Looking for the sternal complex in a tiny pterosaur

All pterosaurs have a sternal complex
(sternum + interclavicle + wrap-around clavicles), even the flightless ones. This tiny specimen (Fig. 1) probably had a sternal complex, but where is it? As everyone knows, it should be between the elbows, but it’s not there.

Figure 1. Tiny pterosaur mistakenly named Pterodactylus? pulchellus. I cannot find the sternal complex here. It should be between the elbows. That tiny red triangle under the mid-humerus is the ventral coracoid.

Figure 1. Tiny pterosaur mistakenly named Pterodactylus? pulchellus. I cannot find the sternal complex here. It should be between the elbows. That tiny red triangle under the mid-humerus is the ventral coracoid.

Pterodactylus? pulchellus BM NHM 42735 is the same size as the closely related Gmu-10157 specimen, but has a longer rostrum. The BM NHM specimen is one node closer to the common ancestor of cycnorhamphids + ornithocheirids in the large pterosaur tree (LPT, 242 taxa). The sternal complex appears to be missing or displaced in this otherwise undisturbed tiny specimen. Soft tissue confirms the narrow chord wing membrane and dual uropatagia. Pedal digit 5 remained long.

Figure 2. The GMU 10157 specimen and the P? pulchellus BM NHM 42735 specimens to scale and full size.

Figure 2. The GMU 10157 specimen and the P? pulchellus BM NHM 42735 specimens to scale and full size.

These tiny adults,
(Fig. 2) derived from slightly larger scaphognathids (Fig. 3) are transitional taxa undergoing phylogenetic miniaturization at the genesis of Cycnorhamphidae + Ornithocheiridae. They have not been given novel generic names by established workers because the traditionalists among them consider these to be babies/juveniles of larger, undiscovered taxa. Thus they have remained relatively ignored, despite their pristine preservation and sometimes gravid condition.

Figure 3. Click to enlarge. Taxa in the lineage of Cycnorhamphidae + Ornithocheiridae in the LPT.

Figure 3. Click to enlarge. Taxa in the lineage of Cycnorhamphidae + Ornithocheiridae in the LPT.

The key to finding the missing sternal complex
on this relatively undisturbed specimen is to look to the only area of the skeleton that is slightly disturbed (Fig. 4). The gastralia basket is expanded beyond its natural contours in the BM NHM specimen and that’s where I find (thanks to DGS) a displaced sternal complex, separated from the coracoids and jammed back into the stomach, surrounded by gastralia, almost hidden from view.

Figure 4. Here the sternal complex of the BM NHM 42735 specimen is colored indigo.

Figure 4. Here the sternal complex of the BM NHM 42735 specimen is colored indigo.

Not sure how that happened during taphonomy,
but there you go: mystery solved!

Shenzhoupterus skull in situ with sternum in blue.

Figure 5. Shenzhoupterus skull in situ with sternum in blue.

Earlier a sternal complex was found beneath the skull
of Shenzhoupterus (Figs. 5, 6) using the same techniques, contra traditional reconstructions (Lü, Unwin, Xu and Zhang 2008; see skull diagram insert matching no other pterosaur skull morphology in Fig. 6). Despite its derived state, the newly reconstructed Shenzhoupterus skull (Fig. 6 standing skeleton) bears all the hallmarks of sister taxa.

Shenzhoupterus reconstructed alongside original interpretation of skull.

Figure 6. Shenzhoupterus reconstructed alongside original interpretation of skull.

While we’re on this subject,
Shenzhoupterus does not nest with azhdarchoids, as originally hypothesized, but with tiny Nemicolopterus, between dsungaripterids and tapejarids in the LPT—and neither of these clades are related to azhdarchids in the LPT, contra traditional thinking that excludes tiny taxa and large swathes of congeneric taxa.


References
both of the tiny taxa listed above await description and publication other than in:
Wellnhofer P 1970. Die Pterodactyloidea (Pterosauria) der Oberjura-Plattenkalke Süddeutschlands. Abhandlungen der Bayerischen Akademie der Wissenschaften, N.F., Munich 141: 1-133.

Shenzhoupterus was first described in:
Lü J, Unwin DM, Xu L and Zhang X 2008. A new azhdarchoid pterosaur from the Lower Cretaceous of China and its implications for pterosaur phylogeny and evolution. Naturwissenschaften 95 (9): online (preprint). doi:10.1007/s00114-008-0397-5. PMID 18509616.

