Description of the metoposauridAnaschisma brownifrom the New Oxford Formation of Pennsylvania

Abstract

Metoposaurids are a widespread and ubiquitous constituent of Late Triassic non-marine paleoenvironments. In North America, this group is practically the only large-bodied temnospondyl clade, and is particularly well documented from the American southwest and south-central regions (Arizona, New Mexico, Texas). However, metoposaurids are poorly documented from eastern North America, with fragmentary, doubtfully diagnostic historical material such as “Dictyocephalus elegans” Leidy, 1856 and “Eupelor durus” Cope, 1866. The Zions View (early Norian?) locality in Pennsylvania preserves more-complete material, which previous workers noted as belonging to “Buettneria perfecta” Case, 1922 (=Anaschisma browni Branson, 1905). However, the material has never been described in a fashion that characterizes the anatomy or that justifies the taxonomic assignment, yet it would represent the most complete material in eastern North America and a substantial expansion of this taxon's geographic range. Here we redescribe the Zions View metoposaurid material in detail, differentiating it from Calamops paludosus Sinclair, 1917, the only other Late Triassic temnospondyl from the eastern seaboard, and demonstrating confident affinities with A. browni. Our study is the first to properly justify the taxonomic referral, underscoring the broader importance of proper documentation of voucher specimens, especially for potential geographic outliers. Anaschisma browni is thus the most widely dispersed metoposaurid. Its easternmost documentation underscores the importance of the undersampled and understudied metoposaurid record on the eastern seaboard for understanding the development of a metoposaurid zone of exclusivity in North America and demonstrates the need for further exploration to refine conceptualizations of Late Triassic tetrapod evolution.

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;…”

To be or not to be heavier: The role of dermal bones in the buoyancy of the Late Triassic temnospondyl amphibian Metoposaurus krasiejowensis

“…Regardless of their amphibious origins, temnospondyls recolonized, and decolonized both aquatic and terrestrial habitats several times in their evolutionary history (Schoch, 2014). During the Late Triassic, a group of temnospondyls within the clade Stereospondyli, the Metoposauridae, started dispersing in different regions of Pangea as known based on the current global distribution of the fossil taxa (Brusatte et al, 2015;Chakravorti & Sengupta, 2019;Fortuny et al, 2019;Gee & Jasinski, 2021;Gee & Reisz, 2018;Sulej, 2007).…”

“…Metoposaurids are characterized by their anteriorly located orbits in the parabolic-shaped skull and massive dermal bones of the pectoral girdle; which are the interclavicles and clavicles (Brusatte et al, 2015;Buffa et al, 2019;Dutuit, 1976;Gee & Jasinski, 2021;Sulej, 2007).…”

“…Regardless of their amphibious origins, temnospondyls recolonized, and decolonized both aquatic and terrestrial habitats several times in their evolutionary history (Schoch, 2014). During the Late Triassic, a group of temnospondyls within the clade Stereospondyli, the Metoposauridae, started dispersing in different regions of Pangea as known based on the current global distribution of the fossil taxa (Brusatte et al, 2015; Chakravorti & Sengupta, 2019; Fortuny et al, 2019; Gee & Jasinski, 2021; Gee & Reisz, 2018; Sulej, 2007). Metoposaurids are characterized by their anteriorly located orbits in the parabolic‐shaped skull and massive dermal bones of the pectoral girdle; which are the interclavicles and clavicles (Brusatte et al, 2015; Buffa et al, 2019; Dutuit, 1976; Gee & Jasinski, 2021; Sulej, 2007).…”