but there are a number of Triassic forms just outside of Dinosauria that have been discovered in the last few decades. The best known non-dinosaur dinosauromorphs are the silesaurids, a group of relatively long-necked, quadrupedal herbivores and omnivores found in Middle Triassic to Upper Triassic rocks of the United States, Brazil, Argentina, Morocco, Zambia, Madagascar, and Poland (Martz and Small 2019). Silesaurids are typically considered to be non-dinosaurian dinosauriforms (e.g., Nesbitt 2011), although some studies recover them as “basal” ornithischians (e.g., Norman et al. 2022) or as the sister taxon to Ornithischia (e.g., Cabreira et al. 2016). Lagosuchus is a non-dinosaur dinosauromorph of uncertain placement. We anticipate that Silesauridae will be a holobaramin, but we are not sure how Lagosuchus will correlate with the other taxa in the analysis. Dinosauria (even excluding birds) is an enormous group full of immense diversity and disparity, from tiny bipeds smaller than chickens to enormous beasts weighing in over 60 tons. Richard Owen named Dinosauria in 1842b, and H.G. Seeley later in 1887 recognized what most today see as the two major groups of dinosaurs: Saurischia (including Theropoda and Sauropodomorpha) and Ornithischia. This classic dichotomy was challenged in 2017 by a scheme that would see Theropoda and Ornithischia as sister taxa in the group Ornithoscelida, to the exclusion of Sauropodomorpha and the enigmatic, Triassic group Herrerasauridae (Baron et al. 2017). Regardless of these higher classification questions, there are some recognizable groups of dinosaurs found in Triassic rocks. Theropods and herrerasaurids both make an appearance as do multiple groups of sauropodomorphs (classic “prosauropods” like Plateosaurus as well as guaibasaurids and theropod-like forms such as Eoraptor). Assuming silesaurids are not ornithischians, there are no definitive Triassic ornithischians known as of yet (as Pisanosaurus may be a silesaurid (Müller and Garcia 2020)). Despite the many classification issues with these Triassic dinosaurs, we suspect that there are multiple holobaramins present, in agreement with Doran et al. (2018). B. Previous Baraminology Work on Archosauromorphs All previous baraminology studies on archosauromorphs have focused on archosaur taxa except one on phytosaurs (Grimes and McLain 2017). The majority of archosaur baraminology studies have focused on avemetatarsalians. Only three studies have investigated pseudosuchians: two focused on extant crocodilians (Cserháti 2023; Hennigan 2014) and the other on both fossil and extant eusuchians (Frederico and McLain 2019). As such, there have been no baraminology studies that have looked at the abundant, diverse, and disparate non-eusuchian pseudosuchian taxa (e.g., “rauisuchians”, aetosaurs, poposauroids, etc.). Avemetatarsalians, the group containing dinosaurs and pterosaurs (Fig. 1), have received a great deal more attention than pseudosuchians. Non-ornithodiran avemetatarsalians (e.g., aphanosaurs) have not been analyzed for baraminic status. Among the pterosauromorphs, there have only been a few pterosaur studies (Clausen and McLain 2021; McLain 2021; McLain 2022), although these have mainly focused on non-pterodactyloid pterosaurs. The large majority of baraminology studies in archosaurs have focused on Dinosauria, with non-dinosaurian dinosauromorphs (e.g., silesaurids) currently lacking specific studies (although a manuscript is currently in preparation). Most major non-avian dinosaur taxa have been analyzed except for sauropods (Aaron 2014; Cavanaugh 2011; Cserhati et al. 2020; Doran et al. 2018; McLain et al. 2018; Wood et al. 2011). Mesozoic non-avian avialans were the focus of one study (Garner et al. 2013). Extant birds (Aves) have been the subject of numerous baraminological studies, both with statistical baraminology (Brophy 2021; Brophy and McConnachie 2021; Matthews et al. 2022; Wood 2005; Wood 2016) and without (Ahlquist and Lightner 2019; Lightner 2010; Lightner 2013; More 1998). METHODS We analyzed a dataset from a recent publication on Triassic archosaurs (Kellner et al. 2022) with statistical baraminological methods. We used BARCLAY (Wood 2020) to analyze the dataset with the following methods: 1) Pearson baraminic distance correlation (BDC), 2) Spearman BDC, 3) three-dimensional multidimensional scaling (3D MDS), 4) partition around medoids (PAM), and 5) fuzzy analysis (FANNY). We recognized that this dataset likely contains multiple created kinds, which would necessitate splitting up the taxa into smaller taxonomic groups, following the example of other studies (e.g., McLain et al. 2018; Wood 2005). The dataset and all subset versions were analyzed at a 0.75 character relevance cutoff. Table 1 shows the character and taxa numbers for each of the different analyses we ran on BARCLAY. RESULTS A. All Archosauromorpha Analyzing all of the archosauromorph taxa required excluding 61 poorly known taxa below a 0.2 character relevance cutoff (Supplemental Table 1). Thus, 135 taxa remained along with only 83 characters at a 0.75 character relevance cutoff. As anticipated, the results at this level were not very informative. The Pearson and Spearman BDC plots (Supplemental Fig. 1 and Fig. 2) show positive correlation uniting almost all of the taxa. Only the rhynchosaurs are set apart by some negative correlation from the rest of the taxa, although even they share positive correlation with many of the taxa in the analysis. The highest average silhouette width for PAM was 0.08 at two groups, with a large number of taxa with negative silhouette values in the red group (Supplemental Fig. 3A). FANNY, by contrast, had an average silhouette width value of 0.33 at two groups (Supplemental Fig. 3B), and it would not work correctly at higher group numbers. The red group in FANNY had many taxa with negative silhouette width values. We did not attempt MDS results as the other methods were demonstrating that it was not worth the effort at this scale. In order to resolve the actual patterns of continuity and discontinuity among these archosauromorph taxa, we split up the dataset into recognizable taxonomic groups. B. “Protorosauria” The Pearson BDC results for the “Protorosauria” subset dataset (Figure 3A) show four blocks of positive correlation with no shared positive correlation between them. The largest block consists of tanystropheids and dinocephalosaurids. Additionally, the enigmatic Jesairosaurus shares positive correlation with the dinocephalosaurid Pectodens, which is in turn positively correlated with Dinocephalosaurus. The three remaining blocks of positive correlation are all different outgroup taxa. One block contains the rhynchocephalians (tuatara relatives) Planocephalosaurus and Gephyrosaurus. Another contains the choristoderes Simoedosaurus and Cteniogenys, a group previously analyzed with statistical baraminology by McLain and Doran (2019). The third outgroup block contains the “basal” diapsids Petrolacosaurus (an araeoscelidian), Youngina (a younginiform), and Acerosodontosaurus (a form of uncertain affinities). MCLAIN, CLAUSEN, PEREZ, BEEBE, AND AHTEN Archosauromorph Baraminology 2023 ICC 492
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