Ephemeral skull in Solnhofen sediments

The holotype
of Pterodactylus miicronyx, aka the Pester specimen  (Meyer 1856) ELTE V 256, is a small, apparently headless. but otherwise complete and articulated pterosaur specimen (Fig. 1).

Figure 1. Tracing of the Pester specimen. The smear at the rostral end of the descending cervical series appears to be an elongate skull with larger sclerotic rings. This is where one should excavate to discover a buried skull.

The Pester specimen 
was originally considered another species of Pterodactylus, but in the large pterosaur tree it nests basal to the cycnorhamphids. Unfortunately there are only a few traits that can be gleaned from the new data (skull length vs. torso length, etc.). Earlier I thought pedal digit 4 was shorter than shown here, but closer examination reveals that the ungual was preserved on top of the p4.3. The other pes shows that digits 2-4 were aligned distally.

Figure 2. The holotype of Pterodactylus micronys, aka the Pester specimen, may preserve ephemeral hints of its apparently missing skull.

References
von Meyer CEH 1856.  Zur Fauna der Vorwelt. Saurier aus dem Kupferschiefer der Zechstein-Formation. Frankfurt-am-Main. vi + 28 pp., 9 pls.
Osi A, Prondvai E and Géczy B 2010. The history of Late Jurassic pterosaurs housed in Hungarian collections and the revision of the holotype of Pterodactylus micronyx Meyer 1856 (a ‘Pester Exemplar’). In: Moody RTJ., Buffetaut E, Naish D and Martill DM (eds) Dinosaurs and Other Extinct Saurians: A Historical Perspective. Geological Society, London, Special Publications, 343, 277–286. DOI: 10.1144/SP343.17 0305-8719/10/
Wellnhofer P 1970. Die Pterodactyloidea (Pterosauria) der Oberjura-Plattenkalke Süddeutschlands. Abhandlungen der Bayerischen Akademie der Wissenschaften, N.F., Munich 141: 1-133.

wiki/Pterodactylus

 

Hamipterus – a closer look at gender and ontogeny

Wang et al. 2014 introduced us
two years ago to a new collection of pterosaur parts from a monotypic population that was swept together and disarticulated by a flood event. As you may recall, five well-preserved three-dimensional eggs were recovered from the Early Cretaceous site in northwestern China. Sexual dimorphism was identified for the first time in pterosaurs with two different types of crests appeared on a variety of sizes of skulls (Figs. 1, 2). They named the new specimen, Hamipterus tianshanensis and the holotype was described as, “One complete presumed female skull (IVPP V18931.1)”.

Figure 1. The female holotype and male paratype from the Hamipterus population assemblage fossil. The second tracing enlarges the male skull to the same length as the female skull. The color bar overprints indicate parts that differ in length from one skull to the other and a second overlay traces tooth position shifts from one to another. The vestigial naris appears between the nasal and jugal beneath the crest. Direct comparisons like this help reveal subtle differences that otherwise might be overlooked.

Such a sweeping together of so many individuals
provides an unprecedented insight into several areas of pterosaur biology, but the data need to be rigorously examined so as not to jump to any conclusions.

Visible differences in the two skulls

1. Crest shape
2. Tooth placement
3. Ventral maxilla shape
4. Lateral extent of the premaxilla
5. Depth of the skull anterior to the antorbital fenestra
6. Concave vs. straight rostral margin (sans crest)
7. Length of the upper temporal fenestra
8. Placement of the vestigial naris
9. Suborbital depth of the jugal

Gender
Wang et al. report, “About 40 male and female individuals in total were recovered, but the actual number associated might be in the hundreds. All of the discovered skulls have crests, which exhibit two different morphologies in size, shape, and robustness. Although morphological variation could be interpreted as individual variation, these marked differences suggest that the skulls belong to different genders. Hamipterus tianshanensis contradicts this hypothesis, because this species indicates that morphology of the crest, rather than its presence.”

Consider what we know about gender differences in birds and lizards,
It may be too soon to generalize over gender differences in pterosaurs. While each gender could have its own signature crest, size, etc., likewise each species likely had its own signature identity/crest/color/call, plumage, etc. At present, no other pterosaurs show verifiable gender differences. That’s why the Wang et al. paper was so important. Gender differences described for both Darwinopterus and Pteranodon were shown to be phylogenetic. Darwinopterus does present a mother with an aborted egg, but the father of the egg has not been identified. Hamipterus offers the best opportunity, so far, to bring some data to the table on this topic. And what Wang et al. indicate may indeed be true.

However, not enough care, IMHO, was administered to the non-crest differences in the skull material was made. Considering just the arrangement of teeth in the jaws (Fig. 1), is it possible that two very closely related species lived near one another? Or did individual variation cover a wider gamut than we now think is reasonable? Remember, among all the Pteranodon specimens now known (to me, at least), no two are identical. The same can be said for the Rhamphorhynchus and Pterodactylus specimens. And when you give Hamipterus a rigorous study, several subtle variations arise. Some of these arise from crushing. Others do not. With given data, one wonders if these could be two Hamipterus variations could be very closely related and.or very closely nesting sister taxa. OR… with present data, gender differences could extend beyond just the crest.

