Sexual selection: a peacock’s tale

Today’s topic began with a YouTube video
featuring Richard Dawkins and Bret Weinstein (click to view). They discussed the peacock’s elaborate plumage with the idea that peahens were choosing the most magnificent displays. Weinstein opined that it may be more difficult for males to survive with such long trains (= tail feathers folded away, extending posteriorly). Thus females were handicapping their male offspring by selecting peacock mating partners with longer and longer more elaborate tail feathers.

According to Wikipedia:
“The function of the peacock’s elaborate train has been debated for over a century. In the 19th century, Charles Darwin found it a puzzle, hard to explain through ordinary natural selection. His later explanation, sexual selection, is widely but not universally accepted. In the 20th century, Amotz Zahavi argued that the train was a handicap, and that males were honestly signalling their fitness in proportion to the splendour of their trains. Despite extensive study, opinions remain divided on the mechanisms involved.”

Figure 3. Peafowl mating. The males stands crouched upon the back and hips of the female.

Figure 1. Peafowl mating. The males stands crouched upon the back and hips of the female.

Phylogenetically,
in the large reptile tree (LRT, 1735+ taxa) peafowl (genus: Pavo) nest with the common chicken (genus: Gallus). Both are terminal taxa.

At the start, I question:

  1. Do peahens always or often or used to pick the most lavish peacock?
  2. Do peacocks actually compete with each other? Or do most of them give up after sizing up the competition?
  3. Do peacocks mate with as many peahens as they can or do they form pair bonds?
  4. In other words, have we examined the situation enough to know?
  5. Were Dawkins and Weinstein just guessing based on end results?
  6. Added after publication, based on a a reader’s comment: What are the differences between domestic and wild peafowl? (If there are any wild peafowl.)

Summarizing earlier studies, Callaway 2011 wrote:
“Size doesn’t always matter for peacocks. Peahens don’t necessarily choose the males with the biggest tails — but small tails are right out.”

Takahashi et al. 2008 concluded,
“our findings indicate that the peacock’s train (1) is not the universal target of female choice, (2) shows small variance among males across populations and (3) based on current physiological knowledge, does not appear to reliably reflect the male condition.”

Yorzinski et al. 2017 write:
“In species where a male trait is only evaluated by one of the sexes, it is often the males that are assessing the trait, suggesting that male traits often evolve initially in the context of male–male competition, and subsequently, in female choice (Berglund et al., 1996; Borgia and Coleman, 2000). 

Like deer antlers or any other tournament species. Meanwhile, what are the peahens doing?

“We know little about how animals selectively direct their attention during mate and rival assessment. Previous work has shown that female peafowl shift their gaze between potential mates and their environment, potentially scanning for predators and other conspecifics while assessing mates. And, when evaluating a mate, peahens selectively direct their attention toward specific display regions of peacocks. In contrast, we do not know how males selectively alter their attention when assessing other males. (Citations deleted).

“We therefore investigated how males direct their attention when they assess potential rivals, using peacocks as a model system.”

“Competition among peacocks is intense as mating success is highly skewed toward a small proportion of successful males. Males compete with each other by displaying their erect trains or walking parallel to other males. If aggression escalates, they chase each other and engage in fights that consist of them jumping and using their spurs Males with longer trains and tarsi establish territories in central locations within leks and engage in more agonistic behaviors with other males. In contrast, males with shorter trains are less likely to establish display territories (Citations deleted).

“it is clear from these sample periods that males spend a significant fraction of their time monitoring their rivals.

“While assessing their competitors, peacocks did not spend very much time looking at females. In fact, they allocated less than 5%

“Further experiments will be necessary to determine how much time males allocate to monitoring females while they are courting them. We found that when males directed their gaze toward females,

Peacocks also devote a significant amount of their daily time budget to preening (Walther, 2003) and directing attention toward themselves could allow them to monitor the condition of their feathers.

“Similar to the results in this study on peacocks, peahens primarily gazed at the lower display regions of males: at their lower trains, body and legs (Yorzinski et al., 2013).”

Here are a few, short ‘peacocks on display’ YouTube videos 
showing the variation in the use of the display behavior or lack thereof.

Callaway 2011 quotes Petrie (of Petrie and Halliday 1994),
“At the end of the day, we will never know what peahens are looking at and how they select their mates. You can’t ask them.”

Figure 2. Peacock flying.

Figure 2. Peacock flying.

One final thought:
Since predators are likely to attack from the rear of the peacock (video #3 above), what a tiger will get is a mouthful or paw-full of feathers, which can detach under sufficient strain, much like the expendable tail of certain lizards. Thus the hypothesis that a long train of feathers is an impediment to survival in an attack may be true only rarely… which is one reason why peacocks are a relatively successful species, all hypothetical doubts aside.


References
Callaway E 2011. Size doesn’t always matter for peacocks. Nature 1107 online
Dakin R and Mongomerie R 2011. Peahens prefer peacocks displaying more eyespots, but rarely. Animal Behaviour doi:10.1016/j.anbehav.2011.03.016
Petrie M and Halliday T 1994. Experimental and natural changes in the peacock’s (Pavo cristatus) train can affect mating success. Behavioral Ecology and Sociobiology 35, 213-217.
Takahashi M, Arita H, Hiraiwa-Hasegawa M and Hasegqawa T 2008. Peahens do not prefer peacocks with more elaborate trains. Animal Behaviour 75(4):1209–1219.
Yorzinski JL, Patricelli GL, Bykau S and Platt ML 2017. Selective attention in peacocks during assessment of rival males. Journal of Experimental Biology (2017) 220, 1146-1153 doi:10.1242/jeb.150946

wiki/Indian_peafowl
https://www.nature.com/news/2011/110418/full/news.2011.245.html

Shedding new light (literally!) on Jianianhualong: Li et al. 2020

Li et al. 2020 used various frequencies of light
and spectroscope technology on the holotype bones and feathers of Jianianhualong (Figs. 1, 2; Early Cretaceous, Xu et al. 2020, DLXH 1218) to identify specific elements in the matrix and specimen.

