to scale.

Figure 2. Jurapteryx, Pseudocrypturus, Apteryx and Proapteryx to scale. Now we know why the gastralia disappeared in this clade!

When you put both Pseudocrypturus and Apteryx together
to scale (Fig. 2) the several reasons (traits) why they nest together become more obvious. This is contra recent DNA studies that nest elephant birds with kiwis (Mitchell et al. 2014). That study represents one more incidence of the loss of validity with DNA over large phylogenetic distances along with the typical problem of taxon exclusion that the LRT attempts to minimize.

Archaeopteryx (Jurapteryx) recurva 
(JM2257; the Eichstätt specimen; Howgate 1985) is one of the smaller Solnhofen birds. Here it nests as the last common ancestor of all extant birds. A gap spanning the entire Cretaceous separates this taxon from extant taxa and their kin. As in other bird lines, the loss of tail length, the fusion of the pygostyle and the fusion of manus elements are convergent.

Pseudocrypturus cercanaxius 
(Houde 1988; Early Eocene) was originally considered a northern hemisphere ancestor to ratites (like the ostrich, Struthio). That is true, but Pseudocrypturus is also close to the ancestry of all extant birds. Today primitive flightless birds are chiefly restricted to the southern hemisphere. It could be that early birds did start in the South and had migrated to the North during the Paleocene (66-56 mya) or earlier. Perhaps something very much like it was one of the few survivors of the K-T extinction event.

It’s notable that Pseudocrypturus has long legs. Early ducks, like Presbyornis, and basal raptors, like Sagittarius, also had long legs. Evidence is building that this is the primitive condition for the clade of living birds arising from the K-T extinction event.

Apteryx 
(Shaw 1813) The extant flightless kiwi has an elongate naris that extends to the tip of its beak. Maybe two teeth are there. Here it nests with Pseudocrypturus, but flightless traits linking it toward Struthio are by convergence. In the pre-cladistic era, Calder (1978, 1984) considered the kiwi a phylogenetic dwarf derived from the larger moa, but that was invalidated by Worthy et al. 2013 and the LRT.

Note that
Proapteryx (Worthy et al. 2013; Miocene), known from a partial femur and coracoid, falls within the size range of Jurapteryx (Late Jurassic). Proapteryx likely was volant.

References
Calder WA 1978. The kiwi. Scientific American 239(1):132–142.
Calder WA 1984. Size, function and life history. 448 pp. Cambridge (Harvard U Press).
Houde PW 1986. Ostrich ancestors found in the northern hemisphere suggest new hypothesis of ratite origins. Nature 324:563–565.
Houde PW 1988. Paleognathus birds from the early Tertiary of the northern hemisphere. Publications of the Nuttall Ornithological Club 22. 147 pp.
Howgate ME 1985. Problems of the osteology of Archaeopteryx: is the Eichstätt specimen a distinct genus?. In Hecht, Ostrom, Viohl, and Wellnhofer (eds.), The Beginnings of Birds: Proceedings of the International Archaeopteryx Conference, Eichstätt 1984. Freunde des Jura-Museums Eichstätt, Eichstätt 105-112.
Mitchell KJ (seven coauthors) 2014. Ancient DNA reveals elephant birds and kiwi are sister taxa and clarifies ratite bird evolution. Science. 344 (6186): 898–900.
Shaw 1813. Naturalist’s Miscellany 19:
Worthy TH et al. 2013. Miocene fossils show that kiwi (Apteryx, Apterygidae) are probably not phyletic dwarves. Paleornithological Research 2013, Proceedings of the 8th International Meeting of the Society of Avian Paleontology and Evolution.

wiki/Jurapteryx
wiki/Pseudocrypturus
wiki/Apteryx, Kiwi
wiki/Proapteryx
wiki/Dipper
wiki/Proapteryx

Study says: toothless beak + grainivory in basalmost Paleocene birds

Larson , Brown and Evans 2016 conclude:
“To explain this sudden extinction of toothed maniraptorans and the survival of Neornithes, we propose that diet may have been an extinction filter and suggest that granivory associated with an edentulous beak was a key ecological trait in the survival of some lineages.” … like birds (Euornithes).

A few days ago we looked at the most likely candidate at present to nest at the base of all extant birds, and it wasn’t a little seed-eater. Unfortunately, the Larson et al. study was done without a phylogenetic analysis based on morphology. So they don’t know what the basalmost Euornithine was or looked like. Rather they looked at tooth shapes in derived theropods… and threw a Hail Mary pass.

The authors report,
“To date, only one Maastrichtian bird has been assigned to a crown group clade based on a phylogenetic analysis [1], suggesting that crown group birds were less common than contemporary non-neornithine birds in the Cretaceous. There are also no Late Cretaceous neornithines or advanced ornithuromorphs with known cranial remains.”

Seed eaters
as basalmost Euornithine birds appears unlikely given that basalmost Euornithine birds resemble cranes and ratites. Moreover, the crown group Maastrichtian bird isn’t part of the crown group according to the LRT.

References
Larson DW, Brown CM and Evans DC 2016. Dental Disparity and Ecological Stability in Bird-like Dinosaurs prior to the End-Cretaceous Mass Extinction. Current Biology 26(10):1325–1333.