Tanytrachelos in New Mexico – taxon exclusion problems

Modified June 09, 2015 with the addition of clades named by Peters 2000 overlooked by Pritchard et al. 2015. 

Pritchard et al. (2015)
report on 3D Tanytrachelos (Fig. 1) individual bones from New Mexico (Late Triassic, Chinle Formation). And I think they’re spot on with regard to bone identification.

Tanytrachelos

Figure 1. Tanytrachelos – close to Tanystropheus, but tiny with a distinct skull. The New Mexico material matches both in shape and size this North Carolina and Virginia material from the Late Triassic.

The problem comes from their phylogenetic analysis.
From the Pritchard et al. text: “Our analysis incorporated a range of fossil taxa that have traditionally been allied with Tanystropheus and Macrocnemus.” Unfortunately that tradition is ‘bogus’ based on the larger taxon list of the large reptile tree in which macronemids and tanystropheids are lepidosauromorphs, not archosauromorphs. In the Pritchard et al. cladogram (Fig. 2) note the separation of Prolacerta and Protorosaurus to make room for a “by default clade” of tanystropheids that should nest within the Lepidosauromorpha when more taxa are added. This abbreviated taxon list and “by default clade” actually separates the two prorotorosaurs from each other.

Figure 2. Cladogram from Pritchard et al. nesting tanystropheids between two protorosaurs, which should have nested together.

Figure 2. Cladogram from Pritchard et al. nesting tanystropheids between two protorosaurs, which should have nested together (Fig. 3 and large reptile tree). Lepidosauromorphs are in yellow. Archosaurmorphs are in white.

A subset
of the large reptile tree taxon list (Fig. 3) matched (as closely as possible) to the Pritchard et al taxon list demonstrates the problems with such a short taxon list using these taxa in which archosauromorphs and lepidosauromorphs are shuffled like a deck of cards. And sister taxa do not resemble one another at each color-shift clade. For instance, in figure 2 Macrocnemus does not resemble Mesosuchus and in figure 3 Macrocnemus does not resemble Petrolacosaurus.

Figure 3. Subset of the large reptile tree matched to the Pritchard et al. taxon list. Here Protorosaurus and Prolacerta nest together, but the other clades interweave archosauromorphs and lepidosauromorphs.

Figure 3. Subset of the large reptile tree matched to the Pritchard et al. taxon list. Here Protorosaurus and Prolacerta nest together, but the other clades interweave archosauromorphs (white) and lepidosauromorphs (yellow). If you think this cladogram needs more taxa, you are right. And you can find them at the large reptile tree. And this cladogram proves there is a limit to taxon exclusion past which the tree topology breaks down. But then, we are cherry-picking here from two widely separated clades.

Traditions need to be tested
The Pritchard et al. studied relied on a traditional taxon list that was falsified four years ago here. So why did the referees let this manuscript get published? (Answer: tradition, status quo, established paradigm, plus shunning, marginalizing, ignoring the larger gamut study).

The sternum issue
Tanystropheids, like all tritosaurs and most squamates (but not Adirosaurus through snakes because the forelimbs are shrinking), have a sternum not found in protorosaurs and other archosauromorphs. I know I just pulled a “Larry Martin” by noting one and only one trait…

So,
below is the list of all the other traits from the large reptile tree that unambiguously separate tanystropheids (T) from protorosaurs (P). There are 30. Many of these traits extend to other tritosaurs (a subset of the Lepidosauria) and are not found in other archosauromorphs or vice versa.

  1. ventral naris: T = chiefly mx; P = chiefly pmx
  2. dorsal nasal shape: T = pmx invasion; P = narrows toward naris
  3. pmx orientation: T = horizontal; P = down
  4. naris placement: T = displaced or elongated; P = snout tip
  5. posterolateral pmx: T = absent; P = narrower than naris
  6. frontal/parietal suture: T = straight and > than nasal suture; P = not
  7. frontal shape: T = wider posteriorly; P = not
  8. frontal posterior process: T = absent; P = present
  9. postparietals: T = absent; P= present
  10. tabulars: T = absent; P = present
  11. friontal/nasal suture: T = anteriorly oriented; P = zigzag
  12. quadratojugal presence: T = jugal ramus only; P = quadrate ramus only
  13. squamosal/quadratojugal indent: T = no qj ascending process; P = semicircle
  14. parietal and frontal fusion: T = both fused; P = no fusion
  15. pterygoid lateral edge: T = ectopterygoid continues margin laterally; P = sharp angle
  16. pterygoid shape: T = narrow; P = broad triangular
  17. procumbent pmx teeth: T = present; P = absent
  18. posterior mandible shape: T = deeper anteriorly; P = mid rise
  19. caudal transverse processes: T = absent beyond 8th caudal; P = present beyond
  20. short lumbar ribs: T = present; P = not short
  21. second sacral rib: T = not bifurcate; P = bifurcate
  22. chevron shape: T = parallel to centra; P = descends, distal wider
  23. anterior caudal spines: T = shorter than centra; P = taller than centra
  24. sternum: T = present; P = absent
  25. scapula shape: T = not robust; P = robust
  26. pubic apron: T = not present; P = present and wide
  27. tarsus: T = not fenestrated; P = fenestrated
  28. calcaneal tuber: T = no tuber: P = lateral tuber
  29. metacarpal 5: T = straighter or twisted: P = hooked
  30. pedal 3.1 longer than p2.1: T = present; P = not

This reference probably snuck under the radar
Pritchard et al. noted several unnamed clades that were actually named in Peters 2000, some 15 years ago. Further work with the large reptile tree has shown that these clades are all lepidosaurian, not archosaurian or protorosaurian.

