Norellius nyctisaurops – a -very- basal pre-snake, -very- close to geckos

A new paper
by Conrad and Daza (2015) rediagnoses and names AMNH FR 21444 (Fig. 1, Early Cretaceous, ), “an important early and relatively basal lizard: (Conrad and Norell 2006).” Conrad and Daza describe the specimen as “a gecko-like basal squamate as identified by its braincase morphology.” it is tiny with a skull length of 1.5 cm. Postcrania is unknown.

Figure 1. Norellius from Conrad and Daza 2015. At upper right I highlight the 'missing' lacrimal and provide an alternate imagined rostrum based on that of sister taxa.

Figure 1. Norellius from Conrad and Daza 2015. At upper right I highlight the ‘missing’ lacrimal in red and provide an alternate imagined rostrum based on that of sister taxa. Look closely at the pterygoid. There are tiny teeth there, the origin of pterygoid teeth in snakes!

Added to 
the large reptile tree, Norelliius nests next to the Gekko clade that has Tchingisaurus at its base. Norelliius nests at the base of the clade that produced Eichstaettisaurus, Tetrapodophis and snakes, further cementing these two clades together. And it’s the fiirst good lock at the palate around this node.

Daza et al. 2013
was not able to resolve the position of AMNH FR 21444. According to Conrad and Daza, “It has large orbits, a complete postorbital bar and supratemporal arch, and a broad pyriform recess (Fig. 1). The skull is broadest at the level of the orbits and, apparently, tapered anteriorly. The lacrimal is absent; the maxilla and prefrontal form the margins of the lacrimal foramen.” 

Funny thing,
they say the lacrimal is absent, and it is absent on the left with a space left over to receive it, but it appears to be present on the right (Fig. 1). Sister taxa all have a lacrimal.

Norellius is difficult to nest
as it lacks important bones at the front and back of the skull. And it nests very close the the origin of several major scleroglossan clades. In other words, it is very plesiomorphic. Nevertheless a few traits do ally it with Ardeosaurus, Eichstaettisaurus and other pre-snakes to the exclusion of other clades.

Conrad and Daza
consider Gekkonomorpha as basal within Squamata. The large reptile tree does not support this, but recovers Iguania and several other taxa as more basal (splitting off earlier).  It should be noted that Conrad and Daza do not yet recognize the Protosquamata or the Tritosauria, two lepidosaur clades/grades basal to the Squamata. They haven’t added pertinent taxa to their studies, including the lepidosaur Macrocnemus and its kin.

Ironically
Conrad and Daza note: “Norellius nyctisaurops shows no gekkotan characteristics in its dermatocranium.” Only the braincase identifies it as a gekknomorph according to their study.

Conrad and Daza consider Norellius close to the base of Squamata (which it is not) and note, “Even so, the elongate postorbital skull, curved and elongate jugal, long postdentary part of the jaw, and very gecko-like braincase differ strikingly from the morphology seen in basal rhynchocephalians [Gephyrosaurus]. Clearly, more Jurassic and Triassic squamates are needed to help bridge the morphological gap between basal lepidosaurs and modern Squamata.” The large reptile tree provides several taxa to fill this purported gap. Again, the conclusions of Conrad and Daza appear to be based on taxon exclusion. The large number of pertinent taxa in the large reptile tree provide a gradual accumulation of derived characters.

Pterygoid teeth!
Look closely at the pterygoid of Norellius. There are tiny teeth there, the origin of large pterygoid teeth in snakes! Mosasaurs grew those pterygoid teeth convergently, hence the confusion with Pythonomorpha, another invalid clade (snakes + mosasaurs, Cope 1869).

References
Conrad JL and Daza JD 2015. Naming and rediagnosing the Cretaceous gekkonomorph (Reptilia, Squamata) from Öösh (Övörkhangai, Mongolia). Journal of Vertebrate Paleontology 35:5, e980891
Conrad JL and Norell MA 2006. High-resolution x-ray computed tomography of an Early Cretaceous gekkonomorph (Squamata) from Öosh ( €Ov€orkhangai; Mongolia). Historical Biology 18:405–431.
Daza JD, Bauer AM and Snively E 2013. Gobekko cretacicus (Reptilia: Squamata) and its bearing on the interpretation of gekkotan affinities. Zoological Journal of the Linnean Society 167:430–448.

Flugsaurier 2015: Reports from Darren Naish

Flugsaurier 2015 (Portsmouth, England) took place recently. More pterosaur guys are in one room at one time whenever these meetings take place.

