Deinocheirus: a giant ornithomimosaur

Updated January 28, 2020
with a new comparison to the ornithomimosaur, Gallimiumus, distinct from Struthiomimus.

Following a long list of blog posts
that reported an inability of the large reptile tree, to nest various theropods in their traditional nodes, today Deinocheirus (Fig. 1) nests with ornithomimosaurs, like Gallimimus,  despite not having a pinched mt3 and having a pedal digit 1.

Figure 1. The skull of Deinocheirus. Note how the mandible does not completely close cranially when the anterior tips touch. I wonder if this was a sieving organ lined with baleen-like structures? That hypothesis goes with the very deep mandible and the equal lengths of both upper and lower jaws.

Previous studies
assumed that Deinocheirus was an ornithomimosaur, because it had very similar manus and forelimb proportions. When the skull was discovered, it was likewise toothless.

Figure 2. Deinocheirus specimens and a composite illustration.

Deinocheirus mirificus (Osmólska & Roniewicz, 1970, Latest Cretaceous, 70 mya 11m) was originally and later considered a giant and basal ornithomimosaur. The large reptile tree nests Deinocheirus with Gallimimus.

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References
Lee YN, Barsbold R, Currie PJ, Kobayashi Y, Lee HJ, Godefroit P, Escuillié F and Chinzorig T 2014. Resolving the long-standing enigmas of a giant ornithomimosaur Deinocheirus mirificus. Nature 515 (7526): 257–260.
Osmólska H and Roniewicz E 1970. Deinocheiridae, a new family of theropod dinosaurs. Palaeontologica Polonica. 21:5-19.

YouTube video featuring Deinocheirus

wiki/Deinocheirus

Bunostegos really is a different sort of pareiasaur

Figure 1. The skull of Bunostegos with color added for clarity. Images from Tsuji et al. 2013.

 

Bunostegos akokanensis (Sidor et al. 2003, Tsuji et al. 2013; Late Permian, 1.5m; MNN-MOR47, Fig. 1) is a large pareiasaur nesting close to small Elginia (Newton 1893) in the large reptile tree (640 taxa), closer to turtles than most other pareiasaurs. Analysis of the limb bones suggested a more upright stance than is typical for pareiasaurs and turtles. It lived in a desert environment. The specimen is known from parts of several specimens.

Figure 2. Elginia and Meiolania, a pre-turtle and a basal turtle, both with supratemporal and other horns, as in the outgroup pareiasaur, Bunostegos.

References
Newton ET 1893. On some new reptiles from the Elgin Sandstone: Philosophical Transactions of the Royal Society of London, series B 184:473-489.
Sidor CA, Blackburn DC and Gado B 2003. The vertebrate fauna of the Upper Permian of Niger — II, Preliminary description of a new pareiasaur. Palaeontologica Africana 39: 45–52.
Tsuji LA, Sidor CA, Steyer JSB, Smith RMH, Tabor NJ and Ide O 2013. The vertebrate fauna of the Upper Permian of Niger—VII. Cranial anatomy and relationships of Bunostegos akokanensis (Pareiasauria). Journal of Vertebrate Paleontology 33 (4): 747. doi:10.1080/02724634.2013.739537

A cladogram issue illustrated

This post is dedicated to
reader Neil B. who suggested I review the reference below (Bapst 2013). It is a paper on the limits of resolution using theoretical cladograms. Frankly, it is over my head. Apologies, Neil. I stand by my large reptile tree cladogram as an reflection of actual evolutionary events. The tree is a practical application, not a theoretical one. However, let me offer some theory below (It probably duplicates something that has been published before that I am unaware of. If so, don’t turn me in!)

Some workers,
perhaps most current workers, follow the paradigm that you need at least 3x as many characters in order to attempt to resolve a list of taxa in phylogenetic analyses. In counterpoint, the large reptile tree currently employs only 228 characters versus a current total of 640 taxa with full resolution.

