Liaoning bird embryo IS a Chinese Archaeopteryx

Updated 11/22/2015 with high rez data sent by Dr. Zhou. A new analysis nests the embryo with the holotype Archaeopteryx lithographica, the London specimen, a basal enantiornithine bird. 

Zhou and Zhang (2004)
described a small, precocial, final stage bird embryo from the Liaoning Province (Early Cretaceous, 121mya, IVPP V14238). Strangely, no eggshell was preserved (Fig. 1), but the tucked shape of the embryo indicated that it had not yet hatched. Northern China was a forested landscape dominated by active volcanoes and sprinkled with lakes and streams at the time. No adults were closely associated, but enantiornithine birds are common in that formation.

Figure 1. Click to enlarge. Liaoning bird embryo IVPP V14238 reconstructed Egg tracing in DGS compared to original tracing (in olive). Note the universally observed long tail and the continuation of the tail vertebrae past the back of the skull. Note the broken clavicles. When rotated they form more of a U shape. The dorsal coracoid is a convex and the ventral scapula is concave, an enanthiornithine key trait.

Figure 1. Click to enlarge. Liaoning bird embryo IVPP V14238 reconstructed Egg tracing in DGS compared to original tracing (in olive). Note the universally observed long tail and the continuation of the tail vertebrae past the back of the skull. Note the broken clavicles. When rotated they form more of a U shape with appropriate spacing of the coracoids. The dorsal coracoid is a convex and the ventral scapula is concave, an enanthiornithine key trait.

The Zhou and Zhang Abstract
“An embryo of an enantiornithine bird has been recovered from the Lower Cretaceous rocks of Liaoning, in northeast China. The bird has a nearly complete articulated skeleton with feather sheet impressions and is enclosed in egg-shaped confines. The tucking posture of the skeleton suggests that the embryo had attained the final stage of development. The presence of well-developed wing and tail feather sheets indicates a precocial developmental mode, supporting the hypothesis that precocial birds appeared before altricial birds.”

Figure 2. The Liaoning bird egg IVPP V14238 in situ with DGS tracing in color. This hirez version updates a prior lo rez version. Length of shell is 3.5 cm.

Figure 2. The Liaoning bird egg IVPP V14238 in situ with DGS tracing in color. This hirez version updates a prior lo rez version. Length of shell is 3.5 cm.

Zhou and Zhang 
did not create a reconstruction (Fig.1) nor attempt to untuck the embryo. Bird embryos shift into a tuck position before hatching as they begin to occupy most of the egg. No egg tooth is present on this specimen.

Figure 3. The Liaoning embryo compared to its closest sister, the London specimen of Archaeopteryx (holotype). The egg is the correct size to pass through the ischia if they were separated distally. like modern birds,

Figure 3. The Liaoning embryo compared to its closest sister, the London specimen of Archaeopteryx (holotype). The egg is the correct size to pass through the ischia if they were separated distally. like modern birds,

Zhou and Zhang report [with my observations in brackets]:
“The embryo has several enantiornithine apomorphies such as a strutlike coracoid with a convex lateral margin [yes], a V-shaped furcula [maybe], metacarpal III extending well past metacarpal II distally  [no], and metatarsal IV being more slender than metatarsals II or III [no]. My observations were improved with a high resolution image (Fig. 2). The Liaoning embryo nests with the holotype Archaeopteryx (London specimen), which nests at the base of the Enantiornithes.

This is the first
Cretaceous avian embryo preserved with feathers, sheathed, not open vanes. These indicate the embryo was precocial, able to move and feed independently shortly after hatching. This specimen demonstrates that the genus Archaeopteryx survived into the Early Cretaceous.

Figure 4. The Liaoning embryo bird nests with several Archaeopteryx specimens in the large reptile tree, AND with enanthiornithes. The large reptile tree does not specifically test for the classic enantiornithine traits, but correctly nested the embryo with adult enantiornithines.

Figure 4. The Liaoning embryo bird nests with several Archaeopteryx specimens in the large reptile tree, AND with enanthiornithes. The large reptile tree does not specifically test for the classic enantiornithine traits, but correctly nested the embryo with adult enantiornithines.