According to director David Martill,
one is not supposed to report on the abstracts if one did not attend or pay the necessary fees. That’s fair. So, based on Darren Naish’s reportage, (not the abstract publication) “there were no big news items at this meeting, but some intriguing possibilities for the future were mentioned.”

Naish reports, “A set of Triassic taxa that have multi-cusped cheek teeth – the eudimorphodontids and/or campylognathoidids – are posited as one of the earliest pterosaur lineages to evolve by some workers (like Brian Andres and Steven Vidovic), but as being far closer to pterodactyloids by others (like David Unwin). So, apparently a bit of confusion/contention there. According to the large pterosaur tree, the Triassic pterosaurs were indeed basal to other taxa.

Naish reports, specimens previously assumed to belong to Eudimorphodon have recently been the subject of revision by Alex Kellner who spoke about his recent naming of Arcticodacylus, Austriadraco and Bergamodactylus (Kellner 2015). As readers know, phylogenetic analysis in Peters (2007) indicated this earlier. Happily Kellner named them.

Naish reports, Mark Witton presented a new integrated view of Dimorphodon’s anatomy and biology — not a ‘puffin pterosaur,’ but highly terrestrial [see Padian 1984 and here] and with poor flight abilities compared to most of its relatives. [Unlikely that a Jurassic pterosaur would have poor flight abilities when it has every trait other good flyers had.]

Naish reports, “Steve Vidovic told us his really intriguing idea that anurognathids might be paedomorphic scaphognathines (or scaphognathids, if you prefer).” [No way, see here]

To his credit, Naish reports, “I don’t think he’s right, but it sure is intriguing. Anurognathids remain one of the most perplexing pterosaur groups of all and they possess a curious mix of anatomical features.” [The problem is no one is doing accurate tracings and creating reconstructions of anurognathid skeletons, as shown here and here]

Naish reports, There are thrilling and (arguably) terrifying rumours about a new anurognathid discovery, soon to be announced.” Hope its a big one from China to match the embryo the size of other adult anurognathids.

Naish reports, Darwinopterus from the Middle or Upper Jurassic Tiaojishan Formation of Liaoning Province, China, continues to be a pivotal taxon as goes our developing understanding of pterosaur evolution and biology. As is well known, Darwinopterus seemingly combines anatomical traits of pterodactyloids in its skull with non-pterodactyloid features in the wrist, feet and elsewhere. This composite anatomy indicates that so-called modular evolution was important in the early evolution of the lineage that led to pterodactyloids, the largest and most successful pterosaur group (Lü et al. 2010). Accordingly, Darwinopterus was – when first published – posited as a key ‘intermediate’ taxon between long-tailed, five-toed pterosaurs like the rhamphorhynchids and the short-tailed, four-toed pterodactyloids (Lü et al. 2010).” [Naish is aware of, but politely not mentioning, competing phylogenetic analysis (by everyone else doing such analyses) that do not nest Darwinopterus where Lü et al. do.]

Naish reports, “Cuspicephalus from the English Kimmeridge Clay was recently reinterpreted as an animal of this sort [a ‘monofenestran] by Witton et al. (2015). Incidentally, the Cuspicephalus holotype specimen was on display at the meeting.”

Naish reports, “Back in 2013, I and colleagues described the new small pterosaur Vectidraco daisymorrisae (based only on a pelvis and its associated vertebrae) from the Vectis Formation of the Isle of Wight (Naish et al. 2013). I’m pleased to say that this animal was the subject of two presentations. The first was by Rachel Frigot and looked at muscle attachment sites on the specimen and what they might tell us about pterosaur biomechanics. And the second was by Liz Martin-Silverstone and concerned an in-prep study (also involving myself and Dan Sykes) on the detailed anatomy of this animal. It turns out that structures originally identified (Naish et al. 2013) as pneumatic foramina are not pneumatic foramina… they’re actually spinal nerve foramina (what a silly mistake). There’s a whole story here that I’ll discuss once the project is closer to publication. Until then, you can get some idea of where we’re going by reading Liz’s excellent article here.”

Naish reports, “Incidentally, the phylogenetic hypothesis that we initially favoured for Vectidraco – that it’s an azhdarchoid, allied in some way to tapejarids – has been supported by other workers (though the relevant conclusions are unpublished, I think). Many provincial fossil taxa named on the basis of scrappy remains are nice additions to our understanding of distribution and diversity but all too often have little to say about big picture stuff. At the moment I like to think that Vectidraco may well be different – it’s already proving quite instrumental as goes several unconnected research strands.” [We looked at Vectidraco earlier here. BTW – Tapejarids are not related to azhdarchids, according to the large pterosaur tree, but share one trait, an elevated antorbital fenestra, which has caused most of the confusion.]