So what’s going on? 
‘In practice’ does not seem to be following ‘in theory.’ Of course, all the theoretical problems go away when you employ subsets of the large reptile tree, using only 12 to 50 taxa instead of the whole list. These subsets also employ 228 characters (most of them, I hope, parsimony informative), and that raises the ratio of those analyses above 3x. But that’s not even necessary.

Here’s a simplified solution that seems to help explain this issue.
You might think 1 character dichotomy should split 2 taxa, and it does. But one character dichotomy also lumps two taxa on each sides of that split. Ratio: 1 character/4 taxa.

Figure 1. Characters vs. taxa in analyses. Note one character lumps and splits 4 taxa. Two characters lumps and splits 8 taxa. Three characters lumps and splits 12 taxa given the present list of traits.

I’ve only extended this example
to three character dichotomies splitting and lumping 12 taxa with complete resolution using a 1:4 character:taxon ratio.

Now imagine
having a trait trichotomy (like fins, feet AND flippers) or four trait options (add limbless to this list) and you can see the possibilities for nesting more taxa with complete resolution increase greatly with relatively few characters. Of course, we’ll never completely fill in the large grids. It gets complicated fast with missing taxa and incomplete taxa and evolution going the way it wants to go without regard for the order of the matrix.

This then
is how the large reptile tree is able to keep adding taxa without adding characters. I don’t think I’ve even come close to hitting the limit for taxa yet. The 3x rule does not appear to hold true here. Rather the maximum number of taxa looks to be several multiples of the number of characters in theory, a smaller number in practice.

If one can define a new species
by a set of traits that no other species has, one should be able to split that taxon apart from all other taxa in phylogenetic analysis. Right? That’s all we’re trying to do here. So far, the large reptile tree is succeeding — and it does better (more robust bootstrap scores) as mistakes are corrected. If anyone has an old matrix, they should ask for for the latest update here.

References
Bapst DW 2013. When Can Clades Be Potentially Resolved with Morphology?
http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0062312

 

 

Dorsal views of basal turtle skulls support the cladogram

Earlier
here, here and here we looked at turtle origins — a controversial topic in mainstream paleontology resolved quickly and surely in the large reptile tree, which gives 639 taxa the opportunity to be ancestral to turtles.

Long story short
Toothy Elginia currently nests outside the turtles (only because we don’t have any post-crania) and toothless Meiolania nests as the basalmost turtle (Fig. 1) because it retains supratemporal horns and the elbows still extend laterally, not anteriorly. These taxa are derived from pareiasaurs, which are themselves sisters to diadectids, bolosaurs and proclophonids.

Figure 1. How the large reptile tree lumps and splits the several Diadectes specimens now included here. Note that bolosaurids, including Phonodus, now nest within other Diadectes specimens.

When the skulls of pertinent taxa
are seen in dorsal view (Fig. 2) it is easier to see the reduction of the horns in  pre- and basal turtle skulls. One also gets the impression that when Proganochelys and Odontochelys arrived on the scene in the Late Triassic, they both represent a much earlier radiation of turtles, both horned and not horned. So there are many more basal turtles out there waiting for us to discover them.

Figure 2. Turtles and their ancestors among the pareiasaurs. Note the soft shell turtle clade rotates the orbits until they are visible dorsally. Click to enlarge. Odontochelys is not so primitive as once considered. AND it appears to have redeveloped teeth. Note the reduction of supratemporal horns in basal turtles.

The Odontochelys tooth problem
Odontochelys is a Late Triassic toothed turtle that originally was considered (Li et al. 2008) a very basal turtle. Not so according to phylogenetic analysis which nests it with soft shell turtles like Trionyx. The odd thing is this soft shell turtle appears to have regrown teeth. More basal and sister taxa do not have teeth (Fig. 3). Odontochelys is also unusual in having nares in the anterior lateral orientation, not completely anterior, as in Trionyx, as in virtually all other turtles, and not dorsal, as in Ocepecephalon, which is also very off for a turtle.