From the abstract:
“Here, we carried out a large-area micro-X-Ray fluorescence (micro-XRF) analysis on the holotypic specimen of Jianianhualong tengi via a Brucker M6 Jetstream mobile XRF scanner.”

Figure 2. Jianianhualong, Serikornis and Jurapteryx to scale.

Figure 1a. Jianianhualong, Serikornis and Jurapteryx to scale.

Figure 1. Jianianhualong tengi in situ. This is the largest among the early birds, a fact overlooked by the Xu et al. 2017. Think of Jianianhualong as a giant Archaeopteryx!

Figure 1b. Jianianhualong tengi in situ. This is the largest among the early birds, a fact overlooked by the Xu et al. 2017. Think of Jianianhualong as a giant Archaeopteryx!

From the abstract:
“Jianianhualong tengi is a key taxon for understanding the evolution of pennaceous feathers as well as troodontid theropods, and it is known by only the holotype, which was recovered from the Lower Cretaceous Yixian Formation of western Liaoning, China.” 

What they didn’t do is to rerun their phylogenetic analysis with more taxa (Fig. 2).

What they didn’t do is to create a reconstruction, perhaps using DGS to precisely trace and segregate the bones to rebuild the skeleton (Figs. 1, 3, 4).

Figure 2. Subset of the LRT focusing on Pennaraptora 2014 = Tyrannoraptora 1999. Here Khaan and Velociraptor substitute for Oviraptor and Deinonychus.

Figure x. Subset of the LRT focusing on birds and their ancestors. Jianianhualong nests within Aves (five taxa from the bottom).

By contrast,
in the large reptile tree (LRT, 1730+ taxa) Jianianhualong nests within Aves (five taxa from the bottom of Fig. 2) even though it was clearly not volant due to its much larger size and smaller forelimbs. Close relatives include Archaeopteryx (= Jurapteryx) recurva (= Eichstätt specimen, Fig. 3) and the privately held #11 specimen of Archaeopteryx.

The authors think Jianianhualong is a troodontid.
According to Wikipedia“A number of characteristics allow Jianianhualong to be identified as a member of the Troodontidae. These include:

  1. the long forward-projecting branch and flange of the lacrimal bone; [✓]
  2. the foramina on the nasal bone; [?]
  3. the smooth transition between the eye socket and the backward-projecting branch of the frontal bone; [✓]
  4. the ridge on the forward-projecting branch of the jugal bone; [✓]
  5. the triangular dentary bearing a widening groove; [✓]
  6. the robust forward-projecting branch of the surangular bone; [✓]
  7. the relatively large number of unevenly-distributed teeth; [✓]
  8. the flattened chevrons with blunt forward projections and bifurcated backward projections; [✓]
  9. and the broad and flat “pubic apron” formed by the pubic bones.” [?]
Figure 3. The Eichstätt specimen, Jurapteryx recurva, nests with the living ostrich, Struthio, presently in the LRT.

Figure 2. The Eichstätt specimen, Jurapteryx recurva, nests with the living ostrich, Struthio, presently in the LRT.

Professor Larry Martin would be so proud!
Why? Because the Wikipedia author (above) is using a list of traits to support an hypothesis of interrelationships rather than using a cladogram to support that hypothesis.  Checkmarks [✓] indicate traits Jurapteryx shares. Question marks [?] indicate traits not shown in Jianianhualong or Jurapteryx. Or did I miss something?

The problem is,
various authors add taxa to the Troodontidae that don’t belong there in the LRT, as we learned earlier here. The LRT; subset Fig. x) recovers Jiaianhualong as the largest known member of the Sapeornis/Jurapteryx clade of birds. Several flightless birds are in this clade. These could be confused with troodontids for that reason. In the LRT the clade Troodontidae include Sinornithoides + Sauronithoides their LCA and all derived taxa. None of these are direct bird ancestors.

Getting back to chemistry
“The bone in Jianianhualong is, as expected rich in calcium and phosphorus, corresponding mineralogically to apatite. The regions where feather remains can be observed show an enrichment and correlation pattern of several elements including manganese, titanium, nickel and copper.”

FIgure 2. GIF animation of the skull of Jianianhualong showing original tracing in line art and colorized bones (DGS) used to create a reconstruction (Fig. 3).

FIgure 3. GIF animation of the skull of Jianianhualong showing original tracing in line art and colorized bones (DGS) used to create a reconstruction (Fig. 3).

Jianianhualong is a troodontid-like bird,
not a bird-like troodontid. Note the odd scapula shape, like that in Sapeornis. Note the retrovered pedal digit 1, showing this taxon was derived from perching birds. The tall naris and long tibia are autapomorphies.

Xu et al. 2014 made a headline out of
the asymmetric feathers found with Jianianhualong. In the present context, Jianianhualong is derived from volant ancestors. So asymmetry is expected, not exceptional. This is the earliest known large flightless bird, not an example of the invalid hypothesis of ‘mosaic’ evolution.

Figure 3. Reconstruction of the skull of Jianianhualong based on DGS tracings in figure 2.

Figure 4. Reconstruction of the skull of Jianianhualong based on DGS tracings in figure 2.

Liaoningventor curriei (Shen et al. 2017; DNHM D3012; Early Cretaceous) was also originally described as a non-avian troodontid, but nests with Jianianhualong as a flightless bird.


