Coryphodon (Mammalia, Pantodonta) From the Hannold Hill Formation, Eocene of Trans-Pecos Texas

Contents: Abstract -- Introduction -- Abbreviations -- Geological Context -- Systematic Paleontology -- Paleobiological Implications of Hannold Hill Coryphodon -- Age of Hannold Hill Formation -- Literature CitedSpeciments of the large extinct pantodont Coryphodon from the Hannold Hill Formation, Brewster County, Texas belong to single species, Coryphodon molestus. A sample of Coryphodon molestus from one locality in the Hannold Hill Formations consists of three adults and at least one juvenille. The sample aids in documenting sexual dimorphism in Coryphodon molestus and provides circumstantial evidence of gregarious behavior in that species. The presence of Coyphodon molestus in the Hannold Hill Formation indicates a late Gray Bull through Lost Cabin (Wasatchian) age. This is consistent with assignment of a late Gray Bull or Lysite age to the entire Hannold Hill vertebrate fauna.Texas Memorial Museu

Taxonomic status of Eohyus Marsh, 1894

In 1977 Marsh mentioned Eohyus as the oldest known artiodactyl but failed to describe or illustrate a type specimen, and thus Eohyus was for many years anomen nudum. The validity of its two species, E. distans and E. robustus, both named by Marsh in 1894, has been the subject of numerous and often conflicting opinions. Reexamination of the type specimens reveals that E. distans is a subjective synonym of Phenacodus primaevus Cope, 1873, and E. robustus is a subjective synonym of Periptychus carinidens Cope, 1881. The type of E. distans is from early Eocene (Wasatchian) age strata of the San Jose Formation, San Juan Basin, New Mexico; that of E. robustus is from middle Paleocene (Torrejonian) age strata of the Nacimiento Formation, also in the San Juan Basin

A new species of Conoryctella (Mammalia: Taeniodonta) from the Paleocene of the San Juan Basin, New Mexico, and a revision of the genus

Specimens from Paleocene strata of the Nacimiento Formation in Kutz Canyon, San Juan Basin, New Mexico, add to our knowledge of the poorly known taeniodont genus Conoryctella Gazin, 1939 and provide evidence for its taxonomic revision. C. dragonensis Gazin, 1939 is only known with certainty from its type specimen from the Dragon local fauna, North Horn Formation in east-central Utah, although a poorly preserved maxillary fragment and canine of uncertain provenance from the San Juan Basin, New Mexico, may pertain to this taxon. C. pattersoni, new species, differs from C. dragonensis in its smaller size, less molariform P4 and relatively narrow upper molars. It is known from: dental remains from the Dragon local fauna previously referred to C. dragonensis by Gazin (1939, 1941); dental remains from Torrejonian strata in Kutz Canyon referred by Wilson (1956, p. 82) to conoryctine, n. gen. and sp. ; and newly discovered dental and postcranial remains from a horizon in Kutz Canyon that, based on magnetostratigraphy (Tomida and Butler, 1980), is temporally equivalent to the Dragon local fauna. The occurrences of Conoryctella in the San Juan Basin extend the geographic range of the genus and also extend its time-stratigraphic range into a typical Torrejonian horizon. These extensions further reduce the distinctiveness of the Dragon local fauna, supporting recent arguments that the Dragon local fauna should be considered early Torrejonian in age

The GSSP Method of Chronostratigraphy: A Critical Review

The use of boundary stratotypes to define chronostratigraphic units began in the 1960s, and, in the 1980s, these were called Global Stratotype Sections and Points (GSSPs). Approximately two-thirds of the GSSPs of the bases of the Phanerozoic stage (71 of 102 in September 2018) have been ratified by the International Commission on Stratigraphy. However, this apparent progress toward precise definition of a Phanerozoic chronostratigraphic timescale is underlain by multiple problems of philosophy and methodology that include: (1) inconsistency in how chronostratigraphic units are being named and defined; (2) arbitrary decisions as to GSSP level, many based on arbitrarily chosen points in hypothetical chronomorphoclines of microfossils; (3) hierarchical reductionism, which makes the stage base the same as the base of the series, system, erathem and eonothem, thereby trivializing the significance of the boundaries of these larger chronostratigraphic units; (4) stability achieved by the non-scientific process of designating a GSSP once ratified as immutable; (5) the unworkable concept of a standard set of global stages; (6) the fallacy that a GSSP location can somehow define a recognizable (correlateable) global time line; (7) imprecision in GSSP correlation because the primary signals are largely single taxon biotic events that are inherently diachronous due to the limitations of fossil distributions by sampling, facies and provincialism; and (8) the politics of the International Commission on Stratigraphy and the small groups of specialists who select and vote on GSSPs. Chronostratigraphy needs to return to the concepts of natural chronostratigraphy, with improvements based on modern techniques like quantitative biostratigraphy. We need to standardize the chronostratigraphic scale, and the International Commission on Stratigraphy needs to rethink the philosophy and practices by which this is being done, so that we can move forward to produce the most informative chronostratigraphy possible based on a consistent methodology that allows the updating and obtaining of high accuracy and precision as new data become available

