It looks A LOT like Gladocephaloideus, but it’s not one

Among the long-necked ctenochasmatids
close to Gegepterus, is Gladocephaloideus (Lü et al. 2012), a taxon originally considered a cycnorhamphid. A new, smaller specimen with an equally impressive set of long cervicals was recently assigned to the same genus (Lü et al. 2016, Fig. 1) as a juvenile.

Figure 1. Gladocephaloideus (the holotype) compared to the new specimen referred to Gladocephaloideus and its two sister taxa in the large pterosaur tree. Long necks in ctenochasmatids made several appearances by convergence.  Of particular interest, note the size of the pelvis in the JPM specimen, no larger than that of the much smaller MB.R. specimen. Lü et al considered the pelvis incomplete and it may be. Sister taxa are illustrated here from figure 2.

Figure 1. Gladocephaloideus (the holotype) compared to the new specimen referred to Gladocephaloideus and its two sister taxa in the large pterosaur tree. Long necks in ctenochasmatids made several appearances by convergence.  Of particular interest, note the size of the pelvis in the JPM specimen, no larger than that of the much smaller MB.R. specimen. Lü et al considered the pelvis incomplete and it may be. Sister taxa are illustrated here from figure 2.

Unfortunately
the two specimens do not nest together in the large pterosaur tree (Fig. 2). Close, but separated by several nodes.

Before leaving Figure 1,
note the size of the relatively tiny pelvis in the JPM specimen, no larger than that of the much smaller MB.R. specimen with a relatively large pelvis of similar shape. This reconstruction was built from scraps that give the appearance of complete bones. Lü et al. 2016 considered the pelvis incomplete and did not attempt a reconstruction. No sacrum is associated with the pelvic elements to confirm or refute the present size reconstruction. New conspecific specimens will help.

Figure 2. Ctenochasmatids arise from these dorygnathids.

Figure 2. Ctenochasmatids arise from these dorygnathids.

Lü et al. amended the diagnosis of Gladocephaloideus
to accommodate the new smaller specimen. That’s not a good idea before determining that they are indeed conspecific. In order to obviate that prospect, in phylogenetic analysis Lü et al. created a chimaera of the two specimens eliminating any possibility of testing one against the other and against all other pterosaur taxa. In my experience it is extremely rare to find conspecific pterosaurs. That is why I try to nest only specimens, not chimaeras.

The pes of Gladocephaloideus

Figure 3. (Left) The pes of Gladocephaloideus compared to (right) the pes of Ctenochasma elegans (a smaller, more primitive Ctenochasma with fewer teeth). Compare to the pes in figure 1.

The feet
of the holotype and referred specimen are similar but not the same in proportion or appearance. They score differently. In pterosaurs, feet are like fingerprints, enabling one to lump conspecific taxa and split convergent look-alikes.

Figure 4. The JPM specimen in situ along with a reconstruction of its skull compared to the holotype of Gladocephaloides.

Figure 4. The JPM specimen in situ along with a reconstruction of its skull compared to the holotype of Gladocephaloideus. The anterior mandible was glued on in the wrong direction, as noted by Lü et al. 2016.

Lü et al. did not test
the MBR stem ctenochasmatid. Lü et al.  nest ctenochasmatids with cycnorhamphids, among other odd yet traditional nestings. This may be due to the low number of included taxa (67) vs. 215 in the large pterosaur tree.

The taxonomy and systematics get a little confusing….
the original Gladocephaloideus was assigned by Lü et al. 2012 to the Gallodactylidae (cycnorhamphids), but in consideration of the smaller specimen Lü et al. 2016 shifted it to the Ctenochasmatidae where it nests with Pterofiltrus, which nests as a cycnorhamphid in the large pterosaur tree. Moreover, Lü et al. include as related taxa, Elanodactylus (a derived germanodactylid, basal to pteranodontids), Beipiaopterus (a basal azhdarchid), Feilongus and Moganopterus (both cycnorhamphids). At the next level of closest kin Lü et al. include Pterodactylus longicollum (a pterodactylid), Gnathosaurus (a ctenochasmatid) and Cearadactylus (an ornithocheirid nesting far from other ornithocheirids).

This buckshot phylogeny only get worse, but I’ll stop here.

I applaud Lü et al.
for re-identifying the holotype Gladocephaloideus as a ctenochasmatid, as first reported here several years ago. But the rest of their phylogenetic analysis has to add taxa to get up to speed with current research. Their pterosaur tree recovered over 3000 MPTs compared to the fully resolved single tree at ReptileEvolution.com.

