‘Armored’ Peltobatrachus enters the LRT

Panchen 1959
reported on a 70cm armored basal tetrapod from the Late Permian of Tanzania. Traditionally considered a temnospondyl, Peltobatrachus (Fig. 1) inspired the addition of several basal tetrapod taxa, including taxa that defined the Temnospondyli (see below).

Figure 1. Armored Peltobatrachus. 

Figure 1. Armored Peltobatrachus.

No teeth or distal limb elements are preserved.
Peltobatrachus is atypical in having wider ribs along their entire length. Related taxa, like Eryops and Sclerocephalus, have only the distal portion of their ribs (intercostal plates) expanded to overlap succeeding ribs.

Intercostal plates disappear in most tetrapods,
but make a reappearance (reversal) in the derived cynodont, Thrinaxodon.

Schoch (2013)  defined the clade Temnospondyli 
as the least inclusive clade of Edops and Mastodonsaurus. In the large reptile tree (LRT, 1423 taxa), Edops and Mastodonsaurus nest in two adjoining sister clades, the latter in the larger specimen clade of the Lepospondyli, distinct from the  smaller specimen clade that includes extant frogs and salamanders.


References
Panchen AL 1959. A new armoured amphibian from the Upper Permian of East Africa. Philosophical Transactions of the Royal Society of London B 242:207-281.

wiki/Peltobatrachus

Tiny flightless Early Cretaceous bird from Spain

Kaye et al. 2019
illuminated feathers with laser-stimulated fluorescence (Fig. 1) in a tiny, unnamed, enantiornithine bird specimen, MPCM-LH-26189 from the Las Hoyas locality (Barreminian, Early Cretaceous) of Spain. Based on the presence of those illuminated feathers and the size of the specimen (Fig. 2) the authors judged it to be a precocial hatchling, capable of walking shortly after hatching. This is the same specimen first described and not named by Knoll et al. 2018.

Figure 1. Specimen MPCM-LH-26189 a tiny enantiornithine bird in situ under white light (above, plate and counter plate) and under laser stimulated fluorescene (below). DGS colors added and used in the reconstruction in figure 2. Not sure what those red highlighted items are at lower right. See figure 2b for skull details. 

Figure 1. Specimen MPCM-LH-26189 a tiny enantiornithine bird in situ under white light (above, plate and counter plate) and under laser stimulated fluorescene (below). DGS colors added and used in the reconstruction in figure 2. Not sure what those red highlighted items are at lower right. See figure 2b for skull details.

A reconstruction of the new extra-tiny bird
is shown (Fig. 2) alongside that of another tiny coeval and closely related enantiornithine bird, Iberomesornis, to scale. Note the tiny fingers in the tiny MPCM specimen indicating flightlessness. The lower crus, distal tail and feet extend off the matrix block, so they remain unknown. Contra Kaye et al. 2019, the tiny MPCM specimen does not appear to have juvenile proportions, despite its reduced size.

Figure 2. Tiny Iberomesornis compared to scale with even tinier MPCM specimen. Note the tiny fingers. Two tibial lengths are presented since this data remains unknown. The tiny MPCM specimen does not appear to have juvenile proportions.

Figure 2. Tiny Iberomesornis compared to scale with even tinier MPCM specimen. Note the tiny fingers. Two tibial lengths are presented since this data remains unknown. The tiny MPCM specimen does not appear to have juvenile proportions.

Figure 2b. Skull of MPCM specimen traced using DGS methods and reconstructed using the resulting color parts.

Figure 2b. Skull of MPCM specimen traced using DGS methods and reconstructed using the resulting color parts.

It is always a good idea
to create a reconstruction (Fig. 2) from ‘road-kill’ taxa (Fig. 1). Such a reconstruction would have indicated the MPCM specimen did not have juvenile proportions, despite its small size… and it did not have traditional bird wings.