It is also possible
that male pterosaurs were rare rogues and this was a colony of females only with lots of individual variation. Do male lizards help raise their young? Do females? No. But pterosaurs might have been different. Wang et al. report on 40 individuals, but not on the male/female ratio or how many skulls are known. There were three in the holotype block. I’m guessing their specimen count was based on 40 skulls.

Figure 2. Finishing up the large skull with the large crest with two smaller candidates reveals that the slightly better fit is with the female skull.

Ontogeny
Wang et al. report, “Ontogenetic variation is reflected mainly in the [lateral] expansion of the [spoon-shaped in dorsal view] rostrum.” Wang et al. reinforce what we know from other pterosaurs that they developed isometrically. Note the similarity between the crests of the smaller and larger ‘male’ specimens (Fig. 2). We’ve seen that before with Tupuxuara juveniles (Fig. 3).

Figure 3. Presumed ontogenetic skull and crest development in Tupuxuara. Note the eyes are small and the rostrum is long in juveniles. Only the crest expands and only posteriorly. Are are these two different sized but otherwise related species? With that longer rostrum, the smaller specimen may be distinct phylogenetically. No small crest Tupuxuara specimens are known.

Sedimentology
Wang et al. report, “Tempestite interlayers where nearly all of the pterosaur fossils are found suggest that large storms caused the mass mortality, event deposits, and lagersta¨ tte of the pterosaur population.”

Phylogenetically
Wang et al. discussed what Hamipterus is not. Their analysis nested it at the base of the Ornithocheiridae with complete lack of resolution. The large pterosaur tree nests Hamipterus with complete resolution between Boreopterus and Zhenyuanopterus.

Eggs
Wang et al. report, “A total of five eggs were recovered from the same site. The outer surface is smooth and exhibits no ‘papilla-like ornamentation,’ as was reported of the first pterosaur egg found in China.” Well that was a giant anurognathid egg, for which finding the parent will be big news. I’d be more interested to see comparisons to the second pterosaur egg found in China, the JZMP egg/embryo, which belonged to a rather closely related [to Hamipterus] ornithocheirid.

Wang et al. report, “Due to the close proximity to Hamipterus tianshanensis, the sole taxon found at the site, all of the eggs are referred to this species. Compared with other reptiles, the Hamipterus eggs show more similarities with some squamates,” I love it when every bit of data supports the theory that pterosaurs are lepidosaurs.

Wang et al. report, a 60µm calcareous eggshell followed by a thin 11µm inner membrane. They compared that to a snake egg of similar dimensions with a 60µm calcareous membrane followed by a much thicker 200µm inner membrane. Then they speculate wildly with this imaginative statement, “It is possible that Hamipterus also had a much thicker membrane, which was not completely preserved. We propose that such an eggshell structure, similar to that of some snakes, may well explain the preservation of the outer surface observed in pterosaur eggs.” IMHO, paleontologists go too far when they try to explain away data, rather than dealing with it directly. Elgin, Hone and Frey (2011) did this with their infamous wing membranes which they speculated suffered from imagined “shrinkage” in order to protect their verifiably false deep chord wing membrane hypothesis.

Wang et al report, “The [egg] size differences might also reflect different stages of development, since mass and dimensions differ between recently laid eggs and more developed ones.” There’s another possibility. Since we know that half-sized female pterosaurs were of breeding age (Chinsamy et al. 2008) they could have laid smaller eggs, producing smaller young, one source of rapid phylogenetic miniaturization.

Wang et al. report, “The combination of many pterosaurs and eggs indicates the presence of a nesting site nearby and suggests that this species developed gregarious behavior. Hamipterus likely made its nesting grounds on the shores of freshwater lakes or rivers and buried its eggs in sand along the shore, preventing them from being desiccated.” There’s another possibility. Since pterosaurs are lepidosaurs, they could have retained the eggs in utero until the young were ready to hatch. That also prevents them from desiccation. Since the flood tore the bones apart, any in utero eggs would have been torn away from the mother as well.

Notable by its absence
is any report of embryo bones inside the eggshells. I presume none were found or they would have been reported. That’s a shame, too, because eggs are nice little containers for complete skeletons, something lacking at the Hamipterus site. Some of the eggs appear to be evacuated, as if they were empty when buried. Or maybe all the juices were squeezed out during the rush and tumble of flood waters. If there was an embryo inside one of the Hamipterus eggs, and that is likely as the egg shell is applied just before egg laying, the embryo might have looked something like this (Fig. 3) based on the other pterosaur embryos inside their own two-dimensional eggs and the appearance of more complete sister taxa. During taphonomy the embryo inside would have been shaken AND stirred (but note some skulls are preserved complete without destruction!). The three dimensional egg contents would not accumulate on the randomly chosen longitudinal saw cut.

Figure 3. Wang et al. sliced one of the eggs lengthwise (yellow). if there is an embryo inside, it might have looked something like this. Since the egg has not been crushed to two dimensions, all the bones would not be now located in the plane of the slice, which was a random cut, not recognizing any embryo inside. Other embryos are typically in this pose.

Pterosaur hatchlings
of this size were precocial, able to fly shortly after hatching and large enough not to suffer from desiccation caused by so much surface area compared to volume.