Figure 3. Odontochelys and Trionyx. Note the teeth in ventral view of the Odontochelys skull. Click to enlarge.

The supratemporal problem
This evolutionary sequence demonstrates that the large supratemporal bones of turtles (the supratemporal horns of pre-turtles and Meiolania) have been traditionally mislabeled. This may be part of the problem that workers have had in nesting turtles in prior studies.

The molecule problem
Some researchers have found that turtle DNA is most closely matched to that of living archosaurs: crocs and birds. Everyone knows morphology does not support that nesting. Someone somewhere will figure this out someday.

References
Li C, Wu X-C, Rieppel O, Wang L-T and Zhao L-J 2008. An ancestral turtle from the Late Triassic of southwestern China. Nature 456: 497-501.

x

 

Let’s open up an old can of worms…

Three and half years ago
ReptileEvolution.com got a sound thrashing from Dr. Darren Naish writing form his Scientific American blog, Tetrapod Zoology. Today with 350 more taxa added and the tree still fully resolved, let’s add some ‘post-its’ to ten images of Darren’s blogpost (Figs. 1-10) to see how things stand today. Both adversaries are still out there on the Internet. Neither has buckled under.

This will be a long post
So the gist of it is:

1. Naish paints me as an outsider, only part of the paleo background. True – for most workers
2. Naish uses art and hypotheses that are not in my website. Some perjorative art he uses are from other artists. He had permission to use all my artwork, so bringing in these oddities was not necessary given his headline. 
3. Naish spends many paragraphs talking about pre-ReptileEvolution errors that I made. One reason for starting a fresh website was to rid myself of old errors, but with this ‘history’ tainting all of my present work Naish provides no possibility for future redemption or honor.
4. Naish claims that I see certain things in fossil photos that are not there in fossils. None of these are present in ReptileEvolution.com. If so, let me know so I can remove them.
5. Naish claims that I see certain things in fossils that are not visible in fossil photos. So, what can one do? (see below)
6. Naish blackwashes the entire ReptileEvolution website, all of its data, all of its images, then and forever in the future. He leaves no stone unturned.
7. Naish supports traditional trees, even those that nest pterosaurs close to phytosaurs and erythrosuchids and those that refuse to include fenestrasaurs. These are problems that need to be resolved in academia.
8. Naish wants me to add hundreds of more characters. As we’ve seen earlier, that doesn’t statistically help much after 200 traits and can be a never ending request.
9. Several times Naish provides high praise before he buries the knife. I won’t do that.
10. Both of us are unmoved regarding our stances.

Bottom line:
No one is perfect. No matrix is perfect. No interpretation is perfect. Even so, superior provisional hypotheses can be advanced by increasing the number of taxa in a taxon list. The more data, the less any single error affects the rest of the matrix and the more unbiased opportunities are present for nesting. If, in the end, all sister taxa look like sisters, with gradual accumulations of traits for all derived taxa, and the tree is completely resolved with high Bootstrap scores, isn’t that what we’re all looking for? Doesn’t that more closely model actual evolutionary events?

On the other hand, if Naish is correct
If my cladogram is built on (hundreds of) thousands of errors, even after fixing tens of thousands of errors, how is a fully resolved tree demonstrating gradual accumulations of derived traits for every taxon even possible?

When Naish is writing on his blog
and as I am writing here, we lose our scientist mantles and become journalists. In that role we have the obligation to name sources, be specific, inform the reader, write about what the headline promises, and try to maintain a balanced unprejudiced view. Any variation from this becomes propaganda. To that end, if you have any questions regarding topics that arise here, look up the answers on previous blog posts or on ReptileEvolution.com or drop me a note.

All of these pages can be enlarged with a click.
Some Carl Sagan quotes break up the long page images here and give you time to digest.

