Thalattosuchia 2024

Young et al 2024
took a deep dive into the marine crocodylomorphs: the clade Thalattosuchia (Fig 1).  They wrote, ” Thalattosuchia are composed of two clades: Teleosauroidea and
Metriorhynchoidea. Both clades are present in the early Toarcian (Early Jurassic) of Western Europe. Teleosauroids have often been considered ‘marine gavialids’ and have particularly been compared to Gavialis gangeticus.”

According to Wikipedia,
“The exact phylogenetic position of Thalattosuchia is uncertain, with them either being interpreted as members of Neosuchia alongside other aquatic crocodylomorphs, or more basal members of Crocodylomorpha, with the similarities to neosuchians being as a result of convergent evolution.”

The authors undertook
a comprehensive presentation of the literature, which goes back to 1814. The citations you seek are here if they are anywhere. The photographs are large and professionally shot.

The team created a Crocodylomorph SuperMatrix.
They note their iteration “has the largest number of changes compared to any previous version of this dataset.”

Figure 2. Several Jurassic sea crocs, apparently derived from Late Triassic Dyoplax. ” data-image-caption=”

Figure 2. Several Jurassic sea crocs, apparently derived from Late Triassic Dyoplax.

” data-medium-file=”https://pterosaurheresies.files.wordpress.com/2017/12/metriorhynchus-lateral588.jpg?w=300″ data-large-file=”https://pterosaurheresies.files.wordpress.com/2017/12/metriorhynchus-lateral588.jpg?w=584″ class=”size-full wp-image-29225″ src=”https://pterosaurheresies.files.wordpress.com/2017/12/metriorhynchus-lateral588.jpg?w=584&h=511″ alt=”Figure 2. Several Jurassic sea crocs, apparently derived from Late Triassic Dyoplax.” width=”584″ height=”511″ srcset=”https://pterosaurheresies.files.wordpress.com/2017/12/metriorhynchus-lateral588.jpg?w=584&h=511 584w, https://pterosaurheresies.files.wordpress.com/2017/12/metriorhynchus-lateral588.jpg?w=150&h=131 150w, https://pterosaurheresies.files.wordpress.com/2017/12/metriorhynchus-lateral588.jpg?w=300&h=263 300w, https://pterosaurheresies.files.wordpress.com/2017/12/metriorhynchus-lateral588.jpg 588w” sizes=”(max-width: 584px) 100vw, 584px” />

Figure 1. Several Jurassic sea crocs, apparently derived from Late Triassic gavialids.

From the abstract
“As we cannot reliably discriminate between the positional hypotheses for Thalattosuchia within Crocodylomorpha, the clades’ origins are as much of a mystery today as they were over a century ago.”

From the text
“The first phylogenetic definition of Thalattosuchia was proposed by Young and Andrade (2009). They followed the post-Ginsburg definition of Thalattosuchia (=Teleosauridae + Metriorhynchidae). Their definition was: the most inclusive clade consisting of Teleosaurus cadomensis (Lamouroux, 1820) and Metriorhynchus geoffroyii von Meyer, 1832, but not Pholidosaurus schaumburgensis von Meyer, 1841, Goniopholis crassidens Owen, 1842, or Dyrosaurus phosphaticus (Thomas, 1893). They chose the type species of the type genera of Metriorhynchidae and Teleosauridae as the internal specifiers, and selected a goniopholidid, a pholidosaurid, and a dyrosaurid as external specifiers.”

“Curiously, the four major differing phylogenetic positions recovered for Thalattosuchia [1] (sister-taxon to Crocodyliformes, [2] outside Metasuchia, [3] sister-taxon to Neosuchia, or [4] within a neosuchian longirostrine clade alongside Dyrosauridae) do mirror, to some extent, the varying historic ergotaxonomies for Thalattosuchia.”

In the large reptile tree (LRT, 2318 taxa,Fig 3) four thalattosuchians are tested:Teleosaurus (2 specimens (Fig 1), Dakosaurus and Metriorhynchus (Fig 1). Proximal outgroup taxa include Pelagosaurus, Dyrosaurus.

The outgroup to that clade in the LRT includes Gavialis, Alligatorellus and Dyoplax.

Abbreviaitons
The team used the abbreviation MPC. That appears to mean “minimum phylogenetic coverage.” Not sure how that differs from MPT = “most parsimonious tree”.

Figure 3. Subset of the LRT focusing on Crocodylomorpha. The new nestings represent just the latest of a changing hypothesis of interrelationships. ” data-image-caption=”

Figure 3. Subset of the LRT focusing on Crocodylomorpha. The new nestings represent just the latest of a changing hypothesis of interrelationships.