Clades named by Peters 2000

Tapinoplatia
Macrocnemus + Characiopoda

Characiopoda
Tanystropheidae + Langobardisaurus + Fenestrasauria

Fenestrasauria
Cosesaurus + Sharovipteryx + Longisquama + Pterosauria

References
Peters D 2000. A Redescription of Four Prolacertiform Genera and Implications for Pterosaur Phylogenesis. Rivista Italiana di Paleontologia e Stratigrafia 106 (3): 293–336.
Pritchard AC, Turner AH, Nesbitt SJ, Irmis RB and Smith ND 2015. Late Triassic tanystropheids (Reptilia, Archosauromorpha) from northern New Mexico (Petrified Forest Member, Chinle Formation) and the biogeography, functional morphology, and evolution of Tanystropheidae. Journal of Vertebrate Paleontology 25(2):e911186 (20pp).

Tree topology change separates protosquamates from tritosaurs

Updated July 7, 2020
the LRT moves Meyasaurus, Indrasaurus and Hoyalacerta to the base of the Yabeinosaurus + Sakurasaurus clade within the Scleroglossa and Squamata.

New data
added to the large reptile tree has changed the topology of the Lepidosauria. This is the biggest change I’ve seen in the last four years, yet it occurred in a fairly dark alley of the Amniota where very few researchers lurk.

Now the Tritosauria has been halved,
extending only from Tijubina to pterosaursPalaegama is still the outgroup.

Figure 1. Palaegama is basal to Coelurosauravus ('rib' gliders), Megachirella (rhynchocephalians), Lacertulus (protosquamates) and Tijubina (tritosaurs)

Figure 1. Palaegama is basal to Coelurosauravus (‘rib’ gliders), Megachirella (rhynchocephalians), Lacertulus (protosquamates) and Tijubina (tritosaurs). Taxa to scale. Note the miniaturization at the base of the Lepidosauria and the similarity of all these sister taxa.

Palaegama is still basal to the so-called ‘rib’ gliders (not ribs, but dermal extensions as we discovered here). It is also basal to all Lepidosaurs.

Among the Lepidosaurs…
Former tritosaurs now form a grade of protosquamates extending from Lacertulus and Bavarisaurus to the primal division of Iguania and Scleroglossa.

Figure 2. Protosquamates to scale. Click to enlarge. Colors indicate clades.

Figure 2. Protosquamates to scale. Click to enlarge. Colors indicate clades.

Tiny Scandensia remains as the last common ancestor of the Lepidosauria and the MFSN 19235 specimen is its larger predecessor.

Other protosquamates include the Daohugou lizard, Carusia, Meyasaurus, Homoeosaurus, Dalinghosaurus and Hoyalacerta.

This change followed the addition of several basal rhynchocephalians, like Megachirella, that shed new light on the origin of the Lepidosauria and the radiations that succeeded them. We looked at those additions here.

Nomenclature
The Tritosauria remains a clade distinct from Squamates. We’ll need a new name for the clade that includes Lacertulus and Iguana, their last common ancestor and all of its descendants. That clade does not include the Tritosauria. A clade that includes the new clade and the Tritosauria is also needed. The Rhynchocephalia is a sister taxon and Palaegama is the current outgroup.

The interesting thing, and we’ve seen this before…
The order of the protosquamates is exactly the opposite as I originally thought. The logic behind this is like folding a piece of paper. The sister taxa at the fold are the same. The beauty of the new topology places the Permian Lacertulus at the base of its clade, where it belongs chronologically and nests the most derived taxon, Scandensia from the Early Cretaceous where it belongs. We’ve seen this before when M. Mortimer nested beaked dinosaurs basal to theropods and I pointed out the hypothesis that the tree was upside-down. See. It can happen to anybody.

The problem with Scandensia is, it looks a lot like the basal rhynchocephalian, Gephyrosaurus and it has long digits like Palaegama. So, I was readily fooled by what appeared to be the real deal — but it was not the real deal. When you look at the protosquamates (Fig. 2), there is no obvious direction to this clade or grade of lepidosaurs. The details of the skeleton reveal their relationships.

Squamate tree of life: Gearty and Gauthier 2014 JVP abstracts

Updated July 7, 2020
the LRT moves Meyasaurus, Indrasaurus and Hoyalacerta to the base of the Yabeinosaurus + Sakurasaurus clade within the Scleroglossa and Squamata.

Resolving the relationships of the Squamate tree of life.
An assessment of new approaches and problems.

In their JVP 2014 abstract Gearty and Gauthier (2014) mix morphological and molecule data on Squamates and this becomes ‘detrimental’ (their words, not mine) to results. So actually they do not resolve relationships. It’s just a topic header. And there’s no mention of the third squamate clade, the Tritosauria, which probably messes up their results, as earlier reported by Conrad (2008, see below) .

