Isistius: the cookie cutter shark, enters the LRT, as a lamprey mimic

The latest addition to the LRT,
Isistius brasiliensis, the extant cookie-cutter shark (Figs. 1–3), was a puzzle to try to figure out, given that the entire skull turned to cartilage and can only be figured out by looking at the bumps and valleys, along with the overall proportions.

To no one’s surprise,
Isistius
nests in the LRT with other small cigar-shaped sharks with large eyeballs, including Carboniferous Falcatus.

Figure 1. Isistius, the cookie cutter shark animated.

Figure 1. Isistius, the cookie cutter shark animated.

Perhaps more importantly,
this taxon addition sparked another look at all the sharks and rays, based on phylogenetic bracketing

Figure 2. Isistius brasiliensis in several views.

Figure 2. Isistius brasiliensis in several views.

But that can only take place
in a valid phylogenetic context, so the shark subset of the large reptile tree (LRT, 1770 taxa) itself came under scrutiny. You might recall, I knew nothing about fish anatomy a year ago when I started posting sharks to the LRT trying to use tetrapod homologs for skull bones. Tinkering remains a good way to learn and not be hamstrung by outdated traditions sometimes found in textbooks.

Figure 3. Isistius skull. Note all the former bones are now fused together into a precise lump of cartilage.

Figure 3. Isistius skull. Note all the former bones are now fused together into a precise lump of cartilage.

Here are the phylogenetic results
subject to further improvements.

Figure x. Subset of the LRT focusing on sharks.

Figure x. Subset of the LRT focusing on sharks.

Isistius brasiliensis
(Quoy and Gaimard 1824) is the extant cookiecutter shark, a living sister to Falcatus. This deep-water shark has light-emiting photophores covering its underside. It migrates to the surface every day to take a circular bite out of giant whales and sharks. In this way it can be seen as a sort of lamprey-mimic. Isistius also consumes smaller free-swimming prey, like squid. Note the anterior nostrils and larger dentary teeth.


References
Quoy JRC and Gaimard JP 1824–1825. des Poissons. Chapter IX”. In de Freycinet, L (ed.). Voyage autour du Monde…exécuté sur les corvettes de L. M. “L’Uranie” et “La Physicienne, pendant les années 1817, 1818, 1819 et 1820. Paris 192–401.

wiki/Isistius

Cetorhinus maximus, the giant, filter-feeding, basking shark, enters the LRT

Revised December 27, 2020
with new light shed by the relationship of Cetorhinus with paddlefish, particularly the short-nosed hatchlings of of paddlefish (Polyodon).

Cetorhinus maximus
(originally Squalus maximus, Gunnerus 1765; Figs. 1, 2) is the extant basking shark, the second largest fish in today’s oceans.

FiIgure 1. The basking shark, Cetorhinus maximus, in lateral and ventral views.

Figure 1. The basking shark, Cetorhinus maximus, in lateral and ventral views.

The basking shark is distinct from the largest fish in the sea,
the unrelated whale shark (Rhincodon typus). In the large reptile tree (LRT, 1768+ taxa), Cetorhinus nests with Polyodonthe paddlefish (Figs. 4, 5).Figure 2. Skull of Cetorhinus adult and juvenile showing differences in the rostrum and fusion of skull elements in the adult.

Figure 2. Skull of Cetorhinus adult and juvenile showing differences in the rostrum and fusion of skull elements in the adult.

Figure 7. Polyodon hatchling. Compare to the Polyodon adult (figure 8) and Cetorhinus (figure 9).

Figure 3. Polyodon hatchling. Compare to the Polyodon adult (figure 8) and Cetorhinus (figure 9).

Figure 4. Skull of Polyodon from a diagram published in Gregory 1938, plus a dorsal view and lateral photo.

Figure 4. Skull of Polyodon from a diagram published in Gregory 1938, plus a dorsal view and lateral photo.