Figure 1 of 10. Click to enlarge. Monitor shot of Tet Zoo blog with annotations in yellow.

Below (Fig. 2) you’ll see some bizarre Pterodactylus art
that Naish says was illustrated as if my hypotheses were correct. To be fair, I show you a Pterodactylus from ReptileEvolution.com (Fig. 1a). Why did Naish choose to show the bizarre artwork of another artist instead of using one from the website he was critical of?

Figure 1a. Pterodactylus scolopaciceps, BSP 1937 I 18, No. 21 in the Wellnhofer 1970 catalog.

 

Figure 2 of 10 from Tetrapod Zoology.

“For me, it is far better to grasp the Universe as it really is than to persist in delusion, however satisfying and reassuring.”
— Carl Sagan —

Figure 3 of 10 from Tetrapod Zoology.

 

The truth may be puzzling.
It may take some work to grapple with.
It may be counterintuitive.
It may contradict deeply held prejudices.
It may not be consonant with what we desperately want to be true.
But our preferences do not determine what’s true.
— Carl Sagan —

Figure 4 of 10 from Tetrapod Zoology.

Here’s one Pteranodon from ReptileEvolution.com. 
(Fig. 4b) Why didn’t Naish use this one by hand instead of the Pteranodon from Hell? Did he venture into propaganda? Did he want to make my work look unworthy of respect?

Figure 4b. The UALVP specimen of Pteranodon. Note the lack of taper in the rostrum along with the small size of the orbit.

Figure 5 of 10 from Tetrapod Zoology.

The poor graduate student at his or her Ph.D. oral exam
is subjected to a withering crossfire of questions
that sometimes seem hostile or contemptuous;
this from the professors who have the candidate’s future in their grasp.
— Carl Sagan —

Figure 6 of 10 from Tetrapod Zoology.

Every kid starts out as a natural-born scientist,
and then we beat it out of them.
A few trickle through the system with their wonder and enthusiasm for science intact.

— Carl Sagan —

Figure 7 of 10 from Tetrapod Zoology.

I think people in power have a vested interest to oppose critical thinking.
— Carl Sagan —

Figure 8 of 10 from Tetrapod Zoology.

It is undesirable to believe a proposition
when there is no ground whatever for supposing it true.
— Carl Sagan —

Figure 9 of 10 from Tetrapod Zoology.

At the heart of science
is an essential balance between two seemingly contradictory attitudes –
an openness to new ideas, no matter how bizarre or counterintuitive,
and the most ruthlessly skeptical scrutiny of all ideas, old and new.
This is how deep truths are winnowed from deep nonsense.
— Carl Sagan —

Figure 10 of 10 from Tetrapod Zoology.

In the end
is it good to have an an adversary/nemesis? Does conflict help advance Science? I think of it as necessary and invigorating. An adversary can be like a cleaner fish, helping one get rid of errors. I think it is also important to recognize value where present and to discuss specifics and details whenever possible.

On the subject of outsiders and insiders
JL Powell 2014 writes: “Luiz Alvarez was another resented outsider, resented by author and geologist Charles Officer. 

Outsiders do not know the mores for a given field and would be unlikely to uphold them if they did. Outsiders can resurrect a question that insiders have long stopped asking, 

Insiders may find it almost impossible to change their mind publicly, which may be equivealent to renouncing their life’s work. Even if insiders do not cast aspersions on the character and training of an individual outsider, they may still resent the implication that their discipline is incapable of solfing its won problems using its own methods.” 

References
Powell JL 2014. Four Revolutions in the Earth Sciences: From Heresy to Truth. Columbia University Press.

 

Did Coelophysis have a digit ‘zero,’ too?

Ran across this image of a Coelophysis manus
(Figs. 1, 2) in the SuppData to Xu et al. 2009 (the paper that introduces us to Limusaurus. Fig. 4), which we looked at earlier here. The fossil appears to be one of the best preserved examples of a Coelophysis manus. Every bone is laid out without disturbance.