From the abstract:
“Since the division of The Deep Scaly Project into separate morphological and molecular teams, a truly integrated project of wide scope has not been attempted. Much more can be done to understand how the members of Squamata are related to one another through an approach that combines the importance of both morphological and molecular evolution. Here we have developed a novel three-step methodological approach to squamate phylogenetics that incorporates the newest phylogeny-creating techniques and data from previous morphological and genetic analyses. First, we analyze a large squamate morphological dataset using Lewis’s Mkv model under both a Bayesian and maximum likelihood framework. Second, we incorporate a previously constructed squamate DNA dataset and analyze the combined data within a ‘total evidence’ framework. Finally, we adopt a methodology that treats genes, rather than nucleotides, as the character of interest. We find that the separate analyses of the morphological and molecular datasets, even under Bayesian and maximum likelihood frameworks, still result in drastically different relationships between higher-order clades within Squamata.

Additionally, we find that the combination of these two datasets results in a phylogeny with limited support for either topology, although it definitively leans in the direction of the molecular results.

Finally, by reducing the molecular dataset to gene characters, we find significantly lower support for the higher-order relationships that are strongly supported in previous analyses. By combining these data with our morphological dataset, we discover that we have inversed the effect of the power in numbers problem.

We conclude that combining datasets, although possibly detrimental to results, should be treated as a source of understanding how the datasets may differ and how they may reflect different evolutionary histories.”

So, ladies and gentlemen… 
Take a lesson from Gearty and Gauthier and don’t mix genetics with morphology. I would trust genetics to find my long lost brother, or a criminal, but not to find any long lost clades. As we learned earlier here, not only can genes be homoplastic, but wrong interpretations can skew results.

From Conrad 2008
Most known squamates fit within one of the seven major radiations (Iguania, Gekkota, Lacertoidea, Scincoidea, Anguimorpha, Amphisbaenia, and Serpentes), but some fossil taxa defy placement within any of these groups. Recent descriptive and phylogenetic work suggests that some fossil taxa fall outside of the crown-group represented by this framework. Among these are Huehuecuetzpalli mixtecus (Reynoso, 1998), Hoyalacerta sanzi (Evans and Barbadillo, 1999; Evans et al., 2004), Scandensia ciervensis, ‘bavarisaurids’, and ‘ardeosaurids‘.

All of the misfits listed above, but the ardeosaurids, are tritosaurs. The ardeosaurids are proto-snakes. So this clade has been long recognized, just not identified in the literature. Yet.

Recent work
I’ve done some recent work with basal squamates from the Early Cretaceaous lithographic limestones and I’ll present a few of them here soon. For now, the tree topology here remains pretty darn close (but new taxa are being added, now up to 425).

References
Gearty W and Gauthier J 2014. Resolving the relationships of the squamate tree of life. An assessment of new approaches and problems. JVP abstracts 2014.

The LH 20523 specimen of Scandensia is really Tijubina

Two lizards were described in 2011.
Bolet and Evans (2011) described what they thought was ‘new material’ of Scandensia (LH 20523), but it had a very long stiff tail and tiny rib osteoderms. This specimen is only known from the posterior half (Fig. 1). Simões (2011) redescribed the complete Tijubina, which also had a very long stiff tail and tiny rib osteoderms. Both are from the Early Cretaceous, the former from Spain, the latter from Brazil.

The large reptile tree nested the LH 20523 specimen with Tijubina, in the middle of the Tritosauria, several nodes away from Scandensia. The holotype of Scandensia nests between basal rhynchocelphalians and basal squamates + tritosaurs. It doesn’t have a long stiff tail or dorsal osteoderms. Distinct from the LH 20523 specimen, Scandensia has a lumbar region of very short ribs.

Figure 1. Tijubina and Scandensia holotypes. Scandensia is a much larger genus. The tail is not well preserved and could be longer in Scandensia. Note the lumbar area in Scandensia not present in Tijubina. Also note the great size of metatarsal 4 in Tijubina, not present in Scandensia.

Figure 1. Tijubina and Scandensia holotypes. Scandensia is a much larger genus. The tail is not well preserved and could be longer in Scandensia. Note the lumbar area in Scandensia not present in Tijubina. Also note the great size of metatarsal 4 in Tijubina, not present in Scandensia.

The LH 20523 specimen has a regenerated tail with cartilaginous growth. The authors estimate the tail was 3x the the snout vent length, which they note contrasts with the holotype of Scandensia, which has subequal tail and snout-vent lengths. This is the first clue that these two are not the same taxon. But then, they reasoned, the Scandensia tail may have been incompletely preserved or regenerating.

The LH 25023 specimen that Bolet and Evans (2011) referred to Scandensia, but nests here with Tijubina.

Figure 2 The LH 25023 specimen that Bolet and Evans (2011) referred to Scandensia, but nests here with Tijubina.

Bolet and Evans (2011) were surprised to see osteoderms around the rib cage because the holotype of Scandensia does not have these. This is the second clue.

The very robust fourth metatarsal is a trait shared with Tijubina, not with Scandensia, a third clue.

Figure 3. Ankles of the LH 25303 specimen. Here Bolet and Evans see a single astragalocalcaneum (in yellow on the drawing) but the photo does not  support a single proximal ankle bone.

Figure 3. Ankles of the LH 20523 specimen. Here Bolet and Evans see a single astragalocalcaneum (in yellow on the drawing, and present in all squamates) but the photo does not support a single proximal ankle bone. Rather a split appears between the astragalus and calcaneum, as in all tritosaurs.

