TABLE 1. Vertebrate faunal list of the Arlington Archosaur Site. Data from Noto (2015), Adams et al. (2017), Adrian et al. (2019, 2021), and Noto et al. (2019, 2022).
| Chondrichthyes | |
| Hybodontidae indet. | |
| Cretodus sp. | |
| Squalicorax sp. | |
| Onchopristis dunklei | |
| Pseudohypolophus (Hypolophus) mcnultyi | |
| Pseudomyledaphus sp. | |
| Osteichthyes | |
| Melvius sp. | |
| Elopomorpha indet. | |
| Coelodus sp. | |
| Enchodus sp. | |
| Lepisosteidae indet. | |
| Osteichthyes - Dipnomorpha | |
| Ceratodus carteri | |
| Amphibia | |
| Caudata indet. | |
| Cryptobranchidae indet. | |
| Anura indet. | |
| Reptilia - Dinosauria - Theropoda | |
| Tyrannosauroidea indet. | |
| Carcharodontosauria indet. | |
| Ornithomimosauria indet. | |
| Dromaeosauridae indet. | |
| Troodontidae indet. | |
| Coelurosauria indet. | |
|
Reptilia - Dinosauria - Ornithopoda |
|
| Protohadros byrdi | |
| Reptilia - Crocodyliformes | |
| Deltasuchus motherali | |
| Scolomastax sahlsteini | |
| Woodbinesuchus byersmauricei | |
| Terminonaris cf. robusta | |
| Eusuchia indet. | |
| Reptilia - Testudinata | |
| Naomichelys sp. | |
| Gehennachelys maini, comb. nov. | |
| Pleurochayah appalachius | |
| Trionychidae indet. | |
| Mammalia | |
| Multituberculata indet. | |
TABLE 2. Comparison of traits from basal baenids and basal baenodds with known skulls, carapaces, and plastra. Data obtained from: Gilmore, 1920; Brinkman, 2003; Lyson and Joyce, 2009a; Joyce and Lyson, 2015; Lively, 2015; Joyce et al., 2020; Rollot et al., 2022a, b.
| Trait | Lakotemys australodakotensis |
Trinitichelys hiatti |
Gehennachelys maini comb. nov. | Arvinachelys goldeni |
| Age | Berriasian-Valanginian | Aptian-Albian | Cenomanian | Campanian |
| Parietal-squamosal contact | Present | Present | Absent | Absent |
| Nasals | Slightly reduced | Reduced | Reduced or absent | Enlarged |
| Squamosal processes | Not elongated | Elongated | Elongated | Not elongated |
| Upper temporal emargination: visibility in dorsal view of anterior portion of otic capsule | Not visible | Not visible | Visible | Visible |
| Crista supraoccipitalis: anterior coverage by parietals | Halfway | Extensive | Minimal | Extensive |
| Jugal contribution to posterior orbital margin | Absent | Absent | Present | Present |
| Relative size of frontals and parietals | Parietals larger | Parietals larger | Parietals larger | Frontals larger |
| Midline extragular contact | Absent | Absent | Present, relatively short | Gular scales absent |
| Larger plastral lobe | Anterior | Posterior | Equidimensional | Posterior |
| Plastral length (cm) | ~28 | ~29 | 36.3 | 29.1 |
| Vertebral scale 1 narrowing | ? | Posteriorly | Posteriorly | Posteriorly |
| Vertebral scale 3 dimensions | Equidimensional | Wider than long | Wider than long | Wider than long |
| Femoral-anal sulcus shaped | Straight | ? | Straight | Omega-shaped |
| Vertebral scale contribution to posterior margin | Probably absent | Probably absent | Absent | Present |
TABLE 3. Relative proportions of complete baenid taxa, plus Glyptops. * indicates estimation of nearly-complete shell. Data from: Archibald (1977, table 53); Lyson and Joyce (2009b, figure 6); Larson et al. (2013, figure 21.5); Joyce and Lyson (2015: figure 2A); Lively (2015, figures 5C, 6C); Lyson et al., (2016, figure 4); Lyson et al., (2019, figure 6).
| Taxon | Anterior lobe length / Posterior lobe length |
Plastron length / Carapace length |
| Glyptops 1 | 0.92 | 0.88 |
| Glyptops 2 | 0.77 | 0.88 |
| Trinitichelys hiatti | 0.66 | 0.87 |
| Neurankylus eximius | 0.86 | 0.72 |
| Thescelus insiliens | 1.06 | 1.00 |
| Plesiobaena antiqua | 0.79 | 0.91 |
| Boremys pulchra | 1.18 | 0.89 |
| Scabremys ornata | 0.98 | 0.92 |
| Denazinemys nodosa | 0.91 | 0.91 |
| Eubaena cephalica | 1.00 | 0.83 |
| Baena arenosa | 0.94 | 0.89 |
| Chisternon undatum | 1.02 | 0.89 |
| Gehennachelys maini comb. nov. | 0.98 | 1.00 |
| Saxochelys gilberti | 1.04 | 1.07 |
| Arvinachelys goldeni | 0.85 | 0.97 |
| Palatobaena cohen | 0.60 | 0.94 |
| Neurankylus lithographicus | 0.84 | 0.81 |
| Cedrobaena brinkman* | 0.60 | 0.89 |
| Neurankylus baeuri | 0.84 | 0.80 |