I count
6 possible phalanges here. Three are vestiges.

Xu et al. (2009)
introduced the concept of a “phase shift” in theropod digits to account  for the medial bud in Limusaurus, which they counted as digit 1 and the similar bud in chicken embryos. In their hypothesis the other digits changed their appearance to resemble the digit that was medial to each one. One through Three became Two through Four.

Figure 1. Coelophysis manus with digit 0, as in Limusaurus, medial to digit 1. This image also includes mt5 with phalanges, identified by Colbert as distal carpal 4. IF that is not digit zero, then it must be a slipped carpal element, but I think I’ve identified them all here. Note the PILs align even withe vestigial digits.

Unfortunately
Xu et al. 2009 did not clarify, but only muddied avian digital homologies. As we learned earlier, that medial digit is actually a ‘throwback” to basal tetrapods that once had an extra digit medially and is lost on almost all other taxa after hatching. Embryos retained it for a short time.

In this revised hypothesis
the appearance of the bud does not represent a “phase shift” of phalanges, but rather the appearance of a very old medial digit, digit “0”. The other digits retain their original pentadactyl numbers 1-5.

That brings us to
a specimen of Coelophysis (Figs. 1,2) that appears to preserve the manus without disturbance and with that rare medial bud. Perhaps this is another digit “0” — and this time with vestigial phalanges — if interpreted correctly.

Figure 2. Carpus of Coelophysis GIF animation. I’m a little confused about the medial bones here. If they don’t represent digit ‘0’, then perhaps some carpals have shifted medially here. The 1+2 carpal could be the medial centrale (Ce1) and the Ce1 could be the 1+2 carpal. Also, this specimen appears to have more carpals than Colbert 1989 illustrated (below).

Apparently
Digit 0 on theropods appears to be retained as a fused medial element in some modern birds (Fig. 3). It’s that little bump medial to metacarpal 1.

Figure 3. A selection of pre-bird and bird hands/wings including Haplocheirus, Limusaurus, Velociraptor, Archaeopteryx, Anser, Passer and two versions of the Hoatzin , Opisthocomus, adult and juvenile. Click to enlarge. Not to scale. Note the medial digit of the outlier, Limusaurus, which is a product of neotony, retained from embryonic tissue recapitulating the seven-finger manus of basal tetrapods (figure 3). Note the return of digit 0 fused to the anterior rim of Anser, Passer and the adult Opisthocomus.

Vestigial digits 
I presume, are lost during excavation every so often. Are they worth scoring in phylogenetic analysis? I score them.

There goes that hypothesis
Earlier I thought digit 0 appeared on Limusaurus because it was an embryological artifact retained on a vestigial manus retained after hatching and maturation  (Fig. 4). As everyone knows, the manus is not vestigial in Coelophysis, so… there goes that hypothesis – if that medial bud is indeed the ephemeral digit “0” and not something else.

Figure 4. Limusaurus also has four fingers and a scapula with a robust ventral area, like Majungasaurus, but those four fingers are not the same four fingers found in Majungasaurus.

References
Cope ED 1889. On a new genus of Triassic Dinosauria. American Naturalist 23: 626
Late Triassic Norian
Colbert E. 1989. The Triassic Dinosaur Coelophysis. Museum of Northern Arizona Bulletin 57: 160.
Xu X, et al 2009. A Jurassic ceratosaur from China helps clarify avian digital homologies. Nature 459, 940-944. doi:10.1038/nature08124

 

Eotyrannus: what is it?

Updated March 28, 2018 with a new reconstruction of the skull after the realization that the purported nasal is actually the nasal + frontals + lacrimals.

Eotyrannus lengi
(Hutt et al. 2001, Naish 2011, Fig. 1) is a mid-sized Early Cretaceous, Barremian, theropod originally and later allied with tyrannosauroids like Tyrannosaurus.