Bolet and Evans report a single astragalocalcaneum, as in Scandensia, but the photo of the LH 20523 specimen shows a split between the proximal ankle bones and the shape is different than shown. Was this wishful thinking? or more precise observation. No tritiosaurs have a fused proximal tarsus, so this would be an autapomorphy if true.

Were Bolet and Evans aware of Tijubina?
I don’t think so. It is not mentioned in their paper. A query to both authors goes unanswered at present.

References
Bolet A and Evans SE 2011. New material on the enigmatic Scandensia, an Early Cretaceous lizard from the Iberian Peninsula. Special Papers in Palaeontology 86:99-108.
Bonfim Júnior DC and Marques RB 1997. Um novo lagarto do Cretáceo do Brazil (Lepidosauria, Squamata, Lacertilia – Formação Santana, Aptiano da Bacia do Araripe. Anuário do Instituto do Geociencias 20:233-240
Bonfim-Júnior F de C and Rocha-Barbosa O 2006. A Paleoautoecologia de Tijubina pontei Bonfim-Júnior & Marques, 1997 (Lepidosauria, Squamata Basal da Formação Santana, Aptiano da Bacia do Araripe, Cretáceo Inferior do Nordeste do Brasil). Anuário do Instituto de Geociências – UFRJ ISSN 0101-9759 Vol. 29 – 2 / 2006 p. 54-65.
Evans SE and Barbadillo LJ 1998. An unusual lizard (Reptilia: Squamata) from the Early Cretaceous of Las Hoyas, Spain. Zoological Journal of the Linnean Society 124:235-265.
Simões TR 2012. Redescription of Tijubina pontei, an early cretaceous lizard (Reptilia; Squamata) from the crato formation of Brazil. An Acad Bras Cienc. Feb 2, 2012. pii: S0001-37652012005000001. [Epub ahead of print].

 

The BES SC 111 specimen of Macrocnemus – DGS helps reconstruct it

Previously considered (Renesto S and Avanzini M 2002) a juvenile due to its size, the BES SC 111 specimen of Macrocnemus (Fig. 1) sheds light on the origin of such diverse lineages as the Tanystropheidae (Langobardisaurus, Fig. 2) and the Fenestrasauria (Cosesaurus through the Pterosauria, Fig. 2). It also nests at the base of other Macrocnemus specimens including the oddly bizarre, Dinocephalosaurus (Fig. 3).

Figure 1. Click to enlarge. Stages in the DGS tracing and reconstruction of the the Macrocnemus BES SC 111 skull. I did not realize the the palatal bones were so visible. There's a palatine and ectopterygoid over the nasal and frontal, for instance. So earlier mistakes were made that are corrected here. The right mandible is traced here only along its ventral rim.

Figure 1. Click to enlarge. Stages in the DGS tracing and reconstruction of the the Macrocnemus BES SC 111 skull. I did not realize the the palatal bones were so visible. There’s a palatine and ectopterygoid over the nasal and frontal, for instance. So earlier mistakes were made that are corrected here. The right mandible is traced here only along its ventral rim.

Derived from
an early Triassic sister to Huehuecuetzpalli and/or Jesairosaurus, the BES SC 111 specimen seems to have at least a depression in the dorsal maxilla that will ultimately become an antorbital fenestra in the Fenestrasauria. Note the resemblance of this skull to that of Cosesaurus and Langobardisaurus (Fig. 2). They all share a retracted naris, large orbit, bent quadrate, short postorbital region and relatively short teeth.

The reduction of pedal digit 5 in all known Macrocnemus specimens demonstrates the BES SC 111 nests at the base of the Macrocnemus lineage. An unknown sister without this reduction would be basal to Langobardisaurus and the Fenestrasauria.

Figure 2. Macrocnemus BES SC 111 compared to sister taxa, Langobardisaurus, Cosesaurus and the basal pterosaur, MPUM 6009. Preserved loose, the orientation of the ectopterygoids could go either way, with the narrow tip contacting the maxilla instead, as in Dinocephalosaurus (Fig. 3).

Figure 2. Macrocnemus BES SC 111 compared to sister taxa, Langobardisaurus, Cosesaurus and the basal pterosaur, MPUM 6009. 

Figure 3. Dinocephalosaurus to scale with the largest Macrocnemus specimen and the smaller ones from figure 2.

Figure 3. Dinocephalosaurus to scale with a large Macrocnemus specimen, T4822, and the smaller ones from figure 2.

The take-away from this is: large odd reptiles sometimes have their origin in not-so-large, not-so-odd reptiles like the BES SC 111 specimen. At the same time, small odd reptiles may have the same origin. Make sure you add the plain, old reptiles to your cladograms. That’s where the spectacular taxa have their origin.

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.
Nopcsa F 1931. Macrocnemus nicht Macrochemus. Centralblatt fur Mineralogie. Geologic und Palaeontologie; Stuttgart. 1931 Abt B 655–656.
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

Phylogenetic bracketing and pterosaurs – part 1

Since pterosaurs (and other tritosaurs) nest between rhynchocephalians and squamates, there are a few traits they likely shared based on phylogenetic bracketing (unless specifically excepted based on fossil evidence). According to Evans (2003) these include:

(1) A derived skin structure with a specialized shedding mechanism involving distinct epidermal generations that are periodically lost and replaced, linked to
a cyclic alternation between a and b keratogenesis. — Ttritosaurs had scales. Pterosaurs also had pycnofibers, hair-like structures that first appear in Sharovipteryx. Unfortunately there is no evidence of skin shedding in any fossil lepidosaur.

