Aurornis (pre-bird) skull, traced using DGS

Updated July 07, 2015 with new images of Aurornis.

Aurornis xui (Godefroit et al. 2013, Late Jurassic, 50cm in length, 160 or 125mya) is one of the many outgroup taxa known for Archaeopteryx and the birds, but it nests here as the closest of the tested ones.

Auronis is a small, gracile dromaeosaur
without a large elevated pedal digit 2. The skull is complete, but slightly disarticulated (Fig. 1). A little DGS colorizes the bones. These can then be reassembled to form a skull in lateral view.

Fig. 1 Aurornis skull in situ, various elements segregated from the in situ fossil and reassembled into a complete and articulated skull. The hole in the surangular is an artifact. The little lavender ovals are displaced sclerotic bones. Below is the original published image of the Aurornis skull.

Fig. 1 Aurornis skull in situ, various elements segregated from the in situ fossil and reassembled into a complete and articulated skull. The hole in the surangular is an artifact. The little lavender ovals are displaced sclerotic bones. Below is the original published image of the Aurornis skull.

Like many other small theropods,
Aurornis was feathered, agile and fast, a descendant of basal dromaeosaurids, like Halplocheirus. In palatal view, the internal nares are located on the anterior palatines and the anterior palate is narrow but solid. The premaxilla is still relatively short and toothed. The pterygoids are narrow and have lost their primitive triangular shape. As a result of taphonomy, tracings for the anterior dentary teeth are distinct from one another. The wider, more typical, pointed teeth are the correct morphology.

Figure 2. Aurornis in several views alongside Archaeoperyx to scale.

Figure 2. Aurornis in several views alongside Archaeoperyx to scale.

On a side note:
Pappochelys (‘grandfather turtle’) has been getting a lot of press, none critical. Take a fresh look at all the PR here.

On another side note:
Chilesaurus, which the large reptile tree nested as the long sought and current most basal member of the Ornithischia, and we looked at earlier here, was given a good look over at the TheropodDatabase blog here.  Evidently others also think the original Chilesaurus report has issues.

Added July 09, 2015
Dr. Andrea Cau’s note and the paper she sent, along with the SuppData downloaded served to increase the accuracy of these Aurornis images.

Figure 3. The manus of Aurornis as originally interpreted (above). As reinterpreted by comparison to Archaeopteryx below. Digit 3 was damaged and difficult to interpret. Digit 0 was originally overlooked. No only was Archaeopteryx smaller, it was more fully feathered and its bones were more gracile, all adaptations for flight.

Figure 3. The manus of Aurornis as originally interpreted (above). As reinterpreted by comparison to Archaeopteryx below. Digit 3 was damaged and difficult to interpret. Digit 0 was originally overlooked. No only was Archaeopteryx smaller, it was more fully feathered and its bones were more gracile, all adaptations for flight.

I have not seen the fossil itself,
but a DGS tracing of this image of the hand (Fig. 3) suggests ungual 2.3 was buried beneath the m2.2, not absent as originally indicated. Digit 3 of Aurornis was badly damaged, but by comparing it to Archaeopteryx a more accurate interpretation can be rendered with the proper number and length of phalanges.

Godefroit et al. reported the frontal was fused medially, but the fossil shows a medial split. They interpreted the pes with a fused metatarsal 3+4. That is probably not true as metatarsal 4 is likely buried in the matrix.

Figure 5. Aurornis hind limbs with bones colored. Here metatarsal 4 is distinct from mt3 and the fibula is identified. Click to enlarge.

Figure 5. Aurornis hind limbs with bones colored. Here metatarsal 4 is distinct from mt3 and the fibula is identified. Original interpretation of fused mt3+4 in gray. Mt5 is a tiny vestige close to the ankle. Click to enlarge.

References
Godefroit P, Cau A, Hu D-Y, Escuillié, Wu, W-H and Dyke G 201. A Jurassic avialan dinosaur from China resolves the early phylogenetic history of birds. Nature 498 (7454): 359–362.

wiki/Aurornis

Eohyosaurus – a new basal rhynchosaur

Eohyosaurus wolvaardti, SAM-PK-K-10159 (Butler 2015, Fig. 1) is a new basal rhynchosaur from the early Middle Triassic (Anisian) of the Karroo supergroup, known from a single skull. It is similar to Mesosuchus.

Figure 1. Eohyosaurus reconstructed. This taxon nests between, Trilophosaurus + Azendohsaurus and the Rhychosauridae.

Figure 1. Eohyosaurus reconstructed from several views of a single specimen. This taxon nests between, Trilophosaurus + Azendohsaurus and the Rhychosauridae (Figs. 2, 3).

Butler et al. did a thorough and excellent job
of describing their specimen. They nested it accurately.

Unfortunately,
Butler et al. added two non-rhynchosaurian outgroups (Prolacerta broomi and Protorosaurus speneri) to their cladistic analysis and omitted many others (Figs. 2, 3).

Figure 2. Rhynchosaur tree from Butler et al. Color area added for rhynchosauridae.

Figure 2. Rhynchosaur tree from Butler et al. Color area added for rhynchosauridae.

In the large reptile tree (Fig. 3 subset) the protorosaurs are not related to the rhynchosaurs. And rhynchosaurs are derived from sphenodontians. That was the original assessment, but the lack of fusion in the ankles of rhynchosaurs caused Cruickshank (1972) and Benton (1983) to consider rhynchosaurs close to protorosaurs and archosaurs, like Prolacerta and Proterosuchus. Carroll (1988) considered this valid in his landmark textbook and Dilkes (1998) agreed. Details here, here and here.

They’re all wrong,
if you include the following taxa (Fig. 3) and all the 556 intervening taxa.

Figure 3. Here is where Eohyosaurus fits on the large reptile tree.

Figure 3. Here is where Eohyosaurus fits on the large reptile tree.

Butler et al. considered
Noteosuchus the earliest known rhynchosaur (Early Triassic). Actually it’s a transitional clade member bridging Clevosaurus, a sphenodontian, to Eohyosaurus and Mesosuchus, basal rhynchosaurs.

All you young and old scientists (paleontologists)
keep adding taxa and see what your tree recovers.