” data-medium-file=”https://pterosaurheresies.files.wordpress.com/2023/08/crocodylomorpha2023.jpg?w=249″ data-large-file=”https://pterosaurheresies.files.wordpress.com/2023/08/crocodylomorpha2023.jpg?w=584″ class=”size-full wp-image-80902″ src=”https://pterosaurheresies.files.wordpress.com/2023/08/crocodylomorpha2023.jpg?w=584&h=704″ alt=”Figure 3. Subset of the LRT focusing on Crocodylomorpha. The new nestings represent just the latest of a changing hypothesis of interrelationships.” width=”584″ height=”704″ srcset=”https://pterosaurheresies.files.wordpress.com/2023/08/crocodylomorpha2023.jpg?w=584&h=704 584w, https://pterosaurheresies.files.wordpress.com/2023/08/crocodylomorpha2023.jpg?w=124&h=150 124w, https://pterosaurheresies.files.wordpress.com/2023/08/crocodylomorpha2023.jpg?w=249&h=300 249w, https://pterosaurheresies.files.wordpress.com/2023/08/crocodylomorpha2023.jpg 588w” sizes=”(max-width: 584px) 100vw, 584px” />

Figure 2. Subset of the LRT focusing on Crocodylomorpha in 2023. The new nestings represent just the latest of a changing hypothesis of interrelationships.

Outgroup taxa
The team cherry-picked Gracilisuchus, and the rauisuchians Batrachotomus and Postosuchus, as outgroup taxa, with Gracilisuchus at the base. While not likely to affect their multiple outcomes with their focus on Thalattosuchia, the LRT nests Gracilisuchus within the Crocodylomorpha – after testing 2300+ competing candidate taxa.

Figure 1. Ten basal bipedal crocodylomorphs descending from a sister to Decuriasuchus. ” data-image-caption=”

Figure 1. Ten basal bipedal crocodylomorphs descending from a sister to Decuriasuchus.

” data-medium-file=”https://pterosaurheresies.files.wordpress.com/2011/10/basalcrocs5883.jpg?w=243″ data-large-file=”https://pterosaurheresies.files.wordpress.com/2011/10/basalcrocs5883.jpg?w=584″ class=”size-full wp-image-17042″ src=”https://pterosaurheresies.files.wordpress.com/2011/10/basalcrocs5883.jpg?w=584&h=720″ alt=”Figure 1. Ten basal bipedal crocodylomorphs descending from a sister to Decuriasuchus.” width=”584″ height=”720″ srcset=”https://pterosaurheresies.files.wordpress.com/2011/10/basalcrocs5883.jpg?w=584&h=720 584w, https://pterosaurheresies.files.wordpress.com/2011/10/basalcrocs5883.jpg?w=122&h=150 122w, https://pterosaurheresies.files.wordpress.com/2011/10/basalcrocs5883.jpg?w=243&h=300 243w, https://pterosaurheresies.files.wordpress.com/2011/10/basalcrocs5883.jpg 588w” sizes=”(max-width: 584px) 100vw, 584px” />

Figure 3. Ten basal bipedal crocodylomorphs descending from a sister to Decuriasuchus from 2014.

The other two outgroup taxa
are indeed tested outgroup taxa in the LRT, but are not proximal to the Crocodylomorpha, which is the sister clade of the Dinosauria, together comprising the clade Archosauria. No other clades are members of the Archosauria in the LRT. The proximal outgroup clade in the LRT is the Poposauria and Turfanosuchus (not mentioned in the text) is at its base. Likewise, the basal dinosaur, Herrerasaurus (not mentioned in the text), might also have been included among the short list of outgroup taxa in Young et al 2024.

As everyone in paleontology should know,
basal crocodylomorphs and basal dinosaurs were both bipedal (Fig 3). That fact seems to have been overlooked by Young et al 2024 when they included those two more distantly related quadrupedal rauisuchians.

Lesson here: Don’t cherry-pick outgroup taxa and hope no one will notice. The LRT has been online for 13 years to provide outgroup taxa for any vertebrate clade you want to focus on. Even so, build your own LRT so you’ll understand hypothetical interrelationships from firsthand experience, not borrowing based on trust. or cherry-picking based on a guess, tradition or rumor.

Characters in Young et al 2024
“885 phenotypic characters (671 craniomandibular and dental characters, 197 postcranial characters, 14 soft-tissue characters, and three behavioural characters.”

That is several times more than the LRT, which uses 238 characters. That bump in character number is likely necessary to lump and split species and specimens. By contrast, the LRT tests the widest possible gamut of chordate taxa seeking to ascertain more generic and suprageneric interrelatiionships.

Results in Young et al 2024
The team reported the shortest tree length recovered  was 185 MPCs. The team published 9 similar cladograms (their figures 4–12). Several included suprageneric taxa. Seemingly (= only guessing here) every known thalattosuchian was tested.

Not every crocodylomorph was tested.
That wasn’t necessary, given the focus of this study, but it would have avoided the problem of cherry-picking academically-approved, but erroneous, outgroup taxa that might have effected tree topology in more derived taxa.

Who knows how a possible ‘butterfly affect’ effects cladograms, so try to not cherry-pick ingroup or outgroup taxa. Test a wide gamut of taxa to find out.
Taxon exclusion continues to be the number one problem in paleontology in 2024.
The LRT is online to help. No credit or citation is necessary.

References
Young MT et al (12 co-authors) 2024. The history, systematics, and nomenclature of Thalattosuchia (Archosauria: Crocodylomorpha). Zoological Journal of the Linnean Society, 2024, XX, 1–71 https://doi.org/10.1093/zoolinnean/zlad165

wiki/Thalattosuchia