(1A) The possession of a crest of projecting scales along the dorsal midline of the body and tail may also be unique to members of this group. — this reaches its acme with the tritosaur fenestrasaur, Longisquama.

(2) Paired male hemipenes housed in eversible pouches at the posterior corners of a transverse cloacal slit. These hemipenes are well developed in squamates and rudimentary in Sphenodon. — the fossil record does not include such structures.

(3) Notching of the tongue tip, possibly in relation to the development of the vomero-nasal system. — Barely notched in Iguana. I don’t see this in known rhynchochephalians or tritosaurs based on the division of the choanae into anterior and posterior fenestra, which appears in basal scleroglossans only.

(4) Separate centres of ossification in the epiphyses of the limb bones (a condition acquired independently in mammals and some birds). — This has never been noted in tritosaurs.

(5) Specialized mid-vertebral fracture planes in tail vertebrae to permit caudal autotomy facilitated by the organisation of associated soft tissue. — This has never been confirmed in any tritosaur, but then again, they are rare as fossils.

(6) A unique knee joint in which the fibula meets a lateral recess on the femur (not end to end as in many tetrapods) — This must be a very subtle trait. I see this trait in Tupinambis, Varanus and Bahndwivici, but not in very many other lepidosaurs.

(7) Specialized foot and ankle characters including a (a) hooked fifth metatarsal, (b) a specialized mesotarsal joint with a fused astragalocalcaneum and (c) an enlarged fourth distal tarsal. —  (a) The hook comes and goes. In basal rhynchocephalians, not present. It is present in Sphenodon through Mesosuchus, starts to fade with Rhynchosaurus and is gone in Hyperodapedon. Something of twisted fifth metatarsal present in most tritosaurs. Minor hook in basal squamata, becomes larger in Varanus, absent in snakes and other limbless lizards, of course. (b) In tritosaurs no ankles are fused except in drepanosaurs. (c) Also large in tritosaurs.

(8) Other soft tissue features include a sexual segment on the kidney; reduction or absence of the ciliary process in the eye; presence of a tenon (cartilaginous
disc) in the nictitating membrane and its attachment to the orbital wall. — These have never been observed in any lepidosaur fossil. But that doesn’t mean they weren’t there.

(9) In addition to these characters, all lepidosaurs show one of two kinds of tooth implantation, pleurodonty and acrodonty. — Basal tritosaurs have pleurodont teeth. Macrocnemus and later tritosaurs have thecodont teeth that happen to be much larger.

Part 2 is posted here.

References
Evans SE 2003.
At the feet of the dinosaurs: the origin, evolution and early diversification of squamate reptiles (Lepidosauria: Diapsida). Biological Reviews, Cambridge 78: 513–551.

 

Vertebrates of the Jurassic Dauhugou Biota of northeastern China – Sullivan et al. 2014

A new paper by Sullivan, et al. (2014) reviewed the current knowledge of the vertebrates of the Jurassic Dauhugou Biota of northeastern China. That list included several lepidosaurs and pterosaurs. Unfortunately their review included several calls for “more testing” to determine phylogenetic relationships. We’ll review those here.

1. Indeterminate Squamate A (IVPP V14386, Figs. 1, 2) was considered a juvenile (total length >9cm) distinct from Dalinghosaurus, but the authors lamented that insufficient morphological information was present to justify the erection of a new taxon.

Figure 1. IVPP-V14386 in situ from Sullivan et al. 2014. Here the scales cover most of the bones.

Figure 1. IVPP-V14386 in situ from Sullivan et al. 2014. Click to enlarge. Here the scales cover most of the bones.

Not sure why Sullivan et al. decided there was insufficient morphological evidence here. I found every major bone but some mid-vertebrae (Fig. 2). It was like looking at an X-ray! This IVPP specimen does indeed nest with Dalinghosaurus and Homoeosaurus at the base of the Tritosauria, a third clade of lizards that Sullivan et al. evidently don’t care to consider. And that may be the source of their confusion because this specimen doesn’t nest within the Squamata. Distinct from Dalinghosaurus, the IVPP specimen has a wider skull (based on the exposed palate), a shorter ventral pelvis, no anterior scapulocoracoid fenestration and several other distinct traits.

Figure 2. IVPP-V14386 with major bones colorized and skull reconstructed.

Figure 2. Click to enlarge. IVPP-V14386 with major bones colorized. Skull and pelvis reconstructed.

2. Indeterminate Squamate B (IVPP V13747) (total length > 12cm) was considered a possible scleroglossan. The large reptile tree found it (the Daohugou lizard in the large reptile tree) also nested with basal tritosaurs.

3. Jeholopterus ningchengensis (IVPP V12705) was correctly considered an adult and referred to the Anurognathidae. Sullivan et al. reported this specimen, “may represent the smallest known adult pterosaur.” This is far from true, and reflects antiquated thinking regarding ontogeny and bone fusion, along with a refusal to consider tiny Solnhofen pterosaurs adults themselves.

The referred specimen (CAGS-IG-02-81) was considered a juvenile by Sullivan et al. because some long bones were half as long.  Unfortunately no reconstructions were attempted. If the workers had only taken this step they would have realized immediately that these two specimens are not even congeneric. Their skulls are nearly the same size. Their post-crania differ greatly. The more gracile one attacked insects. The more robust one attacked dinosaurs for their blood.