Juvenile? Big question that needs new insight to answer:
Lü et al. 2016 report, “The unfused contact between the extensor tendon process and the proximal end of wing phalange 1, as well as the poorly ossified epiphyses of the wing phalanges, indicates that JPM-2014-004 is an early juvenile individual.” It is hard to consider the JPM specimen a juvenile because in phylogenetic analysis it is larger than both proximal adult taxa. The more primitive MB.R. specimen, despite its size is an adult having undergone phylogenetic miniaturization from larger Dorygnathus and Angustinaripterus ancestors, an evolutionary process that often gives rise to new morphologies, in this case, the clade Ctenochasmatidae with all of its synapomorphies. Phylogenetically miniaturized pterosaurs retain, through neotony, juvenile bone microstructure. Lü et al. 2016 report woven bone structure and no LAGs or zones. This may occur in rapidly growing tiny (sparrow-to-hummingbird-sized) adults less than one year in age. Tiny pterosaurs, like tiny birds may have matured in far less than a year, just like small birds. Lü et al. 2016 note that LAGs are uncommon in pterodactyloids, but may be seen in larger specimens that presumably lived longer. Size matters in a phylogenetic context. This has to be considered before making statements about ontogenetic age estimates.

Tibial bone wall thickness
With a radius of 16 units (holding a cm scale up to my monitor) the tibial bone thickness was 5 units, leaving 11 units of hollow cavity. That is same cortex ratio as in the 2x larger (9x heavier) holotype specimen.

But wait! What’s this?? A long rostrum on a juvenile??? 
That can’t be so, IF you follow the work of Bennett, Witton, Wellnhofer and others. That would be internally inconsistent! However, if you follow ReptileEvolution.com and the Pterosaur Heresies you’ll note that many tiny adults AND embryos had long rostra and small eyes. No problem under the isometric growth hypothesis, which I hope will someday gain a little acceptance because it is demonstrably factual. 

References
Lü J-C, Ji Q, Wei X-F and Liu Y-Q 2012. A new ctenochasmatoid pterosaur from the Early Cretaceous Yixian Formation of western Liaoning, China. Cretaceous Research in press. doi:10.1016/j.cretres.2011.09.010.
Lü J, Kundrát M, Shen C 2016. New Material of the Pterosaur Gladocephaloideus Lü et al., 2012 from the Early Cretaceous of Liaoning Province, China, with Comments on Its Systematic Position. PLoS ONE 11(6): e0154888. doi:10.1371/ journal.pone.0154888

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Agilisaurus and the origin of the Pachycephalosauridae

Stegoceras validum (Lambe 1902; Late Cretaceous, Late Campanian; 75mya; 2m length; Fig. 1) was a basal dome-head dinosaur, or pachycephalosaur. Traditionally pachycephalosaurs have been linked to to stegosaurs, like Stegosaurus, troodontids like Sinornithoides, and ceratopsians, like Triceratops, but those are not supported in the large reptile tree (subset Fig. 4).

In the large reptile tree
Stegoceras was recovered as a sister to Agilisaurus (Peng 1990; ZDM 6011; Middle Jurassic; 1.2m length; Figs. 2-4).

In Stegoceras
the nares face somewhat forward, as in Agilisaurus. Similarly the forelimbs are tiny on this biped. The palpebral bones are incorporated into the skull itself. The antorbital fenestra is no longer visible. The dorsal and caudal ribs are quite wide, giving this dinosaur a wider than deep torso and tail first noted by Greg Paul, who kindly provided permission for his famous reconstruction (Fig. 1). The posterior tail is stiffened with ossified tendons originally thought to be gastralia.

Figure 1. Stegoceras, a basal pachycephalosaur from the Mid-Cretaceous is derived from a sister to Agilisaurus.

Figure 1. Stegoceras, a basal pachycephalosaur from the Mid-Cretaceous is derived from a sister to Agilisaurus.

Sullivan 2003 writes,
“Pachycephalosaurian dinosarus, known primarily fro their unusually thickened crania, are perhaps the most enigmatic and poorly understood dinosaurs.” Sullivan, like many traditional paleontologist, used ceratopsids for his phylogenetic outgroup. Traditionally pachycephalosaurs and ceratopsids have been lumped in the clade “Marginocephalia” (Sereno 1986). The large reptile tree (subset Fig. 3) does not support that nesting. Instead, the odd Agilisaurus nests with Stegoceras. It shares many traits including incipient anteriorly facing nares, small fore limbs and a long tail. The presence of upper temporal fenestrae in Stegoceras,though tiny, mark this as a basal pachycephlosaur.

