Cretaceous Of Texas Research Articles

Patterns and function of pneumaticity in the vertebrae, ribs, and ilium of a titanosaur (Dinosauria, Sauropoda) from the Upper Cretaceous of Texas

ABSTRACT Many sauropod dinosaurs exhibit extensive postcranial skeletal pneumaticity that may have facilitated the evolution of extreme body sizes. Among titanosauriforms, complex, irregularly branching camellate chambers are found throughout the presacral vertebral column, often invading the ribs and ilium as well. To explore the function of these camellae, including reduction in bone volume, pneumaticity was examined in a titanosaur sauropod from the Upper Cretaceous Black Peaks Formation of Big Bend National Park, Texas, that includes pneumatic dorsal ribs and ilia. Using natural breaks to non-destructively observe the internal structure, patterns of camellate pneumaticity are described for the dorsal vertebrae, ribs, and ilium. The space occupied by camellae is quantified as the airspace proportion, which is reported here in a sauropod ilium for the first time. Airspace proportions exceed 70% in parts of the dorsal vertebrae and ilium, with lower values near the cotyles of the vertebral centra and the acetabulum. Values in the ribs decrease distally. These values are not appreciably different from those of sauropods with simpler camerate pneumaticity. If camellae did not offer greater weight reduction than camerae, they may have enhanced structural strength, as the chambers appear to align with stress in the vertebral centra and ilium. Apneumatic trabecular bone around the acetabulum, preacetabular process, and postzygapophyses, however, may indicate stresses too great for camellate bone to bear, although an ontogenetic influence cannot be ruled out.

An overview of ichthyosaurian remains from the Cretaceous of Texas, USA

The clade nominal Ophthalmosauridae encompasses all currently recognized ichthyosaurian taxa from the mid-Cretaceous (Albian–Cenomanian) time interval in North America. These would have inhabited what is today known as the Western Interior Seaway. The remains represent mid to large-sized (up to around 5 m in maximum body length) ichthyosaurians that are mainly based upon isolated teeth and vertebrae, although some partial skeletons have been recovered from both the USA and Canada. Most of these fossils have taxonomic affinities with platypterygiines, such as the ubiquitous ‘form genus’ Platypterygius. This taxon has historically been the default identification for most North American Cretaceous ichthyosaur specimens. However, in comparison with remains from elsewhere, the ichthyosaurian fossils from Texas have been relatively understudied. Here, I review the existing records and present a concise list of all Cretaceous ichthyosaurian material currently held in public museum collections across the state. I have recognized 11 Cretaceous ichthyosaurian occurrences from Texas, including an indeterminate tooth, numerous vertebral centra, and some fragmentary skeletal remains attributable to Platypterygius. Ichthyosaurians therefore demonstrably occupied the Cretaceous epeiric seas of Texas from at least the Albian to middle Cenomanian, a distribution that traverses both the western and eastern coastlines of the Western Interior Seaway during its early phase of southern epicontinental incursion.

A new dinosaur tracksite from the Lower Cretaceous Sanbukdong Formation of Gunsan City, South Korea

South Korea has become globally famous for various tetrapod footprints from Upper Cretaceous strata. Here we report the first Early Cretaceous “large” tracksite from the Sanbukdong Formation of an unnamed small basin in the west of Gunsan City, North Jeolla Province. The tracksite (720 m2) produced 425 tracks. Among them, eleven ornithopod and three theropod trackways (189 tracks) were measured and mapped in detail. Most of ornithopod tracks are large (32 cm–51 cm in length) and very similar to pes imprints of Caririchnium lotus from China in that the general track dimensions and large heel pad impressions are typically longer than wide. They are attributable to basal hadrosauroids based on their stratigraphic and palaeogeographic occurrence as well as skeletal evidence in Korea. Eleven ornithopod trackways show gregarious behaviour and two main directions of movements along a lake margin. One movement is that of a group that went back and forth along the lacustrine margin and the other movement showing dinosaurs that came to the lakeshore probably to drink water or any other purposes. One trackway consists of 39 consecutive tracks with the distance of 39 m, representing the longest Early Cretaceous ornithopod trackway ever found in Korea. Sanbukdong ornithopod tracks suggest that basal hadorsauroids had the same growth pattern as derived hadrosaurids such as a brief period where it was very rapid. They also support independently that the majority of Early Cretaceous basal hadrosauroids were smaller than Late Cretaceous hadrosaurids in body size. Two theropod trackways consist of large tracks (more than 40 cm in length) and closely resemble Irenesauripus glenrosensis from the Lower Cretaceous of Texas which was inferred to be of Acrocanthosaurus origin. It is reasonable that they are attributable to carcharodontosaurids because their skeletal materials were already reported from the Lower Cretaceous strata in China and Korea. This new tracksite indicates that large ornithopod and theropod dinosaurs lived in the Early Cretaceous in Korea and strengthens previous hypotheses of their existence based on only isolated teeth.