References
Li J, et al. (8 co-authors 2020. Micro-XRF study of the troodontid dinosaur Jianianhualong tengi reveals new biological and taphonomical signals. bioRxiv 2020.09.07.285833 (preprint) PDF doi: https://doi.org/10.1101/2020.09.07.285833
https://www.biorxiv.org/content/10.1101/2020.09.07.285833v1
Shen C-Z, Zhao B, Gao C-L, Lü J-C and Kundrat 2017. A New Troodontid Dinosaur (Liaoningvenator curriei gen. et sp. nov.) from the Early Cretaceous Yixian Formation in Western Liaoning Province. Acta Geoscientica Sinica 38(3):359-371.
Xu X, Currie P, Pittman M, Xing L, Meng QW-J, Lü J-C, Hu D and Yu C-Y 2017. Mosaic evolution in an asymmetrically feathered troodontid dinosaur with transitional features. Nature Communications DOI: 10.1038/ncomms14972.

wiki/Sapeornis
wiki/Jianianhualong
wiki/Liaoningvenator

“Pulling a Larry Martin” with basal bird pectorals and hands

This is a cautionary tale
The following blog reminds all workers to score the entire specimen if possible, and to score as many more-or-less-complete specimens as possible. Why?

It is of vital importance to use as much data as possible
when scoring each taxon in a phylogenetic analysis to remove any trace of attraction by convergence that happens when just using bits and pieces of cherry-picked taxa.

From Pittman et al. 2020,
“Generally during early avian evolution, the furcula, coracoid, and sternum become more craniocaudally elongate, while the manual digits become reduced and fusion between the metacarpals increases.” 

Not true. In a valid phylogenetic context (Figs. 1–3), like the wide gamut large reptile tree (LRT, 1729+ taxa; subsets Figs. 2, 3), some taxa developed birdy traits quickly while others dawdled or reversed. In this way some bones demonstrated convergence with other less related clades. With this in mind, start with a valid unbiased topology, then let the taxa tell their own story. Avoid the temptation of an easy diagram. Do the necessary work.

Figure 1. Avian furcula aviation from Pittman et al. 2020 and repaired based on LRT results. Let your software decide based on the whole specimen. Convergence is rampant as you can see here.

Figure 1. Avian furcula aviation from Pittman et al. 2020 and repaired based on LRT results. Let your software decide based on the whole specimen. Convergence is rampant as you can see here.

Due to taxon exclusion
Pittman et al. mixed up the order of the pectoral girdles + hands of basal birds (Fig. 1), hoping to tell the story they wanted to tell: gradual evolution. Not only did they skip about a dozen pertinent taxa, they got the order wrong by eyeballing a few traits on cherry-picked taxa.

With more taxa, as in the LRT,
(Figs. 2, 3) the girdles and limbs are phylogenetically re-ordered here (Fig. 1, layer 2 with colors). If Pittman et al. wanted to show gradual evolution, they needed to first establish a valid tree topology by adding more taxa. Instead, by cherry-picking certain traits to show gradual evolution, Pittman et al. were “Pulling a Larry Martin“, putting individual traits on cherry-picked taxa ahead of an entire suite of traits and a wide gamut of taxa.

Figure 2. Subset of the LRT focusing on Pennaraptora 2014 = Tyrannoraptora 1999. Here Khaan and Velociraptor substitute for Oviraptor and Deinonychus.

Figure 2. Subset of the LRT focusing on Pennaraptora 2014 = Tyrannoraptora 1999 = Coelurosauria 1914. Here Khaan and Velociraptor substitute for Oviraptor and Deinonychus.

Figure 2. Subset of the LRT focusing on bird origins. Crown birds and toothed birds are highlighted.

Figure 3. Subset of the LRT focusing on bird origins. Crown birds and toothed birds are highlighted. Figure 2 is slightly more up-to-date, but includes fewer extant birds.

When the phylogenetic order is corrected
based on unbiased results recovered by the LRT (subsets Figs. 2, 3), what seemed to Pittman et al. a gradual transitional series is here revealed to be an example or two of convergence. Note the similarly elongate coracoids on the enantiornithine Parabohaiornis and the unrelated ornithurine, Yanornis (Fig. 1`), derived from an Early Cretaceous sister to a living taxon, Megapodius.

Time after time paleontologists cherry-pick taxa.
That has to stop. Add more taxa and let the software decide the tree topology. Similarly, don’t rely on parts alone (Fig. 1) to illustrate hypotheses, unless they represent taxa already nesting together based on all of their parts and a wide gamut of taxa. Body parts, like hands and girdles, can converge, as they do here.

Figure 3. Mammal tooth evolution alongside odontocete tooth evolution, reversing the earlier addition of cusps.

Figure 4. Mammal tooth evolution alongside odontocete tooth evolution, reversing the earlier addition of cusps.

On a similar note, basal mammal workers
have put too much reliance on tooth traits. Unfortunately, sometimes that’s all they have. If so, what should they do? They should build a tree topology based on complete or more nearly complete specimens. THEN fit it in those tooth and mandible taxa once the tree topology is established in a broader sense, as in the LRT. Earlier (Fig. 4) you saw how odontocete and archaeocete traits brilliantly document a step-by-step reversal to a simple cone shape, like those of basal pelycosaurs. The addition, subtraction and modification of tooth cusps in mammals occurred much more widely than shown by this one example.


References
Pittman M, O’Connor J, Field DJ, Turner AH, Ma W, Makovicky P and Xu X 2020.
Pennaraptoran Systematics. Chapter 1 from Pittman M and Xu X eds. 2020. Pennaraptoran theropod dinosaurs. Past progress and new Frontiers. Bulletin of the American Museum of Natural History 440; 353pp. 58 figures, 46 tables.

https://pterosaurheresies.wordpress.com/2020/08/23/pennaraptora-avoid-this-junior-synonym/

Specimen STM 15-15 of Sapeornis under the laser and DGS

Serrano et al. 2020
used Tom Kaye‘s laser-stimulated fluorescence (LSF) device to reveal more feathers on the STM 15-15 specimen of Sapeornis more clearly than in visible light (Fig. 1). All the glue between the reassembled stones also shows up much more clearly. In this specimen the bones are easier to see in visible light. Under LSF everything organic glows: feathers, bones, guts.

Figure 1. Sapeornis specimen STM-1515, in situ, under laser, under DGS.

Figure 1. Sapeornis specimen STM 15-15, in situ, under laser and under DGS. Ventral view. Here bones are easier to see in visible light, feathers under laser.