It is also a good idea to compare taxa
in a phylogenetic analysis to see how what you have relates to others of its kind. Here in the large reptile tree (LRT, 1423 taxa) the MPCM specimen nests close to Iberomesornis within the clade Enantiornithes.

Reversals
The MPCM specimen is the first enantiornithine to have short un-birdlike fingers (a reversal due to neotony) and such short forelimbs (another reversal).

If the tail lacked a pygostyle, as it currently appears, that would also be a reversal shared with long-tailed descendants, Pengornis and Protopteryx.

The small size of this possible adult specimen is also due to the same forces that led to tiny Iberomesornis in Early Cretaceous Spain. If the MPCM specimen had nested with much larger specimens, rather than tiny Protopteryx and Iberomesornis, then the MPCM specimen would more likely have been considered a juvenile.

Knoll et al. 2018 first studied the MPCM specimen
or its osteological correlates with other juvenile birds, not considering the possibility that phylogenetic miniaturization might make a tiny adult bird appear to be a juvenile. Perhaps that is why they concluded, “the hatchlings of these phylogenetically basal birds varied greatly in size and tempo of skeletal maturation.” Knoll et al. did not create a reconstruction nor put this specimen under phylogenetic analysis, probably on the basis of its presumed juvenile character. As your mother told you, if you assume something, you might miss out on its most intriguing aspects.

Phylogenetic analysis is so important
because it reveals so much more than just ‘eyeballing’ specimens.

Earlier we looked at other birds
that experienced a similar reversal from wings to hands. Among these are Mei long, Jinianhualong and Liaoningvenator.

In the Late Jurassic
tiny pterosaurs experienced a similar size squeeze. Traditionally considered juveniles, tiny hummingbird-sized taxa like B St 1967 I 276 (Fig. 3) and BMNH 42736 with fly-sized hatchlings, were among the few pterosaur lineages to survive the Jurassic and produce Cretaceous taxa.

From NatGeo.com
Paleo bird expert, Jingmai O’Connor reports, “All enantiornithines were super-precocial, born fully-fledged and ready to fly.”

A closer examination
indicates the MPCM specimen was never going to be ‘ready to fly.’ 

Figure 2. Smallest known bird, Bee hummingbird, compared to smallest known adult pterosaur, No. 6 (Wellnhofer 1970). Traditional workers consider this a hatchling or juvenile, but in phylogenetic analysis it does not nest with any 8x larger adults.

Figure 3. Smallest known bird, the bee hummingbird, compared to smallest known adult pterosaur, No. 6 (Wellnhofer 1970). Traditional workers consider this a hatchling or juvenile, but in phylogenetic analysis it does not nest with any 8x larger adults.

Is the MPCM specimen the smallest dinosaur?
If it is an adult, the MPCM specimen appears to be slightly larger than the smallest known dinosaur, the bee hummingbird (Fig. 3).

Since no one else wants to name the MPCM specimen,
probably because others considered this a hatchling rather than a phylogenetically miniaturized adult, let’s call him Microcursor sanspedes (‘tiny runner without feet”) in the meantime.


References
Kaye TG, Pittman M, Marugán-Lobón J, Martín-Abad H, Sanz JL and Buscalioni AD 2019. Fully fledged enantiornithine hatchling revealed by Laser-Stimulated Fluorescence supports precocial nesting behavior. Nature.com/scientific reports (2019) 9:5006 https://doi.org/10.1038/s41598-019-41423-7

Knoll, F. et al. (16 co-authors) 2018. A diminutive perinate European Enantiornithes reveals an asynchronous ossification pattern in early birds. Nature Communications 9, 937 (2018).

Publicity

https://www.nationalgeographic.com/science/2019/03/dinosaur-era-birds-born-ready-to-run-fossil-feathers-show/

Sachicasaurus: the first giant nothosaur, not a pliosaur

Páramo-Fonseca, Benavides-Cabra and Gutiérrez 2018
described Sachicasaurus (Figs. 1-3, MP111209-1, Barremian (Early Cretaceous) Columbia; estimated 10m in length, 2m skull length), a taxon they thought was a giant pliosaur related to Brauchauchenius (Fig. 2).

