Seals are diphyletic. Goodbye Pinnipedia!

This split has been suspected or imagined for quite some time…
…but never documented with fossil taxa in phylogenetic analysis until today in the large reptile tree (LRT 1040 taxa; subset Fig. 1).

Figure 1. Subset of the LRT focusing on Carnivora and the diphyletic nesting of seals, derived from separate terrestrial ancestors. Moving one seal next to the others adds 14 steps.

Figure 1. Subset of the LRT focusing on Carnivora and the diphyletic nesting of seals, derived from separate terrestrial ancestors. Moving one seal next to the others adds 14 steps.

Seals are diphyletic.
These marine Carnivora had two terrestrial origins. Phoca is an earless seal (family: Phocidae) derived from a sister to Paleaosinopa. On the other hand, Zalophus is an eared seal (family: Otariidae) derived from a sister to Hyopsodus and Miacis. Thus the clade Pinnipedia is no longer monophyletic. The last common ancestor of seals in the LRT is the extant common raccoon, Procyon.  Doubtless a similar form that lived closer to the Cretaceous was the actual last common ancestor. Both clades of seals (that’s what we’ll still call them forever) adapted to water in similar, but not identical ways (see below).

Figure 1. Phoca the phocid seal is most closely related to Palaeosinopa of all tested taxa.

Figure 1. Phoca the phocid seal is most closely related to Palaeosinopa of all tested taxa.

Molecular evidence
According to Wikipedia: “While seals were historically thought to have descended from two ancestral lines, molecular evidence supports them as a monophyleticlineage (descended from one ancestral line). Pinnipeds belong to the order Carnivora and their closest living relatives are bears and musteloids (weasels, raccoons, skunks, and red pandas), having diverged about 50 million years ago.”  Of course, if the sister taxa that split seals are extinct (fossil taxa) as they are here, then molecular studies cannot service this issue or answer this question.

Figure 3. Zalophus, an otariid seal, is most closely related to Hyoposodus among tested taxa in the LRT

Figure 3. Zalophus, an otariid seal, is most closely related to Hyopsodus among tested taxa in the LRT

Earlier hypotheses
imagined otariids descended from bears and phocids descended from mustelids (weasels). Below are some of those earlier, mostly molecular studies and their intrinsic problems.

  1. Arnason et al. 2006. Molecular study. Outgroups include bears, minks other Carnivora and no fossil taxa.
  2. Flynn et al. 2005. Molecular study of the Carnivora. Outgroups include no fossil taxa.
  3. Higdon et al. 2007. Molecular study of the Pinnipedia. Outgroups include bears and dogs and no fossil taxa.
  4. Hunt and Barnes 1994. Skull base comparisons link seals to bears, not otters and ferrets.
  5. Lento GM et al. 1995. Molecular study found pinnipeds derived from the bear/raccoon/panda radiation. Outgroups include no fossil taxa.
  6. Sato JJ, et al. 2006. Molecular study allies pinnipeds with otters and ferrets. Outgroups include no fossil taxa.

Issues: Palaeosinopa
was considered a non-Eutherian placental mammal. Here it nests within Carnivora without a priori assumptions clouding the selection of the inclusion group.

Figure 1. Palaeosinopa, complete and largely articulated. Body length about 50 cm. Tail adds 35 cm. From Rose and Koenigswald 2005.

Figure 4. Palaeosinopa, complete and largely articulated. Body length about 50 cm. Tail adds 35 cm. From Rose and Koenigswald 2005. This taxon nests with Phoca in the LRT.

Issues: Hyopsodus
was considered an odd-toed ungulate that was swift and lived in burrows. Here it nests within Carnivora without a priori assumptions clouding the selection of the inclusion group.

Figure 1. Hyopsodus as originally reconstructed (below) and as reconstructed here above in two views. This former condylarth now nests with dogs.

Figure 5. Hyopsodus as originally reconstructed (below) and as reconstructed here above in two views. This former condylarth now nests with dogs.

What about Enaliarctos?
Found in Late Oligocene strata, this earliest otariid (Fig. 6; Mitchell and Tedford 1973) nests between Zalophus and Hyopsodus in the LRT.

Figure 6. Enaliarctos nests between Zalophus and Hyopsodus in the LRT.