References
Benton MJ 1983. The Triassic reptile Hyperodapedon from Elgin, functional morphology and relationships. Philosophical Transactions of the Royal Society of London, Series B, 302, 605-717.
Benton MJ 1990. The Species of Rhynchosaurus, A Rhynchosaur (Reptilia, Diapsida) from the Middle Triassic of England. Philosophical transactions of the Royal Society, London B 328:213-306. online paper
Benton MJ 1985. Classification and phylogeny of diapsid reptiles. Zoological Journal of the Linnean Society 84: 97-164.
Butler R, Ezcurra M, Montefeltro F, Samathi A, Sobral G 2015. A new species of basal rhynchosaur (Diapsida: Archosauromorpha) from the early Middle Triassic of South Africa, and the early evolution of Rhynchosauria. Zoological Journal of the Linnean Society 10.1111/zoj.12246.
Carroll RL 1988. Vertebrate Paleontology and Evolution. WH Freeman and Company.
Cruickshank ARI 1972. The proterosuchian thecodonts. In Studies in Vertebrate Evolution (ed. Jenkins KA and Kemp TS) 89-119. Edinburgh: Oliver and Boyd.
Dilkes DW 1995. The rhynchosaur Howesia browni from the Lower Triassic of South Africa. Paleontology 38(3):665-685.

The PMOL Changchengopterus manus – DGS

A while back we looked at the new Changchengopterus (the one that did not nest with the holotype). Here is a closer look at the hand.

Figure 1. PMOL Changchengopterus manus in situ and reconstructed. Click to animate to show flexor and extensor tendons. Note the presence of digit 5. The unguals invivo  point ventrally,  When crushed, like this, they often show their anterior (medial) faces. Shapes of the unguals are shown in gray. The pteroid articulates with the radiale.

Figure 1. PMOL Changchengopterus manus in situ and reconstructed. Click to animate to show flexor and extensor tendons. Note the presence of digit 5. The unguals invivo  point ventrally,  When crushed, like this, they often show their anterior (medial) faces. Shapes of the unguals are shown in gray. The pteroid articulates with the radiale.

Earlier we solved the problem
of flexor tendon insertion and flexion, here, here and here.

Figure 2. Traditionally digit 5 has been overlooked. Hopefully this GIF animation will help you see it.

Figure 2. Traditionally digit 5 has been overlooked. Hopefully this GIF animation will help you see it. Look for an ungual, two other phalanges, a metacarpal and an carpal, as in Longisquama and Cosesaurus, but in this case all overlain by soft tissue (probably tendons) and riddled with cracks.

Earlier we looked at
the manual digit 5 problem in pterosaurs here, here and here. The reduction of manual digit 5 is documented here. Cosesaurus and Longisquama, two pterosaur outgroups, retain a distinct manual digit 5 of the same morphology.

References
Zhou C-F and Schoch RR 2011. New material of the non-pterodactyloid pterosaur Changchengopterus pani Lü, 2009 from the Late Jurassic Tiaojishan Formation of western Liaoning.  N. Jb. Geol. Paläont. Abh. 260/3, 265–275 published online March 2011.

 

Pappochelys: NOT a turtle ancestor, not even close.

Updated July 1, 2015 with a tracing of the holotype of Pappochelys (Fig. 6). See July 1, 2015 for an update on Pappochelys

The following notes demonstrate 
the great capacity of unrelated reptiles to converge on character traits, in this case, expanded ribs and other traits. In such cases, only a large, species/specimen-based phylogenetic analysis, like the large reptile tree, can resolve such problems with great confidence, parsimony and logic. Otherwise, as in the case of Pappochelys (pah-poe-kee-luss), results can be frustrating (see below).

Fiigure 1. The turtle mimic Eunotosaurus from the Middle Permian was actually closer to Acleistorhinus.

Fiigure 1. The turtle mimic Eunotosaurus from the Middle Permian was actually closer to Acleistorhinus.

Yesterday, a new paper in Nature
by Schoch and Sues (2015) purported to document the transitional taxon between the derived millerttid, Eunotosaurus (Fig. 1), and the basal turtle, Odontochelys (Fig. 2). They employed two cladograms  (Figs.1, 2) based on Lyson et al. 2010. Both recovered topologies that are not supported by the large reptile tree. Both employ several suprageneric taxa, always a bad sign.

Figure 2. Odontochelys is a basal soft-shell turtle with teeth and anterior elbows and extremely pronated forelimbs.

Figure 2. Odontochelys is a basal soft-shell turtle with teeth and anterior elbows and extremely pronated forelimbs.

In the large reptile tree, now with 556 taxa, Eunotosaurus and Odontochelys are not closely related. On that note, Schoch and Sues report in their own  testing, a TNT analysis (Fig. 3) produced a tree topology distinct from their own Bayesian analysis (Fig. 4), especially with regard to their key taxon, Eunotosaurus (Fig.1), which nested far from turtles in the Bayesian analysis.

Odontochelys (Fig. 2) is indeed a basal turtle.
It nests with Trionyx, the extant soft-shelled turtle in the large reptile tree, so it is not as primitive as others suggest. It shared a common Early to Middle Permian ancestor with Elginia and Sclerosaurus, two more primitive horned turtle sisters (Fig. 7). Elginia nests with the giant horned turtle, Meiolania as reported earlier. Sclerosaurus had a broad flat torso with discrete osteoderms prior to carapace formation. This is how the carapace had its genesis according to the large reptile tree (Fig. 7).

Figure 1. from Schoch and Sues 2015 with colors added here to denote clades recovered by the large reptile tree. This is their TNT analysis result.

Figure 3. from Schoch and Sues 2015 with colors added here to denote clades recovered by the large reptile tree. This is their TNT analysis result.

The Schoch and Sues abstract
described the 220 million-year-old, Late Triassic, Odontochelys as having a ‘partly formed shell’, but the large reptile tree nested it with the living soft shell turtle, Trionyx, so the structure was derived, not primitive. So turtles are more ancient than the Late Triassic.

Schoch and Sues listed the 260-million-year-old Eunotosaurus as a hypothetical stem turtle, but it actually nests with Acleistorhinus and Delorhynchus, convergent with turtles in several respects.

Schoch and Sues considered the new reptile, Pappochelys rosinae (“grandfather-turtle”, 20 cm in length, 240 mya, Ladinian, Middle Triassic; SMNS 91360, SMNS 90013 and other referred specimens, including a very small individual), intermediate between Eunotosaurus and Odontochelys (but only in their TNT analysis, Fig. 3).

Figure 2. Second cladogram recovered by Schoch and Sues 2015 recovered by Bayesian analysis.

Figure 4. Second cladogram recovered by Schoch and Sues 2015 recovered by Bayesian analysis. The use of suprageneic taxa is always dangerous due to cherry picking and taxon exclusion. Note where Eunotosaurus (in pink) nests here.