Reassessment of vertebrate ichnotaxa from the Upper Carboniferous ‘Fern Ledges’, Lancaster Formation, Saint John, New Brunswick, Canada

Vertebrate ichnotaxa described by George Frederic Matthew in 1910 from the Upper Carboniferous (Lower Pennsylvanian) ‘Fern Ledges’ of Saint John, New Brunswick, were dismissed as dubious trackways by previous authors. Thus, three new ichnospecies Matthew described appeared in the 1975 Treatise on Invertebrate Paleontology as “unrecognized or unrecognizable” and were mostly forgotten by vertebrate ichnologists. These traces include Hylopus (?) variabilis, Nanopus (?) vetustus and Bipezia bilobata. One ichnospecies, Hylopus (?) variabilis, here is retained as a valid tetrapod footprint ichnotaxon and reassigned to the ichnogenus Limnopus as a new combination, together with other poorly preserved specimens Matthew labeled, but never described. Nanopus (?) vetustus and Bipezia bilobata named by Matthew in the same paper, have been reexamined and remain as nomina dubia.

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

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

A PROPOSAL FOR NEW CHRONOSTRATIGRAPHIC STAGE SUBDIVISIONS OF THE UPPER TRIASSIC SERIES

Chronostratigraphic stages that have a short duration are desirable because they identify brief units that can be used to make more detailed and precise age assignments and correlations. Finer-scale substage and zonal subdivisions naturally remain for correlation, but these are outside the formal decision processes of the Subcomission on Triassic Stratigraphy (STS). The longest Phanerozoic stage is the Norian (approximately 18 Myr duration), which is both mismatched in terms of duration with other Phanerozoic stages, and the Lower and Middle Triassic Series, which together are shorter than the Norian Stage. If the Norian was formally divided it would also enhance our understanding of this interval as well as improve chronostratigraphic resolution. We propose the Norian should be raised in rank, and its substages used as new stages. However, such a modification would also require a re-evaluation of the hierarchical position of the Carnian and Rhaetian stages of the Upper Triassic. Given that the Carnian (approximately 10 Myr duration) is one of the longer stages in the Mesozoic it would also benefit with a raised ranking and subdivision to maintain its historical hierarchy with the Norian. We examine three alternative scenarios that raise the rank of the Carnian and Norian (and the Rhaetian Stage) in the chronostratigraphic hierarchy to either series or subseries rank. The existing Upper Triassic substages are also proposed to be raised in rank to stages, allowing formal definition by GSSP boundary stratotypes. The positive and negative issues with any changes in stage and substage hierarchy are examined

Extending the footprint record of Pareiasauromorpha to the Cisuralian : earlier appearance and wider palaeobiogeography of the group

Pareiasauromorpha is one of the most important tetrapod groups of the Permian. Skeletal evidence suggests a late Kungurian origin in North America, whereas the majority of occurrences come from the Guadalupian and Lopingian of South Africa and Russia. However, Pareiasauromorpha footprints include the ichnogenus Pachypes, which is unknown from strata older than late Guadalupian. A revision of several Pachypes-like footprints from the Cisuralian-Guadalupian of Europe and North America confirm the occurrence of this ichnogenus and of the ichnospecies Pachypes ollieri comb. nov. beginning in the Artinskian. This is the earliest known occurrence of Pachypes and it coincides with the Artinskian reptile radiation. Based on a synapomorphy-based track-trackmaker correlation, P. ollieri can be attributed to nycteroleter pareiasauromorphs such as Macroleter. Therefore, the earliest occurrences of pareiasauromorph footprints precede by at least 10 myr the earliest occurrence of this group in the skeletal record. Moreover, the palaeobiogeography of the group is extended to the Cisuralian and Guadalupian of western Europe