From the abstract
“Unseen and difficult-to-see soft tissues of fossil birds revealed by laser-stimulated fluorescence (LSF) shed light on their functional morphology. Here we study a well-preserved specimen of the early pygostylian Sapeornis chaoyangensis under LSF and use the newly observed soft-tissue data to refine previous modeling of its aerial performance and to test its proposed thermal soaring capabilities.”

Figure 2. Sapeornis skull specimen STM 1515

Figure 2. Sapeornis skull specimen STM 15-15

From the discussion
“Our study is the first to use the preserved body outline of a fossil bird—as revealed under LSF—to refine its flight modeling.”

Figure 3. Sapeornis skull, specimen STM 1515.

Figure 3. Sapeornis skull reconsructed —  specimen STM 15-15.

An overlay of colors in Photoshop
(Figs. 1, 2 = digital graphic segregation, DGS) also helps each bone stand out from the matrix. Moreover, the color tracings are used to build a reconstruction (Figs. 3, 4) from which it is easier to compare features, point-by-point with other Sapeornis specimens (Fig. 4).

In this way, character scores are backed up
with visual data for referees and readers to quickly judge whether the contours of every bone are valid or not without laboriously examining every score and every centimeter of every in situ specimen. Given the world-wide dispersal of fossils and occasional permission restrictions, DGS tracings just make things easier.

An earlier specimen of Sapeornis
(IVPP V13276; Fig. 4), from a previous post, is grossly similar and larger than STM 15-15. Subtle differences (e.g. toe length, coracoid shape, sternae presence, maxillary tooth presence, etc.) separate the two individuals, perhaps splitting them specifically. Even so, the two humeri are nearly identical in size and shape, despite the overall size differences.

Figure 4. Sapeornis specimen STM 15-15 reconstructed from DGS tracing, figure 1 compared to a more robust specimen with larger feet but an identical humerus.

Figure 4. Sapeornis specimen STM 15-15 reconstructed from DGS tracing, figure 1 compared to a more robust IVPP V13276 specimen with larger feet but an identical humerus.

Sapeornis chaoyangensis (Zhou and Zhang 2002. 2003; Early Cretaceous; IVPP V13276) is a basal ornithurine bird, the clade that gave rise to modern birds. Sapeornis nests in the same clade as Archaeopteryx recurva, the Eichstätt specimen, in the large reptile tree (LRT, 1729+ taxa). The short tail was tipped with a pygostyle and a fan of feathers. The coracoids were oddly wide and relatively short.


References
Serrano FJ, Pittman M, Kaye TG, Wang X, Zheng X and Chiappe LM 2020.
Laser-stimulated fluorescence refines flight modeling of the Early Crettaceous bird Sapeornis. Chapter 13 in Pittman M and Xu X eds. Pennaraptoran theropod dinosaurs. Past progress and new Frontiers. Bulletin of the American Museum of Natural History 440; 353pp. 58 figures, 46 tables.

What happened to the postfrontal and postorbital in birds?

Fauth and Rauhut 2020 bring us
“A short overview of the evolution of the skull of birds.”

From the first paragraph (Google translated from German)
“There are a number of advantages to being able to fly, be it the possibility of rapid geographical expansion, the settlement of trees, the escape from predators or the development of new feed sources, including prey capture. However, it cannot be regarded as the sole factor for the success of birds.”

Thereafter
the authors discuss and show (Fig. 1) skull traits, but make a traditional mistake based on a lack of attention to detail. Foth and Rauhut provide only one figure (Fig. 1), in which the postorbital is identified (in orange) only in Allosaurus (B) Archaeopteryx (C) and the enanthiornine, Shenqiornis (D). The postorbital is deemed absent in the extant Crax (A) and the extinct Ichthyornis (E) despite its presence in their diagram.

Figure 1. Theropod and bird skulls from Foth and Rauhut 2020. Postorbital is highlighted in orange, but not the same vestigial postorbital is not highlighted in bird skulls.

Figure 1. Theropod and bird skulls from Foth and Rauhut 2020. Postorbital is highlighted in orange, but not the same vestigial postorbital is not highlighted in bird skulls. Note: ‘Archaeopteryx’ is a wastebasket taxon with variation among the 13 known specimens.

Unfortunately
Foth and Rauhut took the easy way out by using previously provided oversimplified diagrams that lack the data needed to create a valid figure. They also followed paleontological tradition, which, at times like this, fail to provide valid data in the details.

Here are the missing details
in an actual Crax skull (Fig. 2) colorized using DGS methods. It shows a descending postfrontal (orange) and a vestigial postorbital (yelllow splint, but see caption for one more option). The postfrontal is largely fused to the frontal, but that does not negate its presence. No unfused frontal descends beyond mid depth in any vertebrate skull. We should label and score with reason, not with invalid traditions.

Figure 1. Crax tuberosa skull in three views.

Figure 2. Crax tuberosa skull in three views. Note the splint-like post0rbital (yellow). Alternate hypothesis: the splint is the postorbital process of the jugal (cyan, separate ossification from the base below the quadratojugal (olive). That would make the lumpy orange postfrontal the postfrontal + fused postorbital. Time to look at some embryos to see what is happening here: another great PhD dissertation.

The Eichstätt specimen of Archaeopteryx (= Jurapteryx)
shows the separation of the postfrontal (orange) from the frontal and the postorbital (in yellow) disarticulated and shifted slightly posteriorly in situ. This is the specimen basal to extant birds.

Figure 3. The Eichstätt specimen, Jurapteryx recurva, nests with the living ostrich, Struthio, presently in the LRT.

Figure 3. The Eichstätt specimen, Jurapteryx recurva, nests with the living ostrich, Struthio, presently in the LRT.

The tiny Early Cretaceous theropod, Scipionyx
(Fig. 4), demonstrates the separation of the frontal (blue), postfrontal (yellow-green) and postorbital (orange) in non-avian theropods. These elements tend to fuse with size. Phylogenetic miniaturization (= neotony) tends to separate the original elements. When dealing with shrinking taxa, like birds, try to keep this in mind.