Unfortunately
the authors did not consider comparing their discovery to Nothosaurus. The short flippers are the first clue that perhaps they should have done so. Misidentifying several bones was a problem. The large reptile tree (LRT, 1420 taxa) tests each new taxon against all prior taxa, thereby largely avoiding the paleo-sin of taxon exclusion.

Figure 1. Sachicasaurus skull from Páramo-Fonseca et al. 2018, colors added.

Figure 1. Sachicasaurus skull from Páramo-Fonseca et al. 2018, colors added. Some skull bones restored in color. Note the differences in the preorbital region of the skull between the original interpretation drawing and the DGS color applied to the skull photo.

Sachicasaurus vitae (Páramo-Fonseca, Benavides-Cabra and Gutiérrez 2018, 10m in length) was originally considered a short-flippered pliosaur related to long-flippered Brachauchenius characterized by two autopomorphic characters: a very short mandibular symphysis ending at the mid length of the fourth mandibular alveoli and reduced number of mandibular teeth (17-18). Here this giant nests with Nothosaurus (above). Originially several bones were misidentified. The ilium is uniquely bifurcated with a dorsal and posterior process. In dorsal view the mandibles are convex while the maxillae are concave, leaving quite a gap between them.

Figure 2. Sachicasaurus was the size of the pliosaurs, Kronosaurus and Brauchenia, but was related to Nothosaurus. This is the first known giant nothosaur.

Figure 2. Sachicasaurus was the size of the pliosaurs, Kronosaurus and Brauchenia, but was related to Nothosaurus. This is the first known giant nothosaur.

Several bones were originally misidentified.
The former left ‘scapula’ is really the clavicle. The former right ‘scapula’ is really the coracoid. The former sock-shaped ‘radius’ is the tiny scapula.

Figure 3. Sachisaurus pectoral girdle and flippers reconstructed with new identities provided here.

Figure 3. Sachisaurus pectoral girdle and flippers reconstructed with new identities provided here. Pectoral elements are digitally duplicate and flipped left to right.

Real plesiosaurs have long flippers
with more than the usual number of phalanges per digit. By contrast, Sachicasaurus does not have long flippers and It has the plesiomorphic number of phalanges. Yes, the skull is huge and the neck is short. In the LRT those pliosaur-like traits are not enough to attract Sachicasaurus toward the pliosaurs. Note the different interpretations of the skull bones presented here (Fig. 1). The nasals, in particular, are nothosaurian, not pliosaurian.

Figure 4. Data for Nothosaurus for comparison with Sachicasaurus. The interclavicle could easily be lost.

Figure 4. Data for Nothosaurus for comparison with Sachicasaurus. The interclavicle could easily be lost. Note the plesiomorphic number of phalanges on both the manus and pes. Compare these to those in figure 3.

From the same Early Cretaceous formation
three real pliosaurs have been discovered. This would have been the fourth one, except it’s a nothosaur with pliosaur size and proportions by convergence. Earlier we looked at a similar convergence between toothed whales and baleen whales.

Figure 5. Subset of the LRT focusing on the Eusauropterygia, including Sachicasaurus.

Figure 5. Subset of the LRT focusing on the Eusauropterygia, including Sachicasaurus.


References
Páramo-Fonseca ME, Benavides-Cabra CD and Gutiérrez IE 2018. A new large Pliosaurid from the Barremian (Lower Cretaceous) of Sáchica, Boyacá, Colombia. Earth Sciences Research Journal 220(4):223-238. eISSN 2339-3459. Print ISSN 1794-6190.

wiki/Sauropterygia
wiki/Sachicasaurus

Ichthyostega: Becoming more fish-like, not less… part 3

Long hailed as a transitional taxon
linking lobe-fin fish to tetrapods with fingers and toes, Ichthyostega (Fig. 1) nests in the large reptile tree (LRT, 1419 taxa) phylogenetically after the appearance of limbs with fingers and toes.