Figure 6. Enaliarctos nests between Zalophus and Hyopsodus in the LRT. The long bone around the knees is a baculum, or penis bone, found only in males.

What about Puijula?
Pujilia darwini (Rybczynski, Dawson and Tedford 2009; Late Oligocene 23 mya;1m in length) was originally considered an extinct species of seal based chiefly on skull and tooth traits. Here in the LRT it nests at the base of the clade that produced phocid seals, not otarid seals. It was derived from a sister to Mustela the river otter and lived in and near high Arctic lakes.

Figure 6. Pujilia was considered a basalmost pinniped, but here nests at the base on only the phocids, not the otarids.

Figure 6. Pujilia was considered a basalmost pinniped, but here nests at the base on only the phocids, not the otarids.

Differences
According to Wikipedia“Otariids use their front limbs primarily to propel themselves through the water, while phocids and walruses use their hind limbs. Otariids and walruses have hind limbs that can be pulled under the body and used as legs on land. By comparison, terrestrial locomotion by phocids is more cumbersome. Otariids have visible external ears, while phocids and walruses lack these.”

By the way,
moving one seal next to the other in the LRT adds 14 steps.

You might remember
the LRT for all of its faults (the list grows shorter every day) was able to similarly separate toothed whales (Odontoceti) from baleen whales (Mysticeti) and document they each had separate terrestrial ancestors, tenrecs and desmostylians respectively. Given the overall similarity of Otariids to Phocids, their separation in the LRT is another demonstration of the acuity and authority of large gamut phylogenetic analyses.

By the way, since this is science…
this is something anyone can do. Repeat the experiment if you have doubts, and let me know what you get. Apparently earlier workers were excluding pertinent outgroup taxa from their analyses, and this is something we’ve seen over and over again. That’s what set the stage for ReptileEvolution.com and this blog.

References
Arnason U, et al. (6 other authors) 2006. Pinniped phylogeny and a new hypothesis for their origin and dispersal. Molecular Phylogenetics and Evolution. 41 (2): 345–54.
Flynn JJ, Finarelli JA, Zehr S, Hsu J and Nedbal MA 2005. Molecular phylogeny of the Carnivora (Mammalia): Assessing the impact of increased sampling on resolving enigmatic relationships. Systematic Biology. 54 (2): 317–37.
Higdon JW, Bininda-Emonds OR, Beck RM and Ferguson SH 2007. Phylogeny and divergence of the pinnipeds (Carnivora: Mammalia) assessed using a multigene dataset. BMC Evolutionary Biology. 7: 216.
Hunt RM Jr and Barnes LG 1994. Basicranial evidence for ursid affinity of the oldest pinnipeds. Proceedings of the San Diego Society of Natural History. 29: 57–67.
Lento GM, Hickson RE, Chambers GK and Penny D 1995. Use of spectral analysis to test hypotheses on the origin of pinnipeds. Molecular Biology and Evolution. 12(1): 28–52.
Mitchell E and Tedford RH 1973. The enaliarctinae a new group of extinct aquatic carnivora and a consideration of the origin of the otariidae. Bulletin of the American Museum of Natural History 151:284 pp.
Orlov YA 1933. Semantor macrurus (ordo Pinnipedia, Fam. Semantoridae Fam. nova) aus den Neogen-Ablagerungen Westsibiriens. Trudy Paleontologicheskii Institut Akademiia Nauk SSSR 2, 249-253.
Rybczynski N, Dawson MR. and Tedford RH 2009. A semi-aquatic Arctic mammalian carnivore from the Miocene epoch and origin of Pinnipedia. Nature 458, 1021–1024.
Sato JJ, et al. (7 other authors) 2006. Evidence from nuclear DNA sequences sheds light on the phylogenetic relationships of Pinnipedia: Single origin with affinity to Musteloidea. Zoological Science. 23 (2): 125–46.

wiki/Pinniped
wiki/Enaliarctos
wiki/Phoca
wiki/Zalophus
wiki/Hyopsodus
wiki/Palaeosinopa

/tetrapod-zoology/pinnipeds-descended-from-one-ancestral-line-not-two/

Figuring out the upside-down skull of Yanoconodon

Figure 1. Yanoconodon fossil in situ. See the skull in closeup in figure 2.

