A softshell turtle (Testudines: Trionychidae: Plastomeninae) from the uppermost Cretaceous (Maastrichtian) Hell Creek Formation, North Dakota, USA, with implications for the evolutionary relationships of plastomenines and other trionychids

The cranial and postcranial morphology of Hutchemys rememdium and its impact on the phylogenetic relationships of Plastomenidae (Testudinata, Trionychidae)

“…Nonetheless, while the skulls of Gilmoremys lancensis and Plastomenus thomasii exhibit fused frontals and reduced to absent postorbitals, the frontals of Hutchemys rememdium are unfused and the postorbitals are notably large. So, while Gilmoremys lancensis and Plastomenus thomasii were sometimes, but not always, placed as each other’s immediate sisters in previous trees (Edgar et al, 2022 ; Evers et al, 2023 ; Jasinski et al, 2022 ; Joyce & Lyson, 2017 ; Joyce et al, 2016 , 2018 ; Lyson et al, 2021 ; Vitek et al, 2018 ), we consistently find this result in our analyses. In other words, the inclusion of the skull of Hutchemys rememdium enforces the idea that Gilmoremys spp.…”

“…The taxon Plastomenidae was originally coined by Hay ( 1902 , 1908 ) to group an assortment of Late Cretaceous to Eocene trionychids from North America that exhibit a plastron with broad callosities that connect to form a solid shield. Over the course of the last decade, a number of phylogenetic hypotheses focusing on the best-preserved taxa typically confirmed this grouping to be monophyletic (e.g., Edgar et al, 2022 ; Evers et al, 2023 ; Jasinski et al, 2022 ; Joyce & Lyson, 2017 ; Joyce et al, 2016 , 2018 ; Lyson et al, 2021 ; Vitek et al, 2018 ). However, there has been little agreement as to the internal relationships of this clade.…”

Osteology and reassessment of Dineobellator notohesperus, a southern eudromaeosaur (Theropoda: Dromaeosauridae: Eudromaeosauria) from the latest Cretaceous of New Mexico

“…Additionally, some of this variation is particularly hard to definitively identify in the fossil record, especially sexual dimorphism (e.g., Mallon, 2017). Many studies have been conducted on morphological variation, particularly within fossil taxa (e.g., Arbour et al, 2016; Bell, 2011; Burns et al, 2015; Carter et al, 2021; Currie, 2003a, 2003b; Dalman et al, 2017, 2021; Dalman, Jasinski, & Lucas, 2022; Dalman, Lucas, et al, 2022; Delcourt & Iori, 2018; Dodson, 1976; Evans et al, 2013, 2014; Fabrezi et al, 2017; Gee & Jasinski, 2021; Grillo & Delcourt, 2017; Jasinski, 2011, 2013, 2015b, 2018; Jasinski et al, 2018, 2022; Jasinski & Moscato, 2014, 2017; Jasinski & Wallace, 2014, 2015; Ji et al, 2011; Johnson, 2020; Johnson et al, 2021; Lacovara et al, 2014; Lehman, 1987; 2001; Longrich, 2014; Lucas et al, 2011, 2016; Machado et al, 2013; Moscato & Jasinski, 2016; Osborn, 1923; Rivera‐Sylva et al, 2012; Rowe, Colbert, & Nations, 1981; Sampson et al, 2010; Sullivan et al, 2013; Sullivan & Jasinski, 2012; Sullivan, Jasinski, Guenther, & Lucas, 2011; Sullivan, Lucas, & Jasinski, 2011c, 2011d; Vamberger et al, 2020; Voris et al, 2019). While the only definitive specimen of Dineobellator notohesperus is the holotype (SMP VP‐2430), other specimens from the Naashoibito Member argue for the presence of more than one dromaeosaurid taxon in this stratigraphic unit.…”

“…Additionally, some of this variation is particularly hard to definitively identify in the fossil record, especially sexual dimorphism (e.g., Mallon, 2017). Many studies have been conducted on morphological variation, particularly within fossil taxa (e.g., Arbour et al, 2016;Bell, 2011;Burns et al, 2015;Carter et al, 2021;Currie, 2003aCurrie, , 2003bDalman et al, 2017Dalman et al, , 2021Delcourt & Iori, 2018;Dodson, 1976;Evans et al, 2013Evans et al, , 2014Fabrezi et al, 2017;Gee & Jasinski, 2021;Grillo & Delcourt, 2017;Jasinski, 2011Jasinski, , 2013Jasinski, , 2015bJasinski, , 2018Jasinski et al, 2018Jasinski et al, , 2022Jasinski & Moscato, 2014Jasinski & Wallace, 2014Ji et al, 2011;Johnson, 2020;Johnson et al, 2021;Lacovara et al, 2014;Lehman, 1987;2001;Longrich, 2014;Lucas et al, 2011Lucas et al, , 2016Machado et al, 2013;Moscato & Jasinski, 2016;Osborn, 1923;Rivera-Sylva et al, 2012;Rowe, Colbert, & Nations, 1981;Sampson et al, 2010;Sullivan et al, 2013;…”

14th Symposium on Mesozoic Terrestrial Ecosystems and Biota

“…The plastomenine is represented by a distal costal that exhibits fine ridges between pits of varying shape. Laterally, the costal possesses a groove (or splitting into dorsal and visceral lobes, sensu Joyce et al, 2009) that is apomorphic for the clade including Helopanoplia and Hutchemys based on previous phylogenetic analyses (e.g., Edgar et al, 2022;Jaskinski et al, 2022;Joyce et al, 2009). At least two morphotypes of crocodylomorph teeth were recovered from the Neslen Formation.…”