Slow-moving, filter feeding
basking sharks regularly reach 7–8m in length. Marginal teeth are tiny and essentially useless. So is the basking shark’s brain. Gill slits nearly encircle the head, doubling as plankton collectors. They balloon out when the mouth is open, straining great quantities of water for tiny prey items.

The pineal foramen is anterior to the raised frontal (light blue), as in related taxa.

Former skull bones are here fused together and turned to cartilage, more so in the adult where the deteriorated naris capsule is confluent with the orbit.

Developing eggs remain in the mother for over a year. Up to six young may be carried at a time. Sexual maturity and lifespan are similar to humans.

As a juvenile the protruding nasals curl down in front of the mouth and rise with maturity. The rest of the skull also changes shape with maturity.

As an adult the basking shark has few enemies other than skin parasites, including lampreys and cookie-cutter sharks (which we’ll learn about soon).

Figure 6. Adding Debeerius to the LRT helped revise the shark-subset.

Figure x. Adding Debeerius to the LRT helped revise the shark-subset.

Sharp-eyed readers will note
changes in the shark subset of the LRT (Fig. x). Hybodus remains the proximal outgroup taxon to bony fish. The mako shark, Isurus, moves closer to the origin of sharks and closer to the shark-like toothless taxon, Chondrosteus.


References
Gunnerus JE 1765. Brugden (Squalus maximus), Beskrvenen ved J. E. Gunnerus. Det Trondhiemske Selskabs Skrifter, 3: 33–49, pl. 2
Izawa K and Shibata T 1993. A young basking shark, Cetorhinus maximus, from Japan. Japanese Journal of Ichthyology, 40 (2): 237-245, figs 1-4).
Matthews. L. H. and H. W. Parker 1950. Notes on the anatomy and biology of the basking shark (Cetorhinus maximus (Gunner)). Proc. Zool. Soc. Lond., 120: 535- 576. pls. 1-8.
Pavesi, P. 1874. Contribusiine alia storia naturale del genere Selache. Ann. Mus. Stor. Nat. Genova, 6: 5-72, pls. 1-3.

shark-references.com/species/view/Cetorhinus-maximus
shark-references.com/post/526
wiki/Basking_shark

A quick look at the original Tapejara skull

Short one today
told mostly in pictures.

Topic: Simplification. 
Get rid of the extraneous data to better see and understand the basics.

Figure 1. Just take out everything that isn't this side of Tapejara. Rearrange the parts for best fit. Make a guess for the missing parts and this is what you get.

Figure 1. Just take out everything that isn’t this side of Tapejara. Rearrange the parts for best fit. Make a guess for the missing parts and this is what you get.

In this case
the skull of the original Tapejara fossil (Fig. 1) is trimmed back to just the basics and slightly shifted to fit. Missing tips are added based on phylogenetic bracketing.

Figure 4. Click to enlarge. The Tapejaridae arise from dsungaripterids and germanodactylids.

Figure 2. Click to enlarge. Tiny Tapejaridae arise from dsungaripterids and germanodactylids, then grow larger phylogenetically.

Tapejara wellnhoferi
(Kellner 1989; 108 mya, Early Cretaceous) was immediately recognized as something quite different when first discovered. Compared to other specimens, this one appears to have no sharp premaxilla, likely due to taphonomic loss.


References
Eck K, Elgin RA and Frey E 2011. On the osteology of Tapejara wellnhoferi KELLNER 1989 and the first occurrence of a multiple specimen assemblage from the Santana Formation, Araripe Basin, NE-Brazil. Swiss Journal of Palaeontology, doi:10.1007/s13358-011-0024-5.
Kellner AWA 1989. A new edentate pterosaur of the Lower Cretaceous from the Araripe Basin, northeast Brazil. Anais da Academia Brasileira de Ciências 61, 439-446.

wiki/Tapejara

 

Falcatakely: a basal theropod, not a bird

O’Connor et al. 2020 present
a late surviving, Late Cretaceous basal theropod dinosaur lacking maxillary teeth, Falcatakely forsterae (Figs. 1–4). The authors reconstructed their crushed and slightly disarticulated fossil using µCT scans.

