Spinosaurus: Hone and Holtz 2021 minimize the unique traits

Summary for those in a hurry:
A unique morphology + a unique niche + a unique prey assemblage = a unique hunting technique.

From the Hone and Holtz 2021 abstract:
“We conclude that …the pursuit predation hypothesis for Spinosaurus as a “highly specialized aquatic predator” is not supported. In contrast, a ‘wading’ model for an animal that predominantly fished from shorelines or within shallow waters is not contradicted by any line of evidence and is well supported. Spinosaurus almost certainly fed primarily from the water and may have swum, but there is no evidence that it was a specialised aquatic pursuit predator.”

Hone and Holtz pay little attention to the fact that Spinosaurus was the only large theropod that had such short hind limbs and had a dorsal fin much deeper than its ribcage. The authors cherry-picked less obvious traits to support their hypothesis, giving only passing notice to what makes Spinosaurus unique.

From the Hone and Holtz introduction:
“In short, these animals [spinosaurs] acted like large herons or storks, taking fish and other aquatic prey from the edges of water or in shallow water, but also foraging for terrestrial prey and scavenging on occasion.”

In paleontology, if Spinosaurus is going to be compared to large herons or storks, it should look overall like a giant heron or stork. It does not.

Figure 1. Aquatic Spinosaurus to scale with contemporary Early Cretaceous giant fish.

Figure 1. Aquatic Spinosaurus to scale with contemporary Early Cretaceous giant fish.

Hone and Holtz keep hammering away at a single point:
“The hind limbs of Spinosaurus do potentially provide evidence for aquatic locomotion and even striking at prey underwater, but specifically not in the sense of pursuit predation.” 

“Surface swimming is considerably less efficient than submerged swimming and incurs considerable extra wave drag for animals moving at, or just below, the surface.”

The problem is, Hone and Holtz want Spinosaurus to be built for speed, like a sailfish, if they are to grant it a submerged aquatic existence. Unfortunately, the authors are caught in a logic rut based on some sort of straw man. They end up cherry-picking traits less important traits while trying to weave their story away from the larger, unique traits.

Spinosaurus was not built for speed.
It didn’t need to be built for speed. Look at the prey taxa available (Fig. 1). Lungfish, giant bichirs and coelacanths are big, fat and slow-moving fish. Sawfish are lethargic bottom-dwellers. Drag is not a factor when moving slowly, like Spinosaurus.

As the only aquatic dinosaur,
Spinosaurus may have developed a sail to help regulate body temperature while staying submerged (except to lay eggs). It may have never needed to stand bipedally, like its theropod sisters. Hence the small legs and quadrupedal center-of-balance.

The tiny backset naris of Spinosaurus
was on its way to complete closure. That’s not a problem as many extant birds without nares demonstrate. They can all breathe throughout their mouth and throat.

Figure 2. Diagram from Dal Sasso et al. 2005, colors and overlay added to show dorsal expansion of the maxilla to cover an elongate naris.

Figure 2. Diagram from Dal Sasso et al. 2005, colors and overlay added to show dorsal expansion of the maxilla to cover an elongate naris.

Hone and Holtz summarize their study:
“If swimming to engage prey, based on the drag, performance and body shape it would be limited to lunging attack in shallow waters, not pursuit predation at speed in open water.”

No.  Spinosaurus was a slow swimmer, unaffected by drag. It would not be limited to lunging attacks in shallow water, contra Hone and Holtz. Rather, slow, steady underwater predation with its sail exposed to maintain a 99º body temperature in an 80º river is still the best explanation for this unique theropod.

“The information provided through recent discoveries may suggest an increase in aquatic affinities for Spinosaurus, and it may have been able to swim with its tail, and even swim well compared to other theropods, but nothing presented to date contradicts the fundamentals of the ‘wading model’ and does not support active pursuit predation.”

Hone and Holtz failed to consider a semi-active, semi-submerged method of predation. “Nothing presented to date” = failure to consider all options. Spinosaurus is indeed a “highly specialized aquatic predator”, just not a fast one.

Earlier we looked at Spinosaurus in its environment here, its ability to swim deep here and its tiny naris here.

Unfortunately, papers from co-author David Hone are infamous for taxon exclusion, inaccurate observation, and illogical interpretation. Not sure why referees and editors are letting him get away with negating good solid science with bad flimsy science.


