Gehennachelys maini (Adrian, Smith, Noto, and Grossman, 2023) Adrian & Smith & Noto, 2023

Adrian, Brent, Smith, Heather F. & Noto, Christopher R., 2023, A revision of “ Trinitichelys ” maini (Testudinata: Baenidae) and additional material of its new genus from the Lewisville Formation (Woodbine Group, Cenomanian), Texas, USA, Palaeontologia Electronica (a 28) 26 (2), pp. 1-43 : 7

Gehennachelys maini comb. nov. (Adrian et al., 2019)

Figures 2-7

v. 2012 Noto, Main, and Drumheller, figures 2, 4A

v. 2015 Noto, figure 10A, C, E

v. 2019 Adrian, Smith, Noto, and Grossman, figures 2-3

Holotype. DMNH 2013-07 - 0712 , an anterior plastral lobe (Adrian et al. 2019, figure 3.1-4).

Type strata and locality. Upper Cretaceous (early middle Cenomanian) Lewisville Formation, Woodbine Group (Denne et al., 2016). The Arlington Archosaur Site, city of Arlington, Tarrant County, Texas . Exact locality data are on file at the Perot Museum of Nature and Science, Dallas, Texas .

Referred material. See hypodigm of Adrian et al. (2019), and additionally: DMNH 2013-07-1942, a nearly complete shell and cranium with associated postcrania; HMNS- 10-TM, a complete shell; DMNH 2013-07-0784, a partial carapace with well preserved sulci; DMNH 2013-07-1431, right coracoid; DMNH 2013-07-0601, right scapula; DMNH 2013-07-1924, second cervical vertebra; DMNH 2013-07-1369, partial right scapula; DMNH 2013- 07-0681, partial left scapula and associated bone fragments; DMNH 2013-07-0533, partial left scapula; DMNH 2013-07-2005, partial right scapula.

Distribution. Cenomanian of north central Texas.

Revised diagnosis. The newly combined taxon is diagnosed by the following unique combination of characters, rather than particular autapomorphies: deep upper temporal emargination exposing the anterior margin of the otic chamber in dorsal view; absent parietal-squamosal contact; elongated squamosal processes; prominent crista supraoccipitalis that is not covered anteriorly by the parietals; shell co-ossified in adults, with robust bridge peripherals and absent fenestrae; gular and extragular scales paired and similarly sized, with midline extragular contact; curved gular-extragular sulci; single, undivided cervical scale that is wider than long; straight femoral-anal sulcus; a complete ring of 12 marginal scales that separate the posteriormost vertebral scale from the carapace margin; scalloped posterior carapace margin; anterior and posterior plastral lobes that are approximately equidimensional.

Figures

FIGURE 2. DMNH 2013-07-1942, Gehennachelys maini comb. nov. skull: A, dorsal photograph; B, dorsal line drawing; C, ventral photograph; D, ventral line drawing; E, right lateral photograph; F, right lateral line drawing; G, left lateral photograph; H, left lateral line drawing. Arrow indicates anterior orientation for A-D. For E and F, anterior is to the right. Abbreviations: ac= acromion; cm= condylus mandibularis; ct= cavum tympani; fr= frontal; fst= foramen stapediotemporale; ju= jugal; mx= maxilla; or= orbit; pa=parietal; po= postorbital; pm= premaxilla; pr= prootic; qj= quadratojugal; qu= quadrate; so= supraoccipital; sq= squamosal.

FIGURE 3. DMNH 2013-07-1942 carapace in A, dorsal, and B, ventral views. Plastron in C, dorsal, and D, ventral views. E corresponds with the red box in C, showing the left humerus, rotated 180°. Arrow indicates anterior orientation for A-D. Scale increments in mm for E.

FIGURE 4. HMNS-10-TM, shell of Gehennachelys maini comb. nov., in A, dorsal, B, ventral, C, right lateral, D, ante- rior, and E, posterior views. Note separate scales for A-B, C, and D-E.

FIGURE 5. DMNH 2013-07-1942 vertebrae. Cervical vertebrae in A, left lateral, B, anterior, and C, posterior views. Ventral view of indeterminate dorsal vertebrae in D, with anterior to the right.

FIGURE 6. DMNH 2013-07-1942, Gehennachelys maini comb. nov. shoulder girdle and forelimb bones. Partial left scapula of DMNH 2013-07-1942 in A, posteromedial, and B, anterolateral views. Partial right scapula of DMNH 2013- 07-1942 in C, posteromedial, and D, anterolateral views. Partial right scapula of DMNH 2013-07-0601 in E, posteromedial, and F, anterolateral views. Right coracoid of DMNH 2013-07-1942 in G, dorsal, and H, ventral views. Partial left coracoid of DMNH 2013-07-1942 in I, dorsal, and J, ventral views. Right humerus in K, posterior, L, dorsal, M, proximal, N, distal, O, ventral, and P, posterior views. M and N are oriented with B.

FIGURE 7. DMNH 2013-07-1942 pelvic girdle and hind limb bones. Partial pelvis in A, right lateral view, oriented with anterior to the right. Partial pubic plate in B, ventral, and C, dorsal views. Left femur in D, anterior, E, ventral, F, proximal, G, distal, H, dorsal, and I, posterior views. Partial right tibia in J, dorsal, K, medial, L, ventral, and M, lateral views. Dotted line in G indicates margin of acetabulum.