From the Schoch and Sues abstract: “The three taxa [Eunotosaurus, Pappochelys and Odontochelys} share anteroposteriorly broad trunk ribs that are T-shaped in cross-section and bear sculpturing, elongate dorsal vertebrae, and modified limb girdles. Pappochelys closely resembles Odontochelys in various features of the limb girdles. Unlike Odontochelys, it has a cuirass of robust paired gastralia in place of a plastron. Pappochelys provides new evidence that the plastron partly formed through serial fusion of gastralia. Its skull has small upper and ventrally open lower temporal fenestrae, supporting the hypothesis of diapsid affinities of turtles.”

Their analysis, based on Lyson et al. 2010,
included 198 character traits (originally 191) and generated a single MPT.

They had to add 7 traits to achieve their results
When the original data set (191 characters) was analysed using TNT, with scores for Pappochelys included, the analysis yielded three MPTs that differed in the positions of Archosauriformes, Prolacerta, and rhynchosaurs, as well as of kuehneosaurids, lepidosaurs, and the turtle-sauropterygian clade. That’s several big changes! I applaud them for their honesty. They report, in that analysis, Pappochelys was found to nest below Eunotosaurus, but still within a clade with turtles.

In the large reptile tree
deletions and addition don’t produce that sort of anarchy and large changes in tree topology.

Schoch and Sues report,
“Robustness of nodes was assessed by bootstrap, resulting in collapse of many nodes, including Diapsida and the placement of Eunotosaurus at the base of the turtle clade.”

If they only had the large reptile tree to work with, this would not have happened.

Schoch and Sues also note, |
“Although the trunk region is disarticulated in all available specimens, the maximum number of  trunk vertebrae did not exceed nine.”
Since each specimen was incomplete, I wonder how they came up with that number? … except that Eunotosaurus and turtles have a short dorsal series with long vertebral centra. …or no partial specimen had more than nine scattered vertebrae preserved (typically far fewer). Based on the varying sizes and shapes of the dorsal ribs, it would appear that more ribs would be necessary to fill in the shape gaps, and along with more ribs you need more vertebrae (Fig. 6). In the large reptile tree recovered sister taxa among basal enaliosaurs (Figs. 5-7) have far more than nine dorsal vertebrae.

Schoch and Sues further note,
“In ventral view, the anterior gastralia extend anterolaterally, whereas the reverse obtains on the posterior gastralia. None of the available fossils preserves undisturbed pairs of gastralia.” (Fig. 6). Not sure how Schoch and Sues came to this conclusion, based on the evidence they presented, except that appears to be the pattern in Odontochelys (Fig. 2). I know of no other examples where this also happens. Note in the related placodonts, Paraplacodus (Fig. 6) and Placocodus, the lateral gastralia tips point dorsally and crushing could have produced such a pattern as interpreted by Schoch and Sues. I hope they weren’t trying to force fit an interpretation to disarticulated remains.

Figure 1. Pappochelys skull compared to sister taxa including Palatodonta and the original reconstruction of Schoch and Sues.

Figure 5. Pappochelys skull  reconstructed from colorized bone images compared to sister taxa including Palatodonta and the original reconstruction of Schoch and Sues. Pappochelys certainly looks like Palatodonta and Paraplacodus, but not Odontochelys. Note the very narrow frontals, totally unlike turtles, totally like Palatodonta.

In the Bayesian analysis
Schoch and Sues reported, “An unexpected result was the (albeit weakly supported) traditional placement of Eunotosaurus among Parareptilia and completely separate from Pappochelys, Odontochelys and Testudines, all of which were recovered as the sister-group of Sauropterygia among Diapsida. Pappochelys was firmly recovered as the sister-taxon to Odontochelys + (Proganochelys + Testudines).”

Figure 6. Pappochelys compared to placodont sister taxa and compared to the Schock and Sues reconstruction, which appears to have several scale bar errors and underestimated the number of dorsal vertebrae. Click to enlarge. So few ribs and vertebrae are known for Pappochelys that their order, size and number could vary from that shown here. Note the ribs of Paraplacodus are also expanded. The number of dorsal vertebrae is unknown and probably more than nine based on sister taxa.

Figure 6. Pappochelys compared to placodont sister taxa and compared to the Schock and Sues reconstruction, which appears to have several scale bar errors and underestimated the number of dorsal vertebrae. Click to enlarge. So few ribs and vertebrae are known for Pappochelys that their order, size and number could vary from that shown here. Note the ribs of Paraplacodus are also expanded. The number of dorsal vertebrae is unknown and probably more than nine based on sister taxa. The pectoral girdle of Pappochelys is from several specimens.

In figure 6
note the relatively large pelvis, short torso and long legs in the Schoch and Sues version of Pappochelys. Those proportions approach those of speedy terrestrial reptiles, not what one would expect of turtle ancestors. I think their estimates were off. Certainly their scale bars were off, unless the measurements were taken from several different ontogenetic age specimens. The Schoch and Sues reconstruction also overlooks the great variety in rib shapes and sizes in Pappochelys. While creating the reconstruction I also had trouble reconciling the scale bars with their reconstruction in which certain elements are twice or half what they should be. Compare skull sizes to pelvis sizes in their reconstruction vs. mine.

Throughout the Schoch and Sues paper
the authors make note of similarities between PappochelysEunotosaurus and Odontochelys.

  1. The large ribs bear sculpting on the dorsal surface, suggestive an intradermal origin.
  2. The dorsal ribs are T-shaped in cross-section
  3. The scapula is tall and slender
  4. The pelves closely resemble each other
  5. The pubis has a lateral process
  6. The S-shaped femur has an internal trochanter and an offset head.

But ALSO note that in both Schoch and Sues studies
eusaurosphargids and placodonts nest as sisters to the turtles. Schoch and Sues celebrate the fact that Pappochelys had a diapsid skull even though no turtles have  temporal fenestra. Turtles have only nested with diapsids in phylogenetic analyses based on molecular data. Their interpretation of Pappochelys. therefore, comes as something of a wonderful surprise in that it appears to tie morphological and molecular study findings together. To their credit, Schoch and Sues report that those molecular studies typically nest turtles with or close to archosaurs. We all agree that on the face of it such a nesting is out of the question. No morphological study has ever replicated that result.

The authors suggest that Eunotosaurus had upper temporal openings concealed by large supratemporals. The reader is probably already aware that no sister taxa of Eunotosaurus have upper temporal fenestrae and that if a bone covers an opening, it is no longer considered an opening.

Figure x. Two subsets of the large reptile tree focusing on Pappochelys and its enaliosaur relatives (left) and turtle relatives (right). Shifting Pappochelys to turtles adds 37 steps.