Figure 1. Yanoconodon fossil in situ. See the skull in closeup in figure 2. The published tracing is distorted here to match the underlying photo.

Wikipedia reports, “Yanoconodon was a small mammal, barely 5 inches (13 centimetres) long. It had a sprawling posture, Yanoconodon was a Eutriconodont, a group composing most taxa once classified as “triconodonts” which lived during the time of the dinosaurs. These were a highly ecologically diverse group, including large sized taxa such as Repenomamus that were able to eat small dinosaurs, the arboreal Jeholodens, the aerial volaticotherines and the spined Spinolestes. Yanoconodon is inferred to be a generalized terrestrial mammal, capable of multiple forms of locomotion.

Figure 1. Yanoconodon is exposed in ventral view. Even so, if you employ DGS, even on a fuzzy photo, you can put together a reconstruction that shares several traits with Repenomamus.

Figure 2. Yanoconodon is exposed in ventral view. Even so, if you employ DGS, even on a fuzzy photo, you can put together a reconstruction that shares several traits with Repenomamus.

Mammal-like reptiles?
Wikipedia also reports, “The Yanoconodon holotype is so well preserved that scientists were able to examine tiny bones of the middle ear. These are of particular interest because of their “transitional” state: Yanoconodon has fundamentally modern middle ear bones, but these are still attached to the jaw by an ossified Meckel’s cartilage. This is a feature retained from earlier stem mammals, and illustrates the transition from a basal tetrapod jaw and ear, to a mammalian one in which the middle ear bones are fully separate from the jaw. Despite this feature Yanoconodon is a true mammal. It is thought that the feature was retained during early embryo development,[4] whereas it is lost in most other mammal groups. The intermediate anatomy of the middle ear of Yanocodon is said to be a “Rosetta Stone”[5] of mammalian middle ear evolution.”

In the large reptile tree (LRT, 1037 taxa) Yanoconodon, Repenomamus, Jeholodens and Spinolestes are not mammals, but very close to the base of the Mammalia. Both clades share Pachygenelus as last common ancestor. So that means the ‘transitional state’ mentioned above is indeed outside the Mammalia. Other paleontologists consider this list of taxa to be mammals, but here the mammal-like traits they had were developed in parallel and not quite to mammal standards.

Figure 4. Repenomamus reconstructed using DGS methods. The manus and feet are loose figments at present. Despite its predatory nature, note the reduction in canines, a clade trait.

Figure 4. Repenomamus reconstructed using DGS methods. The manus and feet are loose figments at present. Despite its predatory nature, note the reduction in canines, a clade trait.

The skull of Yanoconodon
(Fig. 2) can be largely, but not completely, reconstructed based on the visible bones. The skull is low and wide and without the typical constriction anterior to the jugals. The anterior teeth are large and spike-like while the posterior teeth are molariform. Large teeth typically require deep roots and deep bones to house those roots. The mandibles are as long as the skull. The small orbits are far forward on the skull and the temporal fenestra are correspondingly large.

Figure 2. The origin and radiation of stem mammals and crown mammals. Compare the LRT tree (above) to a recent cladogram by Close et al. 2015.

Figure 2. The origin and radiation of stem mammals and crown mammals. Compare the LRT tree (above) to a recent cladogram by Close et al. 2015.

With the new data on Yanocondon
several taxa within the LRT shifted places, but not far and still within the derived Cynodontia. Something about the Mammalia helped them survive several extinction events that the derived Tritylodontia (= Pseudomammalia) succumbed to. Pseudomammalia LOOK like mammals, but are not mammals. They continued to exist into the Early Cretaceous and some, like Repenomamus, were quite large.

References
Close RA, Friedman M, Lloyd GT and Benson RBJ 2015. Evidence for a mid-Jurassic adaptive radiation in mammals. Current Biology. 25(16): 2137–2142. 
Luo Z, Chen P, Li G, and Chen M 2007.
 A new eutriconodont mammal and evolutionary development in early mammals. Nature 446:15. online Nature

wiki/Yanoconodon

Macrocnemus skull in DGS

This started with
a fuzzy photo of a  complete fossil Macrocnemus specimen, PMR T2472 (Fig 1).

Figure 1. GIF animation of PMR T2472, a large Macrocnemus in situ and reconstructed from a fuzzy photo.