References
Hone DWE and Holtz TR Jr 2021. Evaluating the ecology of Spinosaurus: Shoreline generalist or aquatic pursuit specialist. Palaeontologica Electronica 24(1):a03 Online Here.  

https://doi.org/10.26879/1110

Falcatakely: a basal theropod, not a bird

O’Connor et al. 2020 present
a late surviving, Late Cretaceous basal theropod dinosaur lacking maxillary teeth, Falcatakely forsterae (Figs. 1–4). The authors reconstructed their crushed and slightly disarticulated fossil using µCT scans.

Figure 1. Falcatakely from O'Connor et al. 2020 µCT scans, then moved slightly on frame 2.

Figure 1. Falcatakely from O’Connor et al. 2020 µCT scans, then moved slightly on frame 2.

Unfortunately
the authors mistakenly consider Falcatakely an enantiornithine bird with a “unique development of beak”. This was due to taxon exclusion. They assumed they had ‘a bird in hand’ when analysis indicates they did not.

Figure 1. Falcatakely from O'Connor et al. 2020 µCT scans, then missing elements added in frame 2.

Figure 2. Falcatakely from O’Connor et al. 2020 µCT scans, then missing elements added in frame 2. Note the lacrimal (in red) is partly the jugal (cyan, frame 2).

From the O’Connor et al. abstract:
“Mesozoic birds display considerable diversity in size, flight adaptations and feather organization1,2,3,4, but exhibit relatively conserved patterns of beak shape and development Here we describe a crow-sized stem bird, Falcatakely forsterae gen. et sp. nov., from the Late Cretaceous epoch of Madagascar that possesses a long and deep rostrum, an expression of beak morphology that was previously unknown among Mesozoic birds and is superficially similar to that of a variety of crown-group birds (for example, toucans).”

Note the first two words. They assumed they had a ‘unique’ Mesozoic bird without first testing in a phylogenetic analysis. Evidently they got excited by the possibility of getting published in Nature. That part came true.

Colleagues: The time to get excited is AFTER a wide gamut analysis documents and firmly nests your taxon. Otherwise you’ll end up like the authors of Oculudentavis, which was also mistakenly considered a bird. (I wonder if Nature will demand a similar retraction?)

Figure 3. Falcatakely from O'Connor et al. 2020 µCT scans, then non-palate elements darkened in frame 2. Compare to figure 1 for a more realistic narrowing of the snout.

Figure 3. Falcatakely from O’Connor et al. 2020 µCT scans, then non-palate elements darkened in frame 2. Compare to figure 1 for a more realistic narrowing of the snout.

Whenever you think you have a ‘unique’ anything
add taxa. Expand your taxon list.

Uniqueness in evolution is an oxymoron.
Something should resemble your ‘unique’ taxon.  The O’Connor team’s  mistake was due entirely to taxon exclusion, not looking far enough with a wide enough taxon list.

Figure 4. Cladogram from O'Connor et al. 2020 where they exclude basal theropods and nest Falcatakely with dissimilar enantiornithine birds by default.

Figure 4. Cladogram from O’Connor et al. 2020 where they exclude basal theropods and nest Falcatakely with dissimilar enantiornithine birds by default.

Late-surving Late Cretaceous Falcatakely
nests among the basalmost theropods, in the large reptile tree (LRT, 1768+ taxa) not far from Late Triassic Tawa, within the Late Jurassic Zuolong (Fig. 5) to Late Triassic Marasuchus to headless Late Triassic Procompsognathus (Fig. 6) clade. It’s probably the most ignored of the theropod clades recovered by the LRT.

Figure 2. Zuolong skull revised with a backward tilting lacrimal and other minor modifications.

Figure 5. Zuolong skull revised with a backward tilting lacrimal and other minor modifications.

The lack of maxillary teeth in Falcatakely
is the major difference between it and earlier related taxa. So is the lack of an antorbital fossa. As many other lineages demonstrate, that can happen over tens of millions of years in the Theropoda.

Figure 1. Procompsognathus, Marasuchus and Segisaurus nest together in the Theropoda despite their many differences.

Figure 6. Procompsognathus, Marasuchus and Segisaurus nest together in the Theropoda despite their many differences.

Size-wise
either Marasuchus or Procompsognathus (Fig. 6) provide suitable post-cranial models for Falcatakely. Other bird mimics are documented here.

With so many theropod fans out there,
let’s see how many confirm the basal theropod affinities of Falcatakely. In either case, it’s still a wonderful fossil find and the authors did a wonderful job of documenting the material. (Next time, just add more taxa).

Happy Thanksgiving
from the USA.