A New Ichnospecies of Gyrolithes from the Austin Chalk, Upper Cretaceous, Texas, USA

ABSTRACTGyrolithes, a helical marine trace fossil, occurs in beds of the Austin Chalk near Waco, McLennan County, Texas. The new ichnospecies Gyrolithes texanus is characterized by unique morphology and wall construction. This discovery expands the current geographic and environmental range of Gyrolithes, extending this ichnogenus into the chalk-dominated beds of the Cretaceous of Texas. Irregular bedding features from the Gyrolithes locality indicate this section of the Austin Chalk was deposited within a storm-dominated depositional regime, interspersed with periods of quiescence which allow for firm ground formation and colonization by the trace maker. Occurrences of Gyrolithes have been associated by previous publications with marginal marine settings but not associated with storm deposits; therefore, this discovery constitutes an expansion of associated environment for this ichnogenus.

Cretaceous fossil Raninoida De Haan, 1839 (Crustacea, Decapoda, Brachyura) from northeast Texas

AbstractTwo new Raninoida crabs from the Cretaceous of Texas are described,Planocorystes robreidinew genus new species, andTexicancernew genus to accommodateNecrocarcinus renfroae. All the previously described raninoid-like decapods from the Pawpaw Formation have been reassigned according to Karasawa et al. (2014). Cretaceous raninoid-like crabs are the dominant taxa amongst the fossil decapods found in the Fort Worth, Texas, area, with hundreds of specimens collected. All of these fossils have been collected from limonitic nodules, and most of them present a good degree of preservation, with articulated pereiopods, pleons, venter and in rare occasions even the gills. The decapod fauna of the Pawpaw Formation represents a diverse population, with a large number of taxa in high abundance. One specimen ofP.robreidiappears to exhibit a lethal bite mark.

Two new species of Cenomanocarcinus Van Straelen, 1936 (Decapoda: Brachyura: Paleocorystoidea) from the Lower and Middle Cretaceous of Texas, USA, with remarks on intraspecific variation in Cenomanocarcinus

Two new species of Cenomanocarcinus Van Straelen, 1936 (Decapoda: Brachyura: Paleocorystoidea) from the Lower and Middle Cretaceous of Texas, USA, with remarks on intraspecific variation in Cenomanocarcinus

A gigantic shark from the lower cretaceous duck creek formation of Texas.

Three large lamniform shark vertebrae are described from the Lower Cretaceous of Texas. We interpret these fossils as belonging to a single individual with a calculated total body length of 6.3 m. This large individual compares favorably to another shark specimen from the roughly contemporaneous Kiowa Shale of Kansas. Neither specimen was recovered with associated teeth, making confident identification of the species impossible. However, both formations share a similar shark fauna, with Leptostyrax macrorhiza being the largest of the common lamniform sharks. Regardless of its actual identification, this new specimen provides further evidence that large-bodied lamniform sharks had evolved prior to the Late Cretaceous.