Figure 1. Scipionyx skull and overall. The tail and feet are restored.

Figure 4. Scipionyx skull and overall. The tail and feet are restored.

The enantiornithine, Shenqiornis,
will be considered in greater detail In future blogposts.


References
Foth C and OWM Rauhut 2020. Eine kurze Betrachtung der Evolution des Vogelschädels [A short overview on the evolution of the skull of birds]. Jahresbericht 2019 und Mitteilungen 48. ISSN 0942-5845 ISBN 978-3-89937-253-3

More details on Parahesperornis

Bell and Chiappe 2020
provide additional insight and valuable photos of Parahesperornis alexi (Martin 1984; Fig. 1; Late Cretaceous ~90 mya) a smaller sister/ancestor to Hesperornis (Fig. 1) with more plesiomorphic traits.

Figure 1. Parahesperornis (from Bell and Chiappe 2020) compared to Hesperornis (Marsh 1890) to scale and not to scale. Here the glenoid to tail tip lengths are the same. Everything is exaggerated in Hesperornis.

Figure 1. Parahesperornis (from Bell and Chiappe 2020) compared to Hesperornis (Marsh 1890) to scale and not to scale. Everything is exaggerated in the derived taxon, Hesperornis.

Backstory
According to Bell and Chiappe, “The Hesperornithiformes constitute the first known avian lineage to secondarily lose flight in exchange for the evolution of a highly derived foot-propelled diving lifestyle, thus representing the first lineage of truly aquatic birds. First unearthed in the 19th century, and today known from numerous Late Cretaceous (Cenomanian-Maastrichtian) sites distributed across the northern hemisphere, these toothed birds have become icons of early avian evolution.”

Figure 2. Hesperornis cladogram from Bell and Chiappe 2020. Compare to LRT results in figure x.

Figure 2. Hesperornis cladogram from Bell and Chiappe 2020. Compare to LRT results in figure 3 where more taxa are tested and nested. Gansus should be closer to Hesperornis. Many taxa are omitted between Archaeopteryx and Asparavis here.

Figure 1. Click to enlarge. Toothed birds of the Cretaceous to scale.

Figure 3. Click to enlarge. Toothed birds of the Cretaceous to scale. Compare to figure 2. See the difference when more taxa are added.

Cladistics
Bell and Chiappe and the Large Reptile Tree (LRT, 1694+ taxa, illustrated in figure 3) are in broad agreement regarding the phylogenetic nesting of Parahesperornis (Fig. 2). Unfortunately, Bell and Chiappe don’t include enough taxa to understand the nesting of toothed birds within the clade of toothless birds, as recovered by the LRT (Fig. 3).

And what the heck 
are Gallus, the chicken, and Anas, the duck, doing in figure 2 nesting together? They are not related to one another in the LRT, but… (and here’s the key)… absent ANY pertinent transitional taxa, figure 2 is actually correct, a match with the LRT. Taxon exclusion delivers this oversimplified and misinforming cladogram (Fig. 2). More taxa, not more characters, makes a cladogram more and more accurate.


References
Bell A and Chiappe LM 2020. Anatomy of Parahesperornis: Evolutionary Mosaicism
in the Cretaceous Hesperornithiformes (Aves). Life 2020, 10, 62; doi:10.3390/life10050062
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.

wiki/Hesperornis

Asteriornis: Oldest crown bird fossil yet discovered? No.

Taxon exclusion
is the problem here. Still, it’s a wonderful and rare 3D bird fossil.

Writing in Nature, Field et al. 2020
bring us a new latest Cretaceous bird, Asteriornis (Fig. 1).The authors report, “The fossil represents one of the only well-supported crown birds from the Mesozoic era, and is the first Mesozoic crown bird with well-represented cranial remains.The fossil is between 66.8 and 66.7 million years old—making it the oldest unambiguous crown bird fossil yet discovered.”

Figure 1. Asteriornis skull from Field et al. 2020 colors removed and reapplied and restored here.

Figure 1. Asteriornis skull from Field et al. 2020 colors removed and reapplied and restored here.

The authors note,
“The general appearance of the premaxillary beak resembles that of extant Galliformes, particularly in its gently down-curved tip and delicate construction, with no ossified joints among the rostral components.”

Figure 2. Chauna skull. This sister to Asteriornis in the LRT shares most traits and informs the restoration.

Figure 2. Chauna skull. This sister to Asteriornis in the LRT shares most traits and informs the restoration.

Among crown birds, (Neornithes)
Asteriornis is old (66 mya), but the hen-sized ostrich sister, Patagopteryx, is older (80 mya), more primitive and was descried earlier (Alvarenga and Bonaparte 1992). Later Chiappe (1996, 2002, 2015) nested Patagopteryx between Enantiornithes and Hesperonis. Patagopteryx was not tested by Field et al. Instead the authors report, “The Mesozoic record of well-supported crown birds is restricted to a single latest Maastrichtian taxon, Vegavis iaai.” In the large reptile tree (LRT, 1657+ taxa; subset Fig. 4), gracile, long-legged Vegavis lies just outside the clade of Crown birds.

Figure 1. The two-toed ostrich (Struthio) nests with the four-toed Patagopteryx, when all relatives have only three toes.

Figure 3. The two-toed ostrich (Struthio) nests with the four-toed Patagopteryx, when all relatives have only three toes.

Field et al. nested Asteriornis 
uncertainly either closer to geese (Anseriformes) or closer to chickens (Galliformes), or at the base of the traditional, but invalid clade, ‘Galloanserae’. The authors report, “The specimen exhibits a previously unseen combination of features that are diagnostic of Galliformes and Anseriformes, which together form the crown clade Galloanserae—one of the most deeply diverging clades of crown birds and the sister group to the hyperdiverse extant clade Neoaves.”

Figure 3. Subset of the LRT focusing on birds. Note the separation of the duck clade from the chicken clade.