Figure 7. Two subsets of the large reptile tree focusing on Pappochelys and its enaliosaur relatives (left) and turtle relatives (right). Shifting Pappochelys to turtles adds 37 steps. Click to enlarge.

Testing Pappochelys
in the large reptile tree recovered a nesting close to the basal placodont, Palatodonta (skull only) and the much larger Marjiashanosaurus (post-crania only). Paraplacodus is not far removed and it has ribs with a T-shaped cross-section. Sinosaurosphargis is shaped like a turtle with a carapace and plastron of flat gastralia and it nests close by. Largocephalosaurus nests nearby and it has a tall slender scapula and a pubis with a lateral process. So reptiles near that node were experimenting with several turtle traits by convergence with actual turtles.

Of great interest in Pappochelys
is the lack of elongate dorsal transverse processes, common to eusaurosphargid and placodont sister taxa. However Anarosaurus and Pachypleurosaurus are also sisters and they, like Pappochelys and turtles, also lack elongate dorsal transverse processes.

Fingers and toes
Like EunotosaurusPappochelys has relatively slender fingers and toes, unlike those of turtle and their true ancestors, like Sclerosaurus. But that’s okay, because Eunotosaurus and Pappochelys are not related to turtles.

Convergence!
As noted above, nearly every turtle-like trait found in Pappochelys can be found in pachypleurosaurs, eusaurosphargids and placodonts. There is no doubt that Pappochelys evolved several turtle-like traits. Unfortunately, parsimony reveals that it was not a turtle, but developed those traits by convergence. I understand the excitement that Schoch and Sues must have felt about their discovery and its apparent importance. No wonder Nature wanted to publish it. But just like Limusaurus and Yi qi, more prosaic mundane explanations and interpretations are recovered when more taxa are included in analysis.

Revisiting the new Pappochelys
If Pappochelys had the same number of dorsal vertebrae as its sister taxa, then a new, long-bodied reconstruction emerges (Fig.6). Here we have an elongate, aquatic reptile without specialized teeth. It has relatively short, weak legs and a wider than deep torso with pachystotic bones. With such traits, Pappochelys could have been a bottom-dweller in a shallow lake environment. Large eyes might have given it good night vision.

Now that we have two of these short-snouted, big-eyed placodonts, perhaps we can discard the false idea that Palatodonta was a juvenile. Rather, as in many other novel reptile clades, phylogenetic miniaturization accompanied the development of new body parts and character traits.

For the large reptile tree origin of turtles, click here and here.

The Pappochelys strata
were laid down in a shallow oligohaline or freshwater lake. It is the most common taxon in the Vellberg lake deposit and is represented by several growth stages. The authors consider Pappocehelys “critical evidence for the diapsid relationships of turtles and it provides a new stage for the evolution of the turtle body plan.”

Unfortunately,
Pappochelys is a basal placodont, unrelated to turtles.

However, Pappochelys is important to the large reptile tree because it ties a skull-only taxon (Palatodonta) to a skull-less taxon (Majiashanosaurus). So the tree is once again fully resolved, an unforeseen side-effect.

Added a day later: lots of news online about Pappochelys, some with audio

NPR
CBC.Canada
Smithsonian Magazine
Science Magazine – reports, “So having broad, dense bones and gastralia would have acted like a diver’s weight belt, helping Pappochelys fight buoyancy and forage on the lake’s bottom. But these bones would also have had a beneficial side effect: They would have offered some degree of protection from predators, such as large amphibians or fish living in the lake, by deflecting or blunting their bites.”

References
Lyson TR, Bever GS, Bhullar B-AS, Joyce WG and Gauthier JA. 2010. Transitional fossils and the origin of turtles. Biology Letters 2010 6, 830-833 first published online 9 June 2010. doi: 10.1098/rsbl.2010.0371
Schoch RR and Sues H-D 2015.
A Middle Triassic stem-turtle and the evolution of the turtle body plan. Nature (advance online publication) > doi:10.1038/nature14472 online

wiki/Pappochelys

The Origin of Dinosaurs as told by The Smithsonian, Wiki, etc.

Many of the biggest dino museums in the world
have produced their version of the origin of dinosaurs. Here’s what they have to say online:

Smithsonian – National Museum of Natural History
“The earliest dinosaurs were probably carnivorous, bipedal animals less than two meters long and weighing about 10 kilograms. From these small beginnings evolved thousands of different dinosaurs species.”

Wikipedia
“Dinosaurs evolved within a single lineage of archosaurs 232-234 Ma (million years ago) in the Ladinian age, the latter part of the middle Triassic. Dinosauria  is diagnosed by many features including loss of the postfrontal on the skull and an elongate deltopectoral crest on the humerus.

“The process leading up to the Dinosauromorpha and the first true dinosaurs can be followed through fossils of the early Archosaurs such as the Proterosuchidae, Erythrosuchidae and Euparkeria which have fossils dating back to 250 Ma, through mid-Triassic archosaurs such as Ticinosuchus 232-236 Ma. Crocodiles are also descendants of mid-Triassic archosaurs.

“Dinosaurs can be defined as the last common ancestor of birds (Saurischia) and Triceratops (Ornithischia) and all the descendants of that ancestor. With that definition, the pterosaurs* and several species of archosaurs narrowly miss out on being classified as dinosaurs. Archosaur genera that also narrowly miss out on being classified as dinosaurs include Schleromochlus 220-225 Ma, Lagerpeton* 230-232 Ma and Marasuchus* 230-232 Ma.

“The first known dinosaurs were bipedal predators that were 1-2 metres (3.3-6.5 ft) long. Spondylosoma may or may not be a dinosaur; the fossils (all postcranial) are tentatively dated at 235-242 Ma.

“The earliest confirmed dinosaur fossils include saurischian (‘lizard-hipped’) dinosaurs Nyasasaurus 243 Ma, Saturnalia 225-232 Ma, Herrerasaurus 220-230 Ma, Staurikosaurus possibly 225-230 Ma, Eoraptor 220-230 Ma and Alwalkeria 220-230 Ma. Saturnalia may be a basal saurischian or a prosauropod. The others are basal saurischians.”

* these are false nestings according to the tree topology of the large reptile tree.

University of Bristol
“Those archosaurs most closely related to the dinosaurs are forms such as Marasuchus. The detailed evolutionary relationships are still debated, but by the late Triassic, several early theropods are known, as the dinosaurs rapidly diversified. These dinosaurs, such as Eoraptor, Coelophysis and Herrerasaurus were all carnivores, and, despite their diversity, were quite rare at this time.”