References
Chinsamy A, Codorniú L and Chiappe LM 2008. Developmental growth patterns of the filter-feeder pterosaur, Pterodaustro guinazui. Biology Letters, 4: 282-285.
Elgin RA, Hone DWE, and Frey E. 2011.The extent of the pterosaur flight membrane. Acta Palaeontologica Polonica 56 (1), 2011: 99-111 doi:10.4202/app.2009.0145 online pdf
Wang X et al.*, 2014. Sexually Dimorphic Tridimensionally Preserved Pterosaurs and Their Eggs from China, Current Biology. http://dx.doi.org/10.1016/j.cub.2014.04.054

Four new Rhamphorhynchus specimens added

Over the weekend
I added four new Rhamphorhynchus specimens to the large pterosaur tree (subset Fig. 1). Once again, each is distinct from one another and no two match in all traits…

Figure 1. Rhamphorhynchus cladogram with four new taxa.

…except
the one-third-size juvenile, commonly called “The Vienna specimen” NHMW 1998z0077/0001, which nests with the adult largest Rhamphorhynchus of all, BMNH 37002, n82 in the Wellnhofer 1975 catalog.

Fig. 2. Rhamphorhynchus specimens that have been bitten and fossilized with Aspidorhynchus, a Solnhofen fish of 60cm length.

The four new specimens
include two specimens caught in the jaws of Late Jurassic fish (Fig. 2), the Imhof specimen and WDC CSG 255. Also included are BRI010, again from the Imhof collection and TMP 2008.41.0001, a sister to the dark wing specimen. The latter three bridge the gap between the n81 and n82 rare giants and the smaller more typical specimens, like the dark wing specimen, JME SOS 4784. The Imhof specimen nests basal to the giants.

Are all Rhamphorhynchus specimens congeneric? Or conspecific?
No. Many look similar, but on closer examination, or phylogenetic analysis, the differences are manifold, contra Bennett 1995.

1. Some adults are tiny, others are mid-sized, and a few are relative giants
2. Some have a short rostrum, but most do not.
3. The finger and toe patterns vary greatly. The free finger sizes vary, too.
4. Sternal complex shapes vary greatly.
5. Some have a robust cervical series. Others do not.

Some things do not change between specimens

1. The wing membrane has a shallow chord at the elbow, as in all pterosaurs.
2. The nares and antorbital fenestra are both small
3. The humerus is relatively short and the torso long such that when tucked posteriorly the elbow is still several vertebrae away from the anterior ilium.
4. The teeth lean anteriorly
5. The metatarsals spread and pedal digit 5 is relatively short.

Figure 3. Prior to today’s additions, these were the taxa included in analysis. Bennett 1975 determined that all these Rhamphorhynchus specimens were conspecific and that all differences could be attributed to ontogeny, otherwise known as growth to maturity and old age. Thus only the two largest specimens were adults. O’Sullivan and Martill took the brave step of erecting a new species. Click to enlarge with new taxa added. 

Many of these things don’t become apparent
until you can see the whole lot reconstructed at one glance, or in phylogenetic analysis where you really do pay attention to details that lump and split clades and nodes.

References
Bennett SC 1995. A statistical study of Rhamphorhynchus from the Solnhofen Limestone of Germany: Year-classes of a single large species. Journal of Paleontology 69:569-580.
Smith-Woodward A 1902. On two skulls of the Ornithosaurian Rhamphorhynchus. Annals and Magazine of Natural History, London, (7) 9:1-5.
Wellnhofer P 1975a-c. Teil I. Die Rhamphorhynchoidea (Pterosauria) der Oberjura-Plattenkalke Süddeutschlands. Allgemeine Skelettmorphologie. Paleontographica A 148: 1-33. Teil II. Systematische Beschreibung. Paleontographica A 148: 132-186. Teil III. Paläokolgie und Stammesgeschichte. Palaeontographica 149:1-30.

wiki/Rhamphorhynchus

Testing Matrices

I’m sure I’m behind the times. 
And I’m asking for a little help here.

Evidently it is common practice
not to put characters or their states into published matrices. I don’t know why, but now I’ve seen it twice. Published data apparently comes in two files, a nexus file and an Excel file.

This is at odds
with my practice… to have a complete nexus file, with characters, states and taxa ready to be used, tested, changed, enlarged, etc.

I have both MacClade and Mesquite to work with. 
I don’t know how to mass load all the characters and their states from an Excel file into the  Mesquite program that already includes the taxa and scores. The instructions have not, so far, enlightened me on this, I’m sure, minor problem. I could cut and paste one at a time, but I have a feeling this labor is not common practice.

If anyone has a clue as to 
how this is done, please contact me here. I will post that someone has done so here when someone has done so in order to avoid multiple responses.

The first flightless birds

Yesterday we looked at several early birds (Fig. 1). Earlier we considered the phylogenetic nesting of Balaur (Fig. 2; Csiki Z et al. 2010), which some workers (Cau et al. 2015) considered an early flightless bird.

Figure 7. Bird cladogram with the latest additions. Here the referred specimen of Yanornis nests with enantiornithes while Archaeovolans nests within the Scansoriopterygidae, not with Yanornis.

When determining
the first flightless birds, one must first decide which taxon represents the first or basal bird. In the large reptile tree (subset Fig. 1) the last common ancestor of Enantiornithes and Euornithes is Archaeopteryx siemensi, represented by the Berlin and the Thermopolis specimens. Thus they represent, in this cladogram, the first or basal birds. Both the Enantiornithes and Euornithes produced specimens with a locked down coracoid and expanded sternum, anchors for powerful flight muscles attached to long feathered forelimbs.