Naish reports, “What about the best azhdarchoids, and best pterosaurs of all… the azhdarchids? James Brown had a really neat poster on the neurovascular anatomy of azhdarchid jaws from Morocco (probably referable to Alanqa). The relevant details are most comparable to those of cranes.” [hmm, wading cranes, not stalking hornbills, as some workers surmise, but wait… there’s more >>>]

Naish reports,  “the new bits of data that come in on azhdarchids are consistent with the Witton & Naish (2008) terrestrial stalking model. Not with aerial scoop-netting (see Witton & Naish 2015), or sediment-probing, or skim-feeding, or obligate scavenging, or aerial predation, or heron-like wading. My own talk was on where we are right now as goes the copious new azhdarchid material from the latest Cretaceous of Romania. It seems that azhdarchids were more variable in proportions, and perhaps ecology and behaviour, than thought before, with long-necked and (comparatively) short-necked taxa, and small and large taxa, living in sympatry (Vremir et al. 2013, 2015). There’s a bigger story here which I’ll cover once an in-press paper sees publication.” [Looking forward to seeing some short-necked azhdarchids, which I cannot imagine.]

Naish reports, “One of my personal highlights of the meeting was Mike Habib’s talk on plunge diving and surface foraging in Pteranodon and other pterosaurs. If you’ve been paying attention you might know that there’s been serious consideration for a while now that pteranodontids and other oceanic pterosaurs may well have been capable of plunging and even foraging beneath the surface (e.g., Bennett 1994, Witton 2013). Mike’s quantitative work on biomechanics shows that all of those ideas about pteranodontids being too light or too fragile or too wingy or whatever to perform in, on and under water are probably nonsense. The maths for water launching works out (Habib & Cunningham 2010) and the skeleton could easily withstand impact with water, more so if we postulate a subdermal air sac system like that in some plunge-diving seabirds (like gannets). There are, of course, energetic limits on water-launching, and these might have imposed a size constraint on marine pterosaurs.” [We looked at plunge diving in Germanodactylus earlier here.]

 

 

Pterodactyls Alive! 1984 BBC video with David Attenborough on YouTube

Pterodactyls Alive! on YouTube click here

It’s more than 30 years old.
It’s not HD. It still supports the notion of a inverted hanging pterosaur. It precedes the discovery of eggs. Even so, it features a gliding Pteranodon model, lots of great sea bird scenes (including diving pelicans, soaring, dipping frigate birds and skimming skimmers) along with several great bat scenes (including grounded bats taking off).

And Mr. Attenborough was just starting to get gray hair back then.  :  )

The video also stars a bipedal animated Dimorphodon following the then recent release of Padian’s early work on that pterosaur.

 

Barberenasuchus… now the basalmost phytodinosaur

Updated Feb 8, 2016 with a new nesting for this taxon, away from Herrerasaurus and towards a newly added taxon, Eodromaeus.

According to Wikipedia
“Barberenasuchus brasiliensis (Mattar 1987; Fig. 1) is an extinct genus of an archosauriform. Fossils (poorly preserved skull and axis vertebra) have been found from the Santa Maria Formation of southern Brazil of Late Triassic age. Its phylogenetic position within Archosauriformes is uncertain; the author of its description classified it as a sphenosuchid crocodylomorph, while Kischlat (2000) considered it to be a rauisuchian. Irmis, Nesbitt and Sues (2013) stated that they “could not find any crocodylomorph character states preserved in the holotype specimen”. Based on the presence of an antorbital fenestra the [latter] authors assigned Barberenasuchus to Archosauriformes, but stated that without further preparation and study it is not possible to assign it to any specific archosauriform group.”

Figure 1. Barberenasuchus, the only data I was able to find, a small image in Riff et al. 2012.

Figure 1. Barberenasuchus, the only data I was able to find, a small image in Riff et al. 2012.

In phylogenetic analysis
the line drawing (from Riff et al. 2012)  nests Barberenasuchus with the protodinosaurs Junggarsuchus, Pseudhesperosuchus and Carnufex in the large reptile tree. Tradtiional paleontologists consider these sphenosuchid basal crocs. So did Riff et al.

It’s pretty obvious at first glance, isn’t it? The odd sort of postorbital that rises in a dorsal arc lateral to a crested parietal is a dead giveaway for this clade. No other reptiles have it. Compare this drawing of Barberenasuchus to Pseudhesperosuchus here.