Postcranium of the paradigm elasmosaurid plesiosaurianLibonectes morgani(Welles, 1949)

AbstractElasmosauridae constitutes one of the most immediately recognizable plesiosaurian radiations. Their distinctive body plan represents the popular model for Plesiosauria, and is typified by an osteological morphology especially adapted for hyper-elongation of the neck. Nevertheless, many archetypal elasmosaurids are known only from incomplete and/or inadequately documented material, a problem that has contributed to their uncertain intra-clade relationships. A prime example of this isLibonectes morganifrom the Upper Cretaceous of Texas, USA, which is frequently presented as an elasmosaurid structural proxy because of its three-dimensionally preserved holotype skull. Perplexingly though, both the taxonomic diagnosis and phylogenetic placement ofL. morganirely primarily upon the cervical vertebrae, together with the pectoral girdle and forelimb, yet most of these elements are now lost and figured only as line drawings. We therefore reviewed the remnant postcranial skeleton ofL. morganifirst-hand with the objective of clarifying its defining character states. Our observations showed that the existing diagnosis ofL. morganiis indeed inadequate. Moreover, the only identifiable autapomorphies occurred within the axial skeleton. This concurred with an examination of character scores used in published plesiosaurian phylogenies, and highlights the persistent significance of postcranial elements for discriminating elasmosaurid taxa.

The skeletal morphology of the solemydid turtle Naomichelys speciosa from the Early Cretaceous of Texas

The fossil record of solemydid turtles is primarily based on isolated fragments collected from Late Jurassic to Late Cretaceous sediments throughout North America and Europe and little is therefore known about the morphology and evolutionary history of the group. We here provide a detailed description of the only known near-complete solemydid skeleton, which was collected from the Lower Cretaceous (Aptian–Albian) Antlers Formation of Texas during the mid-twentieth century, but essentially remains undescribed to date. Though comparison is limited, the skeleton is referred to Naomichelys speciosa, which is based on an isolated entoplastron from the Lower Cretaceous (Aptian–Albian) Kootenai (Cloverly) Formation of Montana. The absence of temporal emarginations, contribution of the jugals to the orbits, and a clear subdivision of the middle and inner cavities, and the presence of elongate postorbitals, posteriorly expanded squamosals, a triangular fossa at the posterior margin of the squamosals, an additional pair of tubercula basioccipitale that is formed by the pterygoids, foramina pro ramo nervi vidiani (VII) that are visible in ventral view, shell sculpturing consisting of high tubercles, a large entoplastron with entoplastral scute, V-shaped anterior peripherals, and limb osteoderms with tubercular sculpture diagnose Naomichelys speciosa as a representative of Solemydidae. The full visibility of the parabasisphenoid complex in ventral view, the presence of an expanded symphyseal shelf, and the unusual ventromedial folding of the coronoid process are the primary characteristics that distinguish Naomichelys speciosa from the near-coeval European taxon Helochelydra nopcsai.

New sauropod dinosaur material from Jones Ranch: a large Comanchean nonmammalian tetrapod from Texas

ABSTRACTNew sauropod dinosaur material is described from Jones Ranch, Early Cretaceous of Texas (USA). Originally described as Paluxysaurus jonesi, the material from Jones Ranch has recently been referred to Sauroposeidon proteles. Elements newly prepared from dense concretionary matrix include the sacrum, ilium and proximal portion of the tail. Reconstructions of the skull and sacrum plus pelvic girdles are presented. ‘Paluxysaurus jonesi’ (=S. proteles) is a blunt-faced sauropod that was originally regarded as closely related to Brachiosaurus. Portions of the sacrum are now exposed and show that it is nearly complete, missing only parts of the first sacral (S1). The anterior sacrals are firmly fused, however, a newly discovered opisthocoelous last sacral (S6) remains unfused. A complete sequence of proximal caudal vertebrae shows a rapid transition from anteroposteriorly short and mediolaterally broad centra anteriorly, to more elongate cylindrical centra posteriorly. All proximal caudals have slightly amphicoelous centra. Some middle anterior caudals have a shallow longitudinal groove on the ventral surface of the centrum. Specimens from Jones Ranch exhibit characters of the sacrum and tail that clearly corroborate placement of ‘P. jonesi’ (Sauroposeidon proteles) as a somphospondylan titanosauriform.