Figure 1. GIF animation of PMR T2472, a large Macrocnemus in situ and reconstructed from a fuzzy photo.

Many specimens attributed to Macrocnemus
are known, each one a little different phylogenetically. Reports of a ‘juvenile’ Macrocnemus refer to the phylogenetically basalmost and smallest of the known specimens, the one closest to its outgroup taxon, the tritosaur lepidosaur, Huehuecuetzpalli.

It’s good to remind yourself
before reading the reference titles, that Macrocnemus and kin are not protorosaurs (= prolacertiforms), nor are they archosauriforms. Even I made the same mistake (Peters 2000b) in my more naive days before the LRT recovered Macrocnemus and kin as tritosaur lepidosaurs in Peters 2007.

From this rather ordinary taxon arises 
such diverse and exotic taxa as Dinocephalosaurus, Sharovipteryx, a variety of Tanystropheus, several Langobardisaurus, Longisquama and pterosaurs. Peters 2007 reported, “The basal lizard, Huehuecuetzpalli is the most primitive taxon in this newly revealed third squamate clade between Iguania and Scleroglossa. Two branches arise from it. Jesairosaurus is basal to the Drepanosauridae. Three distinct specimens of Macrocnemus give rise to the Tanystropheidae,the Langobardisaurinae and to the Fenestrasauria respectively.” Jesairosaurus and Drepanosauridae are now basal lepidosauriformes.

References
Li C, Zhao L-J and Wang L-T 2007A new species of Macrocnemus (Reptilia: Protorosauria) from the Middle Triassic of southwestern China and its palaeogeographical implication. Science in China D, Earth Sciences 50(11)1601-1605.
Li C, Wu X-C, Zhao L-J, Nesbitt SJ, Stocker MR, Wang L-T 2016. A new armored archosauriform (Diapsida: Archosauromorpha) from the marine Middle Triassic of China, with implications for the diverse life styles of archosauriforms prior to the diversification of Archosauria. The Science of Nature 103: 95. doi:10.1007/s00114-016-1418-4
Nopcsa F 1931. Macrocnemus nicht Macrochemus. Centralblatt fur Mineralogie. Geologic und Palaeontologie; Stuttgart. 1931 Abt B 655–656.
Peters D 2000b. A Redescription of Four Prolacertiform Genera and Implications for Pterosaur Phylogenesis. Rivista Italiana di Paleontologia e Stratigrafia 106 (3): 293–336.
Peters D 2007. The origin and radiation of the Pterosauria. In D. Hone ed. Flugsaurier. The Wellnhofer pterosaur meeting, 2007, Munich, Germany. p. 27.
Peyer B 1937. Die Triasfauna der Tessiner Kalkalpen XII. Macrocnemus bassanii Nopcsa. Abhandlung der Schweizerische Palaontologische Geologischen Gesellschaft pp. 1-140.
Renesto S and Avanzini M 2002. Skin remains in a juvenile Macrocnemus bassanii Nopsca (Reptilia, Prolacertiformes) from the Middle Triassic of Northern Italy. Jahrbuch Geologie und Paläontologie, Abhandlung 224(1):31-48.
Romer AS 1970. Unorthodoxies in Reptilian Phylogeny. Evolution 25:103-112.

wiki/Macrocnemus

 

Pterodactylus manual digit 5

Tiny, vestigial manual digit 5
sits on the top of the giant axially rotated metacarpal 4 of all pterosaurs. Here (Fig. 1) manual digit 5 is curled up on this Pterodactylus scolopaciceps specimen (BSP 1937 I 18), a pregnant pterosaur. Photoshop helps this digit ‘pop’ making it harder to overlook. A reconstruction unrolls it.

Figure 1. Manual digit 5 on top of the giant metatarsal 4 on Pterodactylus. It's easy to overlook, until you look for it.

Figure 1. Manual digit 5 on top of the giant metatarsal 4 on Pterodactylus. It’s easy to overlook, until you look for it.