Figure 1. Falcatakely from O'Connor et al. 2020 µCT scans, then moved slightly on frame 2.

Figure 1. Falcatakely from O’Connor et al. 2020 µCT scans, then moved slightly on frame 2.

Unfortunately
the authors mistakenly consider Falcatakely an enantiornithine bird with a “unique development of beak”. This was due to taxon exclusion. They assumed they had ‘a bird in hand’ when analysis indicates they did not.

Figure 1. Falcatakely from O'Connor et al. 2020 µCT scans, then missing elements added in frame 2.

Figure 2. Falcatakely from O’Connor et al. 2020 µCT scans, then missing elements added in frame 2. Note the lacrimal (in red) is partly the jugal (cyan, frame 2).

From the O’Connor et al. abstract:
“Mesozoic birds display considerable diversity in size, flight adaptations and feather organization1,2,3,4, but exhibit relatively conserved patterns of beak shape and development Here we describe a crow-sized stem bird, Falcatakely forsterae gen. et sp. nov., from the Late Cretaceous epoch of Madagascar that possesses a long and deep rostrum, an expression of beak morphology that was previously unknown among Mesozoic birds and is superficially similar to that of a variety of crown-group birds (for example, toucans).”

Note the first two words. They assumed they had a ‘unique’ Mesozoic bird without first testing in a phylogenetic analysis. Evidently they got excited by the possibility of getting published in Nature. That part came true.

Colleagues: The time to get excited is AFTER a wide gamut analysis documents and firmly nests your taxon. Otherwise you’ll end up like the authors of Oculudentavis, which was also mistakenly considered a bird. (I wonder if Nature will demand a similar retraction?)

Figure 3. Falcatakely from O'Connor et al. 2020 µCT scans, then non-palate elements darkened in frame 2. Compare to figure 1 for a more realistic narrowing of the snout.

Figure 3. Falcatakely from O’Connor et al. 2020 µCT scans, then non-palate elements darkened in frame 2. Compare to figure 1 for a more realistic narrowing of the snout.

Whenever you think you have a ‘unique’ anything
add taxa. Expand your taxon list.

Uniqueness in evolution is an oxymoron.
Something should resemble your ‘unique’ taxon.  The O’Connor team’s  mistake was due entirely to taxon exclusion, not looking far enough with a wide enough taxon list.

Figure 4. Cladogram from O'Connor et al. 2020 where they exclude basal theropods and nest Falcatakely with dissimilar enantiornithine birds by default.

Figure 4. Cladogram from O’Connor et al. 2020 where they exclude basal theropods and nest Falcatakely with dissimilar enantiornithine birds by default.

Late-surving Late Cretaceous Falcatakely
nests among the basalmost theropods, in the large reptile tree (LRT, 1768+ taxa) not far from Late Triassic Tawa, within the Late Jurassic Zuolong (Fig. 5) to Late Triassic Marasuchus to headless Late Triassic Procompsognathus (Fig. 6) clade. It’s probably the most ignored of the theropod clades recovered by the LRT.

Figure 2. Zuolong skull revised with a backward tilting lacrimal and other minor modifications.

Figure 5. Zuolong skull revised with a backward tilting lacrimal and other minor modifications.

The lack of maxillary teeth in Falcatakely
is the major difference between it and earlier related taxa. So is the lack of an antorbital fossa. As many other lineages demonstrate, that can happen over tens of millions of years in the Theropoda.

Figure 1. Procompsognathus, Marasuchus and Segisaurus nest together in the Theropoda despite their many differences.

Figure 6. Procompsognathus, Marasuchus and Segisaurus nest together in the Theropoda despite their many differences.

Size-wise
either Marasuchus or Procompsognathus (Fig. 6) provide suitable post-cranial models for Falcatakely. Other bird mimics are documented here.