References
O’Connor PM, Turner AH, Groenke JR et al. 2020. Late Cretaceous bird from Madagascar reveals unique development of beaks. Nature (2020). https://doi.org/10.1038/s41586-020-2945-x

wiki/Falcatakely
https://www.ohio.edu/news

Added November 28, a few days after posting:
Others also question the bird hypothesis:

Dinosaur Mailing List: A Theropoda blog post questioning the identification of the fossil as a bird… Falcatakely: heterodoxy and pluralism in the Year of Oculudentavis (in Italian) http://theropoda.blogspot.com/2020/11/falcatakely-eterodossia-e-pluralismo.html

A new ornithischian, Changmiania, enters the LRT

Meet a new fossorial fossil dinosaur,
perfectly preserved in its own burrow.

Yang et al. 2020 bring us
self-buried specimens of Changmiania liaoningensis (Yixian, Early Creteceous; Figs. 1–3).

Figure 1. Changmiania in situ and illustrated in situ from Yang et al. 2020.

Figure 1. Changmiania in situ and illustrated in situ from Yang et al. 2020.

The authors nest this ornithischian
as the basalmost member of the clade Ornithopoda (= duckbills, etc.; Fig. y).

Figure y. Cladogram of the Ornithischia from Yang et al. 2020. Colors added. Green= related taxa in the LRT. Yellow = taxa share with the LRT.

Figure y. Cladogram of the Ornithischia from Yang et al. 2020. Colors added. Green= related taxa in the LRT. Yellow = taxa share with the LRT. Compare to figure x which includes more outgroup taxa to polarize the basal taxa.

By contrast,
the large reptile tree (LRT, 1733+ taxa; subset Fig. x) nests Changmiania (Figs. 1–3) with Kulindadromeus (Fig. 4) and Heterodontosaurus (Fig. 5). That’s several nodes apart from the clade Ornithopoda in the LRT (Fig. x).

Figure x. Subset of the LRT focusing on Ornithischia. This cladogram differs considerably from that published in Yang et al. 2020.

Figure x. Subset of the LRT focusing on Ornithischia. This cladogram differs considerably from that published in Yang et al. 2020. Here Haya is a basal ornithischian. In Yang et al. Haya is deep within the Ornithopoda.

Digging (fossorial behavior)
traits found in Changmiania proposed by the authors include:

  1. fused premaxillae
  2. nasal laterally expanded overhanging the maxillas
  3. shortened neck formed by only six cervical vertebrae;
  4. neural spines of the sacral vertebrae completely fused together, forming a craniocaudally-elongated continuous bar;
  5. fused scapulocoracoid with prominent scapular spine;
  6. and paired ilia symmetrically inclined dorsomedially, partially
    covering the sacrum in dorsal view.
Figure 2. Changmiania skull in dorsal view.

Figure 2. Changmiania skull in dorsal view from Yang et al. 2020. Colors added here.

Figure 3. Changmiania skull in lateral view from Yang et al. 2020. Colors added here.

Figure 3. Changmiania skull in lateral view from Yang et al. 2020. Colors added here.

Several ornithischian taxa
(Orodromeus, Oryctodromeus, and Zephyrosaurus) have also demonstrated (or suggested by phylogenetic bracketing) fossorial behavior. Heterodontosaurus (Figs. 5, 6) shares traits #1, 2 and 3. Heterodontosaurus has longer fingers #2 and #3 (for digging?).

Figure 1. Kulindadromaeus, a sister to Heterodontosaurus with proto-feathers. Images from and traced from Godefroit et al. 2014. Since theropods and heterodontosaurs both had something like feathers, if they were the same kind of feathers, their last common ancestor had feathers. That last common ancestor was a herrerasaur or its proximal predecessor. Note the Godefroit et al. skull does not match their description but has a standard maxilla ascending process. See color overlays for correct ed interpretation.

Figure 4. Kulindadromaeus, a sister to Heterodontosaurus with proto-feathers. Images from and traced from Godefroit et al. 2014. Since theropods and heterodontosaurs both had something like feathers, if they were the same kind of feathers, their last common ancestor had feathers. That last common ancestor was a herrerasaur or its proximal predecessor. Note the Godefroit et al. skull does not match their description but has a standard maxilla ascending process. See color examples for correct ed interpretation. Click to enlarge.

Figure 7. Heterodontosaurus skull. Note the fused premaxillae, overhanging nasals and pmx/mx notch for a lower fang.