Compare this bird embryo to a precocial pterosaur embryo or three
like Pterodaustro, the IVPP embryo or the JZMP embryo. Embryo pterosaurs have the proportions of an adult. They grow isometrically. Hatchling birds, like the Liaoning embryo, had juvenile proportions with a large head, short tibia and short metatarsus. They grew allometrically, but not as allometric as living altricial (helpless) bird hatchlings.

“Several previously known theropod embryos and the late Cretaceous avian embryos all seem to be preocial animals, judged purely from skeletal evidence,” Zhou said.

Nat Geo
reported, “Zhou said several other enantiornithine species are known from the deposit where the latest fossil was found, but that it was difficult to link the embryo to a specific genus or species.” Unfortunately Zhou and Zhang eyeballed the embyro. They did not attempt a phylogenetic analysis (Fig. 4).

Kevin Padian
quoted in NatGeoOnline noted that half of the fossil’s characteristics are not exclusive to enantiornithines. He added that characteristics that would identify the fossil an enantiornithine are “either dubious or not well preserved on the specimen. But then, what else could it be?” Padian asked. I agree, but then neither of us has seen the fossil first hand.

Figure 4. Enanthiornithine birds to scale. Click to enlarge.

Figure 4.  A selection of Enanthiornithine birds to scale. None of these nest closer to the Liaoning embryo. These taxa all have a shorter tail and a more gracile clavicle and other traits listed in the large reptile tree.

Others have warned me
that juveniles and embryo reptiles, like pterosaurs and tritosaurs, cannot be added to phylogenetic analyses because they tend to nest with other adults*. Actually I’d like to see that happen. At present I’m a skeptic. This was a test of that hypothesis, but it was done with a precocial embryo with a relatively larger head, shorter neck and shorter limbs. I don’t see the problem with adding this embryo (Fig. 1) or precocial pterosaur embryos to analyses. But I’m willing to listen to good arguments with valid data.

*Bennett (2006) considered small adult pterosaurs as juveniles of larger germanodactylids based on long bone lengths rather than phylogenetic analysis. Eyeballing, charts and clouds of data points are no replacements for reconstructions and phylogenetic analysis. Hope you agree…

If this is an enantiornithine
which one is it most like? Archaeopteryx lithographica.

If this is an archaeopterygid
we now have some more ontogenetic clues and patterns to work with. You can see (Fig. 1) which body parts get larger and which get smaller during maturation.

Actually it’s both!

References
Bennett SC 2006. Juvenile specimens of the pterosaur Germanodactylus cristatus, with a review of the genus. Journal of Vertebrate Paleontology 26:872–878.
Zhou Z and Zhang F-C 2004. A Precocial Avian Embryo from the Lower Cretaceous of China. BREVIA Science 22 October 2004: 306 no. 5696 p. 653. DOI: 10.1126/science.1100000. online abstract here

NatGeoOnline

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SVP 17 Asilisaurus notes

Nesbitt et al. 2015 (svp abstract)
describe the poposaur, Asilisaurus, as highly convergent with dinosaurs, yet distinct.

True.
But there are still problems here. See the (*) asterisks.