Natural History Museum of Los Angeles County
“The ancestry of dinosaurs can be traced back some 230 million years ago to the Late Triassic. All dinosaurs belong to a group of reptiles called archosaurs-a group that also includes crocodiles and a variety of Mesozoic reptiles (pterodactyls and others) that are often misinterpreted as dinosaurs. The anatomical characteristics of both the earliest known dinosaurs and their archosaurian relatives suggest that the common ancestor of all dinosaurs was a small bipedal predator, which had forelimbs shorter than hind limbs. This ancestor was probably similar to the 235-million-year-old Lagosuchus from Argentina, pictured below.

“From the most primitive Triassic forms to the most advanced ones of the latest Cretaceous, all dinosaurs share defining traits that distinguish them from their closest archosaurian relatives. Among these innovations, the femur (or upper leg bone) developed a distinct head for a tied attachment into a hollow hip socket. These and other changes resulted in a hind limb that was tucked directly underneath the body, providing upright, pillar-like support of the body and also enhancing locomotive abilities. The changes that led to the erect posture of dinosaurs from the sprawling posture of their reptilian predecessors had a profound effect on the evolutionary success of these animals. These transformations may have also been coupled with the evolution of a higher metabolism (a step towards warm bloodedness) that endowed them with a greater capacity for sustained activities such as running.”

Genesis park genesispark.com
“The Bible states that on the fifth day of creation God created great sea monsters and flying creatures. This would have included the great swimming and flying reptiles (like the plesiosaur and pterosaur creatures mentioned at our Genesis Park website). On the sixth day God created the land animals, which would have included all of the dinosaur kinds (Genesis 1:20-25).”

YouTube
Brief Lecture on the Origin of Dinosaurs – one commenter correctly noted, “This doesnt (sp) explain the actual origin of dinasaurs (sp) like the title states.”

The origin and evolution of dinosaurs Paul Sereno
Annual Review of Earth and Planetary Sciences
Vol. 25: 435-489 (Volume publication date May 1997)

“Phylogenetic studies and new fossil evidence have yielded fundamental insights into the pattern and timing of dinosaur evolution and the emergence of functionally modern birds. The dinosaurian radiation began in the Middle Triassic, significantly predating the global dominance of dinosaurs by the end of the period. The phylogenetic history of ornithischian and saurischian dinosaurs reveals evolutionary trends such as increasing body size. Adaptations to herbivory in dinosaurs were not tightly correlated with marked floral replacements. Dinosaurian biogeography during the era of continental breakup principally involved dispersal and regional extinction.”

American Museum of Natural History
Strangely, they don’t have an online account of dinosaur origins.

ReptileEvolution.com
Meet a long list of the best known taxa preceding dinos, the advent of dinos and see their family tree here and here. More specifics here (Fig. 1).

Figure 2. The origin of dinosaurs to scale. Gray arrows show the direction of evolution. This image includes Decuriasuchus, Turfanosuchus, Gracilisuchus, Lewisuchus, Pseudhesperosuchus, Trialestes, Herrerasaurus, Tawa and Eoraptor.

Figure 2. The origin of dinosaurs to scale. Gray arrows show the direction of evolution. This image includes Decuriasuchus, Turfanosuchus, Gracilisuchus, Lewisuchus, Pseudhesperosuchus, Trialestes, Herrerasaurus, Tawa and Eoraptor.

The Dinosaur Heresies NYTimes Book Review from 1986

the_dinosaur_heresies200Now almost 30 years old, here’s something you might like to read (perhaps again?).
This is the NY Times book review of Dr. Robert Bakker’s ‘The Dinosaur Heresies’ from 1986. You can read the complete original here. I went to the prophesies below and marked them with a [+] or a [-] for those supported today or not and for those that are still questionable: [?].

BOOKS OF THE TIMES;
Dinosaur Mysteries
By MICHIKO KAKUTANI
Published: November 8, 1986

THE DINOSAUR HERESIES. New Theories Unlocking the Mystery of the Dinosuars and Their Extinction. By Robert T. Bakker. Illustrated. 481 pages. William Morrow & Company. $19.95.

Mr. [not Dr.?] Bakker has a quirky, free-floating imagination, and in the course of this book – which is generously illustrated with his own charming sketches – he raises many offbeat questions: Were changes in dinosaur eating patterns responsible for the evolution of flowering plants? [+] Did pink pterodactyls exist? [?] What sort of lips did dinosaurs have? [+] Could a human being beat a tyrannosaurus at arm wrestling? [?]

Mr. Bakker, the adjunct curator at the University Museum in Boulder, Colo., has published many papers in the field of vertebrate paleontology, and his book stands as an informative layman’s introduction to the wonderful world of dinosaurs while at the same time making an impassioned case for his own – sometimes heretical – views on their endurance and extinction. ”I’d be disappointed,” he writes, ”if this book didn’t make some people angry”; and given the often fiercely polarized world of vertebrate paleontology, he’s unlikely to be let down.

As Mr. Bakker sees it, dinosaurs have been given a bad rap over the years as ”failures in the evolutionary test of time” – portrayed as small-brained, cold-blooded sluggards who couldn’t ”cope with competition from the smaller, smarter, livelier mammals.” Such portraits, he suggests, are unfair as well as scientifically inaccurate: in the first place, dinosaurs dominated history for 130 million years [+] – a remarkably long period of time that attests to a decided ability to survive (the human species, in contrast, has only been around for 100,000 years). And while Mr. Bakker acknowledges that dinosaurs were probably not brilliant thinkers [+], he makes a persuasive argument for their physiological adaptability and their prodigious energy [+] – he even speculates that tyrannosaurus could gallop about at speeds approaching 45 miles an hour.  [-] 

Much of ”The Dinosaur Heresies,” in fact, revolves around the question of whether the animals were cold-blooded (and more closely related to reptiles) or, as Mr. Bakker contends, warm-blooded (and more closely related to mammals and birds) [+]. While he occasionally stops to summarize opposing viewpoints, he is less interested in presenting an objective overview of the field than in mustering evidence to support his own theories.

He argues that gizzards and large digestive tracts in [some] dinosaurs would have compensated for their weak teeth [+], enabling them to eat high quantities of land plants, necessary to support a high metabolic rate. He argues that birds and pterodactyls – both of which would have had to evolve high-pressure hearts and lungs before flight could have been achieved  [+] – descended from dinosaurs  [+] [-], and that it’s not unlikely that these ancestor dinosaurs were already equipped for high metabolism [+]. He argues that the dinosaurs’ ”adaptations for sex and intimidation” – horns, head-butting armor and all manner of bony frills -suggest that they led active, aggressive lives, uncharacteristic of lethargic, cold-blooded animals  [+]. He argues that the growth rate of dinosaurs more closely resembles that of mammals than reptiles [+]. And, finally, he argues that dinosaurs’ porous bone tissue indicates the sort of high blood-flow rate usually associated with warm-blooded creatures [?].