Remarkable preservation of a new genus and species of limuline horseshoe crab from the Cretaceous of Texas, USA

Abstract: A single specimen, part and counterpart of a carapace, of a horseshoe crab from the Lower Cretaceous (Albian) Glen Rose Formation in north‐central Texas, forms the basis for the definition of a new genus and species, Crenatolimulus paluxyensis. The discovery represents only the fifth limuline known from the Cretaceous. Its preservational style is remarkable in that the carapace exterior is faithfully replicated by a massive overgrowth of serpulid worms.

A new asteroid (Echinodermata) faunule from the Early Cretaceous (Barremian) of Morocco

An asteroid (Echinodermata) faunule of four taxa representing three surviving families and a probable fourth is described from the Barremian (Early Cretaceous) of Morocco, northwest Africa. The four together suggest limited morphologic evolution since the Cretaceous but biogeographic and depth patterns have changed. Marocaster coronatus n. gen. n. sp. (Valvatida, Goniasteridae) combines apparent derived features of the dorsal disk and superomarginal shape with more stemward expressions of the abactinal ossicles. Betelgeusia orientalis n. sp. is a fourth Mesozoic occurrence of the Radiasteridae (Paxillosida), the new species similar to earlier occurrences from the Middle Jurassic of India, the Early Cretaceous of Texas, and the Late Cretaceous of Europe. Reported modern occurrences of the family are few, widely scattered, and limited to deeper water; the extinct species together testify to a once-broader familial distribution. Dipsacaster africanus n. sp., a member of the Astropectinidae (Paxillosida), is remarkably similar to extant congeners. Dipsacaster today is widely distributed in the Pacific Ocean but occurrences in the Atlantic are few. Because of preservation, a single small specimen of the Zoroasteridae? (Forcipulatida) cannot be identified with certainty. Extant zoroasterids are deep-water in distribution, although shallow-water Eocene representatives are known.

Erdtmanitheca portucalensis, a new pollen organ from the Early Cretaceous (Aptian–Albian) of Portugal with Eucommiidites-type pollen

A new lignitised, slightly compressed pollen organ, Erdtmanitheca portucalensis, with affinities to extinct Erdtmanithecales from the Early Cretaceous (Aptian–Albian) of Vale de Água (Lusitanian Basin, western Portugal), is described. The pollen organ is composed of loosely arranged microsporophylls radiating from a central core. The estimated number of microsporophylls is about 100–150. The microsporophylls are sessile and ellipsoidal to barrel-shaped with a flattened or slightly apically depression containing about ten narrow sporangia. The sporangia enclose abundant well-preserved pollen grains of Eucommiidites-type. Pollen grains found in situ are elliptical in equatorial outline, about 16.0–27.2 μm long and 11.9–16.4 μm wide. The main (distal) colpus is long with expanded rounded ends. It is flanked by two subsidiary colpi in an almost equatorial position. The surface of the pollen wall is psilate and occasionally punctate. The ektexine is composed of a distinct tectum, granular infratectal layer and a thin foot layer. The endexine is thick and laminar. The new Early Cretaceous Portuguese pollen-organ is similar in several respects to that of Erdtmanitheca texensis described from the Late Cretaceous of Texas, USA. The new fossil species further documents the importance of the Bennettitales-Erdtmanithecales-Gnetales group in the Early Cretaceous floras of Portugal extending the stratigraphic and geographical distribution of the genus with regard to systematic and phylogenetic significance of the Eucommiidites-producing plants that may have been co-occurring with the Early Cretaceous diversification of angiosperms. It is ascertained that perforate tectum occurs in pollen grains with a well-developed foot layer as well as in pollen grains in which a foot layer is poorly developed or lacking, and that pollen features do not support a separation of the Erdtmanithecales seeds and pollen organs.