From the abstract:
“Asilisaurus kongwe, from the Middle Triassic Manda beds of southwestern Tanzania, is one of the oldest known ornithodirans* and provides new insights into early dinosauriform evolution**. Originally represented by disarticulated bones and one semi articulated partial skeleton from a single locality, recent fieldwork has yielded six sites at approximately the same stratigraphic level, with specimens representing nearly the entire skeleton. A new, exquisitely preserved skeleton of a single individual includes much of the skull, pectoral girdle, forelimbs, pelvis, hind limbs, and tail, and confirms that all of the original, largely disarticulated material belongs to Asilisaurus. The skeleton of Asilisaurus shares several plesiomorphic character states with other dinosauriforms, including a well-developed metatarsal I with a distinct articulation surface for a phalanx, a calcaneum with a clear tuber, a closed acetabulum, and a short deltopectoral crest. Additionally, Asilisaurus shares several features with Silesaurus and other putative silesaurids (e.g., Sacisaurus), such as teeth ankylosed with the jaw, a distinctive scar on the proximal surface of the femur, a bony pointed beak at the rostral tip of the lower jaw, and a notch at the base of the femoral head. Classic ‘dinosaurian’ character states, such as the upper temporal musculature extending onto the frontal and epipophyses on the cervical vertebrae, must be considered plesiomorphies given the phylogenetic position of Asilisaurus. The nearly complete osteology of Asilisaurus allows re-evaluation of other problematic taxa; Agnosphitys*** and Lewisuchus share apomorphies with Asilisaurus and thus represent silesaurids with a carnivorous dentition****. Our comprehensive phylogenetic analysis demonstrates that silesaurids***** are monophyletic and fall just outside Dinosauria (which is diagnosed by very few character states). The most derived silesaurids (e.g., Silesaurus, Sacisaurus) share features with both ornithischian and theropod dinosaurs, illustrating the high degree of convergence among dinosauriforms in the Triassic. In addition, the results of our cladistic analysis imply at least three independent transformations towards quadrupedality and herbivory. The frequency of dietary (carnivorous vs. herbivorous) and locomotor (quadrupedal vs. bipedal) shifts within Dinosauriformes appears unique within Amniota.”

*a diphyletic clade with pterosaurs in the lepidosauromorpha and dinos in the archosauromorpha.
**actually a poposaur, just outside of the Archosauria/Dinosauria in the large reptile tree.
***no mystery, Agnosphitys is a theropod sister to Marasuchus. Lewisuchus is a basal archosaur, a little closer to dinos than to crocs in the large reptile tree.
****Nesbitt et al are confused by convergence, which is resolved by phylogenetic analysis.
*****or do they mean poposaurs? Silesaurus and Sacisaurus are poposaurs. Actually Gracilisuchus and the Crocodylomorpha ‘fall’ (= nest) just outside the Dinosauria with poposaurs the outgroup according to the large reptile tree.

References
Nesbitt SJ et al. 2015. The anatomy of Asilisaurus kongwe (Dinosauriformes: silesauridae) and closely related taxa provides new insights into the anatomical and chronological evolution of dinosauriforms. Journal of Vertebrate Paleontology abstracts.

Adding Compsognathus longipes to the large reptile tree

Updated 1.17.2016 with a revised figures based on higher resolution data. On this date, Compsognathus was nested with Struthiomimus.

Figure 1. Reconstruction of Compsognathus with revised face, fingers and foot.

Figure 1. Compsognathus in lateral view. Small inset at reduced scale shows complete tail. Note the variety of neural spines along the spinal column

For many decades
Compsognathus longipes
(Wagner 1859, Ostrom 1978, Late Jurassic, quarry unknown, 150 mya, 3 ft (89 cm) long, BSP AS I 563 ) was considered the smallest known dinosaur and something close to its contemporary, the first bird, Archaeopteryx, also from the Solnhofen formation.

Here with very few other theropods to nest with, Compsognathus nests in the large reptile tree (604 taxa) with the very much larger Tyrannosaurus. (updated January 17, 2016) This clade includes the feathered theropod, Sinocallioptery, at its base. Many have wondered if Compsognathus had feathers or not. With modern birds lacking body scales one wonders if subsequent scales are all derived from primordial feathers as the scales on the feet of modern birds appear to be. That would be the opposite of traditional thinking, discussed earlier here.

The number of fingers
in Compsognathus has been an issue largely resolved by Gishlick and Gauthier 2007. Here (Fgi. 2) I found four fingers, all from the left hand, except m1.2 from the right.

Figure 3. New reconstruction of Compsognathus fingers from grayscale data in Gischlick and Gauthier 2007, which has two extra phalanges not found in the online color image.

Figure 2. Revised 1.17.2016. Note the addition of m2.1 and m2.2 on the grayscale data. All phalanges except one of the unguals are from the left hand. Here not two, not three, but four fingers are recovered. 

The entire skeleton was traced
and these elements were used in a similar fashion to create the Compsognathus reconstruction (Fig. 1). Inside this specimen is the ingested lizard Bavarisaurus.

