News (and more myth) about Trachelosaurus from Germany

Trachelosaurus
from the Middle Triassic of Germany was a long-neck tritosaur lepidosaur, like Tanystropheus, but with many more cervicals, like, Dinocephalosaurus. Trachelosaurus had larger, more robust cervicals and shorter cervical ribs than either taxon. Very few skull bones are known. Trachelosaurus had a large antorbital fenestra (Fig 1), like Middle Triassic Austronaga, derived from the PIMUZ T2477 specimen of Macrocnemus.

Figure 1. Among the few scattered skull parts these can be assembled to restore the skull of Tanytrachelos. ” data-image-caption=”

Figure 1. Among the few scattered skull parts these can be assembled to restore the skull of Tanytrachelos.

” data-medium-file=”https://pterosaurheresies.files.wordpress.com/2024/03/tanytrachelos_skull_parts588.jpg?w=186″ data-large-file=”https://pterosaurheresies.files.wordpress.com/2024/03/tanytrachelos_skull_parts588.jpg?w=584″ class=”size-full wp-image-84914″ src=”https://pterosaurheresies.files.wordpress.com/2024/03/tanytrachelos_skull_parts588.jpg?w=584&h=940″ alt=”Figure 1. Among the few scattered skull parts these can be assembled to restore the skull of Tanytrachelos.” width=”584″ height=”940″ srcset=”https://pterosaurheresies.files.wordpress.com/2024/03/tanytrachelos_skull_parts588.jpg?w=584&h=940 584w, https://pterosaurheresies.files.wordpress.com/2024/03/tanytrachelos_skull_parts588.jpg?w=93&h=150 93w, https://pterosaurheresies.files.wordpress.com/2024/03/tanytrachelos_skull_parts588.jpg?w=186&h=300 186w, https://pterosaurheresies.files.wordpress.com/2024/03/tanytrachelos_skull_parts588.jpg 588w” sizes=”(max-width: 584px) 100vw, 584px” />

Figure 1. Among the few scattered skull parts these can be assembled to restore the skull of Tanytrachelos.

Holotype.
“MLU.GeoS.1612, a partially disarticulated skeleton comprising a few isolated skull remains, including a right premaxilla, much of the presacral vertebral column, two sacral vertebrae, several caudal vertebrae, an extensive gastral basket, a right ilium, right? pubis, left? femur, and at least one probable metatarsal.”

Too little of this scattered specimen is known to add it to the LRT.

The authors wrote,
“Some of the earliest members of the archosaur-lineage (i.e., non-archosauriform archosauromorphs) are characterised by an extremely elongated neck.”

This breaks (or ignores) one of the most basic rules of evolution, which always starts with simple, plain, plesiomorphic taxa and – over time and generations –  ultimately produces derived taxa with a spectrum of notable traits.

The authors wrote,
“The phylogenetic position of Trachelosaurus fischeri was tested by incorporating it into two separate morphological phylogenetic matrices focused on non-archosaurian
archosauromorph interrelationships.”

Don’t wear blinders. Add taxa. You may be the first academic team to recover tanystropheids as lepidosaurs.

In the large reptile tree
(2315 taxa, LRT) long-necked macrocnemids and tanystropheids are derived tritosaur lepidosaurs arising from small, simple, plain, short-necked lepidosaurs like Huehueceutzpalli.

Figure 2. Trachelosaurus cladogram from Spiekman et al 2024. Taxon exclusion here mixes archosauromorphs with lepidosauromorphs. ” data-image-caption=”

Figure 2. Trachelosaurus cladogram from Spiekman et al 2024. Taxon exclusion here mixes archosauromorphs with lepidosauromorphs.

” data-medium-file=”https://pterosaurheresies.files.wordpress.com/2024/03/trachelosaurus_cladogram588.jpg?w=132″ data-large-file=”https://pterosaurheresies.files.wordpress.com/2024/03/trachelosaurus_cladogram588.jpg?w=451″ class=”size-full wp-image-84916″ src=”https://pterosaurheresies.files.wordpress.com/2024/03/trachelosaurus_cladogram588.jpg?w=584&h=1326″ alt=”Figure 2. Trachelosaurus cladogram from Spiekman et al 2024. Taxon exclusion here mixes archosauromorphs with lepidosauromorphs. ” width=”584″ height=”1326″ srcset=”https://pterosaurheresies.files.wordpress.com/2024/03/trachelosaurus_cladogram588.jpg?w=584&h=1326 584w, https://pterosaurheresies.files.wordpress.com/2024/03/trachelosaurus_cladogram588.jpg?w=66&h=150 66w, https://pterosaurheresies.files.wordpress.com/2024/03/trachelosaurus_cladogram588.jpg?w=132&h=300 132w, https://pterosaurheresies.files.wordpress.com/2024/03/trachelosaurus_cladogram588.jpg 588w” sizes=”(max-width: 584px) 100vw, 584px” />

Figure 2. Trachelosaurus cladogram from Spiekman et al 2024. Taxon exclusion here mixes archosauromorphs with lepidosauromorphs. Note the lack of resolution in this cladogram near Trachelosaurus.

The LRT also divided lepidosauromorphs from archosauromorphs
back in the Viséan with Silvanerpeton as the last common ancestor. Spiekman et al are not aware of this first division within the clade Reptilia (= Amniota). Nor are they aware that the diapsid skull morphology evolved twice by convergence. Instead the authors are stuck in the out-dated, university-approved system in which Petrolacosaurus (Fig 2) is the outgroup for all later diapsids.

Add taxa to find this out for yourself.

The Spiekman et al SuppData supplied two .nex files.
Only the smaller taxon list (Fig 2) was able to be opened. The larger CoArTreeP matrix could not be opened in PAUP.

Three suggestions and two warnings for Spiekman et al:
First: get rid of your partial and scrappy taxa.
Second: add more Carboniferous taxa (see the LRT for suggestions).
Third: Once your tree starts splitting Lepidosauromorpha from Archosauromorpha in the Viséan, then slowly start adding partial and scrappy taxa.
Right now your tree is recovering false positives due to taxon exclusion.
Right now the lack of resolution in your cladogram (Fig 2) is not shedding light on Trachelosaurus.

References
Spiekman SNF et al (6 co-authors) 2024. A redescription of Trachelosaurus fischeri from the Buntsandstein (Middle Triassic) of Bernburg, Germany: the first European Dinocephalosaurus-like marine reptile and its systematic implications for long-necked early archosauromorphs. Swiss Journal of Palaeontology 143:10.
https://doi.org/10.1186/s13358-024-00309-6