With so many theropod fans out there,
let’s see how many confirm the basal theropod affinities of Falcatakely. In either case, it’s still a wonderful fossil find and the authors did a wonderful job of documenting the material. (Next time, just add more taxa).

Happy Thanksgiving
from the USA.


References
O’Connor PM, Turner AH, Groenke JR et al. 2020. Late Cretaceous bird from Madagascar reveals unique development of beaks. Nature (2020). https://doi.org/10.1038/s41586-020-2945-x

wiki/Falcatakely
https://www.ohio.edu/news

Added November 28, a few days after posting:
Others also question the bird hypothesis:

Dinosaur Mailing List: A Theropoda blog post questioning the identification of the fossil as a bird… Falcatakely: heterodoxy and pluralism in the Year of Oculudentavis (in Italian) http://theropoda.blogspot.com/2020/11/falcatakely-eterodossia-e-pluralismo.html

Latest fins-to-fingers paper stumbles due to taxon exclusion

Dickson et al. 2020 bring us their views
on the transition from fins to feet at the base of the Tetrapoda.

Unfortunately,
taxon exclusion (Fig. 1), once again, mars this study published in Nature.

Figure 1. Cladogram from Dickson et al. 2020 with an overlay indicating taxa found in the LRT and key LRT taxa with limbs lacking in Dickson et al. 2020.

Figure 1. Cladogram from Dickson et al. 2020 with an overlay indicating taxa found in the LRT and key LRT taxa with limbs lacking in Dickson et al. 2020.

Cherry-picking taxa in Dickson et al. 2020
nested Ichthyostega and Acanthostega as the first taxa to have fingers and toes. These two were highly promoted in earlier works that included co-author, Jennifer Clack, but that should not excuse the exclusion of pertinent taxa. When more taxa are added to a cladogram (Fig. 2), these two famous basal tetrapods, with their large, well-formed limbs, nest not as transitional taxa, but as derived taxa leaving no descendants (subset Fig. 2). Their polydactyl extremities were evolutionary dead-end experiments perhaps reflecting one of the first returns to a more aquatic existence.

Employing a wider gamut of taxa,
in the large reptile tree (LRT, 1766 taxa; subset Fig. 2), pre-tetrapods with flat morphologies and small fins, like Panderichthys (Fig. 3) had only four finger buds. Strongly similar taxa, like the late-surviving basalmost tetrapod, Trypanognathus, likewise had a flat morphology, small limbs and only four fingers. This finger number is typical of basal tetrapods until the advent of finger 5 in five unrelated clades (Fig. 2) leaving no living descendants, except for reptilomorphs, beginning with Tulerpeton, Utegenia and kin, the clade that ultimately evolved reptiles, mammals, primates and humans.

Figure 4. Subset of the LRT focusing on basal tetrapods. Colors indicate number of fingers known. Many taxa do not preserve manual digits.

Figure 2. Subset of the LRT focusing on basal tetrapods. Colors indicate number of fingers known. Many taxa do not preserve manual digits.

Figure 6. Dorsal and ventral views of Panderichthys and several basal tetrapods demonstrating the low, flat skulls and bodies with small limbs and relatively straight ribs.

Figure 3. Dorsal and ventral views of Panderichthys and several basal tetrapods demonstrating the low, flat skulls and bodies with small limbs and relatively straight ribs.

Adding taxa 
resolves this problem and many others. Excluding taxa only perpetuates traditional myths and hobbles present research.


References
Dickson BV, Clack JA, Smithson TR et al. 2020. Functional adaptive landscapes predict terrestrial capacity at the origin of limbs. Nature (2020). https://doi.org/10.1038/s41586-020-2974-5

The multituberculate, Barbatodon, enters the LRT with iron in its incisors

Yes, the element iron
is incorporated into the teeth of the multituberculate, Barpatodon (Fig. 1, Rãdulescu and Samson 1986; Smith and Codrea 2015), and other members of the gnawing clade, Glires to make them even stronger than ordinary enamel. That’s what gives those teeth that rusty appearance.