Scaphognathus soft tissue in RTI, PTM and UV

Jäger et al. 2019
present a new look at the holotype of Scaphognathus and pay homage to its first describer, Goldfuß 1831. Soft tissue is hard to see in this specimen, whether in white light, UV light or using RTI/PTM (Reflectance Transformation Imaging (see below references) and Polynomial Texture Mapping) methods.

Figure 1. Scaphognathus SIPB Goldfuß 1304a, no. 109 in the Wellnhofer 1970 catalog. Two plates drawn by Goldfuß. Color tracing here. Note the foot and prepubis were overlooked by all prior workers.

Figure 1. Scaphognathus SIPB Goldfuß 1304a, no. 109 in the Wellnhofer 1975 catalog. Plate and counter plate drawn by Goldfuß. UV images from Jäger et al. 2019. Color tracing here. Note the foot and prepubis were overlooked by all prior workers. Note the Goldfuss drawing includes ‘fluff’ over the dorsal vertebrae confirmed by Jäger et al.

Previously I reported
plumes (pycnofibers) emanating from the dorsal region of several pterosaurs, like Jeholopterus (Fig. 5), homologous with those found in Longisquama and Cosessaurus. No one supported these observations in pterosaurs until now (Fig. 2). In fact, this is one of the reasons why workers think I am ‘seeing things’ that others cannot see. So this is confirmation not only of my own observations, but also, as noted in the text, those of Goldfuiß 1833, which have been ignored until this paper.

Figure 4. Jäger et al identify this area as 'dorsal pycnofibers.'

Figure 2. Jäger et al identify this area as ‘dorsal pycnofibers.’I have attempted to trace in color the shapes I see here, Not all the plumes are identified here.

It would be worthwhile
to review Darren Naish’s blogpost that ridiculed my observations of dorsal plumes, now confirmed by several pterosaur specimens.

Figure 2. Reconstruction of Jeholopterus. This owl-like bloodslurper was covered with super soft pycnofibers to make it a silent flyer.

Figure 3. Reconstruction of Jeholopterus. This owl-like bloodslurper was covered with super soft pycnofibers to make it a silent flyer.

Phylogenetic bracketing indicates
that soft tissue fibers/plumes emanating from the dorsal region are present in a wide range of basal pterosaurs, up to the Early Cretaceous. Such plumes likely reduced the speed that these pterosaurs could fly, and reduced the noise they made while flying, as in similarly fluffy owls.

Figure 1. Click to enlarge. The origin and evolution of Longisquama's "feathers" - actually just an elaboration of the same dorsal frill found in Sphenodon, Iguana and Basiliscus. Here the origin can be found in the basal tritosaur squamate, Huehuecuetzpalli and becomes more elaborate in Cosesaurus and Longisquama.

Figure 4. The origin and evolution of Longisquama’s “feathers” – actually just an elaboration of the same dorsal frill found in Sphenodon, Iguana and Basiliscus. Here the origin can be found in the basal tritosaur squamate, Huehuecuetzpalli and becomes more elaborate in Cosesaurus and Longisquama.

We looked at this Scaphognathus specimen earlier
here when the tiny foot was first discovered. That foot was overlooked by the Jäger et al. team, but I thank them for confirming, without citation, the presence of dorsal plumes in this pterosaur.

Figure 1. Bergamodactylus compared to Cosesaurus. Hypothetical hatchling also shown.

Figure 5 Bergamodactylus compared to Cosesaurus. Hypothetical hatchling also shown. Dorsal frills are visible in the fossil of this pterosaur, too.