Thus the purported first flightless bird,
Balaur, nests outside the bird clade (Fig. 1) established by the large reptile tree.

Figure 1. Balaur compared to various dromaeosaurids and to Sapeornis, both to scale and enlarged for detail. Cau, Brougham and Naish wondered if Balaur was the first neoflightless bird, a sort of dodo of the Cretaceous.

Instead
the Scansoriopterygidae produced the first taxa in the Eurornithes with more of a dinosaur/theropod look, with Mei (Early Cretaceous) having the smallest forelimbs relative to the rest of the body in that clade. No doubt it was flightless — and with shorter coracoids and a tiny sternum, reduced its flapping. By contrast, its current sister, Archaeovolans (Fig. 3), retained a robust pectoral girdle and long forelimbs.

Figure 2. Sister taxa at the base of the scansoriopterygidae include Jeholornis, Mei and Archaeovolans, here shown to scale.

As everyone knows,
flightless birds have arisen several times since the Early Cretaceous with Hesperornis and Struthio as examples in the large reptile tree. In evolution everything is gradual and often enough, reversible. And behavior is best determined at the extremes of morphology. More generalized taxa probably had more generalized behavior.

In Dinosaurs of the Air
author Greg Paul Paul “argues provocatively for the idea that the ancestor-descendant relationship between the dinosaurs and birds can on occasion be reversed, and that many dinosaurs were secondarily flightless descendants of creatures we would regard as birds.” According to the large reptile tree, dromaeosaurids and basal troodontids were not birds. But birds are derived troodontids. And troodontids arise from basal dromaeosaurids.

Along these same lines Kavanau 2010 reported
“Varricchio et al. propose that troodontids and oviraptorids were pre-avian and that paternal egg care preceded the origin of birds. On the contrary, unmentioned by them is that abundant paleontological evidence has led several workers to conclude that troodontids and oviraptorids were secondary flightless birds. This evidence ranges from bird-like bodies and bone designs, adapted for climbing, perching, gliding, and ultimately flight, to relatively large, highly developed brains, poor sense of smell, and their feeding habits.” Not so, according to the large reptile tree. But, to their point, bird-like theropods have arisen about 8 times by convergence, as we looked at earlier here.

References
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? PeerJ. 3: E1032. DOI: dx.doi.org/10.7717/peerj.1032
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.
Kavanau JL 2010. Secondarily flightless birds or Cretaceous non-avian theropods? Med Hypotheses 74(2):275-6.
Paul G 2002. Dinosaurs of the Air: The Evolution and Loss of Flight in Dinosaurs and Birds. Johns Hopkins University Press, Baltimore, 472 pp.

wiki/Balaur_bondoc

newslink on secondarily flightless bird Epidexoptryx.

A fresh look back at the ‘Archaeoraptor’ scandal

Updated March 3, 2018 with the updating of certain elements of these crushed fossils orient them toward Yanornis.

Earlier we looked at the ‘Archaeoraptor’ scandal under the heading “chimaeras and fakes.” Here we’ll start with a short history, then consider new discoveries and cladograms.

Figure 1. ‘Archaeoraptor’ in UV light from a page spread in National Geographic. When this was published it was big news. Now such specimens have become more commonplace.

In July 1997
an unidentified Chinese farmer uncovered a rare (at that time) Early Cretaceous dinosaur with feathers (Fig. 1). During collection the plate on which the dinosaur was preserved cracked apart into a dozen or so pieces (Fig. 2). These were cemented together, but lacked feet and a tail. Nearby, from the same locality, a ‘suitable’ set of feet and tail were cemented to the plate to create a complete presentation. A year later the fossil was sold to an unidentified dealer and smuggled into the United States.

In February 1999
the feathered fossil was on display at the Tucson Gem and Mineral Show where it was purchased by The Dinosaur Museum in Blanding, Utah, USA. Artists, Stephen and Sylvia Czerkas ran the museum. A board member provided the $80,000 purchase price. Paleontologists Phil Currie and Xu Xing agreed to study the fossil.

In March 1999
Currie noticed the left and right feet (pedes) were identical: part and counterpart. ‘Improvements’ like this happen more often than one would wish with fossils that are purchased from dealers rather than extricated from a site by museum led expeditions.

Figure 2. Archaeoraptor from Rowe et al. 2000. Colored areas indicate different sources for matrix and fossils there in.

In July 1999
CT scans were made of the fossil (Rowe et al. 2001, Fig. 2). These indicated that the bottom fragments were not part of the upper fossil, but that news did not get out until later.

In August 1999
authors Czerkas, Currie, Rowe and Xu submitted a paper to Nature on the fossil, noting that the legs and tail were composited into the slab. Nature rejected the paper. Shortly thereafter Science rejected the paper, with referees noting the illegal purchase and doctoring of the fossil.

In September 1999
Currie’s preparator concluded the fossil was a composite of 3 to 5 specimens. Again that news did not get out until later.

In October 1999
National Geographic Magazine held a press conference at which they unveiled the fossil  informally named, “Archaeoraptor,” and announced it as a transitional fossil between birds and non-bird theropod dinosaurs (which it is not, see below). Plans were also announced to return the illegally exported fossil to China.