On the question of the dinosaurs’ demise, Mr. Bakker sides with those paleontologists who discount new theories of mass extinction caused by some sort of cosmic catastrophe – he cites evidence suggesting the extinctions occurred not during a single ”doomsday” period but over tens of thousands of years [+] [-] [?]. In his view, the development of new sorts of dinosaurs and other animals, combined with changes in the physical and genetic environment, gradually led to their doom [+] [-].

On a side note:
I liked Dr. Bakker’s quote about making some people angry with his novel ideas based on overlooked data.

On another side note:
like our antiquated notions about dinosaurs from over 30 years ago, pterosaurs today have been given a bad rap. They are still portrayed as ungainly quadrupeds, bound by membranes that tied their legs together and tied their wings to their ankles (along with a long list of other false paradigms). The data deniers, unfortunately, are still out there, thinking that if they just turn a blind eye toward certain data and hypotheses they will go away.

As everyone knows,
this blog, Pterosaur Heresies, was intended to approach data with the same verve and testing of false traditions that Dr. Bakker demonstrated.

 

 

A few words from Steve Jobs.

If you’ve been following
the last four years of squabbles, debates, insults, dismissals, rancor, venom, name-calling and shunning, then you’ll understand why this video was posted. Click to play. 

Click to play.

Click to play. Thank you, Steve Jobs and everyone else who was ever labeled.

From the commercial:
“Here’s to the crazy ones. The misfits. The rebels. The troublemakers. The round pegs in the square holes. The ones who see things differently. They’re not fond of rules. And they have no respect for the status quo. You can quote them, disagree with them, glorify or vilify them. About the only thing you can’t do is ignore them. Because they change things. They push the human race forward. And while some may see them as the crazy ones, we see genius. Because the people who are crazy enough to think they can change the world, are the ones who do.”

What lies beneath? Pterorhynchus part 2: chin fuzz

Added August 09, 2019
That feathery blob or dewlap now appears to be a displaced wing membrane. 

Yesterday we wondered what that feathery blob of tissue was beneath the jaws of the pterosaur Pterorhynchus (Czerkas and Ji 2002). Today, thanks to colleague, Tracy Ford, we now have an image in higher resolution under UV lighting (Fig. 1).

Figure 1. Animated GIF of Pterorhynchus taken in UV light with overlays and tracings. The 'wattle' appears to have two major parts and the lower part appears to be made of at least three feathery ribbons or plumes.

Figure 1. Animated GIF of Pterorhynchus taken in UV light with overlays and tracings. The ‘wattle’ appears to have two major parts and the lower part appears to be made of at least three feathery ribbons or plumes.

Now that we can see ‘the wattle’ better,
how do we interpret it? Here’s my first take on it (Fig. 1) using DGS:

This structure appears to have two parts.
1) proximally: long feathery pycnofibers originating at the back of the throat (relatively uncontroversial)

2) distally: six or seven strips or hairy/feathery plumes hanging from the front to mid-throat, not stiff, but as free-flowing as ribbons. If these are part of the pterosaur, then they would make it a pterosaur-of-paradise. The head crest and tail vanes on a super-long tail (Fig. 2) appear to indicate a pterosaur bent on being beautiful, which supports the chin-ribbon hypothesis (novel).

Watch the GIF animation through a few cycles 
to see if any of the above makes sense. If not, feel free to offer alternate interpretations.

Figure 2. Pterorhynchus with soft tissue.

Figure 2. Pterorhynchus with soft tissue.

References
Czerkas SA and Ji Q 2002. A new rhamphorhynchoid with a headcrest and complex integumentary structures. In: Czerkas SJ ed. Feathered Dinosaurs and the Origin of Flight. The Dinosaur Museum:Blanding, Utah, 15-41. ISBN 1-93207-501-1.

 

What lies beneath Pterorhynchus: Is that a dewlap?

Added August 09, 2019
That feathery blob or dewlap now appears to be a displaced wing membrane. 

Pterorhynchus is a Middle Jurassic pterosaur that preservers soft tissue in the one and only known specimen. Of interest today is the soft tissue below the mandible (Fig. 1). Chris Collinson wrote to the DML: “The dewlap honestly looks more like a “feather” beard of sorts than a pelican pouch.”

Figure 1. Pterorhynchus dewlap. Is this a feathery beard? Has it been torn off of another part of the body? Does it even belong to this pterosaur?

Figure 1. Pterorhynchus dewlap. Is this a feathery beard? Has it been torn off of another part of the body? Does it even belong to this pterosaur? Is it a fish? Or a plant? Click to enlarge. By the way, this is about as far as I manipulate photos, increasing the contrast in the middle and traced on the right.

Some data deniers 
were not happy when I added this ‘beard’ to my reconstruction of Pterorhynchus. Those workers thought I was ‘seeing things’ that are not there. Getting back to reality, several people have seen this structure (see above), so it is definitely there, but no one has defined what it is yet (that I know of).

If it is a secondary sexual trait like a wattle, dewlap or gular sac, then it would have added to aerodynamic drag, but might have been considered ‘sexy’ enough to be selected. Long-winged pterosaurs like Pterorhynchus, may not have been aerial speedsters, drag might not have been such a big problem.

If it is throat tissue torn away from the body, then it would match similar tissues preserved in other pterosaurs and fenestrasaurs. That’s my best guess.

If it is another portion of the pterosaur, I don’t see clues as to where it may go… but then I have not seen hi-rez images.

If this is not an object related to the pterosaur, but coincidentally preserved, then I don’t know what it is. It doesn’t look like familiar animal, plant or mineral material.

What are your thoughts? 

Balaur bondoc: flightless bird? or pre-bird?

This blogpost was modified June 22, 2015 with the addition of the red text and two cladograms pulled from Cau et al. 2015 along with a third from Brusatte et al. 2013.

Another change July 9 after new data on Archaeopteryx and Aurornis shift Balaur to nest with Velociraptor. 

Updated October 27, 2015 with a vertical, rather than a retro, pubis. 

Balaur bondoc (Figs. 1-6; EME PV.313, Csiki et al. 2010, Latest Cretaceous)is a mid-sized theropod dinosaur with not one, but two raised scythe claws on pedal digits 1 and 2 (Fig. 1). More typical forms of similar size, like Deinonychus and Velociraptor (Fig. 4), have only a single scythe claw.