References
Goldfuss GA 1830. Pterodactylus crassirostris. Isis von Oken, Jena pp. 552–553.
Jäger KRK, Tischlinger H, Oleschinski G and Sander PM 2019. Goldfuß was right: Soft part preservation in the Late Jurassic pterosaur Scaphognathus crassirostris revealed by reflectance transformation imaging (RTI) and UV light and the auspicious beginnings of paleo-art. Palaeontologia Electronica: 21.3.4T
https://doi.org/10.26879/713
Wellnhofer P 1975a. Teil I. Die Rhamphorhynchoidea (Pterosauria) der Oberjura-Plattenkalke Süddeutschlands. Allgemeine Skelettmorphologie. Paleontographica A 148: 1-33.1975b. Teil II. Systematische Beschreibung. Paleontographica A 148: 132-186. 1975c. Teil III. Paläokolgie und Stammesgeschichte. Palaeontographica 149: 1-30.

wiki/Scaphognathus
https://palaeo-electronica.org/-scaphognathus-in-rti-and-uv


Notes about RTI:
Bogart J 2013a. Reflectance Transformation Imaging: Guide to Highlight Image Capture. Cultural Heritage Imaging, San Francisco. http://culturalheritageimaging.org/What_We_Offer/Downloads/RTI_Hlt_Capture_Guide_v2_0.pdf
Bogart J 2013b. Reflectance Transformation Imaging: Guide to RTIViewer. Cultural Heritage Imaging, San Francisco. http://culturalheritageimaging.org/What_We_Offer/Downloads/rtiviewer/RTIViewer_Guide_v1_1.pdf

wiki/Scaphognathus

New Jianchangnathus?

Figure 1. The new Jianchangnathus(?) compared to the holotype. The new one has a quite broad skull and an antorbital fenestra that extends below the orbit, unlike the holotype.

Figure 1. The new Jianchangnathus(?) compared to the holotype. The new one has a quite broad cranium and an antorbital fenestra that extends below the orbit, unlike the holotype, but like Scaphognathus. Other differences are just as obvious. 

A new pterosaur PMOL-AP00028 (Zhou 2014) has been attributed to Jianchangnathus IVPP V 16866, Cheng et al. 2012), but that does not seem warranted in this case. The comparable traits are not close matches. Zhou did not make graphic comparisons of the holotype and referred specimen. Rather the two specimens were combined then compared to other rhamph-grade taxa as illustrated by Wellnhofer (1991 and earlier). I think a step or two was skipped in Zhou 2014.

Based on the orbit overhanging the antorbital fenestra, the closer match might be to Scaphognathus itself, which was close to the size of the referred specimen.

References
Cheng X, Wang X-L, Jiang S-X and Kellner AWA 2012. A new scaphognathid pterosaur from western Liaoning, China. Historical Biology iFirst article available online 29 Nov 2011, 1-11. doi:10.1080/08912963.2011.635423
Zhou C-F 2014. Cranial morphology of a Scaphognathus-like pterosaur, Jianchangnathus robustus, based on a new fossil from the Tiaojishan Formation of western Liaoning, China. Journal of Vertebrate Paleontology 34(3):597-605.

wiki/Jianchangnathus

Tiny TM13104 – ancestor to cynorhamphids AND ornithocheirds AND germanodactylids AND pterodactylids

This is a key taxon, long ignored.
While Darwinopterus gathered all the headlines as the “missing link” between long-tailed primitive pterosaurs and short-tailed derived pterosaurs (ahem, total rubbish), this specimen is the real long-sought transitional taxon. And it doesn’t rely on made-up fantasies like “modular evolution.” Ironically it’s been known for 140 years, but relegated to the phylogenetically discarded pile of putative “juvenile” pterosaurs simply because of its diminutive size. As it happens, phylogenetically, size meant survival of the lineage. Without shrinking, pterosaurs might have gone extinct much earlier than they ultimately did (at the end of the Cretaceous).

Figure 1. Tiny TM13104 nests as the ancestor to both the cycnorhamphids and ornithocheirids and germanodactylids.

Figure 1. Tiny TM13104 nests as the ancestor to cycnorhamphids and ornithocheirids and germanodactylids. It’s a little scaphognathid, but distinct in its metacarpal length and tiny size, This specimen was only half the size of the smallest Scaphognathus species (see figure 2), continuing a clear size reduction trend from the twice as tall Scaphognathus holotype.

