A new baenid turtle from the early Paleocene (Torrejonian) of New Mexico and a species-level phylogenetic analysis of Baenidae

Abstract

Abstract.-New cranial and postcranial material of the baenid turtle Neurankylus from the Paleocene Nacimiento Formation (Torrejonian NALMA) of northwestern New Mexico represents a new species, Neurankylus torrejonensis. The material consists of a fragmented but mostly complete skull, a partial carapace and plastron, portions of both humeri, a partial pelvis, a complete right femur, and a distal phalanx. The small, undivided cervical scale, wide vertebrals, complete ring of marginals, and large size (carapace length 520 mm) diagnose the new taxon as belonging to Neurankylus. The narrow fifth vertebral scale and scalloped posterior shell margin reveal affinities with Neurankylus baueri Gilmore, 1916, which is known from Campanian sediments in New Mexico and Utah. The holotype of Neurankylus torrejonensis is the youngest known specimen of the Neurankylus lineage, which is known to reach at least back to the Late Cretaceous (Santonian). A nearly complete species-level analysis of baenids confirms the basal placement of Neurankylus outside of Baenodda and the split of Baenodda into two primary subclades, herein named Palatobaeninae and Eubaeninae.

Morphological variation, phylogenetic relationships, and geographic distribution of the Baenidae (Testudines), based on new specimens from the Uinta Formation (Uinta Basin), Utah (USA)

“…Thus, this relationship should not be considered full resolved, and as more specimens are recovered, the understanding can be refined. Uintan baenid monophyly has not been universally recovered in past studies of baenid phylogeny [6, 36]. However, it is consistent with many historical interpretations of relationships within the Baenidae [2, 37–38], and is also compatible with geotemporal distributions of the species.…”

“…In order to determine whether the new Uintan baenid specimens affected the current understanding of phylogenetic relationships within the Baenidae, we conducted a phylogenetic analysis. We used as our starting point, a recent analysis of baenid phylogeny [ 36 ] which included a compilation of 69 characters from Lyson and Joyce [ 5 , 37 – 39 ], Larson et al . [ 40 ], and novel characters [ 36 ].…”

A Description of the Skull of Eubaena Cephalica (Hay, 1904) and New Insights into the Cranial Circulation and Innervation of Baenid Turtles

“…The available skull material of Neurankylus eximius is similarly incomplete, but neither pictures (Brinkman and Nicholls, 1993) nor CT volume renderings (Larson et al, 2013) show the structures in question. The only available skull of Neurankylus torrejonensis, by contrast, clearly exhibits two foramina on the ventral surface of the basioccipital (Lyson et al, 2016), although their passage is unclear. Hayemys latifrons is known from a partially crushed skull, but although neither the description of Hay (1908) nor the illustrations of Gaffney (1972a) provide evidence of foramina, personal observations of the skull show these structures.…”

“…Opisthotic-The contribution of the opisthotic to the dorsal opening of the stapedio-temporal canal is routinely used to assess phylogenetic relationships within Paracryptodira, although a clear pattern is currently lacking that would reveal this character to have higher significance, because it is unevenly distributed across paracryptodires (see Lyson et al, 2016). We here confirm that Eubaena cephalica lacks a contribution of the opisthotic to the foramen stapedio-temporale but note that the CT scans reveal a contribution of the opisthotic to the stapediotemporal canal.…”

A new species of baenid turtle from the Early Cretaceous Lakota Formation of South Dakota

“…We inserted Lakotemys australodakotensis gen. et sp. nov. into the matrix of Lyson et al (2019), which in turn is based on the phylogenetic analysis of Lyson and Joyce (2009a, b, 2010, 2011, Lyson et al (2011), andLyson et al (2016). To investigate the phylogenetic relationships of Early Cretaceous paracryptodires, we furthermore included Protobaena wyomingensis from the Aptian-Albian of Wyoming to the matrix, based on the original description of Gilmore (1919).…”