From the Hutt et al. 2001 abstract:
“The teeth in the premaxilla are D-shaped in cross-section and the nasals are fused.” These are traits shared with Tyrannosaurus. “The hands are elongate and slender and the hindlimbs are gracile.” These are not traits shared with Tyrannosaurus. “…the new taxon appears to be excluded from the group that comprises aublysodontine and tyrannosaurine tyrannosaurids. We conclude that the taxon is a basal tyrannosauroid and as such it is one of the earliest and (with the exception of some teeth and an isolated ilium from Portugal) the first from Europe.”

Figure 1. Eotyrannus lengi from images in Hutt et al. 2001 and Naish 2011. The scale bars are all over the place. This taxon seems not to nest with Tyrannosaurus, but with Tanycolagreus. The high angle of the naris is unique going back to Herrerasaurus.

Figure 1 revised. The bits and pieces of Eotyrannus restored as a skull. It appears the original nasal is actually the nasal + frontal and some lateral bones.

Unfortunately
the large reptile tree nests Eotyrannus with Tanycolagreus (Fig. 2) at the base of the clade that ultimately gave rise to birds. These two taxa may represent a clade of tyrannosauroid mimics at the base of the pre-bird clade. They may share a naris with a higher ascending angle other theropods.

Figure 2. Tanycolagreus nests as a sister to Eotyrannus in the large reptile tree. This appears to be a clade of tyrannosaur mimics at the base of the pre-bird clade.

Unfortunately
Eotyrannus is not known from more parts. What we do have, though, appears to be most similar to the contemporary Tanycolagreus among tested taxa. It’s a scrappy fossil. Not good for keeping up high resolution in the cladogram (Fig. 3).

References
Hutt S, Naish D, Martill DM, Barker MJ and Newbery P 2001. A preliminary account of a new tyrannosauroid theropod from the Wessex Formation (Early Cretaceous) of southern England. Cretaceous Research 22:227-242.
Naish D 2011. Theropod Dinosaurs, chapter 29 in Batten DJ (ed) English Wealden Fossils. The Palaeontological Association (London), pp. 526-559.
Senter, P 2007. A new look at the phylogeny of Coelurosauria (Dinosauria: Theropoda)”, Journal of Systematic Palaeontology, 5(4): 429-463

Suchomimus and Spinosaurus nest with Sinocalliopteryx and Dilong.

Surprisingly
and several blogs ago the large reptile tree nested the theropod dinosaurs Guanlong and Dilong (Fig. 1), not at the base of the Tyrannosaurus clade, but at the base of the Allosaurus and Sinocalliopteryx (Fig. 2) clade.

Figure 1. A DGS tracing of the theropod dinosaur. Dilong, is longer and lower than originally reconstructed. I wonder if it had a median nasal crest, now broken off. Phylogenetic bracketing indicates that may be so.

Prior to these taxon additions,
there were no long-snouted mid- to large-sized theropods in the large reptile tree other than Sinocalliopteryx, a feathered theropod with a kinked snout. Now we add two more.

Figure 2. Sinocalliopteryx is basal to Suchomimus and Spinosaurus in the large reptile tree. Possible median nasal crest here. Note the narrow cranium and wider jaws.

Adding
long-snouted Suchomimus (Fig. 3) and the short-legged, aquatic, giant Spinosaurus (Fig. 3) nests them both unambiguously with Sinocalliopteryx, The naris had not yet migrated posteriorly in Sinocalliopteryx, but the snout was already filled with long strongly curved teeth. And we see a hint of a nasal crest, narrow cranium, etc.

Figure 3. Suchomimus was a longer snouted sister of Sinocalliopteryx with taller neural spines and a retracted naris. The postorbital is unknown, but phylogenetic bracketing indicates a narrower temporal arch (colored area) that originally traced above.