The November 1999 issue of Nat Geo
featured the fossil in an article about dinosaur feathers (Sloan 1999, Fig. 1). Bird expert Storrs Olson criticized the pre-naming of any fossil in a popular publication without proper peer review in an academic publication. Nobody was able to ‘stop the presses’ at Nat Geo.

In December 1999 Xu Xing
sent emails to Sloan and others announcing he had found the counterpart for the tail of ‘Archaeoraptor’, but it belonged to another genus, a microraptor. Perhaps a bit to harshly, Xu Xing labeled the Nat Geo specimen a ‘fake.’

In February 2000 Nat Geo issued a press release
stating an investigation had begun and indicating the fossil may be a chimaera or a composite, something museums create. or at least used to create, on a regular basis.

In March 2000 Nat Geo published 
the forum letter from paleontologists Xu Xing suggesting that the tail did not match the rest of the body. The word ‘fake’ was replaced with ‘composite’ by the editors. And that seems  appropriate.

In April 2000 Stephen Czerkas
admitted his mistake. Others involved also expressed regret.

In October 2000 Nat Geo published 
the results of their investigation (Simmons 2000), concluding that the fossil was a composite and that most of the pertinent parties had made some mistakes.

In March 2001 Nature published
a short paper by Rowe et al. (2001) who reported on the evidence from the CT scans. They concluded that the top part was a single specimen. A second part provided the left femur, a third both tibiae, a fourth both feet and a fifth separate specimen provided the tail.

Now, here’s where it gets interesting…

In August 2002
Czerkas and Xu (2002) published an anonymously reviewed description of the fossil, renaming it Archaeovolans (Fig. 3), but it was in a self-published book, not an academic journal.

Figure 3. Photo of Archaeoraptor from Czerkas and Xu 2002 along with the original line art tracing and a new color tracing. Click to enlarge.

In November 2002
Zhou et al. (2002) reported the majority of the fossil belonged to the established genus Yanornis (Zhou and Zhang 2001, Fig. 4) an euornithine bird nesting basal to Ichthyornis and Hesperornis in the large reptile tree (subset in Fig. 8). Wikipedia likewise reports that Yanornis is an ornithuromorph, the clade that includes all living birds. Similarly, Zhou and Zhang considered Yanornis a member of the Ornithurae.

Figure 4. Yanornis martini holotype (IVPP V12558, Zhou and Zhang 2001) as originally traced and reconstructed by moving those traced lines back to in vivo positions. This is a euornithine bird with several traits retained by living birds not shared with the STM9-52 specimen (Fig. 6).

I traced
the IVPP V12444 specimen of Archaeoraptor/ Archaeovolans/ Yanornis (Fig. 3) and created a reconstruction (Fig. 5). I did the same with the STM9-52 specimen assigned (by Zheng et al. 2014) to Yanornis (Fig. 6). The holotype of Yanornis was restored to an in vivo configuration from published tracings in Zhou and Zhang 2001 (Fig. 4). Data from all three were added to the large reptile tree (subset in Fig. 7) for phylogenetic analysis.

Figure 5. Archaeovolans with legs imagined, nests with Yanornis.

All three taxa lump together with Yanornis
So Archaeovolans is a junior synonym for Yanornis because it is closely related.

Perhaps even more interesting
Archaeovolans is phylogenetically bracketed by taxa that have a long bony tail. So the farmer was right — but that didn’t make it right to just pull another one off the shelf.

Figure 6. Specimen STM9-52 assigned to Yanornis by Zheng et al. 2014.

The added foot and counter foot
are the right size, and phylogenetically close to Yanornis, too (Fig. 8). The foot and counter foot provided to Archaeovolans have traits found in ornithurine birds, like Yanornis. So, the added parts are counterfeit, based on the matrix, but correct based on the bones.

Figure 8. The foot and counter foot provided to Archaeovolans do not match those of sister taxa but more closely match those of ornithurine birds, like Yanornis. Archaeovolans probably followed the pattern set by its sisters and would have had a relatively shorter digit 2 and digit 4.

 

 

References
Czerkas SA and Xu X 2002. A new toothed bird from China. Pp. 43-60 in Czerkas SJ. ed. 2002. Feathered Dinosaurs and the Origin of Flight. The Dinosaur Museum Journal 1. Blanding, Utah, USA.
Simons LM 2000. Archaeoraptor Fossil Trail. National Geographic 198 (4): 128–132.
Sloan CP 1999. Feathers for T. rex?. National Geographic 196 (5): 98–107.
Zheng X, O’Connor JK, Huchzermeyer F, Wang X, Wang Y, Zhang X, et al. 2014. New Specimens of Yanornis Indicate a Piscivorous Diet and Modern Alimentary Canal. PLoS ONE 9(4): e95036. doi:10.1371/journal.pone.0095036
Zhou Z, Clarke JA and Zhang F-C 2002. Archaeoraptor’s better half. Nature Vol. 420: 285.
Zhou Z. and Zhang F. 2001. Two new ornithurine birds from the Early Cretaceous of western Liaoning, China. Chinese Science Bulletin, 46 (15), 1258-1264.

 

Another flightless pterosaur: the anurognathid PIN 2585/4

This is one of those fossils
I had heard about a long time ago, but never saw until today. I read once, (not sure where, but perhaps in Bakhurina 1988?), that there was a second specimen of Batrachognathus on the holotype Sordes plate. Problem was, I could never see another pterosaur on the Sordes plate. That left a big question mark over my head. Now I know that the widely circulated images of Sordes deletes or separates the second pterosaur from Sordes on the original plate (Fig. 1).