Figure 1. Barpatodon diagram from Smith and Codrea 2015 colorized here.

Figure 1. Barpatodon diagram from Smith and Codrea 2015 colorized here.

Barbatodon transylvanicus (Rãdulescu and Samson 1986; Late Cretaceous) is a small multituberculate preserving iron in its incisors as in several living rodents. Originally considered close to Taeniolabis, here it nests with Catopsbaatar. The premolars have been molarized. The ‘sliding jaw joint’ does not slide much.

Figure 4. Catopsbaatar greatly enlarged.

Figure 2. Catopsbaatar greatly enlarged.


References
Rãdulescu R and Samson P 1986. Précisions sur les affinités des Multituberculés du Crétacé supérieur de Roumaine. C R Acad Sci II: Mec-Phys, Chim, Sci Terre, Sci Univ 303p, p. 1825-1830.
Smith T and Codrea V 2015. Red Iron-Pigmented Tooth Enamel in a Multituberculate Mammal from the Late Cretaceous Transylvanian “Hateg Island”. PLoS ONE 10(7): e0132550. https://doi.org/10.1371/journal.pone.0132550

wiki/Barbatodon

Rostriamynodon: ancestor to elephants + manatees, not a perissodactyl

Holbrook 1999
added Rostriamynodon (AMNH 107635, Fig. 1) to his study on perissodactyls (Fig. 3) following work by Wall and Manning 1986 who thought Rostriamynodon was a basal rhino close to Amynodon, which nests basal to horses in the large reptile tree (LRT, 1763 taxa; subset Fig. 2).

Figure 1. Rostriamynodon skull in three views, colors added.

Figure 1. Rostriamynodon skull in three views, colors added.

So, a bit of a taxonomic mess here.
Taxon exclusion is once again the problem. In the LRT (subset Fig. 2) Rostriamynodon nests between the traditional ‘notoungulate’ Notostylops and the elephant (Fig. 5) + manatee (Fig. 6) clade.

Figure 2. Subset of the LRT focusing on ungulates sans artiodactyls.

Figure 2. Subset of the LRT focusing on ungulates sans artiodactyls.

Figure 3. Cladogram from Holbrook 1999 with LRT colors added. Taxon exclusion mars this cladogram.

Figure 3. Cladogram from Holbrook 1999 with LRT colors added. Taxon exclusion mars this cladogram.

Isectolophus was also added to the LRT,
(subset Fig. 2) and it nested uncontroversially basal to Protapirus in the tapir clade in both competing studies.

Taxa in this blogpost:
Amynodon advenus (Marsh 1877; 1m in length; Oligocene-Eocene, 40-23 mya) was originally considered an aquatic rhino. Here it nests with Mesohippus. The long neck and other traits are more horse-like than rhino-like. Manual digit 5 was retained. The skull was deeper as in basal forms like Hyracotherium.

Isectolophus scotti (Scott and Osborn 1887; Early Oligocene to Early Miocene) nests basal to Protapirus in the large reptile tree.

Figure 1. Notostylops skull colorized in three views.

Figure 4. Notostylops skull colorized in three views.

Notostylops murinis (Ameghino 1897, Riggs and Patterson 1935; 75cm in esitmated length; Eocene; FMNH-P13319; Fig. 4) is widely considered a ‘notoungulate’ a clade that has been split into several parts in the large reptile tree. Here it nests with the above specimen of Ectocion in the clade of elephants, rock hyraxes and sea cows. The jaws narrowed anteriorly. The anterior incisors were enlarged, like those of rodents. The mandible was more robust. No canines were present. The premolars were molarized

Rostriamynodon grangeri (Wall and Manning 1986; AMNH 107635; Eocene) was originally considered amynodontid rhino, but here nests between Notostylops and the elephant + siren clade. Note the splitting of the nasals and the anterior extension of the frontals along with the wide molars and the molarized premolars.