When we first discussed Sinocalliopteryx
in the summer of 2014, its feathers and a lack of many other theropodss allied it with birds. Now with the addition of more theropods, like Suchomimus and Spinosaurus (Fig. 4), along with the realization that feathers were plesiomorphic for dinosaurs, a new phylogenetic picture comes into focus.

Figure 4. Aquatic Spinosaurus to scale with contemporary Early Cretaceous giant fish. Click to enlarge.

Otherwise
the earliest known members of the spinosaur clade are represented by Late Jurassic teeth. Sinocalliopteryx and Dilong help fill that gap with more bones.

Figure 5. Irritator skull GIF animation. Among the spinosaurs, this taxon preserves the cranium, but not the rostrum, just the opposite of the others. So this cranium often models for the others in restorations. Note the narrow frontals and parietals and the much wider pterygoids.

Speaking of more bones
Neither Suchomimus nor Spinosaurus preserve the circumorbital region and cranium. The related taxon, Irritator (Fig. 5) does preserve these regions and little else, and so is often used in chimaera restorations of spinosaurids.

Synapomorphies
Several traits set this clade (spinosaurids + Sinocalliopteryx) apart from other theropods:

1. narrow cranium with wide jaws
2. pmx/mx notch for dentary fangs
3. cranium descends posteriorly
4. snout tends to lengthen
5. skull not < 1.2 x wider than tall at orbit
6. posterior maxilla ascends lacrimal
7. nasal develops parasagittal crest (smaller than in Guanlong)

Other trees
Nest spinosaurids with

1. Baryonyx derived from the abelosaurid Berberosaurus + Coelophysis (Cau et al. 2015).
2. Megalosauroidea derived from a sister to Monolophosaurus (Wikipedia) which likewise as a median nasal crest, like Guanlong.

which are all still in the same branch of the theropod tree.

References
Ibrahim N et al. 2014. Semiaquatic adaptations in a giant predatory dinosaur. Science 345 (6204): 1613–6.
Ji S, Ji Q, Lu J and Yuan C 2007. A new giant compsognathid dinosaur with long filamentous integuments from Lower Cretaceous of Northeastern China. Acta Geologica Sinica, 81(1): 8-15.
Sereno PC, et al. 1998. A long-snouted predatory dinosaur from Africa and the evolution of spinosaurids. Science 282 (5392): 1298–1302.

wiki/Sinocalliopteryx
wiki/Suchomimus
wiki/Spinosaurus

 

Carroll 1988

Figure 1. Vertebrate Paleontology by RL Carroll 1988 is one of the starting points for this blog and ReptileEvolution.com

In 1988
Dr. Robert L. Carroll published a large work devoted to the study of fish and tetrapods: Vertebrate Paleontology and Evolution. Between its black covers and silver dust jacket there was – and is – an immense amount of data on just about every taxon known at the time… a time just before software driven phylogenetic analysis became de rigueur.

My copy
has been used so much it has a broken binder, which makes every section lighter, easier for scanning.

For its time, and for a few decades later
Vertebrate Paleontology and Evolution was the ‘go-to’ textbook for students and artists of this science. (See below).

A few quotes from the Amazon.com website:

1. “This book was my textbook for Vertebrate Paleontology and Evolution at the University of Rochester back in 1992.”
2. “the only easily available work that goes to any depth on this intensely interesting subject.”
3. “The book is very daunting to look at if you just flip through it. However, it does a nice job of introducing concepts and terms to the reader. Its organization is straightforward, starting with the simplest vertebrates and eventually finishing with mammals.:
4. “Just realize that some of the information may not reflect our current understanding since the book is over 10 years old and many new finds have come to light, new ideas have been introduced, and old ideas reexamined.”
5. “It’s an essential for anyone building a library of paleo textbooks.”
6. “I’m a working fossil preparator and this is the primary reference text used in paleontology labs at the American Museum of Natural History, Yale Peabody Museum and others I’m sure.”
7. “I had Romer’s Vertebrate Paleontology, which is an excellent book, until a paleontologist friend directed me to Carroll’s book. He acknowledges Romer’s work in the field but this is an updated version (for the time of publication).”
8. “If you want to chart the course of evolution up to the present – read this book!”