Figure 5. Heterodontosaurus skull. Note the fused premaxillae, overhanging nasals and pmx/mx notch for a lower fang. The general layout of the skull is very much like that of Changmiania. See figures 2 and 3.

Figure 1. Heterodontosaurus with feather quills arising from the lower back, sacrum and proximal tail.Figure 1. Heterodontosaurus with feather quills arising from the lower back, sacrum and proximal tail.

Figure 6. Heterodontosaurus with feather quills arising from the lower back, sacrum and proximal tail.

It’s worth noting
that many extant birds dig burrows, too. They use their bills to peck and their feet to sweep. Progress is often slow. Here’s an online article discussing birds that use and dig burrows.

Figure 7. Changmiania, both specimens in situ.

Figure 7. Changmiania, both specimens in situ.

Here’s a YouTube video
of a belted kingfisher working on its own burrow. Much is not shown, but the feet are back-kicking out the rubble, presumably produced by the pecking of the strong beak at the back wall of the burrow.

References
Yang Y, Wu W, Dieudonne P-E and Godefroit P 2020. A new basal ornithopod dinosaur from the Lower Cretaceous of China. PeerJ 8:e9832 DOI 10.7717/peerj.9832

Changmiania publicity:
naturalsciences.be/en/news/item/19274

4 natural history museum tours on YouTube + 2 bonus videos

Today: Some short YouTube museum tour videos without narration
and two bonus videos on continental drift and on becoming a PhD.

1 Wyoming Dinosaur Center at Thermoplis:

2 San Antonio Museum in Texas:

3 American Museum of Natural History in New York:

Field Museum in Chicago:

Bonus video #1
the best I’ve seen on the history of continental drift:

Bonus video #2
A young man on TEDx discusses the ups and downs of PhD students.

Given these strict parameters, high expenses and meager, postponed rewards,
it’s no wonder why so many PhDs and PhD candidates dismiss and attempt to suppress published and unpublished work by enthusiastic outsiders without a science degree. They must see ReptileEvolution.com as taking an academic short-cut. Not paying the price. Not doing it the ‘right’ (= traditional) way.

By contrast I see ReptileEvolution.com as a retirement project. Every day I simply add taxa to a growing phylogenetic analysis. Sadly, no one with a PhD, worse yet: no one else on the planet, has wanted to do this for the last nine years. So, at present, there is no competing analysis with a similar taxon list. Given that the typical PhD project can last for two to eight years, a competing cladogram would make a great PhD project!

Sciurumimus: a juvenile ornitholestid in the LRT

We looked at tiny,
feathered Sciurumimus albersdoerferi (Germany, Rauhut et al. 2012; BMMS BK 11) and larger bones-only Ornitholestes (North America) earlier as Late Jurassic sisters in the large reptile tree (LRT, 1659+ taxa). After a recent review, these two continue to nest as sisters at the base of the Microraptor (Fig. 3) + Sinornithosaurus clade. So no news here… except now let’s combine the extraordinary size difference between the two and the widely accepted observation that Sciurumimus is a juvenile.

That brings to mind: a juvenile of what?
The LRT indicates a juvenile ornitholestid (Fig. 1). The overall morphologies are strikingly similar and the size difference is appropriate. Other published studies recover other nestings.

Rauhut, et al. 2012
(Suppdata) nested Ornitholestes between ornithomimosaurs and deinonychosaurs, far from Sciurumimus, which Rauhut et al. nested Sciurumimus between an unresolved clade of giant spinosaurs + megalosaurs and giant Monolophosaurus. Like Rauhut et al., the LRT nests also nests Ornitholestes between ornithomimosaurs (+ tyrannosaurs + oviraptors + therizinosaurs) and deinonychosaurs.

Key differences in the LRT include

  1. the use of two Compsognathus specimens. The each nest at the base of their own clade, a hypothesis of interrelationships overlooked by Rauhut et al.
  2. the inclusion of three Microraptor specimens and two Sinornithosaurus specimens, adults of which are closer in size and morphology to Sciurumimus. This brings to mind the possibility that phylogenetic miniaturization and neotony played a part in the evolution of these bird-mimics. These closely related taxa were omitted by the Rauhut et al. selection process.
Figure 1. Sciurumimus compared to Ornitholestes and Microraptor to scale.

Figure 1. Sciurumimus compared to Ornitholestes and Microraptor to scale.