Figure 4. Subset of the LRT focusing on birds. Note the separation of the duck clade from the chicken clade and neither is basal to all other non-ratite birds. Given that both Patagopteryx and Asterornis are Cretaceous, just imagine all the intervening bird fossils still be discovered in that strata.

By contrast,
chickens and ducks are not related to one another in LRT (subset, Fig. 4). Chickens are related to grouse, peacocks, sparrows, hoatzins, parrots and other ground-dwelling seed eaters. Ducks and geese arise from long-legged Presybyornis and other long-legged shorebirds. In the LRT, Asteriornis is closer to Chauna, the screamer, and Fulica, the coot, and Heliornis, the sungrebe, all closer to chickens and sparrows than to ducks and geese. The invalid clade Galloanseriformes typically includes Chauna and Fulica. Heliornis is a grebe-mimic (with similar expanded toe paddles) and a duck-mimic (with a similar swimming mode). That may be at the root of this confusion over convergence.

Field et al. have too few taxa
in their taxon list. Only one Archaeopteryx is shown in their cladogram, but it was not tested in their analysis where Hesperornithes and Ichthyornis are outgroup taxa. By contrast, in the LRT, both of these toothy taxa are members of the crown group, nesting between toothless ratites and all other toothless birds. Neither the chicken clade nor the duck clade are basal clades in the LRT.

Figure 1. Anhima adult and chick compared to Pterocles adults

Figure 5. Anhima adult and chick compared to Pterocles adults

Dr. Kevin Padian (2020) wrote a companion article
explaining the importance of Asteriornis and its relationship to crown birds and stem birds for a broader audience. Padian reports, “Ancient birds are outside the crown group because they lack the structural and physiological features characteristic of living birds. Sometime during the latest Cretaceous, a stem-group lineage of birds evolved that had much higher growth rates than these more basal lineages, and that generally matured within a year or even sooner. These became the crown-group birds.”

Given Dr. Padian’s definitions
several Cretaceous birds, including toothed forms (Fig. 4), qualify as crown group birds because they phylogenetically appear in the LRT after the basalmost extant bird, the kiwi (Apteryx). It only takes one primitive, but extant taxon to define a crown clade.

Dr. Padian also reviews the disagreement
between molecular evidence and the new palaeontological evidence offered by Asteriornis. He reports, “The evidence for Asteriornis reported by Field and colleagues implies that crown-group birds first evolved when the Cretaceous period was nearly over.” That’s not true for many reasons, all based on taxon exclusion.

Asteriornis is unique among known taxa
in exhibiting caudally pointed nasals that overlie the frontals and meet at the midline, and a slightly rounded, unhooked tip of the premaxilla. That first trait marks Asteriornis as a derived and terminal taxon, leaving no ancestors, as shown in the LRT, distinct from the tree topology produced by Field et al. Oddly, the tip of the premaxilla is slightly hooked on one side, not hooked on the other (Fig.1).


References
Alvarenga and Bonaparte 1992. A new flightless land bird from the Cretaceous of Patagonia; pp. 51–64 in K. E. Campbell (ed.), Papers in Avian Paleontology, Honoring Pierce Brodkorb. Natural History Museum of Los Angeles County, Science Series 36.
Chiappe LM 1996a. Late Cretaceous birds of southern South America: anatomy and systematics of Enantiornithes and Patagopteryx deferrariisi; pp. 203–244 in G. Arratia (ed.), Contributions of Southern South America to Vertebrate Paleontology, Münchner Geowissenschaftliche Abhandlungen Volume 30.
Chiappe LM 1996. 
Early avian evolution in the southern hemisphere: Fossil record of birds in the Mesozoic of Gondwana. Memoirs of the Queensland Museum 39:533–556.
Chiappe LM 2002. Osteology of the flightless Patagopteryx deferrariisi from the late Cretaceous of Patagonia (Argentina) pp.281–316 in Mesozoic Birds, Above the Heads of Dinosaurs, Chapter: 13, Editors: Chiappe LM and Witmer LM, University of California Press.
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.
Padian K 2020. Poultry through time. Nature online

Taxon list used by Field et al. 2020.
Ichthyornis_dispar
Tinamus_robustus
Vegavis_iaai
Chauna_torquata
Anhima_cornuta
Wilaru_tedfordi
Presbyornis_pervetus
Conflicto_antarcticus
Anatalavis_oxfordi
Anseranas_semipalmata
Dendrocygna_eytoni
Cereopsis_novaehollandiae
Anser_caerulescens
Tadorna_tadornoides
Leipoa_ocellata
Megapodius_reinwardt
Megapodius_eremita
Alectura_lathami
Macrocephalon_maleo
Gallus_gallus
Phasianus_colchicus
Coturnix_pectoralis
Acryllium_vulturinum
Crax_rubra
Ortalis_vetula
Dromaius_novaehollandiae
Dinornis_robustus
Struthio_camelus
Lithornis_promiscuus
Lithornis_plebius
Paracathartes_howardae
Burhinus_grallarius
Porphyrio_melanotus
Antigone_rubicunda
Cariama_cristata
Asteriornis_maastrichtensis
Gallinuloides_wyomingensis
Pelagornis_chilensis
Protodontopteryx_ruthae

Oculudentavis: not a tiny bird or dinosaur. It’s a tiny cosesaur lepidosaur.

Figure 1. Oculudentavis in amber much enlarged. See figure 2 for actual size.

Figure 1. Oculudentavis in amber much enlarged from Xing et al. 2020. See figure 2 for actual size.

I never thought the tiny Middle Triassic pterosaur ancestor, Cosesaurus
(Fig. 2, 4) would ever be joined by an Early Cretaceous sister taxon that was even smaller. Yesterday the impossible happened when the editors of Nature published a description of tiny Oculudentavis (Xing et al. 2020; Figs. 1, 2; Early Cretaceous, 99 mya; 1.4cm skull), which the authors mistakenly considered a basal bird with teeth and the smallest Mesozoic dinosaur.