Sereno (1986)
based the taxon on four synapomorphies (listed before the publication of Agilisaurus, which does or could share all 4 traits):

  1. narrow parietal shelf
  2. posterior squamosal shelf
  3. short posterior premaxillary palate
  4. short postpubic process (the original retroverted pubis sans the prepubic process)

The most basal member of the Marginocephalia
is reported to be Stenopelix, which we looked at earlier here. With current data,
the clade “Marginocephalia” has no utility because pachycephalosaurs do not nest with ceratopsians to the exclusion of all other taxa.

Sullivan continues
“It is clear that pachycephalosaurids appear rather abruptly in the fossil record (the Santonian). The origin of this group, and the directionality in dispersals of its taxa can only be speculative based on current (2003) information.”

Figure 1. The skull of Agilisaurus (Late Jurassic) provides the bauplan for the skull of more derived pachycephlosaurs, like Stegoceras.

Figure 1. The skull of Agilisaurus (Late Jurassic) provides the bauplan for the skull of more derived pachycephlosaurs, like Stegoceras. Note the anteriorly facing nares. The palpebral bone is in two parts here.

Agilisaurus is an ornithischian oddball.
And, as in other phylogenetic enigmas, like Longisquama and Sharovipteryx, the oddballs (in this case, Agilisaurus + pachycephlosaurs) nest together. The enigmatic structures suddenly become synapomorphies when sister taxa are found to share apparent autapomorphic (unique) traits.

Figure 3. Agilisaurus, like Stegoceras, was a biped with tiny forelimbs and a long tail, providing the blueprint for later pachycephalosaurs.

Figure 3. Agilisaurus, like Stegoceras, was a biped with tiny forelimbs and a long tail, providing the blueprint for later pachycephalosaurs. Note the broad fronts and tiny parietals.

The large and broad frontals
of Agilisaurus, together with the relatively small parietals are precursor traits to the dome skulls of pachypleurosaurs. At this point, and with the limited number of taxa in the ornithischian subset of the large reptile tree, this is how relationships are recovered. Xu et al. 2006 in their paper on Yinlong, recovered Agilisaurus basal to heterodontosaurs in the branch leading to their “Marginocephalia.”

Figure 4. The phytodinosauria. Here Stegoceras and the pachycephalosaurs nest with the Middle Jurassic Agilisaurus.

Figure 4. The phytodinosauria. Here Stegoceras and the pachycephalosaurs nest with the Middle Jurassic Agilisaurus.

One of the problems traditional paleontologists have
with the Ornithischia is they don’t know which taxa are basal. They often use Lesothosaurus, rather than Chilesaurus and Daemosaurus as a basal taxon. Here Lesothosaurus is basal to Stegosaurus through Scutellosaurus. We talked about Chilesaurus earlier here. Traditional paleontologists don’t recognize the clade Phytodinosauria, either. When they do, everything will become clear.

I’d like to know more about
Micropachycephylosaurus, a tiny taxon with a long name, reportedly close to the origin of the Ceratopsia, but I need data.

References
Barrett PM, Butler RJ and Knoll F 2005. Small-bodied ornithischian dinosaurs from the Middle Jurassic of Sichuan, China. Journal of Vertebrate Paleontology 25:823-834.
Currie PJ and Padian K 1997. Encyclopedia if Dinosaurs. Academic Press.
Dodson P. 1990. Marginocephalia. Pp. 562-563 in The Dinosauria (Weishampel DB, Dodson P and Osmólska H, eds.) University of California Press, Berkeley.
Lambe LM 1902. New genera and species from the Belly River series (Mid-Cretaceous). Contributions to Canadian Paleontology. Geological Survey of Canada 3:25-81.
Lambe LM 1918. The Cretaceous genus Stegoceras, typifying a new family referred provisionally to the Stegosauria. Transactions of the Royal Society of Canada. 12(4):23-36. Peng G-Z 1990. New small ornithopod (Agilisaurus louderbacki gen. et sp. nov.) from Zigong, China. Newsletter of the Zigong Dinosaur Museum 2: 19–27.
Peng G-Z 1992. Jurassic ornithopod Agilisaurus louderbacki (Ornithopoda: Fabrosauridae) from Zigong, Sichuan, China. Translated by Will Downs. Vertebrata Palasiatica 30: 39-51.
Sullivan RM 2003. Revision of the dinosaur Stegoceras Lambe (Ornithischia, Pachycephalosauridae). Journal of Vertebrate Paleontology 23 (1): 181–207.
Xu X, Forster CA, Clark JM and Mo J 2006. A basal ceratopsian with transitional features from the Late Jurassic of northwestern China. Proceedings of the Royal Society B: Biological Sciences 273: 2135–40. doi:10.1098/rspb.2006.3566. PMC 1635516. PMID 16901832.