In their study of the wonderfully preserved
anchiornithid, Aurornis, Godefroit et al. nested Sciurumimus between Monolophosaurus + Sinraptor and Zuolong, all more primitive taxa in the LRT. In Godefroit et al. these taxa are far from Ornitholestes, which nested with another small compsognathid, Juravenator. Juravenator nests with equally small, but shorter limbed Sinosauropteryx in the LRT. Evidently few theropod studies agree with one another in the details.

Rauhut et al. 2012 reported,
“Our analysis confirms Sciurumimus as the basalmost known theropod with evidence of feather-like integument.” By contrast, in the LRT, Tawa-like, feathered Sincalliopteryx (Fig. 2) is more primitive, despite its late appearance (Early Cretaceous) in the fossil record.

Figure 4. Sinocalliopteryx currently nests as a provisional sister to Deinocheirus, awaiting the discovery of transitional sister taxa.

Figure 2. Late surviving Sinocalliopteryx currently nests basal to Late Triassic Coelophysis, derived from Late Triassic Tawa. It has the most primitive presence of feathers despite its late appearance.

Sinocalliopteryx
currently nests basal to Late Triassic Coelophysis, and was derived from Late Triassic Tawa. In the LRT, Sinocalliopteryx has the most primitive presence of feathers among theropods despite its appearance tens of millions of years later than its phylogenetic genesis.

Figure 2. Microraptor gui (IVPP V 13352) reconstructed from tracings in figure 1. There are no surprises here, except a provisional closer relationship with Compsognathus than with Velociraptor. Microraptor has a large pedal claw two, but it is not quite the killing claw seen in droamaeosaurs.

Figure 3. Microraptor gui (IVPP V 13352) reconstructed from tracings in figure 1. There are no surprises here, except a provisional closer relationship with Compsognathus than with Velociraptor. Microraptor has a large pedal claw two, but it is not quite the killing claw seen in droamaeosaurs.

The Ornitholestes + Sciurumimus + Microraptor + Sinornithosaurus clade
were bird-mimics and bird-mimic ancestors not directly related to birds or bird ancestors in the LRT.


References
Godefroit P, Cau A, Hu D-Y, Escuillié F, Wu, W and Dyke G 2013. A Jurassic avialan dinosaur from China resolves the early phylogenetic history of birds. Nature. 498 (7454): 359–362.
Rauhut OWM, Foth C, Tischlinger H and Norell MA 2012.
 Exceptionally preserved juvenile megalosauroid theropod dinosaur with filamentous integument from the Late Jurassic of Germany. Proceedings of the National Academy of Sciences. 109 (29): 11746–11751.

 

 

Feathers and fangs: What is Hesperornithoides?

Answer:
Hesperornithoides miessleri (Figs. 1, 2; Late Jurassic, Wyoming, USA; Hartman et al. 2019; WYDICE-DML-001 (formerly WDC DML-001)) is the newest fanged anchiornithid theropod dinosaur to be described, compared and nested (Figs. 3, 4).

From the Hartman et al. abstract
“Limb proportions firmly establish Hesperornithoides as occupying a terrestrial, non-volant lifestyle. Our phylogenetic analysis emphasizes extensive taxonomic sampling and robust character construction, recovering the new taxon most parsimoniously as a troodontid close to Daliansaurus, Xixiasaurus, and Sinusonasus.” [see Figure 3, note: Xixiasaurus is not listed in their cladogram].

“All parsimonious results support the hypothesis that each early paravian clade was plesiomorphically flightless, raising the possibility that avian flight originated as late as the Late Jurassic or Early Cretaceous.” [this is an old hypothesis dating back to the discovery of Late Jurassic Archaeopteryx in the 1860s and it remains a well-established paradigm.]

Figure 1. Published reconstruction of Hesperornithes from Hartman et al. 2019, to scale with Caihong, a similar, though smaller, taxon and Sinusonasus, another sister based on very few bones, but look at that canine fang!

Figure 1. Published reconstruction of Hesperornithes from Hartman et al. 2019, to scale with Caihong, a similar, though smaller, taxon preserved with a complete set of bird-like feathers, and Sinusonasus, another sister based on very few bones, but look at that canine fang!

The cladogram by Hartman et al. 2017
(Fig. 3) is similar to one published by Lefevre et al. 2017 in nesting birds (Avialae) as outgroups to the Dromaeosauridae + Troodontidae, the opposite of the large reptile tree (LRT, 1540 taxa, subset Fig. 4).

Today
we’ll compare the Hartman et al. nesting (Fig. 3) to the one recovered by the LRT (Fig. 4).