References
Gishlick AD and Gauthier JA 2007. On the manual morphology of Compsognathus longipes and its bearing on the diagnosis of the Compsognathidae. Zoological Journal of the Linnean Society 149: 569–581. 
Ostrom JH 1978.
 The osteology of Compsognathus longipes. Zitteliana 4: 73–118.
Wagner JA 1859. Über einige im lithographischen Schiefer neu aufgefundene Schildkröten und Saurier. Gelehrte Anzeigen der Bayerischen Akademie der Wissenschaften 49: 553.
wiki/Compsognathus

 

 

SVP 16 – Cimoliopterus [crested pterosaur], now from Texas!

Myers 2015,
famous for his basal Pteranodon/Germanodactylus, describes a new ornithocheirid with a premaxillary crest in an abstract (see below) and in a JVP paper that just came out.

From the abstract
“Cretaceous strata of Texas have yielded an unexpectedly rich collection of pterosaurs that differ substantially from the prolific, Pteranodon-dominated assemblages of the Western Interior. Two new pterosaur specimens from the Upper Cretaceous Eagle Ford Group in the Dallas/􀂱Fort Worth area enhance our understanding of the fragmentary record of Texas pterosaurs. One specimen (SMU 76892), discovered in the upper Cenomanian portion of the Britton Formation, consists of the rostral section of an upper jaw that bears a prominent, thin premaxillary crest beginning just above the fourth pair of alveoli. The preserved portion of the jaw contains alveoli for 26 teeth, and there is a subtle lateral expansion at the anterior end of the jaw. This partial rostrum is identified as a new species of Cimoliopterus, a monotypic genus previously known only from Cenomanian deposits in England, and represents a significant geographic range extension for this genus. The second new specimen from the Eagle Ford Group (SMU 76942) is a partial upper jaw of Aetodactylus halli, heretofore known only from mandibular material. The jaw fragment was collected at the type locality of A. halli in the middle Cenomanian Tarrant Formation. The dorsoventrally compressed specimen represents part of the anterior half of the jaw, although the exact position within the palate cannot be determined with certainty. The ventral surface bears a thin palatal ridge, and the dorsal surface preserves no evidence of a premaxillary crest. Patterns in tooth spacing along the upper jaw are similar to those observed in the holotype mandible of A. halli (SMU 76383). A phylogenetic analysis of Pterosauria that incorporates the new Cimoliopterus species and new codings for the upper jaw of Aetodactylus indicates that both taxa are basal pteranodontoids. Aetodactylus and Cimoliopterus appear closely related, but are clearly distinct from each other. Identification of Cimoliopterus in North Texas provides further evidence of paleobiogeographic links between the Cretaceous pterosaur faunas of North America and Europe. Discovery of the upper jaw of Aetodactylus confirms that this pterosaur lacked both premaxillary and mandibular crests.”

The Cimoliopterus rostrum
confirms earlier observations of anterior extensions of the nasal and jugal found in other ornithocheirds that extend to the secondary and tertiary nares, both vestigial pores (Fig. 1) recovered by tracing without access to the original specimen.

Destruction
of part of the right side of the rostrum reveals little strips of bone that evidently extended just below the former surface that extend from the nasal and jugal. The fused vomers are the long reported “palatal ridge” described in several ornithocheirids.

Figure 1. Click to enlarge. The rostrum of the North American Cimoliopterus. Every 2 seconds the scenes change. Pink = nasal. Lavender = jugal. Yellow = premaxilla. Green = maxilla. Violet = vomers. DGS enabled the identification of these bones overlooked by first hand observation.

Figure 1. Click to enlarge. The rostrum of the North American Cimoliopterus. Every 2 seconds the scenes change. Pink = nasal. Lavender = jugal. Yellow = premaxilla. Green = maxilla. Violet = vomers. DGS enabled the identification of these bones overlooked by first hand observation.

These extra nares originate also as pores with Scaphognathus (Fig. 2), an ancestral taxon.

Figure 1. Click to enlarge. The reduction of the naris (red arrow), the appearance of the secondary naris, and the appearance of the secondary ascending process of the maxilla in a line of scaphognathids, all to the same scale.

Figure 2. Click to enlarge. The reduction of the naris (red arrow), the appearance of the secondary naris, and the appearance of the secondary ascending process of the maxilla in a line of scaphognathids, all to the same scale. GMu 10157 is basal to the much larger ornithocheirids as recovered in the large pterosaur tree and ignored in the cladograms of other workers.