Carroll 1988 updated
Romer’s Vertebrate Paleontology  (1933, 1945, 1966) which was the ‘go-to’ textbook of its day.

ReptileEvolution.com
updates portions of Carroll 1988. Likewise and in due course, someone someday may want to update ReptileEvolution.com. I hope they do so.

Every so often
it’s good to give credit to one’s mentors and resources. Sometimes you learn by doing. Other times you learn by reading. I suppose everyone who writes such a large gamut book knows he/she is doing something to help future students and enthusiasts who they will never meet. I feel the same way, butI imagine both Carroll and Romer were additionally warmed by a healthy royalty check once or twice a year.

References
Carroll RL 1988. Vertebrate Paleontology and Evolution. W. H. Freeman and Co. New York.
Romer AS 1966. Vertebrate Paleontology. University of Chicago Press, Chicago; 3rd edition

wiki/Vertebrate_Paleontology_and_Evolution

Dracoraptor: a scrappy new earliest Jurassic theropod from Wales

Revised January 30, 2016. Additional taxa and revisions to Compsognathus now nest Dracoraptor with Coelophysis in the large reptile tree. 

Revised again March 11, 2016 with a rearrangement of the manual elements to match those of sister taxa.

A new paper
by Martill et al. 2016 describes a Late Triassic/Early Jurassic slender, mid-sized theropod, Dracoraptor hanigani, (NMW 2015.5G.1–2015.5G.11, Figs. 1-4).

Figure 1. Dracoraptor manus. Like its sisters, metacarpals 2 and 3 are similar in length.

From the Martill et al. paper:
“Diagnosis. A basal neotheropod with the following autapomorphies and unique combination of plesiomorphies: Three teeth in the premaxilla, slender maxillary process of jugal, large narial opening with slender subnarial bar, anteriorly directed pubis considerably longer than ischium, and large dorsal process on distal tarsal IV.”

Figure 2. Dracoraptor premaxillae compared to one another. Almost hard to believe they came from the same plate/counterplate. Together they present a better basis for scoring.

Martill et al nested
Dracroraptor (with long manual digit 3 interpretation, Fig. 3) between Tawa and Coelophysis. Tawas also has a longer manual digit 3. I could not confirm the longer manual digit 3.

Figure 3. Original interpretation of Dracoraptor with color codes for known bones. Above: putting the bones together. Ghosted image represents the jugal/lacrimal impression along with, perhaps two posterior teeth flipped. The reconstruction of the foot on the overall skeletal figure is at an odd tippy-toe angle. It should have more phalanges planted on the substrate and the metatarsus should be angled forward somewhat more.

In the large reptile tree (subset Fig. 4) Dracoraptor now nests with Coelophysis among tested taxa.

Figure 2. Here Dracoraptor nests with Coelophysis, another basal theropod.

Scattered digits
One of the problems with scattered digits is producing scores in analysis. The best practice, IMHO, is to nest the taxon first without scoring the scattered digits, then use phylogenetic bracketing to reassemble the scattered phalanges based on sister taxa patterns.

Generally it is problematic
to score scrappy taxa like this. Basal taxa are always interesting. Happily, enough is known to nest Dracoraptor without losing resolution.

As you can see
(Fig. 3), the published drawing does not accurately reflect the shapes of the published skull bones. In addition, the published tracing of the phalanges had to be warped to fit the published photograph. I wish tracings were taken from published photos so there would be a one-to-one correspondence.

References
Martill DM, Vidovic SU, Howells C and Nudds JR 2016. The Oldest Jurassic Dinosaur: A Basal Neotheropod from the Hettangian of Great Britain. PLoS ONE 11(1): e0145713. doi:10.1371/journal.pone.0145713