Figure 2. Tentative restoration of the skull of Hesperornithes alongside to scale skull of Caihong. The maxillae are similar and both have a distinct fang.

Figure 2. Tentative restoration of the skull of Hesperornithes alongside to scale skull of Caihong. The maxillae are similar and both have a distinct fang.

The Hartman et al. cladogram
(Fig. 3) nested Hesperornithoides with Sinusonasus (IVPP V 11527, Xu and Wang 2004; Early Cretacaceous, Fig. 1), as in the LRT (Fig. 4).

The Hartman et al. cladogram included several taxa not previously included in LRT, 1540 taxa, subset Fig. 4), so I added five to the LRT.

  1. Hesperornithoides (Fig. 1) – sister to Sinusonasus in both cladograms
  2. Sinusonasus (Fig. 1) – sister to Hesperornithoides in both cladograms
  3. Daliansaurus (Fig. 5) – nearby outgroup taxon in both cladograms
  4. Alma (Fig. 6) – more distant outgroup taxon in both cladograms
  5. Protarchaeopteryx (Fig. 7) – primitive oviraptorid in both cladograms
Figure 3. Cladogram published by Hartman et al. 2019, colors added to more or less match those in the subset of the LRT (Fig. 4), a distinctly different topology. Here birds and troodontids/anchirornithids are polypheletic.

Figure 3. Cladogram published by Hartman et al. 2019, colors added to more or less match those in the subset of the LRT (Fig. 4), a distinctly different topology. Here birds and troodontids/anchirornithids are polypheletic.

Issues arise in the Hartman et al. cladogram

  1. Birds arise from the proximal outgroup, Oviraptorosauria
  2. Archaeopteryx is not in the lineage of modern and Cretaceous birds
  3. Anchiornithid troodontids are scattered about
  4. Balaur nests with birds
  5. Microraptors and basal tyrannosaurs nest with dromaeosaurids
  6. The outgroup taxon in figure 3 is: Compsognathus; in the SuppData: Dilophosaurus. Neither is a Triassic theropod.
  7. Running the .nex file results in thousands of MPTs (most parsimonious trees), even when pruned down to well-known, largely articulated taxa. Their phylogenetic analysis included 700 characters (and that means hundreds of less-than-complete taxa) tested against 501 taxa. Changing the outgroup taxon to Sinocalliopteryx resulted in far fewer MPTs, but see here for more validated outgroup taxa. Hartman et al. reported, “The analysis resulted in >99999 most parsimonious trees.” Essentially useless… and they knew that attempting to publish their report.
Figure 4. Subset of the LRT focusing on the theropod-bird transition, distinctly different than in Hartman et al. 2019. Here in a fully resolved cladogram, birds and anchiornithids are monophyletic. Taxon inclusion resolves cladistic issues raised by Hartman et al.

Figure 4. Subset of the LRT focusing on the theropod-bird transition, distinctly different than in Hartman et al. 2019. Here in a fully resolved cladogram, birds and anchiornithids are monophyletic. Taxon inclusion resolves cladistic issues raised by Hartman et al.

By contrast,
in the LRT (Fig. 4):

  1. The cladogram is fully resolved (1 MPT).
  2. Birds, including Archaeopteryx and 12 other Solnhofen bird-like taxa arise from anchiornithids, which arise from troodontids (including dromaeosaurids), which arise from Ornitholestes and kin, which arise from the CNJ79 specimen attributed to Compsognathus and kin (including therzinosaurs + oviraptorids), which arises from the holotype Compsognathus and kin (including ornithomimosaurs and tyrannosaurs).
  3. Double killler-clawed Balaur nests with Velociraptor, not with birds.
  4. The outgroup taxa in the LRT include the Triassic dinosaurs, Herrerasaurus, Tawa and a long list going back to Silurian jawless fish.
  5. Hesperornithoides (Fig. 1) and Sinusonasus (Fig. 1) nest with another anchiornithid with fewer teeth and one elongated canine, Caihong (Fig. 1) and a long list of other shared traits. Caihong has a full set of bird-like feathers, so less well-preserved Hesperornithoides likely shared this trait. Caihong nests closer to Archaeopteryx in the Hartman et al. cladogram.
Figure 6. Daliansaurus reconstructed from the original tracing.

Figure 5. Daliansaurus reconstructed from the original tracing. In the Hartman et al. cladogram, this taxon nests close to Hesperornithoides. In the LRT it nests at the base of the Hesperornithes clade.