Note that Myers also traced the nasals and vomers
in Cimoliopterus (Fig. 1) without realizing what they were. That’s where DGS and a good pterosaur cladogram become valuable.

References
Myers TS 2015. New pterosaur material from the Late Cretaceous of North Texas.
Myers TS 2015. First North American occurrence of the toothed pteranodontoid pterosaur Cimoliopterus, Journal of Vertebrate Paleontology, DOI: 10.1080/02724634.2015.1014904

SVP 15 – Erpetonyx. Still a milleropsid, not a bolosaurid

Modesto et al. 2015a
discuss Erpetonyx, which is still a sister to Milleropsis in the large reptile tree (not a bolosaur parareptile as originally described, Modesto et al. 2015b). And Milleropsis is not a millerosaur.

Note that Millerosauria is included as an ingroup taxon
Unfortunately Millerosaurus ornatus (Broom 1948, Watson 1957) Late Permian (Changhsingian, 30 cm est length) is based on a chimaera of over a dozen skeletons with many common elements distinct from one another. Millerosaurus has been removed from the large reptile tree. Milleropsis is a protodiapsid not related to Milleretta. Milleretta is likely the genera used for the original suprageneric taxon in the cladogram shown in Figure 1,

If this is too confusing, let me know and I’ll walk you through it.

This abstract
has already been published as a paper (Modesto et al. 2015b).

Figure 1. Click to enlarge. When you put the hands and feet and skull back together, you find Erpetonyx nests close to Eudibamus, but closer to Milleropsis.

Figure 1. Click to enlarge. When you put the hands and feet and skull back together, you find Erpetonyx nests close to Eudibamus, but closer to Milleropsis.

From the abstract
Erpetonyx arsenaultorum was recently erected for a single, nearly complete, and mostly articulated skeleton of a bolosaurian* parareptile** collected from the Gzhelian-age Egmont Bay Formation of Prince Edward Island. Erpetonyx arsenaultorum is autapomorphic in possessing 29 presacral vertebrae and a relatively small radiale, fifth distal carpal, and pisiform. The skull is characterized by the presence of plicidentine and by the absence of caniniform maxillary teeth. The neural arches closely resemble those of the Early Permian lanthanosuchian Delorhynchus cifelli in their broadly tongue-shaped zygapophyses, in which the lateral edges of the anterior zygapophyses pass posteriorly onto the lateral surface of the arch and form a conspicuous shelves, emphasized by an anteroventral pocket. The right carpus is well ossified. The preserved unguals are also well ossified, with a prominent flexor tubercle, a suboval proximal portion, and a stout, slightly ventrally curved tip. Together with the observation that the unguals are longer than their respective proximal phalanges, ungual morphology suggests adaptation to a fossorial or semi-fossorial lifestyle. Erpetonyx arsenaultorum is the oldest known amniote with digging adaptations, appearing ca. 3􀂱4 million years after the demise of th coal-swamp forests.

*Not a bolosaurian, but a milleropsid.
**Parareptile is an outmoded name based on traditional cladograms that have been falsified by the large reptile tree.

We looked at Erpetonyx earlier here in this blog.

References
Gow CE. 1972. The osteology and relationships of the Millerettidae (Reptilia: Cotylosauria). Journal of Zoology, London 167:219-264.
Modesto SP, Reisz RR, Macdougall MJ and Scott DM 2015a. Skeletal anatomy of the oldest known parareptile from the Upper Carboniferous of Priince Edward Island, Canada. Journal of Vertebrate Paleontology abstacts
Modesto SP, Scott DM, MacDougall MJ, Sues H-D, Evans DC, Reisz RR 2015b. The oldest parareptile and the early diversification of reptiles. Proceedings of the Royal Society B 282: 20141912. http://dx.doi.org/10.1098/rspb.2014.1912
Watson DMS 1957. On Millerosaurus and the Early History of the Sauropsida. Philosophical Transactions of the Royal Society of London Series B 240(673):325-400.