References
Broili F 1938. Beobachtungen an Pterodactylus. Sitz-Bayerischen Akademie der Wissenschaten, zu München, Mathematischen-naturalischenAbteilung: 139–154.
Wellnhofer P 1970. Die Pterodactyloidea (Pterosauria) der Oberjura-Plattenkalke Süddeutschlands. Abhandlungen der Bayerischen Akademie der Wissenschaften, N.F., Munich 141: 1-133.

wiki/Pterodactylus

Rhamphorhynchus: Zittel wingtip ungual in higher resolution

The Zittel wing
of Rhamphorhynchus preserves a complete and unfolded pterosaur wing (brachiopatagium + propatagium). Because the specimen (B St 1880.II.8) documents a narrow-chord construction it was purposefully omitted from the earlier study by Elgin, Hone and Frey (2010) who wished all their pterosaur wings were of the invalidated and traditional deep chord variety. None are (Peters 2002). Yet the tradition continues as seen in David Attenborough videos and Bennett (2016) papers.

As a scientist,
I prefer cold hard evidence (Figs. 1-3) with regard to pterosaur wing shape. Let’s hope you do, too.

Figure 1. Zittel wing (Rhamphorhynchus) with ungual area color spectrum expanded.

Figure 1. Zittel wing (Rhamphorhynchus) with ungual area color spectrum expanded. Details in figure 2. Note the narrow chord of this nearly perfect specimen with the membrane stretched between the elbow and wingtip, not the hind limb and wing tip. This is hard evidence. This is reality.

Today
we’ll take a closer peek at the typically overlooked wing tip ungual, phalanx 5 of manual digit 4 (m4.5) that we looked at earlier in less detail. Few to no pterosaur workers and other paleontologists recognize the presence of this bone. Rarely workers (Koroljov AV 2017) consider the wing finger to be digit 5 and the pteroid digit 1. Not true (Peters 2009). Just because the wingtip claw is tiny, doesn’t mean it’s not present. You just have to look carefully and use the tools available (Photoshop) to bring it out so others can easily see it (Fig. 2).

Figure 2. Zittel wing m4.5, wingtip ungual in situ, plus with the color spectrum (image levels in Photoshop) expanded.

Figure 2. Zittel wing m4.5, wingtip ungual in situ, plus with the color spectrum (image levels in Photoshop) expanded. Yes, it gets fuzzy when it is enlarged so much, but the hook shape is readily apparent surrounded by excavation.

We nested the Zittel wing
earlier with other Rhamphorhynchus specimens in the large pterosaur tree (LPT, Fig. 3). Although ungual 4.5 is apparent (Figs. 1,2), manual digit 5 is not visible in the Zittel wing due to a ventral exposure of the specimen.

Figure 2. The Zittel wing specimen B St 188 II 8 nests between the 'dark wing' JME specimen and the MTM specimen, both in the Rhamphorhynchus muensteri clade.

Figure 2. The Zittel wing specimen B St 188 II 8 nests between the ‘dark wing’ JME specimen and the MTM specimen, both in the Rhamphorhynchus muensteri clade.

Despite having the specimen in his hands,
Bennett 2016 overlooked the ungual at the wingtip. He proximally extends the propatagium to the neck, rather than the deltopectoral crest. Worse yet, he added lots of proximal wing membrane that was never there in the Zittel wing (Fig. 3). No pterosaur documents wing membranes extending past the knee. No pterosaur documents uropatagia attaching to pedal digit 5. No pterosaur documents a propatagium extending proximally beyond the deltopectoral crest.

Figure 3. Base reconstruction of Zittel wing by Bennett 2016 where he imagined a great deal of patagium between the elbow and knee. Here the hind limbs are rotated laterally, the patagium is stretched between the elbow and wingtip. Femoral and numeral muscles are estimated. 

Figure 3. Base reconstruction of Zittel wing by Bennett 2016 where he imagined a great deal of patagium between the elbow and knee. Here the hind limbs are rotated laterally, the patagium is stretched between the elbow and wingtip. Femoral and numeral muscles are estimated.

Strictly follow your data.
Don’t enhance it with imaginary tissues. And don’t overlook real data.

References
Bennett SC 2016. New interpretation of the wings of the pterosaur Rhamphorhynchus muensteri based on the Zittel and Marsh specimens. Journal of Paleontology 89 (5):845-886. DOI: 10.1017/jpa.2015.68
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
Koroljov AV 2017. The Flight of Pterosaurs.Biol Bull Rev 7: 179. doi:10.1134/S2079086417030045
Peters D 2002. A New Model for the Evolution of the Pterosaur Wing – with a twist. – Historical Biology 15: 277–301.
Peters D 2009. A reinterpretation of pteroid articulation in pterosaurs. Journal of Vertebrate Paleontology 29:1327-1330.