Figure 3. Click to enlarge. The Jeholopterus holotype (left) alongside the referred specimen (right). No doubt they were related, but were likely not conspecific.

Figure 3. Click to enlarge. The Jeholopterus holotype (left) alongside the referred specimen (right). No doubt they were related, but were likely not conspecific. The one on the right was an insect eater. The one on the left was specialized for drinking dinosaur blood. Skull sizes are the same. The post-crania was more robust on the left with a palate designed to transmit face-banging forces to the rear.

4. Dendrorhynchoides mutoudengensis (originally GLGMV 0002, but now JZMP-04-07-3, but this is also the Boreopterus specimen number) was listed, but Sullivan et al. placed doubt on the referral of this specimen to this Dendrorhynchoides. And for good reason! The referred specimen (Fig. 4) nests with the flathead pterosaur, SMNS 811928, both derived from the holotype of Dendrorhynchoides (Fig. 4). Note the tail is even longer on the holotype as we noted before.

The holotype of Dendrorhynchoides

Figure 4. Click to enlarge. (Left) The holotype of Dendrorhynchoides compared to (right) the referred specimen. The latter actually nests with the flat-head pterosaur and the two nest alongside Dendrorhynchoides, so, not far off. Sullivan et al. made a big deal about the long tail in the referred specimen, but the holotype has a longer tail and is more primitive. Lack of careful observation and a refusal to create reconstructions is a common problem among pterosaur workers.

5. Fenghuangopterus lii (CYGB-0037) was considered small, but with an unclear ontogenetic stage. It was originally considered a scaphognathine, but the large pterosaur tree nests it as a long-legged, basal dorygnathid, so not too far from Scaphognathus.

6. Jianchangopterus zhaoianus (YHK-0931) was originally considered small, but a subadult scaphognathine related to Sordes. By contrast, Sullivan et al. wrote “it represents a very young individual.” and it’s relation to other pterosaurs “requires testing.” I have done that testing and this small adult specimen nests between Ningchengopterus and the new Painten pterosaur, all at the base of the genus clade, Pterodactylus. Here  (Fig. 5) all three are compared to Sordes.

Figure x. When you compare the three specimens of Sordes to the three jianchangopterids the purported similarities to Sordes start to fade. Shifting Jianchangopterus to Sordes adds 40 steps.

Figure 5. When you compare the three specimens of Sordes to the three jianchangopterids the purported similarities to Sordes start to fade. Shifting Jianchangopterus to Sordes adds 40 steps.

7. Qinlongopterus guoi (D3080, D3081) was considered a young juvenile very similar to Rhamphorhynchus due to its small size, large orbit and short rostrum. The large pterosaur tree nests it within that genus, close to other small rhamphs. Hone et al. (2012) noted that “juveniles of different pterosaur taxa are harder to distinguish than adults.” That may be so because Hone et al. does not care to test these small pterosaurs in phylogenetic analysis. If they took this little step they would find that, like Zhejiangopterus, Pteranodon and pterosaur embryos, which are identical to adults and can be scored with adults in phylogenetic analysis. In similar fashion Hone deleted fenestrasaurs when he and Benton wrote two papers supporting the archosaur origin for pterosaurs (without providing a viable archosaur candidate with pterosaur traits).

8. Changchengopterus pani (CYGB-0036) was considered a young juvenile by Sullivan et al. but it nests with other small pterosaurs, like the BSP 1994 specimen of Eudimorphodon at the base of all higher single cusp tooth pterosaurs. The referred specimen is a wukongopterid, as Wang (2010) erroneously suggested for the holotype. Sullivan et al. considered the phylogenetic position of these two specimens uncertain. They considered the holotype “one of the smallest pterosaurs specimens known” and considered it a juvenile due to its unfused scapulocoracoid, not realizing that this trait is phylogenetic in distribution, not ontogenetic.

9. Darwinopterus, Wukongopterus, Kunpengopterus, Archaeoistiodactylus are here all lumped together because they all form a clade, the Wukongopteridae, that left no descendants, but developed a long pterodactyloid rostrum and neck by convergence. Unfortunatelly Sullivan et al. followed Lü et al. in supporting their analysis that placed Darwinopterus at a transitional node from long tail rhamphs to short tail pterodcs. Of course the lack of resolution at this node was massive, with no single genus preceding or succeeding Darwinopterus. Nor did Lü et al include the actual transitional taxa, the tiny pterosaurs, which they considered juveniles unworthy or potentially disruptive of analysis. A more inclusive analysis can be seen here. To the credit of Sullivan et al. followed Martill and Etches (2013) and the pterosaurheresies and reptile evolution to break with the original nesting of Archaeoistiodactylus with the ornithocheirid Istiodactylus to suggest (without phylogenetic analysis) that it nested with wukongopterids.

References
Martill DM and Etches S2013. A new monofenestratan pterosaur from the Kimmeridge Clay Formation (Upper Jurassic, Kimmeridgian) of Dorset, England. Acta Palaeontologica Polonica 58 (2): 285–294. doi:10.4202/app.2011.0071.
Sullivan C, Wang Y, Hone DEW, Wanga Y, Xu X and Zhang F 2014. The vertebrates of the Jurassic Daohugou Biota of northeastern China. Journal of Vertebrate Paleontology 34(2):243-280.