wiki/Agilisaurus
wiki/Stegoceras

Stinkbird on steroids = Gastornis!

Figure 1. Gastornis (Diatryma) was a large bird of the late Paleocene,/early Eocene. It appears to share many traits withy the living hoatzin, Opisthocomus.

Figure 1. Gastornis (Diatryma) was a large bird of the late Paleocene,/early Eocene. It appears to share many traits withy the living hoatzin, Opisthocomus. Pedal digit 1 was likely retroverted.

Adding
giant Gastornis (Diatryma) (Fig. 1) to the large reptile tree brings to mind an old Warner Bros. Tweetybird/Sylvester cartoon, nicknamed on YouTube, “Tweety on Steroids” (Fig. 1).

I could not help noticing
a long list of synapomorphies shared between the giant flightless Paleocene bird, Gastornis, with the living stink bird, more commonly known as the hoatzin, Opisthocomus hoazin. The nickname ‘stink bird’ comes from its smell, derived from the rotting vegetation of its herbivorous diet. In Gastornis, a lack of sharp talons, a lack of a hooked beak together with its heavy bones and large gut indicate an herbivorous diet as well.

Figure 1. Warner Bros. cartoon on YouTube (click to view) transforms little Tweety into a giant monster, like Gastornis.

Figure 1. Warner Bros. cartoon on YouTube (click to view) transforms little Tweety into a giant monster, like Gastornis.

A comparison to Opisthocomus 
(Fig. 2) is interesting, and will follow, but perhaps more interesting, Gastornis shares several traits with non-avian dinosaurs, evident atavisms, not visible on known sister taxa.

Figure 2. The hoatzin, Opisthocomus, skeleton is quite similar to that of Gallus, the chicken. Juveniles do not have fused fingers.

Figure 2. The hoatzin, Opisthocomus, skeleton is quite similar to that of Gallus, the chicken. Juveniles do not have fused fingers.

Like non-avian dinosaurs, Gastornis has

  1. complete upper temporal arch (postorbital + squamosal)
  2. orbit not confluent with temporal fenestrae
  3. orbit taller than wide
  4. postfrontal
  5. ribs without uncinate processes
  6. lack of fused dorsal vertebrae
  7. coracoid approaching disc-like
  8. orbit shorter than postorbital skull length
  9. maxilla taller than 40% orbit height
  10. jugal with elongate qj process, short suborbital portion
  11. parietal skull table not broad, weakly constricted
  12. occiput close to quadrates
  13. ilium posterior process longer than anterior process (also as in Struthio and Hesperornis)
Figure 3. Gastornis (Diatryma) skull model with bones identified.

Figure 3. Gastornis (Diatryma) skull model with bones identified.

Like Opisthocomus, Gastornis has

  1. nasals connect medially
  2. descending jugal
  3. large gut/herbivorous diet
  4. dentary contributes to coronoid
  5. mandibular fenestra
  6. mandible ventral shape: 2 tier convex

