With these thoughts in mind, we predict that there will be evidence of continuity within each of the families Doswelliidae and Proterochampsidae, but there may be discontinuity between the two groups themselves, as they are sometimes recovered separately in the phylogenetic trees. We expect to see evidence of discontinuity between Proterochampsia and other non-archosaur archosauromorphs. 6. Phytosauria Phytosauria is a group of extinct crocodile-like archosauriforms with at least 30 valid species and one of the richest fossil records of all Triassic archosauromorphs (Stocker and Butler 2013; Stocker et al. 2017). The first phytosaur was named by Georg Friedrich Jaeger in 1828. He named the creature “plant lizard” because he mistook sediment-filled alveoli in the jaw as herbivore teeth. Since then, many specimens have been found possessing two kinds of teeth: conical, crocodile-like teeth in the front of the jaws and sometimes serrated carnivorous teeth similar to those of theropod dinosaurs farther back in the jaws. Phytosaurs could grow to be up to six meters long. They possessed unique triangular osteoderms that are exclusive to phytosaurs which allow them to be easily distinguished. The placement of the nostrils above or close to the eyes is another distinctive feature of phytosaurs. Numerous phytosaur fossils have been discovered worldwide in what have been recognized as lacustrine and fluvial paleoenvironments, but more recently, it has been shown that some of them may have also existed in marine habitats (Butler et al. 2019a). Many scientists have utilized phytosaurs as index taxa for biostratigraphic and biochronological correlation since they are widely distributed and easy to differentiate (e.g., Lucas and Hunt 1993; Martz and Parker 2017). The phylogenetic position of phytosaurs within Archosauriformes has been debated over time. Many scientists have recognized phytosaurs within Archosauria (e.g., Ezcurra 2016), which matches their possession of the “crocodile-normal ankle joint”, a complex ankle joint where the hinge line zig-zags between the calcaneum and astragalus rather than the simple hinge line between the proximal and distal tarsals found in avemetatarsalians (see below). This feature was believed to show that phytosaurs were pseudosuchians. However, other studies suggest that phytosaurs are a sister taxon of Archosauria, reinterpreting the crocodile-normal ankle joint as plesiomorphic for Phytosauria and Archosauria (Nesbitt 2011). The origin of phytosaurs was shrouded in mystery from an evolutionary perspective as they seemed to suddenly pop onto the scene in the Late Triassic fully formed, like aetosaurs, rauisuchians, and many other archosauromorphs. However, reinterpretation of a Chinese Middle Triassic archosauriform called Diandongosuchus resulted in its recognition as the basalmost phytosaur (Stocker et al. 2017). Diandongosuchus lacks many classic phytosaur traits (e.g., elongated rostrum), but it does share several features in common with phytosaurs (e.g., shape of the scapular blade). Given the uniqueness of the phytosaur bauplan and the clear distinction between phytosaurs and non-phytosaurs, we expect Phytosauria to be a holobaramin. Additionally, we anticipate that Diandongosuchus will be discontinuous with other phytosaurs and will therefore be in a different holobaramin. 7. Pseudosuchia The name Pseudosuchia means “false crocodiles,” which is ironic given that the group includes true crocodiles! The name originated with Karl Alfred von Zittel who coined it to group together Aetosaurus, Typothorax, and Dyoplax. Later authors removed aetosaurs from the group, but made it a suborder of Thecodontia containing animals like Ornithosuchus (e.g., Romer 1956). With the use of phylogenetics in paleontology, Pseudosuchia became the group containing all archosaurs more closely related to crocodilians than to birds (Gauthier 1986). It has a confusing history with another term—Crurotarsi—which Sereno defined to replace Pseudosuchia as the clade containing phytosaurs, ornithosuchids, Prestosuchus, Suchia, and all descendants of their common ancestor. However, Nesbitt (2011) found phytosaurs outside of Archosauria, which means Crurotarsi is a clade that includes phytosaurs and all archosaurs (including avemetatarsalians). Pseudosuchia is a group with immense diversity and disparity. Modern crocodilians look relatively similar to each other, mainly differing in skull shapes and proportions. However, fossil pseudosuchians have radically different appearances from modern crocodilians and from each other. The group includes the armored, shovel-snouted aetosaurs; the hypercarnivorous “rauisuchians;” the agile, ostrich-mimic mimicking shuvosaurids; the sail-backed ctenosauriscids; the marine metriorhynchids; the pug-nosed Simosuchus; and many, many other forms. As such, we predict that the group will contain multiple holobaramins. However, this analysis will not be able to truly investigate the baraminic relationships of pseudosuchians as the list of taxa are mainly focused on non-archosaur Archosauromorpha. 8. Avemetatarsalia Benton (1999) defined Avemetatarsalia as all crown-group archosaurs closer to Dinosauria than to Crocodylia. He erected the group because of his work on Scleromochlus, which he saw as outside the clade containing pterosaurs and dinosaurs (Ornithodira). Scleromochlus has been a difficult animal to classify, and for many years it seemed like Avemetatarsalia may be identical in composition to Ornithodira. However, the description of Teleocrater and recognition of its position along with other taxa in Aphanosauria just outside Ornithodira have confirmed that Ornithodira and Avemetatarsalia are not the same (Nesbitt et al. 2017). We anticipate aphanosaurs to share continuity and to be discontinuous from all other taxa. Ornithodirans can be readily distinguished from pseudosuchians in the anatomy of their ankles (except among some dinosauriforms such as the silesaurid Asilisaurus (Nesbitt et al. 2017), which possess more pseudosuchian-like ankle joints). Ornithodirans possess simple hinge joints between the proximal and distal tarsals, whereas pseudosuchians have a more complex joint that goes between the two proximal tarsals (calcaneum and astragalus) called the “crocodile-normal” ankle. Nesbitt et al. (2017) proposed that the “crocodile-normal” ankle is plesiomorphic for Archosauria. Ornithodira splits into Pterosauromorpha and Dinosauromorpha. Pterosauromorpha contains Lagerpetidae and Pterosauria, a group readily distinguished from all other archosauromorphs by numerous characters, especially those related to flight. Triassic pterosaurs are surprisingly diverse, and all currently known forms were flight capable (see, for example, Britt et al. 2018; Dalla Vecchia 2013). Despite the recognition of the similarities between lagerpetids and pterosaurs (hence their inclusion in Pterosauromorpha (Ezcurra et al. 2020)), conventional scientists are no closer to finding a “proto-pterosaur” than when the first Triassic pterosaur was discovered in 1973. Previous baraminology work has found evidence for discontinuity within Pterosauria, even within the non-pterodactyloids (Clausen and McLain, 2021; McLain, 2021; McLain 2022). As such, we anticipate that this study will find discontinuity surrounding Pterosauria, and— given the inclusion of pterosaurs from multiple families in the dataset—discontinuity separating some pterosaurs from others. We also anticipate that Lagerpetidae will be a holobaramin. Dinosauromorpha contains Dinosauria (and Aves cladistically), MCLAIN, CLAUSEN, PEREZ, BEEBE, AND AHTEN Archosauromorph Baraminology 2023 ICC 491
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