Figure 1. The right foot of Balaur bondoc, a raptor-like theropod dinosaur known chiefly from its limbs and pelvis. Note the two scythe claws here. Yellow phalanges are raised off the substrate during terrestrial locomotion. At left from Cau et al. 2015. Middle derived from that drawing. Right, traced from photo in Cau et al. 2015).

Figure 1. The right foot of Balaur bondoc, a raptor-like theropod dinosaur known chiefly from its limbs and pelvis. Note the two scythe claws here. Yellow phalanges are raised off the substrate during terrestrial locomotion. At left from Cau et al. 2015. Middle derived from that drawing. Right, traced from photo in Cau et al. 2015).

Originally
(Cziski et al. 2010) and later (Brusatte et al. 2013) Balaur nested with velociraptorine dromaeosaurids, based on the Theropod Working Group (TWiG) matrix. However, Cau et al (2015) noted that Balaur had a suite of autapomorphies not present in dromaeosaurids, nor in most other non-avialan theropods. These unique traits include a fused carpometacarpus, loss of a functional third manual digit, proximal fusion of the tarsometatarsus, and an enlarged first pedal digit.

By contrast to the original nesting,
Cau et al. (2015) recovered Balaur more derived than Archaeopteryx among the birds. They used two prior theropod matrices in their study: Brusatte et al. (2014) and Lee et al. (2014). Cau et al. concluded, “Our reinterpretation of Balaur implies that a superficially dromaeosaurid-like taxon represents the enlarged, terrestrialised descendant of smaller and probably volant ancestors.” 

In other words,
Cau et al. nested Balaur after Archaeopteryx, which makes Balaur a flightless (= nonvolent) bird. Unfortunately Balaur was unlike the birds Cau et al. nested Balaur with, Sapeornis and Zhongjiaornis (Fig. 2). These two big-wing birds both have a pygostyle (reduced tail). Balaur does not. Details and other red flags follow.

Figure 2. Balaur compared to Zhongjiaornis and Sapeornis, sisters recovered by Cau et al. 2015. Unfortunagely both these taxa had a pygostyle and the former lacked teeth. Both also were likely volant based on the large size of their forelimbs.

Figure 2. Balaur compared to Zhongjiaornis and Sapeornis, sisters recovered by Cau et al. 2015. Unfortunagely both these taxa had a pygostyle and the former lacked teeth. Both also were likely volant based on the large size of their forelimbs.

Cau et al. 2015 
used the Brusatte et al. (2014) tree (860 characters vs. 152 taxa) to nest Balaur as a sister to Sapeornis (Fig. 1), a taxon with a pygostyle and very large forelimb/wings that was a more derived sister to Archaeopteryx. Cau et al. recovered more than a million MPTs in this test.

In addition, Cau et al. used the Lee et al. (2014) tree (1549 characters vs. 120 taxa) to nest Balaur close to Zhongjianopterus (Fig. 1) several nodes more derived than Archaeopteryx and slightly more derived than Sapeornis. Cau et al. recovered 1152 MPTs in this test.

Figure 3. Balaur nested in the large reptile tree nests with Velociraptor, but that nesting is based on a relatively few limb traits.

Figure 3. Balaur nested in the large reptile tree nests with Velociraptor, but that nesting is based on a relatively few limb traits.

Everyone acknowledges 
that Balaur is different than most other theropods. The goal here is to find out which theropods (birds included!) it is most like.

Added figure 3. Balaur sacral vertebrae colorized.

Added figure 4. Balaur sacral vertebrae colorized. Click to enlarge.

Unfortunately, or perhaps fortunately,
the matrix of the large reptile tree was not designed specifically for theropods. And worse yet, only about two dozen forelimb and hindlimb traits are preserved in Balaur that are listed in the large reptile tree character list. That’s a magnitude fewer than the competing tests (not sure how many of those characters are pectoral, pelvic and limb characters, though). Nevertheless the large reptile matrix recovered a fully resolved tree nesting Balaur with a theropod of similar size, Velociraptor, as in the original nestings (Cziski et al. 2010; Brusatte et al. 2013).

In the evolution and origin of birds
Aurornis represents a clade that was getting smaller and more gracile that ultimately led to all birds — and all tested birds have a reduced scythe claw. Opposite this trend, Balaur was built like a tank. Balaur fuses a long list of bones that otherwise do not fuse in sister taxa, but do occasionally fuse by convergence in more distantly related theropods.

Figure 4. How Baluar fits within the current taxon list, within the Theropoda. Here it nests between Aurornis and Archaeopteryx, flights and pre-bird, nevertheless it did flap its wings based on coracoid length.

Figure 4. How Baluar fits within the current taxon list, within the Theropoda. Here it nests between Aurornis and Archaeopteryx, flights and pre-bird, nevertheless it did flap its wings based on coracoid length.

Cau et al. considered
the sole phalanx of vestigial manual digit 3 to be the fusion of phalanges 1-3. That may be so… OR the distal phalanges might not have been preserved. Either way it makes no difference to the large reptile tree (Fig. 4).

Figure 5. Balaur (in vertical and horizontal configurations) compared to Haplocheirus and Velociraptor, Aurornis, Archaeopteryx and Gallus. Balaur nests with Velociraptor in the large reptile tree.

Figure 5. Balaur (in vertical and horizontal configurations) compared to Haplocheirus and Velociraptor, Aurornis, Archaeopteryx and Gallus. Balaur nests with Velociraptor in the large reptile tree.

Convergent with living birds,
the Balaur anterior sacrum is wide and the pubis of Balaur bows laterally, producing a wide area for the guts between them. This could also be the result of a switch to herbivory (as Cau et al. speculates) and, if so, the twin scythe claws may have been used only for climbing trees. A second scythe-like ungual was not necessary to open the guts of a dinosaur with more efficiency, but a second large claw might have helped a heavier, perhaps less mobile herbivorous Balaur hang more easily on a tree trunk with both medial and lateral digits opposing one another.

Despite the fact
that the manus is subequal to the pes in Balaur, Cau et al. considered those forelimbs ‘reduced’  by comparison to the flying birds, Sapeornis and Zhongjiaornis (Fig.1), perhaps due to insularism (living on an island). They suggested that Balaur may have had a proportionally shorter-tail and a less raptorial-looking foot than previously depicted. The tail was not pygostylic and the pes was trenchant. We’ve seen co-author D. Naish make such hopeful suggestions before, based on a lack of attention to such red flags as that long tail on Balaur. Naish also prefers to shoehorn taxa into existing clades (like pterosaurs into the Ornithodira), rather than allow the tree to recover new clades (like the Tritosauria and Fenestrasauria).