 

Figure 2. Skull of Elephas maximus with color overlays. Most of the bones are fused to one another, so this tracing is provisional, pending confirmation and/or better data. Compare to the skull of Procavis (Fig. 3).

Figure 5. Skull of Elephas maximus with color overlays. Note the separation of the nasals.

Figure 2. Dusisiren, a manatee sister has a robust tail and presumably, flukes.

Figure 6. Dusisiren, a manatee sister has a robust tail and presumably, flukes. Note the separation of the nasals, first seen in Rostriamynodon.

References
Hollbrook LT 1999. The phylogeny and classification of Tapiromorph perissodactyls (Mammalia). Cladistics 15:331–350.
Holbrook LT, Lucas SG and Emry RJ 2004. Skulls of the Eocene perissodactyls (Mammalia) Homolgalax and Isectolophus. Journal of Vertebrate Paleontology 24(4):951–956.
Scott WB and Osborn HF 1887. Preliminary Report on the Vertebrate Fossils of the Uinta Formation, Collected by the Princeton Expedition of 1886. Proceedings of the American Philosophical Society 24(126):255-264.
Wall WP and Manning E 1986. Rostriamynodon grangeri n. gen., n. sp. of amynodontid (Perissodactyla, Rhinocerotoidea) with comments on the phylogenetic history of Eocene Amynodontidae. Journal of Paleontology 60(4):911-919.

wiki/Notostylops
wiki/Rostriamynodon not yet posted
wiki/Protapirus
wiki/Isectolophus not yet posted

 

Plateosaurus enters the LRT

Perhaps the best known, least controversial dinosaur, 
Plateosaurus engelhardti (von Meyer 1837; Moser 2003; Late Triassic, 210mya; 5-10m in length) is a prosauropod, basal sauropodomorph phytodinosaur. Over 100 skeletons are known. In the LRT Plateosaurus nests in a clade apart from the sauropods and their ancestors. Saturnalia is smaller and older. Aardonyx is larger and later.

Figure 1. Skull of Plateosaurus in several views, colorized here. Note the replacement of the postorbital (amber) with the postfrontal (orange). All sister taxa fuse these bones, so this early illustration may be in error.

Figure 1. Skull of Plateosaurus in several views, colorized here. Note the replacement of the postorbital (amber) with the postfrontal (orange). All sister taxa fuse these bones, and not at that point, so this early illustration may be in error.

In figure 1
note the replacement of the postorbital (amber) with the postfrontal (orange) which uniquely articulates with the squamosal. All sister taxa fuse the postfrontal and postorbital, and not at the stem, so this early illustration may be in error. This character was scored as ‘fused’ based on phylogenetic bracketing. Was I wrong?

Figure 2. Plateosaurus skeleton digitized.

Figure 2. Plateosaurus skeleton digitized by Mallison 2010a, b,

Plateosaurus tracks are known from the Moab desert. Stock photos here.


References
Mallison H 2010a. The digital Plateosaurus I: body mass, mass distribution, and posture assessed using CAD and CAE on a digitally mounted com− plete skeleton. Palaeontologia Electronica13 (2, 8A): 26.
Mallison H 2010b. The digital Plateosaurus II: An assessment of the range of motion of the limbs and vertebral column and of previous reconstructions using a digital skeletal mount. Acta Palaeontologica Polonica 55 (3): 433–458.
Meyer H von 1837. Mitteilung an Prof. Bronn (Plateosaurus engelhardti [message to Prof. Bronn (Plateosaurus engelhardti)]. Neues Jahrbuch für Geologie und Paläontologie (in German). 1837: 316.
Moser M 2003. Plateosaurus engelhardti Meyer, 1837 (Dinosauria, Sauropodomorpha) aus dem Feuerletten (Mittelkeuper; Obertrias) von Bayern [Plateosaurus engelhardti Meyer, 1837 (Dinosauria, Sauropodomorpha) from the Feuerletten (Mittelkeuper; Obertrias) of Bavaria]. Zitteliana Reihe B: Abhandlungen der Bayerischen Staatssammlung für Paläontologie und Geologie (in German and English). 24: 1–186.

wiki/Saturnalia
wiki/Aardonyx
wiki/Plateosaurus

 

Blind-snake evolution in dorsal, lateral and palatal views

Today’s blogpost was sparked by
Fachini et al. 2020, who described a new, rather large (~1m) Cretaceous blind-snake lacking a skull, Boipeba.