Unfortunately, 
the line drawing does not do justice to a jpeg of the fossil itself (Fig.2, courtesy of D. Riff). That ‘odd sort of’ postorbital turns out to be not so odd. There is no parietal crest.

Figure 1. Barberenasuchus traced using DGS color over the bones, then transferred and shifted to recreate the in vivo skull in two views. Click to enlarge. Note the parietal does not produce a crust, but is flat. The maxilla ventral rim is convex. The postorbital does not have an acute curve, but standard  right angle shape. Both the lacrimal and postorbital were split longitudinally during taphonomy. All of the bones are cracked, making sutures hard to distinguish. This specimen is a sister to Herrerasaurus in the large reptile tree, based on this skull material, but note the lack of a lateral flange of the nasal.

Figure 1. Barberenasuchus traced using DGS color over the bones, then transferred and shifted to recreate the in vivo skull in two views. Click to enlarge. Note the parietal does not produce a crust, but is flat. The maxilla ventral rim is convex. The postorbital does not have an acute curve, but standard  right angle shape. Both the lacrimal and postorbital were split longitudinally during taphonomy. All of the bones are cracked, making sutures hard to distinguish. This specimen is a sister to Herrerasaurus in the large reptile tree, based on this skull material, but note the lack of a lateral flange of the nasal.

Distinct from most of its sisters (Fig. 3) Barberenasuchus has shorter teeth and a larger orbit. The skull is more gracile, and smaller in size. The rostral tip is not reinforced with laminated bone layers, as in Herrerasaurus or a lateral flange of the nasal, as in other basal dinosaurs, so Barberenasuchus is more plesiomorphic and therefore closer to the basalmost dinosaur. By contrast, look at the nasal of Eoraptor (Fig. 3) and Tawa which compares closely to that of Herrerasaurus. So the Barberenasuchus nasal is similar to that of the protodinosaurs while Herrerasaurus is similar to other dinosaurs.

Shifting Barberenasuchus to proximal nodes adds only 3 steps.

Figure 3. Barberenasuchus to scale with sister taxa, Herrerasaurus, Eoraptor, Lewisuchus and Trialestes and Junggarsuchus, but without the autapomorphies of its sister Herrerasaurus. At present Barberenasuchus is the basalmost dinosaur. Note the difference in the nasal between the dinosaurs and protodinosaurs.

Figure 3. Barberenasuchus to scale with sister taxa, Herrerasaurus, Eoraptor, Lewisuchus and Trialestes and Junggarsuchus, but without the autapomorphies of its sister Herrerasaurus. At present Barberenasuchus is the basalmost dinosaur. Note the difference in the nasal between the dinosaurs and protodinosaurs.

Bottom line:
Barberenasuchus does not look like any true crocodylomorph (agreeing with Irmis, Nesbitt and Sues, i.e. no anterior leaning quadrate/quadratojugal contacting the postorbital) because it is a basal dinosaur, a small (juvenile?) sister to Herrerasaurus. Barberenasuchus does not have a nasal that extends to the base of the naris, distinct from all other dinosaurs and similar to the protodinosaurs, like Junggarsuchus.

Figure 2. The Dinosauria subset of the large reptile tree as of February 5, 2016. Here Proceratosaurus nests with several former long-snouted tyrannosaurs now closer to spinosaurs and allosaurs.

Figure 3. The Dinosauria subset of the large reptile tree as of February 5, 2016. Here Proceratosaurus nests with several former long-snouted tyrannosaurs now closer to spinosaurs and allosaurs.

Too bad
this taxon was not known here when building my ‘Origin of Dinosaurs’ video. It would have been a featured taxon.

References
deFranca MAG, Bittencourt JdS and Langer MC 2013.
Reavaliação taxonomica de Barberenasuchus brasiliensis (Archosauriformes), Ladiniado do Rio Grande do Sul (Zona-Assembleia de Dinodontosaurus). Palaenotogia em Destaque Edição Especial Octubro 2013: 230. 
Irmis RB, Nesbitt SJ and Sues H-D 2013. Early Crocodylomorpha. Pp. 275–302 in Nesbitt, Desojo and Irmis (eds). Anatomy, phylogeny and palaeobiology of early archosaurs and their kin. The Geological Society of London. doi:10.1144/SP379.24.
Kischlat EE 2000.
Tecodôncios: a aurora dos arcossáurios no Triássico. Pp. 273–316 in Holz and De Ros (eds.). Paleontologia do Rio Grande do Sul. Porto Alegre: CIGO/UFRGS.
Mattar LCB 1987. Descrição osteólogica do crânio e segunda vértebrata cervical de Barberenasuchus brasiliensis Mattar, 1987 (Reptilia, Thecodontia) do Mesotriássico do Rio Grande do Sul, Brasil. Anais, Academia Brasileira de Ciências, 61: 319–333.
Riff D et al. 2012.  Crocodilomorfos: a maior diversidade de répteis fósseis do Brasil. TERRÆ 9: 12-40, 2012.