Figure 2. CT scans of Oculudentavis from Xing et al. 2020 and colored here, plus a comparison of Cosesaurus to scale.

Figure 2. CT scans of Oculudentavis from Xing et al. 2020 and colored here, plus a comparison of Cosesaurus to scale.

Taxon exclusion
Unfortunately the authors did not test Oculudentavis with Cosesaurus, a fenestrasaur, tritosaur lepidosaur… a taxon far from dinosaurs. When Oculudentavis was added to the large reptile tree (LRT) as the 1656th taxon, the tree length was 20291.

As a test
I forced Oculudentavis over to the London specimen of Archaeopteryx, which Xing et al. recovered as a sister, and the LRT bumped up to 20324, a mere 33 steps more despite the huge phylogenetic distance.

I’ve said it before,
convergence is rampant in the tetrapod family tree.

To that point, it should be remembered,
the original describers of Cosesaurus (Ellenberger and de Villalta 1974) mistakenly considered it a Middle Triassic stem bird.

In contrast,
Peters (2000) recovered Cosesaurus and kin with pterosaurs using four previously published phylogenetic analyses. Later, with more taxa, Peters (2007) recovered pterosaurs and kin with the lepidosaur Huehuecuetzpalli (Fig. 3). In addition, ResearchGate.net holds an unpublished manuscript and figures redescribing Cosesaurus and kin much more accurately. The pterosaur referees did not want that manuscript published, having ignored the earlier ones for so long.

Figure 3. Oculudentavis added to the LRT.

Figure 3. Oculudentavis added to the LRT with previously untested  tritosaur lepidosaurs.

Ironically
Xing et al. noted in tiny Oculudentavis lepidosaur-like sclerotic (eyeball) bones and acrodont to pleurodont teeth extending below the orbit, as in modern lizards. Even with these clues, they did not add lepidosaurs to their analysis. They assumed from the start they had a tiny dinosaur-bird (with lepidosaur traits).

Figure 2. Cosesaurus running and flapping - slow.

Figure 4. Cosesaurus running and flapping. If you want to know what the Oculudentaivis post-crania looks like, this is the closest known sister taxon, slightly smaller than full scale.

Distinct from Cosesaurus,
(Fig. 2) the palate of Oculudentavis is solid below the rostrum. The antorbital fenestra is reduced. Damage to the skull displaced one ectopterygoid to the mid palate and broke the jugal. The post-crania remains unknown, but Cosesaurus (Fig. 4) is the most similar taxon.

From the Xing et al. 2020 abstract:
“Here we describe an exceptionally well-preserved and diminutive bird-like skull that documents a new species, which we name Oculudentavis khaungraae gen. et sp. nov. The find appears to represent the smallest known dinosaur of the Mesozoic era, rivalling the bee hummingbird (Mellisuga helenae)—the smallest living bird—in size. The O. khaungraae specimen preserves features that hint at miniaturization constraints, including a unique pattern of cranial fusion and an autapomorphic ocular morphology9 that resembles the eyes of lizards. The conically arranged scleral ossicles define a small pupil, indicative of diurnal activity. The size and morphology of this species suggest a previously unknown bauplan, and a previously undetected ecology.”

The authors saw lepidosaur traits not found in basal birds/tiny dinosaurs.
Rather than seeking and testing more parsimonious sister taxa elsewhere, the authors chose to follow their initial bias and described their find as an odd sort of tiny bird.

In a similar fashion
just a few days ago Hone et al. 2020 did much the same as they mistakenly described a large pteryodactylid, Luchibang, as a small istiodactylid, following their initial bias.

The LRT provides a wide gamut of 1656 taxa 
to test your next new taxon. Don’t make the same mistake as the above authors by assuming your odd little something is something it isn’t.


References
Ellenberger P and de Villalta JF 1974. Sur la presence d’un ancêtre probable des oiseaux dans le Muschelkalk supérieure de Catalogne (Espagne). Note preliminaire. Acta Geologica Hispanica 9, 162-168.
Peters D 2000. A Redescription of Four Prolacertiform Genera and Implications for Pterosaur Phylogenesis. Rivista Italiana di Paleontologia e Stratigrafia 106 (3): 293–336.
Peters D 2007.The origin and radiation of the Pterosauria. In D. Hone ed. Flugsaurier. The Wellnhofer pterosaur meeting, 2007, Munich, Germany. p. 27.
Xing L, O’Connor JK,; Schmitz L, Chiappe LM, McKellar RC, Yi Q and Li G 2020. 
Hummingbird-sized dinosaur from the Cretaceous period of Myanmar. Nature. 579 (7798): 245–249.

Thanks to Dr. O’Connor for sending a PDF of the Nature paper. 

wiki/Oculudentavis
www.researchgate.net

John Ostrom: The man who saved dinosaurs

Saw this on Facebook recently
The following is from an online Yale Alumni Magazine article (link below) by award-winning author, Richard Conniff, July/August 2014.

Preview
“In his book The Riddle of the Dinosaur, science writer John Noble Wilford added that Bakker “was the young Turk whose views could be dismissed by established paleontologists. Ostrom, however, could not be ignored.” Late in 1969, Ostrom took the challenge directly to the North American Paleontological Convention in Chicago, declaring in a speech that there was “impressive, if not compelling” evidence “that many different kinds of ancient reptiles were characterized by mammalian or avian levels of metabolism.” Traditionalists in the audience responded, Bakker later recalled, with “shrieks of horror.” Their dusty museum pieces were threatening to come to life as real animals.”

Figure 1. John Ostrom, from young paleo stud to elderly professorial type.

Figure 1. John Ostrom, as a young paleo stud and as an elder statesman several decades later demonstrating a degree of isometry and allometry during ontogeny.

“Against this false negative, Ostrom laid out the positive evidence, listing more than 20 anatomical similarities between Archaeopteryx and various dinosaurs. It wasn’t just that Ostrom could not be ignored. He was far too thorough and meticulous, and for 30 years too persistent in the face of his critics, for anyone to refute.”

