An official website of the United States government
We present a previously discovered but undescribed late Early Cretaceous vertebrate fauna from the Holly Creek Formation of the Trinity Group in Arkansas. The site from the ancient Gulf Coast is dominated by semi-aquatic forms and preserves a diverse aquatic, semi-aquatic, and terrestrial fauna. Fishes include fresh- to brackish-water chondrichthyans and a variety of actinopterygians, including semionotids, an amiid, and a new pycnodontiform, Anomoeodus caddoi sp. nov. Semi-aquatic taxa include lissamphibians, the solemydid turtle Naomichelys , a trionychid turtle, and coelognathosuchian crocodyliforms. Among terrestrial forms are several members of Dinosauria and one or more squamates, one of which, Sciroseps pawhuskai gen. et sp. nov., is described herein. Among Dinosauria, both large and small theropods ( Acrocanthosaurus , Deinonychus , and Richardoestesia ) and titanosauriform sauropods are represented; herein we also report the first occurrence of a nodosaurid ankylosaur from the Trinity Group. The fauna of the Holly Creek Formation is similar to other, widely scattered late Early Cretaceous assemblages across North America and suggests the presence of a low-diversity, broadly distributed continental ecosystem of the Early Cretaceous following the Late Jurassic faunal turnover. This low-diversity ecosystem contrasts sharply with the highly diverse ecosystem which emerged by the Cenomanian. The contrast underpins the importance of vicariance as an evolutionary driver brought on by Sevier tectonics and climatic changes, such as rising sea level and formation of the Western Interior Seaway, impacting the early Late Cretaceous ecosystem.
more »
« less
A partial tyrannosauroid femur from the mid-Cretaceous Wayan Formation of eastern Idaho, USA
The diversity of mid-Cretaceous tyrannosauroids is poorly understood. We describe a partial tyrannosauroid femur from the Albian–Cenomanian Wayan Formation of eastern Idaho that helps to fill in an important spatiotemporal gap in the North American record of tyrannosaurs. This specimen, consisting of the proximal half of the bone, is morphologically similar to the femur of Moros intrepidus, a small-bodied tyrannosauroid from the Cenomanian Mussentuchit Member of the Cedar Mountain Formation of Utah, but not referable to this taxon. The Wayan femur lacks an autapomorphy diagnostic for Moros intrepidus, indicating the presence of a previously unrecognized tyrannosauroid taxon in the early Late Cretaceous of Laramidia. Histological results indicate that, at the time of death, this individual was at least five years old, skeletally immature, and undergoing growth at a moderate rate. The addition of this tyrannosauroid to the Wayan-Vaughn Assemblage provides additional evidence for the widespread distribution of various tyrannosauroid taxa in Laramidia during the early Late Cretaceous.
more »
« less
- Award ID(s):
- 1925973
- PAR ID:
- 10339583
- Date Published:
- Journal Name:
- Journal of Paleontology
- ISSN:
- 0022-3360
- Page Range / eLocation ID:
- 1 to 10
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
Liu, Jun (Ed.)Intensifying macrovertebrate reconnaissance together with refined age-dating of mid-Cretaceous assemblages in recent decades is producing a more nuanced understanding of the impact of the Cretaceous Thermal Maximum on terrestrial ecosystems. Here we report discovery of a new early-diverging ornithopod, Iani smithi gen. et sp. nov., from the Cenomanian-age lower Mussentuchit Member, Cedar Mountain Formation of Utah, USA. The single known specimen of this species (NCSM 29373) includes a well-preserved, disarticulated skull, partial axial column, and portions of the appendicular skeleton. Apomorphic traits are concentrated on the frontal, squamosal, braincase, and premaxilla, including the presence of three premaxillary teeth. Phylogenetic analyses using parsimony and Bayesian inference posit Iani as a North American rhabdodontomorph based on the presence of enlarged, spatulate teeth bearing up to 12 secondary ridges, maxillary teeth lacking a primary ridge, a laterally depressed maxillary process of the jugal, and a posttemporal foramen restricted to the squamosal, among other features. Prior to this discovery, neornithischian paleobiodiversity in the Mussentuchit Member was based primarily on isolated teeth, with only the hadrosauroid Eolambia caroljonesa named from macrovertebrate