A Tanystropheus from China

Figure 1. Click to enlarge GIF animation. The Tanystropheus specimen from China, GMPUKU-P-1527: 1)  in situ; 2) as traced by Rieppel et al. 2010; and 3) with colorized DGS tracings. Note: Rieppel et al. overlooked the interclavicle, and mistook the interclavicle + scapula for an over sized coracoid. Rieppel's clavicle is a dorsal rib. The so-called heterotopic bones are merely larger, unfused chevrons.

Figure 1. Click to enlarge GIF animation. The Tanystropheus specimen from China, GMPKU-P-1527: 1)  in situ; 2) as traced by Rieppel et al. 2010; and 3) with colorized DGS tracings. Note: Rieppel et al. overlooked the interclavicle, and mistook the interclavicle + scapula for an over sized coracoid. Rieppel’s clavicle is a dorsal rib. Clavicles here are in red. The so-called heterotopic bones are merely larger, unfused chevrons. What are those blue triangles in the dorsal area? The distal opposite rib tips apparently. Let me know if there’s a better answer.

Rieppel et al. (2010)
described a new, large (trunk length 93.5 cm), Late Triassic Tanystropheus (GMPKU-P-1527, Fig. 1), the first from China. All priors had come from the Alps of Europe. This one lacks a skull plus three cervicals and the distal tail. Based on the short rib of what used to be considered dorsal 1, the authors report it is now cervical 13. That appears to be the case across all large and small specimens. The last cervical is the size and shape of a dorsal, but the associated rib is not a dorsal-type rib. Every prior worker missed that one. Rieppel et al bucked traditions and relabeled the old first dorsal. Good job guys!

New interpretations
of the clavicle, interclavicle, scapula and one coracoid are introduced above, a little different than the original interpretations.

How similar to the European specimens?
the authors report: “The new Peking University specimen (GMPKU-P-1527) is remarkably similar to the larger specimens of Tanystropheus longobardicus housed in the paleontological collections of Zurich University. If there is any difference, then it is in the extent of chevron bones in the tail and the lack of the slight swellings and associated flexure described here for the first time along the length of the longest cervical ribs in PIMUZ T 2189 (Exemplar Q, Fig. 3.

At first glance (in situ) the Chinese specimen is indeed similar to the European specimens.

Figure 2. The Tanystropheus from China partly reconstructed using DGS methods. No foreshortening of the gastralia and limbs are present here. The preserved ilium is not a broad plate here, as in European specimens. The terminal tail vertebrae is circular suggesting the rest of the tail was preserved in another layer.

Figure 2. The Tanystropheus from China partly reconstructed using DGS methods. No foreshortening of the gastralia and limbs are present here. The preserved ilium is not a broad plate here, as in European specimens. That could be a taphonomic artifact or reality. The terminal tail vertebrae is circular suggesting the rest of the tail was preserved in another layer.

But not the same species
The China specimen is apparently more distinct from the European specimens than Rieppel et al. indicate., but then… they did not create any reconstructions. Sometimes comparisons are best seen directly with accurate reconstructions (Fig. 3). We’ve already seen that two very distinct skulls appear on the European specimens and both were distinct from the original Wild 1973 model based on a chimaera of specimens.

The China specimen
has larger girdles, larger vertebrae, more robust ribs and shorter toes (Fig. 4), among the more readily visible distinctions. The dorsal ilium appears to be much narrower, but it is obscured by an overlying femur. The interclavicle has a large, broad anterior process, making it cruciform, not T-shaped.

Figure 3. The large Tanystropheus specimens to scale. On the right the new China specimen has large girdles, larger vertebrae, more robust ribs and shorter toes, among the more visible distinctions. Click to enlarge. Above right is the new M. Witton reconstruction with erect limbs, an overly large scapula, an overly large ilium, lacking an interclavicle and other minor issues. 

Figure 3. The large Tanystropheus specimens to scale. On the right the new China specimen has large girdles, larger vertebrae, more robust ribs and shorter toes, among the more visible distinctions. Click to enlarge. Above right is the new M. Witton reconstruction with erect limbs, an overly large scapula, an overly large ilium, lacks an interclavicle and other minor issues. Otherwise it is very good looking.