References
Cope ED 1876. On a gigantic bird from the Eocene of New Mexico. Proceedings of the Academy of Natural Sciences of Philadelphia 28 (2): 10–11.
Matthew WD, Granger W and Stein W 1917. The skeleton of Diatryma, a gigantic bird from the Lower Eocene of Wyoming. Buletin of the American Museum of Natural History, 37(11): 307-354.
Hébert E 1855a. Note sur le tibia du Gastornis pariensis [sic] [Note on the tibia of G. parisiensis]. C. R. Hebd. Acad. Sci. Paris (in French) 40: 579–582.
Hébert E 1855b. Note sur le fémur du Gastornis parisiensis [Note on the femur of G. parisiensis]. C. R. Hebd. Acad. Sci. Paris (in French) 40: 1214–1217.
Prévost C 1855. Annonce de la découverte d’un oiseau fossile de taille gigantesque, trouvé à la partie inférieure de l’argile plastique des terrains parisiens [Announcement of the discovery of a fossil bird of gigantic size, found in the lower Argile Plastique formation of the Paris region]. C. R. Hebd. Acad. Sci. Paris (in French) 40: 554–557.
Statius Müller PL 1776. Des Ritters Carl von Linné Königlich Schwedischen Leibarztes &c. &c. vollständigen Natursystems Supplements- und Register-Band über alle sechs Theile oder Classen des Thierreichs. Mit einer ausführlichen Erklärung. Nebst drey Kupfertafeln.Nürnberg. (Raspe).

wiki/Hoatzin
wiki/Gastornis

Paleocene birds

Curious about
the distribution of Paleocene birds, I found a list online and applied it to a globe image (Fig. 1). The Chicxulub impact is added along with its projected ejecta area north to Montana.

Figure 1. The world at the K-T boundary, 65 mya and the distribution of Paleocene birds.

Figure 1. The world at the K-T boundary, 65 mya and the distribution of Paleocene birds. Click to enlarge.

I wondered if the distribution of birds in the Paleocene
reflected some kind of expansion from a refuge, perhaps at the antipodes to the asteroid impact. The answer is ‘no.’

The data shows
that Paleocene birds are found worldwide, with most specimens located in North America and Europe, close to the impact site and close to most paleontologists. How these birds survived when all others did not remains a mystery. If there was an initial refuge at the antipodes, these birds quickly spread out from that zone leaving no clue to their origin.

Figure 2. The hoatzin, Opisthocomus, skeleton is quite similar to that of Gallus, the chicken. Juveniles do not have fused fingers.

Figure 1. The hoatzin, Opisthocomus, skeleton is quite similar to that of Gallus, the chicken. Juveniles do not have fused fingers.

Figure 1. Skull of the hoatzin (Opisthocomus) with bones colorized.

Figure 2. Skull of the hoatzin (Opisthocomus) with bones colorized.

Among living birds
the hoatzin, Opisthocomus hoazin, (Müller 176) a 65cm herbivorous tropical bird from the Amazon, is often considered one of the most primitive of living birds, largely because juveniles have the atavism of individual clawed fingers that fuse upon reaching adulthood.

In the large reptile tree, which includes only three living birds, Opisthocomus nests with Gallus, the chicken. Obviously that will change when more taxa are added, but the overall resemblance is basic.

Wikipedia reports:
“Cladistic analysis of skeletal characters, on the other hand, supports a relationship of the hoatzin to the seriema family Cariamidae, and more distantly to the turaco and cuckoo families.”

Other studies conflict
with those results. Bird phylogenetic studies often do not agree with one another. This may be due to massive convergence based on huge taxon lists.

Hoatzins are currently the only members
of the clade Opisthocomidae and the order Opisthocomiformes. Wikipedia nests them within the Passerea then within the Neoaves, not close to Gallus. Neoaves include all living birds except Paleognathae (ratites and kin) and Galloanserae (ducks, chickens and kin = Fowl).

In Opisthocomus
the feet are large, the premaxilla does not reach the frontals, the nasals are robust, the upper temporal fenestra is located laterally, below the ‘equator’ of the expanded braincase and the sternum is deep.

The other primitive living bird is
one of several tinomous. Here (Fig. 3) the tinamou, Rhynchotus, was added to the large reptile tree. It nests with Struthio (Fig. 5), but shares many traits with Gallus and Opisthocomus.

Figure 4. Rhynchotus is a genus in the basal bird family of Tinamiformes. They are related to living large flightless birds. Note the small feet. 

Figure 4. Rhynchotus is a genus in the basal bird family of Tinamiformes. They are related to living large flightless birds. Note the small feet, like Struthio, figure 5.

Figure 4. Struthio, the ostrich, is currently a sister to the tinamou, Rhynchotus.

Figure 5. Struthio, the ostrich, is currently a sister to the tinamou, Rhynchotus.

I’d be curious to know
which genera crossed the K-T boundary?

References
Statius Müller PL 1776. Des Ritters Carl von Linné Königlich Schwedischen Leibarztes &c. &c. vollständigen Natursystems Supplements- und Register-Band über alle sechs Theile oder Classen des Thierreichs. Mit einer ausführlichen Erklärung. Nebst drey Kupfertafeln.Nürnberg. (Raspe).

wiki/Hoatzin

 

 

How did Moschops take a drink of water?