Today,
I finally saw both pterosaurs on the same plate on an online image (Fig. 1). Apparently this is the only instance of two distinct genera of pterosaurs found on the same plate. Not sure how this image snuck out of Russia.

Figure 1. The holotype of Sordes, PIN 2585-3. includes a small anurognathid, PIN 2585-4. 3 frames, 5 seconds each.

Not sure why this little anurognathid
has not gotten more attention. By the way, It does not nest with Batrachognathus in the large pterosaur tree. Perhaps it did back in 1988 when only a few anurognathids were known. But now we have many more anurognathids to compare it to. Sordes (Sharov 1971) has been known for over 45 years. That’s a long time to overlook/ignore/ a find like this. Apparently this is the specimen that was said to have bristles around the jaws (Bakhurina 1988) because it does and the holotype  (Rjabinin 1948) does not.

Figure 2. Tracing of the anurognathid PIN 2585-4 with soft tissue in gray. This, obviously, is a low-rez image. Even so, nearly all of the major bones preserved on the plate could be traced. The skull, in particular, matches sister taxa at reptileevolution.com, in contrast to the Bennett 2007 interpretation.

The PIN 2585-4 specimen has tiny wings
and large legs. Based on comparisons with other anurognathids, this specimen appears to be yet another flightless pterosaur. An unrelated flightless pre-azhdarchid, SOS 2428, was reported on here several years ago.

Figure 3. Click to enlarge. The PIN 2585/4 anurognathid reconstructed in two views. Note the small wings and large legs on this flightless pterosaur, the second one now known. Finger four retains 5 elements including a tiny ungual.

An obligate biped
with strong hind limbs and extremely long tibiae, the PIN 2585/4 specimen would have been a better bipedal runner and, based on comparisons to volant pterosaurs, probably could not fly with such gracile, small wings. It would also have a tough time walking as a quadruped, so was obligated to walk as a biped, like long-legged Bergamodactylus and Sharovipteryx. We have individual pedal traces for anurognathid pterosaurs. No trackways yet. And no forelimb marks either.

So, the anurognathid could not fly,
but PIN 2585/4 was still a strong flapper. There is nothing reduced about its sternal complex and pectoral girdle. We can image it running and flapping for added thrust, something like Cosesaurus did before the advent of wings in the Middle Triassic (Fig. 4).

Figure 4. Cosesaurus running and flapping – slow.

The forelimbs are gracile
in PIN 2585/4 with shorter elements. unlike its more typical closest known sister, CAGS IG 02-81, which was clearly volant and had shorter hind limbs.  The fore claws of virtually all flying pterosaurs were capable of touching the ground (Fig. 5).

Figure 6. The CAGS IG 02-81 specimen attributed to Jeholopterus. Currently it nests  the sister to the flightless anurognathid. Note the proportional differences.

All of the skeletal elements
in PIN 2585/4 resemble those in sister taxa, except the proportions of the fore and hind limbs. Note that the orbits are in the back of the skull, as in CAGS IG 02-81 and ALL other pterosaurs — in contrast to the misinterpretation offered by Bennett (2007) for the flathead anurognathid that has been widely and erroneously accepted.

Figure 7. The flightless anurognathid, PIN 2585/4, is the same size as other typical anurognathids, but its long legs make it taller. Click to enlarge.

Here’s how it went down today:
When I first saw the image on Google, I wondered what that fossil was… and then I saw that familiar tail and foot of Sordes… and then I realized this is the long sought double pterosaur fossil! I wasn’t expecting the specimen to be flightless, but it soon dawned that the proportions indicated we had a second flightless pterosaur here. So, a very exciting day all around. If this has been published elsewhere, please let me know. I am not aware of it.

I would have published on this find, except…

1. It’s not my fossil.
2. I haven’t seen or studied the specimen first hand.
3. And even if I had, as I’ve done on several specimens before,  past experience tells me that today’s pterosaur referees don’t want me publishing any more. Apparently they want to save the discoveries for themselves.
4. Apologies if someone else is working on this specimen and/or is awaiting publication. I am not aware of anyone doing this.

The PIN 2885-4 specimen has been sitting around for 45 years.
They had their chance. This blog has made a habit of finding discoveries in overlooked and ignored specimens. And once again I demonstrate that you don’t have to see the specimen or have a PhD to make a contribution. Recognition is something else altogether.

References
Bakhurina NN 1988. [On the first rhamphorhynchoid from Asia: Batrachognathus volans Riabinin 1948, from Tatal, western Mongolia]. Abstract of paper in Bulletin of the Moscow Society for the Study of Natural History, Geological Section 59(3): 130 [In Russian].
Rjabinin AN 1948. Remarks on a Flying Reptile from the Jurassic of Kara-Tau. Akademia Nauk, Paleontological Institute, Trudy 15(1): 86-93.
Sharov AG 1971. New flying reptiles from the Mesozoic of Kazakhstan and Kirghizia. – Transactions of the Paleontological Institute, Akademia Nauk, USSR, Moscow, 130: 104–113 [in Russian].

wiki/Sharovipteryx

wiki/Batrachognathus

 

A closer look at the Pterorhynchus wing tip

Pterorhynchus wellnhoferi (Czerkas and Ji 2002) Callovian, Middle Jurassic ~165mya, was the first wukongopterid/darwinopterid to be described. Originally it was famous for its soft rostral crest and later for its chin fuzz.