Check those hands and feet!
Earlier we were able to separate Rhamphorhynchus specimens into clades using pedal traits alone. Here we’ll compare a European Tanystropheus with the Chinese one (Fig. 4). If they don’t match, they are not conspecific.

Figure 4. Above the Chinese Tanystropheus. Below a large European Tanystropheus. They are not conspecific.

Figure 4. Above the Chinese Tanystropheus. Below a large European Tanystropheus. They are not conspecific.This was overlooked by Rieppel et al. 2010. Reconstructions have value.

Mark Witton started this 
A recent blog post by Mark Witton introduced a new reconstruction of Tanystropheus (Fig. 3 top right). He wondered if the neck was too heavy to use on land while reminding readers that my work was “produced with techniques of questionable reliability”. Keep that phrase in mind.

  1. Witton labeled Tanystropheus as a protorosaur. Actually it’s a tritosaur lepidosaur as indicated by a four-year-old cladogram that now tests 602 taxa.
  2. On tradition alone, Witton includes drepanosaurs, Sharovipteryx, Tanytrachelos, Langobardisaurus and Dinocephalosaurus in the protorosaurs. All are indeed related to Tanystropheus, and are likewise tritosaur lepidosaurs.
  3. Witton reports, “I decided to try my hand at producing a new skeletal reconstruction based on the large, near complete Tanystropheus skeleton described in detail by Rieppel et al. (2010): PIMUZ T 2189.” Unfortunately the skeleton described by Rieppel et al. and traced by Witton is GMPKU-P-1527, the Chinese specimen (Figs. 1, 2). The 2189 specimen is European (Fig. 3), represented by a skull and neck only (Fig. 3). Witton’s technique was to trace a published photo. He makes no mention of visiting the specimen first hand. If you’ll remember, the technique of questionable reliability” mentioned above is my sin of tracing fossil from photographs. So Witton is doing exactly what I do. Is Witton aware of this possible hypocrisy?
  4. Witton reports, “I reconstructed missing parts using smaller Tanystropheus specimens (from Nosotti 2007) and Wild’s widely-used ‘adult’ skull reconstruction.” So he created a chimaera. That is almost never a good idea going as far back as to putting a Camarasaurus skull on a Brontosaurus body. It’s easy, but it’s wrong. “Widely used” doesn’t mean it is correct. As mentioned above, that skull is a chimaera, too.
  5. Witton’s reconstruction admits to cheating on the true sprawling pose for his geometrical analysis. That’s fine. I laid limb elements out straight,too, but not in a walking pose. That would be confusing to someone who didn’t know what the illustration was being used for.
  6. Adding to the confusion, Witton draws a medially directed femoral head which is not present in this lepidosaur.
  7. Witton’s Tanystropheus scapula is too large (see above). The pelvis is a chimaera and a shade too large. Otherwise it’s a beautiful reconstruction and part of that beauty comes from free handing certain elements. I won’t say Witton’s work as a whole is produced with techniques of questionable reliability.l like tracing, free handing and creating chimaeras… but I will say that free handing and creating chimaeras is not reliable. Tracing from photographs can be very reliable! Ad hominem blackwashing (see Witton’s comment) is never appropriate for colleagues. Everyone should realize that inappropriate habits, like creating chimaeras, never last forever. And everybody makes honest mistakes (like overlooking the interclavicle). Finally holding a grudge or never granting forgiveness for past errors is never good… Right guys? Okay. Let’s move on…
  8. Witton reports, “Our problem here is that finding a long-necked terrestrial carnivore to compare with Tanystropheus is challenging.” I realize that Witton is wondering if a large Tanystropheus could walk on land, but gut contents are marine organisms and fossils are found in marine sediments. So… what’s the point? And why were these factoids ignored? The big Tanystropheus doesn’t seem to be a terrestrial animal.
  9. Ironically, Witton compares the long neck of Tanystropheus to his favorite pterosaurs, the azhdarchids. And that’s a fair comparison. They are distantly related in the large reptile tree, but for Witton’s purposes shapes are more important.
  10. Witton’s technique for determining mass at every segment of a lateral view misses the greater mass in the wider dorsal and caudal areas visible only in dorsal view. There’s a fat rump there, but you can’t see it in lateral view.
  11. Little known pertinent fact: I once made a full scale model in wood of Tanystropheus and sold it to the AMNH. I had to add lead weights aft of the hind limbs to make it not tip over. All segments being equal, it was front heavy as a 3-D model, not just on paper.  In vivo the torso and tail would have been more dense, even with large lungs. And the air-filled cervical series and trachea would have been less dense.
  12. Check this out for a possible marine lifestyle that seems to fit the facts for Tanystropheus.