Ichthyostega has a neck,
a derived trait not found in fish — despite flattened hind limbs incapable of supporting weight and better suited to paddling. In the LRT the tibia and fibula are not only atypical in Ichthyostega, but derived relative to the more traditional crus of more primitive taxa (see below).

Plus
Ichthyostega had a sacral ‘hump’ not seen in other basal tetrapods. What did it anchor? A dorsal fin? Mighty tail muscles? In dorsal view, Ichthyostega had the tapered shape of a speedy dolphin.

Figure 1. Ichthyostega after CT scanning (grey tones) here colored with light green 'skin' added and pectoral girdle pushed posteriorly to expose the neck.

Figure 1. Ichthyostega after CT scanning (grey tones) here colored with light green ‘skin’ added and pectoral girdle pushed posteriorly to expose the neck. Note the narrow interclavicle, short torso and giant pectoral girdle, distinct from most basal tetrapods and stem tetrapods.

Tradition dictates
the extra toes in Ichthyostega are primitive traits, transitional between lobe fins and the standard five toes per foot per tetrapod.

That hypothesis is falsified
by more primitive Pholidogaster and Greererpeton, which have no more than five toes. A similar-looking relative, Pederpes, also has five toes. A sister taxon in the LRT, Proterogyrinus, likewise has only five toes—and a traditional crus.

Figure 1. Subset of the LRT focusing on the basal (anamniote) Tetrapoda. The last week has been spent reexamining data and letting the taxa sort themselves out again. Please report any untenable relationships.

Figure 1. Subset of the LRT focusing on the basal (anamniote) Tetrapoda. Note the nesting of Ichthyostega after taxa with five toes and a typical hind limb.

So maybe the extra toes in Ichthyostega
are just that, extra toes that developed upon it’s return to the water, perhaps speeding through, rather than plodding along like a salamander.

So… contra tradition,
Ichthyostega is one of the first tetrapods to return to the water, perhaps having never left the water completely. We first examined this ‘secondarily more aquatic’ hypothesis earlier here and here.


References
Ahlberg PE, Clack JA and Blom H 2005. The axial skeleton of the Devonian trtrapod Ichthyostega. Nature 437(1): 137-140.
Jarvik E 1952. On the fish-like tail in the ichthyostegid stegocephalians. Meddelelser om Grønland 114: 1-90.
Jarvik E 1996. The Devonian tetrapod Ichthyostega. Fossils and Strata. 40:1-213.
Ruta M, Jeffery JE and Coates MI 2003. A supertree of early tetrapods. Proc. R. Soc. Lond. B (2003) 270, 2507–2516 DOI 10.1098/rspb.2003.2524 online pdf
Säve-Söderbergh G 1932. Preliminary notes on Devonian stegocephalians from East Greenland. Meddelelser øm Grönland 94: 1-211.

wiki/Ichthyostega

 

Revision to the LRT: basal tetrapods

Here’s a revision to the LRT
that is still being revised and studied (Fig. 1) following the addition of several taxa and two new characters.  I hope readers will report untenable relationships. Most of the taxa are still related to their prior sisters, but the order has changed here and there. It’s been interesting and enlightening going through this process.

Figure 1. Subset of the LRT focusing on the basal (anamniote) Tetrapoda. The last week has been spent reexamining data and letting the taxa sort themselves out again. Please report any untenable relationships.

Figure 1. Subset of the LRT focusing on the basal (anamniote) Tetrapoda. The last week has been spent reexamining data and letting the taxa sort themselves out again. Please report any untenable relationships.

A few novel nestings appear here.
As the days go by I will discuss and illustrate many of the interesting clades and sisters that were recovered here. For instance, earlier I reported Spathicephalus nesting with Tiktaalik.