Unfortunately,
this is a taxon I cannot add to the large reptile tree (LRT, 1765+ taxa; subset Fig. 1) because all included blind-snakes are scored on skull-only traits.

The Fachini et al. cladogram of blind-snakes
differs markedly from the LRT (Fig. 1) in that Fachini et al. nests the most derived taxa in the LRT at basal nodes and vice versa. They also nest extant burrowing snakes basal to extant terrestrial snakes instead of splitting the two at the genesis of snakes.

Fachini et al. report,
“Blindsnakes (Scolecophidia) are minute cryptic snakes that diverged at the base of the evolutionary radiation of modern snakes.”

By contrast the LRT recovers all terrestrial snakes (extant AND extinct) diverging from burrowing snakes at the origin of snakes (Fig. 1). Fachini et al. report both adding and deleting Tetrapodophis from their analysis resulting in no topological changes.

In doing so, Fachini et al. cited an abstract we looked at earlier (Caldwell et al. 2016), proving workers sometimes do cite abstracts.

On this disagreement, we agree:
“there is disagreement between morphological and molecular phylogenetic analyses with regard to their phylogenetic position and monophyly.” 

As often reported here genomic testing too often leads to false positives as compared to phenomic (trait-based) testing in deep time paleo studies. Seemingly the paleo community has not yet realized this, or taken evasive action on this, despite often writing about it (e.g. Fachini et al.).

On this statement we disagree:
Fachini et al. report, “The origin of blindsnakes is unclear.”

In the LRT blind-snakes (burrowing snakes) clearly arise from Tetrapodophis (snake outgroup), Najash and Loxocemus (Figs. 2–4). We looked a phylogenetic problems in snake origins earlier here, here and here in 2013.

Figure 4. Subset of the LRT focusing on snakes. Compare to figure 3.

Figure 4. Subset of the LRT focusing on snakes. Compare to figure 3.

The most derived blind-snake taxa
in the LRT are instead basal taxa in the cladogram of Fachini et al.

Figure 2. Evolution of blind-snake skulls in dorsal view.

Figure 2. Evolution of blind-snake skulls in dorsal view. The white and black backgrounds are not significant, but represent the original background for the photos and drawings.

How was it possible that Fachini et al.
inverted the order of blind-snakes given Najash as a common outgroup taxon? I don’t know. It does not make sense. Given the clear similarity of python-like Loxocemus to Najash (Figs. 2–4) how is it possible that nearly blind Anomochilus through Typhlops (Figs. 2–4) nested closer to Najash? They were following a long tradition.

Figure 3. Evolution of blind-snake skulls in lateral view.

Figure 3. Evolution of blind-snake skulls in lateral view.

When you examine these three illustrations
of blind-snake skull evolution in dorsal, lateral and palatal views (Figs. 2–4, primitive at the top of each), remember, Fachini inverts the order (i.e. primitive at the bottom). In this way Fachini et al. separate python-like Najash and Pachyrhachis from extant pythons, like Boa, with burrowing snakes separating them. They may need to rethink that hypothesis of interrelationships.

Figure 4. Evolution of blind-snake skulls in palatal view.

Figure 4. Evolution of blind-snake skulls in palatal view.