Pterodactylus? micronyx? TM 13104 (Winkler 1870, No. 34 in the Wellnhoger 1970 catalog) ~2.5 cm skull length, was considered a juvenile Pterodactylus, but it is not closely related, according to the results of the large pterosaur family tree. No. 34 was derived from a sister to the Maxberg specimen of Scaphognathus (Fig. 2) and phylogenetically preceded other tiny pterosaurs including Gmu-10157 (basal to cycnorhamphids like, BSP 1968 XV 132 and the basal ornithocheirid, Yixianopterus). Moreover, TM 13104 was also basal to the lineage of pterodactylids and germanodactylids and their kin (that encompasses all the derived short-tailed pterosaurs in this branch of the large pterosaur tree) via some of the tiniest of all pterosaurs like Ornithocephalus and No. 6 (B St 1967 I 2760 (Fig. 2).

The only derived (short-tailed, long-snouted) pterosaurs TM 13104 was NOT ancestral to were the azhdarchids and ctenochasmatids, both of which find their ancestors more directly in various species of Dorygnathus.

Evolution
Overall smaller and distinct from the Maxberg specimen of Scaphognathus (Fig. 2), the skull of No. 34 had a shorter, more pointed rostrum. The skull and mandible were more gracile with smaller teeth. The naris was smaller. This is how the naris was reduced in this line of derived pterosaurs.

The entire vertebral spine was shorter and more gracile, including the tail.

The sternal complex was anteroposteriorly shorter but retained distinct lateral processes. The metacarpus was longer, subequal to the ulna. The fingers were smaller. The proximal phalanges were longer.

The ischium was broad and its rims approach both the pubis and ilium. Metatarsal 5 and digit 5 were shorter. The metatarsals were not appressed.

Just imagine how tiny the hatchlings were
One centimeter tall hatchlings of TM 13104 might not have been volant due to their high surface-to-volume ratios. Instead they may have been restricted to humid leaf litter or risk desiccation as in modern very tiny lizards (Hedges and Thomas 2001).

TM 13104 and kin. These tiny pterosaurs nest at the bases of several clades of much larger and later pterosaurs.

Figure 2. TM 13104 and kin. These tiny pterosaurs nest at the bases of several clades of much larger and later pterosaurs. The longer snouts are beginning to become apparent on these tiny pterosaurs, but not Ornithocephalus, which does not have any known descendants. These are not juveniles. None are identical to larger putative adult pterosaurs. If anyone has access to images of the rest of SMNS 81775, let me know.

The Family Tree
See the pterosaur family tree here. Note the positions of these tiny pterosaurs at the bases of major clades of larger forms. These are the real transitional taxa. Darwinopterus, you’ll note, is an interesting footnote that ultimately did not lead to any higher clades.

The Rio Pterosaur Symposium 2013 featured this talk 
“The basal monofenestratan Darwinopterus and its implications for the origin and basal radiation of pterodactyloid pterosaurs.” by David M. Unwin and Junchang Lü. So these two are unfortunately still promoting this falsified hypothesis.

Darren Naish in Tetrapod Zoology
happily bought into the Darwinopterus transitional taxon fable and the wonders of “modular evolution,” which doesn’t happen anywhere else in the animal family tree. He wrote lavishly about it here. You’ll remember that he’s the one who warned his blog readers against ReptileEvolution.com.

Well…
At least in this instance, it’s not my words and images you have to watch out for, but his (I won’t try to tarnish all of Naish’s works as he did mine, because otherwise he does a damn good job in that blog, and I’m not out for blood). Sadly, in this case, Naish did not put on his scientist cap and test the Darwinopterus hypothesis. He merely accepted the report as a journalist would on the authority of its authors.  Among them was Dr. David Unwin, who has been behind some of the biggest bungles in pterosaur studies including, most famously, the Sordes deep-chord wing membrane myth along with the myth of pterosaur egg burial and others.

So long as pterosaur workers continue to refuse to include tiny pterosaurs in their analyses they’ll have about as much success in resolving their family trees as they have had in the past. I’m here to suggest more inclusive alternatives that work.

References
Hedges SB and Thomas R 2001. At the Lower Size Limit in Amniote Vertebrates: A New Diminutive Lizard from the West Indies. Caribbean Journal of Science 37:168–173.
Wellnhofer P 1970. Die Pterodactyloidea (Pterosauria) der Oberjura-Plattenkalke Süddeutschlands. Abhandlungen der Bayerischen Akademie der Wissenschaften, N.F., Munich 141: 1-133.
Winkler TC 1870. Description d’un nouvel exemplaire de Pterodactylus micronyx du musee Teyler. Archives des Musee Teyler 3: 84-99.