Phylogenetic miniaturization has a name: the Lilliput effect

Just learned this yesterday
and glad to see someone else recognizes and has given a name to phylogenetic miniaturization. Size matters!!! …according to the large reptile tree and large pterosaur tree. New animal taxa tend to originally develop at a small size, as hypothesized by S.M. Stanley (1973).

According to Wikipedia
The Lilliput effect (Urbanek 1993) is a term used to describe a decrease in body size in animals which have survived a major extinction. There are several hypotheses as to why these patterns appear in the fossil record, some of which are: the survival of small taxa, dwarfing of larger lineages, and the evolutionary miniaturization from larger ancestral stocks”

Berv and Field 2017
find an Avian Liilliput Effect at the K-Pg boundary.

From the abstract:
“Survivorship following major mass extinctions may be associated with a decrease in body size—a phenomenon called the Lilliput effect. Body size is a strong predictor of many life history traits (LHTs), and is known to influence demography and intrinsic biological processes. Pronounced changes in organismal size throughout earth history are therefore likely to be associated with concomitant genome-wide changes in evolutionary rates. Here, we report pronounced heterogeneity in rates of molecular evolution (varying up to ∼20-fold) across a large-scale avian phylogenomic data set and show that nucleotide substitution rates are strongly correlated with body size and metabolic rate. We also identify potential body size reductions associated with the Cretaceous–Paleogene (K-Pg) transition, consistent with a Lilliput effect in the wake of that mass extinction event. We posit that selection for reduced body size across the K-Pg extinction horizon may have resulted in transient increases in substitution rate along the deepest branches of the extant avian tree of life. This “hidden” rate acceleration may result in both strict and relaxed molecular clocks over-estimating the age of the avian crown group through the relationship between life history and demographic parameters that scale with molecular substitution rate. If reductions in body size (and/or selection for related demographic parameters like short generation times) are a common property of lineages surviving mass extinctions, this phenomenon may help resolve persistent divergence time debates across the tree of life. Furthermore, our results suggest that selection for certain LHTs may be associated with deterministic molecular evolutionary outcomes.”

Still unrecognized by other pterosaur workers
the large pterosaur tree and large reptile tree recover a Lilliput effect at the base of every major pterosaur clade and elsewhere (turtles, reptiles, lizards, mammals, placentals, bats, etc. ) While other workers find the Lilliput effect in the aftermath of mass extinctions, the LRT found smaller taxa prior to mass extinctions survived the events, while others, like Late Cretaceous large pterosaurs, did not.

References
Berv JS and Field DJ 2017. Genomic Signature of an Avian Lilliput Effect across the K-Pg Extinction. Systematic Biology syx064
Harries PJ and Knorr PO 2009. What does the ‘Lilliput Effect’ mean? Palaeogeography, Palaeoclimatology, Palaeoecology 284:4–10. online
Stanley SM 1973. An explanation for Cope’s Rule”. Evolution. 27: 1–26. doi:10.2307/2407115
Urbanek A 1993.
Biotic crises in the history of Upper Silurian graptoloids: APalaeobiological model. Historical Biology, 7:29-50.

The joy of finding mistakes: fewer stem dinosaurs

Finding mistakes is what I hope to do every day
in my own work, as well as that of others. Each time that happens, the data set improves. Lumping and splitting improves. The hypothetical topology of the large reptile tree (LRT, 1036 taxa) gets closer to echoing the topology of Nature itself. Science is a process of winnowing through the data and finding earlier mistakes.

Figure 1. Revision to the LRT with a focus on the Archosauria. Here taxa with a long carpus all nest within the Crocodylomorpha, following traditional thinking. Dinosaur outgroups are reduced. PVL 4597 is still the basalmost archosaur.

Figure 1. Revision to the LRT with a focus on the Archosauria. Here taxa with a long carpus all nest within the Crocodylomorpha, following traditional thinking. Dinosaur outgroups are reduced. PVL 4597 is still the basalmost archosaur.