Something that does not jump out immediately
is the genesis of tetrapods with fingers and toes deep enough into the Devonian to produce the highly derived near reptile with long digits, Tulerpeton, by the end of the Devonian, prior to the first appearance of nearly all tetrapod fossils with fingers and toes no sooner than the Early Carboniferous.

More reptile ancestors
Several more basal tetrapods are now in the direct lineage of the clade Reptilia. These formerly nested slightly elsewhere.

Middle Devonian tetrapod tracks
were reported earlier here. That trackmaker remains elusive. So the evidence for their presence is known, but the bones are not.

At ReptileEvolution.com
the web pages and their order will be updated this week. Currently the order does not reflect the tree topology shown above.

 

Why did humans evolve ever-growing cranial hair?

How humans evolved to have head / beard hair
“that continues to grow longer than other animals, while losing hair elsewhere, is a topic that many anthropologists & biologists are still not sure about and there is no general consensus as to “why” yet.”

The following hypotheses are copied from the online references below.
They do not represent my original thoughts or anything to do with the LRT. Academic citations follow and can be accessed via the reference links.

The three main views are:

1) Evolution of the “Aquatic Ape.” (Ingram, 2000: Morgan 1997; 1982)

  • Infants, in order to hold onto their mothers in the water, would latch onto her hair. Limiting separation from the mother & increasing chances of survivability
  • Longer hair meant that infants / small children would need to swim less in order to get to their mother
  • Believed to be supported even further when you consider that aquatic mammals are almost always hairless, indicating that at one point, humans were highly “aquatic” mammals.

2) No real benefit, but used as a tool for “mate selection.” (Darwin, 1871; Cooper 1971)

  • The view held by many of the Darwin school of thought is that at first, “hairiness” was sexually attractive, but eventually “hairlessness” became more sexually attractive in most places (i.e. the face to see facial expressions & socialize better; Wong & Simmons 2001)
  • A sign of “virility” & “health” as can be seen in the mate-selection behavior of lions. Which is true even today as human diagnostic material for health (Klevay, 1972).

3) Practical evolutionary benefits for the human species specifically

  • A lot of body heat escapes from the head, probably the most important part of your body. Hair is a good insulator that can keep in heat. This increases survivability in colder climates. (Wong & Simmons 2001; Bubenick 2003). (Disputed but considered credible reason, especially when you compare hair length and types across different regions throughout history)
  • Protection against damaging UV rays (while still permitting adequate Vitamin D3 to come through) & some protection from free-radicals or other harmful particles. Because we became bi-pedal, the head was the main area exposed to the sun (as well as some of our back). Extending hair’s usefulness to even hot environments, while other body hair became less important with the development of sweat glands (Wheeler 1985).
  • Heightened “Situational Awareness” through “Touch sense.” A concept that may seem silly at first but has some evidence to support the theory. Though the hair is not “alive,” it is connected to the follicles & your nerves. In a nutshell, it may help to increase “sensory awareness” & “data gathering” of your environment, which would favor longer hair. This would be an asset in survivability (Kardong 2002; keratin.com 2010; Sabah 1974)
  • Though not a collegiate journal article, if reasonably credible, this small article is an interesting case for supporting hair & “Touch sense” in “recent history” & in combat-survival : http://www.sott.net/article/234783-The-Truth-About-Hair-and-Why-Indians-Would-Keep-Their-Hair-Long.

Other thoughts…

“Evolution selected for intelligence – and for hair. The person who radically shapes his hair, exploiting its continuous growth to demonstrate his on-going Neanderthal chic, is more likely to attract partners than the person whose hair is dull, lifeless and matted.”

“Darwin, noting that every human society, however primitive, invariably paints, tattoos, pierces and otherwise decorates its bodies, argued that, in the remorseless competition for sexual partners, we humans, during the evolutionary past, shed our hair to create a canvas on which to flaunt our creativity, flair and beauty.”


In a tweet:
“The reason we (mostly) still have head hair is mostly because it serves as a sun-screen – and the reason we still have pubic hair is because it traps pheromones.”