Desmatochelys and Santanachelys: the oldest known sea turtles

Santanachelys gaffneyi (Hirayama 1998, Early Cretaceous, 110 mya, 20 cm long, carapace: 14.5 cm, Fig. 1) was once considered the oldest sea turtle, Note the small flippers. The skull is specialized in the manner of later chelonioids, with large interorbital foramina that are indicative of huge lachrymal salt glands surrounding the eyes.

Figure 1. Santanachelys the oldest known sea turtle and Thalassochelys, the living loggerhead turtle. Note the scale bars. Santanachelys is really small.

Figure 1. Santanachelys the oldest known sea turtle and Thalassochelys, the living loggerhead turtle. Note the scale bars. Santanachelys is really small. Interesting that the radiale is missing in Santanachelys, but note its presence in Thalassochelys (or is that another bone?), only not in contact with the radius.

Thalassochelys caretta (Loggerhead turtle) is a living sea turtle. The flippers (hands) are much larger in this much larger extant sea turtle.

You might wonder if the Santanachelys holotype is a hatchling.
You might be right because in 10 million years older sediments we find Desmatochelys padillai (Cadena and Parham 2015, Fig. 2). and it is bigger than some living sea turtles. So we’re not yet seeing any phylogenetic miniaturization at the base of this clade. We may never.

Figure 2. Desmatochelys padillai at 120 mya, the oldest known sea turtle.

Figure 2. Desmatochelys padillai at 120 mya, now the oldest known sea turtle. Not much plastron is preserved here, just a few patches.

Desmatochelys has larger forelimb paddles than Santanachelys and a more open carapace and plastron architecture. So, given the extra bone in the shell and smaller paddles,. Santanachelys may be more primitive, despite its later appearance in the fossil record.

The minimally invasive posterior margin of the skull indicates that sea turtles split from other turtles at an early stage in turtle evolution.


References
Cadena EA and Parham JF 2015. Oldest Known Marine Turtle? A New protostegid from the Lower Cretaceous of Colombia. PaleoBios. 32(1).
Hirayama R 1998. Oldest known sea turtle. Nature 392 (6677): 705–708.

Maybe Araeoscelis DOES have a lateral temporal fenestra

Among basal diapsids,
Araeoscelis (Fig. 1, Williston 1910) has been the traditional outlier, closing up its lateral temporal fenestra shortly after gaining its upper temporal fenestra. Taking another look at the published drawings and moving the bones around a little, exposes a tiny lateral fenestra (Fig. 1). This is not traditional thinking, but also removes an odd autapomorphy.

Short reminder:
Araeoscelis is one sort of diapsid, the sort that ultimately led to dinos and birds. This entire clade is convergent with the diapsid configuration that developed in lepidosaurs according to the large reptile tree.

Figure 1. Araeoscelis fossi skull drawings from Reiz et al. 1984. Reconstructed in the middle.

Figure 1. Araeoscelis fossi skull drawings from Reiz et al. 1984. Reconstructed in the middle.

It’s worthwhile here to bring up Petrolacosaurus (Fig. 2) for comparison.

Figure 2. Petrolacosaurus is an earlier sister to Araeoscelis with a definite diapsid temporal configuration, but oddly the upper temporal fenestra is largely lateral in this taxon.

Figure 2. Petrolacosaurus is an earlier sister to Araeoscelis with a definite diapsid temporal configuration, but oddly the upper temporal fenestra is largely lateral in this taxon. The parietals are quite broad.

Note
in Petrolacosaurus the upper temporal fenestra is high on the lateral side of the skull and the jaw joint is in line with the jaw line, distinct from Araeoscelis. The new data shifts nothing in the large reptile tree.

IMHO,
the reduction of the lateral temporal fenestra in Araeoscelis.has something to do with the decent of the jaw joint and the blunting/thickening of the teeth. It was eating something that was tougher or crunchier than Petrolacosaurus preferred.

Araeoscelis is a terminal taxon, leaving no known descendant taxa.