Pulling Bavarisaurus out of the belly of Compsognathus

Figure 1. Click to enlarge. The little Jurassic lizard Bavariasaurus was found inside the belly of the little Jurassic dinosaur, Compsognathus. But it is not the same genus as the holotype.

Figure 1. The little Jurassic lizard Bavariasaurus was found inside the belly of the little Jurassic dinosaur, Compsognathus. Illustration by Franz Nopcsa 1903.

As everyone knows, one Jurassic lizard, Bavarisaurus macrodactylus (Figs. 1-4, = Homoesaurus macrodactylus Wagner 1852, Hoffstetter 1964; length: ~20cm, (Lower Tithonian), Solnhofen), was found inside the belly of a small Jurassic dinosaur, Compsognathus (BSPHM AS-1-563). All curled up like the good meal it was, Bavarisaurus has been added to various lepidosaur phylogenetic analyses, but, to my knowledge, it has not been reconstructed in the literature. However, Tracy Ford did a good job here.

Figure 2. Like Michelangelo removing the excess marble, I removed every trace of Compsognathus, leaving nothing but Bavarisaurus in step 1.

Figure 2. Like Michelangelo removing the excess marble, I removed every trace of Compsognathus, leaving nothing but Bavarisaurus in step 1.

Not sure how much good this will do, but I took all the bones I could see and segregated from the dinosaur bones (Fig. 2), then rearranged them as well as I could (Fig. 3). Seems like Bavarisaurus had quite a long tail when it is all stretched out! Looking at the maxilla and mandible you’ll notice the teeth don’t match. Small triangle-shaped teeth are on the dentary, but posteriorly-oriented narrow, sharp teeth appear on the maxilla. The presumes that I have the maxilla correctly oriented.

Figure 3. Click to enlarge. Moving the bones of Bavarisaurus into a reasonable reconstruction is step 2.

Figure 3. Click to enlarge. Moving the bones of Bavarisaurus into a reasonable reconstruction is step 2.

The next step was to tentatively nest the elements phylogenetically, then clean them up in a better presentation in dorsal and lateral views (Fig. 4). A final scoring of elements nests Bavarisaurus more securely.

Figure 2. Click to enlarge. Cleaned up reconstruction of the former Bavarisaurus (cololizard at present). Gray areas added based on sister taxa. This is a tritosaur.  Note the large naris bounded ventrally by the maxilla. The ventral pelvis is shallower. I don't understand the pterygoid morphology anteriorly. The upper and lower teeth don't match. That's a red flag, but it is the only data available.

Figure 2. Click to enlarge. Cleaned up reconstruction of the former Bavarisaurus (cololizard at present). Gray areas added based on sister taxa. This is a tritosaur.  Note the large naris bounded ventrally by the maxilla. The ventral pelvis is shallower. I don’t understand the pterygoid morphology anteriorly. The upper and lower teeth don’t match. That’s a red flag, but it is the only data available.

Bavarisaurus is another tritosaur. 
And that’s why it nests uncertainly at the base of the Squamata in prior analyses that did not include any or many other tritosaurs — because it doesn’t nest in the Squamata. In the large reptile tree Bavarisaurus nests between Meyasaurus and the Dahugou lizard + Lacertulus, not far removed from Dalinghosaurus, which it resembles by convergence.

So based on the presence of Lacertulus in the Late Permian, something very much like Bavarisaurus originated in the Permian and continued to the Late Jurassic where we find the first and last of this genus inside the ribcage of Compsognathus.

References
Evans SE, Raia P and Barbera C 2004. New lizards and rhynchocephalians from the Lower Cretaceous of southern. Italy. Acta Palaeontologica Polonica 49:393–408.
Hoffstetter R 1964. Les Sauria du Jurassique supérieur et specialement les Gekkota de Baviére et de Mandchourie. Senckenberger Biologische 45, 281–324.
Nopcsa F 1903. Neues ueber Compsognathus. Neues Jahrbuch fur Mineralogie, Geologie und Palaeontologie 16: 476-494.
Wagner A 1852. Neu-aufgefundene Saurier, Uberreste aus dem lithographischen Schiefern und dem obern Jurakalke: Abhandlungen der Bayerischen Akademieder Wissenschaften Mathematisch-naturwissenschafliche Kl, 3(6): 661-710.

New Middle Jurassic lizard – svp abstracts 2013

From the abstract
Conrad et al. (2013) wrote: “The last three decades has seen a dramatic increase in our knowledge regarding the earliest evolution of the major squamate clades, but most known fossils are Cretaceous or younger. The earliest known squamates are the incompletely known Parviraptor, Eichstaettisauridae, Ardeosaurus, and the Paramacellodidae with their osteodermal armor. We report on a new late Middle Jurassic lizard from the Shishugou Formation of China representing the oldest complete squamate skeleton. The animal possesses vomerine teeth, a rectangular frontal, and incipient cusps on its marginal teeth. The preserved hind limb is very elongate. The entire body was encased in osteoderms.

The resultant phylogenetic hypothesis finds a “gecko-morphotype” (unarmored, relatively large-eyed, morphs with limbs of intermediate length and simple, insectivore-style teeth) to be ancestral for squamates. Our new lizard is recovered as a basal episquamate, related to lateratans, anguimorphs, and iguanomorphs.