On the other hand…
“Left alone, our hair produces a three-foot, smelly, matted, greasy, bug-infested mass that will snag on trees and provide predators with a claw-hold.”


Personally
I prefer this one: “diagnostic material for health (Klevay, 1972).” 


References

https://biology.stackexchange.com/questions/5676/why-does-human-facial-and-head-hair-continue-to-grow

https://www.quora.com/Why-have-humans-evolved-to-have-more-hair-on-their-head

https://www.telegraph.co.uk/comment/4263009/Why-does-the-hair-on-our-heads-keep-growing.html

Tiktaalik and Spathicephalus now united

Among short-snouted stem tetrapods
long-snouted Tiktaalik (Fig. 1) stood alone… so did long-snouted Spathicephalus (Fig. 2), previously nesting just a few nodes away. A reexamination of both revealed overlooked sutures in Tiktaalik that more or less matched those presented in a Spathicephalus diagram. Those traits were re-scored in the large reptile tree (LRT) and now the two loners nest together… along with little Koliops, which has big eyes and a small snout.

Figure 1. Revised skull sutures in Tiktaalik. Compare these to the sutures in Spathicephalus, figure 2.

Figure 1. Revised skull sutures in Tiktaalik. Compare these to the sutures in Spathicephalus, figure 2.

So phylogenetic bracketing indicates
Spathicephalus had fins, not feet. If the post-crania has been published, please let me know. Same for Koliops.

Considering the Late Devonian appearance of Tiktaalik,
Spathicephalus is what the ancestors of Tiktaalik evolved to become by the Late Carboniferous. Despite its traditional transitional status, Tiktaalik had already evolved traits not found in the main lineage that produced frogs, salamanders and reptiles. The branching point must have been much earlier, in the Mid-Devonian.

Figure 1. Spathicephalus, a filter feeding temnospondyl with elongate orbits now nests with Koilops.

Figure 2. Spathicephalus, a filter feeding stem tetrapod close to Tiktaalik, figure 1.

Tiktaalik roseae (Daeschler, Shubin and Jenkins 2006; Late Devonian, 375mya; 4-9 meters in length) nests between Pandericthys and Tetrapoda in the large reptile tree. Distinct from Pandericthys the opercular bones are absent, the orbits are further back and higher on the skull, ribs, a pelvis and large bones within the four digit-less finned limbs are present.

Spathicephalus mirus (Watson 1926; Late Carboniferous, 320 mya) was described, “unlike that of any other early tetrapod, with a flattened, square-shaped skull and jaws lined with hundreds of very small chisel-like teeth.” The extended orbit shape traditionally allied Spathicephalus with Baphetes, but here it nests with the stem tetrapod, Tiktaalik, which is just beginning to show that orbit shape.

The Spathicephalus fossil does not show tooth replacement. Rather every tooth is present without gaps. Tiktaalik also has jaws rimmed with tiny teeth. Distinct from derived temnospondyls, but like basal forms, the palate is closed on this bottom-feeder.

Figure 3. Koliops with bones colorized, nests as a big-eyed, short-snouted, smaller, (perhaps juvenile?) relative of Tiktaalik and Spathicephalus in the LRT.

Figure 3. Koliops with bones colorized, nests as a big-eyed, short-snouted, smaller, (perhaps juvenile?) relative of Tiktaalik and Spathicephalus in the LRT.

Koilops herma (Clack et al. 2016; NMS G. 2013.39/14) Tournasian, early Carboniferous ~375 mya) is a basal tetrapod with a flat skull and large orbits nesting with Spathicephlaus and Tiktaalik. The nares were close to the rim of the short rorstrum. The pineal foramen was enormous. The maxillary teeth were small and sharp. The premaxillary teeth were much larger, distinct from other basal tetrapods. The nasals were broader anteriorly.

