Austronaga: a new macrocnemid tritosaur lepidosaur from Middle Triassic China
Wang, Lei and Li 2024
bring us a new, small adult macrocnemid from the Middle Triassic of China, Austronaga minuta IVPP V18579 (Fig 1). This new taxon and its LRT sister, the PIMUZ 2477 skull of Macrocnemus, are both basal to the dinocephalosaurids mentioned so often in the authors’ text.
This small specimen contrasts in size with the recently described large 5m dinocephalosaurid. Both were adults.
Figure 1. Austronaga in situ and slightly reconstructed compared to scale with the PIMUZ 2477 specimen of Macrocnemus. Here is the value of a DGS reconstruction compared to the authors’ line drawing.
” data-medium-file=”https://pterosaurheresies.files.wordpress.com/2024/03/austronaga_minuta.ivpp-v18579.jpg?w=193″ data-large-file=”https://pterosaurheresies.files.wordpress.com/2024/03/austronaga_minuta.ivpp-v18579.jpg?w=584″ class=”size-full wp-image-84689″ src=”https://pterosaurheresies.files.wordpress.com/2024/03/austronaga_minuta.ivpp-v18579.jpg?w=584&h=907″ alt=”Figure 1. Austronaga in situ and slightly reconstructed compared to scale with the PIMUZ 2477 specimen of Macrocnemus. Here is the value of a DGS reconstruction compared to the authors’ line drawing.” width=”584″ height=”907″ srcset=”https://pterosaurheresies.files.wordpress.com/2024/03/austronaga_minuta.ivpp-v18579.jpg?w=584&h=907 584w, https://pterosaurheresies.files.wordpress.com/2024/03/austronaga_minuta.ivpp-v18579.jpg?w=97&h=150 97w, https://pterosaurheresies.files.wordpress.com/2024/03/austronaga_minuta.ivpp-v18579.jpg?w=193&h=300 193w, https://pterosaurheresies.files.wordpress.com/2024/03/austronaga_minuta.ivpp-v18579.jpg 588w” sizes=”(max-width: 584px) 100vw, 584px” />
Figure 1. Austronaga in situ and slightly reconstructed compared to scale with the PIMUZ 2477 specimen of Macrocnemus. Here is the value of a DGS reconstruction compared to the authors’ line drawing. They missed the antorbital fenestra.
The authors reported,
“This reptile is much smaller than Dinocephalosaurus and different from Dinocephalosaurus and the other dinocephalosaurid, Pectodens, in many aspects, such as an anteriorly tapering long rostrum, the dentition composed of short conical teeth with less heterodonty, relatively but obviously tall neural spines of the axis and the anterior cervical vertebrae. Our phylogenetic analysis suggests that the new archosauromorph is a dinocephalosaurid, and then we erect Austronaga minuta gen. et sp. nov.based on this specimen.”
Pectodens nests with Tanystropheus (Fig 3) in the LRT.
Figure 3. Huehuecuetzpalli skull insitu.
” data-medium-file=”https://pterosaurheresies.files.wordpress.com/2018/11/huehuecuetzpalli-skull_insitu588.jpg?w=300″ data-large-file=”https://pterosaurheresies.files.wordpress.com/2018/11/huehuecuetzpalli-skull_insitu588.jpg?w=584″ class=”size-full wp-image-34270″ src=”https://pterosaurheresies.files.wordpress.com/2018/11/huehuecuetzpalli-skull_insitu588.jpg?w=584&h=363″ alt=”Figure 3. Huehuecuetzpalli skull insitu.” width=”584″ height=”363″ srcset=”https://pterosaurheresies.files.wordpress.com/2018/11/huehuecuetzpalli-skull_insitu588.jpg?w=584&h=363 584w, https://pterosaurheresies.files.wordpress.com/2018/11/huehuecuetzpalli-skull_insitu588.jpg?w=150&h=93 150w, https://pterosaurheresies.files.wordpress.com/2018/11/huehuecuetzpalli-skull_insitu588.jpg?w=300&h=186 300w, https://pterosaurheresies.files.wordpress.com/2018/11/huehuecuetzpalli-skull_insitu588.jpg 588w” sizes=”(max-width: 584px) 100vw, 584px” />
Figure 2. Huehuecuetzpalli skull insitu.
Unfortunately
the authors borrowed the wrong, small, cherry-picked cladogram and so did not realize the lepidosaurian ancestry of macrocnemids, dinocephalosaurids and tanystropheids. In the large reptile tree (LRT, 2313 taxa, subset Fig 3) these clades arise from an Early Triassic sister to the late survivor in the Early Cretacous, Huehuecuetzpalli (Fig 2). This lepidosaur always and everywhere nests outside the Squamata. That is because it nests as a basal tritosaur, a third lepidosaur clade first named here. Other lepidosaur workers need to add taxa to recover this interrelationship.
Adding taxa reveals the lepidosaurian ancestry of this clade of long-necked reptiles, some of which ultimately gave rise to pterosaurs.
The very similar protorosaurs are indeed archosauromorphs, basal to proterosuchians and derived from araeoscelid archosauromorphs.The diapsid skull configuration arose twice. This is still not taught from outdated university textbooks.
Add taxa to recover and resolve this convergence.
Figure 3. Austronaga (Tritosauria, Lepidosauria) subset of the LRT cladogram.
” data-medium-file=”https://pterosaurheresies.files.wordpress.com/2024/03/austronaga.cladogram588.jpg?w=144″ data-large-file=”https://pterosaurheresies.files.wordpress.com/2024/03/austronaga.cladogram588.jpg?w=492″ class=”size-full wp-image-84692″ src=”https://pterosaurheresies.files.wordpress.com/2024/03/austronaga.cladogram588.jpg?w=584&h=1216″ alt=”Figure 3. Austronaga (Tritosauria, Lepidosauria) subset of the LRT cladogram.” width=”584″ height=”1216″ srcset=”https://pterosaurheresies.files.wordpress.com/2024/03/austronaga.cladogram588.jpg?w=584&h=1216 584w, https://pterosaurheresies.files.wordpress.com/2024/03/austronaga.cladogram588.jpg?w=72&h=150 72w, https://pterosaurheresies.files.wordpress.com/2024/03/austronaga.cladogram588.jpg?w=144&h=300 144w, https://pterosaurheresies.files.wordpress.com/2024/03/austronaga.cladogram588.jpg 588w” sizes=”(max-width: 584px) 100vw, 584px” />
Figure 3. Austronaga (Tritosauria, Lepidosauria) subset of the LRT cladogram. Note the value of testing more than one Macroncnemus specimen here.
Taxon exclusion remains the number one problem
in paleontology. Borrowing cladograms is number two. As you might surmise, these two are essentially parts of the same problem. Both can be overcome by adding taxa. In science it is better to test than to trust someone’s borrowed cladogram.
The antorbital fenestra.
postfrontal. postorbital, supratemporal and quadratojugal of Austronaga (Fig 1) were originally overlooked. The authors wrote, “it seems that much of the parietals, the postfrontals, the postorbitals, and anterior parts of the squamosal and the dorsal part of the jugal are broken or lost.”
Supratemporals (green Fig 1) were not mentioned in the text.
References
Wang W, Lei H and Li C 2024. A small-sized dinocephalosaurid archosauromorph from the Middle Triassic of Yunnan, southwestern China. Vertebrata PalAsiatica 62(1):13–32.
Source: https://pterosaurheresies.wordpress.com/2024/03/05/austronaga-a-new-macrocnemid-tritosaur-lepidosaur-from-middle-triassic-china/
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