With fragile, damaged fossils like
Lagosuchus talampayensis (Romer 1971; PULR 09; Late Triassic; Fig. 1), sometimes the fossilized bones alone tell only part of the story.
When bones disappear through taphonomy,
sometimes they leave impressions of their past presence providing workers subtle data that can be used for scoring in phylogenetic analysis, unless overlooked.
These two bipedal archosaur taxa
(Fig. 2) are similar, but the large reptile tree recovered them in distinct clades. The LRT nests Marasuchus with basal theropod Dinosaurs. Lagosuchus nests with Saltopus and other basal bipedal crocodylomorphs. These novel nestings were recovered due to including taxa overlooked by traditional studies.
Lagosuchus sister taxa in the LRT,
also have four sacrals. That fact provided the impetus for the present study searching for additional sacral impressions in high resolution photos from Agnolin and Ezcurra 2019.
As mentioned earlier,
a review of taxa tested within the Crocodylomorpha, like this one (Fig. 1), has resulted in several revisions to the croc subset of the LRT. The work is exciting, necessary and in progress. Results will be announced when they are known.
Agnolin FL and Ezcurra MD 2019.The validity of Lagosuchus talampayensis Romer, 1971 (Archosauria, Dinosauriformes), from the Late Triassic of Argentina. Breviora. 565 (1): 1–21.
Rauhut OMW and Hungerbühler A 2000. A review of European Triassic theropods. Gaia, 15: 75-88.
Romer AS 1971. The Chañares (Argentina) Triassic reptile fauna. X. Two new but incompletely known long-limbed pseudosuchians. Breviora. 378: 1–10.
Romer AS 1972. The Chañares (Argentina) Triassic reptile fauna. XV. Further remains of the thecodonts Lagerpeton and Lagosuchus. Breviora. 394: 1–7.
Sereno PC and Arcucci AB 1994. Dinosaurian precursors from the Middle Triassic of Argentina: Marasuchus lilloensis, gen. nov. Journal of Vertebrate Paleontology. 14 (1): 53–73.