This was low-hanging fruit
that apparently escaped everyone’s view, including my own, until now. Let me know if this relationship was published elsewhere. I would like to credit the authors, if so.


References
Clack et al. (14 other authors) 2016. Phylogenetic and environmental context of a Tournaisian tetrapod fauna. Nature ecology & evolution 1(0002):1-11.
Daeschler EB, Shubin NH and Jenkins FA, Jr 2006. A Devonian tetrapod-like fish and the evolution of the tetrapod body plan. Nature. 440 (7085): 757–763.
Watson DMS 1929. Croonian Lecture. The evolution of the Amphibia. Philosophical Transactions of the Royal Society, London B 214:189-257.

wiki/Spathicephalus
wiki/Tiktaalik
No wikipedia page yet for Koilops.

Convolosaurus enters the LRT basal to pachycephalosaurs

Originally it was considered a basal ornithopod.

FIgure 1. Convolosaurus from Andrzejewski, Winkler and Jacobs 2019, re built from a flock of juvenile specimens.

FIgure 1. Convolosaurus from Andrzejewski, Winkler and Jacobs 2019, re built from a flock of juvenile specimens.

Andrzejewski, Winkler and Jacobs 2019 report,
“The new ornithopod, Convolosaurus marri gen. et sp. nov., is recovered outside of Iguanodontia, but forms a clade with Iguanodontia exclusive of Hypsilophodon foxii. The presence and morphology of four premaxillary teeth along with a combination of both basal and derived characters distinguish this taxon from all other ornithopods.” 

Figure 2. Subset of the LRT focusing on the clade Phytodinosauria. Convolosaurus nests closer to the dome head dinosaurs, not the ornithopods.

Figure 2. Subset of the LRT focusing on the clade Phytodinosauria. Convolosaurus nests closer to the dome head dinosaurs, not the ornithopods.

By contrast
the large reptile tree (LRT, 1419 taxa) nests Convolosaurus basal to the Agilisaurus + Stegoceras at the base of the Pachycephalosauria (dome-head dinos). All these taxa were included in the original paper, but they did not nest together. Andrzejewski, Winkler and Jacobs 2019 did not nest their cladogram on Chilesaurus and Daemonosaurus, two taxa missing from their cladogram. This may have played a part in the different tree topologies.

Then again…
the LRT presently does not include Hypsilophodon or Thescalosaurus, taxa that nest with Convolosaurus in Andrzejewski, Winkler and Jacobs 2019. Soon they will be added. Then we’ll revisit this. 

Figure 3. Convolosaurus cladogram from Andrzejewski, Winkler and Jacobs 2019. Note the complete lack of consensus between the tree topology and figure 2.

Figure 3. Convolosaurus cladogram from Andrzejewski, Winkler and Jacobs 2019. Note the complete lack of consensus between this tree topology and the LRT in figure 2. In the LRT Haya and Pisanosaurus nest together near the base of the Ornithischia, but not here. 

Convolosaurus marri (Andrzejewski, Winkler and Jacobs 2019; SMU 72834; 2.5m in length) informally nicknamed the “Proctor Lake hypsilophodont”, this specimen is known from a flock of subadults.


References
Andrzejewski KA, Winkler DA and Jacobs LL 2019. A new basal ornithopod (Dinosauria: Ornithischia) from the Early Cretaceous of Texas. PLoS ONE. 14 (3): e0207935. doi:10.1371/journal.pone.0207935.

The grrrr…izzly bear enters the LRT

Distinct in skull shape
from the polar bear (Ursus maritimus), the grizzly bear (Ursus arctos) (Fig. 1) had me wondering if perhaps it would nest with dogs like Canis in the large reptile tree (LRT, 1417 taxa). After all there are such things as bear-dogs (genus: Amphicyon). We also looked at the short-face bear (genus: Arctodus) derived from the wolverine (genus: Gulo).

Figure 1. Ursus arctos, the grizzly bear, nests with Ursus maritimus, the polar bear in the LRT, as expected.