References
Reisz RR, Berman DS and Scott D 1984. The anatomy and relationships of the lower Permian reptile Araeoscelis. Journal of Vertebrate Paleontology 4: 57-67.
Vaughn PP 1955. The Permian reptile Araeoscelis re-studied. Harvard Museum of Comparative Zoology, Bulletin 113:305-467.
Williston SW 1910. New Permian reptiles; rhachitomous vertebrae. Journal of Geology 18:585-600.
Williston SW 1913. The skulls of Araeoscelis and Casea, Permian reptiles. Journal of Geology 21:743-747.
wiki/Araeoscelis

Origin of Dinosaurs and Birds Video on YouTube

I just uploaded a dinosaur origins video
on YouTube. Click here to view it.

Click to view Origin of Dinosaurs and Birds video.

Click to view Origin of Dinosaurs and Birds video now on YouTube.

Figure 2. The origin of dinosaurs to scale. Gray arrows show the direction of evolution. This image includes Decuriasuchus, Turfanosuchus, Gracilisuchus, Lewisuchus, Pseudhesperosuchus, Trialestes, Herrerasaurus, Tawa and Eoraptor.

Figure 2. The origin of dinosaurs to scale. Gray arrows show the direction of evolution. This image includes Decuriasuchus, Turfanosuchus, Gracilisuchus, Lewisuchus, Pseudhesperosuchus, Trialestes, Herrerasaurus, Tawa and Eoraptor.

Is this the new face of Tawa the basal theropod dinosaur?

Readers have wondered why I did not include the missing maxillary extensions on Tawa. Here I provide them while continuing to use the bone photo in a reconstruction that still differs from the freehand sketch we’ve all come to know, Sept. 15, 2015.

Figure 1. Tawa skull reconstructed using assembled images of the bones rather than a freehand attempt. Guys, Photoshop is our friend, not something to be avoided.

Figure 1. Tawa skull reconstructed using assembled images of the bones rather than a freehand attempt. Guys, Photoshop is our friend, not something to be avoided. Note the bad fit of the the prefrontal on the lacrimal in the longer restoration. 

Since its publication
a freehand reconstruction of the skull of Tawa (Nesbitt et al. 2009; Theropoda, Dinosauria, Fig. 1) has been our only guide to its in vivo morphology.

However,
if you put the published bone images together, you get a slightly different face (Fig. 1), whether you add the maxillary and mandible extensions or not, and that affects its scoring on phylogenetic matrices. The new reconstruction also does away with the need for those maxillary extensions. The mandible, if correctly restored, helps confirm the new shorter skull length.

Like Herrerasaurus
a sister to Tawa, the lacrimal and quadrate lean anteriorly, the maxilla (part of the jugal block) extends to mid orbit and the squamosal descending process is more robust than originally reconstructed. If valid, this is one more case (of several hundred) of not needing to see the actual fossil firsthand in order to make a contribution to paleontology.

So, this reminds me of joke…
Tawa walks into a bar. Bartender says, “Hey, why the long face?”

References
Nesbitt SJ, Smith ND, Irmis RB, Turner AH,Downs A and Norell, MA 2009. A complete skeleton of a Late Triassic saurischian and the early evolution of dinosaurs”, Science 326 (5959):1530–1533,

wiki/Tawa

Microleter mckinzieorum Tsuji et al., 2010

Microleter (Fig. 1) was described a few years ago (Tsuji et al. 2010) as an Early Permian parareptile (an invalid multiphyletic assembly of early reptiles). Tsuji et al. nested Microleter between millerettids and Acleistorhinus + Lanthanosuchus (another unnatural assembly).

Figure 1. Microleter in situ and reconstructed with a larger lateral temporal fenestra than originally reconstructed. The skull is 3 cm long. That's a pair of fused vomers and a left pterygoid (dorsal view) at lower right. Freehand original reconstruction by Tsuji et al. 2010 at upper left.

Figure 1. Microleter in situ and reconstructed with a larger lateral temporal fenestra than originally reconstructed. The skull is 3 cm long. That’s a pair of fused vomers and a left pterygoid (dorsal view) at lower right. Freehand original reconstruction by Tsuji et al. 2010 at upper left. Note the expansion of the quadratojugal/squamosal in the freehand drawing compared to the in situ tracing. Note the reduction of the postorbital in the freehand drawing. Note the absence of the splenial in the freehand drawing.