Trends in blind-snake evolution recovered by the LRT:

  1. naris shortens and migrates from anterodorsal to anteroventral
  2. sharp snout becomes blunt, then round
  3. vomernasal fenestra shrink and disappear
  4. premaxilla rotates to the palate
  5. maxilla shrinks and fuses to premaxilla
  6. dentary shortens
  7. all marginal teeth reduce and disappear
  8. frontal enlarges vs parietal
  9. parietal retreats away from orbit
  10. circumorbital bones disappear (then reappear only in Liotyphlops)
  11. parietal loses sagittal crest
  12. palatine becomes mobile with transverse axial rotation
  13. ectopterygoid shrinks
  14. pterygoid loses teeth and becomes gracile loose strut
  15. basisphenoid and basioccipital become bulbous
  16. squamosal and supratemporal shrink and disappear
  17. quadrate stretches and leans posteriorly
  18. coronoid enlarges

Backstory
Blind snakes were first added to the LRT years ago. Many were not colorized as they are now (Figs. 2–4). Some new insights were gained by reviewing the taxa after coloring the drawings and recoloring the photos in a consistent manner.

Most snake workers label the squamosal the supratemporal. This topic was examined earlier here in 2018. The dorsal view image documents the reduction and disappearance of the supratemporal (bright green tiny bony near occiput) prior to the reduction and disappearance of the squamosal (magenta larger bone near quadrate)

The quadrate of Typhlops and Liotyphlops (Fig. 3) informed the previously misunderstood fusion of the quadrate with the stem-like articular in Leptotyphlops (Fig 3).

The realization that the unique appearance of circumorbital bones in Liotyphlops (Fig. 3) was a reappearance and a reversal solved an identity problem first posed by Rieppel, Kley and Maisano 2009.

Skull photos above are from Digimorph.org
and used with permission.


Bonus unrelated paleo news item for your enjoyment:
Some recent ‘stunning fossil finds” are listed and shown here:
https://www.boredpanda.com


References
Fachini TS et al. (5 co-authors) 2020. Cretaceous blind snake from Brazil fills major gap in snake evolution. iScience ISCI 101834. https://doi.org/10.1016/j.isci.2020.101834
Rieppel 0, Kley NJ and Maisano JA 2009. Morphology of the skull of the white-nosed blindsnake, Liotyphlops albirostris (Scolecophidia: Anomalepididae. Journal of Morphology, 270, 536-557.

digimorph/Leptotyphlops
wiki/Leptotyphlops
digimorph/Liotyphlops
wiki/Liotyphlops
digimorph/Typhlops
wiki/Typhlops

The taller ancestors of crows to scale

Every so often it’s worthwhile to take a wider view
to appreciate the model of evolution hypothesized by the large reptile tree (LRT, 1761+ taxa) to see the patterns of microevolution it documents. Otherwise, all you have is a long list of under-appreciated taxa on a dense family tree.

Today, let’s look at the ancestry of one of the smartest birds,
(Corvus brachyrhynchosLinneaus 1758; Fig. 1), the extant American crow.  Derived from a long list of longer-legged freshwater shorebirds, Corvus is generalized bird close to the stone curlew (Burhinus) and the grackle (Oedicnemus) and basal to robins, jays, birds of paradise and cuckoos.

Figure 1. Click to enlarge. Taxa in the LRT ancestral to crows. Each taxon represents a branch that has gone its own way since the divergent node.

Figure 1. Click to enlarge. Taxa in the LRT ancestral to crows. Each taxon represents a branch that has gone its own way since the divergent node.

Chronology
The presence of Eogranivora in the Early Cretaceous indicates that sisters to Pseudocrypturus and Crypturus (close to Megapodius) are more ancient. Seriemas, storks and corn crakes are more recent, perhaps radiating in the Late Cretaceous. Short-legged taxa are neotonous, since chicks of long-legged taxa do not have such long bills and long legs as adults. This makes birds different than pterosaurs, in which hatchlings are identical to 8x larger adults.


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.

wiki/Common_grackle
wiki/Corvus
wiki/Blue_jay
wiki/Eurasian_stone-curlew