Blending Rudists with Technology; Non-destructive Examination of the Internal and External Structures of Rudists Using High Quality Scanning and Digital Imagery

Certain formations within the Cretaceous of Texas include zones of silicified rudists. Such diagenetic alteration, combined with the timing of alteration, has preserved many structural features of the rudist suitable for computed tomography (CT scanning). The excellent density differences between those skeletal structures (silica) and the internal sediment (calcitic mud) or later crystallization (calcite), fulfill a fundamental requirement for such analysis. The Jackson School of Geosciences at The University of Texas provides access to a high resolution computed tomography scanning system. This equipment, not identical to medical scanners, provides higher resolution and sophisticated software to analyze the imagery. Several rudist specimens have been scanned, including Caprinuloidea perfecta, from the Lower Cretaceous Edwards Formation (Albian) and Bayeloidea clivi from the Albian (formerly considered Turonian) of Mexico. Other rudist specimens are preserved in a different manner. For example, structures may be replaced with single crystal calcite with external skeletal intricacies especially well preserved. Elsewhere the record is one of internal molds or casts, with a reduction of available detail. Cost, diagenesis, and size determine the mode of specimen imagery used in an NSF sponsored project to image and conserve the type and figured specimens in the collection of the Texas Natural Science Center, Non-vertebrate Paleontology. This paper describes how such imagery can be used to further many aspects of rudist research. CT scanning produces serial sections of minute thickness without destroying a valuable specimen, in contrast to preparing physical serial sections, a more traditional method of analytical study. High resolution digital imagery (35 mm) provides images of great clarity which can be analyzed further and can be used as a surrogate for physical peels of rare or fragile specimens. Both these methods of imagery can be made available on-line and can be studied by scientists throughout the world.

Comptoniaster adamsi nov. sp. (Echinodermata, Asteroidea) from the middle Cretaceous of Texas and its phylogenetic position

Comptoniaster adamsi nov. sp. (Asteroidea, Valvatida, Goniasteridae) is described from the middle Cretaceous (Cenomanian-Turonian) Britton Formation of northcentral Texas, USA. The new species provides the focus for an exploratory cladistic analysis of Mesozoic asteroids of the Comptoniaster- Tylasteria Group sensu G. Breton. The systematics of Mesozoic goniasterids has relied heavily on the morphology of marginal ossicles, which generally are the best-preserved elements of the skeleton. Unfortunately, marginal ossicular data are scanty for most species because ossicles tend to be morphologically simple yet varied even within individuals, and few even partially articulated specimens are available to provide more comprehensive information. Further, both plesiomorphy and homeomorphy have been important. Because of limited available data, phylogenetic reconstruction here is preliminary. Nevertheless, a number of taxon groupings recognized in the literature are recovered, and stratigraphic distribution provides some support for results. Data unfortunately are particularly incomplete for species of Comptoniaster, the focus of the study. Comptoniaster adamsi nov. sp. clustered with three other species assigned to the genus, including the type, all Cretaceous in age. Jurassic species of Comptoniaster are more widely distributed in the analysis, perhaps reflecting an early stage in diversification or perhaps suggesting the need for species assignment reassessment, but also reflecting the limited available data.

Palaeoecological significance of turritelline gastropod-dominated assemblages from the mid-Cretaceous (Albian-Cenomanian) of Texas and Oklahoma, USA

The faunas of three previously poorly known and highly fossiliferous limestones from the upper Lower Cretaceous of Texas are dominated by turritelline gastropods. These faunas consist of turritelline-dominated assemblages in the Whitestone Limestone Member of the Walnut Formation in Travis County (middle Albian), the Keys Valley Marl Member of the Walnut Formation in Coryell County (middle Albian), and the Fort Terrett Formation in Kimble County (middle Albian). A fourth high-spired gastropod assemblage in the Segovia Formation in Pecos County (upper Albian) is not dominated by turritellines. Two other turritelline-dominated assemblages in non-carbonate rocks from the Albian and Cenomanian of Texas and Oklahoma are also described. These turritelline-dominated assemblage occurrences add considerably to our knowledge of the facies occurrence of Cretaceous turritelline-dominated assemblages, and they are consistent with the global facies distribution of these assemblages: i.e., although they are widespread in siliciclastic facies from Cretaceous to Recent, turritelline-dominated assemblages in carbonate facies occur almost exclusively in the Cretaceous and Paleogene.