Character analysis
Tsuji et al. used the matrix of Modesto et al. (2009) which was based on Mülller and Tsuki (2007) consisting of 30 taxa and 137 characters. Both numbers are too small. The analysis recovered six trees in which Microleter nested in an unresolved polygamy with Australothyris and Acleistorhinus  + Lanthanosuchus at the base of the ‘ankyramorphan parareptiles’ (another unnatural assembly).

The large reptile tree (575 taxa, completely resolved) found Microleter nested between Delorhynchus and Eunotosaurus + Acleistorhinus. The clade Australothyris + Feeserpeton is the proximal outgroup. The caseasaurs and millerettids are more distant.

Figure 2. The nesting of Microleter with Delorhynchus, Acleistorhinus and Eunotosaurus.

Figure 2. The nesting of Microleter with Delorhynchus, Acleistorhinus and Eunotosaurus.

With insight Tsuji et al report, “As it is becoming increasingly clear, temporal fenestration is actually a common phenomenon among parareptiles, quite a departure for a group once termed Anapsida.”

Oddly,
Tsuji et al. include mesosaurs in their parareptilia and do not give them temporal fenestra. Oddly Tsuji et al nest Procolophon with Owenetta. Oddly they nest Eudibamus with Belebey. Oddly Tsuji et al nest Acleistorhinus with Lanthanosuchus, but not Eunotosaurus.They think the anapsid condition re-evolved in pareiasaurs. That’s not true. The ‘parareptile’ pseudoclade is a mess. It’s time for a thorough cleaning with more taxa.

Notably
the pterygoids produced a circular opening between them, as in Eunotosaurus, but not so exaggerated. Acleistorhinus does not have this trait. Here (Fig. 1), based on self-evident transfer techniques, the lateral temporal fenestra is reconstructed larger than Tsuji et al. drew it freehand. The lacrimal may not have contacted the naris according to the reconstruction where the maxilla contacts the nasal.

References
Linda A. Tsuji; Johannes Muller; Robert R. Reisz (2010). Microleter mckinzieorum gen. et sp. nov. from the Lower Permian of Oklahoma: the basalmost parareptile from Laurasia”Journal of Systematic Palaeontology 8 (2): 245–255.

BPI 2871 has a new sister: Elachistosuchus huenei

Earlier we looked at a tiny basal choristodere, BPI 2871, which was derived from a line of much larger proterosuchids, according to the large reptile tree.

Recently a new PlosOne online paper (Sobral et al. 2015) reintroduces Elachistosuchus huenei (Janensch 1949, Late Triassicm, Norian, Germany; MB.R. 4520 (Museum für Naturkunde Berlin, Berlin, Germany)) with CT scans.

Figure 1. Elachistosuchus (Janensch 1949, Sobral et al. 2015) is a sister to BPI 2871, a basal choristodere.

Figure 1. Elachistosuchus (Janensch 1949, Sobral et al. 2015) is a sister to BPI 2871, a basal choristodere, has been misidentified for over fifty years.The left upper temporal fenestra has been largely closed by crushing here. Like BPI 2871, the nares were located on top of the skull, close to the snout tip. Note the vestige of the antorbital fenestra.

And they don’t know what it is. 
According to Sobral et al, Elachistosuchus could be “an archosauromorph, a lepidosauromorph or a more basal, non-saurian diapsid.” That confusion arises from using outdated matrices with too few generic taxa and too many suprageneric taxa.

Sobral et al. used the matrix from Chen et al. 2014, which nested Elachistosuchus in a polygamy with Choristodera, Prolacerta + Tanystropheus + Macrocnemus, and Trilophosaurus + Rhynchosauria + Archosauriformes. As readers know the large reptile tree found many of these taxa on opposite sides of the reptile cladogram.

Sobral et al. also used the matrix from Ezcurra et al. 2014, which nested Elachistosuchus with the gliding Permian lepidosauriform, Coelurosauravus.

Hmmmm…

Sobral et al. report: 
“These different placements highlight the need of a thorough revision of critical taxa and new character sets used for inferring neodiapsid relationships.” 

Exactly. 
That’s why large reptile tree and reptileevolution.com are here. It’s good to have hundreds of specimen-based taxa for new taxa to nest with. More choice. More accuracy. Complete resolution.

To their credit,
a Sobral et al. analysis nested Elachistosuchus with choristoderes.

Figure 2. Dorsal, lateral and palatal views of BPI 2871 with bones colorized above. Below, reconstructed images of BPI 2871 tracings. It is more complete than illustrated by Gow 1975. Click to enlarge. Note the tiny remnant of the antorbital fenestra. The squamosal has been broken into several parts.