A few suggestions for Hartman et al. 2019

  1. Build your tree with fewer, but more complete taxa in order to achieve full resolution
  2. Choose a plesiomorphic Triassic theropod or dinosaur outgroup for your outgroup
  3. Practice more precision in your reconstructions. Do not freehand anything. Do not add bones where bones are not known.
  4. Try not to borrow cladograms (like the TWiG dataset) from others, but build your own, especially when the results are so demonstrably poor (>99,999 MPTs)
  5. Include both Compsognathus specimens. They are different from one another and, apparently, key to understanding interrelationships.
  6. Include as many of the 13 Solnhofen birds and pre-birds that you can and show reconstructions so we know you understand the materials. Checking individual scores is like going to Indiana Jones’ government warehouse. Note how the Solnhofen birds split apart and nest at the bases of all the derived bird clades in the LRT (Fig. 4).
FIgure 5. Alma reconstructed and restored (gray).

FIgure 6. Alma reconstructed and restored (gray).

Hartman et al. report, 
“We follow the advice of Jenner (2004) that authors should attempt to include all previously proposed characters and terminal taxa, while explicitly justifying omissions. To this end we have attempted to include every character from all TWiG papers published through 2012, with the goal to continually add characters.”

As their results demonstrate, such efforts are a waste of time.
Pertinent taxa and suitable outgroup taxa were overlooked. The goal is full resolution and understanding. If incomplete taxa and too many characters prevent you from reaching this goal, start pruning, or start digging into the data. There is only one tree topology in Deep Time. Our job is to find it.

Figure 9. Protarchaeopteryx traced in situ, reconstructed a bit and the skull of Incisivosaurus for comparison.

Figure 7. Protarchaeopteryx traced in situ, reconstructed a bit and the skull of Incisivosaurus for comparison. This taxon nests with oviraptorids in both cladograms, basal to Archaeopteryx and birds in Hartman et al. 2019. Not sure if that is all the tail there is, or if more is buried or missing. Probably the latter, according to phylogenetic bracketing.

I sincerely hope this review of Hartman et al. 2019
is helpful. The LRT confirms their nesting of Hesperornithoides with Sinusonasus. Outside of that the two cladograms diverge radically and only one of these two competing cladograms is fully resolved with a gradual accumulation of traits at every node.

The above video tour of the Wyoming Dinosaur Center in Thermopolis
from Wyoming PBS spends a fair amount of time with Hesperornithoides. The conclusions mentioned by the various narrators are not supported by the LRT.


References
Hartman S, Mortimer M, Wahl WR, Lomax DR, Lippincott J and Lovelace DM 2019. A new paravian dinosaur from the Late Jurassic of North America supports a late acquisition of avian flight. PeerJ 7:e7247 DOI 10.7717/peerj.7247
Lefèvre U, Cau A, Cincotta A,  Hu D-Y, Chinsamy A,Escuillié F and Godefroit P 2017. A new Jurassic theropod from China documents a transitional step in the macrostructure of feathers. The Science of Nature, 104: 74 (advance online publication). doi:10.1007/s00114-017-1496-y
Xu X and Wang X-l 2004. A New Troodontid (Theropoda: Troodontidae) from the Lower Cretaceous Yixian Formation of Western Liaoning, China”. Acta Geologica Sinica 78(1): 22-26.

wiki/Sinusonasus
wiki/Troodontidae
wiki/Hesperornithoides
wiki/Xixiasaurus
wiki/Anchiornthidae
wiki/Origin_of_birds

Convolosaurus enters the LRT basal to pachycephalosaurs

Originally it was considered a basal ornithopod.

FIgure 1. Convolosaurus from Andrzejewski, Winkler and Jacobs 2019, re built from a flock of juvenile specimens.

FIgure 1. Convolosaurus from Andrzejewski, Winkler and Jacobs 2019, re built from a flock of juvenile specimens.

Andrzejewski, Winkler and Jacobs 2019 report,
“The new ornithopod, Convolosaurus marri gen. et sp. nov., is recovered outside of Iguanodontia, but forms a clade with Iguanodontia exclusive of Hypsilophodon foxii. The presence and morphology of four premaxillary teeth along with a combination of both basal and derived characters distinguish this taxon from all other ornithopods.” 

Figure 2. Subset of the LRT focusing on the clade Phytodinosauria. Convolosaurus nests closer to the dome head dinosaurs, not the ornithopods.

Figure 2. Subset of the LRT focusing on the clade Phytodinosauria. Convolosaurus nests closer to the dome head dinosaurs, not the ornithopods.