Diverse origins and timing of formation of basinal brines in the Gulf of Mexico sedimentary basin

AbstractA review of five different field areas in the Gulf of Mexico sedimentary basin (GOM) illustrates some of the potentially diverse chemical and physical processes which have produced basinal brines. The elevated salinities of most of the formation waters in the GOM are ultimately related to the presence of the Middle Jurassic Louann Salt. Some of these brines likely inherited their salinity from evaporated Mesozoic seawater, while other saline fluids have been produced by subsequent dissolution of salt, some of which is occurring today. The timing of the generation of brines has thus not been restricted to the Middle Jurassic. The mechanisms of solute transport that have introduced brines throughout much of the sedimentary section of the GOM are not entirely understood. Free convection driven by spatial variations in formation water temperature and salinity is undoubtedly occurring around some salt structures. However, the driving mechanisms for the broad, diffusive upward solute transport in the northern Gulf rim of Arkansas and northern Louisiana are not known. In the Lower Cretaceous of Texas, fluid flow was much more highly focused, and perhaps episodic. It is clear that many areas of the Gulf basin are hydrologically connected and that large‐scale fluid flow, solute transport, and dispersion have occurred.The Na‐Mg‐Ca‐Cl compositions of brines in the areas of the Gulf Coast sedimentary basin reviewed in this article are products of diagenesis and do not reflect the composition of the evaporated marine waters present at the time of sediment deposition. Large differences in Na, Ca, and Mg trends for waters hosted by Mesozoic versus Cenozoic sediments may reflect differences in: (i) the sources of salinity (evaporated seawater for some of the Mesozoic sediments, dissolution of salt for some of the Cenozoic sediments); (ii) sediment lithology (dominantly carbonates for much of the Mesozoic sediments, and dominantly siliciclastics for the Cenozoic sediments); or (iii) residence times of brines associated with these sediments (tens of millions of years versus perhaps days).

The application of Ground Penetrating Radar as a mapping technique at vertebrate fossil excavations in the Cretaceous of Texas

In order to develop a new field method for the science of paleontology, Ground Penetrating Radar (GPR) surveys were conducted at two sauropod (Dinosauria) quarries in the Cretaceous rocks of Texas. These sites were chosen due to the presence of vertebrate fossils and the varying lithologic settings. The surveys were conducted using a Pulse EKKO transmitter and receiver antennae pair at varying frequencies. Higher survey frequencies allow for greater resolution at the cost of decreased survey penetration depth. Anomalies detected in the subsurface were plotted on quarry maps. The GPR-enhanced maps were then given to paleontological field teams to guide their excavation efforts. Fossils were accurately located and excavated using this technique.

Robert Thomas Hill – Father of the Texas Cretaceous

Robert T. Hill, an early Texas geologist, developed a general interest in science and a particular fascination for geology during his late teens in Comanche, Texas. He received his formal geological training at Cornell University in New York. After graduation, he was associated with the Smithsonian Institution and the United States Geological Survey in Washington, D.C. In the late 1880s, he helped organize the Texas Geological Survey, the precursor to the Texas Bureau of Economic Geology. During his colorful career, he made significant contributions to the geography and geology of the southwest. He not only defined and named the physiographic provinces of Texas but also was responsible for organizing and subdividing the Cretaceous strata of Texas and adjacent areas into useful stratigraphic units. He also contributed to our understanding of the structural framework of Texas by recognizing and describing the Balcones fault zone of Central Texas and the Texas lineament of southwest Texas. In 1900, Hill gained national fame for his exploration of major canyons along the Rio Grande in the Big Bend area. Although he was a “giant” in the field of geology, he felt persecuted by some of his geological associates. Hill died in 1941 after an outstanding professional career that spanned more than 60 years.

A new species of Tenontosaurus (Dinosauria: Ornithopoda) from the Early Cretaceous of Texas

ABSTRACT Two articulated skeletons of an ornithopod dinosaur from the Early Cretaceous of Texas form the basis for description of a new species of Tenontosaurus. The new ornithopod, Tenontosaurus dossi sp. nov., is a sister species to Tenontosaurus tilletti Ostrom found in Montana and Wyoming. Specimens of the new species are temporally older than those of T. tilletti, and in most cases of unequivocal polarity they are more primitive. The Texas species is clearly the most primitive iguanodontian, and thus shares many primitive characters with the weakly supported clade Hypsilophodontidae. The specimens from Texas represent unscavenged carcasses entombed in a brackish-water lagoonal or estuarine sands.