Figure 2. Dorsal, lateral and palatal views of BPI 2871 with bones colorized above. Below, reconstructed images of BPI 2871 tracings. It is more complete than illustrated by Gow 1975. Click to enlarge. Note the tiny remnant of the antorbital fenestra. The squamosal has been broken into several parts. This is a sister to Elachistosuchus.

Among earlier workers
Janensch (1949) considered Elachistosuchus a pseudosuchian archosaur with an antorbital fenestra. Walker (1966 ) considered  Elachistosuchus a rhynchocephalian lepidosaur.

The large reptile tree (now 575 taxa)
finds Elachistosuchus nests firmly as a sister to the BPI 2871 specimen (Fig. 3) that Gow mistakenly attributed to Youngina, but it nests far from Youngina at the base of the large and small choristoderes. And these two taxa are both derived from much larger proterosuchids in yet another case of phylogenetic miniaturization at the genesis of a new clade, in this case the Choristodera.

Elachistosuchus has a larger orbit and a maxilla with a straight, not convex, ventral margin of the maxilla than the BPI 2871 specimen. The former extends the geographic range of the latter, from southern Africa to Germany.

Both probably look like juvenile proterosuchids (whenever they are discovered, we can compare them). Phylogenetic miniaturization often takes juvenile traits and sizes and makes them adult traits and sizes to start new clades.

Janensch thought Elachistosuchus had an antorbital fenestra. As in BPI 2871, that is the vestige of the antorbital fenestra found in ancestors and lost in descendants.

Contra the title of the Sobral et al. paper
Elachistosuchus huenei has nothing to do with the origin of ‘Sauria.’

Sauria definition: “.Any of various vertebrates of the group Sauria, which includes most of the diapsids, such as the dinosaurs, lizards, snakes, crocodilians, and birds. Sauria was formerly a suborder consisting ofthe lizards” Rather, Elachistosuchus is a basal choristodere and a derived proterosuchid according to the large reptile tree. Based on the current definition of ‘Sauria’ ‘Sauria’ is synonymous with ‘Amniota’ which is a junior synonym for ‘Reptilia’ because the last common ancestor of lizards and dinosaurs is the basalmost reptile/amniote, Gephyrostegus bohemicus.

The reason why Sobral et al. were confused
with regard to their blurred nesting of Elachistosuchus is due to taxon exclusion. BPI 2871 is a rarely studied taxon and was not included in their analyses. Moreover, traditional paleontologists are not sure what choristoderes are. They don’t recognize them as being derived proterosuchids. And to make matters worse, traditional paleontologists prefer to think of Proterosuchus specimens as members of an ontogenetic series, when they should consider them as a phylogenetic series.

Figure 4. This is where Elachistosuchus nests, next to BPI 2871, at the base of the Choristodera.

Figure 3. This is where Elachistosuchus nests, next to BPI 2871, at the base of the Choristodera. Click to see the complete reptile cladogram.

The large reptile tree (Fig. 3) has proven itself time and again to solve paleontological problems in the reptile family tree. It is unfortunate that it has been rejected for publication so many times. If published, it can be use.

A MacClade file is available on request.

References
Chen X, Motani R, Cheng L, Jiang D, Rieppel O. 2014. The enigmatic marine reptile Nanchangosaurus from the Lower Triassic of Hubei, China and the phylogenetic affinities of Hupehsuchia. PLoS ONE. 2014; 9: e102361. doi: 10.1371/journal.pone.0102361 PMID: 25014493
Ezcurra MD, Scheyer TM, Butler RJ 2014. The origin and early evolution of Sauria: reassessing the Permian saurian fossil record and the timing of the crocodile-lizard divergence. PLoS ONE. 2014; 9: e89165. doi: 10.1371/journal.pone.0089165 PMID: 24586565
Gow CE 1975. The morphology and relationships of Youngina capensis Broom and Prolacerta broomi Parrington. Palaeontologia Africana, 18:89-131.
Janensch W 1949. Ein neues Reptil aus dem Keuper von Halberstadt. N Jb Mineral Geol Palaeont B. 1949:225–242.
Sobral G, Sues H-D & Müller J 2015. Anatomy of the Enigmatic Reptile Elachistosuchus huenei Janensch, 1949 (Reptilia: Diapsida) from the Upper Triassic of Germany and Its Relevance for the Origin of Sauria. PLoS ONE 10(9): e0135114. doi:10.1371/journal.pone.0135114
http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0135114
Walker AD 1966. Elachistosuchus, a Triassic rhynchocephalian from Germany. Nature. 1966; 211: 583–585.

wiki/Elachistosuchus