Today
I discovered some scoring errors among former ‘stem dinosaurs’ that turned them into basal crocodylomorphs. That’s a small shift and it involved turning some ‘absent’ scores in pedal digit 5 to ‘unknown’. It’s noteworthy that some related taxa have two tiny phalanges on pedal digit 5. A related taxon, Gracilisuchu, was illustrated by Romer (1972, Fig. 3) as a combination or chimaera of separate specimens, something I just today realized and rescored. One of those specimens is the so-called Tucuman specimen (PVL 4597, Fig 1), which nests apart from the Gracilisuchus holotype (Fig. 2) in the LRT.

Figure 1. The PVL 4597 specimen attributed to Gracilisuchus by Lecuona et al. 2017, but nesting at the base of the Dinosauria in the LRT.

Figure 2. The PVL 4597 specimen attributed to Gracilisuchus by Lecuona et al. 2017, but nesting at the base of the Dinosauria in the LRT. That fibula flange turns out to be another important trait. 

The corrected results
resolve the long proximal carpal issue in crocodylomorphs very neatly. Now, as in traditional thinking, that trait is restricted to only the crocodylomorphs and it gives us a basalmost taxon with the trait, Junggarsuchus. You might think, and it would be reasonable to do so, that phylogenetic bracketing permitted the addition of a long carpus and long coracoids with more confidence to taxa that don’t preserve this, like Gracilisuchus and Saltopus. But another related basal crocodylomorph, Scleromochlus, has small round coracoids, evidently a reversal. The carpal length is not clearly documented in Scleromochlus (Fig. 4).

Gracilisuchus

Figure 3. A basal archosaur with a very similar nasal bone, Gracilisuchus. Note pedal digit 5 here. This is how Romer 1972 illustrated it. The actual data is shown in figure 2, the Tucuman specimen, PVL 4597. The coracoid is not known in the holotype. 

Despite the short round coracoids of Scleromochlu
and its apparently short carpals, enough traits remain to nest it as a basal crocodylomorph, following the rules of maximum parsimony.

Figure 1. Scleromochlus forequarters. The yellow area shows the hand enlarged in situ. The size of the Scleromochlus hand makes it the last possible sister to pterosaurs, famous for their very large hands.

Figure 4. Scleromochlus forequarters. The yellow area shows the hand enlarged in situ. Large carpals do not appear to be present and the coracoids are not elongated. 

On a more personal note
I found out my art and a short bio were included in a paleoart website:
http://paleoartistry.webs.com while looking for information on friend and paleoartist, Mark Hallett, (wikipage here) whose website is down and I worried about his health. No worries. Mark just let his website lapse.

The author of the paleoartistry page
had both kind words and controversy for me:
“After David Peters’ excellent paintings in Giants, and A Gallery of Dinosaurs and Other Early Reptiles, as well as his own calendar, it seemed he was on his way to becoming one of the most reliable paleoartists of the 1990s, if not of all time. However, very controversial theories on reconstructing pterosaurs led to some harsh critiques obscuring Peters’ artistic brilliance.” 

That’s okay.
“Very controversial” does not mean completely bonkers (or am I reading too little into this?). It just means it inspires a lot of chatter. Or… it could mean that the author of the post follows the invalidated observations of Elgin, Hone and Frey 2010, which are the traditional views (Unwin and Bakhurina 1994), still used in David Attenborough films. If so, that would be a shame. Science is usually black and white – is or isn’t, because you can observe and test (Fig. 5) and all tests, if done the same, should turn out the same.

And you don’t toss out data
that doesn’t agree with your preconception, like Elgin, Hone and Frey did. In reality, my “very controversial reconstructions” remain the only ones built with DGS, not freehand guesswork or crude cartoonish tracings (as in Elgin, Hone and Frey 2010). The membranes (brachiopatagia and uropatagia) were documented in precise detail in Peters 2002, 2009 and here online.

Click to animate. This is the Vienna specimen of Pterodactylus, which preserves twin uropatagia behind the knees.

Figure 5. Click to animate. This is the Vienna specimen of Pterodactylus, which preserves twin uropatagia behind the knees.

References
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
Peters D 2002. A New Model for the Evolution of the Pterosaur Wing – with a twist. – Historical Biology 15: 277–301.
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