The Late Jurassic saw the rise of therian mammals and coelurosaurian dinosaurs. At the same time, squamates enter the fossil record in both the gecko-morphotype and armored forms (e.g., Paramacellodus and our new taxon). We suggest that the selective pressure from this changing fauna may have helped “push” squamates into new morphotypes. Many known Late Jurassic and Cretaceous episquamates possess long legs (e.g., Bavarisaurus, Saichangurvel) and/or extensive osteodermal armor (e.g. Paramacellodus). These pressures may have contributed to the marginalization of the previously diverse and widespread rhynchocephalians.”

Notes
Conrad et al. are following Hedges (2005), a DNA study, in nesting geckos at the base of the squamata, iguania nesting higher. Hedges found legless Dibamus as the most basal squamate. Of the remaining taxa (Bifurcata), the gekkonids form a basal lineage. The Unidentata, squamates that are neither dibamids nor gekkonids, are divided into the Scinciformata (scincids, xantusiids, and cordylids) and the Episquamata. These include Laterata (Teiformata, Lacertiformata, and Amphisbaenia, with the latter two joined in Lacertibaenia) and Toxicofera (iguanians, anguimorphs and snakes). So, distinct from the large reptile tree, Hedges (2005) links Iguana and snakes on the basis of DNA.

It is unfortunate that Conrad et al. used a DNA tree that differs so much from a morphological tree because fossils cannot be tested for DNA.

Lacertulus

Figure 1. Lacertulus, a basal tritosaur lepidosaur, also at the base of the Squamata.

It is also unfortunate that Conrad et al. do not recognize the third squamate clade, the Tritosauria, that reached their origin in the Permian (Lacertulus, Fig. 1) and reached their acme in the Triassic. Tritosaurs dwindled in diversity into the Cretaceous when only Huehuecuetzpalli and pterosaurs survived. These too became extinct by the end of the Cretaceous.

Figure 3. Click to enlarge. Reconstruction of TA1045, an unnamed Early Permian pre-lizard from Germany. Close to Dalinghosaurus, this genus had shorter legs and a longer torso. In grey above are the transverse belly scales.

Figure 2. Click to enlarge. Reconstruction of TA1045, an unnamed Early Permian pre-lizard from Germany. Close to Dalinghosaurus, this genus had shorter legs and a longer torso. In grey above are the transverse belly scales.

TA 1045 (Fig. 2) is an unnamed tritosaur lepidosaur from the Early Permian. Considering the antiquity of TA 1045 and Lacertulus (both Permian) and the diversity of Triassic tritosaurs and Middle Jurassic squamates, there are certainly many more basal squamates  out there to be found in Triassic strata. Odd that they have not been discovered as yet.

I’m looking forward to seeing the new armored lizard to nest it morphologically.

References
Conrad J, Wang Y, Xu X, Pyron A and Clark JG. 2013. Skeleton of a heavily armored and long legged middle Jurassic lizard (Squamata, Reptilia). Journal of Vertebrate Paleontology  abstracts.
Hedges VN 2005. The phylogeny of squamate reptiles (lizards, snakes, and amphisbaenians) inferred from nine nuclear protein-coding genes. CR Biology 328(10-11):1000-1008. Epub 2005 Oct 27.

The unexpected bipedal/marine connection

Several times in the evolution of reptiles bipedal forms have phylogenetically preceded marine forms. Yes, marine forms. It’s bizarre, but true.

Here’s the list, more or less. Did I miss any?

Huehuecuetzpalli (bipedal capable) > Dinocephalosaurus (marine)
Huehuecuetzpalli, a small speedy lizard with short fore limbs and long hind limbs evolves to become Dinocephalosaurus, a giant long-necked sit-and-wait predator via Macrocnemus, something in between.

Langobardisaurus (biped) > Tanystropheus (marine)
Langobardisaurus, a small long-necked strider evolves to become Tanystropheus, a giant stand-and-wait marine predator.

Eudibamus (biped) > Claudiosaurus (marine)
Eudibamus, a small lizard-like diapsid with a long neck and long hind limbs evolves to become Claudiosaurus, a long-necked marine undulating marine predator of tiny prey. Thereafter descendants evolve to become ichthyosaurs and plesiosaurs.

Varanus (biped while fighting) > Mosasaurus (marine)
Okay, so only certain varanids only go bipedal when fighting, even so mosasaurs are giant and marine.

Scleromochlus & Terrestrisuchus (bipeds) > Metriorhynchus (marine)
Scerlomochlus, and Terrestrisuchus, tiny long-legged basal crocs evolve to become large short-paddled marine crocs, like

Storks (biped) > Penguins (marine)
Flying bipeds evolve to fly underwater.

Australopithecines (biped) > Humans (Homo, marine capable)
(grassland roamers evolve to become able to swim)

Evidently it all comes down to 
Conscious control of breathing — if you want to become a marine animal you have to hold your breath.

Not sure what the bipedal connection is with reptiles, because lots of marine reptiles never had a bipedal phase. I just wanted to throw the idea out there.

More on Humans:
Anthropologist Elaine Morgan on TED talks about the origin of bipedal humans from aquatic apes here. Step-by-step: Apes all walk bipedally when they cross streams. For insulation humans have fat migration to a subdermal position, that’s why obesity is possible for humans, not for apes. The nostrils open ventrally, keeping water out by air pressue in humans. Ape nostrils don’t keep out water, except for the proboscis monkey (the most aquatic of primates).  Ability to speak comes by way of the conscious control of their breath, according to Morgan.