The LRT has been online for only 8 years, so only 22 to go!

“Though one or two holdouts still resist the idea, it is now widely accepted that birds evolved from the group of bipedal theropod dinosaurs”

“The idea that birds are in fact living dinosaurs is so commonplace that the debate has largely turned to the question of why they were the only dinosaurs to survive the mass extinction of 65 million years ago.”

“More significantly, Ostrom lived to see his ideas about the dinosaur origin of birds—and the feathered plumage of dinosaurs—vindicated by a series of remarkable fossils from northeastern China.”

Those should have been unnecessary as Ostrom explains below.

“On Ostrom’s death in 2005, age 77, the Los Angeles Times wrote that he had “almost single-handedly convinced the scientific community that birds are descended from dinosaurs.” “John Ostrom,” the Sunday Times (London) added, “did more than anyone else to make dinosaurs interesting, real, and visceral.”

“When NPR’s All Things Considered marked the occasion by interviewing Ostrom’s first research student, Bob Bakker, the paleontological world held its breath for a moment, recalling the troubled relationship between these two allies in the dinosaur renaissance. But when asked how important Ostrom had been to dinosaur paleontology, Bakker graciously commented: “Nobody was more important.”

In the comments section to the online article,
you can read from Paul Sereno’s epitaph of Ostrom, “He did more than simply point out the great number of similarities between this theropod and the early bird Archaeopteryx. He argued that these similarities were derived. That is, that they were synapomorphies—shared morphology from common ancestry.”

We looked at Ostrom’s frustration with
the slow pace of paleontology earlier. Here it is again.

According to the Hartford Courant (2000), “In 1973, Ostrom broke from the scientific mainstream by reviving a Victorian-era hypothesis (see above) that his colleagues considered far-fetched: Birds, he said, evolved from dinosaurs. And he spent the rest of his career trying to prove it.” With the announcement of the first dinosaurs with feathers from China, Ostrom (then age 73) was in no mood to celebrate. He is quoted as saying, ““I’ve been saying the same damn thing since 1973, `I said, `Look at Archaeopteryx!’” Ostrom was the first scientist to collect physical evidence for the theory. Ostrom provoked a debate that raged for decades. “At first they said, `Oh John, you’re crazy,”’ Ostrom said in 1999.”

On the night Ostrom was to be honored
at the annual convention of the Society of Vertebrate Paleontology, I noticed him walking alone to the proceedings. I took advantage of the coincidence to walk with him. He was gracious enough to allow that. I cannot remember the substance of our conversation. As soon as we got to the building, he was swept up into the celebration as everyone else wanted their own moment with the man who saved dinosaurs.


References

https://pterosaurheresies.wordpress.com/2016/03/16/sometimes-it-takes-the-paleo-crowd-an-epoch-to-accept-new-data/

https://yalealumnimagazine.com/articles/3921-the-man-who-saved-the-dinosaurs?fbclid=IwAR1HMFU7cxeqn-iGd8dtO6nAxsjpERhyTza2AnpkCDz05k9fY3w-63-q4Wc

SVP abstracts – Ichthyornis and the origin of extant birds

Benito et al. 2019 dive into bird phylogeny
with a study of the Late Cretaceous toothed bird, Ichthyornis (Fig. 1).

Figure 1. Skull of Ichthyornis in 3 views from Field et al. 2018 and overall skeleton.

Figure 1. Skull of Ichthyornis in 3 views from Field et al. 2018 and overall skeleton.

From their abstract
“The origin of crown birds is poorly understood

By contrast, in the large reptile tree (LRT, 1592 taxa) the origin of crown birds is well understood back to Silurian jawless fish. Ichthyornis is a member of the clade of crown birds in the LRT, not an ancestor to it.

“…and the study of their early evolution must incorporate data from their closest relatives among Mesozoic stem birds. The postcranial morphology of the Late Cretaceous toothed bird Ichthyornis dispar may be more representative of the ancestral condition of crown birds than that of any other known Mesozoic avialan, and its study has crucial implications for understanding morphological evolution prior to the great radiation of the avian crown group.”

By contrast, in the LRT Vegavis (Latest Cretaceous) is basal to all extant birds including Mesozoic toothed birds like Icthyornis. It was a late survivor from an earlier genesis.

“Here we present high resolution scans of new, exquisitely preserved three dimensional specimens of Ichthyornis from the Late Cretaceous of Kansas. These correspond to a partial skeleton from a single individual, more complete and in better condition than the classic material known since the 19th Century. The new material includes a complete sternum and shoulder girdle with evidence of extensive pneumatization. This new skeleton shows certain morphological differences from the classic material, including the absence of some previously proposed autapomorphies of I. dispar. Thus, the new material may represent a previously unknown species, or it could indicate that morphological variation within I. dispar was greater than previously appreciated.”

Good to have these new data.

Figure 3. Subset of the LRT focusing on early birds, including Ichthyornis.

Figure 2. Subset of the LRT focusing on early birds, including Ichthyornis.

Benito et al. continue:
“Phylogenetic analyses incorporating our new morphological data corroborate recent results and recover a grade of predominantly marine taxa close to the origin of crown birds. I. dispar is recovered stemward of Hesperornithes and Iaceornis marshi, which is recovered as the sister taxon to all crown birds. Additional information on the crownward-most portion of the avian stem group will help confirm these results and provide critical information on the ancestral ecology of the crown bird radiation.”
I don’t know if Benito et al. employed all the taxa shown here (Fig. 2) in this subset of the LRT, but you can see Ichthyornis nests in the LRT within the clade of extant/crown birds. Here Ichthyornis is a highly derived member of its own small clade of toothed birds, within extant birds between megapodes and seriemas. Other taxa closer to the main line of Cretaceous bird evolution would probably make a better model for studies like this.

References
Benito J et al. 2019. New Ichthyornis specimens: shedding new light on modern bird origins. Journal of Vertebrate Paleontology abstracts.