By contrast
the large reptile tree (LRT, 1419 taxa) nests Convolosaurus basal to the Agilisaurus + Stegoceras at the base of the Pachycephalosauria (dome-head dinos). All these taxa were included in the original paper, but they did not nest together. Andrzejewski, Winkler and Jacobs 2019 did not nest their cladogram on Chilesaurus and Daemonosaurus, two taxa missing from their cladogram. This may have played a part in the different tree topologies.

Then again…
the LRT presently does not include Hypsilophodon or Thescalosaurus, taxa that nest with Convolosaurus in Andrzejewski, Winkler and Jacobs 2019. Soon they will be added. Then we’ll revisit this. 

Figure 3. Convolosaurus cladogram from Andrzejewski, Winkler and Jacobs 2019. Note the complete lack of consensus between the tree topology and figure 2.

Figure 3. Convolosaurus cladogram from Andrzejewski, Winkler and Jacobs 2019. Note the complete lack of consensus between this tree topology and the LRT in figure 2. In the LRT Haya and Pisanosaurus nest together near the base of the Ornithischia, but not here. 

Convolosaurus marri (Andrzejewski, Winkler and Jacobs 2019; SMU 72834; 2.5m in length) informally nicknamed the “Proctor Lake hypsilophodont”, this specimen is known from a flock of subadults.


References
Andrzejewski KA, Winkler DA and Jacobs LL 2019. A new basal ornithopod (Dinosauria: Ornithischia) from the Early Cretaceous of Texas. PLoS ONE. 14 (3): e0207935. doi:10.1371/journal.pone.0207935.

The near closure of the naris in Spinosaurus

Short note on a long rostrum today:

Figure 1. The rostrum of Spinosaurus. Note the maxilla rising to close off the elongate naris into a reduced anterior and posterior opening.

Figure 1. The rostrum of Spinosaurus MSNM V4047. Note the maxilla rising to close off the elongate naris into a reduced anterior and posterior opening. SF = sub-narial foramen. 

I just found this fascinating.
The naris of Spinosaurus (Stromer 1915; Cretaceous; MSNM V4047) was overlaid by the maxilla sealing off most of what had been the elongate opening (Fig. 1).  I suppose that supports a semi-aquatic niche and reduced olfactory input. As others have noted, the rostrum has sensory pits, perhaps, as in crocodilians, for underwater vibration sensing.

Figure 2. Diagram from Dal Sasso et al. 2005, colors and overlay added to show  dorsal expansion of the maxilla to cover an elongate naris.

Figure 2. Diagram from Dal Sasso et al. 2005, colors and overlay added to show dorsal expansion of the maxilla to cover an elongate naris.

Dal Sasso et al. 2005 wrote:
“The external naris is retracted farther caudally on the snout than in other spinosaurids and is bordered exclusively by the maxilla and nasal.” The authors identified the anterior naris as a ‘sub-narial foramen’. The naris continues to contact the premaxilla in all related taxa (Fig. 1). Here, just thinking about things differently, and more parsimoniously, the naris continues to contact the premaxilla.

According to Wikipedia
MSNM V4047 (in the Museo di Storia Naturale di Milano), described by Dal Sasso and colleagues in 2005, consists of a snout (premaxillae, partial maxillae, and partial nasals) 98.8 centimetres (38.9 in) long from the Kem Kem Beds. Like UCPC-2, it is thought to have come from the early Cenomanian. Arden and colleagues in 2018 tentatively assinged this specimen to Sigilmassasaurus brevicollis given its size. In the absence of associated material, however, it is difficult to be certain which material belongs to which taxon.”


References
dal Sasso C, Maganuco S, Buffetaut E, Mendez MA 2005. New information on the skull of the enigmatic theropod Spinosaurus, with remarks on its sizes and affinities. Journal of Vertebrate Paleontology. 25 (4): 888–896.
Ibrahim N et al. 2014. Semiaquatic adaptations in a giant predatory dinosaur. Science 345 (6204): 1613–1616.
Stromer E 1915. Ergebnisse der Forschungsreisen Prof. E. Stromers in den Wüsten Ägyptens. II. Wirbeltier-Reste der Baharije-Stufe (unterstes Cenoman). 3. Das Original des Theropoden Spinosaurus aegyptiacus nov. gen., nov. spec. Abhandlungen der Königlich Bayerischen Akademie der Wissenschaften, Mathematisch-physikalische Klasse (in German). 28 (3): 1–32.

wiki/Spinosaurus