No doubt
Balaur was feathered and, with those long, but small, coracoids, it flapped feebly. No doubt it was too large and bulky to fly.

Red Flag
Cau et al. (2015) report, “The sister taxon relationship recovered between Balaur and the short-tailed Sapeornis is quite unexpected. According to that topology, the short pygostyle-bearing tail of Sapeornis evolved independently of the same condition in more crownward birds.” 

I’ll print this addition in red: Cau et al. also report, “The topology that results from our use of the dataset modified from Lee et al. (2014) agrees with most analyses of avialan relationships (e.g., Cau & Arduini, 2008; O’Connor, Chiappe & Bell, 2011; O’Connor et al., 2013;Wang et al., 2014) in depicting a single origin of the pygostylian tail among birds. Here we should note that topological discrepancies and alternative placements of problematic taxa may be influenced by artefacts in coding practice, or by the logical basis of character statement definition followed by different authors (Brazeau, 2011).We therefore consider it likely that some discrepancies between the updated analyses of Brusatte et al. (2014) and Lee et al. (2014)—including the alternative placements of Balaur and Sapeornis among basal avialans—reflect artefacts of coding rather than actual conflict in the data. In conclusion, we consider the consensus among the results of these alternative tests (i.e., Balaur as a non-pygostylian basal avian) as the phylogenetic framework for the discussion on its evolution and palaeoecology.” 

Naish’s note is correct.
I glazed over their conclusion, and now I see why. But that’s not the end of this nesting problem. 

Added Figure 1. The Cau et al tree based on the Brusatte et al. tree. Note the nesting of Balaur among long-tailed post-Archaeopteryx birds, but a sister to Sapeornis, which has a pygostyle. This tree is distinct from added figure 2. Click to enlarge. 

Added Figure 1. The Cau et al tree based on the Brusatte et al. tree. Note the nesting of Balaur among long-tailed (pink) post-Archaeopteryx birds, but a sister to Sapeornis, which has a pygostyle (yellow). This tree is distinct from added figure 2. Click to enlarge.

Added figure 2. The Cau et al. tree based on the Lee et al. tree. Note the nesting of Balaur exactly between the long-tailed theropods and pygostylic, perching (retroverted hallux) birds, distinct from added figure 1.

Added figure 2. The Cau et al. tree based on the Lee et al. tree. Note the nesting of Balaur exactly between the long-tailed (pink) theropods and pygostylic, perching (retroverted hallux, yellow) birds, distinct from added figure 1. An odd nesting, especially considering that Jeholornis and Jixiangornis had an proto-retroverted hallux.

That brings up a whole new topic I also glazed over earlier, the retroverted hallux, which originates with Zhongianornis and Sapeornis in the Cau/Lee cladogram. Shenzhourapator (= Jeholornis) and Jixiangornis demonstrate the expected intermediate morphology for perching.  Balaur, on the other hand, shows no sign of an intermediate or reversed hallux. More basal taxa (Rahonavis, Archaeopteryx, etc.) likewise do not have a reversed hallux, the perching toe.

Cau et al. listed the following traits supporting the placement of Balaur among Avialae. With relatively few traits (none listed below), the large reptile tree nested Balaur just outside of the Avialae (Archaeopteryx). Perhaps the solution to the Balaur problem lies somewhere around this node. Traits that could have arisen as a result of a tree-clinging behavior and the strain on the joints that that produces as size increases are marked with a bullet (•). But a size increase may not have occurred until after the bird split. 

  1. the hypertrophied and proximally placed coracoid tubercle •
  2. the anterior placement of the condyles of the humerus •
  3. the proximally fused carpometacarpus with a laterally shifted semilunate carpal •
  4. the closed intermetacarpal space •
  5. the reduced condyles on metacarpals I–II •
  6. the slender metacarpal III – (vestige)
  7. the reduced phalangeal formula of the third digit – (vestige)
  8. the extensively fused tibiotarsus •
  9. the extensively fused tarsometatarsus •
  10. the distal placement of the articular end of first metatarsal  •
  11. the large size of the hallux • (but it is oriented anteriorly, not reversed)
  12. and the elongation of the penultimate phalanges of the pes  • 

Added figure 3. From Brusatte et al. 2013, the nesting of Balaur far from the birds, within the dromaeosaurs.

Added figure 3. From Brusatte et al. 2013, the nesting of Balaur far from the birds, within the dromaeosaurs.Aurornis is missing here. A later paper by Brusatte et al. 2014, (Fig. 1) changed much of this topology and included Aurornis.

Bottom line:
Balaur was derived from dromaeosaurids in the large reptile tree (based on a limited number of theropods and birds). Balaur had a long tail, not a pygostyle. It had forelimbs similar in size relative to the torso, as those of pre-birds, not post-Archaeopteryx birds. The laterally expanded gut indicates a likely switch to herbivory. The second scythe-like claw likely aided tree-clinging. Balaur did not have a perching toe.

References
Brusatte, et al. 2013. The osteology of Balaur bondoc, an island-dwelling dromaeosaurid (Dinosauria: Theropod) from the Late Cretaceous of Romania. Bulletin of the American Museum of Natural History, 374:1-100.
Brusatte S, Lloyd G,Wang S, Norell M. 2014. Gradual assembly of avian body plan culminated in rapid rates of evolution across the dinosaur–bird transition. Current Biology 24:2386–2392 DOI 10.1016/j.cub.2014.08.034.
Csiki Z, Vremir M, Brusatte SL, Norell MA 2010. An aberrant island-dwelling theropod dinosaur from the Late Cretaceous of Romania. Proceedings of the National Academy of Sciences of the United States of America 107 (35): 15357–15361.
Cau​ A, Brougham​ T and Naish​ D. 2015. The Phylogenetic Affinities of the Bizarre Late Cretaceous Romanian Theropod Balaur bondoc (Dinosauria, Maniraptora): Dromaeosaurid or Flightless Bird? PeerJ3: E1032. DOI: dx.doi.org/10.7717/peerj.1032
Lee MSY, Cau A, Naish D, Dyke GJ. 2014. Sustained miniaturization and anatomical innovation in the dinosaurian ancestors of birds. Science 345(6196):562–566 DOI 10.1126/science.1252243.

EME = (TransylvanianMuseum Society, Dept. of Natural Sciences, Cluj-Napoca, Romania)