The dinocephalian synapsid,
Moschops (Fig. 1), looks like it could not bend its neck down to take a drink of water from the shoreline, giraffe-style.

Figure 1. Stiff-necked Moschops did not need to lean down, giraffe-style, to drink water. It could just wade into chin deep water.

Figure 1. Stiff-necked Moschops did not need to lean down, giraffe-style, to drink water. It could just wade into chin deep water.

But Moschops could wade
into chin-deep water, maybe where it’s plant diet sprouted. Okay, no big deal, but I’ve wondered this and the simplest answer did not come to me for some time, probably because I was giraffe- and wildebeest-biased. Watching my dog walk knee deep into a pond cleared the air for me.

Inside Psittacosaurus

Figure 1. Psittacosaurus wood and wire model by yours truly, several years back.

Figure 1. Psittacosaurus wood and wire model by yours truly, several years back, now sitting on a kitchen shelf with other hand made and ITC plastic dino models.

Psittacosaurus is a bipedal/quadrupedal ceratopsid sister to Yinlong, recently added to the large reptile tree (now at 689 taxa). Scoring involved a good look at the skull. Note a recent interpretation (You et al. 2008) deletes the vomer, palatine and ectopterygoid (Fig. 2).

Figure 2. Psittacosaurus major skull from You et al. colorized here withe the addition of the vomer, palatine and ectopterygoid. The great height of the rostrum permits a great height to the internal nares and lingual side of the maxilla. Note, the postfrontals, that are fused to the postorbitals in many sister taxa, do not appear to be completely fused together here. 

Figure 2. Psittacosaurus major skull from You et al. colorized here withe the addition of the vomer, palatine and ectopterygoid. The great height of the rostrum permits a great height to the internal nares and lingual side of the maxilla. Note, the postfrontals, that are fused to the postorbitals in many sister taxa, do not appear to be completely fused together here.

The ceratopsian palate
rises, with essentially vertical maxillary walls lining the central choanae. This obviates the need for the vomers, palatine and ectopterygoid, which become incorporated with the maxilla. Evidently You et al. thought they were gone. I see vestiges here, at least on one side, and note them above.

The ceratopsian ancestral taxon
is currently Hexinlusaurus, a gracile, long-necked, small headed ornithischian close to Dryosaurus. Unfortunately, the premaxilla and naris are missing in the Hexinlusaurus holotype.

The post-crania of Hexinlusaurus reveals it to be a small-skull taxon with long running legs.

Figure 3. The post-crania of Hexinlusaurus reveals it to be a small-skull taxon with long running legs. Currently this taxon is the outgroup to the Ceratopsia, but no pachycephalosaurs are currently included. 

References
Osborn HF 1923. Two Lower Cretaceous dinosaurs from Mongolia. American Museum Novitates 95: 1–10.
Xu X, Forster CA, Clark J M and Mo J 2006. A basal ceratopsian with transitional features from the Late Jurassic of northwestern China. Proceedings of the Royal Society B: Biological Sciences. First Cite Early Online Publishing. online pdf
You H−L, Tanou K and Dodson P 2008. New data on cranial anatomy of the ceratopsian dinosaur Psittacosaurus major. Acta Palaeontologica Polonica 53 (2): 183–196.

wiki/Yinlong 

2015 SVPCA abstract supports troodontid-bird clade

Nice to get confirmation
for a subset of the large reptile tree in a SVPCA poster (Brougham 2015).

From the Brougham results:
“The modified matrix strongly supports a Troodontidae + Avialae clade rather than a monophyletic Deinonychosauria, a topology remarkably convergent on that seen in modified Godefroit phylogeny, in which Aurornis, Eosinopteryx and the Tiaojishan paravians form a sister clade to Anchiornis and more derived avialans, the two of which in turn form a sister clade to Troodontidae.”

Figure 1. Basal theropod subset of the large reptile tree showing troodontids basal to birds and separate from dromaeosaurs.

Figure 1. Basal theropod subset of the large reptile tree showing troodontids (light red) basal to birds (red) and separate from dromaeosaurs (white).

References
Brougham T 2015. Multi-matrix analysis of new Chinese feathered dinosaurs supports troodontid-bird clade. researchgate.net/publication/280728942