Scolomastax sahlsteini, Noto, Drumheller, Adams & Turner, 2019

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 : 5

Scolomastax sahlsteini

Woodbinesuchus byersmauricei

Terminonaris cf. robusta

Eusuchia indet.

Reptilia – Testudinata

Naomichelys sp.

Gehennachelys maini , comb. nov.

Pleurochayah appalachius

Trionychidae indet.

Mammalia

Multituberculata indet.

Flexomornis howei , considered the oldest bird in North America, as well as remains of a coelurosaurian theropod and the ornithopod Protohadros (Main, 2005; Noto, 2015; Noto et al., 2022). Additional remains of chondrichthyans, osteichthyans, turtles, and crocodyliforms have also been recovered, as well as theropod and hadrosaur tracks (Tykoski and Fiorillo, 2010; Noto, 2015). Geological and palynological work is ongoing at the Dam Spillway, and surface collection of fossils continues.

HMNS-10-TM was discovered near Oak Grove Park, on the southwest shore of Grapevine Lake, across the lake from a stratigraphically measured sequence between Murrell Park and Rock Ledge Park (Main, 2005). Shoreline and water level conditions were not recorded at the time of its excavation, but the discovery site is comprised of fine red sandstone beds of unknown thickness. The water in this area is shallow near the shoreline with extensive emergent vegetation. The exposed area is flat, prone to inundation, and covered by modern soils with established terrestrial vegetation.

The measured stratigraphic sequence on the north shore preserves a nearly complete delta sequence from Grapevine Lake exposures (Main, 2005, 2013), ranging from fluvial channel sands (GP-8 TO GP-10) at Murrell Park, to delta front sands and prodelta muds near Rock Ledge Park (section GP-1) (see stratigraphic description in Main, 2005). Though the discovery site of HMNS-10-TM is on the opposite side of the lake, it is less than 2500 m away. If the conditions are similar on both sides of the lake, the red sandstone beds at the discovery site may correspond with a trough cross-bedded red sandstone at the top of sections GP-8 to GP-10 (Main, 2005). The wavy-ripple laminated arenaceous sand bed is divided by a thin iron concretionary bed and is interpreted as a third order fluvial channel sequence that represents medium term variation in hydrodynamic conditions, belonging to the lower Arlington Member of the Woodbine Formation (Main, 2005, 2013; Noto, 2015). Though the depositional model of the Grapevine Lake exposures may be similar between the measured stratigraphy and the discovery site of HMNS-10-TM, there is a possibility for a significant margin of error.