It also has a pretty nice wing tip ungual (Fig. 1) on its broken wing tip. According to most pterosaur experts, that ungual is not supposed to be there.

Figure 1. Several views of the Pterorhynchus wingtip. The ungual (manual4.5) has been colored magenta. Manual 4.4 (green) is broken.

And I noticed something odd
in the lower abdomen. I can’t make out what it is, I’ll let you guess. It could be food. It could be a developing embryo and eggshell. It could be detritus.

Figure 2. Pterorhynchus torso under UV light. There is an unexpected ellipse in the lower abdomen. Only the fan of the perforated prepubis appears here, on top of the ischium + pubis. 3 frames, each 5 seconds. Click to enlarge. 

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.
Lü J, Unwin DM, Jin X, Liu Y and Ji Q 2009. Evidence for modular evolution in a long-tailed pterosaur with a pterodactyloid skull. Proceedings of the Royal Society London B (DOI 10.1098/rspb.2009.1603.)
Lü J, Xu L, Chang H and Zhang X 2011b. A new darwinopterid pterosaur from the Middle Jurassic of Western Liaoning, northeastern China and its ecological implicaitions. Acta Geologica Sinica 85: 507-514.
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.

wiki/Darwinopterus
wiki/Pterorhynchus
Czerkas/Pterorhynchus

Hesperornis walking GIF

Figure 1. Hesperornis compared to a king penguin, Atenodytes. The patella is blue. Hesperornis has larger feet and a longer tibia. Since penguins swim with their forelimbs, they have large pectoral muscle anchors. That is not the case with Hesperornis. Click to enlarge. Marsh 1872 thought Hesperornis could stand upright. I do too. That makes only two of us.

Hesperornis regalis
(Figs. 1,2, Late Cretaceous, Campanian, Marsh 1872, 1.8m long) was a toothed, flightless marine bird with vestigial wings and asymmetrical feet. Although not related to living loons, Hesperornis is often compared to loons, which have no teeth and retain the ability to fly. Both swim with powerful hind limbs. Hesperornis can also be compared to another flightless bird clade, the penguins, with the proviso that penguins swim with powerful forelimbs and their skeletons (Fig. 1) reflect this.

Figure 2. Click to enlarge. Hesperornis walking GIF movie. In this hypothetical scenario Hesperornis walks bipedally. Like penguins and ducks, Hesperornis does not flex its toes while walking. Nor does it take very big steps.

Wikipedia reports,
“In terms of limb length, shape of the hip bones, and position of the hip socket, Hesperornis is particularly similar to the common loon (Gavia immer), probably exhibiting a very similar manner of locomotion on land and in water. Like loons, Hesperornis were probably excellent foot-propelled divers, but ungainly on land. Like loons, the legs were probably encased inside the body wall up to the ankle, causing the feet to jut out to the sides near the tail. This would have prevented them from bringing the legs underneath the body to stand, or under the center of gravity to walk (Reynaud 2006). Instead, they likely moved on land by pushing themselves along on their bellies, like modern [loons].”

It was not difficult
to animate a bipedal Hesperornis (Fig. 2). It appears fully capable of doing so penguin-style. But the comparison to loons is indeed compelling.

Loons are ungainly
on the beach. See a YouTube video here. Yes, it does look wounded, unable to walk like a normal bird. It would probably fly if it was in a hurry. Hesperornis shares many traits by convergence with loons, but, if anything, loon hind limbs are more extreme in their proportions, including a proportionately larger projecting patella (Figs. 3, 4).

Just added after publication: The axis of the acetabulum is further foreword in Hesperornis, at the 51% mark on the torso (measured from the posterior pelvis) versus the 43% mark on the loon. That big butt makes Hesperornis less top heavy.

Figure 3. Loon skeleton with femur (yellow) and tibia/patella (green) highlighted. In this mount the center of gravity is in front of the toes, which makes this an untenable mount, unless the loon is floating on water.

The loon femur is a little shorter and the patella is a little larger
(Figs. 3, 4) than on Hesperornis (Figs. 1,2). It’s up to our imaginations whether or not that would enable a more penguin-like locomotion in Hesperornis. Note that penguins do have a patella (knee bone) but it does not extend above the femur as it does in Hesperornis and loons.

Figure 4. Loon femur and tibia/patella. These proportions are more extreme than those found in Hesperornis. Note the right angle femoral head, as in most birds, but then look at the skeleton (Fig. 3) in which the femora are held laterally, unlike more birds and dinosaurs.

Nat Geo
and Andy Farke report on a bone growth and possible migration study (Wilson and Chin 2014) of Hesperornis here.

According to Marsh:
“The clavicles are separate, but meet on the median line, as in some very young existing birds.The coracoids are short, and much expanded where they join the sternum. The latter has no distinct manubrium, and is entirely without a keel. The wings were represented by the humerus only, which is long and slender, and without any trace of articulation at its distal end.”  

Various authors
believe the humerus would have been hidden beneath the skin and appressed to the ribs. As is typical for Kansas fossils, Hesperornis specimens are typically crushed flat. In the large reptile tree Hesperornis nests with its volant contemporary, Ichthyornis.