Figure 1. Ursus arctos, the grizzly bear, nests with Ursus maritimus, the polar bear in the LRT, as expected.

Alas, U. arctos nested with U. martimus.
Both are bears. Both are derived from mink-weasels like Mustela (extant) and sea weasels like Puijila (Late Oligocene) + Neotherium (Middle Miocene), not dogs.

Ursus arctos (Linneaus 1758 ; up to 3m in length) is the extant grizzly bear. It has a deeper face than U. maritimus, yet nests as a sister taxon here.

Figure 2. Skull of Ursus maritimus, the polar bear. It's worthwhile noting the similarities and differences, which are more distinct than just the colors of their furry coats.

Figure 2. Skull of Ursus maritimus, the polar bear. It’s worthwhile noting the similarities and differences, which are more distinct than just the colors of their furry coats.


References
Linnaeus C 1758. Systema naturæ per regna tria naturæ, secundum classes, ordines, genera, species, cum characteribus, differentiis, synonymis, locis. Tomus I. Editio decima, reformata.

The near closure of the naris in Spinosaurus

Short note on a long rostrum today:

Figure 1. The rostrum of Spinosaurus. Note the maxilla rising to close off the elongate naris into a reduced anterior and posterior opening.

Figure 1. The rostrum of Spinosaurus MSNM V4047. Note the maxilla rising to close off the elongate naris into a reduced anterior and posterior opening. SF = sub-narial foramen. 

I just found this fascinating.
The naris of Spinosaurus (Stromer 1915; Cretaceous; MSNM V4047) was overlaid by the maxilla sealing off most of what had been the elongate opening (Fig. 1).  I suppose that supports a semi-aquatic niche and reduced olfactory input. As others have noted, the rostrum has sensory pits, perhaps, as in crocodilians, for underwater vibration sensing.

Figure 2. Diagram from Dal Sasso et al. 2005, colors and overlay added to show  dorsal expansion of the maxilla to cover an elongate naris.

Figure 2. Diagram from Dal Sasso et al. 2005, colors and overlay added to show dorsal expansion of the maxilla to cover an elongate naris.

Dal Sasso et al. 2005 wrote:
“The external naris is retracted farther caudally on the snout than in other spinosaurids and is bordered exclusively by the maxilla and nasal.” The authors identified the anterior naris as a ‘sub-narial foramen’. The naris continues to contact the premaxilla in all related taxa (Fig. 1). Here, just thinking about things differently, and more parsimoniously, the naris continues to contact the premaxilla.

According to Wikipedia
MSNM V4047 (in the Museo di Storia Naturale di Milano), described by Dal Sasso and colleagues in 2005, consists of a snout (premaxillae, partial maxillae, and partial nasals) 98.8 centimetres (38.9 in) long from the Kem Kem Beds. Like UCPC-2, it is thought to have come from the early Cenomanian. Arden and colleagues in 2018 tentatively assinged this specimen to Sigilmassasaurus brevicollis given its size. In the absence of associated material, however, it is difficult to be certain which material belongs to which taxon.”


References
dal Sasso C, Maganuco S, Buffetaut E, Mendez MA 2005. New information on the skull of the enigmatic theropod Spinosaurus, with remarks on its sizes and affinities. Journal of Vertebrate Paleontology. 25 (4): 888–896.
Ibrahim N et al. 2014. Semiaquatic adaptations in a giant predatory dinosaur. Science 345 (6204): 1613–1616.
Stromer E 1915. Ergebnisse der Forschungsreisen Prof. E. Stromers in den Wüsten Ägyptens. II. Wirbeltier-Reste der Baharije-Stufe (unterstes Cenoman). 3. Das Original des Theropoden Spinosaurus aegyptiacus nov. gen., nov. spec. Abhandlungen der Königlich Bayerischen Akademie der Wissenschaften, Mathematisch-physikalische Klasse (in German). 28 (3): 1–32.

wiki/Spinosaurus