remains. Documentation of a possible rhabdodontomorph in this assemblage, along with published reports of an as-of-yet undescribed thescelosaurid, and fragmentary remains of ankylosaurians and ceratopsians confirms a minimum of five, cohabiting neornithischian clades in earliest Late Cretaceous terrestrial ecosystems of North America. Due to poor preservation and exploration of Turonian–Santonian assemblages, the timing of rhabdodontomorph extirpation in the Western Interior Basin is, as of yet, unclear. However, Iani documents survival of all three major clades of Early Cretaceous neornithischians (Thescelosauridae, Rhabdodontomorpha, and Ankylopollexia) into the dawn of the Late Cretaceous of North America.more » « less
-
Poorly preserved radiolarians of early Late Cretaceous age have been recovered from International Ocean Discovery Program (IODP) Hole U1520C, which was drilled as part of IODP Expedition 375 (Hikurangi Subduction Margin Coring, Logging, and Observatories). Seven radiolarian-rich samples from Cores 375-U1520C-42R and 43R (1027.8–1037.5 meters below seafloor) contain a relatively uniform assemblage that includes species indicative of a middle Cenomanian age (~97 Ma).more » « less
-
Denazinemys nodosais a Late Cretaceous representative of the North American turtle clade Baenidae diagnosed, among others, by a shell surface texture consisting of raised welts. We provide a detailed description of a partial skeleton from the late Campanian Kaiparowits Formation of Utah, USA, including bone-by-bone analysis of its cranium based on images obtained using micro-computed tomography. A revised phylogenetic analysis confirms placement ofDenazinemys nodosaclose toEubaena cephalicaandBoremysspp. within the clade Eubaeninae. Comparison with a second skull from the Kaiparowits Formation previously assigned toDenazinemys nodosaquestions its referral to this taxon. An assortment of specimens from the Early to Late Campanian of Mexico and the USA had previously been referred toDenazinemys nodosabased on shell surface texture alone, even though this characteristic is known to occur in other baenids. Our review of all available material concludes thatDenazinemys nodosais currently only known from the Late Campanian of New Mexico and Utah.more » « less
-
null (Ed.)The eastern foothills in the Colombian Eastern Cordillera have been an important oil-producing region since the discovery of the Cupiagua and Cusiana fields. Three organic-rich units are considered to be the main source rocks. The Aptian Fómeque and the Cenomanian-Coniacian Chipaque Formations comprise a siliciclastic to locally carbonate shallow marine shelf succession with type-II kerogen, whereas the Paleocene Los Cuervos Formation consists of marginal marine to nonmarine siliciclastic rocks with type-III kerogen. We modeled the petroleum systems of these three source units to characterize the hydrocarbon generation-accumulation processes within the basin. The structural record of the Eastern Cordillera shows that the most important tectonic event began in early Oligocene with contractional deformation along the Soapaga through Guaicaramo faults during early Miocene, culminating during the Pliocene with the Cusiana and Yopal faults. These variable rates of burial and exhumation resulted in contrasting time-temperature histories for each of the source rocks. The Fómeque Formation reached the oil window during the Paleocene in the south and the Eocene to the north. In contrast, the Chipaque Formation generation started during Early Oligocene in the south and by Late Oligocene to the north. Conversely, maturation for the Los Cuervos Formation was uniform along the foothills, reaching the oil window during Late Oligocene. Charge history modeling suggested that the Albian sandstones reservoirs were filled between Oligocene to Miocene. In contrast, the proven reservoirs in the area (the Upper Cretaceous, Paleocene, and Eocene sandstones) were filled by late Miocene, with a second episode of recent charge in the Eocene reservoirs, and perhaps active, from the Los Cuervos Formation. The results of this work proved that petroleum system modeling is useful not only to characterize generation-migration processes but it also can be used as a prediction tool in structurally complex areas such as the Colombian foothills.more » « less
- Free Publicly Accessible Full Text
-
Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1017/jpa.2022.42