References
Marsh OC 1872. Discovery of a remarkable fossil bird. American Journal of Science, Series 3, 3(13): 56-57.
Marsh OC 1872. Preliminary description of Hesperornis regalis, with notices of four other new species of Cretaceous birds. American Journal of Science 3(17):360-365.
Marsh, OC 1880. Odontornithes, a Monograph on the Extinct Toothed Birds of North America. Government Printing Office, Washington DC.
Reynaud F 2006. Hind limb and pelvis proportions of Hesperornis regalis: A comparison with extant diving birds. Journal of Vertebrate Paleontology 26 (3): 115A. doi:10.1080/02724634.2006.10010069.
Wilson L. and Chin K 2014. Comparative osteohistology of Hesperornis with reference to pygoscelid penguins: the effects of climate and behaviour on avian bone microstructure. Royal Society Open Science. 1: 140245. doi: 10.1098/rsos.140245

OceansofKansas/Hesperornis

wiki/Hesperornis

Surviving the Permian-Triassic boundary

For those of you
who typically ignore the letters to the editor, this is one exchange that you might find interesting.

Earlier Bill Erickson asked me 
“So, why, in your opinion, did diapsid reptiles suddenly — and I do mean suddenly — become so dominant beginning in or about Carnian time, and remain dominant thereafter throughout the Mesozoic, after millions of years of synapsid dominance beforehand in the mid-to-late Paleozoic and early Triassic?”

I answered
-Why- questions are very tough in Science, Bill. I don’t know the answer to your question. I don’t have an opinion either.

B. Erickson replied
“David – I’d agree for the most part, but I do think Peter Ward made a good case [in his book Gorgon.] that synapsids had a less efficient respiratory system than many archosaurs, and that lower atmospheric oxygen was a major driver in the end-Permian extinction. Of course, some synapsids, especially cynodonts, were diverse in early Triassic, and that’s another story.”

To which I replied
Bill, I have heard of Ward’s hypothesis and it makes a certain sense. Let me toss this off-the-cuff idea at you.

Synapsids, to my knowledge, survived the Permian extinction event by burrowing, or perhaps there was a part of the world they found refuge in. If the former, whether in dirt or leaf litter, both niches seem to support small to tiny tetrapods. See Pachygenelus, Megazostrodon and Hadrocodium for examples. [Well, those are all bad examples as they are all Early Jurassic, but consider the small earliest Triassic cyndont, Thrinaxodon (Fig. 1).]

Figure 1. Thrinaxodon, a burrowing synapsid from the Early Triassic was similar in size and proportion to the Late Permian ancestor of all archosauriformes, Youngoides (Fig. 2). These similar basal taxa were the genesis for all later mammals, dinosaurs and birds.

On the diapsid/archosauriform side, the likely aquatic proterosuchids cross the Permo-Triassic boundary, then give rise to all the familiar archosauriformes. In the water niche larger tetrapods, like crocs, are supported. As Malcolm Gladwell documented so well [in his book Outliers], an initial minor advantage can accelerate or become emphasized over time.

So, again guessing here, the largely nocturnal denizens of the burrows and leaf litter apparently played to their environment and stayed small yielding the otherwise unoccupied largely diurnal aquatic-grading-to-terrestrial taxa the larger size as they played to their niche. Maybe the diapsids just got to the outdoors/daylight niche first.

Figure 2. Updated image of various proterosuchids and their kin. When you see them all together it is easier to appreciated the similarities and slight differences that are gradual accumulations of derived taxa. Youngoides and the earliest proterosuchids were Late Permian. Others were Early Triassic and later.

Along the same lines, the lepidosaur diapsids stayed relatively small and unobtrusive except for the Late Triassic sea-going tanystropheids and Late Cretaceous sea-going mosasaurs, perhaps following the same niche rules and regs as above. Pterosaur lepidosaurs also experienced much greater size in the Late Cretaceous.

Just a thought/opinion supported by what I can recall at the moment. Let me know your thoughts if you’d like to continue this thought journey. [END]

And then beyond that exchange…
I note that EarlyTriassic synapsid taxon list also includes the large dicynodont, Kanneymeira and a number of small therocephalians. Burrowing taxa are pre adapted to a nocturnal existence. The big dicynodont must have survived in some sort to refuge niche.

The standard story
includes the notion that dinosaurs and other archosauriform predators were snapping up every little synapsid they saw, so the survivors became invisible by becoming nocturnal and or really tiny… and that probably continued throughout the Mesozoic, with both clades improving generation after generation.

Figure 3. Basal archosauriforms from the Early Triassic,  including Euparkeria, Proterosuchus and Garjainia.

The twist brought to you by
the large reptile tree is the outgroup for the Archosauriforms, Youngoides, is a small, Thrinaxodon-sized terrestrial younginiform diapsid (Fig. 1). Perhaps an early affinity for rivers and lakes was the key to survival among proterosuchid archosauriforms when the P-Tr problems escalated. But also note that the small ancestors to dinosaurs, the euparkeriids, (Fig. 3) ALSO survived the P-Tr boundary as small terrestrial forms alongside the much larger terrestrial erythrosuchids, otherwise known as giant younginids.

Maybe we’ll never know…
but it’s interesting to put at least some of the puzzle pieces together.