References
Rieppel O, Jiang D-Y,  Fraser NC, Hao W-C, Motani R, Sun Y-L & Sun ZY 2010. Tanystropheus cf. T. longobardicus from the early Late Triassic of Guizhou Province, southwestern China. Journal of Vertebrate Paleontology 30(4):1082-1089.
Wild R 1973. Die Triasfauna der Tessiner Kalkalpen XXIII. Tanystropheus longobardicus(Bassani) (Neue Ergebnisse). – Schweizerische Paläontologische Abhandlungen 95: 1-162 plus plates.
Witton blog post: here

SVP 14 – a new Diandongosaurus

Liu et al 2015
redescribe the basal sauropterygian/placodont Diandongosaurus with a new specimen.

Figure 2. Diandongosaurus exposed in ventral view, skull in dorsal view. Note the small size. At 72 dpi this image is 6/10 the original size.The last common ancestor of Diandongosaurus and Pachypleurosaurus was a sister to Anarosaurus at the base of the Sauropterygia.

Figure 1. Diandongosaurus exposed in ventral view, skull in dorsal view. Note the small size. At 72 dpi this image is 6/10 the original size.The last common ancestor of Diandongosaurus and Pachypleurosaurus was a sister to Anarosaurus at the base of the Sauropterygia.

From the abstract
“The eosauropterygian Diandongosaurus acutidentatus, first reported from the Upper Member of the Guanling Formation (Anisian, Middle Triassic) at Luoping, Yunnan Province, southwestern China, is a small pachypleurosaur-like form characterized by the following features: enlarged and procumbent teeth in the premaxilla and anterior portion of the dentary, fang-like maxillary teeth, clavicle with a distinct anterolateral process, 19 cervical and 19 dorsal vertebrae, and ungual phalanges of the pes extremely expanded. Except for the distinct anterolateral process of the clavicle, this taxon is very similar to Dinopachysaurus dingi, which is from the same locality and the same stratigraphic level, and of similar body size. Herein we describe a new, nearly complete skeleton of Diandongosaurus, which provides new information on the ventral side of the skull, the pectoral girdle and hind limbs. The posterior process of the interclavicle is absent, and the
coracoid foramen is present in the new specimen, features that cannot be seen in the holotype. The anterolateral process of the clavicle is more slender than that of the holotype. Furthermore, the phalangeal formula of the pes of the new specimen is 2-3-4-5-3, whereas the preserved phalangeal formula of the holotype is 2-3-4-6-4, and thus has a higher count for the fourth and fifth digits. The new specimen also shows that there are no vomerine teeth, the ‘anterior interpterygoid vacuity’ is absent, but a natural oval shaped ‘posterior interpterygoid vacuity’ is present, different from the referred specimen,
NMNS-000933-F03498. The results of our phylogenetic analysis also suggest Diandongosaurus is an eosauropterygian, closely related to the Eusauropterygia, and grouped together with Majiashanosaurus to form the sister-group of the Eusauropterygia.”

Different than the Liu et al. study,
the large reptile tree nests Diandongosaurus at the base of the Placodontia, derived from Anarosaurus, as described here. Shifting this specimen to the node suggested by Liu et al. adds 33 steps to the shortest tree.

Figure 2. Diandongosaurus family tree, nesting at the base of the Placodontia, yet still retaining its basal sauropterygian looks.

Figure 2. Diandongosaurus subset of the large reptile family tree, nesting at the base of the Placodontia, yet still retaining its basal sauropterygian looks.

References
Liu et al. 2015. A new specimen of Diandongosaurus acutidentatus (Sauropterygia) from the Middle Triassic of Yunnan, China. Journal of Vertebrate Paleontology abstracts.